Spread Of Injectate Research Articles

Is a Retrolaminar Approach to the Thoracic Paravertebral Space Possible?: A Human Cadaveric Study.

The retrolaminar block (RB) is used for truncal analgesia, but its mechanism of neural blockade remains obscure. We sought to learn the pattern of local anesthetic spread after thoracic RB using cadaveric models. In 8 fresh cadavers, an ultrasound-guided T4 RB was performed with 20 mL of methylene blue 1% and bupivacaine 0.5%. For comparison, an RB at T9 in 1 cadaver and a T4 thoracic paravertebral block in another cadaver were performed. Subsequently, posterior and anterior thoracic dissections were performed to examination where the dye spread. After T4 RB, dye was noted to spread in the ipsilateral retrolaminar plane (all 8 cadavers, median cephalad spread 3.5 cm, caudad spread 10.7 cm, lateral spread 2.5 cm), the contralateral retrolaminar plane (6 cadavers), the paravertebral space (5 cadavers, median of 3 segments, T3-T5), the intercostal space (5 cadavers, median of 3.5 cm laterally), the T4 epidural space (6 cadavers), and the intervertebral foramina (4 cadavers, median of 2 segments, T4-T5). After T9 retrolaminar injection, dye was noted in the ipsilateral retrolaminar plane (5.5 cm cephalad, 13.5 cm caudad, and 2.5 cm lateral), the contralateral retrolaminar plane, and the epidural space. Dye after T4 traditional paravertebral block spread to T1-T6 paravertebral space with 15-cm lateral spread. Injectate spread to the paravertebral space, epidural space, intercostal space, and intervertebral foramina is possible in the RB but is quite variable. In comparison to the thoracic paravertebral block, injectate spread within the paravertebral space is more limited.

Comparison of Epidural Spreading Patterns and Clinical Outcomes of Transforaminal Epidural Steroid Injection with High-Volume Injectate via the Subpedicular Versus the Retrodiscal Approach

The effect of transforaminal epidural steroid injection (TFESI) appears to be influenced by the volume of the injected material because there is a positive correlation between injection volume and extent of pain relief. The purpose of this study was to examine how many vertebral segments are covered by the subpedicular (SP) approach and the retrodiscal (RD) approach and to compare the clinical outcomes of the 2 approaches in TFESI with high-volume injectates. A randomized, active control trial. Medical University centers. Fifty patients were randomly assigned to either the SP group or the RD group. TFESI was performed with high-volume injectates. A total of 9 mL injectate was divided into 3 injections (0.5 mL, 2.5 mL, and 6 mL) given at 10-second intervals. The primary outcome measure was injectate distribution. The spreading patterns were described as unilateral, bilateral, ventral, or dorsal. Ventral or dorsal flow was also described as being cephalad or caudad, respectively. The secondary outcome measures were pain relief and reduction of functional disability at 4 weeks after the procedure. The total numbers of vertebral segments and median levels of contrast spread from the injection site were not significantly different between the 2 groups. However, in 3 mL of injectate, the injectate spread showed more extensive bilateral distribution in the RD group. At 4 weeks after treatment, both groups demonstrated statistically significant pain relief and improvement in functional status. No significant differences were observed between the 2 groups. We enrolled only a small number of patients and did not analyze long-term outcomes. Patients with severe spinal stenosis or herniated nucleus pulposus were included. Slightly different methods were used in the 2 groups to determine the number of levels at which the injectate was spread. Epidural spreading patterns and clinical outcomes of lumbar TFESI with high-volume injectate were not significantly different between the SP approach and the RD approach.Institutional Review Board (IRB) approval: Institutional Review Board of Ewha Womans University Hospital (EUMC 2015-05-003-003). Clinical trials registration number: Clinical Research Information Service (CRIS, registration number: KCT0002288; RCT URL: https://cris.nih.go.kr/cris/search/search_result_st01.jsp?seq=7309)KEY WORDS: Epidural injections, epidural space, low back pain, radiating pain, disability evaluation, steroids, local anesthetics, intervertebral disc disease, spinal stenosis.

