Slipped Capital Femoral Epiphysis

What is it?

Slipped capital femoral epiphysis (SCFE) is a condition that happens in adolescents where the epiphysis (the growth center) of the femoral head displaces or slips out of alignment from the rest of the femur.

The head of the femur, the ball of the hip joint, is formed from a separate growth center from the rest of the femur. This separate growth center is called the epiphysis, and in a growing child is connected to the rest of the femur by rapidly proliferating cartilage called the epiphyseal plate. In SCFE, the displacement or slip occurs at the epiphyseal plate.

What causes it?

SCFE typically occurs in adolescents, and more often in boys than girls (2 or 3 to 1 ratio). The fact that it usually occurs in stocky boys leads to the theory that hormonal imbalance between the growth and sex hormones is involved. However, there has never been conclusive evidence to support this. Studies have shown that the epiphyseal plate is rapidly proliferating and vulnerable to shear stress during adolescence. The extra body weight during this phase of life tilts the balance, and causes the slip to occur.

What are the symptoms?

The epiphyseal slip can occur acutely with a sudden traumatic episode. Such a patient will present after a fall or injury during sports, complaining of severe pain in the hip. The presentation is that of a fracture of the hip, and X-rays will confirm the diagnosis.

The more common presentation is a chronic slip. This is typically a stocky adolescent boy who complains of pain in his knee over a period of weeks or months. There may or may not be a history of trivial trauma. He walks with a very mild limp, or with the affected leg rotated outwards. It is an interesting point to note that the pain is often in the knee rather than the hip, because the hip and knee share the same main nerve.

Another way the patient may present is an acute injury following weeks or months of knee pain. This is the acute-on-chronic slip.

What does your doctor do about it?

When SCFE is suspected, X-rays of the hips should be performed. Two views are needed — AP and frog-leg views. Because the slip occurs posteriorly before it does inferiorly, the frog-leg view is the more sensitive view. It is important to do X-rays of the other hip as well, because there is a 40% incidence of bilaterality.

In case of an acute slip, the patient is admitted to the hospital and placed on gentle traction for a day or two, in an attempt to reduce the slip. The key is gentle reduction, because of the danger of disrupting blood supply to the capital epiphysis, and causing avascular necrosis. The patient is then brought to the O.R., and one or two surgical pins placed across the epiphyseal plate, to maintain the position of the epiphysis and prevent further slip. Over time, it is hoped that the epiphyseal plate will close (or fuse), thus preventing future slip.

In the chronic slip, it is not advisable to attempt any reduction of the slip. Since the slip occurred over a prolonged period of time, the blood vessels supplying the capital epiphysis had adjusted to the slip. Any attempt at acutely reducing the slip will endanger the blood supply of the capital epiphysis and may cause avascular necrosis. The treatment for chronic slip is “pinning in situ”, i.e. pins are placed across the slip “as is”, with no attempt at reduction.

Post-operatively, the patient is placed on non-weight bearing or touch-down gait with crutches for about 6 weeks. Weight-bearing is then gradually increased till full weight-bearing at 3 months after surgery. Sports is usually not advised for 3 to 6 months after surgery.

What can be expected after treatment?

For the patient who has a mild slip, or a slip that was reduced with no complications, full activities can be resumed 3 to 6 months after surgery.

Some severe complications can occur with SCFE. Chondrolysis or acute cartilage necrosis can occur after surgical pinning. The patient will have severe pain and stiffness of the hip which persists for months. The pain gradually resolves, but the stiffness usually remains. The cause is not known. Avascular necrosis or death of the bone of the capital epiphysis can occur with the slip, can may not become apparent for 1 to 2 years after the slip or surgery. The dead bone collapses over time, leading to pain and stiffness. There is no effective treatment for either chondrolysis or avascular necrosis at this time.

For the patient with chronic slip who had pinning in situ, the bone remodels with growth, and after 1 to 2 years, may regain good and pain-free range of motion in the hip. In the severe case where the hip cannot be flexed to 90 degrees, or where the patient walks with a severe external rotation gait, corrective osteotomy can be performed 2 years down the road.

Removal of surgical hardware after successful surgery is not indicated, if the hip is asymptomatic. There is no evidence that surgical pins left in the body will cause any untoward effects, even though one can never be sure. One needs to balance this with the fact that surgical pin removal requires another general anesthetic and surgical incision. Ultimately, it is a decision that has to be made on an individual basis.

The question of bilaterality was mentioned earlier. There is a 40% chance of future involvement of the other hip. Should prophylactic pinning be done routinely, to avoid contralateral slip? Again, this is an individual decision, to be made after due discussion with the surgeon. But the prudent approach will be to be aware of such an eventuality, and seek medical attention if the patient complains of hip or knee pain in the future.