Muscle:Pectoralis Major

Pectoralis major is a large, multi-sectioned muscle of the anterior chest whose trigger points (TrPs) are among the most clinically important sources of chest, breast, and arm pain. Its referred pain patterns closely mimic cardiac ischemia and it has a direct somatovisceral relationship with cardiac arrhythmia. TrPs in this muscle are commonly overlooked as a myofascial source of chest pain that persists long after myocardial infarction.

Anatomy

The pectoralis major consists of multiple overlapping laminae arranged in a playing-card (fan) configuration. It is divided into four sections by origin:

• Clavicular fibers — attach to the clavicle
• Sternal fibers — attach to the sternum
• Costal fibers — attach to the cartilages of the second through sixth or seventh ribs
• Abdominal fibers — attach to the superficial aponeuroses of the obliquus externus abdominis and occasionally to the rectus abdominis

All four sections attach laterally to the crest of the greater tubercle of the humerus (along the lateral lip of the groove for the bicipital tendon) in two layers — a ventral (superficial) layer and a dorsal (deep) layer. The lower sternocostal and abdominal fibers fold upward at the lateral end so that the lowermost fibers have the most proximal humeral attachment. This folding reverses the order of attachment and is essential to understanding the direction of palpable taut bands and the direction of local twitch responses on needle contact.

The subclavius muscle lies beneath the clavicle over the first rib, attaching medially by a short thick tendon to the junction of the first rib with its cartilage and laterally in a groove on the under side of the middle third of the clavicle.

Innervation: The pectoralis major is innervated by the medial and lateral pectoral nerves. The clavicular section is supplied chiefly by spinal segments C5 and C6 (lateral pectoral nerve). The sternal section is innervated mainly by C6 and C7. The costal and abdominal sections are supplied by C8 and T1 through the medial pectoral nerve, which usually pierces the pectoralis minor muscle en route.

Primary actions: When the thorax is fixed, the pectoralis major as a whole adducts and medially rotates the humerus. The upper fibers flex the humerus; the lower fibers depress the shoulder girdle. The clavicular section assists glenohumeral flexion and draws the arm across the chest. The sternal, costal, and abdominal fibers extend (lower) the arm from an elevated position but do not hyperextend. All fibers contribute to adduction, movement across the chest, and medial rotation.

Functional unit: All sections of the pectoralis major contract together during strong adduction, assisted by the teres major and minor, anterior and posterior deltoid, subscapularis, and long head of the triceps. For protraction of the shoulder, the serratus anterior, pectoralis minor, and subclavius assist. The clavicular section and the anterior deltoid work very closely together and are separated only by the groove of the cephalic vein. The major antagonists to the sternal section are the rhomboids and middle trapezius.

Referred Pain Patterns

This muscle is likely to develop TrPs in five areas, each with a distinctive pain reference pattern. Pain and tenderness are referred unilaterally.

Clavicular section TrPs refer pain over the anterior deltoid muscle and locally to the clavicular section itself.

Intermediate sternal section TrPs (three central TrP locations in the midfiber region) refer intense pain to the anterior chest — to the precordium if on the left side — and down the inner aspect of the arm. The arm pain accents the medial epicondyle. When sufficiently active, these TrPs also refer pain to the volar aspect of the forearm and ulnar side of the hand, including the last two or two-and-a-half digits (more than those innervated by the ulnar nerve alone). The uppermost of these sternal TrPs lies at the three-way overlap of the clavicular, manubrial, and sternal sections and the underlying pectoralis minor; TrPs occur frequently in both muscles at this location.

Medial sternal section TrPs refer pain locally and over the sternum without crossing the midline.

Costal and abdominal section TrPs develop in two pectoral regions along the lateral free margin of the muscle. These border TrPs cause breast tenderness with hypersensitivity of the nipple, intolerance to clothing, and often breast pain.

