The knee joint is divided into three compartments: medial, lateral and patella (kneecap)
There is a preponderance of medial arthritis of the medial compartment with a sparing of the other two. Traditional approach to knee replacement has been to replace all three compartments.
Until recently available designs to replace only one compartment had unacceptable failure rates.
Recently released by the FDA is the Oxford Meniscal Unicompartmental knee. The design has a fully mobile bearing that limits the forces and stresses on the implant, lessening the chance of loosening. By only replacing the damaged compartment the healthy knee structures are preserved and more normal knee motion and function occurs.
The Oxford meniscal bearing knee is the only fully mobile bearing Unicompartmental knee system in the United States and has excellent long term results in European series.
The procedure is done through a truly minimally invasive incision approximately 3 inches. Often the patient can begin ambulating with some support the evening after surgery. Usually only an overnight stay is required. Light activities such as driving can begin at 2 weeks and full unsupported weight bearing at 4 weeks. Patients can return to golfing, swimming, walking, bicycling and doubles tennis. High impact or high collision activities such as skiing are discouraged. Good to excellent results of the partial replacement are at 90% at 10 years conversion to a total knee can be necessary if the rest of the joint becomes arthritic.
Unfortunately some criteria must be met for the meniscal bearing implant?s long term success. One must have a fairly flexible knee, intact ligaments (including ACL) and no arthritic defect in the lateral weight bearing compartment. Researchers have estimated that up to one third of all individuals undergoing total knee replacement will fit these criteria.
Considering the small numbers that have conversion to a total knee in the long term versus the much lower complication rate and quicker recovery, the meniscal-bearing Unicondylar knee replacement has become a major treatment option for patients with knee osteoarthritis.