- Risk Factors
Facts you should know about hip dislocations
- Hip dislocations occur most often as a result of motor vehicle crashes. They also can be an athletic injury, most commonly from football or downhill skiing trauma.
- The hip can dislocate forward or backward (anteriorly or posteriorly). Posterior dislocation of the hip is most common.
- It is important to try to relocate (reduce) the dislocated hip joint as soon as possible to prevent complications.
- Doctors usually accomplish reduction of the dislocated hip with traction, but an operation may be required if that is unsuccessful.
- A person may need physical therapy and rehabilitation for many months to regain normal function.
- Complications of hip dislocations include damage to the sciatic nerve, osteoarthritis, and death of the femur bone of the hip (avascular necrosis of the femoral head).
What is a hip dislocation? What are the types of hip dislocations?
The hip is a ball and socket joint. The ball is the head of the femur or thighbone and the socket in the pelvis is called the acetabulum. Surrounding muscles and ligaments and a thick band of cartilage called the labrum stabilize the joint. A hip dislocation occurs when the femoral head is forcibly removed from the acetabulum.
Doctors describe hip dislocations according to where the femoral hip bone moves in relationship to the acetabulum.
- Posterior dislocations, where the femoral head moves backward, are most common and often occur from car wrecks and athletic injuries.
- Anterior hip dislocations occur when the femoral head pushes forward out of the socket of the acetabulum. This type of hip dislocation can occur in downhill skiing accidents.
- Patients who have had hip replacements can also dislocate their prosthetic hip.
- Developmental dysplasia of the hip (dys=bad + plasia=formation) is an abnormal design of the hip at birth (was formerly referred to as congenital hip dysplasia). Developmental dysplasia can lead to hip dislocation in infants and children.
What causes a dislocated hip?
Hip dislocations are an uncommon injury in a normal hip. It takes a lot of energy to dislocate a hip, and most dislocations of the hip are due to motor vehicle injuries. Athletic injuries most often occur in football and rugby, downhill skiing, and snowboarding.
In patients who have had hip replacements, a simple fall or abnormal movement may provide enough energy to dislocate the hip prosthesis.
What are risk factors for hip dislocations?
The risk of a hip dislocation exists with any high-impact, high-energy accident. Hip dislocations occur most commonly in motor vehicle crashes, pedestrians hit by cars and, less commonly, athletic injuries.
What are signs and symptoms of hip dislocations?
On physical examination, the hip and leg will be in an abnormal position and there will be physical deformity.
- For posterior hip dislocations, the hip will be short and internally rotated, meaning that the foot will be pointing inward toward the midline of the body.
- Anterior hip dislocations will have a shortened leg with the foot externally rotated or pointing away from the midline of the body.
How do doctors diagnose a dislocated hip?
Physical examination often clinically diagnoses hip dislocations. The health care provider might be able to observe a deformity at the hip, as well as abnormal positioning of the hip. X-rays confirm the diagnosis of hip dislocation.
The health care provider will also look for complications associated with hip dislocation, including injury to the femoral artery that runs in front of the joint and the sciatic nerve located in the back of the hip.
Depending upon the situation, the health care provider may assess the patient for other injuries that might be present.
What is the treatment for a hip dislocation?
The initial treatment of a dislocated hip is to try to relocate it, replacing the femoral head into the hip socket. Because of pain and muscle spasm associated with the injury, the patient often requires medications for sedation and muscle relaxation to allow the hip to be relocated. There are different techniques that can be used to relocate the hip, but all involve traction on the leg to replace the femoral head back into the acetabulum. This is called closed reduction.
Sometimes the hip cannot be relocated, even with the patient undergoing general anesthesia. A CT scan may be needed to look for small bone fragments that may have fractured (broken off) off the acetabulum or pieces of torn ligament or cartilage that get in the way of the relocation. In this situation, open reduction is required, meaning that an orthopedic surgeon has to operate to remove any foreign objects in the joint and then reduce or replace the hip back into its socket. Sometimes doctors do this using arthroscopic surgery.
What are complications of a dislocated hip?
Common complications include the following:
- Sciatic nerve injury: The nerve runs behind the hip and can be stretched and damaged with a hip dislocation.
- Avascular necrosis of the femoral head (a=loss + vascular=blood supply; necrosis=death): The femoral head, or ball of the hip, gets its blood supply from small arteries that run along the ligaments that help hold the hip joint stable. These arteries can be stretched, damaged, or torn with a hip dislocation and the part of the bone that they supply can die (necrosis). This causes the hip joint to gradually lose its range of motion and potentially require hip joint replacement. For this reason, the goal is to reduce a dislocated hip as soon as possible. A follow-up MRI of the hip is usually recommended at 6 weeks to look for this complication.
- Osteoarthritis of the hip joint
- Recurrent hip dislocation: The structures that keep the hip stable may not heal adequately, leading to repeated dislocations.
What is the recovery time for a hip dislocation?
Physical therapy is important and begins with non-weight-bearing exercises that can start after the first week. This is important to prevent loss of range of motion.
Strengthening of leg muscles can begin when the patient is pain free and can walk without crutches, usually after 4-8 weeks.
If all goes well, it may take 3-4 months to return to full activity after a hip dislocation.
What is the prognosis for a dislocated hip?
Hip dislocations are a significant injury and the prognosis depends upon how long it takes to reduce the dislocation and whether other structures are damaged.
About 70% of patients with posterior hip dislocations will have an associated acetabulum fracture.
Approximately 10%-15% of patients with hip dislocation will have sciatic nerve injury.
About 2%-10% of patients with a hip dislocation will develop avascular necrosis of the femoral head if it is reduced within 6 hours.
Approximately 20% of patients with hip dislocation will eventually develop osteoarthritis in the hip joint.