Robotic arm-assisted bi-unicompartmental knee arthroplasty compared with conventional total knee arthroplasty : five-year clinical outcomes of a randomized controlled trial

The aim of this study was to compare the outcomes between constitutionally aligned, robotic arm-assisted bi-unicompartmental knee arthroplasty (RA-bi-UKA) and conventional, mechanically aligned total knee arthroplasty (TKA) at five years' follow-up. The results at one-year follow-up have previously been reported. This was a prospective, randomized, single-centre study comparing the clinical outcomes of RA-bi-UKA with conventional TKA in patients with medial and lateral osteoarthritis (OA) of the knee. A total of 80 patients were initially randomized to receive either a cemented, fixed-bearing RA-bi-UKA or a cemented, posterior-stabilized, mechanically aligned TKA using conventional instrumentation over a three-year recruitment period. The data which were collected included patient-reported outcome measures (PROMs) and complications. The patients were reviewed at three months, one, two, and five years. After randomization, 80 patients were enrolled in the study (42 in the RA-bi-UKA group and 38 in the TKA group). At five-year follow-up, there were no significant differences between the PROMs including the Oxford Knee Score, Forgotten Joint Score, EuroQol five-dimension three-level questionnaire (EQ-5D-3L), University of California, Los Angeles (UCLA), New Knee Society Score, and Pain or Stiffness visual analogue scale scores, in the two groups. There were significant improvements in all outcomes in both groups. Both groups had simliar complication and adverse event profiles and there were no differences in re-intervention or revision rates. The outcomes from patients with advanced medial and lateral OA of the knee who were treated with constitutionally aligned, RA-bi-UKA were not significantly different from those who were treated with TKA, with similar outcomes and complication rates at mid-term follow-up. Although the specific indications for bi-UKA remain inconclusive, the technique offers a viable alternative to TKA.