Traumatic causes of acute shoulder pain and injury in children and adolescents

INTRODUCTION — The causes of acute shoulder injury in the children and skeletally immature adolescents will be reviewed here. The evaluation of acute traumatic shoulder injury in children and the physical examination of the shoulder is reviewed separately. (See "Evaluation of acute traumatic shoulder injury in children and adolescents" and "Physical examination of the shoulder".)

CLINICAL ANATOMY — Diagnosis and treatment for shoulder injuries in the young athlete is different from treating adults because of the higher likelihood of fracture and anterior shoulder dislocations [1,2]. During the teenage years, participation in many sports puts the young athlete at risk for acute (eg, football, hockey) and repetitive overuse injuries (eg, swimming, baseball, tennis) [3]. Understanding the anatomy and applicable biomechanics of the shoulder is essential to identifying these injuries.

A complex network of anatomic structures endows the human shoulder with tremendous mobility, greater than any other joint in the body. The shoulder girdle is composed of three bones (the clavicle, scapula, and proximal humerus) and four articular surfaces (sternoclavicular, acromioclavicular, glenohumeral, and scapulothoracic) (figure 1A-C). The glenohumeral joint, commonly referred to as the shoulder joint, is the principal articulation. The shoulder is an inherently unstable joint that relies on several delicate interactions to minimize the risk for injury. The shape and interaction of the bones and soft tissues of the shoulder girdle are essential to understanding the factors leading to shoulder stability.

●Glenohumeral structures – The glenohumeral joint is loosely constrained within a thin capsule bounded by surrounding muscles and ligaments (figure 1A-C and table 1). The shoulder's great mobility is due in large part to the shallow depth of the glenoid and the limited contact between the glenoid and the humeral head. Only 25 percent of the humeral head surface makes contact with the glenoid. The labrum, a fibrocartilaginous ring attached to the outer rim of the glenoid, provides some additional depth and stability [1,4]. It also serves as a bumper to decrease the potential for humeral head subluxation. The shallowness and small surface area of the glenohumeral joint make it susceptible to instability and injury and require that stability be provided primarily by extrinsic supports.

Surrounding muscles and ligaments provide these supports:

•The glenohumeral ligaments are collagenous reinforcement of the capsule and quite variable in their thickness, anatomic position, and their contribution to shoulder stability (figure 1B). The glenohumeral ligaments serve as the primary static stabilizer [5-7].

The inferior glenohumeral ligament complex (IGHL) is made up of the anterior and posterior bands and the posterior axillary pouch that form a hammock like structure. In abduction and external rotation, the anterior band is the primary restraint to anterior translation of the humeral head [5,6].

In the absence of the anterior IGHL, the middle glenohumeral ligament may provide some restraint to anterior humeral translation [7].

During flexion and internal rotation, the posterior band of the IGHL and the posterior capsule are the primary restraints for posterior movement (translation) of the humeral head relative to the glenoid [6].

•The rotator cuff serves as the primary dynamic stabilizer. The rotator cuff is composed of four muscles (supraspinatus, infraspinatus, subscapularis, and teres minor) that form a cuff around the head of the humerus, to which these muscles attach (figure 2). The rotator cuff compresses the humoral head in the glenoid fossa, thereby stabilizing the glenohumeral joint, and serves to counterbalance the elevating forces of the deltoid, as well as the forces of other muscles acting on the humerus. (See "Evaluation of the adult with shoulder complaints", section on 'Glenohumeral structures'.)

●Other structures – The clavicle serves as a strut attaching the upper extremity to the axial skeleton through the acromioclavicular and sternoclavicular joints and the scapulothoracic articulation (figure 1A-C). The function of the clavicle includes supporting the weight of the arm, providing additional dynamic mobility to the arm, and transferring force from the arm to the rest of the skeleton.

The sternoclavicular joint has the least amount of bony stability of the major joints of the body, but paradoxically bears the responsibility of being the only true articulation between the upper extremity and the axial skeleton. The convex articular surface of the clavicle is much larger than the curved notch of the sternum resulting in an incongruous mismatch. Despite this instability, dislocation at this joint is rare. Both bones are covered with thick fibrocartilage (not the usual hyaline cartilage) and are separated by an intervening fibrocartilage disk which provide added cushion to the joint.

