Introduction: Surgical treatment of most displaced proximal humerus fractures is challenging due to osteoporosis, which makes stable fixation difficult. Locking plates are intended to provide superior mechanical stability. The NCB^® -PH (Non-Contact-Bridging for the Proximal Humerus) plate is a locking plate of the latest generation that allows both open and minimally invasive (MI) application.

Methods: In a prospective multicenter study 131 patients were treated (n = 78 open, n = 53 MI). The open procedure was performed using a standard deltopectoral approach; the MI technique involved percutaneous reduction and an anterolateral deltoid split approach. Clinical and radiological follow-up was obtained 6 weeks, 3, 6 and 12 months after surgery. An iADL (instrumental activities of daily living) score was used for functional assessment, the subjective outcome was measured using VAS (Visual Analogue Scale) for pain and mobility.

Results: Improvement in function (ROM) was statistically significant in both groups (open and MI) postoperatively. Fracture type had the most significant impact on the complication rate. The most frequent complication was intraarticular screw perforation. The open treated group showed a higher complication rate. However, more C-type fractures (AO) were treated with this technique.

Conclusion: The NCB-PH is suitable as a routine method of treatment for proximal humerus fractures. Complication rate and functional outcome are comparable to the literature. The MI technique, which is limited by percutaneous fracture reduction, provides a less invasive option for patients requiring fast recovery. Complex fractures should preferably be treated with the open technique.

Introduction: Since the introduction of locked implants new possibilities in the treatment of proximal humeral fractures have evolved. Despite the success using locked plates recent publications report the cutting of screws through the humeral head in up to 30% of the cases. The distribution of the bone strength in the humeral head is not linear. Can polyaxial screw positioning in areas with higher bone strength reduce the “cutout” rate? Which effect has an inferomedial screw if the medial hinge is not restored?

Methods: 4 groups were formed from 31 fresh frozen proximal humeral cadavers. A polyaxial proximal humeral locking plate was used to perform the tests. A standardised unstable intraarticular fracture was created. Main Outcome measure was the load and cycle where at least one screw was cutting through the cartilage.

Results: Polyaxial screw placement in areas of incresead bone strength compared to random screw placement had no effect on the cutout behaviour (p=0.7). Increased screw number (3 vs. 5) significantly increases the resistance against cutout (p< 0.04). An inferomedial screw significantly increases the resistance to develop a cutout compared to the control groups(p=0.03 and p< 0.05).

Discussion: The placement of an inferomedial screw significantly increases the resistence to develop a cutout in proximal humeral fractures without a medial hinge independently of the total screw number. In addition we could also show that the number of screws in the humeral head has a significant effect on cutout resistance in a human cadaver setup.