Optimal techniques of ultrasound-guided superficial and deep parasternal intercostal plane blocks: a cadaveric study.

INTRODUCTION: The optimal techniques of a parasternal intercostal plane (PIP) block to cover the T2-T6 intercostal nerves have not been elucidated. This pilot cadaveric study aims to determine the optimal injection techniques that achieve a consistent dye spread over the second to sixth intercostal spaces after both ultrasound-guided superficial and deep PIP blocks. We also investigated the presence of the transversus thoracis muscle at the first to sixth intercostal spaces and its sonographic identification agreement, as well as the location of the internal thoracic artery in relation to the lateral border of the sternum. METHODS: Ultrasound-guided superficial or deep PIP blocks with single, double, or triple injections were applied in 24 hemithoraces (three hemithoraces per technique). A total volume of dye for all techniques was 20 mL. On dissection, dye distribution over the first to sixth intercostal spaces, the presence of the transversus thoracis muscle at each intercostal space and the distance of the internal thoracic artery from the lateral sternal border were recorded. RESULTS: The transversus thoracis muscles were consistently found at the second to sixth intercostal spaces, and the agreement between sonographic identification and the presence of the transversus thoracis muscles was >80% at the second to fifth intercostal spaces. The internal thoracic artery is located medial to the halfway between the sternal border and costochondral junction along the second to sixth intercostal spaces. Dye spread following the superficial PIP block was more localized than the deep PIP block. For both approaches, the more numbers of injections rendered a wider dye distribution. The numbers of stained intercostal spaces after superficial block at the second, fourth, and fifth intercostal spaces, and deep block at the third and fifth intercostal spaces were 5.3±1.2 and 5.7±0.6 levels, respectively. CONCLUSION: Triple injections at the second, fourth, and fifth intercostal spaces for the superficial approach and double injections at the third and fifth intercostal spaces for the deep approach were optimal techniques of the PIP blocks.

Cadaveric study investigating the femoral nerve-sparing volume for pericapsular nerve group (PENG) block.

BACKGROUND: This cadaveric study investigated the maximum effective volume of dye in 90% of cases (MEV90) required to stain the iliac bone between the anterior inferior iliac spine (AIIS) and the iliopubic eminence (IPE) while sparing the femoral nerve during the performance of pericapsular nerve group (PENG) block. METHODS: In cadaveric hemipelvis specimens, the ultrasound transducer was placed in a transverse orientation, medial and caudal to the anterior superior iliac spine in order to identify the AIIS, the IPE and the psoas tendon. Using an in-plane technique and a lateral-to-medial direction, the block needle was advanced until its tip contacted the iliac bone. The dye (0.1% methylene blue) was injected between the periosteum and psoas tendon. Successful femoral-sparing PENG block was defined as the non-staining of the femoral nerve on dissection. Volume assignment was carried out using a biased coin design, whereby the volume of dye administered to each cadaveric specimen depended on the response of the previous one. In case of failure (ie, stained femoral nerve), the next one received a lower volume (defined as the previous volume with a decrement of 2 mL). If the previous cadaveric specimen had a successful block (ie, non-stained femoral nerve), the next one was randomized to a higher volume (defined as the previous volume with an increment of 2 mL), with a probability of b=1/9, or the same volume, with a probability of 1-b=8/9. RESULTS: A total of 32 cadavers (54 cadaveric hemipelvis specimens) were included in the study. Using isotonic regression and bootstrap CI, the MEV90 for femoral-sparing PENG block was estimated to be 13.2 mL (95% CI: 12.0 to 20.0). The probability of a successful response was estimated to be 0.93 (95% CI: 0.81 to 1.00). CONCLUSION: For PENG block, the MEV90 of methylene blue required to spare the femoral nerve in a cadaveric model is 13.2 mL. Further studies are required to correlate this finding with the MEV90 of local anesthetic in live subjects.

The effect of the minimum effective volume for suprainguinal fascia iliaca block in fresh cadavers / El efecto del volumen efectivo mínimo para el bloqueo de la fascia ilíaca suprainguinal en cadáveres frescos

SUMMARY: The goal of ultrasound-guided suprainguinal fascia iliaca block (USG-SFIB) is anesthetic spread to three nerves, which are lateral femoral cutaneous nerve (LFCN), femoral nerve (FN), and obturator nerve (ON). The 90 % minimum effective volume (MEV90) for USG-SFIB is each result of studied showed the successful block and effect in various volume for block. So, Thus, the study purposes to demonstrate the efficiency of the effective volume (MEV90,62.5 ml) for USG-SFIB and confirm the staining of dye in connective tissue of nerve (nerve layer) that focused on the obturator nerve by histological examination in cadavers. The histological result showed the dye staining on the nerve layer of the ON in epineurium (100 %) and un-staining perineurium & endoneurium. Therefore, the minimal effective volume (MEV) is effective for USG-SFIB. Moreover, dye stain at the epineurium of stained obturator nerve only.

