The custom triflange cup: build it and they will come.

The custom triflange is a patient-specific implant for the treatment of severe bone loss in revision total hip arthroplasty (THA). Through a process of three-dimensional modelling and prototyping, a hydroxyapatite-coated component is created for acetabular reconstruction. There are seven level IV studies describing the clinical results of triflange components. The most common complications include dislocation and infection, although the rates of implant removal are low. Clinical results are promising given the challenging problem. We describe the design, manufacture and implantation process and review the clinical results, contrasting them to other methods of acetabular reconstruction in revision THA.

Long-term results of use of the anatomic medullary locking prosthesis in total hip arthroplasty.

A total hip arthroplasty was performed, with use of the anatomic medullary locking hip system, in 223 consecutive, non-selected hips in 215 patients. The mean age of the patients at the time of the operation was fifty-five years (range, sixteen to eighty-seven years). Twenty-one patients (twenty-two hips) were lost to follow-up and twenty-seven patients (twenty-seven hips) died less than ten years postoperatively. The remaining 167 patients (174 hips) were followed for a minimum of ten years (mean, eleven years; maximum, thirteen years). There were twenty reoperations involving a component. The rate of survival at twelve years was 0.97 +/- 0.02 (mean and standard error) for the stem and 0.92 +/- 0.03 for the cup. Patients who had osteolysis were younger than those who did not have osteolysis (mean age, forty-seven compared with fifty-six years; p < 0.01). Similarly, patients who had a reoperation were younger than those who did not have a reoperation (mean age, forty-six compared with fifty-four years; p < 0.01). The radiographic appearance of progressive wear that, in our opinion, was severe enough to cause the femoral head to completely penetrate the polyethylene liner was the most frequent reason for reoperation.

Analysis of temporal wear patterns of porous-coated acetabular components: distinguishing between true wear and so-called bedding-in.

BACKGROUND: Standard radiographic assessment of penetration by the femoral head into a polyethylene liner does not enable clinicians to distinguish between the two processes that cause movement of the head: true wear (the removal of polyethylene particles) and so-called bedding-in (other factors, such as creep and settling-in of the liner). By analyzing radiographs made over time, researchers can distinguish true wear from the bedding-in process. The purpose of the current study was to compare the wear performance of the initial modular acetabular cup design (so-called first-generation components) of three different manufacturers with that of a so-called second-generation component made by one of the manufacturers. METHODS: A two-dimensional computerized radiographic method was used to analyze 1300 radiographs of 315 hips that were followed for 3.0 to 10.5 years. Temporal penetration by the head in the three groups of first-generation cups was compared with penetration in the group of second-generation cups. Multiple linear regression analysis was used to model penetration-versus-time data as a line for each group. The slope of each regression line indicated the true rate of wear, and the intercept of the regression line indicated the amount of bedding-in. RESULTS: Modifications in the design of the second-generation components, including thicker polyethylene and an improved locking mechanism, led to a decrease in the mean penetration by the head; however, the second-generation component did not have a lower true rate of wear than two of the first-generation components. Rather, the decreased penetration by the head into the second-generation component resulted from decreased bedding-in of the liner. CONCLUSIONS: These findings and this technique of analysis are clinically relevant to surgeons who evaluate polyethylene wear radiographically. First, penetration by the head in the early postoperative years might not be due entirely to abrasive wear of the polyethylene liner but, rather, to a change in the position of the head resulting from the bedding-in process. The inclusion of bedding-in in calculations of wear artificially inflates the rate of wear and may result in a misrepresentation of the potential risk of wear-related complications. This is especially true with regard to comparisons of different designs of modular cups, in which conformity and tolerances between the polyethylene liner and the metal shell can vary greatly. Second, analysis of penetration by the head at multiple time-intervals can be used to distinguish true polyethylene wear from the bedding-in process. Such an analysis allows more accurate determination of the true rates of wear of different designs of modular cups and, therefore, of potential wear-related complications.

Radiographic evaluation of penetration by the femoral head into the polyethylene liner over time.

