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Dynamic Changes in Spinal Cord Compression by Cervical Ossification of the Posterior Longitudinal Ligament Evaluated by Kinematic Computed Tomography Myelography

Yoshii, Toshitaka MD, PhD*,†; Yamada, Tsuyoshi MD*,†; Hirai, Takashi MD, PhD*,†; Taniyama, Takashi MD*,†; Kato, Tsuyoshi MD, PhD*; Enomoto, Mitsuhiro MD, PhD*,†; Inose, Hiroyuki MD, PhD*,†; Sumiya, Satoshi MD*; Kawabata, Shigenori MD, PhD*; Shinomiya, Kenichi MD, PhD*,†,‡; Okawa, Atsushi MD, PhD*,†,‡

doi: 10.1097/BRS.0000000000000086
Cervical Spine

Study Design. A prospective clinical study.

Objective. To investigate the dynamic causative factor in the pathogenesis of myelopathy in patients with cervical ossification of the posterior longitudinal ligament (OPLL) using kinematic computed tomography (CT) myelography.

Summary of Background Data. Kinematic CT myelography is useful for dynamically evaluating the cervical spine with high-resolution images, particularly in bony compressive lesions. However, no studies have evaluated the dynamic factors in patients with OPLL using kinematic CT myelography.

Methods. From 2008 to 2013, 51 consecutive patients with OPLL who presented with myelopathy were prospectively enrolled in this study. The patients were examined with kinematic (flexion-extension) CT myelography using a multidetector CT scanner. The range of motion at C2–C7 from flexion to extension was measured in the sagittal view. The segmental range of motion, anterior-posterior diameter and cross-sectional area (CSA) of the spinal cord were measured at the level where the spinal cord was most compressed by OPLL.

Results. The neurological condition of the patients evaluated by Japanese Orthopaedic Association scores were 10.8 ± 2.4 points. The mean range of motion at C2–C7 and at the most compressed segment were 23.1 ± 11.7 and 7.0 ± 4.4°, respectively. Both the anterior-posterior diameter and the CSA at the most compressed levels were significantly decreased during neck extension compared with flexion. Interestingly, the anterior-posterior diameter and the CSA were decreased during neck flexion in 13.7% (7/51) of the patients. All 7 of these patients had massive OPLL with an occupying rate 60% or more. The dynamic change rate of CSA (flexion/extension) was significantly smaller in patients with an OPLL occupying rate 60% or more compared with patients with an occupying rate less than 60%.

Conclusion. Although spinal cord compression was increased during neck extension in most of the patients, greater levels of compression could be placed on the spinal cord during neck flexion when the patients had OPLL with a high occupying rate.

Level of Evidence: 4

We evaluated the dynamic factor in the pathogenesis of myelopathy in patients with ossification of the posterior longitudinal ligament (OPLL) using kinematic computed tomography myelography. Although spinal cord was more compressed by OPLL during neck extension in most patients, the cord compression can increase during neck flexion when the patients have OPLL with a high occupying rate.

*Section of Orthopaedic and Spinal Surgery, Graduate School and

Section of Regenerative Therapeutics for Spine and Spinal Cord, Graduate School, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan; and

Global Center of Excellence (GCOE) Program for International Research Center for Molecular Science in Tooth and Bone Disease, Tokyo Medical and Dental University, Kanda-Surugadai, Chiyoda-ku, Tokyo, Japan.

Address correspondence and reprint requests to Toshitaka Yoshii, MD, PhD, Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan; E-mail: yoshii.orth@tmd.ac.jp

Acknowledgment date: August 2, 2013. First revision date: September 21, 2013. Acceptance date: October 12, 2013.

The device(s)/drug(s) is/are FDA-approved or approved by corresponding national agency for this indication.

No funds were received in support of this work.

Relevant financial activities outside the submitted work: grants/grants pending.

© 2014 by Lippincott Williams & Wilkins