The hip dysplasia (alternative name: hip dysplasia ; English dysplasia hip , developmental dysplasia of the hip , congenital dysplasia of the hip ; Abbreviations: CDH , DDH ) or congenital hip dislocation is a collective term for congenital or acquired deformities and disorders of ossification ( ossification ) of the hip joint in the newborn . The hip dysplasia can occur alone or together with other congenital malformations . Single hip dysplasia is much more common and is found in significantly higher numbers in girls than in boys. Several factors are considered to be beneficial or partially causative: one factor is breech position . The symptoms of hip dysplasia are initially uneven sides of the buttock folds and restricted mobility of the affected hip when kicking. Without treatment, permanent damage to the hip joint with limping , gait disorders and pain occurs in severe forms . The final state of severe forms is hip arthrosis . Lighter forms show no pain. The presence of hip dysplasia is confirmed by the use of sonography in particular , and in rarer cases, X-rays and magnetic resonance or computer tomography . In most cases, the treatment is carried out without surgery by using wide diapers and swaddles or spreading pants . Also immobilization by Spreizgips may be required. Surgery is rarely necessary. The prognosis of hip dysplasia has improved considerably since the introduction of sonographic screening in newborns.
The hip joint is a ball joint and is made up of the hip joint socket ( acetabulum ) and the hip joint head ( caput femoris ). The acetabulum is made up of pelvic bones , the head of the hip joint belongs to the thigh bone. As a ball joint, the hip joint can in principle move freely in all directions. Mobility is limited by the extent to which the acetabulum, ligaments and muscles encircle the femoral head. The acetabulum encloses the femoral head to significantly less than 50% of its surface. On the one hand, this enables a high degree of mobility of the hip joint head in space, on the other hand, the hip joint head can be easily removed (luxated) from the acetabulum. From infancy onwards, the bony structure of the head of the hip joint and the acetabulum has provided bony stabilization; the strengthening ligaments and muscles of the hip joint also stabilize it.
In contrast to toddlers, children, adolescents or adults, the hip joint in the newborn is made of cartilage. As part of normal development, the cartilage substance is continuously replaced by bone substance in infancy (3 to 9 months of age). This takes place both in the acetabulum and in the head of the thigh bone (femur). For the regular ossification of the hip joint, a correct position from the femoral head to the acetabulum is essential, as the forces and loads that arise when the hip joint moves promote ossification. If the position of the femoral head and acetabulum is not correct (malposition), the malposition will ossify without correction. In some cases, the acetabulum and femoral head cannot develop properly in shape and size. In the medium term, this leads to poor functioning of the hip joint with subsequent damage and destruction (osteoarthritis).
In addition to the malpositions, developmental disorders of the cartilaginous abutment of the hip joint can also cause dysplasia. If the cartilaginous abutment of the acetabulum turns out to be too small, the still cartilaginous femoral head cannot be held in the correct (centered) position with sufficient certainty, even if it is initially in the correct position in the acetabulum. The result is that it is easier for the femoral head to slip out of the centered position in the acetabulum. Slipping out slightly corresponds to a subluxation (partial dislocation ), while sliding out completely corresponds to a dislocation (dislocation).
Risk Factors and Epidemiology
The risk of hip dysplasia as the only dysplasia is said to be 13 times higher for girls than for boys; for combined malformations, on the other hand, the gender distribution is almost symmetrical (Dunn 1969, quoted from).
Hip dysplasia occurs more frequently in breeches at the due date, whereby in a meta-analysis of nine predominantly European cohort studies with 35,000 children, a risk of 6.0% for hip dysplasia was found if the birth was performed by caesarean section in breeches, and 6.9% during vaginal delivery.
Other exogenous factors such as lack of intrauterine space, e.g. B. due to lack of amniotic fluid, multiple pregnancies and heavy children should also lead to increased hip dysplasia.
The multiple occurrence in families or in certain regions ("dysplasia nests") is also typical of hip dysplasia. While around 2 to 4% of all newborns throughout Germany are affected by hip dysplasia, significantly higher incidences were found in Hesse, Upper Palatinate, Franconia and Saxony. Hip dysplasia is the most common child orthopedic disease in babies in Germany.
International data on the incidence in newborns vary in the specialist literature from approx. 4% to 50%. This broad range arises from the different classification of the mild forms of dysplasia, from screening programs, and possibly also from technical and qualitative differences in sonography. The highest incidences are reported from small indigenous groups such as Indians and Sami , the lowest from central Africa . Figures between 4% (Scandinavia) and 36% (Eastern Europe) were published from Europe.
