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THE HIP SOCIETY |
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MEETING OF THE HIP SOCIETY Thirty-Fifth Open Scientific Meeting The Thirteenth Combined Open Meeting Hip Society and AAHKS San Diego, CA February 17, 2007 PROGRAM CHAIRMAN Douglas A. Dennis, M.D. CONTENTS: COURSE OBJECTIVES: The objectives of the Open Meeting of the Hip Society are to provide up-to-date information on the treatment of hip problems including non-arthroplasty options and the latest surgical techniques as well as the current thinking on bearing surfaces. Other objectives deal with the difficult primary THA and complication management including an update on revision THA. COURSE DESCRIPTION: This course is divided into eleven symposia. We will look at surgical techniques including computer assisted navigation and a discussion of bearing surfaces. There will be symposia dealing with difficult THA cases and revision technique updates plus a discussion of complication management. There will also be a presentation of the Hip Society Award papers and a special Presidential Guest Speaker included in the program. INTENDED AUDIENCE: The intended audience is orthopedic surgeons and orthopaedic residents. 8:00 a.m. Opening Comments John Callaghan, M.D., President SYMPOSIUM I: NONARTHROPLASTY OPTIONS: OSTEOARTHRITIS & AVN Moderator: Vincent Pellegrini, M.D. Baltimore, MD 8:05 a.m. Hip Arthroscopy: Indications & Limitations Joseph C. McCarthy Jr., M.D. Boston, MA 8:13 a.m. Hip Joint Impingement Robert Trousdale, M.D. Rochester, MN 8:21 a.m. Role of Hip Osteotomy John C. Clohisy, M.D. St. Louis, MO 8:29 a.m. Osteonecrosis of the Hip: Clinical Update Jay R. Lieberman, M.D. Los Angeles, CA 8:37 a.m. DISCUSSION SYMPOSIUM II: BEARING SURFACE UPDATE Moderator: A. Seth Greenwald, D. Phil (Oxon) Cleveland, OH 8:53 a.m. Clinical Performance of First Generation Highly Crosslinked Polyethylenes Harry A. McKellop, Ph.D. Los Angeles, CA 9:01 a.m. Polymer Update for Total Joint Arthroplasty: Second Generation Cross-Linked UHMWPEs Harry Rubash, M.D. Boston, MA 9:09 a.m. Metal-on-Metal THA: Ion & Allergy Issues Joshua J. Jacobs, M.D. Chicago, IL 9:17 a.m. Ceramic Fracture: Past & Present James D'Antonio, M.D. Moon Township, PA 9:25 a.m. Future Bearing Materials William Maloney, M.D. Stanford, CA 9:33 a.m. DISCUSSION 9:48 a.m. BREAK SYMPOSIUM III: UPDATE ON HIP RESURFACING Moderator: Harlan Amstutz, M.D. Los Angeles, CA 10:03 a.m. The Ideal Candidate Thomas Vail, M.D. Durham, NC 10:11 a.m. Technical Tips: Avoiding Complications Thomas P. Schmalzried, M.D. Los Angeles, CA 10:19 a.m. Clinical Results: Past & Present Michael Mont, M.D. Baltimore, MD 10:27 a.m. A Skeptics View Paul Lachiewicz, M.D. Chapel Hill, NC 10:35 a.m. DISCUSSION SYMPOSIUM IV: DEALING WITH THE DIFFICULT PRIMARY THA Moderator: Eduardo Salvati, M.D. New York, NY 10:51 a.m. Developmental Dysplasia Robert B. Bourne, M.D. London, Ontario, Canada 10:59 a.m. Diaphyseal Deformity: Bent But Not Broken Miguel E. Cabanela, M.D. Rochester, MN 11:07 a.m. Dealing With Retained Hardware Steven J. MacDonald, M.D. London, Ontario, Canada 11:15 a.m. Hip Fusion Take Down, Better Late Than Never Aaron Glen Rosenberg, M.D. Chicago, IL 11:22 a.m. DISCUSSION SYMPOSIUM V: PRESIDENTIAL GUEST ADDRESS 11:38 a.m. 3-D Anatomy of the Dysplastic Hip: Consequences For THA Jean-Noel Argenson, M.D. Marseille, France 11:50 p.m. LUNCH SYMPOSIUM VI: SURGICAL TECHNIQUES: TECHNICAL VIDEOS Moderator: Thomas Thornhill, M.D. Boston, MA 12:40 p.m. Minimally Invasive THA: Direct Anterior Joel Matta, M.D. Los Angeles, CA 12:46 p.m. Minimally Invasive THA: Anterolateral William Hozack, M.D. Philadelphia, PA 12:52 p.m. Minimally Invasive THA: Two Incision Approach in 2007 Mark W. Pagnano, M.D. Rochester, MN 12:58 p.m. Minimally Invasive THA: Posterior Thomas P. Sculco, M.D. New York, NY 1:04 p.m. Standard Trochanteric Osteotomy & Advancement Douglas A. Dennis, M.D. Denver, CO 1:10 p.m. Extended Trochanteric Osteotomy Wayne Paprosky, M.D. Winfield, IL 1:16 p.m. Cementing A Liner Into A Well-Fixed Shell William A. Jiranek, M.D. Richmond, VA 1:21 p.m. DISCUSSION SYMPOSIUM VII: HIP SOCIETY AWARDS Moderator: Charles Engh, M.D. Alexandria, VA 1:37 p.m. The John Charnley Award Factors Leading To Low Prevalence Of Deep Vein ThrombosisAnd Pulmonary Embolism After Total Hip Arthroplasty Young-Hoo Kim, M.D. Seoul, Korea 1:48 p.m. The Frank Stinchfield Award The Biomechanical Contribution Of The Labrum To The Stability Of The Hip Matthew J. Crawford, M.D. Houston, TX 1:59 p.m. The Otto Aufranc Award Ceramic-on-Metal Hip Replacements: A Comparative In Vitro and In Vivo Study John Fisher, D.Eng. Leeds, UK SYMPOSIUM VIII: 2:10 p.m. ORTHOPAEDIC RESEARCH SOCIETY REVIEW Richard D. Coutts, M.D. San Diego, CA SYMPOSIUM IX: COMPUTER ASSISTED NAVIGATION Moderator: Kenneth Krackow, M.D. Buffalo, NY 2:21 p.m. Surgical Navigation for Hip ArthroplastyStephen B. Murphy, M.D. Boston, MA 2:29 p.m. Surgical Navigation: What's Available? Philip C. Noble, Ph.D. Houston TX 2:37 p.m. Clinical Results William Bargar, M.D. Sacramento, CA 2:43 p.m. Pitfalls of Computer Navigation Lawrence D. Dorr, M.D. Inglewood, CA 2:50 p.m. DISCUSSION 3:05 p.m. BREAK SYMPOSIUM X: COMPLICATION MANAGEMENT Moderator: William Harris, M.D. Boston, MA 3:20 p.m. Management of Chronic DislocationDaniel J. Berry, M.D. Rochester, MN 3:28 p.m. Persistent Thigh Pain John R. Moreland, M.D. Santa Monica, CA 3:36 p.m. Surgical Treatment of Leg Length Inequality C. Anderson Engh, Jr. M.D. Alexandria, VA 3:44 p.m. Infection After THRArlen Hanssen, M.D. Rochester, MN 3:52 p.m. Periprosthetic Fractures: “What’s New?” Clive P. Duncan, M.D. Vancouver, BC, Canada 4:00 p.m. Pelvic Discontinuity David G. Lewallen, M.D. Rochester, MN 4:07 p.m. DISCUSSION SYMPOSIUM XI: UPDATE ON REVISION THA Moderator: Chitranjan S. Ranawat, M.D. New York, NY 4:23 p.m. Management of Periacetabular Bone Loss Alan E. Gross, M.D. Toronto, Ontario, Canada 4:31 p.m. Management of Femoral Bone Loss Robert Barrack, M.D. St. Louis, MO 4:39 p.m. Acetabular Revision Options William N. Capello, M.D. Indianapolis, IN 4:47 p.m. Femoral Component Options John J. Callaghan, M.D. Iowa City, IA 4:54 p.m. DISCUSSION 5:10 p.m. ADJOURN 8:05 a.m. Hip Arthroscopy: Indications and Limitations Joseph C. McCarthy, M.D. Hip arthroscopy offers minimally invasive treatment for an expanding number of both intra and extra articular hip conditions. These conditions include but are not limited to labral tears, loose bodies, synovial chondromatosis, chondral flap lesions of the acetabulum or femoral head, foreign body removal, capsular shrinkage (Ehler Danlos, etc.), and post Total Hip Arthroplasty (diagnosis of occult sepsis, removal third bodies, scar debridement). There is no disruption of muscle or tendons with hip arthroscopy, therefore, there is minimal scarring and rehabilitation is generally brief. The patient can bear full weight on the hip without support as soon as comfort permits which is usually 3 to 5 days after surgery. Relative contraindications for hip arthroscopy include morbid obesity not only because of difficulty achieving distraction limitations but also the length of instruments necessary to access the joint. Sepsis with accompanying osteomyelitis or abscess formation requires open surgery. Osteonecrosis, moderate dysplasia and synovitis in the absence of mechanical symptoms do not warrant arthroscopy. Joint ankylosis, dense heterotopic bone formation, or considerable protrusio limit the potential for hip distraction and may preclude arthroscopy. In the senior author’s opinion advanced osteoarthritis is a contraindication. Candidates for hip arthroscopy should include only those patients with mechanical symptoms (catching, locking or buckling) that have failed to respond to conservative therapy. Physical exam findings can include any or all of the following: a positive McCarthy sign (with both hips fully flexed, the patient’s pain is reproduced by extending the affected hip, first in external rotation, then in internal rotation), inguinal pain with flexion, adduction and internal rotation of the hip and anterior inguinal pain with ipsilateral resisted straight leg-raising. Gadolinium enhanced MRI imaging is much more sensitive for detecting labral tears than traditional MRI. McCarthy et al. demonstrated 78% accuracy for anterior labral tears. It is not as reliable at detecting chondral defects or nonossified loose bodies. The technical challenge of hip arthroscopy involves a high learning curve. Visiting high volume centers, attending instructional courses, and practicing in bioskills laboratories all contribute to the clinician becoming technically proficient. Meticulous attention to positioning, distraction time and portal placement are essential. Complication rates are reported between 0.5% and 5%, most often related to distraction. Improvements in technique and instrumentation have made hip arthroscopy an efficacious way to diagnose and treat a variety of intra-articular problems. References: 1. Byrd, J. W., and Jones, K. S.: Adhesive capsulitis of the hip. Arthroscopy, 22(1): 89-94, 2006. 2. Schmerl, M.; Pollard, H.; and Hoskins, W.: Labral injuries of the hip: a review of diagnosis and management. J Manipulative Physiol Ther, 28(8): 632, 2005. 3. McCarthy, J. C., and Lee, J.: Hip arthroscopy: indications and technical pearls. Clin Orthop Relat Res, 441: 180-7, 2005. 4. Guanche, C. A., and Sikka, R. S.: Acetabular labral tears with underlying chondromalacia: a possible association with high-level running. Arthroscopy, 21(5): 580-5, 2005. 5. McCarthy, J. C.: The diagnosis and treatment of labral and chondral injuries. Instr Course Lect, 53: 573-7, 2004. 6. McCarthy, J. C., and Lee, J. A.: Acetabular dysplasia: a paradigm of arthroscopic examination of chondral injuries. Clin Orthop Relat Res, (405): 122-8, 2002. 7. O'Leary J, A.; Berend, K.; and Vail, T. P.: The relationship between diagnosis and outcome in arthroscopy of the hip. Arthroscopy, 17(2): 181-8, 2001. 8. McCarthy, J. C.; Noble, P. C.; Schuck, M. R.; Wright, J.; and Lee, J.: The watershed labral lesion: its relationship to early arthritis of the hip. J Arthroplasty, 16(8 Suppl 1): 81-7, 2001. 9. McCarthy, J. C.; Noble, P. C.; Schuck, M. R.; Wright, J.; and Lee, J.: The Otto E. Aufranc Award: The role of labral lesions to development of early degenerative hip disease. Clin Orthop Relat Res, (393): 25-37, 2001. 10. 1Byrd, J. W., and Jones, K. S.: Prospective analysis of hip arthroscopy with 2-year follow-up. Arthroscopy, 16(6): 578-87, 2000. 8:13 a.m. Hip Joint Impingement
The majority of patients who develop hip arthritis have a mechanical abnormality of the joint. The structural abnormalities range from instability (DDH) to impingement. Impingement leads to osteoarthritis by chronic damage to the acetabular labrum and adjacent cartilage.