Comparison of Epidural Spreading Patterns and Clinical Outcomes of Transforaminal Epidural Steroid Injection with High-Volume Injectate via the Subpedicular Versus the Retrodiscal Approach

Background: The effect of transforaminal epidural steroid injection (TFESI) appears to be influenced by the volume of the injected material because there is a positive correlation between injection volume and extent of pain relief. Objectives: The purpose of this study was to examine how many vertebral segments are covered by the subpedicular (SP) approach and the retrodiscal (RD) approach and to compare the clinical outcomes of the 2 approaches in TFESI with high-volume injectates. Study Design: A randomized, active control trial. Setting: Medical University centers. Methods: Fifty patients were randomly assigned to either the SP group or the RD group. TFESI was performed with high-volume injectates. A total of 9 mL injectate was divided into 3 injections (0.5 mL, 2.5 mL, and 6 mL) given at 10-second intervals. The primary outcome measure was injectate distribution. The spreading patterns were described as unilateral, bilateral, ventral, or dorsal. Ventral or dorsal flow was also described as being cephalad or caudad, respectively. The secondary outcome measures were pain relief and reduction of functional disability at 4 weeks after the procedure. Results: The total numbers of vertebral segments and median levels of contrast spread from the injection site were not significantly different between the 2 groups. However, in 3 mL of injectate, the injectate spread showed more extensive bilateral distribution in the RD group. At 4 weeks after treatment, both groups demonstrated statistically significant pain relief and improvement in functional status. No significant differences were observed between the 2 groups. Limitations: We enrolled only a small number of patients and did not analyze long-term outcomes. Patients with severe spinal stenosis or herniated nucleus pulposus were included. Slightly different methods were used in the 2 groups to determine the number of levels at which the injectate was spread. Conclusions: Epidural spreading patterns and clinical outcomes of lumbar TFESI with highvolume injectate were not significantly different between the SP approach and the RD approach. Institutional Review Board (IRB) approval: Institutional Review Board of Ewha Womans University Hospital (EUMC 2015-05-003-003). Clinical trials registration number: Clinical Research Information Service (CRIS, registration number: KCT0002288; RCT URL: https://cris.nih.go.kr/cris/ search/search_result_st01.jsp?seq=7309) Key words: Epidural injections, epidural space, low back pain, radiating pain, disability evaluation, steroids, local anesthetics, intervertebral disc disease, spinal stenosis

The Lateral Femoral Cutaneous Nerve: Description of the Sensory Territory and a Novel Ultrasound-Guided Nerve Block Technique.

Nerve blockade of the lateral femoral cutaneous (LFC) nerve provides some analgesia after hip surgery. However, knowledge is lacking about the extent of the cutaneous area anesthetized by established LFC nerve block techniques, as well as the success rate of anesthetic coverage of various surgical incisions. Nerve block techniques that rely on ultrasonographic identification of the LFC nerve distal to the inguinal ligament can be technically challenging. Furthermore, the branching of the LFC nerve is variable, and it is unknown if proximal LFC nerve branches are anesthetized using the current techniques. The primary aim of this study was to investigate a novel ultrasound-guided LFC nerve block technique based on injection into the fat-filled flat tunnel (FFFT), which is a duplicature of the fascia lata between the sartorius and the tensor fasciae latae muscle, in order to assess the success rate of anesthetizing the proximal LFC nerve branches and covering of the different surgical incisions used for hip surgery. First, a cadaveric study was conducted in order to identify an FFFT injection technique that would provide adequate injectate spread to the proximal LFC nerve branches. Second, a clinical study was conducted in a group of 20 healthy volunteers over 2 consecutive days. On trial day 1, successful complete anesthesia of the LFC nerve was defined by performing a suprainguinal fascia iliaca block bilaterally in each subject. On trial day 2, a triple-blind randomized controlled trial compared the effect of the novel ultrasound-guided LFC nerve block technique for bupivacaine versus placebo. The primary end point was the success rate of anesthesia of the proximal cutaneous area innervated by the LFC nerve for the FFFT injection with bupivacaine versus placebo. Adequate spread of injectate to the proximal LFC nerve branches in cadavers was obtained by injecting 10 mL with dynamic needle-tip tracking in the FFFT. Application of this technique in the randomized controlled trial provided anesthesia of the lateral thigh with a success rate of 95% (95% confidence interval, 73.9%-99.8%) for the active side and 0% for placebo (P < 0.001). The proximal branches were anesthetized with a success rate of 68% (95% confidence interval, 43.4%-87.4%) on the active side. The proximal extent of the anesthetized cutaneous area was on average 7.9 cm distal to the greater trochanter. This novel LFC nerve block technique is easy and quick and reliably produces anesthesia of the lateral thigh. The greater trochanter is rarely included in the area of anesthesia, which reduces the coverage of each specific surgical incision. The success rate of 68% in anesthetizing the proximal nerve branches must be further evaluated by future research.

