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To decrease GRF plantar to the 1st metatarsophalangeal joint, 'Reverse Morton's Extension" is a treatment of choice in many cases.
Do you make it such that it only provides extra depth plantar to the 2-5 metatarsal heads or make a 3/4 length (up to toe sulci) with a 1st ray cut-out? Thanks, mark
I only ask as if a 2-5 met head elevation would increase external STJ (and others) pronatory moments, whereas a full length surely wouldn't (all depending on location of STJ axis) so in a foot where the aim is to reduce 1st MPJ plantar GRF isn't the latter more efficacious?
I use a similar technique to Kevin's but also use a full length EVA with the material 'removed' from under the 1st met head to create the same effect.
The only issue I have had with the modification is that it can create an unwanted dosrsiflexory moment through 2-5 met heads. A compensating heel raise usually sorts this out.
This doesn't seem to be a problems when the modification is used in sports patients but has done when the patient has done more standing around - e. retail workers.
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My experience has been that this must be coupled with some type of 1st ray cutout with the shell of the device or else plantarflexion of the ray is negatively impacted. From using F-scans on thousands of cases over the years, minor changes to the shell shape can have pronounced changes in function. C/O's can vary from small to long to bidirectional and adding a groove to accommodate the shape of the metatarsal itself along the 1st ray axis can aid in promoting timely plantarflexion.
Once this type of modification is added to a CFO, the simplest thing to see in the post adjustment gait observation is speed. If LLD is appropriately corrected, and the 1st ray adequately mobilized, speed automatically increases without any prompting.
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I am a little confused. The drawing Kevin had is exactly what I have been doing.
The way I see it, and feel free to correct me if I am wrong, the plastic is behind the first metatarsal head, so it doesn't lift the metatarsal head. The forefoot extension is under the second through fifth metatarsal heads, so it allow the first to drop.
Do you mean that since the cast position does not capture the shape of the foot with the first metatarsal plantarflexed, the orthoses have to be modified so that the neck of the first metatarsal is not irritated?
Thinking back, the most common modification I have to make is to thin/shorten the distal shell just proximal to the first metatarsal head.
Cutout really help. The other thing I always try to do is to drop the met head while elevating the base of the proximal phalanx of the hallux. Once the toe has mechanical advantage over the metatarsal, proper motion will take place.
The use of either carbon fiber or other rigid materials to prevent or severely restrict MTPJ dorsiflexion is, in my way of thinking, a very poor construct to understand and/or treatment pathomechanics. At the very least, these type of devices should be used only when accompanied with a rocker sole to promote forward movement. Otherwise, why bother with the shoe....you might as well just wear a shoe box!
MTP joint dorsiflexion is a fundamental process in human gait. We would be terribly inefficent bipeds without this mechanism. If your mindset is simply that it hurts to move....restricting the motion makes sense. If you realize however, that it doesn't move at the time when movement is in greatest demand, the enhancing the motion rather than trying to stop it becomes a far more practical method of treatment.
I have very successfully treated hallux limitus for decades by a combination of joint mobilizations and orthotics which enhance plantarflexion. Long term results, both locally (at the MTP joint) and globally (postural changes, ie lower back pain) and far better than when motion is blocked.
Your skill in this area is well known and published. Thank you for your contribution to our profession.
I agree that a rocker/lever mechanism is needed to create a more functional advanced composite device. Otherwise composite orthotics with a high modulas of elastisity will feel like walking around in ski boots, you can keep the shoe boxes that might look a little silly for me...
A Hui Hou,
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