Acute Shoulder Pain

Acute shoulder injuries are a common reason for visits to primary care physicians and EDs. Common acute shoulder injuries include acromioclavicular joint injuries, clavicle fractures, glenohumeral dislocations, proximal humerus fractures, and rotator cuff tears. Evaluation of acute shoulder pain requires an understanding of the mechanism of injury, as well as the appropriate physical examination and radiologic studies needed in the acute setting. A focused history and physical examination is essential and should include inspection, palpation, and a thorough neurovascular exam. Imaging begins with plain radiographs and is occasionally supplemented by MRI or CT imaging. Management includes pain control and varies based on diagnosis.

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Overview: Anatomy

  • Focused anatomy of the shoulder joint
  • The shoulder complex is made up of multiple joints, bones, ligaments, and tendons.
  • The glenohumeral joint has the most mobility of any joint in the body.
  • Glenohumeral joint: 
    • Passive restraints:
      • Joint capsule
      • Glenohumeral ligaments
      • Glenoid labrum
    • Active stabilizers:
      • Rotator cuff muscles
      • Periscapular muscles
  • Rotator cuff muscles (active stabilizers):
    • Supraspinatus, infraspinatus, teres minor, subscapularis
    • Forms a cuff around the head of the humerus
    • Stabilizes the joint while allowing motion
    • Supraspinatus is the most commonly torn rotator cuff tendon.
  • The shoulder complex also includes:
    • Acromioclavicular joint
    • Sternoclavicular joint
    • Scapulothoracic articulation
    • Long head of the bicep tendon
  • Cervical spine evaluation is part of the assessment of shoulder pain.
  • Thorough neurovascular examination is essential after trauma to the upper extremity.

Mnemonic

Remember the rotator cuff muscles with SITS:

  • Supraspinatus
  • Infraspinatus
  • Teres minor
  • Subscapularis

Clinical Presentation

History

  • Mechanism of trauma:
    • Type of trauma
    • Other associated injuries
  • Previous injuries: fractures history, previous dislocations
  • Age of individual

Physical examination

  • Exposure of shoulder
  • Compare to unaffected side.
  • Inspection/observation:
    • Swelling, gross deformity
    • Asymmetry
  • Cervical spine exam: Always consider associated injury.
  • Range of motion: limited because of pain, injury
  • Palpation:
    • Palpate:
      • Cervical spine
      • Sternoclavicular joint
      • Acromioclavicular joint
      • Glenohumeral joint
      • Proximal humerus
    • Assess for warmth and swelling.
  • Neurovascular exam:
    • Evaluation of muscle groups of the upper extremity
    • Evaluation of brachial plexus
    • Vascular status

Imaging

  • Imaging studies helpful to support or confirm diagnosis
  • Plain radiographs: anteroposterior (AP) shoulder, AP glenoid, scapular Y view, and axillary view
  • MRI, CT, or ultrasonography for more difficult cases

Common Causes and Management of Acute Shoulder Pain

Clavicular fracture

  • Common in adults, secondary to trauma to the lateral shoulder
  • Most common location (80%): middle ⅓ of the clavicle (group I)
  • Presents with pain, tenderness, and swelling over the clavicle
  • Often obvious deformity: 
    • Lateral fragment is displaced downward and medially because of unopposed action of pectoralis major muscle.
    • Proximal fragment is displaced upward because of unopposed action of the sternocleidomastoid muscle.
  • Diagnosis is based on clinical examination and is confirmed by x-ray.
  • Careful neurovascular exam should be done because of proximity to the: 
    • Great vessels
    • Lung
    • Brachial plexus
  • Management: based on type of injury, age of individual, and location (the majority of clavicular fractures are treated nonoperatively)
  • Allman classification of clavicle fractures:
    • Group I fractures (midshaft fractures): overlap of > 2 cm or grossly displaced; often undergo surgical intervention
    • Group II fractures (distal ⅓ of fractures): orthopedic referral
    • Group III fractures (medial ⅓ of fractures): generally treated nonoperatively
Allman classification

Allman classification of clavicular fracture

Image by Lecturio.

Acromioclavicular joint injuries

  • Common injury in adults, caused by a fall on the lateral shoulder with the arm adducted
  • Diagnosis is clinical, with pain on palpation of the AC joint and associated deformity.
  • X-ray may be useful in classifying degree of injury and associated fractures.
  • Rockwood classifications:
    • Type I: clavicle not elevated with respect to the acromion
    • Type II: clavicle elevated but not above the superior border of the acromion
    • Type III: clavicle elevated above the superior border of the acromion but < 2× normal
    • Type IV: clavicle displaced posterior into the trapezius
    • Type V: clavicle markedly elevated, > 2× normal
    • Type VI: clavicle inferiorly displaced behind coracobrachialis and biceps tendons (rare)
  • Types I–III injuries: nonoperative
  • Type IV–VI injuries: orthopedic consult for surgical evaluation
Rockwood classification

Rockwood classification of acromioclavicular joint injury

Image by Lecturio.

