Hip Dislocation Management in the ED Workup

Identification and timely management of hip dislocation is highly dependent on imaging, both at presentation and after attempted reduction. It is imperative for the radiologist to understand imaging features that guide management of hip dislocation to ensure timely identification, characterization, and communication of clinically relevant results. ^[19]

Radiography

A portable anteroposterior (AP) radiograph of the pelvis is often ordered as part of an initial trauma workup and should include an image of the pelvis and hip. The presence of a hip dislocation can be subtle, but most should be detected upon careful inspection of the AP pelvis radiograph. Lateral views may be useful in further classifying the type of dislocation.

The position of the femoral head relative to the acetabulum should be symmetrical. The joint space should be examined for bony fragments, for widening, or for evidence of an effusion.

Both femoral heads should be roughly the same size. In a posterior dislocation, the femoral head may appear smaller than the contralateral side because it is farther away from the x-ray beam and is magnified less. The opposite is true of anterior dislocation.

The position of the trochanters in relation to the femoral shaft may reveal abnormal rotation.

Shenton’s line is a smooth curved line defined by the obturator foramen and the femoral metaphysis. If this line is disrupted, a hip fracture or dislocation or a femoral neck fracture should be suspected.

The film must be thoroughly inspected for associated fractures.

If the AP pelvis film is nondiagnostic and a high index of suspicion exists, a lateral hip film, dedicated hip films, Judet views, or computed tomography (CT) scan may be indicated. ^[5]

Radiography should be the initial imaging study in patients with suspected AVN. ^[20]

The image below is a routine AP pelvis film obtained from a patient who experienced a multiple rollover motor vehicle crash. It demonstrates that sometimes radiographic findings can be subtle.

CT scan

Computed tomography (CT) is an accurate test for diagnosing hip injuries, except in patients with prosthetic hips, for whom streak artifact obscures the image. CT accurately delineates the type of dislocation as well as any accompanying fractures (as shown in the image below). CT scans of the pelvis are routinely obtained for patients with major trauma. Information obtained on CT can be used for emergency treatment and for long-term prognosis and management. If a CT scan is performed to evaluate the abdomen and pelvis, the hip should be examined for pathology. However, a dedicated hip CT scan should not delay reduction. After the hip is reduced, a CT scan of the hip will provide information to the orthopedist that is valuable for further surgical or conservative management.

In a series of adolescents after posterior hip dislocation, CT identified all bone injuries but underestimated the involvement of posterior wall fractures. Posterior wall size and fracture displacement could be assessed with magnetic resonance imaging (MRI). All soft tissue injuries that were confirmed at surgery, including avulsion of the posterior labrum, were identified preoperatively on MRI. ^[6]

MRI

Magnetic resonance imaging (MRI) has a limited role in acute diagnosis and delineation of hip dislocation. Patients with multiple trauma are often unstable and cannot undergo MRI, which is time consuming and is often unavailable. Once the patient's condition has stabilized and the hip has been reduced, MRI can provide valuable information about long-term management and prognosis. ^[6]  MRI 2-3 months after reduction can verify proper location and can be used to screen for complications, such as avascular necrosis (AVN), osteoarthritis, and heterotopic calcification, at an early stage.

Intra-articular injuries and loose bodies are common among adolescent and young adult patients undergoing arthroscopy after traumatic hip dislocation. In a study of 12 hips in 12 patients (8 males, 4 females; mean age, 16.3 yr; range, 11-25 yr), loose bodies were identified in 6 of 12 patients (50%) on preoperative imaging and in 8 of 12 patients (67%) at arthroscopy. The 2 patients with unidentified loose bodies on imaging did not undergo preoperative MRI. CT was performed in 11 patients and MRI in 4, and in 3 patients both CT and MRI were conducted. ^[5]

Radionuclide scanning is a sensitive method for depicting AVN, although MRI has greater sensitivity and specificity. ^[20]

ACR guidelines for DDH

The American College of Radiology (ACR) published the following imaging guidelines for DDH ^[11] ​:

• Imaging is not recommended for the initial imaging of children younger than 4 wk with an equivocal physical examination or risk factors shown for DDH.
• Ultrasonography (US) of the hips is usually appropriate for the initial imaging of children between the ages of 4 wk and 4 mo with an equivocal physical examination or risk factors shown for DDH.
• US of the hips is usually appropriate for the initial imaging of children younger than 4 mo with physical findings of DDH at initial imaging.
• Radiograph of the pelvis is usually appropriate for the initial imaging of children 4-6 mo of age with a concern for DDH at initial imaging.
• Radiograph of the pelvis is usually appropriate for the initial imaging of children older than 6 mo with a concern for DDH.
• US of the hips is usually appropriate for children younger than 6 mo with a known diagnosis of DDH during nonoperative surveillance imaging in harness.

