Fractures of the elbow can involve the upper bone (humerus) or the two lower bones in the forearm (radius and ulna). The humerus (upper arm bone) obviously can be broken at the top near the shoulder, in the middle along the shaft of the bone, or at the bottom where it joins the elbow. A fracture at the bottom of the humerus is called a distal humeral fracture.
Bicolumnar is a more complex fracture pattern affecting both sides of the distal humerus where it meets the radius and ulma to form the elbow. The two sides of the humerus involved are the medial side (or inside next to the body) and lateral side (outside away from the body).
When the humerus breaks across or through both sides, different soft tissues (skin, ligaments, tendons, muscles), nerves, and blood vessels can be affected, too. For example, the radial nerve travels down the lateral (outside) of the elbow and forearm, whereas the ulnar nerve takes the medial (inside) track.
Two groups of patients seem to make up the majority of bicolumnar distal humeral fractures: young athletes involved in high-energy trauma and older adults (mostly women) with osteoporosis (brittle bones). Older folks who lose their balance and fall on an outstretched hand/arm or directly onto the elbow are at risk for elbow fractures of all kinds, especially bicolumnar.