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R. Shane Tubbs, Justin D. Hallock, Virginia Radcliff, Robert P. Naftel, Martin Mortazavi, Mohammadali M. Shoja, Marios Loukas and Aaron A. Cohen-Gadol

aspects of each. Search engines such as PubMed and various germane textbooks were used, searching for salient chapters and terms such as the following: ligaments, neck, occipital, atlas, axis, connective tissues, anatomy, biomechanics, pathology, C-1, C-2, membrane, craniocervical junction, and craniovertebral junction. Biomechanics of CCJ The CCJ is composed of 2 major joints: the atlantooccipital and the atlantoaxial joints. These joints are responsible for the majority of the movement of the cervical spine and operate on different biomechanical principles. The

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R. Shane Tubbs, Joshua Dixon, Marios Loukas, Mohammadali M. Shoja and Aaron A. Cohen-Gadol

Object

Knowledge of the anatomy of the ligaments that unite the head with the neck is important to the clinician who treats patients with lesions in this region. Although the anatomy and function of these ligaments have been well described, those of the Barkow ligament (BL) have yet to be studied.

Methods

Via an anterior approach, 13 unembalmed adult cadavers underwent dissection of the craniocervical junction with special attention to the presence, anatomy, and function of the BL.

Results

The BL was found in 92.3% of specimens. The attachment of each ligament onto the medial aspect of the occipital condyle was consistent and just anterior to the attachment of the alar ligaments. In 75% of specimens, there was some connection between the BL and the anterior atlantooccipital membrane. Connections between other adjacent ligamentous structures were not identified. The average width, length, and thickness of the BL were 4, 2.5, and 3.5 mm, respectively. With ranges of motion of the craniocervical junction, only extension of the atlantooccipital joint produced tension in the BL. The mean tension to failure of the ligament was 28 N. Statistical analysis revealed no significant difference in width, length, and thickness of the ligaments based on sex.

Conclusions

The BL was found in all but 1 of our specimens. This ligament appears to resist extension of the atlantooccipital joint and may be synergistic with the anterior atlantooccipital membrane. Interestingly, the function of this ligament as found in this study relies on the integrity of the transverse ligament. Knowledge of this ligament may aid in further understanding craniocervical stability and help in differentiating normal from pathological tissue using imaging modalities.

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R. Shane Tubbs, Paul Grabb, Alan Spooner, Wally Wilson and W. Jerry Oakes

significance historically ascribed to the apical ligament so that clinicians will know whether to focus on disease or disruption of the ligament when considering the craniocervical junction. Materials and Methods Twenty formalin-fixed adult human cadavers were placed in the prone position, and their apical ligaments dissected. Twelve specimens were from males and eight from females. The age range of the patients from whom the specimens were obtained was from 59 to 87 years of age (mean 73 years). No pathological entities were noted at the craniocervical junction in any

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R. Shane Tubbs, John C. Wellons III, Jason Banks, Jeffrey P. Blount and W. Jerry Oakes

clinicians who appreciate the craniocervical junction as part of their discipline. Materials and Methods Fifty dried adult human C-1 vertebrae were used in this study. Twenty-nine specimens were obtained in male cadavers and 21 in female cadavers. All specimens were obtained in elderly caucasian individuals. Three male specimens were from C-1 vertebrae that had assimilated into the occiput. All dimensions were measured using calipers, and No. 2.5 surgical loupes were used for magnification. Measurements were made on both the left and right tubercles of each vertebra

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R. Shane Tubbs, Martin M. Mortazavi, Marios Loukas, Mohammadali M. Shoja and Aaron A. Cohen-Gadol

intracranial denticulate ligament (lig). Note the relationship between the course of the vertebral artery and its branches and the spinal accessory nerve (n) and first cervical rootlets to this ligament. a = artery. Used with permission from Clarian Health. Methods Ten fresh and 5 embalmed adult cadavers (30 sides) underwent dissection of the craniocervical junction. Nine specimens were male and 6 were female, and the age range of the individuals at the time of death was 49–101 years (mean 75 years). In the prone position, the specimens underwent removal of the

