Rate of Change of Cortical Mass with Age over the Femoral Surface
Biomechanics and Bone Quality
Poster Sessions, Presentation Number: SA0037
Session: Poster Session I & Poster Tours
Saturday, October 10, 2015 12:30 PM - 2:30 PM, Washington State Convention Center, Discovery Hall - Hall 4BC
* , UNITED KINGDOM, Andrew Gee, University of Cambridge, Carol Tonkin, Nova Scotia, Canada, Kenneth Poole, University of Cambridge
Purpose: Cortical bone mapping (CBM, Treece MedIA 2015) allows structural properties of the proximal femur, including cortical thickness and density, to be measured from QCT data and displayed as a colour map on the femoral surface. Here we apply CBM to a large cohort of women spanning a wide age range, to investigate in detail how the cortex changes with age at different parts of the femur.
Methods: Mindways Software Inc (Austin, TX, USA) recruited 630 Caucasian women aged 19-97 years (mean 47 ± 17 SD) from 1998 to 2002 at 11 centres in the USA. The cohort comprised women having BMD assessments as part of their clinical evaluation and volunteers who desired an assessment. QCT data, using the Mindways liquid K2HPO4 phantom, was obtained from below the lesser trochanter to above the femoral head. The data was collected for the purposes of FDA (510k) approval (K030330) and was subject to Investigational Review Board oversight. Of the 630, 11 were excluded due to incomplete scans and metalwork. For the remaining 619, CBM was used to measure cortical mass surface density (CMSD mg/cm2, the product of cortical BMD and cortical thickness) across each proximal femur. All measurements were mapped onto a canonical surface and a model was fitted to the mapped data, explaining CMSD in terms of (1 + age + age2) and other confounding variables. Quadratic modelling allows for different rates of change at different ages and the possibility of detecting peaks.
Results: Figure 1 shows the mean CMSD, its rate of change at ages 30 and 80, and (where detectable) the age at which CMSD peaks. Of particular interest are the regions (a) and (b), where CMSD increases until late middle age before starting to plateau (a) or decline (b), and the region (c) where there is steady, significant loss of CMSD across the entire age range. In terms of hip fragility, region (c) is associated with cervical fracture and (b) with trochanteric fracture: our findings are consistent with cervical fractures being more strongly associated with age than are trochanteric fractures [Lofman OI 2002]. Cortical thickening with age in region (a) has been noted previously [Mayhew Lancet 2005].
Conclusion: CBM has produced a more detailed map of ageing across the proximal femur than has previously been available. This "healthy ageing" baseline might find application in finite element models, fracture studies and intervention planning (pharmaceutical and exercise).
* Presenting Authors(s):
, UNITED KINGDOM