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A diaphyseal fracture is a bone break that occurs along the shaft of a long bone like the femur in the thigh or the ulna in the forearm. Diaphysis is the anatomical name for the shaft of a long bone, which is differentiated from the epiphyses, the ends of the bone. Usually the result of a high-impact trauma such as a sports collision or automobile accident, a diaphyseal fracture typically is characterized by a clean, often oblique break across the shaft of the bone. This injury may also be experienced in individuals with weakened bone health as a consequence of repetitive stress of other, less severe trauma.
Afflicting the bones of the arms, legs, fingers, and toes, a diaphyseal fracture may occur anywhere along the shaft of the bone. The humerus in the upper arm, the radius and ulna in the forearm, the phalanx bones in the fingers and toes, the femur in the thigh, and the tibia and fibula in the shin are all susceptible to this type of injury. For one thing, they are long and narrow, a shape that makes them more vulnerable to a fracture. Additionally, they are found in the limbs, which often absorb the weight of a collision or fall, such as using the hands to brace against impact and sending the force into the wrists and forearms.
When a bone like the humerus suffers a diaphyseal fracture, the break may occur in one of several directions. In a transverse fracture, the bone fractures in a direction that is perpendicular to its length. An oblique fracture occurs diagonally, or at an angle; as the broken fragments are thereby pointed, this type of fracture is more likely to be an open or compound fracture, meaning that the broken bone penetrates skin and muscle, increasing the risk of infection as the injury heals. Spiral fractures are common as well, in which the bone twists as it breaks rather than split away linearly. The shaft may also fracture in a linear direction, or parallel to the length of the bone, though this is less likely.
Depending on the bone affected and the severity of the break, treatment of a diaphyseal fracture varies widely. A fractured phalanx in a finger or toe often is simply splinted, provided that the break is closed and does not break the skin. Weight-bearing bones like the femur and the humerus, which supports the weight of the arm hanging below it, may be repaired using a plate or screws. The injury will then be set in a cast as it heals, with a sling often needed to support the arm and crutches to keep weight off the leg. In some cases, a several diaphyseal fracture can damage nerves, blood vessels, and other tissues around the break; these may need to be surgically repaired as well.