Functional Hallux Limitus, my project so far...

YIKES.......maybe we can come up with a better term with a different acronym...

 

Looks like Howard is unavailable to answer my question from a few days ago as to what the exact definition of "sagittal plane blockage" is. Maybe Bruce Williams and/or Graham Curryer, both sagittal plane theorists, can help us out here as to what the definition of "sagittal plane blockage" is?? I thought "sagittal plane blockage" had to do with deceleration or "blocking" the progression of the center of mass but Howard said it isn't. Now I really don't know what "sagittal plane blockage" is.....anyone else want to guess what this term means??

 

Where pathological or insufficient (for physiological gait) sagittal plane motion and function in one or more of the relevant joints (1st > lesser MPJs; Ankle joint > Knee joint > hip); results-in or contributes-to gait dysfunction.

In other words, the pathology associated with the sagittal plane contributing joints influences gait adversely.


That is the way I have always percieved it.



Its not all about stiffness KK.



Ron
Physiotherapist (Masters) & Podiatrist

 

Ron:

Thanks for clearing that up for me. I needed dearly for you to enlighten me.

 

Kevin, you should re-edit your reply. I am a big boy...and thus I can take it. In boxing terms, you can't erase a jab.


As for your edited barb that I am critical of podiatry...well yes, I am more critical of physiotherapy-in-Australia and the heavy weight that the allied health profession places on EBP; the era of suffix importance (masters, PhD.) over results and clinical importance. etc...etc



As for my criticism, the easiest criticism to destroy is wrongful criticism.

Go for it.

 

Now all we need is the definition of limited motion (or position where stiffness increases) and a definition of gait dysfunction.

A more practical definition my include some of the F-Scan findings.

Regards,

Eric Fuller

 

Eric, I'm not sure this is possible, although Kevin saw the humorous side of my argument regarding cause and effect, which was politically convenient, this is also a serious proposition.

Cause and Effect and the Sentient Being

You could say that Saggital plane block is a point in the gait cycle where the momentum of the CoM does not have sufficient velocity to propel itself over the standing leg and therefore and additional muscular action or biomechanical compensation must take place.

This never actually happens of course because if it did those people we would not be able to walk and so the necessary adaption occurs to prevent this. There is however a change in the CoM velocity, as I spoke of in an earlier post, and this change occurs through out all types of gait pattern. Therefore it is only the nature of the difference between these changes in CoM velocity or changes in CoM acceleration that define the tendency toward pathological gait.
The only way to define saggital plane block then is to relate to its effect that we sense and experience. We see the real pathological effect and can assume a real cause that we can name or define as saggital plane block.

To use an analogy, it is like trying to define 'Cold' as a definite entity. Cold only exists as an effect of change of temperature and the ability to sense this change.
Where is cold on the scale of temperature? It is only definable by our own experience of its effect on our body or some other body. Cold has no entity but as a term it is used to communicate our experience or sense of the effect in terms of a cause.

Saggital plane block occurs as an effect of a change in velocity. The scale of accelerations have no absolute limits and within the boundaries of acceleration experienced by humans in ambulation the variations are infinite. The compensations or actions of adaption are not infinite but are many. Trying to formulate an equation along the lines of {[this change in CoM velocity] + [that biomechanical adaption] = pathology, which is equal to => saggital plane block} would be almost impossible I would think.

Therefore to communicate our experience or sense of the real effect, i.e. pathology, we can, with valid reasoning, justifiably use the term saggital plane block to describe the cause, which has the same reality.

Cheers Dave

 

This is not a workable definition since functional hallux limitus occurs at a time during gait when the center of mass (CoM) is descending and muscular effort is therefore required to decelerate the CoM to prevent it from moving too fast forward.

I can't agree with this statement since, #1) we still don't know what "sagittal plane block" is. Apparently, "sagittal plane block" is another one of those clinical terms, like "first ray hypermobility" and "midtarsal joint locking", that clinicians use but doesn't really know exactly what it means. I believe that "sagittal plane block" may be undefinable and, if it is, it is then probably useless as a term for scientific study. #2) It is only a guess that a change in CoM velocity occurs with these supposed "sagittal plane blocks". Do we have any research evidence that changes in CoM velocity occur with ankle equinus or functional hallux limitus? How do we know that CoM velocity doesn't remain constant when functional hallux limitus and ankle equinus occurs?

 

Is hallux rigidus a "sagittal plane block"? This pathology appears to be a more definable blockage of motion in the sagittal plane.

