The Hip Society Home Page

COURSE DESCRIPTION: This course is divided into eight sessions. The first two will address issues of Fixation and Wear in Total Hip Replacement. They will be followed by the Presidential Guest Speaker who will center his remarks on fractures of ceramic prostheses. The third session will address Controversies and Hot Topics in Reconstructive Hip Surgery including mini-incision, surface replacement, robotics, andf others. Symposium fourth will address Complications of Hip Replacement surgery and their management, and this will be followed by The Hip Society award papers. The sixth session will address Issues of Hip Revision and following this there will be a Symposium on Management of Osteonecrosis without femoral head collapse. The final session will consist of a series of Video presentations on Techniques in Revision Hip Replacement.

COURSE OBJECTIVE: The objective of the Open Meeting of The Hip Society will be to provide information on what is known today on fixation and wear issues in primary and revision hip replacement, as well as complications of hip surgery. In addition, an effort will be made to provide unbiased, up-to-date information on current topics of interest to the hip surgeon, including techniques such as mini-incision and robotics on hip replacement. There will be some new information provided on the management of osteonecrosis without femoral head collapse, an unsolved problem in hip surgery. Finally, there will be some practical, up-to-date technical information on popular techniques in revision hip replacement.

8:00 a.m.
OPENING REMARKS
President of The Hip Society - Miguel Cabanela, M.D.,
President of AAHKS - Douglas Dennis, M.D.,

DISCUSSION

WEAR IN THA: A CRITICAL UP TO DATE LOOK AT ALTERNATIVE BEARINGS

Polyethylene Wear Measurements: Evaluation of Current Radiographic Techniques

Early Clinical Results with Metal-Metal Bearing Total Hip Replacement

Metal-Metal: Metal Ions - A Cause For Concern In Metal-Metal Bearings?

Ceramic Prosthesis Fracture: History And Present Status

BREAK

CONTROVERSIES AND HOT TOPICS IN RECONSTRUCTIVE HIP SURGERY

Robotics/Computer Assisted Surgery: What Have We Learned To Date?

Computer Simulation: How Can It Help the Surgeon Optimize Implant Position?
Philip Noble, PhD.
Houston, TX

Femoro-Acetabular Impingement: An Important Cause of Early Osteoarthritis of the Hip

Bone Graft For Revision Hip Arthroplasty

COMPLICATIONS OF HIP SURGERY

Treatment of the Infected Hip Replacement

Recurrent Dislocation: Large Heads vs. Constrained Cups: Pros vs. Cons
William Capello, M.D.
Indianapolis, IN

Avoiding Complications in Hip Arthroscopy

The Dysplastic Femur: 3D Morphology and Implications For Total Hip Replacement

Efficacy of MBP-2 to Induce Bone Ingrowth in Gap and Nongap Regions of a THR Model

REVISION THA

Re-Operation for Pelvic Osteolysis: Unique Complications and Intermediate to Long-Term Results

Revision THA: Modular Fluted Tapered Stems

Femoral Head Resurfacing for the Treatment of Osteonecrosis in the Young Patient

Total Hip Arthroplasty For Avascular Necrosis With All Alumina Bearings Prosthesis.

VIDEO TECHNIQUES IN REVISION THA

The Technique and Early Results of the Two-Incision Minimally Invasive Total Hip Arthroplasty
Richard Berger, M.D.
Chicago, IL

Grafting Of Osteolytic Lesions

Cementing a liner into a well-fixed shell
William Jiranek, M.D.
Richmond, VA

ADJOURN

Charnley total hip arthroplasty has been performed in the United States for over 30 years. The design changed over the years, as did the surface finish of the femoral component. The primary author has evaluated three cohorts of patients performed by the senior author using the polished flat back Charnley femoral component. These groups include the minimum thirty-year results with handpacking techniques, the minimum 20-year results with contemporary cementing techniques and the minimum twenty-five year results in patients under fifty at the time of surgery.

The number of patients in the three groups was 262 (330 hips), 320 (357 hips) and 69 (ninety-three hips). The revision rates for any cause were 11%, 10.9%, and 31%. The revision rates for loosening of the acetabular component were 7%, 5.4%, and 18%. The revision rates for loosening of the femoral component were 3%, 1.8%, and 4.3% respectively. Acetabular radiographic loosening rates were 15.8%, 12.8%, and 35%. Femoral loosening rates were 7.2%, 4.8%, and 13%. The average linear wear rates with these 22-millimeter head components were .1 mm/yr. These figures should serve as a benchmark for the long-term follow-up of other designs.

8:13 a.m.

The Exeter Hip: Long Term Results and Surgical Technique

The Exeter Total Hip Replacement was introduced into clinical practice in October 1970. Over the next 32 years the basic design of a collarless, double-wedge, tapered configuration has remained unchanged. The only difference between the present polished stem and the original, besides improved metallurgy, is the rounding off of the lateral shoulder of the prosthesis and modularity which was introduced in 1988.

Over time it has become clear that the basic design features allow the femoral component to subside within the cement mantle leading to taper engagement without damaging the mantle and accommodated by creep within the cement, leading to a loading regime dominated by compression at the cement-bone interface..

The first 433 hips operated on between 1970 and 1975 have been reviewed at regular intervals. Besides some early problems including prosthetic neck and stem fractures, stem fixation has remained impressive over a 30-year period with an aseptic loosening rate of 2.77%.

In 1976 the surface finish of the component was changed to a matt finish for no very good reason with the shape of the component remaining unchanged. This apparently minor alteration led to a dramatic change in the success of the Exeter hip replacement with 9% of these components requiring revision by 10 years, mainly for endosteal bone lysis. The polished stem was therefore re-introduced in 1986 and modularity in 1988.

The first 325 modular hips in 309 patients have been reviewed at regular intervals. . The outcome of all hips is known. At follow-up now extending to 14 years, survivorship with revision of the femoral component for aseptic loosening as the end point is 100%. Femoral osteolysis is present in only 0.5% of the living cases.

Modularity has not affected the outcome and, indeed, improved cementing techniques reflect results even superior to the original group. Stem-cement interface subsidence (taper engagement) has been significantly reduced and cortical hypertrophy, seen in 30% of the early cases, is now rarely seen.

Since the introduction of cementless total hip arthroplasty in the early 1980s, concern has shifted from component loosening toward polyethylene wear and osteolysis. The current review of 223 consecutive unselected Anatomic Medullary Locking femoral and acetabular components extends the follow-up on a series of patients previously reported on at 5 and 10 years. The purposes are to describe the reasons for revisions and to assess the onset and size of osteolytic lesions, with the hypothesis that osteolysis represents an important cause of loosening. The population included 211 hips (204 patients) with mean follow-up of 13.9 years (range, 2-18 years). Among them, 129 hips (122 patients) had minimum 15-year follow-up. Minimum 2-year radiographs with a mean radiographic follow-up of 12.2 years (range, 2-18 years) were available for 204 hips (197 patients). Of the entire study group, 39 hips (38 patients) had 44 component revisions, increasing the number of revisions by 24 since this series was reported previously. Twenty-six patients (27 hips) had their first revision surgery more than 10 years after the primary surgery. The most common reason for revision of original components was wear or osteolysis occurring in 22 of the 39 hips (21 of 38 patients). The overall loosening rate for components was 3% (seven of 204) for femoral components and 5% (11 of 204) for acetabular components. Twenty-four percent of hips (48 of 204) had evidence of femoral or pelvic osteolytic lesions larger than 1.5 cm². Femoral osteolysis was not associated with any case of femoral loosening, whereas seven of the 11 loose acetabular components were associated with pelvic lesions larger than 1.5 cm².

Tapered Uncemented Stems: Long-term Results and Technique

James A. D’Antonio, M.D., William N. Capello, M.D., Michael T. Manley, Ph.D.,

Activities of daily living create a combination of axial, bending, and torsional stresses in the proximal femur. In order to maintain these stresses at physiologic levels after THR, cementless femoral prostheses must achieve mechanical stability at the time of implantation and maintain fixation thereafter by a combination of stem design and implant fixation coating. The major concerns with uncemented femoral components include fixation, thigh pain, stress shielding, and osteolysis.

Collarless tapered titanium alloy stems of several designs (single wedge, double wedge, rectangular) have had great success for ten to fifteen year follow-up periods. Reports on the use of the Mallory Head, Taperloc, Zweymueller, and HA Omnifit have shown: mechanical failure rates 0-4%; thigh pain 2-6%; femoral osteolysis 0-6%.

We have had a fifteen-year experience with the Omnifit HA femoral stem. The implant is a titanium alloy that achieves initial mechanical stability through its tapered and proximal double wedge design. For long-term stability, anterior and posterior normalization steps facilitate load transmission to bone in the proximal region of the femur, and a plasma sprayed circumferential 50 millimeter thick HA surface coating ensures bone adaptation and apposition to the stem. To prepare for implantation, the proximal femur is machined with a tapered reamer then broached to size creating a high degree of interference fit. The mechanical stability achieved permits immediate weight bearing as tolerated. Finite element analysis of the femur has shown excellent stress distribution for this design, with reduced proximal stress shielding compared to other contemporary cementless implants. These numeric data correlate with the proximal bone preservation demonstrated in three separate DEXA studies with this stem, the progressive bone remodeling observed to occur circumferentially about the stem over the first five years after implantation, a low incidence of both thigh pain, and long-term fixation.

Our current study includes 227 stems implanted in patients with an average age of 51.8 years that have a follow-up of 10-15 years (12.2 years average). Clinically the patients have demonstrated excellent early restoration of function, have an average Harris Hip Score at last follow-up of 88, and an incidence of thigh pain of 2%. One stem was revised at 9.5 years for loosening secondary to progressive osteolysis and all remaining stems are radiographically stable yielding a mechanical failure rate of 0.4%. No distal osteolysis has been observed to date.

Collarless tapered titanium stems provide a very viable option for total hip arthroplasty. They have shown excellent durability for up to fifteen years, have had a low incidence of thigh pain and osteolysis, and provide for relatively good proximal bone preservation.

Results of Uncemented Cups: A Critical Appraisal At 15 Years

One of the most striking changes during the recent 20-years of total hip replacement surgery has been the success of the uncemented acetabular component. The major limitation to cemented acetabular components was the increasing loss of fixation after the first decade among primary total hip replacements. Even more alarming was the increasing loosening during the first decade in total hip replacements in young patients (those under the age of 51) and in revision operations. The mechanism of this failure of fixation is dominated by a linear form of periprosthetic osteolysis, manifested by the radiolucent zone at the interface between the bone cement and the host bone.

