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BACKGROUND: Hypomobility and hypermobility of the first ray have been implicated in the literature as a primary cause of mechanical foot problems because of proposed obligatory and compensatory movements. Despite these theoretical links, research is sparse regarding the effect on kinematic and plantar pressure patterns as a result of altered first ray mobility. The purpose of this study was to determine whether hypomobility or hypermobility of the first ray alters hindfoot kinematics or the distribution of plantar pressures during walking.
METHODS: The magnitude of dorsal first ray mobility in 82 individuals was measured and then classified as being hypomobile, normal, or hypermobile. The plantar pressure under the first and second metatarsal heads, as well as hindfoot kinematics during walking, were then compared between the three categories of first ray mobility.
RESULTS: The results of this study indicate that those feet with a hypomobile first ray had significantly decreased plantar force and pressure values under the first metatarsal compared to the second metatarsal. In addition, feet with a hypomobile first ray showed significantly more hindfoot eversion compared to those with either normal or hypermobile first rays.
CONCLUSION: The results of this study do not support the common theoretical implications of altered mobility of the first ray related to plantar pressure and hindfoot kinematics.
So in modern parlance, reduced 1st metatarsal stiffness (Dr. Kirby has exerted peer pressure) is associated with less plantar pressure over the 1st metatarsal and more hindfoot eversion. ah hem... I am certain I have seen other research pointing to a contrary finding?
So in modern parlance, reduced 1st metatarsal stiffness (Dr. Kirby has exerted peer pressure) is associated with less plantar pressure over the 1st metatarsal and more hindfoot eversion. ah hem... I am certain I have seen other research pointing to a contrary finding?
Dieter,
Clearly Prof. Kirby has not exerted enough pressure to allow accurate understanding and interpretation of the results of the modern "parlance" or the study quoted. You may want to re-read and interpret the results again. I'll try to help:
"The results of this study indicate that those feet with a hypomobile first ray" = Increased dorsiflexion stiffness of the 1st ray, not decreased as you said above.
"had significantly decreased plantar force and pressure values under the first metatarsal compared to the second metatarsal. In addition, feet with a hypomobile first ray showed significantly more hindfoot eversion compared to those with either normal or hypermobile first rays."
Does this still fit with your view of the world?
How was hypo, normal and hyper differentiated? Obviously artificial delineations but what RoMS?
__________________ Science is the antidote to the poison of enthusiasm and superstition
Dieter,
Clearly Prof. Kirby has not exerted enough pressure to allow accurate understanding and interpretation of the results of the modern "parlance" or the study quoted. You may want to re-read and interpret the results again. I'll try to help:
"The results of this study indicate that those feet with a hypomobile first ray" = Increased dorsiflexion stiffness of the 1st ray, not decreased as you said above.
Simon - quite right to put me in my place, and if my name was another I might be given the benefit of doubt about the possibility of a typo. I am in between ops and have only briefly scanned the abstract and left my brain in the OR room. The meaning I intended was as you then stated and remains the same and my original question stands and I remain confused about the implications of the findings. Your subsequent interpretation shows that your own understanding was not unduly influenced by said typo.
Since the full article is not available we are of course assuming the authors are using terminology that might mirror our podiatric understanding of "the world" in relation to 1st metatarsal excursion behaviour, and this might just be an unjustified leap of faith.
Last edited by Admin : 21st July 2006 at 01:50 AM.
Reason: fixed faulty quote
So in modern parlance, reduced 1st metatarsal stiffness (Dr. Kirby has exerted peer pressure) is associated with less plantar pressure over the 1st metatarsal and more hindfoot eversion. ah hem... I am certain I have seen other research pointing to a contrary finding?
Quote:
"In addition, feet with a hypomobile first ray showed significantly more hindfoot eversion compared to those with either normal or hypermobile first rays. "
What we were taught, and what makes sense is that hindfoot eversion essentially provides a weightbearing supinatory 'stretch' to the forefoot. This is one theory behind forefoot supinatus. Stretching the forefoot into supination, stretches the first ray into more dorsiflexion. Can't see how the hindfoot eversion egg becomes the hypomobile first ray chicken?
