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Iatrogenic nerve injury during surgery is a major source of concern for both patients and surgeons. This study aimed to identify the nerves most commonly injured during surgery, along with the commonly associated operative procedures. A literature search was conducted using the PubMed database to identify nerves commonly injured during surgery, along with the surgical procedure associated with the injury. The following 11 nerves, ranked in order with their associated surgical procedures, were found to be the most commonly injured: (a) intercostobrachial nerve in axillary lymph node dissections and transaxillary breast augmentations, (b) vestibulocochlear nerve in cerebellopontine tumor resections and vestibular schwannoma removals, c) facial nerve in surgeries of the inner ear and cheek region, (d) long thoracic nerve in axillary lymph node dissections, (e) spinal accessory nerve in surgeries of the posterior triangle of the neck and cervical lymph node biopsies, (f) recurrent laryngeal nerve in thyroid surgeries, (g) genitofemoral nerve in inguinal hernia and varicocele surgeries, (h) sciatic nerve in acetabular fracture repairs and osteotomies, (i) median nerve in carpal tunnel release surgeries, (j) common fibular nerve in varicose vein and short saphenous vein surgeries, and (k) ulnar nerve in supracondylar fracture surgeries. Although the root cause of iatrogenic nerve injury differs for each nerve, there are four unifying factors that could potentially decrease this risk for all peripheral nerves. These four influencing factors include knowledge of potential anatomical variations, visual identification of at-risk nerves during the procedure, intraoperative nerve monitoring, and expertise of the surgeon.

Introduction Neurologic deficits from lumbar plexus nerve injuries commonly occur in patients undergoing lateral approaches. However, it is not yet clear what types of injury occur, where anatomically they are located, or what mechanism causes them. We aimed to study 1) the topographic anatomy of lumbar plexus nerves and their injuries in human cadavers after lateral transpsoas approaches to the lumbar spine, 2) the structural morphology of those injuries, and 3) the topographic anatomy of the lumbar plexus throughout the mediolateral approach corridor. Methods Fifteen adult fresh frozen cadaveric torsos (26 sides) underwent lateral approaches (L1-L5) by experienced lateral spine surgeons. The cadavers were subsequently opened and the entire plexus dissected and examined for nerve injuries. The topographic anatomy of the lumbar plexus and its branches, their injuries, and the morphology of these injuries were documented. Results Fifteen injuries were found with complete or partial nerve transections (Sunderland IV and V). Injuries were found throughout the mediolateral approach corridor. At L1/2, the iliohypogastric, ilioinguinal, and subcostal nerves were injured within the psoas major muscle, the retroperitoneal space, or the outer abdominal muscles and subcutaneous tissues. Genitofemoral nerve injuries were found in the retroperitoneal space. Nerve root injuries occurred within the retroperitoneal space and psoas muscle. Femoral nerve injuries were found only within the psoas major muscle. No obturator nerve injuries occurred. Conclusions Lateral approaches can lead to structural nerve damage. Knowledge of the complex plexus anatomy, specifically its mediolateral course, is critical to avoid approach-related injuries.

We report a case of bilateral lateral costal branches (LCB) of the internal thoracic artery (ITA). On the left side, the ITA branched from the subclavian artery as a common trunk with the thyrocervical trunk. The left LCB flew into the collateral branch of the fifth intercostal artery after reaching the upper end of the sixth rib and after exiting the left ITA at the upper part of the first rib. The left ITA was disconnected near the second rib because it had been used for coronary artery bypass surgery. The right ITA arose from the anterior surface of the right subclavian artery just after the right ITA diverged from the brachiocephalic artery. The right LCB reached the upper end of the fifth rib and flew into the collateral branch of the fourth intercostal artery. The right ITA descended along the back of the costal cartilages as usual. The mechanism of the development of the LCB is thought to be due to a lateral longitudinal anastomosis connecting the inter-node arteries arising from the dorsal aorta during the embryonic phase. More anatomical and embryological studies are necessary to further elucidate this variant arterial branch.

An 8-year-old female with a history of chronic headaches and uncertain papilloedema was found to have a variant of the posterior intracranial dural venous sinuses on magnetic resonance imaging assessment of the brain. Magnetic resonance venography included in the imaging revealed a circular formation of the confluence of sinuses and absent right-sided transverse sinus. The confluence of sinuses is a highly variable structure; however, to the authors' knowledge, a circular confluence of sinuses variant has not been reported in the literature.