UNLABELLED: We examined the pattern of temporal penetration by thirty-two-millimeter-diameter femoral heads into polyethylene liners in a group of 105 hips (103 patients) in which an Arthropor metal-backed cup had been implanted. Each patient was evaluated radiographically and clinically at a minimum of four different postoperative intervals. The initial evaluation was performed a mean of 2.9 weeks (range, one to fifteen weeks) postoperatively, and the latest evaluation was performed a mean of 7.9 years (range, five to ten years) postoperatively. Two-dimensional wear - that is, penetration by the femoral head into the ultra-high molecular weight polyethylene liner - was determined from anteroposterior radiographs of the pelvis with a computer analysis system that calculated the change in the position of the center of the head relative to the center of the cup. Three new findings are reported. First, there was a large difference (mean, 1.1 millimeters) between the center of the head and that of the cup as measured on the initial postoperative radiographs. This difference underscores the need for researchers to consider the initial displacement of the head when measuring and reporting polyethylene wear. Second, although there was wide variation in responses among individuals, temporal examination of the data revealed a trend toward a decreasing rate of penetration with time. Moreover, the rate of penetration appeared to reach a steady-state value after the sixth postoperative year and remained nearly constant until the ninth postoperative year. Third, by comparing the subsets of patients who had the greatest and the least initial penetration by the head, we found that penetration behavior, although remarkably different between the groups in the first three years postoperatively, became similar with time. CLINICAL RELEVANCE: When making decisions regarding individual patients or hip systems that demonstrate penetration by the femoral head into the polyethylene liner, clinicians should consider the patterns of penetration over time. Measurements of the amount and rate of penetration that are based solely on the most recent radiograph do not represent the full clinical picture. We advocate more frequent radiographic follow-up and, when available, analysis of serial radiographs for patients who have excessive penetration by the femoral head into the acetabular liner.

Acetabular revision with use of a bilobed component inserted without cement in patients who have acetabular bone-stock deficiency.

BACKGROUND: Massive deficiency of acetabular bone stock is a challenging problem in the increasing number of patients who need a revision of a failed hip arthroplasty. The bilobed cup has been presented as one alternative reconstruction technique for hips with extensive acetabular bone loss. The purpose of this study was to assess the results with use of a bilobed acetabular component inserted without cement for revision reconstruction in hips with acetabular bone deficiency in order to clarify the indications for its use and to identify the factors that influence the clinical and radiographic outcome. METHODS: Forty-one hips in thirty-eight patients had an acetabular revision with a bilobed acetabular component inserted without cement between December 1991 and December 1995. These hips were a subset of the 414 hips treated with an acetabular revision during the same period of time. One patient was lost to follow-up, and one died during the study period. Two patients who could not return for radiographic evaluation completed questionnaires. The remaining thirty-four patients (thirty-seven hips) were evaluated radiographically and clinically and were followed for an average of forty-one months (range, twenty-four to sixty-six months). RESULTS: Radiographic analysis demonstrated an improvement in the average vertical displacement of the hip center. At the time of the latest follow-up examination, 76 percent (twenty-eight) of the thirty-seven cups were stable, 8 percent (three) were probably unstable with a change in the screw position but no definite migration of the cup, and 16 percent (six) were unstable. Eight of the nine loose or probably loose components were in patients who had more than two centimeters of superior migration of the component and disruption of Kohler's line on preoperative radiographs. Additionally, implants were more likely to become unstable (demonstrating more than 4 degrees of change in the abduction angle or more than four millimeters of radiographic migration) when the inferior aspect of the component did not extend to or distal to the interteardrop line, which indicated that the component was undersized. CONCLUSIONS: On the basis of our early rate of probable or definite loosening of 24 percent (nine of thirty-seven cups) and the technical difficulties involved, we do not recommend the routine use of this component. We believe that this device is indicated when a patient has an oblong-shaped acetabular defect and the surgeon wants to correct an elevated hip center. However, the medial wall of the acetabulum (Kohler's line) should be intact if the failed component has migrated more than two centimeters. An alternative reconstruction technique, such as use of a structural allograft with or without an acetabular cage, is also an option in this situation.

Long-term clinical consequences of stress-shielding after total hip arthroplasty without cement.

