Objective To investigate the clinical outcomes of treating fractures of the middle-inferior humerus with double plate fixation via the upper arm posterior approach through the inner edge of the joint triceps tendon.Methods From May 2013 through May 2015,32 fractures of the middle-inferior humerus were treated with open reduction and double plate fixation by the upper arm posterior approach via the inner edge of the joint triceps tendon.They were 19 males and 13 females,aged from 17 to 54 years (mean,36.8 years).Involved were 14 left sides and 18 right sides.By AO classification,21 cases were type B and 11 type C,all closed fractures.X-ray examinations were regularly conducted at postoperative follow-ups;function of the elbow joint was assessed according to the Jupiter elbow joint grading system at the final follow-up.Results All the 32 patients were followed up for 6 to 20 months (average,11.5 months).The fractures healed after 4 to 7 months (average,5.0 months).The flexion ranged from 120° to 135° (average,125°),and the extension ranged from 0 to 8° (average,5°).There were no such complications as postoperative infection,plate breakage,or nonunion.According to the Jupiter elbow joint grading system at the final follow-up,there were 15 excellent cases,14 good ones,and 3 fair ones,giving a good to excellent rate of 90.6％.Conclusion Open reduction and double plate fixation by the upper arm posterior approach via the inner edge of the joint triceps tendon is simple for fractures of the middle-inferior humerus and leads to satisfactory reduction,reliable fixation,and fine outcomes.