Anatomical investigation of the segmental vessels for the right-sided anterior surgical approach to the thoracic spine: a human cadaver study.

PURPOSE: Anterior surgical approaches to the thoracic spine are common procedures for the treatment of many diseases of the thoracic spine. Purpose of this anatomic study is to investigate the course of the segmental vessels of the thoracic spine for the anterior and lateral transthoracic approach from the right side. METHODS: 26 formalin-fixed human cadavers (20 femaless/6 male) with an average age of 84.9 ± 8.3 (range 67-97) were included. The segmental arteries and veins of the right thoracic cavity coursing between the third and twelfth thoracic vertebral body have been investigated. To define the localization of the vessels in accordance with the associated vertebral bodies, the distance between the endplates and vessels was measured in the ventral, middle and dorsal parts. RESULTS: The results of the study reveal that not only one, but also two segmental arteries and veins may course over the right hemi-vertebral body, especially in the upper and middle thoracic spine. Furthermore, in the middle and lower thoracic spine (T7-T12) the vessels course over the middle and lower third of the craniocaudal extent of the vertebral body. On the contrary, in the upper thoracic spine (T3-T6), the vessels may course over the entire extent of the vertebral body. CONCLUSION: Due to these common anatomic variations and variability of the course of the segmental vessels, spinal surgeons should remain careful in the identification of the segmental vessels in order to minimize risk of vascular injury in case of right-sided anterior and lateral approach to the thoracic spine.

Azygos vein cannulation after catheterisation of the left internal jugular vein in a toddler.

Central venous catheterisation is routinely performed in paediatric patients to facilitate therapeutic management when long-term vascular access is needed. Misplacement of the catheter tip in thoracic vessels other than the superior vena cava has been described, along with related complications. Hereby, a case of a 15-month-old child is presented with a fully functional Hickman catheter introduced via the left internal jugular vein. The tip of the catheter was misplaced into the azygos vein. Intraoperative spot fluoroscopic images and anatomical explanations for the course of the catheter are presented. An understanding of the aetiology of the radiological appearance may help to increase recognition of such cases and avoid complications.

The Azygos Vein Is at Potential Risk of Injury From Malpositioning of Left Thoracic Pedicle Screw in Thoracic Adolescent Idiopathic Scoliosis Patients.

STUDY DESIGN: A computed tomography study. OBJECTIVE: To evaluate the changed position of azygos vein in patients with thoracic adolescent idiopathic scoliosis (AIS) and to analyze the potential risk of injury of azygos vein from thoracic pedicle screw placement in these patients. SUMMARY OF BACKGROUND DATA: It has been widely recognized that the anatomic positions of structures adjacent to the vertebrae may change in patients with AIS. To date, no study had evaluated such change of azygos vein in patients with AIS. METHODS: Twenty-five patients with thoracic AIS and 17 age-matched normal teenagers were included in the present study. Axial computed tomography images from T7 to T10 level were obtained to evaluate azygos vein-vertebral angle (defined as 0° when the azygos vein was located directly laterally to the left and 180° when directly laterally to the right). The percentage of azygos vein located in the direction of left screw passage was calculated to analyze the potential risk of injury from left pedicle screw placement. RESULTS: The azygos vein-vertebral angles were significantly smaller in patients with AIS when compared with normal teenagers from T7 to T10 level (P < 0.001). The percentage of azygos vein at high risk of injury from left pedicle screw placement was 80% (20/25) at T7 level, 84% (21/25) at T8 level, 76% (19/25) at T9 level, and 72% (18/25) at T10 level in patients with AIS. No azygos vein was found to be at risk of injury from right pedicle screw placement in patients with AIS. The azygos vein was safe from pedicle screw placement on both sides in normal teenagers. CONCLUSION: The changed relative anatomic position of azygos vein in patients with thoracic AIS places the azygos vein at high potential risk of injury from excessively long left pedicle screw placement. Spine surgeons should choose appropriate screw length to avoid anterior cortex perforation. LEVEL OF EVIDENCE: 3.

Injury to Azygos Venous System: A Co-Existing Injury in High-Impact Lethal Trauma.

