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Research Papers

Upper Cervical Spine Loading Simulating a Dynamic Low-Speed Collision Significantly Increases the Risk of Pain Compared to Quasi-Static Loading With Equivalent Neck Kinematics

[+] Author and Article Information
Timothy P. Holsgrove

Department of Bioengineering,
School of Engineering and Applied Science,
University of Pennsylvania,
210 South 33rd Street,
Room 240 Skirkanich Hall,
Philadelphia, PA 19104
e-mail: thols@seas.upenn.edu

Nicolas V. Jaumard

Department of Neurosurgery,
Pennsylvania Hospital,
University of Pennsylvania,
Washington Square West Building,
235 South 8th Street,
Philadelphia, PA 19106
e-mail: njaumard@gmail.com

Nina Zhu

Department of Bioengineering,
School of Engineering and Applied Science,
University of Pennsylvania,
210 South 33rd Street,
Room 240 Skirkanich Hall,
Philadelphia, PA 19104
e-mail: nzhu@seas.upenn.edu

Nicholas S. Stiansen

Department of Bioengineering,
School of Engineering and Applied Science,
University of Pennsylvania,
210 South 33rd Street,
Room 240 Skirkanich Hall,
Philadelphia, PA 19104
e-mail: nsti@seas.upenn.edu

William C. Welch

Department of Neurosurgery,
Pennsylvania Hospital,
University of Pennsylvania,
Washington Square West Building,
235 South 8th Street,
Philadelphia, PA 19106
e-mail: william.welch@uphs.upenn.edu

Beth A. Winkelstein

Department of Bioengineering,
School of Engineering
and Applied Science,
University of Pennsylvania,
210 South 33rd Street,
Room 240 Skirkanich Hall,
Philadelphia, PA 19104;
Department of Neurosurgery,
Pennsylvania Hospital,
University of Pennsylvania,
Washington Square West Building,
235 South 8th Street,
Philadelphia, PA 19106
e-mail: winkelst@seas.upenn.edu

1Corresponding author.

Manuscript received February 10, 2016; final manuscript received September 8, 2016; published online November 3, 2016. Assoc. Editor: Brian D. Stemper.

J Biomech Eng 138(12), 121006 (Nov 03, 2016) (10 pages) Paper No: BIO-16-1053; doi: 10.1115/1.4034707 History: Received February 10, 2016; Revised September 08, 2016

Dynamic cervical spine loading can produce facet capsule injury. Despite a large proportion of neck pain being attributable to the C2/C3 facet capsule, potential mechanisms are not understood. This study replicated low-speed frontal and rear-end traffic collisions in occiput-C3 human cadaveric cervical spine specimens and used kinematic and full-field strain analyses to assess injury. Specimens were loaded quasi-statically in flexion and extension before and after dynamic rotation of C3 at 100 deg/s. Global kinematics in the sagittal plane were tracked at 1 kHz, and C2/C3 facet capsule full-field strains were measured. Dynamic loading did not alter the kinematics from those during quasi-static (QS) loading, but maximum principal strain (MPS) and shear strain (SS) were significantly higher (p = 0.028) in dynamic flexion than for the same quasi-static conditions. The full-field strain analysis demonstrated that capsule strain was inhomogeneous, and that the peak MPS generally occurred in the anterior aspect and along the line of the C2/C3 facet joint. The strain magnitude in dynamic flexion continued to rise after the rotation of C3 had stopped, with a peak MPS of 12.52 ± 4.59% and a maximum SS of 5.34 ± 1.60%. The peak MPS in loading representative of rear-end collisions approached magnitudes previously shown to induce pain in vivo, whereas strain analysis using linear approaches across the facet joint was lower and may underestimate injury risk compared to full-field analysis. The time at which peak MPS occurred suggests that the deceleration following a collision is critical in relation to the production of injurious strains within the facet capsule.

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References

Figures

Grahic Jump Location
Fig. 1

Global view (a) of the occiput (Occ)-to-C3 specimen, with tracking markers at each level. The Occ was fixed to a phantom head. The C3 vertebra was rigidly fixed to the cradle, which was actuated for dynamic tests, with all other levels unconstrained in the sagittal and axial planes. The C2/C3 facet capsule was imaged (b) with two cameras, from which 2D facet kinematics were measured (c), and 3D reconstructions were used to measure the maximum principal strain (MPS) (d) and shear strain.

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Fig. 4

Mean (±95% CI) peak MPS ((a) and (b)) and peak SS ((c) and (d)) of the C2/C3 facet capsule during dynamic actuation of the C3 applied at 100 deg/s from 20 to 8 ms in flexion ((a) and (c)) and extension ((b) and (d))

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Fig. 2

Mean (±95% confidence intervals (CI)) quasi-static kinematics (flexion positive) at the Occ/C1 (a), C1/C2 (b), and C2/C3 (c) levels with respect to the global ROM predynamic (Pre-D) and postdynamic (Post-D) loadings

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Fig. 5

Mean (±95% CI) peak MPS (a) and mean MPS (b) on the C2/C3 facet capsule during flexion and extension at 100 deg/s compared to quasi-static loading. An asterisk (*) denotes a significant difference (p < 0.05).

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Fig. 6

Representative full-field strain for specimen 1 ((a) and (b)) and specimen 4 ((c) and (d)). The peak MPS during dynamic flexion ((a) and (c)) and the MPS at equivalent C2/C3 rotation during quasi-static testing ((b) and (d)) are shown. The variable MPS across the facet capsule was determined; the arrows show the MPS direction within each element.

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Fig. 7

Mean rotation angle (flexion positive) during dynamic actuation applied at 100 deg/s to the C3 level from 20 to 81 ms in either flexion (a) or extension (b). The visual representations above the plots show the shape of the spine at 0, 40, 81, 120, and 150 ms.

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Fig. 3

Mean (±95% CI) rotation angle (flexion positive) at Occ/C1 (a), C1/C2 (b), and C2/C3 (c) levels during dynamic flexion, and dynamic extension (d)–(f) applied at 100 deg/s to the C3 level from 20 to 81 ms

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