In the normal hip joint, there is a tight fit between the femoral head and the hip joint (acetabular) socket. This is maintained by the tension in the hip capsule and the bony contours of the joint. In DDH this close fit is lost and the femoral head can be made to glide in and out of the acetabulum with a palpable sensation.
Alternative name: Congenital Dislocation of the Hip Joint (CDH)
The etiology of DDH is multi-factorial involving both genetic and intra-uterine factors.
There is an at-risk group where the incidence of DDH is higher than average. This group can have a combination of the following factors: breech delivery, first born, female gender, oligohydroamnios, positive family history, asymmetrical gluteal creases, torticollis, limb length discrepancy, and hip deformity.
If the diagnosis is missed at birth, then the hip will develop an abnormal shape and become painful in the future. Also, late treatment is more difficult and the results are less predictable.
All neonates must be clinically screened for hip dysplasia. Sometimes clinical examination can be difficult, particularly if the infant is not relaxed. Also, depending on the experience of the examining physician, results of missed diagnosis vary from 5% - 30%. Hip sonography was introduced in the 1980’s to assess neonatal hip instability.
Screening of neonatal hips for DDH is routinely performed in many centers. Recently, selective screening in the at-risk category has gained popularity.
Any child where clinical examination is less rewarding or there is suspicion of DDH should have an Ultrasonography (USG). Even subtle forms of instability can be diagnosed with USG which can otherwise go undiagnosed.
Since over 90% of neonatal hip instability resolves within the first six weeks, the at- risk category should be selectively screened by USG at 4—6 weeks to rule out DDH.
If there is any evidence of DDH, then treatment is commenced and follow-up scans are done to record the progress.