Reduction of Posterior Hip Dislocation Technique

Updated: Feb 25, 2016
  • Author: Moira Davenport, MD; Chief Editor: Erik D Schraga, MD  more...
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Technique

Posterior Hip Dislocation Reduction

Obtain informed consent. Prepare for and perform procedural sedation. (See Periprocedural Care.)

Have an assistant stabilize the pelvis by grasping the bilateral anterior superior iliac spines and applying gentle posterior force. Apply longitudinal distraction of the injury by grasping the patient’s distal femur, bringing the femoral head from behind the acetabular rim. The leg should be held in a position of relative adduction and internal rotation. Several moments of persistent traction may be needed to relax the large musculature of the hip; this joint laxity helps to facilitate the subsequent maneuvers.

Once the leg has been brought out to length, bring the hip to 90° of flexion while allowing the ipsilateral knee to flex passively. Gently abduct, externally rotate, and extend the hip while distracting the femoral head anteriorly. Large amounts of rotational force should be avoided because they have been associated with iatrogenic femoral neck fractures. When the femoral head returns to the acetabulum, an audible or palpable "clunk" can be appreciated.

While the procedural sedation is still in effect, gently take the reduced hip through a full passive range of motion (ROM), being mindful of any additional fractures or injuries the patient may have sustained. The stable reduced hip should remain in anatomic position through these maneuvers. Repeat hip dislocation during this passive ROM exercise is diagnostic of clinical joint instability. Longitudinal skeletal traction is required to stabilize such an injury. Place the affected extremity in a pillow brace to ensure stability during transport.

Once reduction has been achieved, repeat radiography is required to ensure concentric anatomic placement of the femoral head. Whereas plain film radiography is usually enough to adequately visualize the reduction, computed tomography (CT) is superior in that it may also show small intra-articular fragments and marginal impaction, as well as residual subluxation of as little as 2 mm within the joint. [6]  A study by Mayer et al suggested that magnetic resonance imaging (MRI) is worth considering after closed reduction of posterior hip dislocations in children and adolescents, on the grounds that it permits evaluation of intra-articular pathology without radiation exposure. [9]

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Complications

Osteonecrosis

Osteonecrosis of the femoral head may be caused by traumatic hip dislocation, occurring secondary to acute interruption of the femoral head's vascular supply from the ligamentum teres and retinaculum. The incidence of osteonecrosis is 6-27% in timely reductions and up to 48% in delayed reductions. This complication occurs more often in traumatic hip dislocations that include posterior dislocation rather than anterior dislocation, associated femoral head fracture, or associated acetabular fracture. Avascular necrosis (AVN) of the femoral head has been reported as late as 8 years after the initial injury. [10, 11]

The substantial incidence of osteonecrosis is the reason why traumatic hip dislocations represent a temporal emergency, and reductions performed at longer time intervals from the moment of the injury have been shown by repeated studies to be associated with higher incidences of osteonecrosis.

Although it is widely held that hip reduction should be performed within 6 hours of the injury to reverse the potential impingement of the femoral and posteromedial circumflex vessels, several studies have demonstrated excellent outcomes with reductions performed at even shorter intervals. These results suggest that decreasing the time to reduction as much as possible is advisable for achieving the best probability of either decreasing the severity of osteonecrosis or avoiding it entirely.

Patients who present after successful reduction with groin pain (particularly groin pain that radiates to the ipsilateral thigh) are likely describing the pain of osteonecrosis of the femoral head. Hip radiographs are indicated. Radiographic signs of osteonecrosis within the femoral head are used to stratify patients into a classification system that has prognostic value and aids in future therapeutic decision-making for the treatment of osteonecrosis.

