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MEETING
OF THE HIP SOCIETY Twenty Seventh
Open Scientific Meeting The
Fifth Combined Open Meeting Hip Society and AAHKS HILTON HOTEL ANAHEIM CALIFORNIA C BALLROOM SUNDAY, FEBRUARY 7, 1999 CONTENTS: COURSE DESCRIPTION: COURSE OBJECTIVE: INTENDED AUDIENCE: 8:00 am SYMPOSIUM I 8:05 am 8:15 am 8:25 am 8:35 am 8:45 am 8:55 am 9:05 am PRESIDENTIAL GUEST SPEAKER 9:20 am SYMPOSIUM II 9:40 am 9:50 am 10:00 am 10:10 am 10:20 am 10:30 am 10:45 am SYMPOSIUM III 11:00 am 11:08 am 11:16 am
11:32 am 11:40 am 11:55 am SYMPOSIUM IV 1:00 pm 1:15 pm 1:30 pm 1:45 pm SYMPOSIUM V 2:00 pm
Acetabular Revision: 2:10 pm 2:18 pm 2:26 pm Femoral Revision: 2:34 pm 2:42 pm 2:50 pm 2:58 pm 3:06 pm 3:35 pm SYMPOSIUM VI 3:50 pm 3:58 pm 4:06 pm 4:14 pm 4:22 pm 4:30 pm 4:38 pm 5:00 pm
MEETING OF THE HIP SOCIETY Twenty-Seventh Open Scientific Meeting 8:05 Sterilization and Packaging of Polyethylene John P. Collier, D.E., Lauren S. Bargmann, M.S., Brian C. Bargmann, M.S., Barbara H. Currier, M.Ch.E. Gamma sterilization in an air environment can induce oxidation of polyethylene. This oxidation potentially can lead to polyethylene embrittlement that compromises mechanical integrity and clinical performance of polyethylene liners and inserts. For these reasons, orthopaedic manufacturers have modified their methods of sterilizing and packaging polyethylene. Information from all major manufacturers suggests that they have moved away from the potentially detrimental use of gamma irradiation in air. Two alternative approaches have emerged: sterilization by non-radiation methods and by gamma irradiation in inert environments. Liners and inserts sterilized using alternative methods were tested to examine material characteristics including oxidation level, mechanical properties, and crosslink density. Data from liners and bearings shelf aged up to 3 years following alternative sterilization techniques (both non-radiation and gamma irradiation in an inert environment) exhibit negligible oxidation, ductility above 400%, and ultimate tensile strength near 50 MPa, all exceeding ASTM specifications. There are significant differences in crosslink density depending on the sterilization method. This study suggests that the shelf oxidation problem has been addressed by these new sterilization techniques. However, long term clinical performance and oxidation resistance must be evaluated in the future.
8:15 Assessment of Polyethylene Wear in Total Hip Replacement A Review of Clinical Applications of the 3-D Technique Peter A. Devane, M.B.Ch.B., F.R.A.C.S., M.Sc., J. Geoffrey Home, M.B.Ch.B., F.R.A.C.S., M.Sc. The 3-D technique is a new method for the measurement of polyethylene wear in patients with total hip joint replacement. Application of image processing technology allows automation of point selection from digital images of radiographs scanned into the computer. Validation of this new methodology reveals a three-fold increase in accuracy and a forty-fold increase in reproducibility compared to manual input of points from a digitizer in the bench test situation. A review of 3-D technique application to clinical patients gives new information on the factors which influence polyethylene wear. Increasing age, activity level and femoral head size, as well as decreasing polyethylene thickness and insertion of total hip prostheses without cement, all increase polyethylene wear. Restoration of femoral offset during total hip replacement appears to decrease polyethylene wear. No demonstrable difference in polyethylene wear rate could be found between two groups of patients, one with a stainless steel-polyethylene articulation and the other with a ceramic-polyethylene articulation. Measurement of the serial polyethylene wear of individual patients reveals a high rate of femoral head penetration during the first two years after total hip replacement using metal-backed acetabular components inserted without cement. Interpretation of this femoral head penetration as true polyethylene wear may be erroneous, however, since creep of the polyethylene and acetabular liner movement within its metal shell cannot be measured. 8:25 The New Polyethylenes Harry A. McKellop, Ph.D. Extensive research has shown that crosslinking of UHMW polyethylene acetabular cups improves their wear resistance. Traditional radiation sterilization in air crosslinks the polyethylene, but also initiates immediate and long-term oxidative degradation of the wear resistance and other physical properties. Consequently, while some manufacturers advocate non-irradiation sterilization (Et-O or gas plasma), others continue to sterilize with gamma radiation to crosslink the polymer, but with the components scaled in a low oxygen packet. While the immediate result is less oxidation, and a lower wear rate than for non-irradiated polyethylene, laboratory tests have shown that the free radicals remaining in the irradiated polyethylene can oxidize over time, substantially increasing the wear rate. To retain the advantages of crosslinking without oxidation, extruded bars of UHMW polyethylene can be irradiated and then heated, e.g., overnight, to extinguish the residual free radicals. The oxidized surface of the bar is removed during machining of the cup, providing a crosslinked polyethylene that is very resistant to long-term oxidative degradation. If the radiation (crosslinking) dose is increased to 2-3 times the maximum used for sterilization, wear is reduced to an undetectable level, but this must be balanced against reductions in tensile strength and elongation that accompany the crosslinking.
