CONTRADICTION OF THE CONGENITAL DYSPLASIA-PREDISLOCATION HYPOTHESIS OF CONGENITAL DISLOCATION OF THE HIP THROUGH A STUDY OF THE NORMAL VARIATION IN ACETABULAR ANGLES AT SUCCESSIVE PERIODS IN INFANCY

The acetabular angles were measured radiographically at birth in 627 unselected infants, of whom 551 were re-examined at 6 months, and 527 at 12 months of age. At birth there was a wide variation in the size of the angles. In the different categories, the mean values varied between 29 and 25 degrees; the two-standard-deviation ranges were 39 to 20 and 34 to 15 degrees, respectively. Clinical examination of the hips in a similar neonatal group of 666 infants. which was made up largely of the group examined radiologically, disclosed a high incidence of extra and asymmetrical skin folds in the thighs, and great uncertainty in the determination of limitation of abduction. Abduction was unequal on the 2 sides in 4 per cent of all newborns. At 6 months of age the angles showed marked reduction in size compared with the neonatal values. At 12 months of age the angles were slightly reduced in comparison with those at 6 months. The angles in white and Negro infants are approximately equal in size at birth, but in the same infants, the angles were slightly larger in Negroes at 6 and 12 months of age; notwithstanding the fact that congenital dislocation of the hips is virtually nonexistent in Negroes.