Anything else?

The defect more often affects children from first-time and twin pregnancies, as well as in children born prematurely. As many as 25% of premature babies are affected by MTAand 13% of children born on time. If there is a case of this defect in the family, the risk of its occurrence in siblings increases to 5-10%, just as the risk of having it is higher in monozygotic twins compared to dizygotic twins. And the frequency of occurrence increases in children from twin pregnancies compared to singletons – it increases to 4/1000 births.

The inheritance of adduction of the foot is estimated at 2-4%, and 10-20% of cases have a positive family interview. The inheritance of MTA, like other foot defects, is multifactorial, which means that both genetic and environmental factors can influence the development of the deformity in the child. At the same time, having other defects in a child and additionally an adducted foot suggests some common genetic mechanism, e.g. the defect is associated with genetic mutations that lead to other congenital defects. Therefore, it is the result of another syndrome. Such a foot often occurs in combination with a sequence or syndrome.

MTA can be correlated with other defects. And so we can find it in combination with other foot defromities in infants and children. About 10% of children also have hip dysplasia or cervical torticollis on the side of the foot with the defect.

Sometimes, the hypotheses of abnormal structure are supplemented by excessive activity of the tibialis anterior and posterior muscles in relation to the weakened peroneal muscles. Incorrect attachment of the tibialis anterior, posterior and adductor hallucis muscles is also discussed as a cause of malposition of the foot, of which excessive activity of the adductor hallucis muscle is considered significant. Bone deformities, e.g. abnormal shape of the middle cuneiform bone, and even bone malformations in the form of absence of the bone of this bone or blockage of natural ontogeny also constitute a hypothesis of anomaly.

MTA vs CLUBFOOT

MTA is easy to distinguish from clubfoot or serpentine foot (skewfoot), because in adduction of the forefoot we are dealing only with disorders of the forefoot and in one surface, and the hindfoot is completely correct – the calcaneus is positioned neutrally, similarly to the talus, the Achilles tendon is not shortened, and the calf muscles are fully anatomically correct. Clubfoot is a very complex foot deformity, three-plane, and pathological changes in the soft tissues in the lower leg and foot cause changes in the positioning of the bones, including their anatomical changes. In clubfoot we have 4 overlapping components of the defect hidden in the acronym CAVE:

• C – cavus – an increased height of the vault of the foot
• A – adductus – adduction of the foot (adduction of the front of the foot occurs in the Chopart joint, not Lisfranc as in adduction of the forefoot)
• V – varus – heel varus
• E – equinus – equine position of the calcaneus

The Bleck stiffness assessment involves determining the deviation of the forefoot in relation to the heel bisector line. The HBL (heel bisector line) is a line running along the sole of the foot, leading through the middle of the hindfoot and dividing the heel into two parts (line in the image below). In a healthy foot, it runs between the second and third toes (Kite’s AP calcaneal-talar angle is 15-25 degrees) and is not equivalent to the long axis of the foot (which runs through the middle of the second metatarsal bone, i.e. the second toe). The level of advancement of the deformity is determined based on the deviations of the forefoot in relation to the HBL.

• normal – The HBL runs between the second and third toes
• mild – HBL runs through the third toe
• moderate – HBL runs between the third and fourth toes
• severe – HBL runs between the fourth and fifth toes

Between 87 and 90% of cases of flexible MTA resolve spontaneously without the need for any future treatment, which also means that 10-13% of cases will not self-correct and will need to be treated before the child starts walking. MTA is the only foot deformity that can resolve spontaneously under weight-bearing. However, at the beginning, when the child is small, we are not really able to determine WHICH patient will „self-correct”, so regardless of the severity of the deformity, every child with adduction should undergo treatment (UNFO/casting).

It happens that the deformity is not recognized quickly (after birth) and „appears” only when the child begins to stand up and put weight on its feet, i.e. under the influence of body weight. It also happens that the defect is recognized, but inadequate treatment is implemented, so we waste time.

The flexibility/correctivity score is graded according to the ability to achieve passive forefoot abduction while stabilizing the hindfoot (appropriate pressure should be placed on the cuboid bone with the heel in a neutral position) in relation to the HBL.

