About three to five percent of all newborns suffer from hip dysplasia. This refers to a congenital maturation disorder of the acetabulum. Without therapy, babies and children develop a defective hip joint that can lead to premature joint wear in adulthood. Since obvious symptoms of hip dysplasia are usually absent, an ultrasound of the hip is performed on all babies as part of their preventive examinations. Detected early and treated properly, hip dysplasia usually heals without consequences – but surgery may be necessary in some circumstances.
Hip dysplasia: girls more often affected
The causes of hip dysplasia in babies are not fully understood. One risk factor appears to be the position of the unborn baby in the womb: if the fetus lies pelvis-first in the womb, hip dysplasia is more common. The risk of hip dysplasia also seems to be increased in twin pregnancies or when there is too little amniotic fluid (oligohydramnios). It is also unclear why girls are affected by hip dysplasia about five times more often than boys. In addition, the condition runs in families: If the mother had hip dysplasia, her child’s risk is increased.
Dislocation in an immature hip joint
In hip dysplasia, ossification of the acetabulum is delayed. As a result, the femoral head does not have enough support and slips in the joint. The result is damage to the acetabulum, as the femoral head deforms the still soft bone. Under certain circumstances, dislocation of the hip may even occur. Then the joint must be reset (reduced) as soon as possible to prevent permanent damage and allow the hip to develop normally.
Missing signs in babies
Babies with hip dysplasia usually do not have any symptoms because the babies do not walk yet and therefore do not have pain. Only when there is dislocation of the hip can signs of hip dysplasia be seen: Since the femoral head usually slips upward out of the socket, there is a visible shortening of the affected leg. This also often reveals an asymmetry of the folds in the thigh and buttocks. Some babies also show a conspicuous posture of the legs.
Symptoms in children: pain in the knee
In most cases, however, symptoms of hip dysplasia do not become apparent until children begin to walk: A tilted pelvis and a waddling or limping gait are typical of a dislocated hip. In some cases, the pelvis tilts forward – resulting in a pronounced hollow back. In addition, the mobility of the hip is usually limited. Hip pain, however, is atypical for hip dysplasia – affected children often complain of pain in the knee or groin instead. A characteristic sign of hip dislocation is the so-called Trendelenburg sign: When standing on one leg on the affected leg, there is a tilting of the pelvis to the healthy side.
Hip dysplasia: ultrasound screening at U3.
Since hip dysplasia often causes no symptoms in babies and the condition was often detected too late in the past, screening for hip dysplasia is now integrated into the U3 screening examination in the fourth to fifth week of life. In addition to a physical examination, an ultrasound of the hip is performed. In the ultrasound image, the pediatrician can assess the position of the femoral head and measure the angles of the hip joint. From this, the hip joint maturity is classified into the so-called
Graf hip types:
- I. Normal developed hip
- II. maturation delay (hip dysplasia).
- III. subluxation (partially dislocated hip – the femoral head has slipped in the socket).
- IV. Luxation (complete dislocation – the femoral head is outside the socket).
Diagnostics: radiography in children and adults
In babies, ultrasound examination is best for diagnosing hip dysplasia: The development of the still cartilaginous hip can be assessed very well in the ultrasound image. After the 1st year of life, the joint can be better visualized on X-ray due to increasing ossification. A so-called arthrography may be necessary if the hip of a baby with hip dislocation cannot be set again. Contrast medium is injected into the joint and X-rays are then taken from different angles.This helps to determine if, for example, a tendon is preventing dislocation.
Hip dysplasia in babies: treatment with spreader pants.
If there is only hip dysplasia without dislocation (type II according to Graf), treatment can be done with a spreader pants, splint or bandage that keeps the leg in a bent and spread position. This pushes the femoral head into the socket, promoting maturation of the joint. Such a splint must be worn around the clock for several weeks to months.
Hip realignment using overhead extension.
In the case of a dislocation (type III and IV according to Graf), the hip must first be put back into place. This can be done by what is known as overhead extension: This involves holding the legs in a splayed position on a structure attached above the bed. The traction allows the femoral head to slide into the correct position within a few days to weeks.
Surgery sometimes necessary
Another option is to set it by hand (manual reduction). This usually requires general anesthesia, during which the muscles are relaxed. If the hip still cannot be set, sometimes an obstruction – such as a tendon or fatty tissue – is to blame. In this case, surgery may be necessary to set the hip. Sometimes a wire is also used for temporary fixation. In any case, after a hip dislocation, the baby must wear what is called a sit-squat cast for a few weeks to keep the hip joint in the correct position.
Surgical correction in older children and adults
If treatment with a brace, splint or cast does not achieve a satisfactory result – this is referred to as residual dysplasia – subsequent damage can be prevented by surgery in children from about two years of age and adults. There are various surgical procedures with similar principles: by cutting through parts of the bone in the pelvis or thigh and reattaching them in a modified position, the femoral head is to be “fitted” into the socket in such a way that the joint is loaded as naturally as possible, thus preventing premature wear.
Good prognosis with early therapy
If hip dysplasia is detected in time and treated properly, no consequential damage remains in most cases. The following applies: the earlier treatment begins, the shorter the duration of therapy. This is because the younger the child, the more malleable the hip joint. However, if left untreated, hip dysplasia can lead to premature hip joint wear (coxarthrosis) – possibly as early as the third decade of life. It is not uncommon in these cases for an artificial hip joint to become necessary at an early age.
Sports for hip dysplasia
After successful completion of treatment, affected children usually do not have to limit themselves in sports. However, if there is residual dysplasia or if children are in pain, hip-loading movements should be avoided, depending on the symptoms. These include sports with jerky loads, such as certain ball games, sprinting, jumping or martial arts, as well as breaststroke and downhill skiing. On the other hand, dynamic movements such as cycling, hiking and crawl swimming are recommended, as well as specific exercises to strengthen and stretch the hip muscles.
