The surgical anatomy of the axillary approach for nerve transfer procedures targeting the axillary nerve.

PURPOSE: The exact relational anatomy for the anterior axillary approach, targeting the axillary nerve for nerve transfers/grafts, has not been fully investigated. Therefore, this study aimed to dissect and document the gross anatomy surrounding this approach, specifically regarding the axillary nerve and its branches. METHODS: Fifty-one formalin-fixed cadavers (98 axilla) were bilaterally dissected simulating the axillary approach. Measurements were taken to quantify distances between identifiable anatomical landmarks and relevant neurovascular structures encountered during this approach. The musculo-arterial triangle, described by Bertelli et al., to aid in identification on localization of the axillary nerve, was also assessed. RESULTS: From the origin of the axillary nerve till (1) latissimus dorsi was 62.3 ± 10.7 mm and till (2) its division into anterior and posterior branches was 38.8 ± 9.6 mm. The origin of the teres minor branch along the posterior division of the axillary nerve was recorded as 6.4 ± 2.9 mm in females and 7.4 ± 2.8 mm in males. The musculo-arterial triangle reliably identified the axillary nerve in only 60.2% of the sample. CONCLUSION: The results clearly demonstrate that the axillary nerve and its divisions can be easily identified with this approach. The proximal axillary nerve, however, was situated deep and therefore challenging to expose. The musculo-arterial triangle was relatively successful in localising the axillary nerve, however, more consistent landmarks such as the latissimus dorsi, subscapularis, and quadrangular space have been suggested. The axillary approach may serve as a reliable and safe method to reach the axillary nerve and its divisions, allowing for adequate exposure when considering a nerve transfer or graft.

Emerging Imaging Techniques in Anatomy: For Teaching, Research and Clinical Practice.

Visualisation plays a key role in anatomy, where the depiction of gross anatomical structures is essential in understanding and conceptualising content during research and medical teaching. Technology has allowed us to utilise imaging techniques for the visualisation of anatomical features, pathology and correlating physiological functions in a non-invasive manner which is atypical to traditional forms of anatomical investigation. These imaging methods develop integration between anatomy and clinically oriented medical study as well as biomechanics. The progressive research in anatomy can benefit from the vast field of biomechanics which allows for precise and conclusive results regarding the biomechanical integrity of anatomical structures and allows for intricate planning of procedures. 3D imaging techniques have enhanced the modelling of internal structures which are especially essential when implemented as diagnostic tools. An integration of these modalities into medical training accommodates for a more clinically orientated and immediate visualisation as produced when utilising ultrasound imaging which has the added advantage of 3D modelling and manipulation. Immersive technology has revolutionised teaching and learning particularly during the new age of hybrid education. Visualisation in anatomy has many clinical and educational applications which can optimise research, create interactive learning experiences and aid medical practise.

A quantitative analysis of the dimensions and content of the vertebral triangle.

PURPOSE: The vertebral triangle (VT) located in the root of the neck most commonly contains the vertebral artery (VA), cervical sympathetic chain and certain roots of the brachial plexus. Although other structures have been reported, few studies have reported on the overall content of this space. Based on the current literature, there is a general paucity of anatomical information pertaining to the dimensional anatomy of the VT and specifically the structures related to it. Therefore, this study aimed to quantitatively analyze the size, position, content, and anatomical structures in relation to the vertebral triangle in a South African sample. METHODS: Forty-three VTs were dissected on bodies donated to science. Measurements taken include the dimensions of the triangle, as well as distances between prominent structures and landmarks of the VT. Observations were made on the presence/absence of the varying neurovascular structures within the VT. RESULTS: Mean height was 30.1 ± 1.51 mm (R) and 32.9 ± 1.78 mm (L). Mean width was 18.3 ± 0.74 mm (R) and 19.3 ± 0.98 mm (L). The C8 spinal nerve was found on average approximately halfway [16.4 ± 0.74 mm (R) and 15.9 ± 0.95 mm (L)] in the VT. The VA was present in the VT in 100% of the sample and the C7 spinal nerve and inferior sympathetic ganglia were present in more than 80% of the sample. CONCLUSION: Understanding the VT and the content is of the utmost importance and of great interest to neurosurgeons, to avoid these important neurovascular structures and prevent iatrogenic complications during surgery.

The anatomical features of an ultrasound-guided erector spinae fascial plane block in a cadaveric neonatal sample.

