Wound healing and closure are terms that are ubiquitous in the taxonomy of discourse in the wound care community; however, proportionally we hear fewer discussions about the remodeling phase of wound healing. The purpose of this editorial is to revisit the stages of wound healing with special considerations for the functional rehabilitation of the cicatrix during the remodeling phase.
More questions than answers
When is the wound considered healed? What are the primary and secondary end-points and the criteria for a healed wound in both clinical end points and research metrics? In a study to determine healing rates in venous ulcers, researchers found a great variation in the determination of complete wound healing by "experts." The authors found that precise determination of complete wound healing is quite subjective and variable, even among observers with great experience in wound care.1
Is wound healing the proliferation of new epithelium to cover the wound? In reality, it is the functional restoration of the tissues including the formation of a cicatrix (scar), which in the end, is ready for weight bearing.
Stages of wound healing
Understanding the stages of wound healing are core competencies critical to the assessment of the healing wound. The final common pathway of wound healing is based upon an inter-reliant cascade of complex events that culminate in the resurfacing, reconstitution, and proportionate restoration of the tensile strength2 of the functional barrier of the skin. Transitionally, this remains a thin scar (cicatrix) after the wound is "functionally closed." It is accepted uncritically that re-epithelization and covering of the wound is the end-point of the wound healing process. However, given the construct that the cicatrix is the last stage, re-epithelialization must be the penultimate step in wound healing. In the natural course of wound healing, we know that the tensile strength of healing tissue is precarious or frail during epithelial resurfacing. Moreover, collagen remodeling and other events that lead to maturation of the scar tissue occur for months or years after epithelization is complete-the cicatrix.2
The well-known taxonomic stages of wound healing are sequentially ordered: (1) The pro-inflammatory and the inflammatory phase are important for phagocytosis, debridement, and the stimulation of fibroblastic activity with the subsequent production of new collagen. (2) In the proliferative phase granulation, contraction, and epithelialization are critical for restoration of the barrier function of the wound and contraction (the inward movement of the wound edges) is a critical event during granulation.(3) In the final stage of healing, the remodeling of the wound takes place, new collagen forms, which increases tensile strength to the cicatrix tissue that is only 80% as strong as original tissue. Cicatrization of the wound continues for months after the scar and matrix are formed, remodelization continues with the ultimate goal of decreasing the bulk of the scar and enhancement of its tensile strength through realignment of the collagen fibers. The initial stages of collagen formation in the repair of a wound produce a very thin layer of almost translucent collagen. As the phases of wound healing progress, more collagen is produced and more cross-links established. Blood vessels and extracellular matrix then recede and are replaced by increased levels of collagen. In time, the damaged area becomes stronger than the original tissue. If the damage is large enough, the replacement collagen will contract, making the damaged area smaller. However, any tension or undue strain may damage or dehisce the scar. The wound's long axis is thought to correspond to the greatest static tension of the skin. Therefore, the pull is determined largely by the protrusion of the underlying bone, cartilage, and tissue bulk that the skin covers. Therefore the wound's long axis corresponds to the greatest static tension of the skin.2 Additionally, pressure and shear are pathomechanical detriments to dehisce the cicatrix formation. If we think of the end stages of wound closure as a friable functional cicatrix, how do we protect and enhance the functional barrier of the skin?
Rehabilitation of the cicatrix is important for ultimate full weight bearing
Immobilization of the wound is desirable, while also mobilizing the patient through progressive mobility. Because the cicatrix is trying to increase the tensile functionality of the wound, the use of reinforcement dressings, pressure relief and repetitive cyclic loading versus impact loading methods are useful, especially in areas subject to the greatest tensile strain. These methods maybe particularly useful in patients who are wheelchair mobile or ambulating on a recently closed diabetic ulcer.
There remains a paucity of literature regarding the remodeling phase of wound care, especially functional outcome measures, including long-term followup on the recidivism rates for wounds in clinical trials. We also need to measure success rates with the final end-point of wound closure being the terminal end of the remodeling phase.3
Richard "Sal" Salcido, MD
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