The goal of this study was to investigate the impact of thoracic and lumbar alignment on cervical alignment in patients with adolescent idiopathic scoliosis (AIS).
Eighty-one patients with AIS who had a Cobb angle > 40° and full-length spine radiographs were included. Radiographs were analyzed using dedicated software to measure pelvic parameters (sacral slope [SS], pelvic incidence [PI], pelvic tilt [PT]); regional parameters (C1 slope, C0–C2 angle, chin-brow vertical angle [CBVA], slope of line of sight [SLS], McRae slope, McGregor slope [MGS], C2–7 [cervical lordosis; CL], C2–7 sagittal vertical axis [SVA], C2–T3, C2–T3 SVA, C2–T1 Harrison measurement [C2–T1 Ha], T1 slope, thoracic kyphosis [TK], lumbar lordosis [LL], and PI-LL mismatch); and global parameters (SVA). Patients were stratified by their lumbar alignment into hyperlordotic (LL > 59.7°) and normolordotic (LL 39.3° to 59.7°) groups and also, based on their thoracic alignment, into hypokyphotic (TK < −33.1°) and normokyphotic (TK −33.1° to −54.9°) groups. Finally, they were grouped based on their global alignment into either an anterior-aligned group or a posterior-aligned group.
The lumbar hyperlordotic group, in comparison to the normolordotic group, had a significantly larger LL, SS, PI (all p < 0.001), and TK (p = 0.014) and a significantly smaller PI-LL mismatch (p = 0.001). Lumbar lordosis had no influence on local cervical parameters.
The thoracic hypokyphotic group had a significantly larger PI-LL mismatch (p < 0.002) and smaller T1 slope (p < 0.001), and was significantly more posteriorly aligned than the normokyphotic group (−15.02 ± 8.04 vs 13.54 ± 6.17 [mean ± SEM], p = 0.006). The patients with hypokyphotic AIS had a kyphotic cervical spine (cervical kyphosis [CK]) (p < 0.001). Furthermore, a posterior-aligned cervical spine in terms of C2–7 SVA (p < 0.006) and C2–T3 SVA (p < 0.001) was observed in the thoracic hypokyphotic group.
Comparing patients in terms of global alignment, the posterior-aligned group had a significantly smaller T1 slope (p < 0.001), without any difference in terms of pelvic, lumbar, and thoracic parameters when compared to the anterior-aligned group. The posterior-aligned group also had a CK (−9.20 ± 1.91 vs 5.21 ± 2.95 [mean ± SEM], p < 0.001) and a more posterior-aligned cervical spine, as measured by C2–7 SVA (p = 0.003) and C2–T3 SVA (p < 0.001).
Alignment of the cervical spine is closely related to thoracic curvature and global alignment. In patients with AIS, a hypokyphotic thoracic alignment or posterior global alignment was associated with a global cervical kyphosis. Interestingly, upper cervical and cranial parameters were not statistically different in all investigated groups, meaning that the upper cervical spine was not recruited for compensation in order to maintain a horizontal gaze.
ABBREVIATIONSAIS = adolescent idiopathic scoliosis; CBVA = chin-brow vertical angle; CK = cervical kyphosis; CL = cervical lordosis; C2–T1 Ha = C2–T1 Harrison measurement; LL = lumbar lordosis; MGS = McGregor slope; PI = pelvic incidence; PT = pelvic tilt; SLS = slope of line of sight; SS = sacral slope; SVA = sagittal vertical axis; TK = thoracic kyphosis.
Correspondence Wojciech Pepke: Heidelberg University Hospital, Heidelberg, Germany. firstname.lastname@example.org.
INCLUDE WHEN CITING Published online August 24, 2018; DOI: 10.3171/2018.3.SPINE171263.
Disclosures Dr. V. Lafage owns stock in Nemaris, Inc. She receives support for non–study-related clinical or research effort that she oversees from SRS, NASS (grants), DePuy Spine, K2M, Stryker, and NuVasive (NuVasive funds paid through ISSGF). She is a consultant for NuVasive and has speaking and/or teaching arrangements with AOSpine and DePuy Spine. Dr. Schwab owns stock in Nemaris, Inc. He receives support for non–study-related clinical or research effort that he oversees from DePuy Spine, NuVasive, Stryker, and K2M. He is a consultant for MSD, Zimmer-Biomet, Medicrea, NuVasive, and K2M. He has speaking and/or teaching arrangements with MSD, Zimmer-Biomet, Medicrea, NuVasive, and K2M.
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