Fatigue performance of composite analogue femur constructs

Six 3 ^rd generation and six 4 ^th generation mechanical analogue proximal femur models were implanted with cemented, polished surface femoral components in a mock total hip arthroplasty (THA). The objective of the study was to test whether or not the 4 ^th generation analogue bone models have significantly improved resistance to fracture and fatigue as compared to the 3 ^rd generation bone models in a clinically relevant in situ type test. The average final failure (total structural failure) of the 3 ^rd generation femurs occurred at 3.16 million cycles. Changes in actuator displacement and crazing in the 3 ^rd generation bones occurred at a much lower number of cycles. In contrast, the 4 ^th generation femurs were cycled for 10 million cycles with no total structural failure in any specimen. All 4 ^th generation specimens showed very little change in actuator deflection and only one of the specimens exhibited visible crazing at a high cycle count. These results are in line with previously tested fracture toughness and fatigue crack propagation rate test results. The results from the in situ testing provided evidence that the 4 ^th generation analogue bones exhibit superior performance in fatigue testing applications as compared to the 3 ^rd generation bones.