Hip Dislocation

United States statistics

Up to 70% of all hip dislocations are due to motor vehicle accidents.

Hip dislocations in younger individuals are relatively rare, with only 5% of cases occurring in patients younger than 14 years. Most injuries are in boys and are related to low-energy sports injuries or falls.[10]

Very little documentation concerning the occurrence of hip dislocations during sporting events exists. American football and rugby are the sports in which hip dislocations have been most widely reported.[6] An estimated 3% of all football injuries involve hip fracture or dislocation. Rugby, followed by alpine skiing and snowboarding, is the sport with the second highest number of hip dislocations.[6]

One study found rates of hip dislocation with or without fracture of the hip joint significantly higher in snowboarders than skiers over a 10-year period (5 times higher in snowboarders than in skiers),[7] and one case each of hip dislocation has been documented in the literature in competitive gymnastics and professional basketball.[1, 5] Case reports also exist of hip dislocations and fractures in racecar drivers and equestrians.[12]

A study by Moran et al found that male athletes sustained more sports-related hip dislocations than female athletes, with the greatest number of hip dislocations occurring in adolescents aged 15 to 19 years. The researchers also reported that more hip dislocations were sustained during contact sports (91.2%) than noncontact sports (8.8%). The sports with the highest rates of hip dislocation were football (55.6%), snowboarding (9.5%), skiing (8.8%), and basketball (7.1%). Nearly 83% of football-related hip dislocations resulted from being tackled by or colliding with another player.[13]

The hip joint is based on the articulation of the femoral head and the acetabulum of the pelvis, and it is a synovial ball-and-socket type joint. The femur is held in the acetabulum by 5 separate ligaments as follows:

• The iliofemoral ligament attaches to the anterior inferior iliac spine of the pelvis and the intertrochanteric line of the femur.

• The pubofemoral ligament originates at the superior ramus of the pubis, also attaching to the intertrochanteric line of the femur.

• The ischiofemoral ligament connects the ischium to the greater trochanter of the femur.

• The transverse acetabular ligament consists of the labrum covering the acetabular notch.

• The femoral head ligament joins the femoral head with the transverse ligament and acetabular notch.

The relative strength of these ligaments joined together, along with the angulation of the proximal femur in relation to the acetabulum, make dislocation of the hip joint difficult. The large sciatic nerve lies just inferoposterior to the hip joint, whereas the femoral nerve lies just anterior to the hip. The proximal shaft of the femur and the femoral neck has a plentiful blood supply from the medial circumflex femoral artery and its branches. The femoral head, on the other hand, has an extremely tenuous blood supply from a small branch of the obturator artery that passes with the femoral ligament.

Two general categories of hip dislocations exist, anterior and posterior. Posterior dislocations compose 70-80% of all hip dislocations and 90% of all sports-related hip dislocations. Alpine skiing is an exception, with one study showing higher rates of anterior dislocations in skiers.[7] In order to cause a posterior dislocation, a large force is required to strike the flexed knee with the hip flexed, adducted, and internally rotated. This injury occurs more commonly during contact and collision sports (eg, American football, rugby) when a running player is tackled from behind and falls onto a flexed knee and hip. As the opposing player falls onto the tackled player's back, his added weight drives the torso and pelvis toward the ground, and the femoral head is thus driven out the socket posteriorly.

Anterior dislocations occur when an athlete's hip is flexed, with the leg abducted and externally rotated. The thigh and leg act as a lever, with the fulcrum being the posterior edge of acetabular socket, popping the femoral head out of the socket anteriorly. These injuries are more common in sports (eg, basketball, gymnastics) in which players are running at high speeds, jumping, and landing awkwardly on the inner or medial aspect of the knee. This force drives the femoral head out of the acetabulum anteriorly, tearing ligaments, and often fracturing the femoral head and/or acetabulum. The increased rates of dislocation in alpine skiing are likely due to the large rotational forces, abduction, and external rotation applied to the hip by the ski equipment during a fall.

Related Medscape Reference topics

Acetabulum Fractures

Femoral Neck Fracture

Fracture, Hip

High-speed, high-impact sports are the most common setting for hip dislocations.

