Robotic-arm-assisted conversion of unicompartmental knee arthroplasty to total knee arthroplasty

The purpose of this study was to describe a novel robotic-arm-assisted UKA to TKA conversion technique and evaluate the patient reported and clinical outcomes in these patients. A retrospective review between 2017 and 2022 was conducted of patients that underwent robotic-arm-assisted UKA to TKA conversion. Charts were reviewed for patient demographics, indications for conversion from UKA to TKA, operative technique, implants used, postoperative complications, and patient-reported outcome measures (PROMs). The surgical technique resembles that of primary TKA, with the major exception of registering the robotic arm with retained UKA implants and removing the implants only when verification is complete. There were 44 robotic-arm-assisted UKAs in 41 patients were included in the study. Indications for UKA conversion to TKA included: 33 patients who had osteoarthritis progression (75%), 7 aseptic loosening (16%), 2 unspecified pain (4.5%), 1 polyethylene wear (2.3%), and 1 prosthetic joint infection (2.3%). Uncemented cruciate-retaining (CR) implants were used in 38 of the 44 robotic-arm-assisted TKAs (86.5%). The other six utilized cemented implants: four CR femurs (9.1%), six tibial baseplates (13.6%), four tibial stems (9.1%), and four medial tibial augments (9.1%). The PROMs significantly improved at 1-year follow-up, with the average KOOS JR score increasing from 48.1 to 68.7 (P < 0.001), and the r-WOMAC score decreasing from 25.7 to 10.6 (P = 0.003). Two patients developed prosthetic joint infections (4.5%), one developed aseptic loosening of the femoral component (2.3%), and one developed a superficial surgical site infection requiring superficial irrigation and debridement (2.3%). Overall survivorship was 93.18% at 1.8 years, and aseptic survivorship was 97.73%. Robotic-arm-assisted UKA to TKA conversion exhibited improved patient-reported outcomes and low revision and complication rates. Improved implant placement achieved with robotic-arm-assistance may improve the functional and clinical outcomes following these surgeries.