Ultrasound-guided proximal suprascapular nerve block: A cadaveric study

Erector spinae plane block versus local infiltration anaesthesia for transforaminal percutaneous endoscopic discectomy: A prospective randomised controlled trial

BACKGROUND

Around 60%-80% of the population suffers from back pain, making it one of the most common health complaints. Transforaminal percutaneous endoscopic discectomy (TPED) is an effective treatment for low back pain that can be performed using different anaesthesia techniques. Our primary objective was to test the hypothesis that bilateral Erector spinae plane block (ESP) plus sedation is equally effective as traditional local infiltration anaesthesia plus sedation in TPED.

MATERIALS AND METHODS

Fifty-two patients undergoing TPED were randomly assigned to 2 groups: G1 - intravenous sedation with local infiltration anaesthesia; G2 - intravenous sedation with bilateral ESP.

PRIMARY OUTCOME

volume of fentanyl and propofol administered during surgery.

SECONDARY OUTCOMES

adverse events during sedation reported using the World Society of Intravenous Anaesthesia (SIVA) adverse sedation event tool, level of postoperative sedation measured on the Richmond Agitation-Sedation Scale (RASS), intensity of postoperative pain on a visual analogue scale (VAS), mechanical pain threshold (MPT) measured with von Frey monofilaments on both lower extremities, patient satisfaction with analgesia on 5-point Likert scale.

RESULTS

Volume of fentanyl, propofol, and level of postoperative sedation was significantly lower in G2 (p < 0.001). There was no difference between groups in intensity of pain, patient satisfaction with analgesia, and mechanical pain threshold after surgery. There were no adverse events in G2, but in G1 2 patients presented minimal risk descriptors, 5 presented minor risk descriptors, and 1 presented sentinel risk descriptors that required additional medication or rescue ventilation.

CONCLUSIONS

The ESP was equal to local infiltration anaesthesia in terms of intensity of pain, mechanical pain threshold after surgery, and patient satisfaction; however, ESP reduced the volume of intraoperative fentanyl and propofol, thereby reducing the adverse effects of sedation.

Assessment of 2 distinct anatomical landmarks for suprascapular nerve injection: a cadaveric study

BACKGROUND

The suprascapular nerve block (SSNB) is a commonly used procedure for the management of pain in various shoulder pathologies. Both image-guided and landmark-based techniques have been utilized successfully for SSNB, though more consensus is needed regarding the optimal method of administration. This study aims to evaluate the theoretical effectiveness of a SSNB at 2 distinct anatomic landmarks and propose a simple, reliable way of administration for future clinical use.

METHODS

Fourteen upper extremity cadaveric specimens were randomly assigned to either receive an injection 1 cm medial to the posterior acromioclavicular (AC) joint vertex or 3 cm medial to the posterior AC joint vertex. Each shoulder was injected with a 10 ml methylene blue solution at the assigned location, and gross dissection was performed to evaluate the anatomic diffusion of the dye. The presence of dye was specifically assessed at the suprascapular notch, supraspinatus fossa, and spinoglenoid notch to determine the theoretic analgesic effectiveness of a SSNB at these 2 injection sites.

RESULTS

Methylene blue diffused to the suprascapular notch in 57.1% of the 1-cm group and 100% of the 3-cm group, the supraspinatus fossa in 71.4% of the 1-cm group and 100% of the 3-cm group, and the spinoglenoid notch in 100% of the 1-cm group and 42.9% of the 3-cm group.

CONCLUSION

Given its superior coverage at the more proximal sensory branches of the suprascapular nerve, a SSNB injection performed 3 cm medial to the posterior AC joint vertex provides more clinically adequate analgesia than an injection site 1 cm medial to the AC junction. Performing a SSNB injection at this location allows for an effective method of anesthetizing the suprascapular nerve.

