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In Vivo Changes in Dynamic Adjacent Segment Motion 1 Year After One- and Two-Level Cervical Arthrodesis

October 12, 2022

A study assessing the effects of one- and two-level cervical arthrodesis on adjacent segment motion was published in Annals of Biomedical Engineering. The study was authored by several experts, including UPMC Orthopaedic Care physicians Jeremy D. Shaw, MD; William F. Donaldson, MD; and Joon Yung Lee, MD, as well as biodynamics laboratory director William J. Anderst, PhD.

Biomechanical cadaver testing indicates adjacent segment motion increases after one-level anterior cervical spine arthrodesis, and two-level arthrodesis exacerbates these effects. There is little in vivo evidence to support those biomechanical studies.

In this study, fifty patients received either one-level C56 arthrodesis or two-level C456 or C567 arthrodesis and were tested preoperatively (PRE) and 1 year postoperatively (1YR-POST) along with 23 asymptomatic controls. A validated CT model-based tracking technique was used to measure 3D vertebral motion from biplane radiographs collected during dynamic flexion-extension and axial rotation of the cervical spine. Head and adjacent segment intervertebral end-range range of motion (ROM) and mid-range ROM were compared between one-level and two-level arthrodesis patients and controls.

Small (2.3° or less) but non-significant increases in adjacent segment end-range ROM were observed from PRE to 1YR-POST. Mid-range flexion-extension ROM in the C67 motion segment inferior to the arthrodesis and mid-range axial rotation ROM in the C45 motion segment superior to the arthrodesis increased from PRE to 1YR-POST.

This study provides in vivo evidence that contradicts long-held beliefs that adjacent segment end-range ROM increases appreciably after anterior cervical arthrodesis and that two-level arthrodesis exacerbates these effects. Mid-range ROM appears to be more useful than end-range ROM for detecting early changes in adjacent segment motion after cervical spine arthrodesis.

Read more about this study on PubMed.

Other study authors include:

Collaborators not affiliated with the University of Pittsburgh:

Adam S. Kanter, MD

              Hoag Medical Group