Continuous Interscalene Brachial Plexus Blocks: An Anatomical Challenge between Scylla and Charybdis?

Brachial plexus blocks at the interscalene level are frequently chosen by physicians and recommended by textbooks for providing regional anesthesia and analgesia to patients scheduled for shoulder surgery. Published data concerning interscalene single-injection or continuous brachial plexus blocks report good analgesic effects. The principle of interscalene catheters is to extend analgesia beyond the duration of the local anesthetic's effect through continuous infusion, as opposed to a single injection. However, in addition to the recognized beneficial effects of interscalene blocks, whether administered as a single injection or through a catheter, there have been reports of consequences ranging from minor side effects to severe, life-threatening complications. Both can be simply explained by direct mispuncture, as well as undesired local anesthetic spread or misplaced catheters. In particular, catheters pose a high risk when advanced or placed uncontrollably, a fact confirmed by reports of fatal outcomes. Secondary catheter dislocations explain side effects or loss of effectiveness that may occur hours or days after the initial correct function has been observed. From an anatomical and physiological perspective, this appears logical: the catheter tip must be placed near the plexus in an anatomically tight and confined space. Thus, the catheter's position may be altered with the movement of the neck or shoulder, e.g., during physiotherapy. The safe use of interscalene catheters is therefore a balance between high analgesia quality and the control of side effects and complications, much like the passage between Scylla and Charybdis. We are convinced that the anatomical basis crucial for the brachial plexus block procedure at the interscalene level is not sufficiently depicted in the common regional anesthesia literature or textbooks. We would like to provide a comprehensive anatomical survey of the lateral neck, with special attention paid to the safe placement of interscalene catheters.

[Ultrasound-guided low-volume continuous cervical sympathetic nerve block for treatment of an electrical storm]. / Ultraschallgestützte kontinuierliche zervikale Sympathikusblockade mit Niedrigvolumina zur Therapie bei anhaltender ventrikulärer Tachykardie.

In addition to the treatment for complex regional pain syndrome (CRPS), the stellate ganglion block is a treatment option for refractory intermittent ventricular tachycardia (VT). Despite the use of imaging techniques, such as fluoroscopy and ultrasound, numerous side effects and complications have been reported. These are a result of the complex anatomical site and the volume of injected local anesthetics. This article reports on the catheter placement for continuous block of the cervical sympathetic trunk with high-resolution ultrasound imaging (HRUI) in a patient with intermittent VT. The tip of the cannula was placed on the anterior aspect of the longus colli muscle and 20 mg prilocaine 1% (2 ml) was injected. The VT stopped and a continuous infusion of 1 ml/h ropivacaine 0,2 % was started. Nevertheless, during the next hour the patient developed hoarseness and dysphagia, so that a block of the recurrent laryngeal nerve and the deep ansa cervicalis (C1-C3) was carried out. The infusion was paused and restarted later with 0.5 ml/h. The spread of the local anesthetic was controlled by ultrasound. Over the next 4 days the patient showed no VT or detectable side effects. After implantation of a defibrillator 1 day later the patient could then be discharged home on the following day. This case shows that the HRUI can be advantageously used in the catheter placement and also when adjusting the flow rate. In this way the risk of complications and side effects related to the puncture and local anesthetic volume can be reduced.

[Ultrasound-guided peripheral venepuncture under poor venous conditions]. / Ultraschallgesteuerte periphere Venenpunktion bei schlechtem Venenstatus.

Placement of a peripheral indwelling venous catheter is a routinely performed invasive procedure, in which complications are often underestimated. In difficult venous conditions multiple puncture attempts are often required, which are time consuming, unnecessarily painful for the patients and nevertheless not always successful. Due to the close anatomical relationship between superficial veins and peripheral nerves in the arm, puncture-related nerve injury is not uncommon. Despite limited data it could be shown that ultrasound-guided peripheral venepunctures are superior to traditional landmark techniques in terms of success rates, time saving, avoidance of complications and patient satisfaction. In order to successfully integrate the sonographic puncture technique for vascular access into routine processes, a structured training and further education are prerequisites. This must include anatomical knowledge, basic knowledge of ultrasound formation and training in sonographic needle guidance techniques.

The relationship between the lateral cutaneous antebrachial nerve and the superficial branch of the radial nerve and its impact on regional anesthetic and pain blocks of the thumb; What is more important: Nerves or dermatomes?