Sternoclavicular sprains and dislocations

  • Injured secondary to trauma to lateral shoulder
  • Medical clavicular epiphysis last to develop:
    • May not close until age 25
    • Apparent sternoclavicular joint injury in young adults may be a Salter-Harris I/II injury rather than sprain.
  • Majority are anterior dislocations with prominent medial clavicle.
  • Posterior dislocation can result from direct blow or fall:
    • May cause impingement of superior mediastinal contents
    • Injury to trachea and great vessels is potentially life-threatening.
    • CT scan is imaging procedure of choice.
Normal anterior view of the sternoclavicular joint

Normal anterior view of the sternoclavicular joint

Image: “Gray325” by Henry Gray, Warren H. Lewis. License: Public Domain

Glenohumeral dislocation

  • Most commonly dislocated joint
  • Over 90% of shoulder dislocations are in the anterior direction.
  • Caused by a direct blow, fall, sports injury, or other high-impact trauma
  • May be associated with axillary nerve injury:
    • Function of axillary nerve should be assessed both before and after reduction, along with a complete neurovascular examination.
    • Test: sensation over the deltoid
  • Diagnosis is based on clinical examination and is confirmed by x-ray.
  • Plain x-rays: AP glenoid, scapular Y view, and axillary view
  • Management:
    • Multiple maneuvers have been described.
    • After reduction, repeat radiographs and sling placement
    • Length of immobilization is controversial.
    • Risk of recurrent dislocation varies according to age and activity level.
    • Surgical intervention may be required for repeated dislocations or 1st-time dislocation in athlete participating in a high-impact sport.

Posterior dislocation

  • Uncommon injury (2%–4%); can be missed
  • Classically described in individuals with seizures and electrocution injury; also seen with trauma 
  • May be related to underlying multidirectional instability
  • Individual keeps shoulder adducted and internally rotated; limited external rotation
  • X-ray: 
    • May be missed on AP view of shoulder
    • Requires axillary or Y view for definite diagnosis
    • Classic: “light bulb” sign (internally rotated proximal humerus with circular appearance)
Normal Y-view X-Ray

Normal Y-view X-ray

Image: “Y-projection X-ray of a normal shoulder” by Mikael Häggström. License: CC0 1.0

Proximal humerus fracture

  • More common in older individuals (70% > 60 years); occurs secondary to low-energy fall
  • Related to high-energy trauma when seen in younger individuals
  • Presents with pain/swelling of proximal humerus after fall/trauma
  • Assess neurovascular status, including axillary nerve.
  • Plain x-rays: AP shoulder, AP glenoid, and scapular Y view (consider axillary view)
  • Management varies according to age and activity level.
  • Most treated nonoperatively
  • Nonoperative treatment:
    • Sling for comfort followed by pendulum exercises
    • Then a graduated physical therapy program
X-ray of a proximal humerus fracture

X-ray of a proximal humerus fracture

Image: “X-Ray images showing the progression from injury (a) to 7 days after (b) a non-operative approach” by Woojin Chae, Akib Khan, Sarah Abbott, Angelos Assiotis. License: CC BY 4.0

Scapular fractures

  • Fractures to scapula related to high-impact trauma
  • Most commonly involve fractures of the body of the scapula and/or neck of glenoid
  • The nature of this fracture raises a high suspicion for associated lung injury, rib fractures, and other injuries.
  • Majority nondisplaced and treated nonsurgically

Acute rotator cuff tendon tear

  • Rotator cuff tears may result from acute trauma, falls, or tendon degeneration.
  • Generally, age is helpful in classifying the tear:
    • Younger individuals more commonly have acute tears.
    • Older individuals often have degenerative-type tears.
    • Important: A significant number of individuals > 60 have asymptomatic degenerative rotator cuff tears on MRI.
  • Supraspinatus is the most commonly torn rotator cuff tendon:
    • Shoulder weakness and pain when reaching overhead or behind
    • Often bothersome at night
  • Physical examination/muscle-strength testing specific to location of rotator cuff tendon tear
  • Initial diagnosis based on clinical examination
  • MRI used to confirm diagnosis
  • Management:
    • Based on multiple factors:
      • Age
      • Duration of symptoms
      • Partial versus full tear
      • Comorbidities
    • Generally conservative for elderly individuals or chronic tears
    • Full-thickness tears typically require surgical repair.

Clinical Relevance

  • Axillary nerve injury: Axillary nerve (C5–C6) may be injured in individuals with shoulder dislocation or proximal humerus fracture. The axillary nerve innervates the deltoid and teres minor. Axillary nerve injury results in weakness of the deltoid muscle and numbness on the side of the shoulder. May require surgery if associated with a fracture injury.
  • Recurrent instability: Individuals with a history of shoulder dislocation have an increased risk of recurrent dislocation. Risk factors include younger age, playing contact sports, presence of Hill-Sachs or Bankart lesions, and underlying ligamentous laxity. Management is often with surgery.
  • Fracture malunion: Nonunion or malunion occurs with a relatively small number of clavicle fractures. Whereas the operative management of clavicle fractures has become more common, the surgical indications are uncertain.

References

  1. Vaughan, A., Hulkower, S. (2020). Evaluation of the adult with shoulder complaints. UpToDate. Retrieved August 19, 2021, from https://www.uptodate.com/contents/evaluation-of-the-adult-with-shoulder-complaints
  2. Berkoff, D. (2020). Multidirectional instability of the shoulder. UpToDate. Retrieved August 20, 2021, from https://www.uptodate.com/contents/multidirectional-instability-of-the-shoulder
  3. Sherman, S. (2020). Shoulder dislocation and reduction. UpToDate. Retrieved August 20, 2021, from https://www.uptodate.com/contents/shoulder-dislocation-and-reduction
  4. Young, C. (2019). Throwing injuries of the upper extremity: clinical presentation and diagnostic approach. UpToDate. Retrieved August 19, 2021, from https://www.uptodate.com/contents/throwing-injuries-of-the-upper-extremity-clinical-presentation-and-diagnostic-approach
  5. Chorley, J., Brooks, G. (2020). Traumatic causes of acute shoulder pain and injury in children and adolescents. UpToDate. Retrieved August 19, 2021, from https://www.uptodate.com/contents/traumatic-causes-of-acute-shoulder-pain-and-injury-in-children-and-adolescents

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