In situations of endstage secondary DJD, hip arthroplasty is the most reliable treatment choice. In young patients with viable articular cartilage, joint salvage is indicated. Treatment should be directed at resolving the structural abnormalities that create the impingement. Femoral abnormalities corrected by osteotomy or head-neck offset by chondro-osteoplasty creating a satisfactory head-neck offset. This can safely be done via anterior surgical dislocation. The acetabular-labral lesions can be debridement and/or repaired. Acetabular abnormalities should be corrected by “reverse” PAO in those with acetabular retroversion or anterior acetabular debridement in those with satisfactory posterior coverage and a damaged anterior rim. Often combinations of the above are indicated. This talk will also update issues related to hip impingement and joint salvage surgery that have arisen over the past year. 8:21 a.m. The Role of Hip OsteotomyJohn C. Clohisy, M.D. and Perry L. Schoenecker, M.D. The surgical treatment options for pre-arthritic and early arthritic hip disease have expanded and evolved substantially over the past decade. This is due to enhanced understanding of hip pathomechanics, improved diagnostic and imaging modalities, better patient selection criteria and refinements in alternative surgical procedures. Despite these advancements, the diversity of clinical conditions and the spectrum of surgical options highlight the major need to develop optimal diagnostic and treatment guidelines for mechanical hip disorders. Hip osteotomy surgery is a mainstay treatment modality and provides the potential for improved hip function and preservation of the joint. This presentation will discuss the role and indications for joint preservation hip osteotomies and will review contemporary surgical techniques. The specific indications for hip osteotomy surgery span a wide spectrum of disorders including developmental hip dysplasia (DDH), Perthes deformities, slipped capital femoral epiphysis (SCFE), proximal femoral malunion/nonunion and osteonecrosis. Optimal surgical candidates are less than 50 years old, physically well conditioned, have adequate hip range of motion and have pre-arthritic or early arthritic joint disease. Careful patient selection and preoperative planning are critical to optimizing the clinical results of surgery. The surgical procedure should focus on correcting the joint pathomechanics, selectively addressing associated intra-articular disorders (labral tears, chondromalacia and chondral flaps), avoiding secondary or persistent impingement disease and minimizing distortion of the hip anatomy in case future total hip arthroplasty is required. To accomplish these goals, the fundamental surgical techniques include acetabular reorientation and proximal femoral osteotomy. To optimize the hip reconstruction, these fundamental procedures can be selectively augmented with surgical hip dislocation, trochanteric advancement, hip arthroscopy, osteochodroplasty, relative femoral neck lengthening, acetabular rim osteoplasty, labral repair, and articular chondroplasty. Given this array of surgical tools and improvements in patient selection for surgery, it is likely that continued refinement of hip osteotomy surgery will occur. In the majority of well-selected patients treated with sound surgical technique, improved hip function and lasting preservation of the joint can be anticipated. References: 1. ADDIN EN.REFLIST Clohisy JC, Keeney JA, Schoenecker PL. Preliminary Assessment and General Treatment Guidelines for Young Adult Hip. Clin Orthop Relat Res 2005; 441: 168-179. 2. Clohisy JC, Barrett SE, Gordon JE, et al. Periacetabular osteotomy for the treatment of severe acetabular dysplasia. J Bone Joint Surg Am 2005;87:254-259. 3. Clohisy JC, Nunley R, Curry MC, Schoenecker PL. Periacetabular osteotomy for the treatment of acetabular dysplasia associated with major aspherical femoral head deformities. J Bone Joint Surg Am (in press). 4. Cunningham, T, Jessel R, Zurakowski D et al. Delayed Gadolinium-Enhanced Magnetic Resonance Imaging of cartilage to predict early failure of Bernese periacetabular osteotomy for hip dysplasia. J Bone Joint Surg Am 2006. 88-A, 1540-1548. 5. Ganz R, Gill TJ, Gautier E, et al. Surgical dislocation of the adult hip a technique with full access to the femoral head and acetabulum without the risk of avascular necrosis. J Bone Joint Surg Br 2001;83:1119-1124. 6. Ganz R, Klaue K, Vinh TS, Mast JW. A new periacetabular osteotomy for the treatment of hip dysplasias. Technique and preliminary results. Clin Orthop 1988(232):26-36. 7. Leunig M, Siebenrock KA, and Ganz R: Rationale of Periacetabular osteotomy and background work. J Bone Joint Surg Am 2001;83:438-448. 8. Millis MB, Kim YJ. Rationale of osteotomy and related procedures for hip preservation: a review. Clin Orthop Relat Res 2002:108-121. 9. Myers SR, Eijer H, Ganz R. Anterior femoroacetabular impingement after periacetabular osteotomy. Clin Orthop Relat Res 1999:93-99. 10. Trousdale RT, Ekkernkamp A, Ganz R, Wallrichs SL. Periacetabular and intertrochanteric osteotomy for the treatment of osteoarthrosis in dysplastic hips. J Bone Joint Surg Am 1995; 8(1):3-9. 8:29 a.m. Osteonecrosis of the Hip: Clinical Update Jay R Lieberman, M.D. Osteonecrosis of the hip remains a challenging problem for the patient afflicted with the disease and for the orthopaedic surgeons treating them. There are 20,000 – 30,000 new cases of osteonecrosis annually and treatment success is difficult because there are a number of different diagnoses associated with the disease and the etiology has not been definitively established. In addition, with the improved results associated with total hip arthroplasty the role of femoral head saving procedures needs to be re-evaluated in certain patient populations. The purpose of this lecture is to provide an update of recent advances related to the non-operative and operative treatment of osteonecrosis of the femoral head. The potential clinical applicability of novel therapeutic regimens including bisphosphonates, shock wave therapy, bone marrow therapy and bone morphogenetic proteins will be reviewed. An update of the role of hemi-resurfacing, full resurfacing and total hip arthroplasty will be provided. 8:53 a.m. Clinical Performance of First-Generation Highly Crosslinked Polyethylenes Harry A. McKellop, Ph.D. The common characteristics of the current generation of highly crosslinked polyethylenes is that they are crosslinked by exposure to radiation (either gamma or electron beam) and then thermally treated to reduce residual free radicals, thereby stabilizing them against oxidation. Since 1998, approximately one million hip prostheses with highly crosslinked polyethylene acetabular cups have been implanted. After an initial period of creep deformation, the steady-state wear rates, measured as the apparent penetration of the ball into the socket on serial radiographs, has been very comparable to the predictions from pre-clinical joint simulator testing, with the percent reduction in wear below historical polyethylene reaching 90% or more, depending on the amount of crosslinking, and with a corresponding marked reduction in the incidence of osteolysis. As yet, the concern that the reduction in fracture toughness caused by elevated crosslinking would lead to a marked increase in fracture of the polyethylene has not been realized clinically. Those fractures that have been reported have tended to be initiated by neck-socket impingement, and have occurred primarily with the higher levels of crosslinking (~ 10 Mrads.) Some retrieved cups of a crosslinked polyethylene that was annealed after radiation crosslinking, rather than remelted, have shown levels of oxidation comparable to that which occurred in historical gamma-air sterilized polyethylene after several years of shelf aging in air. However, as yet, this has not been shown to affect their clinical performance. Nevertheless, several new crosslinking processes have been developed that remove the free radicals generated during irradiation by means other than remelting, to maximize fracture toughness while avoiding long-term oxidative degradation. 9:01 a.m. Polymer Update for Total Joint Arthroplasty: Second Generation Cross-Linked UHMWPEs Harry Rubash, M.D., O.K. Muratoglu and Oral Ebru Osteolysis secondary to wear of UHMWPE components limits the long-term performance of total hip arthroplasty. In vitro simulator studies and new in vivo clinical data, with up to 6-year follow-up, have demonstrated that radiation crosslinking of UHMWPE markedly increases the wear resistance of acetabular polyethylene liners. Radiation not only crosslinks the UHMWPE increasing its wear resistance but also generates trapped free radicals, which, if not stabilized, could compromise long-term oxidative stability. First generation highly crosslinked UHMWPEs were either melted or annealed after irradiation to quench the free radicals; melted components proved to have much superior oxidation resistance than annealed ones in vivo. Recently two “second generation” highly cross-linked UHMWPEs have been advanced. One is sequentially irradiated and annealed (X3). The other is irradiated and doped with vitamin-E (E-Poly). Both X3 and E-Poly have equivalent wear resistance comparable to that of the first generation highly cross-linked UHMWPEs. Both X3 and E-Poly exhibit higher crystallinity, mechanical strength, and fatigue resistance when compared to irradiated and melted first generation cross-linked UHMWPE. The oxidation resistance of E-Poly is higher than that of X3. E-Poly can be terminally gamma sterilized without compromising long-term oxidative stability. In contrast, X3 is annealed after each sequential irradiation cycle and contains detectable free radicals. One-second generation cross-linked UHMWPE (E-Poly) is a low-wear material with improved mechanical strength and fatigue resistance and it is expected to maintain these properties over time due to its oxidation resistance. It should gain rapid acceptance in vivo. 9:09 a.m. Metal-on-Metal THA: Ion & Allergy Issues
9:17 a.m. Ceramic Fractures: Past and PresentJames A. D’Antonio, M.D. The major advantages of alumina ceramic bearings include their extreme hardness and scratch resistance, low coefficient of friction, their hydrophilic nature with improved lubrication, and their superior wear resistance compared to other bearing surfaces. The major disadvantage to their use is the risk of fracture. In the 1970’s and 1980’s, reports of ceramic fractures ranged from zero to seven percent. These early failures of alumina bearings were related to suboptimal material properties and to uncontrolled variables such as implants that were poorly designed for fixation as well as poor taper designs for mating of the ceramic to the implant. The combination of significantly improved alumina ceramic material (Biolox forte) with implants that have high fixation track records and metal tapers designed to work with alumina implants for proper transfer of loads have led to a dramatic decline in the risk of ceramic fracture. The risk today is estimated to be 0.02% for the femoral head and 0.0075% for the acetabular component. In a prospective IDE study 1382 alumina ceramic implants were implanted without a ceramic fracture out to ten years. Since FDA approval that same ceramic implant has been used in approximately 52,000 hips and there has been recorded four acetabular fractures (0.008% risk) and nine alumina head fractures (0.017% risk). A major supplier of alumina ceramic bearings (CeramTec) has distributed over two million Biolox forte alumina ceramic total hips between 2000 and 2005. A total of 314 fractures and/or intraoperative chips have been reported (0.016%) and 20% of the fractures were related to a specific adverse event including such issues as severe patient trauma, autoclaving followed by cold immersion of the alumina head, mismatch in diameter of head and acetabular insert, and recurrent instability. While we can assume that the manufacturer’s data may not include all fractures, certain trends have been identified. Fifty percent of ceramic fractures occurred within twelve months following implantation, 70% within twenty-four months, and 83% within thirty-six months. Femoral head fractures were higher for the 28mm compared to 32mm size, and higher for the longer and shorter head sizes compared to the standard zero neck length. Fractures of the femoral head occur more frequently than the acetabular alumina insert. Reports of higher fracture rates since 1995 have involved design or technical issues: a ceramic sandwich design which interposed polyethylene between the alumina ceramic and metal shell; a femoral head fracture rate of 1.9% where the femoral stem was manufactured in-house without specific attention to the design of the femoral trunion; zirconia femoral head fractures as a result of a change in manufacturing technique that led to a defective batch of implants leading to a recall. The risk of alumina ceramic fracture has been significantly reduced by the development of Biolox forte. This material undergoes hot isostatic pressing resulting in marked reduction in grain size and impurities and a significantly higher burst strength. The implants undergo proof testing prior to distribution. Alumina ceramic bearings offer a significant advantage as a bearing surface producing low wear for the young and most active patients. The risk of fracture is extremely low when properly used and less than the risk of fracture of a metal femoral component and/or failure of a polyethylene insert. 9:25 a.m. Future Bearing MaterialsWilliam J. Maloney, M.D. The goal in the development of future bearing materials is to continue to reduce the particle load and thus the biological response to wear debris while at the same time improving on the mechanical properties of the bearing material to reduce fracture risks and to optimize interoperative flexibility. The current bearing surfaces have in part achieved those goals with good follow-up at 5-6 years. There remains room for improvement however. Fracture risk remains a concern with highly-crosslinked polyethylenes especially with elevated rim liners and thin polyethylene. Second generation highly-crosslinked materials have been developed to maintain the improved wear characteristics of the polyethylene and reduce the risk for in vivo oxidation while at the same time improving on the mechanical properties of the existing materials. Similarly, newer ceramic materials currently not approved by the FDA for use in the United States have been used outside this country to improve on the mechanical properties of ceramics. This should allow the use of larger head sizes in some cases. It still however will not give us the flexibility as it relates to interoperative sizing when compared with metal on polyethylene. New bearing combinations such as ceramic on metal are currently being investigated and we can anticipate their introduction into the North American market in the relatively near future. Continued research in bearing materials for total hip replacement has lead to a marked improvement in wear performance. Ongoing work is likely to make further improvements in the excellent existing bearing options. It’s important to remember however that our patients represent the final testing grounds for these new bearings. As a result, follow-up is imperative. 