The clinical examination of the newborn or infant can provide initial indications of the presence of hip dysplasia. When looking at the newborn or infant in the prone position, an inequality ( asymmetry ) of the gluteal folds becomes apparent. This is not conclusive for hip dysplasia, but it is a first indication. The protection of a leg with inhibited splaying or a difference in length of the legs can also be an indication of hip dysplasia. By triggering and using the so-called Ortolani sign , the suspected diagnosis of hip dysplasia can be made: The thigh of the newborn (or infant) is gently pushed out of a dysplastic joint socket and levered in again ( subluxed ) by pushing backwards and then splaying it “Under the hand of the experienced examiner can be felt rather than heard. The implementation is controversial and should not be repeated unnecessarily after a positive result. On the one hand, repeated vigorous examination can dislocate the hip joint by overstretching the joint capsule; on the other hand, this can damage both the acetabulum and the blood supply to the femoral head. A femoral head necrosis (bone infarction of the femoral head) would be the result.
Sonography of the hip performed in the first few weeks of life is therefore the standard in diagnostics . It is painless, quick and easy to use by the experienced examiner, without exposure to radiation, and it generally depicts the cartilaginous structures and bony fixed points well. To eliminate the need for a potentially risky clinical examination, the hips of all newborns were screened in Austria in 1996 introduced by means of sonography. The ultrasound of the hip joints is also part of the U3 preventive medical examination in Germany.
X-ray examinations allow very precise statements to be made about the ossification of the hip joint and the position of the components of the hip joint to one another, but they do not depict any cartilage structures, which is why they are usually only used after the third month of life. The associated radiation exposure is also disadvantageous. The assessment criteria in the hip overview image include various angles of the bony hip head covering (center-corner angle and acetabular roof angle) as well as the Menard-Shenton line and the epiphyseal distance for assessing a malposition.
The MRI is rarely used, but allows a very good indication of cartilage, bone and bone marrow limits and soft tissue conditions. However, it is nowhere near as readily available, quick to perform and standardized evaluable as sonography. It is also difficult to carry out on newborns and infants, since adequate immobilization in the face of the noise associated with magnetic resonance imaging is seldom carried out alone and without the aid of sedatives or sleeping pills.
Depending on the examination method used (ultrasound or sonography, X-ray), there are schemes for the classification and thus the determination and classification of the severity of the congenital hip dislocation. Due to the lack of radiation exposure and the good display of cartilaginous structures, the ultrasound examination in newborns according to the Austrian orthopedic surgeon Reinhard Graf has prevailed. As an assessment aid, Graf developed two measuring angles for assessing the pantile roof. Using the acetabular roof angle α and the cartilage roof angle β, the degree of dysplasia can be assessed, taking into account the age of the child, and forms of therapy derived from it.
With the lighter forms of hip joint malformation, it is usually sufficient to wrap the child consistently wide. Modern diaper systems support the diapering of babies in a spread-leg position. Carrying babies in a sling can also counteract dysplasia. It is essential to ensure that the legs are correctly spread apart, it must reach from the hollow of the knee to the hollow of the knee and should be 30 to 45 degrees on both sides (i.e. on each side). In addition, the legs must not hang down. Rather, the baby should squat in the sling, with a deep bottom and hollow of the knees around the height of the child's navel. This also applies to children with healthy hips. Because the hips are still developing in every child because they have to mature. It is not yet ossified.
If the changes are more severe, a bandage, wearing a splint or plaster of paris will be necessary. It may even be necessary to have surgery to ensure that the femoral heads can slide back into the sockets.
In the case of a surgical intervention, the slipped femoral head is corrected to its original position. The type of operation depends on the age of the sick person: In children, an orthopedic surgical technique is used to cover the femoral head ( Salter osteotomy ). In adults, a triple pelvic osteotomy according to Tönnis ( triple osteotomy ) is performed, in which the pelvis is divided at three points (ilium (ilium), pubis (pubic bone) and ischium (ischium)). This causes the acetabulum (the hip socket) to pivot, which ultimately causes the femoral head to be covered again.
Untreated malformations of minor severity of the hip joints can later lead to premature wear, this is called dysplasia coxarthrosis . One of these can be seen in the picture above on the right: The femoral head is not adequately roofed and has therefore moved upwards. This results in a leg shortening (in this patient by 6 cm). In the course of time there has been a massive rounding of the head. The joint space is almost completely eliminated. The hip joint is stiff.
If the hips are dislocated, this significantly hinders the development of the child's motor skills. Here it is necessary as early as possible to achieve a normal function of the hips by conservative or surgical means. In the past, repositioning operations were often performed to correct the angle between the thigh shaft and neck. At that time it was assumed that this would counteract the development of osteoarthritis . We now know that not all hips that deviate from this ideal angle actually become arthritic earlier. The indication for corrective osteotomy is handled much more restrictively, especially since the results of hip replacement are getting better and better.
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