ABC of Emergency Radiology THE HIP

Abstract

The hip joint is a common site for trauma in adults and damage to the hip may be associated with injuries to the rest of the pelvis, the femur, and the knee. This chapter describes a system of assessment to help interpret hip radiographs. Important anatomical considerations FIG 1 Standard anteroposterior view and line diagram of the hips. Note that the left lesser trochanter is destroyed by a metastasis. The strong hip joint capsule and the surrounding large muscle bulk prevent dislocation except in severe trauma. More commonly the hip is fractured with a resulting high incidence of avascular necrosis of the femoral head, complicating intracapsular fractures, and epiphyseal injuries. The trochanteric apophyses are the insertion points for the gluteus medius (greater trochanter) and iliopsoas (lesser trochanter) muscles and are prone to avulsion in athletic adolescents. In malignant disease the proximal femur, particularly the subtrochanteric region, is a common site for metastases and pathological fracture (fig 2). FIG 2 Left intertrochanteric pathological fracture. Note the large lucent trochanteric metastasis and disruption of Shenton's line. The proximal capital femoral epiphysis is present from the age of 3 months until 18-20 years, with double epiphyseal ossification centres being common. Although asymmetry, irregular contour, and notching of the epiphyses can be normal variants in young children, a smaller epiphysis or any asymmetry in children with symptomatic hips may indicate injury. Flattening of the epiphysis is abnormal. FIG 3 Sites of fracture of the femoral neck: (1) subcapital- intracapsular (most common site); (2) transcervical-intracapsular; (3) interochanteric-extracapsular fracture line along base of neck; (4) pertrochanteric-extracapsular without and with extension into proximal shaft as a spiral fracture. The metaphysis has a rich blood supply and is a common site for osteomyelitis and consequently septic arthritis. These fractures are seen most commonly in elderly osteopenic women after a fall. They also occur …