Superficial Anatomic Landmarks Research Articles

3D models of the cardiac conduction system in healthy neonatal human hearts

Iatrogenic damage to the cardiac conduction system (CCS) remains a significant risk during congenital heart surgery. Current surgical best practice involves using superficial anatomical landmarks to locate and avoid damaging the CCS. Prior work indicates inherent variability in the anatomy of the CCS and supporting tissues. This study introduces high-resolution, 3D models of the CCS in normal pediatric human hearts to evaluate variability in the nodes and surrounding structures. Human pediatric hearts were obtained with an average donor age of 2.7 days. A pipeline was developed to excise, section, stain, and image atrioventricular (AVN) and sinus nodal (SN) tissue regions. A convolutional neural network was trained to enable precise multi-class segmentation of whole-slide images, which were subsequently used to generate high- resolution 3D tissue models. Nodal tissue region models were created. All models (10 AVN, 8 SN) contain tissue composition of neural tissue, vasculature, and nodal tissues at micrometer resolution. We describe novel nodal anatomical variations. We found that the depth of the His bundle in females was on average 304 μm shallower than those of male patients. These models provide surgeons with insight into the heterogeneity of the nodal regions and the intricate relationships between the CCS and surrounding structures.

The Occipitalis Muscle as an Adjunct Superficial Landmark for the Transverse Sinus and Transverse-Sigmoid Junction: An Anatomical Study With Application to Posterior Cranial Fossa Surgery.

Although neuronavigation systems are widely used for identifying deep intracranial structures, additional superficial anatomical landmarks can be useful when this technology is not available or is not working properly. Herein, we investigate the potential of the occipitalis muscle (OM), rarely mentioned in neurosurgical literature, as a superficial landmark for the transverse sinus (TS) and transverse-sigmoid sinus junction (TSJ). Eighteen adult cadaveric heads underwent dissection. The borders of the OM were identified and measured. The muscle was then removed and the bone underlying the muscle was drilled. The relationships between the OM and the underlying dural venous sinuses were then investigated by using a surgical microscope. The OM is a quadrangular-shaped muscle, that invariably crosses the lambdoid suture, showing relationships with the TS inferiorly and the TSJ laterally. The medial border was located a mean of 2.7 cm from the midline and its lower edge was a mean of 1.6 cm above the TS. The inferior border was found between the lambdoid suture and the superior nuchal line in all the specimens. The medial half of the inferior margin was placed on average 1.1 cm superiorly to the TS while the lateral margin ran just above or over the TS. The lateral border was located a mean of 1.1 cm medially to the asterion and approximated the mastoid notch, being within 1-2 cm from it. The TSJ was between 2.1 and 3.4 cm lateral to OM lateral border. A combination of superficial anatomical landmarks can be useful for surgical planning. We found that the OM represents a valuable aide for neurosurgeons and is a reliable landmark for the deeper-lying TS and TSJ.

Superficial anatomic landmarks can be used to triangulate the location of canine peripheral lymphocentrums: superficial cervical, axillary, and superficial inguinal.

To utilize the geometry of superficial anatomic landmarks to guide incisional location and orientation for peripheral lymphadenectomy, document deep anatomic landmarks for lymphocentrum identification, and develop novel surgical approaches to the superficial cervical, axillary, and superficial inguinal lymphocentrums in dogs. 12 canine cadavers. 2 cadavers were used for a pilot investigation to determine optimal body positioning, select superficial anatomic landmarks for lymphocentrum identification, and evaluate novel surgical approaches to the 3 lymphocentrums. These lymphocentrums were then dissected in 10 additional cadavers using these novel surgical approaches. Measurements of the distances from lymphocentrum to landmark and between landmarks were obtained for each lymphocentrum. Deep anatomic landmarks were recorded for each dissection. The mean and SD were calculated for each measurement and used to develop geometric guidelines for estimating the location of each lymphocentrum for these surgical approaches. Each peripheral lymphocentrum was found in the same location relative to the respective, predetermined, superficial, anatomic boundaries in all cadavers. Briefly, the superficial landmarks to each lymphocentrum were as follows: (1) superficial cervical: wing of atlas, acromion process of scapula, greater tubercle of humerus; (2) axillary: caudal border of transverse head of superficial pectoral muscle, caudal triceps muscle, ventral midline; and (3) superficial inguinal: origin of pectineus muscle, ipsilateral inguinal mammary gland, ventral midline. The proposed superficial and deep surgical landmarks were identified within every cadaver. The previously undescribed surgical approaches were effective for lymphocentrum identification. Anatomic landmarks provided in this study may help reduce surgical time and tissue trauma during peripheral lymphadenectomy in dogs. This study was also the first to describe a surgical approach to the superficial inguinal lymphocentrum and ventral approaches to the superficial cervical and axillary lymphocentrums and provided previously unpublished anatomic landmarks for a lateral approach to the superficial cervical lymphocentrum.

