Mutilating hand trauma presents the surgeon with many reconstructive challenges. This article establishes some biomechanical guidelines to help the surgeon evaluate the hand trauma patient. Through a basic understanding of hand biomechanics, the surgeon may access more accurately what motion and function can best be salvaged. By understanding how amputation, fusion, and tendon loss impact on postoperative hand motion, the surgeon can better focus his or her reconstructive efforts to achieve the highest functional outcome for the patient.