Shane,
Good point. Also I find the lateral cuneiform should be included.
If I could expound on your point.
Here's the postural test for these dysfunctions:
Put the feet in neutral position and palpate the ASIS's. Now let the
feet go into relaxed calcaneal stance position. If the ASIS drops on
either side, it is usually a sign of a restriction of movement for the
cuneiforms.
Part of the function as a mobile adapter is to allow the foot to go to
either an inverted of everted position without the upper body getting
affected. Any restriction of the foot joints interferes with the
interdependence of these joints It would not be in primitive man's best
interest to run after prey (or away from predators), and because he
steps on angled ground, have his direction changed just prior to propulsion.
Regards,
Stanley
Shane Toohey wrote:
> Dear Kevin et al,
>
> I've struggled keeping up with this discussion other than in a
> general sense and than you wrote:
>
> What I really wanted to know was what you think of my idea that you
> don't need pronation of the STJ to cause the foot to be a "mobile
> adaptor" and supination of the STJ to cause the foot to be a "rigid
> lever" since this is dependent on the architecture of the foot and
> arrangement of posterior musculature, foot bones and plantar soft
> tissue supporting structures, not just on STJ rotational position or
> motion.
>
> As one who plays with feet, I agree with that comment. Mostly, I find
> that mobility and or lack of mobility for adapting is a function of
> the mid tarsal environment, particularly how 'free' the intermediate
> cuneiform and the cuboid are.
> When they are changed then the feet function differently.
> Unfortunately, I can't ever imagine putting that to any scientific
> testing!
>
> Cheers
> Shane
>
>
>
>
> ---- Original Message ----
> From: [log in to unmask]
> To: [log in to unmask]
> Subject: Re: Midtarsal Joint Biomechanics and Interaction of
> Tension/Compression Elements During Stance Phase
> Date: Sat, 5 May 2007 06:33:42 -0700
>
>
>> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
>> <html>
>> <head>
>> <meta content="text/html;charset=ISO-8859-1"
>> http-equiv="Content-Type">
>> </head>
>> <body bgcolor="#ffffff" text="#000000">
>> <font face="Arial">Dave:<br>
>> <br>
>> </font><font face="Arial" size="2">You wrote:<br>
>> <br>
>> <<As I do not regularly correspond and not feel
>> familiar with Dr
>> Dananberg I used that form of address. It seemed a little disingenuos
>> to use the form of title Dr Dannanberg and not be respectful enough
>> to
>> include that form when addressing both Doctors.>><br>
>> <br>
>> Sorry about that, I was just giving you a "bad time"
>> Dave. Your
>> postings are extremely helpful and informative and I really like the
>> engineering perspective you bring to these topics. What I
>> really
>> wanted to know was what you think of my idea that you don't need
>> pronation of the STJ to cause the foot to be a "mobile adaptor" and
>> supination of the STJ to cause the foot to be a "rigid lever" since
>> this is dependent on the architecture of the foot and arrangement of
>> posterior musculature, foot bones and plantar soft tissue supporting
>> structures, not just on STJ rotational position or motion.<br>
>> </font><br>
>> Sincerely,<br>
>> <br>
>> Kevin<br>
>> <br>
>> *********************************************************************
>> *******<br>
>> Kevin A. Kirby, DPM<br>
>> Adjunct Associate Professor<br>
>> Department of Applied Biomechanics<br>
>> California School of Podiatric Medicine at Samuel Merritt College<br>
>> <br>
>> Private Practice:<br>
>> 107 Scripps Drive, Suite 200<br>
>> Sacramento, CA 95825 USA<br>
>> <br>
>> Voice: (916) 925-8111 Fax: (916)
>> 925-8136<br>
>> *********************************************************************
>> *******<br>
>> <br>
>> <br>
>> David Smith wrote:
>> <blockquote cite="mid001001c78f08$bccfbdf0$eed10250@acervfr9okf50t"
>> type="cite">
>> <meta http-equiv="Content-Type"
>> content="text/html;charset=ISO-8859-1">
>> <meta content="MSHTML 6.00.6000.16414" name="GENERATOR">
>> <style></style>
>> <div><font face="Arial" size="2">Dear Kevin K</font></div>
>> <div> </div>
>> <div><font face="Arial" size="2">As I do not regularly
>> correspond
>> and not feel familiar with Dr Dananberg I used that form of
>> address. It
>> seemed a little disingenuos to use the form of title Dr Dannanberg
>> and
