Friday, September 28, 2018 4:05 PM–5:05 PM abstracts: cervical myelopathy and deformity: 258. The C5-T3 angle: a novel parameter of the cervicothoracic junction

Abstract

BACKGROUND CONTEXT Unlike the thoracolumbar junction (TLJ) angle which is well-defined as T10 – L2, there is no consensus on how to define the CTJ angle. The CTJ consists of mobile lower cervical and rigid upper thoracic spinal segments, giving it unique anatomical and biomechanical characteristics. To our knowledge, this is the first study attempting to define a new parameter for assessing the cervicothoracic junction. PURPOSE Attempting to define a new parameter for assessing the cervicothoracic junction. STUDY DESIGN/SETTING Retrospective Analysis of a Prospective Database. PATIENT SAMPLE Adult spinal deformity patients operated on between the years 2008 and 2016 were included in the analysis. We excluded patients with history of cervical spinal fusion or an upper instrumented vertebra higher than T5. OUTCOME MEASURES The criteria for an ideal CTJ angle would be: constant, significantly correlated with sagittal parameters, and involving maximum number of levels. METHODS This is a retrospective analysis of a prospective surgical database. ASD patients operated on between the years 2008 and 2016 were included in the analysis.We excluded patients with history of cervical spinal fusion or an upper-most instrumented vertebra higher than T5. The criteria for an ideal CTJ angle would be: longitudinally constant, cross-sectionally correlates with other parameters and involves the maximum number of levels. A combination of 12 angles between C5 and T4 were analyzed. The variation in each angle's value over time (preoperative, 6 weeks and 2 years) was assessed using ANOVA. Pearson correlation analysis was performed between the most constant candidate parameters and: demographic data, preoperative sagittal spinopelvic parameters and the amount of correction at 2 years. RESULTS A total of 427 patients (mean age 59.9, 74% women) met our inclusion criteria and were included in the analysis.Seven of 12 CTJ angles; C5-T1, C5-T2, C5-T3, C6-T1, C6-T2, C7-T1 and C7-T2 were constant between preoperative, PO6W and PO2Y measurements (p>.05). All the seven candidate angles showed significant correlation with age and preoperative sagittal angles including pelvic tilt (PT), lumbar lordosis (LL; L1–S1), TLJ angle (T10–L2), thoracic kyphosis (TK, T4–T12), cervical lordosis (CL; C2–C7), pelvic incidence (PI) minus LL, T1 slope (TS) minus CL, T1 pelvic angle (T1PA), sagittal vertical axis (SVA) C2-7 and C7-S1 (p CONCLUSIONS Based on the present study, the C5-T3 angle is the ideal parameter to assess the CTJ, given its constant value over time, involvement of maximal number of segments as well as an appropriate correlation with other major spinal sagittal parameters. Further studies assessing its implications on clinical outcomes may be warranted.