Experimental evaluation of immobilization in operative and non-operative treatment of Achilles tendon rupture. A radiographic study in the rabbit.

Achilles tenotomy in rabbits was followed by operative or non-operative management. Various immobilization periods were used (0, 7, 16 and 35 days). Steel markers were fixed on the tendon ends to allow continuous X-ray monitoring of the distance between them. The separation of the tendon ends followed a biphasic course, with (I) and initial separation, 0-7 days, (II) no separation, 8-12 days, and (III) late separation, 22-35 days, irrespective of the therapeutic procedure. When the tendon was sutured, the initial separation was small if the leg was immobilized, but large if no immobilization was used. When no suture was applied, the initial separation was always large, whether or not the leg was immobilized. Large initial separation of the tendon ends always resulted in disturbed healing of the tendon. The final tendon end separation was independent of duration of immobilization. Good healing of cut Achilles tendon in rabbits thus requires immediate suture and immobilization for at least 7 days. The possible validity of these observations for tendon rupture in man offers interesting prospects.