More than 500,000 total hip replacements are done worldwide each year. 3 Although excellent results after implant arthroplasty have been reported, the long-term clinical outcome in some patients may be compromised by periprosthetic bone resorption and aseptic loosening, the major complications leading to implant failure. 3 Periprosthetic osteolysis and aseptic loosening result from complex events that are triggered by wear debris from various implant, implant-bone interfaces, or cement-bone motion interfaces. 8,22,23 Of the materials used to construct or fix joint implants, polyethylene, a component of most hip and knee implants, is regarded as producing the most destructive wear debris. 2,3 Therefore, implants with an alternative bearing surface might have a significant advantage compared with current metal-on-polyethylene components.
During the 1960s McKee and Watson-Farrar developed a metal-on-metal hip prosthesis made of a CoCr alloy. 24 A large number of these devices were implanted in patients in Europe and the United States. In the mid1970s, the McKee-Farrar design was abandoned in favor of the Charnley low friction metal-on-polyethylene design, despite the fact that the inferiority of the metal-on-metal design never was proven in a prospective randomized trial. 34 Now, with increasing concerns about polyethylene wear debris and its association with periprosthetic osteolysis, 26 the metal-on-metal concept has regained interest and second generation all-metal implants are being studied. 10,25
The current study evaluated the long-term survivorship of McKee-Farrar total hip implants. A large population of patients with arthroplasties done by one surgeon from 1969 to 1973 was examined. During that time 153 consecutive total hip arthroplasties were done in 129 patients who were followed up for as many as 28 years. The results document the excellent long-term survivorship of the McKee-Farrar implant.
MATERIALS AND METHODS
The series consisted of 153 consecutive total hip arthroplasties done with McKee-Farrar components in 129 patients between 1969 and 1973. A retrospective chart review was done and attempts were made to contact all living patients. Efforts to contact the patients included the use of computer-based data searches, driver’s license bureaus, national phone directories, and church directories. Demographic information regarding patient gender, age, and preoperative diagnosis was obtained. Details about revision dates and clinical indications also were obtained.
All arthroplasties were done by the senior author (ABS). A standard posterolateral approach was used in all patients, and all stems and cups were cemented with Simplex polymethylmethacrylate (Howmedica Inc, Rutherford, NJ) using standard first generation cement techniques. All patients were enrolled in the Simplex cement investigation approved by the United States Food and Drug Administration. All implants were of the McKee-Farrar (Howmedica Inc) metal-on-metal design.
A survivorship analysis of the McKee-Farrar prosthesis was done as described by Armitage 4 and Dobbs. 9 When considering total hip replacement, the survival of the prosthesis usually determines the success of the operation. In the current study, the criterion for survivorship was that the prosthesis had not been revised for any reason other than infection. Survivorship was measured from the date of insertion to the date of revision. As with all survivorship analyses, the patients lost to followup were thought at each interval to be doing no better or worse than the cohort still available for study.
Age data for female and male patients and the numbers of patients with diagnoses of rheumatoid arthritis, osteoarthritis, or other were expressed as means with their standard errors. Mean values within each gender or diagnosis group were compared using a Student’s t test assuming unequal variances. Survivorship percentages for patients with a primary diagnosis of rheumatoid arthritis or osteoarthritis were analyzed using a chi square test. A probability of p less than 0.05 was considered statistically significant.
Of the 153 consecutive total hip arthroplasties done in 129 patients, 23 patients (25 implants) were lost to initial followup. The senior author (ABS) has a large referral-based practice and many patients came from out-of-state locations for their surgery and returned home for their postoperative care. The patients who were lost to initial followup were never seen by the senior author after being discharged from the hospital and could not be located at the time of the current study. Five additional patients (five implants), whose implants were removed for infection, were not counted in the data pool. This left a study group of 123 implants in 101 patients. The study group consisted of 63 women and 38 men. The average age at implantation was 59.8 years (range, 29–87 years) for women and 58.9 years (range, 27–74 years) for men (Fig 1A). Primary diagnoses in the majority of patients were osteoarthritis (51 patients, 59 implants) or rheumatoid arthritis (33 patients, 47 implants). Other primary diagnoses (17 patients, 17 implants) included femoral neck nonunions (six patients), posttraumatic degenerative joint disease (six patients), avascular necrosis (four patients), and developmental dysplasia of the hip (one patient) (Fig 1B). In the final study group, 22 patients had bilateral arthroplasties. The number of patients with left or right arthroplasties was not significantly different (Fig 1C). The average ages at implantation for patients with osteoarthritis or rheumatoid arthritis were 66.4 and 51.7 years, respectively (Fig 1D). These ages were significantly different with a probability less than 0.01.