BACKGROUND: Innervation of the thumb and radial part of the dorsum of the hand is achieved primarily by the radial nerve, which is usually blocked for hand surgery. Inefficient blocks occur because the lateral antebrachial cutaneous nerve also extends into this area. The question then arises, whether skin innervation and peripheral blocking techniques should be directed at from the innervation by these nerves or more by the dermatome and its spinal segments. METHODS: In 68 human upper limbs embalmed with Thiel's method, the topography of the lateral antebrachial cutaneous nerve (LACN), the superficial branch of the radial nerve (sbRN) and communicating branch (CB) were investigated by meticulous dissection from the cubital fossa to the most distal macroscopically dissectible branch, and the areas reached by these nerves were compared to the described dermatome. RESULTS: In 52.9% of all specimens, the LACN was found proximal to the rascetta, in 35.3% it extended to the base of the thumb, and in 8 cases (11.8%) it extended distally to the base of the thumb. In 50%, the LACN was anterolateral to the brachioradialis muscle, and in 38.2%, strictly lateral. Only in 8 cases (11.8%) the LACN presented itself running more dorsally and laterally. A CB was observed in 28 specimens (41.2%). Both investigated nerves were found to innervate the dermatomes of C6 and C7. CONCLUSIONS: The LACN should be considered for individual targeted blocks for surgical procedures and pain therapy within the wrist and thumb region as all nerves that might contribute to innervation of a targeted dermatome should be blocked.

Dorsal minimally invasive plate osteosynthesis of the humerus: Feasibility and risk of nervous injury of a modified technique in an anatomical study.

BACKGROUND: The aim of the study was to design a convenient technique for dorsal minimally invasive plate osteosynthesis (MIPO) of extra-articular fractures of both distal thirds of the humeral shaft as well as to characterise the course and proximity of the radial nerve (RN) and the axillary nerve (AN). METHODS: The collective consisted of 20 upper extremities of human adult body donors. A 3.5 mm Locking Compression Plate (LCP), an extra-articular distal humerus plate was inserted through a MIPO approach including two incisions. The primary incision was performed 5 cm in lenght on the dorsal side of the lateral epicondyle. An additional 5 cm incision was conducted distal to the humeral deltoid muscle insertion and the RN was depicted. The longest suitable plate was advanced under nerve protection starting distally and fixed by locking screws. A third incision with a length of 5 cm was made beginning at the distal border of the deltoid muscle, and a muscle split was performed to dissect the AN. The respective plate holes, where the AN and RN were located and the distances between the nerves were examined. RESULTS: The RN was mostly (30%) localised on holes 6 and 7 (starting distally). The AN laid directly on the plate in 65% and on the most proximal plate hole in 12 cases, but was never situated underneath the plate. The distance between the AN and RN was at mean 93.5 mm. CONCLUSIONS: MIPO via a dorsal method proves to be a noteworthy technique and valuable option as indicated by our results. This 5-5-(5) concept may be performed as a two-incision or three-incision technique for extra-articular fractures of both distal thirds of the humerus.

Anatomic-Topographic Investigation of the Branches of the Dorsal Ramus of Thoracic Spinal Nerves.

INTRODUCTION: Percutaneous radiofrequency facet denervation (PRFD) by thermocoagulation is a useful treatment for nonspecific thoracic pain syndrome. To guarantee that maximal thermal lesion is applied to the nerve, it is essential to have precise knowledge of the topography of the thoracic dorsal branches of the spinal nerves. This special anatomy was investigated, and the results were compared with the existing technique for PRFD, where the active needle tip is placed in the junction of the superior articular process and the transverse process. METHODS: Twenty thoracic spines of cadavers (10 females and 10 males) embalmed according to Thiel's method were bilaterally dissected. After careful removal of skin and subcutaneous fat tissue, the lateral and medial branches were traced centrally. In addition, the articular branch to the thoracic facet joint was traced peripherally. The distance of the medial branch to the inferior articular process at the level of the nerve passing the superior costotransverse ligament was measured. RESULTS: The dorsal branch bifurcates into lateral and medial branches medial to the superior costotransverse ligament. The medial branch runs laterally first to pass in between two parts of the intertransverse ligament running dorsally and to turn medially superficial to this ligament. The zygapophysial branch always originated from the medial branch passing the inferior articular process laterally by running caudally to turn medially and send branches to the capsule of the zygapophyseal joint. The distance of the medial branch lateral to the inferior articular process was constantly 3 mm. CONCLUSIONS: The current technique of PRFD at the thoracic spine targets the medial branch distal to the separation of the articular branch, rendering the lesion ineffective at denervating the zygapophyseal joint. For selective thermocoagulation of the articular branches of the thoracic zygapophyseal joint, a new technique should be developed. We propose an anatomically informed needle position that can now be confirmed clinically.

