Prof. Dr. med. Dietrich Tönnis

(Fig. 1)

(Fig. 2)

(Fig. 3)

(Fig. 4)

In what we call dysplasia, as seen here, there is only minimal instability (Fig. 5).

And 3 months of a flexion abduction pillow or splint have healed it, as you can note in Fig. 6.

This is found also in Grafs hip types 2b and c in Fig. 7. In the lower line you see his partial dislocation typ 3 at the left and at the right the full dislocation.

In the arthrogram at Fig. 8 a typ 3 hip is shown. The contrast fluid is filling the acetabular cavity and the femoral head is displaced, but has pulled the labrum with it.

In Fig. 9, in a position of increased flexion and abduction, the femoral head is almost completely reduced. The lower labrum and transverse ligament are only minimally protruding.

(Fig. 10)

(Fig. 11)

For a radiological classification and evaluation of results we introduced these grades (Fig. 12). They express where the femoral head center, or its ossific nucleus, stands in relation to the acetabular rim.

Below, at grade 1, it stands medial of Perkins and Shents vertical line from the acetabular rim. At grade 2 the center stands lateral of the line, but still below the acetabular rim, at grade 3 - at the height of the rim, and and at grade 4 –above it.

For the evaluation of triple pelvic osteotomies we separated 4 degrees of decentration of the femoral head, which will show different results at longer follow-ups. Grade 1 (Fig. 13) classifies spherical and well reduced joints, but the femoral head is not fully covered. These joints have a quite normal congruence of femoral head and acetabulum before and after operation and should have the best long-time follow-ups.

Grade 2 (Fig.14) is characterized by an elongated dysplastic acetabulum and the femoral head is shifted proximally. Yet, postoperatively it also looks quite congruent now. The femoral head is deeper reduced into the socket here.

Grade 3 (Fig. 15) classifies the false acetabulum. Here the femoral head has itself molded a secondary acetabulum. The definition is, that the femoral head is stable in this relatively short and shallow cavity.

A grade 4 (Fig. 16) was chosen in addition for high dislocated femoral heads, that can still be reduced into the acetabulum by abduction. We have to proof on abduction whether the femoral head can be brought more into the joint and acetabular rotation can cover it. The weightbearing area however will still be smaller than in normal joints.

Another classification of the joints and their pre- and postoperative state can be given by measurements of angles and indices (Fig. 17). Our investigation of the normal acetabular index in children by a follow-up to the age of 7 years is well known I believe (Tönnis u. Brunken 1968).

We have then inroduced, in addition to the normal values for each age, degrees of deviation, a grade 2 mildly pathological, degree 3 severly and degree 4 extremely pathological (Tab. 3). In this way we can count how many joints are pathological and to what degree before operation and afterwards. To achieve normal values is the best way to achieve good long-time results.

(Fig. 18)

(Fig. 19)

(Fig. 20)

(Fig. 21)

(Fig. 22)

In our first long-time follow-up of triple pelvic osteotomies (1994) we correlated the absence of pain with the different angle groups (Tab. 4).

For the adults we have now this list of normal values and the degrees of deviation to quantify our results (Tab. 5).

So far we have considered only the classifications of two planes of the hip joint. By computertomographies in prone position to equalize pelvic inclination (tilt) we get pictures of the horizontal or axial plane, in which we can measure the anteversion of the acetabulum and the femur, as seen in Fig. 23.

The decrease of anteversion was either developmental from birth and childhood or going along with a coxa vara or an asymptomatic moderate slip of the capital femoral epiphysis. Hip dysplasia with a CE angle below 20° was evaluated separately, also the deep acetabulum and protrusio acetabuli.

Acetabular and femoral anteversion can be combined in a joint quite differently. When both are decreased or increased, the deformation is worse.

When decreased and increased angles are combined, a compensation is seen. McKibbin has described an instability test, in which he counted the degrees of acetabular and femoral anteversion together.

At 50 - 60 degrees there was a marked instability in the joint. We introduced here the normal angle group and the deviation degrees by doubling the angles. This is the classification of the third plane of the hip joint. The frequency of the groups during the first half year of life. is seen in Fig. 24.

Decreased anteversion of acetabulum and femur is much more symptomatic, than increased anteversion. But it is mostly not diagnosed.

The techniques of measuring should be looked up in our special papers on torsional anomalies of the hip. A short example is given in Fig. 25.

Anteversion is here measured only at the right hip. It is zero. Here the anterior acetabular rim has a normal length and congruency. This is not seen at the left hip. Here the femoral head is cut at a lower level where the anterior acetabular rim is receding more and more and measuring would be wrong.