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

PURPOSE: Several 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. METHODS: Descriptive 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. RESULTS: One-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. CONCLUSIONS: 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 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 EVIDENCE: IV.

The size, number, and distribution of nerve endings around and within the human epiglottis, focusing on tracheal intubation maneuvers.

The aim of this study was to examine the distribution of nerve endings in the mucosa, submucosa, and cartilage of the epiglottis and the vallecula area and to quantify them. The findings could inform the choice of laryngoscope blades for intubation procedures. Fourteen neck slices from seven unembalmed, cryopreserved human cadavers were analyzed. The slices were stained, and cross and longitudinal sections were obtained from each. The nerve endings and cartilage were identified. The primary metrics recorded were the number, area, and circumference of nerve endings located in the mucosa and submucosa of the pharyngeal and laryngeal sides of the epiglottis, epiglottis cartilage, and epiglottic vallecula zone. The length and thickness of the epiglottis and cartilage were also measured. The elastic cartilage of the epiglottis was primarily continuous; however, it contained several fragments. It was covered with dense collagen fibers and surrounded by adipose cells from the pharyngeal and laryngeal submucosa. Nerve endings were found within the submucosa of pharyngeal and laryngeal epiglottis and epiglottic vallecula. There were significantly more nerve endings on the posterior surface of the epiglottis than on the anterior surface. The epiglottic cartilage was twice the length of the epiglottis. The study demonstrated that the distribution of nerve endings in the epiglottis differed significantly between the posterior and anterior sides; there were considerably more in the former. The findings have implications for tracheal intubation and laryngoscope blade selection and design.

The EFSUMB Guidelines and Recommendations for Musculoskeletal Ultrasound - Part I: Extraarticular Pathologies.

The first part of the guidelines and recommendations for musculoskeletal ultrasound, produced under the auspices of the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB), provides information about the use of musculoskeletal ultrasound for assessing extraarticular structures (muscles, tendons, entheses, ligaments, bones, bursae, fasciae, nerves, skin, subcutaneous tissues, and nails) and their pathologies. Clinical applications, practical points, limitations, and artifacts are described and discussed for every structure. After an extensive literature review, the recommendations have been developed according to the Oxford Centre for Evidence-based Medicine and GRADE criteria and the consensus level was established through a Delphi process. The document is intended to guide clinical users in their daily practice.

The EFSUMB Guidelines and Recommendations for Musculoskeletal Ultrasound - Part II: Joint Pathologies, Pediatric Applications, and Guided Procedures.

The second part of the Guidelines and Recommendations for Musculoskeletal Ultrasound (MSUS), produced under the auspices of EFSUMB, following the same methodology as for Part 1, provides information and recommendations on the use of this imaging modality for joint pathology, pediatric applications, and musculoskeletal ultrasound-guided procedures. Clinical application, practical points, limitations, and artifacts are described and discussed for every joint or procedure. The document is intended to guide clinical users in their daily practice.

Sciatic nerve movement in the deep gluteal space during hip rotations maneuvers.

We hypothesize that the sciatic nerve in the subgluteal space has a specific behavior during internal and external coxofemoral rotation and during isometric contraction of the internal and external rotator muscles of the hip. In 58 healthy volunteers, sciatic nerve behavior was studied by ultrasound during passive internal and external hip rotation movements and during isometric contraction of internal and external rotators. Using MATLAB software, changes in nerve curvature at the beginning and end of each exercise were evaluated for longitudinal catches and axial movement for transverse catches. In the long axis, it was observed that during the passive internal rotation and during the isometric contraction of external rotators, the shape of the curve increased significantly while during the passive external rotation and the isometric contraction of the internal rotators the curvature flattened out. During passive movements in internal rotation, on the short axis, the nerve tended to move laterally and forward, while during external rotation the tendency of the nerve was to move toward a medial and backward position. During the isometric exercises, this displacement was less in the passive movements. Passive movements of hip rotation and isometric contraction of the muscles affect the sciatic nerve in the subgluteal space. Retrotrochanteric pain may be related to both the shear effect of the subgluteus muscles and the endoneural and mechanosensitive aggression to which the sciatic nerve is subjected.

