In-vivo Three-dimensional Motion Analysis Correlated with Clinical Outcomes in 11 Cervical Fusion

Patients: A CNS Fellowship Funded StudyVictor Chang MD; Azam Basheer MD; Mokbel K. Chedid MD, FACS; Muwaffak Abdulhak MD; Stephen Bartol MD, MBA,

FACS; Michael Bey PhD; Colin McDonald MDHenry Ford Hospital

Introduction

Anterior cervical fusion (ACDF) is a common

treatment of cervical spondylosis. Better

understanding of cervical motion post ACDF may

reveal which patients will progress to adjacent

segment disease (ASD).

Methods

11 patients who were 2 years post C5-6 ACDF

were enrolled for this study. Motion analysis was

performed using bi-planar fluoroscopy and a

model based tracking technique, accurate up to

0.6 mm and 0.6 degrees (1, 2). Clinical

measures were assessed using: Neck Disability

Index (NDI), Visual Analog Score (VAS) for arm

and neck pain, and the Short Form (36) Health

Survey physical component score (SF36).

Spearman’s method was used to measure

correlation between motion analysis parameters

and clinical scales.

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Results

Inter-vertebral rotation was measured in 3 planes

(axial rotation, flexion/extension, lateral bending)

for neck rotation and extension. Mean NDI was

6±6.08, mean neck VAS was 0.75±1.1, mean

arm VAS 0.52±0.68, and mean SF36 was

44.55±10.11. During neck rotation, there was a

positive correlation with C3-4 axial rotation with

NDI (0.731, p=0.025), neck VAS (0.790,

p=0.011), and a negative correlation with SF36 (-

0.778, p=0.023). During neck extension, there

was a positive correlation with C3-4 extension

and neck VAS (0.685, p=0.042), and C4-5 lateral

bending with SF36 (0.743, p=0.035), with a

negative correlation with C4-5 lateral bending

with NDI (-0.714, p=0.031) and neck VAS (-0.896,

p=0.001).

Conclusions

Our analysis shows that increasing rotation at the

C3-4 level correlates with worsening clinical

outcome, and rotation at the C4-5 level correlates

with better clinical outcome after C5-6 ACDF.

This suggests that a mobile C4-5 segment is a

healthier state, and that increased mobility at C3-

4 indicates an unhealthy state, perhaps

compensatory for C4-5 immobility from

degeneration. These findings may help illustrate

the pathogenesis of ASD. Longitudinal follow-up

may also illustrate the natural history as well.

References1. Bey MJ, Zauel R, Brock SK, et al. Validation of a new model-based tracking technique for measuring three-dimensional, in vivoglenohumeral joint kinematics. J Biomech Eng 2006;128:604-92. McDonald CP, Bachison CC, Chang V, et al. Three-dimensionaldynamic in vivo motion of the cervical spine: assessment ofmeasurement accuracy and preliminary findings. Spine J.2010;10:497-504. Epub 2010 Apr 1

Learning ObjectivesThis study illustrates the following:1) Three dimensional in-vivo motion analysis isfeasible in ACDF patients.2) Correlations between clinical outcome and motionanalysis may establish “pathologic” movement thatmay contribute to ASD.3) Increased mobility at the rostral segment tofusion was observed to correlate with betteroutcome, while increased mobility 2 segments abovefusion was observed to correlate with worseningoutcome.4) Further research and longitudinal follow-up will benecessary to further illustrate the pathogenesis ofASD.

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