Unicompartmental Knee Replacement

Dr Chien-Wen Liew – Hip, Knee, Shoulder surgeon – Adelaide, South Australia

A knee is thought of as having 3 main compartments. Both sides of the knee, and 1 under the patella (Knee cap). When all 3 compartments are involved with arthritis, it requires a total knee replacement. Sometimes only 1 compartment is degenerate and therefore, a unicompartment knee replacement can be used.

A unicompartmental knee replacement requires less damage to the surrounding soft tissue. Only 1 compartment is replaced. In general it is the medial side (inside part) of your knee as found in a varus (angulated to look like bow legs) knees. If the other two compartments are uninvolved as determined usually by arthroscopy, a unicompartmental knee replacement is used.

Replacing 1 compartment rather than all 3 can have advantages, as the national joint registry (A register of all joint replacements performed in Australia) has shown that the results of a revised unicompartmental knee replacement have a lower rate of revision than if a revised full replacement is used. This may be beneficial in those patients with specific pain and only one compartment involved.

When other compartments are involved with arthritis, a unicompartmental knee replacement (UKR) is not suitable, as those parts of the knee will continue to degenerate and cause pain.

Dr Liew performs UKR using patient specific technology. This uses a CT scan to image the hip, knee and ankle and create alignment of the limb to a particular plan. A UKR is not placed in to a perfectly straight alignment of 180 degrees as a total knee replacement is. A slight angle is preferred to prevent the main cause of failure after a UKR – adjacent compartment degeneration. This occurs when the knee degenerates in other compartments at a fast rate after the UKR. UKRs are not suitable for patients with the potential to have further rapid degeneration or those who do not have patent ligaments. If the deformity of a knee is great, a UKR should not be used as it cannot correct for these deformities.

Whilst a UKR is a successful operation, it is more technically demanding than a total knee replacement due to the smaller incision, and reliance on intact ligaments. Dr Liew performs UKR using cement for both the tibia and femoral components and a fixed bearing polyethylene insert.

After your surgery you will be encouraged to bend the knee straight away and are mobilising with a walking aid hours after surgery. Your stay in hospital is on average 2-3 days.

All dressings must remain on until your first review with Dr Liew at 2 weeks post operatively.

To discuss if your knee is suitable for a UKR, please contact the rooms of Dr Chien-Wen Liew on (08) 7099 0188.

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