Scapulothoracic dissociation is rare, resulting from high-energy trauma to the shoulder girdle and disruption of the scapulothoracic articulation. The associated musculoskeletal, vascular, and neurologic injuries carry potentially devastating outcomes. Overall outcomes seem to be closely related to the degree of neurologic impairment sustained. However, given the wide spectrum of injury in scapulothoracic dissociation and limited data concerning outcomes, general recommendations regarding the management of this injury have been difficult to discern. This article reviews the current data regarding the evaluation, diagnosis, treatment, and outcomes after scapulothoracic dissociation.
Key Points
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Scapulothoracic dissociation is a rare injury that results from high-energy trauma to the shoulder girdle, leading to disruption of the scapulothoracic articulation.
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The associated injury patterns represent a wide spectrum of musculoskeletal, vascular, and neurologic injuries with potentially devastating outcomes.
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Overall outcomes seem to be closely related to the degree of neurologic impairment sustained at the time of injury. However, given the wide spectrum of injury in scapulothoracic dissociation and limited data concerning outcomes, general recommendations regarding the management of this injury have been difficult to discern.
Scapulothoracic dissociation is a rare, devastating injury resulting from high-energy trauma to the shoulder girdle. Originally described by Oreck and colleagues in 1984, this injury is defined as a traumatic disruption of the scapulothoracic articulation with lateral displacement of the scapula and intact skin. It is believed to result from a high-energy force applied to the shoulder girdle with massive traction to the ipsilateral upper extremity. Scapulothoracic dissociation represents a spectrum of injury that can also include any of the following injuries: Osseous injury to the acromioclavicular (AC) joint, clavicle, and/or sternoclavicular (SC) joint; vascular disruption of the subclavian or axillary vessels; partial or complete avulsion of the brachial plexus; and severe soft-tissue swelling with disruption of the musculature surrounding the shoulder girdle ( Fig. 1 ). As a result, this injury has been characterized as a closed internal forequarter amputation of the upper extremity.
Evaluation and diagnosis
Diagnosis of scapulothoracic dissociation begins with the clinical history and examination. As a result of improved resuscitation protocols and trauma systems, this rare injury pattern is being identified more frequently, making awareness of this clinical entity critical to making the diagnosis. Although scapulothoracic dissociation typically results from high-energy trauma with considerable traction to the involved extremity, confirmation of the exact mechanism may be difficult given an increased chance for associated head trauma. This injury most frequently occurs as a result of motorcycle accidents among reported cases in the literature, but has also been described as sequelae of motor vehicle crashes, falls from heights, and pedestrian versus automobile crashes. It occurs in both adults and children, and both open and bilateral injuries have been described. Prompt recognition of this injury pattern is paramount given the concern for life-threatening exsanguination or limb-threatening ischemia from vascular disruption. However, recognition of this exceedingly rare injury pattern can be complicated by many factors, thereby increasing the potential for delayed diagnosis and treatment. Patients with scapulothoracic dissociation have an increased risk for polytrauma given the high amount of energy required to produce this injury. Associated life-threatening injuries have the potential to distract the emergency department physician from a detailed examination of the involved extremity, especially in cases where the patient requires intubation and/or sedation in the prehospital setting.
On clinical examination, severe swelling is typically present around the shoulder as a result of soft-tissue edema and/or hematoma. Complete or partial disruption of the deltoid, pectoralis minor, rhomboids, levator scapulae, trapezius, and latissimus dorsi have all been described as a result of scapulothoracic dissociation. Pain, tenderness, and weakness can be present, requiring thorough inspection of the entire shoulder girdle to evaluate for fracture and/or dislocation. Concomitant injuries of the ipsilateral upper extremity as well as other body regions are not uncommon. The appearance and distal perfusion of the involved extremity should be documented. In the patient who is without life-threatening injury and is alert and cooperative, a detailed neurologic examination should be performed to evaluate for brachial plexus injury.
