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Help with Possible MTSS & orthotic prescription

Discussion in 'Biomechanics, Sports and Foot orthoses' started by David Smith, May 11, 2011.

  1. David Smith

    David Smith Well-Known Member

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    Hi Guys

    Need a bit of advise regarding a patient presenting with pain along the right tibial ridge / linea. (Patient calls this shin splints) Not sure if this is MTSS as not painful along medial tibial border and since he has a lateral stj axis how I should design the posting, i.e. lateral posting might increase tibia bending stress and medial posting might cause lateral instability and inversion sprains or tendency to pronate the foot via the peroneals and cause peroneal sprain and further cause him to pronate off/over the device. I would say that the peroneals already fire early to stabilise the STJ in stance phase. Your thought appreciated please.:confused:

    My Notes

    Initial assessment - Complains of Shin splints i.e. right anterior shank pain [Poss MTSS] (NB allergic zinc oxide tape. ) Pain comes on during and after running and resolves with rest. Steve indicates pain is along anterior ridge of right tibia and not the medial tibia, which perhaps suggests not shin splints / MTSS. ??? Only tender to palpate after running.

    Bmech check, very pes planus foot type. Very pronated in stance and gait. Hallux limitus - improved by mobilisation. Ankles = good RoM, tight in hamstrings and restricted hip RoM - right hip flexion tight at about 40dgs, left tight at hip at about 65dgs. Note curve in right tibia from 1/3rd up its length from the inferior aspect curves to the left/medial and then back laterally again within the second third. Small lump on tibial ridge at the 1/3rd mark.

    Make 2D templo video and Amfit scan. Photos taken of foot posture and tibia. NB 1st MPJ cannot plantarflex to ground in NCSP both feet.

    In gait right foot toe in and knee internally rotate. NB Right Malleolar ext rotation to about 37dgs compared to left at 19dgs. Left has slight toe in gait.
    AM3 scan shows early heel lift on left but not right. Maybe intoe is compensation for Func hallux limitus but AM3 shows CoP thru 2nd MPJ and hallux. Lateral foot both left and right bears weight thru most of stance phase. Probably some dorsiflexion of midfoot left in stance but not so apparent on right.

    Lateral STJ axis both feet. No front to rear foot misalignment. Inverted STN position 6dgs right, 9dgs left. NB AM3 FTC shows flat top from early stance to propulsive phase, this is accounted for by the significant increase in midfoot forces at mid stance i.e. the midfoot bears most weight at this time and may indicate a bending midfoot (rocker). This conclusion is backed up by the increase in CoPP velocity at this stage of gait. NB COPP velocity appears slowed at the propulsive stage. NB weak left hip abductors = right hip drop.

    Pictures show still of video running
    1) late swing pre strike right
    2) heel strike right
    3) Midstance right and open chain STJ axis position left
    4) Propulsion right
    5) Hip drop comparison left and right and right STJ axis open chain.






    Many thanks for your considerations - Dave
  2. David Smith

    David Smith Well-Known Member

    Hi again

    Can only put max 6 photos so here are shod stills of running video.




    Regards Dave
  3. David Smith

    David Smith Well-Known Member

    The Force and phasing pressure mat maps and FTC graphs



    Regards Dave
  4. Dave,

    I've only briefly scanned your post but I'm guessing you've ruled out an anterior compartment syndrome with history and/ doppler study? How long does the pain persist following cessation of running?

    He might have a lateral STJ axis in static non-weightbearing exam (you might want to check yourself on this), but where is the axis during weightbearing and dynamic function? Looking at the barefoot stills, I doubt very much that his STJ axis is laterally deviated during barefoot contact periods. Supination resistance?

    What shoes is he running in?

    P.S. Think 4D

    BTW had a lad in today with pes pancake feet- I mean the flatest of the flat- navicular on floor the whole works, really high supination resistance, standing eversion height of virtually nothing. His hallux dorsiflexion stiffness was very low and windlass engaged beautifully with very low force- thought I'd video'd his jacks test on my i-phone... think again- doh.
  5. efuller

    efuller MVP

    From your info, I would put a lower degree of certainty on my diagnosis and not hang on too hard to the MTSS diagnosis. However, without anything better, start treating MTSS.