8:35 Metal On Metal J.D. Bobyn, Ph.D., J.B. Medley, Ph.D., F.W. Chan, Ph.D., S. Yue, Ph.D. Metal-metal hip bearings have traditionally been fabricated from surgical grade cobalt-chromium-molybdenum alloys (Co-Cr-Mo) because of their corrosion and wear resistance. Many of the original metal-metal implants such as the McKee-Farrar experienced problems with early loosening because of poor design and manufacture leading to equatorial seizing and high frictional torque. The central issue of wear, however, was not a cause of failure. As self-bearing materials, Co-Cr-Mo alloys are highly resistant to runaway wear, more so than self-bearing ceramics. First generation metal-metal devices that have survived out to two decades or longer are characterized by low wear rates and small changes in dimensions and surface finish. Metal-metal articulations are currently witnessing a renaissance in several countries worldwide. More than 60,000 Sulzer metal-metal hips have been implanted since 1988. Several US companies, most notably Johnson & Johnson, Biomet, Depuy and Wright Medical Technology have developed implants for clinical trials. There is consensus that the femoral head should be smaller than the acetabular cup to ensure polar bearing and provide clearance for the ingress of lubricating fluids. Diametral clearances for 28 mm second generation clinical devices are generally held within the 50 to 100 micrometer range. Hip simulator studies have demonstrated the importance of tight control over dimensions, sphericity, and surface roughness. With high manufacturing quality, wear volumes of <1mm3 after several million wear test cycles can reproducibly be obtained. The typical wear response is characterized by an early period of run-in wear followed by a more steady-state period of distinctly lower wear. One of the advantages of improved bearing technology is the ability to use larger head/cup sizes without large increases in wear volumes. This can lead to improved range of motion, less impingement, and the use of very large implant sizes as required for surface replacement of the hip. Retrieval analyses of modern total hip devices have indicated very low linear wear rates of 1-5 micrometers/year. The most likely explanation for this behaviour is elastohydrodynamic lubrication, combined with effective boundary lubrication and a wear-resistant microstructure. Theoretical predictions of lubricant film thickness using numerical models of elastohydrodynamic lubrication have indicated that complete protection of the metal surfaces during articulation can occur with the right clearance and surface roughness. There is currently no consensus on which Co-Cr-Mo alloy is preferred for self-bearing applications with the cast alloy, high carbon wrought alloy, and low carbon wrought alloys all presently in clinical use. Characterization of the wear surfaces of simulator-tested metal-metal implants by scanning electron microscopy and atomic force microscopy has revealed several interesting features. This includes the changing morphology of alloy carbides with increasing simulator test cycles, the formation of micropits at carbide sites and within the alloy matrix, the removal of matrix material through a delamination type of process, and the finding of residual material from the grinding and polishing phases of manufacturing that could act as third-body abrasives. Further microscopic study of the subtle changes that occur at the articulating implant surfaces at long cycle intervals is required to elucidate their role in overall wear resistance and any advantages of one alloy type over another. Preliminary indications are that metal-metal wear particles are in the 20-60 nm size range, about an order of magnitude smaller than polyethylene wear particles produced in conventional metal-polyethylene articulations. Thus, very small volumetric wear can equate to a very large number of individual particles possessing a very high surface area. This raises questions about mechanisms of macrophage-mediated osteolysis and the importance of particle size, particle area, and particle chemistry in causing bone resorption. Of important note from a clinical standpoint is that 20-30 year Ring metal-metal hip prostheses implanted without bone cement are notable by their absence of peri-implant osteolysis. Issues of cytotoxicity and the long-term local and systemic tissue response to the various Co-Cr-Mo alloy elements require further study and definition. With all metal-metal hip implants there exists the important issue of integrating the acetabular bearing surface into the overall cup design. The current approaches include molding the bearing surface directly into a polyethylene insert or avoiding polyethylene altogether by connecting the acetabular bearing directly into the metal backing with a large taper-lock. Both approaches involve modularity and therefore need to be carefully studied for mechanical stability and potential for fretting motion. Also important to consider is femoral neck impingement against the acetabular liner. This problem is aggravated by cup malposition and could cause neck notching and metal release, particularly with titanium alloy stems. Close attention to design detail and manufacturing quality must be supplemented with rigorous mechanical testing and hip simulator studies under aggressive loading conditions so that the limitations of the technology are fully understood. The potential for greatly reduced wear and problems with osteolysis clearly exists with metal-metal hip implant technology. Controlled clinical studies should probably be completed prior to consideration for general use.
8:45 Ceramic Bearing Surfaces Harry B. Skinner, M.D., Ph.D. Despite more than 25 years of clinical experience with ceramic materials as bearing surfaces, their role in modern joint replacement surgery remains to be clearly defined. The two primary materials are alumina and zirconia; both are oxides, of aluminum and zirconium, respectively, in their highest oxidation state. The application of these materials is primarily as a femoral head bearing surface against polyethylene, but alumina is also used as both femoral head and acetabulum to provide a polyethylene-free bearing surface. These materials represent a typical cost (risk)/benefit trade-off. The advantages or benefits are biocompatibility, hardness, wetability, strength, ability to obtain good surface finishes, probable low wear of either ceramic against polyethylene, and for alumina, low wear against alumina. Linear polyethylene wear against alumina heads is reported to be as much as a factor of 5 to 10 lower than metal vs. polyethylene. Thus, the ceramic femoral head may be a good choice for the younger patient where it seems necessary to use a 32mm head for stability reasons, although supporting data are sparse. The disadvantages are cost, limited head-neck sizes due to strength limitations, potential for fracture, and occasional high alumina-on-alumina wear. Many of the problems of the past have been design, manufacture, or application related, and have been improved or eliminated. Proper clinical technique in the use of ceramic femoral heads is crucial to preventing fracture and alumina-on-alumina wear is an order of magnitude lower than ceramic-on-polyethylene. The materials hold high promise and should continue to be used so that further experience can help define the clinical indications for components made of these materials.
8:55 The Counterface, Surface Smoothness, Tolerances and Coatings in Total Joint Prostheses Seppo S. Santavirta, M.D., Rello Lappalainen, Ph.D., Asko Anttils, Ph.D. and Panu Pekko, M.Sc.
Surface finish and tolerances of contact surfaces are important in tribology of bearing surfaces in total joint prostheses. Low friction and wear are desirable characteristics to be reached by using proper counterface material combinations and macro- and microgeometry of loading surfaces. In metal/polyethylene and ceramic/polyethylene pairs, the counterfaces match by the elasticity and wear of polyethylene. Although friction is low (coefficient of friction 0.05-0.10), the wear rate of polyethylene remains high compared to metal-metal pairs even with optimized surface geometries and head sizes of hip joint prostheses. The wear is increased by hard third body particles, e.g.methylmethacrylate debris. In hard counterface pairs (metal-metal, ceramic-ceramic), low friction and wear rates should be achieved with continuous lubricating fluid film formed if the head-cup tolerances are about a few ten micrometers. Based on clinical surveys, in most total hip prostheses continuous film lubrication has not been achieved and the clearance does not seem to have an accurate optimal value. In practice, sliding surfaces are in contact at the surface asperities. Local high surface pressures lead to high wear and friction. In principle, low wear rates should be achieved using hard coatings or bulk materials. Diamond is a novel coating material with many superior, desired characteristics such as low friction, high wear and corrosion resistance and well bonding surface to bone. Currently, there is a large variability in tolerances, surface finish and materials quality of commercially available total hip prostheses, leading to differences in friction and durability.
9:20 Introduction of Orthopaedic Devices to the Marketplace Henrik Malchau, M.D. Introduction. Decisions about medical treatment should be based on a careful appraisal of the best evidence available. In order to increase evidence –based decision making in the evaluation of new surgical techniques and implants a stepwise introduction is necessary to expose as few patients as possible to the risk of failure. The history of development of total hip arthroplasty could have been different if the introduction had been more careful and performed in a stepwise manner. Inferior properties would have been revealed earlier thus reducing the number of failures and allowing the necessary improvements. It is therefore desirable that the profession agree on a standardised way to introduce new implants. Based on the Swedish experience the following schedule for stepwise clinical introduction of new implants is suggested. The initial step is a preclinical testing beyond the scope of this paper. The first clinical step is the open prospective and preferably randomised trial including a minimum of patients to obtain a valid evaluation. The strict rules of prospective randomised trials should be addressed. In this first clinical level high accuracy methods such as radiostereometric analysis (RSA) and dualenergy x-ray absorptiometry (DEXA) are required. Within 6 months to 2 years these methods have the potential of identifying implants with inferior/superior fixation, extreme wear or unfavourable/favourable bone remodelling. Results from these methods determine if further clinical evaluation is worth while. It should be noted and underlined that all types of complication cannot be predicted and further follow up is necessary and should be done. If migration analysis is performed with conventional methods (less accurate than RSA) larger cohorts is needed, exposing more patients for potential risks. Step 2. If favourable results are obtained in step 1, the second step, a multi-center trial exposing the new procedure to a broader aspect of the orthopaedic community can be initiated. The implant will then be exposed to various surgical techniques and hospital environments. In Step 1 investigations there is a risk for susceptibility and performance bias as the inventors often perform this first introductory investigations. The protocol of the multi-center study must be carefully prepared and agreed upon by all participating inventors. A sufficient number of patients must be included in order to allow statistical analysis. The witnessed or written patient consent is essential, as is an approval by ethical committee. The ultimate goal will be to make even the multi-center trial randomised using a well-documented implant as the golden standard on baseline control. Step 3 in the evaluation is a continuous quality control effected by register studies based on large population to reveal early or unusual and potential catastrophic complications. In a comparable small community as Sweden the register should be nation-wide and include all units in a specific field.