Although data comparing specific techniques are limited, the individual success rates of most maneuvers range from 60-90%. Each technique has distinct advantages and limitations associated with its use. It is important for emergency physicians to be familiar with several different reduction techniques in case the initial reduction attempt is unsuccessful, or patient characteristics limit the use of certain maneuvers. ^[21]

Particular attention should be taken when reducing hip dislocation in the adolescent population, who may be predisposed to epiphysiolysis (separation of the epiphysis from the bone shaft caused by excessive strain on the proximal humeral growth plate). Preservation of periosteal soft tissue attachments and the use of small-diameter drill holes to promote femoral head blood flow may contribute to optimal patient outcomes. ^[22]

Reduction techniques for posterior dislocation

Allis method 

With the Allis method, the patient is supine and is under procedural sedation. The combined weight of the patient and the physician may exceed the weight limit of the stretcher. It is generally unsafe for the physician to be standing on a stretcher. For these reasons, placing the patient on the floor rather than on the stretcher is most useful. ^{[1, 23]}

An assistant should stabilize the pelvis. At first, the physician should be facing toward the patient’s feet, providing in-line traction. The physician then should gently flex the hip 60-90º while maintaining in-line traction. At this point, the physician is standing directly above the patient’s hip, providing traction in-line with the deformity.

Gently adducting the hip can force the head of the femur laterally and can help it clear the acetabular rim. Alternatively, gentle lateral traction can be applied to the proximal femur.

Reduction can be confirmed by a click that is felt and may be heard as well. The patient should assume a normal anatomic position.

Captain Morgan technique 

Another reduction technique for posterior dislocation is Captain Morgan, which is a modification of the technique reported by Lefkowitz. ^[24] Its name is derived from the resemblance of this position to the pose of the captain on the logo of a popular commercially available rum. ^[25]

With this technique, the patient is placed supine (with the suggestion that the patient be on a backboard with the pelvic strap retained) with the injured side knee flexed to 90º. The physician stands on the ipsilateral side facing across the stretcher and places a foot upon the stretcher (or backboard) with the knee under the ipsilateral knee of the patient. The physician then places 1 hand behind the knee and stabilizes the other by holding the ipsilateral ankle. Traction force is generated when the physician lifts with the hand behind the knee and plantar flexes the foot that is under the knee. Rotational and abduction/adduction forces can be applied to facilitate the maneuver if necessary.

When this technique is used, care must be taken to prevent use of the knee as a fulcrum because ligamentous disruption of the knee can occur. ^[26]

East Baltimore lift 

With the East Baltimore lift, ^[27]  the patient is placed supine, with the physician on the ipsilateral side of injury and an assistant facing the physician across the table. The physician gently flexes the leg so the hip and the knee are in approximately 90º of flexion; then the physician faces the assistant and places 1 hand on the ankle, while crossing the other arm under the proximal calf to place the hand on the assistant’s shoulder, cradling the flexed knee at the elbow. The assistant or a second assistant then braces the pelvis, while the physician and the first assistant squat slightly, bending at the knees; upon rising, they apply gentle, controlled traction to the femur, while the physician manipulates the ankle, allowing rotational control of the hip to facilitate reduction.

Stimson method 

The Stimson method is mechanically the same as the Allis method, but positioning is done in the opposite way. ^{[1, 23]} Although some physicians prefer this method because of its technical ease and high success rate, it is associated with some important disadvantages. This method requires the patient to be in a prone position, which may not be possible for the patient with multiple trauma. Also, monitoring the patient during procedural sedation may be difficult.

The prone patient is placed so the pelvis on the affected side hangs over the end or over the side of the stretcher. The hip and the knee are flexed to 90º. Downward pressure is applied to the popliteal fossa, providing traction in-line with the deformity. An assistant stabilizes the pelvis and the trunk, which prevents the patient from being pulled off the stretcher.

Whistler technique 

With the Whistler technique, the patient is placed supine with the ipsilateral knee flexed to 120º. The physician stands on the affected side and places an arm under the ipsilateral knee, while resting the hand on the contralateral knee. The pelvis and the ankle are stabilized by an assistant or by the physician’s free hand. Upon raising his or her arm, the physician applies an anterior force to the knee and subsequently to the affected hip. ^[1]

Reduction technique for anterior dislocation

Modified Allis technique

With this technique, the patient is placed supine. The physician stands at the foot of the stretcher and applies traction to a neutral hip, while an assistant stabilizes the pelvis. Gentle lateral traction applied to the proximal femur forces the femoral head laterally, clearing the acetabular rim. ^[1]