Partial (Uni) Knee Replacement
Not all patients with severe arthritis of the knee have to undergo total knee replacement surgery when non-surgical measures have failed to provide quality of life. For select patients partial (uni) knee replacement is a wonderful option to consider instead of total knee replacement.
Over the past decade my practice has evolved from doing exclusively total knee replacement surgery for severe arthritis. Currently, one out of three patients in my practice is undergoing partial knee replacement opposed to total knee replacement. I currently perform hundreds of knee replacement surgeries per year, with an increasing percentage of partial knee replacements each year. The single most important factor for successful partial knee replacement is the experience and skill of the surgeon.
The transition in my practice has been based on improved implants, improved surgical techniques and an improvement in the understanding of knee arthritis, particularly when it is isolated to one part of the knee. With this transition, many patients are reaping the benefits of partial knee replacements!
If a patient needs a total knee replacement, than by all means that is the surgery they should have. However, many patients have knee arthritis in a pattern that can be treated successfully with partial knee replacement.
The benefits of partial knee replacement compared to total knee replacement:
- o Shorter length of surgery with most surgeries being 45 minutes or less
- o Less surgical dissection, particularly minimal damage to the thigh muscle
- o Less swelling, pain, and stiffness post-operatively, with almost all patients going home the day after surgery
- o Easier rehabilitation (notice I said easier, not easy!!), with almost all patients going directly home after their hospital stay
- o Less recovery time, less time lost from work and other activities
Most importantly, partial knee replacements function much more closely to the normal knee than a total knee replacement. One of the biggest limitations in total knee replacement is difficulty with high intensity activity, like running, jumping, quick change of direction, and deep knee bending activities like squatting and kneeling. While not all partial knee replacements will be able to do all these activities, many more are able to do these compared to total knee replacements.
Criteria for being a candidate for partial knee replacement include:
- o Isolated arthritis to only one area of the knee (usually the inside half)
- o Limited deformity (not too crooked or “bow legged”)
- o Adequate range of motion, coming nearly straight and bending back deep
- o Osteoarthritis (“wear and tear”), not inflammatory like rheumatoid arthritis
Surgery and Recovery
The surgery involves an incision about 3 inches long starting at the top of the kneecap on the inside extending down in a straight line toward the ankle. Once the joint is opened, the very inside portion of the knee is prepared removing 4-5 mm of bone from the end of the thigh bone and top of the lower leg bone. Metal caps, custom fit to the anatomy of the patient, are then cemented to the bone. Recreating the cushion, a plastic spacer, available in different thicknesses and sizes is inserted between the metal caps. This allows the knee to be “balanced” so the knee has full range of motion and stability to simulate what the knee worked like prior to arthritis setting in. Once the components are inserted, the knee is “rock solid” allowing full weight bearing immediately after surgery, as much as comfort allows. The closure is with a plastic surgery (sub-cuticular) that eliminates the need for staples, clips, or sutures through the skin that have to be removed later. This closure minimizes the pain frequently felt when the skin is pulled and stretched with staples in the skin. This closure also allows patients to use minimal bandages at home and be able to shower very early after surgery.
Most patients come back for their first one month appointment very happy with their new partial knee replacement. At this time interval, most patients are around 70% healed, although there is tremendous variation between patients. Most patients, particularly those with more sedentary jobs, are back at work or ready to be released back to work. Most all patients are back to work within two months from their partial knee replacement surgery.
At three months most patients are about 90% healed, really getting back to their normal self. Past three months, most of the recovery is the gradual loss of a mild feeling of “stiffness” in the knee, and regaining full muscle strength, stamina, endurance, and coordination of the operative leg. Many patients, despite loving their partial knee at three months, frequently note it does take six months to sometimes a full year to be 100% recovered from surgery.
Risks and Complications
Fortunately, risks and complications of partial knee replacement in my experienced hands are less than 1% for almost everything combined. There are some risks relevant to any orthopedic surgery involving bones, joints, and implants made of metal and plastic.