Projection of realistic three-dimensional photogrammetry models using stereoscopic display: A technical note.

The 3D stereoscopic technique consists in providing the illusional perception of depth of a given object using two different images mimicking how the right and left eyes capture the object. Both images are slightly different and when overlapped gives a three-dimensional (3D) experience. Considering the limitations for establishing surgical laboratories and dissections courses in some educational institutions, techniques such as stereoscopy and photogrammetry seem to play an important role in neuroanatomy and neurosurgical education. The aim of this study was to describe how to combine and set up realistic models acquired with photogrammetry scans in 3D stereoscopic projections. Three donors, one dry skull, embalmed brain and head, were scanned using photogrammetry. The software used for displaying the final realistic 3D models (Blender, Amsterdam, the Netherlands) is a free software and allows stereoscopic projection without compromising the interactivity of each model. By default, the model was exported and immediately displayed as a red cyan 3D mode. The 3D projector used in the manuscript required a side-by-side 3D mode which was set up with simple commands on the software. The final stereoscopy projection offered depth perception and a visualization in 360° of each donor; this perception was noted especially when visualizing donors with different cavities and fossae. The combination of 3D techniques is of paramount importance for neuroanatomy education. Stereoscopic projections could provide a valuable tool for neuroanatomy instruction directed at clinical trainees and could be especially useful when access to laboratory-based learning is limited.

Superficial versus deep parasternal intercostal plane blocks: cadaveric evaluation of injectate spread.

BACKGROUND: Deep and superficial parasternal intercostal plane blocks provide anterior chest wall analgesia for both breast and cardiac surgery. Our primary objective of this cadaveric study was to describe the parasternal spread of deep and superficial parasternal intercostal plane blocks. Our secondary objectives were to describe needle proximity to the internal mammary artery when performing deep parasternal intercostal plane blocks, and compare lateral injectate spread and extension into the rectus sheath. METHODS: We performed ultrasound-guided deep and superficial parasternal intercostal plane blocks 2 cm from the sternum at the T3-4 interspace in four fresh frozen cadavers as described in clinical studies. RESULTS: Parasternal spread of injectate was greater with the deep parasternal intercostal plane injection than with the superficial parasternal intercostal plane injection. The internal mammary artery was ∼3 mm away from the needle trajectory in cadaver #1 and ∼5 mm from the internal mammary artery in cadaver #2. Lateral spread extended to the midclavicular line for all deep parasternal intercostal plane blocks and beyond the midclavicular line for all superficial parasternal intercostal plane blocks. Neither block extended to the rectus sheath. CONCLUSIONS: A greater number of parasternal interspaces were covered with the deep parasternal intercostal plane block than with the superficial parasternal intercostal plane block when one injection was performed at the T3-4 interspace. However, considering proximity to the internal mammary artery, and potential devastating consequences of an arterial injury, we propose that the deep parasternal intercostal plane block be classified as an advanced block and that future studies focus on optimising superficial parasternal intercostal plane parasternal spread.

Anatomy of the Ventricular Outflow Tracts: An Electrophysiology Perspective.

Outflow tract ventricular arrhythmias are the most common type of idiopathic ventricular arrhythmia. A systematic understanding of the outflow tract anatomy improves procedural efficacy and enables electrophysiologists to anticipate and prevent complications. This review emphasizes the three-dimensional spatial relationships between the ventricular outflow tracts using seven anatomical principles. In turn, each principle is elaborated on from a clinical perspective relevant for the practicing electrophysiologist. The developmental anatomy of the outflow tracts is also discussed and reinforced with a clinical case.

Detailed anatomical study of the peripheral motor branches of the facial nerve in the swine model: A novel investigative approach for facial paralysis research.

