Clinical and ultrasonographic findings in horses with desmopathy of the palmar/plantar abaxial ligaments of the proximal interphalangeal joint: 20 cases.

Overview

• This study describes the clinical signs and ultrasound findings of a specific ligament injury in horses’ pastern region (the abaxial palmar/plantar ligament of the proximal interphalangeal joint).
• It also assesses how often these horses have other concurrent musculoskeletal injuries in the foot and pastern area.

Background and Objective

• The proximal interphalangeal joint is an important joint in the horse’s foot, stabilized by several ligaments including the abaxial palmar/plantar ligaments (APL).
• Desmopathy refers to injury or disease of a ligament, in this case affecting the APLs located on the palmar (rear-facing) or plantar (bottom-facing) sides of the joint.
• The goal was to characterize the clinical presentation and ultrasound features of horses diagnosed with APL desmopathy and to determine how frequently this occurs alongside other injuries in the distal limb.

Study Design and Population

• Retrospective case series conducted at New Bolton Center from March 2017 to November 2022.
• Included horses were aged 5 to 20 years and presented for lameness localized to the distal limb.
• Only horses with ultrasonographic (ultrasound) confirmation of APL desmopathy and whose lameness improved after diagnostic nerve blocks targeting the palmar/plantar nerve regions were included.

Methods

• Lameness localization was done using diagnostic analgesia with specific nerve blocks: low 4-point nerve blocks, abaxial sesamoid nerve blocks, or palmar/plantar digital nerve blocks.
• Ultrasound imaging of the pastern region was used to identify and confirm the presence of ligament desmopathy.
• Concurrent injuries in soft tissue and bone structures of the foot and pastern were also evaluated using clinical examination and ultrasound.

Results

• 20 horses were diagnosed with APL desmopathy by ultrasound.
• In 5 of these horses, the desmopathy of the APL was the only identified cause of lameness.
• In the remaining 15 horses, additional soft tissue and bone injuries were concurrently identified, suggesting that APL desmopathy often occurs alongside other musculoskeletal pathologies.

Conclusions and Clinical Implications

• Desmopathy of the abaxial APL of the proximal interphalangeal joint is a relatively rare standalone cause of lameness in horses.
• Detection of APL desmopathy by ultrasonography should prompt veterinarians to continue thorough investigation for other concurrent injuries, especially in cases where clinical signs are mild.
• This emphasizes the importance of comprehensive diagnostic work-ups including nerve blocks and advanced imaging when evaluating distal limb lameness in horses.

Significance

• The study helps delineate the clinical and imaging features of a rare ligament injury in the pastern, improving diagnostic accuracy.
• By recognizing that APL desmopathy rarely occurs alone, clinicians can avoid misdiagnosis or incomplete assessment of equine distal limb lameness.