Alternatives to Knee Replacement: Unicompartmental or Partial Knee Arthroplasty
Osteoarthritis is the most common cause of long term disability in patients older than 65 years of age. It affects all ethnic groups and geographic locations, women somewhat more than men, and the knee is the most commonly affected joint. Causes include trauma, inflammatory diseases such as rheumatoid arthritis, infection, obesity, and genetic predisposition. In the knee, end stage arthritis occurs when the articular cartilage (white smooth covering of the bone) and the meniscus (shock-absorber rubbery cushions between the bones) wear out. When people have severe radiographic arthritis (bone-on-bone X-rays), and have severe pain and dysfunction that fails non-operative intervention, total knee arthroplasty (TKA) or knee replacement is usually the best option. This procedure has a success rate approaching 95% in appropriately selected individuals in terms of improved function and pain relief. While survival rates for the implant are generally 90% at 15-20 years, and up to 30 years in some patients, the implants eventually wear out. This may lead to the need for complicated revision TKA surgery, which has inferior results and higher complication rates compared to primary TKA surgery. For these reasons we try to delay TKA surgery until patients are at least 50 years old and have severe radiographic changes. This is a problem for individuals with significant dysfunction but cartilage wear that might not be severe enough to warrant TKA.
One option for these patients is a partial or unicompartmental knee replacement (UKA). Unicompartmental knee replacement is generally considered for patients with severe arthritis that involves primarily one side of the knee, usually the medial side (inside- between the knees). With this surgery, the affected side of the knee is replaced with an artificial knee made out of wear-resistant metal and plastic, while the other parts of the knee with intact cartilage are left alone. The primary advantages of this procedure are that it is less invasive, resulting in lower blood loss, less pain, less muscle and soft tissue damage, and faster recovery compared to TKA. Since the undamaged parts of the knee are preserved, the patient has the option to convert this to a traditional TKA if the rest of the knee wears out in the future. Hopefully the complications of a more invasive revision TKA surgery are minimized with this approach.
For a patient to be a candidate for UKA surgery, they must have minimal damage to the patella (knee cap) and lateral side of the knee, reasonable flexibility, intact ligaments (no ACL tears), BMI or body mass index <30 (not considered obese), and not have inflammatory (rheumatoid-like) arthritis. Studies show that patients who do not meet these criteria have poor outcomes with UKA. Traditionally this procedure was utilized in elderly patients primarily, but it has been expanded successfully to middle-aged patients in the past 15 years. In younger patients who are too young for a TKA but have severe pain and dysfunction from unicompartmental arthritis, UKA may help alleviate pain and improve quality of life significantly. Results for unicompartmental knee replacement from studies published over the last 20 years show survival rates of the prosthesis up to 96% at ten years and 80-90 % at 15 years. This means about 90% of appropriately selected individuals can expect the surgery to work well for at least 15 years. Eventually the implant or the rest of the knee will wear out, resulting in the need for conversion to a total knee arthroplasty. The goal here is to preserve as much of your original knee as long as possible, while maximizing your quality of life with less pain and better knee function. In this regard UKA surgery can be very successful.
If you are struggling with knee pain and would like to discuss options for treatment, including UKA, give us a call at 205-971-1750. I hope this information was helpful.