Spread of injectate around hip articular sensory branches of the femoral nerve in cadavers

Anatomical knowledge dictates that regional anaesthesia after total hip arthroplasty requires blockade of the hip articular branches of the femoral and obturator nerves. A direct femoral nerve block increases the risk of fall and impedes mobilisation. We propose a selective nerve block of the hip articular branches of the femoral nerve by an ultrasound-guided injection in the plane between the iliopsoas muscle and the iliofemoral ligament (the iliopsoas plane). The aim of this study was to assess whether dye injected in the iliopsoas plane spreads to all hip articular branches of the femoral nerve. Fifteen cadaver sides were injected with 5mL dye in the iliopsoas plane guided by ultrasound. Dissection was performed to verify the spread of injectate around the hip articular branches of the femoral nerve. In 10 dissections (67% [95% confidence interval: 38-88%]), the injectate was contained in the iliopsoas plane staining all hip articular branches of the femoral nerve without spread to motor branches. In four dissections (27% [8-55%]), the injection was unintentionally made within the iliopectineal bursa resulting in secondary spread. In one dissection (7% [0.2-32%]) adhesions partially obstructed the spread of dye. An injection of 5mL in the iliopsoas plane spreads around all hip articular branches of the femoral nerve in 10 of 15 cadaver sides. If these findings translate to living humans, injection of local anaesthetic into the iliopsoas plane could generate a selective sensory nerve block of the articular branches of the femoral nerve without motor blockade.

Biceps Tendon Sheath Injection: An Anatomical Conundrum.

Long head biceps tendon peritendinous or sheath injections are routinely administered at or immediately distally to the bicipital groove. The main indication for injection remains the clinical diagnosis or treatment of biceps tendinopathy, although true inflammation of the tendon within the bicipital groove is rare. Because the tendon sheath is merely an extension of the joint cavity, it is plausible to assume that an injection into the sheath would result in intraarticular spread. Surprisingly, such an anatomical tenet has a vague confirmation in the published clinical literature. This experiment was undertaken to investigate patterns of injectate spread when peri-tendon injection at the bicipital groove is performed. An experimental cadaveric study. An institutional clinical anatomy laboratory. Twelve ultrasound-guided methylene blue injections of the bicep tendon sheath were performed on cadaver specimens. Dissections and gross examination of staining of the internal joint surfaces were performed. Visual confirmation of the intra- and/or extra-articular spread of the injectate was performed. In 11 specimens, injected contrast was found spreading onto the entire internal joint surface, including glenoid cartilage. One extraarticular injection was attributable to a technical issue. The experiment confirmed continuity of the joint capsule and the biceps tendon sheath. These results suggest a low diagnostic utility of peritendinous injections at the level of the bicep groove. Such injections would likely result in intraarticular deposit of the injectate. Nonetheless, this approach may be utilized as an alternative simplified access to the glenohumeral joint.

