Abstract
Synostosis is a generic term to indicate the union of two originally separated bones. At the elbow, humeroradial or longitudinal synostosis causes significant disability, which varies depending on hand function, elbow positioning, adjacent joints mobility and contralateral limb function. It is estimated that, to date, a little more than 150 patients have been described with this deformity, which is more common in subjects with deficient ulnar formation or affected by conditions such as Antley-Bixler and Hermann syndromes. The lack of the elbow joint, with the formation of a longer bone due to humerus-radius fusion, results in stiffness. As such, it is assumed that fractures in this topography are not uncommon. However, since synostosis is rare, this lesion was only described twice in the literature. We report two patients with a fracture of the single bone formed by a humeroradial synostosis and Bayne type-IV ulnar formation failure. Both patients were treated surgically with success. We emphasize the need for adequate treatment to not compromise the daily activities of patients who are adapted to their deformity, thus avoiding worsening the function of a previously affected limb.