> > Ray wrote:
> >
> > << During what he calls 'low gear
> >  > push off' (i.e across the axis of the forefoot through metatarsal
heads
> > 2-5)
> >  > the foot was seen to resupinate, the rearfoot to invert , the leg to
> >  > externally rotate and the plantar fascia to remained 'slack'.  It was
> > with
> >  > high-gear axis propulsion (via axis of met heards 1-2) that the
plantar
> >  > fascia was seen to be under great tension. However, the foot did not
> >  > resupinate, there was no inversion of the rearfoot or no external
> > rotation
> >  > of the leg with high-gear propulsion.   >>
> >
> > Ray,
> > I would respectfully disagree with your conclusions of Bosjen-Moller's
> > findings.  He specifically notes that as the foot "shifts" to high gear,
> > that
> > the forefoot become relatively pronated as compared to the rearfoot.  In
> > other words, the rearfoot is relatively supinated to the forefoot. (His
> > choice of terminalogy is at best somewhat confusing in this paper, but
> > careful reading confirms this concept.) He also notes that in low gear,
the
>
> >
> > rearfoot is relatively inverted.  Inverted is not supinated,
particularly
> > in
> > open kinetic chain.  As the weight shifts laterally towards low gear,
the
> > entire foot inverts and the fascia is slack.  A slack fascia is not
> > advantagous to closed packing and stabilization, a fact to which
> > Bosjen-Moller makes considerable reference.  Therefore, a shift to the
> > lateral, low gear axis is not consistent with a supinated foot designed
to
> > function as an efficient, stabilized structure.
> >
> > BSS 2000 should be quite spirited!  :-)
> >
> > Regards,
> > Howard J. Dananberg, DPM
>
> I agree with Howrad on this point (as Ray knew I would). The position of
the
> heel with low gear toe off, whilst inverted, is too inverted. Furthermore,
> the Hallux plantarflexes to help stabilise the foot. This cannot be normal
> function.
>
>
> Trevor Prior

Dear Trevor and Howie,

The photo's in fig. 6 of BM paper (1979) are simply demonstration positions
and not photo's from the study.  Yes, I agree that the heel is abnormally
inverted and the hallux is abnormally plantarflexed in fig. 6b but one must
read the descriptions of BM's observations.

Bojsen-Moller describes high gear propulsion such: "...the contact area was
transferred from the heel to the medial part of the ball of the foot".  This
implies that the forefoot did load from lateral to medial as would be
considered 'normal' by many authors and therefore could be considered as
demonstrating an abnormally pronated foot. I wonder what type of COP line
this would produce on an F-Scan Howie?  I would guess something you would
consider to be abnormal. He continues: "The forefoot was observed to be
pronated in relation to the hindfoot and the lateral part of the ball was
elevated very early from the ground". I have taken the first part of this
observation to mean that the forefoot was seen to be abducted which is a
very common sign of an abnormally pronated foot. Whilst I agree that
pronation of the calcaneo-cuboid (CC) joint is required to engage the
restraining mechanism for mid-foot stability during the propulsive phase, we
must remember that the CC joint can take up a maximally pronated position
with the foot in many positions during the gait cycle, including abnormally
pronated and supinated positions. This was highlighted in the paper by
Phillips & Phillips: Quantitative analysis of the locking position of the
midtarsal joint, JAPA 73: No. 10 (1983). Due to the pronation moment created
by the GRF on the lateral aspect of the forefoot during the forefoot contact
phase of gait, the CC joint will be constantly dorsiflexing abducting and
everting to stay at end range. It's not just a case of getting the CC joint
'locked' during the propulsive phase, it is a matter of having this occur
when the foot demonstrates the most mechanically efficient osseous segmental
relationship (i.e. the forefoot to rearfoot, rearfoot to leg and rearfoot to
ground positions).  I am sorry, but the observation that: "...the lateral
part of the ball of the foot was elevated very early from the ground" is not
a description I have come across when describing forefoot contact during a
normal propulsive phase of gait! I would suggest Howie that this would also
produce an F-Scan tracing that would be classed as abnormal?  With the
lateral aspect of the ground elevated, is it possible that the pronation
moment around the CC joint created by the GRF is significantly reduced?

Furthermore, do you believe that the weight-bearing limb should be
externally rotating during the midstance-phase from opposite side toe off
and full forefoot loading to heel lift?  I think that most authors believe
that this should occur.  If you answer 'yes' to this question, please note
that external rotation of the limb did not occur with high gear propulsion
as observed by Bojsen-Moller.

With kind regards


Ray Anthony



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