BACKGROUND:Proximal humerus internal locking system locking plate is the most commonly used fixation method for proximal humeral fractures,but its failure rate is still high in clinical practice.Reasonable screw placement is an important factor affecting the stability of internal fixation. OBJECTIVE:To investigate the distribution of humeral head screws in the treatment of proximal humeral fractures with proximal humerus internal locking system plate and its influence on internal fixation failure. METHODS:From January 2017 to December 2021,data from patients with proximal humeral fractures undergoing proximal humerus internal locking system plate in Third Affiliated Hospital of Guangzhou University of Chinese Medicine were retrospectively analyzed.A total of 124 patients were enrolled,including 16 males and 108 females,at the age of≥60 years.According to whether there was internal fixation failure after operation,they were divided into normal group(n=101)and internal fixation failure group(n=23).The patient's age,gender,fracture type,the integrity of the medial column,plate height,neck-shaft angle,whether the talus screw was inserted,and the number of humeral head screws,were collected.The humeral head was divided into eight zones according to the postoperative digital radiography anteroposterior film,and the distribution characteristics of the screws in each zone were collected,and the heat map of the screw distribution was drawn. RESULTS AND CONCLUSION:(1)There were no significant differences between the two groups in age,gender,fracture type,the integrity of the medial column,plate height,neck-shaft angle,whether to insert talus screws,and the number of humeral head screws(P>0.05).(2)The heat map showed that the humeral head screws were evenly distributed in the normal group,mainly scattered in zones 4,6,and 7.However,the screw distribution in the internal fixation failure group was not uniform,mainly concentrated in zones 4 and 6.In addition,in the ideal area of talus screws(7/8 zone),there were significantly more screws in the normal group than in the internal fixation failure group.(3)It is indicated that in the treatment of proximal humeral fractures with proximal humerus internal locking system plate,the uniform distribution of humeral head screws is the key to ensuring the internal fixation effect.A reasonable distribution of humeral head screws helps to improve the treatment effect and the success rate of internal fixation.