SURVIVAL AND POLYETHYLENE WEAR OF POROUS-COATED ACETABULAR COMPONENTS IN PATIENTS LESS THAN FIFTY YEARS OLD

BACKGROUND: Younger patients (those who are less than fifty years old) have been shown to have a high rate of failure of cemented acetabular components following total hip arthroplasty. In this report, we present the results associated with the use of an uncemented acetabular component in young patients who were evaluated at a minimum of nine years postoperatively. METHODS: Between December 1984 and December 1989, the senior author performed 174 primary total hip arthroplasties with use of a single design of porous-coated acetabular component. Seventy-one of these procedures were performed in fifty-six patients who were younger than fifty years old. Fifty-six of the seventy-one hips were available for radiographic and clinical analysis after a mean duration of follow-up of eleven years. All hips had been treated with a Harris-Galante-I porous-coated acetabular component that had been placed with a line-to-line fit and fixed with a mean of four screws. Clinical analysis was performed with use of the Harris hip score. Standardized anteroposterior radiographs were analyzed with regard to migration, radiolucent lines, pelvic osteolysis, and two-dimensional linear wear of the polyethylene. RESULTS: No metal shell was revised because of aseptic loosening, and no shell was loose at the time of the latest follow-up. A nonprogressive radiolucent line was seen in one zone in ten hips (18%) and in two zones in six hips (11%). No hip had a radiolucent line in all three zones. Pelvic osteolysis was noted in thirteen hips (23%); the osteolysis was observed in the ischium in eleven hips and around the screws in two. Survivorship analysis revealed that the probability of survival of the metal shell was 98% (95% confidence interval, 96.9% to 99.9%) at ten years. The mean rate of linear polyethylene wear (and standard deviation) was 0.15 +/- 0.10 mm/yr (range, 0.02 to 0.59 mm/yr). The wear rate was significantly increased in patients with an excellent Harris hip score (p = 0.004) and a younger age (less than thirty-eight years) (p = 0.026). With the numbers available, no relationship could be detected between the wear rate and the gender or weight of the patient, the polyethylene thickness, the abduction angle, or the femoral neck length. CONCLUSIONS: The fixation and survival of porous-coated acetabular metal shells in patients less than fifty years old was excellent after a mean duration of follow-up of eleven years. The high rate of linear polyethylene wear and the high prevalence of pelvic osteolysis are of serious concern in this patient population. Continued follow-up will be necessary to evaluate the influence of these findings on the longevity of the fixation of this prosthesis.