Lumbar lordosis is signficantly greater on intraoperative prone X-ray than on preoperative standing or supine images: a retrospetive study of lordosis measurement from the United States.

Abstract

A retrospective cohort study. We aimed to compare intraoperative prone X-ray (IPXray) lumbar lordosis (LL) measurements with preoperative standing lateral X-rays (SLXray) and computed tomography (CT)/magnetic resonance imaging (MRI) and to assess the value of these preoperative imaging measurements in predicting the required lordosis correction for multilevel posterior spinal fusion. Attaining sagittal alignment is critical in multilevel thoracolumbar fusion. The optimal preoperative imaging technique for accurately planning the required intraoperative sagittal correction and how those preoperative measures change with various degrees of spinal deformity remain unelucidated. A retrospective review of multilevel posterior fusion surgeries involving thoracolumbar arthrodesis of ≥4 fusion segments was conducted. After positioning under anesthesia, LL was measured and compared between IPXray and SLXray or CT/MRI using paired <italic>t</italic>-test. Lordosis difference (LD) was calculated as LL on IPXray minus LL on SLXray (Standing LD) or CT/MRI (Supine LD). The association between pelvic incidence (PI)-LL mismatch and different LL measures was analyzed by Pearson coefficient and multivariate logistic regression. Average LL was significantly greater on IPXray than on SLXray (p<0.001) or CT/MRI (p<0.001) but not significantly different in LD when comparing SLXray versus CT/MRI (p=0.730). Standing LD and Supine LD were similar (p=0.600). Patients with greater amounts of preoperative PI-LL mismatch had significantly increased LD (X-ray: R2=0.180, p≤0.001; CT: R2=0.019, p<0.04). Additionally, Standing LD became significantly greater than Supine LD with PI-LL mismatch of >20°. Approximately 10° of additional LD is generated by prone positioning under anesthesia, compared with standing or supine preoperative imaging. Among patients with greater sagittal imbalance, the increased LD suggested they can achieve more correction through positioning. These values should be considered when estimating the amount of lordosis needed to achieve sagittal alignment through surgical maneuvers.