Inferior Shoulder Dislocation: Immediate and Long-Term Complications, Diagnosis, and Management

What are the complications of inferior shoulder dislocation?

Inferior shoulder dislocation, also known as luxatio erecta, is a rare but severe injury that can lead to a range of immediate and long-term complications, primarily due to the high-energy trauma involved and the critical neurovascular structures in the shoulder region.

Introduction

The shoulder joint, or glenohumeral joint, is the most mobile joint in the human body, making it inherently susceptible to dislocation. While anterior dislocations are the most common, accounting for over 95% of cases, inferior shoulder dislocation (luxatio erecta) is a rare variant, representing less than 1% of all shoulder dislocations. Despite its rarity, this type of dislocation is often associated with significant trauma and carries a high risk of severe complications. Understanding these potential complications is crucial for accurate diagnosis, effective management, and optimizing patient outcomes.

Understanding Inferior Shoulder Dislocation

Inferior shoulder dislocation occurs when the humeral head is displaced directly inferiorly, often coming to rest below the glenoid fossa, with the arm typically locked in an abducted and externally rotated position, pointing upwards (hence "luxatio erecta," or "erect dislocation"). This injury typically results from a forceful hyperabduction mechanism, often combined with axial loading. The high forces involved mean that surrounding soft tissues, nerves, and blood vessels are particularly vulnerable.

Immediate Complications

The acute phase following an inferior shoulder dislocation is critical, as several serious complications can occur concurrently with the dislocation itself.

• Nerve Damage:
  • Axillary Nerve (C5-C6): This is the most commonly injured nerve, given its close proximity to the inferior aspect of the humeral head. Damage can lead to weakness or paralysis of the deltoid muscle (impairing shoulder abduction) and teres minor, as well as sensory loss over the "regimental badge" area (lateral shoulder).
  • Brachial Plexus Injury: While less common than isolated axillary nerve damage, the entire brachial plexus can be stretched or compressed, leading to more widespread motor and sensory deficits in the arm and hand.
• Vascular Injury:
  • Axillary Artery and Vein: These major vessels run anterior and inferior to the glenohumeral joint. The extreme displacement of the humeral head can cause contusion, stretching, laceration, or even thrombosis of these vessels, leading to compartment syndrome, ischemia, or life-threatening hemorrhage. Vascular injury is a limb-threatening emergency.
• Rotator Cuff Tears:
  • The forceful hyperabduction can avulse or tear one or more of the rotator cuff tendons (supraspinatus, infraspinatus, teres minor, subscapularis), particularly the inferior aspects. This can severely compromise post-reduction shoulder function and necessitate surgical repair.
• Fractures:
  • Greater Tuberosity Fracture: Often occurs as the humeral head displaces, pulling off a piece of bone where the rotator cuff attaches.
  • Surgical Neck Fracture of the Humerus: The neck of the humerus can impact the glenoid rim or acromion, leading to a fracture.
  • Glenoid Rim Fractures (Bankart Lesion): The humeral head can chip off a portion of the glenoid rim as it dislocates, potentially compromising glenoid stability. A bony Bankart lesion indicates a fracture of the anterior inferior glenoid.
  • Hill-Sachs Lesion: An impaction fracture on the posterior-superior aspect of the humeral head, occurring when the humeral head impacts the anterior glenoid rim during dislocation. While common in anterior dislocations, its presence can indicate the severity of the forces involved in an inferior dislocation.
• Soft Tissue Damage:
  • Capsular and Ligamentous Tears: The inferior glenohumeral ligament and the joint capsule are significantly stretched and often torn, contributing to post-injury instability.
  • Labral Tears: The labrum, a fibrocartilaginous rim around the glenoid, can be torn (e.g., Bankart lesion), further compromising joint stability.

Long-Term Complications

Even after successful reduction, patients who have experienced an inferior shoulder dislocation may face ongoing issues.

• Recurrent Instability:
  • Due to significant damage to the joint capsule, ligaments, and labrum, the shoulder is at a higher risk of subsequent dislocations, particularly anteriorly. This can lead to chronic pain and functional limitations.
• Chronic Pain and Stiffness:
  • Persistent pain and reduced range of motion are common, often due to unaddressed soft tissue injuries, nerve damage, or developing arthritic changes.
• Osteoarthritis (Post-traumatic Arthritis):
  • Repeated dislocations, articular cartilage damage during the initial injury, or persistent joint instability can accelerate the degenerative process, leading to glenohumeral osteoarthritis.
• Adhesive Capsulitis (Frozen Shoulder):
  • Inflammation and scarring of the joint capsule can restrict shoulder movement significantly, leading to a "frozen shoulder" if not managed with appropriate early mobilization and physical therapy.
• Muscle Atrophy and Weakness:
  • Residual nerve damage (especially axillary nerve), prolonged immobilization, or disuse due to pain can lead to significant muscle wasting and persistent weakness, particularly in abduction and external rotation.

Diagnostic Considerations

Given the high rate of complications, a thorough assessment is paramount following suspected inferior shoulder dislocation. This includes:

• Clinical Examination: Assessing neurovascular status (pulses, sensation, motor function), range of motion, and deformity.
• Radiography: X-rays (AP, Y-view, and axillary views) are essential to confirm the dislocation, identify associated fractures, and rule out other pathologies.
• Advanced Imaging (MRI/CT): Often required to fully assess soft tissue damage (rotator cuff, labrum, capsule), nerve integrity, and complex fractures. CT angiography may be necessary if vascular injury is suspected.

Management and Prevention of Complications

Prompt and careful management is key to minimizing complications.

• Emergency Reduction: The primary goal is prompt, gentle reduction of the dislocation, often requiring strong analgesia and muscle relaxation.
• Post-Reduction Assessment: Immediate re-assessment of neurovascular status and repeat imaging are crucial to confirm successful reduction and identify any new or previously missed complications.
• Addressing Associated Injuries: Fractures, significant rotator cuff tears, or vascular injuries often require specific surgical intervention.
• Rehabilitation: A structured physical therapy program is essential to restore range of motion, strength, and stability, reducing the risk of recurrent instability and stiffness. Early, controlled mobilization is often preferred over prolonged immobilization.

Conclusion

Inferior shoulder dislocation, while uncommon, is a severe injury associated with a high incidence of immediate and long-term complications. From critical neurovascular compromise and extensive fractures to chronic instability and degenerative changes, the potential sequelae underscore the importance of rapid diagnosis, meticulous reduction, and comprehensive post-injury management. A multidisciplinary approach, involving emergency physicians, orthopedic surgeons, and physical therapists, is vital to optimize outcomes and mitigate the profound impact of this injury on shoulder function and quality of life.