Aetiology of Hip Dysplasia: Genetic and Environmental Factors

Abstract

The term developmental dysplasia of the hip (DDH) encompasses a wide spectrum of disorders ranging from a complete fixed dislocation at birth to asymptomatic acetabular dysplasia in the adult. Proximal femoral deformities commonly associate with acetabular dysplasia. For the purposes of this chapter, we will be referring to acetabular abnormalities principally. The incidence per 1000 live births of combined childhood and adult DDH ranges from 0.06 in Africans to 76.1 in Native Americans. The aetiology of DDH, in line with other complex diseases, is multi-factorial. Established risk factors for DDH include female gender, breech presentation, a positive family history, and primiparity. These associations suggest a dual theory regarding the aetiology of the disease. Exogenous (or mechanical) factors may lead to DDH as a result of foetal, malpositioning/constriction or the practice of swaddling during infancy. Secondly, endogenous (or heritable) factors may cause ligamentous laxity or formation of a shallow/steep acetabulum. Heritable factors contribute between 50% and 85% to the total risk of disease. Several genetic mapping studies have revealed associations between genetic variants, most notably with growth differentiation factor 5 (GDF5) and DDH. These will be explored further in this chapter.