Complex cemented revision using polished stem and morselized allograft

The aim of this study was to evaluate the results of complex hip revision using a cemented, collarless and polished femoral stem design (CPT, Zimmer, Warsaw, In.) within a tightly impacted morselized allograft. We have now been using the impaction grafting technique in combination with the CPT stem (Zimmer) for 10 years in complex cases of severe bone loss. In this study we have elected to report only those patients who have been revised at least once before revision using the impaction grafting technique. All the patients in the study group have a minimum follow-up of 5 years after the impaction grafting revision. In total, 43 consecutive hips in 40 patients, 22 men and 18 women, with a follow-up time of between 5 and 7 years are included in the study. The complications related to the revised hip consist of three early dislocations managed by closed reduction. Two patients suffered from periprosthetic fracture, both managed with plate osteosynthesis. Two cementless sockets were revised due to aseptic socket loosening. The Endoklinik rating of preoperative bone loss for the revised hips was 2 in 13 hips, 3 in 23 hips, and 4 in 7 hips. During the first year 29 stems subsided 2-4 mm within the cement mantle. In 8 cases, a subsidence of 5-9 mm was measured. The subsidence was nonprogressive, and no subsidence occurred after the 1st year. The Charnley, D'Aubigne, Postel scoring (maximum 6 points) for pain improved from 2.2 points preoperatively to 4.4 postoperatively, function from 2.3 to 4.3, and movement from 2.3 to 4.1. In conclusion, the concept of impaction grafting in THR revision in our study has so far proven to be successful with good clinical results at 5 years despite the relatively high early subsidence of the femoral component.     

Charnley-Kerboull total hip arthroplasty combining zirconia on polyethylene. A minimum eight-year follow-up prospective study

Purpose

Zirconia was introduced in the 1980s for total hip arthroplasty (THA) with the expectation of lower polyethylene wear. The purpose of this prospective study was to evaluate the results of a continuous series of total hip arthroplasties combining a zirconia head with polyethylene socket at a minimum eight-year follow-up.

Methods

We performed an open prospective clinical trial in 1997. Our study involved 51 consecutive patients (55 hips) with a mean age of 52.5 ± 12 years (range, 25–76 years). All patients had a Charnley-Kerboull all-cemented hip replacement. A 22-mm stabilised yttrium tetragonal polycrystalline zirconia head (Y-TZP) was used in association with moderately cross-linked and annealed polyethylene. Clinical and radiological outcomes were assessed yearly. A survival analysis was performed using revision for any reason as the end-point.

Results

At a minimum eight-year follow-up, 12 patients (13 hips) were lost to follow-up (mean 26.8 months), two patients (two hips) had died, and six patients (six hips) were revised. The remaining 31 patients (34 hips) were alive and had not been revised on either the femoral or acetabular side at a mean follow-up of 117.1 months (range, 96–150 months). Mean functional score at last follow-up was 17.7. Mean linear head penetration was 0.23 mm/year. More than 90 % of the remaining hips had signs of periprosthetic osteolysis. Five stems were loosened. The survival at eight years was 87.3 % (95 % IC: 76.7–97.8).

Conclusion

This study confirms earlier short-terms results, and demonstrates that zirconia should no longer be used in THA.     

Shape the implant to the patient. A rationale for the use of custom-fit cementless total hip implants

Most authors agree that "fit" and "fill" of the endosteal canal is critical to the success of cementless femoral components. Yet, there exists a wide variation to the anatomic size and shape of this canal in the normal population. This paper reviews the rationale and the efficacy of using a computed tomography-generated CAD/CAM custom femoral component in cementless total hip arthroplasty. One hundred fifty-six cases (81 primary and 75 revisions) were reviewed with follow-up time of six weeks to three years (mean, 22 months). A subset of 48 hips (25 primary and 23 revisions) has been followed a minimum of two years. For the primary hips, the custom group was found to have statistically higher Harris pain scores (less pain) at all follow-up intervals as compared to a prior series by the same surgeon using an off-the-shelf (OTS) prosthesis. Revision customized hip implants had lower Harris pain and total scores than primary custom hips, but 80% were in the none or slight pain category. In revision cases, the use of custom components decreased the need for structural bone grafting and achieved stability on host bone in situations in which it was not possible using OTS components. Complications included failure by aseptic loosening of one primary and one revision case. Initial subsidence of more than 3 mm of the collarless custom design occurred in 8%, the majority being in revision cases. All cases but one appear to have stabilized. Subsidence occurred mainly in cases done early in the series.(ABSTRACT TRUNCATED AT 250 WORDS)     