Can sural nerve injuries be prevented in posterior leg approaches? Stage 1: Ultrasound evaluation of a new method based on surface anatomical landmarks and sural nerve pathway

Category: Other; Other Introduction/ Purpose: The risk of sural nerve intersection with posterior leg approaches, and its potential risk of injury in some surgeries can range from 60% to 100%. Several authors have described methods to predict the path of the sural nerve through metric units of non-proportional distances, however these distances are altered by patient's height, leg length and body mass index (BMI); none has proposed a reproducible method, proportional to each person based on anatomical references. The aim is to describe ultrasonographically the distance and crossing zone between a new method, proportional to each person, based on a surface reference line and the position of the sural nerve. Methods: Descriptive cross-sectional study, performed between January to April 2022 in patients requiring foot surgery who met inclusion criteria. We located and marked by ultrasound the course of the sural nerve in the posterior aspect of the leg. Landmarks were drawn and marked with a straight line from the posterior aspect of the medial femoral condyle to the tip of the fibula. This line was divided into two equal segments and the distal half was subdivided into 4 zones, this way, we studied areas based on simple anatomical proportions for each patient. The distance between the references and the ultrasound position of the nerve was measured in these 4 zones, creating intersection points and safety areas. Location and distances of the sural nerve from the proposed landmarks were assessed. A size of 96 lower limbs (48 patients) was determined with 95% confidence interval and 80% power to SN concordance between the two legs greater than 15% of that reported in the literature. Results: 100 lower limbs (50 left; 50 right) assessed in 50 patients were included. Forty-four percent female (44/100) and 56% male (56/100). The median age was 45 (range: 22 - 74) years. The median height was 164 (range: 150 - 180) cm with a median BMI of 23.3 (range: 17.7 - 39.7) kg/cm2. The shortest median distance of the nerve passage was 2.9 mm from Point 2. The sural nerve intersection was 59% in Zone B, 19% in Zone C and 20% in Zone A. Safety zones were established. Average 80% of coincidence in sural nerve localization, in the distal half of the leg, in relation to the surface reference line when comparing both legs of each patient. Conclusion: This study proposes a simple, reproducible, non-invasive, and for the first time, person-proportional method that describes the distance and location of the main areas of intersection of the sural nerve with points and areas determined by a line guided by superficial anatomical landmarks.

Ultrasound evaluation of a new surface reference line to describe sural nerve location and safe zones to consider in posterior leg approaches

PurposeSeveral authors have described methods to predict the sural nerve pathway with non-proportional numerical distances, but none have proposed a person-proportional, reproducible method with anatomical references. The aim of this research is to describe ultrasonographically the distance and crossing zone between a surface reference line and the position of the sural nerve.MethodsDescriptive cross-sectional study, performed between January and April 2022 in patients requiring foot surgery who met inclusion criteria. The sural nerve course in the posterior leg was located and marked using ultrasound. Landmarks were drawn with a straight line from the medial femoral condyle to the tip of the fibula. Four equal zones were established in the leg by subdividing the distal half of the line. This way, areas based on simple anatomical proportions for each patient were studied. The distance between the marking and the ultrasound nerve position was measured in these 4 zones, creating intersection points and safety areas. Location and distances from the sural nerve to the proposed landmarks were assessed.ResultsOne-hundred and four lower limbs, 52 left and 52 right, assessed in 52 patients were included. The shortest median distance of the nerve passage was 2.9 mm from Point 2. The sural nerve intersection was 60/104 (57.7%) in Zone B, 21/104 (20.1%) in Zone C and 19/104 (18.3%) in Zone A. Safety zones were established. Average 80.5% of coincidence in sural nerve localization was found in the distal half of the leg, in relation to the surface reference line when comparing both legs of each patient.ConclusionsThis study proposes a simple, reproducible, non-invasive and, for the first time, person-proportional method, that describes the distance and location of the main areas of intersection of the sural nerve with points and zones (risk and safe zones) determined by a line guided by superficial anatomical landmarks. Its application when surgeons plan and perform posterior leg approaches will help to avoid iatrogenic nerve injuries.Level of evidenceIV.