RESUMEN: El objetivo del bloqueo de la fascia ilíaca suprainguinal guiado por ecografía (USG-SFIB) es la propagación anestésica a tres nervios, cutáneo femoral lateral, femoral y obturador. El volumen efectivo mínimo del 90 % (MEV90) para USG-SFIB en cada uno de los resultados mostró el bloqueo exitoso y el efecto en varios volúmenes por bloqueo. Por lo tanto, el estudio tuvo como objetivo demostrar la eficiencia del volumen efectivo (MEV90,62.5 ml) para USG-SFIB y confirmar la tinción de tinte en el tejido conectivo del nervio, el cual se centró en el nervio obturador a través del examen histológico en cadáveres. El resultado histológico mostró tinción de colorante en el epineuro (100 %) del nervio obturador, sin embargo no hubo tinción del perineuro y endoneuro. Por lo tanto, el volumen efectivo mínimo (MEV) es efectivo para USG-SFIB.

Distribution of various volumes of methylene blue injection in suprainguinal fascia iliaca block under ultrasound guidance: a cadaveric study / Distribución de varios volúmenes de inyección de azul de metileno en el bloque suprainguinal de la fascia ilíaca bajo guía por ultrasonido: un estudio cadavérico

SUMMARY: The local anesthetic volume for a single-shot suprainguinal fascia iliaca block (SFIB) is a key factor of a block success because the courses of the three target nerves from the lumbar plexus (LP), the lateral femoral cutaneous nerve (LFCN), femoral nerve (FN), and obturator nerve (ON), at the inguinal area are isolated and within striking distance. Thus, this cadaveric study aims to demonstrate the distribution of dye staining on the LFCN, FN, ON, and LP following the ultrasound-guided SFIB using 15-50 ml of methylene blue. A total of 40 USG-SFIBs were performed on 20 fresh adult cadavers using 15, 20, 25, 30, 35, 40, 45, and 50 ml of methylene blue. After the injections, the pelvic and inguinal regions were dissected to directly visualize the dye stained on the LFCN, FN, ON, and LP. All FN and LFCN were stained heavily when the 15-50 ml of dye was injected. Higher volumes of dye (40-50 ml) spread more medially and stained on the ON and LP in 60 % of cases. To increase the possibility of dye spreading to all three target nerves and LP of the SFIB, a high volume (≥40 ml) of anesthetic is recommended. If only a blockade of the FN and LFCN is required, a low volume (15-25 ml) of anesthetic is sufficient.

RESUMEN: El volumen de anestésico local para un bloqueo de la fascia ilíaca suprainguinal (FISI) de una sola inyección es un factor clave para el éxito del bloqueo, debido a que los cursos de los tres nervios objetivo del plexo lumbar (PL), el nervio cutáneo femoral lateral (NCFL), femoral (NF) y el nervio obturador (NO), en el área inguinal están aislados y dentro de la distancia de abordaje. Por lo tanto, este estudio cadavérico tiene como objetivo demostrar la distribución de la tinción de tinte en NCFL, NF, NO y PL siguiendo el FISI guiado por ultrasonido usando 15-50 ml de azul de metileno. Se realizaron un total de 40 USG-FISI en 20 cadáveres adultos frescos utilizando 15, 20, 25, 30, 35, 40, 45 y 50 ml de azul de metileno. Después de las inyecciones, se disecaron las regiones pélvica e inguinal para visualizar directamente el tinte teñido en NCFL, NF, NO y PL. Todos los NF y NCFL se tiñeron intensamente cuando se inyectaron los 15- 50 ml de colorante. Volúmenes mayores de colorante (40-50 ml) se esparcen más medialmente y tiñen el NO y la PL en el 60 % de los casos. Para aumentar la posibilidad de que el colorante se propague a los tres nervios objetivo y al PL del FISI, se recomienda un volumen elevado (≥40 ml) de anestésico. Si solo se requiere un bloqueo de NF y NCFL, un volumen bajo (15-25 ml) de anestésico es suficiente.

Surgeon-performed pericapsular nerve group (PENG) block for total hip arthroplasty using the direct anterior approach: a cadaveric study.

