Developmental dysplasia of the hip (DDH) is an abnormal formation of the hip joint in which the acetabulum is insufficiently formed, leading to instability or complete dislocation of the hip. The femoral head may also be involved, but the primary dysplasia usually rests in the pelvic portion of the joint. The pathology ranges from a hip that is reduced with an acetabulum that is incompletely formed, to a hip that is subluxable, to a hip that is completely dislocated.

The incidence of DDH is higher—as much as 4 times higher—in females than males, with a risk of 19/1000. Other risk factors include birth order (firstborn), family history, and birth in the breech position. There may be correlation between other “packaging defects” such as torticollis and metatarsus adductus. The left hip is more commonly involved than the right hip.

The diagnosis of DDH is optimal at the time of the newborn examination, but the condition is sometimes not recognized until later in life. Proper screening is imperative, because early recognition of DDH greatly improves outcome. When the condition is not recognized until after walking age, treatment becomes more difficult and less predictable. Left untreated, DDH may result in the development of hip pain, a limp, and joint arthritis at an early age.

Diagnosing DDH
Physical examination is the most important tool in assessing for hip dysplasia. Inspection may reveal differences in leg length or asymmetrical skin folds in the thigh or gluteal region. Galeazzi sign—asymmetry of knee height with hips and knees flexed to 90 degrees—is evident if the hip is truly dislocated.

The Barlow test—bringing the leg from abduction to adduction with the hip and knee flexed—is another screening tool for DDH. The test is positive if the hip is reduced but can be dislocated. If the hip is dislocated but reducible, the Ortolani sign, in which the leg is brought from adducted to abducted position with hip and knee flexed, will be positive. The most sensitive test for hip dislocation is asymmetrical abduction of the hips.

Once the hip becomes fixed in a dislocated position, the Ortolani and Barlow tests may go from positive to negative. This should not be misunderstood to be an improvement in the pathology. Once the child begins to walk, limping is evident with unilateral involvement. A waddling gait is indicative of bilateral involvement. DDH would not be expected to contribute to delay in walking, because the condition is usually painless. If walking and development are delayed, other etiologies should be investigated.

For children older than 3 weeks but younger than 4 to 6 months, ultrasound is the imaging modality of choice (Fig. 1), because the ossification of the femoral head is insufficient for radiographs to provide proper information. If the ultrasound is obtained at younger than 3 weeks, a false-positive result is possible. These young infants may have ligamentous laxity due to maternal hormones, and a false-positive ultrasound may result in unnecessary treatment. If the hip dislocated or dislocates on exam, the child should be placed in a Pavlik harness and an ultrasound performed to confirm reduction. After the age of 4 to 6 months, radiographs are the imaging modality of choice.

The American Academy of Pediatrics (AAP) guidelines regarding imaging in the screening for and diagnosis of DDH recommend ultrasound for female infants who are born in the breech position. It is recommended as “an option” for female infants with a family history of DDH and for male infants who are born in the breech position. The mainstay of screening is the physical examination, which should be carefully performed on all infants at newborn and follow-up exams.

The AAP guidelines are supported by the Pediatric Orthopaedic Society of North America and the AAOS. However, it is imperative to keep in mind that, although recognizing risk factors is important, most infants with DDH have no risk factors.

Treating DDH
The most reliable treatment for DDH in children younger than 6 months is a Pavlik harness, a brace to stabilize and secure the hip joint. After the child reaches age 6 months, closed reduction is more frequently used than reduction with spica casting. Spica casting may involve the trunk and one or both legs; the cast may be left on from 6 to 12 weeks postoperatively.

When treatment is not initiated until the child begins walking, surgical open reduction with bony osteotomy, followed by spica casting, becomes necessary. Treatment of DDH that is unrecognized until skeletal maturity requires more complicated osteotomies that can no longer take advantage of open triradiate cartilage. In recent years, the periacetabular osteotomy has been used more frequently for patients with this pathology.

As hip arthroscopy has become more prevalent, recognition of intra-articular pathology associated with DDH has improved. Patients with a history of DDH, even those who have received treatment, may be more likely to have labral tears, impingement, and chondral damage.

DDH and hip OA
Patients with a history of DDH are more likely to encounter osteoarthritis (OA) at an early age, due to a suboptimal relationship of the femur to the acetabulum. This population is more likely to undergo total hip arthroplasty (THA) at an early age. This etiology accounts for a fair number of women requiring THA at an earlier age than would otherwise be expected, and the risk of arthritis is increased among patients diagnosed at an older age.

Jennifer M. Weiss, MD, and Amy L. McIntosh, MD, are members of the AAOS Women’s Health Issues Advisory Board.

Putting sex in your orthopaedic practice

This quarterly column from the AAOS Women’s Health Issues Advisory Board and the Ruth Jackson Orthopaedic Society provides important information for your practice about issues related to sex (determined by our chromosomes) and gender (how we present ourselves as male or female, which can be influenced by environment, families and peers, and social institutions). It is our mission to promote the philosophy that male and female patients experience and react to musculoskeletal conditions differently; when it comes to patient care, surgeons should not have a one-size-fits-all mentality.

Bottom Line

• Early diagnosis of DDH correlates with less invasive treatment and better outcomes.
• DDH is up to 4 times more common in females than in males.
• Early recognition of DDH and treatment in a Pavlik harness provides the best outcome.
• Although evaluating children who have risk factors for DDH is important, most DDH occurs in infants who have no risk factors.
• Patients whose first-degree relatives have known DDH should be screened with a physical exam and possible imaging.
• For children younger than age 4 to 6 months, ultrasound is the imaging modality of choice; radiographs may be used with children older than 4 to 6 months.

References

1. Milasinović S, Brdar R, Petronić I, Nikolić D: Developmental dysplasia of the hip: Epidemiological determinants and age assessment regarding time of surgical correction. Acta Chir Orthop Traumatol Cech 2011;78(3):249-252.
2. Stein-Zamir C, Volovik I, Rishpon S, Sabi R: Developmental dysplasia of the hip: Risk markers, clinical screening and outcome. Pediatr Int 2008;50(3):341-345.
3. Clinical practice guideline: Early detection of developmental dysplasia of the hip. Committee on Quality Improvement, Subcommittee on Developmental Dysplasia of the Hip. American Academy of Pediatrics. Pediatrics 2000;105(4 Pt 1):896-905.
4. Schwend RM, Schoenecker P, Richards BS, Flynn JM, Vitale M, Pediatric Orthopaedic Society of North America: Screening the newborn for developmental dysplasia of the hip: Now what do we do? J Pediatr Orthop 2007;27(6):607-610.