Anatomical Topographical Investigation of the Medial Branch of the Dorsal Thoracic Branch of the Spinal Nerve in the Segments T10-T12.

INTRODUCTION: The zygapophyseal joints represent one possible cause for back pain. Therefore, many interventions are targeting the denervation of the facet joints. The aim of this study is to describe the course of the medial branch of the dorsal branch of the spinal nerve and its articular branches to the zygapophyseal joints in the segments T10-T12. METHODS: The medial branches in the thoracic segments T10-T12 were dissected in 20 Thiel embalmed cadavers. An Eschenbach magnifying glass (4.0× magnification) was used during dissection preserving the articular branches. The topography and the branching pattern of the medial branches was observed. RESULTS: The course of the nerves in the segments T10-T12 differed from each other because of the different osseous anatomy of each segment. The medial branch at the segment T10 crossed the tip of the transverse process in 28 of the 40 hemivertebral specimens. In the remaining cases it passed superior to the transverse process. At T11 the medial branch ran constantly through an osteofibrous canal. At the segment T12 the medial branches showed a similar course to the medial branches in the lumbar region. In many cases two articular branches, which arose from the medial branch were identified. CONCLUSIONS: The results of this study show a considerable anatomic variety at the segment T10. It also demonstrates that the transverse process is an important landmark to encounter the medial branch. Furthermore, the possibility of a double innervation of the facet joints should always be considered.

Anatomy of the brachial plexus and its implications for daily clinical practice: regional anesthesia is applied anatomy.

Safety and effectiveness are mandatory requirements for any technique of regional anesthesia and can only be met by clinicians who appropriately understand all relevant anatomical details. Anatomical texts written for anesthetists may oversimplify the facts, presumably in an effort to reconcile extreme complexity with a need to educate as many users as possible. When it comes to techniques as common as upper-extremity blocks, the need for customized anatomical literature is even greater, particularly because the complex anatomy of the brachial plexus has never been described for anesthetists with a focus placed on regional anesthesia. The authors have undertaken to close this gap by compiling a structured overview that is clinically oriented and tailored to the needs of regional anesthesia. They describe the anatomy of the brachial plexus (ventral rami, trunks, divisions, cords, and nerves) in relation to the topographical regions used for access (interscalene gap, posterior triangle of the neck, infraclavicular fossa, and axillary fossa) and discuss the (interscalene, supraclavicular, infraclavicular, and axillary) block procedures associated with these access regions. They indicate allowances to be made for anatomical variations and the topography of fascial anatomy, give recommendations for ultrasound imaging and needle guidance, and explain the risks of excessive volumes and misdirected spreading of local anesthetics in various anatomical contexts. It is hoped that clinicians will find this article to be a useful reference for decision-making, enabling them to select the most appropriate regional anesthetic technique in any given situation, and to correctly judge the risks involved, whenever they prepare patients for a specific upper-limb surgical procedure.

The posterior femoral cutaneous nerve contributes significantly to sensory innervation of the lower leg: an anatomical investigation.

BACKGROUND: Incomplete peripheral nerve blocks distal to the popliteal region are commonly considered a sciatic and femoral/saphenous nerve block failure. The existence of a much more distal innervation area of the posterior femoral cutaneous nerve (PFCN) as described has not been assumed yet. We therefore investigated the distal termination of the PFCN in the lower leg. METHODS: In 83 human lower extremities embalmed with Theil's method, the course of the PFCN was investigated from the sub-gluteal fold to the most distal macroscopically dissectible branch. The topographic connection to other landmarks, such as the small saphenous vein or small arteries, was investigated. RESULTS: Popliteal ending of the PFCN was found in 9.7% of cases. The PFCN terminated at the proximal or distal lower leg in 45.7% and 44.6% of cases, respectively. The PFCN had a close connection to the Achilles tendon in 13.2% of cases and was found distally to the medial malleolus in one case. The small saphenous vein was close to the PFCN in 90.3% of cases and can therefore be used as a landmark to identify the nerve. In 40.9% of cases, the PFCN was accompanied by a small descending branch of the inferior gluteal artery. In two cases, an innervation of the fibula or calcaneus periosteum was found. CONCLUSIONS: The PFCN has a much more distal termination in the lower leg than previously demonstrated. To ensure complete anaesthesia of the lower leg and foot, the PFCN must be included in combined peripheral nerve block procedures.

