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Matthew C. Davis, Betsy D. Hopson, Jeffrey P. Blount, Rachel Carroll, Tracey S. Wilson, Danielle K. Powell, Amie B. Jackson McLain, and Brandon G. Rocque


Predictors of permanent disability among individuals with spinal dysraphism are not well established. In this study, the authors examined potential risk factors for self-reported permanent disability among adults with spinal dysraphism.


A total of 188 consecutive individuals undergoing follow-up in an adult spinal dysraphism clinic completed a standardized National Spina Bifida Patient Registry survey. Chi-square tests and logistic regression were used to assess bivariate relationships, while multivariate logistic regression was used to identify factors independently associated with self-identification as “permanently disabled.”


A total of 106 (56.4%) adults with spina bifida identified themselves as permanently disabled. On multivariate analysis, relative to completion of primary and/or secondary school, completion of technical school (OR 0.01, 95% CI 0–0.40; p = 0.021), some college (OR 0.22, 95% CI 0.08–0.53; p < 0.001), college degree (OR 0.06, 95% CI 0.003–0.66; p = 0.019), and holding an advanced degree (OR 0.12, 95% CI 0.03–0.45; p = 0.002) were negatively associated with permanent disability. Relative to open myelomeningocele, diagnosis of closed spinal dysraphism was also negatively associated with permanent disability (OR 0.20, 95% CI 0.04–0.90; p = 0.036). Additionally, relative to no stool incontinence, stool incontinence occurring at least daily (OR 6.41, 95% CI 1.56–32.90; p = 0.009) or more than weekly (OR 3.43, 95% CI 1.10–11.89; p = 0.033) were both positively associated with permanent disability. There was a suggestion of a dose-response relationship with respect to the influence of educational achievement and frequency of stool incontinence on the likelihood of permanent disability.


The authors’ findings suggest that level of education and degree of stool incontinence are the strongest predictors of permanent disability among adults with spinal dysraphism. These findings will be the basis of efforts to improve community engagement and to improve readiness for transition to adult care in a multidisciplinary pediatric spina bifida clinic.

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R. Shane Tubbs, Marios Loukas, Mohammadali M. Shoja, E. George Salter, W. Jerry Oakes, and Jeffrey P. Blount


The authors describe a technique in which the cervical portion of the vagus nerve is exposed during procedures such as neuroma resection or, more commonly, during the placement of a vagus nerve stimulator.


To test their hypothesis that a posterolateral approach to the vagus nerve may be feasible and efficacious, the authors performed dissection of the left-sided vagus nerve in 13 adult cadavers. The carotid sheath was exposed via the posterior cervical triangle, and the vagus nerve was identified posterolaterally. Measurements were made of the length of available nerve, and the anatomical approach was documented. As part of a comparison study regarding the available length of nerve, the authors exposed the left vagus nerve in five additional adult cadavers via a standard anterior approach to the carotid sheath, and compared the results obtained with each technique.

A mean length of 12 cm of the vagus nerve was isolated when using the posterior approach to the carotid sheath, whereas a mean length of 11 cm of the nerve was documented when using the anterior approach. With the aforementioned posterior approach, no obvious injury occurred to the vagus nerve or other local neurovascular structures such as the spinal accessory nerve.


Evaluation of the findings obtained in the present cadaveric study showed that a posterior approach to the vagus nerve is feasible. The technique for posterior exposure of the carotid sheath may prove useful in surgical exposures of the vagus nerve when a standard anterior method is not possible.

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R. Shane Tubbs, Mohammadali M. Shoja, Leslie Acakpo-Satchivi, John C. Wellons III, Jeffrey P. Blount, W. Jerry Oakes, and Bermans J. Iskandar


Surgical exposure of the extracranial part of the vertebral artery (VA) is occasionally necessary. Historically, the greater portion of the extracranial portion of the VA has been approached by traversing the anterior cervical triangle. The authors speculated that this entire segment of the VA could be reached with equal efficacy via the posterior cervical triangle (PCT).


