JOA - 2026-09-14 - Journal Article
Patient-Reported Outcomes Following Custom Unicompartmental Knee Arthroplasty.
Mannina C, Ilyas MH, Kang H, Freeman I, Sampson WT, Kwon YM
Topics
Key Takeaway
Custom UKA carried a 2-year revision rate of 8.9% versus 3.8% for OTS implants (P=0.010), driven by a 6-fold higher aseptic loosening rate (4.8% vs 0.8%, P=0.006), with no PROM advantage.
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Summary
This single-institution retrospective cohort compared PROMs and revision rates between custom and OTS medial UKA at minimum 2-year follow-up. Custom and OTS cohorts showed equivalent absolute PROMIS Global Physical, PROMIS Global Mental, PROMIS PF SF-10a, and KOOS-PS scores, delta scores, and MCID achievement rates across all metrics (all P>0.05). Custom UKA had a significantly higher 2-year revision rate (8.9% vs 3.8%, P=0.010), with aseptic loosening as the dominant driver (4.8% vs 0.8%, P=0.006).
Key Limitation
The retrospective design at a single institution cannot exclude selection bias in which patients received custom versus OTS implants, and the 2-year follow-up is insufficient to determine whether the loosening gap widens or narrows with longer observation.
Original Abstract
BACKGROUND
Custom unicompartmental knee arthroplasty (UKA) implants were developed to improve component fit and alignment compared to conventional off-the-shelf (OTS) implants. However, evidence supporting the clinical advantage of custom UKA remains limited. This study compared patient-reported outcome measures (PROMs) and complication rates following custom and OTS UKA.
METHODS
A single-institution database was queried for patients who underwent medial UKA. Patients who had at least two years of follow-up and completed pre- and postoperative PROMs were included. A total of 623 patients met inclusion criteria, including 124 who received custom implants and 499 who received OTS implants. The Patient-Reported Outcomes Measurement Information System (PROMIS) Global Physical, PROMIS Global Mental, PROMIS Physical Function Short Form 10-a, and Knee Injury and Osteoarthritis Outcome Score Physical Function Short Forms were extracted. The change in (delta) scores and proportions of minimal clinically important difference (MCID) achievement were evaluated. The 90-day complications and two-year revision rates were also assessed. There were no differences in baseline demographics or comorbidities between cohorts.
RESULTS
Patients who received custom and OTS UKA demonstrated comparable absolute PROM scores, delta scores, and rates of achieving MCID across all metrics (all P > 0.05). At a two-year follow-up, patients who received custom UKA had a higher rate of revision surgery compared to those who received OTS implants (8.9 versus 3.8%, P = 0.010). Revision due to aseptic loosening was more likely following custom UKA (4.8 versus 0.8%, P = 0.006). Other indications for revision, and all other assessed complications, were comparable between cohorts (all P > 0.05).
CONCLUSION
Custom UKA implants were associated with a higher revision rate at a two-year follow-up and demonstrated no advantage over OTS implants in terms of PROMs. These findings suggest that the theoretical advantages of custom UKA may not translate to improved clinically meaningful outcomes compared to OTS UKA.