Modular acetabular reconstructive cup in acetabular revision total hip arthroplasty at a minimum ten year follow-up

Purpose

Modular acetabular reconstructive cups have been introduced in an attempt to offer initial rigid fixation by iliac lag screws and ischial pegs, to support bone grafts with a flanged metal socket, and to restore original hip center in acetabular revision. The purpose of this study was to clarify minimum ten year follow-up results of this cup system with morsellised allografts in revision cases.

Methods

We retrospectively investigated 54 acetabular revisions at a mean of 11 years (range, ten to 14 years). The indications were Paprosky’s type 2B (eight hip), 2C (eight hips), 3A (23 hips), 3B (nine hips), and 4 (six hips).

Results

Using aseptic loosening as the endpoints, the survival rate was 89.3 % (95 % CI 81–98). Radiographically, one type 3A hip, three type 3B hips and one type 4 hip showed aseptic loosening while no type 2 hips or no cemented cups showed loosening.

Conclusions

The modular reconstructive cups for acetabular revision showed bone stock restoration and stable implantation.     

Results and prognostic factors of valgus osteotomy in middle-aged patients with advanced or terminal osteoarthritis of the hip

Background  

From 1979 to 2005, a total of 279 hips in 249 patients with advanced and/or terminal-stage osteoarthritis of the hip underwent valgus osteotomy. Among them, we reviewed 256 hips in 229 patients (91.8%) with a minimum follow-up of 1 year. We reviewed the clinical and radiological results and analyzed prognostic factors that may have affected the postoperative outcome.     

Total hip arthroplasty with insertion of the acetabular component without cement in hips with total congenital dislocation or marked congenital dysplasia

BACKGROUND: End-stage osteoarthritis secondary to total congenital dislocation or severe congenital dysplasia of the hip (class B or C according to the system of Eftekhar or type 2 or 3 according to the system of Hartofilakidis et al.) in adults presents special problems with regard to reconstruction of the hip. The purpose of the present study was to assess the intermediate-term results associated with the use of a porous ingrowth acetabular component for the treatment of these difficult cases. METHODS: We performed a prospective study of a consecutive series of twenty-one patients (twenty-four hips) who had had a primary total hip arthroplasty with use of a hemispherical acetabular component that was inserted without cement and fixed with screws. No patient was lost to follow-up. Three patients (four hips) died, of causes unrelated to the total hip arthroplasty, before a minimum duration of follow-up of five years. None of these patients had had revision. Of the remaining eighteen patients (twenty hips), fifteen were women and three were men. Ten hips had total dislocation, and ten had severe dysplasia. RESULTS: After an average duration of follow-up of eighty-three months (range, sixty-four to 102 months), the average Harris hip score was 90 points (range, 68 to 97 points). No patient had revision, loosening, or migration of the acetabular component; pelvic osteolysis; or a continuous radiolucent line at the mesh-bone interface of the acetabular component. The average rate of polyethylene wear was 0.08 millimeter per year (range, zero to 0.21 millimeter per year). CONCLUSIONS: The porous ingrowth acetabular component that was used in the present study functioned well at the time of the intermediate-term follow-up of this group of patients who had marked congenital dysplasia or total dislocation of the hip. The use of this component decreased the need for structural acetabular grafts. This component appears to perform as well as larger components of this design that have been assessed after similar durations of follow-up.     

Ceramic-on-Ceramic Total Hip Arthroplasty: Minimum of Six-Year Follow-up Study

Background

This study examines the clinical and radiologic results of ceramic-on-ceramic total hip arthroplasties with regard to wear, osteolysis, and fracture of the ceramic after a minimum follow-up of six years.

Methods

We evaluated the results of a consecutive series of 148 primary ceramic-on-ceramic total hip arthroplasties that had been performed between May 2001 and October 2005 in 142 patients. The mean age was 57.2 years (range, 23 to 81 years). The mean follow-up period was 7.8 years (range, 6.1 to 10.1 years). Preoperative diagnosis was avascular necrosis in 77 hips (52%), degenerative arthritis in 36 hips (24.3%), femur neck fracture in 18 hips (12.2%), rheumatoid arthritis in 15 hips (10.1%), and septic hip sequelae in 2 hips (1.4%). Clinical results were evaluated with the Harris hip score, and the presence of postoperative groin or thigh pain. Radiologic analysis was done with special attention in terms of wear, periprosthetic osteolysis, and ceramic failures.