Unsafe and poorly maintained playing surfaces may add to the risk of participating in high-impact sports. For instance, wet surfaces provide an environment where athletes are more prone to lose control of their bodies while running and jumping. However, no evidence exists to link these factors with an increased incidence of hip dislocations. One case report describes a basketball player who slipped on a wet court and dislocated his hip.[5]

Although warming up before an activity and stretching on a regular basis may help prevent some sporting injuries, no evidence suggests that this decreases the risk of hip dislocation.

No correlation exists between athletic experience and hip dislocations.

The amount of energy to the hip and the associated trauma during the initial injury are the most important factors related to prognosis. Fortunately, sports-related hip dislocations are usually caused by less energy than is generated during motor vehicle accidents. The prognosis is best when the hip is reduced as soon as possible, preferably less than 12 hours post injury. The prognosis is also dependent upon the amount of related fractures or damage associated with the joint. The less associated damage to the surrounding structures there is, the better the prognosis for full recovery.

Complications

A number of acute and chronic complications of hip dislocations exist, not all of which can be avoided with proper medical care and strict follow-up by the injured athlete. Acutely, avoiding the sequelae of sciatic nerve damage and the existence of bony fragments and soft tissues in the joint space is important. A thorough physical examination and review of the radiographic findings are required to avoid the consequences of these conditions.

Chronic complications (eg, avascular necrosis, osteoarthritis) may not be avoided with good follow-up care. Radiographs should be obtained at the previously described intervals, and an MRI should be performed within 6 weeks post injury to evaluate for avascular necrosis (see Maintenance Phase, Other Treatment). Unfortunately, even with compliant patients, early diagnosis, early and appropriate treatment, and good follow-up, some patients develop chondrolysis, avascular necrosis, and early degenerative joint disease (DJD).

Although no studies on the prevention of hip dislocation exist, athletes who participate in high-performance activities need to understand the importance of performing proper warm-up techniques before competition and maintaining good overall flexibility and strength. These attributes are especially important during athletic events (eg, American football, rugby, alpine skiing) when high speeds can generate relatively large forces, which can cause serious injuries to competing athletes.

The typical history of a hip dislocation during an athletic event involves 1 of 2 mechanisms:

• Most commonly, an athlete is running and lands on the feet or flexed knees, striking the ground while the hip is flexed, adducted, and internally rotated. This type of injury has been well documented in contact sports in which participants are tackled at high speeds and land out of control with other players piling on top of them (eg, football, rugby). A similar injury may occur during high-speed racecar driving accidents.

• The second mechanism involves an athlete landing in the splits, with the hip flexed, abducted, and externally rotated. This type of injury is more likely to be seen during sports involving jumping and landing (eg, basketball, gymnastics).

• The mechanism in skiing and snowboarding injuries is not well described and complex, due to high speeds and additional equipment, but it is likely similar to the aforementioned mechanisms.

Patients often present in obvious severe pain in the hip region and upper leg. They may also complain of knee, lower leg, or even back pain.

Patients usually complain of the inability to walk or move their leg about the hip joint.

Patients may complain of numbness and/or tingling in the legs in cases involving neurovascular damage.

Hip dislocations usually present with the athlete complaining of severe pain around the hip and proximal thigh.

Anterior hip dislocations may present in 2 different ways.

• Superiorly displaced dislocations present with the affected hip extended and externally rotated.

• The inferior type of anterior dislocations presents with the affected hip flexed, abducted, and externally rotated.

However, the affected limb of a posterior hip dislocation most commonly appears shortened, internally rotated, and adducted.

In those patients whose mechanism of injury suggests a posterior hip dislocation but who have no evidence of a dislocation on examination, a traumatic posterior hip subluxation should be considered. This injury carries many of the risks of a true dislocation and may be overlooked.[14]

Assessing the neurovascular status of the injured leg is extremely important. Nerve injury, particularly neurapraxia, is not uncommon. The sciatic nerve and the common peroneal division of the sciatic nerve are most often injured in posterior dislocations. Simple observation and palpation for bony deformity, skin color, and temperature provides clues to the vascular status of the leg. Test reflexes, strength, and sensation in the affected leg, and palpate for femoral and distal pulses.