Remodeling of the femur, or so-called stress-shielding, was observed on the two-year postoperative radiographs of forty-eight (23 per cent) of 207 hips that were part of a consecutive, non-selected series of 223 hips that had had a primary arthroplasty with use of the anatomic medullary locking hip system. Three patients (three hips) died within ten years after the arthroplasty, leaving forty-four patients (forty-five hips) who had a minimum of ten years of clinical follow-up. At the time of the latest follow-up, thirty-eight patients (86 per cent) reported that they had either no or mild pain related to the hip, forty-two (95 per cent) had less pain than they had had preoperatively, and forty-one (93 per cent) were satisfied with the results of the arthroplasty. Two patients had a reoperation, but neither procedure involved the femoral component; specifically, one patient had a revision of a loose acetabular component and one had an exchange of a polyethylene liner. No femoral component was associated with clinical or radiographic evidence of loosening. Femoral osteolysis, confined to zones 1 and 7 of Gruen et al., was observed on the ten-year radiographs of four of the thirty-three hips for which such radiographs were available. Stress-shielding (defined as evidence of pronounced femoral bone-remodeling on the two-year radiographs) had not adversely affected the outcome for these four hips by the time of the latest follow-up. The findings regarding postoperative pain, function, and over-all satisfaction for the forty-four patients (forty-five hips) who were included in the present study were similar to those reported for our larger (parent) series of patients who had been managed with the anatomic medullary locking hip system and to those reported for a similar series of patients who were followed for 9.5 years after the insertion of a porous-coated anatomic prosthesis. In addition, the prevalence of acetabular and femoral osteolysis (four [12 per cent] of thirty-three hips) and that of revision of the femoral component (zero [0 per cent] of forty-five hips) were lower than those for our larger (parent) series (fifty-four [39 per cent] of 137 hips and three [1 per cent] of 201 hips, respectively) as well as those for the series of patients who had been managed with the porous-coated anatomic prosthesis (thirty-five [45 per cent] and four [5 per cent] of seventy-eight hips, respectively).

The accuracy and reproducibility of radiographic assessment of stress-shielding. A postmortem analysis.

BACKGROUND: Although periprosthetic bone loss remains a major concern in total hip arthroplasty, radiographic assessment of such loss is both difficult and subjective. In the present study, we assessed the ability of orthopaedic surgeons to reproducibly recognize changes in periprosthetic bone density on radiographs. We hypothesized that assessment of periprosthetic bone loss on plain radiographs is not reliable enough to justify its use in outcomes research. METHODS: Twenty-nine unilateral total hip replacements and the surrounding bone were retrieved at autopsy, and radiographs were made; radiographs of the contralateral, normal femur were also made after implantation of an identical prosthesis and used as a control. Three orthopaedic surgeons independently examined the specimen radiographs and classified bone loss in each of sixteen femoral zones. Bone loss was recorded as present if the bone of the femur that had had in vivo implantation showed evidence of cortical thinning, increased porosity, or decreased density (either cortical or trabecular) when compared with the control femur. The kappa coefficient was used to quantify interobserver and intraobserver reproducibility in determining bone loss for the 464 zones examined and in determining the Engh and Bobyn stress-shielding classification of each femur. In fourteen femoral pairs, bone loss was also quantified with dual-energy x-ray absorptiometry, and the resulting value was then compared with the bone-loss classification that had been determined radiographically. RESULTS: First, the surgeons agreed on the presence or absence of bone loss in 73 percent (337) of the 464 zones. The interobserver kappa value of 0.58 denoted only good reproducibility. The intraobserver reproducibility was better; the surgeon's initial evaluation of bone loss agreed with his second evaluation for 90 percent of the zones (kappa = 0.74). Second, the three surgeons agreed on the degree of stress-shielding, according to the Engh and Bobyn classification, in 66 percent (nineteen) of the twenty-nine femora. The kappa value for this comparison was only 0.27, indicating marginal reproducibility. Third, although there was some agreement among reviewers when there was 20 to 60 percent reduction in bone-mineral content as determined with dual-energy x-ray absorptiometry, excellent agreement among the examiners (kappa = 0.85) was not achieved until bone loss averaged 70 percent. CONCLUSIONS: On the basis of these results, we suggest caution in interpreting results from studies of femoral bone loss that have used plain radiographic analysis if the authors have not provided interobserver reliability data. We question the utility of evaluating periprosthetic bone loss on radiographs, since the loss is not reproducibly recognized until 70 percent of the bone is gone.

Osteonecrosis of the femoral head treated with cementless total hip arthroplasty.

