Assistant Professor of Neurosurgery Washington University School of Medicine St. Louis, Missouri, United States
Disclosure(s):
Jamshaid M. Mir, MD: No financial relationships to disclose
Introduction: TD represents a distinct radiographic complexity that may develop solitarily or in conjunction with PJK following ASD surgery. Few studies have examined the occurrence of TD following ASD corrective surgery.
Methods: ASD patients with complete baseline (BL) and two-year (2Y) follow-up were included. Patients were divided into groups: those who developed TD: T4-T12 >54.2° (+1SD from the mean of a previously published value by Lafage et al.), and those who developed PJK (PJK). Further analysis assessed outcomes among patients with both TD and PJK (TDPJK). Thoracic compensation was defined as expected pre-op thoracic kyphosis minus BL thoracic kyphosis. Means comparison tests and regression analysis assessed differences between patient groups.
Results: 373 patients met inclusion. Patient breakdown by outcome was: TD (N=31), PJK (N=223), and TDPJK (N=119). Age, gender, and ASD-mFI were similar between TD and PJK. TD were more likely to be osteoporotic than PJK, p < .05. Procedures on TD were less invasive and utilized a shorter construct (9.3 vs 11.5 levels), both p < .05. TD had significantly greater cervical lordosis, thoracic kyphosis, and lumbar lordosis than PJK patients at BL and 2Y follow-up, all p < .05. Thoracic compensation was an independent predictor of TD versus PJK controlling for age, ASD-mFI, and invasiveness (OR 1.07 [CI 1.04-1.09], p < .001). TDPJK had the highest complication rate (84.9%), significantly greater than PJK (70.9%), and TD (61.3%), both p < .05. PJK patients were 78.7% less likely to develop PJF than TDPJK patients (OR .213 [CI .101-.453], p < .001).
Conclusion : Patients who developed thoracic decompensation were more likely to present with osteoporosis, and underwent less invasive procedures with lower levels fused than patients with proximal junctional kyphosis. Thoracic compensation was predictive of postoperative thoracic decompensation in adult spinal deformity correction. Patients who developed both complexities had the highest rate of complications and greater odds of junctional failure than proximal junctional kyphosis patients.
