Anatomy of Supraspinatus

Courtesy: Prof Nabile Ebraheim, University of Toledo, Ohio, USA

SUPRASPINATUS is a small muscle that originates from the superior aspect of the scapula and runs from supraspinatus fossa to the greater tuberosity of the humerus.
THE SUPRASPINATUS TENDON inserts into the superior facet of greater tubercle of humerus.
THE SUPRASPINATUS IS ONE OF THE four muscles of the rotator cuff:
1. TERES MINOR
2. INFRASPINATUS
3. SUPRASPINATUS
4. SUBSCAPULARIS
FUNCTION: Supraspinatus assists the deltoid muscle in abduction of the arm. Supraspinatus demonstrates peak activity in late cocking phase of throwing mechanics

INNERVATION:SUPRASCAPULAR NERVE (c5, C6)

• The suprascapular nerve passes under the transverse scapular ligament at the suprascapular notch.
• The transverse scapular artery runs above the transverse scapular ligament.
• The suprascapular nerve gives branches to the supraspinatus muscle and branches to the infraspinatus muscle.
• Nerve compression at the suprascapular notch affects both the supraspinatus and infraspinatus muscles causing decrease in abduction and loss of external rotation.
• Nerve compression at the spinoglenoid notch affects only the infraspinatus muscle causing loss of external rotation.

Dimensions of the supraspinatus tendon:
•Tendon averages 25 mm wide
•Medial to lateral footprint of 12 mm at mid-tendon.

Examination tests:
•Neer impingement test
•Hawkin’s test
•Jobe test

Pathological entities involving the supraspinatus muscle
1. Subacromial impingement
•Most common cause of shoulder pain (first stage of rotator cuff disease)
•Pain with overhead activity and pain at night
•A continuation of the disease that includes tendonitis and tears,
2. Rotator cuff tears
3.Rotator cuff arthropathy
•Massive chronic cuff tear with arthritis
•Collapse of the humeral head
•Pseudoparalysis with escape of the humeral head anteriorly and superiorly.
4.Suprascapular neuropathy
•Ganglion or entrapment of the nerve at the suprascapular notch, it involves both the supraspinatus and infraspinatus muscles.
5.PASTA (Partial articular-sided Supraspinatus tendon Avulsion)
6.Failure of the supraspinatus following total shoulder arthroplasty or hemiarthroplasty
Results in superior escape of the humerus.
Treatment: Repair of the tendon or revision of the prosthesis into reverse total shoulder arthroplasty.
7.Calcific tendonitis
•Calcification of the tendon
•Usually, occurs in the tendons of the shoulder (rotator cuff tendons of the shoulder (rotator cuff tendons causing pain and inflammation).