Pectoralis muscle and tendon injuries

INTRODUCTION — Injuries to the pectoralis muscle are relatively uncommon but may occur in athletes and active adults. While activities of daily living can be performed without an intact pectoralis major muscle, heavy labor and many sporting activities require full function. Injuries are suspected based on history and examination, but advanced imaging is often necessary to determine the extent of injury and need for surgical referral.

The clinical presentation, diagnosis, and management of pectoralis muscle and tendon injuries are reviewed here. The discussion focuses primarily on complete tears of the pectoralis major insertion at the proximal humerus. Although relatively uncommon, this pectoralis injury is the one most often seen by clinicians. Other injuries of the shoulder, chest, and torso are discussed separately:

●Shoulder (see "Evaluation of the adult with shoulder complaints" and "Biceps tendinopathy and tendon rupture" and "Shoulder dislocation and reduction" and "Presentation and diagnosis of rotator cuff tears")

●Chest and back trauma (see "Initial evaluation and management of blunt thoracic trauma in adults" and "Initial evaluation and management of penetrating thoracic trauma in adults")

●Fractures (see "Proximal humeral fractures in adults" and "Clavicle fractures" and "Initial evaluation and management of rib fractures")

ANATOMY AND BIOMECHANICS — The pectoralis major muscle has a broad origin consisting principally of clavicular and sternal contributions. The sternal head is multisegmented and originates from the sternum and first through sixth ribs (figure 1). The clavicular head originates from the medial aspect of the clavicle. The heads fuse together at the myotendinous junction to form the bilaminar common tendinous insertion on the humerus. The humeral attachment is just lateral to the bicipital groove, with the anterior tendon layer receiving contributions from the clavicular head and the superior sternal segments. The posterior tendon is made up of the two to three most inferior segments and extends approximately 1 cm proximally.

The clavicular head contributes mainly to forward shoulder flexion, along with the anterior deltoid, and contributes to internal rotation. The sternal head is responsible primarily for internal rotation and adduction.

The pectoralis minor muscle originates from the costal cartilages of the third, fourth, and fifth ribs and inserts at the medial border and superior surface of the coracoid process. Its primary action is stabilization of the scapula during shoulder motion by drawing the scapula anterior and inferior against the chest wall. It can also act as a secondary muscle of respiration by assisting in elevation of its rib attachments.

The pectoralis major muscle is innervated by the medial and lateral pectoral nerves, which branch from the medial and lateral cords of the brachial plexus. The medial pectoral nerve originates from the C8-T1 roots and innervates the lower portion of the pectoralis major and the pectoralis minor. The lateral pectoral nerve originates from the C5-C7 roots, primarily innervates the upper and midportions of the pectoralis major muscle, and occasionally contributes to pectoralis minor innervation.

The arterial supply for the pectoralis muscles is divided amongst the pectoral branch of the thoracolumbar artery, the major contributor, and the anterior intercostal perforating branches of the internal mammary artery, along with the lateral thoracic artery.

EPIDEMIOLOGY, MECHANISM, AND RISK FACTORS — The great majority of pectoralis injuries involve the pectoralis major, while pectoralis minor injuries are rare. Pectoralis major injuries, particularly tendon ruptures, were traditionally described as work related in most early literature. Over the last several decades, the majority have been sports related [1-3]. Injuries have also been described in military populations [4,5]. While the true incidence is unknown, rates of 0.5 per 10,000 athletic exposures in professional baseball to 1.1 injuries per year in professional Australian rules football have been reported [3,6].

The most common mechanism for complete tear of the pectoralis major is a heavy eccentric contraction, such as occurs during a bench press when the weight is being lowered to the chest wall (picture 1) [1,2,5]. Other mechanisms described in tackling sports include horizontal hyperextension, hyperflexion-abduction, and horizontal adduction of the shoulder against forceful resistance. In the military, pectoralis major injuries have been described during parachute operations when personnel are holding a line and the arm is forced into hyperabduction-external rotation [4,6]. Among older adults, abrupt force applied to the muscle during transfer (eg, from bed to chair) may contribute [7].

