FINITE ELEMENT ANALYSIS OF AN UNDER-ACTUATED ROBOTIC DEVICE FOR
KNEE LOADING APPLICATIONS

“Knee loading is one form of joint loading modalities, which potentially provides a therapeutic regimen to stimulate bone formation and prevent degradation of joint tissues. Healing of knee injuries is sensitive to many environmental stimuli.  Since mechanical stimuli are crucial for the growth, development, and maintenance of articular cartilage and bone, we have developed an innovative robotic knee loading device to achieve this goal. This device induces mechanical loading to stimulate articular cartilage and bone, and it potentially reduces the healing time of injuries such as bone fractures. The robotic device is an improved version over previous joint loading devices, in which loads are applied at specific points with non-uniform loading around the knee joint. In this paper, finite element analysis (FEA) of this robotic device has been presented that includes static structural analysis and modal frequencies of the device for two different material configurations used in the design. The design with ABS plastic material offers the desired margin of safety while reducing the weight and cost. ”

“The robotic device examined in this paper is designed for small levels of deformation. The intended displacement of the working device is small, a maximum of 13 mm. large
deformations are not recommendable as such deformations will critically affect the effective range of motion of device. “<-we may want larger deformations for our purposes.

” If the stresses are too high for the material selected, the device may yield, resulting in the failure of the device.”<-this can happen with a clamp without enough strength.”

” if very small magnitude of mechanical stimuli is applied fast enough then it may induce a cellular response”<-This is an interesting thought.  It’s very hard to produce a rapid mechanical stimuli physiologically.  How many bicep curls can you perform in one second?

“Osteocytes are the highly mechanosensitive cells which senses the resulting physical stimuli from mechanical forces applied on bones. They constitute of more than 90% of bone cells.
When rapid mechanical loading is applied at the end of long bone, the interstitial fluid present around the osteocytes pressurizes causing the fluid flow which creates hydrostatic
pressure throughout the bone. This hydrostatic pressure excites the osteocytes resulting in enhanced osteogenesis which decreases the healing time of the fractures, increases the bone density and will be helpful in treatment of osteoporosis and osteoarthritis”<-we want additional stimuli from the hydrostatic pressure we want hydrostatic pressure to degrade bone tissue reducing the constraining effect that bone tissue has on growth and we want the stem cells to become more fibrocartilagenous.

“To apply such a load, a device would need to have a means of producing a transverse force directly to the end of a long bone, such as at the knee. A cyclic force applied in such an area would force a slight shift of the fluid within the bone towards the opposite end of the bone in a controlled fashion”<-this is what we do with the clamp.  Produce a transverse(lateral) force directly to the end of a long bone.  It has the potential to be cyclic if you rotate and reverse the rotation of the clamp.  We may want more than a slight shift of fluid and we may not care if it’s in a controlled fashion or not.

“a maximum force of 40 N with the frequency range of 1 Hz to 5 Hz will have a promising effect on a human knee”<-Higher force may be needed for longitudinal bone growth.

” the efficacy of stimulating the osteocytes depended on the stress distribution on the knee. Based on this observation, it is projected that a position specific loading that provides a more
targeted force application on the knee is likely to further improve the efficacy of bone stimulation. It is hypothesized in that this targeted loading would contribute to the
improvement of new bone formation over a distributed loading modality. “<-maybe a smaller clamp pad and instead of clamping the knee as a whole clamping different epiphysis’ separately.  Although we don’t necessarily care about stimulating the osteocytes, we want to degrade bone tissue and stimulate stem cells.  The statement about more targeted loading still applies.

I can’t post an image of the device but look at fig 4 and 5.

” It can be seen that when maximum force of 20 N is applied on human knee, the maximum stress generated is 11.22 MPa. “<-Since around 10MPa is the chondrogenic stimulatory range this is a key pressure however you may need to degrade bone tissue as well.   The study does not indicate exactly where in the knee the stress was generated. This was for alluminum and steel.  Other materials were used and they were all in this same range.