The physician should also examine the patient carefully for other bony injuries. A significant amount of force is required to dislocate a hip. Studies of motor vehicle accidents have shown hip dislocations are commonly associated with knee injuries such as fractures, dislocations, and ligamentous damage. Whether or not sport-related hip dislocations have the same rates of associated knee injuries is not known; however, a careful knee examination should be performed on all patients with hip dislocations.

Related Medscape Reference topics

Fracture, Knee

Knee Injury, Soft Tissue

Peripheral Nerve Injuries

Traumatic Peripheral Nerve Lesions

Laboratory studies should be based on the individual patient, mechanism of injury, and concern about other injuries.

Evaluate the amount of blood loss if a patient has any significant trauma to the hip or if vessel injury is suspected. Observation of serial hemoglobin/hematocrit is important in case of disruption or intimal tear of the femoral vessels.

Radiographs (anteroposterior [AP], lateral, and internal and external oblique views)

A full series of prereduction radiographs should be obtained expeditiously, including the AP pelvis view, which shows most hip dislocations and provides evidence for the type of dislocation. Include other views, such as a cross-table lateral, and Judet (oblique) views. Exceptions would include expedient on-field reduction and not having timely access to a facility with radiographic capability, such as backcountry skiing/snowboarding areas.

In the AP pelvis view, the femoral head will appear small when compared with the uninjured side in a posterior dislocation and large in an anterior dislocation.

Evaluate where the femoral head lies in comparison to the acetabulum (eg, anterior vs posterior, superior vs inferior), if surgery is required to reduce the joint.

Lateral and oblique views are very important to evaluate for fractures of the femoral head, neck, and acetabulum.

Two oblique views are taken:

• The first oblique view is taken with the patient placed on the injured side and angled anteriorly approximately 15°.

• The second view is taken with the patient supine and angled upward about 60°.

A full series of postreduction films must be obtained to assess the adequacy of the reduction maneuver.

Although loose bony fragments or fractures may be difficult to see on a post-reduction x-ray, evaluating the hip joint for these fragments and fractures is imperative, as they may prevent complete reduction and cause further postreduction damage to the joint.

Computed tomography (CT) scanning

Indications for CT scanning of hip dislocations are debatable, although the fact that failure of closed reduction indicates a CT scan or an asymmetric joint space is widely agreed, as discussed below. CT scanning is helpful to the physician for diagnosing loose bodies and fragments that impede closed reduction and to evaluate acetabular fractures as well.

Bony fragments or damaged soft tissues that prevent closed reduction may be present, and the patient would need to be taken to the operating room for open reduction.

The presence of postreduction joint-space widening is a second widely accepted indication for a CT scan. This finding may also be evidence for bony fragment involvement that cannot be seen on x-ray or soft-tissue damage that prevents normal articulation.

Most physicians recommend obtaining a CT scan of the hip in every patient after closed reduction to evaluate for occult fractures and soft-tissue damage.

Magnetic resonance imaging (MRI)

MRI is indicated subacutely in certain cases of acute hip dislocations to evaluate labral tears, chondral injuries and cartilaginous loose bodies, particularly in the elite athlete and other patients who are likely to sustain high stresses to the hip, and in whom surgical repair of labrum and capsular ligaments would be considered.

MRIs should be done in 4-6 weeks to look for signs of osteonecrosis. This is repeated at about 3 months.

A study by Thanacharoenpanich et al that included 27 patients with traumatically dislocated hips reported that MRI is superior to CT scan for detection of structural injuries in children and adolescents with traumatic hip dislocation. Entrapment of posterior labrum and posterior unossified acetabular fractures were only seen on MRI.[15]

Closed reduction

Numerous studies have shown that closed reduction should be attempted as soon as possible after a hip dislocation and certainly within the first 6 hours after injury to minimize long-term joint damage.[6, 16, 17] These techniques should be performed using conscious sedation in the emergency department or under general or spinal anesthesia in the operating room. All of the methods are 2-person closed reduction.

The following are methods of closed reduction of a dislocated hip:

• The Allis maneuver, the most widely performed method, involves having an assistant bilaterally stabilize the anterior superior iliac spines while the patient is supine. First, the knee of the affected side is flexed, and then the hip is flexed, with traction being placed below the knee pulling upward. The leg is internally and externally rotated until the femoral head is rearticulated with the acetabulum.

