This prospective follow-up study investigates the correlation between healing of the tuberosities and the functional outcome after arthroplasty with a trauma shoulder prosthesis in elderly patients with non-reconstructable humeral head fractures. Surgery was performed on 65 patients (66 cases). Patients underwent clinical and radiological evaluation. A total of 56 patients (57 cases) were examined after a mean time to follow-up of 16 months (range 4–62 months). Mean Constant Score was 50 and the age- and gender-corrected value was 73%. The Constant Score was significantly higher (62 points, p=0.015) if the tuberosities healed. Mean ASES index was 68 and correlated significantly to the Constant Score (r=0.77). Healing of the tuberosities is crucial to achieve good functionality in patients treated with a humeral head prosthesis. For elderly patients, the main objectives are to recover the ability to perform activities of daily living, to become pain free, and to reach a high level of satisfaction. All these criteria are largely achieved by the procedure described in this paper.