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

We reviewed the radiographs of 137 patients (137 hips) who had been ma naged with a total hip arthroplasty, with insertion of an extensively porous-coated femoral component without cement, because of osteoarthro sis or avascular necrosis. A porous-coated acetabular component had be en inserted with cement in sixty-three of these patients (Group A) and without cement in seventy-four patients (Group B). The radiographs we re examined for osteolysis, either directly adjacent to the joint or a t locations remote from the joint. The mean duration of follow-up was 105 months (range, fifty-four to 142 months). The rate of osteolysis o f the acetabulum in the unrevised hips in which the acetabular compone nt had been inserted with cement was 37 per cent (nineteen of fifty-on e). The osteolysis was most frequently of the linear type, a pattern t hat was associated with a high prevalence of loosening in the hips tha t had a cemented cup (30 per cent [nineteen of sixty-three]). The rate of acetabular osteolysis (18 per cent [thirteen of seventy-one]) in t he patients who had a cup that had not been inserted with cement and t hat had not been revised was not as high as that associated with the s urviving cups that had been inserted with cement (p < 0.05). The osteo lysis 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 preva lence of osteolysis in the femur than the patients in whom the cup had been cemented (32 per cent [twenty-three of seventy-one] compared wit h 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 fi fty 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 o f the cup, osteolysis was restricted to the bone in the periprosthetic region that was in direct continuity with the joint (the so-called ef fective joint space). With the type of porous-coated stems used in thi s series, the effective joint space of the femur rarely extended dista l to zones 1A and 7A as defined by Gruen et al. As the osteolysis asso ciated with porous-coated acetabular components is not symptomatic unl ess it becomes extensive enough to cause a fracture of the bone, posto perative management of these patients should include annual radiograph ic evaluations.