Pectoralis major injuries are most commonly seen in males [1,2]. There are multiple reports of the injury in bodybuilders and others taking anabolic steroids. Additional risk factors may include nicotine use and recent treatment with fluoroquinolone antibiotics [2].

Injuries may occur at the tendon insertion, at the myotendinous junction, or within the muscle body. Tears at the tendon insertion on the proximal humerus are most common, but injuries at the myotendinous junction may occur more frequently in younger populations [2,5].

An injury classification system has been proposed based on location, extent of the injury, and acuity [1]. While this scheme may be helpful from a descriptive standpoint, it lacks sufficient evidence to help guide treatment.

Pectoralis minor injuries are uncommon but have been reported in contact sports and with noncontact stabilization exercises [8]. The incidence and associated risk factors are not known.

CLINICAL PRESENTATION AND EXAMINATION — The presentation of pectoralis injuries varies depending upon severity and acuity. In nearly all cases of acute, severe tears, patients describe feeling a pop or tearing sensation along the anterior chest wall of the affected side [1,2]. Early evaluation of both pectoralis major and minor tears typically reveals tenderness at the tear site. With complete or large partial tears, swelling and ecchymosis around the anterior shoulder and chest wall are often present and may obscure the extent of the injury [2].

Soon after a muscle or tendon tear, pain may limit the physical examination. Notable findings include loss of the anterior axillary fold in patients with a complete pectoralis major tear [1,2]. In addition, complete tears often cause the nipple on the affected side to lie more inferiorly compared with the uninjured side ("dropped nipple sign"). Having the patient bring their shoulders to 90 degrees abduction with external rotation may accentuate the deformity of the axillary fold and make it easier to palpate for the pectoralis major tendon [1]. A simple way to do this is to have the patient raise their hands to their hips with their elbows angled posteriorly (pointing backward). If the tendon is torn and retracted, it will not be palpable. Resisted shoulder internal rotation accentuates the deformity of the axillary fold and produces dimpling of the skin and deformity of the anterior chest wall. This can be performed with the shoulders in neutral position or slightly forward flexed and internally rotated with the palms together ("hand prayer" or "namaste" position).

Partial tears, subacute injuries, and injuries in patients with a good deal of adipose tissue in the chest wall pose diagnostic challenges. In such cases, diagnostic imaging, close follow-up, or orthopedic referral is important to avoid missing complete tears. (See 'Diagnostic imaging' below and 'Indications for orthopedic consult or referral' below.)

The contour of the axillary fold is usually preserved with partial tears of the pectoralis major, but there is some deformity of the muscle along the anterior chest wall. In chronic cases of complete or partial tear, the investing fascia of the pectoralis major muscle may hypertrophy, creating a cord along the axillary fold that may be mistaken for residual tendon.

The Pectoralis Major Index (PMI) and the cruciform test may aid in the diagnosis of pectoralis major tears [9,10]. To measure the PMI, the patient assumes the "military press" position (shoulders in 90 degrees of both abduction and external rotation). In this position, the distance along a straight line between the nipples and the most laterally prominent apex of the anterior axillary fold are measured. The PMI equals the ratio between the distance of the injured side and the distance of the uninjured side. In an observational study of 50 patients (19 with complete pectoralis tears), a threshold PMI of <0.9 yielded a sensitivity and specificity of 79 and 98 percent, respectively [10].

The cruciform test is performed with the patient supine, the arms abducted to 90 degrees, and the elbows extended [9]. From this position, the patient is asked to adduct their arms toward the midline (ie, middle of chest). Inability to lift the arms or weakness while doing so is considered a positive test. Further study is needed to determine the accuracy and utility of the cruciform test, and it should not be relied on to rule out the diagnosis when clinical suspicion is high.

Pectoralis minor injuries present with pain and swelling along the anterior chest wall [8]. Numbness and tingling have been reported, presumably due to the proximity of the brachial plexus. Examination may reveal tenderness at the coracoid process and pain with scapular protraction.