Radiologic evaluation begins with a well-centered chest radiograph. Significant lateral displacement of the scapula is considered pathognomonic for scapulothoracic dissociation ( Fig. 2 ). This can be quantified by measuring the scapular index, which is the distance from the midline of the spine to the medial border of the scapula of the affected side divided by that of the noninjured side. Normal values lie in the range of 1.07, although 2 small series have reported average scapular indices from 1.29 to as high as 1.50 in patients with scapulothoracic dissociation. Because the scapular index requires a well-centered, non-rotated chest radiograph to accurately determine, there is potential for inaccurate measurement. As such, this value should not be considered alone for a diagnosis of scapulothoracic dissociation. Additional radiographs of the scapula as well as computed tomography (CT) scans can be helpful in confirming this diagnosis and are routinely ordered in most level 1 trauma centers caring for patients with significant shoulder girdle trauma. In addition, associated osseous injuries about the shoulder (AC joint separation, clavicle fracture, SC joint dislocation) occur in association with this injury and appropriate studies should be ordered to evaluate these structures.
Diagnosis of vascular injury begins with evaluation of the clinical appearance and distal perfusion of the affected extremity. Pallor, coolness to touch, and mottling can all be present. Pulses should be checked by manual palpation and/or Doppler ultrasonography. Any suspected case of scapulothoracic dissociation necessitates emergent angiography to evaluate for injury to the subclavian, axillary or brachial vessels ( Fig. 3 ). Vascular lesions have been reported in 64% to 100% of patients in several small series to date. The vascular disruption typically results from either intravascular thrombosis or extrinsic arterial compression; death from uncontrolled hemorrhage secondary to vascular disruption is relatively uncommon. Furthermore, the risk of limb-threatening ischemia of the involved extremity has been reportedly low and may be overestimated in scapulothoracic dissociation. This is likely owing to a protective effect from the extensive collateral circulation around the shoulder girdle.
Clinical history and physical examination are the cornerstones for evaluation and diagnosis of neurologic injury after scapulothoracic dissociation. This can be complicated by an obtunded or uncooperative patient given the potential for severe injuries to other organ systems. It is critical to perform a complete, detailed neurologic examination to determine whether if the deficit is partial or complete. Damage to the brachial plexus determines the functional prognosis of scapulothoracic dislocations. Complete brachial plexus injury may be associated with preganglionic nerve root avulsions or even rupture of the trunks in the interscalene space. Nerve root avulsions have limited potential for spontaneous recovery, and complete brachial plexus avulsions have been shown to be predictive of poor functional outcome. Weakness of the serratus anterior, rhomboids, and levator scapula are all suggestive of preganglionic injury. Horner’s syndrome, consisting of ipsilateral miosis, ptosis, enophthalmos, and anhydrosis, is suggestive of a preganglionic lesion at T1. Lower extremity examination may show evidence of clonus or spasticity, which is suggestive of a cord injury (ie, upper motor neuron).
Rorabeck and Harris originally described 4 prerequisites for establishing an irreversible prognosis for complete brachial plexus injuries: (1) The absence of any clinical recovery; (2) 3 or more pseudomeningoceles on myelography; (3) the absence of voluntary action potentials on repeated electromyographic examinations of C5 to T1; and (4) positive histamine tests in the C5 to T1 territory. CT myelography and magnetic resonance imaging may be considered as a screening tool for nerve root avulsion, particularly in patients with multilevel lesions. Magnetic resonance imaging generally allows for better imaging of the soft tissues and may be helpful for determining the presence of a pseudomeningocele, which has been strongly correlated with avulsion of the corresponding nerve root. However, 1 study has shown that either magnetic resonance imaging or CT myelography can be used to detect cervical root avulsion with 93% sensitivity in patients with traumatic brachial plexus injuries. In cases of complete brachial plexus injury, CT myelography has been suggested as soon as the third week after injury to assess the possibility nerve grafting from an intact root. In the case of incomplete paralysis, neurophysiologic testing may be used to assess trapezius and serratus anterior function, which can assist in planning tendon transfers and soft tissue reconstruction.
Electrodiagnostic studies can be a useful diagnostic aid to determine the involved nerve roots in a patient with a brachial plexus injury. These studies are best delayed until approximately 3 to 4 weeks after injury to best evaluate for complete denervation. Electromyography (EMG) of the deep posterior cervical musculature can be of great value in determining whether the lesion is preganglionic or postganglionic. This determination is made through EMG of the erector spinae, which are innervated by posterior branches of the spinal nerves that exit the root between the spinal cord and the sympathetic ganglion. When there is denervation of the muscles innervated by the plexus that does not include deep posterior cervical musculature, the lesion is presumed to be postganglionic in nature. The combination of clinical examination, upper limb EMG, and paraspinal EMG have been shown to be predictive of the site of the lesion in 80% of patients with either a preganglionic or postganglionic injury and in 67% of patients with a combined injury.
