Definition
Synonyms: Hip joint dysplasia, dysplasia hip A hip dysplasia describes an incorrect or incomplete formation of the hip joint. In this case, the acetabulum is not deep and wide enough to accommodate and cover the femoral head sufficiently.
Epidemiology
Hip dysplasia is the most common congenital deformity (malformation), it occurs in about 3-4% of newborns and mainly affects girls (ratio of girls to boys = 6:1). It is more common in positive family history, i.e. when other family members have already had the disease. It is also more common in births from the breech presentation and in combination with other anomalies (malformations) such as clubfoot.
It also occurs more frequently in the context of neurological diseases such as spina bifida or cerebral palsy. In the newborn, a diagnosis cannot be made clinically (i.e. only on the basis of a physical examination). The only indication of the presence of hip dysplasia is the so-called Ortolani sign, where the examiner can hear a clicking sound when the thigh is being spread.
After a few weeks, additional symptoms appear, such as an inhibition of abduction, i.e. when the child lies on its back, the legs bent by 90° in the hip and knee cannot be spread laterally to the support by the examiner. In some cases, asymmetry of wrinkles (i.e. wrinkles are visible on one side, but not on the other side or in a different place) can be observed in the area of the buttocks and thighs. The Barlow sign can also be positive, in this case a jumping out and in of the femoral head out of the socket can be felt when the legs are spread apart and at the same time the hip is pressed forward and backward with thumb and index finger.
If a hip luxation occurs due to the dysplasia, which is often the case, a leg shortening on the affected side may be noticeable. A lack of movement and – if the child is already of walking age – a limping gait pattern may also be indicative of hip dysplasia. The so-called Trendelenburg sign should be mentioned here.
Here, the pelvis tilts when the child stands on one leg and thus also when walking. In case of bilateral hip luxation, the “waddling gait” is conspicuous. Often, hip dysplasia is accompanied by a malposition of the legs in the sense of internal rotation (antetorsion) and knock-knees (coxa valga).