INTRODUCTION: Large animal models aid in innovating surgical approaches and developing medical devices for the treatment of facial paralysis. However, there is a lack of information on facial nerve anatomy in swine. This study aimed to investigate the branching pattern and histologic characteristics of the swine facial nerve, thereby establishing the anatomical patterns of preclinical models in facial paralysis research. MATERIAL AND METHODS: The five peripheral motor branches of the facial nerve were dissected in 30 hemifaces of fresh swine cadavers. Starting at the stylomastoid foramen, the course, branching pattern, and diameter of each motor branch was recorded. Samples were taken at the start of each branch for epoxy embedding, toluidine blue staining, and histomorphologic analysis. RESULTS: The dissections demonstrated consistent anatomy of the buccal and marginal mandibular branches in contrast to the temporal and zygomatic branches, which showed more variation in branching patterns. The buccal branch had the largest mean diameter of 1.34 mm (± 0.26 mm), whereas the marginal mandibular branch had the largest fascicular area of 0.558 mm2 (± 0.12 mm2) and highest axon count of 3636.35 (± 526.36). The zygomatic branch had both the smallest diameter of 0.74 mm (± 0.25 mm) and fascicular area of 0.187 mm2 (± 0.14 mm2). CONCLUSIONS: The swine facial nerve is anatomically similar to the human facial nerve, making the pig a suitable large animal model. Detailed anatomical and histological information is crucial for developing preclinical models of novel facial nerve reconstruction approaches.

Change in Rheologic Properties of Facial Soft-Tissue Fillers across the Physiologic Angular Frequency Spectrum.

BACKGROUND: The number of soft-tissue filler injections performed in the United States is constantly increasing and reflects the high demand for enhanced facial and body attractiveness. The objective of the present study was to measure the viscoelastic properties of soft-tissue fillers when subjected to different testing frequencies. The range of tested frequencies represents clinically different facial areas with more [lips (high frequency)] or less [zygomatic arch (low frequency)] soft-tissue movement. METHODS: A total of 35 randomly selected hyaluronic acid-based dermal filler products were tested in an independent laboratory for their values of G', G″, tan δ, and G* at angular frequencies between 0.1 and 100 radian/second. RESULTS: The results of the objective analyses revealed that the viscoelastic properties of all tested products changed between 0.1 and 100 radian/second angular frequency. Changes in G' ranged from 48.5 to 3116 percent, representing an increase in their initial elastic modulus, whereas changes in G″ ranged from -53.3 percent (i.e., decrease in G″) to 7741 percent (i.e., increase in G″), indicating both an increase and a decrease in their fluidity, respectively. CONCLUSIONS: The increase in G' would indicate the transition from a "softer" to a "harder" filler, and the observed decrease in G″ would indicate an increase in the filler's "fluidity." Changes in the frequency of applied shear forces such as those occurring in the medial versus the lateral face will influence the aesthetic outcome of soft-tissue filler injections.

Segment-Specific Orientation of the Dorsal and Ventral Roots for Precise Therapeutic Targeting of Human Spinal Cord.

OBJECTIVE: To provide precise description of the dorsal and ventral roots orientation along with the main spinal cord anatomical measurements and their segment-specific variations. PATIENTS AND METHODS: We collected and analyzed the measurements of the spines, spinal cords, and dorsal and ventral roots (C2-L5) of nine adult cadavers (five males and four females). RESULTS: This study for the first time provides analysis of the dorsal and ventral roots orientation along with spinal cord anatomical measurements and their segment-specific distribution. The results of this study showed less variability in rostral root angles compared with the caudal. Dorsal and ventral rootlets were oriented mostly perpendicular to the spinal cord at the cervical level and had more parallel orientation to the spinal cord at the thoracic and lumbar segments. The number of rootlets per root was greatest at dorsal cervical and lumbar segments. Spinal cord transverse diameter and width of the dorsal columns were largest at cervical segments. The strongest correlation between the spinal cord and vertebrae structures was found between the length of intervertebral foramen to rostral rootlet distance and vertebral bone length. CONCLUSION: These results demonstrate consistent variation in spinal cord anatomical features across all tested subjects. The results of this study can be used to locate spinal roots and main spinal cord landmarks based on bone marks on computed tomography or X-rays. These results could improve stereotactic surgical procedures and electrode positioning for neuromodulation procedures.

The Change of Plane of the Supratrochlear and Supraorbital Arteries in the Forehead-An Ultrasound-Based Investigation.

