Dysplasia and Instability

Understanding of young adult hip disorders has improved significantly over the last 2 decades, leading to advancements in surgical treatment of acetabular dysplasia in adults. Acetabular dysplasia describes an underdeveloped or shallow, upwardly sloping acetabulum, with variable areas of deficiency, most commonly in the anterior and lateral coverage of the femoral head. Acetabular deficiencies can be associated with varying degrees of proximal femoral deformity such as coxa valga, excessive femoral neck anteversion, or decreased femoral head-neck offset. Developmental dysplasia of the hip (DDH) may be the result of in utero positioning, with hip flexion and adduction stretching the posterior hip structures. Breech presentation has been found to increase the risk of DDH to more than 40%; even after normal ultrasound screening, the risk is 29%. 1 These conditions may result in a spectrum of disorders from neonatal hip instability, joint subluxation, and frank dislocation, through to adolescent and adult dysplasia. Additional risk factors include a large neonate, or small uterus, joint hypermobility, female gender, family history, and a prima para mother. 1 It is also important to highlight that not all acetabular dysplasia is due to DDH. A concave acetabulum cannot develop without a concentric force exerted by a reduced femoral head. Acetabular growth may be affected by a variety of clinical conditions, including hyperlaxity, Down’s and Ehlers-Danlos syndromes, cerebral palsy, hereditary motor and sensory neuropathies, and poliomyelitis. The triradiate cartilage can be injured by trauma or sepsis, which can also lead to incomplete lateral acetabular growth. Finally, proximal femoral focal deficiency, Legg-CalvéPerthes (LCP) disease, and skeletal dysplasias can also affect the acetabular development. ¹.