What type of X-ray should be ordered for a patient who experienced a fall and landed on their sacrum (sacral bone) first?

From the Guidelines

For a patient who experienced a fall landing sacrum first, I would recommend ordering a sacral X-ray series, which typically includes anteroposterior (AP) and lateral views of the sacrum and coccyx, as the initial imaging study. This approach is supported by the most recent guidelines, including the 2024 update of the ACR Appropriateness Criteria for stress (fatigue-insufficiency) fracture, including sacrum, excluding other vertebrae 1. According to this guideline, radiography is usually appropriate for the initial imaging of a suspected stress fracture, excluding the vertebrae.

If there is concern for more extensive pelvic injury, a complete pelvic X-ray series should be ordered instead, which includes AP, inlet, and outlet views of the pelvis. These X-rays are the appropriate first-line imaging studies to evaluate for sacral fractures following trauma. The use of X-rays as the initial imaging modality is also recommended in other studies, such as the 2017 ACR Appropriateness Criteria for stress (fatigue/insufficiency) fracture, including sacrum, excluding other vertebrae 1.

If the X-rays are negative but clinical suspicion for fracture remains high due to significant pain or neurological symptoms, a CT scan of the sacrum and pelvis would be the next appropriate step, as it offers superior sensitivity for detecting fractures, especially those that may be subtle or non-displaced 1. CT imaging is particularly important if the patient has persistent severe pain, neurological deficits, or if they are elderly or have osteoporosis, as these factors increase the risk of fractures that might not be visible on plain radiographs.

Some key points to consider when evaluating a patient with a suspected sacral fracture include:

• The patient's age and osteoporosis status, as these factors increase the risk of fractures that might not be visible on plain radiographs
• The presence of neurological symptoms, such as numbness or tingling, which may indicate a more severe injury
• The patient's overall clinical presentation, including the severity of pain and mobility issues
• The use of CT imaging as a follow-up to negative or indeterminate X-rays, as it offers superior sensitivity for detecting fractures.

Overall, the initial use of X-rays, followed by CT imaging if necessary, provides a reasonable and evidence-based approach to evaluating a patient with a suspected sacral fracture following a fall.

From the Research

Diagnostic Approach for Sacral Fractures

To diagnose sacral fractures, especially in patients who have experienced a fall and landed on their sacrum, the following steps can be taken:

• A thorough physical examination and medical history are essential to identify potential sacral fractures 2, 3.
• Initial radiographic evaluation may include anteroposterior (AP) and lateral views of the pelvis, as well as oblique views to assess the sacrum and pelvic ring 3.
• However, plain radiographs may not be sufficient to detect sacral fractures, especially in the elderly, due to factors such as bowel gas projection and enteric overlay 4.
• Computed Tomography (CT) scans are highly recommended for accurate diagnosis, particularly in cases of suspected sacral fractures or when plain radiographs are inconclusive 3, 5, 4.
• CT scans can provide detailed images of the sacrum and pelvic ring, helping to identify fractures, dislocations, and other injuries 5, 4.

Importance of CT Imaging

CT imaging is crucial in diagnosing sacral fractures, especially in the elderly, due to its high sensitivity and ability to detect fractures missed by plain radiographs 4.

• A study found that plain radiographs had a sensitivity of only 10.5% in detecting sacral fractures, whereas CT scans were able to identify 56 cases of sacral fractures in 233 patients with blunt pelvic trauma 4.
• CT scans can also help identify accompanying fractures, such as pubic bone fractures or acetabular fractures, which are common in patients with sacral fractures 4.

Classification and Treatment

Sacral fractures can be classified using various systems, such as the DENIS classification, which divides sacral fractures into three zones based on the location of the fracture 3, 5.

• Treatment of sacral fractures depends on the type and severity of the fracture, as well as the presence of any neurological deficits or other injuries 2, 3, 6, 5.
• Operative treatment, including anatomical reduction and internal fixation, may be necessary for displaced or unstable fractures, while non-surgical management may be suitable for non-displaced or stable fractures 2, 6.