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THE HIP SOCIETY |
MEETING OF THE HIP SOCIETY Twenty-Ninth Open Scientific Meeting The Seventh Combined Open Meeting Hip Society and AAHKS San Francisco, California March 3, 2001 PROGRAM CHAIRMEN John R. Moreland, M.D. and Douglas A. Dennis, M.D. CONTENTS: COURSE DESCRIPTION: This course is divided into five sections. The first discusses wear and osteolysis. The second presents femoral fixation in primary surgery followed by the third section, the three Hip Society award papers. In the fourth section the speakers will communicate different aspects of the dislocation problem. Our final section introduces different types of revision surgery. COURSE OBJECTIVE: The Objective of this Open Meeting of the Hip Society is to provide the participants with important information concerning current issues in hip replacement surgery. The Program will convey information on the important subject of wear and osteolysis. The extent, biology, treatment, and prevention of wear will be discussed. The continuing controversy of femoral component fixation will be covered extensively. Dislocation, a major problem in hip replacement, will be outlined and emphasized. Finally, prosthesis removal and cement removal, and the current state of femoral revision will be presented. INTENDED AUDIENCE: Orthopaedic surgeons and orthopaedic residents. 8:00 am SYMPOSIUM I: 8:05
am 8:15 am 8:25 am THE PREVENTION 8:35 am 8:45 am 8:55 am 9:05 am 9:15 am 9:25 am 9:35 am 9:40 am 10:00 am SYMPOSIUM II: 10:20 am 10:30 am 10:40 am 10:50 am 11:00 am 11:10 am 11:20 am 11:30 am 11:40 am SYMPOSIUM III: 1:00 pm 1:10 pm 1:15 pm 1:25 pm 1:30 pm 1:35 pm SYMPOSIUM IV: 1:50 pm 2:00 pm 2:10 pm 2:20 pm 2:30 pm 2:40 pm 2:50 pm
SYMPOSIUM V: 3:05 pm 3:20 pm 3:35 pm FEMORAL REVISION 3:45 pm 3:55 pm 4:05 pm ACETABULAR REVISION 4:15 pm 4:25 pm 4:35 pm 4:45 pm 5:00 pm 8:05 a.m.
Wear And Osteolysis William H. Harris, M.D. The dominant long-term problem with conventional total hip replacements is periprosthetic osteolysis, caused by the macrophage and filoblast response to the ingestion of particulate polyethylene. This cellular response stimulates the osteoclasts, which, in turn, create the periprosthetic osteolysis (PPO). While PPO is commonly recognized as "baloon" lysis in the periacetabular region of the innominate bone, and as endosteal scolloping in the femoral cortex, other forms of PPO are also common and important. PPO is the usual cause of radiolucent zones around acetabular components and contributes to the radiolucent zones in the femur as well. It also can severely weaken the lesser and greater trochanter. Thus, this biologic process underlies or contributes substantially to both femoral and acetabular component loosening and is a major factor in most femoral and pelvic fractures around total hips. The prevalence of PPO can reach 40 to 60% by 10-years. Thus, reduction of particulate debris generation is central to the next major advance in THR. 8:15 a.m.
The Biology Of Osteolysis
J. J. Jacobs, M.D., C. Vermes, M.D., N.J.
Hallab, Ph.D., K. A. Roebuck, Ph.D., Since the recognition of aseptic loosening by Charnley in the early 1960s, a large amount of information has been gained on the basic science of periprosthetic bone loss. Initially termed "cement disease", it is now generally accepted that, in most instances, osteolysis is a manifestation of an adverse cellular response to phagocytosable particulate wear and corrosion debris, possibly facilitated by local hydrodynamic effects. Tissue explant, animal and cell culture studies have allowed us to compile an appreciation of the complexity of cellular interactions and chemical mediators involved in osteolysis. Cellular participants have been shown to include the macrophage, osteoblast, fibroblast, and osteoclast. The plethora of chemical mediators that are responsible for the cellular responses and effects on bone include PGE2, TNF-α, IL-l, and IL-6. However, a growing number of other pro- and anti-inflammatory cytokines, prostenoids and enzymes have been shown to play important roles in this process. Recent and ongoing work in the field of signaling pathways have suggested that protein tyrosine kinase pathways and NF-kB are critical intracellular mediators of this process. The ultimate goal of this basic research is to develop novel strategies for the evaluation and management of patients with osteolysis. While initial animal studies are promising for possible pharmacologic treatment and prevention of osteolysis, well-controlled human trials are required before agents such as bisphosphonates can be recommended for general clinical use. 8:25 a.m. Surgical Management of Osteolysis William J. Maloney, M.D. Currently little data exists to guide the surgeon in the management of periprosthetic osteolysis and stable implants. However, there are some general principles that can be applied. Focusing on cementless implants, the first question is whether the implant is stable and osseointegrated. If the implant is loose, it obviously must be removed. The principles that have been established for bone restoration with loose-cemented implants can then be applied. If the implant is stable and osseointegrated, the surgeon must decide whether to remove a well-fixed implant or debride and graft around the implant. The key question to be answered in this process is: Is there sufficient area of osseointegration with a reliable fixation surface to provide long-term implant stability? For pelvic osteolysis, a classification system has been developed to help in surgical management decisions. A type I case is one in which the socket is stable and the liner exchangeable. In this situation, the lysis can be debrided and grafted and the liner replaced. A type II case is one in which the socket is stable, but the liner not exchangeable and the well-fixed socket must be removed. A type III case is one in which the socket is unstable and must be removed. We have reviewed our experience with Type I and Type II cases. Sixty-eight well-fixed cups with osteolysis in the pelvis and polyethylene wear were identified from a series of 124 consecutive re-operations for failed cementless sockets. In 40 cases, (Type I cases), the polyethylene liner was exchanged and the osteolytic lesions debrided. In 28 cases (Type II cases), the socket was revised. Both strategies were successful in arresting the process of osteolysis. However, removal of well-fixed sockets was associated with significantly more bone loss. 8:35 a.m. Metal-On-Metal Articulation Lawrence D. Dorr, M.D. Introduction.
In the June 2000 JBJS, Metasul® metal-on-metal articulation for total hip replacement was reported with a 4-7 year follow-up using monoblock cemented cups. However, most surgeons use modular inserts into porous coated cups. Therefore, it is important to determine if modular Metasul® cups have results as good as monoblock cups and to justify their continued use. Methods.
