Biomechanical analysis of various operative hip joint rotation center shifts.

A mathematical model was used to evaluate the mechanical situation after various operative shifts of the hip joint rotation center. It was concluded that while performing different pelvic osteotomies and the total hip replacement the hip joint rotation center should be shifted as far medially as is technically possible to reduce the magnitude of the hip joint contact force. By contrast, lateralization of the hip joint rotation center strongly increases the magnitude of the hip joint contact force; therefore this should be avoided whenever possible. The superior shift of the hip joint rotation center decreases the strength of the patient's hip abductor muscles and must therefore also be avoided. The inferior shift of the hip joint rotation center is favorable because it increases the strength of the patient's hip abductor muscles.