Results

The mean Harris hip score improved from 58.3 (range, 10 to 73) to 92.5 (range, 79 to 100) on the latest follow-up evaluation. At final follow-up, groin pain was found in 4 hips (2.7%), and thigh pain was found in 6 hips (4.1%). Radiologically, all femoral stems demonstrated stable fixations without loosening. Radiolucent lines were observed around the stem in 25 hips (16.9%), and around the cup in 4 hips (2.7%). Endosteal new bone formation was observed around the stem in 95 hips (64.2%) and around the cup in 88 hips (59.5%). No osteolysis was observed around the stem and cup. There were 2 hips (1.4%) of inclination changes of acetabular cup, 2 hips (1.4%) of hip dislocation, 1 hip (0.7%) of ceramic head fracture, and 1 hip (0.7%) of squeaking. The Kaplan-Meier survival rate of the prostheses was 98.1% at postoperative 7.8 years.

Conclusions

The ceramic-on-ceramic total hip arthroplasty produced excellent clinical results and implant survival rates with no detectable osteolysis on a minimum six-year follow-up study. The ceramic-on-ceramic couplings could be a reasonable option of primary total hip arthroplasty for variable indications.     

Total Hip Arthroplasty in Young Females With Congenital Dislocation of the Hip,Radically Improves Their Long-Term Quality of Life

Eighty-two female patients with low dislocation (67 hips) or high dislocation (48 hips) were assessed using clinical scores and EQ-5D quality of life (QoL) questionnaire. Assessment was performed at the first to second year postoperatively and at the final follow-up, after a minimum of 12 years (12–37). Patients reported with a high EQ-5D health state VAS scale, VAS index and TTO index at 1 to 2 years follow-up (94,21/0,907/0,931) that remained considerably high despite the long-term follow-up (73,8/0,721/0,746). The scores for pain and range of motion presented with a statistically significant improvement at 1 to 2 years postoperatively and at the time of final follow-up. Function scores have declined with age. Total hip arthroplasty in CHD patients radically improves QoL for a long period of time.     

Advancement and separation of apex hole eliminators with cementless Duraloc 100 cups. A report of nineteen cases

BACKGROUND: From 1992 to 1996, we performed 541 cementless total hip arthroplasties using a Duraloc 100 acetabular component with an apex hole eliminator that did not have a positive stop design. During routine follow-up radiographic evaluation, we noted several hips with advanced or separated hole eliminators. This study presents the clinical consequences of this occurrence and its relationship to polyethylene wear and osteolysis. METHODS: A total of 541 hips (358 with a minimum duration of follow-up of five years) were evaluated clinically with use of the method of Merle D'Aubigné and Postel. Anteroposterior pelvic and iliac oblique radiographs were used to evaluate polyethylene wear, osteolysis, hole eliminator position, and component stability. RESULTS: Nineteen hips that had been followed for an average of eighty-nine months showed advancement or complete separation of the hole eliminator on radiographic evaluation. In most hips, advancement of the hole eliminator was visible on only the iliac oblique radiograph. In all but one hip with separation of the hole eliminator, complete plug separation was detectable on both the iliac oblique and anteroposterior pelvic radiographs. No association was found between polyethylene wear and either advancement or separation of the hole eliminator. No osteolysis was visible radiographically in the hips with hole eliminator advancement, but osteolysis was always visible in the hips that had complete separation of the hole eliminator. CONCLUSIONS: The hole eliminator has been redesigned since November 1995 to prevent possible advancement. However, patients with earlier designs should be followed carefully because advancement or separation can be expected in about 5% of the patients who have been followed for a minimum of five years. Despite this complication, which is seen radiographically, all patients were satisfied with the function of the hip. We do not recommend surgery solely to remove or replace the hole eliminator.     