Results:
Discussion:
8:45 a.m. Ceramic-on-Ceramic Bizot P., Nizard R., Hamadouche M., Hannouche D, Sedel L. Alumina on alumina bearings in total hip replacement has been introduced in patients since 30 years. Excellent tribological properties as well as extra low debris generation could, in theory, provide an answer to osteolysis. The 24 years experience of the Paris group show how osteolysis was no longer a problem and revision if any were related to mechanical failures and not to foreign debris reaction with the exception of few cases when the prosthesis has been loosened for many years resulting in metal on ceramic impingement. Cemented socket and screw in ring metal backed alumina were both bad solutions. Since the nineties, improvements in alumina quality and in ceramic fixation via cementless fully coated HA material, provide an answer that could allow long-term strategy in young and active patients. Preliminary results of the first 100 hips with cementless stem and socket and 32 mm alumina head, alumina liner held both via a Morse Taper experienced excellent short-term results. One socket was revised due to poor initial surgery in a severe acetabular fracture. High level of excellent results even in this young age population, from 14 to 71 (median 45 years) are very encouraging. 8:55 a.m. Alumina Ceramic - Cross Linked Polyethylene
Articulation In The Charnley Low-Friction Arthroplasty B. M. Wroblewski, M.D., P. D. Siney, M.D., P. A. Fleming, M.D. A group of 17 patients, 12 men (2 bilateral LFA’s) and 5 women had Charnley low friction arthroplasties with a combination of an 22.225 alumina ceramic femoral head and a cross-linked polyethylene acetabular cup. Their mean age at LFA was 53 years and 2 months (23 year 7 months to 79 years and 7 months) and their mean weight was 76 kg. (54 to 102) Four patients died. One patient with multiple sclerosis confined to a wheelchair was not followed up. The remaining 12 patients (14 alumina ceramic/XLP LFA’s) now have a follow-up of 14 years and continue to be followed up. None have had a revision. Their activity is in keeping with their age and gender. Total mean cup penetration is 0.37 mm mean (0.2 - 0.41) and a mean penetration rate over the whole period of the follow-up of 0.03 mm/year (0.02 to 0.041) During the first two years the mean total penetration was 0.22 mm (0 to 0.41) and a mean penetration rate of 0.11 mm/year (0 to 0.22) After the second year mean total penetration was 0.15 mm, (0 to 0.39) and a mean penetration rate of 0.02 mm/year (0 to 0.05). Compared with the most recent large series of the Charnley LFA where the penetration rate in patients under the age of 51 years was recorded at 0.11 mm/year, the ceramic XLP combination offers a fivefold reduction in the penetration rate. Whether or not polyethylene wear particles play a part in component loosening remain to be addressed. There is little doubt that reducing wear rates by the use of ceramic polyethylene combination is the next stage of evolution of the Charnley LFA. 9:05 a.m. Direct Compression Molding Merrill A. Ritter, M.D. Direct compression molded polyethylene is a process of creating a net shaped component with finished articular surfaces from ultra high molecular weight polyethylene by applying heat and pressure to the raw resin Hi-fax 1900 with the use of fixed geometry metallic tools. The final product has no machining or finishing. Between 1974 and 1978 there were 378 T-28 stems and 171 TR-28 stems articulating with a cemented direct compression molded acetabular component. Linear wear was 0.06 mm per year for the T-28 stem and 0.05 mm for the TR-28 stems. The revision rates for the acetabulum were 9.5% and 7.9% respectively with two acetabula noting osteolysis. On the femoral side they were 11.1% and 12.8% with 11 and 1 cases of osteolysis respectively. Between 1983 and 1996 4,581 AGC cemented total knee replacements with direct compression molded non-modular tibial components were performed. There was no osteolysis in the non-modular compression molded total knee replacements with 0.1% failure of the femoral components and 0.4% failure of the tibial components. Failure of all of these implants was because of cement technique and/or instability, wear and osteolysis were minimal. Direct compression molded polyethylene has stood the test of time and is an answer for the polyethylene of the present day. 9:15 a.m. Polyethylenes with Elevated Crosslinking Harry A. McKellop, Ph.D. The vast majority of the millions of UHMW polyethylene components that were used in hip and knee prostheses over the past three decades were sterilized using 2.5 to 4 Mrads of gamma radiation, with the implant packaged in air during sterilization and, in some cases, during several years or more of shelf storage prior to clinical use. Clinical follow-ups involving thousands of these gamma-sterilized implants, and retrieval analysis of hundreds in numerous centers internationally, has established that gamma-sterilization had both good and bad effects on the polyethylene. One important benefit was that the moderate level of crosslinking that was induced by the gamma radiation had the potential to improve the wear resistance of the polyethylene. However, oxygen that had diffused into the outermost 1 to 3 mm of the component prior to irradiation caused immediate oxidation during irradiation and, therefore, reduced crosslinking in the surface layer. Unfortunately, it was this surface layer that was subjected to wear in the patient. In addition, residual free radicals produced by the irradiation caused additional long-term oxidative degradation of the polyethylene as oxygen diffused into the implant during shelf storage and/or in vivo. In extreme cases, this led to gross delamination and fracture of the components. Over the past few years, four types of new UHMW polyethylenes with elevated levels of crosslinking received FDA approval and were introduced commercially, and others are undergoing development or approval. The common goals of these new processing techniques is to take advantage of the ability of crosslinking to improve wear resistance, while avoiding oxidative degradation. However, the four materials already in commercial use differ in the type of radiation used to induce the crosslinking, in the amount of crosslinking used, and in whether or not the bulk crosslinked polyethylene is remelted after irradiation but prior to machining into a component, in order to extinguish the free radicals and provide maximum resistance to long-term oxidation. Two of the four new polyethylenes are crosslinked with gamma radiation, as used in the past for routine sterilization. The other two are crosslinked with electron-beam radiation, a technique that is new to orthopaedic implants. Among other potential differences, an electron beam transmits the crosslinking energy into the polyethylene thousands of times faster than with gamma radiation, resulting in considerable heating of the polymer. Although there are laboratory data indicating that crosslinking the polyethylene while it is heated may have positive effects, whether this leads to an advantage or disadvantage in the clinical performance has yet to be determined. Interestingly, the laboratories that developed the new processes are in close agreement regarding the percent reduction in wear rate conferred by a given crosslinking dose (whether induced by gamma or electron beam). Advocates of limiting the crosslinking dose to 5 Mrads (i.e., about 25% higher than the 4 Mrads maximum used historically for radiation sterilization) maintain that a careful review of the literature summarizing the past clinical performance of gamma-air sterilized implants strongly indicates that the 85% to 90% improvement achieved with a 5 Mrad dose will be sufficient to reduce the wear rate well below the biological threshold for osteolysis, even in the most active patients. In contrast, advocates of increasing the dose to 10 Mrads (about 2 ½ times the historical maximum) maintain that the additional 5% to 10% reduction in wear offsets any potential drawbacks of this high level of crosslinking, such as lower fracture resistance. With each of the four new crosslinking processes, the