Total hip replacement is an effective treatment in late stages of ON of the femoral head and usually offers a rapid improvement and pain relief. However, the results are less satisfactory than those obtained for primary osteoarthrosis. 6,10,12,13,16,21,30,33,34,36,45–47,50 A patient’s young age, an increased level of activity, and a presumed poor bone quality have been regarded as risk factors for mechanical failure. 6,9,13,16,21 Because ON occurred mostly in young and active people, there is controversy regarding ON and age acting as independant risk factors for THR. 6,9,16,31 Nevertheless, THR in patients with ON has been advocated to be high risk, regarding aseptic loosening and osteolysis, in series using a metal-on-polyethylene friction couple. 6,13,30,33,45,50 In 1997 midterm studies of THR for ON, 13,33,45,50 the rate of osteolysis ranged from 5% to 20%. Therefore, the use of a material with low wear debris production has become an interesting alternative in these patients with a high activity level. Ceramic alumina tribologic properties now are well-established. 11,15,34,35,52 However, its use in hip replacement is controversial. 38 Results of ceramic-on-ceramic hip arthroplasty have been documented. 2,3,20,23,26,27,31,40–43,48,49 It has been shown that, using a ceramic prostheses, a near absence of wear and osteolysis could be expected, even in patients younger than 50 years. 27,48,49 However, there have been no reports of results of ceramic THR done for ON. The aim of the current study was to present the results of a retrospective and consecutive series of patients with late stage ON who were observed for a minimum of 11 years after they had a primary alumina-on-alumina THA. Special attention will be given to radiologic wear and osteolysis and a survival analysis of the components is presented.
MATERIALS AND METHODS
From 1978 to 1990, 52 consecutive alumina-on-alumina THRs were done in 41 patients with ON of the femoral head at our institution.
Twenty-five patients were men and 16 patients were women. The age of the patients at the time of the arthroplasty ranged from 22 to 79 years (mean, 41+/−13.2 years; median, 40 years). Thirty-nine procedures (75%) were done in patients younger than 50 years. The right hip was treated in 13 patients, the left hip was treated in 17 patients, and bilateral replacements were done in 11 patients. Two senior authors (JW, LS) did the 52 procedures. Because of the French regulation when the patients of the current study had surgery, informed consent from the patients was not required.
Inclusion criteria in this study were late stage ON with a significant amount of flattening of the articular surface, and a young age or a high activity level. Specifically, 33 hips (64%) had Stage IV disease and 19 hips (36%) had Stage III disease according to the grading system of Ficat and Arlet. 18 No hips had Stage II disease. Thirty-eight patients (92%) were involved in strenuous activity or practiced some sport.
The conditions associated with ON were steroid use in 26 hips (18 patients) (including 16 cases after marrow transplantation), trauma in 15 hips (13 patients), alcohol abuse in five hips (five patients) and sicklecell disease in two hips (two patients). The necrosis was labeled as idiopathic in four hips (three patients) (Table 1). The extent of the necrosis (in degree angle) was measured on AP and lateral radiographs according to the method of Kerboul et al. 32 The mean necrosis angle was 240° +/−82.5° (range, 70°–245°).
Total hip replacement was a primary procedure in 29 hips (55%). Twenty-three hips had sustained a previous surgical procedure, including 13 cup arthroplasties, seven internal fixation procedures, two femoral osteotomies, and one core decompression.
The prostheses were manufactured by Ceraver (Ceraver Osteal, Roissy, France). The stem, made of anodized Ti alloy (TiAl6V4), was smooth and collared, and always was cemented. The alumina head was 32 mm in diameter and anchored via a Morse taper. The acetabular component was a plain alumina cup with grooves on the outer surface, and was cemented in the first 39 hips, and press-fit later. Cementation was done with a first-generation technique in the first patients and by a second-generation technique in later patients.
Surgical approaches included posterolateral approach in 43 cases and trochanteric osteotomy in nine cases.
