Lowering the lateral column in the cast for foot orthotics

An untapped oil well, in other words

 

Be good to play with some real feet lift the lateral column and look at the effect insertion at the PL - anyone doing any dissection work or can get there has on a limb where the PL is exposed or got a cadavier/gait model hanging around ?

 

Wait a minute, I'll check the shed. Its been a bit whiffy in theres so there might be a few dead people I'd forgotten to bury!

Failing that, what about if I walked over a pressure mat a few times, then stuck a felt blob under my cuboid and did it again to see about the ORF and whether it reduced the GRF lateral forefoot.

It would be barefoot and N=1 but I know a man with a pingogram. If we get time and I smile sweetly at him he might let me play with it.

 

Ask he of the pingogram but the information while of great benefit to the discussion overall re ORF - GRF and COP changes , may not help with the PL issue, but I think Eric maybe right and me wrong again. Even if there is a tension change would it be strong enough to have a biomechanical effect? Kinetic but Kinematic ?

Ps if he of the pinogram is feeling good and lets you play abit, why not start distal 1st, then increase the pressure under the Cuboid re Craig T post and see what happens to the GRF and COP.

N=1 with pinogram is better than me taking a scapel to the next patient and saying this might hurt a bit , but I need to check something out.

 

This is why I made the statement about what proximal joints are doing impacting the outcomes of the change in casting technique or use of lateral wedging.

When I manipulate the ankle joint, the proximal fibular head at the knee and the lateral cuneiform in the foot I am attempting to increase range of motion in the ankle joint and allow the lateral column to be positioned so it will articulate more appropriately with the medial column thereby stabilising the medial column.

The reason I think that these techniques combined facilitate Peroneus Longus activity and probably more appropriately timely tension of the peroneus longus is that with an increase in ankle joint DFion range of motion during the middle to late midstance the fibula will move upward some, maybe 4mm. This should allow passive tension to the Peroneus longus pulling the medial column against the properly positioned lateral column in late midstance as the heel begins to fully off load and the fascia kicks in to supinate the foot at the STJ.

To me this makes perfect sense. You can cheat around the AJ DFion motion thru use of heel lifts on the pronated side, provided you add an equal amount to the short limb side as well, ie patient with a short limb left of 3mm, so make short limb heel lift 6mm and long limb heel lift 3mm.

I use this in both very flat feet and in patients with limited AJ DFion rom due to FF/Anterior equinus.

I think that by plantaflexing the foot at the ankle you can allow for more Dfion during late midstance and get almost the same result as from a completely successful manipulation. I find it is better to do both though.

Cheers;
Bruce

 

Your modifications/treatments may effect peroneal activity, but not because of passive tension changes in the muscle. There is very little peroneus longus tendon movement with ankle joint range of motion or 1st ray range of motion. To get passive tension you would have to be near the end of range of motion of supination of the STJ. Active tension is CNS mediated and may change with treatments.

Eric

 

How is an intrinsic forefoot valgus post different than a forefoot valgus wedge placed behind the 5th metatarsal head?

Eric

 

Eric,
So you agree With my concept accept for my terminology usage?
Fair enough I think!
Bruce

 

I'm still skeptical, but I'm giving you the benefit of the doubt.
Eric

 

That is what I have not full Sussed out for myself.

The reason I am not sure is because I cast most everyone to maximize the lateral column height, but I still have to use a lateral column valgus wedge in most but not all of these patients according to the in-shoe pressure data.

So, if they were equal then I should get the same result regardless, correct?

Now I will say that I get much more uniform pressure data when I cast this way as opposed to previous techniques. I think the technique is beneficial from an intrinsic standpoint but that wedging of the lateral forefoot is still necessary most of the time to maximize plantar pressures sub 1st mpj.

I have never compared a maximum purposeful flattened position of the lateral column to what I do now. My previous casting technique never did that to maintain the 1/3rd to 2/3rd principle in medial to lateral mid arch comparison.

Bruce

 

LOL!

I'll take what I can get in agreement between the two of us Eric!!

Cheers!
Bruce

 

It also assumes the contribution of dorsiflexion of the lesser digits to plantar fascial tension is insignificant to net moment; it also ignores the fact that digital dorsiflexion will influence the external as well as the internal moments; it also ignores the position of the joint axes in relation to said moments.

Oh, yes it isn't! Oh no...:butcher: He really is behind you. Run.....

 

Gday Bruce, ? if they're exerting a similarly directed force why the difference?

 

Since any force added to the plantar foot which is lateral to the subtalar joint (STJ) axis will increase the external STJ pronation moment, then if foot orthoses only worked by "pushing" the foot into place (i.e. direct mechanical effect), without any central nervous system (CNS) control (neuromotor effect), then we would expect forefoot valgus wedges and lateral column support from the orthosis to increase the pronated position and pronation motion of all feet during gait.

However, this is not what is seen. What I have noted for the last quarter century of doing these clinical experiments on patients and students is that, in many feet, the addition of forefoot valgus wedging or lateral column wedging may cause 1) increased STJ supination in late midstance and propulsion, 2) a longer propulsive period and 3) more active ankle plantarflexion during propulsion. This clearly indicates a strong neuromotor effect (i.e. kinetic and kinematic effects from foot orthoses which can not be solely explained by their direct mechanical effects by pushing on their plantar foot) from any lateral forefoot wedging used in foot orthoses. I have seen a profound influence on the dynamic activity of muscles during walking gait by adding forefoot valgus and lateral column wedges to orthoses over the years and believe this is one of the strongest cases for the neuromotor effects of foot orthoses.

For example, many of you have been discussing peroneus longus function and how supporting the lateral column in a higher position may or may not increase the "mechanical efficiency" of the peroneus longus. However, I believe that the lateral support on the midfoot and forefoot with a valgus midfoot/forefoot wedge has its greatest effect on peroneus longus function not by its direct mechanical effect as you have been discussing, but rather by its neuromotor effect.

This neuromotor effect is described as follows. Due to the increased external STJ pronation moment from the midfoot/forefoot valgus wedge, the CNS now senses that it has sufficient external STJ pronation moment coming from the forefoot to allow extra internal STJ supination moments from increased active peroneus longus contractile activity and increased gastrocnemius-soleus contractile activity without causing abnormal magnitudes of STJ supination moment during late midstance and propulsion.

In other words, with the midfoot/forefoot valgus wedges in place, the CNS is able to recognize that it may fire the peroneus longus and gastrocnemius-soleus complex for a longer, possibly more forceful, duration without causing supination instability (e.g. inversion ankle sprain). As a result, there are times when adding increased midfoot/forefoot valgus wedges may cause a longer duration of peroneus longus activity, cause an increase in STJ supination in late midstance and propulsion and will cause a longer propulsive period with more ankle plantarflexion. I believe this is largely a neuromotor effect, mediated primarily by the afferent input and efferent output of the CNS, and not caused primarily by a direct mechanical effect from the valgus-wedged foot orthosis.

 

Got the first two Mike - attached for you.

IG

 

Craig, I know that the foam box technique does tend to produce a higher calc inclination angle due to more compression of the material used at the heel than the cuboid, thus the need to flatten the lateral arch at times. When? I don't know. Rich