Hip dislocation (luxation)
A healthy hip joint with the femoral had placed correctly in the acetabulum

Definition

The dislocation of the hip occurs when the femoral head forcefully exits the pelvic socket or acetabulum. It can be of congenital or occur from trauma with the first being described in the pathology hip dysplasia.

Hip dislocation occurs with the exit of the femoral head from the acetabulum

Pathology

A traumatic dislocation of the hip is a serious condition needing emergency care as it may occur in concomitance with fractures or injuries elsewhere in the body. The dislodgement of the femoral head from the acetabulum requires high impact forces and provokes sharp pain. It differs from the dislocation of hip prostheses and those dislocations observed in patients with congenital hip dysplasia.

A hip dislocation is divided into three types according to the positioning of the femoral head relative to the hip joint:

Anterior hip dislocation occurs with hip abduction and external rotation. It is associated with femoral head impaction, pubic dislocation and obturator dislocation. Anterior hip dislocation is associated with fracture of acetabulum, femoral head, knee injury and sciatic nerve damage.

Posterior hip dislocation (circa 90% of all dislocations) is typical when impacting to the car dashboard with a flexed hip and knee. 

Central hip dislocation is caused by a lateral impact and mostly linked to acetabular fracture.

A hip dislocation can be simple if isolated or complex when involving the fracture of the acetabulum or proximal femur. This pathology may lead to long-term morbidity such as chronic pain, reduced mobility and posttraumatic osteoarthritis.

Different types of hip dislocation

Classification

Thompson-Epstein classification of hip dislocations when associated with:

 Type 1 – without minor fracture

Type 2 – single fracture of posterior acetabular rim

Type 3 – comminution of acetabular rim, with/without fragments

Type 4 – fracture of acetabular floor

Type 5 – fracture of femoral head

 

Steward and Milford classification of hip dislocation relies on functional changes:

Type 1 – No fracture or small fracture

Type 2 – single or comminuted posterior wall fragment although hip stability is not  affected with movement

Type 3 – severe instability of the hip following loss of structural integrity

Type 4 – fracture of femoral head

Left: Distal radius intraarticular, displaced fracture; Middle: Older distal radius fracture with callus formation; Right: Distal radius and ulna fracture, extraarticular and displaced

No 2.

Intra-articular fracture extends to the wrist joint (or articulation)

Extra-articular fracture is located outside of the wrist joint

Open fracture when bone fragments perforate the skin

Comminuted fracture when the bone breaks into multiple fragments

Non-displaced when the anatomical alignment of the bone is maintained or displaced when the bone fragments move apart.

Melone’s classification describes the characteristics of intra-articular fractures of the radius:

i    Stable fracture

ii    Unstable "die-punch"

iii   "Spike" fracture

iv Split fracture

v   Explosion injuries

Acetabular fracture of the pelvis

Acetabular fractures

These fractures are divided into:

Anterior pillar (not weight bearing part of joint)

Posterior pillar (often associated with dislocation of the hip including the weight bearing part of joint)

Transverse

Comminuted involving both column type 

Sacral / coccygeal fractures

The sacrum is a triangular-shaped bone formed by 5 fused vertebrae, which provide a posterior wall to the pelvic ring. At each side of the sacrum, the ala structures articulate with the ilium bones forming the sacro-iliac joints. Sacral fractures are usually parallel to the spine and can involve the ala. Less frequently sacral fractures may display an “H” shape, including a transversal fracture uniting both sides of the sacrum. Three zones are described where sacral fractures can occur that are along vertical lines relative to the alignment of the foramina. Sacral fractures may result in sacral instability and require treatment via sacroplasty (injection of bone glue into the fracture). Surgery is necessary in case of associated neurological symptoms.

Fractures of the coccyx involve the tailbone, the terminal portion of the spine situated below the sacrum formed by 3 to 5 fused vertebrae. Coccyx fractures occur when falling on a seated position. They are more common in elderly women and seldom require surgical treatment.

Car accidents can cause hip dislocation when the knee violently hits the dashboard

Causes

Traumatic events involving high energy are the main cause of a hip dislocation. The impact is usually applied directly to the hip as it occurs with a fall from a significant height, high velocity motor vehicle accidents or falls during contact sports. 

In children a hip dislocation does not require a high force but can affect the integrity of the growth plates (epiphysis) of the femur. In the young population this pathology is rare but is frequently observed in risk-taking individuals.

