Regional differences in the three-dimensional bone microstructure of the radial head: implications for observed fracture patterns

Introduction A characterization of the internal bone microstructure of the radial head could provide a better understanding of commonly occurring fracture patterns frequently involving the (antero)lateral quadrant, for which a clear explanation is still lacking. The aim of this study is to describe the radial head bone microstructure using micro-computed tomography (micro-CT) and to relate it to gross morphology, function and possible fracture patterns. Materials and methods Dry cadaveric human radii were scanned by micro-CT (17 mu m/pixel, isotropic). The trabecular bone microstructure was quantified on axial image stacks in four quadrants: the anterolateral (AL), posterolateral (PL), posteromedial (PM) and anteromedial (AM) quadrant. Results The AL and PL quadrants displayed the significantly lowest bone volume fraction and trabecular number (BV/TV range 12.3-25.1%, Tb.N range 0.73-1.16 mm(-1)) and highest trabecular separation (Tb.Sp range 0.59-0.82 mm), compared to the PM and AM quadrants (BV/TV range 19.9-36.9%, Tb.N range 0.96-1.61 mm(-1), Tb.Sp range 0.45-0.74 mm) (p = 0.03). Conclusions Our microstructural results suggest that the lateral side is the weaker side, exhibiting lower bone volume faction, less trabeculae and higher trabecular separation, compared to the medial side. As the forearm is pronated during most falls, the underlying bone microstructure could explain commonly observed fracture patterns of the radial head, particularly more often involving the AL quadrant. If screw fixation in radial head fractures is considered, surgeons should take advantage of the stronger bone microstructure of the medial side of the radial head, should the fracture line allow this.

Automated summary

This study used micro-CT to describe the bone microstructure of the radial head and found that the lateral side has weaker bone microstructure compared to the medial side, which may explain commonly observed fracture patterns of the radial head. Surgeons should take advantage of the stronger bone microstructure on the medial side when dealing with radial head fractures.