Objective:To evaluate the efficacy of proximal humerus internal locking system (PHILOS) via the minimally invasive plate osteosynthesis (MIPO) in the treatment of proximal humeral fractures.Methods:This retrospective study analyzed 30 elderly patients with proximal humeral fracture who had been treated by PHILOS via MIPO from September 2016 to March 2020 at Department of Orthopedic Surgery, People’s Hospital of Zhuxi County. They were 19 females and 11 males with an average age of 60.96 years (from 45 to 80 years). All patients were treated by closed reduction. After fracture reduction was confirmed by fluoroscopy, a minimally invasive incision was made below the acromion, with a couple of suture wires reserved at the rotator cuff attachments. A PHILOS plate was inserted at 4 mm lateral to the intertubercular sulcus, with the suture wires passing through the proximal suture holes on the PHILOS. After a lag screw was first screwed up into the compression hole on the PHILOS plate, the crossing suture wires were tightened up to resist the rotator cuff stress and maintain the internal inclination of the humeral head. Kirschner wires were used to temporarily stabilize the reduction. After satisfactory reduction and fine plate positions were confirmed by fluoroscopy, locking nails were screwed up. The internal inclination of the affected humeral head was compared between preoperation and the last follow-up. The therapeutic efficacy was evaluated by the shoulder Neer scoring system, and the visual analogue scale (VAS) pain scores and complications were recorded at the last follow-up.Results:All the 30 patients were followed for 6 to 18 months (average, 12 months). There was no incision infection, neurovascular injury, or internal fixation failure. Anatomical reduction was achieved in 25 patients and functional reduction in 5. The inclination of the humeral head was significantly improved. The VAS scores at the last follow-up averaged 1.9. Follow-up X-ray examination showed that bony union was achieved after 6 to 18 months (average, 9 months) for all patients. At the last follow-up, the inclination angle of the affected humeral head was 130°±5°, significantly improved compared with the preoperative 90°±11.2° ( P<0.05). All patients had good functional recovery of the shoulder. The efficacy was, according to the Neer shoulder scores at the last follow-up, excellent in 22, good in 6 and fair in 2 cases. Conclusions:Treatment of proximal humeral fractures using PHILOS via MIPO technique is suitable for patients with osteoporotic fracture, and may lead to fine therapeutic efficacy.