Fragestellung: Die XLIF-Technik ist eine Modifikation des retroperitonealen Zugangs zur Lendenwirbelsäule und wird sowohl bei degenerativen als auch bei traumatischen Wirbelsäulenerkrankungen eingesetzt. Dieser minimal-invasive Zugang ermöglicht einen direkten Zugang zum Bandscheibenfach[zum vollständigen Text gelangen Sie über die oben angegebene URL], Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2018)

Objectives: Allogeneic blood transfusion-related immunomodulation may relatively suppress the immune system, heightening the risk of infection following spine surgery. This systematic review seeks to determine whether allogeneic blood transfusion increases the risk of postoperative infection and whether[for full text, please go to the a.m. URL], Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2018)

Fragestellung: Die postoperative Dysphagie ist eine schwerwiegende Komplikation nach anteriorer zervikaler Diskektomie und Fusion (ACDF). Die Ätiologie dieser Komplikation ist bisher jedoch schlecht verstanden. Ziel dieser anatomischen Studie ist die Untersuchung der Rami oesophagei (Speiseröhrenäste)[zum vollständigen Text gelangen Sie über die oben angegebene URL], Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2018)

Aims: Kyphoplasty is a minimally invasive treatment used to reduce pain, restore vertebral height and improve mobility in patients with painful spinal VCF. Pain from vertebral compression fractures (VCF) comprises an important health issue with significant social and economic impact, particularly in elderly patients with osteoporosis where treatment options are limited. We assessed outcomes Original Research Article Kicielinski et al.; BJMMR, 10(1): 1-11, 2015; Article no.BJMMR.19370 2 in patients with VCF who failed conservative management and underwent kyphoplasty. Study Design: Prospective and retrospective case series. Place and Duration of Study: At a single neurosurgical practice February 2003 and September 2012. Methodology: A total of 203 patients with 288 treated vertebral body fractures treated with kyphoplasty were enrolled. The Visual Analog Scale (VAS) was used to prospectively measure back pain before and after surgery. Pre and post operative disability and quality of life were retrospectively measured with the Roland Morris Disability Index (RMDI) and EuroQol 5-Domain scale (EQ5D), respectively, via patient survey. Pre and post-operative narcotic analgesic usage and incidence of subsequent fractures were recorded. Results: There was a statistically significant improvement (P < .001) in each of the assessed measures following surgery. The post-operative rate of narcotic use was reduced from 63% to 17%. Eight patients (4.2%) developed and underwent repair of an adjacent fracture with a mean time between surgeries of 461 days. Conclusion: Following kyphoplasty, patients experienced significant, rapid, and sustained reduction of back pain, improved quality of life, and reduced disability with a low complication rate. Timely repair of VCF is indicated, not only to prevent complications associated with prolonged inactivity but also for effective treatment of severe pain in the acute setting.

Anatomical variations involving the internal carotid artery are uncommon. Herein, we present a very rare origin of the internal carotid artery. An adult female presented to the emergency department after falling. Imaging revealed that the left internal carotid artery arose from the contralateral cavernous segment of the internal carotid artery. Such a variation should be kept in mind by radiologists and surgeons who interpret and operate in this area, respectively.

There are multiple anatomical triangles of the skull base. However, to our knowledge, there has been no comprehensive review of these geometric landmarks. To allow for a safe and consistent approach to lesions of the skull base such as those near the internal carotid artery, internal acoustic meatus, and cavernous sinus, a comprehensive review of the variations with illustrations is required. This article provides an overview of the anatomical borders, dimensions, and surgical implications as well as illustrations of the major skull base triangles.

Objectives The incisivus labii superioris muscle, which originates from the floor of the incisive fossa of the maxilla, has previously been described, it is not well understood. The purpose of this study was to investigate the incisivus labii superioris muscle with detailed dissection. Methods Twenty-six halves from thirteen fresh frozen cadaveric Caucasian heads were used in this study. First, the incisivus labii superioris muscle was dissected to reveal its origin and insertion, and its relationship to other mimetic muscles. Secondly, the distance from the midline to the innermost part of the bony attachment of the muscle was measured. The literature describing the incisivus labii superioris muscle was reviewed. Results The incisivus labii superioris muscle consisted of two parts, inferior and superior. The former merged into the orbicularis oris and the latter into the nasalis. The mean distance from the midline to the innermost part of the bony attachment of the incisivus labii superioris muscle was 4.8 ± 1.7 mm on the right side and 4.9 ±1.7 mm on the left. Conclusions The results of the present study suggest that the inferior part of the incisivus labii superioris should be considered as an accessory muscle of the orbicularis oris complex, and the superior part is the nasalis muscle.

