Biomechanical challenges - a new model (or just an old one revisited??)

Giving the benefit of the doubt and saying you were referring to FDL not EDL, could we not argue that active/resisted plantarflexion may elicit pain in tendon injury but not in fat pad? Basic Cyriax- OK I know it has limitations so too does ultrasound, but this little test takes seconds, is quick and easy to learn and costs zero.

 

Correct, my apologies, FDL was intended. Active resistance to pl fl combined with attempts to palpate the structure will reproduce symptoms, but depending on the specific location of the attinuation, how would you differenciate from plantar plate involvement, or the fad pad either in isolation or combination? Most importantly, does a biomechanical model (other than the tissues stress) explain the cause?

Regards

Paul

 

I agree with this, to a point (I think this was the question you were asking for a response on?) I would argue most often we cannot identify a singular traumatic event (which would be nice if we could), but in fact singular traumatic events (to a variety of soft tissues), occur regularly, and because they are never identified, are described as idiopathic. Those specific directional forces... lateral, shear, flexion, rotational, vertical, oblique etc) do occur and differentially affect tissues. We can use any number of techniques to ascertain the structure traumatised (Simon’s example) and my example of the US approach, but the point is still the same. With better accurate identification of the stressed structure, we are in a far better position to appreciate the nature of the force we are dealing with.

All too often I get the sense clinicians attribute the mechanism of injury to a highly predictable algorithm, whereas I feel more comfortable with the "chaos" theory approach. Some pathology lends itself to predictive causal-effect relationships, but certainly not all.

 

Paul B,

I think you'll find that you need to put a little bit of time into this forum or arguments may arise quickly- hampering the real issues. Are you in cool New Zealand or hot Australia today??

I'm in favour of scrutinising the pros and cons of the newfound technology 1st. You are fortunate to have it in an educational setting- so you have the responsibility of learning about it's safety, correct application guidelines before playing with this new technology to your heart's content.

I too would like to hear what you know about it presently-or your references for us to review.

Lucky Lisfranc has an extremelly valid point in regards to this new technology going further in the near future than just exclusive enjoyment for the educational facility and current students- or wealthy few. Some of us in Australia are very well loaded with information from crash units years back, and took many painstaking years to put it all coherently together. You want to make an impact? Help with REBATES so the WHOLE profession can benefit (and obviously the patients as a result). I'm in hot Australia

15 minute decision making is a quick way to teach your recent students to jump the hoops and good luck when you graduate. You may not make alot of money, but utilising all your skills and knowledge may take a frag longer...Consider longer patient appointments to do what it takes to serve them well. Surely a job well done ie diagnosing the ailment, is the biggest satisfaction for us Health Professionals?

In regards to the biomechanical theories and diagnostic skills differentiation, diagnosis takes up considerable time alone, aetiology/cause can be pondered upon after patient leaves-perhaps in your lecture or few minutes with a student afterwards.


Again, agree with LL post pone your theoretical biomechanics education-yr2-3-4, until you train the students in the complex world of accurate diagnosis using all tests pertinent. The spitting back of biomechanics to the lecturer merely reflects where our education focuses. Help them attain the skills of being on par with medical profession in finding the problem EARLY in their studies, and they'll enjoy seeing how biomechanics plays an important part in the overall picture.

It seems from other discussions most Podiatrists want to stay practical and hands on. I envisage biomechanics is pertinent in preventative strategies and such studies focusing on longterm prevention and treatment more than immediate help to the patient(accept immediate padding). Some biomechanics are clearly the main issue in a condition, but certainly not in all or most. A person is complex-wholistic approach is necessary.

Pod777

 

Hi,

great comments above. The 15 minute scenario was purely a metaphor, but I think we are saying the same thing. Thanks for the feedback.

Regards

PB

 

Kevin, I note this post on an earlier thread. Would diagnostic US have a role to play in expediting the decision?

