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Chehrassan M, Nikouei F, Shakeri M, Ghavidel E, Ameri Mahabadi E, Ghandhari H. Cervical Sagittal Alignment After Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis: Is Hypolordosis or Kyphosis a Problematic Condition?. JROS 2026; 13 (1)
URL: http://jros.iums.ac.ir/article-1-2320-en.html
URL: http://jros.iums.ac.ir/article-1-2320-en.html
Mohammadreza Chehrassan1 
, Farshad Nikouei1 , Mohammadreza Shakeri1 , Ehsan Ghavidel1 , Ebrahim Ameri Mahabadi1 , Hasan Ghandhari1
, Farshad Nikouei1 , Mohammadreza Shakeri1 , Ehsan Ghavidel1 , Ebrahim Ameri Mahabadi1 , Hasan Ghandhari1
1- Bone and Joint Reconstruction Research Center, Department of Orthopedics, School of Medicine, Iran University of Medical Sciences, Tehran, Iran.
Abstract: (6 Views)
Background: The impact of posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS) on cervical sagittal alignment remains an area of increasing clinical interest. While the importance of global spinopelvic alignment is well established, the fate of the unfused cervical spine following thoracic curve correction has only recently been recognized as a determinant of patient outcomes.
Purpose: This study aimed to evaluate changes in cervical sagittal alignment following PSF for AIS and to determine whether postoperative cervical hypolordosis or kyphosis constitutes a clinically significant problem.
Study Design: Retrospective single-center cohort study.
Patients and Methods: Over a 5-year period, 214 patients who underwent PSF for AIS were screened, and 176 patients (142 females, 34 males) met the inclusion criteria. Inclusion required AIS without dominant thoracic kyphosis (>50°), dominant coronal deformity, and complete pre- and postoperative clinical and radiographic documentation with a minimum follow-up of 38 months (mean: 52.5 months; range: 38–65 months). Exclusion criteria included previous spinal surgery, cervical spine disorders (discopathy, traumatic conditions), congenital cervical deformities (failure of formation or segmentation), and Arnold-Chiari malformation. Cervical sagittal alignment was measured on standing lateral radiographs and patients were classified into four groups: hyperlordosis (>45°), normolordosis (25°–45°), hypolordosis (0°–25°), and kyphosis (<0°). Shoulder imbalance was evaluated both clinically and radiographically at each visit. Patient-reported outcomes were assessed using the SRS-22r questionnaire preoperatively and at final follow-up.
Results: Preoperatively, 6 patients had cervical hyperlordosis (maximum: 62°), 69 had normolordosis, 86 were hypolordotic, and 15 had cervical kyphosis (maximum: 27°). Immediately postoperatively, a marked shift toward kyphosis was observed: 79 patients (44.9%) fell into the kyphotic group (maximum: 34°), 86 were hypolordotic, 4 hyperlordotic, and 7 normolordotic. By final follow-up, cervical alignment showed substantial improvement, with 64 patients remaining hypolordotic, 7 in the kyphotic group (maximum: 24°), 15 hyperlordotic, and 90 achieving normolordosis. Shoulder imbalance >15 mm was present in 64% preoperatively (maximum: 46 mm), increased to 48% immediately postoperatively (maximum: 37 mm), and improved to 21% at final follow-up (maximum: 28 mm). Cervical alignment–related complications were observed in 24 patients at final follow-up: neck pain (VAS 2–6) in 18, decreased cervical range of motion (predominantly extension) in 22, and inability to gaze upward in 4. Shoulder imbalance–related complications occurred in 45 patients. SRS-22r total score improved from 2.4 preoperatively to 3.3 immediately postoperatively and 4.1 at final follow-up. At final follow-up, SRS-22r scores showed a clear gradient across cervical alignment groups: kyphotic group 3.6, hypolordotic group 3.9 , hyperlordotic group 4.06 , and normolordotic group 4.2 . The kyphotic and hypolordotic groups demonstrated significantly lower SRS-22r scores compared with the normolordotic group (p < 0.05). Patients without shoulder imbalance had higher SRS-22r scores (4.135) compared with those with imbalance (3.98). UIV selection was T2 in 63% of cases, T3 in 26%, and T4 or lower in 11%. UIV fixation used bilateral transverse hooks in 73%, pedicle screws in 11%, and hybrid constructs in 16%.
