[Maturation curve of the ultrasonographic alpha angle according to Graf's untreated hip joint in the first year of life].

In addition to Graf's classification into different hip-types a maturation-curve of the sonographic alpha-angle was established in order to optimize the differentiation between mature hip joints and those ones which need follow-up and those ones which need treatment at any time within the first year of life. The results obtained are confirming our present knowledge about the spontaneous maturation of physiologically immature hip joints: The mean-value of the alpha-angle crosses the 60 degrees-borderline at about the age of two months, then reaches an about 64 degrees-level at about four months. This 64-degrees-level is more or less unchanged up to the end of the first year of life.