Hip dysplasia in the young adult

Developmental dysplasia of the hip (DDH) includes a wide spectrum of conditions ranging from a high (i.e., complete) dislocation of the femoral head to a low-volume acetabulum in the young adult. Adult hip dysplasia is a clinical condition that results from abnormal development of acetabular wall coverage of the femoral head, altering the biomechanics of the hip joint resulting in hip instability and progression to intra-articular derangement. Based on the degree of lateral under-coverage, some have classified dysplasia into evident when the lateral center-edge angle (LCEA) is below 20° and borderline dysplasia when the LCEA is between 20° and 25°, considering normal values as those between 25° and 40°. However, it has been shown that unstable hips may exist with LCEA even beyond 25°. Wilkin et al. described a novel classification of hip dysplasia with different patterns including global, anterior, and posterior deficient predominant, being global the most prevalent. For a better interpretation and diagnosis of hip dysplasia, and in order to classify the condition, it is suggested to always use and standardize the same imaging protocol. Initial screening should be performed with a supine or standing anteroposterior (AP) pelvic radiograph and a lateral view of the affected hip, which can be either a Dunn-45° lateral or a frog-leg lateral view. The gold standard for surgical treatment is the periacetabular osteotomy with or without concomitant hip arthroscopy. When properly indicated, this surgery improves function and decreases pain in most of the patients, also increasing hip joint survival free from total hip arthroplasty. Still, change of natural history of disease with surgical intervention has not been proven.