Validation of single-segment and three-segment spinal models used to represent lumbar flexion

Changes in spinal posture between the erect and flexed positions were calculated using angular measurements from lateral photographs and radiographs of ten adult male subjects. For photographic measurements, the thoracolumbar vertebral column was modelled as either a single segment or as three segments. In the three-segment model, there was a non-significant correlation between the decrease in lumbar concavity and intervertebral motion. In addition, there was a non-significant negative correlation between the increase in thoracic convexity and lumbar motion determined radiographically. In the single-segment model, the decrease in angulation between the thoracolumbar spine and pelvis was a good representation of lumbar spine flexion as determined by the mean lumbar intervertebral angular change. Therefore, modelling the thoracolumbar vertebral column as a single segment allowed better estimation of lumbar intervertebral angular change during flexion than a three-segment model. The results indicate that large range dynamic motion of the lumbar vertebral column can be represented using photographic analysis of the positions of three easily identified anatomical landmarks: the anterior superior iliac spine, posterior superior iliac spine and the spinous process of the first thoracic vertebra.     

Calculation of the strain-deformation condition of the spinal motor segment during loading

A mathematical model is proposed to analyze the spinal strain-deformation condition resulting from axial and lateral g-loads that are generated by changes in the gravity field and/or pilot’s actions during high-performance aircraft maneuvering under flight overload conditions. An algorithm of solution has been developed, which takes into account changes in the intervertebral disk pressure and the fibrous ring shape at the time when loading reaches close-to-critical g-values. Calculation of the spinal-strain deformation condition was implemented using the SPLEN computer system (KOMMEK, Russia). Analysis of the spinal straindeformation condition was made for two types of external loads: normal load and unilateral load with the bending moment. Maximum permissible loads on the spinal segment were evaluated, and a pattern of distribution of strain intensity and mean strains, spinal deformation, and the destruction field was described. The developed computer models can be used as a basis for developing a technique of predicting characteristic spinal injuries due to different extreme loads and pathologies.     

Structural models for human spinal motion segments based on a poroelastic view of the intervertebral disk

Analytical and finite element models (FEMs) were used to quantify poroelastic material properties for a human intervertebral disk. An axisymmetric FEM based on a poroelastic view of disk constituents was developed for a representative human spinal motion segment (SMS). Creep and steady-state response predicted by FEMs agreed with experimental observations, i.e., long-time creep occurs with flow in the SMS, whereas for rapid steady-state loading an "undrained," nearly incompressible response is evident. A relatively low value was determined for discal permeability. Transient and long-term creep FE analyses included the study of deformation, pore fluid flow, stress, and pore fluid pressure. Relative fluid motion associated with transient creep is related to nuclear nutrition and the overall mechanical response in the normal disk. Degeneration of the disk may be associated with an increase in permeability.     

Parametric finite element analysis of vertebral bodies affected by tumors

The vertebral column is the most frequent site of metastatic involvement of the skeleton. Due to the proximity to the spinal cord, from 5% to 10% of all cancer patients develop neurologic manifestations. As a consequence, fracture risk prediction has significant clinical importance. In this study, we model the metastatically involved vertebra so as to parametrically investigate the effects of tumor size, material properties and compressive loading rate on vertebral strength. A two-dimensional axisymmetric finite element model of a spinal motion segment consisting of the first lumbar vertebral body (no posterior elements) and adjacent intervertebral disc was developed to allow the inclusion of a centrally located tumor in the vertebral body. After evaluating elastic, mixed, and poroelastic formulations, we concluded that the poroelastic representation was most suitable for modeling the metastatically involved vertebra's response to compressive load. Maximum principal strains were used to localize regions of potential vertebral trabecular bone failure. Radial and axial vertebral body displacements were used as relative indicators of spinal canal encroachment and endplate failure. Increased tumor size and loading rate, and reduced trabecular bone density all elevated axial and radial displacements and maximum tensile strains. The results of this parametric study suggest that vertebral tumor size and bone density contribute significantly to a patients risk for vertebral fracture and should be incorporated in clinical assessment paradigms.     

