Diagnosis and arthroscopic removal of an intra‐articular epidermoid cyst in the distal interphalangeal joint of a 15‐year‐old horse

Abstract

Summary This case report describes the diagnosis and arthroscopic removal of a ruptured epidermoid cyst in a distal interphalangeal (DIP) joint of a horse. The cyst was the cause of chronic moderate lameness and following removal the horse returned to athletic performance. However, 12 months postoperatively the horse was retired due to the recurrence of lameness. Epidermoid cysts have been diagnosed elsewhere in the equine digit but have not been reported intra‐articularly to the best of our knowledge.

Solving equine distal limb lumps and bumps

“…The ultrasonographic appearance of an equine epidermoid cyst in the foot has been recently illustrated by others (Mageed & Elfadl, 2020). It was also well defined and, similar to the Hibner‐Szaltys et al case (2023), contained heterogenous echogenic material. In contrast, articular synovial cysts are characterised by an outpouching of anechoic fluid from the joint cavity on ultrasonographic examination, with a canal through the joint capsule and communication with the joint space can be detected (Lacourt et al, 2013).…”

“…It is interesting that epidermoid cysts have also previously been identified in the equine distal limb including the distal part of digital flexor tendon sheaths (Joostens et al, 2019; Sanz et al, 2006), distal phalanx (Fraser et al, 2006; Headley et al, 2009) and the foot (Mageed & Elfadl, 2020). The current report (Hibner‐Szaltys et al, 2023) of the DIP epidermoid cyst expands the repertoire of equine distal limb sites where cysts may arise.…”

“…The case report of a ruptured epidermoid cyst in the distal interphalangeal joint (DIP) is the first intra‐articular epidermoid cyst described in the equine veterinary literature (Hibner‐Szaltys et al, 2023). Articular synovial cysts, also called hernias, have been identified previously in many joints but none to date either in the DIP (Lacourt et al, 2013).…”

“…In the report by Hibner‐Szaltys et al (2023), the affected horse was treated for lameness 9 months prior to the final presentation and responded to intra‐articular medication at that time. It is speculated that the epidermoid cyst was present for some time in this 15‐year‐old horse as they are benign and slow growing.…”

“…A take‐home message, based on a very limited number of cases (Hibner‐Szaltys et al, 2023; Joostens et al, 2019; Sanz et al, 2006), is that equine distal limb epidermoid cysts located in joints or tendon sheaths have more favourable outcome than their counterparts within the third phalanx or foot.…”