Definition of a Risk Zone for the Axillary Nerve Based on Superficial Landmarks.

The aim of this study was to investigate the axillary nerve's location along superficial anatomical landmarks, and to define a convenient risk zone. A total of 123 upper extremities were evaluated. After dissection of the axillary nerve, the vertical distance between the upper border of the anterolateral edge of the acromion and the proximal border of the nerve was measured. Furthermore, the interval between the proximal border and the distal border of the axillary nerve's branches was evaluated. The interval between the distal border of the branches and the most distal part of the lateral humeral epicondyle was measured. The distance between the anterolateral edge of the acromion and the lateral humeral epicondyle was evaluated. Measurements were expressed as proportions with respect to the distance between the acromion and the lateral humeral epicondyle. The distance between the acromion and the proximal border of the axillary nerve's branches was at a height of 10 percent of the distance between the acromion and the lateral humeral epicondyle, starting from the acromion (90 percent when starting from the lateral humeral epicondyle). The interval between the proximal and distal margins of the axillary nerve's branches was between 10 percent and 30 to 35 percent of this interval, starting from the acromion (65 to 70 percent when starting from the lateral humeral epicondyle). The authors were able to locate the branches of the axillary nerve at an interval between 10 and 35 percent of the distance between the acromion and the lateral humeral epicondyle, starting from the acromion. This makes the proximal third of this distance an easily applicable risk zone during shoulder surgery.

Projection of the A1-Pulley of the Thumb onto Superficial Anatomical Landmarks: An Anatomical Study and a Useful Guide to Surgeons.

The aim of our study was to project the A1-pulley of the thumb onto the total thumb length to enable its complete division with and without direct sight. The study involved 50 hands from adult human cadavers. The proximal and distal borders of the A1-pulley were measured with reference to the first metacarpophalangeal joint (MCPJ). The length of the thumb was defined as the interval between the first carpometacarpal joint (CMCJ) and the apex of the thumb. The length of the pulley is calculated proportionally with reference to the line between the first CMCJ and apex of the thumb. Approximated by computing 95% confidence intervals, the pulley can be expected to lie in an area between 34.0% (proximal border) and 57.8% (distal border) alongside this line. Percutaneous and minimally-invasive division of the A1-pulley needs to be performed between 34.0 and 57.8% of the length between the first CMCJ and apex of the thumb.

Anatomische Aspekte zur endoskopischen Dekompression beim Interosseus-anterior-Syndrom

Decompression of the anterior interosseous nerve can be performed in an open operative exploration or endoscopically. Using an endoscopic decompression superficial anatomical landmarks serve as reference point. The aim of the study was to determine the location of the distribution of the median nerve in relation to the elbow joint in order to facilitate preparation during endoscopic decompression. The median nerve and the anterior interosseous nerve were dissected in 31 human specimens with regard to the elbow joint. The superficial anatomical landmark was the intercondyle line between the medial and lateral epicondyles. The distance between the origination of the anterior interosseous nerve of the median nerve was measured in relation to the intercondyle line. The anatomical preparation was done using 62 adult cadaveric upper extremities. 11 specimens were formalin fixed and 20 specimens were fresh frozen cadaveric upper extremities. The average of the intercondyle distance was 7.2 cm ± 0.5 (min. 5.8; max. 7.8). The anterior interosseous nerve originated from the median nerve in average 39 mm ± 18 (min. 8; max. 80) distal to the intercondyle line. In 12 cases the distance was within the first 2 cm. There was only a correlation between the length of the upper arm and the nerve junction. The anterior interosseous nerve originated from the median nerve in average 4 cm distal to the intercondyle line. Although there was a distribution under 2 cm in around 20 % of the cases. This is very important with regard to the endoscopically technique and should be considered.

If transversus abdominis plane blocks are to be used in laparoscopy then the gynaecologist is best placed to administer them.

