Unusual presentation of osteomyelitis of the tuber calcanei in a 16-month-old gelding

Abstract

A 16-month-old Morgan gelding was referred for evaluation of a right hindlimb lameness (grade 4/5, AAEP) accompanied by swelling of the right calcaneal region. Clinical signs had been present for approximately 4 weeks prior to referral. Initial diagnostic imaging (radiography and ultrasonography) identified an osseous defect on the plantaromedial aspect of the tuber calcanei, together with mild synovial effusion of the intertendinous calcaneal bursa. Synovial fluid analysis from the bursa was cytologically unremarkable. Repeat imaging 5 days later revealed rapid progression, characterised by substantial lesion enlargement and advanced osteolysis. Computed tomography of the right tarsus was performed on day 8 post-admission to further characterise the lesion's extent and morphology. Owing to the lack of clinical improvement, surgical exploration and debridement were undertaken. A plantar surgical approach was employed, with dissection through the skin, subcutaneous tissues, superficial digital flexor tendon and intertendinous bursa. These structures were retracted to provide direct access to the osseous defect just distal to the insertion of the gastrocnemius tendon. Extensive debridement of the osteolytic lesion was performed. Bone samples submitted for bacterial culture yielded Actinobacillus spp. Postoperative recovery was marked by immediate improvement in comfort, with resolution of lameness at the walk. Long-term follow-up over a 2-year period confirmed sustained clinical resolution without recurrence.