[Reconstructive hand surgery after cervical spinal injury: a new method increases the possibilities to reconstruct...

The sarcomere is the basic unit of force generation in skeletal muscle. Since muscle force generation is highly dependent on sarcomere length, it is important to know the normal range of sarcomere length if informed decisions are to be made regarding surgical procedures affecting muscle length, such as tendon transfer or lengthening. The article reports intraoperative sarcomere length measurement with a laser diffraction technique. Sarcomere length as a function of joint angle was monitored during various tendon transfers performed to restore lost finger, thumb, wrist, forearm and elbow function in tetraplegics. The intraoperative measurements were essentially the same as those obtained in cadaveric muscle sarcomere models. Muscle fiber length, torque and tendon length are the most important structural determinants of the operating range and torque profile of each motor, while the relation between passive tension and active force is the most critical factor in making surgical decisions.