Mechanical loading, damping, and load-driven bone formation in mouse tibiae

Abstract

Mechanical loads play a pivotal role in the growth and maintenance of bone and joints. Although loading can activate anabolic genes and induce bone remodeling, damping is essential for preventing traumatic bone injury and fracture. In this study we investigated the damping capacity of bone, joint tissue, muscle, and skin using a mouse hindlimb model of enhanced loading in conjunction with finite element modeling to model bone curvature. Our hypothesis was that loads were primarily absorbed by the joints and muscle tissue, but that bone also contributed to damping through its compression and natural bending. To test this hypothesis, fresh mouse distal lower limb segments were cyclically loaded in axial compression in sequential bouts, with each subsequent bout having less surrounding tissue. A finite element model was generated to model effects of bone curvature in silico. Two damping-related parameters (phase shift angle and energy loss) were determined from the output of the loading experiments. Interestingly, the experimental results revealed that the knee joint contributed to the largest portion of the damping capacity of the limb, and bone itself accounted for approximately 38% of the total phase shift angle. Computational results showed that normal bone curvature enhanced the damping capacity of the bone by approximately 40%, and the damping effect grew at an accelerated pace as curvature was increased. Although structural curvature reduces critical loads for buckling in beam theory, evolution apparently favors maintaining curvature in the tibia. Histomorphometric analysis of the tibia revealed that in response to axial loading, bone formation was significantly enhanced in the regions that were predicted to receive a curvature-induced bending moment. These results suggest that in addition to bone’s compressive damping capacity, surrounding tissues, as well as naturally-occurring bone curvature, also contribute to mechanical damping, which may ultimately affect bone remodeling and bone quality.

Effects of Loading Duration and Short Rest Insertion on Cancellous and Cortical Bone Adaptation in the Mouse Tibia

“…The loading parameters used here were adopted from a commonly used loading protocol for the mouse tibial loading model [11, 17, 26, 27] and maintained the same for all four loading protocols. Different research groups also use different waveforms applied at different frequencies over a varying number of days than used here [1, 15, 31, 43, 44]. Regardless, our results showing the relative effects of increasing load cycle number should be maintained despite varying some of the other parameters.…”

Resonance in the mouse tibia as a predictor of frequencies and locations of loading-induced bone formation

“…Because of the effects of damping in surrounding tissues, it is expected that transmission of the loading force through surrounding tissues, such as skin, muscle, and joint tissue, may modify the frequencies at which the tibia resonates (Kim and Hwang 2006; Tsuchikane et al 1995; Dodge et al 2012). In addition, frequencies of vibration may vary among individual animals based on slight alterations in size or proportion.…”

Bone Quality and Quantity are Mediated by Mechanical Stimuli

“…For that reason, the addition of finite element analysis models has been crucial in enabling us to understand the strain field engendered on bone for the various animal loading modalities. Numerous studies have explored strain distributions under the loading regimes, each involving increasingly more sophisticated models [65][66][67][68][69][70][71][72]. Digital image correlation (DIC) has also been used to assess surface strains experimentally.…”