BACKGROUND: About 50 cases of azygos venous system injuries following civilian trauma have been published in current literature. The purpose of our study was to investigate the incidence of these injuries, the causative mechanism and type of trauma, the co-existing injuries, and the mortality rate in our institution. METHODS: We performed a retrospective review of all trauma patients who were admitted to the surgical department of the General Hospital of Rethymno during an 11-year period. Our study included patients arriving at our institution dead or alive with an azygos venous system injury following blunt or penetrating civilian trauma. RESULTS: Seven patients-five men and two women-were identified with azygos venous system injuries. Five had an azygos vein laceration, one suffered from both azygos and hemiazygos vein lacerations, and the last one had sustained hemiazygos and accessory hemiazygos vein injuries. All of them suffered from a blunt trauma. Three arrived at our hospital in extremis, and all died within 24 h despite our resuscitation attempts. All of our patients were polytrauma patients. All of them had co-existing torso injuries which were severe in all but one case, three of them suffered also from serious head injuries, and all but one had at least serious extremity's injuries. CONCLUSION: Azygos venous system injuries are rare, although it seems that they are more frequent than current literature would indicate. Blunt trauma mechanism seems to be predominant in civilian trauma setting, and the patients have usually sustained a lot of serious and severe co-existing injuries with high resultant lethality.

Course of major paravertebral vessels and the positional relationship to the vertebral bodies in healthy Chinese subjects: a CT-based study.

BACKGROUND: Several studies, including those done in China, report that paravertebral vascular injury during posterior spinal surgery can greatly harm patients, though it is a relatively rare complication. However, few studies have examined their course and anatomic relationship to the spine. The aim of this study was to measure the course of the major paravertebral vessels and their positional relationships to the vertebral bodies in Chinese subjects using computed tomography. METHODS: We studied a total of fifty subjects who underwent thoracolumbar computed tomography from T1-S1 at our institution. We measured the theoretical distance, actual distance, theoretical angle, and actual angle of the paravertebral vessels at each thoracolumbar intervertebral disc. RESULTS: The paravertebral artery actual angle at T4-L4 ranged from -11.41 to 79.75° and the actual distance from 16.98 to 52.53 mm. The actual angle of the inferior vena cava at L1-L5 intervertebral disc ranged from -40.75 to 34.50° and the actual distance from -36.63 to 61.69 mm. There was no significant difference in the actual angle of the paravertebral vein or in the actual distance in the thoracic segments according to gender (P > 0.05). However, the actual distance in the lumbar segments were significantly different according to gender (P < 0.05). CONCLUSIONS: The major paravertebral vessels' course is closer to the mid-sagittal plane as they move posterior along the vertebrae, and the actual distance of the paravertebral artery and azygos vein increase, while the actual distance of the inferior vena cava decreases. The course of the lumbar paravertebral vessels varies, especially at L4/L5, and may be more prone to intraoperative injury in female subjects.

Life-threatening hemothorax due to azygos vein rupture after chest compression during cardiopulmonary resuscitation.

Hemothorax is not an uncommon cardiopulmonary resuscitation(CPR)­related complication. But hemothorax related to azygos vein injury (AVI) is a rare condition following blunt chest trauma, with no report of CPR-related AVI in the literature. We present a case of azygosve in rupture in a middle-aged woman after repeated chest compression during 1 hour of CPR. She eventually presented with massive hemothorax due to azygos vein rupture diagnosed by computed tomography (CT). When faced with a patient with massive hemothorax after chest compression, azygos vein rupture should be considered as a complication.

Management and outcome of intrathoracic bleeding due to vascular injury during transhiatal esophagectomy.

