Effect of muscle tension during tendon transfer on sarcomerogenesis in a rabbit model

Sarcomere number change was investigated in an animal model of tendon transfer. In 9 adult New Zealand white rabbits, the flexor digitorum longus muscle was cut distally and transferred and woven into the tibialis anterior tendon. Ankles were then immobilized for 3 weeks in 75 degrees flexion. Transferred flexor digitorum longus muscles were harvested and complete architectural analysis was performed. Sarcomere lengths were measured using laser diffraction. Serial sarcomere number in transferred flexor digitorum longus fibers was a strong function of the sarcomere length at the time of transfer. A highly significant negative correlation between these 2 parameters was approximated by a linear relationship. Based on this finding, we conclude that serial sarcomere number is significantly affected by the degree of stretch during the transfer itself. This could easily compromise the purpose of surgical tendon transfer by reducing the procedure to little more than a tenodesis. (J Hand Surg 2000; 25A:138-143.