142. A prospective multicenter evaluation of the relationship between standing and recumbent spinopelvic alignment in supine, lateral or prone position

BACKGROUND CONTEXT Spinopelvic alignment is important for successful spinal fusion outcomes and is traditionally measured on standing X-rays. There is little data on the change in alignment brought about by intraoperative recumbent positioning, and whether there are differences between supine, lateral and prone positions. PURPOSE To assess changes in spinopelvic alignment between preoperative standing X-rays and intraoperative recumbent imaging in supine, lateral and prone positions. Secondarily, to assess the effect of a Wilson frame on alignment among prone patients. STUDY DESIGN/SETTING Prospective observational multicenter. PATIENT SAMPLE Patients undergoing lumbar spinal fusion surgery. OUTCOME MEASURES Pelvic incidence - lumbar lordosis (PI-LL mismatch); ideal lumbar lordosis - lumbar lordosis (ILL-LL) mismatch in pre- and intraoperative imaging. Methods We performed a prospective multicenter study on lumbar spinal fusion patients. Sagittal parameters (lumbar lordosis [LL] and pelvic incidence [PI]) were measured on preoperative standing and intraoperative recumbent images (supine, lateral or prone). Images were deemed as aligned or malaligned, based on whether LL was within 10° of PI or of ideal LL (ILL), defined by the equation 0.5PI + 28. The prone group was sub-analyzed depending on whether a Wilson frame was used. Results A total of 403 patients (53% female) underwent spinal fusion in the following positions: supine (41), lateral (167) and prone (195). Standing to recumbent LL change (mean, median): supine (4.6, 3.0); lateral (-1.6, 0); prone (-1.2, -1.0). Standing to recumbent PI-LL mismatch change (mean, median): supine (-4.6, -4.0); lateral (1.9, 1.0); prone (-0.7, 0). Standing to recumbent ILL-LL mismatch change (mean, median): supine (-3.6, -2.0); lateral (1.7, 1.0); prone (0.2, 0.5). Using the PI-LL method, proportion of aligned patients (standing vs recumbent): supine (46.3% vs 63.4%, p=0.07); lateral (59.3% vs 59.3%, p=1.0); prone (57.9% vs 63.6%, p=0.17). Using the ILL-LL method, proportion of aligned patients (supine vs recumbent): supine (53.7% vs 65.9%, p=0.10); lateral (58.1% vs 61.1%, p=0.45); prone (59.0% vs 64.6%, p=0.15). In the prone position, Wilson frame significantly worsened PI-LL mismatch (6.8 vs -3.3, p Conclusions Mean change in LL brought about by recumbent positioning is small, whether in supine, lateral or prone position, and the proportion of aligned patients did not significantly change. In the prone position, use of a Wilson frame is associated with significantly worsened sagittal alignment. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.