9:40 Evidence Based Operating Room Environment Merrill A. Ritter, M.D. To control the source of environmental contamination and hopefully sepsis following total joint replacement surgery one must realize that man is the source of the bacteria as evidenced by a rise in colony forming units per square foot per hour from 13 to 400 when they are absent or present respectively. The use of inclusive gowning is helpful. Face masks and head covers offer no environmental protection. Some type of an environmental control, such as laminar air flow or ultraviolet light is the most helpful with over a 90% reduction at the wound and 60% reduction in the operating room itself.
9:50 New Organisms and New Antibiotics Associated With Infected Total Hip Arthroplasty Kevin L. Garvin, MA, Craig R. Mahoney, M.D., and Joshua A. Urban, M.D. Introduction: Infection after total hip replacement can be managed successfully in approximately 90% of patients. This high rate of success is potentially at risk because of the emergence of resistant bacteria and our failure to identify new antibiotics to treat these pathogens. Materials, Methods and Results: Since January 1991, 62 total joints of the hip or knee in 59 patients were treated for infection. Forty-six (75%) of these joints were infected with gram positive bacteria and 15 (25%) were methicillin or oxacillin resistant Staphylococcus aureus or coagulase-negative Staphylococcus. Vancomycin resistant organisms (Enterococcus and Staphylococcus) were not identified in this group of patients. Thirty-two of the joints were hips and 25 of the prostheses have been retained or reimplanted. At an average follow-up of 3.3 years, all of the patients are still free of infection. The remaining seven patients have not been reimplanted at the time of this writing. Discussion: Although, vancomycin resistant bacteria were not identified in our series of patients these bacteria have involved orthopaedic patients elsewhere. The use of Vancomycin is clearly a risk factor for the emergence of these resistant bacteria and injudicious use is discouraged. The role of new antibiotics (Synercid, Linezoilid, Teicoplanin and Trovafloxacin) in the treatment of these patients has not been established.
10:00 The Use of Prophylactic Antimicrobial Agents During and After Hip Arthroplasty Arlen D. Hanssen, M.D. and Douglas R. Osmon, M.D. An intravenous antibiotic, just prior to skin incision, effectively reduces the prevalence deep wound infection. Controversies include selection of the optimal antibiotic, appropriate timing, and proper duration of prophylaxis. Currently, a short duration of prophylaxis is recommended. Considerations of the efficacy, cost, and toxicity need to be individualized based on the susceptibility patterns of microorganisms causing prosthetic infection within the practitioners' institution. Institutional antimicrobial compliance strategies are cost-effective and improve the timing of antibiotic administration. Awareness and compliance with published antimicrobial restriction recommendations is warranted due to the concern of emerging antibiotic resistant bacteria. Specifically, restriction of vancomycin in orthopaedic surgery should be critically targeted. Supplemental antibiotic administration during the intraoperative period includes additional antibiotic dosing, use of antibiotic-irrigant solutions, and admixture of antibiotics into acrylic bone cement or bone graft. Experimental efforts are actively underway to evaluate antibiotic-laden surface coating of implants. There are no established standards or clinical guidelines for these supplemental antibiotic applications. Postoperatively, antimicrobial agents are frequently overused for a variety of clinical scenarios and this pattern of antibiotic usage is potentially detrimental. A prophylactic antimicrobial strategy for prevention of early and late hematogenous infection requires deliberation of host risk factors, wound environment variables, and sources of potential bacteremia as well as the cost-effectiveness, efficacy, and complications associated with routine use of antibiotics. Significant efforts are underway by expert panels to provide advisory statements for elective procedures, which may potentially cause bacteremia. Additional research is required to provide data for this area of antimicrobial agent prophylaxis.
10:10 Infection: One Stage vs. Two Stage Exchange John J. Callaghan, M.D., Ralph P. Katz, M.D., Richard C. Johnston, M.D. With the initial poor results reported with the treatment of infection of total hip arthroplasties in North America, two-stage exchange became the preferred treatment. However the morbidity and the cost of the staged procedure as well as the encouraging reports of direct exchange in Europe and the United States have led some surgeons to reconsider direct exchange. Below are the reports of one and two stage exchange procedures TABLE 1. Comparison of One-and Two-Stage Exchanges One stage Two stages Author No. of hips Success % No. of hips Success % Cement with antibiotics Buchholz 667 77.0 --- -- Lindberg 59 90.0 18 78.0 Murray 13 38.5 22 95.5 Turner 101 86.0 --- -- Wroblewski 102 91.0 --- -- Hope 72 87.5 19 100.0 Elson 235 87.5 61 96.5 Garvin 21 90.5 55 92.7 Duncan --- --- 46 93.0 Sanzen 72 76.0 30 74.6 Rant 57 86.0 --- -- Miley 47 87.0 --- -- Ure 20 100.0 --- -- Present study 24 91.7 --- -- Cement without antibiotics Hunter 55 18.0 10 60.0 Talbott --- --- 25 80.0 Cherney and Amstutz 5 80.0 28 64.0 Fitzgerald --- --- 111 90.0 Jupiter 18 78.1 --- -- Salvati 31 91.0 28 89.0 Callaghan 14 86.0 18 94.5 McDonald --- --- 82 86.6 Lieberman --- --- 32 91.0 Hughes 13 92.3 13 84.6 Although we continue to perform staged reimplantation in younger patients, patients with virulent organisms, host compromised patients and patients with poor bone quality we consider direct exchange in older patients, with sensitive organisms and good bone quality. 10:20 The Infected Hip Replacement: Management of the Complex Case Clive P. Duncan, M.D. Complexity is introduced under a number of circumstances when dealing with infection after hip joint replacement. These may relate to the organism (MRSA, VRE, Polyclonal Infection), to patient behaviour (intravenous drug use, alcoholism), to general health (immune compromise) or to the local anatomy (substantial soft tissue or bone loss). This paper will deal with management of the latter: deep-seated infection associated with segmental bone loss of the femur. This is a relatively uncommon but challenging problem, which requires a two-stage approach to management: removal of all foreign material and resection of devitalized tissue in the first stage; followed by complex reconstruction at the second stage. Typically this problem presents against a background of multiple previous operations (multiple revisions, periprosthetic fractures) or following substantial resection of bone at the index procedure for the management of a tumor. The principles of management are similar to the straightforward case and include: identification of the organism and its antibiotic sensitivity profile, adequate imaging to define the location and extent of foreign material (standard radiographs, full-length views of femur, Judet views of pelvis), extensile exposure of the hip and femur without further devascularization of bone, removal of the implant and all cement (with intraoperative imaging if necessary), and consideration of an antibiotic-loaded depot. The second stage is usually more challenging than the straightforward case, as bone stock must be replaced (substantial allograft, special prostheses) and the risk of instability needs special consideration. Furthermore, in the interval between the two stages, in the face of substantial proximal femoral bone loss, there is the unique difficulty of managing the hip, the limb and the patient in a manner that will maintain reasonable limb length, promote mobilization and permit discharge from hospital. It was for this purpose that the PROSTALAC principle (PROSTheses of Antibiotic Loaded Acrylic Cement) was developed in 1986. Its purpose was to substitute for missing or resected bone, using a facsimile of the hip and femur made of antibiotic-selective PMMA over an endoskeleton of metal. The system has been refined over