    The pes planus foot with a laterally positioned STJ axis is very rare. This guy might have one, but it may not function as one. Looking at the running from behind the heel appears to be able to get out from under the leg. That makes it seem unlikely that there is a lateral position to the axis. Also, with the high lateral load, the center of pressure may still be lateral to the STJ axis. That is what I meant by it does not function as a laterally positioned STJ axis.

    Why do you do examination measurements in neutral position? In looking at the video and Max pressure plot I would want to know how much eversion he has available in stance. Stance position will be closer to the position that he is in gait. Why the high lateral load? Is it because he has no eversion available at any joint. If he didn't that would explain the pressure picture and would lead to high bending moments on the tibia from the lateral position of the force.

    John Weed described trying to slide fingers under the medial and lateral side of the feet in stance. If you can't slide your fingers under the lateral forefoot and you can under the medial forefoot, in relaxed stance, then a forefoot varus wedge or extension might be in order to treat both the MTSS and the high lateral forefoot load.

    Again what do you do with neutral position measurements.?

    The midfoot break, easily seen in the picture with the heel off of the ground and the lateral midfoot still on the ground, is going to wreak havoc on what you would normally expect with center of pressure velocity.

    Hope this helps,

  6. Admin2

    Admin2 Administrator Staff Member

  7. David Smith

    David Smith Well-Known Member

    Ahh yes! forgot to include that in the notes above, he (my patient) also has pes pancake feet a low jacks test resistance and is fairly easy to supinate in resting stance

    Cheers Dave
  8. David Smith

    David Smith Well-Known Member

    Thanks for your thoughts Eric and Simon

    Regards Dave
  9. Dave:

    Interesting case.

    A few points are in order:

    1. This patient appears maximally pronated at the subtalar joint (STJ) during running and he almost certainly has a medially deviated STJ axis in gait, not a laterally deviated STJ axis.

    2. Medial tibial stress syndrome (MTSS) does not occur on the anterior tibial crest, it only occurs on the medial tibial border of the tibia.

    3. My best guess is that your patient is developing an anterior tibial stress reaction/stress fracture. X-rays and/or bone scan and/or MRI scan are in order if the patient is A) favoring the injured leg during his runs or, B) having pain in the shin with walking or, C) if the lump you feel on the tibia is at the area of maximum tenderness. Anterior tibial stress fractures are considered "high risk stress fractures" since they more commonly lead to non-union which may cause the "dreaded black line" to appear on the lateral tibial radiograph at the anterior tibial cortical border. Treatment of such stress fractures and subsequent non-unions may included extended rest from running (3-6 months), bone stimulators and/or bone grafting. I don't think you or your patient want to go this route.


    4. If the patient's pain does not cause favoring or limping during running and there is no stress fracture, then I would aim at trying to reduce the impact of running by the following methods:

    A. Instruct the patient to only run on softer surfaces such as grass, good-quality treadmill, all-weather tracks or soft dirt.
    B. Instruct the patient on changing his running gait toward shortening his stride length, minimizing vertical displacement and increasing stride frequency during running. This may require you to actually showing him how this is accomplished and having him practice it in your office until he seems to understand the concept.
    C. Make an anti-pronation orthosis that will be designed to allow his foot to pronate more gradually rather than rapidly pronating to the maximally pronated position during the first half of support phase of running. Using a medial heel skive, rearfoot posted, well-formed medial arch with a slight varus forefoot extension of 2-4 degreees and with an orthosis plate that will flex about 5 mm under the medial arch during the midsupport phase of running should help decrease the shock through the tibia.
    D. Make sure his running shoe is matched to his body weight and foot motion.