Similar Wear in Total Hip Arthroplasties with Metallic or Zirconia Femoral Heads

Ceramic femoral heads have been used in an attempt at reducing polyethylene wear of total hip arthroplasties. Clinical results with zirconia femoral heads have been mixed. This study was undertaken to compare the polyethylene wear and incidence of periprosthetic osteolysis in total hip replacements performed using a 28-mm zirconia versus a 28-mm cobalt chromium femoral head. Thirty-five hips with a 28-mm cobalt chromium head and 68 hips with a 28-mm zirconia head were evaluated after a minimum follow-up of 2 years (average, 4.0 years; range, 2.0 to 9.1 years). A monoblock acetabular component was used in all patients. Polyethylene wear was measured in serial radiographs from 58 of the hips utilizing a computer-assisted vector wear technique. Periacetabular osteolysis developed in three patients (two with a zirconia head and one with a cobalt chromium head). The total wear and the annual wear rate were 0.48 mm and 0.11 mm/year for the cobalt chromium heads and 0.53 mm and 0.14 mm/year for the zirconia heads, respectively. We found no benefit with respect to the rate of polyethylene wear or incidence of osteolysis with the use of zirconia femoral heads.     

Intermediate-term results after hybrid total hip arthroplasty for the treatment of dysplastic hips

BACKGROUND: In recent studies, good intermediate-term results have been reported after primary hybrid total hip arthroplasty (a cementless acetabular component with a cemented femoral stem) for the treatment of primary osteoarthritis. However, few studies have described the results of this technique in patients with developmental dysplasia of the hip. METHODS: One hundred primary hybrid total hip replacements were performed in ninety patients to treat degenerative arthritis of the hip secondary to developmental dysplasia. Seventy-one patients (eighty-one hips) were available for clinical and radiographic evaluation. The average duration of follow-up was 10.6 years. There were ten men and sixty-one women. Seventy hips were classified as type 1 (dysplasia); seven, as type 2 (low dislocation); and four, as type 3 (high dislocation), according to the classification system of Hartofilakidis et al. RESULTS: At the time of the final follow-up, the average Harris hip score was 86 points. Structural autograft was used in fifteen hips to supplement acetabular coverage. Within five years postoperatively, the acetabular component in six of the fifteen hips had an average of 4.5 mm of vertical migration and an average increase in vertical rotation of 3 degrees, but the position appeared to stabilize thereafter. Revisions were performed in two hips because of recurrent dislocation. No acetabular or femoral component was revised because of aseptic loosening. Osteolysis was identified around two acetabular components and two femoral components. The average rate of polyethylene wear was 0.09 mm per year. CONCLUSIONS: Hybrid total hip arthroplasty for the treatment of symptomatic degenerative arthritis secondary to developmental dysplasia provides favorable results at intermediate-term follow-up. With lower grades of dysplasia, the majority of patients can be treated effectively without a structural bone graft by placement of the cementless acetabular component at a medial or high position.     

Minimum 10-Year Follow-Up of Total Hip Arthroplasty With a Collarless Triple-Tapered Polished Cemented Stem With Line-to-Line Implantation Using a Direct Anterior Approach

BackgroundThe Trilliance stem (B. Braun-Aesculap, Tuttlingen, Germany), a novel collarless triple-tapered polished stem, was introduced in 2009. The aim of this study is to evaluate the long-term clinical and radiological results of the Trilliance stem with line-to-line implantation in primary total hip arthroplasty using a direct anterior approach.MethodsA consecutive retrospective series of 130 patients (151 hips) who underwent total hip arthroplasty between February 2009 and August 2011 were evaluated for a minimum of 10 years. Of these, 87.4% had a diagnosis of secondary osteoarthritis based on developmental hip dysplasia. Clinical and radiological results, complications were evaluated and survival analysis was performed.ResultsThe mean follow-up was 10.7 years (range, 10.0-12.1). Thirteen hips (13 patients, 6.8%) were lost to follow-up. Adequate cementation (Barrack grade A) was achieved in 136 hips (93.8%) 1 week post-operatively. Nearly all (144 hips, 99.3%) had been inserted within the range of 3°. No significant differences were identified between high- (≥30 procedures/year) and low- (<30 procedures/year) volume surgeons. The Kaplan–Meier survival analysis with revision of the femoral component for aseptic loosening, revision of the femoral component for any reason and revision of either component for any reason as the end points, cumulative survivorship was 100.0%, 97.6% (95% confidence interval (CI) 95.4-100.0) and 96.5% (95% CI 93.8-99.3) at 10 years, respectively.ConclusionThe Trilliance stem with line-to-line implantation using a direct anterior approach has an excellent clinical and radiological outcome at a minimum of 10 years’ follow-up.Level of EvidenceLevel IV, Retrospective cohort study.     

