In vitro measurement of internal hoof strain.

REASONS FOR PERFORMING STUDY

Strains during stance on the hoof wall surface have been measured by a number of authors in vitro and in vivo. Histological structure and mechanical properties vary through the wall thickness (radially); radial strain measurements may therefore aid the understanding of mechanical function of the capsule and adjacent tissues.

OBJECTIVES

To develop instrumentation capable of measuring internal hoof strain, and to carry out a preliminary comparison of normal and laminitic hooves.

METHODS

Six forelimbs from 4 horses, including 2 with laminitis from the same horse, were tested using an Instron test rig designed to simulate the walk at impact, midstance and breakover. Internal strains were measured at a dorsal site using strain gauges moulded into a plug made of 007 fast-set structural adhesive. In addition, kinetic and kinematic data were collected from each specimen.

RESULTS

When simulating the walk, a significant (P<0.0001) increase in gradient of radial tensile strain was found in a normal hoof wall, from 5.6 +/- 73.9 microepsilon at the outer gauge to 418.5 +/- 170.6 microepsilon at the inner gauge. However, radial strains measured at the inner gauge site in limbs with laminitis were found to be significantly (P<0.0001) compressive, with values of -406.7 +/- 156.3 and -109.9 +/- 72.4 microepsilon for Specimens 1 and 2, respectively.

CONCLUSIONS AND POTENTIAL RELEVANCE

These preliminary data indicate that a marked redistribution may well occur in the wall of laminitic hooves. With a larger sample size, the results should have relevance to the treatment and management of laminitis.