582 - Ranges of Cervical Intervertebral Disc Deformation during in-vivo Dyna...

Oral Posters: Cervical

Presented by: Y. Yu - View Audio/Video Presentation (Members Only)

Author(s):

Y. Yu(1), H. Mao(1), J.-S. Li(1), T.-Y. Tsai(1), K. Khan(1), L. Cheng(1), K. Wood(2), G. Li(1), T. Cha(1)

(1) Massachusetts General Hospital/ Harvard Medical School, Orthopaedic Surgery, Boston, MA, United States
(2) Stanford University Medical Center, Palo Alto, CA, United States

Abstract

Introduction: Cervical disc diseases can result in instability, neurologic deficit, spinal stenosis, facet dysfunction and less cervical lordosis. Despite various biological factors that have been related to disc diseases, abnormal spinal motion and the consequent abnormal loading have been widely assumed to be the etiology of spinal pathology. Therefore, understanding of the spinal biomechanics is critically important for investigation of the mechanisms of cervical spine disc diseases and for development of treatment modalities to restore neck function.

Methods: Ten asymptomatic human subjects were tested using a combined dual fluoroscopic imaging system (Figure 1a) and MRI based 3D modeling technique. Overall disc deformation during maximal flexion-extension of the neck was determined using the changes of the space geometry between the two endplates of each intervertebral segment (C3/4, C4/5, C5/6 and C6/7) between the two extreme neck positions. Five points (anterior, center, posterior, left and right) of each disc (Figure 1b) were analyzed to examine the distributions of the disc deformation. Calculated overall disc deformations at the two neck positions of a typical subject were shown in Figure 2.

Results: The data indicated that between the functional maximum flexion and extension of the neck, the anterior points of the discs experienced large changes of distraction/compression deformation (C3/4 70.3±34.1 %, C4/5 61.9±28.8 %, C5/6 75.9±32.2 %, C6/7 39.1±37.4 %) and shear deformation (C3/4 68.3±34.1 %, C4/5 78.5±41.3 %, C5/6 48.3±20.9 %, C6/7 33.1±18.2 %) (Table 1). The higher level discs experienced higher ranges of disc deformation. No significant difference was found in ranges of deformation of posterior points of all discs.

Discussion: The overall intervertebral disc deformation of the sub-axial cervical spine was investigated during a maximum flexion-extension of the neck. The changes of distraction/compression and shear deformation could reach over 70% in cervical spine discs. The data indicated that the anterior region experienced higher changes of deformation than the center and posterior regions, except for the C6/7 disc. The changes of the distraction/compression and shear deformation of the sub-axial cervical spine between the maximum flexion and extension positions of the neck were segment-level dependent and disc location dependent. The data obtained from this study could serve as baseline knowledge for understanding the cervical spine disc biomechanics and for investigation of the biomechanical etiology of disc diseases. These data could also provide insights for development of motion preservation surgeries for cervical spine.

Significance: These data may be instrumental for investigation of cervical spine biomechanics and for investigation of biomechanical factors that may cause disc degeneration in patients. Further, this study could provide insights into improvement of fusion and disc replacement surgeries that is aimed to restore cervical function and to prevent adjacent segment degenerations after the surgery.

Changes of the disc deformation