DIAGNOSTIC IMAGING — As early examination of severe pectoralis injuries can be difficult, imaging is often important for determining the type and extent of injury. If urgent orthopedic referral is available, this may be obtained in lieu of immediate imaging, as some surgeons may be comfortable using their clinical examination to determine whether surgical intervention is necessary [1]. If there is any doubt, it is often helpful to discuss the case with the consulting orthopedic surgeon. Clinicians skilled with ultrasound frequently perform an examination when pectoralis major tear is suspected.

Plain radiographs — Plain radiographs of the shoulder cannot diagnose pectoralis injuries but can be helpful in ruling out other injuries, such as fractures around the shoulder, particularly in the setting of direct trauma, such as tackling in contact sports. Radiographs in patients with a complete pectoralis major tear may show loss of the pectoralis major shadow and soft tissue swelling but should not be relied upon to determine the extent of injury [1].

Magnetic resonance imaging — Magnetic resonance imaging (MRI) is the modality of choice in most cases of suspected complete tear of the pectoralis major [1,2,11]. MRI should be ordered as a targeted chest sequence from the quadrilateral space to the deltoid in the cranial-to-caudal direction. Communication with the radiologist and/or MRI technicians prior to ordering is helpful for ensuring the proper sequencing is performed.

MRI is reported to have greater than 90 percent sensitivity for pectoralis major tears overall and 100 percent sensitivity for complete tears involving both the sternal and clavicular heads (image 1) [12]. MRI is less sensitive for incomplete injuries and myotendinous injuries, with reported sensitivities around 75 percent [13]. Other associated findings, seen most often with traction-type injuries, may include displacement of the long head of the biceps tendon and injuries to the short head of the biceps, deltoid, coracobrachialis, and subscapularis muscles [1,4].

Ultrasound — Ultrasound examination can be useful as both heads of the pectoralis major insertion can be seen in normal circumstances [1,11,14]. While the sensitivity and specificity of ultrasound for diagnosing pectoralis major injuries has yet to be determined, we have found it to be a useful diagnostic tool when interpreted in the context of information gained from the history and physical examination (image 2). (See "Musculoskeletal ultrasound of the shoulder", section on 'Miscellaneous disorders'.)

DIAGNOSIS — Preliminary diagnosis of pectoralis major and minor muscle and tendon injuries is based upon the history and physical examination. Diagnosis of a complete pectoralis major tear can generally be established based upon the clinical presentation, including loss of the normal pectoralis contours, and the absence of the pectoralis tendon insertion on ultrasound examination. Definitive diagnosis, when necessary, is made by advanced imaging, with MRI the preferred modality.

DIFFERENTIAL DIAGNOSIS — The injuries for which pectoralis tears are most often mistaken include rotator cuff injuries and fracture of the proximal humerus.

Rotator cuff injury — Acute rotator cuff tears may involve a mechanism similar to that causing pectoralis injuries. Bruising and swelling of the anterior shoulder and chest wall may also occur. However, the pain associated with rotator cuff injuries is typically more lateral around the shoulder, and weakness of the rotator cuff muscles is notable with testing. Conversely, active shoulder motion and rotator cuff strength, in particular abduction and external rotation, are generally preserved in patients with pectorals muscle injuries. Diagnostic difficulty may stem from acute pain limiting the shoulder examination. Ultrasound evaluation may be useful in such circumstances. (See "Physical examination of the shoulder", section on 'Examination for rotator cuff pathology' and "Musculoskeletal ultrasound of the shoulder".)

Proximal humerus fracture — Fractures of the proximal humerus occur following direct trauma to the upper arm and typically present with pain at the shoulder. Swelling and ecchymosis of the anterior chest wall are often present, particularly in the subacute period when gravity causes blood to move from the shoulder into the arm and chest wall. Swelling is usually localized to the shoulder area, normal contours of the pectoralis muscle are maintained, and plain radiographs reveal the fracture. In contrast, a pectoralis major tear typically occurs from indirect trauma (often an eccentric load), a complete tear results in loss of the normal pectoralis contours, and no fracture is seen on radiograph.

