One hundred and ninety-nine
total hip arthroplasties were performed, between 1983 and 1987, in 173 patients by three surgeons using the initial design of the porous-coated anatomic
prosthesis. The acetabular component was a preassembled,
metal-backed
polyethylene device, with beads sintered to the
metal backing to allow bone ingrowth and two pegs for initial fixation. Twenty-three acetabular components (12 percent) failed because of either migration or severe
osteolysis. The radiographic appearance of
osteolysis was positively associated with the duration that the implant had been in situ (p < 0.001). The prevalence of
osteolysis was also significantly greater in acetabular components with an outer diameter of fifty-five millimeters or less (a
polyethylene thickness of 8.5 millimeters or less) (p = 0.03). Thirteen hips were revised at a mean of 69.5 months (range, thirty-three to ninety-one months) after the index operation. Examination of the retrieved acetabular components revealed extensive
polyethylene damage on the articular and back surfaces of the liners. Cracks in the
polyethylene rim of the liner and deformation of the anti-rotation notch in the
polyethylene rim were common findings. The density of the
polyethylene was greater than expected, and more particles than anticipated had not fused with the surrounding
polyethylene. The results of this study suggest that factors related to both the design and the material contributed to the failure of these porous-coated anatomic acetabular components.