What is Hip Dysplasia?

“Developmental Dysplasia of the Hip” refers to various abnormalities in the immature hip that can range from subtle dysplasia (underdevelopment) to dislocation.¹ The term describes hips that are unstable, subluxated (partially dislocated), dislocated, and/or have malformed acetabula (the cup-shaped cavity at the base of the hipbone into which the ball-shaped head of the femur fits).² A hip is unstable when the tight fit between the femoral head and the acetabulum is lost and the femoral head is able to move within (subluxated) or outside (dislocated) the confines of the acetabulum.³ A dislocation is a complete loss of contact of the femoral head with the acetabulum.⁴  The reported incidence of hip dysplasia is influenced by genetic and racial factors, diagnostic criteria, the experience and training of the examiner, and the age of the child at the time of the examination.⁵

Proper Screening and Testing for Hip Dysplasia

The American Academy of Pediatrics recommends that all infants regardless of their risk factors, be tested for hip instability at certain prescribed intervals by a qualified physician or nurse who has been trained to detect hip instability by use of tests such as the Ortolani and Barlow maneuvers or with ultrasound.⁶ Testing is done pursuant to an algorithm where the exact timing of the next test is dependent on the results of the previous test.⁷  Testing for hip instability is most reliable during the first few months of life.⁸   The earlier a dislocated hip is detected, the simpler and more effective the treatment will be.⁹

Baby Carrier Position and Hip Dysplasia

The relationship between baby carrier position and hip dysplasia is a complex and controversial subject and there has been very little medical research on this issue.  Some articles have suggested that baby carriers should place an infant’s legs in a position that mimics devices used to treat hip dysplasia, such as the Pavlik harness.¹⁰ These carriers hold a child’s legs in a position of dramatic abduction and flexion, where the child’s hips are spread wide and the knees are at the same level or above the buttocks during the time they are being carried.  This position is sometimes referred to as the “spread/squat” position.  It is usually impossible to wear an infant in the outward facing position using these carriers because the fabric between the baby’s legs is too wide and uncomfortably cuts into the inside of the infant’s legs. 

Because these carriers mimic some of the prescribed treatments for hip dysplasia, they are often touted as a prophylactic against hip dysplasia.  These claims have resulted in the unfounded belief by some that other carriers that do not hold the child’s legs in as dramatic a position actually cause an increased risk of hip dysplasia.

However, there is no evidence of an increased risk of hip dysplasia from the use of carriers that do not hold a child in the spread-squat position.  Over the past thirty years, millions of carriers have been sold that do not hold the baby in the spread/squat position, including carriers such as the Bjorn and Snugli.  There is no indication of an increase in the incidents of hip dysplasia from the use of these carriers.

Indeed, there is medical evidence to suggest that holding a child in the spread/squat position would have no effect on the future outcome of a child with mild undetected hip dysplasia.  In a study conducted at the Nuffield Orthopaedic Centre, Oxford, United Kingdom, researchers determined that for infants who had stable but dysplastic hips (abnormal development but with no dislocation), there was no significant difference in outcomes between infants who were splinted into the desired position and those who were simply observed.¹¹  This study suggests that absent a diagnosis of a truly unstable hip, there is likely to be no benefit to holding a child’s legs in a position that mimics treatments for hip dysplasia.¹²  Another study determined that different brands of splints had different outcomes.¹³  This study suggests that splintage successes may depend on subtle nuances in positioning.  Furthermore, baby carriers are used inconsistently and sporadically during the day, sometimes for only a few hours.  During the remainder of the day, when the baby is sleeping, bathing, or playing, the child’s legs are not held in that carrier’s position.  A harness, splint, cast, or other prescribed treatment for hip dysplasia, is usually used continuously.  For all of these reasons, it is unlikely that amateur attempts to mimic these devices would positively influence hip development.