    Hope this helps and good luck to you and your patient.
  10. David Smith

    David Smith Well-Known Member

    This sounds like good stuff Kevin, thanks:cool:

    Pretty close / spot on to my patients symtomology

    Excellent, learnt something useful today

    Cheers Dave
  11. efuller

    efuller MVP

    STJ axis position is important because of the relative position of the center of pressure to the location of the STJ axis. The center of pressure has to be within the plantar surface contact area. So, when you look from behind and the foot contact area is lateral to the leg, chances are very high that the center of pressure is lateral to the STJ axis, or the axis will appear medially deviated. The relationship of the CoP to the STJ axis is a three dimensional one. Looking at the leg and talus relative to the location of the plantar foot will give you some idea of whether the axis is medially deviated or not.

  12. David Smith

    David Smith Well-Known Member


    My patient reports that he does not limp or favour the opposite leg when running and feels that he favoured the right leg previous to pain starting because of left knee pain previously undisclosed. Do you think that I should disregard the possibility of tibial stress fracture?

    Not quite sure about your meaning here, Just to check, do you mean the orthosis arch should be compliant enough to flex 5mm during maximum loading?

    Regards Dave
  13. Dave:

    Is it possible that the right anterior tibial border pain is due to gait compensation for the left knee pain?

    In addition, I do mean the orthosis arch should be compliant enough to flex 5mm during maximum loading. In other words, the foot orthosis for running, especially in treating running injuries that may be due to shock-related problems, should be tuned to be just stiff enough to help decelerate foot pronation a certain amount. In other words, the orthosis should not be so compliant that it allows excessive foot pronation and should not be so stiff that it prevents a normal amount of foot pronation during the first half of the support phase of the running gait cycle.

    Hope this helps.
  14. podtiger

    podtiger Active Member

    Hi Kevin,
    I've come in late on this case study which has been a very interesting one.
    I just wanted to clarify what you exactly mean by a "forefoot extension". Do you just mean a varus forefoot post of 2-4 degrees? Or does this extend distally from the orthotic shell as well?
    Thanks everyone for such an enlightening post.
  15. Tiger:

    By definition, a forefoot extension is any orthosis modification added to the plantar aspect of the topcover of the foot orthosis which is distal to the orthosis shell (i.e. metatarsal neck level). Most forefoot extensions end distally at the digital sulcus. In medial tibial stress syndrome I add a varus forefoot extension to the sulcus to the orthosis, extending from 0 mm thickness at the 4th intermetatarsal space (i.e. between the 4th and 5th metatarsal heads) and then beveled at a varus angulation to approximately 3-6 mm thick at the medial border of the 1st metatarsal head.

    Hope this helps.

    Attached Files:

  16. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi Kevin

    This is where I think, I, and some of my colleagues, have failed in the past when trying to manage MTSS with orthoses concerning shell stiffness. Apart from bodyweight, are there any other specific factors you are looking for when trying to judge the most appropriate shell thickness?

    Also, if it is possible, could you please provide a guideline of what sort of shell thicknesses you would recommend as body weight increases?

    Lastly, if a runner has a medially deviated axis, and I opt to use a forefoot vaurs extension as part of my orthotic px, wouldn't this cause a pronation moment thus potentially worsening the patients symptoms or is there something I'm not understanding here?

    Thank you

    Daniel Bagnall
  17. Daniel:

    Why would you think that a varus forefoot extension on an orthosis would increase the external subtalar joint pronation moment during running in a patient that has a medially deviated subtalar joint axis?
  18. Daniel, what you need to realise is that the thickness of the shell material is only one factor which will ultimately determine the load/ deformation characteristics of the finished orthoses. The geometry of the device will influence it's deformation under loading too. In general, higher arched shank-independent devices will be stiffer than lower arched shank independent devices, even when the shell material thickness is identical. The span length will influence stiffness too in such devices; in general the shorter the span length, the stiffer the device. The frictional characteristics/ reaction forces at the contact points between the orthosis and shoe will also influence load/ deformation characteristics too.

    Do we know how much load/deformation is the right amount for any patient? No. Can you say this patient needs an Xmm thick shell without considering the geometry of the device? No. So, it's not as simple as the patient weighs Zkg, therefore they need a shell Ymm thick.