BACKGROUND: Injecting soft tissue fillers into the deep plane of the forehead carries the risk of injection-related visual compromise due to the specific course of the arterial vasculature. OBJECTIVES: The aim of this study was to investigate the 2- and 3-dimensional location of the change of plane of the deep branch of the supratrochlear and supraorbital artery, respectively. METHODS: A total of 50 patients (11 males and 39 females; mean age, 49.76 [13.8] years, mean body mass index, 22.53 [2.6] kg/m2) were investigated with ultrasound imaging. The total thickness and the distance of the arteries from the skin and bone surface were measured with an 18-MHz broadband compact linear array transducer. RESULTS: The deep branch of the supraorbital artery changed plane from deep to superficial to the frontalis muscle at a mean distance of 13 mm (range, 7.0-19.0 mm) in males and at 14 mm (range, 4.0-24.0 mm) in females and for the deep branch of the supratrochlear artery at a mean distance of 14 mm in males and females (range, 10.0-19.0 in males, 4.0-27.0 in females) when measured from the superior orbital rim. CONCLUSIONS: Based on the ultrasound findings in this study, it seems that the supraperiosteal plane of the upper and lower forehead could be targeted during soft tissue filler injections because the deep branches of both the supraorbital and supratrochlear arteries do not travel within this plane. The superficial plane of the lower forehead, however, should be avoided due to the unpredictability and inconsistent presence of the central and paracentral arteries.

Team-Based Ultrasound Objective Structured Practice Examination (OSPE) in the Anatomy Course.

The clinical use of ultrasound has dramatically increased, necessitating early ultrasound education and the development of new tools in ultrasound training and assessment. The goal of this study was to devise a novel low-resource examination that tested the anatomical knowledge and technical skill of early undergraduate medical students in a gross anatomy course. The team-based ultrasound objective structured practice examination (OSPE) was created as a method for assessing practical ultrasound competencies, anatomical knowledge, and non-technical skills such as teamwork and professionalism. The examination utilized a rotation of students through four team roles as they scanned different areas of the body. This station-based examination required four models and four instructors, and tested ultrasound skills in the heart, abdominal vessels, abdominal organs, and neck regions. A Likert scale survey assessed student attitudes toward the examination. Survey data from participants (n = 46) were examined along with OSPE examination grades (n = 52). Mean and standard deviations were calculated for examination items and survey responses. Student grades were high in both technical (96.5%). and professional (96.5%) competencies with structure identification scoring the lowest (93.8%). There were no statistical differences between performances in each of the body regions being scanned. The survey showed that students deemed the examination to be fair and effective. In addition, students agreed that the examination motivated them to practice ultrasound. The team-based OSPE was found to be an efficient and student-favored method for evaluating integrated ultrasound competencies, anatomical knowledge, team-work, and professional attributes.

Ultrasound-Guided Fasciotomies of the Deep and Superficial Posterior Leg Compartments for Chronic Exertional Compartment Syndrome: A Cadaveric Investigation.

BACKGROUND: Chronic exertional compartment syndrome (CECS) is a type of leg pain related to elevated intracompartmental pressure with activity in one or more of the four compartments of the leg. Open fasciotomy is the definitive treatment for CECS but has a reported complication rate of up to 15.7% and return to full activity reported up to 16 weeks. Ultrasound-guided (USG) fasciotomy of the anterior and lateral compartments has been translated into clinical practice. OBJECTIVE: To determine the safety and feasibility of a USG fasciotomy of the deep posterior compartment (DPC) and superficial compartment (SPC) of the leg in a fresh-frozen cadaveric model. DESIGN: Prospective, cadaveric laboratory investigation. SETTING: Procedural skills laboratory at an academic institution. CADAVERIC COHORT: Ten fresh-frozen cadaveric knee-ankle-foot specimens from five female and five male donors aged 58 to 93 years (mean 77.4 years) with body mass indexes of 18.1 to 33.5 kg/m2 (mean 25.1 kg/m2 ). METHODS OR INTERVENTIONS: One experienced operator performed 10 USG DPC and SPC fasciotomies. A clinical anatomist performed dissections of each. MAIN OUTCOME MEASURES: Achievement of target length and continuity of release was recorded. Target lengths of 10 cm for the superficial posterior compartment (SPC) and 15 cm for the deep posterior compartment (DPC) were established based on previous studies. Tendinous and neurovascular structures were assessed for damage. RESULTS: No tendon or neurovascular injuries were observed. In the SPC, target length was achieved in 90% and continuous release was observed in 80%. In the DPC, target length was achieved in 60% and continuity observed in 30%. CONCLUSIONS: These findings suggest that SPC USG fasciotomies using the technique described in this study are feasible, may be safe, and warrant further translational research; however, DPC USG fasciotomies are more challenging and require more technical refinement prior to clinical translation.

