Healing of muscle, ligaments, and tendons

The function of muscle, tendons, and ligaments is to transmit tensile forces. Healing by scar tissue compromises this function because scar tissue is weaker and more elastic than the tissue it replaces. First intention healing is promoted by suturing with strong, inelastic materials (eg, monofilament nylon, polyesters, etc) in a locking loop or three-loop pulley pattern to prevent gap formation, maintain vascularity, and decrease adhesions. Postoperative care should include restriction of active motion to avoid rerupture or gap formation across the suture line during tensile loading. However, immobilization for 6 weeks results in a wound with approximately 50% the normal tensile strength for tendons and ligaments and "significant weakening" of muscles. Earlier tension across a muscle, ligament, or tendon wound orients the healing fibers and results in stronger healing. For example, medial collateral ligaments of canine stifles sutured with polyester suture in a locking loop pattern and immobilized for 3 weeks, followed by active motion, resulted in valgus-varus laxity 1.5 times of controls and in strength, 92% that of controls. In comparison, 6 weeks of immobilization resulted in valgus-varus laxity three times that of controls and in strength, 14% that of controls. Canine tendons immobilized for 3 to 6 weeks after surgery also have sufficient strength to allow active motion. Current knowledge of healing muscle, tendons, and ligaments suggests that postoperative immobilization for 3 weeks will allow acceptable return to function while minimizing the risk of rerupture. However, the amount and type of exercise allowed immediately after immobilization devices are removed should be severely limited, and increased gradually as time passes.