Took the words out of my mouth; I was about to ask Dave how he measures CoM velocity. N.B. Dick Fosbury.

 

Kevin.

With regard to the definition you will notice that I kind of agree with you in my next paragraph "This never actually happens ----- etc" (perhaps)

With regard to the change of velocity of the CoM. - Why, for optimum gait progression, would it be desirable to slow the horizontal progression, i.e. reduce the momentum, of the CoM.
The answer is that in fact the leg and muscles act to stop the CoM hitting the ground, i.e. during braking and propulsion they act to accelerate the CoM vertically away from the ground. Therefore a vertical GRF is required, however since the leg is inclined to the ground and there is friction then there must also be a horizontal GRF that will tend to accelerate the CoM, posteriorly at braking and anteriorly at propulsion and zero at midstance.

It would be very energy efficient if there were none or at least significantly reduced forces retarding the horizontal progression or momentum, E.G. a bicycle. Unfortunately wheels don't seem to have been part of evolution, they are not so good uphill and rocky ground etc.

I would say that the walking system in normal gait is designed to reduce the inconvenience of such horizontal forces to be as small as possible, while at the same time utilizing the inertial forces produced to its benefit, it is this design that allows us to walk.

Therefore I would argue that the biomechanics of walking does not

instead they allow the CoM to progress horizontally as fast and efficiently as is possible within the limitations of gravity and friction and the human anatomy.

I would propose then that biomechanical variations that tend to reduce this ability, or tendency towards efficiency, will result in greater muscular forces required to replace lost momentum. **While this may not result in any change in CoM velocity** pattern it will result in greater potential for pathological changes in those muscles.

**I would reason that it would**

Quite possibly, but it is, in my opinion, a useful term at this juncture. However I do agree clarification is justified.

But a great term to stimulate scientific study I would say eh?

Plus Simon Wrote

Yes true, it is only a guess but an educated one and one where I would prefer the term speculative deduction Some might say reasonable deduction.:empathy:

Makin me think hard this one, which is good

All the best Dave

 

Kevin,
I don’t intentionally ignore you….I just have a real life, with Podiatry Arena only very tiny part of it. When I get back to reading the posts, I usually reply.

Sagittal plane restriction/blockage (SBR/SPB): During bipedal walking, there is a normal transfer of weight from the heel to the ball of the foot during the single support phase of the step. This is evidenced by center of pressure’s (CoP) movement from heel to toe. Sagittal plane restriction refers to either a decrease or absence in the speed of this CoP movement. Therefore, conceptually, SPR/SPB is a process…and not an entity. There are entities such as functional hallux limitus which contribute to this phenomena….but the defining event is a failure of CoP progression.

I have discussed my (and others) impression that the CoM is “pulled” forward by the action of the swing limb. (Muscle action can assist…but the less concentric contraction within the lower extremity…the greater the level of efficiency.) While the CoM advances, maximum efficiency dictates that it move up and over the weight bearing limb, with the weight bearing limb simultaneously extending out from under the torso. The weight bearing foot, through its sagittally based motion, permits transfer of weight from heel to toe, resulting in a reactive longitudinal ground thrust to efficiently assist in the movement process. When the CoM is in motion, but the bearing foot fails to permit the expression of the CoM motion to the floor (ie, failed weight transfer…delayed or halted CoP motion), SPB exists.

Howard

 

Dear Howard

Is this a reasonable assumption to make? I'm not sure that it is since it may be possible for the CoP to go posteriorly on the foot while the CoM is moving anteriorly EG toe walking with flexed knee propulsion that allows the heel to contact the ground in mid stance, as in this example below.









The CoP progression (thick black line on the left and right mean pressure characterisations) starts at the forefoot proceeds posteriorly then anteriorly.
The total force time graph (left / right forces graphs) is even very similar to normal. The Forefoot masked forces (right red / left orange) and heel masked forces (right black / left green) show clearly the foot contact progression. This is not a normal progression of forces along the foot and neither is it a SPB. In fact the gait in this example is extremely propulsive.

What would you say about this example in terms of your definition?

Cheers Dave Smith

 

Howard:

Thanks for that. Yes, I have a real life also, only with too few hours in the day to do all the things I enjoy.

So to sum it up, would it be fair to say that you would call any deceleration of the forward progression of the CoP during walking a sagittal plane restriction or sagittal plane blockage? Is there any time that a deceleration of the forward progression of the CoP during walking would not be a sagittal plane restriction/blockage?

