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Interesting paper from the latest Clinical Biomechanics:

The relationship between hallux dorsiflexion and ankle joint complex frontal plane kinematics: A preliminary study

Jill Halstead, , Deborah. E. Turner and Anthony. C. Redmond

Abstract
Background. It has been suggested that the function of the first metatarsophalangeal joint may be related to the motion of the ankle joint complex. Objective. This study explored the relationship between ankle joint complex and first metatarsophalangeal joint motion during gait in a group of 14 who demonstrated clinically limited passive hallux dorsiflexion in quiet standing (cases), and 15 matched controls. Method. An electromagnetic tracking system was used to measure the ankle joint complex frontal plane motion and first metatarsophalangeal joint sagittal plane motion during gait, in both cases and controls. The case group was then evaluated further to investigate the effect of an orthosis on first metatarsophalangeal joint motion. Findings. The correlation between maximum ankle joint complex eversion and maximum first metatarsophalangeal joint dorsiflexion during gait was r = 0.471. Within the case group, maximum rearfoot eversion was reduced following the application of the orthoses, but there was no change in sagittal first metatarsophalangeal joint rotations. Interpretation. The relationship between maximum ankle joint complex eversion and first metatarsophalangeal joint dorsiflexion kinematics found in this study was moderate, and decreasing maximum ankle joint complex eversion with an orthosis did not result in any increase in first metatarsophalangeal joint dorsiflexion during gait in patients with functional first metatarsophalangeal joint limitation. These results do not support the assumption that ankle joint complex eversion influences first metatarsophalangeal joint motion substantially.

Cheers,

Hylton

__________________
Cheers,

Hylton

Hylton B. Menz, PhD
Associate Professor and Reader
NHMRC Australian Clinical Research Fellow
Director, Musculoskeletal Research Centre
La Trobe University

We got strong convincing data that shows that rearfoot inversion/eversion significantly affects the forces needed to dorsiflex the hallux.

__________________
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?

Hylton and Craig:

I can seen how having increased rearfoot pronation would likely cause decrease hallux dorsiflexion. Increased subtalar joint (STJ) pronation moment will cause increased first ray dorsiflexion moment which will, in turn, cause increased hallux plantarflexion moment and tend to decrease hallux dorsiflexion during propulsion.

However, if an orthosis is designed with a high medial arch causing lateral instability and/or increased first ray dorsiflexion moments and is not designed specifically to increase hallux dorsiflexion (but rather is designed specifically to decrease rearfoot pronation) then I can see how this orthosis would limit rearfoot eversion but not necessarily increase hallux dorsiflexion. In other words, the mechanical influence of the orthosis is complex and much, much more than a simple rearfoot pronation-hallux dorsiflexion cause-effect relationship. Multiple foot segments can act in different ways depending on the design and function of the orthosis under the foot during gait.

For example, if I take a foot that has a functional hallux limitus and over invert the foot with the orthosis (without adding a 2-5 extension to the orthosis), it would be unlikely that this orthosis would increase the dorsiflexion of the hallux during gait even though it would easily be able to decrease early midstance rearfoot pronation. We must separate the early midstance effects of the orthosis from the late midstance effects if we are to understand the effects of an orthosis on rearfoot pronation and functional hallux limitus.

By the way, what is wrong with the term "rearfoot eversion"? Why does the term "ankle joint complex eversion" need to be used? It seems like "ankle joint complex eversion" only will create confusion for the clinician and, since the talus and calcaneus are the rearfoot, is not saying anything different than "rearfoot eversion" from a kinematics standpoint.

__________________
Sincerely,

Kevin

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Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College

e-mail: kevinakirby@comcast.net

Private Practice:
107 Scripps Drive, Suite 200
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Quite a mysterious posting, Craig . How about some details?

Cheers,

Hylton

__________________
Cheers,

Hylton

Hylton B. Menz, PhD
Associate Professor and Reader
NHMRC Australian Clinical Research Fellow
Director, Musculoskeletal Research Centre
La Trobe University

I'd be keen to see an investigation of mid-tarsal motion/position vs hallux dorsiflexion and another that looked at angle of descent (don't quite know what else to call it) of first met shaft vs hallux dorsiflexion....a little more specific than ankle joint complex maybe.
Regards Phill

Hylton --- sorry, that post was posted from a internet cafe on Magnetic Island (very limited time)... this one is from Townsville airport (5.10AM).... on the run .... actually off to Queensland SMA conference

Final number crunching not done .... but obvious from quick look at graphs that if rearfoot inverted, force to dorsiflex hallux (ie establish windlass) is lowered a lot (and vice versa)... we did not include ROM of 1st MPJ as others have done.

__________________
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?

Jacks test is great clinically. It gives the clincian another way to assess or pre-empt efficacy.

The only limitation is that we are assessing hallux dorsi-flexion with the heel plantar grade, rather than pure fore-foot loading. Perhaps in the future, testing/research/assessment may incorporate this more functional and specific position.

This view has implications for forefoot modifications to the device.