Shoulder Medial Rotators Group Test

The chief muscles acting in this shoulder medial rotation test are the latissimus dorsi, pectoralis major, subscapu-laris and teres major.

Patient: Supine.

Fixation: The examiner applies counterpressure against the outer aspect of the distal end of the humerus to ensure a rotation motion.

Test: Medial rotation of the humerus, with the arm at the side and the elbow held at a right angle.

Pressure: Using the forearm as a lever, pressure is applied in the direction of laterally rotating the humerus.

Not©: For the purpose of objectively grading a weak medial rotator group against gravity, the test in the prone position (see photo, above right) is I preferred over the test in the supine position. For a maximum strength test, the test in supine position is preferred because less scapular fixation is required.

Patient: Prone.

Fixation: The arm rests on the table. The examiner's hand, near the elbow, cushions against table pressure and stabilizes the humerus to ensure rotation by preventing any adduction or abduction. The rhomboids give fixation of the scapula.

Test: Medial rotation of the humerus, with the elbow held at a right angle.

Pressure: Using the forearm as a lever, pressure is applied in the direction of laterally rotating the humerus.

Weakness: Because the medial rotators are also strong adductors, the ability to perform both medial rotation and adduction is decreased.

Shortness: Range of both shoulder flexion overhead and of lateral rotation are limited.

TERES MAJOR

Origin: Dorsal surfaces of the inferior angle and lower '/3 of the lateral border of the scapula.

Insertion: Crest of the lesser tubercle of the humerus.

Action: Medially rotates, adducts, and extends the shoulder joint.

Nerve: Lower subscapular, C5, 6, Patient: Prone.

Fixation: None usually is necessary, because the weight of the trunk is sufficient fixation. If additional fixation is necessary, however, the opposite shoulder may be held down on the table.

Test: Extension and adduction of the humerus in the medially rotated position, with the hand resting on the posterior iliac crest.

Pressure: Against the arm, above the elbow, in the direction of abduction and flexion.

Weakness: Diminishes the strength of medial rotation as well as adduction and extension of the humerus.

Shortness: Prevents the full range of lateral rotation and abduction of the humerus. With tightness of the teres major, the scapula will begin to rotate laterally almost simultaneously with flexion or abduction. Scapular movements that accompany shoulder flexion and abduction are influenced by the degree of muscle shortness of the teres major and subscapularis.

Subscapuiaris

SUBSCAPULARIS (VENTRAL SURFACE)

Origin: Subscapular fossa of the scapula.

Insertion: Lesser tubercle of the humerus and shoulder joint capsule.

Action: Medially rotates the shoulder joint, and stabilizes the head of the humerus in the glenoid cavity during movements of this joint.

Nerve: Upper and lower subscapular, C5, 6, 7.

Test: (see above)

The illustration above shows the attachments of the latis-simus dorsi to the spine and pelvis, emphasizing the importance of this muscle with regard to its many functions.

LATISSIMUS DORSI

Origin: Spinous processes of last six thoracic vertebrae, last three or four ribs, through the thoracolumbar fascia from the lumbar and sacral vertebrae and posterior % of external lip of iliac crest, and a slip from the inferior angle of the scapula.

Insertion: Intertubercular groove of humerus.

Action: With the origin fixed, medially rotates, adducts and extends the shoulder joint. By continued action, depresses the shoulder girdle and assists in lateral flexion of the trunk. (See p. 185.) With the insertion fixed, assists in tilting the pelvis both anteriorly and laterally. Acting bilaterally, this muscle assists in hyperextend-ing the spine and anteriorly tilting the pelvis or in flexing the spine, depending on its relation to the axes of motion.

Additionally, the latissimus dorsi may act as an accessory muscle of respiration.

See preferred position of forearm on facing page,

Patient: Prone.

Fixation: One hand of the examiner may apply coun-terpressure laterally on pelvis.

Test: Adduction of the arm, with extension, in the medially rotated position.

Pressure: Against the forearm, in the direction of abduction and slight flexion of the arm.

Weakness: Weakness interferes with activities that involve adduction of the arm toward the body or of the body toward the arm. The strength of lateral trunk flexion is diminished.

Note: See facing page regarding shortness oflatis-simus dorsi.

Nerve: Thoracodorsal, CG, 7, 8.

Preferred position for forearm.

Shortness of the latissimus dorsi results in a limitation of elevation of the arm in flexion and abduction, and tends to depress the shoulder girdle downward and forward. In a right C-curve of the spine, the lateral fibers of the left latissimus dorsi usually are shortened. In a marked kyphosis, the anterior fibers are shortened bilaterally. Shortness of this muscle may be found in individuals who have walked with crutches for a prolonged period of time, such as a patient with paraplegia who uses a swing-through gate.

This muscle is important in relation to movements such as climbing, walking with crutches, and hoisting the body on parallel bars, in which the muscles act to lift the body toward the fixed arms. The strength of the latissimus dorsi is a factor in forceful arm movements such as swimming, rowing, and chopping. All adductors and medial rotators act in these strong movements, but the latissimus dorsi may be of major importance.

In the coronal plane, the latissimus dorsi is the most direct opponent of the upper trapezius. Test the strength of the latissimus when a shoulder is elevated (as in cases of tightness of the upper trapezius from holding a telephone receiver on the shoulder). Restoration of the muscle balance may require stretching the trapezius and strengthening the latissimus.

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