JAAOS - 2026-09-10 - Journal Article
Preoperative Frailty Correlates With Progression of Lateral Compartment Osteoarthritis After Medial Unicompartmental Knee Arthroplasty: A Mean 70-month Follow-up Study.
Wang Z, Du M, Li Z, An S, Cao G, Huang Y
Topics
Key Takeaway
Preoperative frailty (CFS >3) independently predicted lateral compartment OA progression after Oxford Phase III mUKA with an OR of 4.36 (95% CI 1.37–13.90) at mean 70-month follow-up.
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Summary
This study asked whether preoperative frailty, assessed by the Clinical Frailty Scale, predicts lateral compartment OA progression (LOP) after Oxford Phase III mobile-bearing mUKA, excluding cases with coronal overcorrection or lateral meniscal extrusion to isolate biological from mechanical confounders. Among 203 knees, LOP occurred in 41.7% of frail versus 11.8% of robust knees (P=0.001), with frailty independently predicting LOP on multivariable analysis (OR 4.36). Frail patients also had significantly lower final OKS (39.39 vs 43.06), FJS (79.56 vs 89.40), and Kujala scores, with smaller functional gains across all metrics.
Key Limitation
Radiographic follow-up was available in fewer than half the cohort (48.8%), which limits the reliability of the LOP incidence estimate and may have introduced selection bias if loss to radiographic follow-up was non-random with respect to frailty status.
Original Abstract
PURPOSE
Lateral compartment osteoarthritis progression (LOP) is a major cause of mid to long-term failure after medial unicompartmental knee arthroplasty (mUKA). This study investigated whether preoperative frailty predicts LOP after mUKA over a mean 70-month follow-up.
METHODS
We retrospectively identified consecutive patients who underwent Oxford Phase III mobile-bearing mUKA between March 2016 and December 2020. Preoperative frailty was assessed with the Clinical Frailty Scale (CFS), and patients were classified as robust (Clinical Frailty Scale ≤ 3) or frail (CFS > 3). To minimize mechanical confounding, cases with postoperative coronal overcorrection and those with preoperative lateral meniscal extrusion on MRI were excluded. Outcomes included hip-knee-ankle angle, lateral compartment Kellgren-Lawrence (K/L) grade, Oxford Knee Score, Forgotten Joint Score, Kujala score, perioperative complications, and revision or conversion to total knee arthroplasty. Univariate and multivariable logistic regression identified risk factors of LOP.
RESULTS
A total of 203 knees (101 robust; 102 frail) from 177 patients were analyzed (mean follow-up, 70.8 months). Baseline characteristics were comparable except for age. At the final follow-up, the frail group had lower OKS (39.39 vs 43.06; P < 0.001), FJS (79.56 vs 89.40; P < 0.001), and Kujala scores (59.88 vs 67.71; P < 0.001), and a smaller OKS gain (13.47 vs 18.72; P < 0.001). Five-year standing radiographs were available for 99 of 203 knees (48.8%): 26 of 99 (26.3%) showed a 1-grade increase in lateral K/L, while 73 of 99 (73.7%) remained unchanged. LOP was more frequent in frail versus robust knees (41.7% vs 11.8%; P = 0.001). On multivariable analysis, frailty independently predicted LOP (OR = 4.36; 95% CI, 1.37-13.90; P = 0.013). LOP increased across higher CFS strata within the frail subgroup (P = 0.043).
CONCLUSION
Preoperative frailty is common and independently associated with a higher midterm risk of lateral compartment progression after mUKA, with risk escalating at higher frailty levels. CFS-based stratification provides a practical adjunct for preoperative counseling, expectation setting, and perioperative planning in candidates for mUKA.