Dislocation of the Hip

Generality

Hip dislocation is the hip injury of traumatic origin in which the head of the hip protrudes from the acetabulum.

A common consequence of frontal car accidents and falls from high positions, hip dislocation is responsible for severe pain and the inability to move the affected limb.
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 less serious cases, while it foresees the surgical intervention, in the more severe cases.

Brief anatomical recall of the hip

An equal anatomical element, the "joint of the hip" (or more simply the hip) comprises a "skeletal scaffolding, which supports and mobility various ligaments and a series of muscles.
The bone components that make up the hip are the femur (thigh bone) and the iliac bone (one of the pelvic bones). The femur contributes with its proximal region, precisely with the so-called head of the femur and the underlying neck of the femur; the iliac bone, on the other hand, participates with a portion similar to a cavity, called the acetabulum.
The hip is one of the largest joints in the human body and belongs to the joint family of the so-called enarthroses. Extremely mobile, enarthroses result from the housing of a convex bone portion (the head of the femur, 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"), the purpose of which is, for both, to reduce interosseous friction and impact shocks (if absurdly they were devoid of these elements, the convex bone portion and the concave bone portion would rub together in order to deteriorate each other).
The hip is fundamental for the motor skills of the human being; thanks to her, in fact, an individual can assume a standing position, walk, run, jump, etc.

What is hip dislocation?

Hip dislocation is an injury to the hip joint characterized by the head of the femur coming out of 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 traumatic hip dislocation, ie hip dislocation following trauma.
However, it should be noted that there is also congenital hip dislocation (or congenital hip dysplasia), the onset of which is linked to a developmental anomaly.
In medicine, the terms dislocation and sprain indicate two distinctly different pathologies of the joints. In fact, while in the dislocation the joint modification is permanent and involves the loss of contact between the bony portions that form the affected joint, in the sprain the anatomical modification of the affected joint is temporary.

Causes

Most episodes of hip dislocation of traumatic origin involve:

Car drivers involved in frontal road accidents. In such situations, in fact, the knees of the victims violently impact against the dashboard of the vehicle and this causes the femur to perform an anomalous and very abrupt movement backwards (think of the victims as sitting people, viewed from the side).
People who are victims, in the home or at work, of falls from a high position. In such situations, the dislocation of the hip depends on the dynamics of the fall or, better, on the dynamics with which the victim of the accident collides with the ground.

Types of hip dislocation

Physicians and experts in musculoskeletal disorders recognize the existence of two types of hip dislocation: the so-called posterior hip dislocation and the so-called anterior hip dislocation.

In posterior dislocation of the hip, the head of the femur protrudes from the acetabulum moving, with respect to the latter, backwards and slightly upwards.
In these circumstances, the typical consequences of the femoral head coming out of the acetabulum are:

Inward rotation of the femur, with consequent inward rotation of the entire lower limb;
Adduction of the hip, with consequent approach of the lower limb to the sagittal plane;
Flexion of the femur, resulting in a shift of the thigh towards the trunk of the body.

Posterior hip dislocation characterizes about 90% of hip dislocation episodes of traumatic origin and, not infrequently, is associated with fracture of the acetabulum and / or fracture of the femoral head.

In anterior dislocation of the hip, on the other hand, the head of the femur protrudes from the acetabulum moving forward and slightly downwards with respect to the latter.
In such situations, the typical consequences of the femoral head coming out of the acetabulum are:

Outward rotation of the femur, with consequent outward rotation of the entire lower limb;
Abduction of the hip, with consequent removal of the lower limb from the sagittal plane;
Flexion of the femur, resulting in an elevation of the thigh.

Epidemiology

Traumatic episodes of hip dislocation are injuries that mainly affect the population aged between 16 and 40 years.
As mentioned above, the most common type of hip dislocation is posterior hip dislocation.

Symptoms and complications

Typical symptoms of traumatic hip dislocation are severe hip pain 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 accompanied by numbness and numbness in the leg, ankle and / or foot (clearly of the foot). lower limb involved).

Signs of hip dislocation

The signs of hip dislocation of traumatic origin are:

For posterior hip dislocation → internal rotation of the femur and the entire involved lower limb, abduction of the hip and flexion of the femur.
For anterior hip dislocation → outward rotation of the femur and the entire affected lower limb, adduction of the hip and flexion of the femur.

Complications

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

Osteonecrosis of the femoral head. In medicine, the term “osteonecrosis” indicates the death of bone tissue due to an absent or insufficient blood supply;
The fracture of the acetabulum and / or the head of the femur. As previously mentioned, fractures of this kind characterize the posterior dislocations of the hip;
The injury of the sciatic nerve. It can characterize posterior hip dislocations;
Paralysis of the femoral nerve. It can distinguish anterior lesions of the hip;
Knee injuries. They can especially affect those who are victims of posterior hip dislocations.

Curiosity

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

Dislocation of the hip and arthrosis

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

Diagnosis

Typically, the diagnosis of a traumatic hip dislocation is based on: physical examination, medical history, and radiological examination such as x-rays of the pelvis or nuclear magnetic resonance imaging of the pelvis.

What are radiological examinations for?

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

Therapy

The treatment of hip dislocation of traumatic origin varies according to the severity of the injury. In fact, if the hip dislocation is mild (where by mild it means that it is not associated with fractures or other complications), to restore the normal joint structure, a manipulation of the affected limb, also known as manual reduction, is sufficient; if instead the dislocation of the hip is strict (where by severe it means that it is associated with complications), surgery is essential to restore the normal position of the hip joint.

Manual reduction

Manual reduction consists of some specific movements of the involved lower limb, which allow the head of the femur to re-enter the acetabulum. Clearly, the manual reduction of a hip dislocation is dealt with by a physician who specializes in similar practices.
Manual reduction of hip dislocations must take place as soon as possible after the injury took place and requires the patient to be given a strong sedative or anesthetic, as otherwise it would be very painful.
To determine if the manual reduction was successful, the doctor who performed the above manipulation subjects the patient to a radiological examination of the pelvis (X-ray, nuclear magnetic resonance or CT scan).

Important

If it is not done within 6 hours of the traumatic event that caused the hip dislocation, manual reduction may not be possible.
In such situations, the only therapeutic solution available is surgery.

Surgical treatment

Surgical therapy of severe hip dislocation can include therapeutic interventions on fractured bones (acetabulum and / or femoral head), therapeutic interventions on damaged nerves, muscles and / or tendons passing near the hip, removal of bone fragments insulated etc.
Surgical interventions for the treatment of a dislocation of the hip 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 dislocation of the hip must rest for a few days, then begin 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.