Suprascapular nerve decompression

Anatomy

Origin C 4-5 cervical spine roots – Upper trunk of brachial plexus. It passes under Transverse scapular ligament

Innervation . Motor – provides 2 collateral motor branches to innervate the supraspinatus (SSP). It has few sensory branches 

Suprascapular nerve entrapment syndrome (SNES)

Suprascapular nerve entrapment syndrome (SNES) is an often-overlooked etiology of shoulder pain and weakness

Treatment varies depending on the location and etiology of entrapment, which can be described as compressive 

In some cases, treating the primary cause of impingement (ie. rotator cuff tear, ganglion cyst, etc.) is sufficient to relieve pressure on the nerveor traction lesions

In other cases where impingement is caused by dynamic microtrauma (as seen in overhead athletes and laborers), treatment is often more conservative.

Primary SSN entrapment syndrome

Most commonly seen in Overhead athletes

It happens due to Overstretching of the SSN at the suprascapular notch can produce posterior shoulder pain with weakness and atrophy of the supraspinatus and infraspinatus muscles 

Investigations

Hyperintense muscle denervation signals on MRI

Positive electromyography (EMG) and nerve conduction velocity test findings

SSN entrapment in Chronic retracted rotatorcuff tear

Muscle atrophy and fatty infiltration may be produced by the tendon tear, the SSN neuropathy, or both. Risk of SSN elongation due to tension on the nerve and the angle between the nerve and its motor branch at the scapular notch with medial SSP tendon retraction. 3 cm of retraction of the SSP, the motor branch of the SSN was stretched 

^{Ref: Tom J, Mesfin A, Shah P, et al. Anatomical considerations of the suprascapular nerve in rotator cuff repairs. Anat Res Int 2014;2014:674179.}

The real incidence of this situation is undetermined, but it has been reported to be present in 8% to 27% of massive rotator cuff tears 

^{Ref: – Yamakado K. Arthroscopic rotator cuff repair with or without suprascapular nerve decompression in postero-superior massive rotator cuff tears. Int Orthop2019;43: 2367-2373}

The SSN native angle correction by tendon repair can be insufficient, and an SSN release may help to decrease pain and achieve better muscle recovery

^{Ref: Costouros J, Porramatikul M, Lie D, Warner J. Reversal of suprascapular neuropathy following arthroscopic repair of massive supraspinatus and infraspinatus rotator cuff tears.Arthroscopy 2007;23:1152-1161.}  

Clinical presentation

SSP atrophy and ISP atrophy are the most frequent findings, with the addition of external rotation and abduction weakness. The cross-arm adduction test and the suprascapular stretch test described by Lafosse et al. Turning the head to the opposite side and depressing the shoulder, can yield positive findings. 

Investigations

Three-dimensional computed tomography reconstructions show the different shapes or narrowing of the suprascapular bony notch. 

MRI images help to rule out paralabral cysts compressing the SSN. In addition, they often show the hyperintense muscle signals frequently found in denervated muscles. 

EMG – Because the SSN entrapment in sports is a dynamic condition, it is not always seen during the EMG assessment. EMG and nerve conduction velocity tests show between 70% and 90% sensitivity in confirming the diagnosis. 

Suprascapular nerve decompression Technique