Orthopaedic Surgeon
Conversion of an Ankle Fusion to an Ankle Replacement
As you are probably aware there are two main surgical ways to treat ankle arthritis- Ankle fusion or ankle replacement. Currently the majority of people with ankle arthritis will still receive an ankle fusion. An ankle fusion relieves pain but at the expense of movement. It is a robust solution because once fused it will not break down or loosen or require revision in the future. For some people Ankle fusion is not a satisfactory solution. This can be for a number of reasons. One reason is the loss of movement - for some people they are acutely aware of this, and it drives them to seek a solution. Even though ankle fusion relieves the pain from the ankle arthritis patients can develop pain from joints around the ankle and this may require fusion of those joints which increases the stiffness. The position of fusion is critical for ankle fusion to be successful and if the fusion is in a suboptimal position, then this can be a source of pain.
Conversion Considerations
With appropriately selected patients, preoperative planning and careful technique, it is possible to successfully convert some patients’ ankle fusions to an ankle replacement thereby restoring some movement, relieving pain and improving function.
Case by Case
Not all ankle fusions can be converted to an ankle replacement. The technique of fusion employed by the original surgeon is critical. It is important that the medial and lateral malleoli are preserved in fusing an ankle. Some techniques resect the fibula and whilst this can achieve ankle fusion it prevents conversion to an ankle replacement at a later date.
Limitations
The movement achieved is usually modest- an arc of 15-30 degrees but this movement is greatly appreciated by the patient, and it is a substantial improvement on their preoperative situation.
Pain Management
Not all patients are completely pain free- Whilst restoration of movement is good sometimes patients still have pain. This can be occurring from within or outside of the ankle and be arising from joints, soft tissue, or nerves.
Complications & Risks
There is a higher risk of complications with fusion conversions. Previous surgery and trauma increase the risk of wound healing problems, nerve injury and other complications that can compromise the result. With previous versions of ankle replacements and conventional instrumentation, the complication rate was extremely high making conversion a risky proposition for the patient.
New Technologies
Recent technology changes make conversion much more achievable. The preoperative CT-based planning (Prophecy) along with the 3D printed patient-specific jigs means that a lot of decisions are made preoperatively and are able to be executed accurately and this improves the predictability of the procedure. In the past, these decisions had to be made intraoperatively (like angle and depth of cuts, rotation) and it was extremely difficult to do this accurately and consistently.