Scapulothoracic dissociation (SD) can be a devastating multisystem emergency that requires immediate evaluation for potential limb-threatening ischemia and neurovascular injury, including trauma to the brachial plexus. Once hemodynamically stable, exploration and repair of vascular injury with concomitant osseous stabilization is undertaken.
Urgent orthopedic and vascular consultations may be required in cases of neurovascular injury. This injury is typically associated with a high-energy mechanism of trauma. This diagnosis can be overlooked in patients presenting with multiple traumas, so a thorough physical examination must be performed.
Causes / typical injury mechanism: SD is typically caused by high-energy trauma involving lateral traction injury to the shoulder girdle, resulting in disruption of the scapulothoracic articulation. This is most commonly seen in motor vehicle accidents and occasionally seen in falls and industrial machine accidents.
Classic history and presentation: Patients with SD present with pain involving the upper extremity (UE) and numbness / tingling in the UE. SD is characterized by orthopedic, vascular, and neurological injury to the affected extremity. Orthopedic injury can involve scapula, proximal humerus, and/or clavicle fractures, acromioclavicular (AC) and sternoclavicular (SC) joint dislocation / separation, and flail extremity. The subclavian artery is the most commonly injured with SD, although the axillary artery can also be injured. The ipsilateral brachial plexus is injured in 90% of SD cases.
Prevalence: Very rare.
Risk factors: High-energy trauma, most commonly motor vehicle collisions.
Pathophysiology: Detachment of the body of the scapula from the thorax secondary to high-energy trauma, potentially causing scapula, proximal humerus, and/or clavicle fractures, AC / SC joint dislocation, subclavian and/or axillary artery injury, and ipsilateral brachial plexus lesions.
Grade / classification system: Zelle et al classification of scapulothoracic dissociations –
- Type 1: Musculoskeletal (MSK) injury alone
- Type 2a: MSK injury + vascular disruption
- Type 2b: MSK injury + incomplete brachial plexus injury
- Type 3: MSK injury + vascular disruption + incomplete brachial plexus injury
- Type 4: MSK injury + complete brachial plexus injury