The main causes are:

High-speed motor vehicle accidents (2/3 of all dislocations; 70%)

Falls from significant height / high velocity onto the hip

Industrial accidents

Unsafe work at hight increases the risk of falls and hip dislocations

Risk factors

The risk factors for a hip dislocation differ in population groups:

Young age: car driving, sports

Older age: falls

Male gender: risk taking behaviours

High speed car accidents

Working at height (carpenters, electricians, builders, painters)

Sport injuries (football, rugby, water skiing, alpine skiing/snowboarding, gymnastics, running, basketball, race car driving, horse riding)

Asymmetric positioning of the legs is a symptom of a hip dislocation

Symptoms

The symptoms of a dislocated hip may vary in relation to associated injuries. Soon after occurring, a hip dislocation triggers severe pain on the hip and pelvis radiating to the lower back and limbs. The patient is unable to move the hip and may suffer from numbness around the hip area and even paralysis of the lower limb (nerve damage).

Deformities may also appear following a hip dislocation including partial rotation, shortening, abduction/adduction of the affected limb. 

Damage to the sciatic nerve manifests via lack of sensation on the back of the leg and foot, inability to dorsiflex and plantar flexion, loss of ankle reflexes. Injury to the femoral nerve causes lost sensation on the thigh, quadriceps weakness, and loss of reflexes at the knee. Vascular injury comprises the appearance of haematomas and absence of pulse. Arterial damage may compromise blood perfusion to the leg of the dislocated hip.

Hip dislocation associated with femoral head fracture

Diagnosis

A hip dislocation is considered an orthopaedic emergency and first care is executed at the hospital. The eventuality of life-threatening injuries must be prioritised over the dislocation and the patient’s cardiovascular condition stabilised. Following admittance, the patient is firstly immobilised and treated with painkillers (analgesics) and fluid replacement, prior to radiologic evaluation with X-rays. Often a CT scan or an MRI is performed to classify the type of dislocation and detect potential fractures, abdominal injuries and nerve damage.

Treatment

Avoiding full weight bearing helps recover from hip dislocation

Nonoperative treatment

A simple, displaced hip when isolated requires a closed reduction, a procedure usually undertaken within 6 hours from the accident at the emergency department or operating theatre. The patient is firstly anaesthetised or sedated. Subsequently a control X-ray is taken to confirm the correct positioning of the femoral head into the acetabulum. A closed reduction is not conducted with a femoral neck fracture.

The patient is advised to follow these recommendations:

Rest

Use crutches to avoid full weight bearing

Administration of NSAIDs for pain relief and reduce inflammation

Physical therapy

Fractures of the hip and femoral head following a dislocation require surgical fixation

Surgical treatment

Surgical treatment for a dislocated hip is necessary when patient presentation to hospital is delayed beyond 6 hours, or with failed closed reduction and continued instability of the hip joint. Prior to surgery the limb of the affected hip may be placed into traction to reduce pressure on the joint. Arthroscopic surgery is suitable for minor procedures, such as removal of bone and cartilage fragments from the joint space and assessment of soft tissue injuries to the cartilage, capsule, labrum. Open reduction and internal fixation (ORIF) is required to repair fractures to the femoral head, neck and acetabulum.

Image (left) and X-ray (right) of avascular necrosis of the femoral head

Complications

Most common complications following a hip dislocation are:

Recurrent dislocations due to ligament laxity and damage

Necrosis of the femoral head (avascular necrosis) due to damage of the vessels around the bone

Post-surgical infection treated with antibiotics

Hip osteoarthritis arising from injury to the cartilage tissue, requiring prosthetic replacement

Neurological deficits due to long-lasting or permanent nerve injury

Medical issues: DVT, pneumonia, pulmonary embolism

Strengthening the muscles around the hip helps rehabilitation from a hip dislocation

Rehabilitation

It is critical that after a period of rest following a hip dislocation the patient begins rehabilitative care with gradual and assisted walking to prevent medical complications. In the elderly, this phase may require admission to a cared facility or regular in-home visits by an occupational therapist to restore independent daily living activities. A wheelchair, crutches, walking stick, or walker may be necessary to support the patient during the first weeks while recovering from a hip dislocation. Physiotherapy care includes:

Rest

Ice/heat treatment

Traction for 2 weeks with abducted legs to prevent secondary dislocation

Antiinflammatory therapy (NSAIDs)

Analgesics for pain control

No weight or partial weight bearing for up to 3 months

Exercise to strengthen quadriceps, hamstrings and gluteal muscles

Stretching of hip and leg muscles

Massage

Joint mobilisation

Guided return to activity and sport

Wearing safety belt and harness prevents falls and numerous injuries

Prevention

A hip dislocation cannot be easily prevented and presents a certain risk for a second dislocation. Prevention is mostly based on guidelines to reduce falls and improve safety in road traffic and workplace. Some preventive measures include:

Keeping floor surfacing in sport halls well maintained

Exercise to maintain muscular strength and flexibility

Use of supporting walking devices in the elderly

Adherence to occupational health and safety procedures (harness, balustrades)

Use of road traffic safety equipment (seatbelt)

Removal of carpets or other items facilitating falls

Modify habits (use laced shoes, house illumination at night, staircase railings, non-skid tiles in bathroom)