FINITE ELEMENT ANALYSIS OF AN ELECTRO-MECHANICAL KNEE LOADING DEVICE

“When a cyclic but controlled load with a specific frequency is applied to the bones (femur and tibia) and surrounding tissues in the knee, it affects the osseous tissue causing physical deformations.  These deformations result in pressure gradient in the intramedullary cavity of the bone. Due to this pressure difference, there is a fluid flow of molecules and nutrients.
This will result in osteoblast differentiation; a phenomenon will initiate new bone formation or osteogenesis. This can be used as a healing technique in case of bone related injuries
like fractures or diseases like osteoarthritis and osteoporosis.”<-slightly more powerful prediction in this study where they predict osteoblast differentiation and physical deformations.  They mention a specific frequency being needed.

“When the device is loaded with a human knee, the inertial load resisting the driving force is considerable.”

Here’s the last LSJL update.

I haven’t done experimentation with the rib cage because I’ve focusing on experimentation with a new clamp to get results in the arms and legs which is primarily what people want.

Using a 1500lbs clamp means there’s far less slippage issues.  Finding the key clamping spot is paramount as if you clamp in a spot with a lot of muscle you’ll never be able to generate enough force.  I found this was the case for clamping the shoulder joint as there’s no good place to clamp without getting a lot of deltoid.  But it was sufficient for the wrists, knee, elbow, ankles, and foot.

Here’s another pic of what the clamp looks like:

So hopefully I can have some leg and arm results to start sharing.

Here’s the feet pictures:

Here’s an overhead shot to show that it’s not flattening of the arches:

Here’s a link to when I was performing LSJL solely on my right foot.  Before right was longer.  Now left is longer.

I’m working still on clamping my right hand and right thumb with the new Bessey clamp hopefully I’ll start getting stronger results and get xray results.  There’s a difference but not as strong as I would like.  I’ll keep going to see if the results can get more and the xrays will be more striking.

I’ve been working hard on trying to increase my hand and feet size via clamping and I’ve had some moderate measurable success and I’m working to get more.

The reason I chose the hands and feet was because I didn’t want to be limited by clamping strength in terms of getting results.  I’ve hard to order clamps that aren’t available in hardware stores and I may have to get even stronger clamps.

But one things I didn’t consider was the shape of the bones and not just the size(hands and feet bones are smaller).

The curved nature of the ribs means that LSJL is going to be more effective think of water in a curved pipe rather than a straight one.

The fluid inside the bone is going to be bouncing around all the curvatures of the rib rather than just flowing down a straight line.  And take a look at how much more cartilage there is in the ribs than there is normally that likely means that the rib bones will behave differently from long bones.

And there is already LSJL going on in the ribs, it’s called scoliosis bracing.  However, it differ from LSJL in that it’s not on the epiphysis(the weakest part of the bone) and that the load is static(although you are moving around in the brace).

Just by breathing you’re doing LSJL on the rib cage by all the expansion pressing against the ribs.

There’s also been reports of people getting larger ribs via pullovers but that is not LSJL.

Papers like this one report growth in the rib cage due to age, Quantification of age-related shape change of the human rib cage through geometric morphometrics, I couldn’t get the full study but the study established correlation between thorax(basically rib cavity size, the larger your ribs the larger the rib cavity) and age, weight, and height with weight being the largest correlation.  And weight can perform lateral loading on the epiphysis, it’s just that due to curved nature of the rib bones it needs a lot less load than other areas and people store a lot of weight in their torso.

And another region of interest is the jaw which has a lot of curves too and a lot of people are interested in the jaw due to it’s importance in sexual dimorphism and it’s perceived impact in male dominance.  Thank of Michael Cera, Zach Braff, and James Ellworth in terms of jaws.

I’m already doing LSJL on the jaw but I’m going to be working harder at it.  Then I’m going to figure out how to do a routine for the ribs.

I’ll see if I can find more evidence of rib growth over time(you can help) and post about it definitively at the next LSJL update.

Here’s the last update.

Here’s the new feet images:

I’ve been loading only my left foot trying with clamping various parts of it.  It looks like the left foot is starting to catch up with the right although I do have confirmation bias(I want to confirm my existing opinions) but I always have confirmation bias and I see greater changes than I did before.

So I’ll keep doing what I’m doing.  See if I can get greater changes in my feet, see if I can clamp my right hand to be bigger as I have before x-rays and I can just get after xrays to get definitive solid proof, my right hand does look bigger to me but I’d rather to see if I can get more definitive growth as again I do have confirmation bias.  And of course I’m trying to clamp to increase height.

