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Reliability of clinical biomechanical assessments

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Admin2, Jun 21, 2012.

  1. Admin2

    Admin2 Administrator Staff Member


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    Inter-assessor reliability of practice based biomechanical assessment of the foot and ankle
    Hannah L Jarvis, Christopher J Nester, Richard K Jones, Anita E Williams and Peter D Bowden
    Journal of Foot and Ankle Research 2012, 5:14
     
  2. wdd

    wdd Well-Known Member

    Nothing new here then.

    Lets play a little game.

    Assume that each subject was symptomatic and that following each examination each podiatrist individually prescribed ortheses.

    Of all the different orthoses prescribed, based on a broad range of different results, what percentage do you think (gut feeling)would imrove or resolve the symptoms, based on your experience?

    I'll suggest 70%.

    What do you think?

    Actually it's not worth the effort.

    We already know that if you forget the examination and just let the patient select a pair of comfortable over the counter 'orthoses' that the 'cure' rate will be very high.

    Maybe it's just not an exact science, ie a few degrees here or their doesn't make much difference?

    I'm in the Rob Kidd school of biomechanics where the guiding principle is "Do something different", ie in an 'expert' way.
    I hope I am not misrepresenting Robb in the above statement but if I am I am sure he will let me know.

    Bill
     
  3. We did some research on the same subject from a decade ago. Chris Nester and I will be having a chat today in Manchester at the hotel and I will see if Chris has anything more of interest to say about this research.

     
  4. David Singleton

    David Singleton Active Member

    Do many people still use relaxed calc stance to devise an orthotic prescription? I thought it was all about using the 'force' these days! Tissue stress theory and all that. Jacks test and Supination resistance test and transverse plane axis location of the subtler joint.
     
  5. blinda

    blinda MVP

    **** my hat I never knew that, our Dave. I need to swat up on my anatomy.

    ;)
     
  6. We need to stop thinking about foot orthoses in terms of posting angles. It is the entire geometry of the device which is important; that and it's load/deformation and frictional characteristics. The belief that there should only be one solution to the patients problem based on achieving the exact "correct" posting angle of a device is lunacy.

    That said, it is possible that "a few degrees here or there" could hypothetically be the difference 'twixt success and failure in foot orthoses therapy:

    1) If we have a zone of optimal stress (ZOOS) for our target tissue, then the orthotic device might be assumed to be successful if we place the tissue which was previously functioning outside of its ZOOS somewhere within its ZOOS via our foot orthoses, allowing the tissue to heal.

    2) When we do this we don't know exactly where the tissue lies within it's ZOOS due to our orthotic intervention; it could be smack bang in the middle or right on the border of it's upper or lower limit, yet all would result in a positive outcome. All we know is that our orthotic has placed the tissue somewhere within it's ZOOS (or not, if we don't get a positive outcome)

    3) If the orthosis places the tissue somewhere near the middle of its ZOOS, we can probably change the orthotic posting by "a few degrees here or there" and the patient will still get better since the orthotic variations all still place the tissue somewhere within its ZOOS.

    4) However, if our orthoses puts the tissue only just within it's ZOOS, then small changes in the prescription might just tip the tissue outside of its ZOOS and result in therapeutic failure.
     
  7. Much wisdom here.

    We still tend to think in terms of the right thing, as opposed to one of the right things.
     
  8. That said, within the solution set, some will be more optimal than others. Finding such optimal solutions is "the real trick"- right, kid?;) This is where our understanding of the kinetic interaction between foot orthoses variables and the foot come into play. A good starting point for the student of foot orthoses therapy should be to list all of the different prescription variables they can think of, consider how manipulating these will influence the 3 primary foot orthoses variables (geometry at foot-orthosis interface, load/ deformation at foot-orthosis interface, frictional characteristics at foot-orthosis interface) then consider the kinetic effects these might have on the distribution of reaction force magnitudes across the foot-orthosis interface and viz. centre of pressure position (I know it's not a full vector analysis, but centre of pressure is pretty easy for everyone to understand, and should provide a reasonable starting point).
     
  9. wdd

    wdd Well-Known Member

    If a tissue is injured will the range of its ZOOS be narrower and its upper and lower limits reduced? Could it be that in some cases the range might be so narrow and the upper an lower limits so low that, until there is some healing the ZOOS could be zero, ie total rest is required?

    As the tissue heals the range and the upper and lower limit of ZOOS increases.

    With continued training the the upper and lower limit if ZOOS will continue to increase towards some upper limit.