Ultrasound-guided genicular nerves block: an analgesic alternative to local infiltration analgesia for total knee arthroplasty: A noninferiority, matched cohort study.

BACKGROUND: Standard analgesic strategies for total knee arthroplasty employ local infiltration analgesia. Blockade and radiofrequency ablation of the genicular nerves are effective treatments for patients with chronic pain because of knee osteoarthritis. OBJECTIVE: To test the noninferiority of the analgesic effect of genicular nerves block in comparison with local infiltration analgesia after 24 h of total knee arthroplasty. DESIGN: Prospective cohort study. SETTING: Perioperative setting. PATIENTS: Thirty-five patients scheduled for total knee arthroplasty were prospectively included in the study and compared with 35 patients in a retrospective cohort. INTERVENTION: Genicular nerve blocks in the prospective cohort were compared with local infiltration analgesia in the retrospective cohort. MAIN OUTCOME MEASURES: The pain numeric rating scale and the cumulative opioid consumption in oral morphine equivalents during the first 24 h. RESULTS: We conducted propensity score-matched analyses of patients using acute postoperative pain-related risk covariates. After one-to-one propensity score matching, 21 patients were included in the local infiltration analgesia group and 21 in the genicular nerve block group. The median difference in numeric rating score at rest at 24 h was -0.99 [95% confidence interval (CI), -1.99 to 0.5, P = 0.012] on the unmatched cohort and -1.9 (95% CI, -2 to 0, P = 0.002) on the matched cohort (meeting the noninferiority criteria, Δ=1). The median difference in cumulative opioid consumption was 2.5 mg (95% CI, -13.5 to 2.5, P < 0.001) for the unmatched cohort and 4.99 mg (95% CI, -11.5 to 2.5, P < 0.001) on the matched group (meeting the noninferiority criteria, Δ = 21 mg). CONCLUSION: Local infiltration analgesia and genicular nerve block are comparable in terms of analgesic results. Therefore, genicular nerves block is an alternative to local infiltration analgesia in patients undergoing total knee arthroplasty. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT04024319.

Preoperative bedside ultrasound assessment of gastric volume and evaluation of predisposing factors for delayed gastric emptying: a case-control observational study.

Perioperative pulmonary aspiration of gastric content is a serious complication. Fasting guidelines try to ensure an empty stomach before intervention. Certain medications or pathologies may cause delayed gastric emptying. Bedside ultrasonography is a useful tool when gastric content status is unclear or in emergency situations where fasting is not feasible. The aim of this prospective case-control observational study was to assess differences in gastric fluid volume between fasted patients with or without predisposing factors for delayed gastric emptying. Patients were preoperatively scanned. Antral cross-sectional area was measured by two tracing methods and total gastric clear fluid volumes were calculated. Data was recorded from September 2018 to March 2019 in a university hospital setting in Barcelona, Spain. Fifty-three patients were enrolled, 23 with delayed gastric emptying predisposing factors (DGEF) and 30 without non-DGEF. Ultrasound-estimated gastric clear fluid volume was 35.21 ± 32.69 mL in the DGEF versus 53.50 ± 30.72 mL in the non-DGEF group (p = 0.08). Average volume per unit of weight was 0.61 ± 0.46 mL/kg. Only 1 patient in the DGEF group had a volume that posed a higher risk of aspiration (1.57 mL/kg). Perfect correlation (R = 0.91; p < 0.01) and concordance (0.91; 95% CI 0.83; 0.95) was found between tracing methods. Minimal gastric content was observed in scheduled surgery in spite of predisposing factors for delayed gastric emptying. Ultrasound clear gastric volume estimation was useful to assess preoperative bedside gastric content.

