While proximal humerus fractures with minimal displacement are usually treated conservatively, displaced fractures require surgical treatment [1]. As the importance of head shaft angles and medial support in proximal humerus fracture surgery was reported, the restoration of medial hinge and proper medial support is related to better functional outcomes [2,3]. A varus displaced fracture has been regarded as unstable fracture type and has been related to varus deformity in proximal humerus fractures [4]. As these fractures are accompanied by angulation and comminutions, the exact identification of the fracture characteristics is an important initial step for surgical repair. While recent advances in implant design and fixation techniques have led to good functional outcomes, displaced proximal humerus fractures are still associated with several complications. These complications include a loss of reduction, implant-related problems, osteonecrosis, nonunion, malunion, axillary nerve neuropathy, and stiffness [5,6].

The principal goal in the treatment of displaced proximal humerus fractures is to achieve anatomical reduction and to make a stable fixation, there are surgical options: 1) open reduction and plate fixation, 2) minimally invasive surgery, 3) intramedullary nailing, and 4) bone graft or fibular allograft augmentation [7,8]. It is important to note that medial buttress stabilization using bone and screw supports recovers shoulder biomechanics and that initial varus displacement is converted to the proper anatomical alignment, resulting in decreased pain and better function [9]. While surgical techniques have developed, varus deformity or loss of reduction continue to happen. Varus progression and screw cutout after surgery are inversely related to functional outcomes [10]. It remains unclear why a high proportion of initial varus displacement is related to poor outcomes and how much head shaft angles should be achieved to recover the shoulder biomechanics in varus displaced fractures. This study was performed to compare fracture characteristics and functional outcomes between patients who underwent surgery for proximal humerus fractures with and without initial varus displacement. We hypothesized that all variables influenced results in healing and good shoulder mobility.