BACKGROUND: The treatment of young patients who have osteonecrosis of the femoral head associated with collapse or substantial secondary degeneration remains a therapeutic challenge, with total hip arthroplasty being a treatment of choice. However, concerns about the durability of the results of hip arthroplasty in this population necessitate long-term evaluation of this treatment option. To determine its advantages and limitations, we evaluated the results of cementless total hip arthroplasty in a consecutive series of young patients with advanced osteonecrosis. METHODS: We reviewed the results of fifty-five consecutive primary total hip arthroplasties, after an average of 117 months of follow-up, in forty-five patients with a preoperative diagnosis of advanced osteonecrosis of the femoral head (Ficat and Arlet stage III or IV). The average age was thirty-one years (range, twenty-one to forty years) at the time of the operation. We collected data prospectively with the use of patient questionnaires and radiographs. RESULTS: Five patients died and one patient was lost to follow-up before the time of the minimum five-year follow-up; this left forty-eight hips in thirty-nine patients for inclusion in the study. Ten (21 percent) of the forty-eight hips required revision. No revisions were due to aseptic failure of the femoral component. Of the remaining twenty-nine patients (thirty-eight hips), twenty-seven (93 percent) reported few or no functional limitations and twenty-three (79 percent) could walk an unlimited distance at the time of the latest follow-up. Pain was absent or mild in twenty-five patients (86 percent). Twenty-three patients (79 percent) were employed full-time. Radiographically, thirty-seven femoral components (97 percent) were bone-ingrown and the remaining component was judged to be fibrous stable. All thirty-eight acetabular components were bone-ingrown. CONCLUSIONS: Cementless total hip arthroplasty remains a reasonable treatment option for advanced osteonecrosis of the femoral head. Wear of the bearing surface continues to limit the long-term success rate, but we are encouraged by the predictable long-term stability of the bone-implant interface achieved with cementless fixation. These results compare favorably with those of published reports of total hip arthroplasty with cement in younger patients with osteonecrosis.

Extended slide trochanteric osteotomy for revision total hip arthroplasty.

BACKGROUND: The purpose of this study was to assess the rate of union, time to union, and complications associated with the extended slide trochanteric osteotomy. We also evaluated how outcomes were influenced by the preoperative cortical-bone thickness, the preoperative cancellous-bone quality of the greater trochanter, the number of cables used to reattach the trochanteric osteotomy fragment, and the use of cortical strut augmentation. METHODS: We reviewed the results for forty-six hips in forty-five patients who underwent a revision total hip arthroplasty with an extended slide trochanteric osteotomy between December 1991 and December 1996. Twenty-three patients were men, and twenty-two were women; the mean age at the time of the operation was 66.3 years. Two hips had an isolated acetabular revision, fifteen had an isolated femoral revision, and twenty-nine had acetabular and femoral revisions. One patient (one hip) was lost to follow-up. RESULTS: At a mean of forty-four months after the operation, the rate of union of the distal osteotomy site was 98 percent (forty-four of forty-five hips), with no change in the femoral component position. The time to union was not significantly correlated with the number of cables, the preoperative cortical-bone thickness, or the preoperative cancellous-bone quality of the greater trochanter. Interestingly, the time to bridging-callus union was significantly longer in the hips with a strut allograft than in the hips without a strut allograft (p = 0.04, t test for independent samples). Two fractures of the osteotomy fragment occurred, but neither necessitated another revision. CONCLUSIONS: The extended slide trochanteric osteotomy allows extensive acetabular and femoral exposure, facilitates removal of distal cement or a well fixed porous-coated stem, and allows reliable reattachment and healing of the trochanteric fragment.

Patterns of osteolysis around total hip components inserted with and without cement.

We reviewed the radiographs of 137 patients (137 hips) who had been managed with a total hip arthroplasty, with insertion of an extensively porous-coated femoral component without cement, because of osteoarthrosis or avascular necrosis. A porous-coated acetabular component had been inserted with cement in sixty-three of these patients (Group A) and without cement in seventy-four patients (Group B). The radiographs were examined for osteolysis, either directly adjacent to the joint or at locations remote from the joint. The mean duration of follow-up was 105 months (range, fifty-four to 142 months). The rate of osteolysis of the acetabulum in the unrevised hips in which the acetabular component had been inserted with cement was 37 per cent (nineteen of fifty-one). The osteolysis was most frequently of the linear type, a pattern that was associated with a high prevalence of loosening in the hips that had a cemented cup (30 per cent [nineteen of sixty-three]). The rate of acetabular osteolysis (18 per cent [thirteen of seventy-one]) in the patients who had a cup that had not been inserted with cement and that had not been revised was not as high as that associated with the surviving cups that had been inserted with cement (p < 0.05). The osteolysis associated with the cups that had not been inserted with cement was localized and expansile, and it was not associated with loosening of the component. However, it produced more loss of bone than did the linear pattern of osteolysis around the cemented cups.(ABSTRACT TRUNCATED AT 250 WORDS)

