Robotic-assisted conversion from unicompartmental to tricompartmental knee arthroplasty for progressive osteoarthritis: A case series of 11 patients

Background: The growth in popularity of unicompartmental knee arthroplasty (UKA) has far outpaced that of total knee arthroplasty (TKA). A major challenge with UKA is symptomatic progression of osteoarthritis (OA), which is typically treated with revision to TKA. This study reports the short-term results of an alternative technique: In select patients, we have performed robotically-assisted resurfacing of the remaining compartments using UKA components — a surgery we refer to as tricompartmental knee arthroplasty (tri-UKA). Methods: Between 2020 and 2024, we retrospectively reviewed patients with well-functioning UKA and progressive OA who underwent robotic-assisted conversion to tri-UKA. We reviewed medical records for demographic data, indications for revision, operative details, operative times, implant information, complications, and patient-reported outcome measures (PROMs). Of the 11 patients included, 10 had medial and 1 had lateral UKA. The surgical technique was similar to that of robotic-assisted primary UKA, with some workarounds to address limitations in the robotic software. Results: The mean Forgotten Joint Score at final follow-up was 42.4. All other outcome scores improved from pre-operative to final follow-up: Knee injury and Osteoarthritis Outcome Score for Joint Replacement (61.3 to 73.5, p = 0.021), Patient-Reported Outcomes Measurement Information System Global Health 10-Item Short Form (mental: 46.6 to 51.4, p = 0.026; physical: 49.4 to 52.4, p = 0.13), and Western Ontario and McMaster Universities Osteoarthritis Index (21.2 to 11.3, p = 0.0042). Complications occurred in 5 of 11 patients. Implant survivorship was 100% at mean follow-up of 2.0 years. The mean operative time was 80 minutes. Conclusion: In select patients with a well-functioning UKA and symptomatic progression of aseptic knee arthritis, robotic-assisted conversion to tri-UKA may be a viable alternative to revision TKA.