The Combination of Preoperative Bone Marrow Lesions and Partial-Thickness Cartilage Loss Did Not Result in Inferior Outcomes After Medial Unicompartmental Knee Arthroplasty.

BACKGROUND: The purpose of this study is to compare patient-reported outcomes and revision rates between medial unicompartmental knee arthroplasty (UKA) patients based on the presence of medial bone marrow lesions (BMLs) and/or partial- vs full-thickness cartilage loss.

METHODS: BMLs were graded on preoperative magnetic resonance imaging (MRI) findings from 174 UKAs performed between 2009 and 2013 using the MRI Osteoarthritis Knee Score criteria by a single evaluator blinded to the patient's outcome. A second evaluator blinded to the MRI findings and postoperative outcomes assessed medial joint space present on both weight-bearing and valgus stress radiographs. Preoperative and postoperative Knee Society Knee Scores, Pain Scores, and Function Scores were then compared between 4 groups of patients: patients with BML with either partial- or full-thickness cartilage loss, and patients without BML with either partial- or full-thickness cartilage loss.

RESULTS: In total, 152 of 174 (87%) patients had minimum 2-year follow-up. One patient in the no BML/full-thickness loss group was converted to total knee arthroplasty secondary to arthrofibrosis; however, there were no statistical differences in revision rate between the 4 groups as no other revisions were performed (P = .61). Similarly, preoperative and postoperative Knee Society Knee Scores, Pain Scores, and Function Scores did not differ between groups, nor did postoperative University of California, Los Angeles activity scores.

CONCLUSION: Medial tibial BMLs were not associated with inferior outcomes, either in patients with partial- or full-thickness cartilage loss. Although the current results do not allow for the presence of preoperative BML to be considered an indication for UKA, these results definitively support that BMLs are not a contraindication for medial UKA.