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The Nuchal Ligament: its Variation and Clinical Significance in the Lower Cervical Spine: Poster #61

Kobayashi, Naoki MD; Fujiwara, Atsushi MD; Kitagawa, Tomoaki MD; Saiki, Kazuhiko MD; Kakazu, Satoshi MD; Kato, Nakayuki MD; Tamai, Kazuya MD1

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Spine Journal Meeting Abstracts: 2005 - Volume - Issue 7 - p 293–294
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INTRODUCTION: The nuchal ligament is one of the ligaments in the posterior cervical spine, and is thought as a major constraint to excessive cervical flexion. In 1976, Fielding et al dissected 8 human cervical spines and described that the nuchal ligament was triangular in shape and was divided into funicular and lamellar portions. The funicular portion (a dense and fibrous midline band) runs from the C7 spinous process to the external occipital protuberance. In our experience during surgical exposure of the posterior cervical spine, the funicular portion of the nuchal ligament sometimes firmly attached to not only C7 but also C6 spinous process. We hypothesized that the longer the C6 spinous process, the more probable that the nuchal ligament attached to C6 spinous process, and that this ligament variation could influence the stability of the C6/7 motion segment, and then could determine the relative segmental range of motion between the C5/6 and C6/7. The purposes of this study were to compare the nucahl ligament between on MRI and during surgical exposure, and to examine the association of the attachment status of the nuchal ligament with the length of spinous processes and the relative segmental range of motion in the sagittal plane between the lower two cervical segments.

METHODS: Study 1 consisted of consecutive 10 patients who underwent laminoplasty because of cervical spondylotic myelopathy. There were 6 men and 4 women with the mean age of 67 years. The attachment status of the nuchal ligament to the C6 and C7 spinous process on MRI was compared with that observed one during surgical exposure. Study 2 consisted of 42 consecutive persons who underwent MRI of the cervical spine for a part of the medical health check. There were 27 men and 15 women with the mean age of 55 years. On MR image, the attachment status of the nuchal ligament to C6 and C7 was reviewed by one of the authors. These images were stored in digitized form, and the length of spinous process at C6 and C7 was measured using an image analysis software by a different author. The ratio of C6 to C7 spinous process length was also calculated. Study 3 consisted of consecutive 49 patients with degenerative spinal disease under the age of 45 who underwent MRI and functional radiography. There were 34 men and 15 women with the mean age of 35 years. Functional flexion/extension radiograph was stored in digitized form, and the segmentalrange of motion at the C5/6 and C6/7 was measured with the same manner. The relative segmental range of motion was also calculated. The patients with collapsed disc at the C5/6 and/or the C6/7 were excluded.

RESULTS: The attachment status of the nuchal ligament to the spinous processes on MRI were well consistent with those observed during surgery. The status was classified into the following 3 types. Type A: the ligament firmly attached to only C7 spinous process. Type B: the ligament firmly attached to C7 spinous process and tied to C6 spinous process through a fibrous band. Type C: the ligament firmly attached to both C6 and C7 spinous processes. In study 2, there were 13 type A, 9 type B and 20 type C ligaments. The length of C6 spinous process in type C was significantly longer than that in type A and B (p<0.05). The ratio of the C6 spinous process length to C7 in type A, B and C was 0.72±0.09, 0.80±0.09 and 0.88±0.06, respectively. The ratio in type C was significantly greater than that in type A and B (p<0.05). In study 3, 12 patients were excluded because of having collapsed disc and/or un‐reflected C7 vertebral body on radiography. There were 14 type A, 10 type B and 13 type C. The ratio of segmental range of motion at the C5/6 to the C6/7 in type A, B and C was 1.12 ± 0.39, 1.43 ± 0.58 and 1.82 ± 0.70, respectively. The ratio in type C was significantly greater than that in type A and B (p<0.05).

DISCUSSION: This study demonstrated the variation of the attachment status of the nuchal ligament to the spinous process in the lower cervical spine. The status was classified into the following 3 types. Type A: the ligament firmly attached to only C7 spinous process. Type B: the ligament firmly attached to C7 spinous process and connected to C6 spinous process through a fibrous band. Type C: the ligament firmly attached to both C6 and C7 spinous processes. If the ligament firmly attached to both C6 and C7 spinous processes (Type C), the length of C6 spinous process was significantly longer. It could be postulated that the variation of this ligament influenced the relative amount of segmental range of motion between the C5/6 and C6/7 level in the individual cervical spine. Further studies are needed to confirm the association of the nuchal ligament variation with the motion segment biomechanics in the lower cervical spine.

If noted, the author indicates something of value received. The codes are identified as: a‐ research or institutional support; b‐ miscellaneous funding; c‐ royalties; d‐ stock options; e‐ consultant or employee; n‐ no conflicts disclosed, and * disclosure not available at the time of printing. For full information, refer to inside of back cover.

© 2005 Lippincott Williams & Wilkins, Inc.