Michel J. Le Duff

Metal-on-Metal Hybrid Surface Arthroplasty: Two to Six-Year Follow-up Study

BACKGROUND Following the reintroduction of metal-on-metal articulating surfaces for total hip arthroplasty in Europe in 1988, we developed a surface arthroplasty prosthetic system using a metal-on-metal articulation. The present study describes the clinical and radiographic results of the first 400 hips treated with metal-on-metal hybrid surface arthroplasties at an average follow-up of three and a half years. METHODS Between November 1996 and November 2000, 400 metal-on-metal hybrid surface arthroplasties were performed in 355 patients. All femoral head components were cemented, but only fifty-nine of the short metaphyseal stems were cemented. The patients had an average age of forty-eight years, 73% were men, and 66% had a diagnosis of osteoarthritis. Clinical and radiographic follow-up were performed at three months postoperatively and yearly thereafter. RESULTS The majority of the patients returned to a high level of activity, including sports, and 54% had activity scores of >7 on the University of California at Los Angeles activity assessment system. Kaplan-Meier survivorship curves demonstrated that the rate of survival of the components at four years was 94.4%. For patients with a surface arthroplasty risk index score of >3, the rate of survival of the components at four years was 89% compared with a rate of 97% for those with a score of </=3. The patients with a higher risk index were 4.2 times more likely to undergo revision to a total hip replacement at four years. Twelve hips (3%) had a revision to a total hip replacement. Seven of the twelve hips were revised because of loosening of the femoral component, and three were revised because of a femoral neck fracture. Substantial radiolucencies were seen around sixteen uncemented metaphyseal femoral stems. No femoral radiolucencies were observed among the hips in which the metaphyseal stem was cemented. The most important risk factors for femoral component loosening and substantial stem radiolucencies were large femoral head cysts (p = 0.029), patient height (p = 0.032), female gender (p = 0.005), and smaller component size in male patients (p = 0.005). CONCLUSIONS The preliminary experience with this hybrid metal-on-metal bearing is encouraging. Optimal femoral bone preparation and component fixation are critical to improving durability. The metal-on-metal hybrid surface arthroplasty is easily revised to a standard femoral component if necessary. LEVEL OF EVIDENCE Therapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.

Quality of life following femoral head-neck osteochondroplasty for femoroacetabular impingement

BACKGROUND Femoroacetabular impingement has been recently described as a common cause of hip pain and labral tears in young adults. We evaluated the early clinical results and quality of life after osteochondroplasty of the femoral head-neck junction for the treatment of femoroacetabular impingement. METHODS Thirty-seven hips in thirty-four patients with persistent hip pain and a mean age of 40.5 years underwent surgical dislocation of the hip and osteochondroplasty of the femoral head-neck junction for the treatment of camtype femoroacetabular impingement. All of the patients had had preoperative evidence of pathological changes in the labrum on imaging. The clinical course and the quality of life were assessed postoperatively. RESULTS The mean score on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) increased from 61.2 points preoperatively to 81.4 points at a mean of 3.1 years postoperatively (p < 0.001), the mean University of California at Los Angeles (UCLA) activity score increased from 4.8 to 7.5 points (p < 0.001), the mean Short Form-12 (SF-12) physical component score increased from 37.3 to 45.6 points (p < 0.001), and the mean SF-12 mental component score increased from 46.4 to 51.2 points (p = 0.031). None of the hips underwent additional reconstructive surgery. There were no cases of osteonecrosis. Nine patients underwent screw removal from the greater trochanter because of persistent bursitis. Six of the thirty-four patients were dissatisfied with the outcome. CONCLUSIONS Cam-type femoroacetabular impingement is associated with insufficient concavity at the anterolateral head-neck junction and with pathological changes in the labrum. Osteochondroplasty of the femoral head-neck junction following surgical dislocation of the hip joint is safe and effective and can provide a significant improvement in the overall quality of life of most patients. LEVEL OF EVIDENCE Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

Fracture of the neck of the femur after surface arthroplasty of the hip.

