Management of skeletal muscle injuries in military personnel

Injuries to the musculoskeletal system, specifically skeletal muscle, are some of the most common injuries faced by military personnel today. Skeletal muscle trauma often results in significant loss of strength and flexibility, a propensity for recurrence of injury, and time off from military duty. The frequency of occurrence of skeletal muscle injuries and the poor outcomes associated with them decrease military readiness and increase monetary costs associated with treatment and lost work. Understanding the processes that occur in the muscle following injury allows a deeper grasp of potential therapeutic interventions to improve outcomes. Following trauma, the involved myofibers undergo 4 interrelated, time-dependent phases: degeneration, inflammation, regeneration, and fibrosis. Hematoma formation at the injury site is accompanied by infiltration of neutrophils, macrophages, and T-lymphocytes, as well as the release of multiple cytokines and growth factors from these infiltrating cells and from native myogenic cells. Regeneration is often accompanied by fibrosis, an overgrowth of fibroblast cells located within the connective tissue network. Skeletal muscle healing following trauma can be understood as a balance between fibrosis and regeneration. Fibrosis formation may lead to inadequate healing and an incomplete functional recovery of the muscle. Factors impacting this balance include inflammation, the growth factor and cytokine milieu at the site of injury, and the interaction between infiltrating inflammatory cells and native myogenic cells. Therapeutic interventions to improve outcomes following muscle injuries revolve around 3 concepts: enhancing regeneration, blocking fibrosis, and regulating inflammation.