In-vivo Three-dimensional Kinematics Comparing Adjacent Segment Motion of Anterior Cervical Fusion

versus Cervical Arthroplasty in 17 PatientsVictor Chang MD; Azam Basheer MD; Stephen Bartol MD, MBA, FACS; Muwaffak Abdulhak MD; Mokbel K. Chedid MD,

FACS; Michael Bey PhD; Colin McDonald MDHenry Ford Hospital

Introduction

Cervical arthroplasty (AD) has

emerged as an alternative to

anterior cervical fusion (ACDF) for

the management of cervical

spondylosis (1, 2). This study aims

to provide three dimensional motion

analysis data comparing patients

after ACDF and AD.

Methods

10 patients who underwent C5-6

ACDF and 7 who underwent C5-6

AD were enrolled. Using bi-planar

fluoroscopy and a model based

track technique, accurate up to 0.6

mm and 0.6 degrees(3, 4), motion

analysis of axial rotation and flexion-

extension of the neck was assessed.

Three non-operative segments (C3-

4, C4-5, and C6-7) were assessed

for both inter-vertebral rotation

(coronal, sagittal, axial planes) and

facet shear (A-P and M-L).

ResultsThere was no difference in total neckmotion comparing ACDF and AD forneck extension (43.3±10.2 vs44.3±12.6 degrees, p=0.866) androtation (36.0±6.5 vs 38.2±9.3degrees, p=0.576). For extension(Figure 1), when measured as apercentage of total neck motion therewas a greater amount of rotation atthe non-operated segments in theACDF versus AD (p=0.003).Comparing specific motion segmentsgreater rotation was seen at C3-4(33.2±4.9% vs. 26.8±6.6%, p =0.036) and C6-7 (28.5±6.7% vs.20.5±5.5%, p = 0.009) but not at C4-5 (33.5±6.4% vs. 31.8±4.0%, p =0.562). For neck rotation (Figure 2)there was greater rotation at the non-operative segments in the ACDFversus AD (p=0.024), but thedifferences between individualsegments did not reach significance(p>0.146). Increased M-L facet shearwas seen on neck extension withACDF versus AD (p=0.008).Comparing each segment, C3-4(0.9±0.5 vs. 0.4±0.1mm, p = 0.039)and C4-5 (1.0±0.4 vs. 0.5±0.2mm, p= 0.022) showed increased shearwhile C6-7 (1.0±0.4 vs. 1.0±0.5mm,p = 0.767) did not.

Figure 1

Normalized motion greater at C5-6

for AD, and greater at C3-4 and C6-

7 for ACDF

Figure 2

Greater motion seen at C5-6 for

AD, no other differences

Conclusions

This study illustrates increased

motion at non-operative segments in

ACDF patients compared to AD.

Whether these changes contribute

to adjacent segment disease will

require further study.

Learning Objectives1. In-vivo three-dimensional motionanalysis can be performed on post-operative patients to assess theconsequences associated with eithercervical fusion or arthroplasty.

2. This study illustrates that there canbe an observed increase in adjacentsegment motion comparing post-ACDFwith post-AD patients.

3. Facet shear can also be measured inaddition to intervertebral rotation, andmay also be a topic of interest in thefuture.

References1.Upadhyaya CD, Wu JC, Trost G, Haid RW,Traynelis VC, Tay B, Coric D, Mummaneni PV.Analysis of the three United States Food andDrug Administration investigational deviceexemption cervical arthroplasty trials. JNeurosurg Spine 2012;16:216-218.2.Coric D, Nunley PD, Guyer RD, Musante D,Carmody CN, Gordon CR, Lauryssen C, OhnmeissDD, Boltes MO: Prospective, randomized,multicenter study of cervical arthroplasty. 269patients from the Kineflex|C artificial discinvestigational device exemption study with aminimum 2-year follow-up: clinical article. JNeurosurg Spine 2012;15:348-58.3.Bey MJ, Zauel R, Brock SK, et al. Validation ofa new model-based tracking technique formeasuring three-dimensional, in vivoglenohumeral joint kinematics. J Biomech Eng2006;128:604-94. McDonald CP, Bachison CC, Chang V, et al.Three-dimensional dynamic in vivo motion of thecervical spine: assessment of measurementaccuracy and preliminary findings. Spine J.2010;10:497-504. Epub 2010 Apr 1

Figure 1

Normalized motion greater at C5-6 for AD, and greater at C3-4 and C6-7 for ACDF

Figure 2

Greater motion seen at C5-6 for AD, no other differences