PT  - JOURNAL ARTICLE
AU  - PROTOPSALTIS, THEMISTOCLES
AU  - TERRAN, JAMIE
AU  - SOROCEANU, ALEX
AU  - MOSES, MICHAEL J.
AU  - BRONSARD, NICOLAS
AU  - SMITH, JUSTIN
AU  - KLINEBERG, ERIC
AU  - MUNDIS, GREGORY
AU  - KIM, HAN JO
AU  - HOSTIN, RICHARD
AU  - Hart, ROBERT
AU  - SHAFFREY, CHRISTOPHER
AU  - BESS, SHAY
AU  - AMES, CHRISTOPHER
AU  - SCHWAB, FRANK
AU  - LAFAGE, VIRGINIE
AU - INTERNATIONAL SPINE STUDY GROUP
TI  - T1 Slope Minus Cervical Lordosis (TS-CL), the Cervical Answer to PI-LL, Defines Cervical Sagittal Deformity in Patients Undergoing Thoracolumbar Osteotomy
AID  - 10.14444/5042
DP  - 2018 Jun 01
TA  - International Journal of Spine Surgery
PG  - 362--370
VI  - 12
IP  - 3
4099  - https://www.ijssurgery.com/content/12/3/362.short
4100  - https://www.ijssurgery.com/content/12/3/362.full
SO  - Int J Spine Surg2018 Jun 01; 12
AB  - Background: Cervical kyphosis and C2-C7 plumb line (CPL) are established descriptors of cervical sagittal deformity (CSD). Reciprocal changes in these parameters have been demonstrated in thoracolumbar deformity correction. The purpose of this study was to investigate the development of CSD, using T1 slope minus cervical lordosis (TS-CL) to define CSD and to correlate TS-CL and a novel global sagittal parameter, cervical-thoracic pelvic angle (CTPA), with CPL. Methods: A multicenter, retrospective analysis of patients with thoracolumbar deformity undergoing three-column osteotomy was performed. Preoperative and postoperative cervical parameters were investigated. Linear regression for postoperative values resulted in a CPL of 4 cm corresponding to a TS-CL threshold of 17°. Patients were classified based on postoperative TS-CL into uncompensated (TS-CL > 17°) or compensated cohorts (TS-CL < 17°); the two were compared using an unpaired t test. Logistic regression modeling was used to determine predictors of postoperative CSD. Results: A total of 223 patients with thoracolumbar deformity (mean age, 57.56 years) were identified. CTPA correlated with CPL (preoperative r = .85, postoperative r = .69). TS-CL correlated with CTPA (preoperative r = .52, postoperative r = .37) and CPL (preoperative r = .52; postoperative r = .37). CSD had greater preoperative CPL (P < .001) and CTPA (P < .001). The compensated cohort had a decrease in TS-CL (from 10.2 to 8.0) with sagittal vertical axis (SVA) correction, whereas the uncompensated had an increase in TS-CL (from 22.3 to 26.8) with all P < .001. Reciprocal change was demonstrated in the compensated group given that CL decreased with SVA correction (r = .39), but there was no such correlation in the uncompensated. Positive predictors of postoperative CSD included baseline TS-CL > 17° (P = .007), longer fusion (P = .033), and baseline CTPA (P = .029).Conclusions: TS-CL and CTPA correlated significantly with established sagittal balance measures. Whereas reciprocal change in cervical and thoracolumbar alignment was demonstrated in the compensated cohort, the uncompensated population had progression of their cervical deformities after three-column osteotomy.Clinical Relevance: The balance between TS-CL mirrors the relationship between pelvic incidence minus lumbar lordosis in defining deformities of their respective spinal regions.