    What I am saying is that there is no single ZOOS for a tissue, it is a dynamic range and depends upon the 'health ' of the tissue. Also the ZOOS for one part of the same tissue might be very different from the ZOOS of another part of the same tissue.

    How would that relate to 1 to 4 above?

    At this time, is the only way of knowing you are outside the ZOOS 'OUCH'!

    Is it currently possible to put a number to a ZOOS? If not can you envisage it becoming possible? What would need to change to make it possible?


    best wishes,

    Bill
     
  10. :good: Bill, those are the best questions I have been asked here in a long time.

    I terms of range, I suspect your contention is correct in that the range will be reduced in a dysfunctional situation. Perhaps, this is one of the reasons the injury occurs in the first place. Clearly, if we have an injury of sufficient magnitude the ZOOS could be zero, in that the tissue cannot develop any strain within it what-so-ever in relation to the stress applied- think Achilles tendon in complete rupture. I used to give a lecture on how the load/deformation of the tissue change with time after injury- I'll see if I can find the powerpoint.

    Certainly healing and training should influence the breadth of the ZOOS.

    ZOOS is indeed dynamic and changes dynamically.

    Regarding "Ouch" as an indicator- its probably the most easily accessible indicator, but obviously if we are seeing things like atrophy of muscle, this may be an early indicator.

    You could put SOME numbers on ZOOS, but probably not get away with it in-vivo or ethically. If we chopped off your leg right now and put the various tissues straight into a materials testing machine we could get reasonable values for the upper limits of the ZOOS, for you, today. The only way you could do it in-vivo, is to use materials testing data obtained as above and then employ CT / MRI data to get an anatomical make up in terms of size etc. then use finite element modelling (FEM) to derive an approximation- it would only be an approximation though, but reasonable for the upper ZOOS. Deriving lower limits of ZOOS should be more tricky and we probably need to look to the research NASA has performed in reduced gravitational fields and animal studies of immobilisation. Again, we could use FEM to model this.

    Cheers for the interesting questions :drinks
     
  11. Rob Kidd

    Rob Kidd Well-Known Member

    I am currently dragged out of retirement and back at work, and I even get quoted in Pod arena! Bill, let us be quite clear. What I have said on several occasions, is that skin line measurements are a nonsense for two reasons. First, as quoted above, their reliability is rubbish. Second, and perhaps more importantly, they tend to replace cognitive processes - people stop thinking. I have always urged students to think ctitically about the issues in front of them. I make the assumption that the world has moved on from the nonsense of 1/3 - 2/3 ratio calculations, but this was a classic example of "cognition replacement theory" - never mind the other arguments.
     
  12. BEN-HUR

    BEN-HUR Well-Known Member


    Two exceptionally well articulated posts on the subject matter (as well as Simon's follow-up response to the above).
     
  13. Brian A. Rothbart

    Brian A. Rothbart Active Member

    Dear Rob,

    Nice to have you back (out of retirement).

    If I remember correctly, you published a paper of regarding forefoot varum (Forefoot Varus: real or false, fact or fantasy, 1997).

    Please correct me if I am mistaken: from an embryological point of view, forefoot supinatus is linked to calcaneal supinatus. That is unwinding of the calcaneus, takes with it, the embryological lateral column of the foot. Unwinding of the talus, takes with it, the embryological medial column of the foot.

    That being said, in the sequential ontogenetic development of the foot (distal to proximal), forefoot supinatus (forefoot varum) can only exist if the calcaneus is in supinatus.

    • That is, if the ontogenetic development of the foot stops when the heel bone is in supinatus, the entire forefoot may be in supinatus.

    • However, if the ontogenetic development of the foot stops when the calcaneus has totally unwound but the talus is still in supinatus, then only the embryological medial column of the foot remains in supinatus (e.g., navicular, medial cuneiform, first metatarsal, proximal phalange and hallux).

    That being said, and if correct, than the notion of forefoot varum, from an embryological point of view, is highly improbable, if not impossible.

    In 2002 I suggested that a abnormal embryological foot structure can exist where only the medial column of the foot remains in supinatus. I termed this foot structure Primus Metatarsus Supinatus. Also, I suggested that another more severe structural embryological deformation can occur if the ontogenetic development of the foot stops when the heel bone is still marginally in supinatus. I termed this foot structure the PreClinical Clubfoot Deformity. (A more severe calcaneal supinatus can be referred to as a Clubfoot Deformity)

    You can read more about these foot structures on my research website at :
    www.RothbartsFoot.es

    with regards,
    Brian R
     
  14. Rob Kidd

    Rob Kidd Well-Known Member

    It is late, and I am tired. It is clear that a comprehensive reply is required of me; tomorrow.
     
