Robotic-assisted TKA Reduces Postoperative Alignment Outliers and Improves Gap Balance Compared to Conventional TKA

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Several studies have shown mechanical alignment influences the outcome of TKA. Robotic systems have been developed to improve the precision and accuracy of achieving component position and mechanical alignment.


We determined whether robotic-assisted implantation for TKA (1) improved clinical outcome; (2) improved mechanical axis alignment and implant inclination in the coronal and sagittal planes; (3) improved the balance (flexion and extension gaps); and (4) reduced complications, postoperative drainage, and operative time when compared to conventionally implanted TKA over an intermediate-term (minimum 3-year) followup period.


We prospectively randomized 100 patients who underwent unilateral TKA into one of two groups: 50 using a robotic-assisted procedure and 50 using conventional manual techniques. Outcome variables considered were postoperative ROM, WOMAC scores, Hospital for Special Surgery (HSS) knee scores, mechanical axis alignment, flexion/extension gap balance, complications, postoperative drainage, and operative time. Minimum followup was 41 months (mean, 65 months; range, 41-81 months).


There were no differences in postoperative ROM, WOMAC scores, and HSS knee scores. The robotic-assisted group resulted in no mechanical axis outliers (> ± 3° from neutral) compared to 24% in the conventional group. There were fewer robotic-assisted knees where the flexion gap exceeded the extension gap by 2 mm. The robotic-assisted procedures took an average of 25 minutes longer than the conventional procedures but had less postoperative blood drainage. There were no differences in complications between groups.


Robotic-assisted TKA appears to reduce the number of mechanical axis alignment outliers and improve the ability to achieve flexion-extension gap balance, without any differences in clinical scores or complications when compared to conventional manual techniques.

Level of Evidence

Level I, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

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