Risk of Bone Fracture in Resurfacing Hip Arthroplasty at Varus and Valgus Implant Placements

It is possible to have a varus or valgus placement of resurfacing hip implants after resurfacing hip arthroplasty based on clinical reports. The likelihood of accidents such as sideways falls during the recovery process after arthroplasty is higher for the patient due to gait adaptation and weaker lower body condition. Hence, a computational study has been conducted to predict the risk of bone fracture with different implant placements during sideways fall accidents. A CT image of a young adult with hip osteoarthritis was imported into biomechanical software to develop the 3D inhomogeneous femoral bone model. A model of the Birmingham Hip Resurfacing implant with the properties of cobalt-chromium alloy was inserted into the femur during the reconstruction of the arthroplasty, which mimics the procedure of clinical practice. The loading and boundary conditions were implemented to simulate the sideways fall accident, and the prediction of bone fracture was based on the formation of failure elements. The loading magnitude was applied based on the patient's body weight, ranging from the patient's body weight (1 BW) to five times the patient's body weight (5 BW). The fracture location was predicted to occur at the neck and trochanteric area of the femur, with the greatest damage occurring to the bone model implanted with varus placement. Our finding concludes that the varus placement of the resurfacing hip implant should be avoided whenever possible in clinical practice to sustain bone survivability.