Hip Joint Instability after the Neonatal Period

In 26 girls with idiopathic hip joint instability, diagnosed after the neonatal period, the acetabular angle is measured before and after treatment. A mathematical analysis of the acetabular growth potential in these hip joints and normal ones is presented. During treatment the monthly reduction of the acetabular angle is greater than in normal hip joints. The age limit for sole treatment in immobilisation without operative procedures is discussed.