BACKGROUND There are two main modes of failure of the femur following surface arthroplasty of the hip: femoral neck fracture and aseptic loosening. The purpose of the present study was to present our experience with femoral neck fractures that occurred after metal-on-metal hybrid surface arthroplasty and to assess their cause. METHODS A series of 600 metal-on-metal surface arthroplasties was performed between late 1996 and early 2003. Failures that occurred during this period were assessed radiographically and with implant retrieval analysis to determine their cause. RESULTS Five femoral neck fractures occurred in this series (prevalence, 0.83%). Four of the five fractures occurred at the component-neck junction within the first five months (average, three months) after surgery. All five fractures were associated with a traumatic episode, but all five also were associated with structural and/or technical risk factors, which we believe weakened the femoral neck. The most important technical deficiency that contributed to three of the five fractures was the failure to cover all of the reamed bone with the component. CONCLUSIONS It is important to avoid or at least minimize notching of the femoral neck by performing the cylindrical reaming at the recommended angle of 140 degrees and to stop reaming before the reamer touches the lateral cortex. Osteophytes should be removed judiciously only if there is notable impingement when the hip is flexed to 90 degrees and internally rotated. We believe that understanding the factors that contribute to femoral neck fracture after surface arthroplasty may reduce the prevalence of this mode of failure.

Early results of conversion of a failed femoral component in hip resurfacing arthroplasty.

BACKGROUND A theoretical advantage of resurfacing arthroplasty of the hip is that a failed femoral component can be safely and successfully revised to a total hip arthroplasty. To our knowledge, this advantage has not been demonstrated to date. METHODS Twenty-one metal-on-metal resurfacing arthroplasties in twenty patients with an average age of 50.2 years were converted to a conventional stemmed total hip arthroplasty because of femoral component failure. In eighteen hips, the acetabular component was retained, and in three hips both components were revised. The results in the resurfacing conversion group were compared with those in a group of fifty-eight patients who had undergone sixty-four primary total hip arthroplasties that had been performed during the same time-period by the same surgeon. Clinical evaluations (the Harris hip score, the University of California at Los Angeles pain, walking, and activity scores and the Short Form-12 score) and radiographic evaluations were performed. The average duration of follow-up was forty-six months for the conversion arthroplasty group and fifty-seven months for the primary conventional total hip arthroplasty group. RESULTS There was no significant difference between the conversion arthroplasty group and the conventional arthroplasty group with regard to operative time, blood loss, or complication rates. At the time of the most recent follow-up, with the numbers studied, there were no significant differences between the two groups with regard to the mean Harris hip score; the University of California at Los Angeles pain, walking, and activity score; or the SF-12 score. As assessed radiographically, the quality of component fixation and the alignment of the reconstruction were equivalent between the two groups. There had been no instances of aseptic loosening of the femoral or the acetabular component in either group, and there had been no dislocations after conversion of a resurfacing arthroplasty. CONCLUSIONS Conversion of a hip resurfacing with a femoral-side failure to a total hip arthroplasty appears to be comparable with primary total hip arthroplasty in terms of surgical effort, safety, and early clinical outcomes. LEVEL OF EVIDENCE Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.

Orientation Of The Femoral Component In Surface Arthroplasty Of The Hip: A Biomechanical And Clinical Analysis

BACKGROUND Although the orientation of the femoral component has been shown to influence the outcome of total hip replacement, its effect on the clinical outcome of surface arthroplasty has not been studied, to our knowledge. The purpose of this study was to examine the relationship between femoral component positioning and the outcome of a surface arthroplasty of the hip. METHODS We reviewed the results of ninety-four hybrid metal-on-metal surface arthroplasties in patients who were forty years old or younger at the time of the operation and were followed for a minimum of two years or until the prosthesis failed. Measurements of the hip reconstruction were made on the anteroposterior pelvic radiograph. The correlation between the orientation of the femoral component and the outcome of the arthroplasty was evaluated, as were stresses within the resurfaced femoral head as a function of the orientation of the femoral component. RESULTS The mean duration of follow-up was 4.2 years. Thirteen hips had an adverse outcome, defined as conversion to a total hip replacement, radiolucency of >1 mm in thickness adjacent to the femoral stem, or narrowing of the femoral neck of >10%. The mean femoral stem-shaft angle in the coronal plane was 138 degrees, with the hips that had an adverse outcome having a significantly lower mean angle than the rest of the cohort (133 degrees compared with 139 degrees, p = 0.03). Hips with an angle of <or=130 degrees had an increase in the relative risk of an adverse outcome by a factor of 6.1 (p < 0.004). In the entire cohort, stresses in the superior aspect of the resurfaced femoral head were substantially lower during slow walking than they were during fast walking (7.1 N/mm(2) compared with 14.2 N/mm(2)). CONCLUSIONS Optimizing the femoral stem-shaft angle toward a valgus orientation during the preparation of the femoral head is important when a hip is being reconstructed with a surface arthroplasty because the resurfaced hip transmits the load through a narrow critical zone in the femoral head-neck region and the valgus angulation may reduce these stresses.

Prevention and treatment of dislocation after total hip replacement using large diameter balls.

