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Published on: May 5, 2023
Unicompartmental Knee Arthroplasty for Isolated Compartment Osteonecrosis: A 20-Year Experience
Nils Meissner1, Brett R Bukowski1, Dirk R Larson2
1Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota.
Background:
Osteonecrosis of the knee, whether primary (spontaneous) or secondary, can often necessitate surgical intervention. If advanced osteonecrosis is confined to a single compartment, unicompartmental knee arthroplasty (UKA) is often considered. The purpose of this study was to update and extend our prior series, with specific emphasis on implant survivorship, radiographic results, clinical outcomes, and complications in a concise cohort of UKAs for osteonecrosis.
Methods:
We retrospectively identified 70 consecutive UKAs for osteonecrosis performed at a single tertiary care academic institution from 2002 to 2022. Of these, 64 UKAs (91%) were performed for primary osteonecrosis, and six UKAs (9%) were performed for secondary osteonecrosis. Osteonecrosis was in the medial femoral condyle in 61 UKAs (87%), medial tibial plateau in six UKAs (9%), and lateral femoral condyle in three UKAs (4%). All UKAs were cemented, with 77% utilizing a fixed-bearing design and 23% utilizing a mobile-bearing design. The mean patient age was 66 years, with 59% being women. The mean follow-up was eight years (range, two to 20).
Results:
The 10-year survivorship free of any revision for the entire cohort was 91%. The predominant indication for revision was the development of osteoarthritis in the lateral compartment in three knees. The 10-year survivorship free of any reoperation was 88%. The secondary osteonecrosis was a significant and substantial risk factor for worse survivorship free of any revision (hazard ratio (HR) = 17; P < 0.001) and any reoperation (HR = 14; P = 0.002). There were no implants that were revised for fracture or wear. Knee society function scores improved from a mean of 54 preoperatively to a mean of 75 postoperatively.
Conclusions:
A UKA is a durable and reliable option for primary osteonecrosis at eight years of follow-up. However, when performed for secondary osteonecrosis, it has a substantially higher failure rate, primarily related to the progression of osteonecrosis or development of osteoarthritis in the lateral compartment.
Level Of Evidence:
III, Retrospective Cohort Study.
