Interface micromotion of cementless hip arthroplasty: Collared vs non-collared stems

Abstract

Cemented and cementless total hip arthroplasty has been used extensively for treatment of hip joint disorder, with the latter gaining popularity due to conservation of bone mass. Major problem associated with the cementless design is the lack of stability. Several design features were introduced to provide the much needed stability for bone integration. These include fins, fiber mesh, beads, indentations and collars. The use of collar has been a subject of controversy with mixed reports of clinical outcomes. In this study, the effectiveness of collar in terms of providing stability was analysed using finite element method. Three dimensional model of a human femur was constructed from CT dataset and hip arthroplasty was simulated. With an applied joint contact load simulating physiological gait, micromotion of the implant relative to the bone was calculated via an experimentally validated algorithm. Results showed that collar did not improve stability of the whole stem but only around the medial calcar region.