Cardiac arrhythmia TrP: A TrP associated with somatovisceral cardiac arrhythmias is located on the right side between the fifth and sixth ribs, just below the point where the lower border of the fifth rib crosses a vertical line midway between the sternal margin and the nipple line. This TrP has been observed only on the right side, except in situs inversus. The spot tenderness of this TrP is associated with ectopic cardiac rhythms but not with any pain complaint. Inactivation of this TrP promptly restores normal sinus rhythm when it is contributing to ectopic supraventricular rhythm.

Subclavius TrPs refer pain across the front of the shoulder and down the front of the arm along the radial side of the forearm, skipping the elbow and wrist to reappear on the radial half of the hand. The dorsal and volar aspects of the thumb, the index finger, and the middle finger may also hurt.

Activation and Perpetuating Factors

Pectoralis major TrPs are activated and perpetuated by a round-shouldered posture, as this produces sustained shortening of the pectoral muscles. Activation is likely to occur during prolonged sitting, reading, and writing, and when standing with a slouched, flat-chested posture. Conversely, TrP shortening in this muscle can induce such posture.

TrPs may be initiated or reactivated by: heavy lifting (especially reaching out in front), overuse of arm adduction (manual hedge clippers), sustained lifting in a fixed position (power saw), immobilisation of the arm in the adducted position (arm in a sling or cast), sustained high levels of anxiety, or exposure of fatigued muscles to cold air.

In acute myocardial infarction, pain is commonly referred from the heart to the midregion of the pectoralis major and minor muscles. The injury to heart muscle initiates a viscerosomatic process that activates TrPs in the pectoral muscles. Following recovery from the acute infarction, these self-perpetuating TrPs tend to persist in the chest wall unless specifically inactivated.

Shortening of the subclavius muscle due to TrPs can contribute to symptoms of a vascular thoracic outlet syndrome by drawing the clavicle down toward the subclavian artery and vein as they pass over the first rib.

Clinical Examination

The patient should be observed initially for a stooped, round-shouldered, head-forward posture and weak interscapular muscles. Observing from the rear, the examiner may see abducted scapulae.

TrPs in the pectoralis major cause minimal restriction of motion at the shoulder when it is involved alone, as shown by the Hand-to-Shoulder-Blade Test. The myofascial TrPs of the pectoral muscles do restrict scapular adduction, which can be tested by having the patient place the back of the ipsilateral hand on the hip and move the elbow posteriorly for range of backward movement. Bilateral comparison is the most sensitive indicator of restriction if muscle involvement is unilateral. Production of interscapular pain is another indicator of restriction.

Weakness of the clavicular and sternal portions for adduction at the glenohumeral joint is tested with the patient supine, the arm held straight up in the air, and the opposite shoulder stabilised against the table. The costal and abdominal sections can be similarly tested by resisting the patient's attempt to adduct the elevated arm obliquely downward toward the contralateral iliac crest.

When a patient complains of breast soreness (referred tenderness), a feeling of congestion in that breast may also be described. The breast may be slightly enlarged and feel doughy — signs of impaired lymph drainage, possibly due to entrapment or reflex inhibition of peristalsis of the lymphatic vessels, which disappear after inactivation of the responsible TrPs in the lateral border of the pectoralis major.

The diagnosis of angina pectoris is sometimes made clinically when there is no definite evidence that the chest pain is due to myocardial ischaemia. In many such patients, one can demonstrate that the pain is referred from TrPs in the pectoralis major muscle.

Cardiac Origin: Distinguishing Features

A definite diagnosis of active myofascial TrPs based on their characteristic signs and symptoms and a dramatic response to local treatment does NOT exclude cardiac disease. A disorder of the heart may coexist and must be ruled out by appropriate tests of cardiac function.

Myofascial TrP pain shows a much wider variability in its response to activity from day to day than does the more consistent exercise response of angina pectoris. Relief of pain by a vapocoolant spray or by local injection cannot be used diagnostically to exclude myocardial ischaemia as a cause of the pain. The cardiac status should be known in every patient who experiences relief of chest pain by these simple measures.

