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Skin Grafts Transplant physiology and clinical findings

Skin Grafts: Transplant physiology and clinical findings Authors: Ruchika Sharma Shyla Bharadia Reviewers: Mao Ding Ryan T. Lewinson A. Rob Harrop* *MD at time of publication STSGs may be meshed for greater coverage of surface area Split thickness donor sites may be re- harvested 6. Graft maturation (months-years) Skin anatomy Sebaceous gland alongside hair follicle Hair Follicle Sweat gland Blood vessels Full thickness donor sites cannot be re-harvested Epidermis Dermis Subcutaneous tissue Full thickness skin graft (FTSG) including the epidermis and entire dermis The full thickness donor site is closed by primary intention (sutured) Skin grafts Indicated when healing by secondary intention (natural closure) is not possible. The graft consists of avascular skin harvested from an uninjured donor site Split thickness skin graft (STSG) including the epidermis and a portion of the dermis The split thickness donor site heals by re- epithelialization Donor grafts are applied to the injured area 1. Initial adherence (8 hrs) A fibrin network fastens the graft to the wound bed Fibroblasts, leukocytes & phagocytes from the wound bed enter the fibrin network, building a fibrous connection between the graft & wound bed 2. Plasmatic imbibition (24-48 hrs) The graft absorbs nutrients and dissolved oxygen from plasma in the recipient wound bed The graft appears white in color 3. Inosculation and capillary ingrowth (2-4 days) Capillary buds from the recipient wound bed anastomose with vessels on underside of graft Physiology of graft take 4. Revascularization (5-7 days) 5. Graft contraction (6-18 months) Actin in myofibroblasts contract & approximate the wound edges Angiogenic factors enable revascularization allowing rapid, high-volume flow through large vessels Lymphatic drainage established Dermal structures such as hair follicles, sweat & sebaceous glands may be partially restored Grafts are pruritic (itchy), discoloured, and do not function or look like normal skin Grafts are reinnervated from periphery to center STSGs are reinnervated faster than FTSGs, though incompletely Graft fails (does not adhere) with a poorly vascularized and unclean wound bed Restoration of vasculature returns color to the graft Successfully adhered grafts are pink (STSG) or marginally paler (FTSGs) and immobile The deep dermal layer in FTSGs better inhibits myofibroblast action STSGs heal with significant contracture, limiting function & mobility Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications First published February 6, 2017, updated March 12, 2023 on www.thecalgaryguide.com