Hip Dislocation
What Is a Hip Dislocation?
A hip dislocation is the forceful separation of the ball at the top of the femur (the femoral head) from its socket in the pelvis (the acetabulum). Because the hip is a stable joint supported by strong ligaments and muscles, a dislocation usually takes a high-energy injury. It is a serious injury that requires emergency treatment.
A delay in putting the femoral head back into place (reduction) increases the risk of a disrupted blood supply to the femoral head and of nerve injury. For this reason a hip dislocation is assessed without delay. For other hip problems you can review the hip page.
Types of Hip Dislocation
Dislocations are classified by the direction in which the femoral head slips; this determines the mechanism of injury and the accompanying damage.
- Posterior dislocation: makes up the large majority. The femoral head slips backwards; the leg is held short, flexed and turned inwards. The sciatic nerve is more at risk in this type.
- Anterior dislocation: is rarer. The femoral head slips forwards; the leg is held turned outwards and the femoral vessels and nerve may be affected.
During the dislocation the ligaments, labrum and muscles that hold the joint in place can be injured, and a fracture of the acetabulum or the femoral head may accompany it. Involvement of the nerves and blood vessels can cause weakness or loss of sensation in the leg.
Causes and Risk Factors
A dislocation of a natural hip takes a large force and so is usually associated with serious accidents.
- Motor vehicle accidents: the most common cause. A bent knee striking the dashboard drives the femoral head backwards.
- Falls from a height and workplace accidents.
- High-energy collisions in contact sports.
A separate situation is dislocation of a hip replacement, which can occur with much smaller forces in certain positions and is managed differently. A hip dislocation is often accompanied by injuries to the pelvis, thigh bone and knee.
Symptoms
The symptoms of a hip dislocation are obvious and are recognised at the moment of injury.
- Sudden, severe pain in the hip, an inability to stand and an inability to bear weight on the leg.
- The leg held in an abnormal, fixed position (short and turned inwards in a posterior dislocation).
- Severe pain and marked restriction on any attempt to move it.
- Weakness, numbness or loss of sensation in the foot and lower leg if a nerve is affected.
Emergency Assessment and First Aid
Because a hip dislocation is a high-energy injury, the initial assessment is not limited to the hip. The patient is treated as a whole; the circulation and breathing are secured and they are monitored for accompanying injuries and bleeding.
The blood supply and nerves of the leg (particularly the sciatic nerve) are checked before and after reduction. No attempt is made to reduce the dislocation without proper conditions; reduction is performed appropriately, usually under anaesthesia.
Diagnosis: Examination and Imaging
The diagnosis is made by examination and imaging. The position of the leg, nerve and blood-vessel findings and any accompanying injuries are assessed.
- X-ray: quickly shows the direction of the dislocation and any fracture.
- CT: before or after reduction; it shows intra-articular bone fragments and fractures of the acetabulum and femoral head in detail.
Treatment: Reduction and Surgery
The first and urgent step of treatment is reduction: putting the femoral head back into the socket under anaesthesia. After reduction the joint is imaged again to check the correct position and whether a bone fragment remains within the joint.
If there is no fracture and the hip is stable, treatment after reduction can be managed without surgery: protected weight-bearing, avoiding certain positions and gradual physiotherapy. If there is a fracture of the acetabulum or femoral head, a fragment trapped within the joint or ongoing instability, surgery is needed; in that case the fractured fragments are fixed and the necessary repair is carried out.
Recovery and Rehabilitation
Recovery varies according to whether the dislocation is simple or accompanied by a fracture. Permission for weight-bearing and its timing are increased gradually according to any accompanying fracture and the treatment given, following the doctor's plan.
Physiotherapy aims to restore range of motion and muscle strength. The hip is followed regularly for a period regarding the state of the blood supply to the femoral head and any cartilage damage, because some problems can appear months to years later.
Possible Complications
A hip dislocation, especially when accompanied by a fracture, can lead to some long-term problems, so follow-up is important.
- Sciatic nerve injury: weakness, numbness or loss of sensation in the leg and foot.
- Osteonecrosis of the femoral head: damage to the bone tissue from a disrupted blood supply.
- Early hip arthritis: can develop in later years as a result of cartilage damage.
For detail on these complications you can review the hip osteonecrosis and hip arthritis pages.
When Should You See a Doctor?
Any suspected hip dislocation is an emergency and needs assessment without delay.
- After an injury there is severe hip pain, an abnormal position of the leg and an inability to bear weight; go to the emergency department immediately.
- There are nerve or blood-vessel signs such as numbness, weakness or coldness in the foot or lower leg; do not delay.
- After reduction, hip pain persists, the limp increases or weight cannot be borne on the leg; seek follow-up.
For treatment and follow-up after a hip injury you can contact Assoc. Prof. Serkan Sürücü, and you can also review the other conditions covered within hip surgery.