 

Dave,

Not only is my assumption reasonable to make, but your example is the exception that proves the rule. If there is anything wrong, it is the analysis of what this represents. Looking again at these graphs, there are force curve aberrations which would actually indicate that this is far from propulsive. And both steps are very, very long...> 1000ms. How can this be "extremely propulsive" when normal steps are 750ms in duration?

On force/time graphic display, propulsion would normally be visible when the 2nd of the "double humps" actually displays a steep slope to a sharp peak (from mid step through the end of single support). In your example, however. this portion of the curve has a fairly plateaued (horizontal/level) 2nd "hump" which runs for the balance of the 2nd half of the step (total red force curve). When you watch these folks (bouncy, toewalkers), they actually fall backwards initially (hence the rearward CoP motion), then bounce up, and the remain relatively static over the forefoot until single support phase terminates. The green graph tends to show a more propulsive end phase (steeper slope), but this step is 200ms shorter than the red side. Is this the shorter of the two limbs? Does this difference demonstrate that the SPB exists more on the red than green side? When you look at the timing of heel off relative to the forefoot mask, there is only about 70ms of forefoot slope rise on the red side after heel off. This is too short and NOT indicative of a true propulsive gait. On the green side, there is no rise in slope after heel off. This is not an energy conserving step....and despite being bouncy...is far from efficiently propulsive.

From my earliest days as a podiatry student, it always bothered me that equinus gait patients found rigid orthotics intolerable. I was taught that they compensated at the MTJ for the equinus...but could not understand why they simply didn't bounce off of these devices. Until I recognized that when the heel raises prematurely, but the metatarsals fail to advance through the sagittal plane (ie functional hallux limitus), it is the combination (early heel lift...no metatarsal sagittal motion) that is responsible for the MTJ compensation (arch collapse). This is certainly visible in the posted graphs....where the exception proves the rule.


Howard

 

Kevin,

Aside from the word "any"...I would generally agree. I am quite sure that Eric can find some exception.... I also feel like I am being questioned by an attorney when the question begins with the phrase "would it be fair to say".

My reasoning for generally agreeing is that the CoP is the expression of the movement of the CoM when the lower extremity is functioning normally. When the CoM is in motion...but the CoP is restricted....SPB exists. The body is then charged with the necessity of managing the difference between a irresistible force and an immobile object.

Howard

 

Howard:

I think that your definition of "sagittal plane blockage" is uncomplicated. Basically, if you are using a force plate or pressure mat/insole and see the center of pressure (CoP) not moving forward "normally", or even reversing during walking, then you call it a "sagittal plane blockage". Now that you have defined the term, we can go into whether this "sagittal plane blockage" as seen on CoP movement, actually translates to movements of the center of mass (CoM) above it.

David Winter's research shows that the movement of the CoM and CoP, during relaxed bipedal stance, are not totally dependent on each other. In other words, the CoP can be moving backwards when the CoM is moving forwards and the CoP can be moving forwards while the CoM is moving backwards (Winter, David A.: A.B.C. (Anatomy, Biomechanics and Control) of Balance During Standing and Walking. Waterloo Biomechanics, Waterloo, Ontario, Canada, 1995). Therefore, using Winter's data, there is likely very little correlation of your "sagittal plane blockage" to the sagittal plane motions of the CoM of the body. Just because there is a "sagittal plane blockage", then this does not also mean that the CoM is decelerating. In fact, using your definition, and using the data from Winter's research, a "sagittal plane blockage", where the CoP is reversing direction (i.e. moving posteriorly), will cause the CoM to accelerate forward, all other things being equal.

Therefore, "sagittal plane blockage" simply references CoP motions, which are the body's passive and active joint responses to the foot-ground interface. "Sagittal plane blockage" does not necessarily allow prediction of CoM motion patterns but certainly may indicate increases or decreases in passive and active dorsiflexion stiffness within the foot and lower extremity joints during walking.

 

Kevin,

Winter showed that the CoM can move independent of the CoP. Agreed...and its no big shock. This demonstrates that these two are capable of independent motion...NOT that they always move independently. So, when the CoM moves forward during normal ambulation, this should be expressed as longitudinal ground shear. Longitudinal ground shear is a function of weight transfer from heel to ball during walking. What I am saying is that for maximum efficiency during level ground walking, the movement of the CoP should correlate with the movement of the CoM. As far as predicting the movement of the CoM from the graphs of CoP motion...you are correct...they are not predictable in random trials of random movements. BUT...when in steady state walking...the CoM is moving forward, and the CoP should move in coordination with it. When the CoP does not progress, but the CoM moves forward...there is a clash of civilizations! It is this factor that is a major contributing element to gait related pathology.


