SUPRASCAPULAR NERVE RELEASE

Suprascapular Nerve Release

William E. Schobert

Suprascapular nerve palsies are an underdiagnosed cause of shoulder pain and rotator cuff dysfunction. Diagnosis of this condition requires identifying supraspinatus and infraspinatus weakness coupled with appropriate electrodiagnostic testing. Nerve compression can be against the transverse scapular ligament at the suprascapular notch or at the spinoglenoid notch. Differentiation between these two sites is accomplished by EMG or nerve conduction velocity evidence of either combined supraspinatus and infraspinatus abnormalities or isolated infraspinatus involvement.

This chapter will discuss surgical release of the nerve at the suprascapular notch. Isolated infraspinatus involvement is felt to be secondary to spinoglenoid notch entrapment; however, I have experienced excellent results to date with releasing the transverse scapular ligament at the suprascapular notch for these patients.

Indications

1. Shoulder pain and dysfunction with weakness of the supraspinatus and/or infraspinatus muscles

2. Positive electrodiagnostic testing

Contraindications

Stretch injuries.

Mechanism of Injury

The mechanism of injury is unknown. Theoretically, the suprascapular nerve migrates superiorly against the transverse scapular ligament with the arm in forward flexion and adduction resulting in a traction injury to the nerve. The neuropathy can be associated with ganglion cysts of the shoulder.

Physical Examination

1. Evidence of impingement style rotator cuff pain.

2. External rotation weakness in the supine position.

3. Abduction weakness at 30 degrees.

4. Atrophy in the infraspinatus fossa.

Diagnostic Tests

1. Standard shoulder X-rays may identify an ossified transverse scapular ligament (usually best seen on the axillary view).

2. Magnetic resonance imaging (MRI) is useful to evaluate for ganglion cysts and other concurrent or associated shoulder pathology.

3. Electrodiagnostic testing is useful to evaluate the supraspinatus and infraspinatus for EMG changes consistent with denervation. Suprascapular nerve conduction testing is performed to evaluate for significant conduction velocity loss between the involved and uninvolved shoulders.

Special Considerations

The transverse scapular ligament and suprascapular notch are located immediately medial to the base of the coracoid. Medially, the transverse scapular ligament becomes confluent with the scapula’s superior margin. With the ligament intact, one can run their finger from the superior scapular margin to the base of the coracoid without dropping into the notch. When the transverse scapular ligament is released, the same maneuver will result in the finger dropping into a distinct notch just medial to the coracoid base. The suprascapular vessels run superiorly over the transverse scapular ligament. The nerve resides in the notch. It then runs across the floor of the supraspinatus fossa sending branches up to the overlying supraspinatus muscle. It passes through the base of the spinoglenoid notch and then arborizes into multiple branches to innervate the infraspinatus.

The procedure is typically performed with concomitant shoulder arthroscopy. This procedure can be performed in the decubitus position with the arm in suspension. Arm abduction during surgery relaxes the trapezius and supraspinatus, facilitating exposure.

Preoperative Planning and Timing of Surgery

Generally, a trial of rest from offending activities and a trial of physical therapy precedes MRI and electrodiagnostic testing. It is important to have patients exercise the rotator cuff and parascapular-scapular stabilizer muscles every other day to allow adequate muscle recovery for these relatively small weak muscles. Throwing athletes have a predisposition to this diagnosis.

Preoperatively, one must know whether a ganglion cystis present by MRI and if the transverse scapular ligament is ossified. If either of these conditions is present, the exposure must be increased. Additional equipment and time will be necessary if bone removal is indicated.

Special Instruments

1. Self-retaining retractors and typical soft tissue instrumentation.

2. A headlight can be used if desired for increased illumination.

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