Review Question - QID 5462

Muscle lacerations immobilized for 2 weeks would likely experience significant muscle atrophy affecting final functional outcome. For muscle injuries, including partial lacerations, current literature suggests the affected extremity should be immobilized no more than 3-5 days, followed by a progressive strengthening and stretching program.

Healing a muscle injury involves two competing processes: regeneration of muscle fibers and formation of granulation tissue. Starting motion too soon after injury may increase the area of fibrous scar, and limit the ability of new muscle fibers to penetrate this area. Prolonged immobilization limits scar production but penetrating muscle fibers will lack appropriate orientation, and the muscle as whole begins to atrophy. Three to 5 days of immobilization has been shown to limit scar tissue production while the early motion helps generate appropriately organized muscle fibers and maintain strength and range of motion.

Järvinen et al. present a review of muscle injury and healing. They found that immediate mobilization led to a large area of dense scar tissue that regenerating muscle fibers could not adequately penetrate. Prolonged immobilization allowed muscle fibers to regenerate but they lacked appropriate morphology. Following 3-5 days of immobilization they found less scar tissue, better penetration of regenerated muscle fibers, and the regenerated fibers were more well aligned with the uninjured fibers surrounding them.

Menetrey et al. present a mouse model of muscle laceration comparing a short period of immobilization (5 days) to suture repair of the muscle. They found quicker healing and greater strength in the suture repair group. Tetanus strength at one month after injury was (compared to an uninjured control) 81% for sutured muscle, 35% for the early mobilization only group, and 18% for the prolonged immobilization group.

Illustration A is a histology section of lacerated muscle after 7 days of immobilization. The area is infiltrated with granulation tissue and few regenerating myofibers. Illustration B is a histology section of lacerated muscle after 14 days of immobilization. Further infiltration with granulation tissue and mononuclear cells can be seen with regenerating myofibers only at the periphery.

Incorrect answers:
Answer 1: Prolonged immobilization leads to less scar tissue formation.
Answer 2: Prolonged immobilization is associated with greater atrophy and fatty infiltration.
Answer 4: Prolonged immobilization shows less regenerative growth of muscle fibers.
Answer 5: Prolonged immobilization produces regenerative mucle fibers with a more disorganized orientation.