Regards

Paul

 

Paul:

Certainly, this string of postings that you have contributed to has given me much more information about the potential diagnostic benefit that ultrasound might be in my practice, as you have pointed out above. In addition, it looks like a neat toy that would probably be just fun to play with from a tissue stresss/biomechanics standpoint, if I only had the free time to do so.

My only disagreements with you have been (A): I don't think that diagnostic ultrasound actually replaces biomechanical theory because 1) biomechanical theory is not about making diagnoses but more about trying to understand how the foot and lower extremity work (please don't confuse classification of structure and taxonomy with theory) and 2) Eric Fuller and I have been writing about the importance of focusing on the stress in tissues for the last 15 years Thinking Like an Engineer , with McPoil and Hunt neatly coining this type of thought process as a term, "tissue stress", 12 years ago (McPoil TG, Hunt GC: Evaluation and management of foot and ankle disorders: Present problems and future directions. JOSPT, 21:381-388, 1995). Therefore, tissue stress theory (which is a biomechanical theory that has been around for some time now) and diagnostic ultrasound should be able to work together with each other quite well. In other words, diagnostic ultrasound does not replace nor is it "better than" existing biomechanics theories: diagnostic ultrasound and biomechanical theory are accomplishing different goals for the clinician, not competing with each other.

My second disagreement with you was (B): just because a certain finding from diagnostic ultrasoud is made, one can not always be so certain of the specific types and magnitudes of tissue stresses that caused the injury or be so certain that those stresses were of a different type or magnitude from another individual that has a different injury. This is due to the countless permutations of structure and mechanical characteristics in the tissues of the feet and lower extremities, and the spatial arrangement of these tissues within the feet and lower extremities of the people we treat. However, this does not also mean that we can't make educated guesses as to what the external forces and internal stresses were that caused an injury. We just can't always be certain.

Other than that, I have enjoyed your comments so far, Paul. I am glad that you started this discussion and am looking forward to further conversations with you in the future. Keep up the good work. I am a shark that only bites snakes.

 

I'm not sure the many of thousands of ultrasonographers around the world would see their equipment the same way? Re free time, yes, I certainly have plenty of that.

Best be guided by the science and history on this one. The health funds here rebate for diagnostic ultrasonography, but not biomechanical examinations. At the end of the day, it about where energy is best invested (given the limited time all clinicians have - as per your above comment).

The one thing we do know, once the affected structure is definitively identified, and the pathology confirmed, then stress of one source or another has caused physical failure (engineering model if you like). More relevantly, the bio-medical (not mechanical) model may be applied. In the absence of this, all else is as you suggest, guesswork, speculation and innuendo.

Yes I've enjoyed your coments too Kevin, however it looks like we've come as far as we can on this one. I'm off now to do some more testing.

Kind regards

Paul.

 

Paul:

Glad you agree that we can't be so certain about the types of stresses that cause injury, even though I'm sure that tests such as US and MRI will eventually give us more information in that regard.

The engineering model is the only way to go as far as us gaining a better knowledge of what causes foot and lower extremity injuries. The biggest problem is that few podiatrists understand engineering concepts. I believe that by about the time I am ready to retire, the rest of the profession will also be coming to the conclusion that the internal mechanical forces and moments of the foot are far more important than the external forces which act upon it during weightbearing activities. Better mechanical models of the foot and better biomechanical theory will produce this knowledge with greater efficiency than even high definition diagnostic ultrasound.

 

Does that make you a mongoose? Rikki tikki tavi?

There's an image

Regards
Robert

 

Even though I have no clue what "rikki tikki tavi" is, maybe I should have instead said that I'm the shark that only likes to bite snake-oil salesmen.

 

Of interest today was a case of chronic pl fascitis, with (on US examination), what appeared to be complex and disorganised collagen matrix at the insertion. Most of the more common cases we see on US have, in the acute phase at least, only deep associated oedema indicating basic inflammation, but with no associated collagen disorganisation. Could suggest that in the chronic case, scar formation may be an important finding?

What’s been others experience of this condition, ie chronic vs acute physiological differences in the manifestation of heel pain?