>> not be respectful enough to include that form when addressing
>> both
>> Doctors. </font></div>
>> <div> </div>
>> <div><font face="Arial" size="2">Cheers Dave</font></div>
>> <div> </div>
>> <blockquote
>> style="border-left: 2px solid rgb(0, 0, 0); padding-right: 0px;
>> padding-left: 5px; margin-left: 5px; margin-right: 0px;">
>> <div
>> style="font-family: arial; font-style: normal; font-variant: normal;
>> font-weight: normal; font-size: 10pt; line-height: normal;
>> font-size-adjust: none; font-stretch: normal;">-----
>> Original Message ----- </div>
>> <div
>> style="background: rgb(228, 228, 228) none repeat scroll 0%;
>> -moz-background-clip: -moz-initial; -moz-background-origin:
>> -moz-initial; -moz-background-inline-policy: -moz-initial;
>> font-family: arial; font-style: normal; font-variant: normal;
>> font-weight: normal; font-size: 10pt; line-height: normal;
>> font-size-adjust: none; font-stretch: normal;"><b>From:</b>
>> <a title="[log in to unmask]"
>> href="mailto:[log in to unmask]">Kevin Kirby</a> </div>
>> <div
>> style="font-family: arial; font-style: normal; font-variant: normal;
>> font-weight: normal; font-size: 10pt; line-height: normal;
>> font-size-adjust: none; font-stretch: normal;"><b>To:</b>
>> <a title="[log in to unmask]"
>> href="mailto:[log in to unmask]">[log in to unmask]</a>
>> </div>
>> <div
>> style="font-family: arial; font-style: normal; font-variant: normal;
>> font-weight: normal; font-size: 10pt; line-height: normal;
>> font-size-adjust: none; font-stretch: normal;"><b>Sent:</b>
>> Saturday, May 05, 2007 6:34 AM</div>
>> <div
>> style="font-family: arial; font-style: normal; font-variant: normal;
>> font-weight: normal; font-size: 10pt; line-height: normal;
>> font-size-adjust: none; font-stretch: normal;"><b>Subject:</b>
>> Midtarsal Joint Biomechanics and Interaction of Tension/Compression
>> Elements During Stance Phase</div>
>> <div><br>
>> </div>
>> <font face="Helvetica, Arial, sans-serif">Dave and
>> Colleagues:<br>
>> <br>
>> Dave wrote:<br>
>> <br>
>> <<</font><font face="Helvetica, Arial, sans-serif">Is it
>> possible
>> for true tensegrity to be maintained with mobility and changing load
>> patterns? Long bones usually snap with bending stress and not from
>> direct tension or compression. (even tho bending stress is
>> tensional at
>> the microscopic level) However most joints can only transmit moments
>> thru the tensional forces of the soft tissues. Due the nature of
>> muscle
>> and ligament arrangement it is very unusual for one muscle and or
>> ligamnet to be entirely reponsible for a single plane rotation about
>> the axis of a joint. Instead each tissue has an oblique pull on the
>> joint and so it is necessary for several muscles to be active at one
>> time to stabilise a limb thru a single plane RoM. This arrangement
>> both
>> enables redundancy and allows muscle tension to be dissapated to many
>> secondary rigid structures IE bone, which in turn reduces local
>> stress
>> at what could be called the primary site of load. If this were not so
>> then lifting relatively small loads would cause the spine to crush or
>> tear apart. The trunk itself acts very much like a
>> tensegrity structure
>> where increasing the tension in the chest and abdomen increases the
>> overall siffness of the structure centered around the spine. Whereas
>> I
>> would say the arms are more like a conventional lever system acting
>> like a crane. I think that the foot is a combination of the two. As a
>> whole unit it is a lever that propells us, about the ankle
>> joint, thru
>> gait but can also be adaptable to ground contours (or whatever
>> is under
>> the foot eg a tree branch). The untensioned bag of bones can adapt
>> and
>> the propelling foot becomes less compliant as tensegrity or
>> internal
>> tension increases. Due to the redundancy factor however if the
>> individual segments and muscles are not operating at their optimum
>> then
>> another segment or muscle must increase its work load which may cause
>> damage to that structure or tissue or may unbalance the whole
>> internal
>> tension system, r</font><font face="Helvetica, Arial,
>> sans-serif">esulting
>> in pathologies various and many. Perhaps as the balanced internal
>> tension is disrupted then the foot experiences more internal bending
>> moments that more easily cause trauma.>><br>
>> <br>
>> Excellent posting, Dave. You are now addressing me
>> formally..................................Dr.
