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Gravity Drive Pronation Unlevels the Pelvis

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Brian A. Rothbart, May 20, 2021.

  1. Brian A. Rothbart

    Brian A. Rothbart Well-Known Member


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    Below is a gait analysis demonstrating the link between gravity drive pronation and resulting pelvic obliquity (unlevel pelvis).

    Pelvic Obliquity.gif
    This patient has the PreClinical Clubfoot Deformity. Note the midstance pronation, a hallmark of this foot structure.

    • Proprioceptive Insoles were used to stabilize (attenuate) the gravity drive pronation (green foot arrow).
    • Note the improvement (leveling) of the pelvis (green pelvic arrow).
    Proprioceptive Insoles do not support the feet. It is theorized that they function by normalizing the distorted proprioceptive signal being sent to the cerebellum.
     
  2. Brian A. Rothbart

    Brian A. Rothbart Well-Known Member

    Below is an example of gravity drive pronation observed in a patient diagnosed with Primus Metatarsus Supinatus foot structure (Rothbart 2010)

    GA-RFS-Animation.gif

    • At flatfoot, the left foot is slightly pronated
      • the left foot motion is being driven by hip drive
    • At Mid Stance, the left foot is pronated
      • the left foot motion is being driven by gravity drive (Rothbart 1988)
      • If the left foot was being drive by hip drive, the counter clockwise transverse plane rotation of the pelvis would rotate the left foot into supination
    This is the typical gait pattern seen in the Primus Metatarsus Supinatus foot structure
    • Rothbart BA, Esterbrook L, 1988. Excessive Pronation: A Major Biomechanical Determinant in the Development of Chondromalacia and Pelvic Lists. Journal Manipulative Physiologic Therapeutics 11(5): 373-379
    • Rothbart BA 2010. The Primus Metatarsus Supinatus (Rothbarts) Foot and the PreClinical Clubfoot Deformity.Podiatry Review, Vol. 67(1):
     
  3. Brian A. Rothbart

    Brian A. Rothbart Well-Known Member

    Below is an animated (GIF) summation of the foot to pelvis shifts observed with gravity drive pronation (Rothbart 2006)

    FLLD-Full-Body-with-bAR.gif

    Right foot - gravity drive pronation:
    1. Right innominate rotates anteriorly
    2. Right acetabulum rotates anteriorly , posterior rim cephalad
    3. Right femur head shifts upward resulting in a functional short right leg (FLLD)
    4. Gravity shifts the pelvis downward right (e.g., pelvic obliquity)
    • Rothbart BA 2006. Relationship of Functional Leg-Length Discrepancy to Abnormal Pronation. Journal American Podiatric Medical Association;96(6):499-507
     
  4. efuller

    efuller MVP

    Brian,

    It is interesting that you have a picture of "gravity drive" during gait and then a picture with the body in anatomical position. This should raise some questions for the curious.

    If "gravity drive" happens on both feet at the same time, or same amount, does the pelvis stay level?

    In the picture, with the body in anatomical position, you can see how with pronation the leg becomes shorter than the other leg. However, in gait this is not a problem because, as the picture shows, pronation occurs during single leg stance, so the pelvis will not become unleveled by the other leg. In single leg stance the angle of the pelvis to the ground will be determined by the hip musculature and not the relative lengths of the two legs or STJ position.

    When I looked at this thread it was nice to see an old thread from 2008 titled Does Gravity cause pronation? Back then we discussed how saying gravity causes pronation was a mistaken idea, because gravity also causes supination. If you want to understand why a motion occurs you have to examine moments, or torques, about that joint. You can look at the force of gravity acting on the whole body as that force is applied by the tibia to the top of the talus and how ground reaction force, applied to the plantar surface of the foot can contribute moment acting on the subtalar joint. Sometimes that moment will be in the direction of pronation and sometimes it will be in the direction of supination.

    Eric
     
  5. Brian A. Rothbart

    Brian A. Rothbart Well-Known Member

    Eric,

    I used the anatomical drawing to facilitate one's understanding on how gravity drive pronation (gDp) can unlevel the pelvis (which results in a FLLD and changes in the spinal curves).

    With a PreClinical Clubfoot Deformity, gDp occurs both statically and dynamically. More frequently, than not, the gDp is asymmetrical (because the PreClinical Clubfoot Deformity is asymmetrical). It is this asymmetry that results in the distortional postural shifts that one sees statically. In the above illustration, the gDp pattern is right > left (actually only the right foot is depicted in gDp). If the gDp pattern is left > right, one would see a mirror image in the postural shift.

    Where the confusion occurs is that we need to separate with happens posturally without pathology vs what happens with pathology - they are entirely different (both statically and dynamically).

    The PreClinical Clubfoot Deformity (PCFD) deforms the posture globally (up to and including the cranial bones). The PCFD forces the body into gDp. And gDp distorts the posture (on Earth, much less on Mars).

    In a 'normal' foot structure, your comments regarding "understanding why a motion occurs you have to examine moments, or torques, about that joint" is very apropro. And I am in complete accordance with you because hip drive motion (pronation/supination) does not distort the normal moments/torques that occur about the postural joints.

    Brian
     
    Last edited: May 28, 2021
  6. efuller

    efuller MVP

     
  7. Brian A. Rothbart

    Brian A. Rothbart Well-Known Member

    What do you mean. Your question is confounding. Expand and be more specific.
     
  8. Brian A. Rothbart

    Brian A. Rothbart Well-Known Member

    Here is an interesting publication on the analysis of the torsional forces in normal (hip drive) pronation vs abnormal (gravity drive) pronation. I thought you would find this paper very interesting based on your comments regarding torsions and moments.

    Yazdani F, et.al. 2020. A comparison of the free moment pattern between normal and hyperpronated aligned feet in female subjects during the stance phase of gait. J. Biomed Phys Eng:10(1).
     
  9. efuller

    efuller MVP

    Brian,
    The whole problem with this notion of unleveling the pelvis is that your are trying to apply what happens in a single static position to the rest of a person's life. Per your description above, the unleveling occurs when a person stands in anatomical position. This does not apply to gait when a person is in single limb stance.




    Brian, I'm not sure what you are saying here. Are you trying to say that physics does not apply in some situations?
     
  10. Brian A. Rothbart

    Brian A. Rothbart Well-Known Member

    When gravity drive pronation is present:
    • The pelvis unlevels when standing (towards the more pronated foot).
    • The pelvis unlevels asymmetrically when walking.
    The dynamics are different, but the results are the same.

    In a gait study above, you can see the pelvis unleveling at midstance due to gravity drive pronation and leveling at midstance when the gravity drive pronation is decreased (using the insole). If you are interested, you can read the specifics in a paper I published in the American Journal of Podiatric Medicine (2006).

    The anatomical model was only used to help one understand the foot to pelvic shifts that are driven by gravity drive pronation, nothing more.

     
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