A computer assisted surgical navigation system and method is disclosed for registering the position of prosthetic hip joint components. Elements are applied to the pelvis and femur, generating a three-dimensional array. These two arrays combine to derive a reference point representing the native joint. A tracking device with a pre-determined shape and dimensions that precisely articulate with an acetabular cup component generates a third three-dimensional array. The device has a further shape and dimensions that independently articulate precisely with a neck portion of a femoral component, which represents a prosthetic joint center that is independently registered in the system. The tracking device concurrently registers the three dimensional positions of the femoral and acetabular prosthetic components, along with the prosthetic joint center and the native joint center, respectively enabling alterations in three dimensional location of the leg length and offset prior to reduction of the prosthetic joint.
