Pressure distribution between the deep digital flexor tendon and the navicular bone, and the effect of raising the heels in vitro.

The research article describes an in vitro experiment on equine anatomy to understand the pressure distribution across the navicular bone due to forces applied by the deep digital flexor tendon and how raising the horse’s heel alters this distribution.

Research Purpose and Methodology

• This study aimed to map the topographical pressure distribution across a horse’s navicular bone, which is found within the hoof. The pressure being examined is that which results from forces applied by the deep digital flexor tendon (DDFT).
• The researchers also analysed how raising the heels – a common practice in equine care, often involving the use of heel wedges – would affect this pressure distribution.
• The methodology involved constructing a rig to hold an equine cadaver limb, thus enabling the application of controlled pressure to the navicular bone from the DDFT. To measure and map the pressure, the scientists used pressure-sensitive paper. Different heel wedge angles (5 degrees and 10 degrees) were used and the resultant changes noted.

Main Findings

• Upon conducting the study, it was found that the regions of the bone subject to the maximum pressure from the DDFT were the central ridge, the paired symmetrical areas next to the ridge, and the distal edge of the palmar bone surface. Interestingly, these same regions correspond to the known sites of navicular pathology, indicating a possible correlation between pressure exerted by the DDFT and navicular disease.
• Using heel wedges did indeed redistribute the pressure exerted on the palmar surface of the navicular bone. However, the distribution of this pressure appeared to be contingent on factors like the fetlock angle and the angle of the heel wedge.

Implications of the Findings

• The results of the study lend support to the hypothesis that navicular disease may be caused by inappropriate forces exerted via the DDFT on the bone of the hoof. This significant finding could guide future equine health protocols and potentially alter treatment strategies for navicular disease.
• Interestingly, the practice of using heel wedges to alleviate navicular disease symptoms was questioned by the study. The findings suggest that although the pressure is redistributed with their use, the pressure adjustment might in fact increase the force on regions of the hoof that are already prone to disease.