Ultrasound-Guided Versus Landmark-Based Approach to the Distal Suprascapular Nerve Block: A Comparative Cadaveric Study

The suprascapular nerve block (SScNB) is easily administered using a landmark-based technique: A cadaveric study to assess nerve staining post-injection

Aims

The suprascapular nerve is an ideal target for nerve blockade to alleviate shoulder pain given its widespread innervation to the shoulder girdle. To widen availability of this treatment, we investigate whether an anatomical landmark technique can be adopted by novice injectors to provide efficacious blockade.

Methods

Five injectors were recruited with varying experience. 10 shoulders of Thiel embalmed cadavers were injected with blue dye. Written instructions and an illustration of the Dangoisse landmark technique were provided prior to injection. Cadavers were dissected and the presence or absence of dye staining reported by three observers and a consensus agreement reached.

Results

Dissection demonstrated diffuse staining in the suprascapular fossa. 90% of shoulders had adequate staining of the suprascapular nerve directly, or distal branches, which would provide adequate anaesthesia. Inter-observer agreement was good (k = 0.73) for staining at the supraspinous fossa and excellent (k = 0.87) for staining distally. The technique was performed by novice injectors with a good success rate.

Conclusion

This technique is reproducible by a range of clinicians to effectively provide anaesthesia of the SScN. Within a resource strained healthcare environment greater uptake of this technique is likely to be of benefit to a wider group of patients.

Infraspinatus-teres minor (ITM) interfascial block: a novel approach for combined suprascapular and axillary nerve block

BACKGROUND

Combined suprascapular and axillary nerve block could be an analgesic option for shoulder pain control. The current description of this technique requires performing the block procedures at two different sites without consideration for catheter placement. We hypothesized that a single site injection to the interfascial plane between the infraspinatus and teres minor would result in an injectate spread to the suprascapular and axillary nerves.

METHODS

We performed 10 injections with this approach using 25 mL dye solution in 10 shoulders of five unembalmed cadavers. Also, we described three case reports, two single-injection cases and one catheter-placement case, using this approach in patients with acute postsurgical pain and chronic pain in their shoulder region.

RESULTS

In cadaveric evaluations, dye spreading to the suprascapular nerves on the infraspinatus fossa and the spinoglenoid notch cephalad and axillary nerves in the quadrilateral space caudally were observed in all injections. In addition, the most posterolateral part of the joint capsule was stained in 8 out of 10 injections. There was no dye spreading on the nerves to the subscapularis or lateral pectoral nerves. Clinically successful analgesia with no adverse events was achieved in all three cases.

CONCLUSION

Our anatomical and clinical observations demonstrated that an injection to the interfascial plane between the infraspinatus and teres minor consistently achieved injectate spreading to both suprascapular and axillary nerves, which innervate the glenohumeral joint.

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.

Ultrasound-Guided Suprascapular Nerve Block at Suprascapular Notch-Do We Really Target Suprascapular Notch or Not? Where Is Our Real Target?

Ultrasound (US)-guided suprascapular nerve block (SSNB) is a widely used procedure and while describing the US-guided SSNB in the suprascapular notch, the suprascapular fossa is often visualized and injection is performed in that location. Although it can be done in both location, to inject the right area, the terminology should be settled and the visualization of these areas which are unclear and confusing in the literature should be clarified. In this sense, we showed the course of the nerve on a cadaver and briefly describe a protocol to correctly visualize the suprascapular notch with US.

A Comparative Evaluation of Combined Nerve Block Versus Periarticular Infiltration on Postoperative Pain Relief in Total Hip Arthroplasty

Introduction

To minimize the side effects of the central neuraxial blockade to obtain postoperative pain relief, there has been an increasing preference for targeting the peripheral structures in patients undergoing total hip arthroplasty (THA).

Patients and Methods

This prospective study was performed between September 2019 and September 2021 and involved 30 patients that were randomized to two groups. One group (n = 15) received combined nerve block (CNB) [obturator nerve, nerve to quadratus femoris, superior gluteal nerve, and femoral nerve], while another group (n = 15) received periarticular infiltrative analgesia (PIA). All the patients were given the same volume and composition of the drug cocktail (20 ml 0.5% ropivacaine, 1 ml (100 mcg) dexmedetomidine, and 29 ml normal saline).

Results

The patients in group CNB had a significantly lower visual analog score (VAS) at 6, 12, 18, 24, 30, 36, 42 and 48 h after surgery (p < 0.05). Patients in group CNB required fewer (p < 0.001) doses of the rescue analgesic (1.67 ± 0.90 doses) as compared to group PIA (3.53 ± 0.64 doses). Time to the first rescue analgesia was significantly longer (p = 0.01) in group CNB (6.71 ± 2.36 h) as compared to group PIA (4.80 ± 1.26 h). However, patients in group PIA had significantly faster sensory (p < 0.001) and motor recovery (p < 0.001) as compared to group CNB. It took significantly longer (p < 0.001) to administer the nerve block (16.87 ± 1.80 min) as compared to periarticular infiltration (6.53 ± 1.18 min). There were no complications in either group.

Conclusion

CNB registered significant superiority over PIA with respect to postoperative pain relief and time to rescue analgesia. However, the time taken to administer CNB was significantly higher and the patients in the PIA group had early recovery in sensory and motor modalities.

Level of Evidence

III (therapeutic).

Osseous suprascapular canal: rare variant that would hinder suprascapular nerve block and posterior surgical approach

PURPOSE

To report atypical anatomical variation of an osseous suprascapular canal, and to elaborate on its clinical significance as a potential anatomical factor that could obscure a direct posterior surgical approach and suprascapular nerve block.