• flexible – passive movement is possible until the foot is re-corrected (forefoot abduction)
• partly flexible – passive movement is only possible up to the heel bisector line of the foot
• rigid/ fixed – there is no possibility of abduction of the front of the foot

When treating forefoot adduction, the end result classified as a „corrected foot” is when the HBL runs between the second and third toes.

What is not MTA?

There are defects that „resemble” adduction of the forefoot, but in reality they are not. For example, we are talking about hallux varus, which can confuse specialists. In this deformity, only the first ray is adducted, i.e. the big toe is directed inwards more than the others. Hallux varus, however, can also be the result of another deformity called epiphyseal bracket – which is a rare deformity of the first metatarsal bone. The bone is „trapped” in a cartilage basket, named bracket and has the shape of a trapezium/delotoid. This deformity always requires surgical intervention.

In-toeing, or turning the big toes inward (pigeon toe) or the entire feet when the child walks or runs, is not adduction of the forefoot, but may be its result. Rarely observed in children under 3 years of age. In the vast majority of children under 8 years of age, the defect will resolve spontaneously without the use of a cast, orthopedic equipment, surgery or other special treatment. The disorder itself does not cause pain or lead to major orthopedic complications. In-toeing can be considered a normal developmental stage that usually resolves spontaneously with age.

Internal Tibial Torsion (ITT) is a condition in which the tibia is twisted inwards relative to the body’s axis. In newborns, internal torsion is from 0 to 5 degrees, but in children aged 1-3 years it increases to 10-15 degrees. ITT is a phenomenon that is a certain stage of shaping the lower limb and is natural and physiological, however, a normal consequence of ITT is turning the foot inwards during walking. An important note here: the entire foot follows the position of the tibia, not just its front.

Increased hip antetorsion, i.e. the angle between the axis of the femoral neck and the transverse axis of the hip joint causes the leg to be positioned inwards. The value of this angle changes with age and has a significant impact on the biomechanics of gait and body posture. Changes in the antetorsion angle are a natural process resulting from the biomechanical development and structural adaptation of the femur to the verticalization of body posture and gait.

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Studies:
1. Bleck E.: „Metatarsus adductus: Classification and Relationship to outcomes of treatment” (1983)
2. Hunziker U.A. et al.: „Neonatal metatarsus adductus, joint mobility, axis and rotation of the lower extremity in preterm and term children 0-5 years of age.” (1988)
3. Castellano B. et al.: „Metatarsus adductus.”
4. Marshall N. et al.: „The identification and appraisal of assessment tools used to evaluate metatarsus adductus: a systematic review of their measurement properties.”
5. Rampal V. et al.: „Forefoot malformation, deformities and other congenital defects in children.”
6. Reimann I. et al.: „Congenital metatarsus varus.”
7. Wan S. C.: „Metatarsus adductus and skewfoot deformity.”
8. Herzenberg E. J. et al.: „Resistant metatarsus adductus: prospective randomized trial of casting versus orthosis.”
9. Agnew P.S.: „Metatarsus adductus (Midfoot Adduction).”
10. Radler C.: „Foot disorders of Newborns.”
11. Li Y. et al.: „Reverse-shoe wearing method for treating toe-in gait in children can lead to hallux valgus.”
12. Williams C.M. et al.: „Metatarsus adductus: development of a non-surgical treatment pathway.”
13. Sass P., Hassan G. et al.: „Lower Extremity Abnormalities in Children.”
14. Farsetti P., Weinstein S.L., Ponseti I.V.: „The long-term functional and radiographic outcomes of untreated and non-operatively treated metatarsus adductus.”
15. Engel V., Damborg F. et al.: „Club foot. A twin study.”
16. Katz K., David R. et al.: „Below-knee plaster cast for the treatment of metatarsus adductus.”
17. Jacobs J.E.: „Pathoanatomy and surgical treatment of metatarsus adductus.”
18. Ponseti I.V., Becker J.R.: „Congenital metatarsus adductus: the results of treatment.”
19. Miron Marie-Claude et al.: „Ultrasound evaluation of foot deformities in infants.”
20. Bohne W.: „Metatarsus adductus.”

Photos and graphics (in order on the page):
1. Etioloy: own
2. Features of theMTA: own
3. Clubfoot: own
4. Classification: own
5. Bleck classification
6. Treatment: own
7. Skewfoot