Biomechanical comparison of inverted triangle and L-shaped screw configurations with medial buttress and anteromedial support plate in Pauwels type III femoral neck fractures

INTRODUCTION: Surgical stabilization of Pauwels Type III femoral neck fractures remains a significant challenge due to high vertical shear forces. While the medial buttress plate is a recognized solution, it requires extensive deep dissection. This study aims to compare the biomechanical performance of various screw configurations combined with either a medial buttress or anteromedial support plate. MATERIALS AND METHODS: Twenty-five third-generation synthetic femurs were used to create a standardized 70-degree (Pauwels III) fracture model. Specimens were divided into five groups (n = 5): (A) Inverted triangle (IT) screws with a Pauwels screw, (B) Inverted triangle (IT) with medial buttress plate (MBP), (C) Inverted triangle with anteromedial support plate (ASP), (D) L-configuration with medial buttress plate (MBP), and (E) L-configuration with anteromedial support plate (ASP). Axial loading was applied at 2 mm/min until construct failure, defined objectively by the real-time force-distance curve. RESULTS: Although no statistically significant difference was found between groups (p = 0.102), a large effect size was observed (η² = 0.309). Group C (IT + ASP) demonstrated the highest mean failure load (1695 ± 494.6 N). Conversely, Group E (L-configuration + ASP) exhibited the lowest stability (977.2 ± 195.4 N) with a remarkably narrow standard deviation. The majority of failures occurred as transverse subtrochanteric fractures distal to the implants. CONCLUSION: The combination of an inverted triangle screw arrangement with an anteromedial support plate demonstrated comparable biomechanical stability to the medial buttress plate, while offering a potentially safer surgical corridor. Conversely, pairing L-shaped screw configurations with anteromedial support plates resulted in the lowest mean ultimate load-to-failure among the tested constructs, likely due to potential stress riser effects.