Revision Total Hip Arthroplasty Using a Cementless Cup Supporter and Iliac Autograft: A Minimum of 15-Year Follow-Up

Background

Bone deficiency in revision total hip arthroplasty is a surgical challenge. The Murata-Chiba cup supporter (MC support ring) is an acetabular component supporter for a cementless porous-coated cup. The purpose of this study is to examine the clinical and radiographic outcomes of reconstruction of acetabular bone deficiency using iliac autografts supported by an MC support ring in a revision setting with minimum 15-year follow-up.

Results of porous-coated anatomic total hip arthroplasty without cement at fifteen years: a concise follow-up of a previous report

The purpose of this study was to update the results of a prospective series of primary cementless total hip arthroplasties after a minimum of fifteen years of follow-up. It is one of the first studies of cementless total hip arthroplasties followed for a minimum of fifteen years. One hundred consecutive Porous Coated Anatomic (PCA) total hip replacements were implanted between October 1983 and January 1986. Fifty-five patients (sixty-four hips) that were alive at a minimum of fifteen years postoperatively are the focus of the present study. At this time of follow-up, at an average of 15.6 years (range, fifteen to seventeen years) after the total hip arthroplasty, 17% (seventeen hips) of the entire cohort and 23% (fifteen hips) of the living cohort had undergone revision because of loosening of the acetabular component or osteolysis. Seven percent (seven hips) of the entire cohort and 6% (four hips) of the living cohort had undergone revision for loosening of the femoral component or osteolysis. Only four femoral stems had been revised for isolated loosening (without osteolysis). The PCA femoral component proved to be durable at a minimum of fifteen years postoperatively, while the acetabular component was less durable.     

Structural bone-grafting for early atraumatic avascular necrosis of the femoral head

Between 1970 and 1987, nineteen patients, thirty-one to fifty-five years old, had twenty core-decompression procedures with corticocancellous bone-grafting for Stage-I or II atraumatic avascular necrosis of the femoral head. A tibial autogenous graft was used in three hips; a fibular autogenous graft, in seven hips; and a fibular allograft, in ten hips. Treatment was considered to have failed when there was clinical or roentgenographic evidence of progression of the necrosis. Eighteen patients who had a minimum follow-up of two years (average, eight years; range, two to nineteen years) were asymptomatic, with no evidence of progression of the necrosis or collapse of the affected segment. In two hips, the necrotic segment of the femoral head collapsed within one year after the operation, and a replacement arthroplasty was carried out.     

Surgical results of developmental dysplasia of the hip in older children based on using three-dimensional computed tomography

Background

The surgical management of developmental dysplasia of the hip (DDH) in older children has been the subject of controversy. The purpose of this study was to evaluate the outcome in patients with neglected DDH who underwent individual procedures based on using three-dimensional computed tomography.

Methods

Forty-seven patients (59 hips) were treated using Pemberton osteotomy or Dega plus Pemberton osteotomy. Subtrochanteric transverse femoral shortening and derotation osteotomy were performed for all patients. The average age at the time of surgery was 10.5 y for group 1 (bilateral dislocation, 24 hips) and 11.2 y for group 2 (unilateral dislocation, 35 hips). Mean follow-up was 5.3 y for group 1 and 5.8 y for group 2.

Results

At the end of follow-up, 13 hips (54.2%) were rated excellent, eight hips (33.3%) were good, and three hips (12.5%) were fair in group 1. In group 2, 20 hips (57.1%) were rated excellent, 10 hips (28.6%) were good, and five hips (14.3%) were fair. There were five patients who had a limb length discrepancy of approximately 1.5 cm in group 2. Six hips in group 1 and seven hips in group 2 had osteonecrosis of varying severity.

Conclusions

We believe that preoperation three-dimensional computed tomography evaluation, personalized operation plans, and experience with the surgical procedure are the main reasons for the satisfactory therapeutic effects achieved in this study in older children with DDH.     