Complaints of circumscribed areas of unilateral parasternal pain should arouse suspicion of parasternal TrPs in the pectoralis major muscle.

Somatovisceral and Viscerosomatic Effects

A common example of a somatovisceral response is found in the patient who experiences episodes of supraventricular tachycardia, supraventricular premature contractions, or ventricular premature contractions without other evidence of heart disease. The patient with such an ectopic rhythm should be checked for an active TrP in the right pectoral region between the fifth and sixth ribs at the specific cardiac arrhythmia site.

A myofascial viscerosomatic interaction begins with coronary artery insufficiency or other intrathoracic disease that refers pain from these visceral structures to the anterior chest wall. As a result, satellite TrPs develop in the somatic pectoral muscles. Among 72 patients with cardiac disease, 61% had tender TrPs in the chest muscles.

Trigger Point Examination

Most TrPs found in the clavicular section and all TrPs in the parasternal section are identified by flat palpation. TrPs in the intermediate and lateral parts of the sternal and costal sections are best located by pincer palpation with the muscle placed on moderate tension by abducting the arm to approximately 90°. Pressure on the tender spot should produce sensations recognised by the patient as recently experienced symptoms. Local twitch responses may be elicited.

To find the cardiac arrhythmia TrP, the tip of the xiphoid process is first located. Then, at this level on the right side, in a vertical line midway between the sternal border and the nipple line, the region of the hollow between the fifth and sixth ribs is examined for a tender spot. This TrP is found by pressing upward against the inferior edge of the fifth rib and exploring for spot tenderness.

For the subclavius muscle, since it must be palpated through the clavicular division of the pectoralis major, the relaxed patient's arm is placed in adduction and medial rotation. The examiner can palpate subclavius central TrPs at the lateral portion of the medial third of the clavicle by rolling the thumb underneath the clavicle, deep into the recess and across the tense fibres. One should distinguish the attachment TrP (ATrP) tenderness just lateral to and below the costoclavicular joint from the central TrP tenderness found closer to midclavicle.

Entrapment

No direct nerve entrapments by the pectoralis major have been confirmed. However, shortening of the subclavius muscle due to TrPs will draw the clavicle down toward the subclavian artery and vein as they pass over the first rib, which can at least contribute to, if not cause, entrapment and the symptoms of a vascular thoracic outlet syndrome.

Lymphatic drainage from the breast usually travels in front of and around the pectoralis major muscle to the axillary lymph nodes. Entrapment of this lymph duct by passage between tense fibres of an involved pectoralis major muscle may cause oedema of the breast. In these patients with TrPs, the signs of entrapped lymphatic drainage and breast tenderness are relieved by inactivation of the related pectoralis major TrPs.

Differential Diagnosis

Condition	Distinguishing features
Angina pectoris / cardiac ischaemia	Must always be excluded; myofascial TrP pain shows wider day-to-day variability in response to activity than consistent exercise-triggered angina; relief by vapocoolant or local injection does NOT rule out cardiac origin; cardiac status must be established
Myocardial infarction — persistent chest pain	Chest pain persisting long after MI is often due to myofascial TrPs activated viscerosomatic ally; these TrPs persist in the chest wall until specifically inactivated
Pectoralis minor TrPs	Similar referred pain pattern and close anatomical relationship; the same muscles commonly associated with pectoralis major involvement are likely to also harbour pectoralis minor TrPs; the two are frequently active simultaneously
Scalene TrPs	Also refer pain to the pectoral region; considered when chest and arm pain pattern matches but pectoral TrPs are absent or insufficient to explain the full pattern
Bicipital tendinitis, supraspinatus tendinitis, subacromial bursitis, medial epicondylitis, lateral epicondylitis	These and C5–C6, C7, C8 radiculopathy, intercostal neuritis, irritation of bronchi/pleura/oesophagus, hiatal hernia with reflux, distension of stomach by gas, mediastinal emphysema, gaseous distension of splenic flexure of colon, and lung cancer are differential diagnoses to consider for chest pain and tenderness
Chest wall syndrome / Tietze's syndrome / costochondritis / hypersensitive xiphoid syndrome / slipping rib syndrome / rib-tip syndrome	Each patient should be carefully examined to determine if symptoms are partially or entirely due to myofascial referred pain and tenderness, especially from pectoralis major TrPs; each of these conditions has been reported as sometimes relieved by injection of the tender area with a local anaesthetic
Fibromyalgia	Tender points consistent with fibromyalgia syndrome occur directly over the sternocostal junction of the second rib

