Cortical thickness index of the proximal femur: a radiographic parameter for preliminary assessment of bone mineral density and osteoporosis status in the age 50 years and over population

Background: Bone mineral density (BMD) is the indicator of bone quality in at-risk individuals. Along with the fracture risk assessment tool (FRAX), a quick assessment of BMD from routine radiographs may be useful in the case of lacking X-ray absorptiometry data. This study aimed to investigate the correlation of cortical thickness index (CTI) and canal flare index (CFI) with BMD and FRAX and to evaluate their ability to predict femoral neck BMD (nBMD) and FRAX in the general elderly population. Methods: A total of 560 volunteers (age ≥ 50 years) who underwent hip-spine X-ray, BMD scanning and FRAX calculation were retrospectively reviewed. CTI and CFI were measured on anteroposterior radiographs and analyzed for their correlation with BMD and FRAX and for their ability to predict nBMD. The ability of CTI to predict osteoporosis status (OPS) and fracture risk status (FRS) was also investigated and the threshold values were calculated. All the analyses were performed separately on male and female subjects. Results: Significant differences in CTI, CFI, nBMD and FRAX between males and females were observed. CTI and CFI demonstrated significant positive correlation with nBMD and FRAX (all p < 0.001) in both males and females. CTI, height, and weight significantly predicted nBMD. CTI statistically predicted OPS and FRS, and the values of 0.56 and 0.62 were computed as CTI thresholds for males and females, respectively. Conclusions: CTI was significantly correlated with nBMD and it predicted nBMD at good prediction levels. Therefore, CTI may be used as a supportive tool in the assessment of OPS and FRS besides BMD and FRAX in clinical practice.