Hip dislocations after trauma are frequently encountered in the emergency setting. Significant force is generally required to dislocate a hip as this ball and socket joint is quite stable due to its bony structure and the associated muscular and ligamentous attachments. Due to the required force, hip dislocations often are associated with other significant injuries; for example, fractures are found in over 50% of these patients. The majority of all hip dislocations are due to motor vehicle accidents. Posterior hip dislocations are the most common type, with anterior occurring only about 10% of the time. These injuries are true orthopedic emergencies and should be reduced expediently. The majority will resolve with a closed reduction in the emergency department.
The hip joint is a synovial ball-and-socket structure with stability related to both its bony and ligamentous arrangement. The acetabulum covers approximately 40% of the femoral head during all maneuvers, and the labrum serves to deepen this joint and adds additional stability. Furthermore, the hip joint capsule is composed of dense fibers that preclude extreme hip extension.
The main blood supply to the femoral head arises from the medial and lateral femoral circumflex arteries, which are branches of the profunda femoral artery. Branches off of this supply enter the bone just inferior to the femoral head after ascending along the femoral neck. This arrangement allows for a plentiful but tenuous blood supply to the femoral neck, especially when considering a traumatic hip injury to the femoral head.
The sciatic nerve exits the pelvis at the greater sciatic notch and lays just infero-posterior to the hip joint. The femoral nerve lies just anterior to the hip joint.
Anterior hip dislocations are usually the result of forced abduction with external rotation of the thigh and often related to a motor vehicle accident or fall. There are three types of anterior hip dislocations: obturator, an inferior dislocation due to simultaneous abduction; hip flexion; and external rotation. Iliac and pubic dislocations are superior dislocations due to simultaneous abduction, hip extension, and external rotation.
Hip dislocations are most common in young, adult males and are most often the result of motor vehicle accidents. A recent study suggested the average age of these patients to be 34.4 with over 90% male. Associated injuries were found in 74.4% of patients with the most common involving fractures of the hip. Over 90% were treated with a closed reduction, and approximately 70% were reduced within 12 hours. One study suggested an increase in long-term complications from 22% to 52% with a delay of over greater 12 hours. Anterior dislocations of the hip in children are rare.
Epstein classification of anterior hip dislocations
Type 1: Superior dislocations
Type 2: Inferior dislocations
Comprehensive classification of hip dislocations
This system includes both anterior and posterior dislocations and incorporated pre- and –post findings.
Patients with hip dislocations generally arrive in severe pain in the hip area; however, reports of pain in the knee, lower back, thigh, or even lower abdomen or pelvis are not uncommon. Superior anterior dislocations classically present with the hip extended and externally rotated while inferior anterior dislocations generally present with the hip abducted and externally rotated. It is important to note that additional bony leg injuries may alter this classic presentation.
A thorough neurovascular exam is also required. Injuries to the femoral artery, vein, or nerve may rarely occur with anterior dislocations and should also be sought out. Femoral nerve motor function may be difficult to assess fully due to pain and the nature of this injury; however, sensory deficits over the anteromedial aspect of the thigh and medial side of the leg and foot should raise suspicion. Sciatic nerve injuries occur more often with posterior dislocations; however, they should be ruled out in any hip dislocation or fracture.
Due to the required mechanism of injury related to these dislocations, a full trauma evaluation for other associated injuries should be considered.
Hip dislocations usually are obvious on standard AP (anteroposterior) images of the pelvis. However, complete imaging usually includes a cross-table lateral of the affected joint.
On a normal AP Pelvis, the femoral heads should appear similar in size with symmetric joint spaces. The joint with an anterior dislocation will project a larger-appearing femoral head. A femoral neck fracture should be ruled out by this image prior to attempting reduction.
Judet views (45 degree internal and external oblique views) may be of some help in evaluating for bone fragments and occult acetabular and femoral head and neck fractures.
CT (Computed tomography) is recommended after a successful, closed hip reduction to evaluate for occult fractures. It may also further elucidate the cause of postreduction joint space widening and find intra-articular bone fragments or soft tissue injury that may prevent appropriate joint articulation.
CT also may be helpful in preoperative planning when a closed reduction is unable to be obtained and surgical, open reduction is required. Similar to postreduction joint space widening, findings on CT after unsuccessful reduction attempts may elucidate bone fragments or soft tissue abnormalities that both explain the inability to perform a closed reduction and assist in surgical planning.
