Mechanical relationship of filum terminale externum and filum terminale internum: is it possible to detether the spinal cord extradurally?

INTRODUCTION: Intradural transection of the filum terminale (FTI) is often used to treat tethered cord syndrome. Recently, some have proposed that the extradural part of the filum terminale (FTE) can be sectioned with equal results but with fewer complications. Therefore, the present cadaveric study aimed to evaluate the anatomical foundation of such procedures. METHODS: A posterior lumbosacral approach was performed on five fresh-frozen cadaveric specimens to expose both the FTI and FTE. Tension was then applied to the FTE and observations and measurements made of any movement of the FTI. Other morphological measurements (e.g., length, diameter) of the FTI and FTE were also made. RESULTS: Although very minimal movement of the FTI was seen in the majority of specimens following tension on the FTE, no specimen was found to have more cranial movement of the conus medullaris or cauda equina. The mean length and diameter of the FTI was 52.2 and 0.38 mm, respectively. The mean length and diameter of the FTE was 77 and 0.60 mm, respectively. The force necessary to move the FTI with tension applied to the FTE had a mean of 0.03 N. The average distance that the FTI moved with distal FTE tension was 1.33 mm. All specimens had a thecal sac that terminated at the S2 vertebral level. And no specimen had a low-lying conus medullaris, cutaneous stigmata of occult spinal dysraphism, or grossly visible adipose tissue in either the FTI or FTE. CONCLUSIONS: Based on our studies, tension placed on the FTE has very little effect on the FTI and no obvious effect on the conus medullaris or cauda equina. Therefore, isolated transection of the FTE for a patient with tethered cord syndrome is unlikely to have significant effect. To our knowledge, this is the first study to quantitate the distal forces needed on the FTE to move the FTI.

The inferior gluteal nerve often has a cutaneous branch: A discovery with application to hip surgery and targeting gluteal pain syndromes.

The inferior gluteal nerve has been traditionally described as a solely motor branch innervating the gluteus maximus. However, during routine dissection of the gluteal region, a cutaneous branch of the inferior gluteal nerve was identified. As the gluteal region is vulnerable to the development of pressure ulcers and iatrogenic injury with for example, surgical approaches and injection therapies, a comprehensive understanding of its cutaneous innervation is important. Therefore, the aim of this study was to elucidate the anatomy of this cutaneous branch of the inferior gluteal nerve in a series of cadavers. Twelve sides from six fresh-frozen cadaveric specimens were dissected. When a cutaneous branch was identified piercing the gluteus maximus, its origin from the inferior gluteal nerve was verified and the diameter and length of it measured. Additionally, for localization, the distance from the midline to the exit point of the cutaneous branch from the gluteus maximus was measured. One to two cutaneous branches were identified as arising from the inferior gluteal nerve on nine sides (75%). The branch(es) were usually located in the lower outer quadrant of the gluteus maximus. These branches had a mean distance of 12.5 cm from the midline. Their mean diameter and length was 0.7 mm and 28.6 cm, respectively. On all sides with a cutaneous branch of the inferior gluteal nerve, the skin over the posterior aspect of the greater trochanter was innervated by superior and inferior cluneal nerves and supplemented by cutaneous branch(es) of the inferior gluteal nerve. Side or sex was not a predictor of the presence of a cutaneous branch of the inferior gluteal nerve. To our knowledge, a cutaneous branch derived from the inferior gluteal nerve has not been previously described. Based on our cadaveric findings, the majority of individuals will have the area of skin over the greater trochanter innervated by this nerve. Therefore, surgeons and pain specialists should be aware of its presence and might develop surgical procedures that help avoid it or develop technical advances that target it for various pain syndromes in this area. We propose naming these cutaneous branches the lateral cluneal nerves, which would necessitate renaming the middle cluneal nerves to medial cluneal nerves. Clin. Anat. 31:937-941, 2018. © 2018 Wiley Periodicals, Inc.

A Novel Microsurgical Procedure for Revascularization of the Vertebral Artery.