polyethylene is irradiated while still in bulk form, such that any oxidized surface layer can be removed when the implant is machined from the central portion of the block or bar, thereby avoiding one of the serious problems of gamma-air sterilization of finished components. In addition, with three of the new polyethylenes, the block or bar is remelted prior to machining, in order to extinguish the free radicals caused by the irradiation. By definition, when UHMW polyethylene is heated above its “melt” temperature (about 155º C), it is transformed from a partially crystalline solid to a completely amorphous solid. This liberates the free radicals (electrons) that are trapped in the crystalline regions, allowing them to neutralize each other, thereby minimizing the potential for long-term oxidative degradation. In contrast, the fourth polyethylene is annealed (i.e., heated below the melt temperature) after irradiation. Since the crystalline regions are not completely transformed, depending on the temperature and duration used, many free radicals may remain in the polyethylene after annealing. Nevertheless, the advocates of annealing maintain that, because the finished implants are stored in nitrogen, and because the concentration of oxygen in the joint fluids is much lower than in air, any oxidation of the residual free radicals that does occur on the shelf or in vivo will have negligible effect on the long-term performance of the implants. On the other hand, they maintain that the changes in the mechanical and morphological properties of the UHMW polyethylene are smaller with annealing than with remelting and, therefore, annealing represents a more conservative approach. In response, the advocates of remelting point out that the UHMW polyethylene used by all of the manufacturers was melted at 170 ºC or higher when the original powder was formed into a molded block or extruded bar. Furthermore, since industrial UHMW polyethylene is not optimized specifically for the orthopaedic market, the subtle changes in mechanical and/or morphological properties caused by remelting (for example, a slightly lower stiffness) are, if anything, as likely to enhance the long-term performance of a prosthetic joint as they are to degrade it. Finally, they maintain that, if the free radicals that remain after annealing do oxidize substantially in vivo, the resultant degradation of the wear resistance and other mechanical properties of the implant could far outweigh any negative effects of remelting. Thousands of implants with elevated levels of crosslinking are being implanted each month internationally, and the respective manufacturers have instituted multi-center, detailed clinical monitoring. Ideally, this will permit early detection of any unanticipated problems and, eventually, demonstrate quantitatively whether or not either of the new polyethylenes constitutes a substantial improvement over alternative bearing materials, including polyethylene that has been crosslinked during routine gamma-sterilization in low-oxygen packaging, as well as metal-metal and ceramic-ceramic hips. 9:40 a.m. Evolution and Results of Conical Straight Titanium Stems with Corundum Blasted Surfaces. Felix Lintner, M.D., G. Böhm, M.D., Ch. Lhotka, M.D., and K. Zweymüller, M.D. Since 1979, the authors have been using a conical rectangular-cross-section titanium stem, for cementless fixation. This device allows stable fixation, at primary arthroplasty, in all but a few extreme cases. Even elderly patients with marked osteoporosis can be successfully managed, as can patients with an extremely high or an extremely low canal flare index. The first-generation stems (1979–1986) had little surface roughness (mean: 1 micrometer); the second (post-1986) generation stems have a mean roughness of 5 micrometers. A histologic and morphometric analysis of 34 stably fixed stems (time in situ: ten days to 15.2 years) was performed, to study the host bone response. The same osseointegration patterns were seen at the two degrees of surface roughness. Morphometry showed a mean osseous implant coverage of between 49% and 71%. In the immediate postoperative period, the mean implant/bone contact area was only 10%, which is adequate for stable primary fixation. At one year, new bone formation had increased up to threefold, from the postoperative values. Second-generation stems have been given an additional sagittal-plane taper, without changing the fixation principle. Morphometry showed a more uniform distribution of bone coverage along these stems. The study confirmed the primary and long-term stability of corundum-blasted conical straight-stem devices, by biologic fixation in the sense of osseointegration. 10:20 a.m. Cemented Femoral Stem In Total Hip Arthroplasty C.S. Ranawat, M.D., V.J. Rasquinha, M.D. The fixation of the femoral stem is reproducible and provides excellent early recovery of hip function in patients 60 - 80 years of age. The durability of fixation has been evaluated up to 20 years with 90% survivorship. The reported clinical failure rate of cemented femoral stem fixation is < 5% at 10-15 years follow-up with second-generation cement technique1,2. However in younger patients (<50 years) the reported failure rates range from 2.1% to 14% at 15-year follow-up3. The radiographic failure rate using cement debonding, progressive, global radiolucency, cement mantle fracture and migration of 3 mm as criteria is 8% at 15 years2,3. The durability of cemented total hip arthroplasty is multifactorial and good cement techniques and reduction in polyethylene is of premier importance. The primary reason for early aseptic loosening, i.e. within 10 years, is failure to achieve good micro and macro interlock at the time of surgery. Later failure involves both mechanical and biological factors as a consequence of an histlocytic response to the wear debris. The importance of an even cement mantle >2 mm thick is critical to ensure optimal stress transfer. Meticulous cement techniques are necessary to achieve a rigid fixation of the implant of suitable geometry to the bone and consequently improved clinical and radiographic results. They include the use of hypotensive epidural anaesthesia, adequate exposure via the posterior approach, preparation of the femoral bed with preservation of stable cancellous bone, pulsatile lavage and drying of the cancellous bone, mixing and pressurization of the cement into the plugged femoral canal and proper insertion/centralization of the femoral component. Undoubtedly the short and long term results of femoral components in total hip arthroplasty are influenced by a host of factors that include patient factors, design features, materials, evaluation criteria and duration of follow-up. However technical factors have a major bearing on the short-term and subsequent long-term results of the cemented femoral component. Since 1991, our experience in 235 cemented THA’s with the direct compression molded all polyethylene socket has demonstrated clinical survivorship of 99% and a mean wear rate of 0.075 mm/yr at a mean follow-up of 8 years. The debate of the role of surface finish and the mechanism of cement fixation of femoral stems continues to be ongoing. Current knowledge has confirmed comparable excellent outcomes with femoral stems that are polished and with a surface roughness Ra=45 microinches. We recommend the use of the cemented femoral stem in total hip arthroplasty as the implant/technique of choice for patients who are 60 years old or older. REFERENCES:
10:30 a.m. HA Coated Femoral Stems: 13 Year Follow-Up James A. D'Antonio, M.D., William N. Capello, M.D., Michael T. Manley, Ph.D. Hydroxylapatite (HA) coatings are osteoconductive and increase the amount, speed and strength of bony attachment compared to uncoated implants of the same design. HA coated stems have been shown to have less micromotion and subsidence than porous coated and cemented stems. Concerns with regards to HA delamination and third body wear have not materialized with thin dense plasma sprayed coatings. In a multicenter study 380 HA coated femoral stems were implanted in a young and active patient population from 1987 through 1990. 268 patients (305 femoral stems) have a minimum 10-year and maximum 13-year follow-up. The average age of the patients was a young 51 years, 55% of patients were males, 66% had a diagnosis of OA and 16% had avascular AVN. Clinically these patients manifested early pain relief and rapid restoration of function. The HHS at last follow-up have averaged 91.5 and 3% of patients complain of activity-related mild to moderate thigh pain. Radiographic analysis shows progressive bone remodeling around these implants through post-op year five, 100% of the stems are bony stable, 40% show proximal zone erosive lesions at the femoral neck resection level, and no patient has distal osteolysis. Two patients have been revised for aseptic loosening; one at two years in a patient who had a subtrochanteric osteotomy that never united and the implant was never stable; one aseptic loosening occurred at 9.5 years. No patient has a radiographically unstable stem. Two high-risk groups of patients include 116 patients under the age of 50 (average age 38), and 48 patients with AVN (average age 42 years). The mechanical failure rate (MFR) in these two subgroups are 1.8% for the patients under 50 and 0.0% for the patients with AVN. These results demonstrate excellent lasting fixation to a grit blasted tapered titanium stem with a dense highly crystalline pure proximal HA coating. This stem has performed well in a young and active patient population and in the hands of a variety of orthopaedic surgeons. 10:40 a.m. Tapered
Titanium Cementless Total Hip Replacement: Robert B. Bourne, M.D., FRCSC, Cecil H. Rorabeck,
M.D., FRCSC, The 10 - 13 year performance of 307 Mallory Head, cementless, tapered total hip replacements in 283 patients was assessed. Ninety percent of patients had a diagnosis of osteoarthritis. Fifty-five percent of patients were female. Mean patient age was 64 ± 10 years. The Hex-Loc acetabular component was used in each patient, as well as titanium alloy femoral heads. At final follow-up, 37 (13%) patients had died, 32 (10%) had undergone a revision and 2 (1 %) were lost to follow-up. No femoral stem was revised for aseptic loosening, but one was revised for sepsis and one for a periprosthetic fracture. Wear, osteolysis and loosening were problems with the Hex-Loc acetabular components and 32 (10%) acetabular components required revision. The mean Harris Hip Score at final follow-up was 87 ± 14. Thigh pain was noted in 3% of patients. Radiographic assessment revealed that no femoral stem or acetabular socket was definitely or probably loose. Three dimensional wear assessment using the Devane technique was 0.35 mm/year. The Mallory Head cementless, tapered femoral component performed well in this study, but unfortunately, the clinical results were compromised by the use of a poorly designed acetabular component, gamma irradiated polyethylene in air and titanium alloy femoral heads. 10:50 a.m. Total Hip Arthroplasty with a Collarless Wedge-Fit Tapered Cementless Stem Richard Rothman, M.D., J.J. Purtill, M.D., W. Hozack, M.D., P. Sharkey, M.D. The authors report 15-year experience with total hip arthroplasty using a collarless wedge-fit tapered circumferentially porous coated femoral stem (Trilock, Dupuy, Warsaw, In and Taperlock, Biomet, Warsaw IN). Excellent clinical results (Charnley pain function and motion scores improved from 3, 2.7 an 3.2 to 5.7, 5.5 and 5.2 respectively and Harris hip score of 91 at 15 years), low rates of thigh pain (1.4% and 4% for the Trilock and Taperlock respectively) combined with low rate of mechanical failure ( 5% for the Trilock and 0% for the Taperlock) were achieved with these implants Successful THA was performed in subsets of the population traditionally thought to have poor bone stock (over 80 years old and rheumatoid arthritis). Initial stability of these implants was confirmed with an Instron machine and fresh frozen cadaveric femora. Excellent stability was noted with similar plastic deformation and micromotion to cemented femoral implants. Clinically, immediate postoperative weight bearing is well tolerated with minimal subsidence (mean 0.86 mm) and no directly attributable failures. Hydroxyapatite coating appears to provide no clinical or radiological advantage at 2-year mean follow-up with Charnley pain, range of motion and function scores of 5.6, 5.6 and 5.6 with hydroxyapatite and 5.6, 5.6, 5.6 without, respectively. Visual analog pain scores however showed less thigh pain at 3 and 6-month evaluations in the hydroxyapatite augmented stems. Design features (collarless tapered wedge-fit circumferentially porous coated) are thought to be responsible for the excellent results. 11:00 a.m. Proximal Porous Coating Kenneth A. Krackow, M.D. The rationale and evolution of proximal porous coating and porous coating in general have to be understood in the context of total hip arthroplasty circa 1978-80. The claims of 98% or even 90%, 10 to 15+ year survival of cemented implants were not being made, both because there was a paucity of results over that time period, and at least USA surgeons felt they were seeing enough short to intermediate term failure, especially in younger people, that an alternative fixation mechanism was warranted. Animal laboratory work extending from an initial observation about screw stability in bone suggested that bone ingrowth into either porous beaded surfaces or fiber metal mesh surfaces may provide a very predictable, sturdy fixation methodology. Choice of metal, porous structure, and extent of porous coating were all considered by a variety of scientists and manufacturers. From the outset there was concern about observations of very strong bony attachment to pegs and rods that were porous coated, feeling that distal coating in the proximal femur could lead to proximal stress shielding. There were then laboratory studies raising this concern, and it is the opinion of many of us that today there are abundant clinical examples corroborating this concern. As a result, some, actually most, of the first “modern” attempts at porous femoral fixation (PCA’s and proximally coated AML’s) restricted the porous coatings to the proximal 25 to 40% of the femoral component surface. In addition to the concern about proximal stress shielding secondary to rigid distal fixation, some saw the broader, obviously vascular, proximal cancellous bone as an attractive bed from which ingrowth would sprout. It is safe to say that the initial experience from 1982-3 out to 1985-7 revealed satisfactory but less than optimal 3 to 5 year results with a slightly higher failure rate for component revision in many surgeon’s hands and the development of a situation, disputed by some surgeons but not by their patients, affectionately referred to then and now as thigh pain. Beyond that early experience we also began to recognize more consistently osteolysis and look for explanations and solutions to it also. The AML group led by Charles Engh pursued the course of increasing the extent of porous coating, while others addressed stem geometry, changes to more flexible metals and stem designs, also HA coatings---still with adherence to the goal of avoiding proximal stress shielding. There is more to the concern about extensively coated stems than proximal stress shielding, and that is the recognized difficulty of stem extraction or bail-out in the event of infection, fracture, recurrent instability associated with component malposition, etc. As a result many of us have held steadfast to the use of the proximally coated stems and today feel increasingly confident in their use. As we review intermediate and now long-term results one can extract any conclusion that he/she desires, and we get down to a choice that is akin to issues of religion and politics. Our task today cannot be to convince someone, one way or the other but to explain the issues and allow therefore a choice which addresses those points an individual surgeon feels are most important for his/her patient. 11:10 a.m. A Low Stiffness Composite Biologically Fixed Prosthesis Andrew H. Glassman, M.S., M.D., Roy D. Crowninshield,