The role of transabdominal plane (TAP) blocks in laparoscopic surgery is unclear, and their implementation is generally left to the discretion of the anaesthetist. The anaesthetist attempts to interrupt sensory innervation across several dermatomes by instilling local anaesthetic below the fascial plane between the internal oblique and the transverse abdominis muscles. The technique may involve one or two entry points on each side of the abdomen. The ‘blind’ TAP block relies upon orientation using superficial anatomical landmarks and a ‘double pop’ sensation indicating the needle is sited correctly. Inadvertent visceral injuries have been reported as well as suboptimal placement in the majority of patients and so visualisation with ultrasound to guide needle placement has been advocated (McDermott et al. BJA 2012;108:499–502). However, the excellent visualisation of the abdominal cavity provided by laparoscopy has promoted laparoscopically delivered TAP blocks. Randomised controlled trials (RCTs) have evaluated TAP blocks across surgical practice and systematic evidence syntheses have found them to be associated with modest improvements in overall quality of recovery and corresponding reductions in postoperative pain up to 24 hours postsurgery and requirements for analgesia (Brogi et al. Can J Anaesth 2016;63:1184–96). Most data pertaining to the impact of TAP blocks on recovery from laparoscopic surgery have come from trials involving laparoscopic cholecystectomy. Data specific to gynaecological surgery are scarce, although two small RCTs evaluating ultrasound-guided TAP blocks in laparoscopic hysterectomy have been conducted, albeit with conflicting results (Kane et al. Am J Obstet Gynecol 2012;207:419.e1–5; De Oliveira GS Jr et al. Obstet Gynecol 2011;118:1230–7.). The study in BJOG by R Kargar et al. (BJOG 2019;126:647–54) reports an RCT comparing laparoscopic TAP blocks with standard port-site infiltration of local anaesthetic and placebo in women undergoing complex laparoscopic endometriosis surgery. A benefit of laparoscopically deployed TAP and port-site blocks was shown compared with placebo in pain relief up to 12 hours following surgery. However, laparoscopic TAP blocks were no more effective than conventional port-site anaesthesia. The investigators missed an opportunity to evaluate the cumulative effect of combining TAP blocks with local port-site anaesthetic. So where are we now? Well, local port-site anaesthesia should be continued but further work is needed to ascertain who may benefit from TAP blocks whether used as an alternative or in combination with port-site blockade. Confounders, such as the type and duration of laparoscopic surgery, the size of ports, patient characteristics such as obesity, and local anaesthetic regimens need to be accounted for. In addition, the question of how TAP blocks should be delivered and by whom will be of interest; blindly or ultrasound-guided by the anaesthetist or under laparoscopic guidance by the gynaecologist? I suspect most surgeons are aware that the amount of time available on operating lists for actual surgery is diminishing because of prolongation of anaesthetic times and the requirement for WHO safety check lists. Peering through the anaesthetic room the eager, optimally prepared but time-poor surgeon can become deflated observing the anaesthetist manipulating a portable ultrasound machine in order to ‘line up’ the TAP blocks. I believe the opportunity to claw this time-consuming task from our enthusiastic anaesthetic colleagues will be welcomed by most surgeons! Dr Clark reports personal fees from Bayer, personal fees from Smith & Nephew, personal fees from Hologic, outside the submitted work. A completed disclosure of interest form is available to view online as supporting information. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Anatomy of the Superficial Venous Structures of the Neck: A Cadaveric Study to Guide Superficial Injections.

Minimally invasive aesthetic procedures of the neck are becoming more popular. However, anatomical studies on the venous structures of the neck in relation to these procedures are lacking. The aims of this study were to identify the locations and communication patterns of the anterior jugular vein and external jugular vein (AJV and EJV) and the communicating vein (CV) based on superficial anatomical landmarks and to determine dangerous areas for dermal filler injections into the neck. Thirty sides of the neck from Korean adult cadavers were dissected for this study. Four anatomical variants were identified. In Type Ia, the CV ran along the anterior border of the sternocleidomastoid muscle (SCM) (33.4%); in Type Ib, a single vein was observed connecting the CV and the EJV at the level of laryngeal prominence (23.3%); in Type Ic, the CV proceeded separately from the medial side of the anterior border of the SCM (13.3%); and in Type II, the CV was absent while the EJV and AJV were observed (30%). Given the 4 anatomical variants identified in this study, the authors recommend exerting caution when performing dermal filler injections approximately 10, 30, and 60 mm lateral to the midsagittal line to avoid iatrogenic side effects.

