Do large femoral heads reduce the risks of impingement in total hip arthroplasty with optimal and non-optimal cup positioning?

The purpose of this study was to assess whether large femoral heads (36–38 mm) improve the range of motion in total hip arthroplasty compared to standard (28–32 mm) femoral heads in the presence of optimal and non-optimal cup positioning. A mathematical model of the hip joint was generated by using a laser scan of a dried cadaveric hip. The range of motion was assessed with a cup inclination and anteversion of reference and with non-optimal cup positions. Large femoral heads increased the range of motion, compared to the 28-mm femoral head, in the presence of a hip prosthesis correctly implanted and even more so in the presence of non-optimal cup positioning. However, with respect to the 32-mm femoral head, large femoral heads showed limited benefits both in the presence of optimal and non-optimal cup positioning.