Fracture of the Femoral Component in Cementless Total Knee Arthroplasty

Abstract

Records of sales revealed that 6172 Ortholoc II cementless total knee femoral components with double bead layers were sold between January 1986 and December 1987. Sixteen thousand two hundred thirty Ortholoc II femoral implants with single bead layers were sold between December 1986 and January 1990. Fractures of the femoral components were reported in 32 knees; all but one occurred in femoral components with porous surfaces consisting of two layers of sintered beads. The overall minimum rate of failure for all sizes with double bead layers was 0.42%. The rate varied with the size of the implant and was much greater in smaller implants. The rate of failure was 0.82% in 852 small components, 0.37% in 2416 medium components, 0.29% in 1729 large components, and 0.09% in 1175 extra-large components. The differences in failure rates were statistically significant for all sizes of implants when compared with other sizes. Sixteen thousand two hundred thirty Ortholoc II components with a single layer of beads were sold worldwide between December 1986 and January 1989. One implant (medium size) failed 18 months after surgery. The minimum rate of failure in the single bead layer implants is 0.006%. This failure rate is statistically significantly less than that of the double bead layer implants. All failures occurred at the junction between one of the bevel surfaces and the distal surface of the implant. In all cases, crack propagation was initiated at the inner surface. This suggests that bending stresses had developed and had opened (straightened) the femoral component.(ABSTRACT TRUNCATED AT 250 WORDS)