INDICATIONS FOR ORTHOPEDIC CONSULT OR REFERRAL — Nearly all patients with suspected pectoralis major injuries that may entail a complete tear should be referred for orthopedic evaluation. The patient should be seen by the orthopedist within about two weeks of the injury, as repair becomes more difficult over time. The primary exceptions are patients with partial intramuscular injuries and patients who are not surgical candidates.

Surgical outcomes — While randomized controlled trials are lacking, multiple observational studies report improved functional outcomes with surgical treatment of complete pectoralis major tendon tears [1,2,15]. A systematic review of 23 studies involving 664 injuries reported substantially better outcomes in function, strength, and appearance among patients treated with surgical repair [15]. The rerupture rate in this study was 3 percent.

A notable exception to these results was in sedentary, older adult patients. As one example, in a study of 13 older adults (median age 86), all patients were pain free and had regained their preinjury function within six months without surgery [7]. The mechanism of injury in these cases is thought to be indirect, caused by an abrupt force applied to the muscle during transfers or repositioning. Two patients required transfusion due to blood loss. The author proposes that this may be a more frequent injury than currently recognized.

INITIAL MANAGEMENT — Patients with a possible pectoralis injury stemming from direct trauma (eg, hard tackle during a sporting event) may have sustained other significant injuries and should be evaluated carefully. If internal injury is suspected, transfer to the emergency department is prudent. (See "Initial management of trauma in adults".)

Early treatment of pectoralis injuries consists of pain management and early mobilization as pain allows [16]. Occasionally, a sling may be used if needed to limit arm motion and thereby reduce pain. If needed, immobilization should be limited to as short a period as possible. Relative rest and ice can be helpful in limiting swelling and bleeding. Ice may be applied for 15 to 20 minutes every one to two hours for the first few days after the injury. Pain management may include nonsteroidal anti-inflammatory medications (NSAIDs) and acetaminophen. NSAIDs appear to be safe and are unlikely to cause excessive bleeding or impaired tissue healing if used for up to five to seven days. Early passive and active assisted range of motion exercises can be started as soon as pain allows. (See "Nonselective NSAIDs: Overview of adverse effects", section on 'Healing of musculoskeletal injury'.)

There are case reports describing adjunctive treatments such as orthobiologics (eg, platelet-rich plasma) in the treatment of pectoralis injuries [17,18]. More research is needed to determine whether these treatments are effective and have a role in the treatment of partial pectoralis tears. The use of orthobiologics for musculoskeletal injury is discussed separately. (See "Biologic therapies for tendon and muscle injury".)

FOLLOW-UP — Viable surgical candidates with possible complete pectoralis tears should be referred to an orthopedic surgeon. (See 'Indications for orthopedic consult or referral' above.)

Patients with less severe, incomplete tears and those who are not surgical candidates are treated with physical therapy as appropriate. Early rehabilitation is focused on regaining mobility. As both the pectoralis major and pectoralis minor play a role in shoulder stabilization, subsequent stages of rehabilitation focus on scapular stabilization followed by rotator cuff and general strengthening. Progression of exercises should be gradual as pain allows. (See "Rehabilitation principles and practice for shoulder impingement and related problems".)

Patients participating in rehabilitation for partial tears may require up to six months to regain full function. Gradual improvement is expected during this period. Patients whose function and strength do not improve at all over the initial four to six weeks of physical therapy or whose progress plateaus should be re-evaluated, in part to determine if unrecognized injuries or conditions may be at play.

COMPLICATIONS — Unrecognized complete tears in patients who are viable surgical candidates may lead to inoperable lesions or more complex surgeries with suboptimal outcomes. Complications of nonsurgical treatment include persistent weakness and anterior shoulder instability. The rerupture rate among patients treated surgically is approximately 3 percent [15].

