Impaired bone quality in the superolateral femoral neck occurs independent of hip geometry and bone mineral density

• Published in: Acta biomaterialia Vol. 141; pp. 233 - 243
• Main Authors: von Kroge, Simon, Stürznickel, Julian, Bechler, Ulrich, Stockhausen, Kilian Elia, Eissele, Julian, Hubert, Jan, Amling, Michael, Beil, Frank Timo, Busse, Björn, Rolvien, Tim
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 15.03.2022; Elsevier BV
• Subjects: Backscattering; Biomedical materials; Bone density; Bone Density - physiology; Bone microstructure; Bone mineral density; Compressive properties; Computed tomography; Coxa; Coxa Valga; Coxa Vara; Dual energy X-ray absorptiometry; Electron imaging; Electron microscopy; Femoral neck; Femoral Neck Fractures; Femur; Femur Neck - diagnostic imaging; Fractures; High resolution micro-CT; Hip; Humans; Mechanical loading; Microstructure; Osteoarthritis; Osteocyte; Osteocytes; Qualitative analysis; Sensation; Total hip arthroplasty; X-Ray Microtomography; Femoral neck; Bone microstructure; Electron microscopy; Osteocyte; High resolution micro-CT
• ISSN: 1742-7061; 1878-7568; 1878-7568
• DOI: 10.1016/j.actbio.2022.01.002

Skeletal adaptation is substantially influenced by mechanical loads. Osteocytes and their lacuno-canalicular network have been identified as a key player in load sensation and bone quality regulation. In the femoral neck, one of the most common fracture sites, a complex loading pattern with lower habitual loading in the superolateral neck and higher compressive stresses in the inferomedial neck is present. Variations in the femoral neck-shaft angle (NSA), i.e., coxa vara or coxa valga, provide the opportunity to examine the influence of loading patterns on bone quality. We obtained femoral neck specimens of 28 osteoarthritic human subjects with coxa vara, coxa norma and coxa valga during total hip arthroplasty. Bone mineral density (BMD) was assessed preoperatively by dual energy X-ray absorptiometry (DXA). Cortical and trabecular microstructure and three-dimensional osteocyte lacunar characteristics were assessed in the superolateral and inferomedial neck using ex vivo high resolution micro-computed tomography. Additionally, BMD distribution and osteocyte lacunar characteristics were analyzed by quantitative backscattered electron imaging (qBEI). All groups presented thicker inferomedial than superolateral cortices. Furthermore, the superolateral site exhibited a lower osteocyte lacunar density along with lower lacunar sphericity than the inferomedial site, independent of NSA. Importantly, BMD and corresponding T-scores correlated with microstructural parameters at the inferomedial but not superolateral neck. In conclusion, we provide micromorphological evidence for fracture vulnerability of the superolateral neck, which is independent of NSA and BMD. The presented bone qualitative data provide an explanation why DXA may be insufficient to predict a substantial proportion of femoral neck fractures. The femoral neck, one of the most common fracture sites, is subject to a complex loading pattern. Site-specific differences (i.e., superolateral vs. inferomedial) in bone quality influence fracture risk, but it is unclear how this relates to hip geometry and bone mineral density (BMD) measurements in vivo. Here, we examine femoral neck specimens using a variety of high-resolution imaging techniques and demonstrate impaired bone quality in the superolateral compared to the inferomedial neck. Specifically, we found impaired cortical and trabecular microarchitecture, mineralization, and osteocyte properties, regardless of neck-shaft angle. Since BMD correlated with bone quality of the inferomedial but not the superolateral neck, our results illustrate why bone densitometry may not predict a substantial proportion of femoral neck fractures. [Display omitted]