With the introduction of the hemispherical porous acetabular component, either pressfit or fixed with screws, in 1984 by Galante and Harris, major progress was made. This holds true for primary acetabular reconstructions in the older patients and most strikingly in acetabular revision surgery. Although other forms and designs of cementless acetabular components have had extensive trials, there is now wide acceptance of this design.

A striking example of the efficacy of that concept in providing lasting fixation is shown by the aggregated figures of three recent reports from Iowa, Rush and the MGH. The aggregated data show that among 446 acetabular revisions using the HG socket, after an average of 12.5 years, the reoperation rate aseptic loosening was 0.9%. Compared with the results of cemented acetabular revisions, this represents a revolutionary change. These improvements in acetabular fixation using this design are independent of diagnosis, gender or age, with the exception of patients with avascular necrosis of the pelvis. This improvement has been a striking advance during the 40-year history of total hip replacement surgery.

David C. Ayers M.D.

Osteolysis due to particulate debris is the most common cause of failure of fixation of total hip replacements. When particulate debris gain access to the bone-prosthesis interface and initiates an osteolytic cascade, failure of prosthetic fixation can occur. Particulates that have been implicated in this process include Ti, CrCo, methylmethacrylate, ceramics and polyethylene. Although particulate debris can be generated from any portion of the surface of the prosthesis, a major source of debris generation occurs at the primary bearing surface. All techniques for quantifying polyethylene wear rely on the radiographic measurement of femoral head penetration within the acetabular component over time. Radiographic femoral head penetration has been measured using manual techniques, computer assisted techniques and RSA (radiostereometric analysis). RSA was developed by Selvik in the early 1970’s and has been used extensively to evaluate the migration of total hip components. RSA has also been used to determine the magnitude and direction of penetration of the femoral head into the acetabular component from wear and creep of the polyethylene. Radiographic techniques to measure polyethylene wear will be reviewed and the strengths and weaknesses of each method discussed. When interpreting clinical polyethylene wear measurements, it is helpful to understand the accuracy and precision of the technique being employed.

G. Digas, J. Kärrholm, J. Thanner, H. Malchau and P. Herberts

Aims: We evaluated a highly cross-linked polyethylene (WIAM, warm irradiated adiabatic melting) in cemented hip arthroplasty.

Methods: 61 Hips (30 women, 30 men) with a median age of 55 years (35-70) were included. All patients received a Spectron stem with 28 mm cobalt-chromium head. The patients were randomized to Acetabular cups made of either WIAM (electron beam irradiation 9.5 Mrad) or conventional polyethylene (gamma irradiation in nitrogen 2.5 Mrad, CP). Radiostereometric examinations (supine) were done 5-7 days after the operation and after 3, 6, 12 and 24 months. Standing examinations were initiated after 3 months. The migration of the femoral head centre in relation to the polyethylene marker represented the femoral head penetration.

Results: 50 hips (23 WIAM, 27 CP) have been followed for 2 years. The mean cup migration and proximal penetration (supine) did not differ between the two groups (p>0.12). The mean proximal penetration (standing) for CP and WIAM were 0.13 and 0.05 mm respectively (p=0.05)

Conclusions: The new polyethylene tended to show less proximal penetration when examined in the standing, but not in the supine position.

Early Clinical Results with Metal-Metal

Bearing Total Hip Replacement

There is now more than a decade of experience with second generation metal-metal bearings that have been combined with a variety of different total hip replacement and hip resurfacing systems. In aggregate, there is no discernable difference in pain relief or function or any other clinical outcome compared to hips with an UHMWPE bearing. Osteolysis can occur but the incidence is low. Given similar manufacturing parameters, the wear of a metal-metal bearing decreases with increasing head size: metal-metal favors large diameters. The in vivo wear performance has closely followed that predicted by wear simulator studies: wear rate during the run-in period is variably higher than the subsequent steady-state wear rate. In general, volumetric wear is a fraction of that seen with UHMWPE but is higher than that of well-functioning ceramic-ceramic bearings. There have been no reported cases of run-away wear or any type of gross material failure of the bearing.

There are measurable increases in the levels of cobalt and chromium ions in the red blood cells, serum and urine of patients with a metal-metal bearing. The clinical significance of this finding has not been determined. The cellular response to metal wear particles is predominantly lymphocytic, resembling an immune response more than a foreign-body response. Delayed-type hypersensitivity or DTH, a rare allergic reaction to metal haptens, may occur more frequently in association with metal-metal bearings and may rarely necessitate revision surgery. The aggregate clinical data do not indicate an increase in the risk of cancer associated with metal-metal bearings. Detailed clinical studies over several decades are needed to fully assess the risk:benefit ratios of the available bearing couples.

In the vast majority of patients, permanent orthopedic implants are biocompatible. However, there is an increasing recognition that, in the long term, permanent orthopedic implants may be associated with adverse local and remote tissue responses in some individuals. These adverse effects are mediated by the degradation products of implant materials which may be present as (1) particulate debris, (2) organometallic complexes, (3) free metallic ions, (4) inorganic metal salts or oxides, or (5) as an organic storage form such as hemosiderin. Concern about the release and distribution of metallic degradation products is justified by the known potential toxicities of the elements used in modern orthopedic implant alloys - titanium, aluminum, vanadium, cobalt, chromium, and nickel. Toxicity may be by virtue of (i) metabolic alterations, (ii) alterations in host/parasite interactions, (iii) immunologic interactions and (iv) by chemical carcinogenesis. The recent reintroduction of metal-metal bearings for hip arthroplasty has heightened these concerns in light of the fact that the serum and urine metal concentrations in patients with these implants are considerably higher than those seen in patients with conventional metal-polyethylene bearings. From previous studies of long term metal-metal McKee-Farrar implants, it seems that these elevated levels will persist for the duration of the implant's lifetime. This is of particular concern in the younger and more active patient where life expectancy after implantation may exceed 30 years. Further study is needed to fully understand the systemic implications of these persistently elevated metal ion concentrations. At this time, the association of metal release from orthopedic implants with any metabolic, bacteriologic, immunologic, or carcinogenic toxicity remains conjectural since cause and effect have not been established in human subjects. However, continued surveillance of patient populations with metal implants, particularly those with metal-metal bearings, is warranted.

Aseptic implant loosening is a major challenge limiting the long-term success of total hip arthroplasty. Particulate debris, particularly polyethylene, is responsible for the inflammatory response that leads to bone resorption and loosening of the implants over time known as osteolysis.^{1, 2} An alumina-on-alumina ceramic bearing couple has many theoretical advantages. It not only eliminates polyethylene from the system, but its extremely low coefficient of friction and potential for far superior wear resistance is very attractive. Previous complications reported with ceramic bearings are attributed to poor implant designs or fixation.⁶Clinical experiences reported from Europe as well as the US have contributed to the evolution and improvement of ceramic materials that are available for us to use today. Improvements in particle density and inclusion grain size have virtually negated previous concerns for fracture.⁴ In-vitro and retrieval studies have shown ceramic-on-ceramic surfaces to have the lowest wear rate of any available bearing.⁴ Laboratory study with alumina and cobalt/chrome particle effects on in-vitro histiocytes and fibroblasts indicate that ceramic debris is less reactive than metal debris.⁵ In addition, alumina ceramics are extremely hard, scratch resistant and stable at high temperatures. Their hydrophilic nature provides for improved lubrication over other bearing surfaces.⁴

Previous work has suggested little difference in average ceramic vs. polyethylene particle size. Retrieval study has shown, however, that ceramic-on-ceramic has 4000 times less linear wear than conventional polyethylene.^4,7 No data is currently available for cross-linked polyethylene in this regard, but previous studies have shown poor resistance of this material to third body wear.⁸ In contrast, reports of ceramic bearing retrievals have shown resistance to scratching from third body wear particles.⁹

Clinical data from two US trials are presented. The ABC (alumina bearing couple) study is a US IDE prospective, randomized trial comparing alumina-on-alumina ceramic bearings to chrome cobalt-on-polyethylene bearings. Included were 514 hips implanted in 458 patients of mean age 53 years. Of these, 349 cases were implanted with the alumina-on alumina components and 165 were controls. At a mean of 35.2 months follow-up, Harris hip scores, pain and patient satisfaction were equal. Complications reported for the alumina-alumina population included revisions for dislocation, postoperative traumatic fracture, and deep joint infection. Nine events of chipping of the alumina insert occurred upon impaction. These were technical problems related to the placement of the ceramic insert within the titanium acetabular component. There were no fractures of ceramic components and no alumina device related failures in the study.¹⁰ In a separate ongoing US IDE clinical prospective study, 446 ceramic-ceramic hip implants were performed, mean age 53 years. At mean follow-up of 32 months, no bearing fracture nor evidence of osteolysis were present in any patients. Re-operations occurred in twelve patients, indications including deep infection, recurrent dislocation, inadequate liner seating, subluxation, and poor osseointegration.⁷ Both clinical trials have reported alumina-alumina ceramic to be a reliable bearing surface at early to mid-term follow-up.

The available literature supports the position that advanced new ceramics show promise in articulating bearing surfaces for total hip implants and that alumina-on-alumina ceramic couplings are a viable alternative to current metal-on-polyethylene designs. By combining new high quality ceramic acetabular and femoral bearing heads with hip systems that have achieved long-term stable fixation, we believe a substantial increase in the longevity of fixation for implants particularly in the younger and more active patients can be achieved.

2 Schmalzried TP, Kwong LM, Jasty M. Peri-prosthetic bone loss in total hip arthroplasty: the role of polyethylene wear debris and the concept of the effective joint space. Journal of Bone and Joint Surgery. July 1992; 74(A): 849-863.

3. Clarke IC. Role of ceramic implants: design and clinical success with total hip prosthetic ceramic-to-ceramic bearings. Clin Orthop. September 1992; 282:19-30.

4. Murphy SB. Ceramic-ceramic bearings in THA: The new gold standard – in the affirmative. Orthopedics. September 2002; 25(9): 933-934.

5. Germain MA, Hatton A, Williams S, Matthews JB, Stone MH, Fisher J, Ingham E. Comparison of the cytotoxicity of clinically relevant cobalt chromium and alumina ceramic wear particles in vitro. Biomaterials. February 2003; 24(3): 469-79.