Ultrasound-guided lateral and subcostal transversus abdominis plane block in calves: a cadaveric study

ObjectiveTo describe and assess the ultrasound-guided transversus abdominis plane (TAP) block feasibility in calf cadavers, to compare two injection volumes and to evaluate possible undesired solution spreads. Study designProspective, descriptive, anatomic study. AnimalsA group of 15 bovine cadavers weighing 47±11 kg (mean±standard deviation). MethodsLateral (n = 24) and subcostal (n = 12) TAP block approaches were assessed. For each approach, two volumes (0.2 or 0.4 mL kg−1) of toluidine blue and contrast medium were injected using both sides of the animals. Nerve staining was assessed by anatomical dissection and spread of injectate by contrast-enhanced computed tomography. Objective and subjective technique feasibility was evaluated by a specific score (poor, good, excellent). ResultsUsing the lateral approach, 58%, 92% and 25% and 75%, 83% and 25% of the thirteenth thoracic, first and second lumbar nerves were stained by 0.2 and 0.4 mL kg−1, respectively. Craniocaudal and dorsoventral solution spread and number of blocks that adequately stained an individual nerve were not significantly different between the volumes. Using the subcostal approach, 67%, 83%, 67%, 67% and 50%, and 83%, 100%, 83%, 83% and 50% of the eighth, ninth, tenth, eleventh, twelfth thoracic nerves were stained by 0.2 and 0.4 mL kg−1, respectively. With both techniques, no intraspinal and one intraperitoneal spread were observed. Objective and subjective feasibility score was excellent for both approaches in the majority of the cases. Conclusions and clinical relevanceTAP injections were easy to perform with both techniques in calf cadavers. The volume of injectate did not influence spread. The authors conclude that a combination of the two approaches is necessary, but perhaps not sufficient, to stain all of the nerves innervating the ventral abdominal wall. Further studies are required to refine the technique and evaluate its efficacy in preventing nociception in calves.

The ultrasound-guided retrolaminar block: volume-dependent injectate distribution.

PurposeThe ultrasound-guided retrolaminar block is one of the newer and simpler alternatives to the traditional, often technically challenging, paravertebral (PV) block. Its feasibility, safety, and efficacy have already been clinically demonstrated in patients with multiple rib fractures using higher volumes of local anesthetic, when compared with the traditional approach. The primary aim of this observational anatomical study was to assess the spread of local anesthetic from the retrolaminar injection point to the PV space and its volume dependence. Second, we assessed the incidence of epidural and contralateral PV spread in the both groups.MethodsTen fresh porcine cadavers were randomized into 2 groups (n=5 each) to receive ultrasound-guided retrolaminar injections at Th4-Th5 level with either 10 mL (low-volume group) or 30 mL (high-volume group) of 2% lidocaine and methylene blue mixture. After the procedure, the cadavers were dissected and frozen. Cross-section cuts (~1 cm thick) were performed to evaluate the injectate spread.ResultsIn the high-volume group, injectate spread from the retrolaminar to the PV space was observed in all specimens (5 out of 5; 100%), while in the low-volume group, no apparent spread to the PV space was found (0 out of 5; 0%). No epidural or contralateral PV spread was observed in any of the specimens.ConclusionFollowing ultrasound-guided retrolaminar injections in fresh porcine cadavers, injectate spread from the retrolaminar tissue plane to the PV space is strongly volume dependent, suggesting that, clinically, high local anesthetic volumes maybe critical for achieving regional anesthesia and analgesia consistent with traditional PV blockade.

Total hip arthroplasty and peripheral nerve blocks: Limited but salient role?

Total hip arthroplasty and peripheral nerve blocks: Limited but salient role?

