Clive,

Sorry to be very brief but today's activities include work, funeral, and our
first day of baseball all star practice.

You wrote:
>  For me rearfoot varus is:
>
> " . . .when a bisection of the heel is inverted relative to the ground
when
> the subtalar joint is in neutral and the subject is standing in the angle
> and base of gait."

The above is called the neutral calcaneal stance position.  It does not take
into consideration the relationship between the calcaneus and the tibia.
While the above example indicates an inverted neutral calcaneal stance
position, it is not necessarily a rearfoot varus.  If the distal 1/3 of the
tibia was parallel to the calcaneal bisection then there would be no
rearfoot varus but there might be a tibial varum resulting in an inverted
NCSP.  I think you need to bisect the distal 1/3 of the tibia and measure it
to the angle of the bisection of the posterior surface of the calcaneus.

The neutral position can be determined in different ways.  The mathematical
or calculated neutral is based on the 1/3 pronation to 2/3 supination
relationship of the frontal plane motion of the posterior calcaneal surface.
This requires the ROM, not position.  You can also measure the angle of the
calcaneus to the distal 1/3 of the tibia in a non-weightbearing situation
(patient prone) and compare it to the NCSP relative to the tibia.

Example: 3 degrees of tibial varum, STJ inversion 16, STJ eversion 8, 3
degree inverted NCSP:  In this case no rearfoot varus but the patient does
have an inverted NCSP.

I don't know how we can differentiate a true subtalar joint varus from a
rearfoot varus (calcaneal varus torsion) since all we have to measure is the
posterior surface of the calcaneus and that is our only form of reference.

Respectfully,
Jeff Root

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