A clinically practical method of manually assessing polyethylene liner thickness.

BACKGROUND: Most orthopaedists do not have access to contemporary computer-assisted radiographic techniques and therefore must use manual radiographic methods to assess polyethylene wear. The accuracy of most manual methods, however, has not been verified on clinical radiographs. In this study, we used manufacturer-developed wear templates to measure polyethylene wear and compared that technique with two other commonly used manual radiographic methods. Our purpose was to compare the accuracy of these techniques and thus determine their usefulness in assessing polyethylene wear in individual patients. METHODS: We analyzed seventeen polyethylene liners that were retrieved during revision operations after a mean of 12.0 years in situ. With use of digital calipers, we directly measured the true minimum polyethylene thickness of the explanted liner. We then measured the polyethylene thickness on anteroposterior pelvic radiographs that had been made before the revision. Three different manual techniques were used to evaluate the radiographs: the Dorr method, the Livermore method, and the newly described wear-template method. The minimum polyethylene thickness that was calculated with use of each of these methods was compared with the thickness as determined by direct measurement of the explanted liner. RESULTS: The mean error for the Dorr method (1.54 +/- 1.21 mm) was significantly greater than that for both the Livermore method (0.07 +/- 0.62 mm) and the wear-template method (-0.04 +/- 0.28 mm) (p < 0.01). The mean error for the Dorr method was significantly greater than zero (p < 0.01), indicating that this method consistently overestimated the true measurement. In contrast, the mean errors for the Livermore and wear-template methods were not significantly different from zero (p = 0.64 and 0.58, respectively), indicating that these methods did not consistently underestimate or overestimate the true measurement. However, the large standard deviations for all three methods suggest that the ranges in error are wide. The limits of agreement for the Livermore technique ranged from a 1.17-mm underestimation to a 1.31-mm overestimation of the true thickness of the polyethylene; those of the wear-template technique were smaller, ranging from a 0.60-mm underestimation to a 0.52-mm overestimation. CONCLUSION: The practicing orthopaedist needs an accurate and efficient method for determining the polyethylene thickness of modular acetabular components. We found that the template method best met this requirement because it involved a simple procedure: placing the template over the radiograph and measuring the distance between the femoral head and the inner surface of the metal shell. The other methods were less accurate, required additional information from the manufacturer, were more time-consuming, and were not as easy to demonstrate to the patient.

Femoral fracture during non-cemented total hip arthroplasty.

A study of the data on 1,318 consecutive non-cemented total hip-replacement arthroplasties revealed thirty-nine intraoperative fractures of the femur (3 per cent), only half of which were diagnosed intraoperatively. The fractures occurred in the proximal region of the femur or at the tip of the stem of the prosthesis. Most were incomplete and minimally displaced, and they did not jeopardize the stability of the femoral component. All complete proximal fractures were stabilized with a four-fifths-coated or fully coated prosthesis to provide distal fixation, and, when diagnosed intraoperatively, were fixed with cerclage wiring. When an incomplete fracture near the tip of the stem was discovered postoperatively and the posterior part of the femoral cortex was intact, a spica cast was applied, and the patient was instructed in protected weight-bearing. For a complete fracture at the tip of the stem, we recommend open reduction and internal fixation. No statistical difference was found with respect to residual pain, the score for walking, or the stability of the implant when we compared the results for the patients who had a fracture with those for the patients who did not. Modifications in surgical technique resulted in a decrease in the incidence of fractures (p less than 0.05).

Severe osteolysis of the pelvic in association with acetabular replacement without cement.

