Divergent single-column fractures of the distal part of the humerus.

We report an unusual intra-articular fracture of the distal part of the humerus that was seen in five patients, including one who had the fracture bilaterally. The fractures were characterized by three features. First, the fractures were initiated in the trochlear groove as a result of a direct impact on the olecranon, which divided the trochlea and then split the two columns of the humerus divergently. Second, the fractures occurred exclusively in adolescents and young adults (average age, fifteen years old; range, thirteen to twenty years old). Third, all of the fractures were seen in patients who had a large fossa or septal aperture between the coronoid and olecranon fossae. Four of the fractures involved the right side and two, the left. There were three fractures of the lateral column and three of the medial column. Because the periosteum, the capsule, and the ligaments remained intact despite intra-articular displacement of the distal part of the humerus, these fractures were also characterized by inherent proximal stability. The fractures were treated with closed reduction and percutaneous internal fixation to reduce the displacement between the two halves of the trochlea. All of the fractures united. Four patients (five elbows) regained full motion by eight months; one patient was lost to follow-up. Current classification systems that describe single-column fractures of the distal part of the humerus should be modified to include this unusual fracture pattern.