• The Stimson maneuver places the patient in the prone position and is the least traumatic of the closed reduction methods. An assistant provides pressure on the patient's lower back for stability, while the injured leg is allowed to hang from the side of the bed with the knee and hip fully flexed. Traction is applied along with the force of gravity behind the knee, while internal and external rotation is applied to pop the femoral head back into place. Note: This technique is contraindicated in the setting of thoracoabdominal trauma or a difficult airway.

• The Bigelow maneuver is the final method of closed reduction. As in the Allis maneuver, an assistant applies pressure to the anterior spines of the patient's pelvis for stability. One hand is used to apply traction on the affected leg by pulling on the ankle, while the other forearm is placed under the knee. The knee and hip are flexed on the injured leg, and abduction, external rotation, and extension of the hip are performed until the femoral head is in the acetabulum.

• Another novel technique for the reduction of a hip dislocation realized high success rates with no reported neurovascular complications or injuries to the knee. The “Captain Morgan” technique involves placing the physician's knee behind the supine patient's flexed knee and lifting with anterior force, with rotation as needed.[18]

Reports of on-field reduction of posterior hip dislocations exist.[6, 8] Although this leads to expedient reduction and may theoretically decrease complication rates from the reduction, caution should be used. Only those with experience in hip reductions should even consider attempting an on-field reduction. However, early reduction within the first 5-10 minutes can often be much easier before the onset of muscle spasm. Also consider early out-of-hospital reduction, if significant transport time will occur, such as in wilderness or backcountry situations.

Rehabilitation Program

Physical Therapy

Acutely after successful reduction, resting and icing the hip and taking anti-inflammatory and/or narcotic medications to reduce pain are helpful.

• For type 1 posterior dislocations, athletes may return to weight bearing as pain allows.

  • Reviews of the literature do not show an increased risk of avascular necrosis with early weight bearing.

  • Athletes with type 2-5 posterior dislocations and anterior dislocations may require longer times to achieve weight bearing.

• Hip joints with associated fractures and/or instability are placed in a hip abduction brace postoperatively, which keeps the hip in abduction and slight external rotation for optimal healing, while allowing controlled (limited) flexion and extension. Within 5-7 days of the injury, patients can perform passive range-of-motion exercises with or without assistance in order to maintain normal flexibility (pendulum exercises).

Medical Issues/Complications

Serious complications include sciatic nerve damage, inability to perform closed reduction, and recurring dislocation.

• The sciatic nerve sits just inferoposterior to the hip joint and is injured in approximately 20% of all hip dislocations. These injuries range from nerve contusion to full laceration. The physician must perform a careful neurologic examination at the time of injury to assess sciatic nerve function. Most sciatic nerve injuries do not warrant acute intervention. Neurologic deficits that occur postreduction warrant immediate surgical intervention to decompress or reconstruct the damaged nerve.

• Reduction should be attempted as expediently as possible, as prolonged times to reduction are associated with more severe and frequent nerve injuries.[19]

• Closed reduction should be attempted under conscious sedation, general anesthesia, or spinal anesthesia immediately after the injury. The inability to perform closed reduction provides evidence for bony fragment involvement in the joint space and/or soft-tissue damage. CT scanning is warranted, followed by excision of loose bodies and open reduction.[20]

• The early phase of rehabilitation, involving traction of the injured leg, has been associated with recurring hip dislocation. A successful closed reduction that appears clinically and radiographically stable may redislocate during the first few weeks of the healing process. This dislocation may be caused by a bony fragment or soft-tissue damage that is preventing normal articulation. Perform a CT scan of the hip and discuss surgical intervention.