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R. Shane Tubbs, Marios Loukas, Bulent Yalçin, Mohammadali M. Shoja and Aaron A. Cohen-Gadol

surgery or any pathological entity in the region of the craniocervical junction. The mean age of this group was 78 years (range 59–102 years). After the skin and the suboccipital muscles were removed, the C-1 and C-2 nerves were identified and dissected toward their origin from the spinal cord. The posterior arch of the atlas was removed with bone rongeurs for better visualization of the C-1 and C-2 nerves and the horizontal part of the VA. With scissors, a square incision was made in the dura mater to expose the spinal cord and all parts of the C-1 spinal nerve

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R. Shane Tubbs, John C. Wellons III, Jeffrey P. Blount, Paul A. Grabb and W. Jerry Oakes

the craniocervical junction does not correlate with the presence of syringomyelia in the Chiari I malformation and that this compression was seemingly due to a posteriorly oriented odontoid, not true basilar invagination. Our present results show that higher grades of odontoid angulation do indeed correlate with syringomyelia: a syrinx was apparent in 74% of patients with a Grade II or Grade III odontoid angulation. Of holocord syringes, 70% were demonstrated in patients with a Grade III odontoid angulation. Curiously, no single grade of odontoid angulation

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R. Shane Tubbs, Martin M. Mortazavi, Marios Loukas, Anthony V. D'Antoni, Mohammadali M. Shoja, Joshua J. Chern and Aaron A. Cohen-Gadol

Object

Occipital neuralgia can be a debilitating disease and may occur following operative procedures near the occipital and nuchal regions. One nerve of this region, the third occipital nerve (TON), has received only scant attention, and its potential contribution to occipital neuralgia has not been appreciated. Therefore, in the present study the authors aimed to detail the anatomy of this nerve and its relationships to midline surgical approaches of the occiput and posterior neck.

Methods

Fifteen adult cadavers (30 sides) underwent dissection of the upper cervical and occipital regions. Special attention was given to identifying the course of the TON and its relationship to the soft tissues and other nerves of this region. Once identified superficially, the TON was followed deeply through the nuchal musculature to its origin in the dorsal ramus of C-3. Measurements were made of the length and diameter of the TON. Additionally, the distance from the external occipital protuberance was measured in each specimen. Following dissection of the TON, self-retaining retractors were placed in the midline and opened in standard fashion while observing for excess tension on the TON.

Results

Articular branches were noted arising from the deep surface of the nerve in 63.3% of sides. The authors found that the TON was, on average, 3 mm lateral to the external occipital protuberance, and small branches were found to cross the midline and communicate with the contralateral TON inferior to the external occipital protuberance in 66.7% of sides. The TON trunk became subcutaneous at a mean of 5 cm inferior to the external occipital protuberance. In all specimens, the cutaneous main trunk of the TON was intimately related to the nuchal ligament. Insertion of self-retaining retractors in the midline placed significant tension on the TON in all specimens, both superficially and more deeply at its adjacent facet joint.

Conclusions

Although damage to the TON may often be unavoidable in midline approaches to the craniocervical region, appreciation of its presence and knowledge of its position and relationships may be useful to the neurosurgeon who operates in this region and may assist in decreasing postoperative morbidity.

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R. Shane Tubbs, Philip C. Johnson, Mohammadali M. Shoja, Marios Loukas and W. Jerry Oakes

position, the overlying muscles (trapezius, splenius capitis, semispinalis capitis) covering the posterior craniocervical junction were removed. Once the muscles that form the suboccipital triangle (that is, the rectus capitis posterior major) were identified, they were removed and the posterior arch of the atlas identified. If a foramen arcuale was present in the cadaveric specimen, the diameter of the VA was measured just before, within, and immediately after it traversed the foramen arcuale. All measurements including the length and thickness of the osseous strut were

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study, this muscle never covered more than 5 mm of the inferior edge of the TS and was found to be a reliable anatomical structure for avoiding the medial segment of the TS. Conclusions. These findings could aid the surgeon in localizing the TS with various midline approaches to the posterior fossa and the craniocervical junction. We read with interest the paper by Tubbs and colleagues (Tubbs RS, Salter G, Oakes WJ: Superficial surgical landmarks for the transverse sinus and torcular herophili ( J Neurosurg 93: 279–281, August, 2000). The authors