"Triceps Brachii Muscle Response to Neurostimulation of the Radial Nerve during Axillary Plexus Blockade: Clinical, Anatomical and Histological Correlation".

Axillary plexus blockade is a common technique in clinical practice with a well-known pattern of structures around the brachial artery. Historically, the only proper response to radial nerve stimulation was considered to be extension of the hand and wrist. Twenty-five axillary blockades were assessed by ultrasound and neurostimulation; the principal objective was to correlate the needle position over the radial nerve with the anatomical and histological structure of that nerve. During the procedure, the needle was directed in two ways to reach the medial or lateral margin of the nerve: above the brachial artery or beneath it. Once the needle reached the nerve, the current was augmented gradually until a response was elicited. For the cadaveric anatomical study, eight axillae were dissected and histological samples were examined. The response of the triceps brachii muscle differed significantly between the two approaches to the radial nerve (P < 0.001), and the mean intensity of stimulation was significantly lower when the nerve was accessed above the artery (0.44 ± 0.15 mA) than below it (0.57 ± 0.17 mA) (P = 0.015). A triceps brachii motor response occurs at lower current intensity and lower needle-nerve distance when the radial nerve is accessed above the artery and over the latissimus dorsi tendon. These findings were correlated with the topography of the radial nerve in the axillary fossa. Clin. Anat. 33:578-584, 2020. © 2019 Wiley Periodicals, Inc.

Another (Internal) Epineurium: Beyond the Anatomical Barriers of Nerves.

The epineurium has been accepted as the outer anatomical barrier of the peripheral nerves. Our objective was to characterize the microanatomy of the layers surrounding nerves using different tissue-specific staining methods. Two hundred forty-two cross sections of human sciatic and median nerves, and brachial plexuses of eight fresh unembalmed cadavers, were examined. The samples were fixed in formaldehyde solution and stained with hematoxylin-eosin, Masson's trichrome, or epithelial membrane antigen under standard conditions. Because epithelial membrane antigen only stains the perineurium, we demonstrated using hematoxylin-eosin and Masson's trichrome that there were different collagen layers inside and outside the nerves. All fascicles had a collagen layer that surrounded the perineurium and were in close contact with it, with no adipose tissue between them. Unlike the perineurium, this layer, an "internal epineurium," contained no cells, and it surrounded one or a small group of fascicles. Bundling these fascicles or small groups of fascicles together was the true epineurium, and between the true and internal epineurium, we consistently found an adipose-containing compartment. More proximal to this, the tibial and common peroneal nerves were bundled together by another collagen layer, the circumneurium, which also had a fat-cell-containing compartment deep to it. There were scattered collagen fibers among the adipocytes. Using tissue-specific staining, we were able to demonstrate a collagen layer, the "internal epineurium." Outside the nerves, we identified several fat-containing concentric compartments. Those compartments were limited by collagen fiber layers that were also similar to the epineurium. Clin. Anat. 33:199-206, 2020. © 2019 Wiley Periodicals, Inc.

Extrafasicular and Intraperineural, but No Endoneural, Spread after Deliberate Intraneural Injections in a Cadaveric Study.

