Shoulder operations

1

What types of orthopedic surgical operations are performed on the shoulder?

The types of shoulder operations that are commonly performed include: arthroscopy for shoulder debridement, impingement syndrome, SLAP repair (superior labrum anterior and posterior), shoulder dislocation, and frozen shoulder, as well as rotator cuff repair, acromioclavicular joint repair, and shoulder replacement.

2

Describe the innervation of the shoulder joint.

The shoulder joint, also known as the glenohumeral joint , is a ball and socket joint with multiple sources of innervation. The brachial plexus supplies the bulk of the joint’s innervation, with the superficial cervical plexus innervating the skin mostly superior to the joint. The glenohumeral joint is primarily supplied by the axillary nerve inferiorly and the suprascapular nerve superiorly. In addition to the glenohumeral joint, the suprascapular nerve also provides sensory innervation to the acromioclavicular joint. The musculocutaneous and subscapular nerves also supply innervation to the joint, but their contribution is much less and has high variability among individuals. Most of the skin surrounding the shoulder joint receives sensory innervation by branches of the axillary nerve.

3

How is an interscalene block performed? Between which muscles does it place local anesthetics?

The most common regional technique performed for shoulder operations is the interscalene block. Historically, interscalene blocks have been placed by palpation of surface anatomy or with nerve stimulators. However, with the advent of new technology, ultrasound guidance has become the standard technique. This not only minimizes the risk of damage to a highly vascularized and innervated region of the neck, but also facilitates confirmation of local anesthetic injection within close proximity of the brachial plexus.

To perform the block under ultrasound guidance, the probe is placed transversely on the neck at roughly the level of the cricoid cartilage. Deep and lateral to the sternocleidomastoid is the anterior scalene muscle and more lateral still is the middle scalene muscle. Between the anterior and middle scalene muscles courses the brachial plexus. The brachial plexus at this point often appears on ultrasound as three circles, but there is variability depending on patient anatomy and physician technique. Regardless of the exact visualization, the target remains the same: the roots of C5, C6, and C7 and the upper and middle trunks they become. If identification of the brachial plexus between the scalene muscles proves challenging, the ultrasound probe can be brought down to the supraclavicular fossa to the level of the divisions. Here, the brachial plexus can be reliably identified lateral to the subclavian artery and then traced back cephalad to the truncal level. Once identified, the needle is introduced lateral to the probe and guided medially toward the plexus. Typically, 20 to 30 mL of local anesthetic is then injected around the trunks, with spread confirmed by the ultrasound visualization.

4

Caution should be used when performing an interscalene block in patients with severe respiratory disease. Why?

In almost all interscalene blocks, the ipsilateral phrenic nerve is inadvertently blocked by the spread of local anesthetics. This results in hemidiaphragmatic paresis and a subsequent decrease in respiratory function. In the healthy patient, this is usually clinically insignificant and often goes unnoticed. However, if a patient has diminished respiratory function at baseline, this loss of diaphragmatic excursion may result into respiratory distress. The risks and benefits of an interscalene approach should be assessed before placing a block in a patient with significant respiratory disease and a more distal approach to the brachial plexus should be considered.

5

What is Horner syndrome?

Horner syndrome is a collection of signs resulting from inhibition of the cervical sympathetic trunk. Notable signs include ipsilateral ptosis (drooping eyelid), miosis (pupillary constriction), and anhidrosis (diminished sweating). There are multiple etiologies of Horner syndrome, one of which is inhibition of the cervical sympathetic trunk by local anesthetics. Following interscalene and supraclavicular blocks, the local anesthetic can migrate medially from the brachial plexus toward the cervical ganglion, resulting in an unintended Horner syndrome. Should this occur following a block, patients should be offered reassurance for this common side effect and instructed to follow-up if it does not resolve in time.

6

Why might a patient’s voice become hoarse after an interscalene nerve block?

During an interscalene block, local anesthetic is injected around the brachial plexus at the level of the C5, C6, and C7 roots. This local anesthetic may spread medially toward the recurrent laryngeal nerve. This results in hoarseness in 10% to 20% of interscalene blocks; however, the incidence may be higher on the right side than the left. In patients with preexisting injury to the contralateral recurrent laryngeal nerve, laryngeal obstruction via bilateral vocal cord paralysis may be a rare but catastrophic complication.