Sensitivity, reliability and accuracy of the instant center of rotation calculation in the cervical spine during in vivo dynamic flexion-extension

While abnormal loading is widely believed to cause cervical spine disc diseases, in vivo cervical disc deformation during dynamic neck motion has not been well delineated. This study investigated the range of cervical disc deformation during an in vivo functional flexion–extension of the neck. Ten asymptomatic human subjects were tested using a combined dual fluoroscopic imaging system (DFIS) and magnetic resonance imaging (MRI)-based three-dimensional (3D) modeling technique. Overall disc deformation was determined using the changes of the space geometry between upper and lower endplates of each intervertebral segment (C3/4, C4/5, C5/6, and C6/7). Five points (anterior, center, posterior, left, and right) of each disc were analyzed to examine the disc deformation distributions. The data indicated that between the functional maximum flexion and extension of the neck, the anterior points of the discs experienced large changes of distraction/compression deformation and shear deformation. The higher level discs experienced higher ranges of disc deformation. No significant difference was found in deformation ranges at posterior points of all the discs. The data indicated that the range of disc deformation is disc level dependent and the anterior region experienced larger changes of deformation than the center and posterior regions, except for the C6/7 disc. The data obtained from this study could serve as baseline knowledge for the understanding of the cervical spine disc biomechanics and for investigation of the biomechanical etiology of disc diseases. These data could also provide insights for development of motion preservation surgeries for cervical spine.

Download Full-text

Subject-Specific Inverse Dynamics of the Head and Cervical Spine During in Vivo Dynamic Flexion-Extension

Journal of Biomechanical Engineering ◽

10.1115/1.4023524 ◽

2013 ◽

Vol 135 (6) ◽

Cited By ~ 7

Author(s):

William J. Anderst ◽

William F. Donaldson ◽

Joon Y. Lee ◽

James D. Kang

Keyword(s):

Finite Element ◽

Cervical Spine ◽

Inverse Dynamics ◽

Total Force ◽

Finite Element Models ◽

Moment Arms ◽

Flexion Extension ◽

Subject Specific

The effects of degeneration and surgery on cervical spine mechanics are commonly evaluated through in vitro testing and finite element models derived from these tests. The objectives of the current study were to estimate the load applied to the C2 vertebra during in vivo functional flexion-extension and to evaluate the effects of anterior cervical arthrodesis on spine kinetics. Spine and head kinematics from 16 subjects (six arthrodesis patients and ten asymptomatic controls) were determined during functional flexion-extension using dynamic stereo X-ray and conventional reflective markers. Subject-specific inverse dynamics models, including three flexor muscles and four extensor muscles attached to the skull, estimated the force applied to C2. Total force applied to C2 was not significantly different between arthrodesis and control groups at any 10 deg increment of head flexion-extension (all p values ≥ 0.937). Forces applied to C2 were smallest in the neutral position, increased slowly with flexion, and increased rapidly with extension. Muscle moment arms changed significantly during flexion-extension, and were dependent upon the direction of head motion. The results suggest that in vitro protocols and finite element models that apply constant loads to C2 do not accurately represent in vivo cervical spine kinetics.

Download Full-text

In vivo 3D kinematic changes in the cervical spine after laminoplasty for cervical spondylotic myelopathy

Journal of Neurosurgery Spine ◽

10.3171/2014.5.spine13702 ◽

2014 ◽

Vol 21 (3) ◽

pp. 417-424 ◽

Cited By ~ 8

Author(s):

Yukitaka Nagamoto ◽

Motoki Iwasaki ◽

Tsuyoshi Sugiura ◽

Takahito Fujimori ◽

Yohei Matsuo ◽

...

Keyword(s):