The muscles primarily responsible for scapular stability and motion are the trapezius, serratus anterior, rhomboids, and levator scapulae (figure 3).

The acromioclavicular (AC) joint is supported by ligaments that span its anterior, superior, posterior, and inferior aspects (picture 1). These ligaments also envelop the distal 1 to 2 cm of the clavicle. In addition to the AC ligaments, the distal clavicle is held in alignment with the acromion by the strong coracoclavicular (CC) ligaments. These ligaments consist of the conoid ligament medially and the trapezoid ligament laterally.

●Bony development – As a general rule, the bones that form the shoulder girdle (ie, scapula, humerus, and clavicle) are not fully ossified in the young athlete [8-15] (table 2). Thus, the skeletally immature athlete has open epiphyses that are two to five times weaker than the surrounding soft tissues and are prone to fracture.

In some patients, skeletal immaturity or variation in ossification can lead to misdiagnosis as follows:

•A lateral epiphysis fracture of the clavicle can be confused with an acromioclavicular joint injury (eg, acromioclavicular sprain or separation)

•Bipartite coracoid may be mistaken as a coracoid fracture

•Salter I fracture of the proximal humerus may be misdiagnosed as a soft tissue injury

•Medial clavicular epiphysis fracture can be confused with a sternoclavicular dislocation

•Os acromiale can be mistaken for an acromion fracture

TRAUMATIC CAUSES — The important traumatic causes of acute shoulder pain and injury are provided in the table (table 3).

LIFE-THREATENING AND SERIOUS CONDITIONS — Life-threatening causes of shoulder pain after an injury include posterior sternoclavicular dislocation and referred pain from a serious underlying injury to the neck, abdomen, or myocardium.

Pathologic fractures represent conditions that are more serious than isolated injuries to a previously normal shoulder.

Sternoclavicular injury — Sternoclavicular (SC) injuries are rare in the young athlete. Because the physis (growth plate) of the medial clavicle does not close until 22 to 25 years of age, Salter-Harris I or II physeal fractures with displacement of the medial clavicular fragment are more common than true SC dislocation [16-20]. These injuries are typically a result of tremendous force applied to the shoulder or medial clavicle. However, patients with hypermobility syndromes, such as Ehlers-Danlos syndrome, Marfan syndrome, or other generalized ligament laxity syndrome, can have this injury following significantly less trauma.

Medial clavicular fracture with anterior displacement or anterior SC dislocation is the most common type of SC injury accounting for up to 90 percent of SC dislocations in one series [16] and the majority of injuries reported in a systematic review [21]. Medial clavicular fractures with posterior displacement or posterior SC dislocation can cause significant life-threatening internal injury including tracheal compression, laceration of the subclavian or brachiocephalic vessels, pneumothorax, or recurrent laryngeal nerve injury.

The mechanism of injury may involve direct trauma to the medial clavicle and sternum (eg, misplaced kick during soccer or during mixed martial arts contest or a helmet blow during American football) or, more commonly, indirect trauma to the SC joint by anterolateral or posterolateral forces applied to the shoulder [22]. When a blow is applied directly to the anteromedial aspect of the clavicle, the clavicle is pushed posteriorly behind the sternum into the mediastinum. With indirect forces, if the shoulder is forced forward and medially, an ipsilateral posterior fracture with dislocation results; if the shoulder is forced backward and medially, an ipsilateral anterior fracture with dislocation occurs.

Diagnosis — Patients with sternoclavicular (SC) injury typically have anterior chest and shoulder pain that is worsened by arm movement. Patients with medial clavicular fracture with posterior displacement or posterior SC dislocation may also complain of difficulty breathing, dysphagia, or upper extremity paresthesias. If posterior displacement of the medial clavicle or clavicular fracture injures the recurrent laryngeal nerve, hoarseness may also be present. On physical examination, the medial end of the clavicle is displaced posterior, posteroinferior, or posterosuperior with respect to the sternum. However, this displacement may be difficult to appreciate. Patients with medial clavicular fracture and anterior displacement or anterior SC dislocation have a prominence at the SC joint that is displaced anteriorly or anterosuperiorly to the sternum.

Plain radiographs are typically sufficient to identify medial clavicular fractures with anterior displacement or anterior SC dislocations. In addition to routine clavicle series, a modified AP view with a 40 degree cephalic tilt or the “serendipitous view” will best visualize the injury [23].

