Unstable Pelvic Fractures Workup

Updated: Oct 01, 2020
  • Author: Kenneth W Graf, Jr, MD; Chief Editor: William L Jaffe, MD  more...
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Laboratory Studies

Each patient observed in the emergency department (ED) with a pelvic fracture must receive a complete laboratory workup, which should include the following:

  • Complete blood count (CBC) with platelets, prothrombin time (PT), and activated partial thromboplastin time (aPTT)
  • Liver function panel, electrolytes, blood urea nitrogen (BUN), and creatinine
  • Blood type and screen
  • Toxicology panel
  • Pregnancy test [29]

It is particularly important to obtain and assess the results of these studies before proceeding to the operating room. They give the treating physician baseline laboratory values to help direct further treatment.


Plain Radiography

The most useful tool in the orthopedic evaluation of patients with pelvic fractures is an anteroposterior (AP) radiograph of the pelvis. This should be performed on every trauma patient observed in the ED and is part of the ED evaluation protocol. The standard AP pelvis radiograph demonstrates 90% of cases of posterior instability.

Stable fractures are characterized by one or more of the following: impacted vertical fractures of the sacrum, nondisplaced fractures of the posterior sacroiliac (SI) complex, and subtle fractures of the upper sacrum as evidenced by asymmetry of the sacral arcuate lines.

Unstable fractures are characterized by hemipelvic cephalad displacement that exceeds 0.5 cm and SI diastasis that exceeds 0.5 cm. Findings suggestive of pelvic instability include cephalad hemipelvic displacement less than 1 cm or a diastatic fracture of the sacrum or ilium less than 0.5 cm. These indeterminate cases may require further imaging to determine stability. Edeiken-Monroe et al [30]  found that standard radiographs accurately identified pelvic stability in 88% of cases.

A fracture of the fifth lumbar transverse process, previously described as a sign of an unstable pelvis, was found in both stable and unstable injuries and consequently was considered not to be a reliable sign of pelvic instability. However, a retrospective matched-pair analysis by Winkelmann et al identified a positive correlation between a transverse process fracture of L4, L5, or both and a biomechanically unstable pelvic ring injury. [31] They found such transverse process fractures to be indicative of increased severity of pelvic injury and thus potentially useful in the planning of emergency treatment.

If the patient is hemodynamically stable, additional radiographs can be obtained to improve the understanding of the fracture pattern. Treatment of an unstable fracture should never be delayed for additional radiographic studies.

The inlet pelvis radiograph is a 40-45° caudal tilt view that demonstrates AP displacement (see the image below). It also exhibits internal rotation associated with lateral compression injuries.

Inlet pelvis radiograph with displaced fracture of Inlet pelvis radiograph with displaced fracture of left sacroiliac joint.

An outlet pelvis radiograph is a 40-45° cephalad tilt view that demonstrates vertical displacement and fractures of the sacral foramina (see the image below).

Outlet pelvis radiograph. Outlet pelvis radiograph.

A lateral sacral view can help identify transverse sacral fractures.

All trauma patients in whom the spine cannot be clinically cleared must receive a full cervicothoracolumbosacral (CTLS) spine series. All fractures or areas not visualized on the plain films must be further evaluated with computed tomography (CT).

Initial evaluation also should include chest radiography to evaluate for pulmonary pathology (eg, pneumothorax, pulmonary contusion, or acute respiratory distress syndrome [ARDS]). Chest radiography should also be used to identify free air in the abdomen.


Computed Tomography

A multiply injured patient, if stable, often undergoes CT of the chest, abdomen, and pelvis. [32, 33]  A dedicated 3-mm thin-slice CT scan of the pelvis can help define the anatomy of the sacrum. The scan assists in the evaluation of crescent fractures (see the image below) and sacral fractures.

Crescent fracture on CT. Crescent fracture on CT.

The chest, abdomen, and pelvis CT scans assist in the evaluation of concomitant injuries to the abdomen and chest, which are often life-threatening. CT identifies intra-abdominal bleeding, as well as the specific organ that is injured. If a head injury is suspected, a head CT scan is obtained. A head CT scan assists in determining the severity of the injury and helps guide the surgical timing.

All spine fractures or areas not well visualized on plain radiographs should be visualized with a CT scan.


MRI and Ultrasonography

Magnetic resonance imaging (MRI) is seldom used in acute pelvic fractures.

Focused assessment with sonography for trauma (FAST) is often used as a first-line screen for intra-abdominal bleeding and fluid. It is inexpensive and can quickly provide valuable information. However, results are operator-dependent.

The extended FAST (e-FAST) is part of the primary survey in patients with high-energy trauma but does not reliably identify retroperitoneal hemorrhage associated with significant pelvic trauma. The so-called FAST-PLUS (FAST-pleural [PL]-ultrasonography [US] of the symphysis) protocol, an addendum to the e-FAST that examines the pubic symphysis in a single transverse scan after the traditional focused evaluation of the abdomen and thorax, correlates well with CT examination and may help achieve quicker identification of patients with unstable pelvis. [34]



Supraumbilical diagnostic peritoneal lavage can be performed to evaluate for an intra-abdominal hemorrhage and a ruptured viscus. It is reported to have a positive predictive value of 98% and a negative predictive value of 97%. The procedure should be performed through a supraumbilical incision to avoid a false-positive result secondary to pelvic hematoma. If the initial aspirate reveals more than 5 mL of gross blood or obvious enteric contents, an emergency laparotomy is indicated.