ObjectiveTo evaluate the effectiveness of minimally invasive osteosynthesis using the helical plate for complex humeral shaft fractures involved proximal metaphysis, and to explore its feasibility and security. MethodsA retrospective analysis was made on the clinical data of 16 patients with complex humeral shaft fractures involved proximal metaphysis who underwent minimally invasive osteosynthesis with the helical plate between December 2009 and May 2015. There were 11 males and 5 females, aged from 18 to 56 years (mean, 34.6 years). The causes of fracture included falling injury in 5 cases, falling injury from height in 3 cases, traffic accident injury in 4 cases, sports injury in 3 cases, and belts twisted injury in 1 case. Accroding to Orthopaedic Trauma Association (OTA) classifications, 6 cases were rated as type 12-C1, 3 cases as type 12-C2, and 7 cases as type 12-C3. The time between injury and operation was 2-13 days (mean, 7.2 days). The operation time, intraoperative blood loss, complications, union time were recorded, the functional outcome of the elbow joint was evaluated by Mayo elbow performance score, and the function of the shoulder was assessed by the University of California at Los Angeles (UCLA) shoulder rating scale. ResultsThe mean operation time was 92 minutes (range, 51-127 minutes), and the mean intraoperative blood loss was 212 mL (range, 100-450 mL). All incisions healed by first intention without neurologic complications or wound infection. All patients were followed up 8-28 months (mean, 16.6 months), and bony union was obtained at 13-36 weeks (mean, 19.2 weeks). No loosening or breakage of internal fixation occurred. The Mayo elbow performance score was 90-100 (mean, 99), and the UCLA shoulder rating scale was 31-35 (mean, 34.6). ConclusionThe technique of minimally invasive osteosynthesis using the helical plate is safe and feasible for humeral shaft fracture, especially for complex humeral shaft fractures involved proximal metaphysis, and it has the advantages of minimal invasion and low risk for iatrogenic nerve injury and satisfactory effectiveness.