The Suprascapular Nerve in the Setting of Rotator Cuff Pathology

Introduction

Suprascapular neuropathy can have multiple potential etiologies, though it is typically secondary to traction or compression. It has usually been considered to be a rare cause of shoulder pain and dysfunction, and it was viewed as a diagnosis of exclusion. However, reports have emerged that have demonstrated a predilection for this condition in athletes who engage in high-level overhead activity and in those with a retracted posterior or superior rotator cuff tear, because traction can be applied to the nerve around the suprascapular notch or base of the scapular spine when the rotator cuff tendon moves medially. Vad et al. observed an 8% incidence of suprascapular neuropathy in 25 patients with a massive rotator cuff tear and associated atrophy, whereas Mallon et al. found that 8 patients with a tear >5 cm developed fatty infiltration. Costouros reported that 7 of 26 (38%) patients with a massive rotator cuff tear had an isolated suprascapular nerve injury. Interestingly, all of their patients in whom the rotator cuff was either partially or completely arthroscopically repaired demonstrated partial or full recovery of the nerve palsy, and this correlated with reduced pain and improved function. This was further explored in a proof-of-concept report by the same group. On the basis of this reported experience, some surgeons routinely release the nerve while performing an arthroscopic rotator cuff repair.

Procedure

Both arthroscopic and open techniques of suprascapular nerve decompression have been reported with successful results. The main portals used as well as approaches vary depending on surgeon preference, though the primary aim is always to release the transverse scapular ligament. In the setting of nerve decompression with a concomitant rotator cuff repair, the nerve can be released prior to the repair to minimize swelling and bleeding during the repair that could make the dissection more challenging. A percentage of transverse scapular ligaments will be ossified, so a Stryker (Kalamazoo, MI) notch view or computed tomographic (CT) scan can be helpful in advance of surgery to identify these. In such cases, a small osteotome or Kerrison rongeur may be needed.

Patient History

• Dull, aching pain over the superior or posterolateral shoulder.

• Difficulty with overhead activity, including weakness and fatigue.

• Presence or absence of night pain, which is variably present.

• There may be a history of repetitive overhead activity.

• The patient may have had an acute trauma with a rotator cuff tear or symptoms suggestive of a more chronic tear.

• Pain relief after a local anesthetic injection to the suprascapular notch, if performed under radiographic control.

Patient Examination

• Perform a thorough examination of the cervical spine to rule out radiculopathy.

• Gross inspection for atrophy of the supraspinatus and/or the infraspinatus fossae.

• Full shoulder examination for other pathology, such as biceps pathology, labral conditions, instability, or acromioclavicular pathology (can cause same distribution of pain).

• Detailed assessment of the rotator cuff tendons, particularly for weakness in abduction and external rotation.

• If nerve injury at the suprascapular notch, look for tenderness between the clavicle and scapular spine.

• If nerve injury at the spinoglenoid notch, look for tenderness posterior and deep to the acromioclavicular joint as well as cross-body adduction pain as the spinoglenoid ligament tightens.

• Posterior pain with the suprascapular nerve stretch test: with one hand rotating the head laterally away from the painful shoulder, one hand is used to gently retract the affected shoulder ( Fig. 30.1 ).

  

Imaging

• Radiographic series including the standard views, the suprascapular notch view (15- to 30-degree cephalad tilt of beam), and the Stryker notch view: assess for fracture, dysplasia, tumor, robust callus formation following an injury, or variants of the notch, to identify ossified transverse scapular ligament.

• CT scanning is the gold standard to visualize an ossified transverse scapular ligament.

• Magnetic resonance imaging (MRI) allows visualization of the nerve in the entirety of its course and can detect a soft-tissue tumor or fibrotic lesion exerting a mass effect, and it allows evaluation of the rotator cuff injury and any associated fatty infiltration.

• Notch cysts can be seen on MRI scans, with increased sensitivity with arthrography.

• Ultrasound is very useful as well, and its use for guidance of injections can improve the diagnostic accuracy.

• Electromyography (EMG) and nerve conduction velocity are standard for diagnosis, particularly in those with pain or atrophy and no rotator cuff tear.

• EMG findings suggestive of neuropathy: fibrillations and sharp waves (not required for actual diagnosis).

• Motor conduction velocity findings suggestive of neuropathy: latency from the Erb point to supraspinatus and infraspinatus and increased latency between the two muscles.

• Bilateral studies can be performed for comparison.

• Fluoroscopically guided injection of local anesthetic can improve the diagnostic accuracy as well, though our preference is to use ultrasound.

Treatment Options: Nonoperative and Operative

Surgical Anatomy

Surgical Indications

• Evidence of nerve compression by a mass or a cyst.

• No improvement with shoulder rehabilitation for rotator cuff strengthening and scapular stabilization exercises.

• No improvement with avoidance of activities that exacerbate symptoms, such as overhead activities.

• Any evidence of advanced muscle atrophy or other signs of severe entrapment, in which case surgical intervention is initiated early.

• Failure of conservative management after 6 to 9 months in the absence of advanced muscle atrophy or other signs of severe entrapment.

• If the patient requires operative intervention for a rotator cuff tear or other shoulder pathology.

Surgical Technique Setup