Arthroscopic and Open Decompression of the Suprascapular Nerve

Arthroscopic and Open Decompression of the Suprascapular Nerve

Umasuthan Srikumaran, Lewis L. Shi, Jeffrey D. Tompson, Laurence D. Higgins and Jon J.P. Warner

Chapter Synopsis

• Suprascapular nerve compression at the suprascapular notch can cause significant shoulder pathology. This condition can be surgically managed with arthroscopic or open release of the suprascapular transverse ligament.

Important Points

• Superior and posterolateral shoulder pain is common.

• Space-occupying lesions or dynamic conditions can cause suprascapular neuropathy.

• Carefully rule out other, more common causes of shoulder pathology.

• Electromyography can support diagnosis, but if negative, fluoroscopically guided anesthetic and cortisone injection can be used to confirm diagnosis.

Clinical and Surgical Pearls

• Achieve good visualization in the subacromial space before exposing the suprascapular notch.

• Use the anterior border of the supraspinatus and the coracoclavicular ligaments as landmarks to guide dissection.

• Protect the suprascapular nerve during resection of the transverse suprascapular ligament.

Clinical and Surgical Pitfalls

• Inadequate visualization:

– Perform a thorough subacromial bursectomy.

– Use arthroscopic instrumentation to retract during dissection and suprascapular nerve release.

• Difficulty identifying transverse suprascapular ligament:

– Mark out surface anatomy; use landmarks (anterior border of supraspinatus, coracoclavicular ligaments, coracoid base) starting laterally and follow medially. Localize with spinal needles as needed.

Suprascapular neuropathy is thought to result from compression or tethering of the nerve as it courses under the suprascapular notch (Fig. 27-1). Compression of the suprascapular nerve (SSN) can result from a variety of causes that narrow the notch: supraglenoid cysts, fracture of the scapular notch with resultant callus formation,¹ an enlarged or thickened transverse scapular ligament, hardware from prior surgical interventions, or any space-occupying lesion in the region of the notch.^1–4 Tethering of the nerve results from more dynamic mechanisms: retraction as the result of massive rotator cuff tears, repetitive traction injuries in overhead athletes such as volleyball players and pitchers, and traumatic stretch injuries associated with glenohumeral dislocations or proximal humerus fractures.^5–10 Injuries to the nerve can result in inflammation and swelling of the nerve, causing further compression at the suprascapular notch.

Figure 27-1 Anatomic course of suprascapular nerve under the transverse scapular ligament and spinoglenoid notch. a, artery; n, nerve.

Preoperative Considerations

The diagnosis of suprascapular neuropathy can be challenging, as the presenting symptoms are generally nonspecific. Patients most often describe a deep or dull aching pain in the posterolateral aspect of the dominant shoulder or directly above the supraspinatus fossa.¹¹ Patients may also report weakness, particularly in abduction and external rotation. Symptoms may start immediately after a traumatic injury or may develop slowly over time.^11,12 Chronic conditions may be more common in individuals with substantial overhead demands, whether athletic or work related.

Owing to the nonspecific nature of the patient’s complaints, it is important to perform a complete examination of the neck and shoulder to determine if other conditions (rotator cuff pathology, stiffness, arthritis, acromioclavicular disease, cervical radiculopathy, fractures) are responsible for the patient’s symptoms or are associated with SSN pathology. Accordingly, the surgeon should thoroughly assess (and compare with the uninvolved side) the appearance of the shoulder, range of motion (actively and passively), strength, and distal neurologic function, in addition to performing typical provocative maneuvers.

On physical examination it is important to completely visualize the shoulders from posteriorly to detect associated atrophy of the supraspinatus and infraspinatus fossa. Isolated infraspinatus fossa atrophy suggests that the nerve injury is at the level of the spinoglenoid notch. Weakness in abduction and external rotation may also be evident. Maneuvers attempting to place the SSN under tension may reproduce the patient’s symptoms. Lafosse and colleagues suggest a stretch test that laterally rotates the head away from the involved shoulder while also retracting the shoulder posteriorly.¹³ Cross-body adduction and internal rotation may also reproduce pain by tensioning the spinoglenoid ligament and further tethering the nerve.¹⁴

Imaging is used primarily to assess for the commonly associated conditions mentioned previously, but also to evaluate for space-occupying lesions near the suprascapular or spinoglenoid notch. The degree of atrophy of the supraspinatus and infraspinatus muscles can also be determined with computed tomography (CT) or magnetic resonance imaging (MRI). Additional diagnostic studies include electromyography and nerve conduction velocity tests.9,15 The reliability of these tests is unclear. If the surgeon has a high degree of suspicion for SSN pathology, a fluoroscopically guided injection of anesthetic and cortisone into the suprascapular notch can be performed.

Indications

• Patients with a space-occupying lesion at the suprascapular notch with pain and weakness

• Patients with electromyographic evidence of suprascapular neuropathy

• Patients with a negative electromyogram (EMG) who experience substantial relief of their symptoms with fluoroscopically guided injection of anesthetic and cortisone

• Patients with massive rotator cuff tears with either a positive EMG or relief of their symptoms with fluoroscopically guided injection of anesthetic and cortisone

Contraindications

• Patients with cervical radiculopathy (address underlying spine pathology first)

• Patients with brachial plexitis (follow conservatively until resolution of general inflammation)

• Patients who do not experience any relief of symptoms after fluoroscopically guided injection of anesthetic and cortisone, in the absence of a space-occupying lesion

Surgical Technique

SSN release can be approached arthroscopically or by open technique. We prefer an arthroscopic approach in most cases, as it is minimally invasive, provides excellent visualization, allows for assessment of the subacromial space and glenohumeral joint, and limits associated surgical morbidity. An open approach may be required in settings where visualization is poor arthroscopically owing to scarring or in situations where partial hardware removal is required (e.g., tip of a previously placed glenoid screw).

In either approach, the surgery can be performed with the patient under regional or general anesthesia with or without an interscalene nerve block. The patient is placed in the beach chair position with the involved extremity in an adjustable arm holder.

Open Suprascapular Nerve Release

Specific steps of this procedure are outlined in Box 27-1.

Box 27-1 Surgical Steps

Open Suprascapular Nerve Release

1. Trapezius-splitting exposure to allow for access to the suprascapular notch.

2. Identify bony surface landmarks: scapular spine, lateral acromion, clavicle, coracoid.

3. Locate the suprascapular nerve 4.5 cm medial to the posterior edge of the acromion.

4. Make a longitudinal incision beginning anteriorly over the trapezius and continuing posteriorly over the spine of the scapula.

5. Elevate the trapezius off of the spine of the scapula and off the medial acromion and split longitudinally, curving the incision somewhat anteriorly relative to the acromioclavicular joint.

6. Identify the supraspinatus muscle belly and carefully retract posteriorly. Locate the coracoid base and transverse scapular ligament.

7. Resect the ligament, sharply or with a Kerrison rongeur. On rare occasions the ligament may be ossified and require removal with the use of small osteotomes. Ligament release may not completely free the nerve, necessitating additional bony resection around the notch.

8. Reattach the trapezius to the scapular spine with sutures through bur holes.

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Sep 11, 2016 | Posted by admin in SPORT MEDICINE | Comments Off

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