Sixteen patients with 20 implants are alive and have an intact McKee-Farrar prosthesis at an average of 25 years (range, 23–28 years) postoperatively (Table 1). In the study group of 101 patients, 48 patients (61 implants) died with their McKee-Farrar prosthesis intact at an average of 14 years (range, 0–25 years) postoperatively. An additional 23 patients (28 implants) were lost to followup during the study period. Fourteen of 123 implants (14 patients) were revised for aseptic loosening at an average of 12 years (range, 0–23 years) after index surgery. According to the surgical records of these patients, eight acetabular cups and 10 femoral stems were loose. No black discoloration of the periprosthetic tissues was described in the operative reports for any patient. Aseptic loosening and subsequent revision surgery were not associated with any one disease. Of the patients requiring revision surgery, five had a primary diagnosis of rheumatoid arthritis, five had a diagnosis of osteoarthritis, and four patients were diagnosed with other conditions.
An implant survivorship analysis was done as described by Armitage 4 and Dobbs. 9 The results (Table 2) showed a 20-year probability of implant survivorship of 84.4% and a 25-to 28-year implant survivorship of 74.4%. Figure 2 shows the survivorship data. Using the same type of analysis for patients having a primary diagnosis of rheumatoid arthritis or osteoarthritis, the 20-year implant survivorships were 88.4% and 83.3%, respectively, and the 26-to 28-year implant survivorships were 81.8% and 69.4%, respectively. The probabilities of implant survivorship for the two patient groups were not statistically different at 20 years or at 28 years.
The most important factors that influence the survivorship of appropriately placed and well-fixed joint implants may be the amount and types of wear debris that are generated by the surgically implanted joints. The biologic consequences of particulate debris have been a topic of extensive research during the past 10 years. 8,12,16,17,21–23 The wear rate of metal-on-metal articulations has been measured to be 100 times less than that of metal-on-polyethylene. 15,35 This decreased production of wear particles might result in less foreign body reaction or metal particles possibly could be removed from the tissues more easily than polyethylene particles. 13 Chan et al 7 suggested that the use of metal-on-metal articulating surfaces may mitigate the problem of osteolysis by offering improved wear performance. Therefore, implants with a metal-on-metal bearing surface might have significant advantages when compared with current metal-on-polyethylene designs. 18,27 Given the inherent problems associated with polyethylene wear particles, second generation metal-on-metal bearing implants may offer a viable alternative to current techniques.
The reported survivorship of metal-on-metal total hip arthroplasties varies from 53% to 89% at 10 to 15 years. 1,5,9,11,13,19,32,33 The reported survivorship of Charnley low-friction arthroplasties varies from 65% to 84% at 20 to 30 years. 6,29,31 Jacobsson et al 14 reported a 20-year implant survivorship of 77% in 107 consecutive McKee-Farrar arthroplasties. This was compared with a 20-year survivorship of 73% for a similar population of Charnley prostheses. The current data support the excellent long-term survivorship reported by Jacobsson et al. 14 A 20-year probability of implant survivorship of 84% and a 28-year implant survivorship of 74% were seen in the current study. These are thought to be the highest survivorship and the largest American series of one surgeon with the longest followup.
Of the 129 patients (153 consecutive total hip arthroplasties) in this series, two groups were lost to followup. One group of 23 patients (25 implants) was lost immediately after hospital discharge because they were from out-of-state locations and received long-term postoperative care from physicians other than the senior author. None of these patients could be located and they were not included in the current study. A second group of 23 patients was lost during the 28-year followup. For the duration of their followup, they were included in the study group of 101 patients. As noted by Armitage, 4 these patients are subject to the same outcome probabilities as patients who remain in the study. Also, these patients were lost at different times, but computationally were assumed to have withdrawn at the midpoint of each annual interval (Table 2). These assumptions are common to survivorship analyses. 4,5
The current study population included 38% of patients who had a diagnosis of rheumatoid arthritis. This percentage is much higher than in other reported series (11% to 17%), 3,13,14 and is a direct result of the patient population seen by the senior author. Patients with rheumatoid arthritis have poorer bone quality but place lower demands on their implants, yet there was no significant difference in implant survivorship between the patients with rheumatoid arthritis and the patients with osteoarthritis. The patients with rheumatoid arthritis tended to do slightly better over the long-term, a result that supports the findings of Sochart and Porter 30 and Joshi et al. 20
Another important aspect of the current study population is the relatively young age of the patients. The average age at implantation was 58 years, and this is thought to be the youngest population of patients reported in the literature. 27,28 Activity has been correlated with young age, 28 and there were many patients in the current study younger than this average age with excellent long-term results. The excellent long-term survival of metal-on-metal implants may infer particular suitability for use in younger patients. 36
The authors thank Patricia Venema for expert technical assistance.
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