Sagittal component alignment is less reliable than coronal component alignment in a Chinese population undergoing navigated TKA

Background: The purpose of our study was to determine whether postoperative sagittal component alignments of primary total knee arthroplasty (TKA) using the conventional and navigated technique differed significantly. Additionally, we determined whether the use of navigation systems resulted in hyperextension of the femoral components in Chinese patients. Methods: This retrospective study reviewed 36 consecutive patients (72 knees) who underwent simultaneous bilateral primary TKAs at our hospital from February 2011 to March 2012. One knee was replaced using a computer-assisted navigation system, and the contralateral knee was replaced with the conventional technique. The radiographic and clinical results of both groups were compared. The relationship between preoperative anatomic angles and component alignments in conventional TKA and navigated TKA was examined. Results: The radiographic results showed statistically significant differences only between the navigated and conventional groups for individual femoral coronal and sagittal component alignment. Femoral sagittal component alignment showed less deviation and tended to have hyperextension using the navigated technique (-0.35 degrees) compared with the conventional technique (2.77 degrees). There was no significant difference observed for the Knee Society Score (KSS) between the two groups at 2 years postoperatively. Conclusions: The sagittal component alignment of primary TKA obtained using the conventional and navigated techniques differed significantly. Navigated TKAs resulted in a higher risk of hyperextension of the femoral components in Chinese patients.