About hip joint
Hip joint is a ball and socket joint. Ball is formed by the femoral head and the socket for the ball is formed by acetabulum, which is a part of the pelvis. Forty percent of ball is covered by socket at any position of hip motion. The labrum is a rubber seal or gasket like structure to help hold the ball in the socket. Labrum helps in increasing the stability of the joint.
Types of hip dislocation
Depending upon the position of the ball with respect to the socket hip dislocations are of following types.
About posterior dislocation
It is also called dashboard injury. They result from trauma to the flexed knee with the hip in varying degree of flexion. The femur thrust upwards and femoral head is forced out of the socket into the buttock.
This is generally observed in a road accident with the person sitting in the car without wearing a seat belt, who is thrown forward striking the knee against the dashboard, so the ball dislocated to the buttock.
Signs and symptoms of posterior dislocation
Usually patient gives a history of road accident. There is a marked shortening and gross restrictions of hip movements. Ball of femur felt like a mass in the buttock and with the movement of the leg the mass moves.
Posterior dislocation of hips may be associated with or without fracture of socket or the ball.
Caused because of hyperextension of the hip that levers femoral head out of socket placing the head towards groin region.so the ball lies in front of the socket. It may be caused by Forceful blow to the back of the patient in a squatted position.
The hip is minimally flexed, externally rotated (rotated outwards) and markedly abducted (moved away from the midline.)
Very rare and very difficult to treat.
This is because of direct blow to the side of the thigh (trochanter) in road traffic accidents. It is always associated with fractures of acetabulum (socket) which is why it is difficult to treat.
It is very important to assess the nerve injury in dislocation of hip. This is conducted by the orthopedician. Two nerves may get injured in the dislocations, namely sciatic nerve and femoral nerve.
Sciatic nerve injury includes loss of sensation in posterior leg and foot. loss of movements at foot joint may be seen.
Femoral nerve injury presents with loss of sensation over the thigh, weakness of the quadriceps.
Diagnosis is by history, examination and imaging like x-ray of hip joint.
There are two options closed reduction and an open reduction.
Closed reduction is a process where the hip joint is manipulated without any incision and the ball of femur is relocated into the acetabulum.
All hip dislocations are emergencies and need to place the ball in the socket to avoid avascular necrosis of hip in which blood circulation to the ball is cutoff.
The closed reduction is done under sedation.
Open reduction is a surgical procedure which is indicated when a closed reduction fails or development of hip instability after closed reduction.