Partial Tarsal Arthrodesis

Partial tarsal arthrodesis is surgical fusion of the foot of the hindlimb, but does not include the ankle joint. If the hock (ankle joint) is also fused, that is a different procedure called pantarsal arthrodesis.

Partial tarsal arthrodesis is indicated when there is instability, arthritis, or fracture of the foot that cannot be otherwise stabilised. This can happen secondary to trauma after which the foot is grossly unstable and may be misaligned (pointing in the wrong direction). Alternatively, the foot can become chronically unstable due to ligament weakness, or it can develop arthritis which is painful. This can happen to any breed of dog, but Shetland Sheepdogs (Shelties) are prone to plantar tarsal ligament weakness which leads to gradual foot weakness and instability.

INVESTIGATION OF TARSAL INSTBILITY

If we are suspicious that your pet is suffering from an unstable tarsus, investigation usually involves:

• Clinical examination of your pet; an unstable tarsus (foot) can be strongly suspected from physical examination
• Followed by sedation for tarsal (foot) x-rays or CT scan.

TREATMENT OF TARSAL INSTABLITY

Treatment options for a dogs with tarsal instability include:

• Conservative management i.e. use of exercise restriction and pain-killer anti-inflammatory drugs to control the secondary lameness (limping) as best possible. If your dog is coping well with this, this is a reasonable option. However, usually the underlying problem will not get better by itself and will likely get worse with time.
• A brace for the tarsal joint to help support the foot and so limit instability and associated discomfort. These can work well in some dogs, but not so well in many dogs. Owners can find them quite fiddly and can struggle to get the brace to work well. Sometimes they don’t fit as well as they should, sometimes they slip and cause rub sores; then owners give up using them, and some dogs do not tolerate them and hate wearing them. A brace can be worth a try, but a good brace is expensive, and you have to accept it may not work as well as hoped for. Also, a brace does not fix the underlying problem; it simply supports the tarsus when present but when removed, the tarsus is still unstable.
• Partial tarsal arthrodesis surgery (foot fusion, not including the ankle). This is the definitive treatment option that is recommended in most circumstance, and if the above options are unsuitable or do not work.

Outcome after partial tarsal arthrodesis surgery is expected to be excellent with normal to near normal hindlimb function expected. As for eny surgery, complications are possible, although the actual complication rate is very low. Potential complications include infection, wound breakdown, implant failure or failure of the bone to heal/fuse.