Bone morphology allows estimation of loading history in a murine model of bone adaptation

Abstract

Bone adapts its morphology (density/microarchitecture) in response to the local loading conditions in such a way that a uniform tissue loading is achieved ('Wolff's law'). This paradigm has been used as a basis for bone remodeling simulations to predict the formation and adaptation of trabecular bone. However, in order to predict bone architectural changes in patients, the physiological external loading conditions, to which the bone was adapted, need to be determined. In the present study, we developed a novel bone loading estimation method to predict such external loading conditions by calculating the loading history that produces the most uniform bone tissue loading. We applied this method to murine caudal vertebrae of two groups that were in vivo loaded by either 0 or 8 N, respectively. Plausible load cases were sequentially applied to micro-finite element models of the mice vertebrae, and scaling factors were calculated for each load case to derive the most uniform tissue strainenergy density when all scaled load cases are applied simultaneously. The bone loading estimation method was able to predict the difference in loading history of the two groups and the correct load magnitude for the loaded group. This result suggests that the bone loading history can be estimated from its morphology and that such a method could be useful for predicting the loading history for bone remodeling studies or at sites where measurements are difficult, as in bone in vivo or fossil bones.

Determination of hip-joint loading patterns of living and extinct mammals using an inverse Wolff’s law approach

“…3). Nevertheless, we know most bone formation takes place at high-load locations and most resorption at low-load locations (Schulte et al 2013), and this seems to be enough for our algorithm to reveal a reasonable loading history as demonstrated in the present and also earlier studies (Christen et al 2013b(Christen et al , 2012.…”

“…However, animals with different locomotion behaviour were chosen to get a first impression how well the approach works across species, and our results encourage conducting more studies to validate the approach for different species and joints. This would also allow rigorous validation of the method for long bones, extending the earlier validation for mice vertebrae (Christen et al 2012) and cubic bone microstructures (Christen et al 2013a). Second, the sensitivity of the load estimation algorithm with respect to the image resolution, location, and number of predefined unit loads was not yet thoroughly investigated.…”

“…Based on the micro-CT images, hip-joint forces were calculated using a recently developed load estimation algorithm (Christen et al 2012). This approach is based on the assumption that bone strives for a uniform tissue loading distribution.…”

“…The formfunction relationship due to bone adaptation implies that it might be possible as well to reversely derive hip-joint loading patterns from the femoral head microstructure by finding a set of joint forces that produce such a state of uniform tissue loading. In an earlier study, we developed a computational algorithm based on this principle (Christen et al 2012). In the present study, we apply this algorithm reconstructing the elaborate loading patterns at the hip joint for human and dog, two species exhibiting different locomotion.…”

Longitudinal Assessment of In Vivo Bone Dynamics in a Mouse Tail Model of Postmenopausal Osteoporosis

“…The real force that CV6 is subjected to under physiological conditions is unknown, but it has recently been found using a novel bone loading estimation method that external loading conditions of CV6 are in the range of 4 N [34]. Changes in the stiffness of the whole bone were analyzed from the lFE results.…”