Myocardial bridges: A meta-analysis.

Myocardial bridges are anatomical entities characterized by myocardium covering segments of coronary arteries. In some patients, the presence of a myocardial bridge is benign and is only incidentally found on autopsy. In other patients, however, myocardial bridges can lead to compression of the coronary artery during systolic contraction and delayed diastolic relaxation, resulting in myocardial ischemia. This ischemia in turn can lead to myocardial infarction, ventricular arrhythmias and sudden cardiac death. Myocardial bridges have also been linked to an increased incidence of atherosclerosis, which has been attributed to increased shear stress and the presence of vasoactive factors. Other studies however, demonstrated the protective roles of myocardial bridges. In this study, using systematic review and a meta-analytical approach we investigate the prevalence and morphology of myocardial bridges in both clinical imaging and cadaveric dissections. We also discuss the pathophysiology, clinical significance, and management of these anatomical entities.

The Course of the Angular Artery in the Midface: Implications for Surgical and Minimally Invasive Procedures.

BACKGROUND: Previous anatomic studies have provided valuable information on the 2-dimensional course of the angular segment of the facial artery in the midface and its arterial connections. The third dimension (ie, the depth of the artery) is less well characterized. OBJECTIVES: The objective of the present study was to describe the 3-dimensional pathway of the angular segment of the facial artery and its relationship to the muscles of facial expression. METHODS: The bilateral location and the depth of the midfacial segment of the facial artery was measured utilizing multi-planar computed tomographic image analyses obtained from contrast agent-enhanced cranial computed tomographic scans of 156 Caucasians aged a of 45.19 ± 18.7 years and with a mean body mass index of 25.05 ± 4.9 kg/m2. RESULTS: At the nasal ala, the mean depth of the main arterial trunk was 13.7 ± 3.7 mm (range, 2.7-25.0 mm), whereas at the medial canthus it was 1.02 ± 0.62 mm (range, 1.0-3.0 mm). This was reflected by the arteries' relationship to the midfacial muscles: at the nasal ala superficial to levator anguli oris in 62.0% but deep to the levator labii superioris alaeque nasi in 53.6%; at the medial canthus superficial to the levator labii superioris alaeque nasi in 83.1% and superficial to the orbicularis oculi in 82.7%. CONCLUSIONS: The results presented herein confirm the high variability in the course of the angular segment of the facial artery. Various arterial pathways have been identified providing evidence that, in the midface, there is no guaranteed safe location for minimally invasive procedures.

Revisit, Reform, and Redesign: A Novel Dissection Approach for Demonstrating Anatomy of the Orbit for Continuing Professional Development Education.

Advanced postgraduate medical education for health-care professionals is constantly evolving. Understanding facial anatomy and especially its vascular system is crucial when performing soft tissue filler injections to avoid adverse events including tissue loss or irreversible blindness. Standard anatomical resources often fall short of elucidating clinically relevant concepts in more highly specialized areas of interest. A novel dissection approach for demonstrating the anatomy of the lateral orbit was presented at scientific meetings to participants from dermatology, plastic surgery, and general practice. Results from the post-course online survey (n = 52) were analyzed. The results of the survey reveal a high educational impact and a high clinical relevance of the novel dissection approach. In addition, the majority of respondents (97.7%; n = 51) felt that the exposed anatomical structure of the orbit and face improved their ability to safely perform cosmetic procedures on the face. More experienced respondents who had previously attended at least five cadaveric dissections were more likely to strongly agree that reviewing anatomy through this novel dissection approach increased their confidence in avoiding periorbital vascular danger zones. As minimally invasive outpatient procedures continue to evolve, practicing physicians and mid-level providers often face the challenge of having to reconcile preexisting anatomical knowledge with new clinical practice. Skills required to navigate high impact anatomy include visualization of structures that form the navigational landscape and avoidance of key danger zones. The novel dissection approach to the lateral orbit reflects the increasing focus on revisiting, reforming, and redesigning anatomy for continuing professional development activities.

A Cadaveric Anatomical and Histological Study of Recipient Intercostal Nerve Selection for Sensory Reinnervation in Autologous Breast Reconstruction.

