Midfoot position, ROM and stiffness

Kevin,

I am much more familiar with the cavus foot that supinates and where the calcaneus is in varus. Until I examined this woman I had never actually seen a high, somewhat rigid arch where dorsiflexion was resistant to manual exam testing but then showed a dramatic level of arch flattening in weight-bearing and gait, medial STJ axis and obvious abrupt and high level of pronation in midstance among other clinical tidbits.

I have been doing some PT on her and while she feels dramatically improved I know that this will not last. I will do a full analysis on here in the next week and post my findings, I cut it short because I wanted to think about what I was seeing and feeling before I casted her and decided on any additions.

This is a tough case which is compounded by her sport of choice; running!

Thanks again,

 

Thanks for that Phil, that is helpful.

But this would be a shank dependant device really, wouldn't it?

Rebecca

 

Rebecca

It is really difficult to know how shank dependent the insole really is until the patient has tried it properly.
I start off by getting the insole in the shoe and asking the patient to try and flatten the arch. If they feel that this is uncomfortable or very rigid, then I remove more material until this no longer occurs.
If they then report that after running they can feel the arch more, then I know that they are loading the arch of the insole and it is being made to be shank dependent = increased ORF.
This is based on my experience of dealing with fatigue related issues with orthoses and so far seems to be helping with tolerance issues
Hope this makes sense.

Cheers

Phil

 

Wouldn't rearfoot plantarflexion stiffness occur simultaneously, same joints (TNJ and CCJ), so why wouldn't the CoP remain stationary?, thanks, mark

 

Prof Kirby, later in the thread, explains that it is the increased ankle plantarflexion moments that result in both increased forefoot dorsiflexion stiffness (and increased rearfoot plantarflexion stiffness) and the anterior displacement of the CoP; again posting before I've finished the thread, mark

 

In a typically made orthosis from cast / scan, the distal half of the 'forefoot' section would increase the deformation under load so if a reduced deformation is desirable why not have the mid-metatarsal shaft region (very approximate middle of the forefoot) as the anterior edge of the arch of the orthosis?

Wouldn't the forefoot plantarflexion moments be increased rather than the forefoot dorsiflexion moments decrease?

 

The orthosis needs to be as long and as broad to maximize its surface area of contact with the foot to reduce the plantar pressure from the orthosis (pressure = force/surface area). If the orthosis ends too short, the midfoot pressures would go up and distal edge of the orthosis couldn't support the metatarsal necks.

Don't know what you are talking about, Mark, the foot or the orthosis?

I have answered your questions, Mark. Now, here are some for you answer, to test your knowledge.

Stand in relaxed bipedal stance barefoot on the ground. I assume your foot has a medial and lateral longitudinal arch as do most feet.

1. What sagittal plane moments exist in your rearfoot from the effects of GRF (i.e. external moments)?

2. What sagittal plane moments exist in your forefoot from the effects of GRF (i.e. external moments)?

3. What internal forces, and from what structures, are present within your foot that prevents the medial longitudinal arch and lateral longitudinal arch from completely flattening during relaxed bipedal stance? What type of moments do they produce to prevent longitudinal arch flattening.

 

Kevin, why in an orthoses meant to increase the magnitude of the GRF to particular plantar surface regions of the foot would reducing the plantar pressure to regions that we wish to increase them, the midfoot, be desirable? Why do we need to support the metatarsal necks, as they?re not normally supported when no orthoses are used?



"Quote:
Wouldn't the forefoot plantarflexion moments be increased rather than the forefoot dorsiflexion moments decrease?"

I was referring to,

rearfoot plantarflexion moments

forefoot dorsiflexion moments

Passive, Plantar Aponeurosis, plantar ligaments (multiple), passive tension in the extrinsic plantar musculature (including both peroneus brevis and longus) and because the intrinsic plantar musculature have proximal attachments to the calcaneus i'd include the passive tension in them also.
Forefoot plantarflexion moments (and thus simultaneously rearfoot dorsiflexion moments)

The CNS can increase the moments by sending efferent signals to the extrinsic musculature, Posterior Tibial, Flexor Hallucis Longus, Flexor Digitorum Longus, Peroneus Longus and Peroneus Brevis

thanks again, mark

 

OK, Mark, you get the gold star today. Excellent answers!!

I would add that the peroneus brevis does not support the longitudinal arch, but the peroneus longus does. In addition, the posterior tibial, flexor digitorum longus and flexor hallucis longus also have some longitudinal arch supporting function.

Next question:

What muscle-tendon of all the extrinsic muscles of the foot makes the most turns from origin to insertion?

 

Peroneus longus; Kevin doesn't the Peroneus brevis, distal attachment base of 5th metatarsal, 'support' the external longitudinal arch?, thanks, mark

 

Peroneus brevis is a strong pronator of the STJ and a dorsiflexor of the 5th ray so I would say the peroneus brevis exerts a flattening moment on the lateral longitudinal arch.

Correct on the question - peroneus longus....you are on fire, Mark!