6. Skinner HB. Ceramic bearing surfaces. Clin Orthop. December 1999; 369: 83-91.

7. Mochida Y, Boehler M, Salzer M, Bauer TW. Debris from failed ceramic-on-ceramic and ceramic-on-polyethylene hip prostheses. Clin Orthop. August 2001; 389: 113-25.

8. Bowsher JG, Shelton JC. A hip simulator study of the influence of patient activity level on the wear of cross-linked polyethylene under smooth and roughened femoral conditions. Wear. 2001; 250: 167-179.

9. Cooper JR, Dowson D, Fisher J, Jobbins B. Ceramic bearing surfaces in total artificial joints: resistance to third body wear damage from bone cement particles. J Med Eng Technol. 1991; 15: 63-67.

10. D’Antonio J, Capello W, Manley M, Bierbaum B. New experience with alumina-on-alumina ceramic bearings for total hip arthroplasty. J Arthroplasty. June 2002; 17(4): 390-397.

Ceramic Prosthesis Fracture: History And Present Status

Brittleness of alumina ceramic material is well known. It is also well controlled since 32 years this material has been in use for total hip replacement.

Our purpose is to present information’s on alumina (Al₂O₃) component fracture collected during 25 years of experience with this material in order to provide a clear perspective about frequency, consequence and treatment. Zirconia fracture problems will not be addressed.

Material and methods: Over a period of 25 years (1977 to 2001) 13 alumina component fractures were recorded retrospectively in the department. During the same period about 5500 alumina components were implanted (3300 with all Alumina bearings and 1200 with Alumina on polyethylene.). These events occurred between 3 months to 23 years after the index operation in 7 females and 6 males. Mean age was 50 years, mean weight was 67 kilogram’s. There were 8 femoral head fractures and 5-socket components’ one (one massive and 4 liners). Five fractures were clearly in relation with trauma in 3 (2 socket and 1 head) or abnormal design in 2 (1 head of 22mm in diameter and one extra long neck). Five fractures occurred without any reasons after 3 to 23 years in use, but for 2 of them which were implanted in the pioneering phase, we could suspect weaker alumina material to be a possible reason for. Finally 3 recent fractures of the liner could be related to a change in the design of the material (socket, shape and thickness of the component); this was now corrected and no further fractures were reported.

Management of this event could be defined; If the prosthesis was revised in emergency condition, the Morse taper being preserved or not aggressively damaged, another ceramic head or liner was inserted in 8, it was exchanged for a metallic head on the previous trunion in 1 and 4 were revised completely (one was revised elsewhere).

Conclusion: Although this dramatic event is of concern it is infrequent, easy to solve by a limited revision procedure if done in emergency and it has to be compared to the difficult and frequent revision when some osteolytic lesion need massive grafting and difficult surgery.

Mini-Incision For THA: Pros, Cons, And Experience To Date

Ninety patients with 105 hips (15 bilateral) had total hip replacement through a 6-10 cm. posterior incision. For an incision of 6-10 cm, new instrumentation was required for ease of surgery and reproducible results. The operation averaged 1 hour, hospital stay averaged 4 days with 88 patients (98%) discharged home. Pain control did not require narcotic infusion and pain scores were 3 of 10 in the hospital. At discharge, 1/3 of patients went home on a cane or a single crutch; at 6 weeks postoperative 2/3 of patients were off all assistive devices; and at 3 months 89 of 90 patients (99%) used no devices. Gait analysis showed stride characteristics were 80-90% of normal except stride length which lacked hip extension. These gait results were 8-12% better than we obtained with standard incisions. Patients’ self-assessment revealed they preferred a mini incision for cosmesis and because it meant less traumatic surgery to them. Radiographic analysis showed reproducible component position and restoration of hip biomechanics. The absence of randomized studies and the lack of sufficient number of patients operated at different centers so that the true prevalence of complications is not known, makes some surgeons remain cautious for universal use of mini-incisions.

INTRODUCTION: THR is still the standard of care for young arthritic patients. Although there has been improvement in fixation and THR durability with new designs and techniques, these are still associated with adverse consequences such as stress shielding and osteolysis. In addition, dislocation remains a problem. Surface arthroplasty utilizing ultra high molecular weight polyethylene was abandoned because: 1) the short-term technical failure rates in many centers were unacceptably high. 2) Generally, more bone was removed from the acetabulum than in THR. 3) The medium and long-term failure rates were higher due to osteolysis because of the larger ball size. With the arrival of new, more wear resistant bearings, new designs and techniques, Surface Arthroplasty (SA) has becomes a viable and promising solution for this patient population.

MATERIALS: The first 400 hips (of 577) in 355 patients underwent M/M hybrid surface arthroplasty. Mean age 48.2; 73% males, 27% females; 198 Charnley Class A; 139 Class B and 18 Class C. Diagnosis at surgery: OA 64%, DDH 11%, ON 9%, Post-traumatic 8%, Inflammatory arthritis 3%, SCFE and LCP 4%, Melorheostosis 0.3%.

RESULTS: Mean follow-up 3.5 years (2.1-6.1). Average UCLA hip scores post-op: pain 9.4, walking 9.5, function 9.4, and activity 7.7. The SF-12 physical and mental components were respectively 31.2 and 46.8 pre-op, and 50.1 and 53.0 post-op. 13 hips were converted to THA (8 in the first 102): 2 for neck fractures, 8 for femoral loosening, 1 due to a socket protrusio secondary to over-reaming, 1 for subluxation due to impingement and 1 for sepsis. The three most important risk factors for femoral loosening and radiolucencies were large cyst formation (p=0.0067), female gender (p=0.0001), and lighter weight in male patients (p=0.0003). The occurrence of femoral loosening or lucency was 18% for the first 100 cases, 9% for the 2^nd, 8% for the 3^rd, and 1% for the last 100 cases.

DISCUSSION: Clinical results are excellent despite very high activity levels. The experience with SA of all cemented metal/UHMWPE bearing demonstrated failure rates of 15%-33% at 3 years. At longer follow-up, the preliminary experience is encouraging (3% failure rate). Dislocation is rare, and acetabular fixation secure. Initial femoral fixation is critical as the fixation area is small, especially with osteopenia and cystic degeneration. Cementing the femoral metaphyseal stem appears as a meaningful technical improvement towards the prevention of early femoral radiolucencies and minimizing long term loosening neck fractures can be prevented by not weakening the neck during femoral head preparation.

Anthony M. DiGioia III, M.D.

Computer assisted orthopaedic surgery (CAOS) is at a crossroads. There have been many initiatives that have now brought CAOS technologies from the drawing board all the way to clinical use and now commercial development. In many sites, CAOS tools are being used on a routine basis. However, there are continued challenges in the clinical adoption and routine use of these surgical tools.

CAOS-based technologies are the “surgical toolbox” of the future and represent a spectrum of devices including: 3D image guided and non-image based navigation systems, intra-operative fluoroscopic navigation, robotic assistive tools, and new intraoperative visualization devices. CAOS tools couple simulations with real time evaluations of surgical performance. This clinical information will be available to surgeons when and where we need it the most – during surgery!

Balancing these new capabilities are the potential negative aspects of the introduction to new technologies into clinical practice: the real costs and time costs for preoperative or intraoperative imaging that may not normally be used in routine practice; costs of the systems themselves; increased operating time; accuracy and validation; and surgeon acceptance.

CAOS technologies have the potential to be used in several different capacities: research tools; training tools; in routine clinical practice; as a commercial proposition; and as an enabler for less and minimally invasive surgical techniques. CAOS technologies will likely be important in all of these roles. However, the most powerful argument for their use may be in enabling surgeons to develop techniques that are not only more accurate, but also less and minimally invasive. When CAOS meets MIS, we are coupling what machines do well (including computers, robotics and navigational tools) with what humans do well, to enable surgical techniques that we could never perform before. Our prediction is that the next generation of less and minimally invasive surgical (L/MIS) tools for orthopaedic surgeons will rely on computer-based technologies to enhance doctors’ abilities, and dramatically improve patient care by converting minimally invasive procedures.

Lastly, we must also remember that CAOS tools provide a unique opportunity for clinician-scientists by “closing the loop” in surgical practice. These computer-based systems are precise intraoperative measurement tools that can be used to measure and document what we are doing during surgery, as well as to train surgeons. This information can be used to directly relate specific surgical techniques to the short- and long-term outcomes of our patients.

Correct sizing and placement of prosthetic components is essential for optimal performance and longevity of total hip replacements. Although this is commonly attempted through radiographic templating, the 2D projections of the skeletal structures depicted on AP and lateral radiographs often lead to significant errors.

Through advances in computer technology, it is now possible to visualize implantation of the femoral and acetabular components in 3D, using computer models. This approach allows surgeons to template with much greater accuracy than was ever possible previously, and provides an intimate view of the fit of the components within the implantation site. Greater accuracy in predicting component position enables the surgeon to reliably assess the effect of a preoperative plan on the restoration of leg length, medial head offset, and even femoral anteversion. More advanced computer routines are also available to predict the functional outcome of a preoperative plan prior to its implementation. Using these routines, it is now possible to demonstrate the expected range of motion of the joint during a variety of activities and to display points of bony and prosthetic impingement which may compromise joint stability. Other tools allow the surgeon to predict the impact of any change in head position on the efficiency of the hip musculature and on the forces developed across the artificial joint.

Several options are also available to facilitate the implementation of a chosen preoperative plan in surgery. Great advances in Surgical Navigation now make this a feasible option within the operating room. Computer technology is also being utilized to train surgeons in the workshop environment. This is an attractive alternative to surgical navigation that makes these tools potentially accessible to all surgeons. The ultimate place of new technologies in assisting the surgeon has yet to be determined. However, with the rapid development of minimally invasive approaches to hip surgery, it is expected that computer-based planning tools will prove increasingly important to assure correct component placement.

11:00 a.m.

Femoro-Acetabular Impingement:

An Important Cause of Early Osteoarthritis of the Hip

Reinhold Ganz M.D., Javad Parvizi M.D., Martin Beck M.D., Michael Leunig M.D.,

A multitude of factors including genetic, morphological, and biochemical abnormalities may contribute to etiology of osteoarthritis of the hip. While the pathomechanism of degenerative process affecting the dysplastic hip is well understood, the exact mechanism for the so-called ‘idiopathic’ osteoarthritis has not been established.

