Hi All
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Got a customer with a type of foot that has me wondering how to prescribe her orthoses and so I thought I would ask for some advice here.
Lady 66yrs old, painful ankles lateral but mainly concerned about waddling gait.
2 x hip replacement.
Both feet - STJ 30dgs inversion and 3-5 dgs eversion,
max STJ pronation in gait and stance,
navicular drop 10mm drift 15mm i.e. forefoot abducted on rearfoot.
Left STJ axis extremely medial and medially rotated, right STJ axis medial,
left leg external femoral torsion = hip neutral is ext rotated ie knee mid range RoM = 35dgs ext rotated and there is no internal rotation available past knee straight ahead.
right leg 15-20mm longer than left by measuring GT to malleolous.
High right hip and illac crest, level ASIS.
In gait foot placement is toe out 30dgs left and straight ahead right.
Rocks onto left side during right swing thru,
very weak left hip abductors by manual testing.
In stance and especially in gait left foot hallux abducts (away from the foot midline) by 12-15dgs
The ankles are painful due to the internal stress resisting pronation and tibial torsion. The waddling gait is mainly due to weak left hip abductors - NB when she uses her stick in the right hand she stabilises frontal plane moments about the left hip and by applying balancing GRF thru the stick and so does not waddle.
The hallux abducts to add stj supination moments in a foot that is toe out externally rotated and abducted with a medial STJ axis, i.e. everything is trying to pronate the foot past max RoM.
It is also interesting to note that and shoe insole template overlaid over her foot print on a podotrack shows that when barefoot her hallux abducts way outside the shoe confines. One might imagine therefore that STJ pronation moments are not as well resisted by hallux GRF andthere would be greater stress in the internal tissues at max pronation. A shoe with a really wide forefoot might be advantageous here except that this will encourage the hallux abductus deformation??
My query here is how to design an orthosis that will encourage the hallux not to abduct but not significantly internally rotate the left foot placement angle since this would lead to torsional stress in the knee at right swing thru if there was insufficient relative hip internal rotation available at this time.
For the left foot I was thinking of a deep medial skive with a high medial arch flange and an excessively wide forefoot on a shank independent shell orthosis with balance heel lift . Fitted in a shoe with a wide forefoot.
Any thoughts?
Regards Dave
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Kind of answering my own questions as I go alone but appreciate your input.
Dave -
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l would be at least (if you dont go with custom shoes) a custom soling.
Left foot "sounds like" it needs a lateral flare and a rocker sole with the fulcrum set at the 30dg abduction you describe, this will cause less pressure/force required to move through the stand and propulsive phase and may well result in less abduction moment of the Hallux.
Example; The fulcrum line of the rocker might run from the distal 5th to the MPJ of the 1st ?
Still do the orthosis but how much correction can you give a 66 year old that has had two hip replacements etc, etc? -
It sounds like the gait is related to weak hip abductors which may not have fully recovered post hip surgery. You mentioned that they were weak, perhaps some muscle strengthening. Especially since the waddling is her main concern.
When the shoe holds the toe in, there will be less motion of the arch of the windlass, and this may alow the windlass to add more supination moment when compared to barefoot. If it's not uncomfortable I would keep the forefoot of the shoe narrow.
It sounds like you are thinking the pain in the ankles is because of pronation to end of range of motion.
I feel that the angle of gait is "chosen" by the patient. That is the patient will put their foot on the floor in the angle where they find the most comfort within their range of motion. So, if your foot device altered their choice of foot placement, I think they would still choose an angle that would not place stress on the hip. Things will change if they are so far internal that during swing, their swing foot hits their stance leg and they trip. (Not a problem in this case.) An orthosis cannot enforce angle of foot placement as it does not contact the ground during swing, nor does it grab on to the leg.
I like the heel lift as the limb length descrepency could be the result of the hip surgeries. You could try the old phone book test where you stand the patient with the short leg on the phone book and flip through the pages until they "feel" level and measure that height for your lift. I also like the medial heel skive to decrease tension in the fascia and decrease internal forces in the sinus tarsi. As long as the shoe is not uncomfortable, I would not get her an extra wide shoe to allow the toe to abdcut. There are pros and cons of shank dependent devices. The physical exam you gave did not tilt the scales one way or the other on using a shank dependent device.
Hope this helps,
Eric -
Boots and Eric
Like the angled rocker idea but compliance might be an issue
Dave -
Dave:
Sorry....coming on a little late on this thread. I pretty much agree with everything that Simon and Eric have said.