the years, to the point where it is an intraoperative custom-made, immediate fit, antibiotic-selective prosthesis, quite adaptable to a wide range of difficult problems. It maintains the length of the limb, motion of the joint, mobility of the patient with protected weight bearing and it leads to a high dose of periprosthetic antibiotic in the infected surgical bed. This principle has been applied in more than forty complex cases to date. Thirty of these were recently studied, with an average duration of follow up measuring four years (range 2-10 years). The organisms were Gram-positive in 23, Gram-negative in 6 and M tuberculosis in one. The antibiotics used were based on the sensitivities of the organisms identified and included a combination of Tobramycin and Vancomycin in 23 cases, Vancomycin alone in 3, Tobramycin and Penicillin in 3, and Streptomycin in the single patient with micobacterial infection. Antibiotics were continued for six weeks after operation. The average duration between stages was twelve weeks and the type of reconstruction at the second stage was based on the requirements to achieve a stable construct. At the time of follow up (minimum 2 years, average 4) infection had recurred in only one patient (3.3%): 12 months after the second stage, due to a different organism. That case was successfully managed with another two-stage protocol using a PROSTALAC in the interval again. 11:08 Cemented All-Poly Socket Fixation in Total Hip C.S. Ranawat, M.D. The ideal bone implant bond should be easy to achieve, reproducible, should provide good pain relief and function, be durable, and without local or systemic ill effect. Thus far, no method of fixation meets all these requirements. The reported clinical failure rate of socket fixation is less than 5% for 10-15 years follow-up. The radiographic failure rate using global radiolucency and migration of 3 mm as criteria is around 25% (Wrobleski). The primary reason for early septic loosening, i.e. within 10 years, is due to failure to achieve good micro and macro interlock at the time of surgery. The interface failure secondary to histolytic invasion occurs with longer follow-up. MODERN CEMENT TECHNIQUE Modern cement technique improves the radiographic appearance (Ranawat et al 1988). This can be further improved by hypotensive epidural anesthesia (Ranawat et al 1990). With the improved cement technique, clinical and radiographic loosening of bone cement interface was 7.2%, with an average follow-up of 9.5 years (Ranawat et al 1995). This includes 0.8% clinical failure rate and 3% radiographic migration and 3.4% of progressive global radiolucency. We believe that the state of bone cement interface, as seen in the early postoperative radiograph, can predict the longevity of the cemented socket to a high degree of probability. PATIENT SELECTION We continue to use cemented all-poly sockets for patients who are 60 years old or older, whose life expectancy is estimated to be 15-20 years longer. A cemented polyethylene socket is not advised in the presence of excessive bleeding and in dysplastic or rheumatoid patients. In summary, fixation of all-poly cemented socket is reproducible and provides excellent hip function for 10 years and longer. The results are comparable with noncemented sockets for 10 years. With noncemented fixation, increase of poly wear and osteolysis are emerging concerns. 11:16 The Optimal Cementless Metal-Backed Acetabular Component A. Seth Greenwald, Ph.D. Metal-backed polyethylene cups have gained widespread use in total hip arthroplasty and are advocated for both cementless and hybrid application. Continued optimization of mechanical design and surgical technique has diminished the frequency of short-term failure of these systems with attention now focused on long-term survivorship. Locking mechanism integrity, cup/liner conformity, polymer material characteristics, machining tolerances, surface finish and the inclusion of holes are design factors which influence the in vivo service life of these components. A series of ongoing laboratory experiments to evaluate the influence of these factors on in vivo implant performance are described. Bench-top evaluations of sixteen metal-backed cup systems particular to their locking mechanism integrity indicate a range of lever-out strength, 43 in-lbf to 890 in-lbf, while cup/liner conformity was found to vary between 3% and 96% of the available polyethylene surface area. The influence of these findings as affecting implant instability and the potential for debris generation, which leads to an osteolytic response, are discussed. Evolving optimization of metal-backed cup design attempts to accommodate the extended in vivo service life demands of younger, more active patients as well as the extended longevity of our senior population.
11:24 Long-Term Results With Modular Cementless Acetabular Components William J. Maloney, M.D., Michael Anderson, M.D., Joshua J. Jacobs, M.D., Jorge O. Galante, M.D., Paul Lachiewicz, M.D., Harry Rubash, M.D., Steve Schutzer, M.D., Steven T. Woolson, M.D., William H. Harris, M.D. Cementless porous coated acetabular components have essentially replaced cemented sockets for both primary and revision surgery in North America. We are now reaching a point in terms of length of follow-up that we can begin to critically examine the implications of that choice. A multicenter review was performed analyzing the radiographic results of more than 1000 cementless, hemispherical porous-coated, first generation acetabular components (Harris/Galante 1, Zimmer, Warsaw, IN). All components were inserted with a line to line reaming technique using screws to provide implant stability. Radiographic analysis consisted of an evaluation of implant stability documenting implant bone interface radiolucency, cup migration or a change in cup position. Osteolysis, screw breakage and porous coating fragmentation were recorded. Polyethylene wear was measured. Patients were followed for a minimum of five years with a maximum follow-up of twelve years. Specific attention was given to patients less than 50 years of age at the time of their index operation. Overall, linear polyethylene wear averaged 0.11 millimeters per year (range: 0 to 0.86 mm/year). Two sockets were revised for aseptic loosening. One case of aseptic loosening was in a pelvis with radiation necrosis and the second had polyethylene and pelvic osteolysis. The second patient had a MVA with associated pelvic fracture. Three additional sockets had migrated. Two of these patients had pelvic radiation. . Pelvic osteolysis was noted in 2.3 % of cases. Patients who were fifty or less at the time of their index operation had a higher rate of pelvic osteolysis. Over the time period of this study, the Harris-Galante acetabular component has proven reliable in terms of both clinical performance and radiographic stability. Measured polyethylene wear in this study is comparable to what has been previously reported with all polyethylene cemented sockets. To date, pelvic osteolysis has not been a major problem, but continued follow-up is required as the prevalence of the problem is likely to increase with time. Screw fixation does not predispose to pelvic osteolysis. 11:32 Fixation Strategies for Cementless Acetabular Cups Michael D. Ries, M.D., Abraham Salehi, Ph.D., Jeff Shea, B.S. Initial stability of oversized press fit acetabular cups is achieved when periacetabular bone strains are concentrated at the periphery of the cup. Stability can also be achieved with supplemental screws, spikes or fins. In this study, periacetabular strains produced by different cementless acetabular cup geometries were compared using an axisymmetric photoelastic model. The cup geometries consisted of tri-spiked, finned, oversized hemispherical, and non-hemispherical (wider than a hemisphere at the periphery) geometries. The cup models were incrementally loaded in the photoelastic material. The peripheral strain distributions and their magnitudes induced by the tri-spiked, and oversized hemispherical cups were similar, but the tri-spiked cup induced localized high strain regions where the spikes penetrate the bone model. The added feature (spikes) increased the force to seat the cup. Use of spikes for fixation may be most appropriate when the spikes do not prevent complete cup seating. The fins cut the periacetabular material into quadrants, which decreased the peripheral strains. This cup produced the least amount of press fit strain near the rim. A geometry with a wider diameter at the rim than a hemisphere increased peripheral strains more than an oversized hemispherical geometry and required less force to seat the implant. 