Effect of hoof angle on joint contact area in the equine metacarpophalangeal joint following simulated impact loading ex vivo.

The study investigates how different hoof-strike conditions can affect impact loading on equine metacarpophalangeal joints. It’s exploration might help in understanding the potential role of such impacts in joint diseases.

Research Objectives and Methodology

• The objective of the research was to study the effects of impact loading on the contact areas between the first Phalanx (P1), proximal sesamoids (PS) and the third metacarpal (McIII), under three different hoof-strike conditions: toe-first, flat, and heel-first.
• The study utilized eight cadaver limbs set up to experience random, repeated trials where the hooves were struck by a pendulum impact machine under the three above-mentioned strike conditions.
• Pressure sensitive film was used to measure total contact areas between P1 and PS (cm(2)), the centroid locations of these contact areas relative to specific anatomical landmarks (the sagittal and traverse ridge), and the dispersion of force distribution (cm(4)) across the medial and lateral condyles of the McIII (medial/lateral).
• To determine the significance of the differences under different hoof-strike conditions, the researchers tested using repeated-measures ANOVA, setting the significance level (α) at 0.05.

Findings

• The research found that hoof-strike had no significant effect on the contact area. Implications being the type of footfall does not increase or decrease impact pressures on these areas.
• The contact area between P1 and McIII during impact was well-defined and located between two anatomical landmarks, the sagittal and traverse ridge.
• The contact area from PS was smaller and dispersed across the protective (palmar) border of McIII. The ratio of contact area between P1 and PS approximately stood at 2.83.

Conclusion

• The results of this experiment show that the greatest contact area during impact was indeed on the dorsal aspect of the medial condyle. Interestingly, this is the same area that undergoes the most significant increase in subchondral bone stiffening in joint disease.
• Such findings indicate that the manner in which horses place their hooves when stepping does not significantly affect the point of contact, nor dispersal of their body weight on the hoof.