Tarsal Arthrodesis in Cats

What is tarsal arthrodesis?

Tarsal arthrodesis is a procedure in which the bones of the hock (ankle) joint are surgically fused to prevent abnormal movement that causes pain. The hock is composed of seven small tarsal bones arranged in a row, connecting the tibia (shinbone) above and the metatarsals below. The joints between these bones have very little movement between them normally. Most of the movement of the hock joint comes from where the larger tarsal bone (talus) meets the tibia (shinbone).

Tarsal arthrodesis may involve fusing all the bones of the hock together (pantarsal arthrodesis), which immobilizes the hock joint, or fusing only the tarsal bones together (partial tarsal arthrodesis), which allows the leg to bend normally.

What conditions can be treated with tarsal arthrodesis?

Tarsal arthrodesis may be recommended for certain conditions that result in abnormal painful movement in the bones of the hock joint, including:

• Full or partial dislocation, usually caused by trauma such as falling from a significant height or being hit by a car
• Certain fractures of the bones of the tarsus if they can’t be repaired
• Severe osteoarthritis or polyarthritis
• Deformities/malformations of the tarsal bones that cause lameness
• Tumors
• Joint infection (septic arthritis)

How is tarsal arthrodesis performed?

There are different techniques for surgery depending on the issue being treated; however, each technique usually involves removing the cartilage from the joint surface of the bones that need to be fused. Metal plates and/or screws and pins are then used to hold the bones in place so they can heal together. Bone grafts may be inserted. Pantarsal arthrodesis is carefully planned so the angle of the affected hock joint is similar to the other hock joint when the cat is standing. This angle helps the cat move more comfortably and prevents strain on the other joints in the leg.

What are potential complications of tarsal arthrodesis?

Complications of tarsal arthrodesis include:

• Implant failure: The metal implants may loosen, bend, or break, especially if the cat overuses the leg before it is fully healed
• Plantar necrosis: Tissue death may occur from the back of the hock to the paw pad, potentially caused by poor blood supply due to placement of a plate on the inside of the leg
• Infection
• Slow bone healing or lack of bone healing may result in the need for prolonged post-operative care or alternative treatment
• Bandage sores can develop due to the ongoing bandaging required after surgery

What can I do while waiting for my cat’s surgery?

If your pet is waiting for tarsal arthrodesis secondary to osteoarthritis, continue to follow your veterinarian’s recommendations to manage their pain, which may include pain medication, a special diet to encourage weight loss, veterinary rehabilitation, and frequent exercise in short, controlled sessions. Following these recommendations can help your pet have the best recovery after the surgery.

What can I expect during recovery?

Your cat will need to wear a soft, splinted support bandage or cast to help support the tarsus as it heals. This support may need to be maintained for four to eight weeks or more, depending on how quickly your cat’s tarsus heals and how often it needs to be monitored for swelling, discharge, or discomfort.

It’s important to restrict your cat’s activity — any abnormal or excessive activity can cause implant failure or prolong healing. Restricting their activity may mean confining them to a small room when you aren’t able to supervise them and ensuring all the surfaces in your home have appropriate traction to prevent slips. Confirm the exact activity restrictions with your veterinarian.

Follow your veterinarian’s recommendation for pain management, rechecks, and follow-up X-rays to assess your pet’s progress. Your veterinarian may also recommend performing massage on your cat’s leg muscles as well as passive range of motion (PROM) on the joints above and below the surgical site to prevent stiffening during their exercise restriction period.

Once the support is removed, your veterinarian may recommend veterinary rehabilitation therapy to help your cat rebuild muscle strength safely and efficiently. Even after recovery, your cat may not walk as fluidly or sit as they did before surgery. It’s important to ensure these changes are due to the planned reduced movement in the hock and not pain.