A case‐control study of the morphological measurements of equine distal interphalangeal joints affected by osseous cyst‐like lesions

Abstract

Summary Background The aetiology and effects of osseous cyst‐like lesions (OCLLs) affecting the distal interphalangeal (DIP) joint are poorly understood. Objectives To describe the magnetic resonance (MR) imaging appearance of OCLLs of the DIP joint and morphological measurements of affected joints. Study design Retrospective case–control study. Methods The low‐field MR imaging appearance of OCLLs affecting the DIP joint diagnosed over a 5‐year period was reviewed. Each case was matched to two horses with foot lameness not affected by OCLLs. Morphological measurements of the articular surfaces were recorded. Results There were 23 horses with OCLLs of the DIP joint (Group 1) and 45 controls (Group 2). The Group 1 horses had a total of 30 OCLLs. Twenty‐one OCLLs were present in the distal phalanx and 9 were present in the middle phalanx. Eight lesions were indentations of the articular surface and 22 had subchondral and trabecular bone involvement. OCLLs were commonly located in the centre of the articular surface of the distal phalanx. The dorsal‐palmar/plantar length of the articular surface of the distal and middle phalanges was greater in Group 1. The depth of the articular surface of the distal phalanx and the height of the articular surface of the middle phalanx were greater in the Group 1. 22/23 horses in Group 1 had evidence of osteoarthritis of the DIP joint compared to 22/45 in Group 2. Main limitations Small number of cases and small values of measurements. Conclusions OCLLs of the DIP joint occur at consistent sites, most commonly the central third of the articular surface of the distal phalanx. Measurements of the joint surfaces suggest that DIP joints affected by OCLLs have different morphology than joints without OCLLs. These findings are consistent with the theory that OCLLs of the DIP joint could be associated with dysplasia of the joint.