Pseudo-dorsiflexion

Dorsiflexion is important. It is essential for proper walking and running — and even for performing a squat. Dorsiflexion is particularly crucial in children with clubfoot. Why?

In children with clubfoot, dorsiflexion indicates that the Achilles tendon and the calf muscles are functioning correctly — structures that are pathological in this condition. The Achilles tendon is naturally too short, which is why in nearly 95% of cases a percutaneous Achilles tenotomy is required (PONSETI METHOD). At the same time, the calf muscles are atrophic (read more about this in our article on PATHOANATOMY).

WHEN TENOTOMY IS NOT PERFORMED

If the simple percutaneous Achilles tenotomy is omitted, dorsiflexion will be absent or will shift to an incorrect location in the foot. This leads to a typical deformity known as a rocker-bottom foot, which has a characteristic rounded sole of the foot. This deformity is a classic mistake seen in improperly performed Ponseti treatment.

TREATMENT ERROR

Such a deformity will occur when the physician is not sufficiently familiar with the fundamentals of the Ponseti method and attempts to force dorsiflexion in a foot that has not had its cavus (C), adductus (A), and heel varus (V) corrected. If the foot has not been abducted to 60–70°, creating this deformity is not difficult. This is a classic treatment error in the Ponseti method.

WHERE DOES DORSIFLEXION AND PLANTARFLEXION OF THE FOOT TAKE PLACE?

Dorsiflexion (and plantarflexion) of the foot occurs in the ankle joint (talocrural joint) — and only there (red more about FOOT MOVEMENTS). Because the talus bone is positioned like a “block” between the tibia and fibula, and its shape is specifically designed for this motion, these movements can take place. Thanks to the fact that the talus has a so-called trochlea — a convex surface — and the tibia and fibula have corresponding concave surfaces, movement occurs through the sliding of the joint surfaces against each other.

The calcaneus also moves during dorsiflexion. When the foot is directed upward, the posterior part of the calcaneus lowers while its anterior part elevates (and slightly abducts and moves into valgus). As the back of the heel lowers, the Achilles tendon becomes tense and the calf muscles stretch.

NOT WHERE IT SHOULD BE

Sometimes the foot dorsiflexes, BUT not where it should… How? When the Achilles tendon is short, the calcaneus has little or no range of motion. This means that in the upper ankle joint there is very limited movement. As a result, the movement of bringing the foot toward the tibia shifts to the Chopart joint. We then refer to this as quasi-dorsiflexion or pseudo-dorsiflexion — these are our own original terms (not a medical).

When there is no movement (or only minimal movement) in the upper ankle joint, the dorsiflexion motion is taken over by the excessively mobile (i.e., hypermobile) Chopart joint (also known as the transverse tarsal joint), which connects the hindfoot to the midfoot. This joint is particularly important because it is responsible for:

• providing inversion and eversion movements
• allowing the foot to adapt to uneven surfaces
• transmitting loads during walking and running
• stiffening the foot during the push-off phase (when the longitudinal arch becomes a firm ‘lever’)

When this joint becomes overly mobile as a result of, for example:

• rapid correction that is inadequate for the severity of the deformity
• incorrect casting and imprecise cast shape (read more HERE)
• prolonged casting (more than 8 casts)
• skipping the percutaneous tenotomy procedure
• an unsuccessful percutaneous Achilles tendon tenotomy — although it is a simple procedure, it is not trivial (a tenotomy may fail for many reasons, the most common being insufficient correction of the foot before the procedure)
• using a foot abduction brace on a foot that is not fully corrected
• improper placement of the brace shoe, with poor attention to positioning the heel inside
• a shoe that is too large, causing the middle strap to sit at the midfoot instead of over the dorsiflexion crease (thus holding the foot down), and the heel to hang above the insole
• performing passive dorsiflexion exercises, especially pulling the foot upward by the toes toward the tibia

— this excessive mobility gives a false impression of increased dorsiflexion, while in reality it may be very limited.

HOW TO RECOGNIZE PSEUDO-DORSIFLEXION IF YOU ARE NOT AN ORTHOPEDIST?

1.

When attempting to dorsiflex the foot, the sole becomes curved: the heel lifts up, the toes lift up, and the middle of the foot stays down.

2.

The heel appears as if it is hollow inside and has a characteristic soft, rounded shape.

3.

There is still a crease above the heel, and when looking at the heel through it, one gets the impression that something under the skin is pulling the calcaneus upward on the inside.

X-RAY IS A HELPFUL TOOL

When this type of dorsiflexion is suspected, an X-ray is very helpful, BUT it must be performed correctly.

DURING THE EXAMINATION, THE ENTIRE FOOT SHOULD REST ON THE BOARD, AND DORSIFLEXION SHOULD BE BROUGHT TO THE MAXIMUM ACHIEVABLE LEVEL, BUT WITHOUT FORCING IT. THE X-RAY SHOULD BE TAKEN IN THE LATERAL PROJECTION.

WHEN CAN YOU NOTICE THAT THIS IS NOT TRUE DORSIFLEXION?

When the foot has been in the brace for some time and there is no improvement: during an attempt to dorsiflex the foot, the sole still bulges. It is difficult to assess this 2 days after the tenotomy, because the foot needs time to settle properly in the shoe. But after 2 weeks, it becomes visible.

HOW IS THIS TREATED?

Sometimes you need to give the heel time to descend on its own, verifying the bar width, the external rotation settings, and the way the brace shoes are applied. If none of the above helps, a return to casting is necessary and, optionally, a repeat tenotomy.