10:03 a.m. Update On Hip Resurfacing: The Ideal CandidateThomas Parker Vail, M.D. Hip resurfacing is an option for a selected group of primary hip arthroplasty candidates who could benefit from bone conservation and a large diameter hard-on-hard bearing. Recently introduced in the United States, the number devices implanted in Europe has more than doubled from 2004 to 2006, comprising approximately 10% of the total volume of hip implants. The device is distinct from a total hip replacement, which can also provide a large diameter metal bearing, in that it does not disrupt metaphyseal or diaphyseal bone, and both spares and loads the femoral neck bone. The indication is limited to end-stage destruction of the articular surface with symptoms resistant to non-surgical management. The ideal candidate is one for whom the benefits of bone conservation are maximal, and the negative consequences of a complication are minimal. Thus, the ideal candidate is generally younger, desires a high activity lifestyle, and possesses good proximal femoral bone quality. While reports indicate that resurfacing patients can achieve high functional levels, it is not known whether the activity level after resurfacing represents an intrinsic advantage or selection bias. The procedure lacks a long term track record. Hip resurfacing introduces the risks of exposure to metal ions and post-operative femoral neck fracture. Thus, patients with large bone cysts extending below the implant coverage area, osteoporosis, a broad femoral neck relative to the femoral head, distorted mechanics (coxa vara, coxa breva), compromised renal clearance, or metal hypersensitivity are not candidates. Retrieval analysis correlates complications with technical factors such as implant sizing, incomplete seating, cement technique, and bone quality. In conclusion, metal-on-metal resurfacing fits the needs of a selected group relative to total hip replacement, seems to have surpassed the outcome of prior resurfacing designs that failed early, but has not displaced total hip replacement as the procedure of choice for most hip arthroplasty patients. 10:11 a.m. Technical Tips: Avoiding ComplicationsThomas P. Schmalzried, M.D. Start with pre-operative planning. The femoral neck determines the smallest possible prosthetic size while the acetabulum determines the largest possible size. Proper patient positioning and exposure are fundamental to success. Even with a posterior approach, the majority of the quadratus femoris can be preserved. A complete capsulotomy may be necessary. Preparing the femur first can facilitate acetabular exposure. Osetophytes and other bone that overhangs or obscures the head-neck junction posteriorly or inferiorly can be judiciously removed. A valgus axis (135-140°) for femoral reaming is preferred as early failure has been associated with varus component position. The guide pin insertion point is commonly superior and anterior to the ligamentum teres and the fovea centralis. Assure that there is adequate clearance of the superior and anterior neck in order to avoid creating a stress-riser (notch) on the tension side of the bone. Acetabular preparation and component insertion is essentially identical to that of a total hip. The author prefers only a slight press-fit with complete seating of the component. Over-penetration of cement, incomplete seating of the femoral component, and insertional trauma have been associated with early femoral side failure. On this basis, the author favors manual application of viscous cement directly onto the bone, as is commonly done with total knee replacement. 10:19 a.m. Metal-on-Metal Hip Resurfacing Clinical Results: Past & PresentMichael Mont, M.D. Introduction: Metal-on-metal resurfacing was first introduced in the mid-1960’s. The early models of metal-on-metal designs were abandoned because of high rates of component loosening, biological incompatibility of the alloy constituents, and high complication rates. More recently, there has been an advent in the use of metal-on-metal resurfacing with the development of new technology. Wear particle generation, osteolysis, and subsequent aseptic implant loosening is reduced by the advances in both metal-on-metal bearing surfaces and cemented fixation of femoral components. To date, there are a limited number of prospective studies evaluating the results of current metal-on-metal designs. The authors will review the current literature, outline the history of metal-on-metal resurfacing, and report the results of an ongoing metal-on-metal FDA-IDE study. Methods: Between August 2000 and December 2006, 1892 metal-on-metal hip resurfacings (in 1629 patients) were performed by ten orthopaedic surgeons in an FDA-IDE study. The metal-on-metal prosthesis was implanted in 1176 men (1375 hips) and 453 women (517 hips). The most common indications for surgery were primary osteoarthritis in 1508 hips (79.8%), osteonecrosis in 177 hips (9.4%), hip dysplasia in 131 hips (6.9%), trauma in 53 hips (3.0%), and inflammatory arthritis in 20 (1%). The mean patient age was 51 years (range, 15-82 years). The mean body mass index was 27.5 (range, 16.3 to 48.2). All patients were evaluated using Harris Hip Scores and SF-12 Health surveys. Patients were radiographically assessed for alignment, loosening and radiolucencies. After an investigator meeting in October 2002, the prosthetic design was slightly altered (thin acetabular shells), the indications modified (excluded BMI >35, osteopenia), and the surgical technique changed (cementing, no notching allowed) to improve outcome. Results: At latest follow-up, the implant freedom from revision survival rate was 96.25% and 1468 hips out of 1640 hips (89.5%) were considered to have successful clinical outcome based on a Harris Hip Score greater than 80 points. The mean postoperative Harris Hip score was 92.5 points (range, 27 to 100 points). The mean latest follow-up SF-12 mental and physical component scores were 55.1 points (range, 17.3-68.5 points) and 49.8 points (range, 15.9 to 64.4 points), respectively. Radiolucencies were documented in 181 hips (9.6%), although none were progressive. Common postoperative complications included heterotopic ossification in 188 hips (9.9%), nerve problems in 39 hips (2.1%), hematoma in 36 hips (1.9%), trochanteric bursitis in 29 hips (1.5%), component loosening in 25 hips (1.32%), dislocations in 22 hips (1.1%), and femoral neck fractures in 21 hips (1.1%). Notable, only eight hips (0.4%) experienced protrusio acetabuli and only four hips (0.2%) showed osteolysis. Conclusion: The results of this prospective FDA-IDE study illustrate the durability and effectiveness of a modern metal-on-metal resurfacing design across patient populations and multiple surgeons. In addition, the results indicate that patients should be carefully selected in order to reduce the incidence of complications and further reflects that there is a significant learning curve associated with this procedure. The authors await long-term follow-up to see if these promising results will be maintained. 10:27 a.m. Metal-Metal Hip Resurfacing: A Skeptic's ViewPaul F. Lachiewicz, M.D. Contemporary metal-metal hip resurfacing is the third attempt by its proponents to eliminate a diaphyseal femoral component. The first two generations of devices had very high rates of revision due to cement failure or polyethylene wear—osteolysis. The current designs have not eliminated cement for femoral component fixation. The author's objections with resurfacing include: the premises for the use of resurfacing are not valid; patient selection issues; steep technical learning curve; femoral neck fractures – early failures – complications; and concerns with the metal-metal articulation. The premises for the use of resurfacing are not valid. There is a high rate of success of circumferential bead or mesh-coated uncemented stemmed femoral components at 10 to 20 years. There have been no adverse consequences of femoral stress shielding with a diaphyseal component in the first 20 years. One study reported that more acetabular bone may be removed with resurfacing, negating its "conservative" premise. One computer simulation suggested that the range of hip motion may be significantly less with resurfacing compared to conventional hip arthroplasty. There are a very limited number of patients for whom hip resurfacing is truly indicated—young males with osteoarthritis and a certain hip anatomy. The femoral head may be unsuitable for resurfacing in 40% of selected patients. Resurfacing is technically more difficult than conventional hip arthroplasty, with a learning curve of 50 to 100 cases for an experienced surgeon. Early complications and revision for femoral neck fractures are more likely with resurfacing. As the femoral neck bone mineral density and modulus decrease from age 30 to 70 in both men and women, the risk of fracture may increase. The early complications of infection, dislocation and heterotopic ossification are not less with resurfacing compared to modern conventional hip arthroplasty. Nerve palsy and joint noise may be more frequent with resurfacing. Blood and urine metal ion levels, capsular lymphocytic aggregation and hypersensitivity are certainly more of a concern with a metal-metal articulation. Metal-metal hip resurfacing should only be used now by a limited number of experienced hip surgeons. Direct marketing of this device to consumers remains problematic. Minimum 10 year follow-up data on contemporary models is needed. At present, the risks and complications of metal-metal hip resurfacing outweigh any possible advantages. The use of modern conventional total hip arthroplasty in young patients should be continued. 10:51 a.m. Dealing with the Difficult Primary THR: Developmental Dysplasia Robert B. Bourne, M.D. Patients with untreated high developmental hip dislocations frequently develop symptomatic secondary hip arthritis in the fourth and fifth decades of life. These patients present a myriad of challenges for total hip arthroplasty (THA) including acetabular and femoral hypoplasia, increased femoral neck anteversion, posterior positioning of the greater trochanter, the risk of neurovascular complications, osteoporosis and leg length issues. Restoration of a normal hip center, the use of a subtrochanteric shortening/derotation osteotomy and the use of cementless modular femoral implants has been a safe and predictable method to treat these patients in need of THA1,2. However, the complication rate is higher in these patients than in other patient groups treated with total hip arthroplasty. Technical tips include use of the posterior surgical approach, preparing the femur before performing the subtrochanteric osteotomy, use of cementless acetabular components with supplemental screw fixation, insuring optimal component positioning, using strut grafts to enhance subtrochanteric osteotomy fixation and use of advanced bearing couples. References: 1. Veal, GA, Rorabeck, CH and Bourne, RB. Subtrochanteric femoral resection in total hip arthroplasty for high riding CDH. J Ortho Tech, 1:33, 1993. 2. Masonis, JL, Patel, JV, Mui, A, Bourne, RB, McCalden, RW, MacDonald, SJ and Rorabeck, CH. Subtrochanteric shortening and derotational osteotomy in primary total hip arthroplasty for patients with severe hip dysplasia: 5-year follow-up. J Arthroplasty, 18:68, 2003. 10:59 a.m. Difficult Primary THA Diaphyseal Deformity: Bent But Not Broken Miguel E. Cabanela, M.D. Proximal femoral deformity can be classified by location (greater or lesser trochanter, metaphysic, diaphysis), by its geometry (angular, rotational, translational, abnormal bone size, or combinations), or by its etiology: 1) primary- usually the result of DDH or congenital coxa vara or, 2) secondary- the result of previous proximal femoral osteotomy (either inter or subtrochanteric) or of previous hip arthroplasty. Primary deformity resulting from DDH may require corrective rotational or shortening simultaneous osteotomy at the time of THA. Congenital coxa vara usually is not a very difficult problem to deal with, but tipically necessitates a trochanteric osteotomy for exposure, as the greater trochanter overlies the femoral canal. Secondary deformity resulting from previous inter or subtrochanteric osteotomy makes the subsequent THA procedure more complicated, increases the operative time and the incidence of intra and post-operative complications and results in a decreased longevity of cemented THA. We believe that this findings of our and other studies underscore the importance of strict adherence to the indications of osteotomy, the need to carefully execute the osteotomy without altering too much the morphology of the proximal femur and the advisability of routine hardware removal after the osteotomy has united. In addition, if the femoral deformity is significant, correction by reosteotomy at the time of THA may be necessary . In these instances, the use of an uncemented prosthesis is preferred. From a technical standpoint routine trochanteric osteotomy for exposure may be advisable in cases of previous varus femoral osteotomies when the trochanter is overlying the femoral canal. Also, the need for a two-stage procedure (the first to remove previous hardware) may be occassionally advisable in instances of old hardware covered by bone remodeling when an “episiotomy” of the femur may be necessary for hardware extraction; then, delaying THA reconstruction until the bone has healed is preferred. Secondary deformity resulting from previous failed THA can be caused by: A. Bone remodeling resulting in angular deformity after a cemented prosthesis loosens and migrates into varus, B. Malunion of an intra or postoperative fracture, or C. A deformity distal to the prosthesis that anteceded the prosthesis implantation. No ”cookbook” approach can be offered for this problem as each case has to be dealt with individually. Preoperative templating on good AP and lateral X-rays will help determine the need for osteotomy, the angle of the correction and whether this correction has to be done in two planes. Generally, corrective osteotomies are done at the apex of the deformity and periosteal stripping should be avoided. We prefer simple osteotomies, use cancellous bone graft liberally and at times need strut allografts for osteotomy reinforcement. It is essential to ensure both osteotomy and prosthetic stability; to ensure the latter, the use of a diaphyseally fixed uncemented prosthesis is favored today. Our reported experience with 31 cases showed a high incidence of complications and reoperations and a steep learning curve. In summary, proximal femoral deformity at the time of THA can be handled in three possible ways: o If very high, it may be ignored. o Sometimes, one can adapt the THA to the deformity. o If deformity is severe, it must be corrected. References: 1. Ferguson GM, Cabanela ME, Ilstrup DM: Total hip arthroplasty following failed femoral intertrochanteric osteotomy. J Bone Joint Surg 76B:252, 1994. 