These significant injuries may be fractures of the acetabulum, obturator ring, injury to the bladder and urethra. The AP view of the pelvis gives important information about the initial assessment of the traumatised patient so as to assess for other more significant underlying injuries. This can be done by aligning the symphysis with the sacrum and checking for the symmetry of the obturator foramina. Pelvic centring also needs to be assessed. The pelvic AP view is generally considered sensitive for the anteroinferior part of the pelvis, reasonable in the region of the acetabulum and Ilium and poor in the region of the posterior ring. In addition elderly patients may have a large belly with thin proximal thighs and hence the exposure may vary significantly. It is important to note that the adequacy criteria may be difficult to meet due to reasons mentioned earlier. The soft tissue shadows which should be seen include the bladder with its perivesical fat, iliopsoas shadows and the rectum and bowel gas. Penetration should be adequate and is assessed by looking at the soft tissue structures.
Ideally the AP view has to cover the pelvis from the level of the iliac crests to the ischial tuberosity and laterally to include both greater trochanters. This gives an overall sensitivity of only 55% stressing the importance of pelvic CT in evaluation of patients with pelvic trauma. In a comparative study between MDCT and plain X ray of the patients with blunt trauma, CT demonstrated 629 fractures in contrast to 405 fractures in a total of 226 patients. It is difficult to assess the stability of the pelvis on the AP view. The x-ray is generally done along with the AP CXR in the trauma protocol series. The routine view is a single AP view of the pelvis. However, flattening is generally considered abnormal. There can be asymmetry of the epiphysis with irregularity and notching, which can be a normal finding. In children, the proximal capital femoral epiphysis is present from the age of 3 months until 18–20 years. There are various muscle attachments around the pelvis and hip region, which may be avulsed in traction injuries. This is more commonly seen in intracapsular rather than extracapsular fractures. Hip fractures may be associated with avascular necrosis of the femoral head. Hip fractures are not commonly associated with dislocations because of the strong joint capsule. The anterior and posterior columns are connected to the axial skeleton through the sciatic buttress. The acetabulum is formed by the anterior and posterior columns and connected by the supra-acetabular region. The femoral head and the acetabulum form the hip joint. The anterior ligaments are the first to disrupt.įigure 5.1 (a)–(d) Normal pelvic and hip anatomy: 1, sacrum 2, sacro-iliac joint 3, ilium 4, iliac crest 5, anterior superior iliac spine 6, anterior inferior iliac spine 7, ischial spine 8, obturator foramen 9, superior pubic ramus 10, inferior pubic ramus 11, ischial tuberosity 12, symphysis pubis 13, femoral head 14, fovea centralis 15, posterior acetabular rim 16, acetabulum 17, neck of femur 18, inter-trochanteric line 19, greater trochanter 20, lesser trochanter 21, Kohler’s tear drop 22, Shenton’s line. The anterior group in contrast is weak and prevents distraction and anteroposterior displacement. The posterior group is strong and complex and attaches the spine to the pelvis. The ligaments are the anterior and posterior sacroiliac ligaments, the sacrotuberous ligament, sacrospinous ligaments and the ligaments of the symphysis pubis. The integrity of this pelvic bony ring can be compromised by disruption of these ligaments ( Figures 5.1 and 5.2). It comprises three separate bones (the sacrum and two iliac/innominate bones) which are held together by a series of strong ligaments. The pelvis is the connection between lower limb and trunk and hence it is inherently unstable. The fractures may be subtle on plain radiographs and may be overlooked in particular in obese and elderly osteopenic patients.
In contrast, hip fractures may occur after relatively minor trauma in elderly patients and are suspected from the clinical history and examination. The mortality rate for closed pelvic fractures is 27% and that for open fractures is 55%. Prognosis is poor if the injuries are not detected and treated promptly. This results from internal visceral injuries (commonly bladder and urethra and rarely uterus, cervix, vagina and rectum) and bleeding due to high impact in RTAs, falls in young patients and associated underlying co-morbidities in elderly population. There is high morbidity and mortality associated with pelvic fractures. Pelvic and hip fractures are seen in the elderly population with trivial trauma whilst the mechanism in young patients generally involves high-impact injuries including road traffic accidents (RTAs).