Effect of motion and tension on injured flexor tendons in chickens.

This study was undertaken to evaluate the individual effects of motion and tension on the healing response of injured flexor profundus tendons in chickens. Partial midsection transverse lacerations of the profundus tendons were produced in 53 chickens. Postoperatively, they were assigned randomly to four management groups: both motion and tension; only motion, no tension; no motion, only tension; no motion and no tension. Biomechanical results at 4 weeks showed that breaking strength significantly increased with both motion and tension, significantly decreased with neither, and was intermediate with only motion or only tension. Histologic evaluation generally showed the greatest cellular activity with both motion and tension, the least with neither, and an intermediate response with one or the other alone. Collagen fiber staining was increased primarily in the tension groups. The finding that both motion and tension enhance the tendon's response to injury encourages the development of active mobilization protocols following tendon repair.