One last question for extra credit:

When there is a lack of normal strength in the gastrocnemius/soleus complex (e.g. spinal cord lesion, polio, Achilles tendon over-lengthening) what type of foot deformity will develop over time? Why?

 

Fibularis these days, Gentlemen, has been for about 28 years. I resisted for years, but have eventually given in. They both mean "pin", or sort of. Fibula is Latin for pin, as in a darning needle. Peroneal (Greek) means pin as in a broach clasp - a bit like a safety pin. Their view was the tib and fib together - do you see a safety pin there, trying to get out? My Greek anatomy mate tells me that the word for the safety pin of a Greek hand grenade is a peroneii!

 

Thanks Kevin, must have missed that lesson, a 5th ray dorsiflexor, locked that one away, mind like a steel trap, at least till i forget anyway ..

Whooa, definitely don't know that one either ...... they are the primary muscles for ankle plantarflexion and I think gastrocnemius is an accessory muscle in STJ supination. so forgetting the accessory role; so if the tendo-achilles was nullified (note still have plantaris) the accessory muscles for ankle plantarflexion are Tibialis posterior (why do they call PTTD PTTD and not TPTD?), FHL, FDL, Fibularis longus, and Fibularis brevis (that's going to be difficult to remember Rob Kidd) so I imagine they would be having, over time, a 'dysfunction' of their own, a form of 'talipes calcaneus'; but i'm really guessing here Kevin, and my good wife just came out and let me know 'to come to bed'. appreciate the time and effort in your attempts at educating me (and others), mark

 

Can't agree with that one, Rob. Peroneus brevis and peroneus longus have been the preferred names within the medical profession for at least three decades, used 10 times more frequently than "fibularis".

Google scholar results:

Peroneus brevis-20,600
Fibularis brevis-1,960

 

Kevin, my wife did precede that, "come to bed", comment with, "Leave Kevin alone and ...", but I'd love to know the answer and more importantly why?
Very minor point, but in my post I mentioned the Plantaris muscle, well if Gastrocnemius has been rendered 'weak' by either lack of incoming efferent signals or from TA lengthening then so would the Plantaris muscle.
Had a look at the Peroneus brevis muscle image and I'm having problems comprehending how it would dorsiflex the 5th metatarsal. the tendon approaches the base from a superior position admittedly but it attaches to the base; if it attached more distally along the shaft of the 5th metatarsal I would have no problems but to my mind I can only imagine it applying a superiorly directed force on the base, thanks, mark

 

The answer is the lack of gastrocnemius-soleus strength and/or lack of Achilles tendon tension during gait will cause a "calcaneus gait" and, over time, may lead to a pes cavus deformity with clawtoes. The increase in longitudinal arch height and clawtoe deformities are due to the deep flexors and peroneal muscles being used much more forcefully during late midstance (due to the gastrocnemius-soleus being unable to do so) to slow the anterior acceleration of the center of mass of the body during the latter half of stance phase of walking.

 

thanks, forgot about their prime purpose
I was trying to work out whether the STJ 'supinators', from the ankle plantarflexors, would 'over-power' the STJ 'pronators', from the ankle plantarflexors.
Is there a difference in power between the two groups?

 

Then you need to look at the nomenclature anatomica, about 1990. Not that I give a stuff! Rob

 

Nor do I. Have read many orthopedic and podiatric textbooks...not once did I see the peroneus longus and peroneus brevis muscles called the "fibularis". Must be the difference between the medical world and anatomists.

 

To expand on this good answer. The second best plantar flexor of the ankle is the flexor halucis longus tendon as it passes further behind the ankle joint axis than all the other extrinsic foot muscles except for the Achilles. So, if the gastroc soleus doesn't create plantar flexion moment and the FHL still can, you would expect a hallux hammertoe to develop.

The pes cavus would likely develop because of the absence, or very small plantar flexion moment created at the ankle. What keeps the forefoot dorsiflexed, is rearfoot plantar flexion moment and forefoot dorsiflexion moment from ground reaction force. Without the Achilles tension very little force can be placed on the forefoot. The muscles that cause forefoot plantar flexion moment will have much less resistance to their action when there is no tension in the Achilles.

Eric

 

Reminds me of a time back in podiatry school where the surgical faculty were making fun of students for pronouncing debridement with a long I. It's not debriiiide, that is the de bride and de groom. It's pronounced debreemaw. Sure enough the English dictionary has debridement with the long I. But, who are you going to believe your instructors in their long white coats or some book?

Isn't language fun

Eric

 

In anatomy language is everything. Apart from the need to think fourth dimensionally (ie ontogenetically, or phylogenetically), one has to get inside the words. CNV: Trigeminal - no prizes for three, but geminal? Twinned - gemini. That is, sensory, sensory, mixed. As in CNIV - the trochlea nerve; trochlea - pulley (as in trochear of the talus. CNIV is the motor supply to the superior oblique orbital muscle, whose tendon goes through a pulley. You are so right Eric, language is such fun! And the one that really cracks me up: CNIV was once known as the pathetic nerve - no kidding here - as if it was defective, the eye went "down and out"! Get it: down and out, pathetic?....................