A laser diffraction method for measuring muscle sarcomere length in vivo for application to tendon transfers.

A technique that uses laser light diffraction to measure muscle sarcomere length allows direct determination of optimal muscle length during tendon transfers. Forearm muscle sarcomere length with the hand in the position of function is 2.4, and muscle length corresponds directly to sarcomere length. We have used these observations to restore optimal muscle length during tendon transfers. Standard high radial nerve tendon transfers in six fresh cadaver forearms demonstrated the efficacy of the laser diffraction method in accurately measuring sarcomere length. In two clinical trials with the laser, standard high radial nerve palsy tendon transfers were performed. In each case the clinical tendency was to overpull the muscle during the transfer. With the laser it was possible to identify excessive muscle stretch and restore optimal muscle length.