Posterior shoulder dislocation (PSD) is a rare injury with an incidence rate of approximately 1.10 per 100,000, accounting for only 2% to 5% of all types of shoulder dislocations. Coupled with its lack of typical symptoms and imaging manifestations, the rate of missed diagnosis at the initial diagnosis is as high as 60% to 79%. Therefore, it is rare in clinical practice and highly challenging in clinical diagnosis and treatment. PSD is often caused by direct or indirect high-energy violence such as car accidents, epileptic seizures, and electric shocks. PSD is frequently accompanied by proximal humeral fractures (PHF). PHF can be classified into six types according to the Neer classification, and the higher the number, the more severe the injury. Among them, Neer typeⅥ is usually accompanied by humeral head fragmentation, bone defect, and severe rotator cuff injury. If PSD combined with Neer typeⅥ PHF is not diagnosed and treated in time, it can easily cause shoulder joint pain, stiffness, shoulder deformity, limited movement, shoulder instability, etc. Over time, it may lead to humeral head necrosis due to a blood circulation disorder. Currently, for patients with Neer typeⅥ PSD-PHF, open reduction and internal fixation treatment should be performed. The goal is to achieve anatomical reduction, stable fixation, and early functional exercise. Although clinical reports on patients with simple PHF are not uncommon at present, for patients with the special type of PSD-PHF, such as "fracture - dislocation", due to the small number of cases and the difficulty of intraoperative reduction, there is still a lack of strong evidence-based medical basis for the selection and operation of surgical methods in clinical practice at present.

To explore the diagnosis and treatment methods of posterior shoulder dislocation combined with proximal humerus fractures (PSD-PHF) .

A retrospective analysis was conducted on six patients with PSD-PHF fractures, classified as typeⅥ by Neer, in our hospital from April 2020 to December 2023. The expanded deltoid groove approach of the pectoralis major muscle was adopted. The dislocated humeral head and joint capsule were exposed, the incarcerated biceps brachii tendon or rotator cuff was released, the humeral head was pried and reduced under direct vision, and each fracture fragment was reduced successively. First, lock the bone plate for fixation. If necessary, hollow screws or bundled cables can be used to enhance the fixation. When combined with the anti-Hill-Sachs injury with an anterior edge loss area of the humeral head reaching 25% to 50%, artificial bone is implanted at the bone defect site under the humeral head to provide support. Finally, suture anchors are used to repair the torn subscapularis muscle and supraspinatus tendon in sequence. Compare the visual analogue scale (VAS) for pain before the operation and the University of California- Los Angeles shoulder function scoring system at the last follow-up after the operation. UCLA score and shoulder joint range of motion.

The surgeries of all six patients with PSD-PHF in this group were completed. The operation time ranged from 50 to 80 minutes, with an average of (65.00±6.42) minutes. The hospital stay ranged from 8 to 29 days, with an average of (11.20±1.59) days. All patients were followed up for more than 12 months. The follow-up period ranged from 12 to 20 months, with an average of (14.30±1.67) months. Bony union was achieved in all 6 fractures, with an average healing time of (5.04±0.62) months. There was no loosening or prolapse of internal fixation. At the last follow-up, the VAS score of the patients was (1.00±0.21) points, which was lower than that before the operation [ (8.00±1.30) points] (P<0.001). The UCLA score was (32.53±1.04) points, which was higher than that before the operation (9.08±1.52) points (P<0.001). Among them, there were 4 cases of excellent, 1 case of good, and 1 case of poor, and the excellent and good rates were 83.33% (5/6). Shoulder joint activity: proneness (138.85+ 18.67) °, outreach (128.69-10.57) °, outside screw (48.61 + 2.28) °, were greater than preoperative (60.14+ 7.21) °, (40.87-4.26) °, ° [- (29.85 + 3.18) ] (P< 0.001) .

Patients with Neer typeⅥ PSD-PHF are relatively rare in clinical practice. Early diagnosis and early surgery can promote fracture healing, relieve pain, improve shoulder joint function, and restore shoulder joint range of motion in patients.