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Mehmet Arslan, Ayhan Cömert, Halil İbrahim Açar, Mevci Özdemir, Alaittin Elhan, İbrahim Tekdemir, R. Shane Tubbs, Ayhan Attar, and Hasan Çağlar Uğur

Object

Although infrequent, injury to adjacent neurovascular structures during posterior approaches to lumbar intervertebral discs can occur. A detailed anatomical knowledge of relationships may decrease surgical complications.

Methods

Ten formalin-fixed male cadavers were used for this study. Posterior exposure of the lumbar thecal sac, nerve roots, pedicles, and intervertebral discs was performed. To identify retroperitoneal structures at risk during posterior lumbar discectomy, a transabdominal retroperitoneal approach was performed, and observations were made. The distances between the posterior and anterior edges of the lumbar intervertebral discs were measured, and the relationships between the disc space, pedicle, and nerve root were evaluated.

Results

For right and left sides, the mean distance from the inferior pedicle to the disc gradually increased from L1–2 to L4–5 (range 2.7–3.8 mm and 2.9–4.5 mm for right and left side, respectively) and slightly decreased at L5–S1. For right and left sides, the mean distance from the superior pedicle to the disc was more or less the same for all disc spaces (range 9.3–11.6 mm and 8.2–10.5 mm for right and left, respectively). The right and left mean disc-to-root distance for the L3–4 to L5–S1 levels ranged from 8.3 to 22.1 mm and 7.2 to 20.6 mm, respectively. The root origin gradually increased from L-1 to L-5. The right and left nerve root–to-disc angle gradually decreased from L-3 to S-1 (range 105°–110.6° and 99°–108°). Disc heights gradually increased from L1–2 to L5–S1 (range 11.3–17.4 mm). The mean distance between the anterior and posterior borders of the intervertebral discs ranged from 39 to 46 mm for all levels.

Conclusions

To avoid neighboring neurovascular structures, instrumentation should not be inserted into the lumbar disc spaces more than 3 cm from their posterior edge. Accurate anatomical knowledge of the relationships of intervertebral discs to nerve roots is needed for spine surgeons.

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R. Shane Tubbs, Jason M. Rogers, Marios Loukas, Ayhan Cömert, Mohammadali M. Shoja, and Aaron A. Cohen-Gadol

Object

The palmar cutaneous branch of the ulnar nerve (PCUN) has received little attention in the literature, and to the authors' knowledge, has received no attention in the neurosurgical literature. The present study was performed to help the surgeon minimize postoperative complications of nerve decompression at the wrist.

Methods

Forty cadaveric upper limbs underwent dissection of the ulnar nerve in the forearm, at the wrist, and in the palm. The PCUN was investigated and when identified, measurements were made and relationships documented between this cutaneous branch and the ulnar artery. The length and width of the PCUN were measured, as was the distance from the medial epicondyle of the humerus to the origin of the PCUN from the ulnar nerve.

Results

A PCUN was found on 90% of sides. The origin of the PCUN from the ulnar nerve was found to lay a mean of 14.3 cm distal to the medial epicondyle. The mean length and width of this branch were 13 and 0.08 cm, respectively. In the forearm, the PCUN traveled lateral to the ulnar artery on 75% of sides and on the medial side of this vessel on the remaining sides. The PCUN perforated the fascia of the anterior forearm just proximal to the distal wrist crease. In the palm, the PCUN traveled superficial to the superficial palmar arch on all but 5 sides, where it traveled deep to this vascular structure's distal extent. On 2 sides each, the PCUN communicated with the superficial and deep ulnar nerves. On 2 sides, the PCUN communicated with the palmar cutaneous branch of the median nerve. The majority of the terminal fibers of the PCUN were found on the ulnar side of a hypothetical line drawn longitudinally through the fourth digit and supplied an area roughly 3 × 3 cm over the proximal medial palm.

Conclusions

The authors hope that the present data may be useful to the surgeon during decompressive procedures at the wrist, such as carpal tunnel and the Guyon canal. Based on this study, skin incisions of the palm made longitudinally along a line through the middle of the fourth digit would minimize injury to the PCUN.

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R. Shane Tubbs, Diala El-Zammar, Marios Loukas, Ayhan Cömert, and Aaron A. Cohen-Gadol

Object

Intradural intercommunications between adjacent nerve roots have received scant attention in the literature. Moreover, the pattern of these connections among individuals harboring normal, pre-, and postfixed brachial plexuses, to the authors' knowledge, has not been explored.

Methods

Sixty adult cadavers were evaluated for the presence of a normal, prefixed, or postfixed brachial plexus. Next, with the cadaver placed prone, laminectomies of all cervical and the upper thoracic vertebrae were performed. The dura mater was opened and observations were made for the presence of neural intercommunications between the roots of adjacent spinal levels. Any correlations between such root communications and pre- and postfixed brachial plexuses were explored.

Results

Among the cadavers, 28% harbored prefixed and 5% harbored postfixed brachial plexuses. Intercommunications between adjacent dorsal roots were more or less equally distributed between left and right sides. A total of 134 interconnections were identified between C-1 and T-2 levels. No interconnection spanned more than one spinal segment. When all sides were included, in ascending order based on the number of interconnections present, interconnections between roots were found between T-1 and T-2, C-1 and C-2, C-8 and T-1, C-2 and C-3, C-3 and C-4, C-4 and C-5, C-7 and C-8, C-6 and C-7, and C-5 and C-6. In this same order, the percent of total connections for each of these levels was 0, 0.8, 2, 7, 13, 15, 16, 20, and 25%. For left and right sides, a total of 73 and 61 interconnections were identified, respectively. This order of concentration was found to have no statistical difference between cadavers that had a normal arrangement of the brachial plexus, a prefixed brachial plexus, or a postfixed brachial plexus. No specimen was found to have interconnections between adjacent ventral roots.

Conclusions

Such variations as intradural interconnections may lead to misinterpretation of spinal levels harboring pathological entities of the spinal axis and should be considered during surgical procedures of this region such as rhizotomy. However, the present study did not find a correlation between the level of these interconnections and whether the brachial plexus was pre- or postfixed (that is, there were no observable shifts intradurally that corresponded to the extradural segmental contributions to the brachial plexus).