We reviewed the cases of fourteen patients (fifteen lesions) who had osteolysis following the replacement of the acetabulum without cement. Nine women and five men, seventeen to sixty-seven years old, were involved in the study. One woman had bilateral pelvic osteolysis. Eight of the fifteen index acetabular reconstructions were done with a titanium-alloy implant and seven, with a chromium-cobalt-alloy implant. Eleven of the fifteen acetabular components had holes in the metal shell that may have acted as a conduit through which wear debris could gain access to the implant-bone interface, but only two of the acetabular components had been fixed with screws. In these two acetabular components, all available screw holes were not filled. The polyethylene liner was eight millimeters thick or less in twelve of the fifteen acetabular components; all of the liners were ten millimeters thick or less. The diameter of the head of eleven of the fifteen femoral components was thirty-two millimeters. Fourteen of the fifteen femoral components were placed without cement, and all but one was radiographically stable. The duration from the index operation to the appearance of pelvic osteolysis ranged from fifty-three to eighty-four months (mean, sixty-five months). At the time of the diagnosis, the patients were functioning well clinically, and all but three had a Harris hip score of 90 points or better, despite extensive destruction of bone in some instances. Since these patients were functioning well, the pelvic osteolysis was diagnosed radiographically at a regular follow-up examination. Only one patient had evidence of migration of the acetabular component on serial radiographs.(ABSTRACT TRUNCATED AT 250 WORDS)

Histological and radiographic assessment of well functioning porous-coated acetabular components. A human postmortem retrieval study.

Nine porous-coated acetabular components were retrieved post mortem. All components had been inserted at our institution and had been in situ for a mean of fifty months (range, seventeen to eighty-seven months). Clinical records revealed that all had been functioning well at the time of death, and clinical radiographs showed signs that all had been stable. Standard backscattered scanning electron microscopy was used to quantitate the amount of bone ingrowth into the porous coating. For each component, the histological appearance of the bone-metal interface was compared with the appearance on clinical radiographs. Light microscopy was used to study the non-ossified areas. Every component had growth of bone into the porous coating, with the ingrowth occupying a mean of 32 per cent (range, 3 to 84 per cent) of the fields that were examined. In areas where bone ingrowth had occurred, the mean area density was 48 per cent (range, 26 to 65 per cent). Use of radiographs consistently led to an underestimation of the presence of gap areas and an overestimation of the occurrence of bone apposition. When fibrous tissue was present in non-ossified areas, it was extremely dense and well organized. Within the limits of light microscopic examination, there was no evidence of granulomatous formation in the non-ossified regions. This is particularly encouraging since the fibrous tissue-bone interfaces seem to prohibit the deposit of particulate debris.

Osteonecrosis of the femoral head treated with total hip arthroplasty without cement.

With use of porous-coated implants, total hip arthroplasty was performed in a consecutive series of thirty patients (thirty-five hips) who had a preoperative diagnosis of late-stage (Ficat and Arlet stage-III or IV) osteonecrosis of the femoral head. The patients were evaluated clinically and radiographically, and the data were recorded in a prospective manner. The average duration of follow-up was seven and one-half years (range, five to ten years). The average age of the patients at the time of the operation was thirty-two years (range, twenty-one to forty years). Signs of osseointegration of the femoral stem to the host bone were demonstrated in thirty-three hips (94 per cent). In the porous-coated hemispherical acetabular cups of these hips, an optimum bone-implant interface was identified and maintained, suggesting bone ingrowth. The rate of revision was 3 per cent (one hip) for the femoral side and 6 per cent (two hips) for the acetabular side, for an over-all rate of 6 per cent. All patients maintained a high level of activity postoperatively. There was moderate or severe remodeling of proximal femoral resorptive bone and stress-shielding in six hips (17 per cent) and osteolytic reactions in six hips. Complications were frequent (six hips) and included one deep infection; two dislocations; two instances of heterotopic ossification; and one fracture of the calcar femorale, which occurred intraoperatively. The thirty patients had a lower rate of revision and improved clinical outcomes compared with other reported series of young patients managed with total hip arthroplasty with cement who had the same diagnosis and similar postoperative follow-up. However, the latter series involved implants of an earlier design that had been inserted with older techniques of cementing. When arthroplasty is considered for the treatment of late-stage osteonecrosis of the femoral head in young patients, the use of total hip implants without cement that allow for bone ingrowth appears to be a viable alternative to arthroplasty with use of cement. However, longer follow-up is needed to determine the outcome of the osteolytic reactions that we observed. We therefore recommend this procedure with some caution because of the high rate of complications and the potential for failure of the arthroplasty related to the osteolytic reactions.