BACKGROUND: There is confusion regarding the spread of intraneurally injected local anesthetic agents during regional anesthesia. The aim of this research was to deliberately inject a marker that does not leave the neural compartment into which it is injected, and then to study the longitudinal and circumferential spread and possible pathways of intraneural spread. METHODS: After institutional review board approval, we intraneurally injected 20 and 5 ml of heparinized blood solution under ultrasound guidance into 12 sciatic nerves in the popliteal fossa and 10 median nerves, respectively, of eight fresh, unembalmed cadavers using standard 22-gauge "D" needles, mimicking the blocks in clinical conditions. Ultrasound evidence of nerve swelling confirmed intraneural injection. Samples of the nerves were then examined under light and scanning electron microscopy. RESULTS: Extrafascicular spread was observed in all the adipocyte-containing neural compartments of the 664 cross-section samples we examined, but intrafascicular spread was seen in only 6 cross-sections of two nerves. None of the epineurium, perineurium, or neural components were disrupted in any of the samples. Spread between the layers of the perineurium was a route of spread that included the perineurium surrounding the fascicles and the perineurium that formed incomplete septa in the fascicles. Similar to the endoneurium proper, subepineural compartments that did not contain any fat cells did not reveal any spread of heparinized blood solution cells. No "perineural" spaces were observed within the endoneurium. We also did not observe any true intrafascicular spread. CONCLUSIONS: After deliberate intraneural injection, longitudinal and circumferential extrafascicular spread occurred in all instances in the neural compartments that contained adipocytes, but not in the relatively solid endoneurium of the fascicles.

Patterns of Distribution of the Nerves Around the Axillary Artery Evaluated by Ultrasound and Assessed by Nerve Stimulation During Axillary Block.

Our objective was to define the positions of the nerves around the brachial artery and, secondarily, to assess the risk of intraneural injection during dual guided axillary block. Sixty ultrasound-guided axillary blocks were performed. The locations of the musculocutaneous, median, ulnar, and radial nerves relative to the brachial artery were determined. The position of the ulnar nerve was defined in relation to that of the brachial vein, and the position of the musculocutaneous nerve in relation to the coracobrachialis muscle. The locations were confirmed by neurostimulation and injection of local anesthetic was avoided when the current intensities were below 0.3 mA. The incidences of intraneural injection and postblock neurological injury were recorded. The median nerve was located in the upper external quadrant in 89% of cases and the ulnar nerve in the upper internal quadrant (95%), superficial (19%), or deep (81%) to the brachial vein. The radial nerve was located in the lower internal quadrant in 97% of cases, and the musculocutaneous nerve in the lower external quadrant in 85%. Its disposition differed depending on its proximity to the artery (106 ± 26°) or whether it was inside the coracobrachialis muscle (119 ± 15°; P = 0.023). Three intraneural injections were observed (0.5%, one in the median and two in the radial nerves) and no patient had postblock neuropathy. Our study evidences slight anatomical variability among the neural structures in the axillary region and confirms the safety of the axillary technique with double monitoring, using ultrasound to monitor the approach of the needle to the nerve and nerve stimulation at currents > 0.3 mA to reduce the incidence of intraneural injection. Clin. Anat., 2018. © 2018 Wiley Periodicals, Inc. 2018.

Functional anatomy of the nerve and optimal placement of the needle for successful (and) safe nerve blocks.

PURPOSE OF REVIEW: Summarize the current thinking concerning the clinically relevant aspects of nerve anatomy and best injection sites for nerve blocks. RECENT FINDINGS: The widespread use of ultrasound in regional anesthesia has changed the practice of regional anesthesia and created new possibilities. Among them is the ability to identify fascial planes, and this has become the basis for a new group of blocks, the fascial plane blocks. In this kind of blocks, the target for injection is the plane itself and not a nerve in particular. transversus abdominis plane, pectoralis muscles, erector spinae plane blocks are some examples of fascial blocks. Because injecting into a fascial plane is not controversial, these blocks are not included in our discussion of optimal placement of the needle.To determine optimal needle placement, it is important to have a clear definition of what constitutes intraneural. Although, there is almost universal agreement that the violation of the epineurium defines the intraneural concept, the literature include several studies where this assessment is erroneous.Although intentional intraneural injection is still considered objectionable, some literature suggests that injecting intraneurally, especially if extrafascicular, may be benign. This evidence is limited and anecdotal. SUMMARY: It is necessary to have a better understanding of what intraneural injection is when dealing with any type of nerve blocks, be that single nerve, plexuses, or the sciatic nerve. Perineural injections provide successful anesthesia without putting the nerve integrity at risk. That practice is supported by years of experience and common sense. Currently, there is no evidence to support any kind of intraneural injections, intrafascicular or extrafascicular.