BACKGROUND: Since its inception, the erector spinae plane block has been used for a variety of truncal surgeries with success in both adults and children. However, the anatomical features, route of spread, and dermatomal coverage are still not fully understood in a pediatric population. OBJECTIVES: To identify the anatomical features of the erector spinae fascial plane space by replicating an erector spinae plane block in a fresh neonatal cadaveric sample. The primary aim was to determine the spread of the dye within the fascial plane, while the secondary aims were to determine whether the needle direction or entry site affected the spread. METHODS: The block was replicated bilaterally using 0.1 mL/kg of iodinated contrast dye in nine fresh unembalmed preterm neonatal cadavers. The dye was introduced under ultrasound guidance at vertebral level T5 and T8. Additionally, the needle was oriented cranial-caudal vs caudal-cranial to determine if the needle orientation influenced the spread of dye. The block was also replicated midway between the adjacent transverse processes as opposed to the lateral tip of the transverse process to determine the spread. RESULTS: From the total sample size, 14 "blocks" were successfully replicated, while 4 "blocks" were either incomplete or failed blocks. Contrast dye was found in the paravertebral, intercostal, and epidural spaces, including posteriorly over the neural foramina. Results revealed that the needle direction or entry site did not influence the spread within the fascial plane. CONCLUSION: Contrast material was found in the paravertebral, epidural, and intercostal spaces over an average of 5 vertebral levels when using 0.1 mL/kg.

The extent of cranio-caudal spread within the erector spinae fascial plane space using computed tomography scanning in a neonatal cadaver.

BACKGROUND: The erector spinae plane block (ESP) is a novel approach for blockade of the spinal nerves in infants, children, and adults. Until recently, the gold standard for truncal procedures includes the paravertebral and epidural blocks. However, the exact mechanism by which this blockade is achieved is subject to debate. METHODS: 2.3 mL (1 mL/kg) of iodinated contrast dye was injected bilaterally into the erector spinae fascial plane of a fresh unembalmed preterm neonatal cadaver (weighing 2.3 kg), to replicate the erector spinae plane block and to track the cranio-caudal spread of the contrast dye using computed tomography. The "block" was performed at vertebral level T8 on the right-hand side and at vertebral level T10 on the left-hand side. RESULTS: Contrast dye was spread over three dermatomal levels from T6 to T9 on the right-hand side, while on the left-hand side, the spread was seen over four dermatomal levels from T9 to T11/12. Contrast dye also spread over the costotransverse ligament, into the paravertebral space and further lateral from the lateral border of the erector spinae muscle into the intercostal space. However, no spread was seen in the epidural space. CONCLUSION: The erector spinae plane block is a versatile technique that can be part of the multimodal postoperative analgesic strategy for truncal surgery. In this study, contrast material dye was tracked over four vertebral levels in the paravertebral space (suggesting an approximate volume of 0.5-0.6 mL per dermatome).

The Association Between Anterior Cruciate Ligament Length and Femoral Epicondylar Width Measured on Preoperative Magnetic Resonance Imaging or Radiograph.

PURPOSE: To determine whether femoral epicondylar width (FECW) obtained from either magnetic resonance imaging (MRI) or plain radiographs could be used to predict anterior cruciate ligament (ACL) length. A secondary purpose was to develop a formula to use maximum FECW on either MRI or plain radiographs to estimate ACL length preoperatively. METHODS: The MRIs and radiographs of 40 patients (mean age 41.0 years), with no apparent knee pathology, surgery, or trauma were included. The ACL length was measured on MRI followed by FECW on both MRI and radiograph of the same patient. This allowed the development of equations able to predict ACL length according to the FECW measured on either an MRI or radiograph. RESULTS: The mean ACL length was 40.6 ± 3.6 mm. FECW measured on both MRIs and radiographs was sufficient to predict ACL length. Pearson's correlations revealed a high positive relationship between ACL length and FECW on MRI (r = 0.89, P < .0001) and ACL length and FECW on radiograph (r = 0.83, P < .0001). The coefficient of determination (R2) was calculated to be MRI: R2 = 0.78 and radiograph: R2 = 0.68 and confirmed that FECW measured on both MRI and radiograph were sufficient to predict ACL length. Based on these models, ACL length can be predicted by FECW using the following formulas: MRI: ACL length = 0.47 (FECW) + 1.93 and radiograph: ACL length = 0.31 (FECW) + 11.33. CONCLUSIONS: This study demonstrated that FECW measured on either MRI or anteroposterior radiograph could reliably estimate ACL length on a sagittal MRI. There was a high positive relationship between ACL length and FECW on both MRI and radiographs, although MRIs do predict ACL length more reliably. CLINICAL RELEVANCE: Preoperative ACL length assessment, using FECW on MRI or radiograph, is useful in graft selection and in preventing inadequate graft harvesting for ACL reconstruction, especially if an individualized anatomical approach is pursued.

A cadaveric study of the erector spinae plane block in a neonatal sample.