Impact of Peripheral Nerve Block Technique on Incidence of Phrenic Nerve Palsy in Shoulder Surgery

Peripheral nerve blocks are an increasingly common method of providing postoperative analgesia for shoulder surgeries. However, the standard technique, the interscalene block (ISB), inevitably causes hemidiaphragmatic paresis (HDP), secondary to phrenic nerve palsy. This can cause morbidity in patients with preexisting respiratory compromise, prompting investigation into alternative "phrenic-sparing" nerve blocks. The aim of this review was to give an overview of these blocks and critically evaluate the current literature to determine if any are suitable replacements for ISB. The incidence of HDP and analgesic efficacy were considered. We queried four electronic databases and one register. Twenty-eight original articles were selected for review. The use of ultrasound guidance, lower volumes of local anaesthetic (LA), and injection 4 mm outside the brachial plexus fascia reduced HDP incidence for the ISB; however, no single modification did so sufficiently. While the anterior suprascapular nerve block (SSNB) showed comparable analgesic effects to the ISB, HDP prevalence was also high. The posterior SSNB produced consistently low HDP incidences but also inferior analgesia to ISB, except when combined with an infraclavicular brachial plexus block. The superior trunk block (STB) provided equivalent analgesia to the ISB while reducing HDP incidence, but not significantly. Lower LA volumes consistently led to lower HDP incidence across all blocks, likely due to a reduced ability to spread to the phrenic nerve. Further investigation into the minimum effective volumes of the extrafascial ISB, anterior SSNB, STB, and combined posterior SSNB with infraclavicular block is warranted to determine if any of these blocks can successfully balance HDP prevention with analgesic efficacy.

Ultrasound-guided anterior suprascapular nerve block versus interscalene brachial plexus block for arthroscopic shoulder surgery: A randomised controlled study

Background and Aims

The interscalene brachial plexus block (ISB) affects the phrenic nerve, resulting in hemi-diaphragmatic paresis (HDP) and, possibly, respiratory distress. Suprascapular nerve block via an anterior approach (SSB-A) is performed more distally at the level of the trunk of the brachial plexus and, thus, may spare the phrenic nerve. This study compares the analgesic efficacy and decline of hemi-diaphragmatic excursion (HDE) following ultrasound (US)-guided SSB-A versus ISB for arthroscopic shoulder surgery.

Methods

This study was conducted on 60 adult participants undergoing arthroscopic shoulder surgery under general anaesthesia. Both US-guided SSB-A (n = 30) and ISB (n = 30) were performed with a combination of 10 ml bupivacaine (0.5%) and 4 mg dexamethasone. The primary objective was to compare the duration of analgesia (time to first rescue analgesia), and secondary objectives were to compare 24-h postoperative numerical rating scale (NRS) scores, 24-h morphine consumption and post block change in HDE, and pulmonary function tests (PFTs) between the two groups. For analysing intergroup differences of NRS, HDE and PFT; Pearson's Chi-squared test or Fisher's exact test, unpaired t test, and Mann-Whitney U test were used. For intragroup differences, paired t test was used. A P value <0.05 was considered significant.

Results

The duration of analgesia (mean ± Standard Deviation) was similar in two groups (SSB-A = 1,345 ± 182 min, ISB = 1,375 ± 156 min; P = 0.8). The reduction in HDE was significantly greater in the ISB group (44%) than in the SSB-A group (10%). Pulmonary function was better preserved in the SSB-A group.

Conclusion

Compared to ISB, SSB-A has a similar analgesic efficacy for arthroscopic shoulder surgeries, but it is superior in preserving diaphragmatic function and pulmonary function.

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.

Proximal vs Distal Approach of Ultrasound-guided Suprascapular Nerve Block for Patients With Adhesive Capsulitis of the Shoulder: Prospective Randomized Controlled Trial

OBJECTIVES

To evaluate the early clinical outcomes of ultrasound (US)-guided suprascapular nerve block (SSNB) using a proximal approach compared with a distal approach for outpatient treatment of adhesive capsulitis.

DESIGN

Randomized controlled trial.

SETTING

Outpatient clinic PARTICIPANTS: Participants (N=47) with symptomatic adhesive capsulitis.

INTERVENTIONS

Participants were randomly assigned to either US-guided SSNB using a proximal approach (n=23, proximal group) or a distal approach (n=24, distal group).

