[Posterior dislocation of the hip and posterior cruciate ligament avulsion in an 8-year-old boy].

Traumatic hip dislocation is a relatively rare entity in children. Posterior cruciate ligament (PCL) avulsion is also very rare in children and only a few cases have been reported. Because of the mechanism of injury, coexistent PCL avulsion with posterior dislocation of the hip is frequently seen in adults. This coexistence, however, has not hitherto been reported in children. We present an eight-year-old boy with traumatic posterior dislocation of hip and PCL avulsion. He was brought to hospital after a car accident in which his knee hit to the front part of the car when he was driving a bicycle. He had limitation of motion in the left hip with adduction and flexion deformity and a mild swelling and ecchymosis on the popliteal fossa of the left knee. Pelvic X-ray showed posterior dislocation of the left hip. Closed reduction was performed under general anesthesia. Six weeks later, he presented again with a complaint of limitation of motion in the left knee. On a knee radiograph, an avulsed bony fragment was noted near the medial femoral condyle. Three-dimensional computed tomography with reconstruction showed avulsion of a 0.5-cm fragment from the medial femoral condyle. Because of delay, no surgical intervention was attempted and he received physical therapy for quadriceps strengthening and improvement in the range of motion of the knee. One month after physical therapy, he had 120 degrees of knee flexion with no flexion contracture. Twelve months after injury, the patient had a normal hip and near-full knee flexion. He had no rotary instability and was active in sport.