The suprascapular nerve block
The suprascapular nerve block (SSNB) is discussed in the literature but not widely adopted as a treatment option for certain shoulder conditions such as adhesive capsulitis or shoulder dislocation. In todays post, we will briefly review the anatomy, discuss the technique and review some of the literature on the indications.
Anatomy
Anatomy of the suprascapular nerve
The suprascapular nerve originates directly off the brachial plexus with contributions from the 5th and 6th cervical nerve roots and less commonly, the 4th cervical nerve root.[1]Moen, Todd C., et al. “Suprascapular neuropathy: what does the literature show?.” Journal of shoulder and elbow surgery 21.6 (2012): 835-846. It then courses posteriorly through cervical triangle and clavicle. It moves across the superior border of the scapular into the suprascapular notch (the target of the block) where it is maintained by the transverse scapular ligament. From there it courses inferiorly to the spinoglenoid notch.
The suprascapular notch innervates two muscles: the supraspinatus and infraspinatus. It also has a sensory component which includes about 70% of the glenohumeral joint as well as the coracoclavicular ligament, coracohumeral ligament, AC joint and subacromial bursal. Note that it dies not innervate teres minor.[2]Ozkan K, Ozcekic AN, Sarar S, et al. Suprascapular nerve block for the treatment of frozen shoulder. Saudi J Anaesth 2012; 6: 52–55.
The suprascapular notch contains the suprascapular nerve, as well as the artery. It can have some anatomic variation. In some patients it is deep, and in others very shallow or entirely flattened out.
The Block
The glenohumeral joint and suprascapular notch (red arrow) seen with the probe posteriorly.
The suprascapular notch and transverse scapular ligament.
The block itself is not technically difficult. There are multiple approaches but we recommend the posterior approach and use of ultrasound guidance. To find the notch, initially look for the view in the first ultrasound image. The probe is placed posteriorly and the glenohumeral joint is the initial landmark of choice. Move the probe in the cranial-caudal plane until you can see the superior aspect of the scapula and the notch. You can then move the probe more medially to centralize the notch on the screen.
It is important to place doppler on the area to identify the suprascapular artery which should be avoided if possible. Once the probe is in position, we recommend an in plane technique with the needle coming lateral to medial. Alternatively, you can approach medial to lateral depending on positioning and setup. We recommend avoiding an out-of-plane technique to avoid accidently over shooting and causing a pneumothorax.
Once the needle is adequately placed, you can hydrodissect around the nerve with as little as 5 mL of anesthetic to achieve total blockade.
Demonstration of probe position with the medial to lateral approach.[3]https://radiologykey.com/suprascapular-nerve-block-2/
Shoulder Dislocation
The SSNB appears to be a safe and effective adjunct for patients presenting with an acute shoulder dislocation. Kaya et al published a case of a recurrent dislocator succesfully using the SSNB for an anterior dislocation.[4]Kaya, Murtaza, et al. “Interscalene or suprascapular block in a patient with shoulder dislocation.” The American journal of emergency medicine 35.1 (2017): 195-e1. The visual analog score went from an 95 to a 45 following the block.
Tezel performed a prospective, randomized trial comparing procedural sedation to SSNB via ultrasound guidance for patients presenting with acute shoulder dislocations.[5]Tezel, Onur, et al. “A comparison of suprascapular nerve block and procedural sedation analgesia in shoulder dislocation reduction.” The American journal of emergency medicine 32.6 … Continue reading The study enrolled a total of 41 patients. There was no differences in reduction success or patient satisfaction. However, the time spent in the emergency department was much greater in the procedural sedation group.
It is unclear how the SSNB compares to other forms of regional anesthesia such as the interscale block or infra- or supra-clavicular block. In theory, these blocks provide greater blockade of the extremity which may better facilitate reduction. Conversely, they carry greater risk of vascular injury as all of the blocks are near a large artery. Additionally, these blocks carry a high likelihood of phrenic nerve paralysis which means the patient will be inspiring with a hemidiaphragm until the anesthetic is completely metabolized.
It is the opinion of this author that the SSNB in combination with a glenohumeral block (anesthetic in the dislocated joint space) as well as either PO or IM medications can easily facilitate reduction of the joint.
Adhesive Capsulitis
Adhesive capsulitis, more commonly termed frozen shoulder, is an excellent candidate for SSNB. Ozkan et al found patients pain scores and range of motion significantly improved after SSNB.[6]Ozkan, Korhan, et al. “Suprascapular nerve block for the treatment of frozen shoulder.” Saudi journal of anaesthesia 6.1 (2012): 52. Jung et al found similar effectiveness when they compared intra-articular injection with or without SSNB.[7]Jung, Tae Wan, et al. “Does combining a suprascapular nerve block with an intra-articular corticosteroid injection have an additive effect in the treatment of adhesive capsulitis? A comparison … Continue reading The patients in the SSNB arm had better range of motion at both 2 weeks and 2 months follow up. At 1 year follow up, the SSNB group still had better pain and range of motion scores than the group that received intra-articular injection only. Shanahan had similar findings with reduction in pain and increased patient satisfaction scores.
Ultrasound and probe position of the block. (click to enlarge).
Another demonstration of ultrasound and probe position. Note this patient has a very flattened notch.
Additional Conditions
Other conditions that have been successfully treated with SSNB include osteoarthritis, rheumatoid arthritis, chronic rotator cuff injuries.[8]Messina C, Banfi G, Orlandi D, Lacelli F, Serafini G, Mauri G, Secchi F, Silvestri E, Sconfienza LM. Ultrasound-guided interventional procedures around the shoulder. Br J Radiol. … Continue reading It has also been used to treat and prevent post-operative pain following arthroscopy. In some cases, it can be used diagnostically for patients suspected of having suprascapular nerve entrapment.
Summary
Suprascapular nerve block is a safe and effective technique. It’s efficacy is well demonstrated for adhesive capsulitis. There are case reports and a small paper assessing its use in shoulder dislocations. Overall, it is likely to gain traction as more literature is published and awareness increases.
– More Shoulder Pain from Sports Medicine Review: https://www.sportsmedreview.com/by-joint/shoulder/
– Read More @ Wiki Sports Medicine: https://wikism.org/Suprascapular_Nerve_Block
References