OBJECTIVE: A broad armamentarium of microsurgical techniques affords flexibility to surgeons when choosing a procedure that is best tailored to fit the anatomy of an individual. Herein, we report on the feasibility of using the deep cervical artery (DCA) to revascularize the vertebral artery (VA) via a DCA-V3 bypass graft. METHODS: Fourteen DCAs from 7 injected cadaveric heads were located and traced. The diameter of the main trunk of the DCA was measured bilaterally at the C3 level. The proximal vertebral branches of each DCA were then severed and the main trunk of the DCA was transposed superiorly onto the V3 segment of the VA, which was also exposed bilaterally. RESULTS: The DCA was identified and traced bilaterally on all specimens. The diameter of the main trunk of the DCA at the C3 level ranged from 1.03 to 2.79 mm. The mean diameter of the main trunk of the DCA at this level was found to be 1.52 ± 0.60 mm for the right side and 1.46 ± 0.54 mm for the left side. After releasing the proximal vertebral branches of the DCA, all arteries were able to be transposed to the ipsilateral VA. CONCLUSIONS: Based on the mean diameter of the DCA reported in extant literature and this study, the blood flow volume of the DCA makes it a viable candidate to bypass the proximal VA.

First Report of a Bifid Mandibular Canal Containing a Large Vein Draining into the Anterior Jugular Vein.

The bifid mandibular canal (BMC) is an anatomical variant of the mandible that is often observed on cone-beam computed tomographic images. We identified a BMC during routine cadaveric dissection. The upper mandibular canal contained the inferior alveolar nerve and artery, and the lower mandibular canal contained a large inferior alveolar vein. This latter vein left the mandible through a lateral lingual foramen and joined the anterior jugular vein. Additionally, this vein gave rise to small tributaries to the mental foramen and anterior surface of the mandible from the second mandibular canal. To our knowledge, this is the first report illustrating the contents of a BMC and drainage of a vein into the large anterior jugular vein.

Injury of the Radial Nerve in the Arm: A Review.

Compression of the radial nerve is most commonly described at the supinator muscle (i.e., arcade of Frohse). However, radial nerve compression can occur in the arm. Therefore, the purpose of this article is to review both etiologies of radial nerve entrapment and the sites at which this can occur in the arm. The clinical presentation of radial nerve entrapment in the arm and how it differs from that of entrapment at other sites is reviewed and the conditions potentially predisposing to nerve entrapment are described. Particular attention is paid to the nerve's course and potential variants of the anatomical structures in the arm. In each case, the recommended course of management for the neuropathy is described. Injury of the radial nerve can arise from a varied set of pathologies including trauma, tumors, anomalous muscles, and intramuscular injections. Physicians should have a good working knowledge of the anatomy and potential mechanisms for radial nerve injury.

May-Thurner Syndrome Variant Identified in a Cadaver: First Reported Case.

May-Thurner syndrome (MTS) is defined as the compression of the left common iliac vein by the right common iliac artery. Herein, we describe an unusual case of a male cadaver with right-sided compression of the inferior vena cava and the left and right common iliac veins by the right common iliac artery. This is an unusual variant of this syndrome and the first known case report. We suggest this variant be termed MTS type II due to the additional compression of the inferior vena cava.

Anatomical Study of the Lingual Nerve and Inferior Alveolar Nerve in the Pterygomandibular Space: Complications of the Inferior Alveolar Nerve Block.

The inferior alveolar nerve block (IANB) procedure delivers anesthetics to the pterygomandibular space through which the lingual nerve (LN) and inferior alveolar nerve (IAN) travel. Injury to the LN has been reported more often than injury to the IAN. However, the number of anatomical studies of LN injury is limited. We aimed to establish evidence by investigating LN and IAN anatomy at the level of the mandibular foramen (MF). Forty-four sides from 22 Caucasian cadaveric heads (16 fresh-frozen and six formalin-fixed cadavers) were used in this study. The LN and IAN were laterally dissected, and the diameter and the distance between the two nerves were measured at the level of the MF. The mean diameters of the LN and IAN were 2.57 mm and 2.53 mm in fresh-frozen specimens and 2.97 mm and 2.93 mm in formalin-fixed specimens, respectively. The mean diameters of the LN and IAN in all the specimens were 2.65 mm and 2.64 mm. The distance between the posterior edge of the LN and anterior edge of the IAN at the level of the MF ranged from 1.62 to 8.36 mm with a mean of 5.33 ± 1.88 mm. These findings could elucidate the risk of LN injury during the IANB procedure.