Based on clinical experience, with over 700 surgical dislocations of the hip, allowing in situ inspection of the damage pattern and the dynamic proof of its origin, we propose femoro-acetabular impingement as a mechanism for development of early osteoarthritis of the non-dysplastic hip. The concept focuses more on motion than on axial loading of the hip. Impingement may arise as a result of morphological abnormalities affecting the acetabulum or the proximal femur, or it may occur in patients subjecting the hip to extreme and supra-physiological range of motion. Depending on the underlying cause, femoro-acetabular impingement results in cartilage and labral lesions at the acetabular rim, and provokes cartilage alterations within the acetabulum adjacent to the rim. Based on the pattern of injury, two distinct types of impingement, termed ‘pincer’ and ‘cam’ abutment, can be distinguished.

Distinct clinical, radiographic, and intraoperative parameters can be used to confirm the diagnosis of this entity with timely delivery of treatment. Surgical management of femoro-acetabular impingement focuses on improving the clearance for hip motion and alleviation of femoral abutment against the acetabular rim. It is believed that early surgical intervention for treatment of femoro-acetabular impingement, besides providing relief of symptoms, may decelerate the progression of the degenerative process for this group of young patients.

11:08 a.m.

Bone Graft For Revision Hip Arthroplasty

Revision total hip arthroplasty often presents surgeons with difficult bone loss problems. The selection of an appropriate bone graft is influenced by the size of the bone defects, the location, and whether or not the graft is required for structural support. Autogenous bone graft remains the gold standard but there is only a limited amount available and there is morbidity associated with the harvesting of these grafts. The most frequently used bone graft materials include autogenous iliac crest bone graft, cancellous allograft chips, demineralized bone matrix, and bulk structural allografts (i.e. femoral head, distal or proximal femoral allograft, whole acetabuli, and femoral strut grafts). It is often difficult to determine on plain radiographs if the nonstructural grafts actually incorporate. Recently, attention has focused on the use of new materials for bone grafting including: new demineralized bone matrices, ceramics, and autologous platelet concentrates. The purpose of this review is to assess the biologic potential of these agents and their limitations. Are these agents actually incorporating into host bone? Future bone graft options, including tissue engineering and gene therapy will be discussed.

The challenges of complex total hip arthroplasty often include bone loss in the proximal femur and acetabulum and deformity, cortex perforation and periprosthetic fracture. The use of bone-graft material has become routine in many cases. The added surgical time, limited supply and morbidity associated with autogenous bone-graft harvest have resulted in the use of various types of allograft bone in most cases. Contained defects are managed effectively with morsellized cancellous allograft. Although allograft bone can heal defects, ingrowth does not occur from the defect to a porous ingrowth surface. In addition, when there is a need for immediate structural support, cortical allografts are often used, which have a much slower rate of incorporation.

Osteogenic proteins, also referred to as bone morphogenetic proteins, are a family of bone matrix polypeptides that induce a sequence of cellular events that lead to the formation of new bone. Preclinical studies have shown that the osteoinductive capacity of autograft and allograft bone can be improved with the addition of the osteogenic proteins. The combination of autograft or allograft bone with an osteogenic bone protein consistently improved the amount and rate of new bone formation compared to bone-graft alone resulting in earlier graft incorporation and consolidation. Preclinical studies have also shown that healing of structural cortical strut allografts to the femur was enhanced by the addition of the osteogenic protein. The quantity and quality of the graft incorporation was improved but most importantly, the time course of healing was significantly accelerated. The role of osteoinductive bone proteins in acetabular defect healing and particularly bone growth from a defect into a porous coating has been evaluated. The osteogenic protein treated defects not only healed more completely than allograft bone filled defects but bone ingrowth occurred to a significantly higher degree achieving a degree of bone ingrowth equivalent to no defect being present.

Osteogenic bone proteins have been successfully utilized in a number of orthopaedic clinical applications. Osteogenic proteins are approved in the United States in the spine for interbody fusions and in trauma for the treatment of nonunion fractures. They have also been used clinically in a number of applications in reconstructive surgery of the hip. There have been anecdotal reports of success with a combination of osteogenic protein with proximal femoral allograft, cortical strut allografts, and with morsellized allograft bone utilized with cementless acetabular components. Animal studies and early clinical experience indicate that osteogenic proteins have great potential to play an important role in reconstructive hip surgery in the foreseeable future.

Arlen D. Hanssen, M.D.

Selection of the appropriate treatment method for an infected hip replacement requires careful assessment of patient-related variables and expected treatment goals. The basic treatment options include antibiotic suppression, open debridement with prosthesis retention, resection arthroplasty, arthrodesis, reimplantation of another prosthesis, and amputation. Successful treatment of infection requires complete debridement of all infected and foreign material and appropriate antimicrobial therapy.

In the current era, patients often present with a higher likelihood of resistant organisms and severe bone loss, which increases the difficulty of treatment and diminishes the potential for direct-exchange techniques. The preferred treatment approach is a delayed reconstructive treatment technique (two-stage) using high dose antibiotic loaded cement spacers to provide local delivery of antibiotics between resection and reimplantation. The use of local antibiotic delivery systems has clearly enhanced the success of treatment protocols. Currently, a carefully performed two-stage approach results in a success rate exceeding 90 percent.

Unfortunately, there are many variables affecting the ultimate success of treatment attempts. The importance of many of these variables has been poorly quantified particularly when these variables co-exist in a given clinical setting. Future directions include refinement of staging systems for more accurate stratification of risk factors to help predict patient outcome with various treatment options, improved of imaging studies and genetic detection technology for diagnosis, improvement in antibiotics resulting in more oral treatment and less intravenous therapy, and technological advances in local antibiotic delivery systems.

Recurrent Dislocation:

Large Heads vs. Constrained Cups: Pros vs. Cons

Total hip arthroplasty both primary and revision continue to improve, loosening rates have fallen and the advent of new bearing surfaces should translate into longer lasting replacements. However, complications still trouble the arthroplasty surgeon, especially dislocation. The causes of instability include mal-positioned components, impingement of either component on component or on fixed obstructions such as heterotopic bone, greater trochanteric migration and osteophytes. In addition the absence of or severe weakness of the abductors can result in recurrent dislocation. Furthermore, neurological conditions such as Parkinson’s disease or dementia are associated with a higher risk of dislocation. Finally there are patients whose causes remain unknown, the so-called enigmatic dislocator.

Surgical management of recurrent dislocation is not 100% successful, even when the etiology is known. Recently, two approaches to this problem have surfaced the use of constrained components and the employment of large diameter heads. Although, nether approach is new, improvements in both make them a viable option in the treatment of this complication. Both approaches have their pros and cons.

Constrained acetabular components have greatly improved since the reporting of Lombardi and Anderson. Recent reports of sizable series followed out 10 years have a recurrent dislocation rate of between three and four percent, (Goetz, et al, Shapiro, et al) and this is one of the pros to using a constrained component- literature support of their durability. They also address a variety of causes of recurrent dislocation, they are easy to use, provide a functional range of motion and can accommodate mono-block stems with fixed heads of a variety of diameters.

However, results are design dependent and failure requires reoperation. They will not overcome mal-positioned components and some have suggested limiting their use to components of 62mm or less. Because of the multiple bearing surfaces associated with successful designs there is a concern of increased polyethylene wear. Although the insert can be cemented into a variety of shells, dedicated components are recommended.

Large diameter heads are not new; bipolars have been used in the treatment of recurrent dislocations with varying results. With the introduction of the improved polyethylenes, it is thought that thinner liners can be used and hence larger diameter heads (>32mm). Theoretically large heads provide increased range of motion before impingement and have a greater resistance to dislocation once impingement occurs. Another advantage is that many manufacturers are now providing large diameter heads. The also may enhance capsular stability and finally another plus is that redislocation may be treated closed.

On the downside is the lack of substantial literature support of their use in treating recurrent dislocation. There is a risk of component failure with the use of thin polyethylene liners. They may not address component mal-positioning and it is unclear if the will stabilize hips whose cause of dislocation is muscle imbalance. In summary, constrained components have literature support for their use but there are limitations to their utility. Large diameter heads theoretically will improve stability and certainly seem ideal in treating those cases of instability where component on component impingement is the cause.

Periprosthetic Femur Fractures: Emerging Treatment Methods

Periprosthetic femur fractures that occur in the anatomic region around the femoral stem (Vancouver Type B fractures) usually are treated operatively, and present challenging treatment problems. New information and techniques have furthered management of these fractures.

Fractures at the tip of a well-fixed stem (Vancouver B1) usually can be treated with prosthetic retention and internal fixation of the fracture. The greatest historic problem of this treatment method is nonunion related to the high stress location and limited fixation options. The author prefers fixation with a lateral cable plate and an anterior cortical strut graft in most cases. A recent report demonstrated healing of 39 of 40 Vancouver B1 fractures treated with ORIF that included use of a strut graft.¹

Fractures around a loose stem (Vancouver B2) usually are treated with revision. The greatest historical problems have been implant loosening and fracture nonunion. A new study demonstrated fracture healing and stable implant fixation at two years or more in 24 of 30 hips revised with an uncemented extensively porous coated stem.²

Fractures around a loose stem associated with non-supportive, unreconstructable proximal bone (Vancouver B3) traditionally have been treated with allograft prosthetic composites or tumor prostheses. A new strategy, employing distally fixed tapered fluted uncemented stems coupled with retention of all proximal bone fragments with their vascularity intact has been developed. In a small series of patients this new strategy led to robust new proximal formation due to a fracture healing response, and stable implant fixation related to the ability of such stems to gain axial and rotational stability distal to severely damaged proximal bone.

1. Haddad, F.S.; Duncan, C.P.; Berry, D.J.; Lewallen, D.G.; Gross, A.E.; Chandler, H.P.: Periprosthetic femoral fractures around well-fixed implants: Use of cortical onlay allografts with or without a plate. J Bone Joint Surg 84A:945-950, 2002.

2. Springer, B.D.; Berry, D.J.; Lewallen, D.G.: Femoral revision to treat periprosthetic hip fractures following total hip arthroplasty. (Submitted J Bone Joint Surg Sept 2002)

Persistent postoperative thigh pain in patients who have had total hip replacement can be both a difficult diagnostic and treatment problem. More attention has been drawn to postoperative thigh pain with the usage of various types of cementless hip replacements, which seem as a group to cause more thigh pain than cemented hip replacements.