Plain radiographs alone are insufficient to characterize medial clavicular fractures with posterior displacement or posterior SC dislocations. When these injuries are suspected, contrast-enhanced computed tomography (CT) of the chest is indicated to assess the full extent of bony abnormality and to identify potential vascular injury [24]. Injuries are classified as follows [25]:

●Grade I – Mild to moderate displacement without dislocation

●Grade II – Acute, traumatic, anterior dislocation

●Grade III – Chronic, traumatic, anterior dislocation

●Grade IV – Chronic, nontraumatic, anterior dislocation

●Grade V – Posterior dislocation

Management — Management of SC fracture and displacement or dislocation is determined by the direction of displacement and the degree of deformity [26]:

●Posterior SC dislocation or medial clavicular fractures with posterior displacement (Grade V) warrant prompt delineation with contrast-enhanced chest CT. Patients with airway compromise should undergo immediate reduction. In patients without airway compromise, reduction should occur within 24 hours, preferably by an orthopedic surgeon. Consultation with a cardiovascular surgeon should be performed prior to reduction in these patients, especially when an underlying hematoma is present on CT. Otherwise, bleeding may occur post-reduction from an untreated vascular injury.

Closed reduction will usually result in a stable reduction of a posterior SC dislocation [21]. Open reduction is reserved for irreducible posterior displacement with symptoms of compression with these injuries. However, displaced fractures of the medial clavicle frequently do not maintain reduction and open reduction with suture stabilization is the first-line treatment in many facilities [19]. Post-reduction treatment consists of a figure of eight brace for four to six weeks, resumption of overhead activities at six weeks, and restriction of contact sports or activities for six to eight weeks.

●Anterior SC fractures with dislocation (Grade III) should undergo reduction by a skilled practitioner but displacement usually recurs. Because of the potential for bone remodeling in the young athlete, proper healing is typically achieved without surgery [27]. Post-reduction treatment is the same as for posterior SC fractures with dislocation.

●Anterior or posterior SC injuries with pain and deformity but no dislocation (Grade I) should immobilized with the application of a figure-of-eight strap or sling and swathe for four to six weeks. Follow up with an orthopedic surgeon is necessary because patients with continued pain and mechanical sensation after six weeks of conservative management may warrant surgery.

●Pain is managed with local ice application and oral analgesics (eg, acetaminophen or ibuprofen).

Reduction of posterior sternoclavicular dislocation — Displaced medial clavicle fractures usually require closed reduction by an orthopedic surgeon but may require reduction by an emergency physician when the airway is compromised. The technique for closed reduction of a posterior SC dislocation is as follows (figure 4) [19]:

●Provide local anesthesia or procedural sedation for pain control. Patients receiving procedural sedation warrant close monitoring of airway and breathing.

●Place the patient supine with a 3 to 4 inch high bolster pad between the scapulae and positioned so that the shoulder on the affected side is placed at the edge of the table.

●Abduct the shoulder to 90 degrees.

●Perform gentle lateral traction on the arm and extend it towards the floor.

●Manually grasp the clavicle and pull it anteriorly.

●If this maneuver is unsuccessful, sterilely prep the area from the medial to proximal clavicle.

●While an assistant provides lateral traction as above, grasp the clavicle near the medial end by piercing the skin with a towel clip and reduce the dislocation.

Referred pain — Referred pain to the shoulder may indicate serious injury to the neck (cervical spine injury with nerve compression), abdomen (abdominal hemorrhage with diaphragmatic irritation), or, rarely, myocardium (blunt cardiac trauma with ischemia). Thus, the young athlete with shoulder pain warrants a careful assessment for these potential injuries and cervical spine immobilization should be maintained or applied to patients whose injury or clinical findings suggest cervical spine trauma. (See "Evaluation of the child or adolescent athlete with neck pain or injury" and "Field care and evaluation of the child or adolescent athlete with acute neck injury".)

Cervical spine injury is suggested by neck pain or cervical spine tenderness, stepoff on palpation, or neurologic deficit on physical examination. Patients with significant trauma and altered mental status or distracting injury (eg, long bone fracture causing significant pain) should be assumed to have a neck injury. Additional evaluation is determined by the clinical assessment (table 4). (See "Evaluation and acute management of cervical spine injuries in children and adolescents", section on 'Mechanism of injury'.)