Arthroscopic treatment of lateral ankle instability. Is there a safe zone? An anatomic study

BackgroundThe purpose of this study is to describe the relative location of superficial anatomic landmarks and likely location of structures at risk in order to predict the proximity of the later and avoid their injury during the arthroscopic treatment of lateral ankle instability. MethodsFifteen cadaver ankles were dissected. Based on superficial anatomic landmarks, the location and distances to the structures at risk (extensor tendons, peroneus tertius, peroneal tendons, main branch or intermediate branch of the superficial peroneal nerve, and the sural nerve) were measured. ResultsThe distance from the lateral malleolus along the peroneus brevis to its intersection by the sural nerve was 38.5±10.5mm and from it to the superficial peroneal nerve was 32.0±7.4mm. Based on the minimum distances, a rectangular area of 25mm×22mm was obtained. The anterior talofibular ligament and the proximal border of the inferior extensor retinaculum were within this area. ConclusionsOur study suggests that based on superficial anatomic landmarks, it is possible to define an anatomic area in order to avoid structures at risk. In addition to the usual precautions, these anatomical references may contribute to lower the complication rate associated to the arthroscopic treatment of lateral ankle instability.

The Nuchal Lines as Anatomic Landmarks to Dissect the Muscles in the Far Lateral Approach.

A critical step in the far lateral approach (FLA) is exposure of the V3 segment of the vertebral artery, located deep in the suboccipital triangle (SOT). Safe exposure of the SOT is achieved by means of a plane-by-plane dissection, which carries the risk of devascularization. A suitable alternative is to lift a cutaneous muscle flap including the 3 first muscle planes and leave the deepest plane (SOT) attached to the skull base. To achieve this, it is necessary to have superficial anatomic landmarks to help identify the cleavage site. We describe the use of the nuchal lines as a safe, effective, and reproducible method to dissect the muscles to expose the SOT and vertebral artery. Eight adult cadaveric heads, fixed with formaldehyde and injected, were studied. On both sides, FLA was simulated by using the nuchal lines as anatomic landmarks to expose the SOT. This technique was later applied on 10 patients requiring FLA. Anatomic dissections confirmed identification, by means of the nuchal lines, of a cleavage site, which made it possible to separate the deepest muscle plane from the rest of the flap. This technique was successfully applied in 10 patients undergoing FLA. The nuchal lines allow dissection of muscles in 2 groups, one superficial and the other deep (SOT), which remains attached to the skull base. The V3 segment of the vertebral artery is easily exposed.

The Relationship of the Posterior Interosseous Nerve to the Supinator Muscle in the Dorsal Approach to the Proximal Radius: A Descriptive and Quantitative Anatomic Study of Filipino Cadavers

Background and Objective. The posterior interosseous nerve (PIN) is vulnerable to injury in the dorsal approach to the proximal radius. The goal of this study is to describe the quantitative relationship of the PIN to the supinator muscle in the context of anatomic landmarks. Knowledge of superficial landmarks related to the PIN would hopefully minimize iatrogenic injury to the posterior interosseous nerve. Methods. 12 cadavers (22 forearms) were dissected and analyzed. The length of the supinator muscle was determined. The oblique distances of the PIN entry and exit points to the proximal and distal borders of the supinator muscle as well as their perpendicular distances to the lateral epicondyle-Lister’s tubercle (LE-LT) reference line were measured and recorded. The number of PIN branches inside the supinator substance was recorded. Mean and median values were determined and subjected to statistical analysis. Results. Mean supinator length was 5 centimeters. Ninety-one percent of the cadaveric forearms had PIN branches inside the supinator muscle substance. Twelve of the 22 forearms (55%) had 2 branches. The mean oblique distances of the PIN from the lateral epicondyle to the entry and exit points in the proximal and distal borders of the supinator muscle was 3.52 and 7.31 centimeters, respectively. The mean perpendicular distances of the PIN from LE-LT reference line to the entry and exit points in the proximal and distal borders of the supinator muscle was 1.13 and 1.26 centimeters, respectively. An imaginary danger-zone 4 centimeters wide overlying the LE-LT reference line depicts the possible area where the PIN and its branches may most likely be located. Conclusion. The dorsal approach to the proximal radius may allow a safe exposure without causing iatrogenic injury to the posterior interosseous nerve through the use of superficial anatomic landmarks and reference lines in combination with mean measurements from our study. Key

Assessment of the potential efficacy of blind perineural injection techniques for blockade of the saphenous, obturator, and lateral cutaneous femoral nerves in dog cadavers.

