Chapter 64

INTRODUCTION

The suprascapular nerve is a branch off the brachial plexus that arises from the C5-C6 nerve roots. It has afferent, efferent, and sympathetic fibers. Seventy percent of the afferent input travels via the suprascapular nerve; specifically, it provides sensory input from the scapula, acromioclavicular joint, and posterior and superior shoulder joint. Its efferent component innervates the supraspinatus and infraspinatus muscles.

The suprascapular block was first described by Wertheim and Rovenstein in 1941 for the use of intractable shoulder pain. This initial technique was essentially “blind” in that it was solely based on landmarks and clinical information without additional modalities that may be used today such as a nerve stimulator, fluoroscopy, or ultrasound. Wertheim and Rovenstein relied on the patient’s perception of paresthesias as the marker that their needle was correctly placed in the suprascapular notch where the nerve exits. Studies have demonstrated significant benefits of the suprascapular nerve block such as pain relief and improved range of motion. With shoulder pain affecting approximately 15% to 30% of adults, the relative ease of this block along with its minimal risks emphasizes the importance of its use in clinical practice.

INDICATIONS FOR SUPRASCAPULAR BLOCK

• Shoulder pain from inflammatory diseases: rheumatoid arthritis, seronegative spondyloarthropathies, crystal arthropathies

• Postoperative pain after shoulder surgery (arthroscopy, acromioplasty)

• Intractable pain from trauma (ie, fracture)

• Bursitis

• Acute anterior shoulder dislocation

• Diagnostic block for suprascapular nerve entrapment

RELEVANT ANATOMY

• The suprascapular nerve is arises from the C5 and C6 nerve roots of the brachial plexus.

• In 50% of instances, the nerve will also arise from the C4 nerve root.

• It runs lateral, posterior, and inferior deep to the posterior belly of the omohyoid muscle and anterior to the trapezius muscles to reach the superior border of the scapula to the superior scapular notch.

• It then runs inferior to the transverse scapular ligament and passes under the supraspinatus muscle through the floor of the supraspinous fossa, around the lateral border of the scapular spine and into the infraspinaous fossa to innervate the infraspinatus muscle.

The suprascapular nerve gives off several branches including:

• Motor nerves to the supraspinatus and infraspinatus muscle

• Sensory nerve branches to the coracoclavicular, coracohumeral ligaments, acromioclavicular joint, glenohumeral joint, and the subacromial bursa

The supraspinous fossa is an important structure to delineate as it is used for the blockade of the suprascapular nerve in several techniques. It is bounded by the following structures:

• Spine of the scapula

• Plate of the scapula

• Supraspinous fascia

Suprascapular Notch

• The suprascapular nerve is the only neural structure that exits through the supraspinous fossa via the suprascapular notch which also serves as point of injection for this nerve block.

• The anatomic variation of this notch can explain the incidence of suprascapular nerve injury as well ...

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