Anterior subcutaneous internal fixation of the pelvis - what rod-to-bone distance is anatomically optimal?

INTRODUCTION: Anterior fixation of the pelvis using subcutaneous supra-acetabular pedicle screw internal fixation (INFIX) has proven to be a useful tool by avoiding the downsides of external fixation in patients where open fixation is not suited. The purpose of this study was to find a rod-to-bone distance for the INFIX that allows for minimal hazard to the inguinal neuro-vascular structures and, at the same time, as little as possible interference with the soft tissues of the proximal thigh when the patient is sitting. METHODS: An INFIX was applied to 10 soft-embalmed cadaver pelvises with three different rod-to-bone distances. With each configuration, the relations of the rod to the neuro-vascular and the muscular surroundings were measured in supine and sitting position. RESULTS: Except for the femoral artery, vein and nerve, all investigated anatomical structures of the groin were under compression with a rod-to-bone distance of 1cm. With a rod-to-bone distance of 2cm most of the anatomical structures were safe in supine position, although less than with 3cm. With hip flexion some structures got under compression, especially the lateral femoral cutaneous nerve (LFCN, 80%) and the anterior cutaneous branches of the femoral nerve (ACBFN, 35%). With a rod-to-bone distance of 3cm almost all anatomical structures were safe in supine position, while with hip flexion most superficial structures of the proximal thigh got under compression, especially the LFCN (75%) and the ACBFN (60%). CONCLUSIONS: Aiming for a rod-to-bone distance of 2cm is the safest way with regard to compression of the femoral neuro-vascular bundle and at the same time leads to the least compression of more superficial structures like the LFCN, the ACBFN, or the sartorius and the rectus femoris muscles in sitting position.

The lumbar sympathetic trunk: its visibility and distance to two anatomical landmarks.

OBJECTIVE: The lumbar sympathetic trunk's (LST) distance to two anatomical landmarks, the costal process and medial margin of the psoas muscle, was assessed due to its use as landmarks for lumbar sympathetic blocks: the costal process for fluoroscopic guided techniques and the psoas major for CT- and MRI-guided techniques. Based on the measurements, we evaluate the trunk's visibility in MR and CT images for accurate positioning of the needle. METHODS: A total of 54 cadavers embalmed with Thiel's method were investigated. The LST's distances to the psoas major's medial margin and to the base of the lumbar vertebrae's costal process were measured on the levels L2/3, L3/4 and L4/5. The measurements were compared to MR and CT images of 20 anonymous patients to identify the LST. RESULTS: LST's mean distance to the psoas major was 0.3 mm at L2/3, 3.1 mm at L3/4 and 4.6 mm at L4/5. The mean distance to the costal process was 31 mm at L2/3, 34 mm at L3/4 and 32.6 mm at L4/5. In both MR and CT imaging, a structure could be determined as the LST correlating to the measurements with decreasing possible identification from cephalad to caudad levels. CONCLUSIONS: The costal process is a usable landmark for fluoroscopic guidance and the psoas major for CT- and MRI-guided techniques. The LST is clearly visible in MR and CT images, which gives both techniques a decisive advantage over fluoroscopy concerning the block of the LST due to a visible target.

The cleidoatlanticus muscle: a potential pitfall for the practice of ultrasound guided interscalene brachial plexus block.

INTRODUCTION: Image interpretation during ultrasound guided interscalene nerve blocks might be difficult and misleading due to rare anatomical variations of the sternocleidomastoid muscle. CASE REPORT: During a routine dissection, we found a cleidoatlanticus muscle, which originated lateral to the regular cleidomastoid portion of the sternocleidomastoid muscle. This muscle separated from the sternocleidomastoid muscle at level of the dorsally crossing omohyoid muscle to fuse with the levator scapulae muscle's origin at the transverse process of the atlas. CONCLUSION: As this muscle crosses at a level, where ultrasound guided interscalene blocks are performed, this unusual structure might lead to misinterpretation of the confusing ultrasound image, resulting in misguided needle positioning and consecutive inefficiency of the block technique.

Eye movements in response to electrical stimulation of the lateral and superior ampullary nerves.