The staging system for osteonecrosis is as follows [12] :

  • Stage 1 – Normal appearance of the femoral head; patient is symptomatic - A technetium-99 bone scan may be used to confirm the diagnosis
  • Stage 2 – Femoral cysts, sclerotic changes, or both
  • Stage 3 – Crescent sign of subchondral collapse of the femoral head
  • Stage 4 – Joint space narrowing with acetabular cysts, osteophytes, and cartilage damage

The size of the osteonecrotic portion of the femoral head and the stage of progression at the time of treatment initiation determine whether or not the ultimate outcome will be the loss of structural integrity and severe osteoarthritic degeneration of the hip.

Neurologic injury

Neurologic injury is one of the most common complications of hip dislocations, even when successful closed reduction is accomplished. [13]  Sciatic neurapraxia, often from damage to the peroneal branch, occurs in as many as 5% of pediatric dislocations and in approximately 10-15% of adult traumatic hip dislocations, though these symptoms partially or entirely resolve in 60-70% of cases. [13]

The sciatic nerve can be lacerated, stretched, compressed, or encased in heterotopic ossification. [13] Neurologic symptoms may become apparent after a patient initially presents with a normal neurologic examination. The symptoms may begin after proper closed reduction has been achieved, and the reduction technique itself may cause notable traction forces to be applied to the sciatic nerve, which may result in further injury.

If sciatic dysfunction is apparent, prevention of equinus deformity must be addressed by ensuring adequate ankle dorsiflexion. [13] The application of ankle dorsiflexion splints is needed if the patient is unable to actively dorsiflex the ipsilateral ankle.

A sciatic stretch test may be used to predict whether future symptoms of damage to the sciatic nerve may occur. This is performed after a successful reduction in patients with no symptoms of neurologic dysfunction. The test is performed as follows:

  • Place the patient supine on a stretcher
  • Have the patient actively flex the relocated hip to a comfortable 90° of flexion
  • Passively extend the knee on the same side as the hip relocation with gentle force; do not attempt to extend the knee past the patient's comfortable range limit
  • If the passive knee extension produces pain in the sciatic distribution of the same leg, damage to the sciatic nerve may have occurred; symptoms of this injury are more likely to reveal themselves in the future, and the patient should be informed of this likelihood and counseled that paresthesia or neurapraxia may occur in the coming weeks or months

If neurologic symptoms persist from the time of the injury despite adequate reduction, surgical nerve exploration may be performed several weeks after the injury. Emergency nerve exploration is usually not indicated if successful concentric closed reduction can be achieved and maintained in a simple traumatic dislocation.

However, if no neurologic deficit is apparent at the time of the injury, and such symptoms do appear several days to weeks later, they may be signs of nerve dysfunction attributable to heterotopic ossification or scar tissue formation and may indicate the need for surgical neurolysis as soon as possible. The patient without initial neurologic deficits should, therefore, be made aware of this possibility and be instructed to seek treatment immediately if such symptoms occur.

Loose foreign bodies

Loose foreign bodies may result from hip dislocations; this may result in residual pain and possible loss of motion. Hip arthroscopy may be required in cases of persistent pain. [14]

Osteoarthrosis

Postdislocation osteoarthrosis is a complication among adults with traumatic hip dislocations. This complication occurs in as many as 24% of adults with traumatic hip dislocations without fractures and in 88% of those with hip dislocations that occurred with concomitant hip or acetabular fracture, particularly in those with acetabular fragments with more than 3 mm of displacement. Although degenerative changes among children have been demonstrated, osteoarthritis after traumatic hip dislocation in the pediatric population has not been described.

Irreducibility

Interposition of the muscle or labrum causes as many as 4% of adult simple posterior traumatic dislocations to be impossible to reduce. Hip dislocations associated with any type of fracture may have a larger subset of irreducible injuries as a consequence of interposition of osseous fragments and connective tissue components. These patients should be brought to the operating room as soon as possible for open reduction; repeated (ie, two or three) attempts at closed reduction should not be performed, becausestudies have associated repeat attempts with poor long-term results.

If adequate closed reduction cannot be accomplished, the dislocated hip should be held in a position of relative extension with the ipsilateral knee in flexion until open reduction is initiated. This is the position that puts the least amount of strain on the sciatic nerve.

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