Objective: In this study, the authors' goal was to develop and validate novel radiographic parameters that better describe total body sagittal alignment (TBSA).
Methods: One hundred sixty-six consecutive operative spinal deformity patients were evaluated using full-body stereoradiographic imaging. Seven TBSA parameters were measured and then correlated to 6 commonly used spinopelvic measurements. TBSA measures consisted of 4 distance measures relating the cranial center of mass (CCOM) to the sacrum, hips, knees, and ankles, and 3 angular measures relating the CCOM to the hips, knees, and ankles. Furthermore, each TBSA parameter was correlated to patient-reported outcome (PRO) scores using the Oswestry Disability Index (ODI) and Scoliosis Research Society-22 (SRS-22) instruments. Thirty patients were randomly selected for inter- and intraobserver reliability testing of the TBSA parameters using intraclass correlation coefficients (ICCs).
Results: All TBSA radiographic parameters demonstrated strong linear correlation with the currently accepted primary measure of sagittal balance, the C7 sagittal vertical axis (r = 0.55-0.96, p < 0.001). Moreover, 5 of 7 TBSA measures correlated strongly with ODI and SRS-22 total scores (r = 0.42-0.51, p < 0.001). Inter- and intraobserver reliability for all TBSA measures was good to excellent (interrater ICC = 0.70-0.98, intrarater ICC = 0.77-1.0).
Conclusions: In spine deformity patients, novel TBSA radiographic parameters correlated well with PROs and with currently utilized spinal sagittal measurements. Inter- and intrarater reliability was high for these novel parameters. This is the first study to propose a reliable method for measuring head-to-toe global spinal alignment.
Keywords: CCOM = cranial center of mass; CL = cervical lordosis; CrAS = cranium-ankle-sacrum angle; CrHS = cranium-hip-sacrum angle; CrKS = cranium-knee-sacrum angle; CrSVA = cranial SVA; CrSVA-A = CrSVA to the ankle; CrSVA-H = CrSVA to the hip center; CrSVA-K = CrSVA to the knee center; CrSVA-S = CrSVA to the sacrum; ICC = intraclass correlation coefficient; LL = lumbar lordosis; ODI = Oswestry Disability Index; PRO = patient-reported outcome; SRS-22 = Scoliosis Research Society–22; SVA = sagittal vertical axis; TBSA = total body sagittal alignment; TK = thoracic kyphosis; TLK = thoracolumbar kyphosis; spinal deformity; spinopelvic alignment; total body sagittal alignment.