Unicompartmental Knee Arthroplasty: A Patient's Guide to Partial Knee Replacement using Minimally-Invasive Surgery (MIS) Techniques.

Figure 1 - X-ray of a traditional total knee replacement. This operation is done for patients who have arthritis throughout the knee. Excellent long-term results are obtained in most patients.

Figure 2 - Model of a traditional total knee replacement. The patella (knee cap) is not shown in this model.

Figure 3 - X-ray of a partial, or unicompartmental, knee replacement. This operation is done for patients whose arthritis is limited to one side of the knee. It may be done through a very small incision, and recovery from this procedure is usually much quicker than that seen with traditional total knee replacement.

Figure 4 - Model of a partial knee replacement. This smaller implant leaves undamaged cartilage in other parts of the knee intact.

Figure 5 - This clinical photograph shows a typical incision used to insert a minimally-invasive partial knee replacement. The average length of the incision used in this procedure is 3 inches. Smaller incisions help permit faster recovery, and lead to less post-operative pain, compared to traditional knee replacement surgery.

Summary

Overview

This article covers topics related to unicompartmental knee arthroplasty (sometimes called unicompartmental knee replacement or partial knee replacement) using minimally-invasive surgery (MIS) techniques for the treatment of arthritis.

Knee replacement is a surgical procedure that decreases pain and improves the quality of life in many patients with severe arthritis of the knees. Typically, patients undergo this surgery after non-operative treatments (such as activity modification, medications, knee injections, or walking with a cane) have failed to provide relief of arthritic symptoms. Surgeons have performed knee replacements for over three decades, generally with excellent results; most reports have ten-year “success rates” in excess of 90 percent.

Broadly speaking, there are two types of knee replacements: total knee replacements (see figures 1 and 2) and unicompartmental (or partial) knee replacements (see figures 3 and 4). Both have long “track records” and good clinical results in this country and in Europe.

Traditional total knee replacement involves a 7-8” incision over the knee, a hospital stay of 3-5 days, and a recovery period (during which the patient walks with a walker or cane) lasting from one to three months. The large majority of patients report substantial or total relief of their arthritic symptoms once they have recovered from a total knee replacement.

Partial (unicompartmental) knee replacements have been around for decades and offer excellent clinical results, just like total knee replacements.

But in the last year or two, surgeons and patients have become very enthusiastic about an exciting new approach to this well-established procedure. “Minimally-invasive” partial knee replacement (or "mini knee") is a surgical technique that allows a partial knee replacement to be inserted through a small (3-3.5”) incision (see figure 5), with minimal damage to the muscles and tendons around the knee.

The small size of the incision and the less-invasive nature of the surgical approach allow patients to recover from the “mini knee” operation much more quickly. Hospital stays are shorter--down to 1 or 2 days for most patients--and the recovery period is much faster. Patients lose less blood, experience substantially less pain than traditional knee replacement, and often walk unassisted (no cane or walker) within a week or two of the operation (see movie 1). Even many patients who have both knees done at once with this newer technique are able to walk without the assistance of a walker or cane fairly quickly.

Quicktime movie

• Movie 1 - Patient walking less than two weeks after having both knees replaced on the same day (0.59 MB)

Surgery for arthritis of the knee at the University of Washington, Department of Orthopaedics and Sports Medicine, Seattle, Washington

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