Novel approach to reducing discrepancies in radiographic and navigational limb alignments in computer-assisted TKA.

This study was conducted (1) to document discrepancies between preoperative and postoperative radiographic measurements and postregistration and postimplantation intraoperative navigational measurements of coronal limb alignments, and (2) to identify predictors of discrepancies between radiographic and navigational measures. In addition, we propose the use of a novel radiographic measuring method, and we demonstrate that this method reduces discrepancies. For 107 total knee arthroplasties performed using a navigation system, coronal alignment were assessed using preoperative and postoperative whole limb radiographs using the standard and novel radiographic methods. During surgery, coronal limb alignment was measured using the navigation system postregistration and postprosthesis implantation. Strengths of correlations and discrepancies between radiographic and navigational assessments were compared between the standard and novel methods. Multivariate regression was performed to identify predictors of discrepancies. Differences between radiographic and navigational measurements were observed for both preoperative and postoperative assessments, but discrepancies were greater for preoperative assessments, despite their stronger correlations. Extent of preoperative varus deformity was identified as the strongest predictor of discrepancy in preoperative radiographic and navigational measurements, and varus malalignment was identified as the strongest predictor of discrepancy in postoperative measurements. Strengths of correlations between radiographic and navigational measurements were similar for the standard and novel radiographic methods, but discrepancies between the 2 were significantly smaller for the novel method for both preoperative and postoperative assessments. The authors propose the use of the described novel radiographic method that reduces discrepancies between radiographic and navigational measurements.