MAIN OUTCOME MEASURES

The primary outcome measure was the visual analog scale (VAS) for pain at week 12. Secondary outcomes included the American Shoulder Elbow Surgeon's (ASES) score, University California Los Angeles score, Short Form-36 mental and physical component summaries, and range of motion. All patients completed clinical follow-up at 2, 6, and 12 weeks after treatment. On US images, depth and insertion angle of needle during injection were measured.

RESULTS

The VAS significantly improved in both groups at week 12. After treatment, no significant differences were found in early clinical outcomes (weeks 2, 6, and 12) between groups (all P>.05), except that ASES at 2 weeks showed a significantly higher score in the distal group than in the proximal group (87.1±4.8 and 83.0±6.3, respectively; P=.014). The mean depth and insertion angle of needle was significantly lower (depth: 13.4±3.9 and 30.6±4.3 mm, respectively; P<.001; insertion angle: 19.6°±6.4° and 38.7°±5.8°; P<.001) in the proximal group than in the distal group.

CONCLUSIONS

This study demonstrated that proximal approach of US-guided SSNB provided favorable short-term outcomes of pain and functional improvement and that outcomes were comparable to those of the distal approach in adhesive capsulitis. The suprascapular nerve was located more superficially and easily identified in the proximal approach, suggesting that this method might improve the accuracy of injection.

"Suprascapular canal": Anatomical and topographical description and its clinical implication in entrapment syndrome

BACKGROUND

Suprascapular nerve (SN) entrapment syndrome accounts for 1-2% of all shoulder pain. The SN travels within a space between the suprascapular notch (SSN) and the spinoglenoid notch (SGN).

PURPOSE

To report a detailed topographical study of the suprascapular canal (SSC) and ultimately sort the different types of SN entrapment by its anatomical localization within the canal.

BASIC PROCEDURES

Observational study on 30 free dissected limbs of formaldehyde-fixed cadavers. The SN and vessels were traced as they passed through the SSC and the boundaries of the SSC were observed and documented. The SSC was then exposed by reflecting away the bordering muscles. Dimensions of the SSC as well as parameters of the SSN and SGN were measured using a digital caliper. Finally, a thorough literature review was made to survey the SN entrapment occurrence by site.

MAIN FINDINGS

The SSC is situated in the spinoglenoid fossa, has an average width of 13 mm, and runs underneath the supraspinatus muscle with an average distance of 25 mm between the SSN and SGN sloping in an infero-postero-lateral direction. The first segment represents the SSC entrance site and is composed of two spaces: osteofibrous and musculofibrous. The second segment is bordered by the supraspinatus muscle fascia, lateral margin of the supraspinous fossa, glenohumeral joint capsule, and the bony surface of the scapula (spinoglenoid fossa). This represents the SSC passage site. The third segment represents the SSC exit site around the spinoacromial arch at the SGN.

PRINCIPAL CONCLUSIONS

The SSC is defined as an osteofibrous canal running between the SSN and SGN enclosed by the supraspinatus fascia. It is anatomically composed of three segments: an entrance, a passage, and an exit. The distal SN passes through the SSC via five intervals that correspond to five potential sites of anatomical nerve entrapment: at the pre-entrance site, entrance site, passage site, exit site, and post-exit site. Each of those sites was found to be associated with specific causes and forms of entrapment.

Determining anatomic accuracy of shoulder field injection: triangular injection technique does adequately reach pain transmitters

Background

Controlling pain after shoulder surgery is a critical component of postsurgical care. Several recent studies have described the use of periarticular, local infiltration anesthesia, and field blocks (FBs) with clinical efficacy after shoulder surgery. The anatomic accuracy and safety of these FBs have not been well described. The purpose of this study was to determine the accuracy of a surgeon performed shoulder field injection. We hypothesized that our field injection would adequately reach the pain transmitters responsible for postsurgical shoulder pain.

