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I found myself questioning a few ideas after Craig Payne's recent biomechanical lectures.

I would be interested to hear some debate/opinions regarding a correlation between the shape of the 1st MTPJ complex and the percieved windlass mechanism. The recent lecture and previous boot camps havent eluded to this possible relationship.

It is of my opinion that the shape of the joint complex will have a huge bearing on the relative function or dysfunction of the windlass mechanism. Squarer less congruent met heads would theoretically result in a greater force required to initiate the windlass and delayed timing of the mechanism; Conversely a rounder more congruent MTPJ will result in a more efficent functioning windlass mechanism.

There is literature that suggests squarer met heads result in hallux limitus/rigidus while rounder met heads are predisposed to HAV deformities. Does this relevant anatomy play a larger role that what has been eluded to in recent seminars??

Any thoughts
Luke Grainger

I think MT head morphology is only relevant to transverse plane issues - ie the proximal phalanx is more likely to sublux over a 'rounder' 1st MT head, than a 'squarer' one.

When it comes to sagittal plane motion, I think it is irrelevant, because I am yet to see the sagittal contour of the MT head change its appearance intraoperatively, or on a lateral X-ray - they all look very similar and quite a ball/socket configuration.

Maybe you should be looking at the sesmoids more closely, as these account for 1/3 of the articular surface of the 1st MTPJ complex...?

LL

Instead of using the terminology "squarer" and "rounder" regarding the shape of the first metatarsal head, let's be a little more exact and scientific and use the terms "increased radius of curvature" to describe a more flat shape and "decreased radius of curvature" to describe a more rounded shape to the first metatarsal head so there is less chance of ambiguity and misunderstanding in our discussion.

A first metatarsal head that has increased radius of curvature in the transverse plane will have more transverse plane stability to adduction/abduction moments acting at the first metatarsophalangeal joint (MPJ). If there is a tendency for increased first MPJ plantarflexion moments at the initiation of propulsion due to a medially deviated subtalar joint (STJ) axis, increased tensile force in the medial band of the central component of the plantar aponeurosis, and a flattened medial longitudinal arch (MLA), then functional hallux limitus (FnHL) will likely result and the patient may likely develop structural hallux limitus as time goes on.

If, however, the first metatarsal head has a decreased radius of curvature in the transverse plane it will have decreased transverse plane stability to adduction/abduction moments acting at the first MPJ. If there is a tendency for increased first MPJ plantarflexion moments at the initiation of propulsion due to a medially deviated STJ axis, increased tensile force in the medial band of the central component of the plantar aponeurosis, and a flattened MLA, then hallux abducto-valgus deformity will likely result due to the lack of transverse plane stability inherent in the first MPJ.

In the sagittal plane, an increased radius of curvature of the first metatarsal head, such as is seen in structural hallux limitus, will tend to cause greater plantar fascial tension for each degree of hallux dorsiflexion during propulsion so that hallux dorsiflexion will be more likely restricted. On the other hand, a decreased radius of curvature of the first metatarsal head will cause less plantar fascial tension for each degree of hallux dorsiflexion during propulsion so that hallux dorsiflexion will more likely occur, all other things being equal.

I don't know of any studies that show the above but it certainly makes good mechanical sense when doing modelling of the foot and first MPJ complex which I started to work on 20 years ago.

__________________
Sincerely,

Kevin

**************************************************
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
Sacramento, CA 95825 USA
My location

Voice: (916) 925-8111 Fax: (916) 925-8136
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Thanks for your reply's. Cerainly some food for thought.
Sorry for the poor terminology radius of articulating curvature is a much more precise description.

No need to be sorry. This is the sort of description I have always used in my lectures since this seemed to me a better way to actually quantify (i.e. put into numbers) the shape of the metatarsal head. However, I don't think I have seen radius of curvature used ever in the literature or in other podiatrist's lectures to describe the shape of the first MPJ. So, I suppose this terminology is new to most podiatrists.

Another factor that should be addressed is the depth of the crista and shape of the sesamoids. Increased sesamoidal groove depth would tend to resist abduction moments of the first MPJ than shallow sesamoidal groove depth. Also increased first MPJ ligamentous tensile stiffness would resist first MPJ abduction moments better than ligaments that are more compliant.

__________________
Sincerely,

Kevin

**************************************************
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
Sacramento, CA 95825 USA
My location

Voice: (916) 925-8111 Fax: (916) 925-8136
**************************************************

I have asked this question recently in another thread but got no reply...

In a nonweightbearing situation:

in a foot where the subtalar joint is maximally pronated (my patient had a peroneus tertius in spasm), dorsiflexing the hallux does not see any plantarflexion of the 1st metatarsal head. However, on releasing the trigger / spasm, windlass was fully functional, nonweightbearing.

Has this got more to do with the spasming muscle or is it about the maximum pronated position of the STJ, does the heel need to invert or something for windlass to kick in?

Rebecca

If the STJ is maximally pronated, the decreased calcaneal inclination will likely increase tension on the plantar fascia. This would increase the force needed for windlass...

__________________
Craig Tanner
Podiatrist
ASPETAR-
Qatar Orthopaedic and Sports Medicine Hospital
Doha
QATAR
http://www.aspetar.com/

I think that an increased tensile force in the medial central band of the component of the to plant aponeurosis, for the reason that is, determines the form of the first head, in this case with an increased radius of curvature.

Have they read this article??

http://www.podiatrytoday.com/article/7486

What do they think??

Regards

Jonatan

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