    Ultimately, it comes down to how rapidly you want to arrest the motion and the distribution and magnitudes of the reaction forces you are trying to achieve at the foot-orthosis interface. This is just Newtons 2nd and 3rd laws of motion. But it's a complex problem. I'm not sure where Kevin gets his 5mm deformation from. You just can't be that specific nor definitive and I'm pretty sure that statement has zero evidence other than Kevin's anecdote to support it. To be honest these are the kind of statements Kevin makes from time to time that he and I argue about. Love him to bits, but every now and again he comes out with these exact numbers which are completely unsubstantiated. Indeed, how on earth do you measure the orthosis deflection under loading conditions, other than using fairly complex finite element models? You could do the orthosis deformation test which Kevin described in one of his newsletters, but this isn't going to put the orthosis under the same loading conditions that will occur in-vivo during running. Remember, 76.78% of statistics are made up on the spot! Think about it, just as navicular drop needs to be normalised for foot length, so too does orthotic deformation; 5mm deformation in the medial longitudinal arch of a foot orthosis which has a length of 150mm isn't necessarily the equivalent of 5mm deformation in an orthosis which has a length of 100mm. In my humble opinion, 5mm deformation is just a number that Kevin has been picked out of the air.

    To help you answer your question re: varus extensions and moments, think about what the varus wedge might do to the centre of pressure position, even if the centre of pressure is lateral to the axis, if it's closer to the axis with the wedge in situ (i.e. less lateral to the axis), than it is without the extension, then the pronation moment will be reduced, even though it is still lateral to the axis. This principle only holds if we accept that wedging will shift the centre of pressure toward the thick end of the wedge and ignore the vectoring effects of the wedge geometry and frictional characteristics....
  19. David Wedemeyer

    David Wedemeyer Well-Known Member

    There is a great Kirby/Spooner-esque thought experiment in Daniel's post. Just as valgus forefoot wedging will shift the COP more laterally in a medially deviated STJ axis, varus forefoot posting should accomplish exactly the opposite. Correct?

    The compliance of the orthosis is important but I should think the goal, slowing pronation moments should be the first order of business and the rest follows.
  20. Depends... The "counter-intuitive spring wedge problem" comes into play with wedged forefoot extensions... So too do frictional and geometrical influences of the wedge on the net reaction vector. Like I said, although it's just Newtons laws of motion, it's a complex problem. Would be happy to discuss it again though.
  21. I'm not sure what slowing pronation moments is, David. However, if we are discussing rate of loading, then load/deformation characteristics of the orthosis are key. I suspect it would help if you were able to reword and expand upon your statement above.
  22. David Wedemeyer

    David Wedemeyer Well-Known Member

    Simon I was responding to Daniel's question "...if a runner has a medially deviated axis, and I opt to use a forefoot vaurs extension as part of my orthotic px, wouldn't this cause a pronation moment..." I don't recall the discussion on "counter-intuitive spring wedge problem" but would love to read it.

    My point was relative to the STJ axis, which Daniel referenced I believe that two very key factors would be the spatial location of the STJ axis and ground reaction force from the medial forefoot wedge foot/orthosis interface.

    I took the liberty of quoting Kevin from his paper Subtalar Joint Axis Location and
    Rotational Equilibrium Theory of Foot Function, Page 6:

    "This consistent experimental observation thus supports the theory that any forces that act on the plantar foot while it is loaded to simulate weightbearing conditions will have a direct effect in producing subtalar joint pronation and supination moments, regardless of whether that force is applied to the plantar rearfoot or plantar forefoot.

    As I read this Kevin is illustrating that a forefoot post will change 'moments' and produce pronation or supination about the STJ axis depending on the spatial location of that patient's STJ; regardless if it is a medial skive or a forefoot post. That it is accomplished by a complex interaction of moving the STJ axis and COP more medially in some feet and possibly not at all in others correct?

