Objective To investigate the association between different number of inferomedial screws (0-3 screws) and their efficacy in locking plate of proximal humerus fractures.Methods Data of 90 patients who had undergone locking plate for proximal humerus fracture between January 2007 and December 2012 were retrospectively analyzed.They were divided into four groups according to the number of inferomedial screws.In the NS (no-screw support) group,36 patients did not have inferomedial screws for mechanical support of the inferomedial region of the proximal humerus; in the OS (one-screw support) group,23 patients had the reconstruction by insertion of only one inferomedial screw; there were 19 patients in the TS (two-screw support) group and 12 in the ThS (three-screw support) group.There were no significant differences among 4 groups in sex,fracture type and age.The Constant scores of the shoulder function,changes in humeral head height at the latest follow-up,incidence of complications and time for fracture healing among the 4 groups were collected.Results The follow-ups for the patients ranged from 12 to 56 months (mean,21.4 months).At the latest follow-up,the ThS,TS,OS and NS groups had a mean Constant score of 76.7 (SD,11.6),74.1 (SD,7.4),66.8 (SD,10.7),65.8 (SD,10.2),respectively; the mean change in humeral head height were 1.4 (SD,1.0) mm,2.9 (SD,1.2) mm,5.3(SD,3.2) mm and 6.7(SD,3.3) mm,respectively.There were no significant differences between the ThS and TS groups in Constant score,and Constant scores in ThS and TS groups were significantly higher than those in OS and NS groups.However,the loss in humeral head height in the ThS group was significantly less than those in the TS,OS and NS groups,and the loss in humeral head height in TS group was significantly less than those in the OS and NS groups.There were no significant differences among 4 groups in time for fracture healing and incidence of complications.Conclusion Locking plate in general do not appear to be a panacea for proximal humerus fractures especially in cases of medial comminution or bone defects because of the malreduction of the medial cortical bone.However,medial support with two or three inferomedial screws being meticulously placed in the inferomedial region may enhance the mechanical stability of medial column support and allow for better maintenance of reduction.