Upper-thoracic versus lower-thoracic upper instrumented vertebra in adult spinal deformity patients undergoing fusion to the pelvis: surgical decision-making and patient outcomes

J Neurosurg Spine. 2019 Dec 20;1-7. doi: 10.3171/2019.9.SPINE19557. Online ahead of print.

Abstract

Objective: Optimal patient selection for upper-thoracic (UT) versus lower-thoracic (LT) fusion during adult spinal deformity (ASD) correction is challenging. Radiographic and clinical outcomes following UT versus LT fusion remain incompletely understood. The purposes of this study were: 1) to evaluate demographic, radiographic, and surgical characteristics associated with choice of UT versus LT fusion endpoint; and 2) to evaluate differences in radiographic, clinical, and health-related quality of life (HRQOL) outcomes following UT versus LT fusion for ASD.

Methods: Retrospective review of a prospectively collected multicenter ASD database was performed. Patients with ASD who underwent fusion from the sacrum/ilium to the LT (T9-L1) or UT (T1-6) spine were compared for demographic, radiographic, and surgical characteristics. Outcomes including proximal junctional kyphosis (PJK), reoperation, rod fracture, pseudarthrosis, overall complications, 2-year change in alignment parameters, and 2-year HRQOL metrics (Lumbar Stiffness Disability Index, Scoliosis Research Society-22r questionnaire, Oswestry Disability Index) were compared after controlling for confounding factors via multivariate analysis.

Results: Three hundred three patients (169 LT, 134 UT) were evaluated. Independent predictors of UT fusion included greater thoracic kyphosis (odds ratio [OR] 0.97 per degree, p = 0.0098), greater coronal Cobb angle (OR 1.06 per degree, p < 0.0001), and performance of a 3-column osteotomy (3-CO; OR 2.39, p = 0.0351). While associated with longer operative times (ratio 1.13, p < 0.0001) and greater estimated blood loss (ratio 1.31, p = 0.0018), UT fusions resulted in greater sagittal vertical axis improvement (-59.5 vs -41.0 mm, p = 0.0035) and lower PJK rates (OR 0.49, p = 0.0457). No significant differences in postoperative HRQOL measures, reoperation, or overall complication rates were detected between groups (all p > 0.1).

Conclusions: Greater deformity and need for 3-CO increased the likelihood of UT fusion. Despite longer operative times and greater blood loss, UT fusions resulted in better sagittal correction and lower 2-year PJK rates following surgery for ASD. While continued surveillance is necessary, this information may inform patient counseling and surgical decision-making.

Keywords: 3-CO = 3-column osteotomy; ASA = American Society of Anesthesiologists; ASD = adult spinal deformity; CCI = Charlson Comorbidity Index; EBL = estimated blood loss; HRQOL = health-related quality of life; ISSG = International Spine Study Group; LL = lumbar lordosis; LSDI = Lumbar Stiffness Disability Index; LT = lower thoracic; ODI = Oswestry Disability Index; OR = odds ratio; PI = pelvic incidence; PJA = proximal junction angle; PJF = proximal junctional failure; PJK = proximal junctional kyphosis; PT = pelvic tilt; SRS-22r = Scoliosis Research Society 22-r questionnaire; SVA = sagittal vertical axis; TK = thoracic kyphosis; UIV = upper instrumented vertebra; UT = upper thoracic; adult spinal deformity; complications; lower thoracic; outcomes; proximal junctional kyphosis; scoliosis; upper instrumented vertebra; upper thoracic.