Scapulothoracic Dissociation - A Rare and Severe Traumatic Injury

Introduction

The scapula, or shoulder blade, is a flat, triangular bone on the chest wall's posterior aspect. It plays a pivotal role in shoulder movement, primarily through its articulation with the clavicle and the humerus. The scapulothoracic joint is unique because it lacks articular cartilage, synovium, capsule, or ligaments. Instead, it relies on muscles and bursae for its functioning. The scapula's connection to the thorax occurs indirectly through the clavicle and the acromioclavicular and sternoclavicular joints.

What Is Scapulothoraccic Dissociation?

Scapulothoracic dissociation is a rare and severe traumatic injury that occurs when the scapula, or shoulder blade, separates from the thoracic wall, the ribcage, and the chest wall. Severe injuries to the brachial plexus and subclavian vessels typically accompany this condition. Diagnosis of this life-threatening condition is often delayed, particularly in patients with multiple injuries. Survivors of scapulothoracic dissociation frequently experience significant disability due to neurological deficits, vascular injuries, or a combination of both.

What Are the Causes of Scapulothoracic Dissociation?

Scapulothoracic dissociation occurs due to high-energy trauma that forces the scapula away from the ribcage. The injury mechanism involves a forceful, direct blow or sudden deceleration when the affected upper limb is immobilized, such as gripping a steering wheel or motorcycle handlebar.

Common causes are:

• Motor vehicle and motorcycle accidents.

• Direct trauma from industrial machine accidents or other workplace accidents.

• Falls from heights.

• Athletic injuries.

What Are the Clinical Features of Scapulothoracic Dissociation?

Common patient symptoms include

• Severe pain.

• Significant uneven swelling of the affected shoulder.

• Noticeable hematoma (blood collection).

• Obvious shoulder displacement or deformity resulting due to the dislocated scapula.

• Weakness, numbness, and tenderness in the affected area.

• Sometimes, the skin over the affected area may appear normal, concealing the severe underlying injury.

• Vascular signs like a lack of pulse, paleness, and coolness in the affected arm.

Classification of Scapulothoracic Dissociation

• Type 1 - Injury limited to the musculoskeletal system without vascular or brachial plexus involvement.

• Type 2A - Musculoskeletal injury accompanied by vascular disruption.

• Type 2B - Musculoskeletal injury with an incomplete injury to the brachial plexus.

• Type 3 - Musculoskeletal injury combined with vascular disruption and an incomplete injury to the brachial plexus.

• Type 4 - Musculoskeletal injury with a complete injury to the brachial plexus.

How Is Scapulothoracic Dissociation Diagnosed?

Clinical Assessment

• If the patient's condition allows, a comprehensive examination of the injured upper extremity and a thorough neurological assessment is performed.

• A clavicular fracture or disruption of the acromioclavicular joint is often palpable.

• Vascular injuries are quite common in scapulothoracic dissociation cases (64 to 100%) and are often caused by thrombosis or external pressure on the subclavian or axillary arteries.

• Medical evaluation should include an assessment for signs of vascular or nerve injuries and fractures in the same-side upper limb. It's essential to note that pulselessness should not be wrongly attributed to a more distal injury when a proximal, life-threatening lesion might be present.

• Determining the level and extent of injury can be challenging, as the clinical findings for arterial injuries and nerve issues overlap.

• A detailed neurological evaluation is done to assess the presence, extent, and location of nerve injuries. Roughly 52 percent of affected patients experience a non functional upper extremity with complete loss of motor and sensory functions.

• Scapulothoracic dissociation can sometimes occur without significant nerve or vascular injuries, particularly in children, possibly due to the elasticity of their soft tissues.

Imaging Evaluation

• Radiographs : An anteroposterior chest radiograph is a part of the initial trauma assessment. An initial chest X-ray in the emergency room may reveal lateral displacement of the scapula and disruptions like acromioclavicular separation, displaced clavicle fractures, or sternoclavicular joint problems. Orthogonal radiographs are done for suspected upper extremity fractures or dislocations in addition to initial radiography.
• Vascular Imaging : Immediate vascular imaging work-up is advised, typically using CT angiography.
• Evaluation of Brachial Plexus Injuries : Brachial plexus injuries can be assessed based on the severity of trauma. Neurologic injury extent affects the functional prognosis and can be evaluated through physical examination, imaging techniques like CT myelography and MRI, electrodiagnostic studies, and surgical exploration.

Other Tests

• CT scan of the affected shoulder girdle is performed or may be obtained or reformatted from chest CT scans taken during admission.

• Magnetic resonance neurography is effective for evaluating postganglionic injuries.

• CT myelography and MRI are useful for differentiating nerve root avulsions from postganglionic brachial plexus injuries.

• CT myelography should not be performed earlier than 3 weeks after injury to allow for pseudo meningocele formation and resolution of potentially dye-displacing hematomas.

How Is Scapulothoracic Dissociation Managed?

A multidisciplinary approach is essential due to the complex nature of coexisting injuries in scapulothoracic dissociation. While there is no universally accepted treatment algorithm for this rare condition, the following approaches are commonly considered:

Phase I - Emergent Interventions (Acute phase)

• Diagnosis and resuscitation are done in the acute phase after the injury. Early recognition plays a major role in the survival of the patient.

• Emergent angiography is done to locate vascular injury is conducted.

• Vascular injuries require immediate surgical intervention to prevent hemorrhage and ischemia.

• Exploration and repair of neurologic injury may also be carried out.

• Bony stabilization procedures might be needed for associated fractures and joint disruptions.

• Venous injuries can be safely ligated without significant consequences.

• Early and appropriate soft tissue coverage is important for open injuries.

• Scapular suspension procedures may be considered.

Phase II - Subacute Phase (24 hours to 2 weeks after injury):

• This focuses on treating immediate sequelae and complications arising from the initial injury.

• Patients may undergo glenohumeral arthrodesis or above-elbow amputation in cases of complete brachial plexus injury at the cervical root level.

• The level of amputation is determined by the zone of demarcation in the skin.

• Glenohumeral arthrodesis can assist in prosthetic fitting.

• Psychological counseling and early fitting of prosthetics are important in this phase.

• Some patients may refuse amputation despite the flail arm.

• Patients with severe causalgia, pressure sores, and injury risk should be closely monitored.

Phase III - Chronic Phase

• This phase focuses on further evaluation of nerve injuries and reconstructive options.

• Electromyography and cervical myelography are performed to assess nerve damage.

• Nerve reconstruction, such as neurotization or nerve grafts, may be attempted within 2 to 6 months of the injury.

What Are the Complications Associated With Scapulothoracic Dissociation?

• Chronic Pain - Some patients may experience long-term pain and discomfort, even after surgical intervention.

• Loss of Function - Despite rehabilitation, there can be residual limitations in shoulder and arm function, affecting daily activities and quality of life.

• Psychological Impact - The traumatic nature of the injury and its long recovery process can psychologically impact patients, leading to anxiety, depression, or post-traumatic stress disorder (PTSD).

• Vascular Complications -Delayed or inadequate treatment of vascular injuries can result in ischemia and potentially the need for amputation.

Conclusion

Promoting safety measures like seatbelt use, fall safety, motorcycle, and sports safety can help reduce the incidence of more serious injuries. Increasing awareness of this condition and emphasizing preventive measures can further reduce the incidence of scapulothoracic dissociation.