ObjectiveAnalyze the results of unipolar modular radial head arthroplasty in the treatment of complex fractures associated with elbow joint instability. Material and methodRetrospective design study of 44 patients, 17 men and 27 women with a mean age of 51 years (17-78) who suffered radial head fractures (Mason III) in the context of an unstable elbow injury. Mean follow-up was 21.2 months (12-60). Radial head replacement was performed with a unipolar modular prosthesis with a fixed stem (Ascension® Modular Radial Head [MRH]), associating repair of concomitant lesions. The Mayo scale Elbow Performance Score (MEPS) was used to perform the functional assessment. A radiological evaluation was performed at the last follow-up and the complications were recorded. ResultsFinal arc of flexion-extension was 108° with an average of 135° of prono-Supination. At final follow-up, 82% of results were satisfactory according to the MEPS. The 40% of patients (17) had radiographic signs of lucencies around the stem, although most of them were asymptomatic. Two of them needed a second surgical procedure because of painful prosthetic loosening and further surgery was required for a prosthesis dislocation. DiscussionRadial head implants are an adequate treatment option for restoring stability in complex radial head fractures. Modularity allows a wide range of size combination and helps to avoid overstuffing. Periprosthetic osteolysis could be associated with the presence of pain, so it is necessary to perform long-term studies to test the potential complications of this finding.