    You're correct Simon. I should have said by altering the magnitude of pronation moments. I feel that these basic points about foot orthosis therapy need to be understood and addressed prior to determining the load/deformation characteristics and writing a prescription for that patient. Your thoughts Simon?
  23. I'll let the rest go for now as this is more interesting to me. How do foot orthoses change the magnitude of pronation moments?
  24. David Wedemeyer

    David Wedemeyer Well-Known Member

    The magnitude of moments are changed by altering forces via the foot/orthosis interface, specifically moment lever arms.
  25. OK, so how does a bent piece of plastic do that? Go back to first principles: what is force? Newtons second tells us that force is = to the rate of change of momentum. How might the load/deformation characteristics of a foot orthosis influence the rate of change of momentum? Hint: try walking into a lamp-post, then try walking into a lamp-post with a mattress tied around it...
  26. David Wedemeyer

    David Wedemeyer Well-Known Member

    The plastic will alter the geometry, load-deformation and frictional characteristics at the foot orthosis interface. I feel this explanation suffices when discussing how foot orthoses "work" in changing the magnitude of forces and mediating complaints.

    Simon I believe that what you are getting at is the subject of "stiffness"? Relative to it's "stiffness" you're getting into an area way beyond me Simon but I'll try and keep up. I feel that you are trying to impart something valuable to us although I admit that I am not the scientist that you are.
  27. David, all i'm trying to say is that the load/deformation characteristics of the device are quintessential. That you cannot separate the compliance of the orthosis from the goal of altering the moments. So in terms of altering the three orthoses variables, there isn't necessarily an order of business. There are just three variables which we don't really understand how to control, yet.

    If only I were the scientist I'd like to be, I'd have solved these problems by now rather than getting frustrated by them. Hey ho. By talking through ideas we can sharpen our understanding. We all play our parts in that.

    Bed now.
  28. David Wedemeyer

    David Wedemeyer Well-Known Member

    That makes perfect sense Simon, I'm with you as much as I can be on this. Orthosis compliance is a crucial aspect of the balancing act between control, function and comfort.

    I'm going to reread the "stiffness" thread. I'm sure if anyone can figure out the answers to these questions its you Simon.
  29. Daniel Bagnall

    Daniel Bagnall Active Member

    Hi Kevin

    Wouldn’t the plantar reaction force (PRF) from a forefoot varus extension cause a pronation moment arm to occur, as the PRF from a forefoot varus extension is still lateral to the subtalar joint axis (STJA)?

    In your advice you gave to, Dave, you suggested that he uses a medial heel skive, a rearfoot post and an orthotic that has a well formed medial arch. I understand that those prescriptions variables will help increase the magnitude of the STJ supination moment. I’m still not clear on how a forefoot varus extension will cause a supination moment to occur as the PRF is still lateral to the STJA in the example I’ve given.


  30. Daniel Bagnall

    Daniel Bagnall Active Member


    Thanks for elaborating on this. So even though there is still a pronation moment arm, by shifting the CoP more medially we have reduced the magnitude of the pronation moment, which is still a good thing, right?


  31. Daniel Bagnall

    Daniel Bagnall Active Member

    To everyone:

    I just wanted to clarify the goals of orthoses treatment when treating MTSS and to see if my understanding is correct. Anybody, feel free to correct me if I’m wrong.

    The 2 major likely pathological loading forces to take into consideration in MTSS are:

    1. Excessive valgus bending moments acting on the tibial shaft.

    2. Excessive tensile loading forces acting on the Flexor digitorum longus, Soleus, and possibly Tibialis Posterior.

    When designing an orthoes px we have to reduce the magnitude of the valgus bending moments acting on the tibial shaft, and secondly, reduce the tensile loading forces on the muscles/tendons/fascia that attach to the medial boarder of the tibia.

    The most useful orthotic px variables in reducing these pathological forces would be:

    1. Inverting the cast balancing position to help increase the external supination moment and to increase the medial longitudinal arch (MLA) height of the orthoses.

    2. Minimal medial arch expansion/arch fill so that that the medial arch height of the orthoses contours the MLA and to also transfer the CoP more medially. This will cause either a supination moment or reduce the magnitude of pronation moments at the STJA.