Mixing of hot and cold fluid inside a square chimney model for a pool type research reactor – An experimental study

Mixing of hot and cold fluid inside a scaled down model of chimney structure for a pool type nuclear research reactor was studied experimentally. Chimney structures are often used in pool type reactors to prevent mixing of radioactive water from reactor core and reactor pool water. This helps in reducing radiation field at the reactor pool top so that the pool top area can be accessible during reactor operation. During normal operation, chimney top opening serves as the inlet for the cold fluid from the reactor pool and the chimney bottom opening serves as the inlet for the hot fluid from core outlet. The chimney structure considered in the present work has two arms which act as the outlets for the mixed flow of core outlet water and pool water. These arms are connected to the pump suctions of two independent recirculation loops of the primary coolant system. Depending on the reactor operation with one loop or two loops, outlet flow from the chimney structure to the pump suction will take place either through single arm or through both the arms. To study the difference in mixing behaviour for one-loop operation and two-loop operation, experimental investigations were carried out inside a 2/9th scaled down model of the chimney structure of a pool type research reactor being developed at BARC. The bypass flow was varied from 0 to 15% of the core flow. Flow visualization of the mixing zone was carried out using dye injection and vortex spread height was observed. Fluid temperatures were measured in the mixing region and temperature profile was obtained. It was observed that increase in bypass flow reduces vortex spread height and pool temperature front height. Larger mixing zone and higher temperature front height were found for one-loop operation than that for two-loop operation. It was observed that minimum bypass flow should be 10% of the core flow in case of one-loop operation and minimum chimney height should be six times the hydraulic diameter of chimney.

Ultrasound-Guided Posterior Femoral Cutaneous Nerve Block: A Cadaveric Study.

To identify any anatomic barriers to local anesthetic spread between the sciatic nerve (SN) and the posterior femoral cutaneous nerve (PFCN) at the level of the infragluteal crease and to describe a potential technique for an ultrasound (US)-guided subgluteal PFCN block in a cadaveric model. Bilateral US-guided subgluteal injections of a colored latex solution were performed around the SN (15 mL) and PFCN (10 mL) in 4 unembalmed cadavers, for a total of 8 cadaver thighs. The specimens were dissected after latex polymerization to observe the spread of the latex solutions. With US guidance, the PFCN was visualized deep to the gluteus maximus and slightly superficial or lateral to the SN at the level of the infragluteal crease. The SN and PFCN were found on dissection to be coated with their respective colored latex in all 8 thighs. The SN and PFCN were consistently separated by the deep investing muscular fascia of the thigh, with only 2 thighs showing substantial mixing of latex injectates. The deep investing muscular fascia of the thigh appears to impede the spread of injectate between the SN and PFCN in a most unembalmed cadaver specimens. A US-guided subgluteal PFCN blockade may be a feasible technique to complement an SN block when complete anesthesia of the posterior thigh is required.

The Pathway of Injectate Spread With the Transmuscular Quadratus Lumborum Block: A Cadaver Study.

The spread of injectate resulting from a transmuscular quadratus lumborum (TQL) block and a transverse oblique paramedian (TOP) TQL block has never been examined. The aim of this cadaveric study was to investigate by which pathway the injectate spreads cephalad into the thoracic paravertebral space and which nerves were dyed by the injectate cephalad and caudad to the diaphragm when performing a TQL and a TOP TQL block. We also aimed to investigate whether the thoracic and lumbar sympathetic trunks as well as the lumbar plexus were covered by the injectate. Ultrasound-guided bilateral TQL and TOP TQL injections were administered in 8 cadavers. A total of 16 injections were performed. With the TQL injection, the curvilinear transducer was oriented in the transverse plane above the iliac crest at the posterior axillary line to identify the Shamrock sign. With the TOP TQL injection, the same transducer was placed with a TOP orientation 3 cm lateral to the L2 spinous process to identify the L2 transverse process and the adjoining quadratus lumborum muscle. For both techniques, the needle was advanced in-plane to the transducer, with the end point in the interfascial plane between the quadratus lumborum and psoas major muscles. Thirty milliliters of dye solution was injected bilaterally for each technique. The spread of the dye was evaluated by subsequent dissection. In all successful injections, the dye was seen to spread into the thoracic paravertebral space and the intercostal spaces to surround the somatic nerves and the thoracic sympathetic trunk. The main pathway of spread of injectate was posterior to the medial and lateral arcuate ligaments. Caudad to the diaphragm, the injected dye surrounded the subcostal, iliohypogastric, and ilioinguinal nerves in all cases, whereas the genitofemoral and lateral femoral cutaneous nerves were dyed in a varying degree. No dye was seen to surround the lumbar plexus, femoral nerve, or lumbar sympathetic trunk. The pattern of spread was similar with the TQL and TOP TQL injections. The spread of injectate with the TQL and TOP TQL approaches is cephalad from the lumbar point of administration between the quadratus lumborum and psoas major muscles, predominantly via a pathway posterior to the arcuate ligaments and into the thoracic paravertebral space to reach the somatic nerves and the thoracic sympathetic trunk in the intercostal and paravertebral spaces. The lumbar plexus and lumbar sympathetic trunk are not affected.