The xiphoid process is a small bony feature of the anterior thoracic wall just inferior to the sternum corpus. Although the xiphoid process is commonly represented as a straight, fully ossified bone in educational textbooks, reports of anomalous processes flood the literature. The xiphoid process can be broad, thin, monofid, bifid, trifid, curved, or deflected and contain foramina. Variations can be mistaken for epigastric masses. Herein, we report an extremely unusual bifid xiphoid process that is deflected anteriorly. This case is discussed in the context of the misdiagnosis of xiphoid process variations and its importance to the clinician.

Wormian bones are a relatively rare skeletal anomaly that present as accessory bone(s) within the sutures of the cranium and even more rarely within the fontanelles. It is believed that they arise from the formation of abnormal cranial ossification centers. Although not extensively reported in the literature, this anomaly is thought to be associated with other anatomical anomalies such as osteogenesis imperfecta, rickets, and other bone dysplasias. When located within the fontanelles, the most likely site of occurrence is the posterior fontanelle. This case report describes a rare incidence of wormian bone within the anterior fontanelle of an infant who had concurrent craniosynostosis. More research and reporting of this anomaly is necessary to verify any correlated syndromes, and determine the underlying etiology.

Extramedullary tumors composed of myeloblasts or monoblasts can present in various locations. Patients with a history of acute myeloid leukemia (AML) can present with neuropathic pain and no evidence of relapse of their leukemia. Neuroleukemiosis is a form of extramedullary tumor present in the peripheral nervous systems (PNS) of leukemia patients. We report two AML patients who were in remission and later presented with neurological symptoms due to neuroleukemiosis with negative bone marrow biopsies.

Retrospective cohort study.The objective of this study is to compare the incidence of infection in patients who do and do not receive blood transfusions in major deformity surgery (8 levels).Postoperative infections increase morbidity and mortality rates in spine surgery and generate additional costs for the health care system. It has been proposed that blood transfusions increase the risk of wound infection, urinary tract infection, pneumonia, and sepsis.A total of 56 patients met the study criteria, receiving spine surgery involving the fusion of 8 levels or more. Patient-specific characteristics, starting and ending hematocrits, number of units transfused and infections including urinary tract infection, wound infection, pneumonia, and sepsis were documented. Differences in infection risk between those who did and did not undergo a transfusion and their 95% confidence intervals were calculated.Groups were similar with respect to baseline and surgical characteristics except for smoking status, operative time, estimated blood loss, and ending hematocrit. The overall infection rate was greater in patients who underwent transfusion than those who did not (36% vs. 10%; P=0.03). Wound infections (n=5) were only observed in those who underwent a transfusion. Smokers were more likely to receive a transfusion and more likely to experience infection. A stratified analysis demonstrated an increased risk of infection associated with transfusion; however, the risk was greater in smokers, suggesting the effect of transfusion on infection could be modified by smoking. Patients undergoing transfusion experienced a significantly longer hospital stay (P=0.01).Allogeneic red blood cell transfusion in major spine surgery could be a risk factor for postoperative infection. This increased risk seems to be magnified in those who smoke. Further studies are warranted, and risks of blood loss and transfusion-related complications in smokers also potentially merit exploration.Level 3.

Injury to the nerves of the lumbar plexus can result in significant disability. Therefore, the clinician should be knowledgeable of both the normal and variant anatomy of these branches. We report what we believe to be the first description of the accessory obturator nerve providing a branch to the psoas major muscle. Such a variant innervation to the psoas major muscle should be kept in mind by those who examine patients or operate near the lumbar plexus.

With the entrance of the video microscope over the recent few years into the microsurgery optical field, a third modality has emerged alongside the endoscope and operating microscope to accomplish some of the microsurgical procedures. One such approach that could potentially utilize any of the three is the transnasal transsphenoidal (TNTS) approach that provides access to the anterior brainstem, the anterior skull base, and of course the sellar region. Here, we provide a descriptive comparison of the three modalities on cadaveric specimens with joint ENT and neurosurgery teams performing the approach. Each provides unique advantages and disadvantages as part of the surgeon’s optical armamentarium. As more optical devices become available to surgeons, selection of the optimal device can present a challenge best compared by head-to-head comparison. The aim of this paper is to compare these modalities for the TNTS approach.