Focal potentials of Clarke's column neurons

In experiments on cats, we investigated focal potentials of Clarke's column neurons and discharges of individual neurons recorded extracellularly. An ultrasonic scalpel was used to remove the part of the spinal cord between Th₁₃ and L₃, and an electrode was inserted into the face of the caudal segment of the spinal cord along the axis of Clarke's column. Orthodromic excitation of Clarke's column neurons was evoked by stimulating cut nerves of the ipsilateral extremity; antidromic excitation was evoked by stimulating the dorsolateral funiculus, which was preliminarily separated from the removed portion of the spinal cord. It was found that the orthodromic potential, antidromic potential, and discharges are distinctly registered when the method of electrode insertion is used, whereas they were not recorded when the microelectrodes were sunk into the dorsal surface in these experiments. It is demonstrated that orthodromic and antidromic focal potentials of Clarke's column neurons are similar to motoneuron focal potentials with respect to time characteristics. Inversion of the charge sign was recorded with the approach of the microelectrode's tip to the soma of Clarke's column neurons. It is hypothesized that the success of recording focal potentials and extracellular discharges of Clarke's column neurons resulted from the fact that the orientation of dendrites of these cells matches the direction of microelectrode movement. The slender portion of the microelectrode penetrates the interdendritic space, where tension of the extracellular field is the greatest; it then moves through this space to reach the soma.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad; A. A. Bogomol'ets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 2, No. 5, pp. 528–535, September–October, 1970.     

Load sharing among spinal elements of a motion segment in extension and lateral bending

A linear optimization model was formulated using a semi-experimental protocol to estimate the forces in the spinal elements of a lumbar motion segment subjected to an extension or lateral bending moment with and without a 120 N compressive preload. A morphometer was used to acquire the three-dimensional locations of the disk center, facet centers and ligament origin and insertion sites with the specimen in a "neutral" position. The relative motion of the superior vertebra, under the loading conditions tested, was monitored using a Selspot II system. These data allowed the formulation of the static equilibrium equations for the superior vertebra at each of the loading conditions mentioned above. A linear optimization technique was used, along with a suitable cost function, to find an optimum solution for the set of equations and imposed constraints. Results showed that for 6.9 Nm of extension moment, each facet carried a load of 52 N, with the disk carrying an axial tensile load of 104 N. At the 6.9 Nm extension moment coupled with 120 N preload, each facet carried a load of 77.2 N and the disk an axial tensile load of 37 N. In right lateral bending, with and without preload, the load was distributed among the right facet, the disk, the left ligamentum flavum and the left capsular ligament. At the 6.9 Nm load step without preload the right facet carried an axial load of 127.01 N with the disk carrying an axial compressive load of 7.8 N. Ligament forces for this step for the left ligamentum flavum and capsular ligament, respectively, were 61.03 N and 65.14 N. The addition of 120 N of preload reduced the load on the right facet to 83.5 N. The compressive load in the disk increased to 107.5 N. The corresponding ligament forces were 43.2 N (left ligamentum flavum) and 50.7 N (left capsular ligament).     

Tissue platinum after clinical treatment with cisplatin or carboplatin in tumor-bearing patients

Tissue platinum (Pt) levels were measured in tumor-bearing patients treated with either cisplatin or carboplatin. Cisplatin was given by intra-arterial, intraperitoneal, and intravenous (iv) administrations. After death, vertebrae and intervertebral disks were removed from eight human subjects, and livers and kidneys were removed from the half of them. When cisplatin was administered intraperitoneally, Pt of the liver was higher than that of the kidney, and a high content of Pt was detected in the vertebra by comparing with the other administration methods. At the intra-arterial administration of cisplatin, Pt was mainly accumulated in the kidney. At the iv administration of cisplatin, a high level of Pt was found in the vertebra and intervertebral disk, especially at the highest value at 10.31 μg/g in the intervertebral disk of one case, whereas a low level of Pt was detected in the liver. On the contrary, it was found that the iv administration of carboplatin did not result in high accumulations of Pt in the liver, kidney, intervertebral disk, and vertebra. Therefore, Pt is accumulated in different organs, depending on the way cisplatin is administered, but Pt is accumulated least in them by the administration of carboplatin.     