RETURN TO SPORT OR WORK — Return to sport and heavy labor is achieved gradually. For surgically repaired injuries, regaining full mobility and function may take six months or longer, as initial immobilization of up to six weeks is standard. For injuries managed nonoperatively, there are no evidence-based criteria to guide rehabilitation. Clinicians should follow fundamental rehabilitation principles, including relative rest to allow for healing of partial injuries, followed by appropriate physical therapy. In all patients but sedentary older adults, complete tears managed nonoperatively result in significant residual weakness. Rehabilitation in such cases should include physical therapy to strengthen compensatory muscle-tendon units in order to provide some accommodation for these deficiencies.

PREVENTION — To our knowledge, no formal studies assessing measures to prevent acute pectoralis muscle injuries have been published. A thorough warm-up and appropriate progressions in weight or resistance are recommended as good practice for strength training participants, but it is not clear if these reduce the risk of pectoralis muscle injuries. Caregivers should always use caution when transferring patients who require full or partial assistance, as sudden force exerted by the pectoralis muscles may contribute to injury in older adults.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Shoulder soft tissue injuries (including rotator cuff)".)

SUMMARY AND RECOMMENDATIONS

●Anatomy and biomechanics – The pectoralis major and minor aid in shoulder forward flexion, internal rotation, and adduction and assist with shoulder stabilization. Basic shoulder function is maintained with complete pectoralis tears, but strength is significantly compromised without repair. (See 'Anatomy and biomechanics' above.)

●Epidemiology and mechanism – Injuries of the pectoralis are uncommon overall, but most involve the pectoralis major. Forceful, eccentric contraction is the most common mechanism. A large portion occur in young males while performing the bench press. In older adults, the injury may be sustained while transferring. (See 'Epidemiology, mechanism, and risk factors' above.)

●Clinical presentation and physical examination – Presentation varies depending on severity and acuity. In nearly all cases of acute, severe tears (most common), the diagnosis can be made clinically. Patients describe feeling a pop or tearing sensation along the anterior chest wall. Swelling and ecchymosis around the anterior shoulder and chest wall are often present, and the tear site is tender. Other notable findings include loss of the anterior axillary fold. Resisted shoulder internal rotation accentuates the deformity. (See 'Clinical presentation and examination' above.)

●Diagnostic imaging – Plain radiographs of the shoulder cannot diagnose pectoralis injuries but can help to rule out other injuries, such as fractures. Magnetic resonance imaging (MRI) is the modality of choice when complete tear of the pectoralis major is suspected and definitive diagnosis is required. Ultrasound examination shows both pectoralis major insertions in normal circumstances; loss of these landmarks is consistent with a tear. (See 'Diagnostic imaging' above.)

●Differential diagnosis – The presentation of rotator cuff injuries and fractures of the proximal humerus may be similar to pectoralis injuries but can be distinguished clinically in most cases. (See 'Differential diagnosis' above.)

●Indications for surgical referral – Nearly all patients with suspected pectoralis major injuries that may entail a complete tear should be referred for surgical consideration. The primary exceptions are older adult patients who are not good surgical candidates. (See 'Indications for orthopedic consult or referral' above.)

●Management

•Complete tear – For most healthy patients with complete tears of the pectoralis major, we suggest surgical repair rather than conservative management (Grade 2C). Based on the observational evidence available, surgical repair results in better functional and cosmetic outcomes. This recommendation applies to younger individuals with a mechanism of injury related to sports or other strenuous activity. Conservative management may be more appropriate than surgery for complete pectoralis tears occurring in older, more sedentary adults. (See 'Indications for orthopedic consult or referral' above.)

•Less severe injuries can often be managed with physical therapy. (See 'Initial management' above and 'Follow-up' above.)

●Complications and return to activity – Complications may include weakness and shoulder instability with strenuous activities. Six months or longer may be required for surgically repaired injuries to regain full mobility and function. (See 'Complications' above and 'Return to sport or work' above.)