How to order a hip X-ray (radiograph) to evaluate after a traumatic injury?

From the Guidelines

To order a hip X-ray for evaluation after an injury, specify that you need an anteroposterior (AP) view of the pelvis and a cross-table lateral view of the affected hip, as these are considered the standard and most appropriate initial imaging modalities for assessing acute hip pain with suspected fracture 1. When placing the order, include relevant clinical information such as the mechanism of injury, location of pain, and any physical examination findings to help guide the radiologist's interpretation.

• The patient should remove metal objects, jewelry, and sometimes clothing around the hip area before the X-ray.
• Hip X-rays are particularly important after injuries to assess for fractures, dislocations, joint effusions, or degenerative changes.
• They serve as the initial imaging modality because they are quick, relatively inexpensive, and provide good visualization of bony structures.
• If the X-ray results are negative but clinical suspicion remains high for injury, additional imaging such as CT or MRI may be warranted for more detailed evaluation, as radiographs of the hip, radiographs of the pelvis, or radiographs of the pelvis and hips are usually appropriate for the initial imaging of the hip with acute pain, fall or minor trauma, and suspected fracture 1. Some institutions may include three views: an AP view of the pelvis, a separate AP view of the symptomatic hip, and the cross-table lateral view, but there is no specific literature to compare these two approaches 1. However, the inclusion of a pelvis radiograph allows for comparison of potential abnormalities to the contralateral asymptomatic side, making it a valuable component of the initial imaging series 1.

From the Research

Ordering a Hip X-ray to Evaluate an Injury

To order a hip X-ray to evaluate an injury, the following steps can be taken:

• Initial plain radiography of the hip should include an anteroposterior view of the pelvis and frog-leg lateral view of the symptomatic hip 2
• If acute fracture, dislocations, or stress fractures are suspected, radiography should be performed 2
• If the initial X-ray is normal but there is ongoing clinical suspicion of a fracture, alternative imaging such as computed tomography (CT) or magnetic resonance imaging (MRI) should be used 3, 4, 5, 6

Choosing the Right Imaging Modality

The choice of imaging modality depends on the clinical suspicion and availability of resources:

• MRI is the preferred modality for detecting occult fractures, stress fractures, and osteonecrosis of the femoral head 4, 2, 6
• CT scans can be used when MRI is not available, but may not have sufficient sensitivity to detect all occult hip fractures 3, 5, 6
• CT scans may be more readily available in emergency departments, but may cause delays to diagnosis and surgery 5

Interpreting Imaging Results

When interpreting imaging results, the following should be considered:

• Sensitivity and specificity of CT scans for detecting occult hip fractures are 86% and 98%, respectively 6
• MRI has higher diagnostic accuracy than CT in detecting occult fractures of the hip 4
• Interobserver agreement for CT and MRI findings can be substantial, but may vary depending on the radiologist and orthopedic surgeon 4