Howard

 

Hi all,

This highlights what my discussions with Howard has taught me. The explanation is separate from the observation. Howard has observed that when he changes the center of pressure path from a certain pattern to another pattern he notices and improvement in patient symptoms. This is a very important and valuable ovservation. Clinically, this observation is more important than the explanation. We can have a heated academic debate about the explanation of why something happens, but the debate still does not effect the outcome.

Having a valid explanation helps us know when we can extapolate further. These observations in level ground walking may not be aplicable to toe-heel walking or running. But treatment of the "observations" may relieve pain in other situations.

Having a valid explanation also helps us know when we should not extrapolate further. Howard has often said that a rearfoot varus wedge or post can make the problem worse. I don't know if Howard uses them. However, someone who hears Howard speak may hear him saying don't use rearfoot varus wedges. In my opinion, there are people with functional hallux limitus who can benefit greatly from a rearfoot varus wedge. And there are others for who a rearfoot varus wedge will make things worse. Subtalar joint axis position is a excellent predictor for this. Some people with functional hallux limitus have medially deviated STJ axis and others have laterally deviated STJ axes. You could look at an F-scan and figure this out or you can look at the axis position to figure this out. You can come to the same ortotic from different paths.

Regards,

Eric

 

Eric,

Well said...

And, for the record, I do use RF posting when appropriate. It is just my impression that it is not as commonly required as believed in the general podiatric community.
This is particularly true in subjects with lower back pain. The use of RF varus posts restricts internal rotation of the hip. This can create issues with the mechanics of the pelvis, SI joints and lumbar spine.

I think the principles of STJ axis location are valid....I just think that also looking proximally and distally is extremely important in patient pain management.

Howard

 

Agreed, both on varus wedges and looking proximally.

Eric

 

Howard and Eric:

I agree also. Amazing....we all three agree.....I'll mark this day on my calendar......:drinks

 

Howard:

:good: I really liked what you wrote above. I would tend to agree with your analysis above. However, it would be nice to have some good data to support your hypothesis regarding maximum efficiency and CoP and CoM movements.

 

The top graph is walking fast with very long strides (very propulsive)
The bottom graph is walking much more slowly with a flat footed short step apropulsive gait.

I think this would indicate that time of stance phase does not indicate the propulsiveness of the gait.

I would agree that this gait is inefficient in terms of energy consumption however it is definitely propulsive even if a lot of that propulsion is vertical (hence inefficient) the horizontal progression was still very fast and the CoM definitely does not move posteriorly at any time.

The plateau characterises the time from start of heel off ipsilateral foot and toe off contralateral foot where there is now no propulsion from the contarlateral leg and the CoM momentum carries the body over the MPJs and where the toes remain dorsiflexed. You will note that the plateau peak force is 130 Kgf or approx 1300N at a body weight for this person of 100kg (981N) therefore some vertical acceleration is still taking place above GRF due to gravity. This must equal a vertical and fairly constant acceleration of almost 3 m/s/s for about 150ms. If this is not indicative of a true propulsive gait how does he manage to walk so fast. Is it because he uses a lot of knee extension to add to propulsion? Are you defining propulsion as a ratio between energy consumption and power in terms of CoM translation? I.E. Yes the subject is walking fast but since he is using a lot of energy to achieve this he is apropulsive. Yes, the right (green curve) leg is the short leg

I would hazard a guess that in my example subject there is no significant midtarsal joint collapse after heel off.

I understand what you are saying about CoP progression as characterised by the pressure mat and I use this technique as a guide to gait evaluation where the gait is within what we might describe as normal pathological parameters. However when the gait is so far outwith those parameters this becomes more difficult. Therefore I don't think you can always use the lack of CoM progression as a definitive criteria of SPB.


Cheers Dave

 

I have followed this thread and tried to dissect what I perceive to be the personal anger and meanness that seems to follow any thread that goes against 30 years of Dr. Kirby's observations.

Howard said:
"And, for the record, I do use RF posting when appropriate. It is just my impression that it is not as commonly required as believed in the general podiatric community.
This is particularly true in subjects with lower back pain. The use of RF varus posts restricts internal rotation of the hip. This can create issues with the mechanics of the pelvis, SI joints and lumbar spine.
...I just think that also looking proximally and distally is extremely important in patient pain management'.