• Traumatic subluxation also carries a risk of complications and can be easily missed. Suspect this injury in patients who have an injury mechanism that is consistent with posterior hip dislocation and painful, limited hip motion. An MRI can be helpful in the diagnosis of this injury.[14]

• Anterior dislocations, although less common, have less risk of poor outcomes based on the available data.[21]

• Adolescents may be predisposed to epiphysiolysis during the reduction of a hip dislocation. A case was reported of a teenage football player in whom attempted closed reduction of a posterior hip dislocation resulted in complete separation of the epiphysis from the femoral neck metaphysis, with associated femoral head fracture and posterior dislocation of the femoral head.[22]

Surgical Intervention

Surgical intervention should be performed if closed reduction is unsuccessful, bony fragments or soft tissue remains in the joint space, or the joint remains unstable. Open reduction is typically performed using a posterior approach, owing to the decreased rate of avascular necrosis relative to the anterior approach.

Thoroughly irrigate the joint to assure adequate cleansing of any loose bone fragments or soft tissue that would prevent proper articulation. Internal fixation of large fracture fragments using screw and plate fixation should be performed by surgeons with experience in managing pelvic fractures.

Hip arthroscopy can be used to remove intraarticular fragments, evaluate intraarticular fractures and chondral injuries, and repair labral tears. When appropriate, hip arthroscopy is preferred to open surgery by those surgeons who are experienced in its use due to its minimally invasive nature, lower morbidity, and quicker recovery.

Consultations

Consult an orthopedic surgeon for any dislocated hip joint. Orthopedic surgeons should be present when attempting a closed reduction. If the closed reduction is unsuccessful, the patient will need to go to the operating room for an open reduction. Usually, keeping an unstable hip reduced with traction while awaiting surgical intervention is helpful (a postreduction hip should be held in traction for 6-8 weeks or until the leg is pain free). A CT scan is typically obtained before proceeding to the operating room.

Rehabilitation Program

Physical Therapy

• Dislocation of the hip joint is an extremely serious injury. The hip joint is crucial for weight bearing and ambulation. Proper rehabilitation must be performed to retain normal musculoskeletal function. Weight bearing with the help of crutches should begin immediately after the patient is pain free and transitioned to full weight bearing as pain allows.

• Rehabilitation may progress based on the athlete's clinical symptoms, and by 4 weeks, most type 1 hip dislocations can progress to functional weight-bearing exercises, such as shallow squats.

• An MRI should be considered at week 6 to assess for any signs of femoral head ischemia.

  • If any evidence of ischemia is present, the athlete should be made partial weight bearing and return to range-of-motion exercises only.

  • If no evidence of femoral head abnormalities is present, the athlete may continue his or her progression.

• Most athletes with type 1 hip dislocations can return to full activity in 3-4 months. Those with other injuries may require longer time periods to return to sports activity.

• Cardiovascular activities and stretching exercises are important early in the rehabilitation process to maintain full range of motion about the hip joint. Examples of these activities include upper-extremity cycling, weight training, and floor exercises such as push-ups.

Medical Issues/Complications

A number of chronic complications of hip dislocations can be very severe in nature. These include avascular necrosis, arthritis, chondrolysis, and myositis ossificans.

• Avascular necrosis is reported in up to 40% of patients because of the disruption of blood supply to the femoral head and from the mechanical force applied to the femoral head during the injury. The risk factor most associated with avascular necrosis is delayed reduction.

  • Generally, the consensus is that reduction should be performed as soon as possible (within 6 hours of injury), and certainly no later than 24 hours after the injury when no appropriate facilities are immediately available.[6, 16, 17] One study found that the risk of avascular necrosis further decreased when reduction was performed within 6 hours of injury.[17]

  • Avascular necrosis has been diagnosed radiographically from a few months to a few years post injury. Scheduling close follow-up visits every few months is imperative after hip dislocation. Serial radiographs should be taken to evaluate for evidence of avascular necrosis.

  • An MRI of the hip should be considered at 6 weeks after dislocation to assess for the possibility of avascular necrosis of the femoral head.

  • Case reports of late avascular necrosis have been rarely reported; therefore, hip pain in an athlete with a history of dislocation should be investigated regardless of the time interval that has passed.[23]

• Arthritis is the most common long-term complication after hip dislocation, affecting up to 50% of all patients. Arthritis is thought to occur from damage to the articular cartilage from traumatic injury. Open reduction has been said to decrease the incidence of postdislocation arthritis, although this is not widely accepted. Radiographs are important for diagnosing arthritis and nonsteroidal anti-inflammatory drugs (NSAIDs) should be prescribed to decrease pain and inflammation in the arthritic hip joint.