All patients were evaluated preoperatively and were followed up with clinical examinations and radiographs at regular intervals. All of the surviving patients were evaluated clinically or interviewed by telephone by the same independent observer (ESA). Patients who were unable to return for followup were asked to have radiographs done locally and then sent to us.
Hip function results were rated according to the grading system of Merle d’Aubigné and Postel. 39 This score classified the clinical results into six categories: excellent, 18 points; very good, 17 points; good, 16 points; fair, 15 points; poor, 14 points; and bad, 13 points or less.
Serial AP and lateral radiographs of each hip were taken before and immediately after the operation, and 6 weeks after discharge from the hospital, and 3 months, 6 months, 1 year, and every 2 years postoperatively. The radiographic followup was done by an independent observer (ESA) using AP and lateral standard views of the hip.
The presence and progression of radiolucent lines according to the zones described by DeLee and Charnley 14 were evaluated on the AP radiographs of the pelvis. Loosening of the socket was defined as cup migration exceeding 3 mm, angular rotation exceeding 3°, or a continuous radiolucent line wider than 2 mm.
Despite the difficulties to accurately differentiate the alumina head from the alumina cup on standard radiographs, a trial was made to measure linear wear of the alumina socket. The latter was determined by measuring the change in the shortest distance between the center of the femoral head and the periphery of the acetabular component as seen on the radiograph taken immediately postoperative compared with that seen on the radiograph taken at the last followup, as described by Livermore et al. 37
Parameters investigated on the femoral side included progression of radiolucent lines according to the 14 zones described by Gruen et al, 22 calcar resorption, subsidence, periprosthetic osteolysis, and cortical hypertrophy. Loosening of the stem was defined as migration exceeding 3 mm or a continuous radiolucent line wider than 2 mm.
Heterotopic ossifications, if present, were graded according to the classification of Brooker et al. 7
A survival analysis was calculated using the Kaplan-Meier method. 29 Revision for any reason and revision for aseptic loosening at the time of followup were considered the end points. The statistical significance among the survival of the different groups was determined by the Wilcoxon rank test, with a probability less than or equal to 0.05 was considered as a significant difference. Statistical analysis was done using nonparametric tests.
At the time of followup, 21 patients (27 hips) were alive and had not had acetabular or femoral revision. Twelve patients (16 hips) had revision of either component or revision of both components. Eight patients (nine hips) died of unrelated causes at a mean of 4.7 +/− 4.1 years (range, 0.35–7.8 years). All patients had good to excellent clinical results with no abnormalities seen on radiographs. No patients were lost to followup.
Therefore, the clinical and radiologic status of the original 52 hips was known at the last followup and 27 hips were available for analysis at a minimum of 11 years, with a mean of 16 +/− 3.87 years followup (range, 11–23.65 years). Clinical and radiologic results were assessed for the 21 patients (27 hips) who were alive and had not had revision surgery at the time of the last followup. There were eight women and 13 men. The duration of followup and the demographic data according to the patients’ final status are summarized in Table 2.
Postoperative complications occurred in five patients. Three deep vein thromboses occurred, complicated by a nonfatal pulmonary embolism in one patient. Postoperative dislocations without recurrence occurred in two patients, but no additional surgery was required because the functional hip scores for these patients were very good.
Sixteen hips in 12 patients (four women and eight men) required THR revision at a mean of 11.1 +/− 4.14 years (range, 2.7–19.7 years). The mean age of the patients at the time of the index arthroplasty in this group was not significantly different from the mean age of the patients in the global series (Mann-Whitney U test, p = 0.73) (Table 2).
Bilateral deep infection occurred in a 26-year-old woman with immunosupression who sustained an allogenic bone marrow transplant and had a chronic graft versus host disease develop, for which she was treated with continuing steroids. Bilateral hip replacements were done after an early failure of core decompression. She had a deep infection identified as Enterobacter develop in her right hip (press-fit socket) after 2.7 years, and was treated by one-stage revision. After 10 years she had recurrence of infection for which she was treated successfully by a one-stage revision procedure. The left THR (cemented socket) necessitated revision for deep infection 9.5 years postoperatively. The patient had a two-stage procedure, including a Girdlestone procedure followed by implantation of a metal-on-polyethylene prosthesis. At the last followup, the clinical result was rated poor because of hip stiffness.