Thigh pain can be caused by multiple etiologies including a mechanically loose stem, stress concentration at the tip of a well-fixed stem overloading the bone locally, back problems with referred pain to the thigh, trochanteric bursitis with referred lateral thigh pain, prosthetic infection, meralgia paresthetica and other causes of soft tissue inflammation such as that caused by stretching when the extremity has been lengthened. Differentiation of thigh pain due to fixation problems from the other etiologies is aided by considering factors such as severity, location, character, persistence and association with certain activities. Diagnosis is also aided by diagnostic testing such as serial plain radiographs, bone scans, CAT scans, aspiration, and local anesthetic injections.

Fixation problems causing thigh pain can be due to simply a loose stem causing pain from the mechanical movement of the stem within the femur. Persistent thigh pain, after non-fixation problems have been ruled out, must be considered as due to a loose stem until proven otherwise. Thigh pain from a mechanically loose stem is usually activity related, has start-up characteristics, occurs often rolling over in bed, is usually in the anterior or lateral thigh, causes shortening and external rotation of the extremity as the prosthesis subsides, is associated with a Trendelenburg lurching type of gait which is worse with the first step, and generally the symptomatology gets worse with time. Serial plain radiographs are particularly useful to detect sometimes-subtle stem movement. Any movement detected between the earliest film and the latest almost always means a loose stem. Other radiographic signs such as stress shielding, bone hypertrophy under a prosthetic collar, pedestal formation, radiodense and radiolucent peri-prosthetic lines, etc. also can help make the diagnosis of a mechanically loose stem.

Cementless stems that are biologically fixed with bony ingrowth or ongrowth can cause postoperative thigh pain. This pain probably is the result of stress concentration at the stem tip, which overloads the femoral bone at the stem tip. This type of thigh pain occurs in association with large stiff prostheses and osteoporotic femurs. In fact, thigh pain in cemented stems is also more common in osteoporotic femurs. Strut allografting to treat persistent thigh pain in a patient with a well-fixed cementless stem has had mixed results.

Avoiding Complications in Hip Arthroscopy

Joseph C. McCarthy, M.D.

Arthroscopy of the hip, while more recently developed than the knee or the shoulder, has greatly increased our understanding of cartilage pathology and early hip disease. It is an evolving procedure with its own unique anatomical constraints, technical considerations and complications. When faced with a loose body or labral tear, the surgeon must choose between open arthrotomy and arthroscopy. Comparing known complication rates of open versus arthroscopy (the author’s experience of >1500 cases):

	Arthroscopy	Arthrotomy
Infection	0.5%	0%
D.V.T.	10-24%	0.05%
P.E.	1-2%	0%
Avascular necrosis	2-5%	0%
Permanent NV injury	1-2%	0%
Heterotopic bone	8-15%	0%
Trochanteric nonunion/ muscle weakness	5-19%	0%

While recognizing these differences, arthroscopy has its own group of problems. These complications can be described as permanent or transient. Although described in the literature, the author has had no sciatic or femoral palsy, A.V.N., compartment syndrome, broken instruments, P.E. or death. Less than 2% of patients have experienced transient peroneal or pudendal nerve effects. Two patients with meralgia parasthetica resolved within 2 weeks. Mild chondral scuffing occurred in 1% of patients. All of the above have been associated with difficult or protracted distraction.

Relative contraindications include morbid obesity, sepsis, Stage 3 or 4 osteonecrosis, moderate dysplasia and synovitis in the absence of mechanical symptoms. Joint ankylosis, dense heterotopic bone formation, or considerable protrusio limit potential for hip distraction. In the author’s opinion advanced osteoarthritis is contraindicated.

Avoiding complications involves achieving sufficient distraction (7-10mm), dedicated hip instruments, and precise surgical skills. Judicious patient selection includes only those patients with mechanical symptoms (catching, locking or buckling) that have failed conservative therapy. Positive exam findings include: McCarthy sign (with both hips fully flexed, pain is reproduced by extending the affected hip, first in external rotation, then in internal rotation), inguinal pain with flexion, adduction and internal rotation, and inguinal pain with resisted straight leg-raising. McCarthy et al. demonstrated 78% accuracy for anterior labral tears with gadolinium enhanced MRI, but not as reliable detecting chondral defects or nonossified loose bodies. Hip arthroscopy involves a high learning curve. Visiting high volume centers, attending instructional courses, and practicing in bioskills laboratories contribute to becoming technically proficient. Meticulous attention to positioning, distraction time and portal placement are essential. Complication rates are reported between .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.

1. Byrd JW: Hip arthroscopy utilizing the supine position. Arthroscopy 10:275-80., 1994.

2. Byrd JW: Labral lesions: An elusive source of hip pain case reports and literature review. Arthroscopy 12:603-12,1996.

4. Byrd JW: Hip arthroscopy. The supine position. Clin Sports Med 20:703-31.,2001.

5. Byrd JW, Jones KS: Prospective analysis of hip arthroscopy with 2-year follow-up. Arthroscopy 16:578-87.,2000.

6. Byrd JW, Pappas JN, Pedley MJ: Hip arthroscopy: An anatomic study of portal placement and relationship to the extra-articular structures [see comments]. Arthroscopy 11:418-23,1995.

7. Dienst M, Seil R, Godde S, et al.: Effects of traction, distension, and joint position on distraction of the hip joint: An experimental study in cadavers. Arthroscopy 18:865-71.,2002.

8. Dorfmann H, Boyer T: Arthroscopy of the hip: 12 years of experience. Arthroscopy 15:67-72,1999.

9. Eriksson E, Arvidsson I, Arvidsson H: Diagnostic and operative arthroscopy of the hip.Orthopedics 9:169-76,1986.

10. Farjo LA, Glick JM, Sampson TG: Hip arthroscopy for acetabular labral tears. Arthroscopy 15:132-7.,1999.

11. Glick JM: Hip arthroscopy using the lateral approach. Instr Course Lect 37:223-31,1988.

12. Glick JM: Hip arthroscopy. The lateral approach. Clin Sports Med 20:733-47.,2001.

13. Griffin DR, Villar RN: Complications of arthroscopy of the hip.J Bone Joint Surg Br 81:604-6,1999.

14. McCarthy J, Day B, Busconi B: Hip Arthroscopy: Applications and Technique.J Am Acad Orthop Surg 3:115-122,1995.

15. McCarthy J, Marchetti M, Newberg A, Palmer W, Bono J. Improving Diagnostic Accuracy of Chondral Injuries: Correlation of Gadolinium MR Imaging with Arthroscopic Surgery, AAOS, New Orleans, 1998.

16. McCarthy JC, Noble PC, Schuck MR, Wright J, Lee J: The Otto E. Aufranc Award: The role of labral lesions to development of early degenerative hip disease. Clin Orthop :25-37.,2001.

17. Sampson TG: Complications of hip arthroscopy. Clin Sports Med 20:831-5.,2001.

18. Sweeney HJ: Arthroscopy of the hip. Anatomy and portals. Clin Sports Med 20:697-702.,2001.

The Dysplastic Femur: 3D Morphology and Implications For Total Hip Replacement

Total hip arthroplasty is the treatment of choice for osteoarthritis secondary to congenital dysplasia of the hip (CDH). However, the presentation of the dysplastic femur at surgery is highly variable, making selection of hip prostheses and restoration of joint biomechanics difficult. This study was performed to evaluate the three-dimensional anatomy of the dysplastic femur, in an attempt to relate changes in anatomy to the degree of subluxation of the hip joint and to identify factors complicating hip replacement.

CT scans were obtained from 154 female patients with hip dysplasia and 53 age- and sex-matched controls (average age: 51.7 years (range: 18-82 years)). Forty-three percent of the dysplastic hips were graded as Class I (less than 50% subluxation), 48% as Class II or III (50 to 100% subluxation) and 8% as Class IV (dislocated). Three-dimensional computer models of each individual femur were generated by reconstructing the CT data. Each femur was represented by a set of six 3D “objects” corresponding to the head, neck, greater and lesser trochanters, the femoral cortex and the distal condyles. Geometric parameters were derived to describe the size and shape of each anatomic object and their relative positions and orientations. The medullary canal of each cortical reconstruction was measured using a novel ”virtual gauging” technique . Differences between these parameters were examined as a function of the severity of dysplasia and the age of the patient. The rotational orientation of the medullary canal was also studied from the level of the canal isthmus to the center of the femoral head.

The shape and dimensions of the dysplastic femora differed significantly from the normal controls. Crowe I femora were found to have shorter necks with a smaller and more tapered canal than normal controls. In the Crowe II or III femur, the femoral neck is even shorter and more varus than in Crowe Class I. Femora from congenitally dislocated joints (Crowe Class IV) were hypoplastic, with narrower, straighter canals than the femora of Classes I, II, or III or normal controls. The primary deformity of the dysplastic femur occurs in axial torsion, with a significant reduction in the twist that normally occurs between the femoral neck and the canal isthmus. On average, the dysplastic femora were 5-16 degrees more anteverted than the normal controls, independent of the degree of subluxation of the hip.

This study demonstrates that there is a significant difference in the geometry of the normal and CDH femora, even in cases of mild dysplasia. Our observations confirm that the dysplastic femur presents unique challenges to the joint replacement surgeon because of the abnormal rotational deformity of the medullary canal and a significant incidence of excessive anteversion. An additional factor is the high incidence of abnormally bowed canals in mildly dysplastic cases, and straight hypoplastic canals secondary to congenital dislocation. In view of these challenges, the authors recommend the use of short anatomic stems for simple cases and modular components where rotational correction is necessary. Cement fixation is reserved for osteoporotic femora with medullary canals of sufficient size to allow formation of an adequate cement mantle.

Robert L. Barrack, M.D., Stephen D. Cook, Ph.D., Samantha L. Salkeld, M.S.E.,

Laura P. Patrón, B.S.E., Edward Szuszczewicz, M.D. and Thomas S. Whitecloud, M.D.