1:00 The Otto Aufranc Award Wear and Lubrication of Metal-on-Metal Hip Implants Frank W. Chan, Ph.D., J. Dennis Bobyn, Ph.D., John B. Medley, Ph.D., Jan J. Krygier, CET and Michael Tanzer, M.D. The implication of polyethylene wear particles as the dominant cause of periprosthetic osteolysis has created a resurgence of interest in metal-on-metal implants for total hip arthroplasty because of their potential for improved wear performance. Twenty-two cobalt chromium molybdenum metal-on-metal implants were custom manufactured and tested in a hip simulator. Accelerated wear occurred within the first million cycles followed by a marked decrease in wear rate to low steady state values. The volumetric wear at three million cycles was very small, ranging from 0.15 to 2.56 mm³ for all implants tested. Larger head-cup clearance and increased surface roughness were associated with increased wear. Implant wear decreased with increasing lambda ratio, a parameter used to relate lubricant film thickness to surface roughness, suggesting some degree of fluid film lubrication during testing. This study provided important insight into the design and engineering parameters that control the wear behavior of metal-on-metal hip implants and indicated that high quality manufacturing can reproducibly lead to very low wear. 1:15 The John Charnley Award Practice Surveillance: A Practical Method to Assess Outcome and to Perform Clinical Research John J. Callaghan, M.D., Richard C. Johnston, M.D., Douglas R. Pedersen, Ph.D. The senior author began systematically collecting preoperative and postoperative data on all the total hip arthroplasties he performed starting in July of 1970. The data collected represents a twenty-six year experience using practice surveillance (preoperative and regular interval postoperative collection and analysis of outcomes) as a method to document the outcome of the total hip arthroplasty procedure and as a method to evaluate the need for changes in the procedure based on this practice surveillance. As the senior author made few selected changes in the operative procedure over the follow-up period, the primary author has been able to evaluate the change in outcome based on these changes. The six studies reported in this manuscript demonstrate the durability of the long term results of cemented total hip arthroplasty, the improvement in radiographic reproducibility obtained on the femoral side of the construct with improved cementing techniques, the deleterious effects of using cable to reattach the greater trochanter, the deleterious effects of changing femoral component design which included a change in surface finish, the improvement in acetabular fixation using cementless fixation, and the optimization of bearing surface wear using smaller diameter femoral heads. All of these findings have been incorporated into the primary surgeon's practice today based on this practice surveillance. As demonstrated, practice surveillance has also provided a tool for performing clinical research. Although practice surveillance of controlled cohorts will never supplant prospective randomized clinical trials in evidence based medicine it should help each individual surgeon with his or her own practice and can be used as an important research tool to study the optimization of outcomes of a surgical procedure.
1:30 The Frank Stinchfield Award Sudden Death During Primary Hip Arthroplasty Javad Parvizi M.D., Allan D. Holiday M.D., Mark H. Ereth M.D., David G. Lewallen, M.D. Intraoperative hip arthroplasty deaths between 1969 and 1997 were reviewed and compared to Total Joint Registry data on all arthroplasties. Mortality cases were reviewed in detail along with autopsy findings. Practice changes in 1988 aimed at minimizing fat embolization in high-risk patients prompted comparison of patients before and after 1988. Those changes included noncemented implant use in some and avoidance of pressurization and canal plugging, or drill holes to vent the femur above a plug, in others considered at risk. Results: 23 deaths occurred in 38,488 arthroplasties (0.06%). All deaths occurred among 14,469 cemented primary arthroplasties (0.159%). No deaths occurred during 15,411 noncemented arthroplasties, or during 8,608 revisions, 18/23 had a fracture diagnosis (4 pathological). 21/23 had known cardiovascular disease. Incidence of death for fracture cases was 5 times that for non-fracture cases (0.30% vs. 0.06%) (p<0.03). Incidence of death for all arthroplasty patients between 1969 and 1988 was 19/21,895 (0.087%) vs. 4/16,593 (0.024%) after 1988, a greater than threefold difference (p< .05). This reduction was due to a greater than fivefold difference in mortality among acute fracture patients receiving a cemented implant after 1988 (p < .05) and the elimination of deaths among 2,138 selective cemented arthroplasties. After that date, versus 5/6,364 (0.08%) between 1969 and 1988 (p < .05). Autopsy in 13 showed pulmonary fat and marrow microemboli (11/13) and methacrylate particles (3/13). Conclusion: Elderly patients with pre-existent cardiovascular conditions, undergoing cemented arthroplasty, especially for fractures, are at increased risk for intraoperative death compared to elective patients. Altering patient implant selection and using techniques designed to minimize intramedullary hypertension in at risk patients can produce significant reductions in intraoperative mortality.
2:00 Cost Analysis of Revision Total Hip Arthroplasty: A Five Year Follow-Up Study Robert L. Barrack, M.D., Jaswin Sawhney, M.D., Joseph Hsu, M.D., Robert H. Cofield, M.H.A. Introduction: A study was undertaken to determine the resources required of the surgeon and the hospital in performing revision total hip arthroplasty (THA). Results were compared between 1990-1992 and 1995-1997 to determine if any changes had occurred over that five year span. Methods: A stratified, unselected sample of thirty revision THAs performed between 1990-1992 in which complete clinical and financial data was available was studied. Clinical data included age, sex, diagnosis, length of stay (LOS), operative time and blood loss. Financial data included cost of implants, bone graft and accessories, hospital charge and surgeon reimbursement. Results were compared to an analogous group of fifty revision THAs performed at the same institution between 1995-1997. Cases were classified as simple (involving revision of only acetabular liner and/or femoral head), routine (revision of acetabular and/or femoral components) or complex (major structural graft, antiprotrusio cage, impacted grafting). Results: For routine revision THA a dramatic decline of 52% occurred in length of stay over the five year time span (10.7 days to 5.1 days, p< .001). The average operative time also declined significantly (238 minutes to 199 minutes, p< .05) as did the average implant cost (4,349 to 2,827, p< .001). In spite of this, the average hospital charge increased 16% (29,666 to 34,328, p< .05). There was a significant and dramatic 35% decline in surgeon reimbursement (3,240 to 2,178, p<001). There was no significant difference in surgeon reimbursement between simple, routine and complex THA. Complex cases had significantly greater LOS (7.3 vs. 5.1 days, p< .05) and operative time (297 vs. 199 minutes). The hospital charge, was dramatically higher for complex cases (51,290 vs. 34,328) but the surgeon reimbursement was lower on average, although not statistically significant (1,926 vs. 2,178). Discussion and Conclusion: There was a significant increase in the number and complexity of revision THAs between the two time periods. Significant decreases were achieved in LOS, OR time and implant cost. Benefits from these changes were accrued to the hospital but not the surgeon as hospital charges increased significantly while surgeon reimbursements declined dramatically.