2. Glassman AH, Engh CA, Bobyn JD: Proximal femoral osteotomy as an adjunct in cementless revision total hip arthroplasty. J Arthroplasty 2:47, 1947. 3. Boos N, Krushell R, Ganz R, Müller ME: Total hip arthroplasty after previous proximal femoral osteotomy. J Bone Joint Surg 79B:247, 1997. 4. Holtgrewe JL, Hungerford DS: Primary and revision total hip replacement without cement and with associated femoral osteotomy. J Bone Joint Surg 71A:1487, 1989. 5. Papagelopoulos PJ, Trousdale RT, Lewallen DG: Primary and revision total hip arthroplasty with associated femoral osteotomy for proximal femoral deformity. Orthop Trans 18:993, 1994-95. 6. Becker DA, Gustilo RB: Double-chevron shortening derotational subtrochanteric osteotomy combined with total hip arthroplasty for the treatment of complete congenital dislocation of the hip in the adult. Preliminary report and description of a new surgical technique. J. Arthroplasty 10: 313-8,1995. 7. Chareancholvanich K, Becker,DA, Gustilo RB: treatment of congenital dislocated hip by arthroplasty with femoral shortening. CORR 360:127-35, 1999. 11:07 a.m. Dealing with Retained Hardware Steven J. MacDonald, M.D. Introduction: Occasionally the adult reconstructive surgeon will be faced with retained hardware, either acetabular or femoral, at the time of primary total hip arthroplasty. This paper will discuss the issues involved, including common reasons for hardware and potential complications, preoperative planning, and an approach to addressing this hardware, on both the acetabular and femoral sides. Etiology: It is critical to have a thorough understanding of the underlying reason for the presence of the retained hardware. The most common reasons for acetabular hardware, in patients subsequently undergoing total hip arthroplasty, will be from a previous acetabular fracture or previous pelvic osteotomy. In patients having had a previous acetabular fracture, the surgeon must be aware of the potential challenges of possible nonunion, segmental avascular necrosis and acetabular bone stock loss. If a patient has had a previous acetabular osteotomy, challenges can include nonunion, acetabular deformity and bone deficiency. The most common reasons for femoral hardware include previous femoral fracture and previous femoral osteotomy. In patients having had a previous femoral fracture, one can predict challenges with potential calcar bone loss, greater trochanteric nonunion and femoral deformity. Patients having had a previous femoral osteotomy may have abnormal femoral anatomy with metaphyseal-diaphyseal mismatch and challenges with obtaining a straight shot at the femoral canal. Pre-operative Planning: Any patient having had previous surgery must be carefully evaluated for the possible presence of active infection with screening blood work and possibly an aspiration if indicated. To adequately assess bone stock concerns, further imaging with Judet views and CT scan may also be indicated. A knowledge of the actual implants present, particularly plates and screws, may be necessary to have available appropriate removal instruments. A metal cutting high-speed burr is essential when dealing with acetabular hardware that cannot be accessed for removal. Lastly acetabular and femoral implants must be available to address the possible bone stock challenges and additionally bone graft in cases of significant bone loss. Acetabular Technique: Clearly a knowledge of exposure techniques employed in previous surgery is important in any given case, however, the surgical approach used for the primary total hip arthroplasty should not be dictated by the previous approaches or presence of retained hardware. Acetabular hardware is often unnecessary to remove. In the majority of cases acetabular reaming can begin prior to hardware removal and only metal that prevents proper reaming needs to be removed either by direct access or by burring with a metal cutting high-speed burr. As mentioned earlier it is critical to assess host bone stock for the presence of a nonunion, avascular segment or significant defect. Implant selection will be driven by these factors. Femoral Technique: In contradistinction to the acetabulum, the vast majority of femoral hardware will be removed at the time of the primary hip replacement. There is a risk of fracture at a previous hardware site, so ideally the hip should be dislocated first, and then the hardware removed, therefore minimizing stress through previous screw hole sites. Additionally the femoral component selected should bypass the distal screw hole by two cortical diameters to minimize a stress riser. Significant femoral deformities and bone loss may be present requiring specific implant selection or rarely repeat osteotomy. References: 1. Mears, DC, Velyvis JH. Primary total hip arthroplasty after acetabular fracture. AAOS Instructional Course Lectures. 2001;50:335-354. 2. Weber M, Berry DJ, Harmsen WS. Total hip arthroplasty after operative treatment of an acetabular fracture. J Bone Joint Surg Am. 1998;80:1295-1305. 3. Haidukewych GJ, Berry DJ. Hip arthroplasty for salvage of failed treatment of intertrochanteric hip fractures. J Bone Joint Surg Am. 2003;85:899-904. 4. Minoda Y, Kadowaki T, Kim M. Total hip arthroplasty of dysplastic hip after Chiari pelvic osteotomy. Arch Orthop Trauma Surg. 2006;126:394-400. 11:15 a.m. Hip Fusion Take Down, Better Late Than NeverAaron Rosenberg, M.D. Conversion of a hip fusion to THA requires consideration of the quality and quantity of femoral and acetabular bone, the presence of hardware and any inherent difficulty in its removal, and the quality of the abductor mass. Surgical takedown requires the ability to access the entire fusion mass in a circumferential fashion. This is most easily done with removal of the trochanteric segment either through a standard traditional trochanteric osteotomy, a trochanteric slide or extended trochanteric osteotomy. Once the trochanter is displaced anteriorly, circumferential subperiosteal dissection between the intertrochanteric region of the femur and the pelvis allows for transection of the fusion mass freeing the limb from the pelvis. Continued soft tissue dissection about the root of the pelvic portion of the fusion mass allows for differentiation of the anterior and posterior columns of the acetabulum. The pulvinar and the inferior aspect of the pelvic portion of the fusion mass frequently provide an accurate guide to the true acetabulum, but a steinman pin placed in the remaining pelvic portion of the fusion mass and an intra-operative radiograph can be used to confirm position. Accurate patient positioning helps insure accurate component positioning when standard landmarks are distorted Femoral canal abnormalities may dictate alterations in femoral preparation but in most cases is straightforward. Soft tissue tension is achieved by positioning of the trochanteric segment and rarely the abductor mass is insufficient. In these cases transfer of the remaining tensor fascia or gluteus maximus into the ilio-tibial band will provide a soft tissue buttress laterally, but occasionally a constrained cup may be needed. 11:38 a.m. The 3-D Anatomy of the Dysplastic Hip. Consequences for THAJean-Noel Argenson, M.D., Xavier Flecher, M.D., Sebastien Parratte, M.D. and Jean-Manuel Aubaniac, M.D. Total hip arthroplasty for osteoarthritis following developmental dysplasia of the hip (DDH) is challenging due to the modified anatomy of the proximal femur and the acetabulum. We studied the three-dimensional morphologic parameters of 247 hips from 218 adult patients with osteoarthritis following dysplasia or congenital dislocation, using X-rays and CT. A cohort of 310 primary osteoarthritic hips studied with the same protocol was used as a control group. According to the classification of Crowe et al 32 of the 78 dislocated hips were graded as class I, 26 as class II and 20 as class III or IV. The 169 hips graded as dysplasia had no subluxation. The anteroposterior diameter of the acetabulum was smaller in patients with DDH, especially for completely dislocated hips. The intramedullary femoral canal had reduced mediolateral and anteroposterior dimensions for all groups compared to primary osteoarthritis. The individual variability was important when measuring the CT-scan canal flare index, despite the subluxation class considered. The extramedullary parameters showed a decrease in femoral neck shaft angle for high subluxation and an increase for low grades especially in class II . The proximal femur had more anteversion than in the control group with individual vaiations ranging from 1° to 52° for dysplasia and from 2° to 80° for congenital dislocation. The importance of the dislocation may reflect the difficulty to achieve hip center location in the true acetabulum, but the large individual morphologic variability showed that the femoral prosthesis cannot be chosen on the single basis of the severity of the subluxation. Preoperative CT evaluation may have a role for THA in the DDH patient, allowing measurement of the true acetabulum anteroposterior diameter and assessment of the individual femoral anteversion for femoral prosthesis selection. 12:40 p.m. Anterior Approach THAJoel M. Matta, M.D. The anterior approach follows the Smith-Petersen interval distal to the ilium. The goals of anterior THA are: maximal soft tissue preservation and enhanced accuracy of acetabular position as well as leg length and femoral offset. The technique originated with Robert Judet in Paris who in 1947 first implanted his acrylic femoral head replacement through the anterior approach utilizing the Judet Orthopedic Table. Judet originally chose this approach for several reasons: the patient is supine, the hip is most superficial from anterior, the approach is internervous, the approach does not disturb muscle attachments or require muscle splitting. This approach gives excellent acetabular access while the femoral access can present special problems. Femoral access however is best facilitated with specially designed orthopedic tables that position the extremity in extension, adduction and external rotation during femoral preparation and prosthesis insertion. An additional feature of two orthopedic tables (OSI PROfx and OSI HANA, Union City, California) is a hook-jack device that directly lifts and supports the proximal femur to further facilitate access. Besides Judet’s original reasons for choosing this approch, other advantages include: small incision, preservation of hip deltoid, improved control of component position and leg length, no post op dislocation precautions, applicable to all patients regardless of BMI, facilitates bilateral replacement. It is the author’s preference to enhance accuracy and reproducibility with “fluoroscopic image guidance” during the procedure for checks of acetabular position, leg length and offset. With the orthopedic table however, the femoral and acetabular visualization is excellent and therefore not all surgeons using this technique utilize intra operative x-ray. Computer guidance is another option. Documentation of the initial North American experience is being performed by the Anterior THA Collaborative and includes data regarding 1277 THA in 1152 patients (125 bilateral) from 9 clinical sites. All acetabular components were uncemented with 94% of femoral components uncemented and 6% cemented. Complications included: Greater trochanter fx 1%, calcar split 0.5%, shaft fx 0.6%, infection 0.6%, and dislocation 0.6%. Median time to discarding assistive devices was 14 days. References: 1. Matta, J.M. et al: Single-Incision Anterior Approach for THA on an Orthopaedic Table. CORR, no. 441, p 115-124, December 2005. 2. Yerasimides, J.G. et al: Primary THA with a Minimally Invasive Anterior Approach. Seminars in Arthroplasty, vol. 16, no. 3, p. 186-190, Sept 2005 3. Siguier, T. et al: Mini-Incision Anterior Approach Does Not Increase Dislocation Rate. A Study of 1037 THA. CORR, no. 426, p 164-171, 2004. www.hipandpelvis.com, www.athac.org 12:46 p.m. Mini-Invasive Total Hip Arthroplasty: Anterolateral ApproachWilliam Hozack, M.D. There is some controversy as to the real meaning of minimally invasive total hip surgery. For me it means that the surgical procedure lessens the impact of surgery on the patient’s daily routine. This means a good operation with no complications and a relative rapid recovery period. It does not mean just a small incision. Minimally invasive refers to what is going on beneath the skin surface. My minimally invasive approach involves an anterolateral approach through a smaller incision with direct visualization of all structures using modified techniques. I still adhere to the classic surgical principles of good visualization, gentle and atraumatic technique, avoiding nerves and arteries, getting good hemostasis, putting parts in proper position and orientation and doing the surgery relatively quickly. The following technical tips may be helpful: 1. Don’t over-commit on the initial skin incision. Make it initially in the center of where you think it will ultimately lie and once you are down to the fascia, extend it as needed for proper exposure. 2. Mobilize the fat and skin on the fascia to create a mobile window of exposure. 