Evolution of Technology

Unicompartmental (partial) Knee Replacement

Partial knee replacement components are designed and manufactured by many different companies in the United States and throughout the world. These implants are unique in that only one area or compartment of the knee is replaced, and are either a fixed bearing ( the plastic is locked into place) polyethylene( “poly” or plastic) or a mobile bearing, meaning that plastic moves with your knee joint movement. All currently utilized partial knee replacement components have a long track record of success and have been thoroughly tested and approved by the US Food and Drug Administration. Currently the most common materials used for components are various metal alloys to include titanium and cobalt-chrome, as well as high grade molecular weight polyethylene or poly.

There are various implants that may be used to replace or resurface any of the three compartments within the knee, the inside part, outside part, or the knee cap joint, depending on which area has been found to have damaged cartilage and become symptomatic for the individual patient. Which component or compartment of the knee that is to be resurfaced for an individual patient must be determined prior to surgery with a conversation between the patient and his or her surgeon, with various xrays or even MRI’s confirming. Unicompartmental knee replacement has been shown to be an effective treatment for patient’s who meet the correct indications for surgery with a greater than 90% success rate and survivorship of implants at 12- 15 years post-operatively.

A discussion on what’s best for you or your loved with your surgeon is important, as not all patients are candidates for partial knee replacement. It should be well understood that overall success for pain relief and increased function are excellent for partial knee replacement, in general surviorship, or how long a partial knee replacement lasts compared to a total knee replacement, is generally less. Therefore, revision surgeries may ne necessary earlier or more often with partial knee replacement.

Evolution of Procedure

Partial Knee Replacement Surgery

Partial knee replacement surgery is the process of surgically removing a few millimiters of damaged cartilarge and bone from the affected compartment and replacing or resurfacing the that single area with metal and plastic. It can be performed for any of the above mentioned three compartments, although is is most commonly performed to replace the medial or inside region of the knee. The advantages of this procedure are that more of the native knee are retained by the patient which is thought to lead to faster recovery and more anatomic or normal motion within the knee joint.

In order to benefit from partial knee replacement, patient’s must meet certain indications prior to surgery which include pain in only one region of the knee, x-rays demonstrating loss of cartilage in only one are, a stable knee without evidence of ligamentous injury, good range of motion, and a body mass index within an acceptable range. The surgery is performed by making a small incision and the front of the knee and with the use of cutting guides, resecting the regions of damaged bone and cartilage and replacing them with metal and plastic components. Following surgery patients are typically permitted to walk on their new knee the same day and are discharged from the hospital within 24, and more often this operation is performed on an outpatient setting, same day surgery.

Evolution of Diagnosis

Partial (unicompartmental) Knee Osteoarthritis

The knee joint consists of three anatomic compartments. These include the medial (inside), lateral (outside), and anterior (front) compartments. Osteoarthritis (or simply arthritis) is a degenerative condition of the joint which causes progressive loss of articular or joint lining cartilage . This is a separate but similar diagnosis as autoimmune arthropathies, such as Rheumatoid or Psoriatic Arthritis. Degenerative arthritis of the knee most commonly affects the entire knee for which the treatment is a total knee replacement. However, if arthritis has only affected a single compartment, unicompartmental arthritis, you may be an excellent candidate for pain relief and increased function with a partial or unicompartmental knee arthroplasty. It is distinguished from complete or tri-compartmental osteoarthritis , and subsequently total knee arthroplasty, as the operative treatment for partial knee arthritis can consist of replacing only a single joint compartment, rather than the entire joint.