Specific Radiologic Risk Factors for Implant Failure and Osteonecrosis of the Humeral Head after Interlocking Nailing with the Targon PH(+) of Proximal Humeral Fractures in a Middle to Old Population

Background: Operative management of proximal humeral fractures is still challenging. While antegrade nailing has become a valid option in fracture fixation, risk factors for adverse events, and failure have not been sufficiently clarified. Methods: All patients of a single trauma center undergoing surgery for proximal humeral fractures with the Targon PH(+) nail between 2014 and 2021 were evaluated retrospectively. This included complications, revisions, and failures. Pre- and postoperative radiographic imaging were assessed regarding fracture’s complexity, anatomic reduction, reconstruction of the medial hinge, metaphyseal head extension, and fixation of the implant in the calcar region. Follow-up was at a minimum of 12 months. Results: A total number of 130 patients with a mean age of 74.5 years (range 63–94, SD ± 8.2) are included in this study. Two- and three-part fractures were found in 58 patients, while 14 patients showed four-part fractures. Overall, a complication rate of 34.2% and an implant failure rate of 15.4% was found. Four-part fractures showed a significantly higher complication rate than two- and three-part fractures. Four-part fractures also showed significantly higher revisions (p = 0.005) and implant failures (p = 0.008). The nonsufficient anatomical reduction was found to be a risk factor for complications (p < 0.0001), implant failures (p < 0.0001), and later humeral head osteonecrosis (p < 0.0001). Insufficiently reconstructed medial hinges (p = 0.002) and a metaphyseal head extension of over 8 mm (p = 0.005) were also demonstrated as risk factors for osteonecrosis of the humeral head. Conclusions: Four-part fractures in an elderly population show high complication, revision, and implant-failure rates. Therefore, demonstrated radiologic risk factors should be evaluated for improvements. Anatomical reduction and fixation near the calcar proved to be vital for successful antegrade nailing of complex fractures. To prevent osteonecrosis of the humeral head, reconstruction of the medial hinge and metaphyseal head extension should be evaluated.