Dislocation, Hip, Posterior

By admin On Dec 10, 2023

Ovid: 5-Minute Sports Medicine Consult, The

Greg Nakamoto

Basics

Description

Hip dislocations can be classified into congenital and traumatic (1):
- Congenital hip dislocations occur in 2–4 cases per 1,000 live births.
- ∼80–85% of congenital dislocations occur in girls.
- Congenital hip dislocations are commonly the result of femoral head or acetabular dysplasia.
The remainder of this topic is dedicated to the evaluation and management of traumatic (posterior) hip dislocations:
- Posterior hip dislocation is an orthopedic emergency in which the femoral head is displaced posteriorly relative to the acetabulum.
- Of primary concern when evaluating the patient with a posterior hip dislocation is the attainment of early reduction (within 6 hr) to prevent long-term sequelae and the search for additional injuries (often life- or limb-threatening due to the excessive forces necessary to create this injury).
- In the case of posterior dislocation without fracture, the experienced physician may perform 1 attempt at closed reduction. If reduction is not accomplished with ease, or if there is an associated fracture of the hip, then emergent orthopedic consultation is warranted.

Epidemiology

Because of the forces required for this injury, it is relatively uncommon in contact sports. Seen more often in high-energy trauma, such as with motor sports, equestrian events, and high-speed mountain sports.
Posterior dislocations account for ∼90% of all hip dislocations.
More common in young males because these injuries are associated with risk-taking behavior (1)
Age (1):
- Trauma (such as motor vehicle accident) is a more common cause in patients younger than 35 yrs than in older patients.
- Falls are a more common cause in those older than 65 yrs than in younger patients.

Risk Factors

High-energy trauma
Mechanism is forced adduction, internal rotation, and some degree of flexion of the hip (2).
Most common cause is knee striking the dashboard in a head-on motor vehicle accident:
- Depending on the position of the hip, this can result in either anterior or posterior dislocation.
- This mechanism of injury is associated with an incidence of simultaneous severe knee injury in 26% of patients (including patellar fracture in 4%) (2).
In athletic competition, low-energy mechanisms of injury include a forward fall onto the knee with a flexed hip or a blow from behind while down on all 4 limbs (3).

Commonly Associated Conditions

Life-threatening internal organ damage, bleeding, and shock
Ipsilateral sciatic nerve injured in 10–14% of cases; changes a posterior hip dislocation from an orthopedic urgency to a true surgical emergency
Irreducible dislocations occur in up to 16% of simple posterior dislocations.
Fractures of the pelvis, acetabulum, femoral head, neck, and shaft:
- 81% of adult posterior hip dislocations have an associated posterior acetabular fracture (2).
Ligamentous injury to the ipsilateral knee is not uncommon when the mechanism of injury involves a blow to the anterior knee.
Delayed reduction increases risk of avascular necrosis (AVN).
Other chronic complications include recurrent posterior dislocation, post-traumatic arthritis, and heterotopic bone formation (myositis ossificans) of the thigh or buttocks.

Diagnosis

History

Mechanism? Can help guide the search for associated visceral and orthopedic injuries.
Position at time of injury? Simple posterior dislocation most commonly occurs with force on a flexed knee with the hip in varying degrees of flexion and adduction. Addition of hip abduction increases the risk of associated acetabular fracture or anterior dislocation.

Physical Exam

Immediate, severe pain and disability
Limb shortening with hip flexion, internal rotation, and adduction
Classic position may be absent if there is an associated femoral shaft fracture.
Vital signs and complete trauma evaluation essential because of the high association with life-threatening injuries
Look for classic presenting position as described above. Femoral head may be palpable in the buttocks.
Pelvic rocking and pubic compression tests to examine for associated pelvic rim fractures
Distal neurovascular examination to assess for sciatic nerve or vascular injures, which merit more urgent reduction

Diagnostic Tests & Interpretation

Lab

Laboratories are ordered as needed on the basis of the trauma assessment and for preoperative planning.
Type and cross of blood products may be necessary.

Imaging

Initial x-rays: Anteroposterior (AP) and lateral views of the pelvis (4)[A]. AP often reveals the dislocation, but a true lateral may be needed to confirm the direction.

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Search for associated pelvic rim, acetabular, femoral head, neck, and shaft fractures generally merits additional x-rays, including 3/4 internal and external obliques of the pelvis as well as femur films.
Of particular importance is the ruling out of femoral neck fractures before reduction procedures are performed (3).

Differential Diagnosis

Anterior dislocation of the hip
Combined fracture-dislocation
Fracture of the pelvis, acetabulum, or femur
Traumatic hip subluxation
Hip pointer
GI or genitoureteral visceral injury

Treatment

Pre-Hospital

Patients suffering a high-energy trauma sufficient to cause hip dislocation commonly have associated injuries that take precedence for overall patient stabilization. Attempts to reduce the dislocation in the field are ill advised (1):

Establish ABCs with appropriate spinal stabilization.
If the hip dislocation is detected in the field, the patient should be placed on a backboard and allowed to assume the leg position of maximal comfort (ie, hip slightly flexed with leg adducted).
Transport to a center with trauma care appropriate to patient's overall clinical status.
One might consider attempt at early reductions in the field if significant transport time will occur (eg, wilderness or backcountry situations) (5)[C].