STUDY OBJECTIVE: The objective of this study was to ascertain the incidence and outcome of intrathoracic vascular injury during transhiatal resection of the esophagus. BACKGROUND: Resection of the esophagus is indicated for a variety of benign and malignant diseases and can be performed via the transhiatal or transthoracic route. As the esophagus is in close vicinity to the aorta, pulmonary vessels and the azygous vein, these blood vessels can be injured during its resection. METHODS: We extracted data on the incidence, management, and outcome of intrathoracic vascular injuries that occurred during transhiatal esophagectomy between 1983 and 2010 from a prospectively maintained esophageal diseases database. RESULTS: During this period, 710 transhiatal esophagectomies were done for malignant (n = 617) and benign causes (n = 93). Intrathoracic vascular injury occurred in ten patients (1.4%). The indication for esophagectomy was malignancy (nine patients) and corrosive stricture (one patient). All nine patients with malignancy had squamous cell carcinoma, and the tumor was located in the midthoracic esophagus in seven and lower thoracic esophagus in two patients. Eight of nine patients with cancer had received preoperative radiotherapy. The site of injury was the aorta/its esophageal branch (six patients), azygous vein (three patients), and inferior pulmonary vein (one patient). The estimated median intraoperative blood loss was 4,450 ml (range, 2,000-6,000 ml), and the median duration of the surgery was 5 h (range, 4-7 h). On a multivariable analysis, location of tumor (in the midthoracic esophagus) was a significant risk factor for the occurrence of vascular injury. Seven patients required a thoracotomy to control the bleeding while in two patients, it could be identified and controlled transhiatally. Two patients died intraoperatively due to massive bleeding and another two died in the postoperative period. Of the patients who survived (n = 6), three patients had an uneventful recovery, one patient developed a cervical anastomotic leak, and two patients developed chest infection. CONCLUSION: Vascular injury during transhiatal esophagectomy is a rare but life-threatening complication. There may be a higher risk in tumors located in the mid esophagus. Management involves prompt identification and control via a dilated hiatus or a thoracotomy.

Azygous vein laceration secondary to blunt thoraco-abdominal trauma.

Less than 25 cases of azygous vein lacerations secondary to blunt trauma have been published in the medical literature, most of these injuries were resulting from motor vehicle accidents, but have been described due to falls or assaults. These lesions should be considered as thoracic great vessels injuries and if not recognized promptly carry a high morbidity and mortality. We report a case of a young male involved in a high-speed car collision, admitted to the emergency room in an unstable condition secondary to hypovolemic shock due to azygous vein injury. The patient underwent emergent right antero-lateral thoracotomy followed by sternotomy for surgical control of the vascular injury and resuscitation. Laparotomy and splenectomy were also required, the abdomen was closed. The thoracic cavity was left packed and closure was delayed for 48 h. The patient survived and was transferred to another hospital seven days later.

Evaluation of thoracic pedicle screw placement in adolescent idiopathic scoliosis.

Pedicle screw fixation is a challenging procedure in thoracic spine, as inadvertently misplaced screws have high risk of complications. The accuracy of pedicle screws is typically defined as the screws axis being fully contained within the cortices of the pedicle. One hundred and eighty-five thoracic pedicle screws in 19 patients that were drawn from a total of 1.797 screws in 148 scoliosis patients being suspicious of medial and lateral malpositioning were investigated, retrospectively. Screw containment and the rate of misplacement were determined by postoperative axial CT sections. Medial screw malposition was measured between medial pedicle wall and medial margin of the pedicle screw. The distance between lateral margin of the pedicle screw and lateral vertebral corpus was measured in lateral malpositions. A screw that violated medially greater than 2 mm, while lateral violation greater than 6 mm was rated as an "unacceptable screw". The malpositions were medial in 20 (10.8%) and lateral in 34 (18.3%) screws. Medially, nine screws were rated as acceptable. Of the 29 acceptable lateral misplacement, 13 showed significant risk; five to aorta, six to pleura, one to azygos vein and one to trachea. The acceptability of medial pedicle breach may change in each level with different canal width and a different amount of cord shift. In lateral acceptable malpositions, the aorta is always at a risk by concave-sided screws. This CT-based study demonstrated that T4-T9 concave segments have a smaller safe zone with respect to both cord-aorta injury in medial and lateral malpositions. In these segments, screws should be accurate and screw malposition is to be unacceptable.

Azygos vein injury in blunt chest trauma.

Injuries to the azygos vein in a blunt chest trauma are uncommon and have previously been described in only 21 cases. The diagnosis is crucially based on massive right haemothorax with signs of shock, hypotension and altered mental status. The severity of the trauma, speed of transport and surgical intervention are often decisive for the survival of the patient. This is confirmed by the three cases we report below.

Injuries to the azygous venous system.

