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'Root' vs 'sagittal plane facillitation' models

Discussion in 'Biomechanics, Sports and Foot orthoses' started by lally, Jan 4, 2006.

  1. lally

    lally Welcome New Poster

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    Hi all,
    can anyone offer me a bit of advice, I am a second year student, training as a podiatrist. I would like to appear that I know something about biomechanics, (but thats a another story) in fact I am totally useless. I just can not seem to grasp the topic, its just not sinking in this blob of a brain that I have got. I would like to go into my class tomorrow and astound my peers, with the sagittal plane facillitation model and argue why it is a more up to date theory than the Root theory, but dont know where to start. Please can someone HELP ME. I have read both theories but my problem is I can not start an argument to save my life. Please save me.
  2. Craig Payne

    Craig Payne Moderator

    Check this thread:

    Here are our lecture notes for students:

    I would not say one is more up-to-date than the other. They are both simply theroretical frameworks through which to interpret "facts" ... one as a framework is just more recent than the other.

    For eg. Take a political "fact" ...say the unemployment rate is 3.6% of the workforce. The conservative/right wingers interpretation of the fact is very different to a liberal/left wingers interpretation of the same fact. They will never agree, but the fact of 3.6% stays the same. Take the role of women in the workforce --- a Marxist has a very different interpretation of that to a feminist (Marxism and Feminism are nothing more than theoretical frameworks).

    It is the same with different theoretical approaches in "podiatric" biomechanics (whatever that is) ... a "Root" theory interpretation of a fact may be different to a "sagittal" theory interpretation of that very same fact (though they may not be).

    For example, a simplistic eg is that there is no doubt that functional hallux limitus exists --- but Mert Root talked about that in Vol 2, but as being secondary to excessive pronation of the rearfoot. A Sagital theory approach to this "fact" of FHL is that the FHL is primary and the cause of the reafoot pronation. ....make sense? ... start your arguments with this.
  3. You will probably not begin to "know something" about biomechanics until you can correlate your studies with the observations made on numerous feet of numerous patients. Don't worry, when I was a 2nd year podiatry student, I didn't really know a whole lot about biomechanics either, even though I probably knew more than 99% of my classmates at the California College of Podiatric Medicine.

    And, if you want to try to understand foot biomechanics and the mechanical basis behind foot and lower extremity injuries, I would suggest you would do better at trying to understand the complexities of foot biomechanics from theories that are based on the well-established laws of Sir Isaac Newton and the physics principles currently being taught in engineering classes around the world. The theory that I am currently teaching is one that I have coauthored in an unpublished book chapter with Dr. Eric Fuller titled "Subtalar Joint Equilibrium and Tissue Stress Approach to Biomechanical Therapy of the Foot and Lower Extremity". I am hoping that this book will be published within the next 6 months.

    In addition, both Craig Payne and Eric Lee have done nice review articles on the various theories of foot function, which may give you a better perspective on different theories than what you have mentioned in your posting.
  4. footdoctor

    footdoctor Active Member

    hey lally


    Like Craig and Kevin say it is impossible at this stage of your learning to jump straight in to complex biomechanical theorum with out a solid understanding of foot mechanics.

    I know in my 2nd year I tried to skip the basics and I've spent years back tracking.

    If it's really your thing and your interested in biomechanics I suggest you go back to the fundementals.Know your anatomy inside out!

    It will save a whole lot of confusion and mistakes clinically,believe me.

    But in short,you can never disregard or try and compare the work of root et al and danenberg.

    I guess the main difference is that danenberg believes that if a blockage of hallux dorsiflexion occurs due to a blockage of 1st ray plantarflexion then flexion to propel you forward must come from one of the other joints,the ankle,knee or lower back and this excessive flexion can cause overuse injuries to the affected tissue.
    Dananbergs main theory is called Function Hallux Limitus,where the hallux is unable to dorsiflex when the foot is weightbearing,but has an avaliable R.O.M nonweightbearing.This is usually caused by excessive S.T.J pronation which causes the M.P.J to 'JAM UP'.The facilitation model really means allowing the hallux to dorsiflex sufficiently during propulsion.To do this you must control the excessive s.t.j pronation and subsequent arch collapse which causes the 1st joint to lock up and not restricting the plantarflexion moment of the 1st met by placing a hard plastic shell underneath it.

    A root device would likely remove extra shell material from the 1st met bisection to allow the 1st met to plantarflex, a danenberg device would have a 1st ray or met cut out and a functionl hallux limitus accomadation padding added to the forefoot area.

    This pad extends from the distal margin of the plantar shell extends to the sulcus.The material is usually either a cork or eva material with a area cut out where the 1st met would sit.This area is filled with a compressive material such as poron or plastazote.This pad will load the lateral aspect of the forefoot to take the pressure of the 1st and the soft addition will allow normal 1st plantarflxion and subequently hallux dorsiflexion to give an adaquate push off.

    There is probably little difference between the hindfoot concepts of root and danenberg the main difference is that dnanbergs main theoary looks at getting the hallux to work properly by offloading the 1st mpj.

    Look at it this way too, if you plantarflex your hallux(try it) get one of your friends to look at the position of your heel as you do so.You will notice that the heel inverts.(this is cos the old windlass mechanism is coming into play)Therefore it could roughly be said that allowing the mpj to platarflex and the hallux to dorsiflex again in a pronated foot type will reduce the pronation at the stj that may have been seen in the propulsive phase.

    I have tried here briefly and very incompletely to try and let you understand one of the key differences betwen the models.

    Its late though,apologies for any mistakes.

    Good luck.

  5. gendel99

    gendel99 Active Member

  6. Craig Payne

    Craig Payne Moderator

    Sorry, we no longer put our lectures in the public domain.
  7. Rob Kidd

    Rob Kidd Well-Known Member

    Kevin, for once I totally agree with you. My mentor (Professor Charles Oxnard) loves to tell the story about the time he attended a course at The University of Salford (UK) in the 60's. In those days Salford was renowned for its engineering. All the others were there with there "box girder bridges", or whatever. He was there with his bag of still bloody bones from the butcher. Start with Newton and work up - we agree. Rob
  8. Rob:

    Wrote that posting well over 6 years ago.......the chapter still hasn't been published...:craig:

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