This fracture type is classified by the AO/OTA as 13A1.1.
This is an avulsion fracture of the lateral epicondyle. By definition, there is no involvement of the joint (capitellum). The fracture is the equivalent of an avulsion of the humeral attachment of the lateral collateral ligament. Typically, this injury occurs in young patients.
The fragment may become incarcerated in the lateral elbow joint cavity (see x-ray below).
To avoid varus instability of the elbow, the fragment should be fixed.
Image taken from Orozco R, et al. (1998) Atlas of Internal Fixation. Used with kind permission.