METHODS

Osteological observational study of the scapula with emphasis on the suprascapular space. The pool of investigated sample size was collectively 768 specimens composed of 529 adult dry scapulae (240 paired, 289 un-paired), 54 children dry scapulae, 135 wet scapulae observed during cadaveric dissections, 47 retrospective 3D CT reconstructions, and 3 retrospective full sequence shoulder MRI. The two reported cases came from the 240 (120 skeleton) observed paired scapulae. Furthermore, the osseous suprascapular canal was examined by X-rays and its internal path was exposed by CT sections. A narrative review was conducted to investigate any relevant reports on the subject matter.

RESULTS

Two left dry bone scapulae with unilateral osseous suprascapular canal were found. The incidence of this atypical morphology of an osseous canal is probably five cases reported in three studies including this cases study.

CONCLUSIONS

The reported cases aid in explaining additional possible anatomical factors that could lead to below threshold anesthetic effect in posterior suprascapular nerve block procedures. Therefore, it is more practical to visualize the suprascapular canal by some imaging method before attempting to blindly access the suprascapular nerve in nerve block or posterior surgical approach due to the rare potential existence of an ossified barrier hindering the procedure.

LEVEL OF EVIDENCE

V Basic Science Research.

The Impact of Suprascapular Nerve Interventions in Patients with Frozen Shoulder: A Systematic Review and Meta-Analysis

BACKGROUND

Frozen shoulder is a common condition resulting in severe pain and restricted range of motion. An assessment of the effectiveness of interventions may provide an improved understanding of the development and management of frozen shoulder.

METHODS

A literature search was conducted using Embase, the Cumulative Index of Nursing and Allied Health (CINAHL), the Cochrane Central Register of Controlled Trials (CENTRAL), and National Center for Biotechnology Information PubMed using relevant terms. Studies were included if they assessed the outcomes of interventions on the suprascapular nerve that aim to improve the symptoms of frozen shoulder.

RESULTS

A database search returned 196 articles. After review, 9 articles met the inclusion criteria and were included in the analysis. Suprascapular nerve interventions (nerve block, pulsed radiofrequency lesioning) are associated with improvement in pain, motion, and function. Meta-analysis showed that pain (Hedges g, -3.084 [95% confidence interval (CI), -4.273 to -1.894]; p < 0.001) and range of motion (Hedges g, 2.204 [95% CI, 0.992 to 3.415]; p < 0.001) improved significantly following suprascapular nerve block (SSNB).

CONCLUSIONS

SSNB is associated with significant improvements in shoulder pain and range of motion in patients with frozen shoulder. Further randomized controlled trials comparing SSNB with intra-articular injection and other nonoperative treatments are required to fully define its role in the management of frozen shoulder.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Surgeon-Administered Nerve Block During Rotator Cuff Repair Can Promote Recovery with Little or No Post-operative Opioid Use

BACKGROUND

The use of opioid analgesia is common in both the acute and extended post-operative periods after rotator cuff repair. The current opioid crisis has prompted surgeons to seek alternatives that minimize or even eliminate the need for oral opioids after surgery.

QUESTIONS/PURPOSES

We sought to investigate the effects on post-operative opioid use of a surgeon-administered block of the suprascapular and axillary nerves in arthroscopic rotator cuff repair (ARCR), in particular to quantify outpatient opioid consumption and duration.

METHODS

In this prospective observational study, all patients undergoing primary ARCR performed under general anesthesia by a single surgeon were studied over a 15-month period. Of 91 ARCRs performed, 87 patients were enrolled and followed prospectively. At the conclusion of the procedure, the surgeon performed "local-regional" nerve blockade with injections to the sensory branches of the suprascapular nerve and the axillary nerve, as well as local infiltration about the shoulder. Use of medications in the post-anesthesia care unit was left up to the anesthesiologist. Patients were prescribed oral opioids (hydrocodone/acetaminophen 5/325 mg) for analgesia after discharge. The quantity and duration of opioid use and pain scores were recorded for 4 months. Statistical analysis was performed to evaluate factors that could account for greater opioid use.

RESULTS

Total opioid consumption ranged from 0 to 30 opioid tablets (average, 4.2 tablets) over the 4-month period. Post-operatively, 91% of patients took between ten or fewer tablets, and 39% took no opioids. The average duration of opioid use was 2.4 days. No patients were taking opioids at the 4- to 6-week or 4-month follow-up visits, none required refills, and none received prescriptions from outside prescribers. No statistically significant differences were seen in opioids taken or duration of use in regard to tear size, sex, body mass index, surgery location, or procedure time. There was a significant inverse correlation between opioid use and age. In addition, the cost of the surgeon-performed procedure was substantially lower than that associated with pre-operative nerve blockade performed by an anesthesiologist. All patients were satisfied with the post-operative pain management protocol. Average reported post-operative pain scores were low and decreased at each visit.

CONCLUSION

With this local-regional nerve-blocking protocol, opioid use after ARCR was unexpectedly low, and a large proportion of patients recovered without any post-surgical opioids. The correlation seen between opioid use and age may not be clinically significant, given the low use of post-operative opioids overall. These results may be useful in guiding post-operative opioid prescribing after ARCR, as well as in lowering costs associated with ARCR.

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.

Editorial Commentary: Mounting Evidence for a Landmark-Based Approach to Suprascapular Nerve Block

The surgeon-administered landmark-based approach for suprascapular nerve block (SNB) alone for postoperative pain relief after arthroscopic shoulder surgery as an alternative to interscalene nerve block (ISB) has been proven as effective as ultrasound-guided ISB. Questions remain about the SNB. For instance, is ultrasound guidance necessary for SNB or can it be performed using a landmark-based approach?