Ph.D., A novel total hip femoral component was designed to simultaneously achieve stable skeletal fixation, structural durability, and reduced femoral stress shielding. The prosthesis combines a thin, forged, cobalt chrome core, surrounded by a polyaryletherketone material that is molded between the core and an extensive porous bone ingrowth surface comprised of titanium metal fibers. The resultant construct allows for proximal and distal canal filling, yet is significantly less rigid than all-metallic femoral stems crafted of either cobalt chrome or titanium alloy. Canine studies revealed favorable biological fixation and stability. Clinical experience is now approaching six years of duration, with a cohort of 366 patients (386 hips) treated at 21 institutions under a structured, multicenter clinical evaluation protocol. To date, complications have been unremarkable, and no femoral implants have required revision. Clinically, patients have shown excellent return to function, and exhibit very high Harris hip scores at each annual evaluation beyond one year postoperatively. Low levels of hip and thigh pain characterize the clinical outcome. Radiographically, the implants appear well fixed and exhibit no progressive radiolucencies or osteolysis. Radiostereometric analysis (RSA) studies on one subset of patients showed strong initial fixation and minimal stem micromotion in direct comparison to other metallic porous and cemented control implants. Dual-energy x-ray absorptiometry (DEXA) analysis on another subset of patients revealed excellent periprosthetic bone mineral density retention, with significant reduction in stress shielding as compared to literature reports on other fully porous coated, all-metallic implants. Additional clinical and radiographic follow-up of this novel prosthesis is planned, in hopes that the long-term biological response to a low-stiffness hip implant may become better understood and appreciated. 11:20 a.m. Long-Term
Results of Primary Total Hip Arthoplasty Using the C. Anderson Engh, Jr., M.D., Alexandra M. Claus,
M.D., Ph.D., This review reports long-term outcomes of 223 consecutive nonselected cementless primary total hip arthroplasties using extensively (>50%) porous-coated nonmodular AML stems and Trispike acetabular components. The arthroplasties were performed from October of 1982 through December of 1984. Mean patient age was 55. Eleven patients (12 hips) did not have minimum 2-year follow-up, leaving 204 patients (211 hips) with a mean follow-up of 13.4 years and a radiographic follow-up of 12.1 years. Thirty-nine patients (39 hips) had primary component revisions. One complete revision was performed for infection. Three stems were revised for aseptic loosening. Eighteen acetabular shells were revised: 7 for loosening, 4 for osteolysis, 3 for wear, 3 for recurrent dislocation, and 1 for sepsis. Seventeen polyethylene liners were exchanged: 9 for wear, 6 for osteolysis, and 2 for recurrent dislocation. Five rerevisions were performed. Accounting for revisions for loosening and the stability of the remaining components, the loosening rate was 3.4% for femoral components and 4.9% for acetabular components. In summary, porous coated fixation with the AML stem and Trispike acetabular component is durable. The most common reasons for reoperation are polyethylene wear and osteolysis. Factors contributing to wear-related acetabular revisions included younger patient age, the use of nonmodular 32-mm femoral heads, and proactive polyethylene liner exchanges to avoid wear-through. 11:30 a.m. Fixation of the Femoral Component in Total Hip Arthroplasty Leo A. Whiteside, M.D. and Daniel S. McCarthy This study was designed to test the hypothesis that press-fit femoral components with proximal press-fit and distal mechanical interlock can achieve fixation sufficient to allow bone ingrowth in osteoporotic as well as in normal bone. Addition of steps along the tapered distal stem improved fixation in osteoporotic bone enough to reduce micromotion to less than 20 microns in response to physiologic axial and torsional load. The clinical portion of the study included 226 consecutive hips (223 patients) with two-to-four year clinical results after total hip arthroplasty with a rectangular femoral component using proximal porous coating and distal mechanical interlock. Patient age ranged from 36 to 92 years. At two years postoperative, four percent of the femurs with type A (normal) bone, three percent with type B (intermediate) bone, and none with type C (osteoporotic) bone had thigh pain. No clinical cases of loosening have occurred either in normal or osteoporotic femurs. 1:00 p.m. The Otto Aufranc Award: The Role of Labral Lesions in the Development of Early Degenerative Hip Disease Joseph C. McCarthy, M.D., Philip C. Noble, Ph.D.,
Michael R. Schuck, M.D., It is well recognized that the etiology of osteoarthritis of the hip is multifactorial, with significant contributions from genetic, structural, biochemical and morphologic factors. Moreover, previous attempts to classify degenerative hip disease as either idiopathic or secondary have failed to explain the underlying cause of many cases of hip pathology, despite sensitive and exacting measures of normal skeletal morphology and intraarticular pressures. These observations have led us to suspect that, in many cases of so-called “idiopathic” degeneration, predisposing factors may have been present that are not readily appreciated using conventional diagnostic and radiographic modalities. Previous authors have postulated that the high incidence or early arthritis observed in dysplastic hips is due to the instability of the articulation und the repetitive shearing of the articular surface with functional joint motion. This suggests that other disturbances of the soft-tissue structures stabilizing the hip may also precipitate degenerative changes due to compromised joint stability. Potentially, one such condition is mechanical disruption of the hip labrum. Although lesions of the acetabular labrum were once considered a rarity, the prevalence of labral pathology has become more evident with the refinement and increased utilization of hip arthroscopy. However, the natural history of labral lesions has yet to be well defined and the functiona1 significance of the nom1allabrum remains a subject of debate. Moreover, though some authorities have suggested that acetabular labral pathology could conceivably contribute to the development of hip osteoarthritis, this hypothesis has yet to be adequately investigated. This study was conducted in three stages to examine the hypothesis that labral lesions contribute to early degenerative hip disease and to determine the feasibility of measures to prevent joint pathology through treatment of labral injuries. The goal of the first stage was to define the relationship between articular degeneration and labral lesions in patients whose joint symptoms were suggestive of labral pathology. The second stage was to determine whether similar correlations exist in individuals without symptoms without a documented history of joint disease. The third stage was to determine whether the hip labrum has a vascular supply that might potentiate the repair and regeneration of labral lesions, thereby preventing articular degeneration. 1:15 p.m. The John Charnley Award: 3-D Analysis of the Cement Mantle in THA Gonza1o G. Valdivia, M.D., FRCSC, Michael J. Dunbar,
