PATTERNS OF OSTEOLYSIS AROUND TOTAL HIP COMPONENTS INSERTED WITH AND WITHOUT CEMENT

We reviewed the radiographs of 137 patients (137 hips) who had been managed with a total hip arthroplasty, with insertion of an extensively porous-coated femoral component without cement, because of osteoarthrosis or avascular necrosis. A porous-coated acetabular component had been inserted with cement in sixty-three of these patients (Group A) and without cement in seventy-four patients (Group B). The radiographs were examined for osteolysis, either directly adjacent to the joint or at locations remote from the joint. The mean duration of follow-up was 105 months (range, fifty-four to 142 months). The rate of osteolysis of the acetabulum in the unrevised hips in which the acetabular component had been inserted with cement was 37 per cent (nineteen of fifty-one). The osteolysis was most frequently of the linear type, a pattern that was associated with a high prevalence of loosening in the hips that had a cemented cup (30 per cent [nineteen of sixty-three]). The rate of acetabular osteolysis (18 per cent [thirteen of seventy-one]) in the patients who had a cup that had not been inserted with cement and that had not been revised was not as high as that associated with the surviving cups that had been inserted with cement (p < 0.05). The osteolysis associated with the cups that had not been inserted with cement was localized and expansile, and it was not associated with loosening of the component. However, it produced more loss of bone than did the linear pattern of osteolysis around the cemented cups. The patients in whom the cup had been inserted without cement also had a higher prevalence of osteolysis in the femur than the patients in whom the cup had been cemented (32 per cent [twenty-three of seventy-one] compared with 12 per cent [six of fifty-one]; p < 0.01). Osteolysis occurred more frequently in younger patients than in older ones; the mean age was fifty years for the patients who had osteolysis compared with fifty-nine years for those who did not (p < 0.02). With both types of fixation of the cup, osteolysis was restricted to the bone in the periprosthetic region that was in direct continuity with the joint (the so-called effective joint space). With the type of porous-coated stems used in this series, the effective joint space of the femur rarely extended distal to zones 1A and 7A as defined by Gruen et al. As the osteolysis associated with porous-coated acetabular components is not symptomatic unless it becomes extensive enough to cause a fracture of the bone, postoperative management of these patients should include annual radiographic evaluations.