Navigated minimal invasive total hip arthroplasty.

All lines of development in Computer Aided Orthopaedic Surgery (CAOS) can be seen as critical steps in a broader effort to innovate the orthopaedic field. CAOS addresses the need to perfect implant placement and joint alignment. Minimally invasive techniques represent equally important new developments in the field of arthroplasty. It seems inevitable that these two fields converge. A navigation system for a minimally invasive approach to the hip would follow these primary design concepts: pure intraoperative system, planning included on plane X-rays, small trackers for acetabular and femoral navigation, control of leg-length change through implant placement as well as joint offset, kinematic test of range of motion (ROM).