Please can someone guide me to specific resources regarding information about
rearfoot valgus. Any other personal input would also be of much help e.g. what this condition is, why it is a rare condition, treatment, etc.
Here is something to think about.
Take a "normal foot" as defined by Root et al that stands with the heel vertical and in subtalar joint neutral position.
Now if you redraw the heel bisection 5 degrees more everted you will now no longer have a "normal foot" but will have a 5 degree "rearfoot valgus deformity" with a 5 degree "forefoot varus deformity".
If you, instead, redraw the heel bisection 5 degrees more inverted you will now no longer have a "normal foot" but will have a 5 degree "rearfoot varus deformity" with a 5 degree "forefoot valgus deformity".
Considering that the range of heel bisection error from one clinician to another clinician is easily +/- 5 degrees, this type of measurement error in not unrealistic and points to one of the main problems with the subtalar neutral theory as proposed by Root et al.
Unless clinicians can consistently measure the STJ neutral position and heel bisection relative to other clinicians, using the term "rearfoot valgus" to communicate the structure and function of the foot to another clinician is basically a useless exercise in communication futility.
Thanks for that definition of a rerfoot valgus when the STJ is in neutral. I assume, then, that a rearfoot valgus in it's compensated position includes an inverted calcaneus with over pronation of the STJ and MTJ?
Rearfoot varus occurs when the bisection of the heel is inverted to the distal third of the tibia when the STJ is in the neural position.
Rearfoot valgus occurs when the bisection of the heel is everted the distal third of the tibia when the STJ is in the neural position.
The presence of rearfoot varus or rearfoot valgus can be determined mathematically in the following manner:
1. Bisect the distal third of the tibia
2. Maximally supinate the foot at the stj and bisect the heel using palpation of the upper half of the posterior calcaneal surface, then extend the bisection line down the inferior half of posterior heel surface.
3. Maximally pronate the foot at the stj and re-bisect the heel as stated above.
Due to soft tissue movement (especially superior, posterior heel area and achilles tendon movement) the bisections will merge inferiorly and separate superiorly creating a somewhat "Y" like appearance.
4. Measure the angle of the calcaneal bisection relative to the tibia with the STJ maximally supinated and again with the STJ maximally pronated.
Here is an example of some possible findings:
Case #1: with full stj supination, calcaneal inversion to tibia = 16 degrees, with full stj pronation calcaneal eversion to tibia= 8 degrees.
Total stj rom = 24 degrees.
Neutral position occurs when the heel is parallel (0 degrees) to the tibia.
No rearfoot varus or valgus is present.
Case #2: calcaneal inversion to tibia = 16 degrees, calcaneal eversion to tibia = 5 degrees.
Total stj rom
= 21 degrees.
Mathematical neutral position 21 /3= 7, therefore the patient has a 2 degree rearfoot varus.
Case #3: calcaneal inversion to tibia = 14 degrees, calcaneal eversion to tibia = 11 degrees.
Total stj rom = 25 degrees.
Mathematical neutral position 25 /3= 8.3,
(rounded to 8) therefore the patient has a 3 degree rearfoot varus.
Case #4: with stj supination, calcaneal inversion to tibia = 16 degrees, with stj pronation calcaneal bisection remains 2 degrees inverted to tibia.
Total stj rom = 14 degrees.
Mathematical neutral position 14/3 =
4.6 (rounded to 5), therefore the patient has 7 degrees of rearfoot varus.
It should be noted that there is no method to measure the actual rom of the stj, only that motion which occurs in the frontal plane.
It is a relative measure of stj supination and pronation.
It is possible in some cases to recognize rearfoot varus or rearfoot valgus simply by observing the relative motion of the heel in the frontal plane.
Rearfoot varus is fairly common, so when you can observe but do not necessarily measure that the foot has an increased range of inversion to eversion, beyond the 2/3 to 1/3 relationship, you can assume a rearfoot varus.
Conversely, if calcaneal eversion to the tibia exceeds 1/3 then you can assume a rearfoot valgus.
Another way to determine the presence of rearfoot varus or rearfoot valgus is to bisect the heel with the stj in the neutral position and compare it to the bisection of the distal third of the tibia.
If the heel bisection is inverted to the tibia when the STJ is in the neutral position, then you can assume rearfoot varus and if it is everted to the tibia with the stj in the neutral position, you can assume rearfoot valgus.
Needless to say, it is easier to appreciate these conditions when they are extreme, especially when you factor in the margin for error.