Two main classification systems have been proposed for scapulothoracic dissociation. Damschen and colleagues first proposed a logical system in 1997 to allow for improved clinical decision making regarding diagnosis and management. This was modified in 2004 by Zelle and colleagues in a study on the long-term functional outcome following scapulothoracic dissociation, which differentiates between patients with complete and incomplete brachial plexus avulsion ( Table 1 ). A type 1 injury involves musculoskeletal injury alone, whereas type 2A or B adds vascular compromise or incomplete neurologic impairment, respectively. A type 3 pattern consists of musculoskeletal injury with both vascular injury and incomplete neurologic impairment, whereas a type 4 includes a musculoskeletal injury with complete brachial plexus avulsion. This classification scheme reflects their finding that long-term functional outcomes in their cohort of patients correlated poorly with the classification system proposed by Damschen and colleagues, and that complete brachial plexus avulsion remains the most predictive parameter for poor functional recovery.
| Type | Clinical Findings |
|---|---|
| 1 | Musculoskeletal injury alone |
| 2A | Musculoskeletal injury with vascular disruption |
| 2B | Musculoskeletal injury with incomplete neurologic injury |
| 3 | Musculoskeletal injury with vascular disruption and incomplete neurologic injury |
| 4 | Musculoskeletal injury with complete neurologic injury |
Evaluation and diagnosis
Diagnosis of scapulothoracic dissociation begins with the clinical history and examination. As a result of improved resuscitation protocols and trauma systems, this rare injury pattern is being identified more frequently, making awareness of this clinical entity critical to making the diagnosis. Although scapulothoracic dissociation typically results from high-energy trauma with considerable traction to the involved extremity, confirmation of the exact mechanism may be difficult given an increased chance for associated head trauma. This injury most frequently occurs as a result of motorcycle accidents among reported cases in the literature, but has also been described as sequelae of motor vehicle crashes, falls from heights, and pedestrian versus automobile crashes. It occurs in both adults and children, and both open and bilateral injuries have been described. Prompt recognition of this injury pattern is paramount given the concern for life-threatening exsanguination or limb-threatening ischemia from vascular disruption. However, recognition of this exceedingly rare injury pattern can be complicated by many factors, thereby increasing the potential for delayed diagnosis and treatment. Patients with scapulothoracic dissociation have an increased risk for polytrauma given the high amount of energy required to produce this injury. Associated life-threatening injuries have the potential to distract the emergency department physician from a detailed examination of the involved extremity, especially in cases where the patient requires intubation and/or sedation in the prehospital setting.
On clinical examination, severe swelling is typically present around the shoulder as a result of soft-tissue edema and/or hematoma. Complete or partial disruption of the deltoid, pectoralis minor, rhomboids, levator scapulae, trapezius, and latissimus dorsi have all been described as a result of scapulothoracic dissociation. Pain, tenderness, and weakness can be present, requiring thorough inspection of the entire shoulder girdle to evaluate for fracture and/or dislocation. Concomitant injuries of the ipsilateral upper extremity as well as other body regions are not uncommon. The appearance and distal perfusion of the involved extremity should be documented. In the patient who is without life-threatening injury and is alert and cooperative, a detailed neurologic examination should be performed to evaluate for brachial plexus injury.
Radiologic evaluation begins with a well-centered chest radiograph. Significant lateral displacement of the scapula is considered pathognomonic for scapulothoracic dissociation ( Fig. 2 ). This can be quantified by measuring the scapular index, which is the distance from the midline of the spine to the medial border of the scapula of the affected side divided by that of the noninjured side. Normal values lie in the range of 1.07, although 2 small series have reported average scapular indices from 1.29 to as high as 1.50 in patients with scapulothoracic dissociation. Because the scapular index requires a well-centered, non-rotated chest radiograph to accurately determine, there is potential for inaccurate measurement. As such, this value should not be considered alone for a diagnosis of scapulothoracic dissociation. Additional radiographs of the scapula as well as computed tomography (CT) scans can be helpful in confirming this diagnosis and are routinely ordered in most level 1 trauma centers caring for patients with significant shoulder girdle trauma. In addition, associated osseous injuries about the shoulder (AC joint separation, clavicle fracture, SC joint dislocation) occur in association with this injury and appropriate studies should be ordered to evaluate these structures.