Regards

Paul.

 

How does this additional information change your care strategy?

 

Hi Simon,

The amount of disorganisation, in this case, seemed somewhat extreme. The patient has been quite recalcitrant to treatment. Most of the pl fascia cases seen in our clinic respond well to typical conservative care, directed at reducing traction forces, even in the more long standing cases. This one (on US investigation) seems different. Perhaps entrapment of the medial branch? A small percent of cases of this type are Rxed with partial release of the fascia. Perhaps this should be expedited?

Simon, your thoughts?

Paul

 

I think I'd like to see some data which shows the relationship between "disorganisation" and treatment response. How many pt's out there who have reponded to the usual conservative care have a similar degree of "disorganisation" ?

Not a big fan of fascial release, but playing Devil's advocate: given that a typical care plan for the "plantar fasciitis" patient should probably begin by exhausting conservative measures prior to surgery being considered, does the ultrasound really change the care plan? I suppose you could argue that you should go straight to surgery when you see things like this on ultrasound. Personally, I'd first need to be convinced by big number research which provides the data I described above before advocating the knife without exhausting conservative measures first.

I know one of our Spanish colleagues, Javier Pascual Huerta (javier.pascual@uem.es) has some interesting ultrasound data on plantar fascial thickness. I was hoping to be able to do some predictive modelling with him, but my fathers death last year got in the way and I couldn't give it the time it needed. Viz, I dropped the ball on him- sorry Javier. Maybe you and he should hook up?

 

Hi Simon,

Thanks for your comments. Sorry to here about your fathers death.

A really interesting point you raise, re the Rx indications. Most of the more acute fascia problems (and even some of the semi acute / chronic) were showing up on US as not much more the "inflamed structures", ie the marker being the oedema. These can produce what appears to look like quiet swollen fascia structures, however when we follow them up after about 2-3 weeks of conservative Rx, the swelling reduces significantly (no surprises there). A few are showing signs of, what appears to be a more complicated recovery (hence what is coming up as significant hyper echoic signals, an indicator of increased collagen production). This is what I think may have been happening in the recalcitrant case. As you suggest the US is probably guiding us more re prognostic value, and it does appear to give everyone in the management loop (patient included) a bit more realistic expectations.

Paul B.

 

Kevin

I got the snake oil thing. Rikki tikki tavi was a mongoose in a Rudyard Kipling book of the same name. The story tells of his defense of a british family moved to india. Although his first fight is against a small sand snake who threatens the child, his main struggle is against Two cobras, Nag and Nagiana. The conflict is long and multifaceted with some great narrative and, as with most kipling books, heavy use of metaphor. In the end the mongoose goes down the Cobra's hole and after an agonised wait emerges unscathed. He remains as the pet of the family and the vigilant defender of the garden.

Its a great book, get it to read to your Kids / grandkids. They'll love it.

I have no idea if there is any animal which routinely attacks snake oil salesmen so i prefer your original metaphor!

Regards
Robert

PS. I've a long, long way before i reach Cameron's level of fascinating but irrelevant information but i try.

 

If you want to attract sharks, just insult someone's pet idea.

Paul B originally wrote:

I believe this (now much more affordable diagnostic US) may be one of the most important adjuncts to clinical podiatry practice of biomechanics, than any other current "system", "theory" or "approach".


Now, Paul's statements were no where near as inflamitory as Ed Glasser's. I still felt a twinge and a need to defend the tissue strress approach in light of that statement. I have no problem debating the approach. Debate is a good thing. But attacking an idea will bring out the sharks to defend the idea. Is that not the purpose of the forum?

Cheers,

Eric

 

Eric, certainly, and i (along with i assume many others) have enjoyed this discussion; it's the occasional sarcasm that irritates me (and i assume many others), mark c

 

Mark:

I actually like the sarcasm on Podiatry Arena, unless it is directed towards me.

 

You boys crack me up every time!!!! LOL. Great to see a sense of humour out there in cyber space. I readily agree with all of the last 4 comments......classics.

