Deciding Which is Best for Your Knee Condition

ANATOMY

The words “partial” and “total” in reference to knee replacement may be confusing. Surgeons and anatomists think of the knee as being made up of three compartments: the medial and lateral compartments and the patella-femoral compartment. These are the three areas in the knee where bones move against each other. Normally the surfaces of the bones in these compartments are covered by cartilage, which allows painless motion and function of the knee.  But when arthritis destroys the cartilage, motion and load in these compartments causes pain. In knee replacement surgery, the surfaces of the bones are “resurfaced” with metal and plastic. This allows movement and function of the knee to again become pain free.

If the cartilage wear involves more than one compartment, the surgeon will usually recommend a “total” knee replacement. In this procedure, all three compartments of the knee are replaced. But, if the cartilage wear involves just one compartment, the surgeon may recommend a “partial” (frequently also called “uni-compartmental”) knee replacement. In this case, only one compartment is resurfaced.

This might sound like a straight-forward decision, but in fact there is much debate on the issue. Some surgeons feel that performing a total knee replacement in all cases of severe arthritis is the best thing to do, even if the wear is mainly in one compartment. Others feel that uni-compartmental knee replacement should be considered in selected patients. The reasons for the differences of opinion have to do with the history of the development of the two procedures as well as the pro’s and con’s of the current alternatives.

HISTORY

Uni-compartmental knee replacement began in the 1950’s and 60’s, but the results were not particularly good. The modern concept of cementing the metal surface to the femur and the plastic surface to the tibia was introduced in the 1970’s and the results were much better. In this same time period of the 1970’s, the modern concept of total knee replacement was also developed. By the 1980’s comparisons of the results were possible, and it appeared that total knee replacement lasted longer and there was less chance of needing a subsequent “revision” surgery. Naturally, the uni-compartmental procedure fell out of favor.

These early comparisons were difficult, because the specific indications for uni-compartmental replacement were not well understood, and many patients included in those early studies would not be considered good candidates for the procedure today. A few surgeons continued to do the procedure and eventually refined the indications and the techniques. Their results were similar to those of total knee replacement. But what really changed the attitude of most surgeons about uni-compartmental replacement was the advent of minimally invasive techniques. With improvements in instrumentation, smaller incisions with less muscle dissection were possible. This was found to result in faster recovery from the procedure and shorter hospital stays. INDICATIONS FOR

PARTIAL KNEE REPLACEMENT

1. The wear must be mainly limited to either the medial or lateral compartment.
2.  The anterior cruciate ligament as well as the other ligaments in the knee must be intact.
3. The angular deformity (knock-knee or bow-leg) must be less than 15 degrees.
4. The deformity must be passively correctable.
5.  The range of motion should be at least 10-100 degrees.

PROS AND CONS

Now that we know the results at 5-10 years after surgery are similar, when the correct indications and contra-indications are followed, the decision rests with comparison of the pros and cons of each procedure. This is where you as the patient come in. Your surgeon would not offer you the alternative of partial knee replacement unless he felt it is appropriate for you. You must be the one to decide between the pros and cons as they fit your needs and desires.

Pros of Partial Knee Replacement - 90-95% last 10 years - Faster recovery (~6wks) - Slightly better function (patients report that the knee feels “normal”)

Pros of Total Knee Replacement - 90-95% last 15-20 years - Less chance of second surgery if age 65 or older at time of surgery - Second (revision surgery) may be a tibial liner change only

Cons of Partial Knee Replacement - 5-10% chance of a second surgery (and a greater chance if less than 75 at time of surgery) - Second (revision) surgery will be to remove the partial knee and insert a total knee replacement

Cons of Total Knee Replacement - Slower recovery (~12 wks) - Slightly worse function (for some patients the knee may not feel like a “normal” knee)

SUMMARY

Deciding if a partial knee replacement is right for you will take some thought and self analysis. Considerations include life expectancy, the difficulty of the recovery period, and concern about the possible need for another surgery. Each patient has their individual desires and concerns over these issues. Talk them over with friends of family…and especially with your surgeon.