Non-imaging, computer assisted navigation system for hip replacement surgery

A method of attaching an tracking marker to the upper femur, suitable for tracking the upper femur during hip arthroplasty or a similar operation, comprising the steps:

• positioning a collar in contact with the greater trochanter of the femur, said collar adapted for mounting thereon a tracking marker;
• attaching a ligature to said collar;
• wrapping said ligature around the upper femur;
• and
• tightening said ligature around the femur to pull said collar tightly against said greater trochanter.

A method of determining changes between pre-operative and post-operative relationships between a femur and a pelvis, suitable for use during a hip arthroplasty operation, comprising the steps of:

• maneuvering the femur into a reference position;
• measuring, with a non-radiological locating system, pre-replacement femoral parameters in relation to the pelvis;
• after implanting a prosthetic, returning the femur to the reference position;
• again measuring, with a non-radiological locating system, post-replacement femoral parameters in relation to the pelvis;
• and
• comparing said pre-replacement and said post-replacement parameters in a computer model.

A system for measuring and assessing the skeletal geometry of a hip joint during surgery, suitable for surgical navigation of a hip arthroplasty operation, comprising:

• an locating system which determines positions and orientations of trackable markers;
• a computer, interfaced to said locating system to receive tracking data, and calculating from said tracking data the positions of tracked objects in relation to a generic computer model of a patient's hip geometry;
• a software module, executable on said computer, which defines the patient's pelvic plane without reference to previously obtained radiological data, by locating at least three pelvic landmarks;
• and
• a pelvic tracking marker, fixable to the pelvic bone and tracked by said locating system, to track in real time the orientation of said pelvic plane.

A method of verifying reliability of a computer assisted, optically tracked surgical navigation system, comprising the steps of:

• fixing a an optically trackable marker to a bone at a point of attachment;
• placing a mark on said bone at a location removed from said point of attachment;
• inputting an initial position of said mark into an optical tracking system by touching said mark with an optically trackable probe, while simultaneously tracking said optically trackable marker;
• calculating an initial vector locating said mark in the reference frame of said optically trackable marker;
• at a later time, inputting a later position of said mark into the optical tracking system by touching said mark again with the optically trackable probe, while simultaneously tracking said optically trackable marker;
• calculating a second vector locating the later position of said mark in the later reference frame of the optically trackable marker;
• and
• comparing said initial and said later vectors to verify that said optically trackable marker has remained fixed relative to said mark.