Methods

A total of 10 cadaveric specimens were used in the study. A mixture of liposomal bupivacaine, normal saline, and methylene blue totaling 60 cc was prepared. After injection, the specimens were left for 4 hours to allow medication diffusion. The dissection of specimens was performed to identify 4 areas: axillary nerve, suprascapular nerve, supraclavicular nerves, and joint capsule. On dissection, accuracy rates were determined for each area.

Results

All 10 cadaveric specimens were injected and dissected to completion. The dissection of the axillary nerve showed methylene blue dye surrounding the nerve in 10 of 10 (100%) specimens, the suprascapular nerve in 9 of 10 (90%), and the supraclavicular nerves in 10 of 10 (100%). Zero of 10 (0%) specimens had any dye penetrate into the glenohumeral joint or capsule.

Conclusion

The accuracy rates of the injection of the mixture into the shoulder specimens suggest potential to reproduce an FB to the tissues that are responsible for postoperative pain after shoulder surgery. This may represent an option when interscalene nerve block is not desired or contraindicated.

Subomohyoid Anterior Suprascapular Block versus Interscalene Block for Arthroscopic Shoulder Surgery

Background

Interscalene brachial plexus block, the pain relief standard for shoulder surgery, is an invasive technique associated with important complications. The subomohyoid anterior suprascapular block is a potential alternative, but evidence of its comparative analgesic effect is sparse. The authors tested the hypothesis that anterior suprascapular block is noninferior to interscalene block for improving pain control after shoulder surgery. As a secondary objective, the authors evaluated the success of superior trunk (C5–C6 dermatomes) block with suprascapular block.

Methods

In this multicenter double-blind noninferiority randomized trial, 140 patients undergoing shoulder surgery were randomized to either interscalene or anterior suprascapular block with 15 ml of ropivacaine 0.5% and epinephrine. The primary outcome was area under the curve of postoperative visual analog scale pain scores during the first 24 h postoperatively. The 90% CI for the difference (interscalene-suprascapular) was compared against a –4.4-U noninferiority margin. Secondary outcomes included presence of superior trunk blockade, pain scores at individual time points, opioid consumption, time to first analgesic request, opioid-related side-effects, and quality of recovery.

Results

A total of 136 patients were included in the analysis. The mean difference (90% CI) in area under the curve of pain scores for the (interscalene-suprascapular) comparison was –0.3 U (–0.8 to 0.12), exceeding the noninferiority margin of –4.4 U and demonstrating noninferiority of suprascapular block. The risk ratio (95% CI) of combined superior trunk (C5–C6 dermatomes) blockade was 0.98 (0.92 to 1.01), excluding any meaningful difference in superior trunk block success rates between the two groups. When differences in other analgesic outcomes existed, they were not clinically important.

Conclusions

The suprascapular block was noninferior to interscalene block with respect to improvement of postoperative pain control, and also for blockade of the superior trunk. These findings suggest that the suprascapular block consistently blocks the superior trunk and qualify it as an effective interscalene block alternative.

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What We Already Know about This Topic

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Clinical indications for image guided interventional procedures in the musculoskeletal system: a Delphi-based consensus paper from the European Society of Musculoskeletal Radiology (ESSR)-part III, nerves of the upper limb

BACKGROUND

Image-guided interventional procedures of the nerves are commonly performed by physicians from different medical specialties, although there is a lack of clinical indications for these types of procedures. This Delphi-based consensus provided a list of indications on image-guided interventional procedures for nerves of the upper limb based on updated published evidence.

METHODS

An expert panel of 45 members of the Ultrasound and Interventional Subcommittees of the ESSR participated in this Delphi-based consensus study. After revision of the published papers on image-guided interventional procedures for nerves of the upper limb updated to September 2018, the experts drafted a list of statements according to the Oxford Centre for evidence-based medicine levels of evidence. Consensus on statements regarding clinical indications was considered as strong when more than 95% of experts agreed, and broad if more than 80% agreed.