Hyperostosis indicates that it’s possible to form new bone as an adult.  Hyperostosis seems to affect ligaments which would make it hard for height growth as there ligaments really placed to add to height.  It may be linked to insulin as diabetes may affect hyper ostosis.

Morphological characteristics of diffuse idiopathic skeletal hyperostosis in the cervical spine.

“(A) Plain lateral radiograph shows a 69 year old male with DISH in the cervical spine. A solid formation of new bone is extending over at least four vertebral bodies. (B) Computed tomography (CT) visualizes the thoracic spine of a 72 year old male in the sagittal view. The scan shows a flowing ossification of the anterolateral spine with bridging over more than four contiguous vertebral bodies. The intervertebral discs and apophyseal joints are relatively intact in both images. (C + D) The CT scans in axial view demonstrate the differences in position of the new bone formation depending on the region. (C) The CT scan of the cervical spine corresponds to the radiographic image (A) and demonstrates symmetrical hyperostosis (yellow) anterior to the vertebral body and possible displacement of the trachea. (D) The axial CT of the mid thoracic spine in a 58 year old male with DISH shows the newly formed bone on the right anterolateral side with the aorta clearly located on the left anterolateral side.”<-So this is all over time.

“It has been hypothesized that vascular structures act as a natural barrier for the formation of new bone in DISH”

If blood vessels do block bone growth than that fact can be exploited to increase height.  There is an epiphyseal artery though that doesn’t block growth.

“arteries may act as a natural barrier for newly formed bone in DISH. The lack of crossing segmental vessels in the cervical spine may permit linear bone growth creating a bar-like structure in contrast to the flowing pattern typical for DISH in the thoracic spine where segmental vessels are present.”

Some people have claimed to have grown taller in a non-epiphyseal plate driven method via HGH.  Now it’s important to note that acromegaly is not solely based on HGH and there are some cases in gigantism where HGH levels are lower than people who supplement via HGH so it’s possible there’s another factor driving the length.  This topic was discussed before here.  In that page there are additional acromegalic x-rays and additional discussion of non-growth plate driven height growth.

You don’t just grow interstitially, you also grow appositionally even on the longitudinal ends of the bones.  For most, this is insignificant but for someone with high HGH and thereby higher bone turnover this could be much more significance but the question then becomes if they are gaining height in the feet and hands due to the larger number of bones there then in legs and arms then why aren’t the growing in the torso.

It follows logically that if two people are growing by different methods interstitial growth(traditional growth plate growth) and appostional growth on the longitudinal ends(endochondral ossification of the articular cartilage or some other bone thickening method) then the two bone shapes will look differently on the x-ray.

Here’s a “normal” hand x-ray:

Here’s an acromegalic hand x-ray:

One thing that strikes immediately is the greater whiteness between the acromegalic x-rays and the normal x-rays but the two bone shapes seem largely the same.  However there does seem to be greater articular cartilage spacing which could explain the increased hand size.

I couldn’t find a spine xray of someone with acromegaly but here’s a chest x-ray:

Unfortunately you can’t really tell anything about the spine because the bones are so thick.

Here’s a normal chest x-ray:

So basically the x-rays tell you that acromegaly may or may not cause a form of non-growth plate based longitudinal bone growth.  There’s just not enough x-rays of people with acromegaly to draw conclusions.  Or x-rays of people who supplement with HGH like Richard Piana.

Here’s a study(Unfortunately I couldn’t get the full study) that may have some insights:

Acromegaly and bone.

” Growth hormone (GH) and insulin-like growth factor-I (IGF-1) have pleiotropic effects on the skeleton throughout the lifespan by influencing bone formation and resorption. Despite these positive effects on skeletal metabolism, in presence of GH and IGF-1 excess, bone turnover increases excessively leading to deterioration of bone microarchitecture and high risk of fragility fractures, thereby impairing quality of life.

Coexistent hypogonadism, diabetes mellitus, hypovitaminosis D, hyperparathyroidism and over-replacement with glucocorticoids impair bone framework, however, the effects of acromegaly on bone mineral density (BMD) are still controversial and despite normalization of bone turnover after treatment, the risk for fractures remains increased. As a matter of fact, a major clinical aspect emerging from the studies published so far is the lack of clinical-diagnostic tools able to reliably predict the appearance of fractures in patients with acromegaly occurring even in the presence of normal or low-normal BMD.”

So bone turnover could potentially alter bone architecture and make non-growth plated based growth a possibility.