Tuesday, November 12, 2013

Rotator Cuff Muscles

Remember them with the mnemonic SITS (Supraspinatus, Infraspinatus, Teres Minor, Subscapularis).
Also remember the "Empty can supraspinatus test" used to evaluate this muscle asking the patient to abduct his/her arm to 90 degrees and flex the arm from that position 30 degrees (horizontally) with thumbs pointing to the floor, then apply downward force to his/her arms. This maneuver will elicit pain and weakness on the affected side due to impingement of the supraspinatus tendon (the most commonly affected structure in Rotator cuff Sd) between the acromion and the head of the humerus.

Nerves and Muscles responsible for abduction of the arm:

• Initiates arm abduction (initial 10 degrees) → Supraspinatus muscle <Suprascapular nerve>
• Abduct arm beyond 10 degrees → Deltoid muscle <Axillary nerve>
• Raise arm above horizontal → Serratus ant & Trapezius muscles <Long thoracic & Spinal acc nerves>

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