UNICOMPARTMENT KNEE REPLACEMENTS

UNICOMPARTMENT KNEE REPLACEMENTS (UKR)

WHAT IS A UNICOMPARTMENT KNEE REPLACEMENT?

The knee joint has three major compartments, Medial, Lateral, and Patellofemoral. (See Figure 1.)

FIGURE 1. 

A joint can become arthritic on only one side of the joint with the rest of the knee completely normal in which case only that side of the knee needs to be replaced and this is a Unicompartment or partial knee replacement. (Figure 2)

FIGURE 2:  Post op X-ray of Unicompartment Knee

WHO IS ELIGIBLE FOR A UNICOMPARTMENT OR PARTIAL KNEE REPLACEMENT ?

We follow very strict inclusion criteria to decide which patients are suitable for a Unicompartment knee replacement. The typical patient will usually have a medial compartment osteo arthritis that is significantly advanced whilst the rest of the knee including the ligament structures, the lateral, and patellofemoral compartments are normal. The lateral compartment is less commonly involved than the medial compartment, and occasionally the patellofemoral joint is the only one involved.

The knee deformity must not be excessive and the patient should have an adequate range of movement. Patients who have a high BMI would not be ideal for a Unicompartment knee replacement. Patients whose arthritis is caused by an inflammatory condition such as rheumatoid arthritis, ankylosing spondylitis, or psoriatic arthritis are not suitable because their underlying condition will affect the other compartments of the knee. Your surgeon will discuss the possibilities for a Unicompartment knee replacement for you.

WHAT ARE THE ADVANTAGES AND DISADVANTAGES OF A UNICOMPARTMENT KNEE REPLACEMENT OVER A TOTAL KNEE REPLACEMENT?

Because only one side of the joint needs to be worked on the surgery is less invasive. Therefore recovery is quicker than with a total knee replacement. The knee, after a Unicompartment knee replacement, may feel more normal and function more normally than after a Total Knee Replacement. However many patients who have had one knee replaced with a Unicompartment and the other with a Total Knee Replacement cannot tell the difference.

The lifespan of a Unicompartment knee replacement is not the same as that of a total knee replacement. Although Unicompartment knee replacements do last a very long time there is a higher early failure rate for Unicompartment knee replacements compared to total knee replacements. (See figure 3.) However, a good Unicompartment knee replacement would probably last 15 – 20 years in over 85% of the patients. The complications of infection and deep vein thrombosis are considered to be less in a Unicompartment Knee Replacement than in a Total Knee Replacement.

FIGURE 3. Early failure of Unicompartment vs Total Knee Replacements

Should your knee fail and you require a revision then a full knee replacement will be done to replace your Unicompartment replacement. Although this is not the same as a primary Total Knee Replacement, it is less of a procedure than revising a failed Total Knee Replacement to another Total Knee Replacement.

WHY DO UNICOMPARTMENT KNEE REPLACEMENTS FAIL?

The prosthetic components can come loose (more common than in Total Knee Replacements). Another cause of failure is the other compartments may develop osteo arthritis and become symptomatic.

HOW LONG WILL IT TAKE TO RECOVER?

After a Unicompartment Knee Replacement patients generally, go home on the first or second day following the surgery; this being about a day quicker than a Total Knee Replacement. Crutches are used for up to 4 weeks by which time most patients can walk comfortably without crutches. You will be able to return to a desk job around about the 3 weeks mark and to more physical work after 8 weeks. Sporting activities such as golf will take between 2 and 3 months. Bicycle riding, however, is usually commenced around the 6th to 8th week.