Three-dimensional cortical and trabecular bone microstructure of the proximal ulna

Area of Science:

• Orthopedics
• Biomechanics
• Anatomy

Background:

• The three-dimensional (3D) microstructure of the proximal ulna's cortical and trabecular bone remains undescribed using high-resolution 3D imaging.
• Understanding this microstructure is key to elucidating its role in resisting impact loads.

Purpose of the Study:

• To characterize the proximal ulna's bone microstructure using micro-computed tomography (micro-CT).
• To correlate microstructural findings with gross morphology and functional implications.

Main Methods:

• Micro-computed tomography (micro-CT) scans were performed on five dry human cadaveric ulnae at 17 μm/voxel resolution.
• Qualitative and quantitative analyses assessed cortical thickness and trabecular microarchitecture in the olecranon, bare area, and coronoid regions.

Main Results:

• Trabeculae in the bare area formed struts spanning anteriorly and posteriorly; in the coronoid, they were orthogonal to the joint surface.
• The coronoid exhibited the greatest cortical thickness (1.66 ± 0.59 mm), while the olecranon had the least (0.33 ± 0.06 mm).
• The bare area showed the highest bone volume fraction (43.7 ± 22.4%) and trabecular thickness (0.40 ± 0.09 mm), with a plate-like structure (SMI = -0.28 ± 2.20).

Conclusions:

• The bare area appears to be the primary site of load concentration in the proximal ulna.
• The coronoid and its anteromedial facet are critical for elbow joint bony stabilization.
• Analysis of proximal ulna microstructure aids in understanding mechanical loading and fracture mechanisms.