Absence of Intraspinal Sprouting in Dorsal Root Axons Caudal to a Partial Spinal Hemisection: A Horseradish Peroxidase Transport Study

Primary afferent sprouting in the spinal cord was evaluated by comparing the central projection of horseradish peroxidase (HRP)-labeled sciatic nerve afferent axons in nonlesioned control rats, and in rats subjected to acute or chronic partial spinal hemisections as adults. The lesions were performed at various levels from T₁₀ to L₃, and removed supraspinal and varying amounts of descending propriospinal afferents to lumbar segments receiving the maximal sciatic projection. The hemisections typically involved all but the dorsal column, although in some cases a portion of the dorsal column, including the corticospinal tract, was also transected.

The distribution pattern and density of spinal HRP reaction product was not significantly different in experimental and control preparations in any segment below the lesion, regardless of the quantity of denervation, or the density of the normal sciatic projection in a given terminal region. These results, together with our previous finding concerning an absence of primary afferent sprouting following long-term dorsal root ganglionectomies, suggest that current concepts concerning collateral sprouting as a factor in functional plasticity in the mature mammalian spinal cord warrant re-evaluation.     

Contribution of vertebral [corrected] bodies, endplates, and intervertebral discs to the compression creep of spinal motion segments

Spinal segments show non-linear behavior under axial compression. It is unclear to what extent this behavior is attributable to the different components of the segment. In this study, we quantified the separate contributions of vertebral bodies and intervertebral discs to creep of a segment. Secondly, we investigated the contribution of bone and osteochondral endplate (endplates including cartilage) to the deformation of the vertebral body. From eight porcine spines a motion segment, a disc and a vertebral body were dissected and subjected to mechanical testing. In an additional test, cylindrical samples, machined from the lowest thoracic vertebrae of 11 porcine spines, were used to compare the deformation of vertebral bone and endplate. All specimens were subjected to three loading cycles, each comprising a loading phase (2.0 MPa, 15 min) and a recovery phase (0.001 MPa, 30 min). All specimens displayed substantial time-dependent height changes. Average creep was the largest in motion segments and smallest in vertebral bodies. Bone samples with endplates displayed substantially more creep than samples without. In the early phase, behavior of the vertebra was similar to that of the disc. Visco-elastic deformation of the endplate therefore appeared dominant. In the late creep phase, behavior of the segment was similar to that of isolated discs, suggesting that in this phase the disc dominated creep behavior, possibly by fluid flow from the nucleus. We conclude that creep deformation of vertebral bodies contributes substantially to creep of motion segments and that within a vertebral body endplates play a major role.     

Vascular and vegetative spinal cord disorders in disruptions of the mobile vertebrae

Microcirculatory disorders can be a source of nerve cell pathology in spinal cord gray matter. Subluxation of a vertebra as the result of disruption in carrying capacity of an intervertebral disc due to spinal osteochondrosis is one of the trigger mechanisms for these disorders. In this condition, the richly innervated soft tissues of a certebral segment are stretched, and its receptors are the source of chronic irritation of segmentary nervous structures, including the vegetative structures. In subluxation of a vertebra, changes in the vegetative connections of spinal cord gray matter and the microcirculatory vessels arise simultaneously; this suggests interdependence between them.Scientific-Research Laboratory Center, A. A. Bogomolets Medical Institute, Kiev. Translated from Neirofiziologiya, Vol. 24, No. 6, pp. 667–672, November–December, 1992.     

Role of computed tomography in the estimation of the density of the bony block of an injured vertebral column segment at different stages of treatment with an external transpedicular fixation apparatus

A Somatom AR.HP computed tomograph (Siemens) was used to make studies in 54 patients with injury to the vertebral column and spinal cord in order to determine the formation of a bony block and its density in different portions of an injured segment at the stages of treatment. During therapy, the highest values of bony block density were observed in the dorsal portions of an injured segment (mean 377.32 +/- 184.57 HU). This may be accounted for by a slight effect of artefacts of an external transpedicular fixation apparatus, the main components of which are present at the posterior supporting complex. After treatment, the highest values of bony block density were noted in the central portions of an injured segment (mean 353.11 +/- 208.01 HU). This may be associated with rather serious intervertebral disk damage in this portion. The bony block density index was 339.75 +/- 139.41 HU in the left lateral portions and as high as 312.56 +/- 135.07 HU in the right ones. In the late period, the highest bony block density index (mean 397 +/- 193.07 HU) was seen in the right portions of an injured segment, which may be due to slight scoliotic deformity with the angle being open to the right.     

Can periods of static loading be used to enhance the resistance of the spine to cumulative compression?