BACKGROUND: The aim of this article was to provide a detailed description of the neonatal anatomy related to the erector spinae plane block and to report the spread of the dye within the fascial planes and potential dermatomal coverage. METHODS: Using ultrasound guidance, the bony landmarks and anatomy of the erector spinae fascial plane space were identified. The erector spinae plane block was then replicated unilaterally in two fresh unembalmed neonatal cadavers. Using methylene blue dye, the block was performed at vertebral levels T5-using 0.5 mL in cadaver 1-and T8-using 0.2 mL in cadaver 2. The craniocaudal spread of dye was tracked within the space on the ultrasound screen and further confirmed on dissection. RESULTS: Craniocaudal spread was noted from vertebral levels T3 to T6 when the dye was introduced at vertebral level T5 and from vertebral levels T7 to T11 when the dye was introduced at vertebral level T8. Furthermore, the methylene blue spread was found anteriorly in the paravertebral and epidural spaces, staining both the dorsal and ventral rami of the spinal nerves T2 to T12. Small amounts of dye were also found in the intercostal spaces. CONCLUSION: In two neonatal fresh cadavers, the dye was found to spread to multiple levels and key anatomic locations.

Determining the extent of the dural sac for the performance of caudal epidural blocks in newborns.

BACKGROUND: Information regarding the position and relationship of vital structures within the caudal canal is important for anesthesiologists who perform a caudal block. This information can be acquired by anatomical dissection, with ultrasound technology, or radiological studies. AIMS: The aim of this study was to determine the position of the dural sac in neonates by measuring the distance of the termination of the dural sac from the apex of the sacral hiatus in neonatal cadavers. METHODS: After careful dissection, the distance from the apex of the sacral hiatus to the dural sac was measured in a sample of neonatal cadavers. RESULTS: In 39 neonatal cadavers, the mean distance from the apex of the sacral hiatus to the dural sac was 10.45 mm. The range of this distance was between 4.94 and 26.28 mm. The mean distance for females was 9.64 mm (range from 6.66 to 15.09); that for males was 10.90 mm (range between 4.94 and 26.28). Linear regression with the log of this distance as the outcome variable gave an estimated 3.3% increase in the distance for each 1 cm increase in the length of the neonate (95% CI for this proportion was 1.91-4.71). CONCLUSION: Anesthesiologists should be aware of the short distance between the sacral hiatus and the dural sac when performing caudal blocks, the shortest distance was 4.94 mm. Armed with this knowledge, caudal techniques should be modified to improve the safety and reduce the risk of complications, such as dural puncture.

Anatomical description of the sciatic nerve block at the subgluteal region in a neonatal cadaver population.

INTRODUCTION: Sciatic nerve blocks provide intraoperative and prolonged postoperative pain management after lower limb surgery (posterior knee, foot, skin graft surgery). Accurate needle placement requires sound anatomical knowledge. Anatomical studies on children are uncommon; most have been performed on adult cadavers. We studied the location of the sciatic nerve at the gluteal level in neonatal cadavers to establish useful anatomical landmarks. METHODS: We identified the sciatic nerve in the gluteal and thigh region of 20 neonatal cadavers. The skin covering the gluteal and thigh region was reflected laterally, and the underlying structures and muscles were identified. We located the sciatic nerve and measured the distance from the nerve to the greater trochanter of the femur and to the tip of the coccyx with a mechanical dial caliper. The total distance between the two landmarks was then recorded. RESULTS: We combined measurements from both sides to form a sample size n = 40. The sciatic nerve was 14.9 ± 2.4 mm lateral to the tip of the coccyx. The total distance between the greater trochanter and the tip of the coccyx was 27.3 ± 4.0 mm. CONCLUSION: Our results provide anatomical evidence that the optimal needle insertion point is approximately halfway between the greater trochanter and the tip of the coccyx-a landmark readily palpable in neonates and infants.

A theoretical alternative intraosseous infusion site in severely hypovolemic children.

BACKGROUND: Studies have shown that the venous system tends to collapse during hypovolemic shock. The use of the bone marrow space for infusions is an effective alternative, with the tibial insertion site being the norm. OBJECTIVES: This study was conducted to determine a quick intraosseous infusion method that could be an alternative to the tibial route in neonates during emergency situations. METHOD: A sample of 30 neonatal cadavers was dissected to explore a possible alternative to the tibial insertion site. The needle was inserted in the superolateral aspect of the humerus. The needle infusion site was then dissected to determine possible muscular and neurovascular damage that might occur during the administration of this procedure, with the greatest concern being the posterior circumflex humeral artery and axillary nerve exiting the quadrangular space. The distance of the needle insertion site was measured in relation to the soft tissue as well as to bony landmarks. RESULTS: The calculated 95% confidence interval shows that the needle can be safely inserted into the intraosseous tissue at the greater tubercle of the humerus 9.5 mm-11.1 mm from the acromion. This is about a little finger's width from the acromioclavicular joint. CONCLUSION: Anatomically, the described site is suggested to offer a safe alternative access point for emergency infusion in severely hypovolemic newborns and infants, without the risk of damage to any anatomical structures.

