Hoof wall wound repair

Abstract

Summary Reasons for performing study: Surgical stripping of the hoof wall results in a wound that heals remarkabley well. In contrast, lamellae recovering from laminitis are often deformed. Investigating lamellar wound healing may aid understanding of laminitis. Objectives: To document temporal changes in the lamellar basement membrane (BM), dermis and epidermis after surgery. Methods: Wall strips were made in the dorsal hoof wall midline of 6 mature horses. Immunohistochemistry was used to document changes in the basement membrane (BM) and detect proliferation of epidermal cells in lamellar tissues harvested at intervals. A conforming metal plate was screwed to the hoof wall to maintain alignment of the wound edges. Results: Wall stripping caused lamellar tips to snap and remain behind in the dermis along with the majority of the lamellar BM and some lamellar basal cells. Three days later the BM was intact and new lamellae had been reconstructed by proliferation of surviving epidermal cells. By 5 days the surface of the stripped zone was covered with yellow epidermis that subsequently thickened and hardened. Eventually the hoof wall deficit was replaced by new wall growing down from the coronet. The conforming metal plate and post operative analgesic ensured minimal lameness. Conclusions and potential relevance: In wall stripped lamellae the BM survives virtually intact and is used as a template for proliferating cells, from snapped‐off lamellar tips, to migrate and quickly achieve repair to near normality. In laminitis epidermal dysadhesion and lamellar BM destruction occurs and lack of a functional BM template may explain the prolonged and abnormal repair of affected lamellae.

The Lamellar Wedge

“…These findings are consistent with other studies that have reported hyperproliferative wound healing responses within the stratum lamellatum after hoof wall stripping in the normal horse 19 and lamellar histopathology 7 days after experimental induction of laminitis. 20 Consistent with the histologic findings seen in 7-day laminitis is the aberrant nature of the resultant horn production and the abnormal lamellar architecture.…”

“…6 and 7). [1][2][3][4]6,18,19 The resultant dysplastic horn structure ( Fig. 8) has been described as ectopic white line, 6 because the histologic appearance (a lamellated array of tubular and nontubular horn) resembles that of the white line, the sole-hoof wall junction, seen in the distal part of the hoof capsule.…”

Application and viability of full-thickness coronary band grafting in equids

“…Despite this, horn restitution appeared to mirror that reported previously (Pollitt and Daradka 2004) and while there is no histological evidence to support complete removal of horn producing tissue in the experimental horses, the presence of the common digital extensor tendon at the bottom of the surgical wound would suggest that total removal had occurred. Epithelialisation from the wound margins must have resulted in restoration of the coronary band.…”

“…The hoof horn was elevated by inserting a curved osteotome into the bottom cut and applying downward pressure to lever the hoof horn upwards from the underlying lamina. The horn was peeled away from the coronary band using a single lateral to medial motion as reported by Pollitt and Daradka (2004). A number 10 scalpel blade was subsequently introduced into the cuts in the hoof horn and used to continue the lines of excision proximally, following the marked line, through the coronary band and into the skin of the distal limb, to the depth of the common digital extensor tendon, extending to a point 1 cm proximal to the upper limit of the coronary band.…”

“…Pferdeheilkunde 31 (2015) 120 included the skin and subcutaneous tissue of the distal limb, the corium of the lamellae and the coronet, was then removed as a single unit (Pollitt and Daradka 2004), leaving the common digital extensor tendon and loose connective tissue in the wound bed exposed.…”