Modalities for Visualization of Cortical Bone Remodeling: The Past, Present, and Future

Area of Science:

• Bone biology and skeletal remodeling
• Biomaterials and tissue engineering
• Orthopedics and sports medicine

Background:

• Bone remodeling by basic multicellular units (BMUs) renews bone and repairs microdamage.
• Traditional 2D methods extensively studied secondary osteons but limited understanding of BMU 3D morphology and function.
• Osteoporosis involves imbalanced resorption, increasing bone fragility and fracture risk, a growing concern with increased life expectancy.

Purpose of the Study:

• To review methodologies for 3D investigation of cortical bone remodeling.
• To explore the 3D morphology and function of BMUs and their associated structures (resorption spaces and secondary osteons).
• To highlight the importance of 3D insights for understanding the 'why' behind bone architecture and remodeling.

Main Methods:

• Review of existing literature on 3D investigation techniques for bone remodeling.
• Discussion of methods ranging from histology to advanced ex vivo imaging modalities.
• Exploration of the potential of in vivo imaging for studying bone remodeling in real-time.

Main Results:

• Current 3D imaging techniques offer unprecedented insights into BMU morphology and activity.
• A gap exists in understanding the initiation and regulation of BMU activity within cortical bone.
• 3D analysis provides a more comprehensive view of bone structure dynamics compared to 2D methods.

Conclusions:

• Advancing 3D imaging methodologies is crucial for a deeper understanding of bone remodeling.
• Improved 3D characterization of BMUs will elucidate their role in skeletal health and disease.
• Understanding the 'how' of bone remodeling through 3D analysis is key to addressing the 'why' of bone architecture and function.