ARTICULAR COVERAGE, ACETABULAR PROCEDURES

Abstract

In this paper operations are discussed that improve the dysplastic acetabular roof in developmental dislocation of the hip (DDH) of children up to 10 years. In the first year of life acetabular dysplasia can be treated successfully by flexion-abduction splints and plaster casts in „human position“. From the second year on, only slight dysplasias can heal spontaneously or be treated conservatively. Then the steep acetabular roof has to be osteotomized and levered down to a normal angle and coverage to avoid redislocation or residual dysplasia.

Different procedures have been described in the course of time. Two osteotomies are chiseling in the anterior to posterior direction. Salters innominate osteotomy levers the whole acetabulum with the lower part of the pelvis in an anterolateral direction around an axis passing through the pubic symphysis and the posterior part of the osteotomy. In Pembertons osteotomy the hinge for turning down the acetabular roof is the last, posterior, transverse cortical segment over the tri-radiate cartilage, short before the sciatic notch.

Osteotomies chiseling from lateral in medial direction have been described already by Albee (1915) and Jones (1920). Lance (1925) propagated this technique in Europe. Here the acetabular roof is partially osteotomized in a thickness of 5–7 mm. Only the lateral part of the acetabulum is brought into the horizontal position. Wiberg in 1939 used this technique, but in 1953 he was the first to publish a full osteotomy what Dega called 1973 a transiliac osteotomy. Dega had originally learned the technique of Lance, but in 1963 when he reduced high dislocations after the technique of Colonna, he performed also a full transiliac osteotomy. After the Symposium of Chapchal in Basel 1965 we started in Berlin also with the complete acetabular osteotomy. With the control of an image intensifier the blade of the osteotome is driven toward the posterior rim of the tri-radiate cartilage leaving only a small bony rim above. Anteriorly the blade passes through the ant. inf. iliac spine. Posteriorly it just enters the sciatic notch. Here we check the blade position by direct palpation. The acetabulum is bent down partly in the small rim of bone left and mainly in the triradiate cartilage. Angles up to 50° have been achieved, which you cannot reach by other techniques.

In the beginning we have combined after Mittelmeier and Witt this acetabuloplasty with a varus osteotomy of the femur. In our long-time follow-up (Brüning et al. 1988,1990) however, we found in almost 50% a subcapital coxa valga or a so-called head-in-neck-position of the femoral head. Then we avoided varusosteotomies and had good results without it (Pothmann).

To keep the acetabular roof in the new position we used first bone wedges from the varus osteotomy, then deproteinized bone wedges from animals, and today deep frozen wedges of human femoral heads of the bone bank, sterilized at 121 degrees C for 20 min. (Ekkernkamp, Katthagen). A firm layer of cortical bone laterally is necessary. Reinvestigations have proven the stability of this material too ( Pothmann). This type of acetabular osteotomy in our and other authors opinion is the best. Salters osteotomy is not as efficient in severe dysplasia. And in older children it produces a decrease in anteversion of the acetabulum, which may limit internal rotation of the hip and cause osteoarthritis if it does not improve. In Pembertons osteotomy one cannot use the image intensifier, which is of great help to perform the osteotomy exactly and also the levering of the acetabulum to the optimal coverage.

Our first long-time follow-up of children with additional varus-osteotomies (Brüning et al.) reviewed 90 hip joints in 67 children. The age at operation was in average 3.6 years, the age at follow-up 15 years.

Clinical results. 98% of the patients had no pain or only occasional, no limitation of movement and normal or almost normal gait. The Trendelenburg sign was negative in 71% of the cases, grade 1 in 15.5% and grade 3 in 13.5%.

Radiological evaluation. The mean value of the AC-angle (acetabular index) preoperatively was 33.8°, postoperatively normal with 16.3°. The acetabular angle of the weightbearing zone was at follow-up 9.7°, which is normal too. At the age of less than 18 years the CE angle of 25,9° was normal too, as well the instability (protrusion) index of Reimers of 12.3 % and the distance femoral head to teardrop figure with 8.8 mm.

In our study group of hip dysplasia we introduced a score of normal values of hip measurements and 3 grades of deviation from normal, slightly pathological, severely pathological and extremely. When we counted normal values and slightly pathological ones together as a good result, we found for the different measurements of the acetabulum percentages mainly between 82 and 93 %. Remarkable were two measurements of the femoral neck, the epiphyseal index with only 50 % of normal and slightly pathological angles and the head-neck index with 47.7% respectively. This was due to the head-in-neck position of the femoral neck after varus osteotomy as we have mentioned already.

Acetabular coverage is achieved best in transiliac osteotomies up to 10 years. Then, only by triple pelvic osteotomies the acetabulum in total can be redirected to a normal coverage. But this operation is more difficult. Residual dysplasias therefore should be treated as early as possible in the way demonstrated here.