Effects of femoral offset on the stress level of total hip arthroplasty in the elderly : a three-dimensional finite element analysis

Abstract

Objective To evaluate the effects of femoral offset (FO) on the stress level of bone cement total hip arthroplasty (THA) in the elder patients by the three-dimensional finite element analysis. Methods The normal bilateral hip joints in two cases was determined with CT imaging,with parameters including FO,neck shaft angle and neck length.The three-dimensional finite element model of THA was built so as to make Von Mises stress analysis of the changes of different neck lengths,neck shaft angles and FO. Results Stress levels in the prosthesis and bone cement reduced monotonically with the increase of neck shaft angles.In the meantime,the stress levels were lowered when neck length was in a range of 35-44 mm,but beyond the range they showed monotonous increase. Conclusions The reduction of stress levels of prosthesis and bone cement,promotion of femur stress and extension of range of motion of hip joints are closely related to FO.FO reconstruction benefits the restoration of abductor force arm and biomechanical function of normal hip joints. Key words: Femur; Arthroplasty,replacement,hip; Finite element analysis; Offset