Surgical instrument system for total knee replacement with force sensor adapters and force sensor systems

A surgical instrument comprising:

• a first paddle-shaped spacer block having a lateral extension configured to couple with a lateral condyle of a patient's femur and a medial extension configured to couple with a medial condyle of the patient's femur, wherein the first paddle-shaped spacer block includes a proximal side and a distal side opposite the proximal side;
• a second paddle-shaped spacer block including a lateral extension configured to couple with a lateral condyle of the patient's femur and a medial extension configured to couple with the medial condyle of the patient's femur;
• an elongated handle, wherein the first paddle-shaped spacer is attached to a first end of the elongated handle and the second paddle-shaped spacer block is attached toa second end of the elongated handle opposite the first end, the elongated handle usable to position the first paddle-shaped spacer block or the second paddle-shaped block into a knee joint of the patient;
• and
• a sensor substrate located on the proximal side of the paddle-shaped spacer block, the sensor substrate including a plurality of force sensors configured to measure corresponding forces of the knee joint of the patient,
• wherein the sensor substrate is in contact with the paddle-shaped spacer block and configured to be selectively detached from contact with the paddle-shaped spacer block.