Evaluation of Degradable Mg-Alloy Implants for Femoral Neck Fractures: Subject-Specific Finite Element Analysis...

Stable internal fracture fixation is essential for femoral neck fractures to achieve better healing and minimise post-operative (PO) complications. Though conventional Ti-alloy used in implant materials provides adequate strength, it induces high strain shielding and also requires secondary removal surgery. In contrast, biodegradable magnesium alloys demonstrate better biocompatibility and are emerging as promising alternatives for implant applications. To evaluate the biomechanical behaviour of femoral neck fractures (Pauwels Types I-III) in a subject-specific femoral model treated with the femoral neck system (FNS) made from Ti-alloy and time-dependent biodegradable Mg alloy. A femoral model was reconstructed from the CT-scan data of a healthy adult male and Pauwels Types I-III fracture patterns were subsequently generated. Finite element simulations were conducted under both normal walking and stair-climbing load conditions. Ti-alloy properties were constant, while Mg-alloy modulus was updated daily over 1 year using an exponential degradation model. Bone remodelling was simulated using a strain energy-based algorithm. Strain shielding at the equilibrium state decreased by as much as 45.55% in the Mg-alloy implant model compared with its immediate PO condition and a similar decrease of around 11.44% was observed in the Ti-alloyed model. The cut-out risk after reaching the equilibrium (AE) condition was reduced by up to 6.74% for the Mg-alloy case compared to the PO scenario. Mg-alloy implants demonstrated greater bone apposition (up to 1.13 g/cm³) compared to the Ti-alloyed implant in AE conditions. Micromotion remained below 150 μm in all models and decreased by approximately 24% after reaching equilibrium. Mg-alloy FNS implants enhance physiological load transfer, reduce shielding and maintain fixation stability during degradation, indicating strong potential as biodegradable alternatives to Ti-alloy implants for femoral neck fracture fixation.