Treatment

Trigger Point Release

Correction of round-shouldered posture and maintenance of good dynamic posture are essential for lasting relief. In addition to spray-and-stretch, other techniques including trigger point pressure release, postisometric relaxation, and contract-relax are effective for release of central TrPs in the pectoralis major. The primary therapeutic approach to attachment TrPs is to inactivate the central TrPs causing them.

For spray and stretch, all sections of the pectoralis major are usually more effectively stretched with the patient seated than supine, as the seated position permits greater motion of both the scapula and arm. The muscle must be effectively stretched across three articulations (sternoclavicular, acromioclavicular, and glenohumeral). Traction is applied to the arm as part of the stretch.

For the clavicular section, the arm is laterally rotated and horizontally extended (abducted) slightly below 90° at the shoulder to fully take up the slack in the clavicular fibres. Vapocoolant spray is swept laterally from the clavicle across the muscle and then over the shoulder and upper limb to cover the referred pain pattern.

For the intermediate sternal fibres, the arm is placed at approximately 90° of abduction, then laterally rotated and moved slowly toward the back into extension. Parallel sweeps of vapocoolant are directed laterally and upward across the sternal portion of the muscle, starting at the sternum and continuing over the upper limb to cover all referred pain patterns.

For the lowest costal section, the arm is flexed at the shoulder while held in lateral rotation. When there is no more slack, sweeps of spray or icing are directed downward and medially from the humerus over the passively stretched fibres, also covering the tender breast.

Latent TrPs of the antagonistic rhomboid and middle trapezius muscles can be activated by unaccustomed shortening during stretch of the pectoralis major. These interscapular muscles should be released by vapocooling and non-stretch procedures followed by strengthening exercises.

Residual TrPs (including those in the subclavius) can usually be inactivated by trigger point pressure release or by injection with 0.5% procaine solution, followed by brief stretch and spray and then moist heat. Three slow cycles of full active range of motion follow immediately after TrP injection; this activity "re-educates" the muscle in its normal range of motion.

Arrhythmia Trigger Points

Before attempting to inactivate the arrhythmia TrP itself, it is best to inactivate all of the sternal division TrPs first. The arrhythmia TrP and the parasternal TrPs require repeated application of trigger point pressure release, stripping massage, and, as a last resort, local anaesthetic injection. The patient with arrhythmias should be taught the self-application of trigger point pressure release using the thumb of one hand on top of the finger of the other hand to reinforce it, increasing pressure directed onto the tender TrP against the rib for a minute or more. Some patients can learn to abort a paroxysmal ectopic tachycardia as soon as the attack is recognised.

Trigger Point Injection

The patient lies supine for all injections of TrPs in the pectoralis major.

Clavicular section: Using flat palpation, the clinician localises these TrPs between the fingers for injection. The needle is aimed cephalad and nearly tangent with the chest wall.

Upper sternal section: TrPs are usually located by flat palpation and injected in the region of the uppermost X. In patients with highly mobile subcutaneous tissue, active TrPs in the upper and midsternal sections may be reached using pincer palpation by inserting the fingers between the underside of the pectoralis major and the chest wall.

