JOA - 2026-03-11 - Journal Article
Patients Who Have a Preoperative Flexion Contracture Demonstrate Inferior Outcomes Following Unicompartmental Knee Arthroplasty Compared to Total Knee Arthroplasty.
Acuña AJ, Potluri AS, Yadav AS, Forlenza EM, Alfonsi S, Della Valle CJ
Topics
Key Takeaway
UKA patients with preoperative flexion contracture ≥10° had a 10.9% revision rate versus 0% in matched TKA and UKA controls, with 3.6° less contracture correction and inferior final KSS objective scores (88.5 vs. 94.9).
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Summary
This study asked whether UKA patients with preoperative flexion contracture ≥10° have inferior outcomes compared to matched TKA patients with contracture and UKA patients without contracture. Using 1:1 matching on age, sex, BMI, smoking, CCI, and diabetes, 46 patients per cohort were analyzed for ROM, KSS, and revision rates. UKA-contracture patients achieved less contracture correction (8.4° vs. 12.0°, P<0.001), lower final KSS objective scores (88.5 vs. 94.9, P=0.004), and a 10.9% revision rate versus 0% in both control groups.
Key Limitation
Retrospective design with a minimum 2-year follow-up does not capture late revisions, and the study does not report mean follow-up duration, making durability conclusions uncertain.
Original Abstract
INTRODUCTION
The traditional criteria for unicompartmental knee arthroplasty (UKA) excluded patients who have a flexion contracture greater than 5˚. However, the outcomes of patients undergoing UKA who have a flexion contracture remain poorly studied.
METHODS
Patients undergoing primary UKA and total knee arthroplasty (TKA) between 2010 and 2022 who had a minimum of 2-year follow-up were retrospectively identified. Patients undergoing UKA who had a flexion contracture ≥ 10° were matched in a 1:1 manner based on age, sex, body mass index, smoking status, Charlson Comorbidity Index (CCI), and diabetes prevalence to two cohorts: TKA patients who had a flexion contracture ≥ 10° (TKA controls) and UKA patients, who did not have a flexion contracture (UKA controls). Changes in range of motion (ROM) as well as Knee Society Score (KSS) were compared. A total of 138 patients were included in the final analysis (n = 46 per cohort).
RESULTS
There were comparable changes in ROM and KSS values for UKA patients who had a flexion contracture and UKA controls. Patients undergoing UKA who had a flexion contracture had a smaller change in their contracture postoperatively relative to TKA controls (8.4 versus 12.0˚; P < 0.001). Despite similar preoperative KSS scores, patients undergoing UKA who had a flexion contracture had lower KSS objective scores at final follow-up relative to TKA controls (88.5 versus 94.9; P = 0.004). The UKA patients who had a flexion contracture were more likely to undergo revision relative to both TKA and UKA controls (10.9 versus 0 versus 0%, respectively; P = 0.02). Revisions in the UKA flexion contracture cohort included two for unexplained pain, two for aseptic loosening, and one for infection.
CONCLUSION
Patients undergoing UKA who had a flexion contracture experienced significantly less improvement in their flexion contracture, inferior patient-reported outcomes, and higher revision rates relative to matched TKA controls. These findings support the historical contraindication for performing UKA procedures in this patient population.