The influence of load repetition in bone mechanotransduction using poroelastic finite-element models: the impact of permeability

Abstract

Experimental evidence suggests that interstitial fluid flow is a stimulus for mechanoadaptation in bone. Bone adaptation is sensitive to the frequency of loading and rest insertion between load cycles. We investigated the effects of permeability, frequency and rest insertion on fluid flow in bone using finite-element models to understand how these parameters affect the mechanical stimulus. A simplified 3D poroelastic finite-element model of a beam in bending was developed, in order to simulate the behavior of interstitial fluid flow in the lacunar-canalicular system of mouse cortical bone. Two different load sets were considered: (1) a continuous haversine sinusoid, with frequency ranging from 1 to 30 Hz, and (2) a 10 Hz haversine with rest-insertion times ranging from 0 to 10 s. For both load sets, a range of intrinsic permeability from [Formula: see text] to [Formula: see text] was tested, and fluid flow was determined. Models with permeabilities down to [Formula: see text] follow a dose-response relationship between fluid flow and sinusoidal frequency. Smaller orders of magnitude of permeability proved to be relatively insensitive to frequency. Our results also suggest that there is a minimum time of rest between load cycles that is required to maximize fluid motion, which depends on the order of magnitude of the intrinsic permeability. We show that frequency and rest insertion may be optimized to deliver maximal mechanical stimulus as a function of permeability.

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“…Previous computational studies (Pereira and Shefelbine, 2014) showed that poroelastic models with bone permeability k = 10 −22 m 2 simulate relaxation times similar to in vivo measures in mice and consistent with recent experimental estimations (Benalla et al, 2014).…”

“…Some of the used constitutive values were estimated or measured for different specimens, as the literature lacks estimation of some poroelastic parameters in murine bone. Pereira and Shefelbine (2014), † Steck et al (2003a), ¶ Dillaman et al (1991) Sensitivity studies (not included in this paper) were conducted to determine the influence of trabecular bone and growth plate stiffness on the calculations of the mechanical environment in the diaphysis. A wide interval of stiffness values was considered for each compartment, ranging from cartilage (10MPa) to cortical bone (17GPa).…”

A Design Method for FES Bone Health Therapy in SCI

“…The stress distribution model may be improved by adjusting thresholds that better predict actual clinical scan data and further extended by including a porosity stage that may provide a deeper understanding of the basic mechano-transduction, poroelastic fluid low and cellular signaling. 9 The proposed technique may also be extended using simulated force data derived from biomechanical models of the therapeutic activity – in this case it may even be possible to design and evaluate a candidate FES bone therapy in-silico prior to clinical trials. This is illustrated in Figure 5 where the bi-lateral force actions of the gluteus maximus muscles were biomechanically simulated and added to the quadriceps actions during the drive phase.…”

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“…Previous computational studies (Pereira and Shefelbine, 2014) showed that poroelastic models with bone permeability k = 10 , for low flow rates, roughly 5 orders of magnitude higher than the permeability of the lacunar-canalicular porosity. The same value was assigned to both surfaces, despite the fact that the literature often characterises the endosteum to be more permeable than the periosteum.…”

“…Elastic elements were considered in the rest of the cortical region (blue colour in Figure 7a), where no adaptation was considered. Intrinsic permeability in the poroelastic bone regions was set to k = 10 −22 m 2 (Pereira and Shefelbine, 2014). Osteocyte canaliculi are predominantly oriented longitudinally, rather than transversely (Dillaman et al, 1991), and, therefore, this value was assigned to the longitudinal component, k l .…”