Trabecular bone adaptation to loading in a rabbit model is not magnitude‐dependent

Abstract

Although mechanical loading is known to influence trabecular bone adaptation, the role of specific loading parameters requires further investigation. Previous studies demonstrated that the number of loading cycles and loading duration modulate the adaptive response of trabecular bone in a rabbit model of applied loading. In the current study, we investigated the influence of load magnitude on the adaptive response of trabecular bone using the rabbit model. Cyclic compressive loads, producing peak pressures of either 0.5 or 1.0 MPa, were applied daily (5 days/week) at 1 Hz and 50 cycles/day for 4 weeks post-operatively to the trabecular bone on the lateral side of the distal right femur, while the left side served as an nonloaded control. The adaptive response was characterized by microcomputed tomography and histomorphometry. Bone volume fraction, bone mineral content, tissue mineral density, and mineral apposition rate (MAR) increased in loaded limbs compared to the contralateral control limbs. No load magnitude dependent difference was observed, which may reflect the critical role of loading compared to the operated, nonloaded contralateral limb. The increased MAR suggests that loading stimulated new bone formation rather than just maintaining bone volume. The absence of a dose-dependent response of trabecular bone observed in this study suggests that a range of load magnitudes should be examined for biophysical therapies aimed at augmenting current treatments to enhance long-term fixation of orthopedic devices. Keywords: trabecular bone; bone adaptation; rabbit; microcomputed tomography; mechanical stimulation Mechanical loading plays a central role in skeletal development and maintenance via both modeling and remodeling processes. 1-3 Throughout life the skeleton adapts by changing bone mass and architecture to the functional demands placed on it by mechanical stimuli. In cortical bone, loading must be dynamic rather than static to elicit an anabolic response 4 and adaptive remodeling is preferentially responsive to short periods of strain change. 5 For example, high-magnitude strains, varied by regulating the applied load 6-8 and strain rate, 9 enhanced cortical bone mass.Age-related bone loss, disuse-related bone loss, bone healing, and osseointegration around implants are all intimately coupled with the mechanical loading environment in trabecular bone. Despite the importance of studies on cortical diaphyseal bone adaptation to mechanical loading, prevention and treatment of osteoporosis and osteoarthritis requires investigation of trabecular bone adaptation. In addition, important questions remain concerning trabecular bone functional adaptation to a variety of loading parameters.Well-controlled and minimally invasive experimental models of loading in trabecular bone have been difficult to develop. [10][11][12][13] In vivo intermittent compressive loading via a hydraulic bone chamber stimulated bone matrix synthesis in trabecular bone of the canine tibial and femoral metaphyses. 14 While clearl...

Time course of peri-implant bone regeneration around loaded and unloaded implants in a rat model

“…We only investigated the bone remodeling response up to 14 days of loading, thus focusing on the initial tissue differentiation phase and not long-term bone remodeling. Our loading applied is not in the direction it is normally loaded in vivo such as in knee replacements, perpendicular to the lateral surface of the tibia, 50 as this was deemed not feasible in a rat model. A limitation is that dynamic histomorphometry was not performed and it can detect bone formation at higher resolution than our micro-CT based method.…”

Interrelation between external oscillatory muscle coupling amplitude and in vivo intramedullary pressure related bone adaptation

“…Axial loading applied between 5N and 13N on mouse tibiae showed significant load magnitude-related increases in cortical bone formation [24]. However, it is with interest to observe that no magnitude dependence on trabecular bone adaptation was found in a cyclic compressive loading study in a rabbit model [25]. In the current study, the observed ImP inductions were found to be positively proportional to DHS cuff pressure, namely, which indicates promising potential of DHS loading dose dependency on ImP related bone adaptation.…”

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

“…( 24 ) However, using a rabbit femoral cancellous loading model, Yang and colleagues found that trabecular bone adaptation to loading is not magnitude‐dependent at the strain levels examined. ( 25 ) The axial tibial loading model can provide a more physiological mechanical environment to examine the effects of loading in both cortical and cancellous bone simultaneously. ( 26 ) Similar to the response observed in other cortical loading models, cortical bone in the tibial loading model is dose‐dependent and governed by a load threshold.…”