40 THE JOURNAL OF BONE AND JOINT SURGERY PERSISTENT JOINT LAXITY AND CONGENITAL DISLOCATION OF THE HIP

This paper reports an investigation of the incidence of persistent generalised joint laxity in patients with congenital dislocation of the hip and in normal school children. Capsular laxity has attracted much attention in studies of the etiology of congenital dislocation of the hip joint. At first it was thought to be an isolated result of mechanical stretching. but it is now usually considered to be part of a generalised joint laxity affecting both axial and limb jOiIlts. It seems probable that there are two forms of generalised joint laxity which develop during pre-natal life, one being temporary and disappearing during the neo-natal period, the other persisting into adult life. The temporary laxity is confined to girls and is believed to have a hormonal origin, whereas the persistent laxity may occur in either sex and usually has a familial incidence. FIG. 1 FIG. 2 Figure I-Passive apposition of the thumb to the flexor aspect of the forearm. Figure 2-Passive hyperextension of the fingers so that they lieparallel with the extensor aspect of the forearm. Temporary hormonal /axity-Most interest has been shown in temporary hormonal laxity. Heusner (1902) was the first to discover a greater degree of capsular laxity in the hip joints of female than of male stillborn infants. He did not appreciate its hormonal origin, and Hisaw (1926) first demonstrated a pelvic laxity which was dependent on the female hormones. In immature and in mature guinea-pigs he produced joint laxity by injection of oestrogen and then progesterone. He believed that the responsible agent was a hormone, relaxin, which was produced in the uterus. Recently, Wilkinson (1963) showed that, in immature rabbits, the FIG. 3 Hyperextension of the elbow