Unicondylar balancer and method

A method of knee surgery, the method comprising:

• using a unicondylar balancer, comprising:
• a first body portion including a first jaw for contacting a femoral condyle of a patient;
• a second body portion slideably attached to the first body portion, the second body portion comprising second jaw for contacting a tibial plateau of the patient;
• an adjustment mechanism for moving the first body portion relative to the second body portion selectively to distance the first jaw from the second jaw, wherein the adjustment mechanism comprises:
• a threaded collar captured in a slot in the second body portion;
• and
• a threaded rod received through the threaded collar;
• wherein the first body portion is coupled to the threaded rod via a biasing element, wherein the biasing element biases the first jaw away from the second jaw;
• and
• a manually operable locking mechanism, separate from the adjustment mechanism, to lock the first body portion with respect to the second body portion selectively to prevent movement of the first jaw with respect to the second jaw against the action of the biasing element, by:
• placing a leg of the patient in a flexion position;
• inserting the first and second jaws between a tibial plateau and a selected femoral condyle of the leg, the selected femoral condyle being only one of a medial femoral condyle and lateral femoral condyle of the leg;
• operating the adjustment mechanism to move the first body portion relative to the second body portion to distract the femoral condyle from the tibial plateau until an applied force between the first jaw and the second jaw by the biasing element reaches a desired force;
• determining a distance between the selected femoral condyle contacting surface of the first jaw and the tibial plateau contacting surface of the second jaw at said desired force;
• placing the leg in extension;
• inserting the first and second jaws between the selected femoral condyle and the tibial plateau of the leg;
• operating the adjustment mechanism to move the first body portion relative to the second body portion to distract the selected femoral condyle from the tibial plateau until an applied force between the first jaw and the second jaw by the biasing element reaches the desired force;
• determining a distance between the selected femoral condyle contacting surface of the first jaw and the tibial plateau contacting surface of the second jaw at said desired force;
• and
• determining a position of a resection plane in the femur based on the distances read off using the plurality of first markings in the flexion position and the extension position.