ED Treatment

Initial management focuses on achieving rapid reduction of the dislocation. A 2nd phase of management focuses on performing definitive care (3).
Will often require IV analgesics, muscle relaxants, and/or sedation to overcome severe pain and muscular spasm before closed reduction can be attempted
May require spinal or general anesthesia to achieve closed reduction
Simple posterior dislocation without fracture should be reduced by closed reduction as early as possible, as reduction under 6 hr reduces the rate of AVN (3,6)[A].
Some authors advise orthopedic consultation for any dislocated hip and that the orthopedist should be present when attempting closed reduction (5)[C].
For the experienced treating physician, 1 attempt at reduction of a simple dislocation might be reasonable. However, urgent orthopedic consultation should be obtained for simple dislocations that are not easily reducible with 1 attempt, as multiple attempts at closed reduction are also associated with poorer outcomes (6)[A].
Fracture-dislocations or dislocations with associated sciatic nerve injury also merit urgent orthopedic consultation.
Numerous methods of reduction have been described, with no one method having been proven superior. 3 of the more common methods include:
- Allis method: An assistant stabilizes the pelvis of the supine patient with downward pressure on the anterior superior iliac spine. The operator applies axial traction in line with the deformity by pulling with his or her hands from behind the flexed knee. While maintaining this traction, the hip is gently flexed to 90° and then gently internally and externally rotated until reduction occurs. Requires 2 operators (1,6,7,8).
- Stimson method: Patient placed prone, with affected hip hanging down over edge of bed. Downward traction is applied to the leg while an assistant applies stabilizing pressure to the pelvis. Requires 2 operators; might be difficult to move multiply injured patient into proper position and difficult to monitor the airway in the prone position (1,6,7,8).
- Whistler method: Patient supine with unaffected knee flexed to 120° such that the unaffected foot is placed firmly on the bed. Standing on the affected side, the operator reaches his hand under the affected knee and places his hand onto the unaffected flexed knee. By straightening his arm and lifting his shoulder, the operator adducts the patient's leg and applies traction until the hip reduces. Requires only 1 operator and airway easily monitored in supine position (1,8).
If 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 can be performed. This position puts the least strain on the sciatic nerve (2)[C].

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Additional Treatment

Postoperatively, repeat neurovascular examination of the injured limb
Repeat AP and lateral x-rays immediately (4).
CT scan with fine cuts (2–3 mm) through the hips:
- To evaluate for presence of osteochondral or intra-articular fragments, femoral head injuries, and acetabular fractures (any of which might make the reduction unstable)
- Essential in assigning proper classification of posterior fracture-dislocations of the hip, which in turn determines optimal treatment
- CT scan should be part of the standard postreduction evaluation of a traumatic posterior hip dislocation (3,4,7)[A].
MRI may aid in the diagnosis of labral injuries, femoral head contusions/microfractures, sciatic nerve injury, and intra-articular fragments (3)[C].
After successful closed reduction, immobilize in slight abduction (pad between legs) to prevent adduction until further orthopedic evaluation is completed and traction instituted (1).
After initial reduction, further orthopedic examination and radiographic evaluation as above helps determine presence of coexisting fractures, other injuries, and the likelihood of stability with the current reduction.
Patients with stable, concentric reductions without associated significant fractures may be treated nonoperatively (6,7)[A].
Patients with unstable reductions, displaced fractures, or acetabular fractures that would likely compromise stability are generally treated operatively (6,7)[A].

General Measures

Dislocation of the prosthetic hip is a special concern (1)[C]:

Hip prostheses can deteriorate over time and consequently dislocate with minimal force (eg, crossing of legs, standing up).
Prosthesis is most susceptible to dislocation at 3–4 mos after initial surgery.
Reduction of a prosthetic hip dislocation is less urgent than for a native hip if neurovascular status is intact:
- Concern for AVN or osteoarthritis is nonexistent.
Reduction is accomplished with same maneuvers as for native hip:
- However, less force is used so as to avoid iatrogenic fracture.