Re

I still felt a twinge and a need to defend the tissue stress approach in light of that statement. I have no problem debating the approach. Debate is a good thing. But attacking an idea will bring out the sharks to defend the idea. Is that not the purpose of the forum?
Cheers,
Eric

Eric, I too am a big subscriber to (what I call) the pragmatic tissue stress (natural history) bio-medical model of disease (more aligned than mal-aligned to Kevins earlier post re the engineer model), which I think I see personally as more akin to a "bio”-engineer perspective (probably not the right choice of words, but I think you know what I mean).

I still hold firm to the statement

I believe this (now much more affordable diagnostic US) may be one of the most important adjuncts to clinical podiatry practice of biomechanics, than any other current "system", "theory" or "approach".

Because (a) set of beliefs is a set of parameters which for the individual cant be wrong (a bit like an opinion, and like religious belief which is another good example, but lets not go there, Its Friday), (b) I said "maybe" (nice each way bet) and (c) it was stated as “one of the……..”. which is designed to attribute a relative value to the knowledge (one is better than the other). But of course it is only a belief.

Have a good weekend.

Cheers

Paul.

 

Paul:

When diagnostic ultrasound can:

1. Provide the clinician with a theoretical model of how the foot and lower extremity functions during weightbearing activities,

2. Provide the clinician with a theoretical model of how injuries are created in the foot and lower extremity during weightbearing activities, and,

3. Provide the clinician with a theoretical model of effective mechanical treatment for the injuries caused by abnormal biomechanical function of the foot and lower extremity,

then I will agree with you.

However, until that time, diagnostic ultrasound will be just another diagnostic modality that may be used to confirm or rule out diagnoses of some of the injuries seen commonly in a podiatrists office.....nothing more, nothing less.

 

Hi Kevin,

Ultrasound is not designed to do any of the above, so we can obviously both agree on that one. What ultrasound is doing (not speculating about) is helping clinicians place emphasis where contempoarary research should be focused. Accessing quantifiable, visual, dynamic hard data in routine clinical practice simply takes the guesswork out of much of what we do. If MRI's were as inexpensive as US, then I'd probably be advocating their use, however even thoses systems cannot match dynamic testing of the US systems. Have you ever actually used a high definition one in your office/uni?

Regards

Paul

 

Paul, this ultrasound sounds like a wonderful clinical tool to have on hand. Obviously used as a research tool but are they used in private practice at all to your knowledge. Can you give me some details on suppliers in Australia.

Rebecca

 

I am glad that you agree with me that diagnositic ultrasound (US) is not designed to replace or improve on podiatric biomechanics theory. This is the point that I have been making over the past few weeks to you. In fact, I wouldn't have even brought up this curious idea of how a diagnostic test should even be considered to be a replacement or improvement on biomechanics theory if it weren't for your initial posting in this thread where you made the following statement:

Then you went on to claim the following a few days ago:

Now, Paul, instead of the statement above, if you had started the thread with the following statement:

"I believe this (now much more affordable diagnostic US) may be one of the most important diagnositic adjuncts to clinical podiatry practice of biomechanics."

then I would probably never have commented on this thread at all. I am not an expert on diagnostic US, don't own one, but have experimented with them a few times at trade shows with the help of my friend, Jeff Stone, DPM, who often shows them at podiatry meetings here in the States.

Again, diagnostic US is simply another diagnostic test available to the podiatric clinician that seems no less or more valuable than plain film radiography, technetium bone scans, white blood cell scans, CT scans, MRI scans, in-shoe pressure analysis systems, pressure mats, video gait analysis, blood and urine tests, wound gram stains, cultures and sensitivities, segmental doppler tests and many others. Because diagnostic US does not replace or improve on podiatric biomechanics theory, I still stand by my earlier statement:

If you can provide me meaningful evidence that diagnositic US is something more than a diagnostic tool, then I would be willing to amend my statement above. Until that time, I will hold firm to my statement.

