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Post by davidsmith on Nov 10, 2008 19:05:03 GMT
Hi all
Just to get things stirring how about a bit of problem solving for an interesting case I saw recently.
Yesterday I saw a guy with huge size 17 feet that were severely pronated about the stj and abducted about the mid tarsal joint.(banana foot). The Talocrural joint is medially displaced and the STJ axis is medially rotated. The ankle joint is equinus when near the neutral position. The STJ rom is restricted with 2dgs inversion and 10dgs eversion on couch and a bit more in gait.
He has sinus tarsi syndrome and peroneal pain.
In gait he externaly rotates the leg and abducts the foot in an effort to clear the ground during swing phase. The forefoot is in a valgus position the 1st ray is maximally plantarflexed and the STJ is close to maximal pronation at foot strike. Also the tibia is in slight genu valgum at foot strike, heel strike tends to be on the medial side. The whole gait cycle is quite apropulsive.
I have made his Amfit orthoses with a large valgus (lateral) forefoot post extended into the met heads, plus a large 1st ray/MPJ cut out.
Why would I add a valgus post and 1st ray c/o to an already severely pronated foot and how would this reduce symptoms caused by pronation and f/foot abduction.
Happy thinking Dave
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Post by lawrencebevan on Nov 11, 2008 16:52:53 GMT
Sounds a bit like a foot-type that might have been classified as rearfoot valgus under the old-speak. Medial heel strike + genuvalgum + forefoot valgus = supination moment = peroneal contracture = pronation = sinus tarsitis  Funnily enough i believe the working practice of Mert Root would have been to take a cast and capture the FF valgus and post the orthotic with a valgus FF post. I presume that the foot movements are being accepted as finite and not improvable with mobilisation. |
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Post by davidsmith on Nov 12, 2008 17:37:24 GMT
Lawrence
Funnily enough this is just about the point of my question.
Paradigm. Using paradigm without logical reasoning.
Not that i'm suggesting you have Lawrence just that this is often how things go (in my experience)
IE;
Root - rearfoot valgus = valgus f/foot post
Kirby - medial STJ axis = increased pronation moments = don't post lateral to the axis.
I have been on courses where people keep these paradigm in their memory and roll them out when making a prescription and find it difficult to understand why they do what they do or why sometimes it might be better to do something else. They become confused when two paradigms apparently contradict each other.
I think that a custom device is one that is prescribed using logical reasoning and not just based on the fact that it is moulded to the anatomical shape of the foot and the prescription fits a certain predetermined paradigm.
In this case someone else had also looked at this mans feet and advised that an accomodative orthosis was the best that could be done and reduction in pain was unlikely. Despite detailed questioning they could give no reason for the pain other than the foot was flat and malpositioned. This, in my opinion, was either a case of lazy apathy or ineptitude or both on the clinicians part.
He was advised that the device would take 16 weeks to make, which is when he decided to come to me.
In this case the STJ is medially rotated, if it were not medially rotated would it still be possible for the dorsiflexion of the 1st ray to increase net pronation moments? IE if the STJ axis was lateral to the 1st ray then as the 1st ray dorsiflexes, the increase in 1st ray dorsiflexion stiffness would also increase the GRf acting medial to the STJ axis and so increase supination moments due to GRF.
As is often found with this type of foot the foot placement at foot strike is externally rotated due the the need to clear the ground during swing thru. This external placement also increases pronation moments acting about the STJ axis due to horizontal and posteriorly directed GRF. If the STJ axis is normaly positioned and the foot placement is straight ahead then the horizontal forces do not tend to pronate the STJ. And, if there is genu valgum this will tend to create a medially directed horizontal force that will supinate the foot.
So now the foot that intuitively should supinate due to the valgus fore foot, genu valgum and plantarflexed 1st ray, will in fact pronate quite forcefully since most of the forces acting on the foot, horizontal and vertical are acting to cause pronation moments about the STJ axis. Precise knowledge of the mechanics of this action will ensure the correct prescription. Therefore the clinician will then appreciate why you can valgus post lateral to the STJ axis and yet still reduce pronation moments aboout the STJ axis.
All the best Dave
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Post by blinda on Nov 12, 2008 17:45:18 GMT
Yup...exactly what i was going to say |
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Post by robertisaacs on Nov 12, 2008 18:42:25 GMT
Try this.
