Ankle arthrodesis is performed more commonly than that of the hip or knee. It is also called ankle fusion.
Most common indication for performing this surgery is arthritis following an injury to ankle also called post-traumatic arthritis.
Other indications are
- Rheumatoid arthritis
- Neuromuscular disorders
- Failed total ankle arthroplasty.
- Bone tumors around the ankle
Before proceeding with arthrodesis, the surgeon might give you a below-knee cast to see if you are a suitable candidate for arthrodesis.
The optimal position for ankle fusion is
- 0 degrees of flexion
- 0 to 5 degrees of valgus
- 5 to 10 degrees of external rotation with a slight posterior displacement of the talus.
Approaches of Ankle Arthrodesis
Access for ankle arthrodesis can be anterior, transmalleolar and posterior.
The ankle is approached from the anterior [front] side with or without an additional small incision.
This approach provides slightly better access to the posterior aspect of the ankle joint. Exposure is improved by medial and lateral transmalleolar osteotomies.
The posterior approach can be used in patients with compromised anterior skin from previous trauma or surgery.
Fixation in Ankle Arthrodesis
Depending on the fixation method used, the techniques of ankle arthrodesis can be classified as –
- Charnley fixation clamp
- Calandruccio compression device
- Ring Fixator
- Tubular external fixators
Internal fixation has several theoretical advantages over external fixation.
- Ease of insertion
- Patient convenience
- Comparable rates of delayed union, malunion, nonunion, and infection
- Greater resistance to shear stress.
Following modalities are used in internal fixation
- Cancellous screws – parallel or crossed
- Direct compression plates
- Kirschner wires
- Steinmann pins
- Intramedullary rods
- Lateral T-plate
- Posterior blade plate fixation.
Procedure of Ankle Arthrodesis
The procedure involves denuding the remaining articular cartilage and making two parallel cuts, one through the distal tibia and one through the dome of talus to resect a minimal amount of bone to allow apposition of large cancellous surfaces and translation of the talus posteriorly beneath the tibia.
Addition of bone grafting is said to increase the fusion rate. Bone graft can be taken from tibia or either lateral or medial malleolus.
Arthroscopic Ankle Arthrodesis
Arthroscopically assisted ankle arthrodesis offers advantages of
- Quicker fusion because of the limited exposure and less extensive periosteal stripping
- Preservation of the overall contour of the ankle mortise, giving a better cosmetic result.
Prognosis of Ankle Arthrodesis
In general overall shortening generally is less than 1 cm and fusion rate is 80% to 90%.
Arthrodesis offers good pain relief but there is limited hindfoot motion which can result in difficult walking on uneven surfaces.