Synonyms and Keywords
Bean-shaped foot, forefoot varus, hooked-foot, in-toeing, metatarsus adductovarus, metatarsus varus, MTA, pigeon toe.
What is a Metatarsus Adductus?
Looking at the bottom of a newborn’s foot, you’ll notice the inner border of the foot curves slightly off-center. This is normal and not to be confused with any foot deformity. By the time the baby reaches 4-6 months old, the foot usually straightens out on its own. Otherwise, the infant may have metatarsus adductus.
Also known as metatarsus varus and MTA for short, metatarsus adductus is a condition where the front half of the foot, or forefoot, is angled inward relative to the hindfoot (or heel). The bones in the middle of the foot bend in toward the body, slanting the forefoot toward the midline while leaving the midfoot and hindfoot pointing straight ahead.
The incidence of MTA is reported to fall between 0.1 and 1 percent of live births. Babies born with metatarsus adductus may also have a higher risk for developmental dysplasia of the hip (DDH), a condition of the hip joint in which the top of the thigh (femur) slips in and out of its socket, because the socket is too shallow to keep the joint intact.
What Causes a Metatarsus Adductus?
The probable origin of MTA is how a baby’s feet are turned in persistently while held in the womb. The forefoot at this stage is very flexible, so pressing against the uterus wall bends and shapes it into a curve. The condition improves over 6-12 weeks after birth in nearly all children when their feet become unrestricted and free to move. In about 10% of cases, however, the deformity becomes less flexible and turns into a metatarsus adductus.
A baby’s sleeping position may contribute to the condition, since babies sleeping on their stomach may increase the tendency of the feet to turn inward.
Who Gets a Metatarsus Adductus?
The risk factors for metatarsus adductus include:
- Babies born in breech position (buttocks or feet coming out first)
- Genetics, as babies with a family history of metatarsus adductus tends to have a higher chance of developing the condition
- A condition called oligohydramnios, in which the pregnant mother does not produce enough amniotic fluid to nurture and cushion the unborn fetus sufficiently in the womb
- Firstborn children are more likely to have MTA
- Female infants are slightly more likely than male infants
Are There Different Types of a Metatarsus Adductus?
Usually, metatarsus adductus is divided into two categories:
- Non-flexible, in which the angling of the forefoot is fixed (because the bones are slanted toward the midline) and cannot be straightened by hand
- Flexible, where the misalignment can be straightened to a degree by hand by pulling on the front part of the foot (because the bones are not fixed in a slanted angle in their attachment to the midfoot)
What are the Symptoms of a Metatarsus Adductus?
The primary sign of a metatarsus adductus is that the front of the foot is bent inward, though the back of the foot and the ankles remain normal. The entire foot is shaped like a banana or the letter “C”. The base of the fifth metatarsal (toe bone), called “styloid”, is prominent and sticks out as a bony “bump”. Usually, there is an abnormally wide space between the big toe and the second toe, because the first metatarsal (toe bone), attached to the big toe, is the only slanted bone. The foot has a high arch. Metatarsus adductus is very often evident by the crease at the midpoint of the inner border of the foot, between the forefoot and hindfoot where the turning in occurs. About half of children with MTA have the problem in both feet.
How do You Diagnose a Metatarsus Adductus?
A physician makes the diagnosis of metatarsus adductus with a physical examination. The physician will get a complete birth history of the child and ask if other family members were known to have the condition.
The physician will examine the front of the foot and the big toe (and perhaps some of the other toes) to see if they are slanting inward. A common method for infants when their feet are still tiny is the V-Finger Test: The physician forms a “V” with his second and third finger, and tucks the infant’s heel into the V until it touches the base, with the inside of the foot resting against the index finger, the outside resting against the middle finger. This lets the physician observe whether if the midline of the forefoot is abnormally crooked and, if so, how badly by the gap between the forefoot and the middle finger. The physician will also try to passively move the foot by hand into a straight-ahead position. This technique, known as passive manipulation, involves gentle pressure on the forefoot while holding the heel steady. If such manipulation is not successful or difficult, the condition is non-flexible because the deformity is fixed at the toe joint.
X-rays are not typically used in the diagnosis, since the condition can be quite discernible to the eyes, but they are often done in the case of rigid/non-flexible metasarsus adductus to check the extent of the deformity.
How do You Treat a Metatarsus Adductus?
Metatarsus adductus diagnosed at birth does not require treatment. It is usually posture-related, and with growth, the condition normally goes away on its own within 6-12 weeks. If the curve is severe, a podiatrist will handle this deformity by placing the baby’s foot in a cast that gently nudges the foot back into its correct position.
For adults with pain or problems linked to MTA, stretching exercises to relieve pain are often recommended. However, if the forefoot does not improve after about 3-4 months of observation and stretching, podiatrists will consider the following treatment options:
- A special arch support called an orthotic to help balance the foot by placing it in a more normal position.
- Serial castings are reserved for the very severe and rigid cases. The procedure consists of castings every one or two weeks until the deformity is corrected, which usually takes about 3-4 sets of casts, followed by corrective shoes to hold the correction for about 3 months. This is very time-consuming and expensive.
- Corrective bracing has recently become a popular option, because it avoids the inconvenience and emotional grief that repeated castings can cause.
- Surgery may be needed if the deformity cannot be corrected by the measures above.
Your doctor will decide the timing and method of correction. Once the deformity is corrected, recurrence is unlikely.
Self-Care at Home
First, it’s important to know that 85% of metatarsus adductus resolve without treatment. The “deformity” often straightens out after the foot has the time and space to flex itself, develop, and grow.
A podiatrist can show you how to stretch the child’s foot to help the foot get straighter. The manipulation corrects the deformity faster and typically the only “treatment” you need. If the condition is very noticeable and manipulation is successful, follow up by putting the foot in special shoes to keep it in a neutral position.
When you see the child sleeping on his/her stomach, turn him/her around on his/her back. Sleeping on stomach encourages the feet to turn inward.
Topical Professional Treatments
A physician will determine the specific treatment for your child’s MTA based on:
- Your child’s age, overall health, and medical history
- Extent of the condition
- Your child’s tolerance for specific medications, procedures, or therapies
- Expectations for the course of the condition
- Your opinion or preference
When a severe deformity is detected early, i.e., less than 1 year old, the typical treatment combines manipulation and plaster casting for 10 weeks, or up to 6 months of age. Long leg casts, applied from the upper thigh to the foot, help stretch the soft tissues of the forefoot. The plaster casts are changed every one to two weeks by your child’s pediatric orthopedist. For infants of 6 months and older, special padded shoes may be used for arch support and hold the forefoot in place as it heals.
A very severe or rigid case might require an operation to straighten the toe bone at its junction with the middle part of the foot. A corrective surgery should only be performed, however, after the child is at least 2 years old to allow for natural correction. Procedures involving the soft tissue or cartilage are saved for patients of 2-6 years of age, and osseous (bone-related) procedures are reserved for children whose bones are sufficiently mature, at 6-8 years old.
How to Prevent a Metatarsus Adductus?
Since oligohydramnios, a condition in which there is too little amniotic fluid around the fetus, is a probable cause, its prevention should decrease the chance of an infant born with severe MTA. This involves good control of maternal diabetes and prevention of infections transmittable from mother to fetus.
Children with MTA may often sit or rest with their legs crossed, or in a “W” position. Encourage the child to sit in a chair with their legs uncrossed instead, though this often cannot be done until they are school age.
Because metatarsus adductus is something a child is born with, there is virtually no surefire way to stop the problem from occurring. However, applying the proper home or professional care will speed up the corrective process.