3. Concentrate on making the fascial incision in the proper place, staying anterior and not splitting the muscle fibers of the gluteus maximus. 4. I visualize splitting the gluteus medius in the middle third as a means of minimizing trauma to that muscle. Too far anterior in the split prevents adequate exposure of the femur with resultant trauma to the muscle. Controlled release of a muscle insertion allows for a more gentle overall exposure and operation with less indirect muscle trauma. This actually may be less invasive than the approaches which do not incise muscle insertions, but yet manage to traumatize muscles quite extensively. 5. Use special equipment that is available to make the operation easier and less traumatic. These include special acetabular retractors, lighted retractors, curved reamers, curved cup insertors, special femoral retractors, and modified broach handles. 6. Femoral component preparation and insertion is easier if there are fewer steps. Choose your component with this in mind. Absolute hip stability is generally conferred by the anterolateral approach. This allows us to eliminate all hip precautions, which greatly facilitates physical therapy and recovery speed. In addition, proper anesthesia and pain management techniques are critical for the MIS approach regardless of surgical technique. I would like to emphasize that this approach is designed for faster rehabilitation, with earlier discharge from the hospital only as a secondary potential benefit. The specific advantage of the anterolateral approach is that the patient does not require any hip precautions. The approach is extensile if needed. 12:52 p.m. Minimally Invasive THA: Two Incision Approach in 2007Mark W. Pagnano, M.D. Proponents of 2-incision total hip arthroplasty (THA) have claimed that the recovery after that procedure is dramatically quicker than after other methods of performing THA. To date however there is no data that directly compares 2-incision THA to another method of THA in similar groups of patients using the same advanced anesthetic and rehabilitation protocol. We performed a prospective randomized trial of 2-incision THA versus mini-posterior THA and sought to: (1) determine if patients recovered faster after 2-incision THA than after mini-posterior THA as measured by the attainment of functional milestones that reflect activities of daily living; (2) determine if the clinical outcome after 2-incision THA was better than that after mini-posterior THA as measured by SF-12 scores; and (3) evaluate the technical difficulty of the 2-incision THA compared to the mini-posterior THA as judged by the operative time and the prevalence of early complications. A computerized randomization process dynamically balanced the groups based on age, gender, race, and body mass index (BMI). Seventy-two patients with a mean age of 66 and mean BMI of 29.5 were enrolled and this included 20 males and 16 females in each group. The 2-incision patients recovered more slowly than the mini posterior patients as measured by the mean time to discontinue a walker or crutches, to discontinue all ambulatory aids, and to return to normal daily activities. The clinical outcome as measured by the SF-12 score was similar in both groups at both 2 months and 1 year postoperatively. The 2-incision THA was technically more difficult with a mean operative time that was 24 minutes longer than the mini-posterior THA. The prevalence of complications was the same between the 2 groups (2.7 percent). This prospective randomized trial dispels the notion that the two-incision THA technique dramatically improves short-term recovery after THA; instead it was the mini-posterior patients who had the quicker recovery. Bibliography: 1. Berger RA: Mini-incisions: Two for the price of one! Orthopedics 25:472, 498, 2002. 2. Berry DJ, Berger RA, Callaghan JJ, Dorr LD, Duwelius PJ, Hartzband MA, Lieberman JR, Mears DC: Minimally invasive total hip arthroplasty. J Bone Joint Surg 85A:2235-2246, 2003 3. Cameron HU: Mini-incisions: Visualization is key. Orthopedics 25:473, 2002. 4. DiGioia III AM, Plakseychuk AY, Levision YJ, Jaramaz B: Mini-incision technique for total hip arthroplasty with navigation. J Arthroplasty 18:123-128, 2003. 5. Huo MH, Brown BS: What’s new in hip arthroplasty? J Bone Joint Surg 85A:1852-1864, 2003. 6. Mardones R, Pagnano MW, Nemanich JP, Trousdale RT: Muscle damage after total hip arthroplasty done with the two-incision and mini-posterior techniques. Clin Orthop 441:63-67, 2005. 7. McConnell T, Tornetta III P, Benson E, Manuel J: Gluteus medius tendon injury during reaming for gamma nail insertion. Clin Orthop 407:199-202, 2003. 8. Pagnano MW, Leone J, Lewallen DG, Hanssen AD: Two-incision THA had modest outcomes and some substantial complications. Clin Orthop 441:86-90, 2005. 9. Pagnano MW, Trousdale RT, Meneghini RM, Hanssen AD: Patients preferred a mini-posterior THA to a contralateral two-incision THA. Clin Orthop 2006 December. 12:58 p.m. Posterior MIS THRThomas P. Sculco, M.D. The phrase “minimally invasive surgery” when performing a hip arthroplasty has always seemed like an misnomer in that hip replacement surgery requires considerable alteration of anatomy regardless of the exposure or technique. The term “less invasive” describes more accurately what these procedures encompass. These techniques now are being utilized in many different approaches to the hip and knee and embody less deep dissection as well as a more conservative skin incision. Performing hip and knee arthroplasty through less traumatic exposures is feasible but the surgeon must use good judgment and be expert in his ability to perform these arthroplasties expeditiously and without compromising the quality of the arthroplasty. The surgeon interested in performing these arthroplasties through more limited exposures must be experienced in arthroplasty surgery. The concept of performing a total hip replacement utilizing a smaller incision and a more limited soft tissue exposure surfaced during a hip replacement about eight years ago. The procedure was being carried out through the conventional posterolateral approach and the incision length was approximately 8-9 inches in length. The PGY 4 resident assisting me at the procedure queried why the incision was as long as it was and he remarked that the lower portion of the incision was not being used. Indeed this was the case and on the subsequent hip arthroplasty the incision was reduced by one inch without undue struggle. This led to a progressive decrease in incision length and soft tissue release during hip replacement surgery. Subsequently instrumentation has been developed to facilitate exposure and acetabular and femoral preparation and the length of the skin incision has been reduced to 3-4 inches in length. Proper patient selection, surgical experience and instrumentation and careful dissection have led to satisfactory results in over 2500 patients to date. The key surgical concept is that the result of the arthroplasty should not be compromised by the surgical incision and exposure. If excessive or undue tension is being applied to the soft tissues about the hip femoral or sciatic neuropraxia may occur and this complication must be avoided. When attempting to reduce the length of the surgical incision it is recommended that the surgeon gradually limit the incision length in increments of ½ - 1 inch until a level is reached where hip arthroplasty progresses without difficulty and with adequate exposure to correctly and safely perform the procedure. These techniques require customized instrumentation to facilitate these exposures as well as significant arthroplasty training. Hypotensive regional anesthesia reduces bleeding and facilitates the procedure. Less invasive total hip replacement requires proper patient selection to lessen rate of complication and promote a successful arthroplasty. Certainly as body weight and obesity increase more extensive exposures will be necessary. As a rule less invasive surgery is not recommended in patients with BMI >35. Additionally patients with complex primary hip pathology are best performed through more extensive approaches. These include patients with high riding hip dislocation (Crowe 4), severe hip ankylosis with or without protrusion and patients with severe soft tissue scarring secondary to extensive prior hip surgery. An additional group that may pose a problem with visualization and soft tissue retraction is the heavy, well muscled, short stature usually male patient. In these patients, especially if the hip joint is stiff, exposure is difficult and exposures should be extended. Patients undergoing revision hip surgery also are not ideal candidates for these less invasive approaches as failed implant removal, bone grafting and augmentation usually require additional visualization. More extensile exposures must be used whenever needed to improve the outcome of the procedure. However, the advantages of these more limited procedures are real and include more rapid rehabilitation, less blood loss, better cosmesis and in our series there has not been an increase in complications or implant malposition. 1:04 p.m. Standard Trochanteric Osteotomy & AdvancementDouglas A Dennis, M.D. Current indications for trochanteric osteotomy include improving exposure to the femoral intramedullary canal through correction of proximal femoral angular deformities, such as medial greater trochanteric overhang, improving general exposure to the acetabulum and femoral canal in cases of complex primary and revision hip total hip arthroplasty (THA), and facilitating exposure to the anterosuperior acetabular rim and femoral neck in operative management of femoral-acetabular impingement. An additional indication for classic trochanteric osteotomy is in the patient with recurrent dislocation following THA with well-aligned components and no evidence of mechanical impingement. In many of these patients, the soft-tissue envelope (myotendinous units, hip capsule,etc) surrounding and supporting the hip is not adequately tensioned to maintain hip stability. Classic trochanteric osteotomy and distal advancement of the greater trochanter have been used in these cases to tighten the surrounding capsuloligamentous structures and abductor mechanism, increasing the moment arm and the force generating capacity of the abductor musculature, to improve hip stability. Although the classic technique of greater trochanteric osteotomy provides multiple advantages such as excellent surgical exposure, correction of proximal femoral deformity, and enhanced soft-tissue tension of the hip, it has been associated with numerous complications including trochanteric fracture, soft-tissue irritation secondary to fixation hardware, and nonunion rates as high as 39%. Nonunion, when associated with superior trochanteric migration, has also been shown to increase the incidence of hip instability and loss of abductor power. Prolonged rigid fixation following standard trochanteric osteotomy is therefore critical to facilitate union and limit complications. This presentation demonstrates a technique of trochanteric osteotomy, advancement, and fixation, which has proved reliable with high union rates. Bibliography: 1. Kaplan SJ, Thomas WH, Poss R. Trochanteric advancement for recurrent dislocation after total hip arthroplasty. J Arthroplasty, 2:119-124, 1987. 2. Koyama K, Higuchi F, Kubo M, Okawa T, Inoue A. Reattachment of the greater trochanter using the Dall-Miles cable grip system in revision hip arthroplasty. J Orthop Sci. 6:22-27, 2001. 3. Ritter MA, Eizember LE, Keating EM, Faris PM. Trochanteric fixation by cable grip in hip replacement. J Bone Joint Surg Br. 73B:580-581, 1991. 4. Glassman AH. Complications of trochanteric osteotomy. Orthop Clin North Am. 23:321-333, 1992. 5. Nutton RW, Checketts RG. The effects of trochanteric osteotomy on abductor power. J Bone Joint Surg Br. 66B:180-183, 1984. 1:10 p.m. Extended Trochanteric OsteotomyWayne G. Paprosky, M.D., F.A.C.S. Despite the overwhelming success and long term reliability of total hip arthroplasty, several situations necessitate the revision of the femoral component. The use of an extended trochanteric osteotomy is a method which allows exposure of the proximal femur through the use of a controlled cortical fracture. The extended proximal femoral osteotomy has been used primarily in conjunction with cementless fixation, but has been described for use with cemented stems as well. The extended proximal femoral osteotomy is indicated for the removal of well-fixed cemented and cementless implants, as well as removal of cement in patients with a loose femoral component in a well-fixed cement mantle. Although the osteotomy is not required for many femoral revisions, it is an absolute indication in patients with femoral component loosening and subsequent varus remodeling of the proximal femur. The osteotomy diminishes the risk of an inadvertent fracture of the often compromised greater trochanter especially upon removal of a failed femoral component from its subsided or migrated position. The osteotomy enhances the exposure of the acetabulum, which may be difficult in the revision setting due to multiple surgeries, severe migration of the acetabular component or heterotopic ossification. The extended proximal femoral osteotomy can also be used in the primary setting when a proximal femoral deformity interferes with straight reaming of the femoral canal, such as in patients with various dysplasias, previous corrective osteotomies or malunions. Familiarity with this surgical technique is crucial for surgeons who frequently perform revision arthroplasty or primary total hip arthroplasty in patients with proximal femoral deformity. 