The Overlooked Intraoperative Image: Radiographic Analysis of Intraoperative Multilevel Posterior Column Osteotomies for Precision Spinal Deformity Correction

Introduction: Adult spinal deformity (ASD) surgery reconstructs spinal alignment via a series of operative maneuvers. Multi-level posterior column osteotomies (mPCOs) sum correction across levels, building gradual, but significant alignment changes. Intraoperative scoliosis films assessing post-mPCO alignment could provide a unique image of spinal flexibility prior to prebent-rod implantation and/or additional maneuvers to achieve target alignment goals. To what degree lumbar lordosis (LL) changes from pre-operative standing/supine films to intraoperative post-mPCOs is not well described.

Methods: Patients were prospectively consented into an IRB approved study if fulfilling the following criteria: >18 years old, ASD diagnosis, >6 level fusion planned, LIV >L4, and 3+ PCOs. All patients received a pre-op (1) standing and (2) supine film, intraoperative (3) post-osteotomy and (4) standing 6 week post-operative clinic film. Predictive analytic targets for lumbar lordosis (LL) was recorded. Radiographic global and spinopelvic alignment were measured at each time point. Lumbar lordosis was statistically compared across x-rays using a paired student t-test. Factors impacting intraoperative rod lumbar lordosis were evaluating in a multivariable logistic regression, including pre-operative supine LL, post-mPCO LL, and mPCO number.

Results: 15 patients were included The average age was 66.2 ± 13.0; 8 were female (8/15, 53.3%). Average BMI was 25.5 ± 5.0 kg/m2. Five cases were revisions (5/15, 33.3%); 8.5 ± 2.9 levels were fused per patient. The most common UIV and LIV were T10 and S2AI, respectively (11/15, 73.3%; 14/15, 93.3%). Pre-op standing and supine LL were -26.1 ± 19.3° and -27.7 ± 13.9°, respectively. The average number of PCOs was 4.0 ± 1.8. Post-osteotomy LL was greater than pre-op standing (-12.8°, 95% CI –[17.4 - 7.2°], p < 0.05) and supine LL (-13.9°, 95% CI –[21.9 – 5.9°], p < 0.05). There was moderate correlation between supine LL and post-osteotomy when controlling for PCO number (r2 = 0.56 p < 0.05). There was strong correlation between post-op LL and post-osteotomy LL but not pre supine, standing, or planned LL (model r2 = 0.86, p < 0.05).

Conclusion : Post-mPCOs lumbar lordosis is a unique measurement in deformity correction that better approximates final alignment than pre or planned measurements.