Below is a demonstration of me performing LSJL on the femoral epiphysis.  The key to chondroinduction as is expanded on below(need to get the studies from UCSD, does anyone have access to them?) is to achieve between 0.1 – 10(or more) MPa in the epiphyseal bone marrow.    A blood pressure cuff can achieve 120mmHg during a heart beat which is about 0.015MPa an order of magnitude below what we need.  The highest recorded blood pressure is 300mmHg which is still below what we need.  Systolic blood pressure is “specifically the maximum arterial pressure during contraction of the left ventricle of the heart.”  We’re not specifically looking for the arterial pressure we’re looking for the bone marrow hydrostatic pressure.

The key to distraction osteogenesis may be the blood clot that’s formed during the fracture.  This creates a chondrogenic environment.  And this fracture does not pose a large risk to health.  So the goal is to mimic the hydrostatic pressure creation in the bone marrow without inducing fracture.  Note in the video that my knee is bent to increase the pressure.

Nothing much in the video.  Just me performing the new LSJL method on my left knee epiphysis.  This is exactly the way I do it except I’m usually lying down on my back so it’s easier to perform.

Pressure and shear stress in trabecular bone marrow during whole bone loading.

“Skeletal adaptation to mechanical loading is controlled by mechanobiological signaling. Osteocytes are highly responsive to applied strains, and are the key mechanosensory cells in bone. However, many cells residing in the marrow also respond to mechanical cues such as hydrostatic pressure and shear stress, and hence could play a role in skeletal adaptation. Trabecular bone encapsulates marrow, forming a poroelastic solid. According to the mechanical theory, deformation of the pores induces motion in the fluid-like marrow, resulting in pressure and velocity gradients. The latter results in shear stress acting between the components of the marrow. To characterize the mechanical environment of trabecular bone marrow in situ, pore pressure within the trabecular compartment of whole porcine femurs was measured with miniature pressure transducers during stress-relaxation and cyclic loading. Pressure gradients ranging from 0.013 to 0.46kPa/mm were measured during loading. This range was consistent with calculated pressure gradients from continuum scale poroelastic models with the same permeability. Micro-scale computational fluid dynamics models created from computed tomography images were used to calculate the micromechanical stress in the marrow using the measured pressure differentials as boundary conditions. The volume averaged shear stress in the marrow ranged from 1.67 to 24.55Pa during cyclic loading, which exceeds the mechanostimulatory threshold for mesenchymal lineage cells{but we have to be in the range to stimulate chondrodifferentiation}. Thus, the loading of bone through activities of daily living may be an essential component of bone marrow health and mechanobiology. Additional studies of cell-level interactions during loading in healthy and disease conditions will provide further incite into marrow mechanobiology.”

Intermittent hydrostatic pressure can induce chondrostimulation.  0.1 to 10 MPa tend to be the levels to induce chondrogenic differentiation.  There are 1 million Pascals in a MegaPascal so the average shear stress in the bone marrow from cyclic loading is below the levels needed to induce chondroinduction.  0.1MPa is needed to induce proteoglycan production and above 10MPa induces more chondrogenic markers.

The in situ mechanics of trabecular bone marrow: the potential for mechanobiological response.

“Bone adapts to habitual loading through mechanobiological signaling. Osteocytes are the primary mechanical sensors in bone, upregulating osteogenic factors and downregulating osteoinhibitors, and recruiting osteoclasts to resorb bone in response to microdamage accumulation. However, most of the cell populations of the bone marrow niche,which are intimately involved with bone remodeling as the source of bone osteoblast and osteoclast progenitors, are also mechanosensitive. We hypothesized that the deformation of trabecular bone would impart mechanical stress within the entrapped bone marrow consistent with mechanostimulation of the constituent cells. Detailed fluid-structure interaction models of porcine femoral trabecular bone and bone marrow were created using tetrahedral finite element meshes. The marrow was allowed to flow freely within the bone pores, while the bone was compressed to 2000 or 3000 microstrain at the apparent level.Marrow properties were parametrically varied from a constant 400 mPas to a power law rule exceeding 85 Pas. Deformation generated almost no shear stress or pressure in the marrow for the low viscosity fluid, but exceeded 5 Pa when the higher viscosity models were used{high viscosity is high internal friction?. The shear stress was higher when the strain rate increased and in higher volume fraction bone. The results demonstrate that cells within the trabecular bone marrow could be mechanically stimulated by bone deformation, depending on deformation rate, bone porosity, and bone marrow properties{we need to alter this with LSJL}. Since the marrow contains many mechanosensitive cells, changes in the stimulatory levels may explain the alterations in bone marrow morphology with aging and disease, which may in turn affect the trabecular bone mechanobiology and adaptation.”

