Closer to Native, Not Clinically Superior: Bi-Unicompartmental versus Total Knee Arthroplasty for Bicompartmental Femoro-Tibial Osteoarthritis, A Randomized Trial.

BACKGROUND: Bi-unicompartmental knee arthroplasty (Bi-UKA) has been proposed as an alternative to cruciate-retaining total knee arthroplasty (CR-TKA) for patients who have bicompartmental femoro-tibial osteoarthritis. However, comparative evidence remains limited. This study compared patient-reported outcomes at 24 months after simultaneous Bi-UKA and CR-TKA.

METHODS: This exploratory randomized clinical trial was conducted at a tertiary center in Tehran, Iran. Patients who had severe bicompartmental femoro-tibial osteoarthritis, clinically and radiographically intact anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL), and absent or minimal patello-femoral involvement were considered eligible. Final eligibility was confirmed intraoperatively before randomization. Eligible patients were randomized in a 1:1 ratio to undergo simultaneous Bi-UKA or CR-TKA. Persian-validated patient-reported outcome measures were assessed at baseline and 24 months. The primary outcome was the Forgotten Joint Score (FJS) at 24 months. Final analyses were performed on a per-protocol, complete-case basis and included 26 patients in the Bi-UKA group and 30 patients in the CR-TKA group.

RESULTS: There was no statistically significant between-group difference observed in the FJS at 24 months (mean difference [Bi-UKA minus CR-TKA], -4.91 points; 95% confidence interval [CI]: -17.92 to 8.09; P = 0.453). There were no statistically significant between-group differences observed in the Western Ontario and McMaster Universities Osteoarthritis Index, Knee Society Score, Oxford Knee Score, or visual analog scale pain score. A sensitivity analysis using a linear mixed-effects model yielded findings consistent with the primary analysis. There were no major postoperative complications, reoperations, or revisions documented in either group during the 24-month follow-up.

CONCLUSION: In this exploratory trial of carefully selected patients who had severe bicompartmental femoro-tibial osteoarthritis, intact ACL and PCL, and absent or minimal patello-femoral involvement, simultaneous Bi-UKA did not demonstrate superior patient-reported outcomes compared with CR-TKA at 24 months. Follow-up beyond 24 months is required to characterize implant durability, revision risk, and survivorship after both procedures.