If Kevin, Eric and Howard all agree to the above, perhaps I could calm the waters of personal slander and unite all camps by throwing a curve ball and asking if could one or all of you could attach to The Tenets of The Centering Theory of Biomechanics when fabricating and evaluating foot orthotics.
Orthotics should:
1. Make The Vault of the Foot more supported and reduced of stress
2. Balance the rearfoot to the three body planes (personally, very often without varus posting or skiving)
3. Balance the forefoot to the three body planes (sagital plane works admirably here).
4. Balance the rearfoot and the forefoot to each other (I believe SALRE fails in this area)
5. Balance the left foot to the right (I have not read much referencing this tenet by Dr. Kirby and F-scan weighs this heavily)
6. Improve the ability of the extrinsic and intrinsic musculotendonous units that affect the foot to fire with power and in phase (have any of us gotten to this area yet?)
Dennis

 

DRSHA/Dennis

WTF! stirring for the sake of it, completely irrelevant, deliberately inflammatory, and utter nonsense is my polite response to your post. All your trying to do is put Centring terms on a web site that will increase your SEO and media attention.

If I was less polite I would say ef off but of course that's too rude for this site.

Luv and best wishes Dave

 

Eric, Kevin, Howard

I put together a small experiment to see how the CoP progression changed between normal and simulated equinus gait on a single subject i.e. me.
The two conditions are Normal walking (bottom set) and a simulated equinus gait (top set). The equinus condition was achieved by firmly taping a long plastic shoe horn to the anterior of the shin and across the ankle joint to the dorsum of the foot. This allowed no dorsiflexion of the ankle past 90dgs and was stiff to dorsiflexion by GRF from about 10 dgs plantarflexion from this equinus block.

I walked over an Amcube AM3 pro 500mm x 600mm pressure mat with 4900 capacitive sensors scanning at 200Hz and recorded the plantar forces as characterised by the software.

The PDF attached shows characterisations of my own gait in the two conditions and in terms of progression of the CoP (called Centre of Gravity by the software designer) and force / time graphs.

(I used PDF attachment because the reproduction was much better especially when viewed full screen)

It was impossible to progress saggitally past the equinus block without some kind of compensatory action. I chose, **thru necessity since there was no other way**, to hyperextend the knee and flex the hip to project the HAT over the foot and then lurch forward with a hip extension and throwing the left swing leg through landing heavily on the left heel. To achieve this it was necessary to utilise the heel rocker of the right foot for longer than in normal walking to avoid the forefoot GRF pushing me backward.

(**Later I found it was possible to progress in a different way by lifting the left swing leg high like a sprinter, i.e. 90dgs hip flexion and 90dgs+ knee flexion, and extending the knee to reach forward to the next step. I did not record this action**)

The differences between normal and equinus are consistent with Howard’s explanation of SPB in terms of CoP progression. Interestingly enough, with regard to the normal set, the right foot, which has a slightly short leg and a more supinated foot position in stance, also can be evaluated as having a SPB in comparison to the left foot.

With regard to Kevin’s contention that the mean CoM velocity is not slowed by equinus block (or otherwise called SPB) it is interesting to note that it was in fact difficult to walk very slowly in the simulated equinus condition. It was a case of fairly fast lurching or stop. As a comparison, in normal walking the time to walk a 6 meter walkway was 5 seconds on average. The time for simulated equinus walking was 6 seconds on average. So in fact the average speed was slower and this is reflected in the mean velocity of the CoP progression of both feet in the equinus condition when compared to the normal condition. The effort required to ambulate for the equinus condition was considerably more than the normal condition. If there were calculated, a coefficient ratio of energy used to work done by each walking condition then the equinus condition would be considerably high and in these terms may be thought of as highly apropulsive or resistant to progression. EG work done both conditions = 5 units, energy used - equinus condition = 100 units – Normal condition 50 units. Therefore 100/5 =20 (equinus) and 50/5 = 10 (normal).

The compensation described above made fine control of CoM progression difficult and so it lurched from right to left foot. Therefore it would appear that while the right foot action itself was apropulsive the mean CoM progression velocity was maintained by initiating large changes in segment and whole body CoM accelerations.