Results of in vitro studies conducted on isolated bone specimens have indicated a higher tolerance to static load than exists when exposed to cyclic loading, when controlled for creep rate. If this difference in load tolerance exists, it may be exploited to extend the life of vertebral bone exposed to repetitive compression, and potentially alter the development of spinal injury. However, little work has been conducted on functional spinal units to determine if bone displays this characteristic within an intact joint. Additionally, static loading may result in load redistribution within the intervertebral disc forcing more of the compressive load towards the periphery of the endplate away from the nucleus. In order to examine these potential mechanisms, 218 osteoligamentous porcine functional spinal units were assigned to one of 15 loading scenarios. This involved one of three normalized peak load magnitudes (50%, 70% and 90% of estimated compressive tolerance) and one of five normalized static load applications (0%, 50%, 100%, 200% and 1000% of the total dynamic work duration). Load magnitude significantly altered the resistance to cumulative compression with decreased peak magnitudes corresponding to both increased cumulative load tolerance and increased height loss. Static load periods did not alter the resistance of the spinal unit to cumulative compression or impact the number of cycles tolerated to failure. The insertion of static load periods impacted the total survival time to failure, but only for the 1000% static load group, an exposure unlikely to occur for most in vivo exposures. The insertion of static load periods decreased the amount of height loss during testing which may play a protective role by allowing load redistribution within the vertebral bone and intervertebral disc.     

Radio-translucent 3-axis mechanical testing rig for the spine in micro-CT

To date, no apparatus has yet been devised which would allow the study of bone microstructure of the whole vertebrae under mechanical loading. This paper outlines the design and development of a 3-axis radio-translucent mechanical testing rig for spinal research and testing. This rig is to be used in conjunction with a Shimadzu micro-CT scanner. Several tests were conducted to verify the feasibility of the rig design. First, the maximum range of deformation in compression, flexion\extension, and lateral bending that could be exerted on a goat lumbar functional spinal unit was evaluated using the noncontact digital markers method. Stepwise compression loading was also conducted on a single porcine vertebra and the loading data was compared to results obtained from an industrial grade compression testing machine. Finally, micro-CT scans of a porcine vertebra prior to and at a compression failure strain were obtained. The rig was confirmed to be able to exert pure moment loading in the above mentioned modes of deformation and the extent of deformation was comparable to previous documented results. The stepwise compression loading conducted in the rig was also found to effectively approximate a continuous loading of the same specimen in an industrial grade compression testing machine. Finally, resultant micro-CT images of isotropic resolution 32.80 mum of a porcine vertebra loaded in the rig were obtained. For the first time, trabecular microarchitecture detail of a whole vertebra buckling under 12.1% failure compression strain loading was studied using voxel-data visualization software. These initial series of tests verify the feasibility of the rig as an apparatus incorporating spinal testing and imaging.     

Muscle tissue changes in vertebrogenic myofascial syndromes

Asymmetrical electrical activity of paired deep segmentary (short) muscles of the back at the level of a vertebra rotation subluxation was found in 50 patients with early neurological thoracic column osteochondrosis (recorded with point electrodes). The proposed experimental simulation of spinal column osteochondrosis (rotation subluxation of the second thoracic vertebra in rabbit) establishes the presence of persistent tonic activity of the deep short paired back muscles at the level of the subluxation and exposes the dynamics of ultrastructural change in the muscle group. Persistent excitation irritation in that segment of the spinal cord and disorganization of deep short back muscle function are associated with over-stretching of richly innervated soft tissues of the same dislocating segment.Scientific-Research Laboratory Center, A. A. Bogomolets Medical Institute, Ukrainian Public Health Ministry, Kiev. Translated from Neirofiziologiya, Vol. 24, No. 3, pp. 298–306, May–June, 1992.     

The occurrence of Chlamydia spp. in pigs with and without clinical disease

Background

Disk-associated cervical spondylomyelopathy (DA-CSM) is a multifactorial neurological disorder in which progressive caudal cervical spinal cord compression is mainly caused by one or more intervertebral disk protrusions. The Doberman pinscher breed seems predisposed for this condition. The underlying cause and pathophysiology of DA-CSM are currently unknown. Recently, wider intervertebral disks have been put forward as a risk factor for development of clinically relevant DA-CSM. However, little is known about other factors affecting intervertebral disk width. Therefore the aim of this study was to assess the association between intervertebral disk width, measured on magnetic resonance imaging (MRI), and clinical status, age, gender and intervertebral disk location in dogs with and without clinical signs of DA-CSM.

