Postural Consequences of Cervical Sagittal Imbalance - A Novel Laboratory Model Journal Article

Authors: Patwardhan, A. G.; Havey, R. M.; Khayatzadeh, S; Muriuki, M. G.; Voronov, L. I.; Carandang, G; Nguyen, N. L.; Ghanayem, A. J.; Schuit, D; Patel, A. A.; Smith, Z. A.; Sears, W.
Article Title: Postural Consequences of Cervical Sagittal Imbalance - A Novel Laboratory Model
Abstract: STUDY DESIGN: A biomechanical study using human spine specimens. OBJECTIVE: To study postural compensations in lordosis angles that are necessary to maintain horizontal gaze in the presence of forward head posture and increasing T1 sagittal tilt. SUMMARY OF BACKGROUND DATA: Forward head posture (FHP) relative to the shoulders, assessed radiographically using the horizontal offset distance between the C2 and C7 vertebral bodies (C2-C7 SVA), is a measure of global cervical imbalance. This may result from kyphotic alignment of cervical segments, muscle imbalance, as well as malalignment of thoracolumbar spine. METHODS: Ten cadaveric cervical spines (Occiput-T1) were tested. The T1 vertebra was anchored to a tilting and translating base. The occiput was free to move vertically but its angular orientation was constrained to ensure horizontal gaze regardless of sagittal imbalance. A 5kg mass was attached to the occiput to mimic head weight. FHP magnitude and T1 tilt were varied and motions of individual vertebrae were measured to calculate C2-C7 SVA and lordosis across C0-C2 and C2-C7. RESULTS: Increasing C2-C7 SVA caused flexion of lower cervical (C2-C7) segments and hyperextension of sub-occipital (C0-C1-C2) segments in order to maintain horizontal gaze. Increasing kyphotic T1 tilt primarily increased lordosis across the C2-C7 segments. Regression models were developed to predict the compensatory C0-C2 and C2-C7 angulation needed to maintain horizontal gaze given values of C2-C7 SVA and T1 tilt. CONCLUSIONS: This study established predictive relationships between radiographic measures of FHP, T1 tilt, and postural compensations in the cervical lordosis angles needed to maintain horizontal gaze. The laboratory model predicted that normalization of C2-C7 SVA will reduce sub-occipital (C0-C2) hyperextension; while T1 tilt reduction will reduce the hyperextension in the C2-C7 segments. The predictive relationships may help in planning corrective strategy in patients experiencing neck pain, which may be attributed to sagittal malalignment.
Journal Title: Spine
Volume: 40
Issue: 11
ISSN: 1528-1159; 0362-2436
Publisher: Unknown  
Date Published: 2015
Start Page: 783
End Page: 792
Language: ENG
Notes: LR: 20150315; JID: 7610646; aheadofprint
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