Unicompartmental Knee Arthroplasty Viable Option for Patients with Osteonecrosis in One CompartmentOsteonecrosis (death of bone tissue) of the knee often requires management by a knee arthroplasty, or replacement. Spontaneous osteonecrosis usually occurs on in one compartment or section of the knee, while secondary osteonecrosis - caused by disease or medical therapy - affects more than one compartment. Spontaneous osteonecrosis usually occurs in patients older than 55 years, while secondary osteonecrosis can occur at any age.
Total knee arthroplasties replace the whole knee, while unicompartmental knee arthroplasties (UKA) only replace a part of the knee. The authors of this study wanted to examine whether UKA was effective in relieving pain and improving knee function for people with spontaneous osteonecrosis, if the lower leg would be aligned properly, and if the UKA is as durable as a total replacement.
To perform the study, researchers reviewed 30 patients, average 71 years (range: 51-88 years), who had 31 knees treated with UKA. Twenty one knees had spontaneous osteonecrosis and 10 had secondary. The researchers used Knee Society scores to evaluate pain and function, and they evaluated lower leg alignment and durability of the implant through imaging tests. All patients were seen before surgery, at 3 months after surgery and then yearly until the last follow up.
The results showed an improvement in knee function by final follow-up assessment. On a scale of 100, the average pre-operative score was 56 for the pain and 50 for function. At the end of the study, the average was 95 for pain and 88 for function. Seventeen patients were enthusiastic about their experience, 11 were satisified, 1 did not notice any change and 1 was dissatified.
When assessing the alignment of the lower leg, the researchers found that 27 of the 31 knees achieved an acceptable alignment. Finally, the 12-year survival rate of the UKA was almost 97 percent.
The authors wrote that there were some drawbacks to the study. They indicated there was no control group, for example. However, they said that by using their selection criteria, they felt that the UKA is a viable option for both spontaneous or secondary osteonecrosis of the knee if it is contained to one section or compartment.
Sebastien Parette, MD et al. Unicompartmental Knee Arthroplasty for Avascular Osteonecrosis. In Clinical Orthopaedics and Related Research. November 2007. Vol. 464. Pp. 37-42.
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