A good, stable connection at the hip joint is what lets us walk, run, jump, and many other things. But in some kids — particularly those who are obese — the thighbone and the hipbone are a little less well connected than they should be because of a condition called slipped capital femoral epiphysis(SCFE). SCFE is a shift at the upper part of the thighbone, or femur, that results in a weakened hip joint.
Fortunately, when caught early, most cases of SCFE can be treated successfully.
About Slipped Capital Femoral Epiphysis
To understand SCFE, it helps to know a little about the hip joint. The hip is a ball-and-socket joint, which means that the rounded end of one bone (in this case, the "ball" of the thighbone) fits into the hollow of another bone (the acetabulum, or cup-shaped "socket" of the pelvis). Ball-and-socket joints offer the greatest range of movement of all types of joints, which explains why we can move our legs forward, backward, and all around.
Kids and teens who are still growing also have a growth plate at the top of the thighbone, just under the "ball" portion (also known as the femoral head) of the joint. This growth plate is called the physis and it's made of cartilage, which is weaker than bone. The job of the physis is to connect the femoral head to the thighbone while allowing the bone to lengthen and grow.
In SCFE, the femoral head of the thighbone slips through the physis, almost the way a scoop of ice cream might slip off a cone. Sometimes this happens suddenly — after a fall or sports injury, for example — but often it happens gradually with no prior injury.
Usually, SCFE is classified as:
Stable SCFE. A stable SCFE causes some stiffness or pain in the knee or groin area, and possibly a limp that causes a child to walk with a foot outward. The pain and the limp usually tend to come and go, worsening with activity and getting better with rest. With stable SCFE, a child still can walk, even if crutches are needed.
Unstable SCFE. An unstable SCFE is a more severe slip that usually happens suddenly, and is usually much more painful. A child will not be able to bear weight on the affected side. An unstable SCFE is also more serious because it can restrict blood flow to the hip joint, leading to tissue death in the head of the femur.
Sometimes SCFE can irritate the nerves that run down the leg, causing referred pain (pain that starts in one part of the body but is felt in another). In this case, pain begins in the abnormal hip joint but is felt in the normal knee joint.
Some cases of SCFE affect only one hip, but many are eventually found to affect both hips (be bilateral). When SCFE affects one hip, doctors may closely watch the other to see if it develops SCFE; or, if that's considered very likely, they might treat both hips at the same time. Catching SCFE early makes a big difference in how easily doctors can treat it.
Causes of SCFE
No one knows for sure what causes SCFE. But most cases are in kids between 11 and 16 years old who are going through a growth spurt. SCFE is more common in boys, though girls can be affected, too.
SCFE is also more likely in kids who have these risk factors, all of which can affect bone health:
obesity (carrying extra weight puts increased pressure on the growth plate)
endocrine disorders such as diabetes, thyroid disease, or growth hormone problems
A child thought to have SCFE will see an orthopedic doctor, a specialist in the treatment of bones. The doctor will do a thorough physical examination, checking the range of motion of the hips and legs and seeing if there is any pain. The doctor will also take X-rays of the hips to look for any displacement at the head of the thighbone.
In rare cases, X-rays will come back normal, but the pain, stiffness, and other problems will still be there. In these cases, a magnetic resonance imaging study (MRI) might be ordered. An MRI can catch very early SCFEs, before they start to slip very far.
SCFE is always treated with surgery to stabilize the growth plate that slipped. But even before the surgery, the doctor will try to prevent any further slipping by encouraging rest and the use of crutches to avoid putting weight on the affected leg. Many doctors recommend admission to the hospital as soon as the SCFE is discovered to make sure the patient rests, and so surgery can be done as soon as possible.
Surgery for SCFE is done under general anesthesia (when a patient is completely asleep). Using a fluoroscope — a special X-ray machine that produces a real-time image of the hip on a TV screen — as a guide, the surgeon will make a tiny incision near the hip, then put a metal screw through the bone and across the growth plate to hold it in place. The screw is placed deep into the bone, and cannot be felt by patients after surgery.
Because some patients have a high risk of an SCFE in the other hip, the surgeon might also stabilize that side too, even if it hasn't slipped yet.
Doctors decide how much weight can be placed on the affected leg after surgery based on the severity of the slip. Patients usually can walk with crutches, but those who have both hips treated may need to use a wheelchair for the first couple of weeks after surgery.
Most kids do well when SCFE is caught and treated early. Doctors will continue to order follow-up X-rays to monitor the condition. In the majority of cases, more surgery isn’t needed.
However, kids with unstable SCFEs have a greater chance of developing other problems later, such as stiff hips, early arthritis, leg length differences, or avascular necrosis (where part of the "ball" dies from lack of blood supply). They're also more likely to require additional surgery to take care of their hip.
Not everyone can prevent SCFE. But reaching and maintaining a healthy weight can spare bones and joints from the excess wear and tear that can weaken and damage them. If your child is overweight and you need help developing a safe diet and exercise plan, talk to your child's doctor.