Methods

Doberman pinschers with clinical signs of DA-CSM (N=17),clinically normal Doberman pinschers (N=20), and clinically normal English Foxhounds (N=17), underwent MRI of the cervical vertebral column. On sagittal T2-weighted images, intervertebral disk width was measured from C2-C3 to C6-C7. Intra ?Cand interobserver agreement were assessed on a subset of 20 of the 54 imaging studies.

Results

Intervertebral disk width was not significantly different between Doberman pinschers with clinical signs of DA-CSM, clinically normal Doberman pinschers or clinically normal English Foxhounds (p=0.43). Intervertebral disk width was positively associated with increasing age (p=0.029). Each monthly increase in age resulted in an increase of disk width by 0.0057mm. Intervertebral disk width was not significantly affected by gender (p=0.056), but was significantly influenced by intervertebral disk location (p <0.0001). The assessed measurements were associated with a good intra ?Cand interobserver agreement.

Conclusions

The present study does not provide evidence that wider intervertebral disks are associated with clinical status in dogs with and without DA-CSM. Instead, it seems that cervical intervertebral disk width in dogs is positively associated with increase in age.     

Simulation of the behaviour of the L1 vertebra for different material properties and loading conditions

Three-dimensional finite element models of the thoracolumbar junction (T12–L2) and isolated L1 vertebra were developed to investigate the role of material properties and loading conditions on vertebral stresses and strains to predict fracture risk. The geometry of the vertebrae was obtained from computed tomography images. The isolated vertebra model included an L1 vertebra loaded through polymethylmethacrylate plates located at the top and bottom of the vertebra, and the segment model included T12 to L2 vertebrae and seven ligaments, fibrous intervertebral discs and facet joints. Each model was examined with both homogeneous and spatially varying bone tissue properties. Stresses and strains were compared for uniform compression and flexion. Including material heterogeneity remarkably reduced the stiffness of the isolated L1 vertebra and increased the magnitudes of the minimum principal strains and stresses in the mid-transverse section. The stress and strain distributions further changed when physiological loading was applied to the L1 vertebra. In the segment models, including heterogeneous material properties increased the magnitude of the minimum principal strain by 158% in the centre of the mid-transverse section. Overall, the inclusion of heterogeneity and physiological loading increased the magnitude of the strains up to 346% in flexion and 273% in compression.     

Synchondroseal growth in the first cervical vertebra of the rat

Growth and remodelling of the first cervical vertebra were studied in the rat by means of biometry, vital staining (alizarin red S and oxytetracycline), and histology. The measurements showed a change in the ratio of the dorso-ventral to the transversal diameter in the lumen after obliteration of the dorsal synchondrosis. The pattern of labelling between the three segments of the vertebrae joined by synchondroses in the young animals indicated that expansion of the vertebral lumen took the form of a displacement of all three parts making up the bony ring. After closure of the dorsal synchondrosis the two ventral ones were still active and the lumen size increased more in the dorso-ventral direction than transversally. Alizarin red S and oxytetracycline tended to persist in the ventral part of the vertebra, while the staining almost disappeared from the dorso-lateral segment. Resting lines were found laterally to the ventral synchondroses in haematoxylin and eosin stained sections, but not in the ventral segment between the cartilages. The growth of the rat atlas is the result of an early rapid cartilage-mediated expansion of the vertebral lumen in conjunction with the growth of the spinal cord and, at a later age, mainly of a displacement of the ventral vertebral segment, leading to the final form of the vertebra and its lumen.     

