At the recent annual meeting of the American Academy of Orthopedic Surgeons in San Diego, California, in February 2011, there were many papers on partial or unicompartmental knee replacement. It is generally agreed there is an indication for unicompartmental knee replacement. The current usage in the United States is somewhere around seven percent of all knee replacements performed.
There is debate as to whether or not fixed bearing versus mobile bearing implants perform better at long-term followup. Registry data indicates that both of appropriate designs seem to work quite well. In the Scandanavian registry the patient satisfaction with unicompartmental knee replacement is very similar to those with complete knee replacement. In the Australian registry there is a higher revision rate at nine years for unicompartmental versus total knee arthroplasty, while the indications are different and the patient expectations are also different, making side-to-side comparison somewhat difficult.
There is general agreement that the factors most important include surgeon volume and experience with unicompartmental knee replacement, the indications for performing unicompartmental knee replacement, and certain conditions involving the knee, i.e., that the arthritis is limited to one compartment and that the opposite compartments are preserved and the anterior and posterior cruciate ligaments are intact.
There has been recent interest in the use of robotic devices to assist in performing the procedure, though there is no long-term followup data to document that this will improve the outcome over time, and the implants associated with that particular procedure do not have long-term followup data.
William P. Barrett, MD