I am with you Mr. Fellner, this research doesn't quite fit.
Since the full article is not available we are of course assuming the authors are using terminology that might mirror our podiatric understanding of "the world" in relation to 1st metatarsal excursion behaviour, and this might just be an unjustified leap of faith.
Given who the authors are, I would expect that they do. The results seem to suggest that with increased dorsiflexion stiffness we adopt a propulsive strategy which limits sub 1st MTPJ pressure. In other words, a so called "low-gear strategy". Is this really so difficult to understand? I think this probably fits with BM's view of propulsion. That is, with low gear propulsion = reduced windlass activity, lack of calcaneocuboid locking, blah blah = increased foot pronation. As I've always said BM is a genius and his concepts are rock solid. Wouldn't hear a bad word said against him etc etc etc..
Interesting that from the abstract the authors grouped the rays by dorsal excursion. Wonder what the plantar excursions were?
__________________ Science is the antidote to the poison of enthusiasm and superstition
One needs to be carefull in use of some of the terminology here .... hyper- and hypo- mobility used by the authors above were refering to the available range of motion.
Whereas, 'stiffness' (the more appropriate terminology in this context) is more a measure of the force needed to produce the movement (which the authors did not measure).
Another research question worth pursuing is the relationship of first ray stiffness to plantar pressures - I would assume there is more likely to be a relationship there than just to the range of motion of the first ray.
__________________
Craig Payne
Department of Podiatry
La Trobe University
Melbourne, Australia http://www.latrobe.edu.au/podiatry
__________________________________________________ ___________________________________ God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
The views expressed above are those of the author and not that of La Trobe University This is where I am, where are you?
One needs to be carefull in use of some of the terminology here .... hyper- and hypo- mobility used by the authors above were refering to the available range of motion.
Whereas, 'stiffness' (the more appropriate terminology in this context) is more a measure of the force needed to produce the movement (which the authors did not measure).
Another research question worth pursuing is the relationship of first ray stiffness to plantar pressures - I would assume there is more likely to be a relationship there than just to the range of motion of the first ray.
I have scanned over a full text version of Cornwall et al's paper. They acknowledge that their results are contrary to previously published literature on the subject, but don't offer any possible explanations for their results other than to say that their results may have been due to using a young, asymptomatic population or to using a population with relatively small ranges of first ray mobility values. They used a plantar loading force of both 10 N and 55 N using Glasoe's first ray mobility device to determine "mobility" on a total of 164 feet.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
RESULTS: The results of this study indicate that those feet with a hypomobile first ray had significantly decreased plantar force and pressure values under the first metatarsal compared to the second metatarsal. In addition, feet with a hypomobile first ray showed significantly more hindfoot eversion compared to those with either normal or hypermobile first rays.
This is something I've been thinking about a long time. Perhaps the increased range of motion is the result of high plantar pressures. High plantar pressures would cause more strain on the ligaments and lead to possible stretch or tear that would result in increased range of motion. This would also be consistant with the observation that you tend to see a more pronated gait with more hypermobille (increased range of motion) first rays. More pronation leads to more medail weight bearing, more force on first met head etc.
Anybody have access to a large population of children to look at the incidence of hypermobility? How does this compare to the adult population?
Just some thoughts,
Eric
Last edited by Admin : 19th July 2006 at 10:36 PM.
Reason: fixed quote
This is something I've been thinking about a long time. Perhaps the increased range of motion is the result of high plantar pressures. High plantar pressures would cause more strain on the ligaments and lead to possible stretch or tear that would result in increased range of motion. This would also be consistant with the observation that you tend to see a more pronated gait with more hypermobille (increased range of motion) first rays. More pronation leads to more medail weight bearing, more force on first met head etc.
Anybody have access to a large population of children to look at the incidence of hypermobility? How does this compare to the adult population?