BACKGROUND: Autologous breast reconstruction (ABR) has grown in popularity due to improved aesthetic and long-term patient reported outcomes, but data regarding sensory reinnervation of autologous flaps remain limited. Traditionally, the lateral cutaneous branch of the fourth intercostal nerve has been used for flap neurotization, but the use of the anterior cutaneous branch of the intercostal nerves (ACB) offer a more optimal location to the microsurgical field when using internal mammary vessels for the microanastomosis. This study aimed to evaluate the optimum ACB recipient site level for sensory nerve coaptation in ABR. METHODS: Twelve hemi-chests were dissected from six fresh cadaveric females. Costal cartilages were removed and the anterior cutaneous intercostal nerve (ACB) and the lateral (subcutaneous) division of the anterior cutaneous branch (LACB) of the intercostal nerve were exposed. Anatomical measurements were recorded, and nerve samples were evaluated histologically with carbonic anhydrase staining to differentiate sensory fascicles. Assessment of fascicular diameter, axonal counts, and fascicular area were compared. RESULTS: A total of 75 nerve specimens were assessed. The ACB was identified at all levels (100%) and the subcutaneous LACB was noted consistently in the second to fourth rib space (96% cadavers), with a median length of 43, 37.5, and 37 mm, respectively. Across all rib spaces, the fascicular and axonal counts were comparable between the LACB and ACB. Nerves in the second intercostal space had a significantly larger mean fascicular area mean (112,816 ± 157,120 µm2) compared with that in the fourth (mean 26,474 ± 38,626 µm2), p = 0.03. Axonal count of sensory fascicles was the highest in the second intercostal nerves (p < 0.05). CONCLUSION: This study provides anatomical and histological basis to determine the optimum recipient site choice for sensory coaptation in microsurgical breast reconstruction. This would aid in operative decision-making regarding the ideal recipient anterior cutaneous intercostal nerve branches for recipient site coaptation in ABR.

Ultrasound-Guided Iliopsoas Tendon Release: A Cadaveric Investigation.

BACKGROUND: The iliopsoas is a common source of anterior hip pain. Refractory cases may require surgical intervention, with reported complication rates ranging from 3% to 50%. Development of a minimally invasive, outpatient method of iliopsoas tendon release is desirable and may reduce costs, lower complications, and improve recovery time. OBJECTIVE: To describe and evaluate the safety and reproducibility of an ultrasound-guided (USG) iliopsoas tendon release using a spinal needle in a cadaveric model. DESIGN: Prospective, cadaveric laboratory investigation. SETTING: Academic Institution Procedural Skills Laboratory. PARTICIPANTS: Five unembalmed cadaveric specimens (three female, two male), 69 to 93 years of age (mean 83.2 years), with a mean body mass index (BMI) of 24.5 kg/m2 (range 19.2 to 30.3 kg/m2 ). INTERVENTIONS: Two operators each performed five USG iliopsoas tendon releases. Three additional investigators dissected the pelves to assess completeness of tendon release and damage to adjacent structures. MAIN OUTCOME MEASURES: Successful transection, completeness (%) of the tendon transection, damage to adjacent structures, and procedural time. RESULTS: Nine of 10 releases achieved the target release of ≥75% tendon transection. One procedure achieved 50% tendon release. No injury to adjacent structures was identified. The mean duration of the procedure was 6.19 minutes. CONCLUSIONS: USG iliopsoas tendon release can be performed in a cadaveric model, consistently achieve the desired percentage of tendon release, does not result in injury to adjacent neurovascular structures, and takes approximately 6 minutes to perform. Although results cannot be generalized to a clinical setting, due to the minimally invasive nature of the procedure, it is likely that this procedure can be performed safely in an outpatient setting under local anesthesia, will cost less, and will facilitate a more rapid recovery when compared to standard surgical procedures. Further research is warranted for clinical application.

Motivating Self-Efficacy in Diverse Biomedical Science Post-baccalaureate and Graduate Students Through Scientific Conference Implementation.

