Trabecular bone score (TBS), derived from the spine dual-energy x-ray absorptiometry (DXA) image, and hip axis length (HAL), derived from the hip DXA image, are bone mineral density (BMD)-independent risk factors for fracture. To date, no studies have directly compared the additive benefits of using TBS and HAL in combination. We found that TBS and HAL made independent contributions to fracture risk, with TBS having a larger benefit for major osteoporotic fractures (MOF) whereas HAL had a larger benefit for hip fractures. AIM: To compare the effects of TBS and HAL on fracture risk, separately and in combination.
POPULATION: A total of 55,068 individuals (mean age 63.5 years, 90.9% female) from the Manitoba Bone Density Program aged  ≥  40 years with baseline assessment of TBS and HAL measurements.
METHODS: Incident MOF and hip fractures were assessed from population-based linked healthcare data. The effects of TBS and HAL were assessed in Cox regression models, adjusted for multiple covariates.
RESULTS: TBS and HAL were significantly associated with incident MOF and hip fracture in all regression models independent from other covariates including BMD. There were minimal differences when TBS and HAL were evaluated separately versus in combination. TBS showed a consistently greater effect on MOF risk compared with HAL, but also showed greater BMD attenuation. In a fully adjusted model with total hip BMD, with both variables evaluated simultaneously, TBS (per SD decrease) was associated with a 16% increase in MOF risk (HR 95% CI 1.12-1.19) whereas HAL (per SD increase) was associated with an 8% increase (HR 95% CI 1.05-1.11). HAL showed a greater effect on hip fracture risk when adjusted for BMD. With both variables evaluated simultaneously, HAL (per SD increase) was associated with a 24% increased risk of hip fracture (HR 95% CI 1.18-1.30) compared with TBS (per SD decrease) 13% (HR 95% CI 1.07-1.19).
CONCLUSION: TBS and HAL showed mutually independent and complementary benefits for fracture prediction. This supports the use of TBS and HAL in combination for improved fracture risk assessment.