Descriptive study of the differences in the level of the conus medullaris in four different age groups.

In performing neuraxial procedures, knowledge of the location of the conus medullaris in patients of all ages is important. The aim of this study was to determine the location of conus medullaris in a sample of newborn/infant cadavers and sagittal MRIs of children, adolescents, and young adults. The subjects of both the samples were subdivided into four developmental stages. No statistical difference was seen between the three older age groups (P > 0.05). A significant difference was evident when the newborn/infant stage was compared with the other, older stages (P < 0.001 for all comparisons). In the newborn/infant group the spinal cord terminated most frequently at the level of L2/L3 (16%). In the childhood stage, the spinal cord terminated at the levels of T12/L1 and the lower third of L1 (21%). In the adolescent population, it was most often found at the level of the middle third of L1 and L1/L2 (19%). Finally, in the young adult group, the spinal cord terminated at the level of L1/L2 (25%). This study confirmed the different level of spinal cord termination between newborns/infants less than one-year-old and subjects older than one year. In this sample the conus medullaris was not found caudal to the L3 vertebral body, which is more cranial than the prescribed level of needle insertion recommended for lumbar neuraxial procedures. It is recommended that the exact level of spinal cord termination should be determined prior to attempting lumbar neuraxial procedures in newborns or infants.

Clinical anatomy of the maxillary nerve block in pediatric patients.

BACKGROUND: Anatomical landmarks in children are mostly extrapolated from studies in adults. Despite this, complex regional anesthetic procedures are frequently performed on pediatric patients. Sophisticated imaging techniques are available but the exact position, course and/or relationships of the structures are best understood with appropriate anatomical dissections. Maxillary nerve blocks are being used for peri-operative analgesia after cleft palate repair in infants. However, the best approach for blocking the maxillary nerve in pediatric patients has yet to be established. OBJECTIVE: To determine the best approach for blocking the maxillary nerve within the pterygopalatine fossa. METHODS: In an attempt to define an optimal approach for maxillary nerve block in this age group three approaches were simulated and compared on 10 dried pediatric skulls as well as 30 dissected pediatric cadavers. The needle course, including depth and angles, to block the maxillary nerve, as it exits the skull at the foramen rotundum within the pterygopalatine fossa, was measured and compared. Two groups were studied: Group 1 consisted of skulls and cadavers of neonates (0-28 days after birth) and Group 2 consisted of skulls and cadavers from 28 days to 1 year after birth. RESULTS: No statistically significant difference (P > 0.05) was found between the left and right side of each skull or cadaver. Only technique B, the suprazygomatic approach from the frontozygomatic angle towards the pterygopalatine fossa, exhibited no statistical significance (P > 0.05) when other measurements made on the skulls and cadavers were compared. Technique A, a suprazygomatic approach from the midpoint on the lateral border of the orbit, as well as technique C, an infrazygomatic approach with an entry at a point on a vertical line extending along the lateral orbit wall, showed statistical significant differences when measurements of the skulls and cadavers were compared. CONCLUSIONS: On the basis of these findings technique B produces the most consistent data for age groups 1 and 2 and supports the clinical findings recently reported.

Revisiting the anatomy of the ilio-inguinal/iliohypogastric nerve block.

BACKGROUND: The ilio-inguinal/iliohypogastric nerve block (INB) is one of the most common peripheral nerve block techniques in pediatric anesthesia, which is largely due to the introduction of ultrasound (US) guidance. Despite the benefits of US guidance, the absence of an US machine should not deter the provider from performing INB, considering that many institutions, especially in developing countries, cannot afford to provide ultrasound machines in their anesthesiology departments. The aim of this study was to revisit the anatomical position of the ilio-inguinal and iliohypogastric nerves in relation to the anterior superior iliac spine (ASIS), in a large sample of neonatal cadavers, and compare the results with a similar group in a previously published US-guided study. METHODS: With Ethics Committee approval, the ilio-inguinal and iliohypogastric nerves were carefully dissected in 54 neonatal cadavers. RESULTS: In the total sample, the ilio-inguinal nerve was found to be 2.2 ± 1.2 mm from the ASIS, on a line connecting the ASIS to the umbilicus. The iliohypogastric nerve was on average 3.8 ± 1.3 mm from the ASIS. For the entire sample, the optimal needle insertion site was 3.00 mm from the ASIS. Although there is a strong correlation between the needle insertion point and the weight of the neonate, this will only 'fit' for 60% of the population. CONCLUSION: The linear regression formula; needle insertion distance (mm) = 0.6 × weight + 1.8 can be used as a guideline for the position of the ilio-inguinal and iliohypogastric nerves.