The higher the temperature is, the lower a substance’s viscosity is. Consequently, decreasing temperature causes an increase in viscosity.

Bone is considered to have laminar flow in that the bones move in separate layers.  Bone is a viscous tissue meaning “having a thick, sticky consistency between solid and liquid; having a high viscosity”<-Salt, cornstarch, and flour are ways to increase bone marrow viscosity.

A blood pressure cuff generates 120mmHg ish which is about 0.015MPa.  You need about 75000mmHg to generate 10MPa.    Specifically we want to increase the intraosseous pressure.

According to a study on the relationship between intraosseous pressure and intra-articular pressure selective compression of veins can increase intraosseous pressure.

According to Intraosseous Pressure in the Patella in Relation to Simulated Joint Effusion and Knee Position: An Experimental Study in Puppies,  the intraosseous pressure of the patella is about 12mmHg.  “During extension of the knee joint, a significant rise in intraosseous pressure of the tibial epiphysis and patella was observed, whereas during flexion femoral epiphyseal pressure and patellar pressure increased significantly.”

Pressure increased with degree of knee flexion.  This is like doing a hamstring curl.

A method of measuring bone marrow blood pressure is mentioned here:

Bone marrow pressure in osteonecrosis of the femoral condyle (Ahlbäck’s disease)

Bone-Marrow Pressure and Bone Strength

“During rapid dynamic loading, however, a slight rise in intra-medullary pressure was observed. Contraction of the femoral muscles also resulted in a greater bone-marrow pressure increase. A correlation of 0.98 between stimulus strength and intra-medullary pressure was obtained. The rise in intra-medullary pressure with femoral muscle contraction is suggested to have a possible role under extreme stresses in living conditions.”

“The normal resting range of bone-marrow pressure in all the rats studied in the present
series varied from 1.07 to 2.40 kPa (8 to 18 mmHg) [mean resting pressure 1.65 kPa (12.4
mmHg), standard error of the mean 0.08 kPa (0.6 mmHg)]. The most frequently observed
values were between 1.6 kPa to 1.87 kPa (12 to 14 mmHg). The marrow pressure tended
to vary within the range of 0.267 kPa under resting conditions. “<-This is about 3 orders of magnitude of the pressure we need.

“The bone-marrow pressure did not alter [during slow loading] either during the period of loading or on completion of the process and maintenance of the load. ”

“In slow loading experiments the compression was applied over a period of 1 minute to gaps of
1.36 kg from 0 to 12.25 kg by slow rotation of the central loading screw. Each applied load was
maintained for 2 minutes to allow for any gradual pressure build-up. Any rise in the marrow
pressure following loading was permitted to settle before the next incremental load was applied.  During fast loading similar loads were applied but the process of each loading was completed within 2 seconds. After each step of loading there was an observational pause of 2 minutes. A sudden loading omitting two and more of the intermediate steps was also tried. ”

“During fast loading, bone-marrow pressure variations were normal within the range of 0
to 2.7 kg. Beyond this level as the loads were swiftly applied, sudden pressure changes were
observed, these being more pronounced if the loading omitted two of the intermediate
steps. A rise of 2 kPa (15 mmHg) was observed when the compression was raised
from 4 kg to 12.25 kg. Generally, a higher magnitude of compression engendered greater increases in the intra-medullary pressure. ”

“Stimulation of the femoral nerve, causing contraction of the quadriceps muscles
resulted in a considerable rise in bone marrow pressure. There was a progressive increase in bone-marrow pressure with each increment in stimulus strength. A maximum pressure rise of 8 kPa (60 mmHg) was recorded with 5 V stimulation.”

“In life, excessive compression stress tends to cause bone fracture which can be resisted by
the sudden and significant rise of marrow pressure caused by simultaneous contraction of the overlying muscles”

This next study found that pressure increased by approximately 3X in response to load which still doesn’t get us up three orders of magnitude:

Microfluidic Enhancement of Intramedullary Pressure Increases Interstitial Fluid Flow and Inhibits Bone Loss in Hindlimb Suspended Mice

“Increases in ImP may be induced by deformations in the matrix that result in volumetric decreases in the intramedullary cavity”

“dynamic IFF rather than pressure was the primary factor driving skeletal adaptation in our studies.”<-Perhaps it is the same for inducing chondroinduction?

” in vitro in sheep tibia (up to 300 mmHg in response to a load of 2000 N over 0.15 second) and excised human femurs (93.5 mmHg in response to a load of 980 N over 0.03 second)”

According to the LSJL study

Knee loading dynamically alters intramedullary pressure in mouse femora

“sinusoidal forces of 0.5 Hz and 10 Hz, pressure amplitude increased up to 4-N loads and reached a plateau at 130 Pa.”<-which is 3 orders of magnitude below where we need to be but maybe it is interstitial fluid flow that can induce chondrogenesis and not hydrostatic pressure.