1:16 p.m. Cementing A Liner Into A Well-Fixed ShellWilliam Jiranek, M.D. Introduction: Revision situations exist where the acetabular liner must be changed but the socket is well fixed. Removal of a well-fixed porous coated shell is often difficult and carries the risk of substantial bone loss. Consequently, many surgeons have advocated cementing a polyethylene liner into the existing shell. With appropriate liner selection and preparation, and with proper cement technique, it is possible to create a construct with reasonable lever out resistance. Methods: Preoperative preparation is critical for success. First and foremost, the stability of the existing shell should be assessed radiographically. The presence of significant osteolytic lesions or the absence of ingrowth remodeling may preclude retention of the shell. The surgeon should know the diameter of the existing metal shell, the thickness of the shell (so that the inner diameter of the shell may be calculated) the surface treatment of the articular side of the shell, and the geometric configuration of the shell (ie. how much of a hemisphere). Two mechanical studies have demonstrated the importance of accurately sizing the liner to be cemented, with oversized liners failing at much lower levels. In the operating room the surgeon should test the stability of the cup. If stable, the next step is to verify the sizing of the liner, which should be done with trials similar to the final liner. The literature is unclear regarding whether the shell, or the liner, needs to be roughened to improve the interference, but all mechanical studies have shown failure occurs at the cement-liner interface, and not at the cement-metal interface. Bonner et al. demonstrated that if the liner is sized appropriately, adding grooves in the liner does little to improve the lever out strength, and Haft et al. noted that texturing the shell is unnecessary unless the shell is polished and without holes. There is little data to suggest whether the use of a cementable shell or a liner manufactured for use in cementless cups is preferential. Cement is mixed after liner selection and is inserted into the cup in dough phase. The cement may be pressurized with a round ball such as a bipolar trial that is 4 mm smaller than the selected liner. The use of face changing and lateralizing liners can compensate for socket malposition or soft tissue laxity, but the surgeon should be alert for positions which can cause neck – rim impingement during a normal arc of motion. Results: Beule et al reported a 5 year survival of 78% in unconstrained liners cemented into well fixed shells. Haft et al. reported a 94% survival of 17 cemented liners at 2.5 years. Laporte et al. noted that 7 of 8 unconstrained liners were still in service at up to 7 years. Callaghan et al reported a 94% survival at 4 years of constrained liners cemented into well fixed shells. Shapiro et al. reported that 14 of 16 constrained liners were still in service at 4.6 years. Ranawat et al. reported a 94% survival of 10 cemented constrained liners at 2 yrs. f/u. Conclusion: Biomechanical and short term clinical data support the practice of cementing both constrained and unconstrained liners into well fixed shells, and have provided guidelines for the surgical technique. References: 1. Callaghan, JJ et al, JBJS, V 86-A: 2206-11, 2004 2. Beaule, P et al., JBJS, V86-A: 929-34, 2004 3. Bonner, K.F. et al. JBJS, V. 84A: 1587-1593, 2002. 4. Meldrum, R.D. and Hollis, J.M., J. Arthroplasty, V16: 748-752, 2001 5. Haft, G.F. et al. J. Arthroplasty, V. 17: 167-170, 2002 6. Kummer FJ, Adams MC, Dicesare PE, J. Arthroplasty, V.17:1055-7, 2002 7. Mountney J et al., Instr. Course Lect., V:53:131-40, 2004. 8. LaPorte DM et al, J Arthroplasty, V. 13: 348-53, 1998. 1:37 p.m. The John Charnley Award: Factors Leading To Low Prevalence Of Deep Vein ThrombosisAnd Pulmonary Embolism After Total Hip Arthroplasty Young-Hoo Kim, M.D. and Jun-Shik Kim, M.D. The aim of this prospective study was to identify prothrombotic factors leading to low prevalence of deep vein thrombosis (DVT) and pulmonary embolism (PE) after total hip arthroplasty (THA) in patients who had not received any thromboprophylaxis. One hundred and four patients who had a primary cementless THA were included. Coagulation assays, a full blood count and serum chemical profile tests were performed. Molecular genetic testing was performed for factor-V Leiden mutation, prothrombin promoter G20210A mutation and methylenetetrahydrofolate reductase C677T. Bilateral simultaneous or unilateral venograms were performed on the 6th or 7th postoperative day and perfusion lung scans preoperatively and on the 7th or 8th postoperative day. Further venograms were performed at 6 months after operation in all patients who had thrombi. In the patients with bilateral THA, 16 (25%) of 64 venograms were positive for thrombi; while in the patients with unilateral THA 12 (17%) of 72 venograms were positive (P=0.158). Factor V Leiden mutation and the prosthrombin promoter G20210A mutation were absent in all patients. Antithrombin-III level was normal in all patients. Further venograms in all 28 patients who had thrombi at 6 months after operation showed that they resolved completely and spontaneously regardless of their site and size. No patient had symptoms of pulmonary emboli and the perfusion lung scans were negative in all patients. No patient died from thromboembolic complications. Combinations of absent thrombophilic polymorphisms with low prothrombotic risk factors led to low prevalence of DVT and virtually absent PE after THA in the current series of patients who had not received any thromboprophylaxis. 1:48 p.m. The Frank Stinchfield Award: The Biomechanical Contribution Of The Labrum To The Stability Of The Hip Matthew J. Crawford, M.D., Christopher J. Dy, Jerry W. Alexander, B.S., Matthew T. Thompson, M.S., Stephen J. Schroder, Charles E. Vega, Rikin V. Patel, Andrew R. Miller, Joseph C. McCarthy, Walter R. Lowe, M.D. and Philip C. Noble, Ph.D. Introduction: Lesions of the labrum present as a clinical cause of hip pain in the athletic population and are also commonly observed in anatomic studies of acetabular pathology. This study was performed to investigate the biomechanical factors leading to the formation of labral tears and the effect of these lesions on the kinematics of the hip at the extremes of joint motion. Methods: Biplanar radiography was utilized with six cadaveric specimens to measure strains developed in the labrum during a variety of loading maneuvers known to impose anterior loads on the joint margin. Similar maneuvers were simulated in a controlled testing apparatus in which a 3D motion analysis system separately tracked the femur and pelvis, and thus the movement and stability of the hip in an intact specimen and then following “venting" of the capsule, and the creation of a 15mm labral tear. Results: Maximum principal strains in the labrum varied from 8.0% ± 6.6% during abduction at 10° of extension and 20° of ER to 10.6% ± 6.4% during the abduction maneuver from neutral. External rotation at 30° of flexion resulted in a maximum principal labral strain of 10.2% ± 6.4%. On average, 43% and 60% less force relative to the intact hip was required to distract the femur 3mm in the vented and torn specimens, respectively. In an external rotation maneuver at 30° of flexion, the vented and torn specimens rotated 1.5° ± 2.7° and 7.1° ± 4.7° past the intact specimen's external rotation of 28.8° ± 9.7° under the same matched ER torque of 177 in-lbf. Conclusions: A breach of the integrity of labral function is shown to permit increased displacement of the femur relative to the acetabulum during extreme ranges of motion. It is in these positions that compromise of labral function may have its most dire consequences, leading to increased strain at the anterior articular rim of the acetabulum. In addition, the reduced stiffness of the injured labral segment makes the joint susceptible to increased impact loading and repetitive trauma through loss of the protective function provided by the intact labrum and its seal. In view of these findings, and the potential outcome of irreversible joint degeneration, advances in the early detection, treatment, and monitoring of labral pathology appears to be critical if the joint is to be preserved and normal hip function restored. 1:59 p.m. The Otto Aufranc Award: Ceramic-on-Metal Hip Replacements: A Comparative In Vitro and In Vivo Study Sophie Williams, Ph.D., Anton Schepers, MBBCh, Graham Isaac, Ph.D., Cath Hardaker, M.Sc., Eileen Ingham, Ph.D., Dick van der Jagt, MBBCh, Anke Brakon, M.Sc., and John Fisher, D.Eng. The performance of novel ceramic-on-metal bearing couples have been compared to metal-on-metal and ceramic-on-ceramic bearing couples in laboratory and short-term clinical studies. Laboratory studies compared ceramic-on-metal to metal-on-metal and ceramic-on-ceramic bearings with diameters of 28 and 36mm under standard conditions and under adverse conditions with head loading on rim of the cup. Clinical studies compared metal ion levels in ceramic-on-metal to metal-on-metal, ceramic-on-ceramic and ceramic-on-polyethylene bearings in a randomized prospective study. In the laboratory studies friction, wear and ion levels were significantly lower in ceramic-on-metal bearings compared to metal-on-metal, with similar results to ceramic-on-ceramic couples. Under adverse conditions and rim loading all bearings showed increased wear, with lower wear and absence of stripe wear in ceramic-on-metal compared to metal-on-metal bearings. Short-term studies in 31 patients at six months revealed lower metal ion levels in those with ceramic-on-metal compared to metal-on-metal bearings. 2:10 p.m. Summary Of Research Society Proceedings Richard Coutts, M.D. A synopsis of selected papers presented at this year's Orthopaedic Research Society related to the hip will be summarized. 2:21 p.m. Surgical Navigation for Hip ArthroplastyStephen B. Murphy, M.D. and Timo M. Ecker, M.D. Acetabular component malposition and postoperative leg length discrepancy are the two most common technical problems associated with hip arthroplasty. Acetabular component malposition can lead to early revision due to impingement, wear-induced osteolysis, or instability. Post-operative leg length discrepancy is often immediately apparent to the patient and is a leading cause of dissatisfaction. The application of surgical navigation during hip arthroplasty offers the potential to greatly reduce the incidence of these two common problems. Surgical maneuvers can be tracked using either optical or electromagnetic methods. Coordinate systems for the pelvis and/or femur can be established by directly digitizing landmarks (image-free), using intra-operative fluoroscopic images, or using pre-operative CT imaging and intra-operative registration. Our current experience includes 359 hip arthroplasties performed using CT-based navigation and 93 hip arthroplasties performed using intraoperative fluoroscopy. 112 of these hip arthroplasties have been performed with a simplified method of measuring leg length change. All procedures were tracked using optical methods. Skeletal reference frames were affixed to the bone using two-pin percutaneous fixation in all cases. 336 of the procedures were performed using a superior capsulotomy technique with an average incision length of 7.8 ± 1.5 cm (range, 5-18). Simply using cup abduction on the post-operative AP pelvis as a measure, 97.1 % of the hips are within the range of 35 and 50 degrees. Comparison of leg length change measured during surgery to leg length change measured on pre- and post-operative magnification corrected radiographs demonstrates a non-significant mean difference of - 0.5 mm with a standard deviation of 1.8 mm. There have been no instances of neurovascular injuries, broken hardware, debridement or IV antibiotic treatment for infection of the prosthesis, or in association with the use of the pin fixation. Less than 0.5% of patients were treated with oral antibiotics for treatment of pin sites. The incidence of intra- or post-operative fracture was less than 0.5 percent. Both acetabular component positioning and measurement of leg length change can be reliably controlled using surgical navigation techniques, even as incisions become smaller. Percutaneous fixation of reference frames is a safe method. The application of computer-assistance can greatly reduce or eliminate the two most common technical problems associated with hip arthroplasty. 2:29 p.m. Surgical Navigation: What’s Available? Philip C. Noble, Nobuhiko Sugano, Molly M. Usrey, and Stephen S. MurphyThroughout the world, surgical navigation systems are manufactured by at least 10 different companies for use in hip replacement surgery. In the United States, the principal surgical navigation systems available for use in THR today are manufactured by Medtronic, Brain-Lab, Stryker, Aesculap, and OrthoSoft. Each system consists of an infra-red camera which locates the position and orientation of arrays of markers mounted on the pelvis and the femur, and a computer which processes and displays the relative position and orientation of the bones and any implanted components. Some systems also create a computer model of the pelvis and femur from preoperative CT scans which is registered to the patient’s bony anatomy intraoperatively. In hip surgery, the applications of surgical navigation range from confirmation of cup position in primary THR to complex reconstructions in revision THR or dysplasia. Cup positioning in primary THR only necessitates attachment of a marker array to the pelvis and acquisition of acetabular and pelvic landmarks. Previous authors have demonstrated that placement of the cup is far more accurate and reliable under navigated guidance with a virtual guarantee of implant placement within the “Safe Zone”. Most companies support cup positioning independent of the specific brand or design of implant, and provide intraoperative information defining cup position and orientation on a real-time basis. Surgical navigation can also be utilized to measure the position and orientation of the femoral component. Most systems are equipped to display the change in leg length during hip replacement and the position of the prosthetic head center. However, this does require attachment of a second marker array to the femur which increases the length of the procedure. Moreover, several companies (BrainLab, Stryker) will only provide data describing the position of the femur to surgeons using specific implant systems. Confirmation of leg length restoration is one of the significant benefits of computer navigation, particularly in minimally invasive THR where access to anatomic landmarks is limited, resulting in larger inequalities using traditional methods for checking leg length. In addition, several manufacturers (Stryker, BrainLab, Aesculap ) provide advanced software routines which allow the surgeon to perform an assessment of the range-of-motion of the hip intra-operatively, and the location of sites of impingement. Although each navigation system is relatively similar, there are significant differences between products in terms of versatility and ease of use. With development of this technology, the computer hardware has become more compact and mobile, with each system being mounted on a mobile cart. Several systems (Aesculap and Medtronic) can also be controlled with