OBJECTIVE To evaluate the potential efficacy of blind perineural injection techniques to provide nerve blockade of the saphenous, obturator, and lateral cutaneous femoral nerves by assessing the distribution along those nerves of 3 volumes of an injected staining solution in dog cadavers. ANIMALS 18 canine cadavers. PROCEDURES The anatomic characteristics of the target nerves were evaluated by dissection in 3 cadavers. The saphenous nerve was located by the use of superficial anatomic landmarks and a loss-of-resistance test. The obturator and lateral cutaneous femoral nerves were located by the use of superficial anatomic landmarks. Following perineural administration of 3 volumes (0.1, 0.2, and 0.3 mL/kg) of staining solution near the target nerves in 15 cadavers, the distribution of the staining solution along the nerves was evaluated. Staining that extended ≥ 2 cm along the target nerves was considered to be compatible with an effective clinical nerve block. RESULTS In all cadavers, nerves were appropriately stained by the blind techniques used here. The staining distribution along the nerves was considered to be optimal after perineural injection of 0.2 mL of staining solution/kg in the obturator and lateral cutaneous femoral nerves and 0.3 mL of staining solution/kg in the saphenous nerve. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that the evaluated blind perineural injection techniques may be an inexpensive, safe, and clinically effective method to block the saphenous, obturator, and lateral cutaneous femoral nerves in dogs.

Carpal tunnel release: Safe and simple identification of the flexor retinaculum based on superficial anatomical landmarks.

The aim of our study was to project the borders of the flexor retinaculum (FR) onto superficial landmarks since its insufficient splitting is the most common reason for persistence of symptoms after carpal tunnel release. In 60 hands the radial and ulnar styloid processes were linked by a horizontal line and a longitudinal line was laid through the ring finger's radial side. These were intersected resulting in the reference point "A" on the forearm. As the second basing point "B", the radial margin of the ring finger at the palmar digital crease was chosen. Measurement of the FR was carried out with regard to the reference points. The proximal margin of the FR was located at 4% of the reference line A-B starting from point A and extended up to 52% of this total length. Results indicate that splitting alongside the proximal half of line A-B divides the FR completely. Clin. Anat. 30:512-516, 2017. © 2017 Wiley Periodicals, Inc.

External cortical landmarks and measurements for the temporal horn: Anatomic study with application to surgery of the temporal lobe.

Background:The location of the temporal horn is important to neurosurgeons during procedures such as amygdalohippocampectomy and intraventricular electrode placement for temporal lobe seizure monitoring. However, sometimes the temporal horn is difficult to localize, especially without neuronavigation. The authors aimed to better localize this structure using superficial anatomic landmarks.Methods:Twenty-two brain halves were dissected from the midline, and the fornix identified and followed toward the left and right temporal horns. Once the temporal horn was isolated from a mesial approach, 6-cm long needles were placed into its anterior and posterior walls of the temporal horn and passed laterally from the axial plane to the cortical surface. Pin exit sites were marked externally and measurements taken between the outer temporal lobe cortex and the underlying temporal horn.Results:No statistical differences were noted between left and right sides. The temporal horn was generally directed anteroinferiorly and best marked externally by the inferior temporal sulcus. The mean length of the temporal horn was 4.4 cm. Mean distance from anterior temporal tip to anterior wall of the temporal horn was 3.3 cm. The mean distance from the anterior temporal tip to the posterior wall of the temporal horn was 7 cm. The anterior wall of the temporal horn was a mean of 3 mm superior to the inferior temporal sulcus. The posterior wall was a mean of 1.2 cm superior to the inferior temporal sulcus.Conclusions:These landmarks and measurements may help neurosurgeons better localize this part of the lateral ventricular system.

