Hoof position during limb loading affects dorsoproximal bone strains on the equine proximal phalanx.

The research study focuses on how the position of a horse’s hoof during limb loading can influence the strains experienced on the bone of the proximal phalanx (P1), particularly in relation to sagittal fractures observed in racehorses running on turf surfaces. The study hypothesizes that the restriction of foot movement might increase the P1 bone strains when the metacarpophalangeal joint (MCPJ) is hyperextended.

Methodology

• The study was conducted using unilateral limbs from six equine cadavers.
• The researchers used strain gauges and bone reference markers to measure dorsoproximal P1 bone strains and MCPJ’s extension, collateromotion, and axial rotation during in vitro limb loading to 10,500 N.
• Three different foot conditions – forward, free, and restricted – were applied by constraining the movement of the distal actuator platform.
• The motion of P1 relative to MC3 was determined by analyzing the bone reference markers recorded by video.
• The data from the rosette strain was used to figure out the magnitudes and directions of principal and shear.

Results

• Under a 10,000 N load, the restricted foot condition resulted in higher P1 axial compressive, maximum shear, and engineering shear strains compared to the forward foot condition.
• Compared to the free foot condition, the restricted foot condition had higher compressive and lower tensile principal strains.
• For the same magnitude of principal or shear strains, axial rotation and collateromotion angles were greatest in the restricted foot condition.

Conclusions

• The findings revealed an increase in P1 principal compressive and shear bone strains associated with restricted foot slip.
• They suggest that alterations in foot-ground interaction due to conditions such as racing on turf surfaces might contribute to the occurrence of fracture in horses.