Definition
By: Gregory R. Waryasz, MD
The teres minor muscle of the musculoskeletal system is characterized by being the only rotator cuff supplied by the axillary nerve.
It is part of the scapulohumeral muscles and rotator cuff. It consists of skeletal muscle fibers.
Its unique structural features include helping to form the triangular and the quadrangular space. The muscle is long and narrow. It is completely hidden by the deltoid and may not be clearly separated from the infraspinatus, however has a different innervations.
The origin is the middle part of the lateral scapula border.
The insertion is the inferior facet of the greater tubercle of the humerus.
The blood supply is from the posterior circumflex humeral artery and the circumflex scapular arteries and venous drainage is from the accompanying veins.
The innervation is from the axillary nerve.
The teres minor muscle as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in the embryo.
The function of the teres minor is to stabilize the glenohumeral joint and to laterally rotate the humerus. The teres minor supplies 45% of the power for lateral rotation. The teres minor also adducts and extends the arm. It works synergistically with the infraspinatus and subscapularis.
The rotator cuff tendons blend with the joint capsule to help reinforce it. Rotator cuff muscle contraction helps to hold the larger humeral head into the glenoid.
Common diseases include rotator cuff tendinitis, tears, and impingement syndrome. These injuries more commonly affect the supraspinatus component of the rotator cuff.
Impingement syndrome refers to a microtrauma to the rotator cuff due to decreased space between the humeral head and the structures above the rotator cuff. The trauma leads to inflammation, swelling, pain, and decreased rotator cuff function.
Rotator cuff tendinitis is a condition of overuse associated with irritation and swelling of the cuff tendons. It most commonly is the supraspinatus tendon. Patients have pain with moving the shoulder and the pain may awaken them at night.
Rotator cuff tears can be asymptomatic or symptomativ. The prevalence increases with age. The tear can be partial or complete. Pain is worse at night and with overhead activities.
Rotator cuff tear arthropathy is a condition of shoulder arthritis with a rotator cuff tear. Patients may have pain, decreased shoulder range of motion, and significant arthritic changes and damage to the glenohumeral joint.
Quadrilateral space syndrome is a transient blockage of the posterior humeral circumflex artery and axillary nerve when the arm is abducted, extended, and externally rotated. Patients may have shoulder pain and paresthesias with overhead activities. The teres minor may be atrophied with this condition.
Commonly used diagnostic procedures include clinical history, physical exam, and MRI.
It is usually treated with physical therapy and NSAIDs for impingement syndrome and tendinitis. Rotator cuff tears may require arthroscopic repair by a surgeon. Rotator cuff tear arthropathy may require a shoulder joint replacement. Quadrilateral space syndrome may require decompressive surgery.
References
Lieberman J (ed), AAOS Comprehensive Orthopaedic Review, American Academy of Orthopaedic Surgeons, 2008.
Moore K, Dalley A (eds), Clinically Oriented Anatomy (5th edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.
Wheeless’ Textbook of Orthopaedics: Teres Minor (http://www.wheelessonline.com/ortho/teres_minor)