RETRACTED: Ultrasound-guided “lateral” thoracolumbar interfascial plane (TLIP) block: A cadaveric study of the spread of injectate

• Lateral TLIP block injects a local anesthetic the iliocostal muscle and longissimus muscle.

Ultrasound-guided lumbar plexus block in volunteers; a randomized controlled trial

BackgroundThe currently best-established ultrasound-guided lumbar plexus block (LPB) techniques use a paravertebral location of the probe, such as the lumbar ultrasound trident (LUT). However, paravertebral ultrasound scanning can provide inadequate sonographic visibility of the lumbar plexus in some patients. The ultrasound-guided shamrock LPB technique allows real-time sonographic viewing of the lumbar plexus, various anatomical landmarks, advancement of the needle, and spread of local anaesthetic injectate in most patients. We aimed to compare block procedure outcomes, effectiveness, and safety of the shamrock vs LUT. MethodsTwenty healthy men underwent ultrasound-guided shamrock and LUT LPBs (2% lidocaine–adrenaline 20 ml, with 1 ml diluted contrast added) in a blinded randomized crossover study. The primary outcome was block procedure time. Secondary outcomes were procedural discomfort, number of needle insertions, injectate spread assessed with magnetic resonance imaging, sensorimotor effects, and lidocaine pharmacokinetics. ResultsThe shamrock LPB procedure was faster than LUT (238 [sd 74] vs 334 [156] s; P=0.009), more comfortable {numeric rating scale 0–10: 3 [interquartile range (IQR) 2–4] vs 4 [3–6]; P=0.03}, and required fewer needle insertions (2 [IQR 1–3] vs 6 [2–12]; P=0.003). Perineural injectate spread seen with magnetic resonance imaging was similar between the groups and consistent with motor and sensory mapping. Zero/20 (0%) and 1/19 (5%) subjects had epidural spread after shamrock and LUT (P=1.00), respectively. The lidocaine pharmacokinetics were similar between the groups. ConclusionsShamrock was faster, more comfortable, and equally effective compared with LUT. Clinical trial registrationNCT02255591.

The Spread of Ultrasound-Guided Injectate From the Adductor Canal to the Genicular Branch of the Posterior Obturator Nerve and the Popliteal Plexus: A Cadaveric Study.

The popliteal nerve plexus contributes to afferent knee-pain conduction. It is mainly formed by genicular branches from the posterior obturator and the tibial nerves, innervating the intra-articular and posterior knee region. A subinguinal obturator nerve block alleviates pain after total knee arthroplasty. Reduced hip adductor motor function could be avoided by a posterior obturator nerve block inside the popliteal fossa.The aim of this study was to evaluate the spread of dye after a distal adductor canal (AC) injection to the popliteal fossa and coloring of the popliteal plexus and the genicular branch of the posterior obturator nerve by dissection. We also assessed the spread of dye into the popliteal fossa after a distal femoral triangle injection. Ten milliliters of dye was injected into the distal part of the AC in 10 cadaver sides and into the distal part of the femoral triangle in 3 sides. Dissection was used to assess the spread of the injectate and coloring of the popliteal plexus and the genicular branch of the posterior obturator nerve, as well as the saphenous and medial vastus nerves. The popliteal plexus and the genicular branch of the posterior obturator nerve were dyed in all 10 dissections after AC injections. No dye spread into the popliteal fossa after femoral triangle injections. Injection of 10 mL of dye into the distal part of the AC spreads into the popliteal fossa and colors the popliteal plexus and the genicular branch of the posterior obturator nerve.