M.D., FRCSC, David A. Parker, M.D., Quality of the cement mantle around the femoral stem is often quoted as a critical factor in the success of cemented total hip arthroplasty. Concern has been raised about the reliability of plain radiographs for its assessment. A new in vitro method of cement mantle measurement is described. Exact plastic replicas of six contemporary designs were implanted into cadaver femora using modern techniques and following the manufacturers' instructions. One-millimeter thick axial images were obtained every five millimeters with a high-speed helical CT scanner. Computer assisted analysis of mantle thickness was performed. A deficient mantle was defined as less than two millimeters. Comparisons were made between designs. A subset was compared to standard radiographs. Standard radiographs overestimated thickness (p<0.05) and underestimated the deficiencies. There is significant variability in the mantle produced by different designs (p<0.001). Commonly used designs have significant deficiencies in their mantles. 1:30 p.m. The Frank Stinchfield Award: Acetabular and Femoral Morphology: Anteversion Angle and Implant Positioning Masaaki Maruyama, M.D., Judy R. Feinberg, Ph.D., Morphology of the hip joint, in particular those features germaine to the determination of acetabular and femoral anteversion angles and offset of the femoral head, was studied in 50 male and 50 female human skeletons with bilateral normal hip joints. Age distribution typified that of a total hip arthroplasty (THA) population. Four distinct configurations were identified relative to the anterior acetabular ridge. The majority (121,60.5%) were curved; 51 (25.5%) were angular; 19 (9.5%) were irregular; and 9 (4.5%) were straight. The anteversion angle (AA) of the acetabulum measured 19.9 ± 6.6º (range, 7 - 42º) and was significantly larger in females (21.3 ± 7.1º) versus males (18.5 ± 5.8º). The notch acetabular angle (NA), which can easily be identified intraoperatively, was defined as the angle created at the intersection of a line from the sciatic notch along the posterior acetabular ridge and a line from the posterior to the anterior acetabular wal1. The NA was measured as 89.0 ± 3.5º and, as a result of being nearly perpendicular, this angle may be useful for determining an accurate estimate of acetabular anteversion and component placement during THA. Knowledge of the anatomic differences found between sexes with regard to the acetabular anteversion angle, the anterolateral bowing of the femur, and the neck shaft angle may assist the surgeon in decreasing the relatively higher incidence of dislocation in females and may possibly lead to different implant designs for males and females. 1:50 p.m. Dislocation: The Problem John J. Callaghan, M.D., Richard C. Johnston, M.D., Devon D. Goetz, M.D. Dislocation following total hip arthroplasty is stressful to the patient and surgeon. Prevention rather than treatment of dislocation is preferable to the surgeon and patient. Issues related to prevention include patient education and compliance, soft tissue reconstruction considerations, and component positioning considerations. With the expanded indications for primary hip surgery and the increasing need for revision hip surgery the need for preoperative education and, especially in the early postoperative period, postoperative compliance is essential. In fact some patient compliance is probably necessary throughout life as 20% of dislocations occur after five years. Over the past decade, the use of modularity and higher offset stems have enabled the surgeon to adequately reconstruct the soft tissues of the hip without performing trochanteric osteotomy. However the surgeon must understand that some aspects of modularity including skirted modular heads and extended liners can also compromise stability. When the present authors switched to small modular heads the dislocation rate significantly increases. In addition to soft tissue considerations the surgeon needs to be aware of bony impingement to include peripheral osteophytes. Accurate component positioning requires proper positioning of the patient at the time of surgery as well as identifying bony landmarks and using trial components intra-operatively to adequately position the acetabular component in the 30 to 50 degree “safe abduction zone” and to avoid retroversion of either component. Especially in the revision situation, in the lower demand patient, when adequate stability cannot be obtained consideration should be given to the use of constrained acetabular components. Postoperative bracing or casting can also be helpful. Dislocation, especially in the revision situation has been reduced with this approach (constrained components or early immobilization). These considerations will help minimize dislocation but will never eliminate the problem. 2:00 p.m. Reduction of Early Posterior Dislocation Following Posterolateral Approach in Primary Total Hip Replacement by Formal Posterior Capsular Repair Richard E. White, Jr., M.D., Timothy J. Forness,
M.D., The posterolateral surgical approach with complete posterior capsulectomy for total hip replacement is complicated by a significant incidence of early posterior dislocation. Formal repair of the posterior capsule and short external rotator tendons has been described as an approach modification to reduce the incidence of this early complication. The purpose of the study was to compare the incidence of early postoperative dislocation in the first six months following primary total hip replacement using the posterior capsulectomy technique and the posterior capsular repair technique. The identical posterolateral approach was used in all primary total hip replacement patients with the exception of management of the posterior capsule. The posterior capsulectomy technique (Group I) involved complete excision of the posterior capsule with no attempt at repair or reattachment of the short external rotators. Group I had 1,078 total hip replacements. The posterior capsular repair technique (Group II) involved reattachment of a broad flap of posterior capsule and short external rotators through drill holes in the posterior border of the greater trochanter. Group II had 437 total hip replacements. Only dislocations noted in the first six months were recorded because this is the high-risk period during which the posterior capsule is either reforming or re-adhering. In Group I (posterior capsulectomy), 52 of 1,078 total hip replacements (4.8%) had an early posterior dislocation. In Group II (posterior capsular repair), 3 of 437 total hip replacements (0.7%) had an early posterior dislocation. This difference was statistically significant. Internal rotation was reduced by approximately 50% by the reattachment process. No external rotation contracture was noted. A small avulsion fracture of the greater trochanter was noted in 4 of 437 total hip replacements (0.9%). The posterior capsular flap could not be reattached in 3 of 437 total hip replacements (0.7%). In posterolateral approach in primary total hip replacement, formal reattachment of the posterior capsule and short external rotators resulted in a statistically significant reduction of posterior dislocations when compared to patients who had complete posterior capsulectomy. 2:10 p.m. Dislocations in Primary Total Hip Arthroplasty with the Direct Lateral Approach Harry A. Demos, M.D., Cecil H. Rorabeck, M.D.,
FRCSC, FACS, Instability following a total hip arthroplasty is a serious complication. Dislocation rates up to 6.5% following posterior approaches have been reported within the last decade. For this reason, our institution favors the direct lateral approach for primary and revision total hip arthroplasty. A review of our arthroplasty database yielded 1,515 primary total hip arthroplasties performed via a direct lateral approach in 1,333 patients. These arthroplasties were all performed within a 10-year period and patients with follow-up data of less than 12 months were excluded. At most recent examination, 11.7% of the patients had a moderate or severe limp and 2.6% had severe heterotopic ossification. Only 5 hips (0.33%) had a dislocation or episode of instability. Two patients had more that one dislocation and required revision surgery. The results of this study demonstrate that dislocation after primary total hip arthroplasty can be nearly eliminated with the use of the direct lateral approach. The associated risks of heterotopic ossification or limp are felt to be acceptable. 