• Myositis ossificans occurs because of muscle and soft-tissue damage after hip dislocation. The rate of this complication is about 2% and is higher in patients who have undergone open reduction. Early closed reduction appears to be the most effective way of preventing myositis ossificans.

• Another possible complication is a labral tear, which is diagnosed by MRI in the acute setting or MRI arthrogram in the subacute setting. Labral tears are typically treated by hip arthroscopy.

Rehabilitation Program

Physical Therapy

Leg muscle strengthening exercises may begin once the patient is pain free and ambulating without crutches. Patients may work to strengthen the hip flexors, hip extensors, and the muscles nearest the hip, including the quadriceps and hamstrings. Over the next few months, gradually increasing the patient's level of cardiovascular training may be attempted, which should include brisk walking and swimming. Jogging or running may begin at 6-8 weeks but will differ by individual athlete and injury. Full return to sports is generally within 3-4 months.

Other Treatment

Imaging

X-rays should be repeated at 3 weeks, 6 weeks, 3 months, and 6 months to follow the healing of fractures.

An MRI arthrogram should be considered if the athlete develops symptoms with rehabilitation and has negative radiographic findings.

Athletes recovering from hip dislocations must follow a strict physical therapy regimen to ensure complete recovery of function. Stretching and range-of-motion exercises are important early in the recovery process, advancing to walking on crutches when the patient's pain fully resolves. Strengthening exercises of the muscles around the hip are important during the rehabilitation to take stress off the injured joint. The athlete should advance his or her rehabilitation regimen over time as tolerated, with light jogging by 6-8 weeks post injury, and regain full function in high-performance athletes by 3-4 months post injury.

No literature on the prevention of hip dislocations exists.

As these injuries are generally high-velocity injuries, the success of any prevention program, other than high-risk activity avoidance, would be unlikely.

Patients who have experienced hip dislocation are usually in severe pain. The pain should be evaluated on a scale (0-10) and the patient provided with sufficient analgesia. While in the hospital, intravenous narcotics are the best choice for pain relief. Intravenous morphine (0.1 mg/kg q2-4h) is recommended for optimal analgesia. Postdischarge oral narcotics should be prescribed to keep the patient comfortable at home and during their rehabilitation period. Decreasing the inflammation near the site of injury by giving NSAIDs (eg, ibuprofen, naproxen) every 6 hours is also important. This enables the patient to be as comfortable as possible, while aiding in the healing process.

Class Summary

Pain control is essential to quality patient care. Analgesics ensure patient comfort, promote pulmonary toilet, and have sedating properties, which are beneficial for patients who have sustained trauma or who have sustained injuries.

Related Medscape Reference topic

Toxicity, Narcotics

Hydrocodone and acetaminophen (Lorcet, Lortab, Norcet, Vicodin)

Drug combination indicated for moderate to severe pain.

Oxycodone and acetaminophen (Percocet, Roxicet, Roxilox, Tylox)

Drug combination indicated for the relief of moderate to severe pain.

Oxycodone and aspirin (Percodan, Roxiprin, Codoxy)

Drug combination indicated for the relief of moderate to severe pain.

Class Summary

NSAIDs have analgesic and antipyretic activities. The mechanism of action of these agents is not known, but NSAIDs may inhibit cyclooxygenase activity and prostaglandin synthesis. Other mechanisms may exist as well, such as inhibition of leukotriene synthesis, lysosomal enzyme release, lipoxygenase activity, neutrophil aggregation, and various cell membrane functions. Treatment of pain tends to be patient specific.

Related Medscape Reference topic

Toxicity, Nonsteroidal Anti-inflammatory Agents

Ibuprofen (Ibuprin, Advil, Motrin)

Drug of choice (DOC) for mild to moderate pain. Inhibits inflammatory reactions and pain by decreasing prostaglandin synthesis.

Naproxen (Naprelan, Naprosyn, Aleve, Anaprox)

For the relief of mild to moderate pain; inhibits inflammatory reactions and pain by decreasing the activity of cyclooxygenase, which is responsible for prostaglandin synthesis.