Deep digital flexor tendon force and digital mechanics in normal ponies and ponies with rotation of the distal phalanx as a sequel to laminitis.

This research explores the effect of laminitis, a serious disease in horses, on the force exerted by the deep digital flexor tendon and the ground reaction forces. The study compares six healthy ponies with six ponies who have experienced a degree of rotation in one of their foot bones as a consequence of laminitis.

Objective and Methodology

• The study aimed to compare the force exerted by the deep digital flexor tendon (DDFT), and the ground reaction forces (GRFs), in normal ponies and those with a rotated distal phalanx following laminitis.
• The researchers used force plate and motion analysis to study six healthy ponies (Group 1) and six ponies with a 6-13 degree rotation of the distal phalanx in relation to the dorsal hoof wall (Group 2) at a trotting gait.
• The force in the DDFT was calculated based on the assumption that the extending moment at the distal interphalangeal (DIP) joint caused by the GRF was equal to the flexing moment created by the force in the DDFT during the stance phase.

Findings

• The research discovered that peak DDFT force during early stance was 1.92±1.63 N/kg in the normal ponies. However, in Group 2, where the zero moment point was palmar to the rotation center of the DIP joint for the initial 40% of the stance phase, the DDFT force was zero.
• The researchers found the force in the DDFT peaked at 10.00±3.56 N/kg at 60.7±5.6% of stance in Group 1 and 6.41±1.37 N/kg at 79.2±9.6% of stance in Group 2.

Conclusion and Implications

• The study concluded that the DDFT force in Group 2 ponies, those with a consequent rotation of the distal phalanx after laminitis, was significantly reduced until late stance, when it approached normal values.
• Further research on ponies with pathology similar to Group 2 should assist in developing farriery techniques designed to decrease the force in the DDFT during the breakover phase of stance, in turn, helping to protect the damaged dorsal laminae.