These accelerations where facilitated by the use of hip extensors right side and hip flexors left side in the propulsive phase or the phase that at least allowed the left leg to swing thru far enough to continue walking. This action is probably causing very little propulsion in terms of GRF horizontal forces since the CoM of the leg and the CoM of the HAT are producing balanced moments at the right hip that are not resisted by muscle action and therefore do not transmit much force to the foot. At the end of this action right hip flexor muscle fire and reverse the inertial forces. The inertial force of the braking swing leg CoM, which had an exaggerated acceleration for swing through, now has high inertial forces that help carry the whole body CoM over the foot. At this point the hip lurch extends the right hip and allows the body CoM to be slightly anterior to the ground support or line of action and gravity now also helps to propel the body thru the saggital plane.
Clearly these actions that maintain average CoM velocity also require unusual and increased power output by muscle groups firing out of the normal phase for walking. Since walking is a highly repetitive and repeated action that is done daily for long periods the probability of pathology resulting from these unusual actions is clearly high.

It would appear, from this example at least, that this technique, as described by Howard, of evaluating the CoP progression in terms of SPB and CoM progression is a useful criterion for evaluation providing that the evaluator is aware of the limitations as described in an earlier post.

I’ll leave it there so as not to make this post endless and await your responses, if you would like to give them.

All the best Dave

 

Dave,

You wrote "I understand what you are saying about CoP progression as characterised by the pressure mat and I use this technique as a guide to gait evaluation where the gait is within what we might describe as normal pathological parameters. However when the gait is so far outwith those parameters this becomes more difficult. Therefore I don't think you can always use the lack of CoM progression as a definitive criteria of SPB."

This is absolutely true. I have always noted that you CANNOT use in-shoe pressure analysis as the only method of evaluation. You can recognize that asymmetries exist...but cannot see why. When combined with some type of video analysis (hopefuly including a side (sagittal) view), there is a far more complete understanding as to what is happening and how this can be managed. Once the reasons are determined, then subsequent orthotic adjustments can be accurately assessed with additional modifications performed to move towards improved gait and postural symmetry.

I will review you 2nd post a bit later. I am in Stowe, Vermont for a short ski break. We have had 57" of snow in the past 7 days....so hitting the slopes currently has the highest priority.


Howard

 

Dave wrote:
"All your trying to do is put Centring terms on a web site that will increase your SEO and media attention".

I apologize for interrupting this important site but don;t misunderstand or once again predict what you think my motives are. The media attention I get from The Arena is very small and not worth my time. Furthermore, my work and personna has been abused (as per your WTF) so who needs that kind of attention. I made 6 or 7 of your top quotes for meanness in 2008 thread and started posting in October!!

I have answered totally unrelated threads to Neoteric Biomechanics with posts in order to educate the flock. I have tried to conform. I am not confrontational, I am disagreeing with your core precepts.

As I agree with Dr. Dannenberg that The Arena treats opposing points of view with bias and I agree that SALRE is rearfoot focused and provides less than optimal treatment this seemed a moment to echoe his thoughts with one more voice and perhaps find further common ground between camps. That is why I wrote my post.

This is a learning experience for me and if none of the three professors responds to my posting honestly, I will not entertain a posting like the one I put on this thread in the future.
Dennis

 

Howard

Hey! Righteous call dude, you'll be up to your armpits on the North slope then. Then there's the apre's ski to enjoy, Man you'll never be back.

Dave

 

Dennis

Much as I hate to disturb the flow of the current thread by answering you and pandering to your id.

So your just stirring up a bit of trouble for fun of it then (your id is really restless)

Is this your all purpose response for discussion forum occasions? Just insert into any thread and since you've added the qualifier of

this gives you the right to make any point or ask any question you like, whether relevant or not. It's like a Monty Python sketch " and now for something completely different" it don't work, it's not big and its not clever, so take your funny face and you funny hat and f,f,f,f,f find some traffic to play with.

So no apologies there then:empathy:

Dave

BTW when your foot fires do you tend to shoot yourself in it? Because it looks like you did this time.

 

Dave:

I believe what I said was that we are not certain that an ankle equinus condition would necessarily cause a deceleration in the forward progression of the center of mass (CoM). I agree that the CoM probably changes directions because of an ankle equinus which may be seen as an earlier upward acceleration of the CoM at the time of heel off. Whether this earlier upward acceleration of the CoM also is associated with a deceleration of forward motion of the CoM, I don't know.

It would be very interesting to experiment with taping the ankle in an equinus position to see the change in CoP and CoM motions vs normal (non-taped) walking. This would be a more clinically realistic simulation of the kinetic and kinematic effects of an ankle equinus condition than just having the subect fire their ankle joint plantarflexors earlier in the stance phase.

