Evaluation of clinical and diagnostic imaging findings of bilateral superficial digital flexor tendon luxation in the tarsus of a gelding.

Superficial digital flexor tendon (SDFT) plays an important role in the locomotion of the horses with flexion of the limbs. In the hind limb, it passes over the calcaneal bone and attaches to medial and lateral surfaces of calcaneous by two bands of connective tissue; while, the medial band is weaker than the lateral one. Occasionally, severe trauma, over-extension or fracture of the calcaneous may cause rupture of the supportive bands leading to tendon luxation. An 11-year-old Thoroughbred jumping gelding with symptoms of lameness in both legs, after examination by an internal specialist veterinarian in equine practice field was referred to the Teaching and Research Hospital of the Faculty of Veterinary Medicine of the University of Tehran, Tehran, Iran. Clinical examination showed lateral luxation of SDFT in the right and left tarsal joints. Radiography revealed no sign of calcaneal involvement, except soft tissue swelling. In the radiography of the tarsal joints, the calcaneus bones did not show significant changes, but among the bones of the central and 3^rd tarsal bone (distal intertarsal joint) of the tarsus, osteophyte formation was observed to a mild extent, indicating mild bone spavin in both tarsal joints. In ultrasonography, SDFT thickenings accompanied by hypoechoic regions in tendons were seen, confirming the signs of tendonitis. Moreover, fibrous tissue formation was diagnosed. In the left leg, anechoic fluid in the calcaneous bursa was seen. Evaluation of diagnostic imaging findings enables veterinarians to diagnose the site and extent of the lesions, choosing the appropriate therapeutic approach in addition to clinical symptoms.