Two clinical manifestations of desmopathy of the accessory ligament of the deep digital flexor tendon in the hindlimb of 23 horses.

This research focuses on desmopathy of the accessory ligament of the deep digital flexor tendon (ALDDFT) in horses’ hind legs, a rare cause of lameness. Examining 23 horses at three referral centers, two clinical conditions of the disorder were identified. Acute onset lameness has a more favorable prognosis, whereas onset of postural abnormalities is more challenging to reverse.

Study Details and Methodology

• The study evaluated the medical records of 23 horses from three different referral centers. These horses showed ultrasonographic evidence of desmopathy of the ALDDFT in one or both hindlimbs.
• Details regarding the horses’ age, breed, sex, duration, and nature of clinical signs were recorded. Additionally, results of clinical and lameness examinations, treatment protocols, and outcomes were documented.
• The horses were grouped into two categories: Group A with an acute onset of unilateral lameness and Group B with an insidious or sudden onset of postural abnormality.

Findings

• All horses revealed an enlargement of the ALDDFT in the affected hindlimb(s). In 44% of these, ultrasonographic abnormalities were localized to part of the ALDDFT.
• The sample included 10 cobs, 5 British native-breed ponies, and 8 large breed horses. Most were used for general purposes and the average age was 12 years.
• Two distinct clinical manifestations were associated with the ALDDFT of the hindlimb. Group A experiencing an acute onset of lameness resulted from trauma while Group B experienced onset of postural abnormalities.
• Treatment across cases largely consisted of box-rest and controlled exercise, with 10 horses undergoing desmotomy or desmectomy of the ALDDFT.

Conclusions and Implications

• 73% of horses in Group A (acute lameness) returned to full function after treatment, while 90% in Group B (postural abnormalities) remained lame.
• The study suggests trauma-induced injury resulting in acute onset lameness has a better prognosis with most horses returning to their previous activities.
• However, once postural changes occur, they seem irreversible and this suggests a poor prognosis.
• Therefore, desmopathy of the ALDDFT should be investigated as a potential cause of hindlimb lameness in horses, particularly when a horse presents a flexural deformity of the metatarsophalangeal joint, which may accompany this condition.