    3. A medial heel skive in order shift CoP/orthoses reaction force (ORF) more medially in order to create a STJ supination moment.

    4. A forefoot varus extension in order to shift CoP more medially, which will reduce the magnitude of pronation moments at the STJA. Depending on how medially deviated the STJA is, this may result in a shorter lever arm lateral to the STJA reducing the magnitude of the pronation moments at the STJA, or there will only be a compressive force due to there potentially being no lever arm. In both cases, CoP has been shifted medially which to me is a good thing.

    5. An orthoses shell which has the desired degree of stiffness (whatever that might be?) in order to reduce compression loads in the tibial shaft and to possibly also assist in the Zone of Optimal Leg Stiffness (Not sure if I’m correct on this last point thought?)

    As a result, by reducing the magnitude of the external pronation moments at the STJA, this will result in the following:

    1. Reduced tensile loading forces on the muscles, tendons and fascia which attach medially to the tibial shaft.

    2. Reduce valgus bending moments by aligning the ground reaction force vector with the longitudinal axis of the tibial shaft which reduces the eccentric axial loads.


  32. efuller

    efuller MVP

    Daniel, What you have to do is look at pre and post addition of the forefoot varus wedge. The assumption is that the varus wedge will shift the center of pressure medially compared to no wedge. With a medially deviated STJ axis the center of pressure will still be lateral to the metatarsal head (and still cause a pronation moment.) However, the pronation moment will be smaller than if there was no forefoot varus wedge. The forefoot varus wedge will also tend to increase force on the medial forefoot, specifically the first ray. If you want to reduce force on the first ray, then a forefoot varus wedge may not be ideal, because you may have reduced the pronation moment from the ground, but you have simultaneously increased force on the structure you are trying to reduce force. So, a forefoot varus wedge may be fine for a posterior tibial dysfunction patient, but may increase symptomatology in a patient with pain in the first MPJ from a functional hallux limitus.

  33. Daniel:

    The varus forefoot extension, when added to a foot orthosis, will shift the ground reaction force (GRF) acting on the plantar metatarsal heads more medial. As a result, there will be now a shorter pronation moment arm to the subtalar joint (STJ) axis from the center of pressure (CoP) acting on the forefoot. In other words, with the varus forefoot extension in place on the orthosis, GRF acting on the forefoot will cause a lower magnitude of STJ pronation moment than if there had been no varus forefoot extension added to the orthosis.

    When considering such things as how a foot orthosis affects the moments across the STJ axis, not only one must consider the spatial location of the STJ axis but also must consider how various orthosis modifications may shift the GRF acting on the plantar foot relative to the STJ axis. In the case of the varus forefoot extension, the medial shift in GRF in the forefoot caused by the varus forefoot extension will cause a net increase in STJ supination moment from the orthosis since it decreases the STJ pronation moment from the metatarsal heads.

    The mechanical analogy of the see-saw is very helpful in better understanding the interplay of various internal and external forces acting on the foot at any instant and how they may affect STJ moments. Remember that there are at least two ways to make a see-saw balanced with two children at opposite sides rotate in the clockwise direction: you may either increase the clockwise moments by having the child on the right of the see-saw move farther right toward the right end of the board, or you may decrease the counter-clockwise moments by having the child on the left of the see-saw move farther right toward the hinge of the see-saw.

    Here are a few of the illustrations I drew for my paper from a decade ago that may help you visualize this mechanical concept more clearly (Kirby KA: Subtalar joint axis location and rotational equilibrium theory of foot function. JAPMA, 91:465-488, 2001).

    Attached Files:

  34. It's might be a good thing if you want to reduce the pronation moment. But remember, the centre of pressure only represents one aspect of the net reaction force vector. You can have a centre of pressure which is medial to the axis, yet still have a vector which passes lateral to the axis. We tried to explain this concept here....

    Attached Files:

  35. RobinP

    RobinP Well-Known Member

    Thanks Simon, I have been looking or that for a while in my computer as I saved it somewhere random - wanted to re read it again after the summer school

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