Predictors of incidental durotomy in patient undergoing pedicle subtraction osteotomy for correction of adult spinal deformity

Introduction: Pedicle subtraction osteotomy (PSO) is a powerful tool for sagittal plane correction in rigid adult spinal deformity; however, it is invasive and associated with increased risk of durotomy. The objective of the present study was to identify intraoperative techniques and baseline patient factors capable of predicting intraoperative durotomy.

Methods: A tri-institutional database was retrospectively queried for all patients who underwent PSO for ASD. Data on baseline comorbidities, surgical history, surgeon characteristics and intraoperative maneuvers were gathered. PSO aggressiveness was defined as conventional (Schwab 3 PSO) or an extended PSO (Schwab type 4). Primary outcome of the study was the occurrence of durotomy intraoperatively. Univariable analyses were performed with Mann-Whitney U tests, chi-square analyses, and Fisher exact tests. Statistical significance was defined by p< 0.05.

Results: One hundred sixteen patients were identified (mean age 61.9±12.6; 44.8% male), of whom 51 (44.0%) experienced intraoperative durotomy. There were no significant differences in baseline comorbidities between those who did and did not experience durotomy, with the exception that baseline weight and body mass index were higher in patients who did not suffer durotomy. Having undergone prior surgery (OR 2.73; 95% CI [1.13, 6.58]; p=0.03) and, more specifically having previously undergone decompression at the PSO level (OR 4.23; 95%CI [1.92, 9.34]; p< 0.001) were predictive of durotomy. Comparison of surgeon training showed no statistically significant difference in durotomy rate between fellowship and non-fellowship trained surgeons, or between orthopaedic and neurosurgeons. PSO level, PSO aggressiveness, the presence of stenosis at the level of the PSO, nor the surgical instrument used predicted odds of durotomy occurrence. Those experiencing durotomy had a non-significantly longer average stay, but experienced similar rates of reoperation and nonroutine discharge.

Conclusion : In this large multisite series, a history of prior decompression at the PSO level was associated with a four-fold increase in intraoperative durotomy risk. Extended [versus] standard PSO, surgical technique, nor baseline patient characteristics predicted durotomy. Durotomies occurred at a nontrivial rate and may prolong operative times. Additional prospective investigation is merited.