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Your surgeon may discuss some of these additional options with you.

Fixed-bearing versus rotating knee platform. In a fixed-bearing knee prosthesis—the most common type—the tibial component of the prosthesis is topped with a flat metal piece that securely holds a polyethylene insert. When the knee is in motion, the femoral component glides across the polyethylene. In a rotating platform knee prosthesis, the polyethylene insert can rotate slightly, theoretically lessening stress and wear on the implant and improving movement.

According to some experts, rotating knee prostheses slightly improve on the knee range of motion offered by fixed-bearing prostheses, but have a slightly greater risk of complications. Two 2012 studies published in the Journal of Bone and Joint Surgery demonstrated that rotating-platform knee implants deliver durability and good to excellent results in terms of pain and range of motion after more than ten years of follow-up. Also reported in that journal in 2012 was a randomized trial of 240 knee replacement patients. The researchers found neither style of implant bested the other at the two-year and five-year marks in scores of knee range of motion, function, and stair-climbing. Usually, total knee replacement revision surgery requires a more constrained prosthesis with more supportive metal stems that extend into the femoral and tibial canals.

Gender-specific knees. Knee implants used to come in a limited variety of shapes and sizes. Now there are implants that are specifically designed for a woman's anatomy, known as gender-specific knees. However, in a study that followed 85 women with knee replacements for two years after surgery, the gender-specific knees scored about the same as standard knee replacements in terms of range of knee motion and patient satisfaction.

Partial knee replacement ("mini-knee"). If your knee damage is limited to one of the bumps (condyles) on the end of your femur, you may benefit from a partial (unicompartmental) replacement that leaves the rest of the joint intact. This technology has been around for decades, but became more popular once surgeons were able to install the partial implant through a small incision (about three inches rather than eight) with minimal impact on muscles and ligaments—a surgery nicknamed the "mini-knee."

The potential advantages are clear: less blood loss, shorter hospitalization, and quicker recovery. However, a unicompartmental replacement lasts only about 10 years, compared with 15 to 20 years for a total knee replacement. They aren't well suited for people who are very bowlegged or knock-kneed. You may be offered this option only if damage is limited to one portion of the knee, if the damage results from a traumatic injury rather than arthritis, if your ligaments are intact, and if your knee still contains a fair amount of healthy cartilage. The ideal patient for this surgery is an older, thinner person rather than a younger, more active one. It may be suggested to buy time before total knee replacement in someone young and active, however.

Minimally invasive knee surgery. Minimally invasive knee surgery accomplishes the same goal as traditional knee replacement, using the same types of artificial knee implants as those used in traditional procedures, but through much smaller incisions. Despite the name, it is still major surgery. The size of the incision depends on the person's size (bigger knees mean bigger incisions). On average, the incision for minimally invasive surgery is four to six inches, compared with an eight- or 10-inch incision with traditional knee replacement. Some minimally invasive techniques require small incisions to be made in the quadriceps muscle, while "quadriceps-sparing" techniques protect the quadriceps tendon and muscle. The results from several studies comparing minimally invasive surgery to traditional knee replacement have shown some benefits, including less blood loss, shorter hospital stay, and better range of motion. However, other studies show a higher complication rate with minimally invasive surgery, including less precise placement of knee implants.

Patellar resurfacing. In some knee replacements, the kneecap is unaltered, and the artificial implant is shaped to glide easily beneath it. But in another approach, called patellar resurfacing, the surgeon attaches a separate piece to the back of the kneecap to fit smoothly with the implant, resurfacing the patella. Studies of patellar resurfacing have offered varying results: some find it reduces long-term pain, and others find it leads to more complications and a higher failure rate. A meta-analysis of 1,223 knee replacements suggested that patellar resurfacing may modestly reduce the risk of revision surgery and pain at the front of the knee. Some surgeons resurface the patella in most knee replacements; others try to avoid this step unless special circumstances warrant it. Patellar resurfacing may be a better option for younger patients, in whom the results tend to be more predictable.



Last Annual Review Date: 2012-09-01 Copyright: © Copyright Harvard Health Publications

Reference: Bones, Joints and Muscles section on Better Medicine