 

Hi Everybody,

I have been following this thread with interest because of the work I have been doing on US and plantar fascia. Because of the high level of this forum and my lack of english I do not ussually tend to make any post, however, Simon dropped me a ball I think I can add my two cents to this topic.

We conducted a research on plantar fascia ultrasound on my university two years ago, examinating plantar fascia of 50 healthy students (no foot pain or disabilities) with a 10 Mhz US. Ultrasound was performed by a radiologist with broad experience in foot and ankle problems. We did a paper which has been admitted for its publication in the europan journal of radiology. Now is in press (Pascual Huerta J, Alarón García JM, Effect of gender, age and anthropometric variables on plantar fascia
thickness at different locations in asymptomatic subjects, Eur J Radiol (2007), doi:10.1016/j.ejrad.2007.01.002). Basically, we measure plantar fascia thickness at four locations and try to understand how weight, height, sex and age were predictive of thickness at these locations in asymptomatic subjects. Last year we continued with this project and tried to correlate plantar fascia thickness with ankle joint dorsiflexion range of motion, subtalar joint pronation in static stance and Body Mass Index (BMI) (I have recenty sent this paper to JAPMA).

In the later study, we found no correlation with ankle joint dorsiflexion, inverse correlation with subtalar joint pronation in static stance (the less the pronation in static stance, the more the plantar fascia thickness) and positive correlation with body mass index. Unfortunately, we could not measure collagen organization/disorganization as Paul did. However, the transverse design of the research makes imposible to ascertain some type of "causality" .

So, we are not really sure of the meaning of the results... But, my conclusions (and this is my opinion of the whole thread) US is helpful to make hypothesis to work with regarding foot function and foot injuries. However, in my opinion, it does not replace biomechanical theories. I think both can be supplemental to increase our knowledge in foot biomechanics and foot injuries.

Hope this helps,

Cheers

 

Good work Javier- you really have so much to offer and should contribute more to the forum. For those who don't know Javier, I'd like to tell you that he is one of the smartest podiatrists I have had the pleasure of working with and a very "bad boy". My conclusion from your research- form follows functional requirement.

 

Javier:

Good to see you contributing to Podiatry Arena. You are one of the "shining stars" of the Spanish podiatry community.

In your US study, I found it interesting that you found greater plantar fascial thickness with less subtalar joint pronation. Since increased thickness of the plantar fascia would tend to give the plantar fascia increased tensile stiffness, and since increased plantar fascia tensile stiffness would also increase the dorsiflexion stiffness of the first ray and medial column, this may mechanically result in the foot being better able to resist subtalar joint pronation. Could it be that those feet that have increased plantar fascial thickness are also those that are destined to have more normal medial longitudinal arch (MLA) structure and those that have decreased plantar fascial thickness are those that are destined to have a lower MLA structure (i.e. pes planus)?? Maybe your research could help answer some of these questions for us.

Keep up the good work and please continue to contribute more to this forum. By the way, your English is better than some of the postings on this forum from podiatrists that live in English speaking countries!!

 

Kevin,

Very smart comment, as always...

Research on plantar fascia and US has consistently shown that plantar fascia thickness is bigger in plantar fasciitis patiens compared to controls and to the uninvolved feet in unilateral cases. However, two studies have showed that thickness of the uninvolved feet of unilateral cases of plantar fasciitis is bigger than thickness in control subjects. As both feet "tend to be similar" regarding foot function (I know this is an oversimplification) uninvolved feet of unilateral cases of plantar fascia could tend to have similar tension forces in the plantar fascia that the involved side. That is the reason we did the second study. We try to test risk factors for plantar fasciitis (body mass index, subtalar pronation and dorsiflexion ankle range of motion) and their correlation to plantar fascia thickness in non painful subjects.