a foot pedal, and most systems (Medtronic, BrainLab, Aesculap and Stryker) have touch-screens which eliminates the need for a mouse or keyboard. Additionally, Stryker’s navigation system can be controlled with a wireless registration stylus that has on-tool control, and Medtronic’s StealthStation has a laser incorporated for use with the registration process. Most systems display a generic model of a pelvis, yet Praxim (not yet available in US) and BrainLab generate a best-fit prediction of the surface topography of the pelvis based on digitized landmarks and a reference atlas of human anatomy. For specialized cases involving complex joint reconstruction, specialized software is under development and is routinely used in some centers. However, this generally requires CT data for accurate representation of bony anatomy and is supported by only a few manufacturers. Nonetheless, advanced software routines have been developed for hip resurfacing, assessment of femoro-acetabular impingement, resection and reshaping of the femur and acetabulum to increase range-of-motion, and surgeon training and evaluation. The cost of these systems typically ranges from $150-400K, with disposable costs of $100 to $300 per procedure. Use of these systems increases operative time by 8-20 minutes per case. In 2004, it was estimated that the additional cost of navigated cases ranged from $384 (utilization: 250 cases/year) to $1920 (50 cases/year). However, actual costs will vary depending upon capital expenditure for acquiring a navigation system, the cost of disposables, and the amount of time added to each procedure. Though the potential benefits of these systems are undeniable, especially for complex cases, the equipment required necessitates extensive capital expense and maintenance. These systems undoubtedly lead to increased dependence of the surgical team on high-tech equipment. This forces hospitals to acquire specialized support staff and/or to become more dependent on equipment vendors who may supply expertise in operating navigation systems in exchange for use of their implants. The present reality is that the increased procedure costs associated with computer–assisted surgery is incurred without additional reimbursement. Recommendations: · In the hip, surgical navigation is useful for guiding inexperienced surgeons and for training fellows and residents. · At present, computer guidance offers clear advantages for difficult or problematic cases. It enables surgeons to plan and perform new and more demanding procedures with less trauma and better outcomes. · However, in view of the cost, time, and training required, the use of navigation systems in routine THR does not appear feasible at the present time. · In the near future, navigation software will be available for more demanding procedures, including resurfacing arthroplasty and recontouring of the femoral neck in cases of femoro-acetabular impingement. In these applications, it is expected that surgical navigation will offer clear advantages which may justify more widespread adoption of this technology. 2:37 p.m. Clinical ResultsWilliam Bargar, M.D. A literature search in December, 2006 (Entrez-PubMed) with search terms “Navigation” AND “Hip” limited to the English language and humans revealed 44 citations. When the additional restriction of clinical trials was used, only 6 citations were found. Most published results concern acetabular cup orientation in total hip replacement, but a few concern fracture or osteotomy applications. None of the studies report results for femoral component placement, leg length or offset, although most systems offer this measurement capability. All papers comparing manual acetabular cup placement to navigated placement show more accuracy and less outliers for the navigated cases. A fundamental problem is the lack of an agreed upon target for cup orientation. The so-called “safe zone” (Lewinnek) has been called into question due to lack of clinical correlation to the incidence of dislocation and errors in radiographic measurements. Pelvic flexion/extension variations among patients make set target positions impractical and cause significant radiographic measurement errors. Validation studies comparing the orientation of the cup as measured by the navigation system to the actual achieved orientation as measured by post-op CT are rare. Potential errors in pelvic registration have been documented and can result in placement errors of up to 10 degrees. Image-free systems are more susceptible to registration errors because they rely on surgeon identification of bony landmarks. Contour matching registration with pre-operative CT scans, either by fluoroscopic spot images or the collection of random bone surface points, offers improved accuracy. Despite this potential for better accuracy, CT-based systems are not commonly used due to perceived cost and time constraints. No clinical trail publication has yet shown any improvement in clinical patient outcomes such as pain, walking, function, implant longevity or reduced complications. A serious problem in this literature is the lack of “surrogate variables” linking radiographic measurements to clinical outcome. Although the potential is great for computer navigation in hip surgery, its clinical utility is yet to be proven. Despite this lack of proof, however, clinical adoption should be considered based on computer navigation’s ability to improve accuracy and reduce outliers. 2:43 p.m. Pitfalls and Lessons of Computer NavigationLawrence D. Dorr, M.D. The primary pitfalls with computer navigation occur with the registration process. As long as pins are used for optical registration, there is the risk of complications with these. Our experience has been that the pins used in the femur cause discomfort in some patients for as long as six weeks postoperatively. There are no complaints about the pelvic pins. For correct registration of the AP plane, the pointer must be very close to bone. This means that for pubic registration the pointer must always be pushed through skin and fat to the bone because the thickness of the fat over the pubis always is enough to cause distortion of registration. Registration of the anterior superior spines in thin people does not require perforation of the skin, but it does in fat people. The registration of the tilt requires that this be done in the position of the operation. If the patient is being operated supine, the longitudinal axis of the body can be registered from the operating table. If patients are operated in the lateral position, registration of the longitudinal axis from the table in the supine position does not permit accuracy of cup position. The registration must be done in the lateral position and we use the posterior supports for the pelvis and the chest and have proved accuracy with this. The lessons from the computer are that it provides better accuracy for component positions than the surgeon can do alone. The accuracy of cup position, as measured by the computer position to postoperative CT scans, shows no outliers greater than 5 degrees. The precision for both inclination and anteversion is between 4-5 degrees and the bias is less than 1 degree. For an experienced surgeon the outliers beyond 5 degrees are 33% with outliers of 10 degrees or more between 5 and 10%. For inexperienced surgeons, the outliers beyond 5 degrees are 50% and the outliers beyond 10 degrees are 15%. A second lesson from the computer is that femoral anteversion is often not 10-15%. This is particularly true with men and it is more common with straight stems than anatomic stems. The advantage of knowing the anteversion of the femoral stem is that the cup can be customized for that stem position to provide a combined anteversion of 30-45%. The computer measurements of leg length and offset are yet to be validated. 3:20 p.m. Management of Chronic DislocationDaniel J. Berry, M.D. Dislocation has represented the most common early complication leading to reoperation after total hip arthroplasty for the past decade. Improved operative approaches, soft tissue closures and routine use of larger head sizes hopefully will reduce dislocation rates. Most patients with chronic dislocation are eventually treated with operative management. Traditional management has focused on remedying specific identified problems: implant malposition is treated with implant revision and repositioning; inadequate soft tissue tension is treated with trochanteric advancement or component revision to increase length or offset; and intra- or extra-articular impingement are treated with procedures to remove the source of impingement. These methodologies have yielded success in 60-80% of cases. Recently, a number of new technologies to treat recurrent instability have become available. These include: large diameter fixed femoral heads, non-constrained tripolar implants, and improved constrained implants. Each of these technologies has strengths and weaknesses. Large diameter heads improve head-neck ratio and increase the displacement distance required for dislocation. They have only one bearing surface and no constraint. In most cases, the size is limited to 36 to 40 mm by availability. Tripolar implants provide a large head size relative to the cup, have the self-centering effect of the bipolar articulation, are not constrained at the bipolar-fixed socket interface, and are compatible with many stem designs that may not be compatible with new large fixed heads. However, they have two bearing surfaces, and the bipolar implant usually is made of conventional polyethylene, hence wear debris generation potential is greater than for large fixed heads. Constrained implants lock the ball in the socket and therefore resist dislocation most forcefully. However, constrained implants have reduced range of motion to impingement, and may transmit high loads to multiple interfaces, including the constraining polyethylene interfaces and the implant-bone interfaces. The latest data pertaining to the efficacy of each of these interventions will be summarized and discussed in this presentation. Specific attention will be paid to the efficacy or lack of efficacy of these newer technologies in specific challenging clinical scenarios. 3:36 p.m. Surgical Treatment of Leg Length Inequality C. Anderson Engh, Jr. M.D. Postoperative leg length inequality is an uncommon but quantifiable complication of total hip arthroplasty. Two types of leg length inequality have been described. Functional leg length inequality (FLLI) is described as a perceived leg length inequality (LLI) greater than the actual or measured LLI 1. It is common and has been reported as occurring in 14% of cases. FLLI virtually always resolves at three to four months postoperatively. Persistent LLI is the second type and has been reported in 0.3% to 7% of cases. Predisposing factors for a LLI include preexisting spine or knee deformity, female gender, femoral varus, acetabular protrusio and a preexisting ipsilateral long leg. Prevention includes proper physical examination, preoperative templating, use of recognizable surgical landmarks and patient counseling. A history and physical examination identifies predisposing factors. Templating using acetate overlays defines the acetabular and femoral position needed to recreate hip biomechanics. Operative measurements such as femoral length at the knee or a shuck test are useful but subjective compared to measurements made with an iliac pin or computer assistance. Treatment of LLE is virtually always nonoperative. LLI is usually a combination of FLLI and a smaller persistent LLI. Treatment includes patient counseling and/or explanation combined with observation, physical therapy and a shoe lift. Jasty reported requiring shoe lifts for the treatment of 2 out of 85 total hip patients2. In nine cases with persistent LLI identified over a 15‑year period, Ranawat treated five patients with a shoe lift, two with physical therapy, and two cases with surgery1. Parvizi reported on 21 revision hip surgeries to treat leg length inequality3. Indications for surgery included severe pain, recurrent dislocations, and nerve injuries. 15 hips were treated with an isolated acetabular revision to correct the instability or a low‑positioned acetabular component. Three of those cases required a constrained acetabular liner. Three patients were treated with an isolated femoral revision and three with the revision of both components. Complications included heterotopic ossification, a reoperation to place a constrained liner, one persistent subluxation and one patient with continued severe pain. In summary, with modern techniques, an actual leg length inequality greater than 1 cm is uncommon, occurring in 0.3% to 7% of cases. The majority of cases can be treated with a shoe lift and/or physical therapy. Operative treatment is rarely needed except in cases associated with pain, instability, or improper implant position. References: 1. Ranawat CS, Rodriguez JA. Functional leg-length inequality following total hip arthroplasty. J Arthroplasty. 1997;12:359-64. 2. Jasty M, Webster W, Harris W. Management of limb length inequality during total hip replacement. Clin. Orthop. 1996;333:165-71. 3. Parvizi J, et.al. Surgical treatment of limb-length discrepancy following total hip arthroplasty. JBJS 2003, 85-A, 2310-2317 3:44 p.m. Infection After THRArlen D. Hanssen, M.D. 1. Antibiotic Suppression: rarely indicated (Success is 1/3). Indications include: Prosthesis removal is not feasible, low virulence microorganism, microorganism is susceptible to an oral antibiotic, antibiotic tolerated without serious toxicity, prosthesis is well-fixed. 2. Debridement with Prosthesis Retention: Success possible in Type II and Type IV infections. Success related to duration of symptoms (eg. S. aureus < 48 hours). Do not attempt in Type III (chronic) infections: universal failure treatment should be prompt and considered emergent once the diagnosis has been confirmed. 3. Resection Arthroplasty: usually a temporizing procedure; occasionally is definitive. 4. Arthrodesis: rare 5. Disarticulation: also extremely rare; reserved for life-threatening infection. 6. Insertion of a New Prosthesis Direct Exchange: Requires careful selection process (75-80% success). Most series are highly selected cases.
Limited opportunity in current era due to increasing multi-drug-resistant organisms and many current revisions use cementless implants. Delayed Reconstruction (2-stage): Preferable approach with >90% success for all patients including those excluded for direct exchange.
