ObjectiveTo analyze the outcome and prognostic factors of using locking plate for treating proximal humerus fracture. MethodsBetween January 2005 and January 2012, 45 aged patients with a displaced 3-part or 4-part fracture of the proximal humerus were treated by locking plate. Range of motion and Constant-Mudey score were observed during the follow-up. ResultsForty-three patients were followed up from 12 to 48 months with an average of 18 months. The mean final Constant-Mudey score was 72.3±9.5 and 6 of them needed a second surgery. In addition to fracture type, other prognostic factors included redisplacement (4 cases, 9.3%), nonunion (3 cases, 7.0%), crashing (3 cases, 7.0%), necrosis of the humeral head (6 cases, 14.0%) and screw cut-out (5 cases, 11.6%). Among the patients with disrupted medial calcar, 4 needed a second surgery at the final follow-up, 3 had redisplacement, 2 had nonunion, and 2 had screw cut-out. ConclusionLocked screw-plates provide more secure fixation of fracture in aged patients, but the complication rate remains high. We suggest anatomic reduction, and plate and screws position, length of the screws, the medial cortical contact and stability may be the chief prognostic factors affecting the shoulder function following a proximal humeral fracture.