Manubriosternal dislocation

Manubriosternal dislocation (or sternomanubrial dislocation) represents a range of dislocation injuries of the sternomanubrial joint.

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:

• chest wall

  • sternal body and/or manubrial fractures

  • rib fractures

  • costal cartilage fractures

• pulmonary

  • pneumothorax

  • hemothorax

  • pulmonary contusion

• 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.

• type I

  • sternal body dislocates posteriorly with respect to the manubrium

  • least common

  • usually due to direct traumatic anterior compression of the sternal body

• 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.