Manubriosternal dislocation (or sternomanubrial dislocation) represents a range of dislocation injuries of the sternomanubrial joint.
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Terminology
Joint dislocations are named according to the distal component in relation to the proximal bone. Thus, as the manubrium is superior to the sternum a posterior dislocation is when the sternum is pushed posterior with respect to the manubrium. It is worth noting, however, that this convention is not universally adopted for this joint 2 and thus it is prudent to be explicit in the report rather than relying on the expectation that all readers will interpret a "posterior dislocation" to mean the same thing.
Epidemiology
Sternomanubrial dislocation is a rare injury, reported in 1-3% of trauma cases 1,3. Dislocation is the result of high-energy blunt direct or indirect trauma and is almost always associated with other chest wall and intrathoracic injuries, which include 3:
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chest wall
sternal body and/or manubrial fractures
-
pulmonary
-
mediastinal
mediastinal hematoma
great vessel injury
Risk factors
female 2
advanced age 2
use of a seatbelt 2
Clinical presentation
Dislocation causes a palpable deformity or gap at the sternomanubrial joint. Further signs of chest trauma are often present due to the high association with other chest wall and intrathoracic injuries.
Pathology
The injury can be classified into two types based on the position of the body of the sternum relative to the manubrium and is representative of the mechanism of injury 4.
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type I
sternal body dislocates posteriorly with respect to the manubrium
least common
usually due to direct traumatic anterior compression of the sternal body
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type II
sternal body dislocates anteriorly with respect to the manubrium
most common
due to either direct trauma to the manubrium or indirect upper thoracic hyperflexion which transfers compressive forces via the first ribs to the manubrium
Radiographic features
Plain radiograph
A lateral chest radiograph may show malignment or separation of the sternomanubrial joint but these should not be performed in major trauma. A frontal radiograph is useful for identifying other traumatic injuries of the chest.
CT
joint space widening and asymmetry of the sternomanubrial joint
associated injuries of the mediastinum, chest wall and lungs
Treatment and prognosis
Conservative treatment can be trialed but often fails. Complications include 2:
periarticular calcification
ankylosis
chronic pain
structural deformity
Operative management is indicated for severe intractable pain, respiratory distress and/or deranged chest wall mechanical function. Patients with significant concomitant injuries often undergo surgical treatment. Surgical fixation (ORIF) is performed with plates and screws or cerclage wires and often based on surgeon preference.