Tactics to increase the number of underrepresented (UR) students in biomedical research PhD training programs have not yet translated to UR faculty numbers that reflect the diversity of the United States. Continued interventions are required to build skills beyond those that result in placement into a PhD program. We hypothesize that successful interventions must build skills that give UR students foundations for confident self-efficacy in leadership. We seek interventions that allow UR students to envision themselves as successful faculty. We posit that development of such skills is difficult in the classroom or laboratory alone. Therefore, novel interventions are required. As part of the NIH-funded Post-baccalaureate Research Education Program (PREP) and Initiative for Maximizing Student Development (IMSD) at the Mayo Clinic Graduate School of Biomedical Sciences, we designed and implemented a unique intervention to support development of student leadership skills: a biannual student-organized and student-led national research conference titled "Scientific Innovation Through Diverse Perspectives" (SITDP). This initiative is based on the concept that students who actively live out realistic roles as scientific leaders will be encouraged to persist to scientific leadership as faculty. Here we describe the motivation for, design of, and outcomes from, the first three pilot conferences of this series. We further discuss approaches needed to rigorously evaluate the effectiveness of such interventions in the future.

The Influence of the Insertion Angle on Middle and Lower Face Tissue-Mechanics When Treating the Nasolabial Folds with Facial Suspension Threads-An Experimental Split-Face Cadaveric Study.

A novel treatment approach to address the nasolabial fold is the insertion facial suspension threads. However, there is a paucity of data available to guide insertion techniques and material selection. Three female and two male cephalic specimens of Caucasian ethnicity (73.6 ± 6.5 years; 21.41 ± 2.2 kg/m2) were included into this experimental split-face study. One facial side was treated with polycaprolactone (PCL) thread: 180 mm, bidirectional, 18G 100 mm cannula, 20 degrees trajectory, preauricular approach whereas the contralateral side was treated with polydioxanone (PDO) thread: 100 mm, bidirectional, 19G, 60 mm cannula, 50 degrees trajectory, infraorbital approach. Three-dimensional imaging outcome measures included vertical and horizontal skin displacement and volume changes at the nasolabial sulcus, at the labiomandibular sulcus, and along the jawline. Comparing PCL 180 mm 20 degrees to PDO 100 mm 50 degrees: vertical lifting effect 1.42 ± 2.63 mm versus 1.24 ± 1.88 mm (p = 0.906); horizontal lifting effect 3.42 ± 1.44 mm versus -2.02 ± 1.84 mm (p = 0.001); nasolabial volume change -0.80 ± 0.65 mL versus -0.52 ± 0.17 mL (p = 0.367); labiomandibular volume change -0.45 ± 0.42 mL versus -0.16 ± 0.16 mL (p = 0.191); jawline volume change 0.02 ± 0.43 mL versus -0.01 ± 0.21 mL (p = 0.892). The study provides objective evidence for the short-term effectiveness of facial suspension threads in treating the nasolabial folds. The results point toward a better aesthetic outcome when utilizing long facial suspension threads that can effect full-face changes as compared with short facial suspension threads.

Anatomy of the Dorsum of the Foot and Its Relevance for Nonsurgical Cosmetic Procedures.

BACKGROUND: Operative procedures to enhance the aesthetic appearance of the feet are associated with risks. Minimally invasive procedures to volumize the dorsum of the foot are to this point not described. The present study investigates the safety and efficacy of such procedures in a retrospective clinical, anatomical, and ultrasound-based study. METHODS: A total of 106 feet from 53 female patients (mean age, 64.1 ± 8.3 years) were investigated retrospectively after the injection of a commercially available calcium hydroxylapatite product using a single-entry proximal-to-distal fanning injection technique. Anatomical dissections in 20 fresh, nonembalmed feet from 10 human body donors (mean age, 83.1 ± 8.8 years) were dissected, and 20 feet from 10 healthy volunteers (mean age, 26.5 ± 6.2 years) were examined by ultrasound imaging to help guide conclusions. RESULTS: Aesthetic outcome after 3 months was graded by the patients as 4, connoting good improvement (range, 3 to 5). No allergic reactions or other types of adverse events were documented. The layered anatomy of the dorsum of the foot was confirmed by anatomical dissections and ultrasound imaging as follows: skin, dorsal superficial fatty layer, dorsal superficial fascia, dorsal intermediate fatty layer, superficial lamina of the dorsal deep fascia, dorsal deep fatty layer, and deep lamina of the dorsal deep fascia. CONCLUSIONS: Minimally invasive injections of soft-tissue filler in the dorsum of the foot can provide an alternate solution to enhance the aesthetic appearance of feet. The present study provides support for the safety and efficacy of volumizing procedures using a 22-gauge, 50-mm, blunt-tip cannula. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.