Great discussion!:drinks

 

All

Do you think it reasonable to define SPB as that time when

1) The physiological energy expense of the body is greater to maintain a walking speed approximating that of a normal gait or where the energy expenditure is similar to normal gait but walking speed is much slower or some position on a scale between these two parameters.

2) The intra stance phase accelerations of the CoM and its segments are far greater than would be reasonably expected in normal gait.

The evidence of this can be extrapolated from an evaluation of the vertical plantar forces by noting

E.G..

a) Bunching of the data points sampled at regular time intervals. Low mean velocity of CoP progression and large differences between max and minimum velocities. Disturbances in the smooth progression of the plantar CoP.

b) Patterns and timing of the total and masked force time curves that indicate apropulsiveness, such as, extended time of stance phase, flat curves and low propulsive peaks relative to braking peaks.

Dave Smith

 

Dave,

Great discussion.

In regards to your in-shoe pressure experiement, you wrote "It was impossible to progress saggitally past the equinus block without some kind of compensatory action. I chose, **thru necessity since there was no other way**, to hyperextend the knee and flex the hip to project the HAT over the foot and then lurch forward with a hip extension and throwing the left swing leg through landing heavily on the left heel. To achieve this it was necessary to utilise the heel rocker of the right foot for longer than in normal walking to avoid the forefoot GRF pushing me backward."


I think that this comment is the most telling in your post. Without the ability to advance smoothly and efficiently over the weight bearing limb, "IT WAS IMPOSSIBLE" to walk without compensation. This has been my major point since I started to write about SPB in 1984. It has also been my contention that the late phase, pronation we have come to recognize as pathologic is but another of these compensatory mechanisms you described. While it seems obvious that ground adaption was the cause of pathologic pronation.....with in-shoe measurements, cavus feet which pronated and flat feet which pronated could, for periods of time, exhibit the same force/time graphic display characteristics....level F/T curves at times of peak CoM movement. Since ground adaption cannot be the same as these two foot types are diametrically opposed in form, yet the dysfunction was comparable, then looking past the foot shape and towards the timing of force application vs. force utilization becomes a much more appealing way to view pathologic gait. This is not to say and foot shape is irrelevant, but rather adds the element of precise timing concept to the debate about what is stressful to the foot and body.

How a clinician achieves a successful orthotic outcome can vary....and there are elements of all that has been discussed on Podiatry Arena that have great value. Understanding though, that in-shoe pressure analysis provides a way to visualize the time of stress buildup and consequently, the ability measure when this has been relieved, provides great relevance primarily to improve the science of our clinical practice and secondarily to improve the patient outcomes.


Howard

 

Not being the expert in this area, one of the Chiropodists I worked with developing my own product explained how his own condition affected his gait, producing swirls in the forefoot section of his shoes, because of twisting to compensate for FHL. It would make sense to me that this sort of twisting action could follow all the way to the hip and cause lower back problems, at least at the pushoff stage of gait. My own feet have this condition, more so on the right foot than the left. I also have a congenital hip disorder, which will ultimately result in fusion of the bones that are separating over time. As I was diagnosed with the hip disorder 20 years ago, and I've been wearing orthoses for 13 years now, 7 of them with first metatarsal cutouts, I have to wonder if the doctor who made his diagnosis started at the right part of the anatomy.

 

Howard

Yes and this is the point that I have been trying to emphasise. The SPB may not actually reduce CoM mean velocity, although it may, but it will require additional, increased and what might be termed *spurious* muscular actions to maintain the forward progression speed than would otherwise be required for the standard walking model. The standard model suffers a **perturbation** in the normal frequencies and actions and therefore increases the energy required for the same distance travelled. Perturbation describes the cause and effect of a disruption in the normal flow and so may be a useful term to use in this case.
So perhaps Saggital plane perturbation (SPP) might be a useful description to accommodate the cause and effect of what we presently call saggital plane block.
Spurious muscular actions SMA can be associated with SPP since these action are not of the genuine walking model and are a ***bastardised*** modification that allows the continuation of ambulation at a sub optimum level.

* Spurious;
1) Not true or genuine; false, counterfeit,
2) Like in appearance but unlike in structure or function
3) Designating or of an unwanted signal transmitted or received at other than the desired frequency
4) illegitimate, bastard

**Perturbation (pŭr'tərbā`shən),I
In physics, a small force or other influence that modifies the otherwise simple motion of some object. The term is also used for the effect produced by the perturbation, e.g., a change in the object's energy or path of motion

***Bastardize
1) Debase, to lower the value or quality of something
2) Deriving from more than one source or style

How does that sound?

