traumatology

Dislocation of the Hip

Generality

The dislocation of the hip is the injury of the hip, of traumatic origin, in which the head of the femor comes out from the acetabulum.

A common consequence of frontal motor vehicle accidents and falls from high positions, the dislocation of the hip is responsible for severe pain and the inability to move the affected limb.

The diagnosis of hip dislocation is generally based on physical examination, medical history and a radiological test such as X-rays of the pelvis.

The therapy consists in the manual reduction of the dislocation, in the less serious cases, while it foresees the surgical intervention, in the most severe cases.

Brief anatomical recall of the hip

Equal anatomical element, the articulation of the hip (or more simply hip ) includes a skeletal scaffold, to the support and mobility of which various ligaments and a series of muscles contribute.

The bony constituents of the hip are the femur (thigh bone) and the iliac bone (one of the bones of the pelvis). The femur contributes with its proximal region, precisely with the so-called femoral head and the underlying neck of the femur ; the iliac bone, instead, participates with a portion similar to a cavity, called acetabulum .

The hip is among the largest joints in the human body and belongs to the articular family of the so-called enartrosis . Extremely mobile, the arthrosis results from the housing of a convex bone portion (the femoral head, in the case of the hip) in a concave bone portion (the acetabulum, in the case of the hip); moreover, they are provided with synovial fluid and layers of cartilage (" articular cartilage "), whose purpose is, for both, to reduce interosseous frictions and impact shocks (if absurdly they were devoid of such elements, the convex bone portion and the concave bone portion would rub against each other so as to deteriorate each other).

The hip is fundamental for the motor skills of the human being; thanks to her, in fact, an individual can take up a standing position, walk, run, jump, etc.

What is hip dislocation?

Dislocation of the hip is the injury to the hip joint, characterized by the exit of the femoral head from the acetabulum of the iliac bone.

Episodes of hip dislocation are medical emergencies and therefore require immediate treatment.

Two important clarifications

  • This article focuses its attention on the traumatic dislocation of the hip, that is on the dislocation of the hip following a trauma.

    However, it should be pointed out that there is also congenital dislocation of the hip (or congenital dysplasia of the hip ), whose onset is linked to a developmental anomaly.

  • In medicine, the terms dislocation and distortion indicate two clearly different joint pathologies. In fact, while in dislocation articular modification is permanent and involves the loss of contact between the bony portions forming the affected joint, in the distortion the anatomical modification of the affected joint is temporary.

Causes

Most episodes of hip dislocation of traumatic origin involve:

  • Drivers of motor vehicles involved in frontal road accidents. In such situations, in fact, the knees of the victims impact violently against the dashboard of the vehicle and this causes the femur to perform an abnormal movement and very abruptly backward (think of the victims as seated, viewed from the side).
  • Persons who are victims, from home or work, of falling from an elevated position. In such situations, the dislocation of the hip depends on the dynamics of falling or, better, on the dynamics with which the victim of the accident impacts with the ground.

Types of hip dislocation

The doctors and experts of diseases of the musculoskeletal system recognize the existence of two types of hip dislocation: the so-called posterior dislocation of the hip and the so-called anterior hip dislocation .

  • In the posterior dislocation of the hip, the femoral head emerges from the acetabulum, moving backwards and slightly above the latter.

    In these circumstances, the typical consequences of the exit of the femoral head from the acetabulum are:

    • Rotation towards the inside of the femur, with consequent rotation towards the inside of the entire lower limb;
    • Hip adduction, with consequent approach of the lower limb to the sagittal plane;
    • Flexion of the femur, with consequent displacement of the thigh towards the trunk of the body.
    The posterior dislocation of the hip characterizes about 90% of episodes of dislocation of the hip of traumatic origin and, not infrequently, is associated with the fracture of the acetabulum and / or fracture of the femoral head .
  • In anterior dislocation of the hip, on the other hand, the femoral head emerges from the acetabulum, moving forward and slightly lower than the latter.

    In such situations, the typical consequences of the exit of the femoral head from the acetabulum are:

    • Outward rotation of the femur, with consequent rotation towards the outside of the entire lower limb;
    • Hip abduction, with consequent removal of the lower limb from the sagittal plane;
    • Flexion of the femur, with consequent raising of the thigh.
    The episodes of anterior dislocation of the hip constitute, substantially, the remaining 10% of the cases of dislocated hip of traumatic origin.

