Patients Have Acceptable Patient-Reported Outcome Measures After Medial Unicompartmental Knee Arthroplasty Regardless of Age

BACKGROUND: Contemporary evidence-based indications no longer consider age regarding eligibility for medial unicompartmental knee arthroplasty (mUKA). This has led to more surgical candidates; however, whether patients still have satisfactory outcomes lacks evidence. This study examined the association between age and change in patient-reported outcome measures after mUKA as well as the achievement of patient acceptable symptom state (PASS) and minimal important change (MIC).

METHODS: We included 782 mUKAs performed between February 1, 2016, and April 26, 2023. The mean change from preoperative Oxford knee score (OKS), forgotten joint score (FJS), and activity and participation questionnaire (APQ) was assessed at 3, 12, and 24 months after surgery, respectively. The achievement of 12-month PASS (OKS ≥ 30) and MIC (changes in OKS ≥ 8; FJS ≥ 14) was also assessed. Patients were divided into the following age groups: <55, 55 to < 65, 65 to < 75 years (reference group), and ≥ 75 years. There were 432 women (55%), and patients had a mean age of 67 years (range, 29 to 93) and a mean body mass index of 30 (range, 20 to 53).

RESULTS: Median OKS, youngest to eldest, were 34, 35, 36, and 35 (3 months); 40, 39, 41, and 43 (12 months); 42, 41, 43, and 42 (24 months), respectively. We found no differences in change in OKS between groups. Patients aged 55 to < 65 years had lower changes in FJS at 24 months and APQ at 12 and 24 months. Patients ≥ 75 years had lower 24-month changes in APQ. We found no association between age and the fraction achieving either PASS or MIC (youngest to eldest, 90, 90, 94, and 95%).

CONCLUSIONS: We found good patient-reported outcome measures improvements and satisfactory outcomes after mUKA in all age groups; however, patients aged 55 to < 65 years had worse changes in FJS and APQ. Results support contemporary indications for mUKA, and applying an age cutoff is unwarranted.