The effects of limb posture on relationships between in vitro radial hoof strain, load and joint angles

Abstract

Reasons for performing study: Radial strain in normal hooves has been found to vary with strain gauge location, limb posture and sample limb but reported magnitudes were considered to be low. More accurate measurement of radial strain may enhance the understanding of hoof function.
Objectives: To explore in vitro radial hoof strain in relation other kinetic and kinematic variables that may be related.
Methods: Five normal forelimbs were removed at the proximal articular surface of the third metacarpal bone (McIII). The limbs were loaded using a modified Instron test machine. Six calibrated infrared cameras captured movement from markers on the hoof and bone fixed markers on the second and first phalanxes and McIII, whilst radial hoof strain was measured using a calibrated instrumented plug. Change in strain, joint angle and load were found at simulated walking postures and bivariate correlations were used to compare the relationships between them.
Results: Radial strain was moderately correlated with proximal interphalangeal joint (PIPJ) rotation (r = -0.519). Large reductions in radial strain were found in loading and midstance with 10° of heel lift postures.
Conclusions and potential relevance: PIPJ rotation has previously been linked to the magnitude of deep digital flexor tendon (DDFT) loads and it is therefore suspected that these loads may have the greatest influence on radial strain magnitudes. Further investigation of radial strain is needed to describe the patterns fully during the stance phase in vivo.