Systems and methods for measuring parameters in joint replacement surgery

A method for determining changes in parameters of a hip joint after a hip arthroplasty procedure, the method comprising:

• estimating a first position of a center of a native femoral head of a hip joint;
• estimating, after modification of the hip joint, a position of a center of rotation of the modified hip joint;
• establishing mechanical and epicondyle axes of a femur associated with the modified hip joint;
• virtually positioning the mechanical axis of the femur as substantially parallel with the superior/inferior axis of a pelvis associated with the hip joint and the epicondyle axis of the femur as substantially parallel with the coronal plane of the pelvis;
• estimating a second position of the center of the native femoral head, based on the virtual positioning of the mechanical and epicondyle axes;
• and
• estimating leg length and offset associated with the modified hip joint based on the first and second positions.

A method for determining a change in a parameter associated with a joint caused by a modification of a portion of the joint, the method comprising:

• establishing a first point of reference relative to a first bone of a joint, the first point of reference indicative of an estimated pre-operative center of rotation of the joint in pelvic space;
• establishing, after a modification of the joint, a second point of reference indicative of an estimated post-modification center of rotation of the joint;
• positioning a virtual representation of the first bone in a predetermined pose based on the second point of reference and relative to a second bone;
• approximating, based on the positioning of the virtual representation of the first bone in the predetermined pose, a third point of reference in pelvic space indicative of a position of the first point of reference maintained in a fixed relationship relative to the first bone;
• and
• estimating a change in a parameter associated with the joint based on a difference between the third point of reference and the first point of reference.

A computer-implemented method for determining a change in a parameter of a hip joint caused by modification of a portion of the hip joint, the method comprising:

• establishing a first point indicative of a first position of a center of a native femoral head relative to the femur in pelvic space;
• approximating a reference point between femoral epicondyles;
• approximating, after modification of the femur, a position of a center of rotation of a prosthetic femoral component in a pelvic space;
• establishing a first axis associated with the modified femur, the first axis comprising the approximated position of the center of rotation of a prosthetic femoral component and the approximated reference point between the femoral epicondyles;
• establishing a second axis associated with the modified femur, the second axis comprising a transverse axis through the femoral epicondyles;
• virtually positioning the first axis as substantially parallel with the superior/inferior axis of the pelvic space and the second axis as substantially parallel with the coronal plane of the pelvic space;
• approximating a second point indicative of a second position of the center of the native femoral head in the pelvic space based on the virtually-positioned first and second axes;
• and determining, in the pelvic space, a difference between the first and second points.