[Essential bone cysts in children. Value of systematic cystography. Apropos of a series of 42 cysts]

The treatment of children's essential bone cysts, is controversial. Intra focal injection of a corticoid, the Methylprednisolone, described by Scaglietti in 1974, given in most of the case serials, a rate of healing of more than 30 per cent.The case serial we present include 42 essential bone cysts treated between 1975 and 1992 in the orthopaedic department of Necker Enfants Malades hospital. These children have been reviewed with a mean follow up of 4 years. A healing rate over 35 per cent has been noticed. However, some failures stayed completely an understanding even if nothing at the beginning let suppose a slower evolution.Attempting to explain those phenomenes, the authors realised in 70 per cent cases, an opaque cystography, before the Methylprednisolone injection. This simple radiological technique permitted to reveal abnormal aspect in 75 per cent cases. Most of the time, it shows massive-veinous licks in an abnormal veinous system or one or plurial separations of the cystic area. This type of picture could perfectly explain the defect of the corticoids action by a lick of the solution or by a partial unefficacity of the solution because of the separation in the cyst area. The hypothetic idea has been completed by the calcul of the duration of the evolution. Effectively, the cysts showing an abnormal cystography had a longer healing delay compared to the cyst whose cystography was normal.The opaque cystography is for us a necessary element in the treatment of essential bones cysts, once the diagnostic is certain and the indication of intra focal corticoid injection has been retained. The radiographic study of the cyst area permits to precise the treatment; for example multiplying the injections in the areas of the cysts when there is separations and overseing the evolution.