Future directions include accurate prediction of specific risk factors, improved imaging studies and bacterial genetic detection technology for diagnosis, improvement in antibiotics with more oral treatment and less intravenous therapy, use of new staging systems for patient outcome with various treatment options, and technological advances in local antibiotic delivery systems. 3:52 p.m. Periprosthetic Fractures: “What’s New?” Clive P. Duncan, M.D., F.R.C.S.C. The Vancouver Classification of femoral fractures after hip replacement is now widely used to identify important variables and to guide treatment. It also underpins the categorization of these injuries during outcome analysis. It has improved our understanding of the factors that influence results and it has emphasized the importance of differentiating between the B1 and B2 fracture because of the profound effect of a loose stem if open reduction and internal fixation is chosen, instead of revision. On the subject of “What’s New?” there have been three potential advances in the recent past. The first has been the development of hook-plates for the management of pathological avulsion fractures of the greater trochanter, usually secondary to wear-debris cavitary osteolysis. This important modification of the pre-existing cable-grip technology, by the addition of a plate extension for screw and/or cable fixation, adds important stability to the fixation of these difficult fractures in fragile bone. The second advance has been the introduction of minimally invasive locked plate osteosynthesis to the management of femoral shaft fractures in the presence of a stable stem (B1 fracture). Initial reports have indicated favorable outcomes, when applied to suitable cases in expert hands, with a minimal risk of nonunion. The role of this technique in the presence of very weak bone (to which we have traditionally added a cortical onlay allograft) remains to be seen. Thirdly, management of periprosthetic fractures in the presence of badly damaged bone (the B3 fracture) has remained a challenge. Traditional techniques have included substitution of the proximal femur with a tumor prosthesis or a segmental allograft. The recent introduction of modular titanium stems, particularly those with a fluted-tapered stem tip, has afforded more reliable fixation to the remaining distal fragment, and assembly of the damaged proximal femur around the proximal stem (with or without onlay allografts). Initial experience with this approach has been encouraging with impressive proximal union and bone regeneration in many cases. 4:00 p.m. Pelvic DiscontinuityDavid G. Lewallen, M.D. Pelvic Discontinuity is a distinct pattern of acetabular bone deficiency, usually seen in association with failed THR, in which an acetabular fracture or nonunion separates the superior (iliac) portion of the pelvis from the inferior (ischial) portion. The AAOS classification of acetabular bone deficiencies defines pelvic discontinuity as Type-IV bone loss2. Based on a review of the Mayo experience with this problem1, three subcategories have been recognized:
Recognized risk factors include female sex, a diagnosis of rheumatoid arthritis, massive lysis and/or a history of prior therapeutic pelvic radiation1. Radiographic features that suggest the possibility of pelvic discontinuity include a visible fracture line, translation or rotation of the inferior aspect of the hemipelvis relative to the superior portion (visible as asymmetry of the obturator rings), violation of Kohler’s line by the failed socket, especially with > 2 cm superior migration of the hip center. Intraoperative inspection with a high index of suspicion is sometimes needed for detection. Stress applied in an anterior-posterior direction will produce motion at the fracture but this may at times be difficult to detect. Keys to treatment include recognition of the problem, stabilization of the fracture (usually via plate and screws), cancellous grafting to encourage union, and stable cup fixation. After plate application a stable socket can often be achieved with an uncemented cup and multiple screws into the dome, posterior column and ischium. Additional traditional methods include use of an antiprotrusio cage, structural allografting, and custom triflange cups. Three newer methods designed to try and improve on the relatively prior poor results seen with massive defects and segmental nonunions using prior methods include: use of combined anterior and posterior column plating, use of a porous ingrowth cup-cage construct, and a method described by Paprosky using an uncemented cup with porous metal acetabular augments and distraction of the nonunion in order to achieve host to implant ingrowth and fixation on either side of the discontinuity without fracture union. Further follow-up on these more recent techniques will be required to determine whether they will improve on the durability of results in this most challenging of acetabular reconstruction problems. References: 1. Berry, D. J.; Lewallen, D.G., Hanssen, A.D., and Cabanela, M.E.: Pelvic discontinuity in revision total hip arthroplasty. J. Bone and Joint Surg. 1999; 81-A(12):1692-1702. 2. Berry, D. J.; and Müller, M. E.: Revision arthroplasty using an anti-protrusio cage for massive acetabular bone deficiency. J. Bone and Joint Surg. 1992; 74-B(5):711-715. 3. D'Antonio, J. A.; Capello, W. N.; Borden, L. S.; Bargar, W. L.; Bierbaum, B. F.; Boettcher, W. G.; Steinberg, M. E.; Stulberg, S. D.; and Wedge, J. H.: Classification and management of acetabular abnormalities in total hip arthroplasty. Clin. Orthop. 1989; 243:126-137. 4. Garbuz, D.; Morsi, E.; and Gross, A. E.: Revision of the acetabular component of a total hip arthroplasty with a massive structural allograft. Study with a minimum five-year follow-up. J. Bone and Joint Surg. May 1996; 78-A:693-697. 5. Miller, A. J.: Late fracture of the acetabulum after total hip replacement. J. Bone and Joint Surg. 1972; 54-B(4):600-606. 6. Ranawat, C. S.; and Greenberg, R.: Tripartite fracture of the acetabulum after total hip arthroplasty: a case report. Clin. Orthop. 1981; 155:48-51. 4:23 p.m. Management of Periacetabular Bone LossAllan E. Gross, M.D., F.R.C.S.C., Catherine F. Kellett, B.Sc., B.M., B.Ch., F.R.C.S. and Petros J. Boscainos, M.D. The goals of acetabular revision surgery are to restore the anatomy and to achieve stable fixation for the new acetabular component. The existing bone stock and the type of defect are determining factors in the surgical decision making. When necessary, and especially in younger patients, attempt should be made to restore the bone stock by grafting. The advent of modern reconstruction options, like the trabecular metal revision system and the cup-cage combination, provides more options in addressing situations that so far have had only moderate results. In acetabular revision, most cases can be reconstructed with an uncemented hemispherical cup with screws with or without bone graft. More severe defects would require structural graft, trabecular metal cup with or without augments, a cage or a cup-cage, depending on the type of bone loss. A classification system of bone defects and a treatment algorithm has been formulated by the senior author at Mount Sinai Hospital: · Gross I. No significant loss of bone (Paprosky I). Conventional components, no bone graft ·
Gross II. Contained
(cavitary) loss of bone with intact columns and rim. (Paprosky II A, B, C).
Morcellised ·
Gross III. Uncontained
(segmental) loss of bone stock involving less than 50% of the acetabulum. ·
Gross IV. Uncontained loss of
bone stock involving greater than 50% of the acetabulum. (Paprosky III B). ·
Gross V. Pelvic discontinuity
with uncontained loss of bone. Cup-cage with or without a posterior column From the authors’ experience with new reconstruction modalities, results at 27 months of a cup-cage construct in major acetabular bone loss show excellent rates of radiographic implant stability, no migration and 82% of excellent or good clinical outcome. With trabecular metal cups, results at 30 months have shown good early clinical outcomes. Radiographic outcomes have been excellent with no significant difference between the greater than and less than 50% host bone contact groups. Filling-in of post operative lucencies may imply construct stability and biologic fixation. After the introduction of trabecular metal cups, the roof ring use is very limited at the authors’ institution. Trabecular metal augments use the oblong cup principle (of filling the defect), but since the augment is separate to the cup, one can place the cup independently. They are a particularly attractive solution in low demand patients. On high demand patients that may require another revision in their lifetime, a trabecular metal cup and a shelf graft is the authors’ treatment of choice. 4:31 p.m. Management of Femoral Bone LossRobert L. Barrack, M.D. Variable degrees of bone loss are frequently encountered in the course of revision THA. In general it is desirable to restore bone stock as one of the goals of the revision procedure. Many techniques and combinations of bone graft, bone graft substitutes, and bone proteins are currently available to attempt to achieve this goal. The proliferation of choices of materials to utilize has far outpaced the clinical evidence of efficacy for the variety of indications for which these materials are used. Most new materials have mostly osteoconductive properties with an extremely variable degree of osteoinductive potential. The exception are the osteogenic bone proteins. These materials have approved orthopaedic indications in specific spine and trauma applications. Their use in hip revision surgery, would therefore generally be on an off-label basis with the possible exception of a nonunion of a periprosthetic fracture. Strategies for managing femoral bone loss depend on a number of factors including the location and size of the bone deficit; patient age, activity level, level of symptoms, healing potential, life expectancy, and the planned femoral reconstruction. When bone graft substitutes are utilized, the biologic environment must be considered. Osteoconductive materials must be utilized in an osteoinductive environment; that is one with enough blood supply to provide growth factors to allow eventual formation of bone in the scaffold formed by the bone void fillers. Trochanteric lesions are often treated when they become symptomatic, demonstrate progression, and/or impending fracture with potential loss of abductor function. It is important to avoid use of abrasive materials in uncontained defects adjacent to the joint to minimize the risk of third body wear. In the proximal femur host bone and soft tissue attachment should be maintained when possible, occasionally supplemented by “wrap around” allograft or strut grafts. There is support in animal studies for use of bone protein to augment strut graft healing, but this again would be an off-label application. When there is complete absence of structurally supportive proximal bone, structural grafting including allograft – prosthetic composites can be utilized particularly in younger patients. Techniques combining use of a distal femur turned upside down and shaped as a proximal femur with attachment of the native trochanter with newer cable plate devices can reliably restore abductor function in most cases and improve the quality of the result. 4:39 p.m. Acetabular Revision OptionsWilliam N. Capello M.D. Acetabular revisions continue to be one of the most difficult reconstructive procedures facing an implant surgeon. Bone loss, both cavitary and segmental, as well as poor quality remaining bone, pose significant challenges even in cases where radiographically the revision would seem to be straight forward. For the past 10 years the mainstay of our armamentarium has been the large oversized cementless acetabular component with newer iterations of these componenets including foamed and trabecular metal options. This remains the prosthesis of choice in up to 90% of the acetabular revisions. Direct cementing into a revision acetabulum is no longer thought to be a viable option; however, cementing into packed allograft continues to be a proven reconstructive method, particularly in those settings where there are large cavitary defects requiring significant quantities of morsellised bone graft. The major change in acetabular revision surgery has come in the use of reconstructive or reinforced cages, at one time one of the mainstays in reconstructing severely involved acetabuli. Recent articles have suggested that these devices provide reasonably good early results but because of their lack of an ingrowth surface do not hold up over the long term and broken devices and loosening have become increasingly common. In addition, they are difficult to use and are frequently associated with a high intra and perioperative complication rate. The use of structural allografts also has diminished, primarily because even when reinforced with a reconstruction cage, their longevity is questionable. Recently the use of trabecular mental augments to replace segmental bone loss in the acetabulum combined with trabecular metal acetabular shells has shown promise as a means of reconstructing difficult acetabular problems and may provide long term durable results. In the extremely complex cases, the use of these devices in conjuction with cages is now being advocated. Today, I believe, the most common options in revision surgery include; the large or jumbo cup, cementing into packed allograft, and the use of trabecular metal shells with and without the supplemental metal augments. References: 1. Schreurs, B.W.; Bolder, S.B.T.; Gardeniers, J.W.M.; Verdonschot, N.; Sloof, TJ. J.H.; Veth, R.P.H. Acetabular revision with impacted morsellised cancellous bone grafting and a cemented cup: A 15 to 20 year follow up. JBJS Br. 2004;86-B(4):492-497. 2. Gross, Allen E.; Goodman, Stuart. The current role of structural grafts and cages in revision arthroplasty of the hip. CORR 2004; 429:193-200. 3. Gross, Allen E.; Goodman, Stuart. The intraoperative use of trabecular metal in revision total hip arthroplasty. JOA 2005:20:91-93. 4. Berry, Daniel J. Antiprotrusio cages for acetabular revision. Clin Orthop 2004; 420:106-112. 5. Berry, Daniel J. Rings, things, and cages: still the measure of last resort? Orthopedics 2005:28:973-974. 6. Gustke, Kenneth A. Jumbo cup or high hip center: is bigger better? JOA 2004:19(4):120-123. 7. Hendricks, Kelly J.: Harris, William H. Revision of failed acetabular componenets with use of so-called jumbo noncemented components. A concise follow up of a previous report. JBJS Am. 2006:88:559-563. 4:47 p.m. Femoral Component OptionsJohn J. Callaghan, M.D. Most surgeons in the United States and in many countries have not been satisfied with the results using cemented femoral components in the revision total hip arthroplasty construct. Although cement with impaction grafting is an option, the difficulty of the procedure and need for extensive bone graft have limited its use. Cementless femoral fixation has been utilized for over 20 years in the revision situation in the United States. Initially, sizes of implants and design options were limited. Today, three basic design categories are utilized: extensively porous coated implants; modular implants with proximal ingrowth surfaces and stems that provide distal stability (S-ROM type); and modular implants that provide distal stability with ingrowth or ongrowth surfaces and with cylindrical or tapered distal stems. The longest follow-up of extensively coated stems in revision total hip replacement was of 187 cases reported by Paprosky et al at a minimum of 10 years follow-up (average 13.2 years). 82% of cases demonstrated evidence of bone ingrowth and 14% stable fibrous fixation. The mechanical failure prevalence was 4.1% with only 6 stems revised. The longest follow-up of S-ROM modular femoral components in revision total hip replacement by Christie et al evaluated 129 hips at average 6.2 years follow-up (range 4-7 years). 2.9% of stems were loose. The longest follow-up of Wagner taper stems in revision total hip replacement by Bohm et al evaluated 129 revisions at average 4.8 years of follow-up. 88% of hips demonstrated some “bone restoration”. Other than two cases of early subsidence, there were no revisions for aseptic loosening. Extensively coated stems are usually inserted with a lateral extended osteotomy, modular distal fixation stems with a coronal plane osteotomy, and S-ROM type stems without osteotomy. Today when the distal isthmus fixation is less than four centimeters, many surgeons are considering distally tapered modular implants. References: · Bohm P, Bishcel O. Femoral revision with the Wagner SL revision stem. J Bone and Joint Surg Am. 2001;83:1023-1031. · Christie MJ, DeBoer DK, et al. Clinical experience with a modular noncemetned femoral component in revision total hip arthroplasty. 4 to 7 year results. J Arthroplasty. 2000;15:840-848. · Paprosky WG, Greidanus NV, Antoniou J. Minimum 10-year results of extensively porous-coated stems in revision hip arthroplasty. Clin Orthop. 1999;369:230-242. President: John Callaghan, M.D. First Vice-President: Lawrence Dorr, M.D. Second Vice-President: Wayne Paprosky, M.D. Secretary-Treasurer: William Maloney, M. D. Member At Large: Adolph Lombardi, M.D. Chairman Ed Committee: Robert Barrack, M. D. Immediate Past President: James D'Antonio, M. D. President: William J. Hozack, M.D. 1st Vice President: Daniel J. Berry, M.D. 2nd Vice President: David G. Lewallen, M.D. 3rd Vice President: William J. Robb, III, M.D. Secretary: James B. Stiehl, M.D. Treasurer: Carlos J. Lavernia, M.D. Immediate Past President: Joseph C. McCarthy, Jr., M.D. Members at Large: Richard E. White, M.D. Brian J. McGrory, M.D. Michael H. Huo, M.D. Audley Mackel, M.D. Educational Committee Chair: Peter F. Sharkey, M.D. |
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