Here’s some papers on how hydrostatic pressure and interstitial fluid flow play a role in the initial creation of bone epiphysis and growth plate.

According to Mechanobiology of mandibular distraction osteogenesis: finite element analyses with a rat model., “A 0.25 mm distraction was simulated and the resulting hydrostatic stresses and maximum principal tensile strains were determined within the tissue regenerate. When compared to previous histological findings, finite element analyses showed that tensile strains up to 13% corresponded to regions of new bone formation and regions of periosteal hydrostatic pressure with magnitudes less than 17 kPa corresponded to locations of cartilage formation. Tensile strains within the center of the gap were much higher, leading us to conclude that tissue damage would occur there if the tissue was not compliant enough to withstand such high strains, and that this damage would trigger formation of new mesenchymal tissue. These data were consistent with histological evidence showing mesenchymal tissue present in the center of the gap throughout distraction.”<-So it is possible to form cartilage with less than 0.1MPa.

” In reality, tensile hydrostatic stresses (i.e., negative pressures) greater than 47.07 mmHg (=6.3 kPa), which is the vapor pressure of water at 37 degrees C, would cause the water in the tissue to boil.”

Pressure in a liquid is the force exerted over a given area, a fluid’s pressure pushes on the walls of the surrounding container, as well as on all parts of the fluid itself.

The pressure in the liquid increases with depth because of gravity. The liquid at the bottom has to bear the weight of all the liquid above it, as well as the air above that.

Here’s a study that states that maybe it’s interstitial fluid flow and not necessarily hydrostatic pressure that can induce changes in bone(and therefore chondroinduction):

Fluid pressure gradients, arising from oscillations in intramedullary pressure, is correlated with the formation of bone and inhibition of intracortical porosity

“Fluid flow that arises from the functional loading of bone tissue has been proposed to be a critical regulator of skeletal mass and morphology. To test this hypothesis, the bone adaptive response to a physiological fluid stimulus, driven by low magnitude, high frequency oscillations of intramedullary pressure (ImP), were examined, in which fluid pressures were achieved without deforming the bone tissue. The ulnae of adult turkeys were functionally isolated via transverse epiphyseal osteotomies, and the adaptive response to four weeks of disuse (n=5) was compared to disuse plus 10min per day of a physiological sinusoidal fluid pressure signal (60mmHg, 20Hz). Disuse alone resulted in significant bone loss (5.7±1.9%), achieved by thinning the cortex via endosteal resorption and an increase in intracortical porosity. By also subjecting bone to oscillatory fluid flow, a significant increase in bone mass at the mid-diaphysis (18.3±7.6%), was achieved by both periosteal and endosteal new bone formation. The spatial distribution of the transcortical fluid pressure gradients (∇Pr), a parameter closely related to fluid velocity and fluid shear stress, was quantified in 12 equal sectors across a section at the mid-diaphyses. A strong correlation was found between the ∇Pr and total new bone formation (r=0.75); and an inverse correlation (r=-0.75) observed between ∇Pr and the area of increased intracortical porosity, indicating that fluid flow signals were necessary to maintain bone mass and/or inhibit bone loss against the challenge of disuse. By generating this fluid flow in the absence of matrix strain, these data suggest that anabolic fluid movement plays a regulatory role in the modeling and remodeling process. While ImP increases uniformly in the marrow cavity, the distinct parameters of fluid flow vary substantially due to the geometry and ultrastructure of bone, which ultimately defines the spatial non-uniformity of the adaptive process.”

“one is a highly structured composite material comprised of a collagen-hydroxyapatite matrix and a hierarchical network of lacunae-canaliculi channels. These tunnels permit interstitial flow of fluid through tiny microporosities, and thus ‘‘by-products’’ of load, such as the change in fluid velocities or pressures, represent a means by which a physical signal could be translated to the cell{Mesenchymal Stem Cells are cells so could be affected by fluid pressures as well}”

“intracortical fluid flow is induced not only by bone matrix deformation, but also by the intramedullarypressure (ImP) generated during loading.  Applying anabolic oscillatory ImP alone can induce transcortical fluid flow as measured by streaming potential”<-So there are two alternatives to achieving 0.1 MPa in the epiphyseal bone marow: oscillitary intramedullary pressure and bone matrix deformation to induce fluid flow.

” maximum fluid pressure on the order of 8 kPa will result in approximately 0.8 [microstrain] in the matrix.”

“While the endosteum is permeable, theyhave found that the periosteum is, in essence, impermeable unless the periosteal superficial layer is removed in the adult canine tibial cortex.”