Cervical Spine ◽

Cervical Spondylotic Myelopathy ◽

Head Rotation ◽

Upper Cervical Spine ◽

Registration Method ◽

Flexion Extension ◽

Upper Cervical ◽

Head Flexion ◽

Age Range

Object Cervical laminoplasty is an effective procedure for decompressing the spinal cord at multiple levels, but restriction of neck motion is one of the well-known complications of the procedure. Although many authors have reported on cervical range of motion (ROM) after laminoplasty, they have focused mainly on 2D flexion and extension on lateral radiographs, not on 3D motion (including coupled motion) nor on precise intervertebral motion. The purpose of this study was to clarify the 3D kinematic changes in the cervical spine after laminoplasty performed to treat cervical spondylotic myelopathy. Methods Eleven consecutive patients (6 men and 5 women, mean age 68.1 years, age range 57–79 years) with cervical spondylotic myelopathy who had undergone laminoplasty were included in the study. All patients underwent 3D CT of the cervical spine in 5 positions (neutral, 45° head rotation left and right, maximum head flexion, and maximum head extension) using supporting devices. The scans were performed preoperatively and at 6 months after laminoplasty. Segmental ROM from Oc–C1 to C7–T1 was calculated both in flexion-extension and in rotation, using a voxel-based registration method. Results Mean C2–7 flexion-extension ROM, equivalent to cervical ROM in all previous studies, was 45.5° ± 7.1° preoperatively and 35.5° ± 8.2° postoperatively, which was a statistically significant 33% decrease. However, mean Oc–T1 flexion-extension ROM, which represented total cervical ROM, was 71.5° ± 8.3° preoperatively and 66.5° ± 8.3° postoperatively, an insignificant 7.0% decrease. In focusing on each motion segment, the authors observed a statistically significant 22.6% decrease in mean segmental ROM at the operated levels during flexion-extension and a statistically insignificant 10.2% decrease during rotation. The most significant decrease was observed at C2–3. Segmental ROM at C2–3 decreased 24.2% during flexion-extension and 21.8% during rotation. However, a statistically insignificant 37.2% increase was observed at the upper cervical spine (Oc–C2) during flexion-extension. The coupling pattern during rotation did not change significantly after laminoplasty. Conclusions In this first accurate documentation of 3D segmental kinematic changes after laminoplasty, Oc–T1 ROM, which represented total cervical ROM, did not change significantly during either flexion-extension or rotation by 6 months after laminoplasty despite a significant decrease in C2–7 flexion-extension ROM. This is thought to be partially because of a compensatory increase in segmental ROM at the upper cervical spine (Oc–C2).

Download Full-text

Prediction of in vivo lower cervical spinal loading using musculoskeletal multi-body dynamics model during the head flexion/extension, lateral bending and axial rotation

Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine ◽

10.1177/0954411918799630 ◽

2018 ◽

Vol 232 (11) ◽

pp. 1071-1082 ◽

Cited By ~ 1

Author(s):

Hao Diao ◽

Hua Xin ◽

Zhongmin Jin

Keyword(s):

Cervical Spine ◽

Axial Rotation ◽

Intervertebral Disk ◽

Lateral Bending ◽

Spinal Loading ◽

Flexion Extension ◽

Body Dynamics ◽

Head Flexion ◽

Multi Body

Cervical spine diseases lead to a heavy economic burden to the individuals and societies. Moreover, frequent post-operative complications mean a higher risk of neck pain and revision. At present, controversy still exists for the etiology of spinal diseases and their associated complications. Knowledge of in vivo cervical spinal loading pattern is proposed to be the key to answer these questions. However, direct acquisition of in vivo cervical spinal loading remains challenging. In this study, a previously developed cervical spine musculoskeletal multi-body dynamics model was utilized for spinal loading prediction. The in vivo dynamic segmental contributions to head motion and the out-of-plane coupled motion were both taken into account. First, model validation and sensitivity analysis of different segmental contributions to head motion were performed. For model validation, the predicted intervertebral disk compressive forces were converted into the intradiskal pressures and compared with the published experimental measurements. Significant correlations were found between the predicted values and the experimental results. Thus, the reliability and capability of the cervical spine model was ensured. Meanwhile, the sensitivity analysis indicated that cervical spinal loading is sensitive to different segmental contributions to head motion. Second, the compressive, shear and facet joint forces at C3–C6 disk levels were predicted, during the head flexion/extension, lateral bending and axial rotation. Under the head flexion/extension movement, asymmetric loading patterns of the intervertebral disk were obtained. In comparison, symmetrical typed loading patterns were found for the head lateral bending and axial rotation movements. However, the shear forces were dramatically increased during the head excessive extension and lateral bending. Besides, a nonlinear correlation was seen between the facet joint force and the angular displacement. In conclusion, dynamic cervical spinal loading was both intervertebral disk angle-dependent and level-dependent. Cervical spine musculoskeletal multi-body dynamics model provides an attempt to comprehend the in vivo biomechanical surrounding of the human head-neck system.

Download Full-text

Cervical Disc Height During Dynamic In Vivo Flexion-Extension

ASME 2011 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2011-53154 ◽

2011 ◽

Author(s):

William J. Anderst ◽

Thomas P. Lacek ◽

William F. Donaldson ◽

Joon Y. Lee ◽

James D. Kang

Keyword(s):

Cervical Spine ◽

Cervical Disc ◽

Dynamic Motion ◽

System A ◽

Spine Kinematics ◽

Flexion Extension ◽

The Us ◽

Custom Software ◽

Vertebral Kinematics

Cervical disc degeneration is a common and potentially debilitating disease. Over 100,000 surgical procedures are performed per year in the US to treat degenerative cervical spines1. However, the in vivo kinematics and arthrokinematics of the cervical spine have yet to be adequately characterized due to the inability to precisely track vertebral movement during dynamic motion. We have recently established the validity of a set of tools, including a biplane x-ray system, a model-based tracking technique and custom software, to precisely measure in vivo cervical spine kinematics and arthrokinematics with sub-millimeter accuracy2. Consequently, we can now begin to investigate the interdependent relationship between cervical vertebral kinematics and disc morphology and mechanical properties.

Download Full-text