Postoperative regimens after Achilles tendon rupture can be broadly categorized as delayed rehabilitation or early functional rehabilitation. Delayed rehabilitation utilizes cast treatment to immobilize the tendon. This common postoperative practice after open Achilles repair includes a 4-to 6-week period in a non-weight bearing, short leg cast that begins in equinus and is gradually brought to neutral. Full weight bearing is typically permitted at 4 to 6 weeks in a short leg cast, after which the cast is removed and physio therapy is begun. Prolonged immobilization, although fully protecting the repair from traumatic rerupture and gapping at the repair site, is associated with multiple complications such as arthrofibrosis, muscle atrophy, deep vein thrombosis, adhesions, and articular cartilage degeneration. Immobilization is causally related to a decrease in muscle size, a decrease in the force-generating capacity per unit area, and interstitial fibrosis. Immobilization impacts the tendon itself, resulting in lower tensile strength and strain at failure with altered physiologic characteristics. The goal of postoperative care is to protect the repair while providing the optimum conditions for regeneration. A strong body of evidence suggests that postoperative casting and immobilization does not provide ideal conditions for tendon healing. Gelberman et al., in a canine model, has shown that early protected passive mobilization after flexor tendon repairs produced tendons with higher ultimate load to failure after 12 weeks compared to those that were immobilized. Enwemeka et al. has demonstrated in a rat model that early functional activity provided increased tendon strength without an increased rerupture rate. Controlled tension on the tendon during the healing phase leads to improved collagen synthesis and fiber orientation, resulting in improved tensile strength. Clinical studies have demonstrated the detriments of immobilization, documenting a 10% to 20% decrease in the strength of the operative side as compared to normal. Many clinical studies emphasize early mobilization as a core component of the postoperative protocol. Concerns about early postoperative mobilization relate to increased gap formation at the repair site, with associated lengthening and rerupture. Overlengthening leads to functional weakening secondary to increased excursion distance required to generate tension on the tendon.
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