Anatomical Study of the Extreme Lateral Transpsoas Lumbar Interbody Fusion with Application to Minimizing Injury to the Kidney.

Objective Since the extreme lateral lumbar interbody fusion procedure was first reported by Ozgur in 2006, a large number of clinical studies have been published. Anatomical studies which explore methods to avoid visceral structures, such as the kidney, with this approach have not been examined in detail. We dissected the retroperitoneal space to analyze how the extreme lateral transpsoas approach to the lumbar spine could damage the kidney and related structures. Methods Eight sides from four fresh Caucasian cadavers were used for this study. The latissimus dorsi muscle and the thoracolumbar fascia were dissected to open the retroperitoneum. The fat tissue was removed. Steel wires were then put into the intervertebral disc spaces. Finally, the closest distance between kidney and wires on each interdiscal space was measured. Results The closest distance from the wire in the interdiscal space on L1/2, L2/3 and L3/4 to the kidney ranged from 13.2 mm to 32.9 mm, 20.0 mm to 27.7 mm, and 20.5 mm to 46.6 mm, respectively. The distance from the kidney to the interdiscal space at L4/5 was too great to be considered applicable to this study. Conclusions The results of this study might help surgeons better recognize the proximity of the kidney and avoid injury to it during the extreme lateral transpsoas approach to the lumbar spine.

Clinical Anatomy of Blockade of the Pterygopalatine Ganglion: Literature Review and Pictorial Tour Using Cadaveric Images.

Pterygopalatine ganglion block (sphenopalatine ganglion block) is a well-known procedure for treating cluster headache and for relieving cancer pain. In this review, the history and anatomy of the pterygopalatine ganglion are discussed, and images, including computed tomography and endoscopy, are presented to improve understanding of the clinical anatomy of the ganglion regarding the block procedure.

"False" Ligaments: A Review of Anatomy, Potential Function, and Pathology.

This paper, although not an exhaustive review of "false" ligaments in the body, describes eight such ligaments. False ligaments are defined as ligamentous structures connecting separate parts of the same bone and are thus immobile. The ligaments reviewed include the suprascapular ligament, the transforaminal lumbar ligaments, the mamillo-accessory ligament, the transverse atlantal ligament, the transverse occipital ligament, the transverse humeral ligament, the coracoacromial ligament, and the transverse part of the ulnar collateral ligament. In this review, the anatomy and histological characteristics of each ligament are reviewed. Furthermore, possible functions and associated pathologies are described.

Piercing of the Lumbocostal Ligament by the Subcostal Nerve: A Previously Unreported Case.

As lateral approaches gain popularity in lumbar spine surgery, detailed discussions regarding anatomical variations in the innervation of the thoracolumbar region are of increasing importance. Damage to intercostal or subcostal nerves can lead to post-operative complications including regional loss of sensitivity, motor function, or abdominal wall hernias. More specifically, the subcostal nerve has been identified in the literature as one of the more vulnerable structures during such procedures. A clear understanding of the position of the subcostal nerve relative to nearby anatomical structures is therefore important for medical professionals. We herein report a rare anatomical variation in which the subcostal nerve pierces the lumbocostal ligament.

Winged Scapula: A Comprehensive Review of Surgical Treatment.

Winged scapula is caused by paralysis of the serratus anterior or trapezius muscles due to damage to the long thoracic or accessory nerves, resulting in loss of strength and range of motion of the shoulder. Because this nerve damage can happen in a variety of ways, initial diagnosis may be overlooked. This paper discusses the anatomical structures involved in several variations of winged scapula, the pathogenesis of winged scapula, and several historical and contemporary surgical procedures used to treat this condition. Additionally, this review builds upon the conclusions of several studies in order to suggest areas for continued research regarding the treatment of winged scapula.