Mechanism of injury (MOI) is the force or forces that cause injury when applied to the human body. Forces have characteristics such as speed,
size and direction. Your observations of the mechanism of injury are an important element in a patient’s care. There are four factors
to consider when assessing a mechanism of injury.
Factor
Examples
Speed
Traveling approximately 50 MPH
Fall from standing
Fall from height of 15 feet
Landed on concrete floor
Type/Size
Car versus bicycle
Automobile collision with utility pole
12-gauge shotgun at close range
High-powered rifle (30-06)
Stabbing with a 3-inch paring knife
Air-powered nail gun (1-inch nails)
Direction
Ankle flexed outward
Shot in the head from behind
Stabbed in side of the thorax
T-boned by station wagon
Other Evidence
Significant damage sustained by vehicle
Intrusion into the passenger compartment
Rider was not wearing helmet
Driver was wearing safety belts
Vehicle airbags deployed
Patient states the perpetrator kicked him in the belly
A direct force is one that can cause injury at the point of impact. An indirect force can result in an injury at a point distant from the point of impact. An example of a direct force is the abdomen slamming into a steering wheel that damages the spleen. An example of an indirect force is a person falling and landing on his feet with the indirect force causing a fracture of the spine.