Epidemiology

Traumatic episodes of dislocation of the hip are injuries affecting above all the population in the age group between 16 and 40 years.

As already mentioned, the most common type of hip dislocation is posterior hip dislocation.

Symptoms and complications

The typical symptoms of traumatic dislocation of the hip are severe pain in the hip and inability to move the affected lower limb .

If the trauma triggering the injury in question has also affected the good health of some nerve structures passing through the hip, the aforementioned symptoms are also added numbness and insensitivity to the level of the leg, ankle and / or foot (clearly of the lower limb involved).

Signs of dislocation of the hip

The signs of traumatic dislocation of the hip are:

  • For posterior dislocation of the hip → rotation towards the inside of the femur and the entire lower limb involved, abduction of the hip and flexion of the femur.
  • For anterior dislocation of the hip → rotation towards the outside of the femur and of the entire interested lower limb, adduction of the hip and flexion of the femur.

Complications

Among the possible complications of traumatic episodes of dislocation of the hip, stand out:

  • Osteonecrosis of the femoral head. In medicine, the term "osteonecrosis" indicates the death of bone tissue due to an absent or insufficient supply of blood;
  • Fracture of the acetabulum and / or femoral head . As previously stated, fractures of this kind characterize the posterior dislocations of the hip;
  • The lesion of the sciatic nerve . It can characterize posterior hip dislocations;
  • The paralysis of the femoral nerve . It can mark the anterior lesions of the hip;
  • Knee injuries . They can especially catch those who are victims of posterior hip dislocations.

Curiosity

The involvement of the sciatic nerve affects between 8 and 20% of cases of posterior hip dislocation.

Hip dislocation and osteoarthritis

Statistics show that people who are victims of traumatic hip dislocation develop a predisposition to hip osteoarthritis, a condition also known as coxarthrosis .

Diagnosis

In general, the diagnosis of a traumatic dislocation of the hip is based on: physical examination, medical history and a radiological examination such as an X-ray of the pelvis or a nuclear magnetic resonance of the pelvis.

What are radiological exams for?

Radiological examinations are used to confirm what emerged during the physical examination and anamnesis, and to clarify the precise consequences at the musculoskeletal level of dislocation of the hip (damage to ligaments or tendons, events of osteonecrosis, presence of fractures at the level of the acetabulum or femoral head etc.).

Therapy

The treatment of dislocated hip dislocation varies depending on the severity of the injury. In fact, if the dislocation of the hip is mild (where for mild it is meant that it is not associated with fractures or other complications), to restore the normal joint structure it is sufficient to manipulate the affected limb, also known as manual reduction ; if instead the dislocation of the hip is severe (where for severe it is meant that it is associated with complications), to restore the normal structure of the hip joint it is essential to resort to surgery .

Manual reduction

Manual reduction consists of some specific movements of the lower limb involved, which allow the femoral head to re-enter the acetabulum. Clearly, a doctor who specializes in similar practices deals with the manual reduction of a hip dislocation.

Manual reduction of hip dislocations must take place as soon as possible after the injury has occurred and requires the patient to be given a strong sedative or anesthetic, as otherwise it would be very painful.

To establish whether manual reduction has been successful, the physician who performed the aforementioned manipulation subjects the patient to a radiological examination of the pelvis (X-rays, nuclear magnetic resonance or CT scan).

Important

If it does not occur within 6 hours of the traumatic event that caused the dislocation of the hip, manual reduction may not be possible.

In such situations, the only therapeutic solution available is surgery.

Surgical treatment

Surgical treatment of severe hip dislocation may involve therapeutic interventions on fractured bones (acetabulum and / or femoral head), therapeutic interventions on nerves, damaged muscles and / or tendons passing near the hip, removal of bone fragments isolated etc.

Surgical procedures for the treatment of a hip dislocation are invasive operations, which require the use of general anesthesia.

What to do after the treatment?

Both after manual reduction and after surgical treatment, the patient who has been the victim of a hip dislocation must rest for a few days, then start a specific physiotherapy rehabilitation program.

The duration of physiotherapy rehabilitation is much longer, the more severe the hip dislocation was and the more invasive the treatment was.

Prognosis

If the treatment is timely and adequate, the dislocated hip dislocation has a benign prognosis.

Recovery times

For a satisfactory recovery from most episodes of dislocation of the hip, it takes from 2 to 3 months.