The Patient

When Mr. K, a relatively healthy 65-year-old, first presented to UAMS Medical Center’s Orthopaedic Surgery department in 1997, he had been experiencing pain in his left knee for five years. His osteoarthritis affected all three compartments of the knee and became progressively worse, until he was no longer able to control the pain with medication. In January of 1997, a total knee replacement was performed on his left knee. His postoperative care went well, and he was released from the hospital in five days.

However, Mr. K began having pain in his opposite knee. He returned in April 1999, and it was noted that he had unicompartmental arthritis in the right knee and that he was an excellent candidate for a unicondylar knee arthroplasty.

As in most unicondylar knee "retreads," general anesthesia and local anesthetics were administered and narcotic usage was kept to a minimum. The incision was three inches long, compared to the eight- to 10-inch incision required for total knee replacement. The patient went home early the next morning. His postoperative care went well; no rehabilitation or physical therapy was required.

This patient was in a position to compare the total left knee replacement with the less invasive procedure performed on his right knee. In a television airing, he testified that he was quite pleased to have the unicondylar knee replacement and go home the next morning. At last contact, he was doing well and both knees were pain-free.

The Concept

Many patients with unicompartmental arthritis of the knee, even elderly patients, have received total knee replacements rather than less invasive unicompartmental replacement. The reason: unicondylar knee replacement once required the same eight- to 10-inch incision and typically the same hospital stay, recovery time and rehabilitation. It made sense for these patients to have total knee replacement, rather than face much of the same trauma and expense to repair only one compartment, and possibly undergo another, more extensive operation years later.

However, advances in unicondylar knee arthroplasty and in the implant have made the procedure a viable option for many patients with unicompartmental arthritis. The current technique was developed by an orthopaedic surgeon and former dentist, and it makes use of surgical instruments similar to those used in dentistry. A course in the technique was presented at UAMS Medical Center in 1998.

Patients who are younger than 55, overweight or who expect to engage in heavy work or sports are not good candidates for unicondylar knee replacement. However, traditional unicondylar arthroplasty has been reported to have a success rate of 90 percent at 10 years out for this select group of patients. In a recently presented study, 98 percent of the patients with a traditional unicondylar knee replacement were successful. Ten trouble-free years may mean the end of the problem for elderly patients, and some younger patients may benefit from buying some time before total knee replacement becomes a necessity.

The Benefit

The minimally invasive procedure offers several benefits over traditional total knee replacement for older patients who are within normal weight ranges and who have a typically active lifestyle.

A much smaller incision is one advantage. No patellofemoral disruption is needed, and only a small amount of bone is removed. Blood loss is minimal and normal tissue is preserved. Morbidity is greatly reduced. Patients report less postoperative discomfort and generally heal much more quickly. Patients are walking on their resurfaced knee just two to three hours after surgery, and most patients do not require overnight hospitalization. Within two weeks, most patients are able to resume their normal activities.

Another major advantage is the reduced need for anesthesia and postoperative medication. Intraoperative narcotics are seldom used. Anti-inflammatory drugs are administered pre-incision, local anesthetics are used, and anesthesia is maintained with inhalation agents during surgery.

The reduced hospitalization, medication and post-operative care add up to another clear advantage for these patients; the estimated cost of unicondylar knee arthroplasty is about one-half that of total knee replacement.

Bottom line

Unicondylar knee arthroplasty is much less invasive and successful. When osteoarthritis is present in only one compartment, it often makes sense to replace only that compartment, just as a dentist fills only the tooth that has a cavity and leaves the rest of the teeth intact.

Unicondylar knee arthroplasty can not prevent arthritis from developing in other compartments, just as filling one tooth does not guarantee that other teeth will remain healthy. When one compartment is replaced, total knee replacement may become necessary later in life.

Good results from unicondylar knee replacement depend largely on patient selection. Patients younger than 55, those who are overweight and those who expect to engage in heavy work or sports are not good candidates for unicondylar knee arthroplasty. However, when good surgical technique is combined with appropriate patient selection, the vast majority of patients-as many as 90 to 98 percent-are still trouble-free 10 years later.

CARL L. NELSON, M.D., is chairman of the Department of Orthopaedic Surgery and director of the Center for Hip and Knee Surgery at UAMS Medical Center.

DEGREE: Indiana University School of Medicine, Indianapolis, Indiana

INTERNSHIP: Rotating - Los Angeles County General Hospital, Los Angeles, California

RESIDENCIES: General Surgery - The Cleveland Clinic Foundation, Cleveland, Ohio

Orthopaedic Surgery - The Cleveland Clinic Foundation, Cleveland, Ohio

FELLOWSHIP: Nuffield Scholar, Nuffield Orthopaedic Centre, Oxford, England

CERTIFICATION: Orthopaedic Surgery

Department of Orthopaedic Surgery 501-296-1400