The purpose of this study was to review safety and efficacy of total hip arthroplasty using large-diameter femoral heads in treatment and prevention of dislocation. One hundred forty hips in 135 patients were replaced using femoral heads at least 36 mm in diameter. The average age of the patients was 61.6 years. The patients were grouped into three categories depending on their diagnoses: recurrent dislocations from previous total hip replacements (Group 1; 29 hips); revision surgeries not including revisions for dislocations (Group 2; 54 hips); and primary surgeries (Group 3; 57 hips). The average followup was 5.5 years (range, 1-17 years). A total of 16 hips were revised: six for instability, four for fracture or disassociation of a conventional polyethylene liner, three for aseptic loosening of the socket, and three for sepsis. One hip from Group 1 dislocated at 12.5 years postoperatively, was treated with closed reduction, and since has been nonrecurring. UCLA hip scores all improved significantly. The prevalence of dislocation varied among the three groups, with 13.7% for Group 1, 1.8% for Group 2, and 3.5% for Group 3. The failure in the six cases that required revision for instability was attributable to poor socket orientation. All the hips became stable after revision without the use of a constrained acetabular liner. Large-diameter femoral heads provide additional stability not only for patients with recurrent dislocations, but also for patients having revision. The new, more wear-resistant bearings now enable the surgeon to extend the use of big femoral heads to primary total hip arthroplasty. Metal-on-metal seems to be the material of choice for a bone-conserving reconstruction with large femoral heads.

Eleven Years of Experience With Metal-on-Metal Hybrid Hip Resurfacing

Hip resurfacing is currently the fastest growing hip procedure worldwide. We reviewed 1000 hips in 838 patients who received a Conserve Plus (Wright Medical Technology, Inc., Arlington, Tenn) resurfacing at a single institution. The mean age of the patients was 50.0 years with 74.7% male. The hips were resurfaced irrespective of femoral defect size or etiology. The mean follow-up was 5.6 years (range, 1.1-11.0 years). All clinical scores improved significantly (P < .05). There was no acetabular component loosening. Ten were converted to total hip arthroplasty for femoral neck fracture, 20 for femoral loosening, 2 for sepsis, and 1 for recurrent subluxations. The 5-year survivorship was 95.2% with no failures in hips implanted since 2002. Short-term failures can be prevented. First-generation surgical technique and a low body mass index were the most important risk factors for the procedure. Improvements in bone preparation significantly increased prosthetic survival in hips with risk factors for failure.

Clinical and Radiographic Results of Metal-on-Metal Hip Resurfacing with a Minimum Ten-Year Follow-up

BACKGROUND There was a need for information about the long-term performance of the modern generation of hip resurfacing implants. A retrospective review of the first 100 hips that had implantation of one resurfacing design and had been followed for a minimum of ten years was performed. METHODS Between 1996 and 1998, 100 CONSERVE PLUS hip resurfacing devices were implanted by a single surgeon in eighty-nine patients. The mean age of the patients was 49.1 years, and fifty-nine patients were male. Primary osteoarthritis was the etiology for sixty-four hips. All patients were assessed clinically and radiographically. RESULTS The mean duration of follow-up was 11.7 years (range, 10.8 to 12.9 years). Two patients were lost to follow-up, and five patients died of causes unrelated to the surgery. Eleven hips had conversion to total hip arthroplasty because of loosening of the femoral component (eight), a femoral neck fracture (one), recurrent subluxation (one), and late infection (one). The Kaplan-Meier survivorship was 88.5% at ten years. None of the resurfacing arthroplasties failed in the twenty-eight hips that had a femoral component of >46 mm and no femoral head cystic or necrotic defects of >1 cm. Five hips had narrowing of the femoral neck, three had radiolucent zones interpreted as osteolysis, and twenty had signs of neck-socket impingement. Five hips had radiolucencies around the metaphyseal stem (two partial and three complete) that had been stable for 7.8 to 10.2 years. The mean scores on the University of California at Los Angeles (UCLA) system at the time of the latest follow-up were 9.5 points for pain, 9.3 points for walking, 8.9 points for function, and 6.8 points for activity; the mean scores on the physical and mental components of the Short Form-12 (SF-12) were 47.3 and 50.5 points, respectively; and the mean Harris hip score was 90 points. CONCLUSIONS The results of the present series constitute a reference point to which subsequent series should be compared. These ten-year results in a group of young patients are satisfactory, and the low rate of osteolysis is encouraging, but longer follow-up is required for comparison with conventional total hip arthroplasty.

Metal-on-metal hybrid surface arthroplasty. Surgical Technique.