2:10 Cementless Acetabular Revision at 9-15 Years Aaron G. Rosenberg, M.D., Laura Quigley R.N., Joshua J. Jacobs M.D., Rich Berger M.D., Jorge O. Galante M.D. We prospectively followed all revisions of cemented cups from 1983 to 1988. Titanium fiber mesh hemispherical cups were implanted line to line with supplemental screws. Of 176 hips in 167 patients, 35 died prior to 9 years and 33 had less than 9 year follow-up (none requiring revision) leaving 106 hips followed an average of 130 (102-169) months. 87% of cups were radiographically stable and not revised, however, 7% were radiographically and clinically stable but required revision for: recurrent dislocation-5, late sepsis-5 and at the time of loose stem revision-2. No revisions for aseptic loosening were required. An additional 7 (4%) were possibly unstable (4 of 5 zones with radiolucent lines (RLL) of < 2 mm), while 4 (2%) were unstable (migration or RLL of > 2mm in 4/5 Zones). No screw breakage was seen, but at the cup periphery, separation of the fiber metal pad from the underlying shell was seen in 2, with pad fragmentation in 11 additional cases (noted on average at 113 mos.). 2 lucencies were seen about a single screw and 12 cases demonstrated periacetabular lytic lesions at the component periphery. These were noted at an average of 118 (59 -166) months. None have required treatment to date. 2:18 Acetabular Revision The Role of Rings and Cages Joseph Schatzker, M.D. The acetabular roof ring and antiprotrusio cap are used to protect bone grafts and restore normal acetabular biomechanics. They depend on press fit and screws for fixation. The polyethylene cup is cemented into them. The roof rings are used for small cavitatory defects, osteoporosis or acetabular dysplasia. The antiprotrusio cages are used for major cavitatory and segmental defects, pelvic discontinuity and global acetabular deficiency. Of 128 patients 95 were revisions. The follow-up is from 1-16 years with a mean of 6.5 years. 61 patients had ARRings and 34 patients APCages. Of the revisions 91% were for aseptic loosening, 3% for septic loosening, 3% for broken implants, and 3% for girdlestones. 15% had previous stem and acetabular revisions and 8% previous acetabular revisions. At 13 years 14.7% ARRings and 5.8% APCages had failed. The average pre- and post-operative HHS was 43 and 85 for the ARRings mid 47 and 83 for the APCages. Evaluation by patients was 76% good to excellent for the rings and 65% for the cages. The principle advantage of these devices is the restoration of normal acetabular biomechanics and the major restoration of lost acetabular bone. 2:26 Restoration of Bone Stock for Revision Arthroplasty of the Acetabulum Allan E. Gross, M.D. Bone defects on the acetabular side are defined as contained (cavitary) and uncontained (segmental). Contained (cavitary) defects can be managed by morsellized allograft bone with an uncemented cup if contact can be made with 50% host bone. If contact cannot be made with 50% host bone, we prefer to use a ring and a cemented cup. Defining success as a stable implant, no further surgery, and improvement in hip score of at least 20 points, the success rate was 90% in 50 hips at an average follow-up of 7 years. Segmental defects involving between 30 to 50% of the acetabulum are managed by minor column allografts (shelf graft), and a cemented or an uncemented cup. In 29 hips with an average follow-up of 7 years the success rate was 86%. Segmental defects involving more than 50% of the acetabulum are managed by major column allografts. These grafts are fixed by cancellous screws and protected by a reconstruction ring that extends from ileum to ischium. In 33 hips with an average follow-up of 7 years, the success rate was 76%. 2:34 Revision Hip Arthroplasty: The Femoral Side Cecil H. Rorabeck, M.D., James W. Taylor, M.B., Ch.B.
Total hip arthroplasty has proven to be a highly successful procedure but with its increased use both in the elderly and in young high demand patients there is an increase in the numbers of joints requiring revision. Revision of the femoral component presents many challenges to the orthopaedic surgeon, including the necessity for careful preoperative planning, the operative approach, removal of the failed implant and the cement mantle, the choice of implants, dealing with bone defects and the management of complications. We present an outline of our approach to these problems as well as a review of the literature focusing particularly on the selection of the prosthesis used, the technique of reconstruction of bone defects and the classification system used to guide these decisions. We also present the results of the senior authors' experience with 380 revision hip arthroplasties performed over a 17-year period. An algorithm for revision of the femoral component, based on this experience, will be presented suggesting indications for cementless or cemented fixation and impaction grafting. 2:50 Structural Grafting For Femoral Reconstruction William C. Head, M.D., Roger H Emerson, Jr., M.D., Theodore I Malinin, M.D. Structural grafting for femoral reconstruction is indicated when there is advanced bone loss associated with femoral prosthetic failure. Total segmental grafts are used when the proximal femur is severely compromised or totally absent. Cortical onlay grafts are useful to reconstruct the intact but bone deficient femur. An alternative to total segmental grafts is a mega-prosthesis for proximal femoral replacement. Mega-prostheses have higher both early and late complication rates, and are reserved for sedentary patients or those patients with a life expectancy of less than 10 years. The major early complication with a mega-prosthesis is dislocation. Late complications include dislocation, loosening with associated osteolysis, breakage of the implant and late infection. Zehr and Enneking reported a 28% early instability incidence with mega-prostheses. When a mega-prosthesis is utilized, a constrained acetabular component is indicated. Primary concerns related to prosthesis and segmental proximal allograft reconstructions are dislocation, nonunion and infection. Our current complication rates are: dislocation, 10%; nonunion, 8% and early infection, 3%. To date, we have not noted a late infection. The techniques for total segmental grafts are to cement the prosthesis into the graft but not into the host bone, obtain junctional stability and to surround the construction with as much host bone as possible. The junction should be grafted with autograft bone. Onlay grafts are used to supplement the deficient Type III femur. They cannot be used for primary prosthetic support. There are attached with circumferential wires with an autograft/allograft slurry at the interface. They basically unite 100% of the time and go through the phases of union, revascularization, cancellization, remodeling and maturation. They do supplement bone stock long term and perform best when utilized with a proximal load bearing prosthesis. The histology regarding the two types of grafts is quite different. Total segmental grafts unite to host bone and then gradually undergo bone replacement from the junction proximal-ward at a rate of about 1 - 2 millimeters per year. Spotty revascularization occurs over the outer cortex of the graft via the soft tissue muscle cuff. Problems of bone resorption have not been noted. The onlay grafts are rapidly revascularized via a zone of mesenchymal tissue that grows in at the host/graft interface. Osteoclasts form cutting cones into the graft. Vascular buds then invade the graft through these portals and rapid revascularization takes place. Both types of grafts are prepared in a freeze-drying method from the University of Miami Tissue Bank. BMP is retained in the graft, utilizing this method of preparation and preservation. There has not been an incidence of disease transmission reported utilizing freeze-dried bone. 2:58 Twenty Year Experience of Femoral Revision of Total Hip Replacement using Second Generation Cementing Techniques William T. Wester, M.D., Daniel M. Estok II, M.D. and William H. Harris, M.D. Fifty-seven consecutive, unselected cemented femoral revisions done in fifty-five patients using second generation femoral cementing techniques and bead-blasted, monoblock, chrome cobalt femoral stems were studied prospectively over 20 years. None were lost to follow-up. Adverse features were:
