Siriraj Medical Journal (Feb 2004)
Local Compressive Strength at the Middle of the Weight-bearing Surface of the Femoral Head and Talar Dome : A Biomechanical Study
Abstract
Objective : To compare the local compressive strength at the middle of the weight bearing surface of the femoral head and talar dome. Design : Cadaveric and comparative experimental study. The compressive strength of the talar dome and the femoral head were measured and compared. Background : The prevalence of late collapse of femoral head from avascular osteonecrosis is higher than that of the talar dome. The femoral head and acetabulum form a hip joint with monoarticulation whereas the talus itself has several articulations with several bones, so the talar dome distributes load more effectively from it the surroundings than does the femoral head. Compressive strength of the weight bearing surface of the femoral head and talar dome, however, may play a role in late collapse. Methods : Ten fresh cadaveric normal adult femoral heads and tali were obtained. A compressive load was applied through an indenter at the middle of the superior quadrant of the femoral head and talar dome by using a universal testing machine until a maximum load was obtained. The maximum load and depth of depression at maximum load were recorded. Results : The middle of the weight bearing surface of the femoral head could withstand an average maximum pressure of 30.42 MPa. Its stillness was 929.04 N/mm and its depth of depression was 1.11 mm. The corresponding figures for the talar dome were 49.64 Mpa, 1631.65 N/mm, and 0.96 mm respectively. Conclusion : This study showed that local compressive strength at the middle of the weight bearing surface of the talar dome was 1.63 times greater than that of the femoral head. Relevance : This finding may explain the higher prevalence of late collapsing avascular necrosis of the femoral head than that of the talar dome.
