Local irradiation alters bone morphology and increases bone fragility in a mouse model

Area of Science:

• Biomedical Engineering
• Orthopedics
• Radiology

Background:

• Radiation therapy (RTx) can lead to challenging insufficiency fractures.
• Standard bone mass measurements are insufficient for predicting these fractures.
• Understanding radiation's impact on bone mechanics is crucial for patient care.

Purpose of the Study:

• To develop a mouse model for studying radiation-induced bone weakness.
• To quantify temporal changes in bone morphology and strength post-irradiation.
• To assess if the bone morphology-strength correlation persists after radiation.

Main Methods:

• Focal irradiation (5 or 20 Gy) of mouse hind limbs, with contralateral limbs as controls.
• Axial compression tests of the distal femur to measure bone strength.
• Micro-computed tomography (micro-CT) for bone morphology analysis.
• Non-linear finite element (FE) analyses using different material failure models.

Main Results:

• Irradiation caused dose-dependent increases in cortical bone density and loss of trabecular bone.
• Early increases in bone volume were linked to increased strength, but strength declined later despite higher bone volume.
• Correlation between bone volume and strength was lost in irradiated bone.
• FE analysis with an 'embrittled' material model best predicted irradiated bone strength (r²=0.46).

Conclusions:

• Focal irradiation significantly alters bone morphology and strength over time.
• Bone strength decreases post-irradiation, even with increased bone mass.
• Non-linear FE models incorporating material embrittlement are superior for simulating radiation-induced bone changes.