Overall, 14 percent (eight of fifty-seven) were re-revised for aseptic loosening. Among those with congenital hip dislocation or dysplasia 21 percent (three of fourteen) were re-revised, statistically significant (p< .04) more than those without congenital dysplasia or dislocation (12 percent or five of forty-three). Among those re-revised, the average time until re-revision was 14 years. The average age of those re-revised was 42 years at the index revision, significantly younger than those not re-revised (59 years). In the entire group over the full 20 years eighteen of fifty-seven (32 percent) were re-revised or removed. Second generation femoral cementing led to a re-revision rate for aseptic loosening over a 20 year span that appears less than many prior reports. 3:06 Cementless Femoral Revisions Wayne G. Paprosky, M.D. The poor results with cemented revision of the femur with cement techniques led investigators to explore cementless options. Difficulty in obtaining initial stability in poor quality proximal bone led to poor intermediate term results. There are currently no acceptable results of proximally coated stems published in the literature beyond five years. Fully coated stems bypass the often-deficient proximal bone and obtain initial diaphyseal fit and stability in the relatively normal distal bone, allowing for reliable biologic fixation with the possibility for long term bony ingrowth. There are several published series at intermediate and long term intervals with low failure rates. Long term success is dependent on achieving initial axial and torsional stability by maximizing canal fill at the time of implantation. This stability can be achieved if there is at least 4 cm. of intact diaphysis available. Between 1983 and 1988,191 femoral revisions were performed with 171 cases available for follow-up at ten to sixteen years (mean 13.2). The average age was 61.2 years (28-85) with 97 females and 73 males. Indications for revision were 139 cases (82%) for aseptic loosening, fourteen (8%) for septic loosening, ten (6%) peri-prosthetic fractures and seven (4%) for malpositioning. Most common stem diameters were 15.0 mm and 16.5 mm. (65%). Femoral bone loss include 11% in Type I femurs, 30% in Type II, 48% in Type 3A and 11% in Type IIIB. According to ENGH'S stability scales, 82% were bone ingrown, 13.9% were stable fibrous and 4% were unstable. Stem subsidence occurred in 16% of cases. All cases with > 90% canal fill were stable. In Type 3B cases, 21% proved to be unstable. There was 21% proximal osteolysis and 6% severe stress shielding occurring only in DORR Type C bone. Clinical results using D'Aubigne and Postel scales showed pain improvement from 2.6 to 5.6 and overall 5.6 to 10.8. Complications were as follows: Intra-op fractures, 8.9%, dislocations, 6.8%, infections, 2% and sciatic nerve injuries, 2%. Overall, these results at a mean of 13.2 years are very encouraging for the prospects of long term success.
3:50 THA in Special Cases -DDH William N. Capello, M.D., Yuichi Itoh M.D., Judy Feinberg, Ph.D. Developmental dysplasia of the hip (DDH) poses a number of technical challenges for the arthroplasty surgeon. The femur is often excessively anteverted and the canal narrow. The anatomic acetabulum may be rudimentary, and bone quality on both sides may be poor. The goals of THA in DDH include:
Restoration of leg length is not a goal of the reconstruction. Femoral transection and removal of an intercallary section of the femur has advantages over other approaches. These advantages include:
By decompressing the femur the likelihood of nerve damage is minimized. A potential disadvantage of this approach is a delayed or nonunion of the osteotomy site. Our experience includes 26 hips in 20 patients. A transverse femoral osteotomy was used in 18 cases (oblique in the other 8). Stem fixation included 12 proximally coated, 11 extensively coated and 3 cemented. Average follow-up is 50 months (range, 13 to 104). No stems and three cups have been revised (2 for aseptic loosening, 1 post-fracture). Complications include two hips with osteotomy nonunion and one hip with a femoral nerve injury. Clinically 96% are pain-free. A mild limp only is noted in about one-half of the cases. Based on our experience to date, we believe that the transfemoral approach to THA in DDH is a versatile approach to a difficult problem. We currently recommend the use of the transverse osteotomy in conjunction with an extensively fixed cementless implant (either monoblock or modular) to secure the osteotomy site on the femoral side. 3:58 Single-Stage Bilateral Total Hip Arthroplasty William Macaulay, M.D., Eduardo A. Salvati, M.D., Thomas P. Sculco, M.D., and Paul Pellicci, M.D. This work reviews the current knowledge and literature with regard to bilateral total hip arthroplasty (THA) performed during a single stage. Special emphasis is placed on the Hospital for Special Surgery experience over three decades. Relative indications, contraindications, techniques and anticipated complications for the surgery are reviewed. The main conclusion is that single-staged bilateral total hip arthroplasty is a viable option for the motivated patient with few medical comorbid conditions. The decision to undergo single-stage THA must be arrived at by the patient with agreement and consultation of the physicians involved.
4:06 Total Hip Arthroplasty in Paget's Disease David G. Lewallen, M.D. Paget's disease is a localized disorder of bone marked by increased bone turnover. With a probable viral etiology, the disease is marked by increased resorption and formation with monostotic and polyostotic patterns possible. The pelvis and upper femur are involved in 20-80 percent of patients with Paget's disease. This fact, combined with a disease incidence that rises with age from approximately 5 percent of those over 40 to as high as 15 percent of the elderly, leads to a not infrequent association with disabling hip pathology and hip arthroplasty. Serum alkaline phosphatase is elevated due to increased bone resorption with elevated urine hydroxyproline caused by the breakdown of type I collagen in bone. With progression, the characteristic radiographic features emerge with mixed sclerosis and adjacent osteoporosis and coarse and irregular trabeculae. The altered mechanical properties caused by these pagetoid changes can lead to enlargement of the involved bone, thickened cortices, and bone deformities: varus bowing of the femur, coxa vara, and acetabular protrusio. Subcapital fractures and nonunions, along with stress fractures of the proximal femur, can complicate management. It is unclear whether osteoarthritis is any more common in Paget's disease than in age-matched controls, but the pattern of involvement and wear of the joint can be altered. Atypical destructive bone changes superimposed on typical pagetoid patterns should suggest the possibility of sarcomatous change. Technical challenges imposed by the disease can range from minor to extremely complex and can involve the need for special implants and simultaneous femoral osteotomy. Careful preoperative assessment and appropriate medical management are important in order to optimize outcome. If arthroplasty is indicated, preoperative planning and preparation of any needed equipment and implants is very important. Total hip arthroplasty is highly successful in the management of patients with Paget's disease, with reported results of conventional cemented arthroplasty similar to, though slightly less durable than, those seen in routine cemented total hip arthroplasty populations. The potential value of uncemented acetabular fixation and extensively porous-coated uncemented femoral implants in the management of patients with Paget's disease requiring total hip arthroplasty remains to be established with long-term follow-up data needed. 4:14 Primary and Revision Total Hip Replacements in Jehovah's Witnesses Carl L. Nelson, M.D. The concept of performing elective primary or revision total hip replacement arthroplasties without the option of allogeneic transfusion is controversial. However, there are studies showing that elective reconstructive surgery can be done in Jehovah's Witnesses without the use of allogeneic transfusion and without a high rate of complications related to blood loss. The strategies that are used include meticulous hemostatis, preplanned surgery, intraoperative autotransfusion (in some cases), hypotensive anesthesia, and erythropoietin therapy. The challenge is to determine the best blood management strategies to implement for the individual patient. It is essential to understand the importance of blood volume and have the ability to calculate the patient's blood volume when one chooses to do elective surgery without the use of allogeneic transfusion. The volume of blood loss that can be tolerated in any surgical setting is directly related to the initial total blood volume. A simplified calculation assumes that males have approximately 65 to 75 mL of blood per kilogram of body weight and because females typically have more adipose tissue than males, it is estimated that females have approximately 55 to 65 mL of blood per kilogram (kg) of