Superior mesenteric artery (SMA) syndrome is a rare clinical entity. We report a female patient presenting with abdominopelvic pain and diagnosed with superior mesenteric artery syndrome. Direct venography revealed a large ovarian varix that was treated with hysterectomy and unilateral oophorectomy. SMA syndrome can have many presentations often with small bowel obstruction. Obstruction of only the ovarian vein with resultant ovarian varix is an unusual presentation.

Arachnoid granulations are hypertrophied arachnoid villi, which extend from the subarachnoid space into the venous system and aid in the passive filtration and reabsorption of cerebrospinal fluid. These macroscopic structures have been described in various locations, with the transverse and sigmoid sinuses seen as normal variants on imaging. Here we present the occurrence of an enlarged arachnoid granulation at the foramen rotundum where a variant intracranial venous sinus was identified during routine dissection. Variations, such as the one described herein, should be recognised by those who operate or interpret images of the skull base.

Of patients who have undergone lateral approaches to the thoracic spine, surgical site postoperative pain appears to be greater among those who have undergone transection and removal of a rib segment than those who have not. Therefore, techniques that conserve anatomical position and minimize tissue disruption would theoretically result in less pain and a quicker recovery. Herein, we describe a rib-sparing osteoplastic technique used when rib segments need to be displaced in order to create an unobscured corridor to the operative target. Our approach minimizes soft tissue disruption and restores the anatomical function of the rib. Based on our experience, these patients report less pain, mobilize earlier, and are discharged sooner than those who have had rib segments sacrificed as part of a lateral approach to the spine.

Cavernous angiomas usually occur in the parenchyma of both the supra and infratentorial compartments. At times, they can both clinically and radiologically mimic other dural-based lesions. We present a case of a patient with chronic occipital headaches, initially thought to have a meningioma, but proven to be a cavernoma with histological analysis.

Lumbar hernias are protrusions of intra-abdominal contents classically through the superior (Grynfeltt) and inferior (Petit) lumbar triangles. The anatomy of the triangles is variable and quantitative data are few. No radiological data on the anatomy of the triangles are available. Fifty computed tomography angiography of the upper abdomen (M25, F25, mean age 72.5-year-old) were analyzed. The dimensions and the contents of the lumbar triangles were analyzed. The characteristics of the space between the two triangles were also documented. The superior lumbar triangle showed a mean surface area of 5.10 ± 2.6 cm2. In the area of the triangle, the 12th intercostal pedicle and the 1st lumbar branches of the iliolumbar vessels were found in 42 and 46 %, respectively. The inferior lumbar triangle had a mean surface of area 18.7 ± 8.4 cm2. In this area, the 2nd, 3rd, and 4th lumbar branches were found in 9, 67, and 8 %, respectively. On oblique coronal images, a direct tunnel between the superior and the inferior lumbar triangles was found, showing an oblique course, with a postero-anterior direction (mean length 36.5 ± 5.8 mm, mean caliber 7.4 ± 3.1 mm). Among the anatomical factors of weakening of the abdominal wall, the course of branches of the lumbar vessels was documented not only in the superior but also in the inferior lumbar triangle. A real musculoaponeurotic tunnel between the superior and the inferior lumbar triangles located in the oblique coronal plane was found, that could play a role in the development of incarceration or strangulation of lumbar hernias.

Background Context Injuries to the lumbar plexus during lateral approaches to the spine are not uncommon and may result in permanent deficits. However, the literature contains few studies that provide landmarks for avoiding the branches of the lumbar plexus. Purpose The present anatomical study was performed to elucidate the course of these nerves in relation to lateral approaches to the lumbar spine. Study Design This is a quantitative anatomical cadaveric study. Methods The lumbar plexus and its branches were dissected on 12 cadaveric sides. Metal wires were laid on the nerves along their paths on the posterior abdominal wall. Fluoroscopy was performed in the anteroposterior and lateral positions. The relationships between regional bony landmarks and the branches of the lumbar plexus were observed. Results When viewed laterally, the greatest concentration of nerves occurred from the posteroinferior aspect of L4, inferior along the posterior one-third of the body of L5, then at the level of the sacral promontory. On the basis of our study, approaches to the anterior two-thirds of the L4 vertebra and anterior third of L5 will result in the lowest chance of lumbar plexus nerve injury. In addition, lateral muscle dissection through the psoas major should be in a superior to inferior direction in order to minimize nerve injury. Laterally, the widest corridor between branches in the abdominal wall was between the subcostal and iliohypogastric nerves. Conclusions The findings of our cadaveric study provide surgeons who approach the lateral lumbar spine with data that could decrease injuries to the branches of the lumbar plexus, thus lessening patient morbidity.