The results of thickness and inverse correlation with static subtalar joint pronation were unexpected. However, we do not know if plantar fascia thickness in US is related to the tension of the fascia, but your idea of the stiffness of the longitudinal arch is a good hypothesis. Unfortunately, we did not measure that in our study. We hypothetized that the greater the fascia, the greater its control of pronation, so that could be the reason of its inverse correlation with pronation in static stance.... Does it make sense??

And Kevin and Simon, Thank you very much for your very very kind comments, spetially if they come from you. Thanks again,

Cheers,

 

Kevin and bad boy,
I only scanned Javier's posting late last night, perhaps what I should have said was form follows functional requirement and function follows form. However, (and this was the bit I wanted to look at with you Javier) what happens when we normalise the thickness data for the other predictor's cross-products amd then compare thickness versus pronation?

P.s. Javier, could you translate: "Cuando una ortesis no hace daño deberíamos alegrarnos y no exigir además que sirva para algo" for me please?

 

Javier:

I believe I lectured on the biomechanics of the plantar fascia when I was in Madrid a few years ago? Anyway, the biomechanics of the plantar fascia has been a topic of interest of mine for some time now and I am very interested in the biomechanical research in this area.

Biomechanical computer modelling studies (i.e. forward dynamics and finite element analysis) clearly show that decreasing the elastic modulus of the plantar fascia results in more longitudinal arch deformation and greater tensile stresses on the long plantar ligament, short plantar ligament, and other plantar tensile-load bearing structures of the plantar arch of the foot. Even though, to my knowledge, the thickness of the fascia hasn't been used as an input variable in these computer models, certainly it would make sense that increased cross-sectional area of the plantar fascia would increase the tensile stiffness of the plantar fascia and make the longitudinal arch deform less (i.e. increase the forefoot dorsiflexion stiffness) with a given plantar loading force.

Other variables which have been shown to increase plantar fascia tensile forces during weightbearing activities are increased Achilles tendon tensile force and decreased longitudinal arch height. The paradox is that plantar fascial tensile force is necessary to help prevent longitudinal arch flattening during gait, but that same tensile force is also the cause of plantar fasciitis.

A plantar fascia with a thinner cross-sectional area would be more compliant, would allow more longitudinal arch flattening for a given plantar load, but would not necessarily mean that the plantar fascia would be subjected to greater tensile forces. This is because other deep plantar arch ligaments and/or plantar intrinsic muscles and/or muscles of the deep posterior compartment and/or peroneus longus may be able to resist arch flattening (i.e. cause increased forefoot plantarflexion moments) "better" than the plantar fascia can. This creates a modelling nightmare with multiple unknown variables due to the redundancy and duplication of arch supporting structures. In other words, we can truly only guess which plantar arch tensile load-bearing structure is contributing the most tensile load-bearing force to help prevent longitudinal arch flattening during weightbearing activities.

However, Javier, if you could show, through the experimental use of ultrasound or MRI, that asymptomatic younger individuals with feet that were higher arched and had increased forefoot dorsiflexion stiffness had increased thickness of the plantar fascia and those feet that were lower arched and have decreased forefoot dorsiflexion stiffness had decreased thickness of the plantar fascia, certainly this would be very useful research to help us better understand both the congenital and acquired nature of many foot deformities and help us better comprehend biomechanical problems of the foot and lower extremity.

Le Saluda Atentamente,

Kevin

 

Simon,

I understand what you mean and I also understand that what you proposed would be a more interesting data to analyze. However, at the moment I did the data analysis my lack of statistics was so huge that I did not take care of that. That is the reason I asked you to colaborate with the research. Fortunately, we have more projects we can work together in the future.

Cheers,

PD: “Cuando una ortesis no hace daño deberíamos alegrarnos y no exigir además que sirva para algo” could be tranlated as “When an foot orthoses does not make harm, you should be happy enough to not to demand it to be helpful/beneficious at the same time”... more or less...

