Related Experiment Video
Updated: Sep 21, 2025
Three-Dimensional Preoperative Virtual Planning in Derotational Proximal Femoral Osteotomy
Published on: February 17, 2023
The deformity angular ratio: can three-dimensional computed tomography improve prediction of intraoperative
Varun Puvanesarajah1, Gerard F Marciano2, Fthimnir M Hassan2
1The Daniel and Jane Och Spine Hospital, New York Presbyterian, Columbia University Medical Center, 5141 Broadway, New York, NY, 10034, USA. vp2452@cumc.columbia.edu.
Purpose:
Assess whether a novel deformity angular ratio (DAR) calculated using preoperative three-dimensional computed tomography (3D CT) is more accurate than total DAR (T-DAR) radiographic measurements at predicting intraoperative neuromonitoring (IONM) events during vertebral column resection (VCR).
Methods:
Consecutive, unique patients undergoing thoracic VCR by a single surgeon from 2015 to 2021 were identified. The T-DAR was calculated by dividing the total radiographic Cobb angle by the number of vertebral segments the angle subtends. 3D CT DAR was calculated for each patient from a preoperative CT scan by finding the maximum angle subtended by three contiguous vertebral segments. All patients were assessed for IONM events. A binary threshold of 25 was used for T-DAR and 3D CT DAR measurements for predictive analysis. p < 0.05 indicated significance.
Results:
In total, 68 patients were identified. Mean age was 28 years. Mean levels fused was 15. Twenty-one patients (31%) had IONM events. In patients, with and without an IONM event, mean T-DAR was 26.6 ± 9.8 and 21.5 ± 8.8 (p = 0.04), respectively. 3D CT DAR mean values were 26.4 ± 10.8 and 18.4 ± 5.6, respectively (p < 0.001). 3D CT DAR accurately classified 81% of patients with a positive predictive value (PPV) of 75%. In comparison, T-DAR accurately classified 60% of patients with a PPV of 39%.
Conclusion:
3D CT substantially improves preoperative IONM event prediction when compared to traditional radiographic measurements. A 3D CT DAR of 25 or greater was correlated with an increased rate of IONM events. 3D CT reconstructions are a useful adjunct for planning prior to a VCR.