Fourteen hips were revised for aseptic loosening of either acetabular or femoral component. Thirteen revision procedures were done in 10 patients for mechanical failure of the socket, including 10 cemented and three press-fit sockets at a mean of 11.8 +/− 1.1 years (range, 6.3–19.7 years). Loosening of the cups were associated with minor bone loss, and no patients required acetabular reconstruction at the time of revision. The details of these revisions are shown in Table 3.
Four procedures were done on the acetabular and the femoral sides, and nine procedures were done on the acetabular side only. No osteolysis was detected at the time of revision.
One hip in a 43-year-old man, with a diagnosis of posttraumatic ON, required revision for aseptic loosening of the femoral component. Revision had been done on the acetabular and the femoral sides at another institution at 12-year followup.
The mean Merle d’Aubigné and Postel functional hip score was 17.8 +/− 0.4 (range, 16–18) at the time of the last followup versus 8.7 +/− 2.7 (range, 1–14) before surgery (Wilcoxon rank test, p < 0.001). The hip score was not significantly different according to the age of the patients at the index procedure, nor to the underlying cause of ON. Of the 27 hips in 21 patients with no additional revision, 26 hips were rated as excellent or very good (96.3%), and one hip was rated as good because the patient had a moderate limp. None of the hips were classified as fair or poor. Hip function was not restricted by pain and 20 patients had a normal gait. At the latest followup, the mean range of flexion was 109° +/− 12° (range, 70°–130°) versus 81° +/− 20° (range, 20°–140°) before surgery (p < 0.001).
Twenty-one sockets (78%) had no radiolucencies; six sockets had a partial lucent line, localized to Zone I (four hips), or to Zones I and III (two hips). One socket had a complete radiolucent line. The radiolucent lines always were less than 1 mm and were nonprogressive during the followup. None of the unrevised acetabular components were considered loose according to the criteria described previously.
On the femoral side, no radiolucent lines were recorded and none of the unrevised femoral components were loose. At the last followup, nine hips (33%) had an isolated and moderate calcar resorption from 1 to 3 mm.
Wear, as measured on plain AP radiographs of the pelvis, was undetectable at the latest followup. None of the 27 unrevised hips had a lytic lesion on either the femoral or the acetabular side (Fig 1).
Twenty-five hips had no heterotopic ossifications (92.6%); one hip was classified as having Stage I heterotopic ossification according to the classification of Brooker et al;7 and one hip was classified as having Stage II heterotopic ossifications. No hips had Stage III or Stage IV heterotopic ossifications.
When considering THR revision for any cause as the end point, the cumulative survival rate was 84.5% (range, 73.7%–95.2%) at 10 years and 65% (range, 49.7%–80.8%) at 16 years (95% confidence interval) (Fig 2). With revision of either component for aseptic loosening as the end point, the cumulative survival rate was 88.5% (range, 79%–98%) at 10 years and 68% (range, 52.3%–83.7%) at 16 years (95% confidence interval) (Fig 3). The cumulative survival rate with revision for aseptic loosening as the end point for the acetabular component was 88.5% (range, 79%–98%) at 10 years and 70.1% (range, 54.7%–85.4%) at 16 years (95% confidence interval) (Fig 4A). The cumulative survival rate with revision for aseptic loosening as the end point for the femoral component was 100% at 10 years and 96.7% (range, 90.2%–103.1% ) at 16 years (95% confidence interval) (Fig 4B).The survivorship data are summarized in Table 4.
