Phase 1: The Four Phases of Wound Healing
If the area is not properly immobilized or protected, the inflammatory process can be extended which retards the healing process. Excess and prolonged local swelling increases pain, decreases function, and extends the amount of time that tissues are hypoxic causing greater collateral damage. The longer inflammatory phase creates more metabolic waste and debris in the injured area as well as increased adhesions and larger, more disorganized fibroblastic activity. An exuberance of fibroblastic proliferation can result in hypertrophic or keloid scar formations.
Not to be confused with the four phases of rehabilitation, the wound healing process consists of four phases as well: Hemostasis, Inflammatory, Proliferative, and Remodeling. Each of the phases follow a relatively predictable timeline and consist of a complex series of events that run concurrent to the rehabilitation process, the majority of which occur within the acute phase. For your review, the four phases of wound healing are listed below:
| Hemostasis | Hemostasis begins with vasoconstriction at the moment of injury. Platelet aggregation promotes thrombocyte coagulation which work together to dam the wound and staunch bleeding. Cytokines and histamine are released which will trigger the start of the next phase of wound healing and stimulate vasodilation |
| Inflammatory | The inflammatory phase begins within the first few hours of the insult and lasts 2-5 days. As with the rehabilitation process, there is some overlap in the phases and the inflammatory phase is started before hemostasis is complete. Vasodilation is triggered during phase I which allows exudate to flood the area with leukocytes including neutrophils and macrophages, which will perform phagocytosis to rid the area of bacteria and debris. The macrophages also release a multitude of growth factors which will progress the healing to phase III. |
| Proliferative | The proliferative phase begins approximately day 3 and is in full swing by day 7. In this phase, fibroblasts that have been summoned to the area by the macrophages in the previous phase initiate the process of granulation. The bed of remedial, type III collagen is formed across the wound and angiogenesis occurs to provide blood supply to the new tissue. Contraction of the wound edges pulls the uninjured tissues closer together in an effort to reduce the defect allowing epithelialization of the repaired tissue to begin. The proliferative phase is an ongoing process that can last up to 3 or 4 weeks |
| Remodeling | The final phase of the healing process is the remodeling phase. This phase can last up to 2 years before it is complete. In this phase the collagen in the original scar tissue is exchanged for new, type I collagen. This continuous degradation of the original scar tissue and replacement with new collagen organizes the direction of the fibers in regards to the direction of stress on the tissue to increase its tensile strength and decrease the size of the scar tissue patch. |