The forefoot is in valgus =>
The big toe hits the ground first=>
The 1st ray is dorsiflexed sooner and more forcefully=>
The foot loses its buttress and very probably its effective windlass (to resupinate the foot).=>
Hurty badness.
Stick a valgus forefoot post in especially with a ist met cutout you delay 1st ray loading and avoid much of the above.
Is that what you are driving at Dave? I'll admit you lost me a bit as well!
Regards
Robert
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Post by blinda on Nov 12, 2008 19:04:34 GMT
Ahh, much better thanks  Was thinking along same lines re 1st met cut out? Cheers, Blonde Bel |
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Post by dtt on Nov 12, 2008 19:23:05 GMT
Hi Rob I have just sent you photos what I think is the foot type Dave is talking about (for an Rx FOOTPRINT ORTHOTIC :-)) perhaps you could put them up here minus the Pt details ?? May help in picture form ?? cheers D  |
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Post by ianl on Nov 13, 2008 8:44:23 GMT
YES
At last!!
A Biomechanical term that has universal understanding. Well done Rob.
"Hurty badness."
Cheers
Ian
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Post by blinda on Nov 13, 2008 8:47:53 GMT
;D
I also like the way that Lawrence described;
Perhaps we could give this foot type a symbol, or refer to it as the foot type formerly known as....
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Post by robertisaacs on Nov 13, 2008 11:02:01 GMT
Its part of the Maidstone scale for biomechanical dysfunction. Still a work in progress i'm afraid. Its a two segment measure with Personal Internal Sensitivity Score which runs between "canes like a cast iron B*****d" to "ickle bit sore", and Total Anatomical Kinematic Error, which runs from "looks ok to me" through to "Seriously Fubar". Hurty badness falls somewhere in the middle.
A lot of wrinkles to be ironed out still not least the name! I was going to use the acronym for the two parts but i'm not sure tht really works.
Regards
Robert
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Post by davidsmith on Nov 13, 2008 11:48:43 GMT
Del Good idea, here's a clip of the person. Left foot is the one of most interest. Sorry its horizontal but that's how I recorded it and my video software turns it vertical but I can't do rotate thru 90dgs from the original recording. www.youtube.com/watch?v=2XIZjVSN1MIIn slow motion on a large screen the 1st ray /mpj is very low approaching foot strike. Note, since the foot is more equinus approaching the neutral STJ position, the foot is everted by the peroneals thru swing phase in an effort to assist in ground clearance of the foot. Thus the forefoot is also extremely valgus at foot strike. Dave |
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Post by dtt on Nov 13, 2008 12:16:43 GMT
Dave just a point, do you think the appearence of his toes touching the sideplate on the treadmill have had an effect on his gait ?? He seemed to adduct both feet after they came in contact. I shall now find my cervicle collar to stop the pain in my neck from studying the horizontal video ;D ;D Chees buddy D |
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Post by davidsmith on Nov 13, 2008 13:16:38 GMT
Del
Possible, but no, I've not assessed him based soley on this little vid clip, Walking on a treadmill itself often changes the gait style but in this case walking along my 10mtr walk way or outside he is still the same but its difficult to video with the changing perspective.
Just turn your laptop on its side like a book or if you have a PC lay horizontally on you left side along your desk facing the screen.
In this way you will avoidymost hurty badness of the necklode.
Dave
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Post by lawrencebevan on Nov 13, 2008 13:33:08 GMT
Looks a bit "rearfoot valgus" to me, i.e. in NCSP the heel is everted.
Basically, Well Dodgy Foot Syndrome.
Davo, hows that Amfit machine like then? Makes EVA's innit?
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Post by davidsmith on Nov 13, 2008 13:49:24 GMT
Lawrence
Amfit makes direct milled EVA orthoses from a 3D scan. Or you can make a shell type orthosis by milling a positive blank and pressing over that. Amfit are also just designing a mill that will direct mill in polyprop or nylon or simmilar from the Amfit 3D scan.
I wasn't really brought up on Root, except for the early years, so I dont use those terms so much. I think that Root is still a good system if you understand its principles in terms of mechanics without resorting to rote and strict paradigm.
Therefore I just evaluate how the foot is and how to put it right using mechanical principles, without first having the interim requiring classification of foot type to enable correct intervention modality.
Cheers Dave
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