Cementing Constrained Liners Into Secure Cementless Shells: A Minimum 15-Year Follow-Up Study

Background

The authors and others have previously described the technique of cementing constrained liners into secure cementless acetabular shells and reported the short-term, average 3.9-year follow-up, using that technique. The purpose of the present study was to report the minimum 15-year follow-up of this same cohort.

Studies of nontraumatic osteonecrosis. The role of core decompression in the treatment of nontraumatic osteonecrosis of the femoral head

This study reports a five-year experience with core decompression for treatment of nontraumatic osteonecrosis of the femoral head. There were 25 patients (39 hips) with predominantly steroid-associated osteonecrosis followed postoperatively for a minimum of two years. All patients were evaluated functionally, roentgenographically, histologically, and hemodynamically. At latest follow-up examination, two of 12 hips (17%) with Stage I disease, seven of 12 hips (58%) with Stage IIA disease, four of four hips with Stage IIB disease, and nine of 11 hips (82%) with Stage III disease have progressed roentgenographically and/or clinically. A lack of correlation between pressure manometrics, venography, and clinical outcome in this study suggests that mechanisms other than progressive ischemia may be involved. Current indications for core decompression are Ficat Stage 0, I, and IIA (sclerotic predominant) disease.     

Photodynamic therapy in the management of neoplasms of the perianal skin.

Perianal extramammary Paget's disease, Bowen's disease, and squamous cell carcinoma are three entities that are very rarely reported. Overall, it is generally accepted that wide surgical excision is adequate treatment except under certain circumstances. Consideration has to be given to invasiveness, metastatic potential, multicentricity, and tendency to recur. We describe four patients who, following unsuccessful multiple attempts at achieving microscopically clear margins with surgical excision, were treated at Roswell Park Cancer Institute with photodynamic therapy with a surface illumination method. With a minimum follow-up of 6 months (more than 1 year in three patients), there have been no recurrences to date.     

Characterization of long-term femoral-head-penetration rates. Association with and prediction of osteolysis

BACKGROUND: We examined the relationship between long-term femoral-head-penetration patterns and osteolysis in a ten-year follow-up study of a well controlled patient population. The purposes of this study were to characterize the linearity of long-term head-penetration patterns over time, to describe the relationship between ten-year true wear rates and osteolysis, and to determine whether the occurrence of osteolysis at ten years could be predicted by penetration data obtained prior to five years. METHODS: Temporal femoral-head-penetration patterns were examined at a minimum of ten years after forty-eight primary total hip arthroplasties. The arthroplasties were performed with the use of an Arthropor acetabular cup (Joint Medical Products) and a thirty-two-millimeter-diameter cobalt-chromium femoral head (DePuy). Using a computer-assisted radiographic technique, we evaluated two-dimensional head penetration on serial annual radiographs. Linear regression analysis modeled penetration-versus-time data as a line for each patient. The slope of the regression line indicated the true wear rate for each patient. In a subgroup of thirty-four hips for which three annual radiographs had been made less than five years after the arthroplasty, we compared early head-penetration patterns with the later occurrence of osteolysis. RESULTS: For all forty-eight hips, the true wear rate averaged 0.18 millimeter per year (range, 0.01 to 0.44 millimeter per year) and temporal head-penetration patterns tended to be linear (mean r2 = 0.91 +/- 0.16). Osteolysis at ten years was strongly associated with increasing true wear rates (p < 0.001). Osteolysis did not develop in any of the nine hips with a true wear rate of less than 0.1 millimeter per year. However, osteolysis developed in nine (43 percent) of twenty-one hips with a rate between 0.1 and less than 0.2 millimeter per year, in eight of ten hips with a rate between 0.2 and 0.3 millimeter per year, and in all eight hips with a rate of greater than 0.3 millimeter per year. Evaluation of early true wear rates as a predictor of late osteolysis showed a similar relationship. CONCLUSIONS: This study demonstrates that true wear rates tend to be constant and that increased true wear is significantly associated with osteolysis at ten years after the operation. A similar relationship was also found at the early follow-up interval, indicating that early true wear rates (determined from serial radiographs) might enable orthopaedists to predict if patients are at risk for the development of osteolysis. CLINICAL RELEVANCE: On the basis of these findings, we use temporal femoral-head-penetration data in our practice to evaluate polyethylene inserts in asymptomatic patients, to estimate the time to component wear-through, and to adjust the frequency of follow-up evaluations for monitoring the development of osteolytic lesions in at-risk patients.