Hip Dislocation

Original Editor - Annelies Noppe

Top Contributors - Annelies Noppe, Leana Louw, Lucinda hampton, Kim Jackson, Lokiru Paul, WikiSysop, Vidya Acharya, Anas Mohamed and Kirenga Bamurange Liliane

Definition/Description

Hip dislocation is the displacement of the femur head from the acetabulum. Most of the times this causes damage at the tissue around the hip.

Clinically Relevant Anatomy

The ball-and-socket joint of the hip anatomy exist of the acetabulum and the femur head. The acetabulum has the shape of a cup and the femur head the shape of a ball.

The hip is a weight bearing ball joint mainly functioning as support. The stability of the hip joint is provided mainly by the capsule and the surrounding muscles and ligaments. They stabilise the femur head in the acetabulum and ensure that the hip joint are able to move in all available planes.

Epidemiology /Etiology

Characteristics

The following patients characteristics leads to an increased risk of developing a hip dislocation:

• Female > male
• Alcohol abuse
• Various pre-operative disorders
• Older age:
  • Decreased muscle mass reduces the stress on the hip prosthesis and decreases the natural protection against hip dislocation
  • Increased risk of falling due to compromised balance
  • Neuromuscular dysfunction associated with old age - e.g. neuropathy or cerebrovascular accident
  • Cognitive impairments
• Great dexterity
• Poor follow instructions
• Increased tendency to fall
• Chronic hip instability

Causes

The causes of hip dislocations can mainly be devided into two groups, mainly congenital and aquired hip dislocations.

Congenital hip dislocation (CHD)

Also known as developmental dysplasia of the hip (DDH). All newborn babies have their hips assessed for DDH within a few days of birth and at six weeks in order fr treatment to commence early if necessary. CHD occurs with an incidence that vary between 1.5 and 20 per 1.000 births and is 8 times more commonly in girls than in boys. This is explained by the greater mobility of the hip in women. More than 80% of clinically unstable hips noted at birth have been shown to resolve spontaneously.

Acquired hip dislocation

Young adults are most affected by traumatic hip dislocations, mostly caused by car accidents and is always the result of an external force with high intensity. Hip dislocations are thus rarely isolated, and often goes together with other injuries or fractures. Fractures to the acetabulum and femur head is most commonly associated with traumatic hip dislocations. Hip dislocations are classified as either anterior or posterior, depending on the displacement of the femur head in relation to the acetabulum. Posterior hip dislocations are more common, and makes about 85-90% of the cases. The position of the hip will be in flexion, adduction and internal rotation, with notable shortening of the leg. With anterior hip dislocations, the hip will be minimally flexed and positioned in abduction and external rotation.

Dislocation after hip replacement surgery has the highest incidence rate immediately after the surgery or in the first three months. The incidence of hip dislocation following hip replacement surgery depends on patient, surgical and hip implant factors. In general, the larger the head of the femur post surgery, the less likely a patient is to experience dislocation.

Characteristics/Clinical Presentation

• Pain:
  • Severe pain is the most common symptom. With the separation of the femur head from the acetabulum, surrounding muscles and tendons can be damaged as well. Subsequent knee injuries might also be present.
  • Radiating knee pain

• Swelling

• Leg length discrepancy and deformity:
  • In most of the cases is the affected leg will appear shortened and the hip joint deformed

• Hip immobility:
  • Reduced hip range of motion
  • Inability to walk as a result of pain and swelling

• Traumatic hip dislocations:
  • Male > female
  • Posterior > anterior

Differential Diagnosis

• Hip dysplasia
• Hip sublaxation

Diagnostic Procedures

• X-rays: AP pelvis and lateral
  • To confirm dislocation or successful relocation
  • Assess for associated fractures
• CT:
  • To rule out concomitant injuries in traumatic dislocations (e.g. acetabulum or femur head fractures)
  • Clearance of lumbar spine

Complications

Immediate:

• Associated soft tissue injuries
• Neural injuries, especially to the sciatic nerve in posterior dislocations
• Fractures, mostly to the femur head or acetabulum

Long term:

• Avascular necrosis:
  • Incidence of 1.7-40% is reducable to 0-10% if relocation is done within 6 hours post traumatic dislocation
• Post-traumatic osteoarthritis
• Chronic dislocations
• Leg length discrepancy

Medical Management

Conginital dislocation

Conservative management

• Newborns: Flexion / abduction maneuvers .
• Bracing: A brace, splint or harness can be used to keep the hip in flexion and abduction for one or two months by the use of a brace, splint or harness.
  • This aims to keep the femur head in the right position while the ligaments and bones grow and strengthen around it.

Surgery

Surgery is indicated for failed conservative management.

Surgery entails release the of the adductor longus muscle, lengthening the psoas tendon, and insertion of a Kirschner wire. This results in marked improvement in hip function and prevents complications later in life.

Acquired hip dislocation

A dislocated hip should be relocated as soon as possible, as the complication risk of avascular necrosis, neural damage and subsequent dislocations increases with the time between the dislocation and relocation. The Allis maneuver is normally the reduction method of choice for posterior dislocations

Non-surgical

Relocation of the hip is done by a traction force performed in the opposite direction of the dislocation, with the hip in 90° flexion. This should preferably be done under general or regional anesthesia and muscle relaxation to prevent greater damage to cartilage and soft tissue. After the relocation, the stability of the hip should be tested very carefully. A period of bed rest might be recommended depending on the stability of the hip and the extent of the soft tissue injuries.

Surgical

Indications:

• Failed conservative relocation
• Instability following conservative relocation
• Associated fractures of the femur head or acetabulum
• Loose bone fragments in joint space after relocation

Hip arthroscopy can be used to evaluate intra-articular fractures and chondral injuries and to remove intra-articular fragments, Hip replacement surgery can also e considered if optimal stability is not achieved with relocation and fixation of the associated injuries. Open reduction is used with challenging relocations. Dislocation following hip replacement surgery might indicate revision surgery to ensure the stability of the hip in the long run.

Physiotherapy Management

• Improve hip range of motion: Especially extension in children after the use of a brace/splint/harness that kept the hip in flexion
• Strengthening of muscles around the hip, with special focus on hip stabilizers
• Stretching
• Joint mobilization
• Graded return to activity/sport