Gemelli-obturator complex in the deep gluteal space: an anatomic and dynamic study.

OBJECTIVE: To investigate the behavior of the sciatic nerve during hip rotation at subgluteal space. MATERIALS AND METHODS: Sonographic examination (high-resolution ultrasound machine at 5.0-14 MHZ) of the gemelli-obturator internus complex following two approaches: (1) a study on cadavers and (2) a study on healthy volunteers. The cadavers were examined in pronation, pelvis-fixed position by forcing internal and external rotations of the hip with the knee in 90° flexion. Healthy volunteers were examined during passive internal and external hip rotation (prone position; lumbar and pelvic regions fixed). Subjects with a history of major trauma, surgery or pathologies affecting the examined regions were excluded. RESULTS: The analysis included eight hemipelvis from six fresh cadavers and 31 healthy volunteers. The anatomical study revealed the presence of connective tissue attaching the sciatic nerve to the structures of the gemellus-obturator system at deep subgluteal space. The amplitude of the nerve curvature during rotating position was significantly greater than during resting position. During passive internal rotation, the sciatic nerve of both cadavers and healthy volunteers transformed from a straight structure to a curved structure tethered at two points as the tendon of the obturator internus contracted downwards. Conversely, external hip rotation caused the nerve to relax. CONCLUSION: Anatomically, the sciatic nerve is closely related to the gemelli-obturator internus complex. This relationship results in a reproducible dynamic behavior of the sciatic nerve during passive hip rotation, which may contribute to explain the pathological mechanisms of the obturator internal gemellus syndrome.

A novel marker for identifying and studying the membranes, barriers, and compartments surrounding peripheral nerves microscopically.

Recent anatomical discoveries indicate the importance of identifying membranes and compartments surrounding peripheral nerves into which local anesthetic agents can be injected and continuous nerve block catheters placed during regional anesthetic procedures. However, current markers used in anatomical studies have multiple drawbacks, specifically extravasation into noninjected locations, which can result in inadequate treatment. We studied a readily-available new marker, heparinized blood solution (HBS), which is easy to identify by microscopy and can remain in the nerve compartment into which it is deposited without distorting the tissue. We collected blood from 22 patients and prepared it as HBS. This was then injected into four fresh cadavers as in routine clinical practice for ultrasound-guided nerve blocks to form a so-called "doughnut" by "hydro-dissecting" at 32 sites. All samples, including nerves and neighboring tissues, were then prepared and examined by light microscopy. Although no deliberate intraneural injection was attempted, the marker was identified inside all the nerve compartments except the fascicles. Apart from leaking through the needle entry site in some instances, there was no extravasation of the HBS into neighboring nerve compartments in either direction. The tissues were not distorted and the erythrocytes did not form a thrombus. Nerve membranes and compartments could be clearly identified with routine staining. This technique enabled us to study the longitudinal and circumferential spread in all nerve compartments and to collect data for better interpretation of factors influencing an anesthetic nerve block and situations in which complications could possibly arise. HBS seemed superior to other markers because it did not leave the compartments into which it had been injected, did not distort the tissue, and was easily visible under the light microscope. Clin. Anat., 31:1050-1057, 2018. © 2018 Wiley Periodicals, Inc.

Pythagoras and Cosines: The skin-dural sac distance and optimal angles in paramedian spinal anesthesia.

