Magnitude of preoperative cervical lordotic compensation and C2-T3 angle are correlated to increased risk of postoperative sagittal spinal pelvic malalignment in adult thoracolumbar deformity patients at 2-year follow-up

Background context Cervical deformity (CD) is prevalent among patients with adult spinal deformity (ASD). The effect of baseline cervical alignment on achieving optimal thoracolumbar alignment in ASD surgery is unclear. Purpose This study assesses the relationship between preoperative (preop) cervical spinal parameters and global alignment after thoracolumbar ASD surgery at 2-year follow-up. Study design/setting This study is a retrospective review of a multicenter, prospective database. Patient sample Surgical ASD patients with 2-year follow-up and cervical X-rays were included. Outcome measures The outcome measures were radiographic parameters and self-reported health-related quality-of-life measures (Short-Form 36 [SF-36], Oswestry Disability Index [ODI], and Scoliosis Research Society 22 [SRS-22]). Methods Surgical ASD patients of 18 years and older with scoliosis greater than or equal to 20°and one of the following radiographic parameters were included: sagittal vertical axis (SVA) greater than or equal to 5 cm, pelvic tilt (PT) greater than or equal to 25°, or thoracic kyphosis (TK) greater than 60°. The SRS-Schwab sagittal modifiers (PT, global alignment, and pelvic incidence and lumbar lordosis [PI-LL]) were assessed at 2-year postoperatively as either normal ("0") or abnormal ("+" or "++"). Patients were classified in the aligned group (AG) or malaligned group (MG) at 2-year follow-up if all three sagittal modifiers were normal or abnormal, respectively. Patients were assessed for CD based on the following criteria: C2-C7 SVA greater than 4 cm, C2-C7 SVA less than 4 cm, cervical kyphosis (CL greater than 0), cervical lordosis (CL less than 0), any deformity (C2-C7 SVA greater than 4 cm or CL greater than 0), and both CD (C2-C7 SVA greater than 4 cm and CL greater than 0). Univariate testing was performed using t or chi-square test, looking at the following preop parameters: CD, C2-C7 SVA, C2-T3 SVA, CL, T1 slope (T1S), T1S-CL, C2-T3 angle, LL, TK, PT, C7-S1 SVA, and PI-LL. Results One hundred four patients met the initial inclusion criteria with 70 in the AG and 34 in MG. Preoperative, patients in the MG had a higher CL (11.7 vs. 4.9, p=.03), higher C2-T3 angle (13.59 vs 4.9 p=.01), higher PT (p<.0001), higher SVA (p<.0001), and higher PI-LL (p<.0001) compared with the AG. Interestingly, the prevalence of CD at baseline was similar for both groups. There was no statistically significant difference among groups in the amount of improvement more than 2 years on the ODI or the Physical Component Summary of SF-36. Conclusions Patients with sagittal spinal malalignment associated with significant cervical compensatory lordosis are at increased risk of realignment failure at 2-year follow-up. Assessment of the degree of cervical compensation may be helpful in preop evaluation to assist in realignment outcome prediction.