Increased accuracy in component positioning using an image-less robotic arm system in primary total knee arthroplasty: a retrospective study

Background Robotic-assisted total knee arthroplasty (RTKA) and navigated total knee arthroplasty (NTKA) have shown improved knee alignment and reduced radiographic outliers. Recent studies have proven that conventional mechanical alignment may not be the optimal goal for every patient. The aim of this study was to compare the accuracy of the planned implant positioning of a novel image-less robotic technique with an established navigated technique (NTKA).Method The study is a retrospective analysis of prospectively collected data that compared the implant positioning and lower-limb alignment of 86 image-less RTKA with 86 image-less NTKA. Radiographic analysis was performed to evaluate the lower-limb overall alignment, femoral and tibial components positioning in the coronal and sagittal planes. Outliers were evaluated with a cutoff of +/- 3 degrees.Results No difference was noted between the two groups for radiographic outliers within +/- 3 degrees from neutral (p = 0.098). The mean hip-knee-ankle angle deviation from target was 1.3 degrees in the RTKA group compared to 1.9 degrees in the NTKA (p < 0.001). Femoral sagittal deviation (femoral component flexion) was smaller in the RTKA group (0.9 degrees vs 1.9 degrees; p < 0.001). Similarly, tibial coronal deviation (0.8 degrees vs 1.5 degrees; p < 0.001) and tibial sagittal deviation (tibial slope) were smaller in the RTKA group compared to the NTKA group (0.9 degrees vs 1.7 degrees; p < 0.001). Conclusions The RTKA group reported a substantial and significant reduced error from the planned target angles for both tibial and femoral components. No difference in terms of radiographic outliers was noted between navigation and robotic assistance.