Outcome of revision hip arthroplasty done without cement.

Between 1980 and 1986, ninety-three femoral revision arthroplasties without cement were performed on ninety-one patients who had symptomatic loosening of a stemmed femoral component of a total hip prosthesis. Eighty-one of these patients (eighty-three hips) were followed for at least five years (range, five to thirteen years; mean, nine years). Forty-three hips also had a revision of a cemented acetabular component with use of a hemispherical, porous-coated implant inserted without cement. The results are presented in a traditional manner in terms of implant survivorship, radiographic evaluation for stability of the implant, and standardized hip scores. Changes due to the treatment are presented as outcomes in terms of the physician's criteria for the success of the operation, the patient's criteria for the success of the operation, and the patient's economic status. No hips that needed additional operations were excluded, and we reported the outcome regardless of any interim operative procedures (including re-revisions). At the latest follow-up examination, nineteen (23 per cent) of the eighty-three hips had had an additional operation, including seventeen hips (20 per cent) for which re-revision had been necessary. In ten (12 per cent) of the eighty-three hips, the re-revision had involved an index implant. The rate of re-revision of the index femoral component was 10 per cent and the rate of mechanical loosening of that component was 11 per cent. The rate of re-revision of the index acetabular component was 7 per cent and the rate of mechanical loosening of that component was 11 per cent.(ABSTRACT TRUNCATED AT 250 WORDS)

Total hip arthroplasty with porous-coated prostheses fixed without cement in patients who are sixty-five years of age or older.

We reviewed the results of 212 total hip arthroplasties performed without cement in 203 unselected, consecutive patients who were sixty-five years of age or older. The outcome was known for 196 hips, thirty-seven of which had been followed until the death of the patient and 159 of which had been followed for a minimum of five years. A reoperation was done in 4 percent (seven) of the 196 hips. These reoperations included one revision because of loosening of the stem and five revisions of the cup. Three of the acetabular revisions were done because of fracture due to polyethylene wear; one, because of recurrent dislocation; and one, because of polyethylene wear and a fracture due to lysis. In the seventh reoperation, a cup and stem were exchanged because of infection. The probability that a hip prosthesis would survive twelve years without a reoperation was 0.92 (95 percent confidence interval, 0.85 to 0.99). We evaluated the clinical results for 152 patients who had not had a reoperation and had been followed for at least five years (mean, 8.5 years; range, five to fourteen years). Of these patients, thirteen (9 percent) had pain that limited activity: five (3 percent) had pain in the thigh (four patients) or groin (one patient), and eight (5 percent) had trochanteric pain and tenderness. One hundred and forty-four (95 percent) of the patients noted an improvement in overall function, and 149 (98 percent) reported satisfaction with the outcome. One hundred and thirty-five hips that were not revised were followed radiographically for at least five years (mean, 8.2 years; range, five to fourteen years). In this group, osteolysis was observed in three hips (2 percent); loosening of the cup, in three (2 percent); and loosening of the stem, in one (1 percent). Stress-shielding was seen on the two-year postoperative radiographs of forty-five (26 percent) of the 174 hips that were followed for at least that duration. The prevalence of osteolysis, loosening of a component, and reoperations was no greater in this subgroup than in the overall group. These results indicate that total hip arthroplasty without cement can be successful in older patients. This study also provides a reference for comparison with the results of total hip arthroplasty performed with cement and those of so-called hybrid total hip arthroplasty (an acetabular component fixed without cement and a femoral component fixed with cement) in patients who are sixty-five years of age or older.

Modular component exchange for treatment of recurrent dislocation of a total hip replacement in selected patients.