Reliable ingrowth of bone into cementless porous coated total hip components can be expected in primary surgery. In the revision scenario, however, bone deficiency is frequently encountered and the remaining bone may have less ingrowth potential. Allograft bone and bone graft substitutes may be successful in healing bone defects, but have virtually no capacity to induce bone growth from the defect into the porous surface. Increasing the reliability and extent of bone ingrowth is critical to long-term success. In order to evaluate the role osteoinductive bone proteins may play in enhancing bone ingrowth, six canines underwent bilateral total hip arthroplasty with a cementless press-fit porous coated acetabular component. A defect 8 mm in diameter and 5 mm in depth was created in the superior weight-bearing area of each acetabulum. One defect in each animal was filled with recombinant human osteogenic protein-1 (rhOP-1). Each contralateral defect was filled either with allograft bone, left empty (defect healing control), or no defect was created (intact) to serve as a control for ideal conditions for bone ingrowth.

The osteogenic protein treated defects healed more completely than allograft bone treated or empty defects and achieved a bone density equivalent to the intact acetabulum. Bone ingrowth also occurred to a significantly higher degree in the osteogenic protein group compared to the allograft or empty defects achieving a degree of ingrowth equivalent to the intact acetabulum controls. The osteogenic bone protein was successful in achieving both complete defect healing and inducing extensive ingrowth from the defect into the adjacent porous coating. These proteins may be expected to be an important adjunct to bone grafting in reconstructive surgery of the hip.

Charles R. Bragdon, B.S., Arin M. Doherty, B.S., Harry E. Rubash, M.D., Murali Jasty, M.D.,

X. Jian Li, M.D., Howard Seeherman, Ph.D., V.M.D. and William H. Harris, M.D.

The effect of recombinant human bone morphogenic protein to induce bone ingrowth across gap and non-gap regions in a porous acetabular component and in non-gap regions of porous femoral components was examined using a canine total hip replacement model. The ingrowth regions of both components, as well as the acetabular defect, were filled with rhBMP-2/αBSM in five dogs and αBSM in five dogs. Five dogs served as untreated surgical controls. At 12 weeks, SEM evaluation indicated the acetabular defects persisted in the surgical control group with little bone ingrowth in the acetabular component underlying the defect. Partial bone bridging of the defect and bone ingrowth into the acetabular component underlying the defect was noted in three of the five BSM dogs. In contrast the defects were bridged and bone ingrowth was observed in the acetabular components underlying the defect in all 5 dogs in the BMP/BSM group. This study demonstrates rhBMP-2/αBSM promotes consistent bone bridging of 2 mm periprosthetic acetabular gaps and bone ingrowth into the porous coating at the gap region, both of great value to the future of total joint replacement.

The Frank Stinchfield Award

This study reports the outcome of total hip arthroplasty in a cohort of patients with complete long-term radiographic and clinical follow-up information from our database of over 58,000 hip replacements. The purpose of the study was to evaluate the influence of demographic factors and patient comorbidity (Charnley Classification) on long-term outcome of total hip arthroplasty.

This cohort comprised of 24,889 total hip replacements in 9,801 male and 11,144 female patients with a mean age of 64.9 years (range, 22 to 97 years) at the time of arthroplasty.

This study confirms that the total hip arthroplasty has an impressive efficiency and reliability in alleviating pain and improving function for almost all the patients. Furthermore, the results are enduring with over 85% of patients being satisfied with the outcome at 15 years. Clinical outcome measures reach a maximum at two to five years post-arthroplasty and thereafter they decline gradually over the ensuing years. The decline in outcome over years could be attributed to the process of aging, increase in the incidence of mechanical problems with the arthroplasty and the development of arthropathy affecting other joints over time. Furthermore, patients with single joint involvement preoperatively (Charnley A) demonstrated the most striking gains in Harris Hip Score following the arthroplasty. Subanalysis of outcome demonstrated that patients with bilateral hip arthritis (Charnley B) or those with other coexistent conditions (Charnley C), despite having comparatively lower Harris Hip Scores, were equally satisfied and had comparatively less decline in function over the decade that followed maximum improvement after total hip arthroplasty.

Uncemented Cups in Revision THA:

How Far Can We Push the Indications?

Uncemented acetabular components have emerged as the workhorse method for revision of a failed socket. Ten-year results for uncemented components are available and show a considerable improvement over cemented sockets in the revision setting. (Leopold SS et al: Cementless acetabular revision. Evaluation at an average of 10.5 years. Clin Orthop 1999 369:179-186) These predictable results, and the versatility and ease of insertion of uncemented cups, have made them the preferred choice for over 90% of revisions. But some limitations of the method exist. Review of all 2,443 uncemented sockets placed during revision THA at our institution over a 15-year period has documented a non-linear survivorship for all 6 designs used, with increasing failures as patients enter the second decade post surgery. Overall cup survivorship was less than 80 % by 12 to 15 yrs postop. (Lewallen DG et al : Survivorship of Uncemented Acetabular Components after THA. Proceedings of the 69^th Annual Meeting of AAOS 3:637, 2002) Most at risk for failure by migration or loosening are those cases with severe acetabular bone deficiency or impaired bone quality where bone ingrowth has likely never occurred. Alternative methods are available and under development for the management of the rapidly increasing numbers of such cases. The limitations of structural allografts when critical mechanical support is needed are now better appreciated. Use of anti-protrusio cages for protection of such grafts and spanning of major defects is currently recommended, but an increase in failures of these purely mechanical reconstructions has also been seen. Such problems make improved biologic fixation by newer porous materials, implant coatings or bioactive substances worthy research topics. Oblong or bilobed implants with their advantages and problems have stimulated development of custom and more recently modular acetabular systems to allow for maximal mechanical support for the implant construct on viable host bone to aid bone ingrowth. Long-term follow-up data are needed to allow for the appropriate use of these alternatives in achieving more durable results in these challenging cases.

Osteolysis in association with well-fixed cementless acetabular components is now a well-recognized complication associated with these implants. Unlike cemented sockets in which significant osteolysis is associated with implant loosening, cementless cups may remain osteointegrated and asymptomatic despite the presence of large osteolytic lesions. The surgeon addressing this problem has two options: revision with removal of a well-fixed socket or bearing exchange with debridement and grafting of the osteolytic lesion. Bearing exchange with debridement and grafting of the osteolytic defect are the procedure of choice provided there is sufficient area of osteointegration and provide long-term stability. Relative contraindications for bearing exchange include malpositioned socket, severely damaged shell, a socket in which a liner is not available and one cannot be satisfactorily cemented in place, and a cup with poor track record. At a minimum of five year follow-up, up to eleven years, none of the sockets that underwent liner exchange had come loose or required revision surgery. However, the dislocation rate following this procedure in the absence of femoral revision was high.

For those cases requiring removal of a well-fixed socket, the surgeon must be prepared to deal with significant bone loss. Removing a well-fixed socket can lead to medial wall defects, column defects and pelvic discontinuities. The surgeon has to be prepared to deal with such complication should they occur and should have available in the operating room the appropriate bulk graft, pelvic reconstruction plates and implants including cages.

Impaction Grafting in Femoral Revision

Introduction

Both favorable and less favorable midterm results have been reported with the technique of impaction grafting for femoral revision. For the past decade we have reserved this technique for patients with marked proximal femoral cavitary bone deficiency associated with a canal or size geometry that would render them less suitable for other femoral revision methods. We are reporting here our results of the first group of patients treated in this manner.

Materials

Between 1993 and 1997, of 404 consecutive femoral revisions, impaction grafting with particulate fresh frozen cancellous allograft was utilized in 57 (14%). All had severe AAOS cavitary or combined cavitary and segmental proximal femoral bone loss or Paprosky types III or IV bone loss. There were 24 males and 30 females (3 had bilateral procedures) with a mean age of 62.7 years (range 36 to 79). All were revised with impacted particulate fresh frozen cancellous allograft and a cemented collarless polished tapered (CPT) stem. Strut allografts were used for femoral reinforcement in 40 hips. Patients were followed 3 to 9.3 years (mean 6.3 years). No patient was lost to follow-up.

Results

Preoperatively 46 patients had moderate or severe pain. At the time of last follow-up two patients had moderate pain, 14 had mild pain, and 36 had no pain. One patient developed an infection and his prosthesis was removed after 18 months. Three patients had died of causes unrelated to the hip. Radiographic evaluation showed no evidence of loosening in any of the 52 surviving hips. Subsidence of 4 to 6 mm occurred in two hips, of 1 to 3 mm in 40. Cancellous bone graft remodeling was observed in 42.

Complications included the above mentioned infection in one hip, instability in three (two required socket revision, one was late, related to decreased myofascial tension and has not required surgical management), intraoperative femur fracture in four, one partial sciatic palsy which recovered and six postoperative femoral fracture (all located at the level of the distal end of the prosthesis, not associated with prosthetic loosening and all treated successfully with ORIF without prosthetic revision).

Discussion

We have continued to reserve impaction grafting for femoral revision in patients with severe cavitary bone loss. In this selected group of patients the good clinical and radiographic results reported earlier after three years have remained very satisfactory after six years of follow-up. We believe that careful attention to technical details (with meticulous and vigorous cancellous bone impaction) may explain the excellent radiographic results and the limited subsidence observed. However, even with generous use of strut graft augmentation, postoperative femoral fracture remained our most serious complication. This, however, did not appear to jeopardize prosthetic fixation. It remains to be seen whether the use of long stem prosthesis may help reduce the incidence of this disturbing complication.

Fully Coated Stems: What Are The Limits?

Background: Fully porous coated femoral implants have become the standard prosthesis to be utilized during the majority of revision femoral surgery due to the poor long-term results of revision cemented femoral stems. However, there are specific surgical situations where a fully porous coated stem may not provide reliable long-term results and the use of such components is relatively contraindicated. Previous studies have demonstrated a 21% failure rate for Paprosky type IIIB femoral defects when utilizing an 8 or 7 inch calcar fully coated stem. As a result, larger and longer fully porous coated implants, bone packing and modular Wagner type tapered stems have been placed in an attempt to provide improved component survival.

Materials and Methods: All patients that had a femoral revision utilizing either a 10 inch or 9 inch calcar fully porous coated stem, a modular Wagner type prosthesis or impaction bone grafting between 1991 and 2001 were identified through the hospital surgical database using CPT codes for revision surgery. Patients were examined yearly with clinical and radiographic evaluation. Radiographs were reviewed to assess femoral component stability and the need for revision.

