Cancellous Bone May Have a Greater Adaptive Strain Threshold Than Cortical Bone

Abstract

Strain magnitude has a controlling influence on bone adaptive response. However, questions remain as to how and if cancellous and cortical bone tissues respond differently to varied strain magnitudes, particularly at a molecular level. The goal of this study was to characterize the time‐dependent gene expression, bone formation, and structural response of the cancellous and cortical bone of female C57Bl/6 mice to mechanical loading by applying varying load levels (low: −3.5 N; medium: −5.2 N; high: −7 N) to the skeleton using a mouse tibia loading model. The loading experiment showed that cortical bone mass at the tibial midshaft was significantly enhanced following all load levels examined and bone formation activities were particularly elevated at the medium and high loads applied. In contrast, for the proximal metaphyseal cancellous bone, only the high load led to significant increases in bone mass and bone formation indices. Similarly, expression of genes associated with inhibition of bone formation (e.g., Sost) was altered in the diaphyseal cortical bone at all load levels, but in the metaphyseal cortico‐cancellous bone only by the high load. Finite element analysis determined that the peak tensile or compressive strains that were osteogenic for the proximal cancellous bone under the high load were significantly greater than those that were osteogenic for the midshaft cortical tissues under the low load. These results suggest that the magnitude of the strain stimulus regulating structural, cellular, and molecular responses of bone to loading may be greater for the cancellous tissues than for the cortical tissues. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Arthroscopic versus open cancellous bone grafting for scaphoid delayed/nonunion in adults (SCOPE-OUT): study protocol for a randomized clinical trial

“…The arthroscopic technique is potentially less invasive with minimal donor site morbidity and potentially faster time to union [15] because of minimal trauma to the ligament structures, joint capsule and the tenuous blood supply [19]. It may also have advantageous osteogenic properties compared to a structural graft [39]. Differences in time to union between the open technique and the arthroscopic technique have, to our knowledge, never been investigated.…”

Arthroscopic versus open cancellous bone grafting for scaphoid delyed/nonunion in adults: study protocol for a randomized clinical trial

“…The arthroscopic technique is potentially less invasive with minimal donor site morbidity and potentially faster time to union [15] because of minimal trauma to the ligament structures, joint capsule, and the tenuous blood supply [19]. It may also have advantageous osteogenic properties compared to a structural graft [39]. Differences in time to union between open technique and the arthroscopic technique has, to our knowledge, never been investigated.…”

Cortical and Trabecular Bone Modeling and Implications for Bone Functional Adaptation in the Mammalian Tibia

“…A separate section is dedicated to discussing cortical and trabecular bone collectively. This distinction is important because previous studies have demonstrated that due to the larger surface-to-volume ratio of trabecular bone tissue, bone modeling and bone remodeling act differently in trabecular bone compared to cortical bone (except for, possibly, endocortical surfaces) [18][19][20][21][22]. Furthermore, recent studies have revealed differential gene expression and unique transcriptional profiles in cortical and trabecular bone tissues from mechanically loaded murine tibiae models [23,24], indicating that bone modeling and, thus, bone functional adaptation may be mediated differently in these two bone tissues.…”

“…One of these open questions is related to which property or properties of mechanical stimuli affect bone adaptation to load (Table S1, see online Supplementary Material). Possible properties include mechanical stimuli magnitude (peak stresses and strains) [20,28,[31][32][33][34][35][36][37], sign (compression, tension, or shear) [38,39], duration (number and length of loading cycles) [31,[39][40][41], circadian rhythm (i.e., time of the day) [42], strain rate (change in strain with respect to time, e.g., running vs. walking) [43], frequency (number of loading cycles per second) [32,44,45], and length of rest in between stimuli [41,[46][47][48][49].…”