Chapter 5

1. Chapter 5 The Healing Process

2. Overview • Injuries to the musculoskeletal system can result from a wide variety of causes. Each of the major components of the musculoskeletal system have varying capacities to heal

3. Musculoskeletal Injuries • Injuries to the soft tissues can be classified as primary or secondary: • Primary injuries can be self-inflicted, caused by another individual or entity, or caused by the environment • Acute • Chronic • Acute on chronic

4. Musculoskeletal Injuries • Secondary injuries are essentially the inflammatory response that occurs with the primary injury

5. Wound healing • Fortunately, the majority of soft tissue injuries heal without complication in a predictable series of events • However, healing abnormalities can occur. These abnormalities can be due to such complications as: • Infection • Compromised circulation • Neuropathy

6. Wound healing • Three main phases: • Inflammatory • Proliferative • Remodeling

7. Inflammatory phase • The reaction that occurs immediately after wounding includes a series of defensive events that involves the recognition of a pathogen and the mounting of a reaction against it. This reaction involves both coagulation and inflammation

8. Inflammatory phase • Coagulation. Apart from an initial period of vasoconstriction lasting for 5-10 minutes, tissue injury causes vasodilation, the disruption of blood vessels and extravasation of blood constituents, including platelets • The main functions of the exudate are to: • Provide cells capable of tissue reconstruction • Dilute microbial toxins • Remove contaminants present in the wound

9. Inflammatory phase • Inflammation. Inflammation is mediated by chemotactic substances, including anaphylatoxins, which attract neutrophils and monocytes • Neutrophils are white blood cells that bind to microorganisms, internalize them, and kill them • Monocytes are white blood cells that develop into macrophages, and provide immunological defences against many infectious organisms

10. Inflammatory phase • The complete removal of the wound debris marks the end of the inflammatory process • This stage can last from 1-6 days to longer than 6 months

11. Common causes for a persistent chronic inflammatory response include: • Infectious agents • Persistent viruses • Hypertrophic scarring • Poor blood supply • Edema • Repeated direct trauma • Excessive tension at the wound site • Hypersensitivity reactions

12. Inflammatory phase • Clinically, during the inflammatory phase there is pain: • At rest • With active motion • When specific stress is applied to the injured structure • The pain, if severe enough, can result in muscle guarding, and a loss of function.

13. Proliferative phase • Characteristic changes during this phase include: • Capillary growth • Granulation tissue formation • Fibroblast proliferation with collagen synthesis and increased macrophage and mast cell activity

14. Proliferative phase • This phase lasts from 5 to 15 days, and often up to 10 weeks depending on the type of tissue, and the extent of damage.

15. Remodeling phase • The remodeling phase of wound healing involves a conversion of the initial healing tissue to scar tissue • This lengthy phase of contraction, tissue remodeling and increasing tensile strength in the wound lasts for up to a year

16. Remodeling phase • Imbalances in collagen synthesis and degradation during this phase of healing may result in hypertrophic scarring or keloid formation • If left untreated, the scar formed is less than 20% of its original size • Scarring that occurs parallel to the line of force of a structure is less vulnerable to re-injury than a scar, which is perpendicular to those lines of force

17. Muscle healing • The capacity of muscle for regeneration is based primarily upon the type and extent of injury • Broadly speaking, there are three phases in the healing process of an injured muscle: • The destruction phase • The repair phase • The remodeling phase

18. Ligament and tendon healing • Healing of ligaments and tendons generally can be broken down into four overlapping phases: • I. Hemorrhagic • II. Inflammatory • III. Proliferation • IV. Remodeling and maturation

19. Articular cartilage healing • The capacity of articular cartilage for repair is limited • The repair response of articular cartilage varies with the depth of the injury

20. Articular cartilage healing • Injuries of the articular cartilage that do not penetrate the subchondral bone become necrotic and do not heal • These lesions usually progress to the degeneration of the articular surface

21. Articular cartilage healing • Injuries that penetrate the subchondral bone undergo repair due to access to the bone’s blood supply • These repairs are usually characterized as: • Fibrous • Fibrocartilaginous • Hyaline-like cartilaginous

22. Bone healing • The striking feature of bone healing, compared to healing in other tissues, is that repair is by the original tissue, not scar tissue • Bone healing involves a combination of intramembranous and endochondral ossification

23. Bone healing • In classic histologic terms, fracture healing has been divided into two broad phases: • Primary fracture healing • Secondary fracture healing

24. Bone healing • Primary healing involves a direct attempt by the cortex to reestablish itself once it has become interrupted • Bone on one side of the cortex must unite with bone on the other side of the cortex to reestablish mechanical continuity

25. Bone healing • Secondary healing involves responses in the periosteum and external soft tissues with the subsequent formation of a callus • The majority of fractures heal by secondary fracture healing