Ex vivo analysis of cortical microarchitecture of the distal clavicle: implications for surgical management of fractures

Abstract

Background: Cortical thickness and porosity are two main determinants of cortical bone strength. Thus, mapping variations in these parameters across the full width of the distal end of the clavicle may be helpful for better understanding the basis of distal clavicle fractures and for selecting optimal surgical treatment.

Methods: Distal ends of 11 clavicles (6 men, 5 women; age: 81.9 ± 15.1 years) were scanned by micro-computed tomography at 10-µm resolution. We first analyzed cortical thickness and porosity of each 500-μm-wide area across the superior surface of distal clavicle at the level of conoid tubercle in an antero-posterior direction. This level was chosen for detailed evaluation because previous studies have demonstrated its superior microarchitecture relative to the rest of the distal clavicle. Subsequently, we divided the full width of distal clavicle to three subregions (anterior, middle, and posterior) and analyzed cortical porosity, pore diameter, pore separation, and cortical thickness.

Results: We found the largest number of low-thickness and high-porosity areas in the anterior subregion. Cortical porosity, pore diameter, pore separation, and cortical thickness varied significantly among the three subregions (p < 0.001 p = 0.016, p = 0.001, p < 0.001, respectively). Cortex of the anterior subregion was more porous than that of the middle subregion (p < 0.001) and more porous and thinner than that of the posterior subregion (p < 0.001, p = 0.030, respectively). Interaction of site and sex revealed higher porosity of the anterior subregion in women (p < 0.001). The anterior subregion had larger pores than the middle subregion (p = 0.019), whereas the middle subregion had greater pore separation compared with the anterior (p = 0.002) and posterior subregions (p = 0.006). In general, compared with men, women had thinner (p < 0.001) and more porous cortex (p = 0.03) with larger cortical pores (p < 0.001).

Conclusions: Due to high cortical porosity and low thickness, the anterior conoid subregion exhibits poor bone microarchitecture, particularly in women, which may be considered in clinical practice.

Levels of evidence: Level IV.

Keywords: Cortical porosity; Cortical thickness; Distal clavicle; Placement; Screws.