BACKGROUND: During total hip arthroplasty (THA) using the direct anterior approach, orthopaedic surgeons can identify all anatomical landmarks required for pericapsular nerve group (PENG) blocks and carry out the latter under direct vision. This cadaveric study investigated the success of surgeon-performed PENG block. Success was defined as dye staining of the articular branches of the femoral and accessory obturator nerves. METHODS: 11 cadavers (18 hip specimens) were included in the current study. To simulate THA in live patients, an orthopaedic surgeon inserted trial prostheses using the direct anterior approach. Subsequently, a block needle was advanced until contact with the bone (between the anterior inferior iliac spine and iliopubic eminence). 20 mL of 0.1% methylene blue was injected. Cadavers were then dissected to document the presence and dye staining of the femoral, lateral femoral cutaneous, obturator and accessory obturator nerves as well as the articular branches of the femoral, obturator and accessory obturator nerves. RESULTS: Methylene blue stained the articular branches of the femoral nerve and the articular branches of the accessory obturator nerve (when present) in all hip specimens. Therefore, surgical PENG block achieved a 100% success rate. Dye stained the femoral and obturator nerve in one (5.6%) and two (11.1%) hip specimens, respectively. No dye staining was observed over the accessory obturator nerve in the pelvis nor the lateral femoral cutaneous nerve. CONCLUSION: Surgeon-performed PENG block during direct anterior THA reliably targets the articular branches of the femoral and accessory obturator nerves. Future trials are required to compare surgeon-performed PENG block with anaesthesiologist-performed, ultrasound-guided PENG block, and surgeon-performed periarticular local anaesthetic infiltration.

Innervation of the clavicle: a cadaveric investigation.

BACKGROUND: This cadaveric study investigated the innervations of the clavicle and clavicular joints (ie, sternoclavicular and acromioclavicular joints). METHODS: Twenty cadavers (40 clavicles) were dissected. A skin incision was made to permit exposure of the posterior cervical triangle and infraclavicular fossa. The platysma, sternocleidomastoid, and trapezius muscles were cleaned in order to identify the supraclavicular nerves. Subsequently, the suprascapular and subclavian nerves were localized after removal of the prevertebral layer of the deep cervical fascia. In the infraclavicular region, the pectoralis major and minor muscles were retracted laterally in order to visualize the lateral pectoral nerve. The contribution of all these nerves to the clavicular bone and joints were recorded. RESULTS: Along their entire length, all clavicular specimens received contributions from the supraclavicular nerves. The latter innervated the cephalad and ventral aspects of the clavicular bone. The caudal and dorsal aspects of the clavicle were innervated by the subclavian nerve (middle and medial thirds). The lateral pectoral nerve supplied the caudad aspect of the clavicle (middle and lateral thirds). The sternoclavicular joint derived its innervation solely from the supraclavicular nerves whereas the acromioclavicular joint was supplied by the supraclavicular and lateral pectoral nerves. CONCLUSION: The clavicle and clavicular joints are innervated by the subclavian, lateral pectoral, and supraclavicular nerves. Clinical trials are required to determine the relative importance and functional contribution of each nerve.

Accuracy of sonographic identification of suprascapular nerve at supraclavicular fossa: a cadaveric study / Precisión de la identificación ecográfica del nervio supraescapular en la fosa supraclavicular: un estudio cadavérico

SUMMARY: Sonographic identification of suprascapular nerve (SSN) is essential for diagnosis of suprascapular neuropathy and ultrasound-guided suprascapular nerve block. This study aims to demonstrate the accuracy of identification of SSN at supraclavicular region by ultrasonography in fresh cadavers. Ninety-three posterior cervical triangles were examined. With ultrasonography, SSN emerging from the upper trunk of brachial plexus was identified and followed until it passed underneath the inferior belly of omohyoid muscle. Sonographic visualization of SSN in supraclavicular fossa was recorded. Then, cadaveric dissection was performed to determine the presence or absence of SSN. An agreement between sonographic identification and direct visualization was specified and categorized the following three patterns: "correctly identified" (pattern I), "incorrectly identified" (pattern II), and "unidentified" (pattern III). The identification of SSN using sonography was correct in almost 90 %. The diameter of SSN with pattern I was the largest compared to those of other two patterns. In pattern I, SSN ran laterally from the upper trunk of brachial plexus and passed underneath the inferior belly of omohyoid muscle. Therefore, SSN was easily identified under ultrasonography. In pattern II, nerve identified by ultrasonography was literally the dorsal scapular nerve. In pattern III, SSN was unable to be identified because of its anatomical variation. The accuracy of ultrasonographic identification of SSN at supraclavicular fossa is high and the key sonoanatomical landmarks are the lateral margin of brachial plexus and the inferior belly of omohyoid muscle. The anatomical variants of SSN are reasons of incorrect or unable identification of SSN under ultrasonography.