Six adult cadavers underwent dissection of the left and right VAs via the PCT. The entire extracranial VA was easily exposed through this approach. Only three of 12 sides required the transection of the clavicular head of the sternocleidomastoid muscle for exposure of the most proximal segment of the VA as it originated from the subclavian artery. No gross injury to the VA or other regional vessels or nerves was noted.


The authors found that the extracranial VA can be exposed easily through the PCT. Following confirmation of this technique in vivo, this approach may be added to the surgeon’s armamentarium for exposing the extracranial segment of the VA.

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R. Shane Tubbs, E. George Salter, John C. Wellons III, Jeffrey P. Blount, and W. Jerry Oakes

Object. The spinal accessory nerve (SAN) within the posterior cervical triangle (PCT) is the most commonly iatrogenically injured nerve in the body. Nevertheless, there is a paucity of published information regarding superficial landmarks for the SAN in this region. Additional identifiable landmarks of this nerve may assist the surgeon in identifying it for repair, use of it in peripheral nerve neurotization, or avoiding it as in proximal brachial plexus repair. The present study was undertaken to provide reliable superficial landmarks for the identification of the SAN within the PCT.

Methods. The PCT was dissected in 30 cadaveric sides. Measurements were made between the SAN and surrounding landmarks. The mean distances between the entry site of the SAN into the trapezius and a midpoint of the clavicle, mastoid process, acromion process, and lateral aspect of the sternocleidomastoid (SCM) muscle were 6, 7, 5.5, and 3.5 cm, respectively. The mean distances between the angle of the mandible and the mastoid process and the exit point of the SAN from the posterior border of the SCM muscle were 6 and 5 cm, respectively. The mean width and length of the SAN were 3 and 3.5 cm, respectively.

Conclusions. It is the authors' hope that these data will aid those who may need to locate or avoid the SAN while undertaking surgery in the PCT and thus decrease morbidity that may follow manipulation of this region.

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R. Shane Tubbs, E. George Salter, John C. Wellons III, Jeffrey P. Blount, and W. Jerry Oakes

Object. Reports describing surgical landmarks with which to identify the branches of the lumbar plexus found on the posterior abdominal wall are lacking in the English-language literature.

Methods. The authors examined 22 sides from six female and five male cadavers. Measurements were made between the branches of the lumbar plexus and various bone landmarks such as the midline vertebral bodies, supracristal plane—a horizontal line connecting the superior-most aspect of the left and right iliac crests approximating the L4–5 vertebrae—and anterior superior iliac spine (ASIS).

The mean distances from the midline and as they emerged through or lateral to the psoas major muscle to the subcostal, iliohypogastric, ilioinguinal, lateral femoral cutaneous, genitofemoral, and femoral nerves, were 5.5, 6, 6.5, 6, 4.5, and 4.5 cm, respectively. At a vertical line through the midpoint between the ASIS and the midline, the subcostal, iliohypogastric, and ilioinguinal nerves were superior to the supracristal plane at mean distances of 8, 4, and 5 cm, respectively. Inferior to the supracristal plane and in a vertical line through a midpoint between the ASIS and the midline, the lateral femoral and femoral nerves were found to have mean distances of 5 and 5.5 cm, respectively. The obturator nerve had a mean distance of 3 cm lateral to the midline. Additionally, the lateral femoral cutaneous nerve had a mean distance of 1.5 cm inferomedial to the ASIS.

Conclusions. A good working knowledge of the locations and anatomy of the nerves of the lumbar plexus on the posterior abdominal wall is necessary for the surgeon who operates in this region. The measurements provided herein will aid the surgeon who wishes to expose or avoid these nerves, thus precluding injury.

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

Object. To the best of the authors' knowledge, no quantitative analysis of the atlantoaxial interlaminar distance in flexion (ILD) in children exists in the medical literature. In this study they sought to determine the age-matched relationship between the posterior elements of the atlas and axis in children in cervical spine flexion, to be used as an adjunct to the atlantodental interval in common clinical use.

Methods. Lateral radiographs of the cervical spine in full flexion were analyzed in 74 children. The atlantoaxial ILD was defined as the distance between a midpoint of the anterior cortices of the atlantal and axial posterior arches.