Mid- and lower-sternal sections: TrPs are injected with a 37mm (1.5 in) needle directed upward toward the coracoid process, nearly parallel to the thoracic cage. The needle is not directed nearly tangent to the chest wall — beware of entering the pleura.

Costal section: The muscle is grasped between the thumb and fingers of one hand so that the TrPs can be precisely injected by palpating and localising the TrP between the fingers. The needle may be directed perpendicularly to the skin so it can reach a cluster of TrPs in the middle or on the far side of the fold.

Cardiac arrhythmia TrP: After locating the precise spot tenderness by flat palpation, the needle is directed cephalad toward the fifth rib. The needle is aimed nearly tangential to the skin, since the TrP lies no deeper than the anterior surface of the lower border of the rib.

For all parts of the pectoralis major, TrP injection is followed by 3 slow cycles of full active range of motion.

Corrective Actions

Patients who have no demonstrable evidence of heart disease but who suffer from chest pain that they understood to be of cardiac origin need patient education: by demonstrating to these patients that the kind and distribution of their pain is reproduced by pressure on the TrPs and by demonstrating local twitch responses, the patients are convinced that the pain is indeed myofascial and not life-threatening cardiac in origin.

Good static and dynamic posture must be learned and maintained. The In-doorway Stretch Exercise is useful to stretch all the adductors and medial rotators at the shoulders. The patient stands in a narrow doorway with the forearms flat against the door facings to anchor the forearms, and steps forward through the doorway to stretch the muscles. The patient does NOT grasp the doorjamb. The hand position against the doorjamb is adjusted to apply the stretch to different taut bands: fibres of the clavicular section are stretched best in the lower hand-position; by raising the hands to the middle hand-position with the upper arms horizontal, the sternal section is stretched; moving the hands as high as possible while keeping the forearms against the doorjambs stretches the costal and more vertical abdominal fibres that form the lateral margin of the muscle.

When sleeping, the patient must avoid shortening the pectoralis major — the arms should not be folded across the chest. The corner of the pillow should be tucked between the head and shoulder to drop the shoulder backward. When lying on the pain-free side, the uppermost forearm should be supported on a pillow to prevent the arm from dropping forward and thus shortening the affected pectoralis major. When lying on the affected side, the pillow fits in the axilla between the arm and chest to maintain some degree of pectoralis major stretch.

Patients with large heavy breasts commonly have bras that exert constricting pressure around the chest that makes deep indentations in the skin, which can aggravate and perpetuate pectoralis major TrPs. The tension around the chest must be eased either by adding a bra extender between the hooks or by releasing some of the elasticity built into the bra by using a hot iron.

Satellite Trigger Points

• Pectoralis minor — one rarely finds active TrPs in the pectoralis minor without active TrPs in the pectoralis major; the same muscles commonly associated with pectoralis major involvement also harbour pectoralis minor TrPs
• Anterior deltoid — especially likely to develop satellite TrPs as it lies within the pain reference zone of the pectoralis major; closely associated functionally
• Scalene muscles — active TrPs in the scalenes refer pain to the pectoral region; pectoralis major TrPs may develop as satellites
• Subscapularis and latissimus dorsi — also part of the synergistic functional unit; may develop active TrPs before long
• Rhomboids and middle trapezius (antagonists) — can develop latent TrPs activated by unaccustomed shortening during stretch of the pectoralis major

Related Pages

• Pain:Ear and TMJ — pain algorithm for head and neck
• Muscle:Pectoralis Minor — intimately co-active muscle
• Muscle:Scalene — satellite and functional unit overlap
• Muscle:Sternalis — overlying anomalous muscle; satellite TrPs from lower sternal SCM division refer downward over sternum

References

• Travell JG, Simons DG. Myofascial Pain and Dysfunction: The Trigger Point Manual, Volume 1: The Upper Half of Body. 2nd ed. Baltimore: Williams & Wilkins; 1999. Chapter 42.