Deltoid Anterior Supine And Posterior Prone

ANTERIOR DELTOID

Patient: Supine.

Fixation: The trapezius and serratus anterior should stabilize the scapula in all the deltoid tests, but if these muscles are weak, the examiner should stabilize the scapula.

Test: Shoulder abduction in the position of slight flexion and medial rotation. One hand of the examiner is placed under the patient's wrist to make sure that the elbow is not lifted by reverse action of the wrist extensors, which may occur if the patient is allowed to press his or her hand down on the chest.

Pressure: Against the anterior surface of the arm, just above the elbow, in the direction of adduction toward the side of the body.

POSTERIOR DELTOID

Patient: Prone.

Fixation: The scapula must be held stable, either by the scapular muscles or by the examiner.

Test: Horizontal abduction of the shoulder, with slight lateral rotation.

Pressure: Against the posterolateral surface of the arm, in a direction obliquely downward and midway between adduction and horizontal adduction.

PECTORAUS MAJOR, UPPER

Origin of Upper Fibers (Clavicular Portion): Anterior surface of the sternal V2 of the clavicle.

Insertion of Upper Fibers: Crest of greater tubercle of the humerus. Fibers are more anterior and caudal on the crest than the lower fibers.

Action of Upper Fibers: Flex and medially rotate the shoulder joint, and horizontally adduct the humerus toward the opposite shoulder.

Nerve to Upper Fibers: Lateral pectoral, C5, 6, 7.

Action of Muscle as a Whole: With the origin fixed, the pectoralis major adducts and medially rotates the humerus. With the insertion fixed, it may assist in elevating the thorax, as in forced inspiration. In crutch-walking or parallel-bar work, it will assist in supporting the weight of the body.

Patient: Supine.

Fixation: The examiner holds the opposite shoulder firmly on the table. The triceps maintains the elbow in extension.

Test: Starting with the elbow extended and with the shoulder in 90° flexion and slight medial rotation, the humerus is horizontally adducted toward the sternal end of the clavicle.

Pressure: Against the forearm, in the direction of horizontal abduction.

Weakness: Decreases the ability to draw the arm in horizontal adduction across the chest, making it difficult to touch the hand to the opposite shoulder. Decreases the strength of shoulder flexion and medial rotation.

Shortness: The range of motion in horizontal abduction and lateral rotation of the shoulder is decreased. Shortness of the pectoralis major holds the humerus in medial rotation and adduction and, secondarily, results in abduction of the scapula from the spine.

Note: The authors have seen one patient with rupture and another with weakness of the lower part of the pectoralis major resulting from arm wrestling. The arm was in a position of lateral rotation and abduction when a forceful effort was made to medially rotate and adduct it.

PECTORALIS MAJOR, LOWER

Origin of Lower Fibers (Sternocostal Portion): Anterior surface of the sternum, cartilages of first six or seven ribs, and aponeurosis of the external oblique.

Insertion of Lower Fibers: Crest of the greater tubercle of the humerus. The fibers twist on themselves and are more posterior and cranial than the upper fibers.

Action of Lower Fibers: Depress the shoulder girdle by virtue of the attachment on the humerus, and obliquely adduct the humerus toward the opposite iliac crest.

Nerves to Lower Fibers: Lateral and medial pectoral, C6, 7, 8, Tl.

Action of Muscle as a Whole: With the origin fixed, the pectoralis major adducts and medially rotates the humerus. With the insertion fixed, it may assist in elevating the thorax, as in forced inspiration. In crutch-walking or parallel-bar work, it will assist in supporting the weight of the body.

Patient: Supine.

Fixation: The examiner places one hand on opposite iliac crest to hold the pelvis firmly on the table. The anterior parts of the external and internal oblique muscles stabilize the thorax on the pelvis. In cases of abdominal weakness, the thorax, instead of the pelvis, must be stabilized. The triceps maintains the elbow in extension.

Test: Starting with the elbow extended and with the shoulder in flexion and slight medial rotation, adduction of the arm obliquely toward the opposite iliac crest.

Pressure: Against the forearm obliquely, in a lateral and cranial direction.

Weakness: Decreases the strength of adduction obliquely toward the opposite hip. Continuity of muscle action is on the same side also lost from the pectoralis major to the external oblique on the same side and internal oblique on the opposite side, with the result that chopping or striking movements are difficult. From a supine position, if the subject's arm is placed diagonally overhead, it will be difficult to lift the arm from the table. The subject will also have difficulty holding any large or heavy object in both hands either at or near waist level.

Shortness: A forward depression of the shoulder girdle from the pull of the pectoralis major on the humerus often accompanies the pull of a tight pectoralis minor on the scapula. Flexion and abduction ranges of motion overhead are limited.

PECTORALIS MINOR

Origin: Superior margins; outer surfaces of the third, fourth and fifth ribs near the cartilages; and fascia over corresponding intercostal muscles.

Insertion: Medial border, superior surface of the cora-coid process of the scapula.

Action: With the origin fixed, tilts the scapula anteriorly (i.e., rotates the scapula about a coronal axis so that the coracoid process moves anteriorly and caudally while the inferior angle moves posteriorly and medially). With the scapula stabilized, to fix the insertion, the pectoralis minor assists in forced inspiration.

Nerve: Medial pectoral, with fibers from a communicating branch of the lateral pectoral; C(6), 7, 8, Tl. (For explanation, see page 467.)

Patient: Supine.

Fixation: None by the examiner unless the abdominal muscles are weak, in which case the rib cage on the same side should be held down firmly.

Test: Forward thrust of the shoulder, with the arm at the side. The subject must exert no downward pressure on the hand to force the shoulder forward. (If necessary, raise the subject's hand and elbow off the table.)

Pressure: Against the anterior aspect of the shoulder, downward toward the table.

Weakness: Strong extension of the humerus is dependent on fixation of the scapula by the rhomboids and le-vator scapulae posteriorly and by the pectoralis minor anteriorly. With weakness of the pectoralis minor, the strength of arm extension is diminished.

With the scapula stabilized in a position of good alignment, the pectoralis minor acts as an accessory muscle of inspiration. Weakness of this muscle will increase respiratory difficulty in patients already suffering involvement of the respiratory muscles.

Shortness: With the origin of this muscle on the ribs and the insertion on the coracoid process of the scapula, a contracture tends to depress the coracoid process of the scapula both forward and downward. Such muscle contracture is an important contributing factor in many cases of arm pain. With the cords of the brachial plexus and the axillary blood vessels lying between the cora-coid process and the rib cage, contracture of the pec-toralis minor may produce an impingement on these large vessels and nerves.

A contracted pectoralis minor restricts flexion of the shoulder joint by limiting scapular rotation and preventing the glenoid cavity from attaining die cranial orientation necessary for complete flexion of the joint.

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