Just some thoughts,
Eric
This is a good point, Eric. However, I think that Craig also makes a good point that the actual dorsiflexion stiffness of the first ray should be measured relative to the other lesser metatarsal ray stiffnesses in order to provide more answers.
One other very important point we must all realize: just because you may be attempting to assess the passive ligamentous restraints of the first metatarsal (i.e. first ray) during a clinical exam, you are not then assessing the only means that plantarflexion moments can be generated at the first ray during weightbearing activities.
First ray plantarflexion moments may also be generated actively by contractile activity of the peroneus longus, flexor hallucis longus, flexor hallucis brevis, abductor hallucis and adductor hallucis which can not be measured by our currently available non-weightbearing or simulated partial weightbearing clinical examination methods. In addition, as the center of mass (CoM) progresses more anteriorly, the center of pressure (CoP) will also progress more anteriorly on the plantar foot during gait. This will cause increased magnitudes of passively generated tensile force within the central component of the plantar aponeurosis which will, in turn, generate additional first ray plantarflexion moments, especially with feet that have increased medial longitudinal arch height. The partial weightbearing-knee flexed method used by Cornwall et al and described by Glasoe in this study will not load the Achilles tendon and/or plantar fascia adequately to give a good representation of how much the plantar fascia can contribute to first ray dorsiflexion stiffness (what Cornwall et al call "hypomobile" and "hypermobile"). I am sorry that Cornwall et al did not discuss all of these above problems with the Glasoe method in their paper as potential sources of their unexpected experimental results.
The tendency of all metatarsal rays to accommodate to the flat surface of the ground, regardless of the individual dorsiflexion stiffnesses of the metatarsal rays, will tend to cause all the metatarsal rays to dorsiflex just enough to remain in contact with the ground. Therefore, both the first and second metatarsal rays will tend to dorsiflex a similar amount as the subtalar pronates since the magnitude of their dorsiflexion motions relative to each other will be determined more by their tendency to accommodate to the contours of the weight-bearing surface than by their relative dorsiflexion stiffness. As a result, a decrease in first ray dorsiflexion stiffness will not necessarily result in an increased amount of first ray dorsiflexion motion but will, instead, cause a decrease in GRF plantar to the first metatarsal head and an increase in GRF plantar to the second metatarsal head (Figure 2).
A decrease in first ray dorsiflexion stiffness may be caused by either anatomical or functional factors (Figure 3). Anatomical factors may include increased laxity of the plantar ligaments (i.e., decreased ligamentous tensile stiffness) of the navicular-first cuneiform and/or first metatarsal-cuneiform joints. Surgical transection of the medial fibers of the central component of the plantar aponeurosis will also reduce first ray dorsiflexion stiffness since the plantar aponeurosis (plantar fascia) functions to help prevent dorsiflexion of the first ray.16
Functional factors include a decrease in contractile activity of muscles (e.g., peroneus longus, flexor hallucis longus, abductor hallucis, and flexor hallucis brevis) that may cause a first ray plantarflexion moment. Decreased contractile activity of any of these muscles during the late midstance phase of walking gait, when the dorsiflexion loading forces on the first ray are at their greatest, will tend to decrease the magnitude of the first ray plantarflexion moment, which will in turn mechanically decrease the dorsiflexion stiffness of the first ray.17 Stokes et al18 developed a model of the first ray-first metatarsophalangeal joint complex that provides considerable insight into the functional factors that likely affect the mechanical resistance and response of the first ray to dorsiflexion loading forces during weight-bearing activities.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
One other very important point we must all realize: just because you may be attempting to assess the passive ligamentous restraints of the first metatarsal (i.e. first ray) during a clinical exam, you are not then assessing the only means that plantarflexion moments can be generated at the first ray during weightbearing activities.
A great point Kevin and indeed one of the problems with the "walking cadaver" work that Erin Ward and "The Nester" have done was that they can't get the plantar intrinsics "working". I think these muscles have received too little attention.
__________________ Science is the antidote to the poison of enthusiasm and superstition
First ray mobility and plantar pressures
Linear Mode