Conclusion: Transient cervical kyphosis is common in the immediate postoperative period following PSF for AIS but largely resolves spontaneously. However, persistent cervical hypolordosis and, particularly, cervical kyphosis at final follow-up are associated with inferior patient-reported outcomes and a higher burden of cervical symptoms. Maintaining or restoring cervical lordosis within the normal range (25°–45°) appears to be an important surgical goal. Shoulder imbalance also negatively affects outcomes and warrants careful attention during preoperative planning and UIV selection.
Purpose: This study aimed to evaluate changes in cervical sagittal alignment following PSF for AIS and to determine whether postoperative cervical hypolordosis or kyphosis constitutes a clinically significant problem.
Study Design: Retrospective single-center cohort study.
Patients and Methods: Over a 5-year period, 214 patients who underwent PSF for AIS were screened, and 176 patients (142 females, 34 males) met the inclusion criteria. Inclusion required AIS without dominant thoracic kyphosis (>50°), dominant coronal deformity, and complete pre- and postoperative clinical and radiographic documentation with a minimum follow-up of 38 months (mean: 52.5 months; range: 38–65 months). Exclusion criteria included previous spinal surgery, cervical spine disorders (discopathy, traumatic conditions), congenital cervical deformities (failure of formation or segmentation), and Arnold-Chiari malformation. Cervical sagittal alignment was measured on standing lateral radiographs and patients were classified into four groups: hyperlordosis (>45°), normolordosis (25°–45°), hypolordosis (0°–25°), and kyphosis (<0°). Shoulder imbalance was evaluated both clinically and radiographically at each visit. Patient-reported outcomes were assessed using the SRS-22r questionnaire preoperatively and at final follow-up.
Results: Preoperatively, 6 patients had cervical hyperlordosis (maximum: 62°), 69 had normolordosis, 86 were hypolordotic, and 15 had cervical kyphosis (maximum: 27°). Immediately postoperatively, a marked shift toward kyphosis was observed: 79 patients (44.9%) fell into the kyphotic group (maximum: 34°), 86 were hypolordotic, 4 hyperlordotic, and 7 normolordotic. By final follow-up, cervical alignment showed substantial improvement, with 64 patients remaining hypolordotic, 7 in the kyphotic group (maximum: 24°), 15 hyperlordotic, and 90 achieving normolordosis. Shoulder imbalance >15 mm was present in 64% preoperatively (maximum: 46 mm), increased to 48% immediately postoperatively (maximum: 37 mm), and improved to 21% at final follow-up (maximum: 28 mm). Cervical alignment–related complications were observed in 24 patients at final follow-up: neck pain (VAS 2–6) in 18, decreased cervical range of motion (predominantly extension) in 22, and inability to gaze upward in 4. Shoulder imbalance–related complications occurred in 45 patients. SRS-22r total score improved from 2.4 preoperatively to 3.3 immediately postoperatively and 4.1 at final follow-up. At final follow-up, SRS-22r scores showed a clear gradient across cervical alignment groups: kyphotic group 3.6, hypolordotic group 3.9 , hyperlordotic group 4.06 , and normolordotic group 4.2 . The kyphotic and hypolordotic groups demonstrated significantly lower SRS-22r scores compared with the normolordotic group (p < 0.05). Patients without shoulder imbalance had higher SRS-22r scores (4.135) compared with those with imbalance (3.98). UIV selection was T2 in 63% of cases, T3 in 26%, and T4 or lower in 11%. UIV fixation used bilateral transverse hooks in 73%, pedicle screws in 11%, and hybrid constructs in 16%.
Conclusion: Transient cervical kyphosis is common in the immediate postoperative period following PSF for AIS but largely resolves spontaneously. However, persistent cervical hypolordosis and, particularly, cervical kyphosis at final follow-up are associated with inferior patient-reported outcomes and a higher burden of cervical symptoms. Maintaining or restoring cervical lordosis within the normal range (25°–45°) appears to be an important surgical goal. Shoulder imbalance also negatively affects outcomes and warrants careful attention during preoperative planning and UIV selection.
Keywords: Adolescent idiopathic scoliosis, cervical sagittal alignment, cervical hypolordosis, cervical kyphosis, posterior spinal fusion, SRS-22r, shoulder imbalance, Lenke classification, upper instrumented vertebra, coronal decompensation
Type of Study: Research Article |
Subject:
Spine surgery
Received: 2026/05/3 | Accepted: 2026/05/4 | Published: 2026/02/24
Received: 2026/05/3 | Accepted: 2026/05/4 | Published: 2026/02/24
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