Spinal tracts producing slow components of spinal cord potentials evoked by descending volleys in man

Slow negative (N) and slow positive (P) waves are frequently produced in the posterior epidural space at the lumbosacral enlargement by epidural stimulation of the rostral part of human spinal cord. The production of these slow potentials are thought to be responsible for analgesia at the stimulated segment as well as below that level. In order to define the spinal tract which mediates these slow potentials, we stimulated directly or from the epidural space the dorsal, dorsolateral, lateral and ventral columns at the cervical or thoracic level, and epidurally recorded spinal cord potentials (des.SCPs) at the lumbosacral enlargement in 7 patients who underwent spine or spinal cord surgery. The des.SCPs recorded in the lumbosacral enlargement consisted of polyphasic spike potentials followed by slow N and P waves. At a near threshold level of stimulus intensity the slow N and P potentials were consistently elicited only by stimulation of the dorsal column. The slow waves were also produced by intense stimulation of other tracts, but remained significantly (P < 0.05−P <0.01) smaller than those evoked by dorsal column stimulation when compared at the same stimulus intensity. Moreover, the slow P wave could not be elicited even by intense stimulation (10 times the threshold strength for the initial spike potentials) of the ventral column. Thus, the results suggest that the slow N and P waves are mostly mediated by the antidromic impulses descending through the dorsal column.     

伤椎置钉联合短节段内固定与单纯短节段固定治疗胸腰椎爆裂性骨折的比较研究

目的:比较伤椎置钉联合短节段内固定与单纯短节段固定治疗胸腰椎爆裂性骨折的临床疗效、固定效果及其对患者炎症反应和脊髓损伤的影响。方法:选取2014年3月到2016年12月期间我院收治的胸腰椎爆裂性骨折患者94例,根据手术方法的不同将患者分为伤椎置钉组(40例)和短节段内固定组(44例)。短节段内固定组患者采用单纯后路短节段椎弓根螺钉内固定进行治疗,伤椎置钉组采用伤椎置钉联合后路短节段椎弓根螺钉内固定进行治疗。比较两组患者的手术时间、术中出血量、住院时间、伤椎前沿高度比、Cobb’s角、伤椎椎体楔形变角、视觉模拟评分(VAS)和Oswestry功能障碍指数(ODI),炎性因子指标、脊髓损伤指标及术后并发症。结果:伤椎置钉组的手术时间长于短节段内固定组(P<0.05),术后6个月、术后12个月伤椎置钉组的伤椎前沿高度比明显高于短节段内固定组,Cobb’s角、伤椎椎体楔形变角明显低于短节段内固定组(P<0.05),术前、术后1周、术后6个月、术后12个月两组患者的VAS评分和ODI比较差异无统计学意义(P>0.05),术后3 d两组患者血清中IL-1β、IL-6、IL-8、TNF-α和pNF-H、NSE、S100β、GFAP水平比较差异均无统计学意义(P>0.05)。随访期间两组患者均未出现严重并发症。结论:伤椎置钉联合后路短节段椎弓根螺钉内固定可有效改善胸腰椎爆裂性骨折患者的椎体高度、Cobb’s角和伤椎椎体楔形变角,并且不会增加脊髓损伤和机体的炎症反应。     

In situ deformation of growth plate chondrocytes in stress-controlled static vs dynamic compression

Longitudinal bone growth in children/adolescents occurs through endochondral ossification at growth plates and is influenced by mechanical loading, where increased compression decreases growth (i.e., Hueter-Volkmann Law). Past in vivo studies on static vs dynamic compression of growth plates indicate that factors modulating growth rate might lie at the cellular level. Here, in situ viscoelastic deformation of hypertrophic chondrocytes in growth plate explants undergoing stress-controlled static vs dynamic loading conditions was investigated. Growth plate explants from the proximal tibia of pre-pubertal rats were subjected to static vs dynamic stress-controlled mechanical tests. Stained hypertrophic chondrocytes were tracked before and after mechanical testing with a confocal microscope to derive volumetric, axial and lateral cellular strains. Axial strain in hypertrophic chondrocytes was similar for all groups, supporting the mean applied compressive stress’s correlation with bone growth rate and hypertrophic chondrocyte height in past studies. However, static conditions resulted in significantly higher lateral (p < 0.001) and volumetric cellular strains (p ≤ 0.015) than dynamic conditions, presumably due to the growth plate’s viscoelastic nature. Sustained compression in stress-controlled static loading results in continued time-dependent cellular deformation; conversely, dynamic groups have less volumetric strain because the cyclically varying stress limits time-dependent deformation. Furthermore, high frequency dynamic tests showed significantly lower volumetric strain (p = 0.002) than low frequency conditions. Mechanical loading protocols could be translated into treatments to correct or halt progression of bone deformities in children/adolescents. Mimicking physiological stress-controlled dynamic conditions may have beneficial effects at the cellular level as dynamic tests are associated with limited lateral and volumetric cellular deformation.