The aim of the study was to assess the rate of greater tuberosity non union in reverse shoulder arthroplasty performed for proximal humerus fractures and to assess if union is related to type of fracture or the intraoperative reduction of the greater tuberosity.

All cases of reverse shoulder arthroplasty for proximal humerus fractures at our institution over a three year period were retrospectively reviewed from casenotes and radiologically and the position of the greater tuberosity was documented at immediate post op, 6 months and 12 months. Any malunion or non union were noted.

A total of 27 cases of reverse shoulder arthroplasty for proximal humeral fractures were identified. 4 cases did not have complete follow up xrays and were excluded from analysis. The average age at operation of the cohort of the 23 remaining patients was 79 years (range 70–91). The greater tuberosity was anatomically well positioned intraoperatively in 17 of the 23 cases.

At the end of 12 months there were 4 cases of tuberosity non union (17%), all except one occurring in poorly intraoperatively positioned greater tuberosity. 50% (3 out of 6) of greater tuberosities displaced further and remained ununited if the intraoperative position was poor. Only 6% (1 out of 17) greater tuberosities did not unite if the greater tuberosities was reduced anatomically. Intra operatively position of the greater tuberosity was strongly associated with their union (Fischer's exact test p<0.05). Union of greater tuberosity was not statistically associated with fracture pattern (Fischer's exact test p=0.48).

Our case series show a low rate of tuberosity malunion after reverse shoulder arthroplasty for proximal humerus fracture. Good positioning and fixation of the greater tuberosity intra operatively is a strong predictor of their uneventful union to shaft.