Etiology of developmental hip dysplasia or dislocation: review article.

There is no consensus in the literature regarding the impact of several, so-called, etiological factors in the appearance of developmental dysplasia or dislocation of the hip (DDH). Furthermore, the mechanism explaining the appearance of a dislocated or subluxated hip in the perinatal period is not well defined. The latter explains, as well, the different terms used to describe the same clinical entity. Terms like congenital dislocation of the hip (CDH), developmental dysplasia/dislocation of the hip or teratological dislocation of the hip are usually applied for the description of the same condition. Constitutional and mechanical disorders are accused of encouraging the evolution of an antenatal or neonatal hip towards instability, subluxation or even dislocation. An understanding of the predisposing factors as well as the natural history is essential in order to prevent and/or treat them effectively as well as to decide on the most appropriate nomenclature. A review of the multiple published theories affirms that the determining predisposing factors for hip dislocation or subluxation are mechanical and are associated with intra-uterine posture in full hip flexion, adduction and external femoral rotation together with abnormal pressure on the greater trochanter tending to expel the femoral head in a supero-posterior direction relative to the acetabulum. The role of genetic factors is secondary, but present, and can influence the natural history of a patient if the primary mechanical and postural factors are not inhibited.