2:20 p.m. Component Positioning William N. Capello, M.D., James A. D'Antonio, M.D., Proper component positioning is essential if post-operative dislocations are to be avoided. We undertook a computer analysis of ROM of a total hip prosthetic construct using impingement as an end point in order to determine the effect of component position on hip stability and ROM. The ideal position for maximal motion in all planes before impingement was 45 degrees of abduction and 25 degrees of flexion of the acetabular component with the femoral component in 15 degrees of anteversion. Increased abduction to 55 degrees allowed more motion than less abduction (35 degrees). Other factors that influence stability were femoral neck geometry, head diameter, and neck diameter. A cadaveric anatomic study was done to look at the relationship of the greater sciatic notch and acetabular anteversion. It was found to reflect anteversion accurately and is easily accessible at surgery. Finally two of the authors (WNC and JAD) routinely use the posterior approach in total hip arthroplasty and use only internal landmarks for acetabular orientation particularly the greater sciatic notch. Both contributed patients to a multi-centered prospective randomized controlled study investigating a ceramic on ceramic bearing used with a hydroxyapitite coated stem and either a HA coated socket or a porous coated socket, and into a continued access extension of the study. A total 717 hips were entered into this study nationwide. Nineteen dislocations have occurred for a rate of 2.6%. The two authors contributed 225 patients one of whom has dislocated for a rate of 0.4%. If one subtracts the authors patients from the 717 the dislocation rate increases to 3.6% (18/492) p<.05. We believe that dislocations with the posterior approach can be reduced if proper component positioning is understood and internal bony landmarks are used to orient the components. 2:30 p.m. Dislocation Treatment Daniel J. Berry, M.D. Treatment of recurrent hip dislocation in part is predicated upon understanding the etiology of the hip dislocation. Implant malposition usually is treated with component repositioning; soft tissue tension problems usually are treated with procedures designed to re-tension the soft tissues (using modular implants, component revision or greater trochanteric advancement) and problems with prosthetic or extra-articular impingement usually are treated with procedures designed to remove the source of impingement. Not all patients with a dislocation problem have a clearly definable etiology and even for those with a clearly definable etiology not all problems can be solved with the methods outlined above. Fortunately, other methods of treating recurrent hip dislocation are available: these include conversion to a constrained socket, conversion to a bipolar hemiarthroplasty and conversion to a non-constrained socket with a very large bipolar or monopolar femoral head. Each of these methods have theoretical and practical advantages and disadvantages, which will be discussed in this paper. Data from analysis of the various methods used to treat recurrent dislocation over the last three decades of total hip arthroplasty will be presented that demonstrate how operative methods of treating recurrent dislocation have evolved over time. The early and mid-term success rates associated with each of the available techniques to treat dislocation will be delineated. 3:05 p.m. Component and Cement Removal in Revision Total Hip Arthroplasty Wayne G. Paprosky, M.D., FACS, Steven H. Weeden, M.D., and Jack W Bowling, Jr., M.D. One of the first steps in revision hip arthroplasty surgery is the extraction of retained components prior to surgical reconstruction. In revision arthroplasty, the removal of well-fixed components and cement can be extremely demanding, time consuming, and damaging to the remaining host bone. Competent preoperative planning is imperative and assures that the appropriate equipment is accessible. Furthermore, preoperative planning aids in determining the proper extraction technique best suited for each particular implant. The preservation of host bone stock is of utmost importance, especially during the extraction of well-fixed cementless components. The revision of acetabular components may only require polyethylene exchange. In contrast, the removal of cemented acetabular components and well-fixed porous coated implants can be dangerous, especially in cases with mediallized acetabular components. One may elect to section the acetabular implant prior to removal in an attempt to preserve bone. During femoral implant removal, restricted access to the in-growth surface or cement may make component removal exceedingly difficult and increase the risk of iatrogenic damage to the remaining femoral bone. A preponderance of femoral components and the surrounding cement can be removed without the use of any trochanteric osteotomy. However, the use of an extended proximal femoral osteotomy may hasten implant removal, simplify cement removal, and protect the remaining bone stock These emerging implant removal techniques should allow the orthopaedic surgeon to extract both acetabular and femoral components skillfully and expeditiously, thus improving the efficacy of reconstruction. Our results in patients with noncemented porous coated acetabular component removal and noncemented femoral component removal are described. 3:20 p.m. Component And Cement Removal: How I Do It William Hozack, M.D. Experience is the best educator. Careful pre-operative planning minimizes complications and maximizes clinical results. Standardization of instrumentation with careful elimination of all superfluous tools makes the intra-operative experience more pleasant for both surgeon and surgical team. However, a full range of tools and equipment is crucial. A systematic approach to surgical exposure and component or cement removal is critical. On the other hand, the surgeon must have the flexibility and adaptability to change course in mid-operation should the situation dictate. Whatever surgical approach is chosen, the surgeon must have the ability intra-operatively to expand the exposure. Keep things simple. If there are two ways to solve a situation that are equally appropriate, choose the way that is the simplest and easiest. Preoperative planning
Surgical approach Any approach used for revision surgery should have the potential to be expanded incrementally into a more extensile exposure. Acetabular component and cement removal
Cementless stem removal
Cemented stem removal
Cement removal
3:45 p.m. Femoral Revision: Impaction Grafting G. A. Gie, M.D. The Exeter experience with Impaction Femoral Bone Grafting now extends to almost 14 years. It was introduced in 1987 in view of the poor results with simple re-cementing of femoral components and use of proximally coated uncemented stems. The aim was to achieve component stability in the presence of poor bone stock, to restore bone stock while loading the proximal femur, eliminate the need for long stems and to improve the prospects of further revision surgery in younger patients. The first 68 cases performed without specific instrumentation have been reviewed on a regular basis. Besides 3 early re-revisions for technical errors, only 3 further femoral revisions have been required, 1 at 7.5 years for a non-union of an intra-operative femoral fracture, one for deep infection after cup revision where the stem remained well fixed and one for sepsis at 12 years. At an average follow-up now exceeding 11 years, there has been no recurrence of endosteal bone lysis and there are no impending revisions for loosening. Bone stock recovery in this group of patients has been impressive. In late 1990 dedicated impaction instruments were introduced into clinical practice. These allowed for improved packing and better alignment of femoral components but led to increased intra-operative fractures. The continued use of short stems in Grade 3 femora led to an unacceptable incidence of post-operative femoral shaft fractures. These complications were overcome by the more liberal use of prophylactic cerclage wires and use of wire meshes and strut grafts. For the problem of lysis near the stem tip, a fully tapered 205mm stem was introduced to bypass such defects. It also became clear that long stems are occasionally required, such that, with the recent upgrade of impaction instruments, specific instruments have been designed for long stem use. In Exeter we remain enthusiastic about Impaction Femoral Grafting. Clinical and radiological results indicate that good long-term success can be expected. Survivorship to 12 years is 94%. The causes of complications and concerns with regard to cement mantle thickness have been addressed. The technique is particularly attractive for the young patient with bone stock loss but there is little doubt that the clue to success is surgical technique. 