RESULTS

Ten statements were drafted on procedures for nerves of the upper limb. Only two statements reached the highest level of evidence (ultrasound guidance is a safe and effective method for brachial plexus block; ultrasound-guided non-surgical approaches are safe and effective methods to treat carpal tunnel syndrome in the short term, but there is sparse evidence on the mid- and long-term effectiveness of these interventions). Strong consensus was obtained on 6/10 statements (60%), while 4/10 statements reached broad consensus (40%).

CONCLUSIONS

This Delphi-based consensus study reported poor evidence on image-guided interventional procedures for nerves of the upper limb. Sixty percent of statements on clinical indications provided by the expert board reached a strong consensus.

KEY POINTS

• An expert panel of the ESSR provided 10 evidence-based statements on clinical indications for image-guided interventional procedures for nerves of the upper limb • Two statements reached the highest level of evidence • Strong consensus was obtained on 6/10 statements (60%), while 4/10 statements reached broad consensus (40%).

Diaphragm-sparing nerve blocks for shoulder surgery, revisited

Although interscalene brachial plexus block (ISB) remains the gold standard for analgesia after shoulder surgery, the inherent risks of ipsilateral phrenic nerve block and hemidiaphragmatic paralysis (HDP) limit its use in patients with preexisting pulmonary compromise. In a previous Daring Discourse (2017), our research team has identified potential diaphragm-sparing alternatives to ISB for patients undergoing shoulder surgery. In recent years, the field has been fertile with research, with the publication of multiple randomized controlled trials investigating supraclavicular blocks, upper trunk blocks, anterior suprascapular nerve blocks, costoclavicular blocks, and combined infraclavicular-suprascapular blocks. To date, the cumulative evidence (pre-2017 and post-2017) suggests that costoclavicular blocks may provide similar postoperative analgesia to ISB coupled with a 0%-incidence of HDP. However, in light of the small number of patients recruited by the single study investigating costoclavicular blocks, further confirmatory trials are required. Moreover, future investigation should also be undertaken to determine if costoclavicular blocks could achieve surgical anesthesia for shoulder surgery. Anterior suprascapular nerve blocks have been demonstrated to provide surgical anesthesia and similar analgesia to ISB. However, their risk of HDP has not been formally quantified. Of the remaining diaphragm-sparing nerve blocks, supraclavicular blocks (with local anesthetic injection posterolateral to the brachial plexus), upper trunk blocks, and combined infraclavicular-anterior suprascapular blocks merit further investigation, as they have been shown to achieve similar analgesia to ISB, coupled with an HDP incidence <10%.

Ultrasound-Guided Proximal and Distal Suprascapular Nerve Blocks: A Comparative Cadaveric Study

Objectives

The primary aim of our study was to evaluate and compare the accuracy of ultrasound (US)-guided distal suprascapular nerve (dSSN) and proximal SSN (pSSN) blocks. Secondary aims were to compare the phrenic nerve involvement between groups and to describe the anatomical features of the sensory branches of the dSSN.

Methods

pSSN and dSSN blocks were performed in 14 cadavers (28 shoulders). Ten mL of 0.2% ropivacaine colored with methylene blue was injected under US guidance. Accuracy was determined using SSN staining and the distance between predefined anatomical landmarks and the targeted SSN. The phrenic nerve (PN) was judged to be colored or not. The distribution of the sensory branches that originate from the 14 dSSNs is described. Quantitative data are expressed as median (range).

Results

The pSSN was dyed more frequently than the dSSN (13 vs 11, P = 0.59). The targeted SSN was close to the suprascapular notch (1.3 [0–5.2] cm) and the origin of the SSN (1.4 [0.2–4.5] cm) for dSSN and pSSN blocks, respectively (P = 0.62). For dSSN blocks, the most frequent injection site was the supraspinous fossa. Three PNs were marked in pSSN blocks, compared with none in dSSN blocks (P = 0.22). Three sensory branches were identified for all 14 dSSNs: the medial subacromial branch, the lateral subacromial branch, and the posterior glenohumeral branch.

Conclusions

US-guided pSSN and dSSN blocks can be realized with accuracy. A distal approach to the SSN could be an alternative to interscalene brachial plexus block for the management of postoperative pain after shoulder surgery in high–respiratory risk patients.