Evaluation of architectural changes along the proximal to distal regions of the dorsal laminar interface in the equine hoof

OBJECTIVE: To describe architectural changes along the dorsal laminar interface of the equine foot. SAMPLE POPULATION: 6 macroscopically normal forefeet obtained from 6 equine cadavers. PROCEDURE: Histologic sections of 8 evenly spaced, proximal to distal, samples of the dorsal laminar interface were photographed, digitized, and examined for differences in architecture. Laminar depth; secondary laminar density; number and consistency of bifurcations occurring within the secondary laminae, and areas composed of primary dermal lamina, primary epidermal lamina, and secondary laminar interface were recorded. Data were examined to test for differences in architecture associated with the proximal to distal positioning of the sample. RESULTS: With exception of the areas of the primary epidermal and primary dermal lamina, all measured variables were significantly different between the proximal and distal regions of the dorsal laminar interface. Changes included increases in laminar depth and the secondary laminar density. Bifurcation of secondary laminae principally occurred proximally and had an increased depth of bifurcation distally. The secondary laminar dermal-epidermal interface had a 109% increase in area between the most proximal and distal sections. CONCLUSIONS AND CLINICAL RELEVANCE: Results of this study indicate that the interface normally contributes a substantial volume of dermal components to the internal surface of the wall. These data also indicate that 2 distinct mechanisms (i.e., bifurcation of secondary laminae and an increase in the length of secondary laminae) contribute to changes in the architecture of the laminar interface, which allows for the hypothesis that the normal laminar interface is capable of responding to mechanical load.