  15. PodAus

    PodAus Active Member

    Where's the data on reliability of prescription variables;
    (Supination Resistance,
    Windlass resistance Force,
    Lunge Test,
    SALRE
    etc.)

    vs. FFO design features

    vs. outcomes

    Gotta be high...
     
  16. Rob Kidd

    Rob Kidd Well-Known Member



    I am not sure how much help I have been; I suspect we are not coming from the same place, so to speak.

    Kind regards

    Rob
     
  17. Brian A. Rothbart

    Brian A. Rothbart Active Member

    Dear Rob,

    We may not be coming from the same place, but I believe we may well be headed to the same place (different spokes on the wheel all leading to the same hub, so to speak).

    For the past thirty years or so, I have been convinced that identifying the cause of abnormal pronation lies in isolating and delineating the variances in the ontogenetic development of the embryo which can result in abnormal congenital foot structures. I believe it is these abnormal congenital foot structures that force the foot to abnormally pronation.

    For the past 30 years or so I have been researching a plausible link between abnormal foot pronation and the development of chronic musculoskeletal pain. I have developed a theory that suggests the way the foot moves produces patterns of stimulation from the embedded plantar mechanical receptors in the skin. These patterns of stimulation provide information to the cerebellum, moment to moment, where the body is in space. From this information, the cerebellum makes adjustments in the posture to maintain balance. If these patterns of stimulation are skewed (e.g., the foot is abnormally pronating), the cerebellum acts on these distorted signals resulting in a distorted posture. In time this distorted posture results in chronic muscle and joint pain.

    I mention all this, because your publications have provided me with much 'food for thought' (no flattery intended, just factual).

    I believe the degree talar torsion present at birth has a great deal to do with the structure and functioning of the foot. I say this based on my surgical experience, my research and the research done by an orthopod by the name of Daniels (1966 Jour Bone Joint Surgery, Am). Daniels found a direct correlation between the varum alignment of the talar neck and the horizontal plane position of the forefoot (in vitro study using 12 cadaver feet).

    True, this rearfoot to forefoot relationship he described, is transverse plane relationship. What I am suggesting is that the valgus torsion of the talar head determines, in large part, the frontal and sagittal plane position of the entire embryological medial column of the foot. I first observed this talar head to medial column relationship while I was a performing triple arthrodesis (some 30 years ago). I observed that the position I fused the subtalar joint, impacted the sagittal plane position of the forefoot. That is, the sagittal plane position of the talar neck and head, in large part, determined the sagittal plane position of the first metatarsal and hallux.

    My research over the past many years has extended my vision where now I believe it is the torsion within the head of the talus that determines the sagittal and frontal plane position of the embryological medial column (See: http://rothbartsfoot.es/TalarHeadUnwinding.html).

    An interesting study was done by Cummings et. al. at Georgia University (Physiotherapy Research International, 1997). He set out to see if he could reliably measure the foot that resulted from this theorized talar torsion (a foot structure I termed Primus Metatarsus Supinatus and described as an abnormal embryological foot structure - Bodywork and Movement Therapies, 2002 - a peer reviewed journal). His study and conclusion was as follows:

    Study: Thirty-two volunteers, 18 females (mean age 38.9 ± 15.3 yr) and 18 males (mean age 44.8 ± 20.6 yr) participated in the study. Four examiners performed repeated forefoot measures on both feet using the weight bearing technique during two test sessions separated by a week. Intrarater and interrater reliability (ICC (3,1)) ranged from 0.90 to 0.95 and 0.87 to 0.94, respectively. Day-to-day reliability (ICC (1,1)) ranged from 0.84 to 0.88 for all measures.

    Basically Cummings found that this foot structure could be easily and accurately measured with high Intrarater and Interrater reliability.

    The ontogenetic development of the talar head may well continue to develop until adulthood. To date, I have read of no studies to confirm this, quantify this, or reject this premise.

    I have read, with a smile on my face, your loud and clear statement that both forefoot varum and forefoot supinatus are fictitous, simply does not exist. However, in one point you are wrong. There is another person who has the balls to say this, me!

    It is good to hear from you.

    with best regards,
    Brian
     
  18. JB1973

    JB1973 Active Member

    is there any great research on the intra-assessor reliability? or is it much the same story.

    cheers
    JB
     
  19. NewsBot

    NewsBot The Admin that posts the news.

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