Head positioning and the degree of rotation for anterior communicating artery aneurysm surgery is controversial. With this anatomic study, we aimed to give a broad description of head positioning for various aneurysm dome projections. In addition, with the use of a corrosion-cast technique, a three-dimensional arterial tree was demonstrated, an anterior communicating artery region aneurysm model was prepared, and pictures were taken at various angles. According to our observations, 30-degree head rotation was found to be the most suitable position for the anterior and superior projected aneurysms. For posterior projection, aneurysm neck was best viewed with 15-degree head rotation. Aneurysms projecting inferiorly necessitated the greatest rotation at 45 degrees. Each aneurysm dome projection of the anterior communicating artery aneurysm should be individually considered, and the head position should be adjusted accordingly. The use of appropriate head positions during surgery will prevent the development of postoperative ischemic complications and will increase the success of surgery by preventing unnecessary tissue manipulation.

Head positioning and the degree of rotation for anterior communicating artery aneurysm surgery is controversial. With this anatomic study, we aimed to give a broad description of head positioning for various aneurysm dome projections. In addition, with the use of a corrosion-cast technique, a three-dimensional arterial tree was demonstrated, an anterior communicating artery region aneurysm model was prepared, and pictures were taken at various angles. According to our observations, 30-degree head rotation was found to be the most suitable position for the anterior and superior projected aneurysms. For posterior projection, aneurysm neck was best viewed with 15-degree head rotation. Aneurysms projecting inferiorly necessitated the greatest rotation at 45 degrees. Each aneurysm dome projection of the anterior communicating artery aneurysm should be individually considered, and the head position should be adjusted accordingly. The use of appropriate head positions during surgery will prevent the development of postoperative ischemic complications and will increase the success of surgery by preventing unnecessary tissue manipulation.

Introduction: The trochlear nerve is important to preserve during approaches to the skull base. Traditionally, this nerve has been divided into cisternal, cavernous, and orbital segments. Materials and Methods: Twenty latex-injected cadaveric sides (10 adult cadavers) were dissected with the aid of an operating microscope. Standard microdissection techniques were employed to examine the course of the distal cisternal segment of the trochlear nerve. Results: In all specimens, a fourth segment of the trochlear nerve was identified. This part of the nerve coursed between the entrance of the trochlear nerve into the posterior corner of the oculomotor trigone, and the posterior wall of the cavernous sinus. This segment of trochlear nerve was, on average, 3 mm in length. Conclusions: We have identified a new segment of the trochlear nerve not previously described. We propose that this be referred to as trigonal segment. Hence, the new proposed classification would be cisternal, trigonal, cavernous, and orbital. Knowledge of the microanatomy of the trochlear nerve may be of assistance to the skull base surgeon, especially during entrance into the cavernous sinus.

Background: Although persistent trigeminal artery (PTA) is uncommonly identified, knowledge of this structure is essential for clinicians who interpret cranial imaging, perform invasive studies of the cerebral vasculature, and operate this region. Methods: A review of the medical literature using standard search engines was performed to locate articles regarding the PTA, with special attention with anatomical descriptions. Results: Although anatomical reports of PTA anatomy are very scarce, those were analyzed to describe in detail the current knowledge about its anatomical relationships and variants. Additionally, the embryology, classification, clinical implications, and imaging modalities of this vessel are extensively discussed. Conclusions: Through a comprehensive review of isolated reports of the PTA, the clinician can better understand and treat patients with such an anatomical derailment.

Background: Neurosurgical intervention involving the scalp may cause neuralgia or other pain syndromes. Therefore, a comprehensive understanding of scalp innervation may be helpful in prevention of pain potentially induced by surgery. Methods: Using standard search engines, a review of the literature regarding the anatomy of the nerves that innervate the scalp was performed with attention given to anatomic landmarks. Results: This paper provides a comprehensive review of the anatomy, embryology, pathology, and neurosurgical application of the knowledge of the innervation of the scalp. Conclusions: Knowledge of the nerves that supply the scalp is important to the neurosurgeon who hopes to maximize patient recovery and minimize post-procedural complications.

Background: Cerebral pseudoaneurysms, especially of the anterior communicating artery (ACoA), are rare. Case Description: Herein, the authors report a 66-year-old patient who underwent successful clip ligation of a small ruptured ACoA aneurysm. Eighteen days after surgery, he suffered from another episode of subarachnoid hemorrhage due to the rupture of a newly formed pseudoaneurysm adjacent to the previously clipped aneurysm. This pseudoaneurysm was treated through clip ligation as well. Conclusion: A pseudoaneurysm may rarely form adjacent to a previously clipped cerebral aneurysm and should be included in the differential diagnosis of recurrent subarachnoid hemorrhage. Potential mechanisms of formation and management strategies for this challenging problem will be discussed.

