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What is Metatarsus Adductus?
Metatarsus adductus is a type of abnormal foot rotation in children. More specifically it refers to increased internal rotation (in-toeing) of the forefoot relative to the hindfoot. The toes point inward.
It is observed in neonates and infants and is classified as a "packaging disorder". Packaging disorders occur during pregnancy when the fetus is squished (packaged too tightly within the uterus) and causes abnormal bending of the extremities. Packaging disorders are more common in female babies, the first baby (oldest child), gestational diabetes and other conditions that cause the baby to be too big or the amount of amniotic fluid to be too little. Other packaging disorders include torticollis (wry-neck, see talk) and developmental dysplasia of the hip (DDH, see talk).
The abnormal amount of intrauterine pressure causes the foot is pushed inward causing metatarsus adductus. The tip of the foot (forefoot), specifically the tarsometatarsal joints, are pulled inward due to an overactive Hallicus abductus muscle.
Diagnosing Metatarsus Adductus:
Examination of the foot will show a inward pointing tip. An imaginary line through the center of the heel should intersect the webspace between the 2nd and 3rd toe. Mild metatarsus adductus will cause this line to intersect the 3rd toe, the line will interesct the 3-4th webspace in moderate cases, and will intersect the 4-5th webspace in severe cases.
Its important for the doctors to look at the entire leg to make sure the in-toeing is not caused by rotation occurring further up the leg (see in-toeing talk).
X-rays are not required in infants, and are really only helpful in older children (if surgery is recommended).
Treating Metatarsus Adductus:
The good thing about metatarsus adductus is that it resolves in 90% of children by age 4.
If a child can actively straighten their curved foot, then theres a very high chance alignment will improve on its own and nothing beyond observation is recommended. In cases where the child cannot straighten their own foot, but a doctor can straighten it (the foot isnt stuck in that position) then its recommended for parents to stretch the foot daily so that it remains flexable and can correct with time. In cases where the child cannot straighten their own foot, and the doctor cannot either, because the foot is too stiff, then the foot should be casted (and the cast changed every few weeks) to put more pressure of the foot to grow straight.
In rare cases when the foot remains curved inward despite treatment, if when a child isnt brought to a doctor until they are 5 years old or more, then surgery may be needed. By 4 years old, there is a low chance that the foot will correct further. Surgery corrects the deformity by adjusting the foot bones. Our foot has an inner column and an outer column of bones. The outer column of bones is too long in Metatarsus Adductus, and therefore, surgery will shorten the lateral column of bone (called a cuboid closing wedge osteotomy) and will lengthen the medial column (called a cuneiform opening wedge osteotomy with an abductor hallicus longus release).
1) Bleck EE. Metatarsus adductus: Classification and relationship to outcomes of treatment. JPO 1983; 3:2. full article.
2) Lincoln TL, Suen PW. Common rotational variations in children. JAAOS 2003 11: 312-20. full article.