# Canal-to-Bone Ratio as an Independent Predictor of Hip Bone Mineral Density Scores: A Retrospective Analysis

## TL;DR

This study finds that the canal-to-bone ratio from routine X-rays can predict hip bone density, offering a potential alternative when advanced scans are unavailable.

## Contribution

The canal-to-bone ratio is shown as an independent predictor of hip bone mineral density scores, using plain radiographs.

## Key findings

- CBR strongly correlates with lower hip T- and Z-scores (r = -0.63 to -0.65, P < 0.01).
- CBR remains an independent predictor of hip BMD scores after adjusting for age.
- Each 0.1 increase in CBR is linked to significant decreases in hip T- and Z-scores.

## Abstract

Hip fractures are a major consequence of osteoporosis. While dual-energy X-ray absorptiometry (DXA) is the gold standard for bone mineral density (BMD), radiographic indices may complement DXA. The canal-to-bone ratio (CBR)—the intramedullary canal diameter divided by the outer cortical diameter on plain radiographs—may reflect bone quality. We examined the relationship between CBR and BMD and whether CBR independently predicts hip T- and Z-scores.

The study retrospectively analyzed 90 patients with femoral radiographs and DXA. Canal-to-bone ratio was measured 7 cm distal to the lesser trochanter. Lumbar and hip T-/Z-scores were recorded. Associations were tested with Pearson/Spearman correlations and linear regression; multivariable models adjusted for age.

Canal-to-bone ratio correlated negatively with hip BMD (T-score r = −0.63, P = .005; Z-score r = −0.65, P = .004), but not with lumbar scores (P > .20). Each 0.1 increment in CBR was associated with a 0.67-unit decrease in hip T-score and a 0.59-unit decrease in hip Z-score. After adjusting for age, CBR remained an independent predictor of hip T-score (β = −6.09, P = .012, R2 = 0.44) and hip Z-score (β = −5.59, P = .009, R2 = 0.43).

Canal-to-bone ratio shows a strong, independent association with hip BMD. As a simple metric obtainable from routine radiographs, CBR may serve as a surrogate marker of hip bone quality and fracture risk, particularly in settings with limited DXA access.