RESUMEN: La identificación ecográfica del nervio supraescapular (NSE) es esencial para el diagnóstico de neuropatía supraescapular y bloqueo del nervio supraescapular mediante la ecografía. Este estudio tiene como objetivo demostrar la precisión de la identificación de NSE en la región supraclavicular por ecografía en cadáveres frescos. Se examinaron noventa y tres triángulos cervicales posteriores. Se identificó el NSE emergente de la parte superior del tronco del plexo braquial con la ecografía, y se siguió hasta su trayecto por debajo del vientre inferior del músculo omohioideo. Se registró la visualización ecográfica del NSE en la fosa supraclavicular. Luego, se realizó disección cadavérica para determinar la presencia o ausencia de NSE. Se especificó un acuerdo entre la identificación ecográfica y la visualización directa y se categorizaron los siguientes tres patrones: "identificado correctamente" (patrón I), "identificado incorrectamente" (patrón II) y "no identificado" (patrón III). La identificación de NSE mediante ecografía fue correcta en casi el 90 %. El diámetro del NSE con el patrón I fue el más grande en comparación con los de los otros dos patrones. En el patrón I, NSE corría lateralmente desde la parte superior del tronco del plexo braquial y pasaba por debajo del vientre inferior del músculo omohioideo. Por lo tanto, el NSE se identificó fácilmente mediante ecografía. En el patrón II, el nervio identificado por ecografía era literalmente el nervio escapular dorsal; en el patrón III, el NSE no pudo ser identificado debido a su variación anatómica. La precisión de la identificación ecográfica del NSE en la fosa supraclavicular es alta y los puntos de referencia sonoanatómicos clave son el borde lateral del plexo braquial y el vientre inferior del músculo omohioideo. Las variantes anatómicas de NSE son razones de identificación incorrecta o incapaz de NSE bajo ecografía.

Cadaveric study investigating the phrenic-sparing volume for anterior suprascapular nerve block.

BACKGROUND: This cadaveric study investigated the maximum effective volume of dye in 90% of cases (MEV90), required to stain the suprascapular nerve while sparing the phrenic nerve during the performance of an anterior suprascapular nerve block. METHODS: In cadaveric neck specimens, using ultrasound guidance, the block needle was advanced until its tip was positioned underneath the omohyoid muscle next to the suprascapular nerve. The dye was injected in order to achieve circumferential spread around the latter. Successful phrenic-sparing suprascapular nerve block was defined as the non-staining of the phrenic nerve on dissection. Volume assignment was carried out using a Biased Coin Design, whereby the volume of dye administered to each cadaveric specimen depended on the response of the previous one. In case of failure (ie, stained phrenic nerve), the next one received a lower volume (defined as the previous volume with a decrement of 2 mL). If the previous cadaveric specimen had a successful block (ie, non-stained phrenic nerve), the next one was randomized to a higher volume (defined as the previous volume with an increment of 2 mL), with a probability of b=0.11, or the same volume, with a probability of 1 - b=0.89. RESULTS: Thirty-one cadavers (56 cadaveric neck specimens) were included in the study. Using isotonic regression and bootstrap CI, the MEV90 for phrenic-sparing anterior suprascapular nerve block was estimated to be 4.2 mL (95% CI 3.0 to 5.0 mL). The probability of a successful response was estimated to be 0.90 (95% CI 0.84 to 0.96). CONCLUSION: For ultrasound-guided anterior suprascapular nerve block, the MEV90 of dye required to spare the phrenic nerve is 4.2 mL. Further studies are required to correlate this finding with the MEV90 of local anesthetic in live subjects.

Cadaveric investigation of the minimum effective volume for ultrasound-guided suprainguinal fascia iliaca block.

BACKGROUND: This cadaveric dose-finding study investigated the minimum effective volume of dye in 90% of cases (MEV90), required to stain the femoral, lateral femoral cutaneous and obturator nerves for ultrasound-guided suprainguinal fascia iliaca block (SIFIB). METHODS: In cadaveric specimens of the lower limb, the block needle was advanced, medial to the anterosuperior iliac spine, until its tip was positioned between the internal oblique and iliacus muscles underneath the fascia iliaca. The dye was injected inside the fascia iliaca compartment. Volume assignment was carried out using a biased coin design, whereby the volume of dye administered to each cadaveric specimen depended on the response of the previous one. In case of failure, the next one received a higher volume (defined as the previous volume with an increment of 2.5 mL). If the previous cadaveric specimen had a successful block, the next one was randomized to a lower volume (defined as the previous volume with a decrement of 2.5 mL), with a probability of b=0.11, or the same volume, with a probability of 1-b=0.89. Success was defined as the staining of the femoral, lateral femoral cutaneous, and obturator nerves on dissection. RESULTS: Thirty-six cadavers (60 cadaveric specimens) were included in the study. Using isotonic regression and bootstrap CI, the MEV90 for ultrasound-guided SIFIB was estimated to be 62.5 mL (95% CI 60 to 65). CONCLUSION: For ultrasound-guided SIFIB, the MEV90 of dye required to stain the femoral, lateral femoral cutaneous and obturator nerves is 62.5 mL. Further studies are required to correlate this finding with the MEV90 of local anesthetic in human subjects.