The long-term durability of the implants is a challenge in THR for ON. Multiple factors are suspected to have a negative impact in THR done for ON, including the cause of the disease (hemoglobinopathy, steroids, alcohol, transplantation), extensive and bilateral hip involvement, poor bone quality, previous surgery, young age, and high activity level. 1,10,12 Moreover, the problem of PE wear and reaction to debris has become a major concern, especially in young and active patients, leading to aseptic loosening and periprosthetic bone resorption. 8,9,17,51 Independence of age and ON as risk factors for THR still is controversial. 6,9,16,31
Ortiguera et al 44 reported no significant difference in the failure rates and the long-term survivorship of Charnley THA when comparing ON and OA groups, except in the subset of patients younger than 50 years. These findings suggest that age may be the most important risk factor for THR for ON.
Because there now is a general agreement to consider that one of the major causes of long-term failure is PE wear, it is likely that this accelerated PE wear is related to the youth of the patient and his or her activities. The average rate of PE wear has been estimated at approximately 100 μm per year in THR for osteoarthrosis 25,54 and ranged from 300 to 800 μm per year in THR for ON. 33,45 These findings are consistent with the high rate of loosening and osteolysis reported in some series of THR for ON using a metal-on-polyethylene couple. 6,13,28,30,33,45,50
In comparison with PE, the use of alumina as a sliding component has many theorical advantages, including a low friction couple, a much better wettability, less reactive wear particles, and a friction torque improving with time at the opposite of PE. 11,15,34,35,52 In 1981, Boutin and Blanquaert 5 reported an overall rate of wear of alumina-on-alumina combination less than 10 μm per year. Mittelmeier and Heisel 41 published similar results. Nevertheless, the poor quality of alumina used before 1980 probably has led to relatively high wear rates. Considerable changes have been made to the quality of the material and design so that the wear rate in retrieved stable components ranged from 0.025 μm to 2 μm per year. 4,52
In our report, ceramic wear and osteolytic lesions were undetectable. 23 The difficulty in measuring wear in alumina components when using standard radiographs was reported previously. 23 Wear rates can be evaluated to be less than 25 μm per year according to the accuracy of the calipers. These observations also have been made by others. 41
The very low incidence of osteolysis reported in this series is consistent with the results of other reports of alumina-on-alumina THR. 20,23,27,38,41,42,49 However, the few reported cases of osteolysis have been attributed more likely to metal debris from metal abrasion by ceramic or zirconia particles found in the cement than to alumina debris. 34,35
However, the survival of the Ti stems, with either revision or radiographic loosening as the end point, compared favorably with the survival of other cemented prostheses. 54 Previous reports have controversly shown that, using a cemented Ti stem combined with an alumina-on-alumina couple, a near absence of periprosthetic osteolysis could be expected. 2,3,23
The high incidence of alumina cup loosening reported in the literature 2,3,20,21,23,26,53 and the risk of components fractures 19,24 have made its worldwide application limited. It was reported previously that acetabular fixation was the weak link of alumina-on-alumina THR and the most common reason for revision. 23,42,48,49 Hamadouche et al 23 reported a 61.2% 20-year survival rate for the cemented cups in a long-term review of 118 alumina THRs. This is consistent with the current results, which show the difficulties of socket fixation. Reasons for failure included an inadequate choice of alumina designs. Late loosening of cemented alumina cups could be explained by the high rigidity of bulky alumina, which created a mismatch between bone, cement, and ceramic. We now are working on socket fixation improvement using press-fit metal-backed Ti shell either covered by a grid (since 1989) or coated with HA (since 1997). Revision rates for these new devices are very limited at short-term to midterm followup. 2,3 However, despite the young patient age and level of activity, no alumina component fracture occurred in this series.
To our knowledge, the current study is the first report on hip replacement using a ceramic-on-ceramic prosthesis for ON. With the alumina-on-alumina hip replacement done for ON, absence of osteolysis can be expected for as many 24 years after the operation. The excellent femoral fixation and the absence of osteolysis at long-term may be attributable to minimum wear debris particles. Socket fixation was the weak link and new methods of fixation now are being explored.
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