 

Kevin,

I understand your point and this is one of the points of discussion of the paper. I understand that the modelling of the arch supporting structure is quite variable in each foot (“modelling nightmare”, I loved that word) and a thinner plantar fascia measured by US does not mean that the plantar fascia is subjected to greater plantar forces for the reasons you explained above. However, a plantar fascia with a thinner cross sectional area would be more subjected to “damage” than a plantar fascia with a thicker cross sectional area for the same given plantar load to both. Is it OK?. Our research showed that the more pronated the foot in static stance, the thinner the plantar fascia in healthy young adults.

I apreciate your idea of plantar fascia thickness and forefoot dorsiflexion stiffness. I think that would be a very interesting research we can conduct in the future. Fortunately, the radiologist I worked with is a very close friend who studied podiatry after finishing his MD studies, now he is doing his PhD on musculoexqueletal ultrasound and we could have access to that type of research in the future.

Cheers

Kevin, nice to see you are improving your spanish...

 

For a given tensile force being exerted by the plantar fascia, a smaller cross-sectional area would result in increased tensile stress within the plantar fascia (i.e. stress = force/cross-sectional area). Since increased tensile stress within the plantar fascia would tend to move the fascia away from its elastic range and toward its plastic range, then there is more likelihood of plantar fascia elongation, partial rupture or complete rupture as tensile stress is increased. In other words, increased tensile force within the plantar fascia will be more likely to cause damage to the plantar fascia due to the increase in tensile stress.

However, we must be careful to not necessarily equate "plantar load", as you said, with plantar fascial tensile force. Longitudinal arch height has a huge effect on the actual plantar fascial tensile loads. For example, if we compare two otherwise identical feet with identical plantar loading forces (i.e. GRF) but one foot has a high longitudinal arch in weightbearing compared to another foot that has a low longitudinal arch height, the foot with the lower longitudinal arch height will have significantly increased tensile force with the plantar fascia compared to the foot with the higher longitudinal arch height. I have previously described these concepts with one of my Thought Experiments Thought Experiment #1: Tie Tensile Force in Loaded Arch

Therefore, to say "However, a plantar fascia with a thinner cross sectional area would be more subjected to “damage” than a plantar fascia with a thicker cross sectional area for the same given plantar load to both." would not be accurate since plantar load, by itself, does not determine plantar fascia tensile force. Other factors that determine plantar fascia tensile force, other than just the magnitude of "plantar load", include anterior-posterior CoP position during midstance (i.e. the more anterior the CoP the greater the plantar fascial tensile force), longitudinal arch height, tensile force within plantar arch ligaments, tensile force within the plantar intrinsic muscles, and tensile force within FDL, FHL, PT and PL muscles.

If, Javier, you made the statement: "However, a plantar fascia with a thinner cross sectional area would be more subjected to “damage” than a plantar fascia with a thicker cross sectional area for the same given plantar fascia tensile force.", then I would definitely agree with you.

As you noted, this type of research is potentially very interesting and is hopefully something that you, or some of the other research-minded individuals following along with this interesting discussion, may consider to investigate in the future. Keep up the good work.

 

Kevin,


Yes, I was refering to this stament. I understand your point and I agree. "plantar load" is not a good term to refer to plantar fascial tensile force, because they mean different things. Next time I will try to be more specific participating in this forum.

Cheers,

 

Javier and Colleagues:

One other point which I didn't explain fully is that it is not just the magnitude of the plantar loading force which is important but the location of the plantar loading force which is as important, or possibly is more important, in helping to determine plantar fascia tensile force. For example, 350 N applied to the plantar heel would produce no plantar fascia tensile force whereas 350 N applied to the plantar metatarsal heads and plantar digits would produce considerable plantar fascia tensile force. As the CoP moves more anteriorly during gait, the plantar fascia tensile force increases (Erdimir A, Hamel AJ, Fauth AR, Piazza SJ, Sharkey NA: Dynamic loading of the plantar aponeurosis in walking. JBJS, 86A:546-552, 2004). Therefore, the plantar fascia tensile force is a dynamic variable, affected by numerous structural and functional parameters.

Of course there is the corresponding influence of the Achilles tendon tensile force which is a whole other topic.

Good discussion!