Total hip arthroplasty: first experiences with pinless THA software to determine leg length and offset.

A rigid body fixation on the proximal femur is required for navigation during total hip arthroplasty. In surgery requiring a small incision, the fixation mechanism (C clamp or screw) may cause soft tissue damage and may force enlargement of the approach. New software available for the OrthoPilot navigation system (B. Braun Aesculap, Tuttlingen, Germany) eliminates the need for a rigid body at the femur. Only one rigid body is placed on the iliac crest. Two additional palpations, one at the greater trochanter and one at the patella, establish the system of coordinates between pelvis and femur so that leg length and offset changes can be indicated.