3:55 p.m. Femoral Revision: Titanium Modular David A. Mattingly, M.D. Advantages of proximally coated titanium modular stems include: optimum proximal and distal fit and fill occur independently; the sleeve is oriented independent of stem to maximize contact with best available proximal bone converting proximal sheer and hoop stresses to compressive load to prevent proximal stress shielding; the femoral stem is not weakened by porous coating and is placed independently of the sleeve to provide maximum joint stability; the low modular titanium stem has distal flutes for rotational stability and a distal clothespin to increase flexibility and decrease end stem thigh pain; and complete modularity allows “off-the-shelf” customization to manage all types of femoral revisions. Five to nine year follow-ups of 47 hips at our institution revealed stems to be ingrown in 93%, stable fibrous in 5% and unstable in 2%. The seven-year radiographic survivorship was 92% with no osteolysis distal to the porous sleeve. Proximal femoral trabecular consolidation and/or hypertrophy occurred in 80.6%. Clinical results were good or excellent in 82%, fair in 9% and poor in 9%. Modular titanium stems provide clinical results superior to unitized cemented or proximally coated cementless stems while avoiding proximal stress shielding seen in fully porous stems. 4:05 p.m. Cementless Femoral Revision Arthroplasty: Minimum Five Year Follow-Up John R. Moreland, M.D. Between January 1984 and December 1991 one hundred eighty-five consecutive cementless femoral revision arthroplasties were performed using extensively porous-coated cobalt-chrome stems. All patients had their surgeries by the same surgeon and were followed prospectively until death, stem removal or minimum five years follow-up. Twenty-nine patients died with less than five years of follow-up. Nineteen additional patients failed to return for a minimum five years follow-up evaluation. Thus, one hundred thirty-seven hips were available for this minimum five-year follow-up study series. Mean follow-up was 9.3 years (range 5 to 15.8 years). Mean age at surgery was 62.6 years (range 27.8 to 86.2 years). Ten (7 %) of the stems have been removed. Only five (4 %) have been removed for fixation problems. Four of these five were not bone ingrown and were re-revised. The fifth stem removed for fixation failure was bone ingrown but had significant thigh pain. The stem was removed and a cemented stem was placed with a good result. The other five of the ten removed stems required removal for infection (one early and four late infections). Excluding the one stem removed for early infection and using Engh radiographic criteria, 83.1 % of the stems (N = 136) achieved bone ingrowth. Late failure of bone ingrowth was not observed. Canal filling prostheses were more likely to have bone ingrowth as were stems placed in femurs with lesser degrees of bone stock deficiency. Significant thigh pain was seen in 7.1 % of bone ingrown stems, 16 % of stable fibrous fixated stems, and 75 % of unstable stems. Significant thigh pain in bone ingrown stems was seen more commonly in osteoporotic femurs and bone stock deficient femurs. Severe stress shielding correlated with pre-operative osteoporosis and larger diameter stems. No failures due to stress shielding have been identified. Other component reoperations were: 16 (11.7 %) for acetabular loosening, 4 (2.9 %) for wear, and 3 (2.2 %) for dislocation. 4:15 p.m. Reconstruction
Of Acetabular Bone Loss During Revision THA Tom J.J.H. Slooff, M.D., Ph.D., B. Willem Schreurs,
M.D., Ph.D., The major problem in revision total hip surgery is the loss of bone stock, which frequently results in combined central and peripheral cavitary segmental defects at the acetabular side. In 1979, a biological method was introduced with tightly impacted cancellous allografts in combination with a cemented polyethylene cup for the acetabular reconstruction. With the technique it is possible to replace the loss of bone and to repair normal hip mechanics and hip function in combination with a standard hip prosthesis. This biological method is scientifically supported by animal experiments and by clinical investigations. Several long-term outcome studies both in primary total hip arthroplasty and revision have confirmed that a long-lasting stable reconstruction can be achieved. From human biopsies and histologic data in animal experiments it is demonstrated that the impacted allograft was successfully incorporated. 4:25 p.m. Cementless Acetabular Revision at 9-15 Years Aaron G. Rosenberg, M.D., Laura Quigley, R.N.,
Joshua J. Jacobs, M.D., From 1983 to 1988 we revised 176 failed cemented cups with cementless acetabular sockets in 167 patients. Implants were placed line to line with supplemental screws. 35 patients died prior to 9 years (none requiring revision) leaving 139 components in which 33 had less than 9-year follow-up (none requiring revision) leaving 106 hips for radiographic and clinical evaluation at an average of 130 (102-169) months. Of the original 176 revised sockets, bulk structural graft was required in 9 cases (5%). All grafts healed radiographically. At final follow up, 87% of cups were radiographically stable and not revised, however, 7% were radiographically and clinically stable but required revision: 5 for recurrent dislocation, 5 for late sepsis and 2 were revised at the time of loose stem revision at 71 and 75 months. No revisions for aseptic loosening were required. An additional 4% (7) were noted to have 4 of 5 modified Charnley zones with radiolucent lines (RLL) of <2 mm and were considered possibly unstable, while 4 cups (2%) were unstable demonstrating 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 cases, with pad fragmentation noted in 11 additional cases (noted at an average of 113.6 months). 2 cases had lucencies about a single screw while 12 additional 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. Following the principles of obtaining intrinsic mechanical stability via debridement and reshaping of remaining bone, the use of dome screws, allograft particulate bone to manage defects, and the rare use of the high hip center, cementless acetabular revision remains the treatment of choice in 95% of our socket reconstructions. Indications for cages or bulk grafts include combined findings of superior migration over 3 centimeters combined with medial protrusion and loss of posterior column support. 4:35 p.m. Bridging
Massive Acetabular Defects with the Triflange Cup: Michael J. Christie, M.D., Steven A. Barrington,
M.D., An unresolved issue in total hip arthroplasty is acetabular reconstruction when there is bone loss that results in pelvic discontinuity, that involves radiation-compromised bone stock, or that is significant enough to exceed the limits of jumbo hemispherical cups. Achieving pain relief and initial and long-term implant stability on host bone are the major goals of this type of reconstruction. Seventy-nine hips in 77 patients in which a large acetabular defect was bridged using a custom-designed, triflanged component were retrospectively reviewed. The preoperative deficiency was classified as a combined deficiency in 40 cases and as a pelvic discontinuity in the other 39. There were 8 primary and 71 revision cases. Six patients died prior to achieving a minimum of 2 years follow-up. With 5 patients considered lost to follow-up, there were 68 hips in 66 patients with an average follow-up of 53 months (range 24-107 months). No triflange cup has been removed. Pain scores improved from a mean of 16/44 preoperatively to 40/44 postoperatively. Radiographically there are two cases of incompletely healed discontinuities but both patients are asymptomatic. The dislocation rate is 17.4%. The triflange cup offers an alternative method of repair that reliably provides pain relief, initial and long-term implant stability, and pelvic stability in cases of discontinuity. President: 1st
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