Surgical correction of a bilateral congenital tarsal hyperextension deformity in a cat

Summary Case description: An approximately three-month-old, 0.45 kg female Domestic Short-haired kitten with stiff hyperextended hind-limbs distal to the talo-central joint is reported. Attempts at repositioning of the joints by flexion failed while increased manipulative forces caused signs of pain and vocalization. Orthogonal radiographic views revealed a significant malarticulation of the tarsus. Goniometric measurments revealed a 145° extensor and 95° internal torsional deformity. Treatment and outcome: Pantarsal arthrodesis with a transarticular external fixation system was performed for both limbs in two separate stages. Pre-assembled frames were composed of two 40 mm diameter half rings (on the medial side) and two 40 mm diameter full rings connected with two pre-contoured (125° flexion) rods from proximal to distal. Following transection of the superficial and deep digital flexor tendons, cartilage was removed from the articular surfaces, autologous cancellous bone graft was inserted, and joints were fixed in 125° flexion with pre-contured external frames. The cat commenced weight-bearing bilaterally immediately postoperatively. Frames were removed 32 and 27 days after application. Two months after frame removal, joint fusion was confirmed and full weight-bearing at the walk and run was achieved. Clinical relevance: To our knowledge, this is the first report of surgical correction of a bilateral congenital tarsal hyperextension deformity by pantarsal arthrodesis using a transarticular external fixation system.