There has been an association between certain traditional ethnic groups and an increase in hip dysplasia.¹⁴ These groups also use cradleboards or tight swaddling practices, suggesting that there might be a relationship between these practices and the incidents of hip dysplasia.¹⁵  However, both cradleboarding and swaddling typically involve holding the child’s legs out straight for long periods of time, a practice not facilitated by most commercial carriers on the market today, including outward facing carriers like the Bjorn and Belle.  Moreover, hip dysplasia is strongly genetic, suggesting that the condition may be genetically influenced in these ethnic groups.¹⁶

To further complicate matters, there is some evidence that using a baby carrier as a prophylactic against hip dysplasia may result in some cases of hip dysplasia going undetected and untreated.   Modern advances in detection and treatment of hip dysplasia have resulted in the American Academy of Family Physicians recommending against the practice of triple diapering (which, like the spread/squat position, was touted as a way to treat hip dysplasia for the same reasons), because it may increase the chance of hip dysplasia going undetected and a child not receiving early proper treatment, such as the Pavlik Harness.¹⁷ In the summary, the author suggested that additional diligence was required when an infant presented for examination triple diapered.¹⁸  Double or triple diapering also has been contraindicated by some who consider the dramatic extension position to be unfavorable for normal hip development.¹⁹  Similarly, with smaller children, the spread/squat position, especially in the front carry position, can place the child’s legs in a hyper-extended position beyond the 35-40 degree angle that some consider to be “natural.”²⁰ Unlike prescribed treatments for hip dysplasia, the exact position of a child’s legs in a baby carriers and any other carriers will vary, based on the current size of the child and how the carrier is worn (hip, front, or back).

There are contradictory recommendations that make this issue even more muddled.  For instance, sometimes parents are advised to use slings and infant inserts with newborns.  (Infant inserts are sometimes used for newborns in carriers that utilize the spread/squat position, because a newborn’s legs are too small to be carried in the spread/squat position without a dramatic and uncomfortable spreading of the hips.)  The infant insert and most methods of carrying in a sling hold a child’s legs out straight.  However, it is during the first few months of an infant’s life when an infant’s hips are most underdeveloped and when hip dysplasia is most commonly diagnosed and treated.²¹ If the spread/squat position were necessary to prevent hip dysplasia, it would be inconsistent to recommend slings and infant inserts during this critical time.

In short, no baby carrier should be considered a substitute for proper testing and treatment of hip dysplasia.  If after proper testing, your child is diagnosed with hip dysplasia, please discuss with your pediatric orthopedist what kind of treatment is necessary and how to carry your child during that treatment.

The Importance of Carrying Diversity

Jeanne Ohm, a chiropractor for Ask the Experts on Parenting Magazine online, has clarified that the real concern is using any single carrier exclusively for long periods of time.  In her column, she indicated that parents should use a variety of carriers and positions.   And, in discussing the concern over upright carriers, she states “There is discussion that the ones which ‘spread the hips apart’ are not recommended to keep the child in for long periods of time.”  Her primary concern is that she believes babies should be held close to the parent, rather than spending so much time on their backs, and that the child be held in various positions in moderation.²²

The Belle Design

In designing the Belle Baby Carrier, the Belle team considered that the science around the leg position was inconclusive and contradicting, that some advocated for the spread-squat position, but that the leg positioning of some spread/squat carriers was sometimes contraindicated, especially for very young babies, and was not necessarily the ideal position for carrying.

Faced with so much inconclusive science, we concluded that the most important thing is that babies are carried by their parents. (See Babywearing [hyperlink])  Our goal was to design a carrier that would encourage babywearing.  We focused on simplicity, comfort, and style, and we wanted to provide an outward facing option for parents who desire it.  The Belle Baby Carrier holds the baby’s legs in a comfortable, moderately spread position.  The fabric between the child’s legs is as wide as possible to allow for a gentle and natural position, while still allowing the infant to sit in the outward facing position on occasion.  As with all carriers, the exact positioning of the baby’s legs will vary based on the size of the child.   The leg position of a smaller child or newborn will be closer to the spread/squat position, whereas a larger child will have less abduction and flexion.

We also recommend that you use different kinds of carriers and vary the kinds of positions in which you carry your child.   The Belle provides for an outward facing and inward facing carry.  A sling would be an excellent complimentary product as it provides an alternative to all the upright front carriers.  Another complimentary alternative would be a hip carrier.

No matter what baby carrier you use, we advise you to make sure your infant receives the proper screening for hip dysplasia.  Please do not consider any baby carrier to be a substitute for proper testing and treatment of hip dysplasia.