Hip dysplasia: easy to treat in babies

About three to five per cent of all newborns suffer from hip dysplasia. This is a congenital maturation disorder of the acetabulum. Without therapy, the hip joint in babies and children develops incorrectly, leading to premature joint wear in adulthood. Since there are usually no obvious symptoms of hip dysplasia, all babies have a hip ultrasound for their check-ups. If recognized early and treated correctly, hip dysplasia usually heals without consequences – however, an operation may also be necessary under certain circumstances.

Hip dysplasia: girls are more often affected

The causes of hip dysplasia in babies are not fully understood. One risk factor is the position of the unborn child in the womb: if the fetus is in the uterus pelvis first, hip dysplasia is more common. The risk of hip dysplasia also appears to be increased in twin pregnancies or when there is insufficient amniotic fluid (oligohydramnios).

It is also unclear why girls are affected five times more often than boys by hip dysplasia. The disease also tends to run in families: if the mother has hip dysplasia, the risk for her child is higher. 

 

Dislocation in immature hip joint

In the case of hip dysplasia, the ossification of the acetabulum takes place with a delay. As a result, the femoral head does not have sufficient support and slips in the joint. The result is damage to the acetabulum, as the femoral head deforms the still-soft bone. 

It can even lead to a dislocation (luxation) of the hip. The joint must then be reset (repositioned) as quickly as possible to prevent permanent damage and allow the hip to develop normally.

Missing signs in babies

Babies with hip dysplasia usually have no symptoms because the babies are not yet walking and are, therefore, not in pain. Signs of hip dysplasia can only be seen if the hip is dislocated: Since the femoral head usually slides up out of the socket, the affected leg becomes visibly shortened. This also often reveals an asymmetry in the folds on the thighs and buttocks. Some babies also show a conspicuous posture of the legs. 

 

Symptoms in children: knee pain

In most cases, however, symptoms of hip dysplasia only appear when the children start to walk. A crooked pelvis and a waddling or limping gait are typical for a hip dislocation. In some cases, the pelvis tilts forward, resulting in a pronounced hollow back. 

In addition, the mobility of the hip is usually restricted. However, hip pain 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, the pelvis tilts to the healthy side.

Hip dysplasia: Ultrasound screening at U3

Since hip dysplasia in babies often does not cause any symptoms, and the disease was often only recognized too late in the past, screening for hip dysplasia is now integrated into the U3 check-up in the fourth to fifth week of life. 

In addition to a physical examination, a hip ultrasound is performed. In the ultrasound image, the paediatrician can assess the position of the femoral head and measure the angle of the hip joint. This results in a classification of hip joint maturity into the so-called

Hip types, according to Graf:

  • I. Normally developed hip
  • II. Delayed maturation (hip dysplasia)
  • III. Subluxation (partially dislocated hip – the femoral head has slipped in the socket)
  • IV. Dislocation (complete dislocation – the femoral head is outside the socket)

Diagnostics: X-rays in children and adults

In babies, the ultrasound examination is best suited for diagnosing hip dysplasia: the development of the hip, which is still cartilaginous, can be assessed very well in the ultrasound image. After the first year of life, the joint can be shown better in the X-ray image due to increased ossification. 

An arthrography may be necessary if the hip cannot be relocated in a baby with a dislocated hip. A contrast medium is injected into the joint, and X-rays are taken from different angles. In this way, it can be determined whether, for example, a tendon is preventing the adjustment. 

 

Hip dysplasia in babies: treatment with spreader pants

If there is only hip dysplasia without dislocation (type II, according to Graf), therapy can be carried out using braces, splints or bandages that hold the leg in a bent and spread position. This forces the femoral head into the socket, encouraging joint maturation. Such a splint must be worn around the clock for weeks to months.

Hip reduction with overhead extension

In the case of a dislocation (types III and IV, according to Graf), the hip must be put back into place. This can be done with a so-called overhead extension: The legs are spread on a structure attached above the bed. Due to the train, the femoral head can slip into the correct position within a few days or weeks.

surgery sometimes necessary

Another possibility is a reduction by hand (manual reduction). This usually requires general anaesthesia to relax the muscles. If the hip still cannot be straightened, an obstacle – such as a tendon or fatty tissue – is sometimes to blame. 

Then, an operation may be necessary to set the hip in place. Sometimes, a wire is also used for temporary fixation. In any case, the baby must wear a so-called sit-squat cast for a few weeks after a hip reduction so that the hip joint remains in the correct position.

 

Surgical correction in older children and adults

Suppose the treatment with braces, a splint, or a cast is not satisfactory. In that case, this is then referred to as residual dysplasia – consequential damage can be prevented in children from around two years of age and adults using an operation. 

There are various surgical procedures with a similar principle. By severing bone parts on the pelvis or thigh and reattaching them in a different position, the femoral head should be “fitted” into the socket so that the joint is loaded as naturally as possible and thus, premature wear is prevented.

Good prognosis with early treatment

If hip dysplasia is recognized in good time and treated correctly, there will be no consequential damage in most cases. The following applies: The earlier the treatment begins, the shorter the duration of therapy. Because the hip joint is all the more malleable, the younger the child is.

However, if left untreated, hip dysplasia can lead to premature wear and tear of the hip joint ( coxarthrosis ) – possibly as early as the third decade of life. In these cases, an artificial hip joint is often necessary at an early stage.

Sport in hip dysplasia

After completing the treatment, affected children usually do not have to limit themselves in sports. However, if there is residual dysplasia or the 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, breaststroke, and downhill skiing. On the other hand, dynamic movement sequences such as cycling, hiking, crawling, swimming, and specific exercises to strengthen and stretch the hip muscles are recommended. 

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