Abstract
The term of hip dysplasia means an abnormality of shape, size or spatial configuration of the acetabulum. It also concerns the femoral head, with mutual relationships, proportions and alignment between the femoral head and the acetabulum the most crucial factors. The reason of any symptoms in hip dysplasia is the dysplastic acetabulum and its disproportion in relation to the femoral head. Dysplasia of the acetabulum appearing at puberty has been attributed to secondary “absorption” of bony acetabulum. The presence of fatigue fractures at a later age has been considered as resulting from trauma. However, the fragments of the acetabular rim should be ascribed to overloading of the rim in dysplastic hips, causing fracture and separation of its segment. They are sometimes associated with cysts in the acetabular roof. Limbus tears with or without an associated bony fragment are known to occur after traumatic dislocation of the hip but also without any history of injury. There is no explanation of their cause or their relation to acetabular dysplasia. Limbus tears have been diagnosed by arthroscopy, arthrography and CT scans.
Clinical signs. No hip dysplasia in adults is really symptom-free. A casual examination applied between the painful episodes may appear so normal, that the articular origin of the pain may be doubted. In most cases pain is elicited by passive movement of the thigh into full flexion, adduction and internal rotation. This combination of movements brings the proximal and anterior parts of the femoral neck into the contact with the rim of the acetabulum, exactly at the point where the labrum is likely to be damaged.
Preop imaging. An anteroposterior radiograph, or “faux profil” view of Lequesne de Seze may demonstrate a congruent but short acetabular roof (Type II) or an incongruent hip with a shallow acetabulum and a more vertical than normal acetabular roof (Type I). Type I hip is potentially or really unstable. The femoral head has migrated laterally or anteriorly or in both directions, distorting the spherical shape of actebular inlet into an oval. A simple 3-dimensional classification is recommended by myself using conventional X-ray and CT scan on equatorial level. The CE angle and sectors angle acc. Anda are used to describe the anterior, lateral and posterior coverage. To check the possibilities of reduction, the anteroposterior radiograph is made in max. abduction of the hip. To simulate the correction movement of the acetabular part we use our own “Super pelvis” software.
Intra-op control. For intraoperative correction control we use a C-arm, which also controls step by step all stages of the periacetabular osteotomy. To check the final correction the X-ray of both hips is absolutely obligatory. What we should check is: the displacement of the acetabular fragment (to avoid lateralization, if necessary to make medialisation) and the positions of the anterior and posterior acetabular rim. If this is impossible with the normal a-p X-ray, the C-arm is used for achieving the “faux profil”. The computer assisted orthopaedic surgery system appears the most accurate intra-op control.
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