MRI may be indicated to evaluate for soft tissue injuries and cartilaginous bodies that continue to cause issues after the acute period. Osteonecrosis also may been seen in the subacute period (4 to 8 weeks), and some have suggested that MRI is superior to CT for children with hip injuries as CT may miss unossified labrum and acetabular fractures.
Laboratory studies should be tailored to the individual patient; however, if significant blood loss is suspected due to femoral vessel injury, serial hemoglobin/hematocrit and a type and screen may be requested.
Prompt reduction of any hip dislocation is imperative. Attempts should be made to impart a reduction within 6 hours as long term prognosis may be significantly worsened by greater delays. As these patients are in significant discomfort, initial analgesia should be given with thought to the possibility of other associated injuries.
Indications for Open Reduction
Patients who do not have an indication for an open reduction should have a prompt closed reduction in the emergency department under procedural sedation.
Anterior Hip Dislocation Reduction Techniques
This is the most commonly used method and varies slightly from the Allis maneuver used for posterior hip reductions. The patient lies supine with the practitioner standing over them. An assistant stabilizes the pelvis by applying pressure over the bilateral anterior superior iliac spines. The practitioner holds the affected leg just below the knee and, while slightly flexing the hip, applies constant traction to the hip joint along the long axis. The hip may be internally rotated and adducted. A gentle lateral force to the thigh may be of some assistance. This is continued until an audible click is heard, suggesting a successful reduction.
“Captain Morgan” Technique
This is a more novel approach named after the character on the spirit bottle. The patient lies supine with both the knee and hip flexed. The practitioner places a foot on the patient’s stretcher with their own knee bent (hence the “Captain Morgan” moniker) and positioned behind the patient’s knee. The practitioner places a hand under the patient’s knee and the other on their ankle. With the first hand, the practitioner lifts the patient’s femur up while plantar flexing their own ankle to raise the patient’s femur up. The practitioner then applies gentle down-ward pressure over the patient’s ankle. This "leverages" the hip back into place. Stabilization of the pelvis by a strap tied to a board under the patient, or by an assistant, may be helpful.
Reverse Bigelow Maneuver
The patient is positioned supine with the hip partially flexed and abducted. A firm jerk is then applied to the thigh. Another variation has the practitioner apply traction longitudinally with hip adducted and and apply abrupt internal rotation and extention of the hip
This technique also is less frequently used due to difficult patient positioning; however, it is often suggested to be a less traumatic process. The patient is placed in the prone position with the affected leg allowed to hang from the side of the bed; the knee and hip are flexed while an assistant stabilizes the patient’s lower back. Traction is applied downward by the practitioner who is holding the leg just below the knee. This allows gravity to assist with the traction. Internal and external rotation are applied until a successful reduction is felt.
Post Reduction Care
Patients should be positioned with legs immobilized in slight abduction with a pillow or device between the knees. Ice packs should be applied, and analgesia is required. The patient should have post reduction x-rays done and admission for continued orthopedic care.
Multiple surgical approaches for reducing an anterior hip joint are possible; however, all require irrigation of the joint to remove any possible loose bodies and ensure that there are no soft tissue abnormalities that would prevent proper joint articuation. Postoperatively reduced hips should be held in traction for 6 to 8 weeks or until the pain has completely resolved.
The differential diagnosis for a hip dislocation includes femoral neck fracture, hip subluxation, bony contusion, other femur or knee injuries, slipped capital femoral epiphysis, other pelvic or back injuries, or rarely, intra-abdominal or pelvic pathology.
Patients should be positioned with legs immobilized in slight abduction with a pillow or device between the knees. The patient should have post reduction x-rays and admission for continued orthopedic care.
Orthopedic surgery consultation should be requested after a successful emergency reduction or if there is an indication for emergent operative reduction (most commonly the inability to reduce the dislocation). Trauma surgery also may be consulted if there are other non-bony injuries.
Anterior hip dislocations must be reduced expediently. Delays of more than 6 hours correlate with increased long-term morbidity, most notably osteonecrosis of the femoral head. Anterior hip dislocations without indications for surgical repair are generally reducible in the emergency department under procedural sedation using one of the multiple techniques. Postreduction orthopedic consult and admission are appropriate.