Real-Time Ultrasound/MRI Fusion for Suprasacral Parallel Shift Approach to Lumbosacral Plexus Blockade and Analysis of Injectate Spread: An Exploratory Randomized Controlled Trial.

Fused real-time ultrasound and magnetic resonance imaging (MRI) may be used to improve the accuracy of advanced image guided procedures. However, its use in regional anesthesia is practically nonexistent. In this randomized controlled crossover trial, we aim to explore effectiveness, procedure-related outcomes, injectate spread analyzed by MRI, and safety of ultrasound/MRI fusion versus ultrasound guided Suprasacral Parallel Shift (SSPS) technique for lumbosacral plexus blockade. Twenty-six healthy subjects aged 21–36 years received two SSPS blocks (20 mL 2% lidocaine-epinephrine [1 : 200,000] added 1 mL diluted contrast) guided by ultrasound/MRI fusion versus ultrasound. Number (proportion) of subjects with motor blockade of the femoral and obturator nerves and the lumbosacral trunk was equal (ultrasound/MRI, 23/26 [88%]; ultrasound, 23/26 [88%]; p = 1.00). Median (interquartile range) preparation and procedure times (s) were longer for the ultrasound/MRI fusion guided technique (686 [552–1023] versus 196 [167–228], p < 0.001 and 333 [254–439] versus 216 [176–294], p = 0.001). Both techniques produced perineural spread and corresponding sensory analgesia from L2 to S1. Epidural spread and lidocaine pharmacokinetics were similar. Different compartmentalized patterns of injectate spread were observed. Ultrasound/MRI fusion guided SSPS was equally effective and safe but required prolonged time, compared to ultrasound guided SSPS. This trial is registered with EudraCT (2013-004013-41) and ClinicalTrials.gov (NCT02593370).

A Cadaveric Study of Ultrasound-Guided Subpectineal Injectate Spread Around the Obturator Nerve and Its Hip Articular Branches

The femoral and obturator nerves are assumed to account for the primary nociceptive innervation of the hip joint capsule. The fascia iliaca compartment block and the so-called 3-in-1-block have been used in patients with hip fracture based on a presumption that local anesthetic spreads to anesthetize both the femoral and the obturator nerves. Evidence demonstrates that this presumption is unfounded, and knowledge about the analgesic effect of obturator nerve blockade in hip fracture patients presurgically is thus nonexistent. The objectives of this cadaveric study were to investigate the proximal spread of the injectate resulting from the administration of an ultrasound-guided obturator nerve block and to evaluate the spread around the obturator nerve branches to the hip joint capsule. Fifteen milliliters of methylene blue was injected into the interfascial plane between the pectineus and external obturator muscles in 7 adult cadavers. The spread of the injectate into the obturator canal and around the obturator and accessory obturator nerve branches to the hip joint was evaluated by subsequent dissection. The injected dye spread into the obturator canal and colored all obturator branches to the hip joint capsule in all 14 sides. Furthermore, the accessory obturator nerve was present in 3 sides (21%), and the nerve and its branches to the hip joint capsule were colored in all cases. In cadavers, injection of 15 mL of methylene blue into the interfascial plane between the pectineus and the external obturator muscle effectively spreads proximally to reach the obturator canal, as well as the obturator nerve branches to the hip joint capsule and the accessory obturator nerve.

A radiologic and anatomic assessment of injectate spread following transmuscular quadratus lumborum block in cadavers

We performed bilateral transmuscular quadratus lumborum blocks in six cadavers using iodinated contrast and methylene blue. Computed tomography imaging was performed in four cadavers and anatomical dissection was completed in five. This demonstrated spread to the lumbar paravertebral space in 63% of specimens, laterally to the transversus abdominis muscle in 50% and caudally to the anterior superior iliac spine in 63% of specimens. There was no radiographic evidence of spread to the thoracic paravertebral space. Anatomical dissection revealed dye staining of the upper branches of the lumbar plexus and the psoas major muscle in 70% of specimens. Further clinical studies are required to confirm if the quadratus lumborum block might be a suitable alternative to lumbar plexus block.

