A traumatic hip dislocation is when the ball of the hip joint is pushed out of the socket. This injury most commonly occurs during an auto collision or a high-impact fall, workplace or sports injury, especially those that also result in a broken leg or pelvis. A dislocated hip can lead to serious long-term debilitating problems, especially if it is severe or not adequately treated within hours of occurrence. If a person experiences any forceful impact that results in serious hip pain or pain in the groin, leg or even the knee, he or she should be examined by orthopedic specialist to determine whether there is a hip dislocation.
The hip joint is a ball-and-socket joint. The ball, at the top of the femur (thighbone) is called the femoral head. The socket, called the acetabulum, is a part of the pelvis. The ball rotates in the socket, allowing the leg to move forward, backward, and sideways. Smooth cartilage lines the ball and the socket help them glide together and secure the joint.
In most hip dislocations, the femoral head of the thighbone is forced out of the acetabulum toward the rear (posterior dislocation). Less often, the displaced ball is pushed out forward from the pelvis (anterior dislocation).
Hip dislocation is very painful and can cause tears or strains in adjacent blood vessels, nerves, muscles, ligaments and other soft tissues. The most serious complications associated with hip dislocations are avascular necrosis (bone death), and sciatic nerve damage. The sciatic nerve extends from the lower back to the upper thigh and then divides into the tibial and common peroneal nerves, which enable movement of the ankles and toes. Significant damage to these nerves can limit a person’s mobility, sometimes permanently.
HIP JOINT ANATOMY
Inability to move the hip are common symptoms and signs of hip dislocation.
You may not be able to bear weight or stand on the hip.
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.
Motor vehicle collisions are the most common cause of traumatic hip dislocations. The dislocation often occurs when the knee hits the dashboard in a collision. This force drives the thigh backwards, which drives the ball head of the femur out of the hip socket. Wearing a seatbelt can greatly reduce your risk of hip dislocation during a collision.
A fall from a significant height (such as from a ladder) or an industrial accident can also generate enough force to dislocate a hip.
With hip dislocations, there are often other related injuries, such as fractures in the pelvis and legs, and back, abdominal, knee, and head injuries. Perhaps the most common fracture occurs when the head of the femur hits and breaks off the back part of the hip socket during the injury. This is called a posterior wall acetabular fracture-dislocation.
If there are no other injuries, the doctor will administer an anesthetic or a sedative and manipulate the bones back into their proper position. This is called a reduction.
In some cases, the reduction must be done in the operating room with anesthesia. In rare cases, torn soft tissues or small bony fragments block the bone from going back into the socket. When this occurs, surgery is required to remove the loose tissues and correctly position the bones.
Following reduction, the surgeon will request another set of x-rays and possibly a computed tomography (CT) scan to make sure that the bones are in the proper position.
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