The classical recommendation for paramedian approaches is needle insertion 1-2 cm paramedian and an angle of 10°-15° medial-cephalad to the plane of the back, but contact with vertebrae is frequent. A mathematical approach to individualizing punctures is proposed on the basis of skin-dural sac distance (d): Optimal angle ∼ inverse cosine [d/ √(1+d^2) ] and the distance covered by the needle ∼ √(1+d^2) for 1 cm paramedian punctures. The inferred angles were compared to optimal angles leading to the central dorsal part of the dural sac from 1 to 2 cm paramedian, measured by Magnetic Resonance Imaging (MRI) in seven cases and in a short stature volunteer (1.58 m, Body Mass Index (BMI) 23.2), to study supine and fetal positions using both closed MR and ultrasound. The average (d) decreased rostrally [6.8 cm (L4-L5)-4.3 cm (T11-T12)] while the mean optimal incidence angles increased [8.3°-16.5° (L4-L5) to 12.7°-24.1° (T11-T12) at 1-2 cm paramedian, respectively] and coincided with the estimated angles with a correlation coefficient = 0.98. In the volunteer, the optimal lateromedial angles increased from 14.4° to 26.7° (L3-L4) to 17.1°-30.3° (T11-T12) for a (d) = 3.7 cm (L3-L4)-3.1 cm (T11-T12) and increased ≤3.7° and ≤5.1° at 1 and 2 cm paramedian, respectively, in fetal positions in MR. Ultrasound yielded comparable figures. The range of possible angles for dural punctures is wider at 1 cm paramedian in lower approaches in lateral decubitus [from 3.6° at T12L1 (12.2°-15.8°) to 9° at L3L4 (8.8°-18.7°)]. The classically recommended angles of 10°-15° differ from the optimal angles, particularly in small patients, suggesting the need for ultrasound guidance or for inferring angles prior to spinal anesthesia. Clin. Anat. 29:1046-1052, 2016. © 2016 Wiley Periodicals, Inc.

Permanent upper trunk plexopathy after interscalene brachial plexus block.

Interscalene brachial plexus block (IBPB) has been widely used in shoulder surgical procedures. The incidence of postoperative neural injury has been estimated to be as high as 3 %. We report a long-term neurologic deficit after a nerve stimulator assisted brachial plexus block. A 55 year-old male, with right shoulder impingement syndrome was scheduled for elective surgery. The patient was given an oral dose of 10 mg of diazepam prior to the nerve stimulator assisted brachial plexus block. The patient immediately complained, as soon as the needle was placed in the interscalene area, of a sharp pain in his right arm and he was sedated further. Twenty-four hours later, the patient complained of severe shoulder and arm pain that required an increased dose of analgesics. Severe peri-scapular atrophy developed over the following days. Electromyography studies revealed an upper trunk plexus injury with severe denervation of the supraspinatus, infraspinatus and deltoid muscles together with a moderate denervation of the biceps brachii muscle. Chest X-rays showed a diaphragmatic palsy which was not present post operatively. Pulmonary function tests were also affected. Phrenic nerve paralysis was still present 18 months after the block as was dysfunction of the brachial plexus resulting in an inability to perform flexion, abduction and external rotation of the right shoulder. Severe brachial plexopathy was probably due to a local anesthetic having been administrated through the perineurium and into the nerve fascicles. Severe brachial plexopathy is an uncommon but catastrophic complication of IBPB. We propose a clinical algorithm using ultrasound guidance during nerve blocks as a safer technique of regional anesthesia.

Temporal profile of the effects of regional anesthesia on the cutaneous reflexes of foot muscles.

We analyzed the effects of an anesthetic sciatic nerve block on the cutaneomuscular reflex (cMR) and the cutaneous silent period (cSP) of foot muscles, in order to investigate further the type of fibers involved in their generation. In 14 neurologically normal patients with indication for surgical treatment of hallux valgus, we recorded from the extensor digitorum brevis muscle the reflex responses elicited by high-intensity electrical stimulation of the big toe at various time periods, ranging from 0 to 20 min, after ultrasound-guided sciatic nerve popliteal anesthetic block. The first effect was a delay in cSP onset latency, with no changes in end latency. The cMR remained unaltered up to when subjects were no longer able to maintain the contraction. The effects of local anesthetics on peripheral nerves allow for recognition of the different types of fibers contributing to the cMR and the cSP in muscles of the lower limb.