>> Kirby?............................ ;-) <br>
>> <br>
>> Let's look at the biomechanics of the foot without the need to use
>> the
>> term "tensegrity" (so I can ensure that JISCmail will light up over
>> the
>> weekend with postings from the lovers of tensegrity that inhabit this
>> list). ;-)<br>
>> <br>
>> The passive mechanical structure of the human foot is composed of
>> both
>> compression load-bearing elements, known as bones, that are held
>> together and attached to each other by tension load-bearing
>> elements
>> known as ligaments and fascia. It is the combination of the
>> specific
>> geometric arrangements of these passive structural elements of the
>> foot
>> along with the mechanical interaction of these elements during
>> weightbearing activities that is very important in allowing the foot
>> to
>> both assume the function of a mobile adapter during early stance
>> phase
>> and a rigid lever during late stance phase.<br>
>> <br>
>> Ground reaction force (GRF) acting on the forefoot will cause a
>> compression force on the metatarsal heads and digits and will, in
>> turn,
>> also cause a forefoot dorsiflexion moment. In early stance
>> phase, the
>> magnitude of forefoot GRF will be relatively low causing decreased
>> metatarsal head and digital compression forces and low forefoot
>> dorsiflexion moments. The relatively small magnitudes forefoot
>> dorsiflexion moments seen in early stance phase causes only small
>> increases in the magnitudes of passive tensile forces within the
>> plantar ligaments and plantar aponeurosis that will, in turn, cause
>> relatively small magnitudes of forefoot plantarflexion moments to
>> counterbalance the forefoot dorsiflexion moments. Therefore,
>> due to
>> the relatively small magnitudes of passive plantar ligament and
>> plantar
>> fascia tensile forces in early stance phase, there will be relatively
>> small interosseous compression forces within the midfoot and
>> midtarsal
>> joints during early stance phase. The combination of smaller
>> plantar
>> ligament tensile loads and smaller interosseous compression forces
>> within the midfoot and midtarsal joints allow greater dorsiflexion
>> compliance of the individual metatarsal rays that will, in turn,
>> ensure
>> that the plantar forefoot has sufficient compliance to optimize
>> surface contact of all the metatarsal heads with any uneven
>> weightbearing surfaces that may be encountered by the individual
>> during
>> the early stance phase of gait.<br>
>> <br>
>> During late stance phase, this unique geometric arched structure of
>> compression and tension load-bearing elements that constitute the
>> human
>> foot will allow passive sagittal plane stiffening of the longitudinal
>> arch and metatarsal rays of the foot so that the more compliant
>> forefoot in early stance is then rapidly converted into a more stiff
>> forefoot to allow for greater efficiency of force transfer during
>> propulsion. In late midstance, GRF acting on the plantar
>> forefoot will
>> rapidly increase that will </font><font
>> face="Helvetica, Arial, sans-serif">cause an increased compression
>> force on the metatarsal heads and digits and will also cause rapidly
>> increasing forefoot dorsiflexion moments. The relatively
>> large
>> magnitudes of forefoot dorsiflexion moments seen in late stance phase
>> will cause relatively large magnitudes of passive tensile forces
>> within
>> the plantar ligaments and plantar aponeurosis that will, in turn,
>> cause
>> relatively large magnitudes of forefoot plantarflexion moments to
>> counterbalance the forefoot dorsiflexion moments. In turn,
>> these large
>> magnitudes of passive plantar ligament and plantar fascia tensile
>> forces in late midstance phase will cause large magnitudes of
>> interosseous compression forces within the midfoot and midtarsal
>> joints
>> during late stance phase. As a result, these rapidly increasing
>> counteropposing forefoot dorsiflexion and forefoot plantarflexion
>> moments in late stance cause significant increases in forefoot
>> dorsiflexion stiffness which will, in turn, reduce the capacity of
>> the
>> individual metatarsal rays to conform to uneven surfaces (i.e. will
>> reduce their compliance) but will have the positive mechanical
>> benefit
>> of significantly increasing the dorsiflexion stiffness of the
>> forefoot
>> to allow for more efficient propulsion. <br>
>> <br>
>> This above mechanism is dependent only on the passive integrity of
>> the
>> ligaments and fascia of the foot, on the passive integrity of the
>> bones
>> of the foot and on the specific geometric arrangement of the
>> structural
>> elements into an arched dorsally-oriented series of compression
>> load-bearing elements that are supported by linear arrangements of
>> plantarly-oriented tension load-bearing elements. And, contrary
>> to
>> universally taught and widely-accepted podiatric biomechanics dogma,
>> this mechanism of early stance phase compliance (i.e. mobility) and
>> late stance phase stiffness (i.e. rigidity) will occur independent of
>> subtalar joint rotational position or subtalar rotational motions as
>> long as the forefoot is plantigrade to the ground during stance
>> phase.
>> <br>
>> <br>
>> I have previously published this alternative theory of early stance
>> phase mobility and late stance phase rigidity previously in my May,
>> June and July 2006 Precision Intricast Newsletters titled
>> "Transmission of Forces and Moments Within the Foot - Volume I, II
>> and
>> III".<br>
>> </font><font face="Helvetica, Arial, sans-serif"><br>
>> </font>Sincerely,<br>
>> <font face="Helvetica, Arial, sans-serif"> <br>
>> Kevin<br>
>> <br>
>> *********************************************************************
>> *******<br>
>> Kevin A. Kirby, DPM<br>
>> Adjunct Associate Professor<br>
>> Department of Applied Biomechanics<br>
>> California School of Podiatric Medicine at Samuel Merritt College<br>
>> <br>
>> Private Practice:<br>
>> 107 Scripps Drive, Suite 200<br>
>> Sacramento, CA 95825 USA<br>
>> <br>
>> Voice: (916) 925-8111 Fax: (916)
>> 925-8136<br>
>> *********************************************************************
>> *******</font><br>
>> <br>
>> <blockquote
>> cite="mid000701c78e82$b91f7e10$61500150@acervfr9okf50t"
>> type="cite">--------------------------------------------------------
>> ----
>> </blockquote>
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