Lee, Alexander C. PA-C; White, Marie PA-C
In the George Washington University Medical Faculty Associates' Department of Emergency Medicine in Washington, D.C., Alexander C. Lee is a clinical instructor of emergency medicine and Marie White is an assistant clinical professor. The authors have disclosed no potential conflicts of interest, financial or otherwise.
Bryan Walker, MHS, PA-C, department editor
ABSTRACT: Acetabular fractures are frequently missed on plain view radiographs of the hip and pelvis. A high degree of clinical suspicion for an acetabular fracture should be maintained in any patient with persistent traumatic hip, pelvic, or buttock pain, and inability to ambulate.
A 56-year-old woman presented to the ED with a complaint of left hip pain after a mechanical fall just before hospital arrival. She reported tripping over a small wastebasket and landing onto her left side. The patient denied hitting her head. She denied neck, back, or abdominal pain. Although she reported no pain, weakness, or paresthesias elsewhere in her lower extremities, she had been unable to ambulate since her fall. The patient denied previous injury or surgery to her back or hip. On physical examination, she was alert, cooperative, and in no acute distress. She had mild tenderness to palpation of her left lateral hip. Left hip flexion and internal/external rotation were limited secondary to pain. She had no ecchymosis or edema to the hip or groin, no pelvic instability, and no sign of shortening or rotation in her left lower extremity. Examination of the distal left lower extremity revealed no tenderness, normal pulses, and normal sensation. Her back and abdomen were also nontender and atraumatic. Radiographs of the left hip and pelvis were obtained (Figures 1 and 2). What do the images show?
Plain film radiographs of the left hip and pelvis (Figures 1 and 2) did not demonstrate any obvious acute bony abnormalities, although ED providers noted a small, questionable cortical defect in the acetabulum. Upon consultation with the radiologist, the studies were interpreted as normal. The patient was reassessed clinically and, despite multiple doses of IV opioid pain medications, was still in pain and unable to ambulate. A follow-up axial view CT scan (Figure 3) with reconstructed anteroposterior (AP) views (Figure 4) and 3D views (Figure 5) showed an acute comminuted nondisplaced fracture of the posterior wall of the acetabulum. Involvement of the posterior wall can best be appreciated on a lateral view of the CT scan (Figure 6).
Acetabular fractures result when the head of the femur is driven into the pelvis.3 In younger, healthy patients, these fractures typically are caused by high-energy trauma, such as a blow to the knee during a motor vehicle accident or a fall from a height. In older adults, acetabular fractures may result from a simple low-energy fall from standing.5 The fractures frequently are missed on plain film radiographs, and a high clinical suspicion should be maintained for any patient with persistent hip or pelvic pain, inability to ambulate, or gait abnormalities despite normal radiographs. Failure to appropriately address the fracture in a timely manner can lead to secondary arthritis, avascular necrosis of the femoral head, and severe disruption of the weight-bearing portion of the hip joint.3
Physical examination If the acetabular fracture is not associated with a dislocation, the leg will not likely show any degree of shortening or rotation. A hip contusion may or may not be present and range of motion may even be intact, though painful.3,5 The ability to bear weight and even ambulate does not rule out an acetabular fracture, although the patient may have gait abnormalities secondary to pain. The patient will often complain of persistent hip, buttock, or pelvic pain. Posterior fractures may cause injury to the sciatic nerve and cause pain or paresthesias radiating down the leg.3
CLASSIFYING ACETABULUM FRACTURES
The five types of acetabular fractures are detailed using Tile's classification system.
* Type 1 fractures involve the acetabulum wall and affect the depth of the socket.
* Type 2 fractures involve the anterior column. They are uncommon and have a good prognosis as they do not interfere with weight bearing.
* Type 3 fractures involve the posterior column and are often associated with a posterior dislocation. They involve the weight-bearing portion of the joint and require more urgent surgical intervention.
* Type 4 fractures run transversely through the acetabulum.
* Type 5 fractures are complex and involve portions of the acetabulum roof and floor.3
Although patients who have sustained high-energy trauma often receive CT scans of the pelvis after initial trauma resuscitation, patients with less-severe mechanisms of injury often initially receive plain film radiographs in the ED. A plain film hip series including AP and lateral views and an AP pelvic view are often obtained together, as the pelvic view allows comparison to the unaffected side and better visualization of the entire pelvic ring.
If an acetabular fracture is suspected clinically—such as in this patient based on her inability to ambulate—either a noncontrast pelvic CT scan or a Judet view radiograph can be obtained. Judet radiographs show 45-degree anterior and posterior-oblique views of the hip and allow better visualization of the acetabulum and femoral head.6
In one study comparing agreement of radiologists in diagnosing acetabular fractures on plain films versus CT scans, the investigators found the greatest agreement among radiologists when they viewed axial CT scans and Judet radiographs together (71% agreement). Judet radiographs alone had 52% agreement and were judged to be insufficient to rule out an acetabular fracture. Reconstructed 3D and AP CT scan views had 65% and 68% agreement, respectively.2 In general, CT scans are less influenced by a patient's body habitus, are more comfortable for the patient, and provide a better view of fracture lines and position of fracture patterns. Fracture lines lying parallel to the axial plane, however, may be missed on an axial view CT scan.1 MRI has a sensitivity approaching 100% for diagnosing occult acetabular fractures, has largely replaced bone scans, and should be considered when CT scans are negative but clinical suspicion remains high. MRI has the advantage of also providing better evaluation of soft tissue injuries involving the joint.4
For this particular patient, the Judet view radiographs shown were requested and obtained by the consulting orthopedic surgeon after the diagnosis was made using CT. Judet views alone, had they been obtained prior to CT, likely would have been sufficient to make the diagnosis, as fracture lines are visible in the anterior-oblique view (Figure 7).
Acetabular fractures can be treated conservatively or with surgery. Nondisplaced fractures and those not involving the acetabulum roof are typically treated with 6 to 8 weeks of nonweight bearing status and, occasionally, limb traction. Surgical intervention is indicated when the patient has significant disruption to the weight-bearing portion of the acetabulum, concomitant injury to the femoral head, or retained bone fragments in the joint space. Surgical treatment is also more likely to be considered in younger patients who bear a great risk of secondary osteoarthritis from their injuries.3
In this case, the patient was admitted to the orthopedic surgery service where her fracture was managed conservatively. She was discharged after a 7-day hospital course with appropriate rehabilitation resources and outpatient follow-up.
1. Mouzopoulos G, Lasanianos N, Mouzopoulos D, et al. Occult acetabulum fracture. A case report. Emerg Radiol
2. O'Toole RV, Cox G, Shanmuganathan K, et al. Evaluation of computed tomography for determining the diagnosis of acetabular fractures. J Orthop Trauma
3. Solomon L, Warwick D, Selvadurai N. Apley's Concise System of Orthopedics and Fractures
. 3rd ed. London, United Kingdom: Edward Arnold; 2005:358–360.
4. Tintinalli J, Stapczynski J, Ma J, et al.. Tintinalli's Emergency Medicine: A Comprehensive Study Guide
. 7th ed. New York, NY: McGraw Hill; 2011:1850.
5. Törnkvist H, Schatzker J. Acetabular fractures in the elderly: an easily missed diagnosis. J Orthop Trauma
© 2014 American Academy of Physician Assistants.