Ankle replacment

The current generation of ankle replacements are prostheses which resurface the two main bones articulating at the ankle which are the talus and the tibia.

In other words they realign the joint, by replacing the worn out joint surfaces. These components are made of metal.
Between the two components sits a plastic spacer, the meniscus.

This allows movement on both its surfaces. The addition of this component, though not present in the normal ankle, allows the artificial joints movement to match the normal ankle more closely.

This involves rotation as well as up and down movement (flexion and extension)

This ability to match the normal ankles movement also significantly improves the durability of the joint ..

Principle  ankle replacement
An ankle replacement works by removing the worn out joint surfaces which are generating the pain and as a result the ankle symptoms disappear.  Replacing them with a mobile weight bearing surface means that existing ankle movement can be retained. Adequate muscle and tendon function is required.
Both components have bioactive coatings which encourage the growth of your own bone onto them, forming a natural bond.

The talar component showing polished upper surface

The tibial component showing polished lower surface

When and for whom?
This is a procedure whose indication is chronic severe arthritic pain (as with other joint replacements).
 It is not a 'prophylactic' procedure to prevent the occurence of severe symptoms . The progression of an arthritic ankle is often unpredictable. Generally patients should be over the age of fifty. This relates to probable higher functional requirements in the younger age group and as a result likely reduced longevity of the joint. The age of fifty is not an absolute figure.

This age is not an absolute lower limit. The good evidence on longevity of ankle replacements mainly relates to patients over this age. It is likely that, as with other joint replacements, in younger and more active patients an ankle replacement will not last as long as the quoted figures. An exception to this would be a younger patient with multiple arthritic joints (such as with severe rheumatoid disease) who is likely to have low functional requirements.

As important as age are the functional requirements of any patient. Those in 'heavy manual' occupations (builders, farmers, heavy industry workers) who are over fifty are probably better advised for a fusion if they have isolated ankle arthritis.

Improving the RANGE of movement per se is not an indication, though may occur.  The pre-operative range is probably maintained.
Improved MOBILITY is possible, as a result of the pain free joint.

Alternatives to replacement
The most common operative alternative is ankle fusion for severe arthritic symptoms. However other options do exist such as arthroscopic debridement and Ilizarov joint distraction (see ankle arthritis, other options).

Replacement v/s fusion
The following are also the factors which your Surgeon will consider when giving his recommendation to you.

PAIN RELIEF :

• Both procedures are equally effective in relieving pain.

MOVEMENT:

• A Replacement:This will probabaly maintain the movement you have in the area that you are used to it occuring.  If you have surrounding arthritic and stiff joints then they are probably less likely to become more painful with a replacement.

• A Fusion: If the neighbouring joints are not stiff and arthritic then you are likely to be left with a good, though reduced, range of movement following fusion. The neighbouring joints can compensate for some of the ankles movement.

LONGEVITY :

• A Replacement: With any joint replacement this is probably the most important figure to consider. The most reliable figures available are an 8 year survivorship of the implant 88% and a 14 year survivorship of 75%. Many replacements have a considerably shorter follow up and it is not reliable to extrapolate from these specific results to other implants.

• A Fusion: Once an ankle is fused it doesn't 'wear out'.
  There is strong evidence however that neighbouring joints will become arthritic, due to the increased forces going through them, as they compensate for the fused ankle.
  The most likely joint to suffer is the subtalar. It is probable that this joint will subsequently become arthritic by 15 to 20 years. That however is not to say that it will require any treatment.
   

Contraindications to Ankle replacement
Neurological dysfunction: Normal muscle/tendon function is Required to 'drive' the ankle.

History of Ankle joint infection
Heavy manual occupations
Severe deformity
Soft tissue problems at the ankle: eg persistant ulcers ,skin grafts.