Femur Fracture Risk Assessment in Patients with Lytic Metastases Using CT-Based Finite Element Models and Bone Crack Simulations Technique.

Abstract

Purpose: Femoral bone metastases represent a frequent and severe complication in patients with advanced solid tumours. Although fracture risk assessment commonly relies on Mirels' score, its limited specificity often leads to unnecessary surgical interventions. Patient-specific finite element (FE) models have shown improved accuracy; however, current approaches vary widely in methodology and rarely capture the full fracture process. This study investigates for the first time the application of a linear FE approach based on an incremental element deletion technique to simulate both fracture initiation and propagation in femurs with lytic metastases.

Methods: Twenty-four patients with femoral lytic lesions were retrospectively analyzed, and model outcomes were compared with clinical results. The proposed approach was evaluated for its ability to stratify patients according to pathological fracture risk, in comparison with conventional simulation methods and the clinically accepted Mirels' score. In addition, a new failure threshold parameter derived from the work required to fracture the femur was investigated.

Results: The simulations successfully replicated clinically observed fracture paths and demonstrated strong capability in differentiating high- and low-risk patients. The failure criterion based on the last applied load during simulated crack propagation provided the highest diagnostic performance, achieving excellent sensitivity and specificity. The fracture initiation parameter showed comparable performance, while the work-based parameter appeared more affected by variability in femur visibility.

Conclusion: The proposed modeling framework offers the advantage of predicting fracture paths, providing clinically valuable insight, and represents a further step toward improved stratification methods for the clinical management of femoral metastases.