Objective To investigate the effectiveness of proximal humerus internal locking system (PHILOS) plate combined with rotator cuff reinforcement suture in the treatment of Neer type Ⅳ proximal humerus fracture. MethodsThe clinical data of 48 patients with proximal humeral fractures admitted between January 2016 and December 2020 were retrospectively analyzed, including 18 males and 30 females. The age ranged from 28 to 69 years (mean, 56.3 years). The causes of injury included falling in 39 cases and traffic accident in 9 cases. The time from injury to operation was 2-5 days (mean, 2.8 days). All of them were Neer type Ⅳ proximal humerus fractures, including 11 patients with dislocation. All patients underwent internal fixation with a PHILOS plate after anatomical reduction of the greater nodule, and the rotator cuff was sutured to the plate to reinforce fixation. The operation time was recorded, the wound healing, fracture healing, and complications were observed. The visual analogue scale (VAS) score, Constant-Murley shoulder score, University of California Los Angeles (UCLA) score, and American Shoulder and Elbow Surgeons (ASES) score were used to evaluate shoulder function before operation, at 3 months after operation, and at last follow-up. Results The operation time ranged from 65 to 90 minutes (mean, 76.9 minutes). All incisions healed by first intention. All patients were followed up 9-16 months (mean, 12 months). Fracture reduction was good and all fractures healed, the healing time was 2-6 months (mean, 4.6 months). There was no complication such as subacromial impingement, fracture redisplacement, and screw removal during follow-up. One patient had humeral head necrosis, but the basic function of the shoulder joint was acceptable, the symptoms were mild, and no treatment was performed. At 3 months after operation, the upper limb function of the patients basically recovered. The VAS score, Constant-Murley score, UCLA score, and ASES score significantly improved at 3 months after operation and at last follow-up when compared with preoperative, and further improved at last follow-up than at 3 months after operation (P<0.05). ConclusionPHILOS plate combined with rotator cuff reinforcement suture in the treatment of Neer type Ⅳ proximal humerus fracture has the advantages of promoting early postoperative rehabilitation exercise, improving postoperative function of shoulder joint, and reducing complications.