What is the evidence regarding the association between baby carriers and the risk of developmental dysplasia of the hip (DDH)?

From the Guidelines

Baby carriers that position the infant's legs in an extended, adducted position can increase the risk of developmental dysplasia of the hip (DDH), whereas carriers that support the "M position" or "frog-leg position" are recommended. The evidence suggests that the healthiest position for hip development is with hips flexed and abducted, and knees bent 1. Carriers that allow the baby's legs to straddle the caregiver's body in a spread-squat position, such as ergonomic carriers or traditional wrap-style carriers, are preferred.

Key Considerations

• Narrow-based carriers that allow the legs to hang straight down should be avoided, especially for prolonged periods or for infants with existing hip dysplasia risk factors.
• Parents should look for carriers labeled as "hip-healthy" by organizations like the International Hip Dysplasia Institute.
• The carrier should support the thigh from knee to knee to ensure proper hip positioning.
• Limiting time in any carrier that doesn't allow proper hip positioning is crucial, especially for babies under six months when hip joints are developing rapidly.

Risk Factors

• Female gender, breech positioning in utero, and a positive family history are significant risk factors for DDH, with relative risks of 2.5,3.8, and 1.4, respectively 1.
• Infant swaddling is also a risk factor for DDH 1.

Screening and Diagnosis

• The most important screening method is a hip examination at every well-baby visit, according to the recommended periodicity schedule for well-baby examinations 1.
• Universal US screening for DDH in newborns is not recommended, as it may lead to overtreatment and iatrogenic avascular necrosis 1.
• Selective screening, based on physical examination findings or risk factors, is recommended by the American Academy of Pediatrics (AAP) 1.

From the Research

Association between Baby Carriers and Developmental Dysplasia of the Hip (DDH)

• The evidence regarding the association between baby carriers and the risk of developmental dysplasia of the hip (DDH) is limited, but studies suggest that improper post-natal positioning of the baby's hips in extension-adduction can increase the incidence of DDH 2.
• "Hip safe" swaddling, which allows unrestricted flexion-abduction movements of the infants' hips, and the use of baby-wearing devices that keep the lower limbs in an attitude of hip flexion-abduction and knee flexion, are considered optimal for hip development 2.
• Populations that practice these "hip-safe" techniques of infant immobilisation have a lower incidence of DDH compared to those that practice restrictive immobilisation 2.

Risk Factors for DDH

• Traditional swaddling, which implies restrictive immobilisation of the infant's lower limbs with the hips in forced extension and adduction, has been shown to be a risk factor for DDH 2.
• Age is also a significant factor, with the success rate of Pavlik harness treatment decreasing in children over 4 months old 3.
• The severity of hip dysplasia, defined by ultrasonography, is also associated with differences in the success rate of Pavlik harness treatment 3.

Treatment of DDH

• The Pavlik harness is a commonly used treatment for DDH, with a success rate ranging from 45% to 100% 4.
• The treatment is generally safe and does not lead to clinically significant delays in unaided sitting and independent walking, although some minor delays may occur due to extended orthosis use 5.
• Long-term follow-up outcomes after treating DDH with the Pavlik harness have shown very good therapeutic success and a low rate of residual dysplasia 6.