Tuesday, December 07, 2010
Forefoot varus is rare, yet some researchers always seem to manage to recruit enough subject for their research that have what they claim is forefoot varus. I suspect that they are not forefoot varus, but the much more common forefoot supinatus and they got confused. The reason that this is a problem is that they are totally different beasts. One is osseous and causes rearfoot pronation and cannot be reduced. The other is soft tissues and is the result of rearfoot pronation and can be reduced. Yet they look the same. They will both respond very different to foot orthoses … kinda think that the distinction between the two would be important in research projects don’t you? Also forefoot varus will respond very differently to rigid compared to flexible/semi-rigid foot orthotics.
To be clear, forefoot varus is a forefoot that is inverted when the subtalar joint is in its neutral position and the midtarsal joint is maximally pronated. As the forefoot is inverted, the rearfoot has to pronate to bring the medial side of the foot to the ground. To treat forefoot varies, you are supposed to use a medial forefoot post to bring the ground up to the foot, so the foot does not need to pronate the rearfoot to bring the medial side of the forefoot down to the ground. Right?
Consider the very rigid plastic orthotic with a forefoot varus post, when the foot is placed on top of it the forefoot varus post will invert the rearfoot (or stop it pronating/everting) through its effects on the rearfoot via the rigid plate of the orthotic.
Consider the less than totally rigid foot orthotic with a forefoot varus post. How will that affect the rearfoot pronation? The only way it can affect the rearfoot pronation is by dorsiflexing the first ray to end range of motion, then invert the midfoot joints to end range of motion, then it has a shot at affecting the subtalar joint. As the orthotic shell is not totally rigid, the forefoot varus post has to affect the rearfoot “through the foot”. Whereas if the shell was rigid, the forefoot varus posts work directly on the rearfoot by tilting the orthotic shell. It cannot do this with a less than rigid orthotic when the person is standing on it.
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Labels: foot biomechanics