BACKGROUND Following the reintroduction of metal-on-metal articulating surfaces for total hip arthroplasty in Europe in 1988, we developed a surface arthroplasty prosthetic system using a metal-on-metal articulation. The present study describes the clinical and radiographic results of the first 400 hips treated with metal-on-metal hybrid surface arthroplasties at an average follow-up of three and a half years. METHODS Between November 1996 and November 2000, 400 metal-on-metal hybrid surface arthroplasties were performed in 355 patients. All femoral head components were cemented, but only fifty-nine of the short metaphyseal stems were cemented. The patients had an average age of forty-eight years, 73% were men, and 66% had a diagnosis of osteoarthritis. Clinical and radiographic follow-up was performed at three months postoperatively and yearly thereafter. RESULTS The majority of the patients returned to a high level of activity, including sports, and 54% had activity scores of >7 on the University of California at Los Angeles activity assessment system. Kaplan-Meier survivorship curves demonstrated that the rate of survival of the components at four years was 94.4%. For patients with a surface arthroplasty risk index score of >3, the rate of survival of the components at four years was 89% compared with a rate of 97% for those with a score of <or=3. The patients with a higher risk index were 4.2 times more likely to undergo revision to a total hip replacement at four years. Twelve hips (3%) had a revision to a total hip replacement. Seven of the twelve hips were revised because of loosening of the femoral component, and three were revised because of a femoral neck fracture. Substantial radiolucencies were seen around sixteen uncemented metaphyseal femoral stems. No femoral radiolucencies were observed among the hips in which the metaphyseal stem was cemented. The most important risk factors for femoral component loosening and substantial stem radiolucencies were large femoral head cysts (p = 0.029), patient height (p = 0.032), female gender (p = 0.005), and smaller component size in male patients (p = 0.005). CONCLUSIONS The preliminary experience with this hybrid metal-on-metal bearing is encouraging. Optimal femoral bone preparation and component fixation are critical to improving durability. The metal-on-metal hybrid surface arthroplasty is easily revised to a standard femoral component if necessary.

Metal-on-metal hip resurfacing for obese patients.

BACKGROUND The effect of obesity on the outcomes of metal-on-metal resurfacing arthroplasty is not currently known. In this study, we assessed the influence of body mass index on the survival of a metal-on-metal hybrid hip resurfacing prosthesis by comparing the clinical results of patients with a body mass index of >or=30 with those of patients with a body mass index of <30. METHODS We retrospectively reviewed our registry to identify all patients who had been followed for at least two years after a metal-on-metal hip resurfacing arthroplasty, and we divided those patients according to whether they had had a body mass index of >or=30 (the study group) or <30 (the control group) at the time of the surgery. One hundred and twenty-five patients (144 hips) with an average weight of 104.6 kg and an average body mass index of 33.4 were included in the study group, and 531 patients (626 hips) with an average weight of 78.3 kg and an average body mass index of 25.4 were included in the control group. We compared the clinical results (UCLA [University of California at Los Angeles] and Harris hip scores, SF-12 [Short Form-12] survey results, and complication rates), radiographic results, and prosthetic survival rates of the two groups. RESULTS There was no significant difference postoperatively between the groups with regard to the UCLA pain or walking scores or the mental component score of the SF-12. However, the UCLA function and activity scores were lower in the study group than in the control group (9.2 compared with 9.6 points [p = 0.001] and 7.1 compared with 7.6 points [p = 0.002], respectively). The control group had a significantly higher postoperative physical component score on the SF-12 (51.4 points compared with 49.3 points in the study group, p = 0.01) and postoperative Harris hip score (93.8 compared with 90.6 points, p = 0.0003). Two hips (1.4%) were revised in the study group. In contrast, thirty-one hips (5.0%) were converted to a total hip replacement in the control group; twenty of the thirty-one were revised because of loosening of the femoral component. The five-year survivorship of the hip prostheses was 98.6% in the study group and 93.6% in the control group (p = 0.0401). When the entire cohort was divided into three groups according to whether the body mass index was <25, 25 to 29, or >or=30, the risk of revision was found to have decreased twofold from one group to the next as the body mass index increased (p = 0.013). No acetabular component loosened in either group. The average diameter of the femoral component was 48.3 mm in the study group and 46.8 mm in the control group (p = 0.0001). There were no revisions for any reason and no radiolucencies were observed in a subset of twenty-seven patients with a body mass index of >or=35. CONCLUSIONS Metal-on-metal resurfacing hip arthroplasty is performing well in patients with a high body mass index, although the function scores are reduced compared with those for patients with a body mass index of <30. The protective effect of a high body mass index on survivorship results may be explained by a reduced activity level and a greater component size in this patient population.