Novel Approach to Reducing Discrepancies in Radiographic and Navigational Limb Alignments in Computer-Assisted TKA

Abstract

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.

Imageless Navigation System Does Not Improve Component Rotational Alignment in Total Knee Arthroplasty

“…In addition, the dis-crepancies between radiographic and navigation measurements may have resulted from differences in weight-bearing status and presence of knee deformities [102,104,105]. Postoperative full-length radiographic measurements have inherent limitations [102][103][104][105][106], which we believe affected our results substantially.…”

Femoral Lateral Bowing and Varus Condylar Orientation Are Prevalent and Affect Axial Alignment of TKA in Koreans

“…Navigated procedures were performed as recommended by the manufacturer [18]. Briefly, after tracking devices were placed, kinematic and anatomical registrations were performed, and the accuracy of registration was confirmed using preoperative radiographic measurements [7]. Bone resections started with the tibia; neutral coronal alignment and a posterior slope of 0°to 1°were targeted, and the level of bone resection was aimed for 9 to 10 mm at the intact plateau, typically the lateral tibial plateau.…”

Femur Positioning in Navigated Total Knee Arthroplasty

“…The radiographic evaluation of postoperative limb alignment is difficult due to flexion or rotational failure. 18,19 This can lead to a significant measurement failure toward varus or valgus if unrecognized.…”

“…14,34,35 One limitation of this study is the sensitivity of the whole-leg standing radiographs. 18,19 Particularly, rotational errors can falsify the measurements for the femur and the tibia. The used implant requires 0° of slope at the tibial bone cut, so rotational errors should not influence the measurement of tibial component alignment.…”