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Longitudinal Study of the Six Degrees of Freedom Cervical Spine Range of Motion During Dynamic Flexion, Extension, and Rotation After Single-level Anterior Arthrodesis

Anderst, William J. PhD; West, Tyler BS; Donaldson, William F. III MD; Lee, Joon Y. MD; Kang, James D. MD

doi: 10.1097/BRS.0000000000001629

Study Design. A longitudinal study using biplane radiography to measure in vivo intervertebral range of motion (ROM) during dynamic flexion/extension, and rotation.

Objective. To longitudinally compare intervertebral maximal ROM and midrange motion in asymptomatic control subjects and single-level arthrodesis patients.

Summary of Background Data. In vitro studies consistently report that adjacent segment maximal ROM increases superior and inferior to cervical arthrodesis. Previous in vivo results have been conflicting, indicating that maximal ROM may or may not increase superior and/or inferior to the arthrodesis. There are no previous reports of midrange motion in arthrodesis patients and similar-aged controls.

Methods. Eight single-level (C5/C6) anterior arthrodesis patients (tested 7 ± 1 months and 28 ± 6 months postsurgery) and six asymptomatic control subjects (tested twice, 58 ± 6 months apart) performed dynamic full ROM flexion/extension and axial rotation whereas biplane radiographs were collected at 30 images per second. A previously validated tracking process determined three-dimensional vertebral position from each pair of radiographs with submillimeter accuracy. The intervertebral maximal ROM and midrange motion in flexion/extension, rotation, lateral bending, and anterior-posterior translation were compared between test dates and between groups.

Results. Adjacent segment maximal ROM did not increase over time during flexion/extension, or rotation movements. Adjacent segment maximal rotational ROM was not significantly greater in arthrodesis patients than in corresponding motion segments of similar-aged controls. C4/C5 adjacent segment rotation during the midrange of head motion and maximal anterior-posterior translation were significantly greater in arthrodesis patients than in the corresponding motion segment in controls on the second test date.

Conclusion. C5/C6 arthrodesis appears to significantly affect midrange, but not end-range, adjacent segment motions. The effects of arthrodesis on adjacent segment motion may be best evaluated by longitudinal studies that compare maximal and midrange adjacent segment motion to corresponding motion segments of similar-aged controls to determine if the adjacent segment motion is truly excessive.

Level of Evidence: 3

Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA

Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA

Department of Orthopaedic Surgery, Brigham and Women's Hospital, Boston, MA.

Address correspondence and reprint requests to William J. Anderst, PhD, Orthopaedic Research Laboratories, 3820 South Water Street, Pittsburgh, PA 15203. E-mail:

Received 5 November, 2015

Revised 26 March, 2016

Accepted 4 April, 2016

The manuscript submitted does not contain information about medical device(s)/drug(s).

NIH/NIAMS (#1R03AR056265) grant funds were received in support of this work.

No relevant financial activities outside the submitted work.

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