Surgery/Other Procedures

Given this injury often occurs in the setting of high-energy trauma, orthopedic evaluation usually occurs in conjunction with the initial trauma evaluation.
In the case of pure dislocations without other trauma, as sometimes occurs with a low-energy mechanism, a single attempt at reduction may be attempted if orthopedic consultation is delayed. However, urgent orthopedic referral should be made for any patient in whom closed reduction does not result in easy reduction, as reduction in <6 hr is the goal to reduce the risk of AVN, and multiple attempts at reduction results in poorer long-term outcomes. More urgent reduction is needed if there is associated neurovascular compromise.
Postreduction, orthopedic, and radiographic evaluations as above are needed to guide surgical decision making.
Indications for open reduction include (1)[A]:
- Irreducible dislocation (∼10% of all dislocations)
- Persistent instability following closed reduction (eg, fracture-dislocation of the posterior acetabulum)
- Fracture of the femoral head or shaft
- Neurovascular deficits that occur after closed reduction

Ongoing Care

Follow-Up Recommendations

Given the high-energy mechanism of injury, most patients require admission, often to a trauma service, for continued evaluation and treatment of associated injuries.
The duration of traction and nonweight-bearing immobilization is controversial (1)[C]:
- Evidence suggests early weight-bearing (eg, 2 wks after reduction) may increase severity of AVN in patients at risk.
- However, early weight-bearing decreases the incidence of other complications (eg, venous thromboembolism, decubiti)

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Physical therapy as directed by the orthopedist often starts with range-of-motion exercises while the patient is still in traction, and continues to include muscle rehabilitation and strengthening once out of traction.
Consider MRI at wk 6 to assess for signs of AVN (5)[C]:
- If evidence of AVN, keep patient partial weight-bearing and return to range-of-motion exercises only.
- If no evidence of AVN, the patient may continue to progress through therapy.

Complications

Complication rate increases directly with time elapsed before relocation.
Up to 50% of patients will have limited use or chronic pain as a result of hip dislocation (1).
The main complications are AVN, osteoarthritis, and heterotopic bone formation (8):
- Risk of avascular necrosis is the reason that traumatic posterior hip dislocations represent an orthopedic emergency.
- Incidence of AVN is between 6% and 27% in timely reductions, and up to 48% in delayed reductions (2).
Sciatic neurapraxia occurs in up to 5% of pediatric dislocations and 10–15% of adult dislocations. Symptoms partially or entirely resolve in 60–70% of cases (2):
- New neurologic deficits that occur postreduction warrant immediate surgical intervention. Hence, the importance of a complete neurovascular exam before and after reduction (5)[C].

References

1. Tham E, Doty C. Dislocation, hip. 2008. eMedicine. Retrieved Aug 10, 2009 from http://emedicine.medscape.com/article/823471-overview

2. Davenport M. Joint reduction, hip dislocation, posterior. eMedicine. 2009. Retrieved Aug 10, 2009, from http://emedicine.medscape.com/article/109225-overview

3. Shindle MK, Ranawat AS, Kelly BT. Diagnosis and management of traumatic and atraumatic hip instability in the athletic patient. Clin Sports Med. 2006;25:309–326, ix–x.

4. Brooks RA, Ribbans WJ. Diagnosis and imaging studies of traumatic hip dislocations in the adult. Clin Orthop Relat Res. 2000;337:15–23.

5. Gammons M. Hip dislocation. eMedicine. 2009. Retrieved Aug 10, 2009, from http://emedicine.medscape.com/article/86930-overview

6. Yang EC, Cornwall R. Initial treatment of traumatic hip dislocations in the adult. Clin Orthop Relat Res. 2000;337:24–31.

7. Alonso JE, Volgas DA, Giordano V, et al. A review of the treatment of hip dislocations associated with acetabular fractures. Clin Orthop Relat Res. 2000;337:32–43.

8. Newton EJ, Love J. Emergency department management of selected orthopedic injuries. Emerg Med Clin North Am. 2007;25:763–793, ix–x.

Additional Reading

Kum CK, Tan SK. Traumatic posterior dislocation of the hip—a local experience and review of the literature. Singapore Med J. 1990;31:22–25.

Rockwood C, Green D, Bucholz R, et al., eds. Rockwood and Green's fractures in adults, 4th ed. Philadelphia: Lippincott-Raven Publishers, 1996.

Schlickewei W, Elsässer B, Mullaji AB, et al. Hip dislocation without fracture: traction or mobilization after reduction? Injury. 1993;24:27–31.

Codes

ICD9

835.01 Closed posterior dislocation of hip
835.11 Open posterior dislocation of hip

Clinical Pearls

Of primary concern when evaluating the patient with a posterior hip dislocation is the attainment of early reduction (within 6 hr) to prevent long-term sequelae and the search for additional injuries (often life- or limb-threatening due to the excessive forces necessary to create this injury).
In the case of posterior dislocation without fracture, the experienced physician may perform 1 attempt at closed reduction. If reduction is not accomplished with ease, or if there is an associated fracture of the hip, then emergent orthopedic consultation is warranted.
Postreduction, orthopedic and radiographic evaluations are needed to guide surgical decision making. CT scan should be part of the standard postreduction evaluation.
In an isolated posterior dislocation without fracture treated with closed reduction within 6 hr of injury, the managing orthopedist might allow the patient to start weight-bearing as soon as comfort allows. This may be as early as 2 wks after injury.
Whereas a significant delay between dislocation and reduction may increase the risk of AVN, the overall long-term prognosis is most dependent on the severity of the initial trauma.