Abdominal hemorrhage with diaphragmatic irritation may occur from a splenic or liver laceration after a direct blow to the upper abdomen. Variably present signs of abdominal injury include (see "Liver, spleen, and pancreas injury in children with blunt abdominal trauma", section on 'Evaluation'):

●Ecchymoses

●Abrasions

●Abdominal distension

●Tenderness

●Rigidity

●Masses

●Pain in the left shoulder induced by palpation of the left upper quadrant (Kehr sign)

Abdominal tenderness is typically present and may be accompanied by hemodynamic instability. Computed tomography of the abdomen with intravenous contrast is diagnostic.

The evaluation and management of liver or spleen injury after blunt abdominal trauma is discussed in detail separately. (See "Liver, spleen, and pancreas injury in children with blunt abdominal trauma", section on 'Evaluation' and "Liver, spleen, and pancreas injury in children with blunt abdominal trauma", section on 'Definitive management'.)

Myocardial infarction following blunt cardiac injury is rare and results from coronary artery dissection, laceration, or thrombosis. Chest pain referred to the left shoulder or arm, nausea, diaphoresis, or altered mental may be present. When indicated on the basis of severe mechanism of injury, hemodynamic instability, or physical findings pointing to significant thoracic trauma electrocardiogram and measurement of cardiac troponin assist in identifying this uncommon occurrence. (See "Initial evaluation and management of blunt cardiac injury", section on 'Clinical features' and "Initial evaluation and management of blunt cardiac injury", section on 'Evaluation and diagnosis of adult with blunt chest trauma'.)

Pathologic fracture — The proximal humerus is a preferential site for benign and malignant bone tumors. In patients with these lesions, minor injury may cause a fracture through the weakened bone (pathologic fracture) and lead to the diagnosis of the underlying tumor.

Common benign tumors of the proximal humerus include unicameral bone cysts (image 1), chondroblastomas (image 2), osteochondromas, enchondromas, and periosteal chondromas. (See "Nonmalignant bone lesions in children and adolescents".)

Osteosarcoma and, less commonly, Ewing sarcoma, also can occur in the proximal humerus and may come to attention following a pathologic fracture. (See "Osteosarcoma: Epidemiology, pathology, clinical presentation, and diagnosis" and "Clinical presentation, staging, and prognostic factors of Ewing sarcoma", section on 'Clinical presentation'.)

COMMON CONDITIONS — The common causes of shoulder pain in the young athlete include:

●Superficial contusion

●Clavicle contusion, fractures, or osteolysis

●Proximal humeral fractures

●Shoulder (glenohumeral) dislocation

●Acromioclavicular joint dislocation (separated shoulder)

Superficial contusion — Bruises in the shoulder area typically occur after a direct blow and may cause significant pain. Patients who can demonstrate a complete active range of motion without bony point tenderness may not require any further evaluation. Otherwise, normal plain radiographs and full motion after ice application and oral analgesia (eg, acetaminophen or ibuprofen) help to differentiate a shoulder contusion from more serious injuries.

Clavicle injuries — Distal clavicular contusions ("shoulder pointer") and clavicle fractures comprise the common clavicle injuries seen in children and adolescents.

Distal clavicle contusion (shoulder pointer) — Contusion to the distal clavicle without ligamentous involvement occurs after a fall onto the shoulder or a direct blow. Sometimes termed a "shoulder pointer", findings include pain over the distal clavicle rather than the acromioclavicular ligaments and no evidence of separation on radiographs [28]. Oblique radiographic views should be performed to exclude distal clavicle fractures. Treatment consists of a rest, sling for comfort, application of ice, and oral analgesics (eg, acetaminophen or ibuprofen). These injuries typically resolve in two to four weeks.

Clavicle fractures — Clavicle fractures are typically caused by a fall onto the shoulder and, in the young athlete, most commonly involve the middle third of the clavicle. The presenting features of a clavicle fracture depend upon the fracture site:

●Midshaft clavicle fractures – Pain in patients with fractures of the middle third of the clavicle is usually well localized and exacerbated by movement of the arm. The patient may describe a snapping or cracking sensation at the time of the injury and may notice localized swelling over the affected area. (See "Clavicle fractures", section on 'Clinical presentation and examination'.)