Results: At an average follow-up of 4.2 years, 71 patients had undergone femoral revision. 17 patients with Paprosky type IIIA, 26 patients with type IIIB and 8 patients with type IV defects were treated with either a 10 inch or 9 inch calcar fully porous coated stem, 10 patients with type IV defects were treated with impaction bone grafting, 7 patients with type IIIB defects and 3 patients with type IV defects were treated with a modular Wagner type tapered stem. At the time of follow-up, 9 patients required revision, 2 bone packing (2 for instability), 6 fully coated stems (3 for infection, 2 for instability, 1 aseptic loosening) and 1 modular Wagner stem (aseptic loosening). Three additional fully coated stems were radiographically loose.

Conclusions: Patients with Paprosky type IIIB and IV femoral defects are not amendable to standard fixation with an 8” fully porous coated stem due to the high failure rate. Patients with type IIIB defects and a femoral canal less than 19 mm can be treated successfully with either a 10” or 9” calcar fully porous coated stem. While patients with IIIB defects and an endosteal canal greater than 19 mm or a type IV defect require a modular Wagner type stem or bone packing procedure.

Revision THA: Modular Fluted Tapered Stems

While popular in Europe for many years, tapered revision stems have only recently been utilized in America. The original Wagner stem was implemented for severe femoral bone defects where proximal bone quality mandated distal fixation. Subsidence, and dislocation related to poor offset, limited its popularity in America. Newer modular tapered stems have recently been introduced (Link, T3, ZMR) in an attempt to address these shortcomings. Only short-term follow-up gleaned from several centers using modular components is available. One study compared 60 Wagner stems followed for 4-9 years to 22 modular stems followed for 1-4 years. Subsidence > 5 mms occurred in 23% of Wagner stems but in none of the modular stems. Positive bone remodeling occurred in 85% of cases in each group. No aseptic loosening occurred. Another study followed 40 modular stems for a minimum of 2 years. Subsidence of 10 mms occurred in 2 patients, but in each case subsequently stabilized and no revisions were required for aseptic loosening. The author has experience with 95 modular tapered revision stems over the past 2 years. There were 48 men and 47 women with a mean age of 67 and a mean weight of 171 lbs. Paprosky bone damage was Type 1 in 16, Type 2 in 25, Type 3 in 42, and Type 4 in 12. Three patients required revision for stem loosening. Subsidence continued to occur with >10mms in 15%. Subsidence occurred in 71% of patients with Type 4 preoperative bone defects. Transfemoral osteotomy (aka extended trochanteric osteotomy) may be integral in achieving satisfactory clinical results – a higher incidence of positive bone remodeling appears to occur when this technique is employed. Subsidence can be minimized through alterations in surgical technique. Modular tapered stems improve upon the clinical results of the original non-modular design. Severe Type 4 bone defects continue to present difficulties even with the modular designs.

Various treatment modalities are being used for the management of osteonecrosis of the femoral head in order to prevent or delay the need for total hip arthroplasty. This talk will review the results of nonvascularized bone grafting through a window at the femoral head-neck junction (light-bulb procedure). Nineteen patients (20 hips) were followed for a mean of 31.4 months (range 25 to 40 months) after a nonvascularized bone grafting procedure in which diseased bone was replaced with a bone graft substitute (combination of demineralized bone matrix, processed allograft bone chips, and a thermoplastic carrier matrix). Seven Ficat Stage II and thirteen Stage III hips were enrolled in the study. Clinical success was defined as a Harris Hip score greater than 80 points and radiographic success included evidence of graft healing and no head collapse. Seventeen out of twenty hips (85%) were clinically successful at 31.4 months (range, 25 to 40 months). Three patients required revision: one for a femoral neck fracture two weeks postoperatively, possibly, because of non-compliance with weight bearing instructions, the second and third were revised at a mean of 25 months for persistent groin pain. Of the seventeen clinical successes, two have shown minimal radiographic progression of disease (less than two millimeter collapse). This bone grafting procedure may be effective in avoiding or delaying the need for total hip arthroplasty in patients with osteonecrosis.

Bone Impaction Grafting As Treatment For

Osteonecrosis of theFemoral Head

A Prospective Single Surgeon Study Of 28 Hips In 27 Patients

Prof. Jean W.M. Gardeniers, Wim H.C. Rijnen, Tom J.J.H. Slooff and B. Willem Schreurs

Even in extensive osteonecrosis of the femoral head, in younger patients a femoral head preserving method is preferable. After a core biopsy and removal of the osteonecrotic area impacted morsellized bone allografts were used to fill the head, regain sphericity and prevent a collapse.

In this single surgeon study we included 28 consecutive hips of 27 patients with extensive osteonecrotic lesions (ARCO classification stage 2 (11 hips), 3 (14 hips) and stage 4 (3 hips)), 14 hips had a pre-operative collapse. The mean age of the patients was 33 years (15-55). At a mean follow up time of 42 months (24-119 months) 8 hips. Of the 20 reconstructions who were in situ, 18 were clinically successful (64%) and 54% were radiologically successful. Patients who were under 30 years at surgery had a significantly better outcome, even in higher stages. Patients with a pre-operative collapse and use of corticosteroids had disappointing results. This method is attractive as a salvage procedure, is relatively simple, quick and it does not intervene with an eventual future hip arthroplasty.

3:36 p.m.

Femoral Head Resurfacing for the Treatment of

Osteonecrosis in the Young Patient

Surgical treatment for osteonecrosis of the femoral head in a young patient remains a controversial subject. We reviewed the clinical and radiographic results of twenty-nine consecutive femoral head resurfacing procedures in twenty-eight patients performed from February 1997 through to October 2000. There were 18 males and 10 females with an average age of 31.6 years (range, 12 to 48). The average follow up was just under 3 years (range, 2 to 5.2 years). There were three patients with Ficat and Arlet stage II osteonecrosis, 25 with stage III, and one with early stage IV disease. The average Harris Hip score significantly improved from 48.1 preoperatively to 79.3 at last follow up. Preoperatively, all patients had a Harris hip score of poor. Postoperatively, twelve hips (42.8 percent) had an excellent or good result. Seventeen patients (62.5 percent) reported feeling much better or better than they did prior to hemiresurfacing at final follow up. There were three postoperative complications: one patient with a persistent wound drainage that resolved uneventfully, one dislocation that was treated with closed reduction, and one implant that fractured which was revised to a total hip arthroplasty. The overall survivorship was 76.7% at three years. Eight hips (29.6 percent) were converted to a total hip arthroplasty at an average 1.4 years (range, 0.6 to 3.6 years) post resurfacing. The results of this study suggest that femoral head resurfacing in a young patient with osteonecrosis can greatly improve symptoms at the intermediate follow up. The majority of patients were satisfied with the procedure but pain relief is unpredictable with only 62.5% reporting satisfaction and good pain relief. We continue to offer this procedure in young patients with large necrotic lesions with the understanding that this procedure provides less reliable pain relief than a total hip arthroplasty; however, hemiresurfacing avoids the negatives associated with a bearing surface.

Laurent Sedel, M.D.

Introduction

Alumina on alumina total hip were designed to reduce debris diseases and osteolytic lesions; As osteonecrosis was suspected to increase osteolytic lesions, we looked at our long term experience.

Fifty-two hips were consecutively operated from 1977 to 1990 with all ceramic bearings in 41 patients. Twenty-two in men and 19 in women. Ages were from 22 to 79 (mean 41±13,2). Thirteen patients had bilateral procedures. Twenty-nine were performed primarily, while 23 had some previous surgery excluding total hip revision ie cup arthroplasty, core decompression, ORIF for fracture of the pelvis or the femoral neck. The stem was made of titanium alloy, smooth collared and cemented with always the largest stem to fit the medullary canal; the head was of 32 mm in diameter secured on the cone via a Morse taper. The socket was plain alumina 39 times cemented and 13 times cementless.

No patient was lost. Twenty-seven hips in 22 patients were reviewed at a follow up of 11 to 23 years (mean 16±3,87). Eight patients (9 hips had died) and 16 hips in twelve patients had revision at a mean of 11±4 years. Two hips were revised for deep infection including one in an immunodepressed woman who developed a deep infection 2,7 years after the index operation. From the 14 aseptic loosening 13 were related to socket loosening (10 in cemented and 3 in cementless fixation). For nine of them only the socket was exchanged while in 5 the stem was exchanged as well even if it was not loosened. .

Clinical results in the 22 patients alive and followed (27 hips) regarding Postel and Merle d’Aubigné rating system was 17,8 (maximum 18): Radiographic results: no osteolysis, at the socket: 21 had no radio lucent lines, 5 had limited radio lucent lines and one had a complete radio lucent lines; At the stem level no radio lucent line, no osteolysis, 9 experienced limited (1 to 3 mm) calcar resorption. Survivorship regarding revision for aseptic loosening of the socket depicted 88.5% at 10 years and 70,07 at 15 years. At the stem level: the figures are 100% at ten years and 96.7 at 15 years.

Discussion Conclusion

Although fair, these results confirmed previously reported results with number of failure of cemented bulky alumina components; they confirmed as well the effect on osteolysis and the excellent results at the stem level. New ways of socket fixation might decrease these complications.

Extended Osteotomy With An Anterior Approach

Steven J. MacDonald, M.D., F.R.C.S.C. and Richard W. McCalden, M.D., F.R.C.S.C.

The use of an extended trochanteric osteotomy combined with an extensively porous coated cementless femoral component has greatly simplified revision total hip arthroplasty. Unfortunately, when an extended trochanteric osteotomy is performed through the posterior approach, dislocation is not an infrequent post-operative complication. In order to avoid dislocation, we have developed an extended trochanteric osteotomy, which can be performed through an extensile direct lateral approach to the hip. In this procedure, the lateral one third of the proximal femur is opened like a book, hinged on the linea aspera. The advantages of this approach are that the osteotomized fragment is better vascularized and the risk of post-operative dislocation is minimized. We prefer to secure the osteotomy with cables. Post-operative management for an extended trochanteric osteotomy through either the direct lateral or posterior approaches are similar.

We have utilized the extended trochanteric osteotomy through a direct lateral approach in 45 patients with more than 2 years follow-up. The most common indications were facilitation of distal cement removal (25) and correction of proximal femoral varus remodeling (14). Cable fixation was superior to wire fixation. The osteotomies all went on to union at a mean time of 10 months. The prevalence of limp and the need for walking aids is similar to other exposures used in revision total hip arthroplasty.