Bony Anatomic Landmarks to Avoid Injury to the Marginal Mandibular Nerve

Marginal mandibular nerve injuries are more likely to be symptomatic than other facial nerve injuries following facelift procedures. The marginal mandibular nerve courses over the facial artery in the region of the mandible. The nerve is most susceptible to injury in this location because it lies superficial to the anterior facial artery. The authors describe the location of the marginal mandibular nerve based on superficial anatomic landmarks as it crosses the facial artery above the mandibular border, in order to help surgeons avoid injury to this nerve during facelift procedures. Eighteen cadaveric facial halves were dissected with the aid of loupe magnification. The distance from the facial artery to the palpable masseteric tuberosity at the angle of the mandible was measured. The distance from the masseteric tuberosity to the mental midline was also measured to determine a ratio of the facial nerve from the masseteric tuberosity to the mental midline. The facial artery was found to be an average of 3.05 ± 0.13 cm anterior to the masseteric tuberosity along the mandible. The marginal mandibular nerve crossed the facial artery along the mandibular border approximately 3 cm anterior to the masseteric tuberosity. The distance from the masseteric tuberosity to the mental midline averaged 11.3 ± 0.54 cm. Therefore, the marginal mandibular nerve courses superficial to the facial artery at approximately one-fourth of the distance from the masseteric tuberosity to the mental midline. Knowledge of the masseteric tuberosity and mental midline landmarks of the facial artery can provide a reliable and safe approach to surgery of the lower face.

Accuracy of Anatomical Landmarks in Locating the Internal Jugular Vein Cannulation Site Among Different Levels of Anesthesia Trainees

Internal jugular vein (IJV) cannulation is a common practice procedure employed by anesthesiologists to access large central veins. The purpose of this study is to examine the accuracy of the use of superficial anatomical landmarks to locate the IJV as well as to delineate differences in accuracy at various levels of anesthesiology trainees, and staff. We prospectively evaluated the accuracy of locating the left and right IJV on the skin surface by anesthesiology residents and board certified anesthesiologists. Twenty-four patients with body mass index (BMI) <30 and 24 morbidly obese patients with BMI > 40 were employed across all groups. Ultrasound imaging of the actual IJV course was utilized as a reference. Experienced operators (Third year residents and faculty) achieved better accuracy in locating the IJV compared to first and second year residents. Higher accuracy was achieved when the carotid pulse was used as a landmark compared to the sternocleidomastoid muscle, particularly for experienced operators in morbidly obese patients. Overall, there was no difference in accuracy between the right and left IJV, although medial deviation was greater on the left side. The accuracy of locating the IJV on the skin surface improved with operator experience in our anesthesiology training program. Experienced operators improved their accuracy using the carotid pulse as the external landmark. Ultrasound may be a useful tool to improve IJV localization early during training, and for cannulation of the left IJV.

Anatomic Guides to Precisely Localize the Zygomatic Branches of the Facial Nerve

Descriptions of superficial anatomic landmarks for the identification of the zygomatic branches of the facial nerve, and their relevance for plastic surgery, are lacking in the literature. This paper provides such a description and discusses its relevance to facial surgery. Sixty-six specimens, including the parotid region, from 33 adult cadavers were dissected and studied. All specimens were fixed in formaldehyde, and the superficial tissues were removed and the zygomatic branches of the facial nerve, the parotid gland, the tragus and the lateral palpebral commissure were identified. The vertical and horizontal relationships were recorded and analyzed. A total of 69.7% of the cadavers had two branches, 25.8% had three branches, and 4.5% had a single zygomatic branch. The mean horizontal distance of the zygomatic branch (the most upper one) as it emerged from the anterior border of the parotid gland and the tragus was 30.71 mm, whereas the mean vertical distance of the zygomatic branch from the midpoint between the tragus and the lateral palpebral commissure was 19.29 mm. The branching patterns with the buccal branches were reported. There were no statistical differences between the left and right sides or between the sexes. The zygomatic branches of the facial nerve were always under the oblique line between the tragus and the lateral palpebral commissure and have a close relationship with the buccal branches of the facial nerve under this anatomic landmark. Application of the results in facial surgery is discussed.

Anatomic landmarks for the cervical portion of the thoracic duct.

Avoidance of injury to the thoracic duct during neurosurgical procedures involving the cervical region depends on a working knowledge of its location. This study evaluates superficial anatomic landmarks for the cervical portion of the thoracic duct that may be encountered in neurosurgery of the neck. Fifteen dissections of human cadavers were performed to study the relationship between the proximal thoracic duct and superficial landmarks (e.g., the cricoid cartilage and sternal notch of the manubrium). The cervical portion of the thoracic duct was found to be approximated by a roughly 4.4-cm(2) region in the left supraclavicular area beginning approximately 2.0 cm lateral to the midline and 3.5 cm superior to the sternal notch, extending superiorly to a point roughly 3.5 cm from the midline and 2.5 cm inferior to the cricoid cartilage, and terminating within the venous system at a point approximately 4.5 cm lateral to the midline and 3.0 cm superior to the sternal notch. Through an increased appreciation for its location, injury to the thoracic duct may be minimized.