Because the clavicle lies close to the skin, examination often reveals a visible bulge due to hematoma (often with associated ecchymosis), bone angulation, or displaced bone edges. Tenting of the skin, if present, suggests significant angulation or displacement. There is point tenderness over the fracture site. In addition, firm pressure on the clavicle, even if not applied directly to the fracture site, may elicit crepitus or palpable motion of the fragment.

The evaluation and management of fractures of the middle third of the clavicle are discussed in greater detail separately. (See "Clavicle fractures", section on 'Fractures of the middle third (midshaft) of the clavicle'.)

●Distal clavicle fractures – Fractures of the distal third of the clavicle are easily confused with acromioclavicular (AC) separations. Both present with pain and tenderness around the AC joint, often with swelling and ecchymosis. The cross arm test (adduction of the arm across the chest) increases pain in both conditions. Little or no deformity is seen on examination, unless a type II fracture is present (image 3).

The location of maximal tenderness may provide a clue to the diagnosis. With fractures, maximal tenderness is usually located medial to the AC joint, instead of directly over the joint. Radiographs (including oblique clavicle views) should be considered if there is clinical suspicion that the injury includes the bone.

The evaluation and management of the distal clavicle fractures are reviewed in greater detail separately. (See "Clavicle fractures", section on 'Fractures of the distal third of the clavicle'.)

●Proximal clavicle fractures – Fractures of the proximal third of the clavicle are the least common type of clavicle fracture and are usually seen after high force vehicular trauma. Acute fractures are often complicated by serious injury to the head, neck, chest, or abdomen.

Stress fractures may occur from repetitive injury in rowers and gymnasts and cause chronic pain over the sternoclavicular area. Evaluation and management of proximal clavicle fractures are discussed in greater detail separately. (See "Clavicle fractures", section on 'Fractures of the proximal third of the clavicle'.)

Proximal humeral fractures — Fractures of the proximal humerus commonly occur due to a fall on an outstretched hand (FOOSH) or from a direct blow to the lateral aspect of the shoulder (figure 5). Physeal fractures are most common in adolescents. Before adolescence, proximal humeral fractures typically occur at the metaphysis, although Salter-Harris type I injuries are seen occasionally (figure 6 and figure 7). Pathologic fracture through a benign or malignant bone tumor may occur after very minor trauma. (See "Proximal humeral fractures in children", section on 'Children and adolescents' and 'Pathologic fracture' above.)

The child or adolescent with a proximal humeral fracture typically presents with a history of trauma, severe shoulder pain, and marked pain on arm movement. For nondisplaced proximal humeral fractures, the physical findings may be limited to tenderness and mild swelling. For displaced fractures, significant anterior swelling and altered shoulder appearance relative to the unaffected side are often present, and the arm is usually shortened and held in extension. (See "Proximal humeral fractures in children", section on 'Physical findings'.)

Routine AP and axillary lateral views of the humerus are generally sufficient to diagnose a proximal humeral fracture. If the injured child is tender at the physis, the treating physician should suspect a Salter-Harris I fracture, even in the presence of normal radiographs. If clinical concern for a shoulder injury is present, a complete three view shoulder series (ie, AP, axillary, and scapular "Y" views) should also be obtained. (See "Proximal humeral fractures in children", section on 'Radiographic findings'.)

Management of proximal humeral fractures in children and adolescents is discussed in more detail separately. (See "Proximal humeral fractures in children", section on 'Initial treatment' and "Proximal humeral fractures in children", section on 'Definitive care'.)

Shoulder dislocation — Shoulder dislocation refers to dissociation of the humeral head from the glenoid cavity and may occur anteriorly, posteriorly, or inferiorly. These injuries require reduction. (See "Shoulder dislocation and reduction", section on 'Reduction procedure'.)

Athletes with shoulder subluxation or instability and acute trauma may have similar findings to those with shoulder dislocation, but are less likely to have long term dysfunction.

●Anterior – An anterior shoulder dislocation is usually caused by a blow to the abducted, externally rotated, and extended arm (eg, blocking a basketball shot or arm tackling in American football as a player runs past). Less commonly, a blow to the posterior humerus or a fall on an outstretched arm, or any forceful forward swinging of the arm (missed punch), may cause an anterior dislocation [29,30]. (See "Shoulder dislocation and reduction", section on 'Mechanism of injury'.)

