Recent progress in flexor tendon healing.

Although advances in the treatment of flexor tendon injuries have led to improved clinical outcomes during the past several decades, a subset of patients continue to experience a loss of function. Using a canine model of sharp transection of the flexor digitorum profundus tendon followed by repair and rehabilitation using clinically relevant techniques, we have examined the influence of multistrand suture and postoperative rehabilitation variables on digital function and tendon strength. Our findings highlight the critical role of repair technique in providing a stiff and strong repair and indicate that continued refinement of suture techniques is warranted in order to minimize repair-site elongation (gap). Gap formation continues to occur at a high frequency, and the formation of gaps greater than 3 mm delays the accrual of repair-site strength that occurs with time. Furthermore, our results indicate that passive-motion rehabilitation that produces a moderate amount of tendon excursion (2 mm) at low levels of tendon force (5 N) is sufficient to inhibit adhesion formation and to promote healing. Increases in excursion or force beyond these levels do not accelerate the healing process. These findings suggest that we are approaching the limit of the extent to which we can modulate healing by manipulating rehabilitation variables such as tendon excursion and force. Future advances will probably require manipulation of the biological factors that promote healing.