Case summary A 9-year-old neutered male domestic shorthair cat was referred for assessment of a chronic non-weightbearing left forelimb lameness that had an acute onset following a suspected cat bite to the distal limb 4 weeks previously. There was minimal improvement following conservative management. On examination there was discomfort on palpation of the left palmar metacarpal region. An orthopaedic examination performed under sedation identified a moderate effusion of the left fourth metacarpophalangeal joint. A CT scan was performed, which identified fragmentation of the medial palmar sesamoid of the fourth digit (sesamoid V). Arthrocentesis of the fourth metacarpophalangeal joint identified septic inflammation. Surgical removal of the fragmented palmar sesamoid was performed and was submitted for histopathology and bacteriology analysis. Postoperative CT confirmed the removal of all fragments. Pasteurella species were isolated from the sesamoid fragments. Histopathology revealed osteomyelitis, neutrophilic inflammation and multifocal necrosis, with evidence of fibrosis present. The cat was re-examined 3 months postoperatively, at which point there was no evidence of lameness and orthopaedic examination of the limb was unremarkable.

Relevance and novel information To our knowledge, this is the first reported case of fragmentation of a palmar sesamoid in a cat. This case study describes the diagnosis and the successful management of a cat with fragmentation of a palmar sesamoid, following an altercation with another cat.