BACKGROUND: Exchange of modular components is a treatment option for the correction of recurrent dislocation of a total hip replacement. In this study, we reviewed our experience with this technique in order to define patient selection criteria and to report the outcome of treatment. METHODS: Of 2935 hips treated with primary porous-coated total hip arthroplasty, fourteen (in fourteen patients) that met certain preoperative and intraoperative criteria were treated with modular component exchange because of recurrent hip instability. The primary arthroplasties in these fourteen patients had been performed through a posterior approach. At the revisions, we removed any sources of osseous or soft-tissue impingement that contributed to dislocation. Acceptable stability at the completion of component exchange was defined as stability in maximum flexion, in full extension with external rotation, and in at least 45 degrees of internal rotation with the hip in 90 degrees of flexion and maximum adduction. RESULTS: One patient was lost to follow-up. At a mean of 5.8 years (range, 2.8 to 11.8 years) after the revision, ten of the remaining thirteen patients had not had a dislocation. Of the three patients in whom the hip dislocated after the modular component exchange, only one had recurrent dislocation; thus, recurrent dislocation was eliminated in twelve of thirteen patients. CONCLUSIONS: In selected cases, modular component exchange for the treatment of recurrent hip dislocation has a success rate comparable with that of more extensive operations. This method should be considered because it avoids the morbidity associated with revision of well-fixed components. However, to ensure the appropriateness of this surgical option, each patient must be thoroughly evaluated to identify all factors that contribute to instability and adequate intraoperative stability must be achieved.

Treatment of pelvic osteolysis associated with a stable acetabular component inserted without cement as part of a total hip replacement.

Thirty-five patients who had had a primary total hip replacement with a porous-coated acetabular component inserted without cement had a revision procedure to treat pelvic osteolysis. The mean age at the time of the revision operation was forty-nine years (range, twenty-nine to eighty-five years). Forty-six distinct pelvic osteolytic lesions were noted radiographically around the thirty-five cups. These lesions ranged in size from 0.5 by 0.5 centimeter to 6.3 by 2.7 centimeters (mean, 2.6 by 1.7 centimeters). Fourteen of the thirty-five patients had no or only slight occasional pain at the time of diagnosis of the pelvic osteolysis, fifteen patients had pain attributed to a loose femoral component, one had pain related to a spontaneous fracture of the greater trochanter, and one had pain related to recurrent subluxation. The remaining four patients had pain in the groin despite radiographically stable implants. All of the metal-backed porous-coated acetabular components were stable according to the preoperative radiographs, and the stability was confirmed at the time of the revision. The metal shell was left in place and the acetabular liner was exchanged in all thirty-five patients. The osteolytic lesions were debrided, and thirty-four of the forty-six lesions were filled with allograft bone chips. The patients were evaluated a minimum of two years (range, two to five years; mean, 3.3 years) after the revision operation, and all thirty-five sockets were found to be radiographically stable. The bone grafts appeared to have consolidated, and none of the osteolytic defects had progressed. One-third of the lesions were no longer visible on radiographs, regardless of whether or not they had been filled with bone graft. The remaining lesions had decreased in size. It appears that, in the short-term, exchange of the liner and debridement of the granuloma, with or without use of allograft bone chips in the osteolytic defect, is a reasonable alternative to revision of the socket provided that the metal shell is solidly fixed at the time of the revision operation. If the metal shell has been markedly damaged by the femoral head, the locking mechanism for the polyethylene liner is not intact, or a satisfactory replacement liner is not available, then revision of the porous-coated acetabular component is indicated. These results must be considered preliminary. Since osteolysis may take several years to redevelop after a revision, additional follow-up is required.

A quantitative evaluation of periprosthetic bone-remodeling after cementless total hip arthroplasty.

Dual-energy x-ray absorptiometry analysis was used to determine the periprosthetic bone-mineral content of ten femora that had been obtained at the autopsies of five elderly patients who had had an AML (anatomic medullary locking) prosthesis in situ for seventeen to eighty-four months. Clinical radiographs showed resorptive remodeling changes characteristic of femora containing this implant. Before the absorptiometry was performed, an identical prosthesis had been inserted into the contralateral, normal femur of each cadaver. The mean difference in the periprosthetic bone-mineral content between the remodeled femora and the femora in which the prosthesis had been implanted post mortem ranged from 7 to 52 per cent, with the bone-mineral content always less in the remodeled femora. The greatest mean decrease in bone-mineral content (45 per cent) occurred adjacent to the proximal one-third of the remodeled femora. The percentage decrease in periprosthetic bone-mineral content in the remodeled femora had an inverse linear relationship with the corresponding bone-mineral content of the contralateral control femora. Preoperative analysis of bone density may therefore be useful for prediction of the extent of resorptive bone-remodeling after total hip replacement.