Since 1991, we have used an extended trochanteric slide osteotomy. The osteotomy is only used with the posterior approach and with extensively porous-coated femoral components designed for distal fixation. The primary indication is distal femoral exposure, usually to remove cement plugs or correct deformity^1-3. We have extended the indications to include difficult acetabular cases and cases that require trochanteric advancement. The main advantage of the technique is that the vastus lateralis and the gleuteus medius are kept in continuity, decreasing the chances of trochanteric escape. Another advantage is that the large fragment of trochanter improves trochanteric fixation and decreases the trochanteric nonunion rate. The main disadvantage is that the large osteotomy fragment makes proximal cementless fixation more difficult or impossible.

We published the results of our first 46 osteotomies, which were done between 1991 and 1996. Two hips had an isolated acetabular revision, 15 had an isolated femoral revision, and 29 had both components revised¹. The osteotomy union rate was 98%. There were two fractures of the osteotomy; neither escaped proximally. The mean osteotomy length was 12 cm (range, 7-19 cm). The stem bypassed the osteotomy a mean of 14 cm (range, 5-22 cm). The osteotomy was repaired with 2-3 cables (range, 2-5). Currently we have done 96 extended osteotomies. Eighty three percent of these involved the femoral component.

Video segments of several cases illustrate the osteotomy technique and variations. The first step is a basic posterior exposure. The abductors are identified, followed by the capsulectomy and hip dislocation. The second step is the actual osteotomy, which can be done before or after the femoral component is removed. The third step is a soft tissue release of the trochanteric fragment and the proximal femur. The fourth step is femoral preparation. This involves removal of cement, neocortex, and the bony pedistal followed by femoral reaming and stem insertion. The last step is trochanteric repair with two or more cables.

1. Chen, W. M.; McAuley, J. P.; Engh, C. A., Jr.; Hopper, R. H., Jr.; and Engh, C. A.: Extended slide trochanteric osteotomy for revision total hip arthroplasty. J Bone Joint Surg Am, 82(9): 1215-9, 2000

2. Miner, T. M.; Momberger, N. G.; Chong, D.; and Paprosky, W. L.: The extended trochanteric osteotomy in revision hip arthroplasty: a critical review of 166 cases at mean 3-year, 9-month follow-up. J Arthroplasty, 16(8 Suppl 1): 188-94, 2001.

3. Younger, T. I.; Bradford, M. S.; Magnus, R. E.; and Paprosky, W. G.: Extended proximal femoral osteotomy. A new technique for femoral revision arthroplasty. J Arthroplasty, 10(3): 329-38, 1995.

The Removal of Well-Fixed Cementless Femoral Components

Cementless femoral components remain popular for primary and revision total hip arthroplasty. Inevitably, certain components will require removal for reasons other than fixation failure. The most obvious example is late hematogenous infection. Other reasons include component malposition resulting in recurrent dislocation or excessive leg lengthening, osteolysis, periprosthetic fracture, persistent thigh pain, and, occasionally, in order to accommodate cup revision. The keys to success include careful pre-operative planning, adequate exposure, proper instrumentation and technique, and finally, patience.

One must first be able to recognize the radiographic signs of bone ingrowth/ ongrowth and appreciate that their presence dictates that special techniques will be required for implant removal. The implant design and manufacturer should be identified to assure an awareness of the location and extent of the ingrowth/ ongrowth surface, and to avail oneself of any implant specific extraction devices. An exposure should be chosen which not only provides access to the bone-implant interface but also facilitates reimplantation, if indicated at the time of removal. Dedicated instruments, designed specifically for removing cementless implants are essential. The removal techniques to be described have proven both safe and effective. Patience is key; one should never resort to excessive force for implant removal.

In most cases, an extended trochanteric osteotomy is advised. This affords excellent exposure of the proximal bone-implant interfaces anteriorly, posteriorly, and laterally. These interfaces are divided using small oscillating saws, high-speed burrs, or thin osteotomes. The proximal-medial interface is divided with a Gigli saw looped around the implant and drawn distally through the osteotomy. Most proximally coated implants can then be removed. After proximal interface division, extensively porous coated implants are transected at the junction between the metaphyseal segment and the distal, cylindrical diaphyseal segment using a tungsten carbide bit on a high-speed cutting instrument. The distal stem is then cored out using an appropriately sized hollow trephine.

Minimally invasive total hip replacement surgery has the potential for minimizing trauma, pain, and recovery. This technique uses one incision for preparation and insertion of the acetabular component and the other for preparation and insertion of the femoral component. Unique instruments have been developed to aid in this challenging technique. Fluoroscopy aids in many steps in this procedure to ensure the proper placement for the incisions and accurate component positioning and alignment.

The first minimally invasive two-incision total hip technique was performed in at Rush Presbyterian St Luke’s hospital two years ago. Since then, more than 300 hundred of these surgeries have been performed in eighteen centers nationally and internationally; over 100 at Rush-Presbyterian-St Luke’s hospital. While the first cases had long operative times, the operative time for last 80 cases was between 80 and 120 minutes. Complications in the first 100 cases at our institution were 1%; one femoral fracture occurred during insertion of a taper stem. The stem was removed and replaced with stem with distal fixation; the incision was not changed or extended. The stem has ingrown and the fracture has healed. No other complications have occurred at our institution. There has been no failure of ingrowth, no dislocations, and no other complications.

This minimally invasive two-incision THA technique has allowed a quicker recovery and a shorter length of stay. In our last eighty cases, all patients have chosen to go home either the day of surgery or the next day. No patient has stayed more than a 23-hour admission. These patients have gone home, not to other care facilities. In these last 80 patients, over 80% have gone hone the same day. There have been no readmissions and no post discharge complications.

Radiographically, since fluoroscopy is used during component preparation and insertion, the overall alignment and fit of the components have been excellent. In the first 70 cases, 94% of the femoral stems were in neutral alignment and the abduction angle for these acetabular components averaged of 45°, (Range 35° to 55°). All components with more than 3-month follow-up have shown ingrowth without migration.

This two incision minimally invasive THA technique continues to show great promise; however, it must be emphasized that this technique is still investigational and continues to be refined. Moreover, this technique is technically extremely challenging and is very different from a standard total hip. The technique should only be attempted with specially designed instruments and proper hands-on training in this difficult surgical technique.

Grafting of Osteolytic Lesions

Osteolysis of the pelvis is a common and well-recognized complication associated with total hip arthroplasty. The diagnosis and treatment of pelvic osteolysis continues to be a challenging and controversial problem. Pelvic osteolysis is often asymptomatic and does not present with symptoms until considerable bone loss and loosening of the acetabular socket occurs. Radiographs are the most common way to detect and monitor osteolysis around an implant. However, lesions viewed radiographically are usually underestimations of the lesions found intra-operatively. Moreover, some advocate computed tomography to evaluate these lesions. The indications for treatment of osteolysis with cemented acetabular components are more clearly defined than with a cementless component. If the cemented or cementless acetabular component is loose, then revision is necessary. However, it is less clear when to intervene surgically with a well-fixed cup with osteolysis. Many early reports advocated the removal of a well-fixed socket during revision surgery for osteolysis and polyethylene wear. However, the removal of a well-fixed socket has the potential for significant damage and loss of the surrounding bone resulting in loss of integrity of a column or pelvic discontinuity which may compromise placing another acetabular component. Recently, a new treatment strategy of retaining a well-fixed socket, exchanging the liner, and grafting lesions has proven successful. Without the removal of the acetabular shell, different techniques are needed to graft the osteolytic lesions. Osteolysis is a difficult problem, however with radiographic surveillance to monitor patients for lesions, proper indications, and good surgical techniques, the treatment of pelvic osteolysis can result in a well functioning total hip arthroplasty.

Cementing A Liner Into A Well-Fixed Shell

Many revision situations require the exchange of a polyethylene liner in the setting of a well-fixed cementless acetabular shell. Unfortunately, a replacement liner is not always available, the locking mechanism of the metal shell may be damaged or incompatible with the desired liner, or the shell is malpositioned. In this setting, cementing a polyethylene liner into the existing shell is an option, although there are no long-term results of this technique.

The stability of the existing shell should be critically assessed. The presence of continuous radiolucent lines or significant osteolytic lesions may preclude the retention of the shell. The surgeon should know the diameter of the existing metal shell, the thickness of the shell (thus the inner diameter), and its geometry (how much of a hemisphere), in order to ensure the proper liner size is available. Bonner et al. have demonstrated the importance of accurately sizing the liner to be cemented, with oversized liners having much lower fixation strengths.

In the OR the surgeon should verify proper liner size, which should be done with trials similar to the final liner. The literature is unclear regarding whether the shell or liner need to be grooved. Circumferential cuts in the shell made with a burr would seem to give more resistance to lever out, although the need for these cuts is lessened if the shell has an inside rim, screw holes, or other surface disruption. There is little data to suggest whether the use of a cementable cup or a liner manufactured for use in cementless cups is preferable. Cement is mixed after liner selection and is inserted into the cup in dough phase. Compress the cement with a bipolar trial ball (6 mm smaller than the selected liner), covered with a surgical glove. The ball should be centralized as much as possible. 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.

Use of Allografts and Cages in a Deficient Acetabulum

Introduction: Fortunately most acetabular revisions can be managed successfully with the use of uncemented porous coated acetabular components. Such biological fixation has provided consistent results when dealing with varying types of acetabular deficiencies. There are circumstances, however, when predictable biologic fixation with this type of device is not possible. Severe combined segmental and cavitary acetabular bone deficiencies may not provide enough native bone contact to assure predictable long-term stability. In this situation, an acetabular reinforcement cage can provide stability to a salvage situation.

Technique: Most reconstructions of this nature require extensile exposure techniques. An anti-protrusio cage with iliac and ischial flanges or a custom triflange cage are the devices of choice for management of these severe acetabular deficiencies. Concomitant plating of a pelvic discontinuity can be performed as necessary.

It is critical to have the cage rest on intact native bone. If this is not possible, structural allografting must be performed. The acetabulum is debrided and cavitary defects are packed tightly with morcellized allograft. The cage is then contoured to fit the remaining native bone. Once contoured the cage is secured first to the ilium with large cancellous screws through the dome. Supplemental transverse screws in the ilium and ischium are then placed.

A socket is then cemented into the cage. Because the cage has a tendency to be more vertical and less anteverted than the optimal acetabular component, it is important to position the socket independent of cage position. Protected weight-bearing is recommended for at least three to six months depending on the degree of deficiency and amount of bone grafting necessary.