Background: The prevalence of atherosclerotic renal artery disease has increased with improved life expectancy. Because renal artery stenosis is a potentially correctable cause of hypertension and ischemic nephropathy, early identification of this entity may lead to proper hypertension control and improved renal function and survival. The aim of this study was to determine the prevalence and patterns of subclinical renal artery stenosis in patients with aorticoiliac atherosclerosis. Patients and methods: The abdominal angiographies of 44 patients with high-grade aorticoiliac occlusive disease (> 70% stenosis) were reviewed for evidence of renal artery stenosis. This was compared to a group of 20 patients with mild-to-moderate aorticoiliac disease (< 70% stenosis). These patients had no history of renal artery disease or renal failure. Results: In patients with high-grade aorticoiliac occlusive disease, renal artery stenosis was found in 25 patients (56.8%); 13 with unilateral (29.5%) and 12 (27.3%) with bilateral involvement. A hemodynamically significant stenosis (> 50%) was found in 11 patients (25%), one of whom had bilateral stenosis (2.3%). High-grade renal artery stenosis (> 70%) or complete arterial occlusion was noted on seven sides (7.9%). The most common sites of stenosis were the origin and first centimeter of the renal artery. In patients with mild-to-moderate aorticoiliac disease, renal artery stenosis was found in two patients (10%). Conclusions: The present study revealed that subclinical renal artery disease may be present in more than half of the patients with high-grade aorticoiliac atherosclerosis highlighting the need for proper risk stratifications and screening programs. Based on our results, we suggest that examination of the renal arteries in these patients may be necessary in order to delay or prevent complications. Additionally, such information may have important therapeutic implications in planning reconstructive vascular surgeries or percutaneous angioplasties.

We review and describe the neurological presentation and long-term outcome of patients with meningocele manque, and describe the dysraphic features associated with this entity. Our series of patients was collected over a 25-year period with a mean follow-up of 11.5 years. The mean age of presentation was 10.4 years and 72% of the patients presented with an abnormal neurological examination. At most recent follow-up, symptoms were stable, improved, and progressed in 47, 37 and 16%, respectively. Meningocele manque was associated with focal hirsutism in 37% of the cases. These bands were primarily found in the lumbar spine and involved two sequential vertebral levels in 42% of cases. Sectioning of meningocele manque has good long-term results in the majority of patients. These bands should be sought in the evaluation of patients with spinal dysraphism and surgically transected.

OBJECTIVEFor purposes of neurotization of the musculocutaneous nerve (MCN) with the medial pectoral nerve (MPN) after upper trunk brachial plexus injuries, the anatomic relationship between these two nerves was defined in a cadaveric model.METHODSThirty-five brachial plexuses in 18 adult cadavers were dissected. The distance between the origin of the MPN from the medial cord to the origin of the MCN from the lateral cord was measured. The length, diameter, branching, and location of the MPN were recorded. The diameter of the proximal MCN was recorded.RESULTSThirty-seven percent of the MPNs, when detached from the pectoralis muscles, were too short to reach the proximal MCN by a mean distance of 15 mm. The MPN pierced the pectoralis minor muscle in 80% of the dissections. The cross sectional area of the MCN was always larger than the cross sectional area of the MPN by an average factor of 2.5.CONCLUSIONWhen planning to use the MPN for neurotization of the MCN, one should be prepared to harvest an interposition graft, because over one-third of MPNs may not have enough length to reach the MCN in a tension-free manner. Diameter mismatch occurs predictably between the distal MPN and the proximal MCN.

The standard approach for sectioning of the filum terminale for a tethered spinal cord can be achieved via a limited S1 exposure. This is performed with the commonly believed idea that the filum fuses with the dura at S2. We dissected 27 cadavers to exclusively look at the level at which the filum pierces/fuses with the dura and also the level at which the dural sac ends. Most of the fila fused at S2 with a range from L5 to S3. The majority of dural sacs ended at S2 with a range from S1 to S3. However, 15% of the fila (4 of 27) fused above the S1 level. In addition, 11% of the fila (3 of 27) fused off the midline. We hope that this anatomical information may be useful for neurosurgeons when standard approaches fail to identify the filum at its usual level and location.