Summary
A 2‐year‐old Lipizzaner colt presented for removal of a mass over the left eye. The colt had no blepharospasm or significant ocular discharge, but the cornea underlying the mass was mildly oedematous. The mass protruded from the conjunctiva at the dorsotemporal aspect of the globe and was covered in normal conjunctiva. It had a gross appearance similar to the cartilaginous flap of a nictitating membrane, but in an aberrant location. It was moveable to cover the dorsal aspect of the cornea when the globe was retropulsed. Excision of the mass under general anaesthesia was elected. Histopathology supported a diagnosis of an accessory nictitating membrane, consisting of a cartilaginous band surrounded by glandular epithelium. The colt recovered from surgery without complication and no problems were reported by the owner at 8.5 months post‐operatively. To the author's knowledge, there have not been previous reports of accessory or ectopic nictitating membranes in equine or other species.
Objective
To describe the presence of fragments in the dorsal proximal interphalangeal (PIP) joint and to report flat racing performance after surgical treatment.
Study design
Retrospective study.
Sample population
Thirty‐nine affected thoroughbred flat racehorses and 169 age‐ and sex‐matched maternal siblings.
Methods
Medical records from 2000 to 2015 were reviewed for thoroughbred horses that underwent arthroscopic removal of osteochondral fragments in the dorsal aspect of the PIP joint. The horses’ 2‐year‐old year, 3‐year‐old year, and career athletic performances were compared with their matched siblings.
Results
Thirty‐nine thoroughbred horses were included, varying in age from 4 months to 4 years, with osteochondral fragments in 42 PIP joints. Hind limbs (92%) were more commonly affected than forelimbs (8%). Fragments were located within the origin of the collateral ligament of the distal sesamoid (navicular) bone. After surgery, the likelihood of starting a race did not differ between treated horses (27/39 [69%]) and maternal siblings (129/169 [76%], P = .15). Race earnings did not differ between treated horses and their siblings during their 2‐year‐old year (P = .66), 3‐year‐old year (P = .43), or career (P = .60).
Conclusion
Removing osteochondral fragments from the origin of the collateral ligament of the distal sesamoid bone did not impair the ability to race or earning potential for affected thoroughbred racehorses compared with their maternal siblings.
Clinical significance
Fragments from the dorsal aspect of the PIP joint in racehorses can be removed arthroscopically resulting in a good clinical outcome and future flat racing performance comparable to matched controls.
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