BACKGROUND: Azygous venous system injuries are rare. Although not commonly classified as a thoracic great vessel, the azygous system manifests morbidity and mortality that is similar to that of other great vessel injuries. METHODS: Over a 40 year period, data were retrospectively collected and charts reviewed from a vascular injury database. RESULTS: A total of 22 injuries to the azygous venous system were identified with 21 to the azygous vein and 1 to the hemiazygous vein. All were secondary to penetrating trauma, with 19 from gunshot wounds and 3 from stab wounds. Eight of 22 patients died for an overall mortality of 36%. All patients had associated injuries, with concomitant injury to the lung noted in all cases. CONCLUSIONS: Injuries to the azygous venous system have a significant associated lethality. As an azygous venous injury is not typically the indication for operation, anterior incisions are often employed, making exposure difficult. In the majority of injured patients, the azygous system injury was found after excluding injuries to the heart, lung, and great vessels. A key finding in detecting these injuries through an anterior incision is continued hemorrhage of dark blood from a posterior location in the thoracic cavity. The azygous venous system should be considered early as a source of significant hemorrhage from the posterior mediastinum.

Thoracoscopic sympathetic clamping in a patient with an azygos fissure.

We believe that an azygos fissure may predispose to bleeding during thoracoscopic surgery. An azygos fissure causes important morphologic changes in the superior mediastinum and thereby poses a risk of massive bleeding during thoracoscopic procedures. We report on a successful thoracoscopic procedure conducted in a patient with palmar hyperhidrosis and an azygos fissure and emphasize that the course of the thoracic sympathetic chain runs laterally along the base of the azygos fissure.

Variaciones del sector anterior del polígono de Willis. Correlación anatomo-angiográfica y su implicancia en la cirugía de aneurismas intracraneanos (Arterias, ácigos cerebral anterior, mediana del cuerpo calloso y cerebral media accesoria) / Variants of the anterior circle of Willis, Anatomic and angiografic correlation and its implications in the surgery of itnracranial aneurysms

Es universalmente aceptado que el polígono de Willis presenta variantes en su anatomía habitual, hasta en el 60% de los casos. Algunas de éstas se asocian a malformaciones vasculares, como los aneurismas. El conocimiento de estas variantes anatómicas es de fundamental importancia con vistas al acto quirúrgico, con el fin de preservar arterias en topografía poco habituales y cuya lesión puede determinar secuelas invalidantes. Los autores, en revisión anatómica de 192 hemisferios cerebrales, encuentran tres variantes del sector anterior del Polígono de Willis: arteria ácigos cerebral anterior, arteria mediana del cuerpo calloso y arteria cerebral media accesoria. Se realiza la descripción anatómica de los hallazgos, la correlación con la angiografía y finalmente cómo influyeron estos cambios en el acto quirúrgico de aneurismas de las regiones implicadas (AU)

It is worlwide accepted that in almost 60% of cases, anatomical variants in the Circle of Willis can be found. Some of them are associated with vascular malfor¬mations such as aneurysms. The knowledge of these anatomical variants is of vital importance when facing surgery, being the aims to preserve arteries in unusual localisations, which when injured can determine invali¬dating sequelae. The authors have reviewed 192 cerebral hemis¬pheres, finding three variants in the anterior Circle of Willis: Azigos anterior cerebral artery; Median artery of the corpus callosum and accesory middle cerebral artery. The authors make an anatomical description of the findings, their angiographical correlation, and describe the influence of these changes during surgery of aneurysms in the involved regions (AU)

Anatomical comparison of a defect in the hepatic segment of the inferior vena cava with the normal azygos system

During anatomical practice between 2001-2002 at the Tokyo Women's Medical University, a defect in the hepatic segment of the inferior vena cava was encountered in a 94-year-old male cadaver. Although this type of defect has often been observed clinically using imaging diagnosis, the topological changes in the small vessels and surrounding structures have not been described previously. Here, the topological changes in small vessels and surrounding structures, in addition to the morphology of a defect in the hepatic segment of the inferior vena cava, are described in detail. Normal variations in the venous system were also examined using 26 human cadavers for comparison. The following results and interpretations were obtained: The thoracic portion of the anomalous vein originated from the azygos system, judging from the topological relationships among the main venous trunk, small vessels, and the autonomic nerves. Although a close relationship between the inferior vena cava and the azygos system was recognized, the development of each venous system should be regarded as independent, based on the normal variations observed in 26 human cadavers and the currently available medical literature. The boundary between the cardinal vein (inferior vena cava) and the azygos system might be the lower border of the renal vein, since the renal vein drained into the ventral aspect of the inferior vena cava and the left renal artery ran superficially across the abdominal portion of the anomalous vein. Examination of topological changes in the surrounding structures may provide important clues regarding the morphogenesis of defects in the hepatic segment of the inferior vena cava and normal venous systems (AU)

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