Kinematic characteristics of patients with cervical imbalance: a weight-bearing dynamic MRI study

  • Koji Tamai
  • Phillip GrisdelaJr.
  • Joshua Romanu
  • Permsak Paholpak
  • Zorica BuserEmail author
  • Jeffrey C. Wang
Original Article


Study design

It is a retrospective analysis of 1806 consecutive cervical magnetic resonance images taken in weight-bearing flexion, neutral, and extension positions.


The aim was to identify the kinematic characteristics of patients with cervical imbalance. Additionally, factors were analysed in the neutral position that could predict the characteristics.

Summary of background data

Little is known about the kinematic characteristics during cervical flexion and extension positions of the patient with cervical imbalance (cervical sagittal vertical axis (cSVA) in neutral position ≥ 40 mm).


After evaluating the whole images, cervical imbalance group (cSVA ≥ 40 mm, n = 43) and matched control group (< 40 mm, n = 43) were created using propensity score adjusting for age, gender, and cervical alignment. They were compared for cervical motion, changes in disc bulge, and ligamentum flavum (LF) bulge from flexion to extension. Multinomial logistic regression analysis and receiver operating characteristic curve analysis were calculated to verify the predictive factors and cut-off value of the identified characteristics.


There were no significant differences in range of motion and the change in bulged discs. There was significant difference in the presence of LF bulge from flexion to extension (p = 0.023); the incidence of LF bulge increased sharply from neutral to extension in imbalance group, while there was linear increase in control group. The canal diameter (odds ratio = 0.61, p = 0.002) and disc height (odds ratio = 1.60, p = 0.041) showed significant relationship with the segments with LF bulge observed in extension but not in neutral position in the imbalance group; the cut-off values were 10.7 mm for canal diameter (sensitivity 82.5%, specificity 66.7%) and 7.1 mm for disc height (70.8%, 58.5%).


Patients with cervical imbalance had a stark increase in LF bulge from the neutral to extension position. Canal diameter < 10.7 mm and disc height > 7.1 mm on neutral images may predict the segments with LF bulge observed in extension, but not in the neutral position.

Level of evidence

II (Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding).

Graphical abstract

These slides can be retrieved from Electronic Supplementary Material.


Cervical Imbalance Sagittal vertical axis Ligamentum flavum Kinematic magnetic resonance images Flavum bulge Disc height Canal diameter 


Compliance with ethical standards

Conflict of interest

No conflicts of interest for the current study.


JCW—Royalties-Biomet, Seaspine, Amedica, DePuy Synthes; Investments/Options—Fziomed, Promethean, Paradigm Spine, Benvenue, Nexgen, Vertiflex, Electrocore, Surgitech, Expanding Orthopedics, Osprey, Bone Biologics, Pearldiver; Board of Directors—North American Spine Society, North American Spine Foundation, AO Foundation, Cervical Spine Research Society; Fellowship Funding (paid to institution): AO Foundation. ZB—consultancy: Xenco Medical, AO Spine (past); research support: SeaSpine (paid directly to institution).

Supplementary material

586_2018_5874_MOESM1_ESM.pptx (224 kb)
Supplementary material 1 (PPTX 224 kb)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Orthopaedic Surgery, Keck School of MedicineUniversity of Southern CaliforniaLos AngelesUSA
  2. 2.Department of OrthopedicsOsaka City University Graduate School of MedicineOsakaJapan

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