OBJECTIVES: Recently, we demonstrated that it was possible to elicit vertical eye movements in response to electrical stimulation of the posterior ampullary nerve. In order to develop a vestibular implant, a second site of stimulation is required to encode the horizontal movements. METHODS: Three patients with disabling Meniere's disease were included in the study. Before a labyrinthectomy via a standard transcanal approach was performed, their lateral and anterior ampullary nerves were surgically exposed under local anesthesia through a procedure we recently developed. The attic was opened, the incus and malleus head were removed, and a small well was drilled above the horizontal portion of the facial nerve canal to place an electrode. This electrode was used to deliver balanced biphasic trains of electrical pulses. RESULTS: The electrical stimuli elicited mainly horizontal nystagmus without simultaneous stimulation of the facial nerve. CONCLUSIONS: It is possible to stimulate electrically the lateral and superior ampullary nerves without simultaneous stimulation of the facial nerve. Because the nerves run close to each other, electrical stimulation provoked eye movements that were not purely horizontal, but also had some vertical components. Nevertheless, this site can be used to encode horizontal movements, because central adaptation may correct unnatural afferent vestibular cues delivered by a prosthetic sensor. The range of stimulus intensities that produced a response was broad enough for us to envision the possibility of encoding eye movements of various speeds.

Superior vestibular neurectomy: a novel transmeatal approach for a denervation of the superior and lateral semicircular canals.

OBJECTIVE: To assess morphologically a transmeatal approach to the lateral and superior ampullary nerves performable under local anesthesia and simultaneously with the existing approach to the singular nerve developed by Gacek during the same operation. MATERIALS AND METHODS: Eighty halves of human heads preserved with the Thiel method were operated on by an otologist. Two surgical approaches were tested on each specimen, 1 superior and 1 inferior to the tympanic segment of the facial nerve. The 80 specimens were divided into 2 groups. In the first group, the osseous canal of the nerves of the lateral and superior semicircular canal were previously probed and next operated. In the second group, the osseous canal of the nerves were operated prior assessment by dissection. Afterward, all 80 halves underwent computed tomographic investigation to measure the distance between the entrance point of the drill in the medial wall of the tympanic cavity and the osseous canal the ampullary nerves. RESULTS: Inferior approach to the canal of the nerves could not be done without wide opening of the vestibulum in all 80 specimens. In the superior approach, the nerve could be reached directly in 5 cases, and only via the osseous ampulla of the lateral semicircular canal in 28 cases in the first group. In 7 cases, the nerves could not be reached without damage to the membranous labyrinth. In the second group, the nerve could be reached directly in 2 cases, via the osseous ampulla in 36 cases, and was unreachable in 2 cases. Significantly, distances longer than 3 mm between the surgical access and the nerve were found on the inaccessible cases. CONCLUSION: A transmeatal approach is possible superiorly but not inferiorly to the facial nerve, although it is necessary to open the osseous ampulla but not the membranous labyrinth in most cases.

Comparison of different injectate volumes for stellate ganglion block: an anatomic and radiologic study.

BACKGROUND: Volumes from 5 to 20 mL of local anesthetic are used for stellate ganglion block. The variation of practice gave us the impetus to investigate the distribution of 3 different volumes of solution. We documented the regions reached by each volume to assess the possibility to reduce the injectate to 5 mL. MATERIALS AND METHOD: A total of 42 cadavers (84 halves), fixed by Thiel's method and on which pulse simulation was performed, were investigated. Of these 84 halves, 28 were injected with 5 mL of contrast (group A), 28 halves with 10 mL (group B), and 28 halves with 20 mL (group C), according to the tissue-displacement method. Immediately after injection, the cadavers were investigated by use of CT scans with a possible 3-dimensional reconstruction. In addition, 4 halves of group A and group B were dissected, and the contrast distribution was determined by photography. RESULTS: Group A showed a constant dissemination from C4 to Th2-Th3, without spreading to ventral or lateral regions. In group B, a persistent spread from C4 to Th3 was documented. Ventral and lateral regions were also reached in one third of the specimens. Group C showed a constant dissemination from C3 to Th4-Th5, with additional spread to ventral, lateral, and posterior regions of the neck similar to that in group B. CONCLUSION: The use of 5 mL results in an almost ideal vertical distribution in most of the cadavers, whereas high volumes--20 mL more so than 10 mL--are at risk of spreading extensively in both the vertical direction and also uncontrollably to other regions of the neck.