Diaphragmatic injuries are relatively rare and result from either blunt trauma or penetrating trauma. Diagnosis and treatment are similar regardless of mechanism, although many management issues are specific to blunt trauma. Thus, this article focuses on blunt injuries and details their specific differences from penetrating injuries.
Diaphragmatic injuries were described first by Sennertus in 1541. Riolfi performed the first successful repair in 1886. Not until 1951, when Carter et al published the first case series, was this injury well understood and delineated.
For related information, see Medscape's Trauma Resource Center.
Presently, 80-90% of blunt diaphragmatic ruptures result from motor vehicle crashes (MVCs). Falls and other traumatic events rarely are implicated. The mechanism of rupture is related to the pressure gradient between the pleural and peritoneal cavities. Lateral impact from an MVC is 3 times more likely than any other type of impact to cause a rupture, since it can distort the chest wall and shear the ipsilateral diaphragm. Frontal impact from an MVC can cause an increase in intra-abdominal pressure, which results in long radial tears in the posterolateral aspect of the diaphragm, its embryologic weak point.
Review of the historical clinical literature, including the series of Carter et al  , reveals that the majority (80-90%) of blunt diaphragmatic ruptures have occurred on the left side. The less common right-sided ruptures have more severe associated injuries and result in greater hemodynamic instability. They required greater force of impact, possibly because the liver provides protection or because of a weakness in the left diaphragm.  An autopsy series, however, revealed that left- and right-sided ruptures occurred almost equally. Most likely, these ruptures do occur equally, but the more severe injuries associated with right-sided ruptures cause more deaths and thus a lower rate of patient survival until diagnosis in the hospital. The relative frequencies of right-sided (20-30%) and bilateral (5-10%) ruptures have increased each decade, probably because improvement in trauma care has increased survival rates of patients with significant injuries.
In MVCs, the direction of impact may determine if an injury occurs and on what side. The likelihood of injury is related directly to the direction of impact and the person's position in the car. Persons involved in an ipsilateral impact are more likely to sustain diaphragmatic injury, commonly on the ipsilateral side. In the United States and Canada, this is seen as left-sided injuries in drivers and right-sided injuries in passengers.
Blunt trauma typically produces large radial tears measuring 5-15 cm, most often at the posterolateral aspect of the diaphragm. In contrast, penetrating trauma can create small linear incisions or holes, which are less than 2 cm in size and may present late after years of gradual herniation and enlargement.
Penetrating injuries to the chest or abdomen also may injure the diaphragm. This specific injury is seen commonly where penetrating trauma is prevalent. This occurs most often from gunshot wounds but can result from knife wounds. Typically, the wounds are small, although occasionally a shotgun blast or an impalement causes a large defect. [3, 4]
Development of diaphragmatic injury in blunt trauma is relatively rare; these injuries are seen in fewer than 5% of all patients with blunt trauma. The incidence increases each decade probably because of the increased occurrence of high-speed MVCs. Improved survival rates are probably due to advances in prehospital care, trauma center triage, and early recognition.