THE LABRUM ACETABULARE IN DDH

Abstract

The fibrocartilaginous labrum acetabulare enlarges the acetabular socket and contributes to the stability of the femoral head. In DDH the labrum is everted and pushed upward by the femoral head. In the dislocated hip the labrum is often inverted into the acetabular cavity and obstructs anatomic reduction. In the past, excision of the labrum was performed to allow the reduction of the femoral head. The aim of this study was to evaluate the position of the labrum in early detected decentered hips and its role in the early treatment of DDH. During the eleven-year period from 1992–2002, 21,709 neonates (43,418 hips) were examined both by ultrasound and by Ortolanis test to establish the diagnosis of DDH. According to Grafs classification the following hips were present: 298 type D-hips, 252 type IIIa, 4 type IIIb and 20 type IV. Therefore 431 of the patients (356 females and 75 males) showed 574 sonographically unstable hips affected by DDH (1.32%). Due to its echogenic structure, the fibrocartilaginous labrum is clearly visible by ultrasound. In type D, type IIIa, and type IIIb it was always located cranially to the femoral head; in type IV it was located medially to the femoral head. The average age of the children at the time of the diagnosis was 42 33 days (mean value SD). Ortolanis test was positive in 61 hips (10.63%) and negative in the remainder of the hips (89.37%). 21.5 % of the cases were diagnosed within the second week of life, 52.9 % between the third and the eighth week, and 25.5 % after the eighth week. The labrum was not inverted in any of these cases, nor was an open reduction necessary in order to remove it as an obstacle to the closed reduction. Only the ultrasound examination allowed the early diagnosis of the unstable decentered hips. The importance of the labrum decreases when an early diagnosis can be made and an early treatment can be performed.