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The acetabular index (AI; Hilgenreiner 1925) has proven to be a reliable parameter for the radiological diagnosis of developmental hip dysplasia (DDH). Age-dependent normal values and ranges of the AI are well documented. These data, however, have so far not been presented graphically in a way which would have made them suitable for patient data documentation on a routine basis (calculation of percentiles, time-axis with log scale, smoothing). We have therefore created graphs meeting these requirements, based on a previous examination of the AI of 719 girls and 428 boys (Tönnis and Brunken 1968). These graphs have meanwhile proven to be a useful and time-saving tool for the diagnosis as well as quality control of the treatment in children with DDH.

On the basis of findings published in the literature, morphologic changes seen among the author's patients were classified as anthropologic and teratologic dislocations. The anthropologic dislocations were sub-classified into four groups, identified as dysplasia, subluxation, severe subluxation and luxation. Their anatomic peculiarities were described and illustrated. One observation which appears important, and which has already been reported by other authors, is that the limbus is not an infolded free joint border; also, that even in cases of severe luxation the femoral head often does not go beyond the acetabular labrum, which is displaced far upward. A number of special features appear to be of major importance for therapy. Mechanically, a severe subluxation behaves in the same manner as a subluxation. No reduction maneuver is needed to reposition the joint. On plain radiographs, subluxation are often mistaken for luxations. In dislocated hips the tendon of the iliopsoas muscle lies between the anterior portion of the acetabulum and the femoral head. When the extremity is extended, the psoas tendon is an obstacle to reduction. The real articular obstacle to reduction is not the limbus (primary limbus) but the primary joint cavity, which is too narrow. The limbus is only an obstacle on the way to the primary acetabulum.

The author comes to the conclusion that palpatory determination of the antetorsional angle, if executed by a skilled diagnostician, can often save an x-ray film and hence cost and radiation exposure, especially in nonadipose children, supplying satisfactory information on the torsional conditions at the end of the femur near the hip, within a few seconds' time, taking the examination technique into consideration. Antetorsion of the femur at the hip is defined. The aetiomorphology of the antetorsional angle cannot be considered as an independent phenomenon, since it can be viewed only within the overall interplay of the torsional conditions of the leg. In this connection it becomes evident that there is a well-defined relationship between antetorsion of the femur near the hip and apical position of the trochanter major. The so-called "antetorsion-ddependent, externorotatory trochanter major effect" ist expressed mathematically by the trochanter major retrotorsional angle, which is in fact the only way to properly determine the antetorsional angle via manual palpation.

121 children with cdh, which haven been treated between June 84 and December 85 in our out-patient-ward with Aktivspreizhose (abduction-pants), have been followed by ultrasound examination. Reliability of hip ultrasonography, duration of treatment and results have been evaluated. At the beginning of treatment the diagnosis were: 24.8% type IIa, 29.6% type IIb, 13.2% type IIG or IID and 5.8% type IIIa according to Graf; in 6.6% of the cases cdh was diagnosed only by x-rays. Hip ultrasonography was highly reliable according to quality controls in comparison to x-rays and short-ended the duration of treatment. With the exception of 3 children (1 Myelodysplasia, 2 start of treatment after the 6 months of life) all children with "Aktivspreizhose" treatment showed anatomic healing. Duration of treatment was 4.2 months on the average, 3.5 months when treatment started in the first 3 months of life, and 4.7 months, when started after the first 3 months of life. X-ray-controls at the end of treatment showed mild forms of femoral head necrosis (type I and II) in two cases, which healed completely according to follow up controls. For the treatment of cdh in babies the Aktivspreizhose is the optimal therapy, especially when started in the first 3 months of life. A general legal orthopaedic clinical and ultrasound screening of babies hip in the first week of life should be introduced.

In this work own ideas regarding etiology of dysplasia i.e. luxatio coxae cong, and the dysplasia epiphysealis capitis femoris as a result of personal autopsy findings will be represented. In the same way, these pathological changes in the region of the hip may be reduced to a common denominator.

Sonographic hip diagnosis depends on anatomical identification. Makromorphological studies by plastination and cryosectioning was done using small hips. Details of the anatomy are presented. Different positions of the proximal femur are demonstrated, as well as the physiological development of the hip.

In a prospective study 120 hips of preterm babies below 2,000 g were investigated by ultrasound studies in order to determine the distribution of the types according to Graf's classification. Compared with unselected newborns, preterm babies show a significantly higher incidence of ultrasound types Ib and IIa. The distribution of the ultrasound types of the hips of both groups is compared.

By means of transmission sonography with incoherent ultrasound it is possible to obtain areal cross-section images of infants' hips which are free of interference and demonstrate axes accurately. It is possible to assess the condition of tendons, ligaments, capsular structures, and the bones, and their relative positions. The authors report on experience gathered since 1982 with the instrument developed at the Gesellschaft für Strahlen- und Umweltforschung (Society for Radiation and Environmental Research) in Munich. In addition to a brief description of the unit and an explanation of the examination technique, they discuss criteria of assessment and demonstrate on the basis of sample results that transmission sonographic findings can be assessed reliably in patients up to the age of 9 months. The possible significance of transmission sonography in the diagnosis and observation of congenital dislocation of the hip is discussed.

The results of measurement of length and angles in the x-ray and ultrasound image of the infantile hip joint are dependent on the different shape of the joint but also on different x-ray projections, on a limited accuracy and incorrect technique in measurement. From our investigations on the accuracy of measurement a differentiation between normal and pathological infantile hip joints is not possible by measuring geometrical data in the x-ray resp. ultrasound image. In the x-ray the greatest possible error of the acetabular angle is +/- 3 degrees, that of the so-called "AMC-angle" +/- 5 degrees and of the Alpha- and Beta-angle in the ultrasound image +/- 10 degrees. Thus the collection of geometrical data in the x-ray and ultrasound image of the infantile hip joint is not more reliable than a qualitative assessment orientated on the osseous resp. cartilaginous corner of the acetabulum.

Ossification of the upper femoral epiphysis is dependent on biomechanical laws. In babies with normal hips, the osseous nucleus develops in the centre of the epiphysis. In babies with hip dislocation, however, the altered biomechanical factors result in a different location of the nucleus. Ossification begins in a more lateral and cranial position. After reduction of the dislocated hip, either a second nucleus forms and grows together with the first nucleus, or the eccentric nucleus extends in a caudal direction. Both of these alternatives are physiological processes and should not be confused with necrosis of the epiphysis. The eccentric development of the nucleus is hardly mentioned in the modern literature, but it is of the greatest importance for diagnosis and therapy. Ignorance of the phenomenon of eccentric ossification may lead to a false assessment of the position of the femoral head. This mistaken impression may be heightened by an inappropriate X-ray technique: only by using techniques which take into account that the middle rotation position in children is different from that in adults can mistaken diagnoses and unnecessary operations be avoided. Examples are presented.