Low‐level accelerations applied in the absence of weight bearing can enhance trabecular bone formation

Abstract

High-frequency whole body vibrations can be osteogenic, but their efficacy appears limited to skeletal segments that are weight bearing and thus subject to the induced load. To determine the anabolic component of this signal, we investigated whether low-level oscillatory displacements, in the absence of weight bearing, are anabolic to skeletal tissue. A loading apparatus, developed to shake specific segments of the murine skeleton without the direct application of deformations to the tissue, was used to subject the left tibia of eight anesthesized adult female C57BL/6J mice to small (0.3 g or 0.6 g) 45 Hz sinusoidal accelerations for 10 min/day, while the right tibia served as an internal control. Video and strain analysis revealed that motions of the apparatus and tibia were well coupled, inducing dynamic cortical deformations of less than three microstrain. After 3 weeks, trabecular metaphyseal bone formation rates and the percentage of mineralizing surfaces (MS/BS) were 88% and 64% greater (p < 0.05) in tibiae accelerated at 0.3 g than in their contralateral controls. At 0.6 g, bone formation rates and mineral apposition rates were 66% and 22% greater (p < 0.05) in accelerated tibiae. Changes in bone morphology were evident only in the epiphysis, where stimulated tibiae displayed significantly greater cortical area (þ8%) and thickness (þ8%). These results suggest that tiny acceleratory motions -independent of direct loading of the matrix -can influence bone formation and bone morphology. If confirmed by clinical studies, the unique nature of the signal may ultimately facilitate the stimulation of skeletal regions that are prone to osteoporosis even in patients that are suffering from confinement to wheelchairs, bed rest, or space travel. ß

Extremely Small-magnitude Accelerations Enhance Bone Regeneration: A Preliminary Study

“…Furthermore, it is likely the body of the animal also received at least a certain component of the physical signal despite efforts to primarily target the cranium. As in previous studies [6,14,15,37], systemic perturbations were not evident but cannot be excluded as a factor that influenced the results. Finally, transmissibility Fig.…”

“…Among the many factors influencing bone modeling and remodeling, functional mechanical loading from muscle contractility may be sensed by bone cells as a potent extrinsic signal [12,14]. Muscle loading not only includes large forces generated by vigorous physical activities such as running or weightlifting, but also has much more prevalent, very small-magnitude forces associated with subtle events such as posture [12].…”

“…Although the efficacy of the much larger exercise-induced mechanical signals has been related to the magnitude of the generated tissue deformation [8], matrix deformation per se does not appear necessary for high-frequency, low-level mechanical stimuli to influence cell activity [22], and high-frequency oscillatory accelerations applied as unconstrained motions may serve as a regulatory physical signal to increase bone formation in healthy bone [14] and to attenuate the decline in bone formation [15] and mechanical properties [31] during disuse. Oscillatory accelerations, rather than deformations, can be readily applied to any skeletal segment, weightbearing or not, and the potential clinical advantages of a stimulus that is barely perceptible and involves motions on the order of only 100 lm are apparent.…”

High-frequency, low-intensity vibrations increase bone mass and muscle strength in upper limbs, improving autonomy in disabled children

“…The studies of Garman and colleagues (20) and Hwang and colleagues (21) showed that bone does not need to be loaded to be responsive to mechanical signals, and thus it may be that osteoblasts and their progenitors (mesenchymal stem cells) are sensitive to acceleration, thus facilitating application of the HFLMV signal. Our study supports these findings in a clinical setting.…”

Transmission of low-intensity vibration through the axial skeleton of persons with spinal cord injury as a potential intervention for preservation of bone quantity and quality

“…Pharmacological approaches to prevent bone loss have not been generally accepted as efficacious, and they are not routinely administered. 10,11 However, low-magnitude mechanical signals of lowintensity vibration (LIV) delivered by an oscillating platform have been shown to be safe, [12][13][14][15] easy to administer, and anabolic to bone in both animal [16][17][18][19] and human studies. 14,20 This preliminary evidence, although not yet studied in persons with SCI, has demonstrated efficacy in reducing or preventing bone loss in persons with low bone density, as reported in postmenopausal women 14 and children with cerebral palsy.…”