An anteriorly dislocated shoulder causes the arm to be slightly abducted and externally rotated. The patient resists all movement. The acromion appears prominent in thin individuals and there is loss of the normal rounded appearance of the shoulder (picture 2). Axillary nerve dysfunction is common after this injury. Thus, careful evaluation for nerve dysfunction with sensory loss over the lateral deltoid is an essential part of the examination. (See "Shoulder dislocation and reduction", section on 'Examination'.)

Radiographs are typically performed before and after reduction of an anterior shoulder dislocation when evaluated in the ED. Initial radiographs confirm the diagnosis and exclude fractures (image 4); postreduction radiographs confirm successful reduction and exclude any fracture caused by the procedure. Routine films include an anteroposterior (AP), a scapular "Y" view, and an axillary view. In skeletally mature patients with a prior history of shoulder dislocation, some clinicians may proceed with reduction without obtaining radiographs. (See "Shoulder dislocation and reduction", section on 'Imaging studies'.)

Injuries associated with anterior dislocations include a cortical depression of the humeral head (Hill-Sachs deformity) (image 5) and glenoid labrum disruption with or without an avulsion fracture (Bankart lesion) (image 6). (See "Shoulder dislocation and reduction", section on 'Associated injuries (Hill-Sachs and Bankart)'.)

Anterior shoulder dislocations typically require urgent reduction. The techniques for reduction of an anterior shoulder dislocation are reviewed separately. (See "Shoulder dislocation and reduction", section on 'Reduction procedure'.)

●Posterior – Posterior shoulder dislocation is much less common than anterior dislocation [2,29]. Posterior shoulder dislocation typically arises from a blow to the anterior portion of the shoulder, axial loading of an adducted and internally rotated arm or violent muscle contractions following a seizure or electrocution. Examination reveals prominence of the posterior shoulder with flattening anteriorly. The coracoid process appears prominent. The patient holds the arm in adduction and internal rotation and is unable to externally rotate (picture 3 and movie 1). (See "Shoulder dislocation and reduction", section on 'Posterior shoulder dislocation'.)

Radiographic evidence of a posterior shoulder dislocation on a standard anteroposterior (AP) view is subtle and may go undetected in up to 50 percent of cases. Clues to the diagnosis include the "light bulb" sign, rim sign, and trough line sign (image 7 and image 8). Posterior shoulder dislocations are commonly associated with tuberosity and surgical neck fractures of the humerus, reverse Hill-Sachs lesions, and injuries to the labrum and rotator cuff. Computed tomography may be necessary to characterize the full extent of injury. (See "Shoulder dislocation and reduction", section on 'Posterior shoulder dislocation'.)

Consultation with an orthopedic surgeon is typically warranted prior to attempting reduction of a posterior shoulder dislocation. (See "Shoulder dislocation and reduction", section on 'Posterior shoulder dislocation reduction'.)

●Inferior – Inferior shoulder dislocations (luxatio erecta) are the least common type of shoulder dislocation and are typically caused by axial loading of a fully abducted arm or forceful hyperabduction. Patients with this injury hold the involved arm above their head and are unable to adduct the arm. A prominence in the axilla is also present. The forearm is pronated and in most cases rests on the top of the head. Approximately 60 percent of patients will have some degree of neurologic dysfunction, with the axillary nerve most commonly involved. Radiographs reveal the humeral head beneath the coracoid or the glenoid (image 9). Associated fractures include the greater tuberosity (most common), acromion, scapula, humeral head, coracoid, and glenoid. (See "Shoulder dislocation and reduction", section on 'Inferior shoulder dislocation (luxatio erecta)'.)

The technique for reduction of an inferior shoulder dislocation is provided separately. (See "Shoulder dislocation and reduction", section on 'Inferior shoulder dislocation reduction'.)

Acromioclavicular injuries — Injury to the acromioclavicular (AC) joint usually occurs from direct trauma to the superior or lateral aspect of the shoulder (acromion) with the arm adducted, such as a direct blow or falling onto the shoulder (figure 8). Force correlates with injury. Low force typically causes an AC sprain. Progressive increases in force cause AC ligament rupture, and then sprain and rupture of the coracoclavicular (CC) ligaments (picture 1).

