Inferior Shoulder Dislocation (Luxatio Erecta): Signs, Symptoms, and Management

What are the signs and symptoms of inferior shoulder dislocation?

Inferior shoulder dislocation, also known as luxatio erecta, is a rare but severe injury where the humeral head displaces directly downwards, often resulting in the arm being fixed in an overhead position, accompanied by intense pain and a high risk of neurovascular compromise.

Understanding Inferior Shoulder Dislocation

The shoulder joint (glenohumeral joint) is the most mobile joint in the human body, making it highly susceptible to dislocation. While anterior dislocations are by far the most common, and posterior dislocations are less frequent, inferior dislocations represent a very rare subset, accounting for less than 5% of all shoulder dislocations. This type of dislocation occurs when the humeral head is forced inferiorly, typically by a strong hyper-abduction force, often combined with external rotation, such as a fall onto an outstretched hand or a direct blow to the top of the shoulder while the arm is elevated. Due to the significant force required and the anatomical structures involved, inferior dislocations are often associated with serious complications.

Immediate Signs and Symptoms

Identifying an inferior shoulder dislocation promptly is crucial for effective management and to mitigate potential long-term complications. The presentation is typically dramatic and unmistakable:

• Arm Fixed in Abduction: This is the most characteristic and striking sign. The affected arm will be held rigidly in a position of extreme abduction (often 90-180 degrees), with the elbow flexed and the hand resting on or behind the head. The individual will be unable to adduct (bring down) the arm.
• Severe, Acute Pain: The pain is typically excruciating and immediate following the traumatic event. It is localized to the shoulder joint and often radiates down the arm.
• Visible Deformity:
  • Prominent Humeral Head in Axilla: A distinct bulge can often be seen or palpated in the armpit (axilla), representing the displaced humeral head.
  • Flattening of Deltoid Contour: The normal rounded contour of the shoulder, provided by the deltoid muscle, will be lost, appearing flattened or depressed.
  • Prominent Acromion: The tip of the shoulder blade (acromion) may appear more pronounced due to the absence of the humeral head beneath it.
• Inability to Move the Arm: Beyond the fixed abducted position, the individual will have a complete inability to perform any active or passive movements of the shoulder joint, especially adduction.
• Neurovascular Compromise: This is a critical concern due to the close proximity of the brachial plexus (a network of nerves) and the axillary artery and vein to the inferior aspect of the glenohumeral joint. Signs of neurovascular compromise include:
  • Numbness or Tingling: Sensations of pins and needles or complete numbness in the hand, fingers, or forearm, indicating nerve impingement or stretch.
  • Weakness or Paralysis: Difficulty or inability to move the hand or fingers, suggesting motor nerve involvement.
  • Pallor or Cyanosis: The hand or fingers may appear unusually pale or bluish, indicating compromised blood flow.
  • Diminished or Absent Pulses: A weakened or absent pulse in the radial or ulnar artery of the affected arm is a medical emergency, signaling potential axillary artery compression or injury.
• Swelling and Bruising: These may develop rapidly around the shoulder joint due to tissue damage and internal bleeding.

Associated Complications and Long-Term Considerations

Given the significant forces involved in an inferior shoulder dislocation, associated injuries are common and must be carefully assessed:

• Rotator Cuff Tears: The forceful nature of the injury can tear one or more of the rotator cuff tendons (supraspinatus, infraspinatus, teres minor, subscapularis).
• Labral Tears: The labrum, a rim of cartilage surrounding the glenoid socket, can be torn (e.g., Bankart lesion).
• Fractures: Fractures of the greater tuberosity of the humerus, humeral neck, or glenoid rim can occur.
• Nerve Damage: As mentioned, damage to the brachial plexus, particularly the axillary nerve, is a significant risk, leading to persistent weakness or sensory deficits.
• Vascular Injury: Although less common than nerve injury, damage to the axillary artery or vein can lead to severe bleeding or ischemia (lack of blood flow) to the limb.
• Recurrent Instability: Once dislocated, the shoulder may be more prone to future dislocations, especially if significant soft tissue damage occurred.

Differentiating Inferior from Other Dislocation Types

While the fixed overhead arm position is highly indicative of an inferior dislocation, a brief comparison helps highlight its uniqueness:

• Anterior Dislocation: The most common type. The humeral head displaces forward. The arm is typically held in slight abduction and external rotation, and there's a prominent bulge anteriorly with a flattened deltoid.
• Posterior Dislocation: Rare, often missed. The humeral head displaces backward. The arm is typically held in adduction and internal rotation, and there's a flattening of the anterior shoulder with prominence posteriorly.

When to Seek Medical Attention

Any suspected shoulder dislocation, especially an inferior dislocation, is a medical emergency requiring immediate professional evaluation. Do not attempt to reduce the dislocation yourself, as this can cause further damage to nerves, blood vessels, or surrounding tissues.

Seek immediate medical attention if you or someone you know experiences:

• A traumatic injury to the shoulder.
• Severe pain and inability to move the arm.
• Visible deformity of the shoulder.
• Any signs of numbness, tingling, pallor, or weakness in the arm or hand.

Diagnosis and Treatment Overview

Diagnosis is primarily clinical, based on the characteristic presentation and mechanism of injury. X-rays are crucial to confirm the diagnosis, determine the direction of dislocation, and rule out associated fractures. Advanced imaging like CT scans or MRI may be used to assess soft tissue injuries (e.g., rotator cuff tears, labral tears) or nerve damage.

Treatment involves prompt closed reduction (manually repositioning the humeral head back into the socket) by a trained medical professional, often under sedation or anesthesia. Following reduction, the arm is typically immobilized for a period, followed by a comprehensive rehabilitation program focusing on pain management, restoring range of motion, and strengthening the surrounding musculature to prevent recurrence.

Prevention Strategies

While not all shoulder dislocations are preventable, particularly those resulting from high-impact trauma, strategies to reduce risk include:

• Strength Training: Regularly strengthening the rotator cuff muscles and scapular stabilizers can enhance joint stability.
• Proper Technique: Using correct form during sports and exercises to avoid extreme ranges of motion that put the shoulder at risk.
• Awareness: Being mindful of environmental hazards that could lead to falls or direct impacts.

In conclusion, inferior shoulder dislocation is a distinct and serious injury demanding immediate medical attention. Recognizing its unique signs, particularly the arm fixed overhead and potential neurovascular compromise, is paramount for ensuring timely and appropriate management to optimize recovery and minimize long-term complications.