Hypercomplex pedicle subtraction osteotomies: definition, early clinical and radiological results and complications

To describe hypercomplex pedicle subtraction osteotomies (HyC-PSO) for adult spine deformity with sagittal imbalance in terms of preoperative, intraoperative and postoperative outcomes and complications.From a prospective single centre database, patients undergoing PSO between January 2016 and May 2017 were reviewed. HyC-PSO were defined as those in patients with one of the following conditions: sagittal correction > 45A degrees needed at a single level or at 1-3 consecutive vertebrae, more than 60A degrees of total sagittal correction needed and PSO on segments of the spine with congenital deformities.22 patients were included, 14 had standard PSO (group A) and 8 had HyC-PSO (group B). Significant correction of lumbar lordosis (LL) and pelvic (PT) was noted in both groups (p < 0.01). Operative time was longer in HyC-PSO, 604 min compared to standard PSO, 478 min. A trend versus greater intraoperative blood loss (3837 vs 2285 ml) and greater intraoperative blood infusion (from cell saver plus homologous, 2306 vs 1280 ml) was recorded in HyC-PSO (ns). Patients in group B received significantly more blood units intra and postoperatively (8.25 vs 4.71 units, p = 0.006). Sagittal correction at the PSO level (54.7A degrees-30A degrees to 85A degrees-vs 26.8A degrees-8A degrees to 39A degrees-, p = 0.000) and total sagittal correction (64.5A degrees-50 to 95A degrees-vs 39.8A degrees-20A degrees to 51A degrees-, p = 0.000) were greater in HyC-PSO. PROMs at the last available follow-up did not show significant differences between groups for any of the outcomes analyzed. Complications were similar in both groups.This is the first report on hypercomplex pedicle subtraction osteotomies. Hypercomplex PSO describes a subset of clinical scenarios with increased surgical effort that can be measured as longer surgical time and greater blood transfusion requirements. Successful correction of misalignment can be achieved in this specific group of patients, and clinical results and complications profile could be similar to standard PSO procedures.