The patient with an AC injury generally exhibits tenderness directly over the AC joint, possibly with deformity. Initial radiographic evaluation of a suspected AC injury can be pursued using either of two approaches: a single anterior-posterior (AP) Zanca view including both AC joints (image 10); or two AP radiographs, one of the involved shoulder and a comparison film of the uninvolved side. A system for classification is presented in the accompanying table (table 5). (See "Acromioclavicular joint injuries ("separated" shoulder)", section on 'Differential diagnosis'.)

Treatment of AC injuries varies according to degree of injury and is discussed in detail separately. (See "Acromioclavicular joint injuries ("separated" shoulder)", section on 'Management'.)

Burners (stingers) — The diagnosis of burners can usually be made by the history and physical examination. In most cases, it is a brachial plexopathy involving the upper trunk (figure 9). The mechanism of injury is usually either direct trauma to Erb's point (located just posterior to the midpoint of the sternocleidomastoid where the upper trunk of the brachial plexus passes) or stretch injury when the neck is laterally flexed away from the injury while the shoulder is depressed. It is characterized by immediate onset of sharp, burning pain radiating from the supraclavicular area down the arm and into the thumb/index finger. The player might also note numbness, paresthesias, and/or weakness in the extremity. Frequently the discomfort resolves spontaneously in a few minutes. (See "Burners (stingers): Acute brachial plexus injury in the athlete", section on 'Clinical features'.)

On physical examination, the player might shake the upper extremity or hold it against the body to reduce discomfort. Sensory or motor deficits in burners usually involve muscles innervated by C5 or C6, the nerve fibers of which travel through the upper trunk of the brachial plexus (figure 9). Each of these areas should be tested manually for muscle strength directly either with hand held dynamometer or manually. Although weakness can resolve within a few minutes of the acute injury, it can also develop hours or days later. Reexamination of patients with burners until normalization is imperative. The baseline strength of some athletes is so high that manual muscle testing might not detect subtle deficits; comparing one side to the other can be helpful. (See "Burners (stingers): Acute brachial plexus injury in the athlete", section on 'Examination findings'.)

Focal neck tenderness should alert the clinician to the possibility of a serious cervical injury, such as fracture or disc herniation, and is not typical of burners. Patients with this finding warrant cervical immobilization and appropriate imaging. (See "Evaluation and acute management of cervical spine injuries in children and adolescents", section on 'Cervical spine imaging' and "Field care and evaluation of the child or adolescent athlete with acute neck injury", section on 'Spinal motion restriction (immobilization)'.)

The management of burners is discussed separately. (See "Burners (stingers): Acute brachial plexus injury in the athlete", section on 'Management'.)

OTHER CONDITIONS — Scapula fractures typically occur after a direct forceful blow to the anterior or posterior shoulder and are rarely associated with sports injuries.

Scapula fractures — Scapula fractures are rarely encountered after sports injuries and are more commonly associated with high force trauma such as motor vehicle collisions. These fractures are frequently associated with life-threatening injuries to the head, neck, and thorax. Specific patterns are as follows:

●Scapula body and spine fractures – The most common sports mechanism is direct blows in American football [12]. Associated injuries include rib fractures, pulmonary contusion, brachial plexus disruption, and axillary artery laceration. Most fractures heal with supportive measures but fractures with >10 mm of displacement are associated with malunion and worse long-term outcomes [31].

●Glenoid fractures – Glenoid neck fractures are relatively rare in the pediatric age group, but have been reported as a skiing injury [32]. On plain radiographs, these fractures will extend from the suprascapular notch to the lateral scapular border inferior of the glenoid rim. When this fracture is associated with a midclavicular fracture, it is considered a “floating shoulder” injury because these structures are essential to providing a foundation to suspend the arm to the axial skeleton. Indications for surgical and nonsurgical management are debated [31,32]. Displaced fractures may be treated with open or closed reduction, but regardless of treatment, usually have good functional outcomes [33-35].

Glenoid fossa fractures (excluding bony Bankart lesions associated with shoulder instability injuries) result from a direct blow to the lateral aspect of the shoulder, driving the humeral head into the glenoid fossa. The fracture can extend inferiorly through the lateral scapular border, medially through the body of the scapula, or produce comminution of the glenoid [36]. In the pediatric population, a fall on the tip of the shoulder will drive the scapula inferiorly while the fracture fragment is held in place by the stronger coracoclavicular ligaments [37,38]. The fracture will track along the epiphysis of glenoid fossa, located at the upper one-third of the glenoid and inferior to the coracoid process. It is rarely complicated by a suprascapular nerve injury. This injury can mimic an acromioclavicular separation and the Stryker Notch view may help to demonstrate the fracture on radiography. Most of these injuries are treated nonoperatively with immobilization for four to six weeks, but displacement of more than 10 mm or more than 40 degrees of angulation requires surgical management.

