As a new mom I was excited to get a front carrier so I could tote my new bundle of joy around like a kangaroo and enjoy the many benefits of "baby wearing." However, as a physical therapist I was concerned about positioning in the carrier and the health of my baby's hips. This post will detail how infants' hips develop, risks for and signs of hip dysplasia, the benefits of baby wearing, how some carriers place baby's hips in an unhealthy position, and proper positioning and examples of carriers that are "hip healthy."

First a brief lesson on hip anatomy: The adult hip joint is a ball and socket joint where the head of the femur or thigh bone attaches to the pelvis at the acetabulum (socket). The head of the femur is held in place by strong ligaments and muscles. The nature of the hip joint allows the lower extremity to flex, extend, internally and externally rotate, abduct and adduct, and circumduct allowing us to sit, walk, run, jump and kick, among other things.

There are several important differences between an infant's and adult's. First, an infant hip joint is made of soft cartilage that slowly turns into hard bone during the first few years of life. An infant also has a shallow acetabulum meaning that the femoral head is less seated in the socket. Additionally, the angle of inclination or angle between the shaft of the femur and the neck of the femur is highest in infancy around 150 degrees and slowly lessens to 125 to 135 degrees in adults. Another important difference is torsion, or the amount of rotation present in the femur. At birth, one has the largest of amount of rotation 30 to 40 degrees. By age 16 most people reach the adult value of 16 degrees. Changes occur over time through muscle pull, bone growth and upright standing and walking to form the mature adult hip joint.

Due to the state of infants' hips at birth approximately 1 in 5 babies will have or develop hip dysplasia or instability. Risk factory include:

Family history of hip dysplasia
Breech position in utero
Other orthopedic concerns at birth including clubfoot, and other congenital conditions
Female gender
Positioning after birth (more on that later)

Signs of hip dysplasia include:

Limitation or asymmetry in abduction, or moving the leg out to the side
Difference in skin folds at the hip crease, noted when changing diapers
One leg appearing longer than another
Pistoning and positive Ortoloni and Barlow signs

Now, onto the fun part: "Baby wearing!" While this list is not scientific and is largely anecdotal, the benefits of carrying baby in a front carrier may include: Less crying (yay!), convenience, bonding, improved development, and helps to regulate infants physiologic responses. I love the idea of having babies in carries as it is a great alternative to carrying them in a car seat or putting the car seat in the stroller. Babies spend a lot of time on their backs, which is important for sleeping, but can cause babies heads to flatten in the back. A carrier allows the baby to rest it's head against the caregiver or hold it up themselves as they advance. Also, a car seat is designed to fully support an infant in the event of a crash, so it is very passive for the baby and does not contribute the babies development. In a carrier the baby has to hold it's head up, at least partially, and respond to the walking, bending, reaching and other movements of the wearer.

In utero, babies are in a position where there knees and hips are flexed, or bent: As in the fetal position. It takes several months for the legs to naturally stretch out. After birth the healthiest position for the hips is for the knees hand hips to be bent and for the knees to fall out to the side, like a frog-leg position. The opposite of this position is for the legs to be straight and held together. Being held this unhealthy position for long periods of time may increase the risk for hip dysplasia or dislocation.

The International Hip Institute has an image that demonstrates how being in a carrier effects a baby's hip joint. A carrier should have the following features in order to be "hip healthy:"

The thigh should be supported from the hip to the knee
It should allow the hips and knees to be bent so that the knees are at or above the hip
The knees should be apart, wrapping around the caregiver
Avoid the "crotch dangling" position

It is important to keep the above features in mind when choosing a baby carrier. I personally use the Ergobaby Original, and love it. My little guy feels snug and secure and seems comfortable during walks, errands and house work. He even falls asleep in it sometimes. There are other carriers that are also "hip healthy," including : Beco Gemini, Boba Air, and Tula Gossamer. This is by no means an exhaustive list or an endorsement for these products other than the hip positioning. When shopping for a carrier make sure that the above 4 criteria are met and you will be on your way to happy, "hip healthy," baby wearing!

References

http://hipdysplasia.org/developmental-dysplasia-of-the-hip/causes-of-ddh/

http://pediatrics.aappublications.org/content/105/4/896

http://www.stanfordchildrens.org/en/topic/default?id=developmental-dysplasia-of-the-hip-ddh-90-P02755

Campbell, Susan. (2005) Meeting the Physical Therapy Needs of Children. Philadelphia, PA: F.A. Davis.

http://hipdysplasia.org/developmental-dysplasia-of-the-hip/prevention/baby-carriers-seats-and-other-equipment/