Accuracy of imageless versus roentgenographic image-based robotic total knee arthroplasties: a comparative study

INTRODUCTION: The Robotic Surgical Assistant (ROSA ® ) system (Zimmer Biomet, Warsaw, IN, USA) used in robotic total knee arthroplasties (rTKAs) employs either an image-based or an imageless pathway for surgical planning. While the image-based pathway requires preoperative two-dimensional radiographs, the imageless pathway does not require specific preoperative preparation. We evaluated the radiographic outcomes of ROSA rTKAs with and without preoperative imaging to compare the accuracy of both pathways. METHODS: A retrospective review of registry data was conducted for patients who underwent ROSA rTKAs with and without preoperative imaging at a single tertiary centre between 1 January 2023 and 31 December 2023. Two reviewers independently measured coronal alignment of femoral and tibial implant components relative to the mechanical axis at 3 months postoperatively. These angles were compared to planned intraoperative femoral and tibial cuts to assess for variations. RESULTS: A total of 97 patients were included: 35 in the image-based pathway and 62 in the imageless pathway. The imageless group showed greater variation in tibial component alignment compared to the image-based group (-0.8° ± 0.1° vs. -0.3° ± 0.1°, P < 0.001). No significant difference was found in femoral component alignment between the two groups (-0.1° ± 0.8° vs. -0.2° ± 1.3°, P = 0.546). CONCLUSION: Preoperative imaging provides greater component alignment accuracy in ROSA rTKAs. Although the difference is small, its potential clinical impact warrants further investigation. Preoperative imaging should therefore be strongly considered to enhance alignment accuracy in ROSA rTKAs.