Adjusting Fracture Probability by Trabecular Bone Score
Calcif Tissue Int
Adjusting Fracture Probability by Trabecular Bone Score
Eugene V. McCloskey 0 1 2 3 4
Anders Ode´n 0 1 2 3 4
Nicholas C. Harvey 0 1 2 3 4
William D. Leslie 0 1 2 3 4
Didier Hans 0 1 2 3 4
Helena Johansson 0 1 2 3 4
John A. Kanis 0 1 2 3 4
0 MRC Lifecourse Epidemiology Unit, University of Southampton , Southampton , UK
1 Centre for Metabolic Bone Diseases, University of Sheffield Medical School, University of Sheffield , Beech Hill Road, Sheffield S10 2RX , UK
2 & John A. Kanis
3 Center of Bone Diseases, Lausanne University Hospital , Lausanne , Switzerland
4 University of Manitoba , Winnipeg , Canada
The aim of the present study was to determine the impact of trabecular bone score on the probability of fracture above that provided by the clinical risk factors utilized in FRAX. We performed a retrospective cohort study of 33,352 women aged 40-99 years from the province of Manitoba, Canada, with baseline measurements of lumbar spine trabecular bone score (TBS) and FRAX risk variables. The analysis was cohort-specific rather than based on the Canadian version of FRAX. The associations between trabecular bone score, the FRAX risk factors and the risk of fracture or death were examined using an extension of the Poisson regression model and used to calculate 10-year probabilities of fracture with and without TBS and to derive an algorithm to adjust fracture probability to take account of the independent contribution of TBS to fracture and mortality risk. During a mean followup of 4.7 years, 1754 women died and 1639 sustained one or more major osteoporotic fractures excluding hip fracture and 306 women sustained one or more hip fracture. When fully adjusted for FRAX risk variables, TBS remained a statistically significant predictor of major osteoporotic fractures excluding hip fracture (HR/SD 1.18, 95 % CI 1.12-1.24), death (HR/SD 1.20, 95 % CI 1.14-1.26) and
Epidemiology; Fracture probability; FRAX; Osteoporosis; Trabecular bone score
-
hip fracture (HR/SD 1.23, 95 % CI 1.09–1.38). Models
adjusting major osteoporotic fracture and hip fracture
probability were derived, accounting for age and trabecular
bone score with death considered as a competing event.
Lumbar spine texture analysis using TBS is a risk factor for
osteoporotic fracture and a risk factor for death. The
predictive ability of TBS is independent of FRAX clinical risk
factors and femoral neck BMD. Adjustment of fracture
probability to take account of the independent contribution
of TBS to fracture and mortality risk requires validation in
independent cohorts.
Introduction
The measurement of bone mineral density (BMD) by dual
X-ray absorptiometry (DXA) remains the cornerstone for
the assessment of skeletal strength and fracture risk in the
clinical setting [
1
]. The wide recognition that BMD has
limitations in terms of capturing other skeletal
determinants of bone strength (for example, bone structure,
geometry, cortical and trabecular architecture, and bone
turnover), and has led to many attempts to provide
supplementary information to improve the predictive ability of
skeletal assessments. Such approaches include indices such
as hip axis length, hip structural analysis including
buckling ratios, cortical thickness, cortical porosity, and more
complex techniques such as finite element analysis [
2–9
].
The gain from such developments has been disappointing
and none has been incorporated into routine clinical
practice. More recently, a novel gray-scale textural analysis of
antero-posterior lumbar spine DXA images has produced
an index, the trabecular bone score (TBS), that shows
promise as a BMD-independent predictor of skeletal
strength [10]. TBS appears to be an index of bone
microarchitecture that provides skeletal information
additional to the standard BMD measurement. Higher values of
TBS correlate with better skeletal microstructure. A recent
literature review determined that TBS consistently
discriminated between fracture cases and non-fracture
controls in both cross-sectional and longitudinal studies, and
that the discrimination is complementary to BMD derived
from the same images [
10
]. TBS can therefore be regarded
as another potential clinical risk factor for fracture and, as
such, its ability to predict fracture independently of other
well-established risk factors needs to be determined.
Risk factors that are partly independent of both age and
BMD have been incorporated into FRAX . FRAX estimates
the 10-year probability of hip and major osteoporotic
fracture based on the individual’s risk factor profile [
11, 12
], and
is now the leading risk assessment model used worldwide
[13]. The probability of fracture is calculated from age, body
mass index (BMI), a number of dichotomised risk variables,
and additionally femoral neck BMD.
The aim of the present analysis was to determine
whether TBS could predict fracture risk independently of the
risk factors incorporated in FRAX, and if so, to derive
adjustment a (...truncated)