The mean ILD for the entire group was 19 mm (range 8–30 mm). No significant difference was seen between male and female patients (p = 0.084). When stratified by age, the mean ILD was 12.3 ± 3 mm (15 cases) in children age 3 years or younger and 20.5 ± 4.7 mm (59 cases) in children age older than 3 years. Further stratification of the groups yielded a mean ILD of 10.4 ± 1.4 [eight cases]) in children age 1 to 2 years, and 14.4 ± 4.7 mm (seven cases) in children age 3 years. In children older than 3 years of age the mean ILD was consistently approximately 20 ± 5 mm regardless of age.

Conclusions. Rapid, safe, and accurate diagnosis of the cervical spine is essential in critical care. Knowledge of the distance between the posterior elements of the atlas and axis in flexion should enhance the clinicians' (those who clear cervical spines) ability to diagnose accurately atlantoaxial instability on lateral radiographs obtained in flexion.

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

Object. The quantitative analysis of odontoid process angulation has had scant attention in the Chiari I malformation population. In this study the authors sought to elucidate the correlation between posterior angulation of the odontoid process and patients with Chiari I malformation.

Methods. Magnetic resonance images of the craniocervical junction obtained in 100 children with Chiari I malformation and in 50 children with normal intracranial anatomy (controls) were analyzed. Specific attention was focused on measuring the degree of angulation of the odontoid process and assigning a score to the various degrees. Postoperative outcome following posterior cranial fossa decompression was then correlated to grades of angulation. Other measurements included midsagittal lengths of the foramen magnum and basiocciput, the authors' institutions' previously documented pB—C2 line (a line drawn perpendicular to one drawn between the basion and the posterior aspect of the C-2 body), level of the obex from a midpoint of the McRae line, and the extent of tonsillar herniation.

Higher grades of odontoid angulation (retroflexion) were found to be more frequently associated with syringomyelia and particularly holocord syringes. Higher grades of angulation were more common in female patients and were often found to have obices that were caudally displaced greater than three standard deviations below normal.

Conclusions. These results not only confirm prior reports of an increased incidence of a retroflexed odontoid process in Chiari I malformation but quantitatively define grades of inclination. Grades of angulation were not found to correlate with postoperative outcome. It is the authors' hopes that these data add to our current limited understanding of the mechanisms involved in hindbrain herniation.

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

Object. The medial tubercles of the atlas serve as the attachments of the transverse ligament and provide an important anchoring site for which no discussion of their fine anatomy is published in the literature. In this study the authors examine this anatomy along with its osseous relationships.

Methods. One hundred dry cadaveric atlantal tubercles were assessed for size and relationship to nearby anatomical osseous structures. In addition, eight cadaveric specimens were evaluated for their anatomy in this area.

All specimens exhibited atlantal tubercles for the attachment of the transverse portion of the cruciate ligament of the atlas. Right-sided tubercles tended to be of a larger caliber. Overall, right-sided vertical distances between these tubercles and the superior articular facets and inferior articular facets were greater, although distances from each tubercle to the lateral margin of the dental facets anteriorly were found to be constant, as were intertubercular distances. The mean angle formed between both tubercles and the dental facet was 75°.

Conclusions. The data derived in this study should be useful to the clinician for whom the craniocervical junction is a vital anatomical area.

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

✓ The authors describe the use of autogenetic posterior atlantooccipital (PAO) membrane for duraplasty following after posterior cranial fossa surgery. The PAO membrane is routinely exposed for procedures of the posterior cranial fossa and merely needs to be dissected free of the underlying dura mater. Recently this membrane was obtained in several pediatric patients following procedures of the posterior cranial fossa such as duraplasty in case of Chiari I malformation. No postoperative complications were found at 6-month follow-up examination. The advantages of this intervention include less manipulation of muscle and fascia than that involved in other procedures and, therefore, seemingly less postoperative pain and the negation of issues inherent with foreign-body graft sources. The authors believe this structure to be of use as a dural substitute in small dural openings of the posterior cranial fossa.