Oral Presentation ANZBMS-MEPSA-ANZORS 2022

Geometry and bone mineral density determinants of femoral neck strength changes following exercise (#71)

Dermot O'Rourke 1 , Belinda R Beck 2 3 4 , Amy T Harding 2 3 , Steven L Watson 5 , Peter Pivonka 1 , Saulo Martelli 1
  1. Queensland University of Technology, Brisbane, QLD, Australia
  2. Griffith University, Gold Coast, QLD, Australia
  3. Menzies Health Institute Queensland, Gold Coast, QLD, Australia
  4. The Bone Clinic, Brisbane, QLD, Australia
  5. Gold Coast University Hospital, Gold Coast, QLD, Australia

INTRODUCTION Physical exercise elicits spatially heterogeneous adaptation in bone to mitigate bone loss and improve strength [1]. The aim of the study was to determine the principal changes in geometry and BMD induced by exercise with the greatest relation to femoral neck strength.

METHODS Pre- and post-intervention proximal femur DXA scans were obtained (Medix DR) from 92 male participants (67 ± 7 years) in an exercise trial [2]. The 3D shape and BMD distribution of the femur was reconstructed from the planar DXA images with a statistical shape and appearance model and converted into volume meshes with element-by-element correspondence [3]. Femoral neck strength under single-leg stance and sideways fall was estimated using a maximum principal strain criterion [4]. Partial Least Squares (PLS) regression models were developed with predictor variables: (1) geometry changes and (2) BMD changes.

RESULTS The BMD-model required 4 PLS components and the geometry-model 8 components to account for 90% of the strength variance. BMD changes in PLS 1 were related to cortical bone density in the calcar region, greater trochanter, and femoral neck (Fig. 1a). Geometry changes in PLS 1 were related to scaling changes in the trochanteric and femoral head regions. VIP scores indicated that changes in the femoral neck were important for single-leg stance strength and in the lateral-superior neck and greater trochanter for sideways fall (Fig. 1b).

DISCUSSION Changes in femoral neck strength were primarily governed by changes in BMD distribution. The superior neck and distal cortex were most important for single-leg stance. The superior neck, medial head, and lateral trochanter were most important for sideways fall. BMD changes in the calcar region, superior neck, and greater trochanter regions accounted for the greatest strength changes.

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  1. Rubin et al., Calcif. Tissue Int 1985 37(4): 411-417
  2. Harding, et al. J Bone Miner Res 2020 35(8):1404–1414
  3. O'Rourke, et al., J Biomech, 2021. 119: 110315
  4. Schileo, et al., J Biomech, 2008. 41(2): 356-367.