Bony balancing apparatus and method for total knee replacement

Abstract

Total knee replacement surgery is improved through custom cuts on the distal femur without resorting to expensive computer navigation. The method involves measurement, on plain radiographs prior to surgery, the amount of bone that would be resected on each knee, medially and laterally on the distal femur. In the preferred embodiments, the predetermined distance is in the range of 8-10 mm, more preferably 10 mm, and the resulting distance from the second line to the apex of the lateral condyle is in the range of 6 to 7 mm. A cutting fixture is provided and used to resect the medial condyle at the predetermined distance and the lateral condyle at the measured resulting distance.

Description

FIELD OF THE INVENTION[0001]This invention relates generally to total knee replacement and, in particular to surgical techniques and instrumentation to more precisely balance the knee joint.BACKGROUND OF THE INVENTION[0002]In classical arthroplasty alignment, the distal femoral cut is perpendicular to the femoral mechanical axis. This axis is defined as a line drawn through the center of the femoral head to the center of the knee, which is defined by the center of the intercondylar notch, with the patient standing and weight bearing. Under current practice, most surgeons prefer a zero degree cut; that is, a perpendicular cut on the tibia. This is a line from the center of the tibial anatomy, which is at the center of the tibial spines, to the center of the talus. The goal here is a right angle cut to that alignment axis. When these two landmarks are combined, the result should be a well-balanced knee in the coronal plane, meaning with the knee in full extension at 30 and 60 degrees ...

AI Technical Summary

Benefits of technology

This invention improves upon total knee replacement surgery by facilitating custom cuts on the distal femur without resorting to expensive computer navigation. The method involves measurement, on plain radiographs prior to surgery, the amount of bone that would be resected on each knee, medially and laterally on the distal femur, based upon the perpendicular measurement from the center of the femoral head to the center of the intercondylar notch. The anatomy of each patient is unique, and each requires a unique amount of resection. With the exception of computer navigation, all other existing approaches merely guess at these amounts. The method provides a cutting fixture that includes at least one cutting slot and one or more devices for measuring the distance between the apex of the medial condyle and the slot for resecting the medial condyle, and between the apex of the lateral condyle and the slot for resecting the lateral condyle. The cutting fixture ensures that the medial and lateral cuts are at all times co-planar.

Problems solved by technology

Historically, if the alignment is not appropriate and there is imbalance present after the bone cuts have been made, most surgeons assume that there are problems with the soft tissue balancing and that there are contractures of the medial or lateral structures which are preventing perfect balancing of the knee.

While this may be true in a small portion of knees with significant combined sagittal and coronal deformity, I believe that improper bone cuts are the problem and not ligament balancing.

However, as learned from computer navigation, these historically elected angles may be inappropriate most of the time.

The fact is, true accuracy can never be realized with an educated guess.

However, computer navigation is expensive, it is time consuming, and it will probably not ever be available to every surgeon.

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