Imageless robotic-assisted total knee arthroplasty accurately restores the radiological alignment with a short learning curve: a randomized controlled trial

The study compared a novel imageless robotic-assisted total knee arthroplasty (RATKA) and conventional TKA by considering (1) radiological outcomes, (2) outliers of radiological outcomes, and (3) learning curve. This prospective randomized controlled study performed by a single surgeon evaluated 152 patients (152 knees): 75 patients undergoing RATKA and 77 patients undergoing conventional TKA. Mechanical alignment, radiological implant positioning, and outliers were analyzed for radiological outcomes. Cumulative summation (CUSUM) analysis was used to assess the learning curve for operative time in RATKA. The RATKA had significantly better accuracy of knee alignment and component positioning than conventional TKA. The hip-knee-ankle axis and implant position outliers were significantly lower in the RATKA, with 94.7% of patients had achieved an overall mechanical alignment within 3° of a neutral mechanical axis. Changes in posterior condylar offset and joint line were significantly lower in the RATKA. A learning curve of seven cases for operative time was obtained for the RATKA. The imageless RATKA has better alignment accuracy with a short learning curve; thus, it presents an attractive option for TKA.