Experimental study on the effects of tension-reduced early mobilization on extensor tendon healing

Numerous clinical and experimental studies have been reported on early postoperative mobilization after flexor tendon repair. However, there have been only a few experimental studies reported on extensor tendon repair. In 1989, Ishiguro reported the usefulness of tension-reduced early mobilization in clinical cases of extensor tendon ruptures. The purpose of this experimental study was to examine the in vivo effect of tension-reduced early mobilization on extensor tendon healing in chicken. An experiment was performed on the extensor tendons of 218 chickens in an attempt to examine the effects of tension-reduced early mobilization on tendon healing and adhesion. The extensor tendon of the fourth toe was cut and the distal stump of the tendon was transferred to the extensor tendon of the third toe. Postoperatively two protocols were employed. In the immobilization group, a cast was applied for three weeks. In the early-mobilization group, immediate active motion of the digits was allowed. A tension-reduced position was maintained by taping the fourth toe to the dorsum of the third. The findings from the early mobilization group and from the immobilization group were as follows: 1. Macroscopically, sutures at the repair site of the early-mobilized tendon were not evident after three weeks because of fibrous connective tissue growth. Despite this abundant connective tissue, tendon gliding was observed to be smooth. Between the suture site and the gliding floor, loose connective tissue, similar to normal paratenon, was observed. Histology confirmed this observation. 2. The tensile strength required to extend the MP joint was significantly lower for the early-mobilization group than for the immobilization group, suggesting minimal adhesion between the sutured tendon and the gliding floor in the early-mobilization group. 3. No significant difference in tensile strength among the various tendon repair techniques employed was observed at the suture site.