The plantar fascia is probably the main source of the internal hallux abduction moment, which is, of course, a passive force, not an active one. The abductor hallucis obviously has more mechanical advantage to cause hallux abduction than the medial slip of the central component of the plantar aponeurosis (i.e. plantar fascia), but the plantar fascia probably develops at least 10 times more tensile loading force within it than does the abductor hallucis during the stance phase of gait.
I would try to use the shoe to resist further hallux abduction since these deformities (i.e. hallux varus) will tend to get worse over time. However, too much external hallux adduction force from the shoe can cause medial hallux irritation, so the patient may try getting a leather upper shoe with a normally shaped toe box initially that can then be stretched a little bit if hallux irritation develops. Otherwise, your initial orthosis design recommendations seem reasonable to me. As far as angle of gait, this is most likely related to her transverse plane hip position.
One of the tests I have used for many years, and I demonstrate regularly to the podiatric surgical residents that rotate through my office, is to have the patient lie flat on the table (i.e. plinth), and then internally and externally rotate both limbs (by grasping the ankles) and find the position where the hips "want" to lie in (trying to eliminate the rotational effects of gravitational acceleration on the mass of the feet). The knee and foot angles are noted here and correlated to their position during stance and gait. I find this test gives me a better idea of the internal transverse plane rotational moments from the soft tissue acting across the hip joints of the patient that are important factors in determining their self-selected angle of gait.
Good luck with this interesting case. -
"Like the angled rocker idea but compliance might be an issue"
Its not that noticeable and the pressure relief for the client will amaze you both.
We use this method where needed, one client we were able to allow a 3 year old pressure wound over the navicular to heal, just by reducing the pressure/force used to move the foot through the propulsive phase of gait, which for her is just proximal of her 1st MPJ.
The client is so effected by arthritis no change of the joints position was possible.
l would post a pic of the feet up, but both my tech adviser are studying for exams at the moment......i hope :hammer:hope -
Are you saying that the abducted hallux will put more foot in a more medial position relative to the STJ axis. The assumption is that there is significant amount of force on the hallux for a significant amount of time. I'm not sure that you are getting that much movement of the center of pressure with abduction of the hallux.
Regards,
Eric -
Cheers Dave -
At heel contact, with the foot abdcuted from the midline the anterior to posterior shear will be on the posterior heel which would tend to be closer to the mdiline of the body than the leg so there would be an eccentric force tending to internally rotate leg at this point in time. However, this would change after forefoot loading. At that point in time there will be anterior to posterior shear on the forefoot and the heel. It would be hard to say what the next internal or external moment on limb would be.
Interesting to think about, but so many variables.
Regards,
Eric -
This vertical force graph shows total force (Red), heel force (thin red), forefoot force (blue), 1st MPJ force (green), hallux force (purple). I would say that braking ends at about 425ms of the 800ms stance phase. The fore foot loading is quite significant if you consider the forefoot has a longer moment arm than the heel. In fact at this time CoP is just behind the 3rd MPJ and max pressure is over the 2nd MPJ.
If we consider this diagram then it can be imagined how the moments about the STJ and ankle joint might be. (assuming experienced based proportional relationship of horizontal to vertical forces) Like you say its all interesting speculation. (oh! and the point of application of the forces in the diagrams is the same as the vertical CoP position for that time and the dashed arrow in the 3D diagram is the GRF vector pointing 12dgs lateral and 35dgs posterior.)
Cheers Dave -
It would be an unusual gait that would still have force from the ground being from anterior to posterior after heel lift. The time you describe is right about heel lift as the heel forces are close to zero. So, the a-p forces should be close to zero at this point in time (425ms).
Cheers,
Eric -
Eric
Oh yes made a bit of a faux par there, you are quite right about the horizontal forces at 425ms, in my casual haste I confused the issue. The End of braking is at around 425ms but the CoP position I should have showed was at 325ms which is about 20mm posterior to the 425 position. At this position the GRF forces I assume would be about right. The principle remains the same tho in my opinion.
My main point was that the foot that is toe out in placement will tend to have GRF that tend to externally rotate the foot and so cause a relative internal rotation of the tibia, this coupled with the braking forces will tend to pronate the foot more than a foot placement that is straight ahead. Also that abducting the hallux (away from the foot midline) will add significant supination moments about the STJ.
From what you have said it seems that you disagree with this synopsis and considering your reasons for these proposals is useful in consideration of orthotic design for my patient, which was the purpose of this thread. Thanks Eric and all.
All the best Dave
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