body weight. The ability to predict tolerable perioperative blood loss is an important step in planning a blood management strategy. It is important to determine the lowest safe level of hematocrit (HCT) the individual patient can tolerate. After establishing the lowest acceptable limit for postoperative HCT, the estimated blood loss (EBL) that can occur without reducing the postoperative HCT below that established limit can be calculated: EBL = VOL x (HCTpre - HCTpost) HCTpre Where EBL = Estimated blood loss VOL = Total blood volume HCTpre = Preoperative hematocrit HCTpost = Postoperative hematocrit This equation was used to derive the plots in Figures 1 and 2 and are based on postoperative HCT levels of 21% and 30%, respectively. Each plot represents an estimate of the volume of blood that can be lost in 100 kg, 70 kg, and 50 kg individuals without breaching the lower postoperative HCT limit of 21% and 30%, and includes the range of values that would result from calculating total blood volumes for lean and obese males and females. The solid line within each range represents the average of the range. Once the amount of tolerable blood loss that can occur during the perioperative period is determined, the surgeon then must estimate the amount of blood loss that will occur during surgery and in the perioperative period. If the estimated blood loss is greater than the calculated tolerable blood loss, then strategies may be used to decrease red blood cell loss or increase red blood cell mass. In any operative procedure, careful surgical dissection with precise hemostasis is one of the most effective ways to minimize surgical blood loss and reduce the need for allogeneic red blood cell transfusion. Clearly, the combination of operative technique and hypotensive anesthesia is cumulative and synergistic and good surgical technique is essential to reap the full benefit of hypotensive anesthesia. A well-planned surgical procedure that progresses step-by-step in a controlled, efficient manner effectively reduces the amount of time spent and the amount of blood loss. In eighty-nine patients who were Jehovah's Witnesses who underwent total hip replacement arthroplasty without transfusions were performed under hypotensive anesthesia with modified surgical technique. There was a 43 percent reduction in blood loss compared to matched controls. There were no complications related to blood loss. Jehovah's Witnesses who require revision total hip replacement arthroplasty can be successfully managed by the use of hypotensive anesthesia, modified surgical technique and the use of erythropoietin. In five Jehovah's Witnesses undergoing revision total hip replacement arthroplasty received preoperative recombinant erythropoietin. The average hematocrit was 39.5 percent before therapy and 47.6 after therapy and before the operation. The average hematocrit was 36.8 percent immediately after the operation and 30.8 percent at the time of discharge. The use of erythropoietin preoperatively is particularly suited for revision joint replacement surgery because of the elective nature and the moderately flexible timing associated with the procedure and provides for the Jehovah's Witness an increased red cell mass and an increased margin of safety. The graphs provide an easy way to determine the red blood cell requirement to maintain hematocrits of 21 or 30%. With reliable estimates of total blood volume and expected blood loss, predictions about the need to blood management strategy can be made with more accuracy. The techniques used in Jehovah's Witness patients have included erythropoietin therapy, hypotensive anesthesia, meticulous hemostasis and on occasion, intraoperative blood cell salvage. When the margin of safe blood loss is anticipated, the most appropriate blood conservation options can be implemented perioperative blood management optimized. Fig. 1 Fig. 2 The range of estimated blood loss (mL) for male and female patients to maintain a postoperative hematocrit of 21% -30% calculated according to EBL = VOL x (HCTpre - HCTpost) HCTpre Dot = 50-kg patients; slash = 70-kg patients; and lined = 100-kg patients. Instructions for using graph:
4:22 Total Hip Arthroplasty for Hip Fractures M. E. Cabanela, M.D. At present in this country the majority of displaced femoral neck fractures in patients older than 65 years is handled by arthroplasty. The vast majority of the patients are treated by hemiarthroplasty and a small number by total hip replacement. Although one can find literature support for any kind of therapeutic attitude, the general trend is to utilize uncemented unipolar prostheses in very elderly patients with expected short survival and poor ambulatory status; patients with an active lifestyle, estimated good survival and no other health problems are treated with cemented bipolar prostheses, or in some centers cemented unipolar prosthesis (primarily for cost reasons); total hip replacement is usually reserved today for patients who have hip disease predating their femoral neck fracture. However, some trends appear to be developing towards use of total hip replacement in active patients over the age of 65 and a strong case could be made for this treatment philosophy based on the information available from the literature. Against the use of hemiarthroplasty in active individuals are the known facts of persistent groin pain and acetabular erosion that may necessitate conversion to a hip replacement arthroplasty. This has been reported both with unipolar and bipolar prostheses, less frequently with the latter, while it is infrequent with total hip arthroplasty. Several studies have reported good results with total hip replacement for femoral neck fractures. Lower revision rates, higher functional scores and better pain relief are common with total hip replacement. However, a significantly higher number of early postoperative complications including dislocation have been reported. These complications, particularly dislocations, seem to occur within the first 3-4 months after the replacement and not later. Our own experience with hip replacement for femoral neck fractures was reported by Lee et al and showed a remarkable prosthesis survivorship of 95% at five, 94% at 10, 89% at 15, and 84% at 20 years in 126 patients with an average age of 75 years. Furthermore, two prospective studies comparing hemiarthroplasty and total hip arthroplasty show better results with total hip arthroplasty with follow-ups of six months to one year and the mortality was similar in both treatment groups. It would appear then that cost issues aside, total hip arthroplasty can be considered as a reasonable and even desirable treatment alternative in patients with displaced femoral neck fractures, particularly those healthy and active. Exquisite attention to technical detail and careful repair of the soft tissues may help diminish the main problem with total hip replacement in this setting, namely that of postoperative dislocation. For the very elderly patient with low physical demands and poor health, hemiarthroplasty is a faster and more predictable treatment alternative.
4:30 Total Hip Arthroplasty in Patients with Proximal Femoral Deformity Daniel J. Berry, M.D. Most proximal femoral deformities encountered during hip arthroplasty are secondary to developmental processes, previous osteotomy or fracture. Deformities may be categorized anatomically by level and geometry. Anatomic levels include femoral neck deformities, metaphyseal deformities, metaphyseal-diaphyseal junction deformities and diaphyseal deformities. Deformities at each level may be angular (varus, valgus, flexion, extension), rotational or translational or a combination thereof. Treatment is individualized according to patient needs and anatomic demands of the deformity. Careful preoperative planning is essential. If cemented implants are used, care must be taken to obtain reasonable alignment and a continuous cement mantle. For uncemented implants, obtaining a good fit is more challenging and risk of intraoperative fracture is elevated. Access to a wide range of implants helps the surgeon manage unique femoral geometries. Implants fixed in the diaphysis allow some proximal femoral deformities to be bypassed. Modular or custom implants simplify management of certain deformities. For severe deformities femoral osteotomy may be required. Successful osteo-tomy requires deformity correction, maintaining vascular supply of fragments, obtaining fixation of osteotomy fragments (with the implant or adjunctive fixation) and obtaining implant stability. Though most deformities can be managed during hip arthroplasty, occasionally there is a role for two-stage management: deformity correction followed later by arthroplasty.
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