Currently Recommended TON Injectate Volumes Concomitantly Block the GON: Clinical Implications for Managing Cervicogenic Headache

Background: Headache (HA) is a significant cause of morbidity globally. Despite many available treatment options, HAs that are refractory to conservative management can be challenging to treat. Third occipital nerve (TON) and greater occipital nerve (GON) irritation are potential etiologic agents of primary and cervicogenic HAs that can be targeted using minimally invasive treatment options such as nerve blocks or radiofrequency ablation. However, a substantial number of patients that undergo radiofrequency ablation do not experience pain relief despite a positive diagnostic medial branch block (MBB). Objective: In this study, we investigate the underlying cause for the high rate of false positives associated with MBBs by evaluating injectate spread in cadaveric subjects. Study Design: Cadaveric study. Setting: Academic medical center. Methods: After obtaining exemption status from our Institutional Review Board, TON injections were performed on 5 preserved cadavers, a total of 10 TONs, using anatomic landmarks, partial dissection, and palpation to guide needle placement. Cadaveric dissections were performed to evaluate the location, vertical spread, and grossly observed injectate coating of the TON and GON for each quantity of methylene blue injectate, 0.3 mL and 0.5 mL, administered. Results: The average distance between the TON and GON at their respective foraminal exit points was 1.81 cm. The average vertical spread for 0.3 mL and 0.5 mL of methylene blue injectate was 2.02 + 0.35 cm and 3.26 + 0.48 cm when performing a TON block. When using 0.3 mL injectate, both the TON and GON were simultaneously coated 60% of the time. After increasing the injectate volume to 0.5 mL, both the TON and GON were simultaneously coated 100% of the time. Limitations: The cadaveric design of this study presents limitations when translating cadaveric findings to the clinical setting. Also, the small sample size limits its power and generalizability. Lastly, the potential for researcher bias exists as the investigators were not blinded. Conclusions: This study demonstrates that currently recommended injectate volumes for TON blocks may result in concomitant coating of the GON. Conventional radiofrequency ablation (RFA) of these nerves may not lesion both the TON and GON given its restrictive circumferential lesioning diameter of 5 – 7 mm. As such, interventionalists should consider performing radiofrequency ablation to both the TON and GON after a positive TON block. Key Words: Chronic pain, cervicogenic headache, third occipital nerve, greater occipital nerve, injectate spread, radiofrequency ablation

A cadaver study comparing spread of dye and nerve involvement after three different quadratus lumborum blocks

BackgroundPosterior variants of abdominal wall block include the quadratus lumborum type I, quadratus lumborum type II and quadratus lumborum transmuscular blocks. Our objectives were to compare the spread of injectate and nerve involvement, after conducting blocks using ultrasound guidance in soft embalmed cadavers. MethodsAfter randomization, an experienced anaesthetist conducted three quadratus lumborum 1, three quadratus lumborum 2 and four transmuscular blocks on the left or right sides of five cadavers. All cadavers were placed in the lateral position and the quadratus lumborum muscle seen using a 3–9 MHz ultrasound probe placed in the flank. For each block, a 20 ml mixture of 17.75 ml water, 2 mls latex and 0.25 ml India ink was injected. The lumbar region and abdominal flank were dissected 72 h later. ResultsWe conducted 10 blocks. Two quadratus lumborum 1 and two quadratus lumborum 2 blocks were associated with spread of dye within the TAP plane. One quadratus lumborum 1 block spread to the deep muscles of the back and one quadratus lumborum 2 block dispersed within the subcutaneous tissue surrounding the abdominal flank. All transmuscular quadratus lumborum blocks spread consistently to L1 and L3 nerve roots and within psoas major and quadratus lumborum muscles. ConclusionsConsistent spread to lumbar nerve roots was achieved using the transmuscular approach through the quadratus lumborum.