SKIN GRAFTING FOR THE GENERAL EQUINE PRACTITIONER Yes you can do it in the field! Sarah J. Waxman, DVM, MS, Diplomate ACVS- LA Clinician in Equine Community Practice Purdue University LEARNING OBJECTIVES Understand why skin grafting is useful and when you should pursue it. Understand the expected outcome of skin grafting. Review the types of grafts available and understand what are the most useful in general practice and the field setting. Understand how to perform punch and pinch grafts. WHY GRAFT? A large wound that cannot heal Decrease wound healing time More cosmetic than epithelium More resilient than epithelium Auer and Stick, 4 th ed., 2012 1
TYPES OF GRAFTS Pedicle grafts Free grafts Autograft Allograft Xenograft Full thickness grafts Epidermis/entire dermis Partial thickness grafts Epidermis/part of dermis Auer and Stick, 4 th ed., 2012 The thickness of the dermis within the graft is directly proportional to the graft s durability and cosmesis but inversely proportional to the graft s ability to survive Surface: solid or mesh Embedded: punch, pinch, tunnel WHAT SHOULD I EXPECT? Punch Grafts Relatively quick and easy Can be done standing No special equipment 60-75% (or better) graft survival Variable cosmesis Heal primarily via epithelial scar Tufts of divergent hair Auer and Stick, 4 th ed., 2012 Pinch Grafts Relatively easy, takes some practice Can be done standing No special equipment 50-75% (or much better) graft survival, even under adverse conditions Relatively poor cosmesis (epithelial scar with tufts of divergent hair) WHAT S IT GOING TO LOOK LIKE? Punch Grafts Pinch Grafts Photo courtesy of Dr. Jan Hawkins 2
PHYSIOLOGY OF GRAFTING Recipient bed Vascular, free from infection and devitalized tissue Joint capsules, ligaments, adipose Fresh wounds Granulation tissue Adherence Fibrin binds to collagen within graft Vessels and fibroblasts invade fibrin matrix around 4-5 days Firm union around 10 days Auer and Stick, 4 th ed., 2012 PHYSIOLOGY OF GRAFTING Plasmic imbibition: process of graft nourishment Inosculation: process of new capillary generation in recipient bed traversing fibrin layer to anastomose in graft Neovascularization: invasion of preexisting vessels within graft by new capillaries from recipient bed and cutting of new vascular channels into the dermis Organization Hyperplasia of graft- 2 weeks Sloughing of epidermis Pigmentation- 4 weeks Regeneration of glands- months, if ever Hair regrowth- 4-6 weeks Reinnervation- 7-9 weeks (full>partial) Contraction Auer and Stick, 4 th ed., 2012 PHYSIOLOGY OF GRAFTING Graft Failure Fluid accumulation Infection 10 5 organisms per gram of tissue Pseudomonas spp. and β-hemolytic streptococci Inflammation Motion Auer and Stick, 4 th ed., 2012 3
HOW TO GRAFT FIELD SETTING! PREPARATION OF RECIPIENT SITE Assessment Adequate vascularity? Fibrous? Debride if necessary, delay 48 hours Infection? Penicillin Topicals Deeper structures? Problems within wound? Biopsy Habronema Neoplasia Clip surrounding hair Aseptically prepare surrounding skin Physiologic saline only on wound bed Auer and Stick, 4 th ed., 2012 4
C lipped and cle ane d, re ady to ac c ept g raf ts 5
PREPARATION OF DONOR SITE Inconspicuous location Neck under mane Ventrolateral abdomen Perineum Clip hair Aseptically prepare Rinse with saline Local anesthesia DONOR SITE 6
PUNCH GRAFTING Full-thickness plugs harvested directly or from excised full-thickness sheet of skin Use biopsy punches Use a punch 2mm smaller for the recipient site than is used for the donor site (ex. 7mm for donor, 5mm for recipient) Auer and Stick, 4 th ed., 2012 PUNCH GRAFTS Prepare donor site first Smaller punch, ~6mm apart Place cotton-tipped applicator into each hole to prevent clot formation and identify each site Harvest grafts Larger punch, ~1cm apart Need to remove the fascia and fat from the underside of plug Store on saline or blood soaked gauze sponges 7
PUNCHES ON SALINE PUNCH GRAFTING Insert grafts into recipient holes Try to align hair in correct orientation PINCH GRAFTING Small discs of skin that vary in thickness (partial thickness at periphery, close to full thickness at center) harvested directly 8
PINCH GRAFTING Elevate cone of skin and excise ~3mm disc of skin with #11 blade Use forceps or bent hypodermic needle to elevate skin Store on saline or blood soaked gauze PINCH GRAFTING Stab a #15 scalpel blade into the granulation tissue at an acute angle Start distally Lay graft onto wound, epidermal side up, and slide into pocket Use tip of mosquito hemostats (or the blade) to shove into pocket Implant ~3-5mm apart Tips I do 1 at a time because I don t have luck with them sticking to wound I do try to align hair correctly Shove in and hold down with finger to keep them from popping out Make sure grafts are not too big 9
Inse r t #15 blade at st eep ang le into g ranulation tissue to c ut pocket Shove g raf t disc into pocket w ith instrum e nt Graf ts all im planted 10
POST-GRAFT CARE Cover graft site with non-adherent bandage Moisten with gentamicin Inner sanctum Conforming gauze Elastic adhesive Padded bandage +/- immobilization Tie-over/stent bandage if in difficult to wrap area Can leave open +/- Primary closure of donor site defects BANDAGE Gentamicin on dressing Sterile cling gauze BANDAGE Inner Sanctum Cotton Bandage 11
IMMOBILIZE IF NECESSARY SUTURE DONOR SITES POST-GRAFT CARE First bandage change at 4-5 days Unless concern for virulent nosocomial infection Sedate, even if good horse to avoid movement Soak the dressing with saline if seems stuck Protect with bandage until completely epithelialized Change every 3-5 days as needed If hyperesthesia Tie or neck cradle Lanolin or vitamin E/aloe ointment if scaly/dry 12
1 ST BANDAGE CHANGE 2 ND BANDAGE CHANGE MOCHA PIG Dog bite wounds 13
1 ST ATTEMPT Par tial thickne ss sheet g raf t 2 ND ATTEMPT Punch grafts SUCCESS! 6 days postg raf ting 14
DAY 0 DAY 3 DAY 13 15
DAY 30 DAY 53 DAY 56 Graft Day! 16
DAY 64 8 days postg raf ting DAY 69 13 days postg raf ting 17
DAY 73 17 days postg raf ting DAY 78 22 days postg raf ting DAY 90 34 days postg raf ting 18
DAY 103 47 days postg raf ting DAY 123 67 days postg raf ting 19