Cheers Dave

 

I am enjoying reading through the dissucsions that this post has created, however it is taking a little bit of time to digest each post...

I am currently filling out my ethics form (i decided to do a narrative review of the current research as i didnt feel as of yet i have the skill base to preform a valid study, and that a review would give me more of an insight).

whilst doing the ethics form it raised a question in my head - has anyone looked at the longterm effects of limiting hallux dorsiflexion via an orthoses? and the effects that it may have?

just a thought - wouldnt like to try for ethical approvial for that though!

 

While not directly looking at the long-term effects, Kilmartin and Wallace performed a bone pin study of the effects of modified Root devices on 1st MTPJ dorsiflexion http://www.japmaonline.org/cgi/content/abstract/81/8/414

It may be extrapolated that any longitudinal study of foot orthoses that employed similar devices to those in the Kilmartin study may inadvertently have also demonstrated the effects of limiting hallux dorsiflexion. For example, using similar devices Kilmartin looked at the long-term effects of foot orthoses on juvenile hallux valgus:

Kilmartin TE, Barrington RL, Wallace WA. A Controlled Prospective Trial of a Foot Orthosis for Juvenile Hallux Valgus. J Bone Joint Surg Br. 76-B:210-214, 1994.

Abstract: In a survey of 6000 children between 9 and 10 years of age, 122 were found to have unilateral or bilateral hallux valgus. These children were randomly assigned to no treatment or to the use of a foot orthosis. About three years later 93 again had radiography. The metatarsophalangeal joint angle had increased in both groups but more so in the treated group. During the study, hallux valgus developed in the unaffected feet of children with unilateral deformity, despite the use of the orthosis.


Landorf also used modified Root devices: Effectiveness of Foot Orthoses to Treat Plantar Fasciitis. A Randomized Trial Karl B. Landorf, PhD; Anne-Maree Keenan, MAppSc; Robert D. Herbert, PhD Arch Intern Med. 2006;166:1305-1310.

While we can give little certainty as to the effects these specific devices had on 1st MTPJ dorsiflexion in each subject, in either trial, the Kilmartin bone pin study suggests that they MAY have decreased the hallux dorsiflexion.

Moreover, since footwear in itself appears to limit dorsiflexion of the hallux, comparatives between shod and unshod populations to some extent reveal the long-term effect of restriction of hallux dorsiflexion.

 

Dave,

Saggital plane perturbation (SPP) is PPPerfect. I think you have hit on a term which accurately describes the essence of what occurs when sagittal plane function is disturbed. It is also not limited to the foot. Excellent!

The term, "Spurious musclar action" is not quite what I would think appropriate, but the description of the process is fairly accurate. As I see this clinically, functional strength is a complex neuromuscular activity and there is inhibition potential overriding mechanical function. Managing this involves more than fitting the right CFO, and the term "spurious" connotates, at least to me, some type of underhandedness. I think there is a better term...we should give this more thought.

As far as ***bastardised*** goes, the sagittal plane gait accommodation process is actually quite predictable unless severe foot deformation or neurological issues exists. The lower extremity either normally extends during the 2nd half of single support or abnormally flexes. I think SPP fits perfectly for the entire process.


BTW, skiing was great. Have you ever skied "North Slope" in Stowe?

Howard

 

My daughter goes skiing with her Aunt and Uncle in the Big Bear California but I've never skied in my life. Every where has a North Slope and just to check I looked it up on the world wide wonder web.

All the best Dave

 

I think that"sagittal plane perturbation" is a more scientifically accurate term than "sagittal plane block" to describe the multitude of dynamic anomalies that occur within the bipedal human and which results in abnormal center of pressure paths/velocities/accelerations when force plate or pressure mat/insole analyses are performed.

However, "sagittal plane perturbation" is also a very broad term that may not be specific enough to describe the selected mechanical phenomena that Howard is trying to describe here. My problem comes with the word "block", which implies no motion occurs whereas, in fact, both functional hallux limitus and ankle joint equinus are known to be variable in nature, with variable dorsiflexion stiffnesses that, hopefully, will be able to be mathematically quantified in the future. I would think that a term should be chosen to reflect the specific mechanical nature of this phenomenon and that would persist once the joint stiffness to CoP path/velocity/acceleration correlation has been better identified.

Any other suggestions for improved terminology from anyone?