●Acromion fractures – Fractures of the acromion are rare and often misdiagnosed in the presence of an os acromiale because they both are most commonly located at the junction between the meso and meta-acromion. Fractures can occur with an inferiorly directed blow to the superior aspect of the acromion or a fall with a superiorly directed axial load that translates the humeral head superiorly [39,40]. The first mechanism will usually result in an acromioclavicular separation, but if fractured, it may be complicated by a brachial plexus root avulsion. The latter, when associated with significant superior displacement, may be complicated by injury to the rotator cuff [40]. The os acromiale is bilateral in 60 percent of patients [41]. Thus, contralateral radiographs may be helpful in distinguishing between a nondisplaced fracture and an os acromiale.

●Coracoid fractures – Coracoid fractures have been caused by both direct and indirect trauma. Direct trauma to the tip of the coracoid is associated with the rare subcoracoid glenohumeral dislocation [42]. Indirect trauma can occur from avulsion injury during strong muscular contraction of the pectoralis minor muscle and short head of the biceps when the arm is in the abducted and extended position [43]. An avulsion injury can result from a fall on the acromion that usually results in an acromioclavicular separation, but in this case, results in tearing the coracoid attachment of the coracoclavicular ligament [37]. Most fractures without displacement and intact coracoclavicular and acromioclavicular ligaments will heal with immobilization in a sling in internal rotation. Those with more displacement (>5 mm) and disrupted ligamentous structures may benefit from surgical management. The more distal on the coracoid process the fracture is located, the more likely that healing will be delayed [44].

DIAGNOSTIC APPROACH — The evaluation of shoulder pain and injury is discussed in greater detail separately. (See "Evaluation of acute traumatic shoulder injury in children and adolescents".)

The clinician should first exclude life-threatening conditions including sternoclavicular injury and referred pain from serious cervical spine, thoracic, or abdominal injury. (See 'Life-threatening and serious conditions' above.)

Once these important extrinsic causes of shoulder pain have been excluded, careful history, physical examination, and, in most cases, radiographs help identify the specific etiology. Unlike older patients, young athletes are more prone to fractures and thus plain radiographs are typically indicated.

A diagnostic approach is provided in the algorithm (algorithm 1). Clinical findings of specific conditions are discussed above by diagnosis and in greater detail separately. (See "Evaluation of acute traumatic shoulder injury in children and adolescents".)

SUMMARY AND RECOMMENDATIONS

●Anatomy – Diagnosis and treatment for shoulder injuries in the young athlete is different from treating adults because of the higher likelihood of fracture caused by skeletal immaturity. (See 'Clinical anatomy' above.)

●Traumatic causes – The important traumatic causes of acute shoulder pain and injury are provided in the table (table 3). (See 'Traumatic causes' above.)

●Life-threatening and serious conditions – Life-threatening causes of shoulder pain after an injury include posterior sternoclavicular dislocation and referred pain from a serious underlying injury to the neck, abdomen, or myocardium. Pathologic fractures represent conditions that are more serious than isolated injuries to a previously normal shoulder. (See 'Life-threatening and serious conditions' above.)

●Common conditions – Common causes of shoulder pain after trauma include superficial contusions, clavicle and proximal humeral fractures, shoulder (glenohumeral) dislocation and acromioclavicular joint injuries. (See 'Common conditions' above.)

●Other conditions – Scapular fractures typically occur after a direct forceful blow to the anterior or posterior shoulder and are rarely associated with sports injuries. (See 'Other conditions' above.)

●Diagnostic approach – In children and adolescents, the clinician should first exclude life-threatening conditions including sternoclavicular injury and referred pain from serious cervical spine, thoracic, or abdominal injury. Once these important extrinsic causes of shoulder pain have been excluded, careful history, physical examination, and, in most cases, radiographs help identify the specific etiology. Unlike older patients, young athletes are more prone to fractures and thus plain radiographs are typically indicated. (See 'Diagnostic approach' above.)