COMPARISON OF INTERFACE MEMBRANES OBTAINED FROM FAILED CEMENTED AND CEMENTLESS HIP AND KNEE PROSTHESES

Biochemical and histologic analyses were performed on interface membra nes obtained at revision of aseptically loosened hip implants (n = 36) and knee implants (n = 16). Clinical failure occurred sooner in patie nts with uncemented total hip implants (Group 1) than in patients with cemented implants (Group 2) (p < 0.02). There was no difference in ti me to revision between the patients with uncemented implants (Group 3) and patients with cemented total knee implants (Group 4). Histologica lly, more small (<5 mu) polyethylene particles were found within macro phages and fibroblasts in membranes from Groups 1 and 2. Polyethylene particles from failed total knees (>10-100 mu) were larger than those from failed total hips. Large polyethylene fragments and foreign-body giant cells were more common in failed knees than failed total hip mem branes. Biochemically, proteinase and cytokine activity in the tissue culture supernatant from all groups was higher than in the control tis sue (p < 0.01). The activities of stromelysin, prostaglandin E(2), int erleukin-1 alpha, interleukin-1 beta, and tumor necrosis factor-alpha were higher in Groups 1 and 2 than in Groups 3 and 4 (p < 0.05). These findings support the hypothesis that interface membranes enveloping f emoral (hip) and tibial (knee) components of failed total joint implan ts may promote bone resorption and aseptic loosening. The reason for s lower failure of knee implants as compared with hip prostheses may be the lower level of biochemical activity and macrophage density that co rrelates closely with larger polyethylene particles.