Remember that old childhood song about how "The thighbone's connected to the hipbone"? Well, the song may be silly, but one thing is true: 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). Though the term's quite a mouthful, it simply refers to 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, you first have 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.

In kids and teens who are still growing, there is also 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 epiphysis and it's made of cartilage, which is weaker than bone. The job of the epiphysis is to connect the femoral head to the thighbone while still allowing the bone to lengthen and grow.

When a child has SCFE, the femoral head of the thighbone slips off the epiphysis, 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 seemingly occurs out of nowhere with no prior injury.

Usually, SCFE is classified as:

• Stable SCFE. This is referred to as a "mild slip," which causes a child to experience some stiffness or pain in the knee or groin area, and possibly to develop a limp. The pain and the limp usually tend to come and go, worsening with activity and getting better with rest. With stable SCFE, a person is still able to walk (sometimes with crutches).
• Unstable SCFE. This is a more severe slip that is usually much more painful. A child might not be able to bear weight on the affected side, and because range of motion tends to be severely limited, the affected foot and leg might begin to turn outward. An unstable SCFE is also more serious because it can restrict blood flow to the hip joint, leading to tissue death in the area.

Sometimes SCFE can irritate the nerves that run down the leg, causing referred pain (pain that originates in one part of the body but is felt in another). In this case, pain originates in the abnormal hip joint but is felt in the normal knee joint.

Though many cases of SCFE affect only one hip, up to 40% are bilateral (affecting both hips). If doctors diagnose SCFE in one hip, they will closely watch the other to see if it develops the same problem. Catching SCFE early makes a big difference in how easily doctors are able to treat it.

Causes of SCFE

No one knows for sure what causes SCFE. However, it is known that it mostly occurs in kids between 11 and 16 years old who are going through a growth spurt. It's more common in boys, though girls can be affected, too. It's also more likely to happen in kids who have the following risk factors, all of which can have an affect on bone health:

• obesity (carrying extra weight puts increased pressure on the growth plate)
• endocrine disorders such as diabetes, thyroid disease, or growth hormone problems
• kidney disease
• cancer treatments like radiation and chemotherapy
• certain medications, such as steroids
• a family history of SCFE

Diagnosis

A child suspected of having SCFE will need to see an orthopedic doctor, a specialist in the treatment of bones. The doctor will perform a thorough physical examination, checking the range of motion of the hips and legs and seeing if there is any pain. He or she will also take X-rays of the hip to look for a displacement at the head of the thighbone.

Sometimes, though, the X-rays will come back normal even when symptoms are present. In these cases, a magnetic resonance imaging study (MRI) or bone scan will likely be ordered. Both are more sensitive than an X-ray. The MRI, in particular, has the ability to highlight contrasts in soft tissue, which makes it especially useful in understanding problems with joints and cartilage.

Treatment

SCFE is always treated with surgery to stabilize the bone that slipped. But even before the surgery, the doctor will try to prevent any further slippage by recommending lots of rest and the use of crutches to avoid putting weight on the affected leg.

With milder slips, the surgery is often done as an outpatient procedure, which means a child can leave the hospital the same day or the day after the surgery if there are no complications.

More severe slips may require more extensive surgery and a longer hospital stay. This type of surgery is performed 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 small incision near the hip, then put a metal screw or pin through the bone and the growth plate to hold it in place.

Sometimes the surgeon will stabilize the other side as well, even if it hasn't slipped yet, just because the risk is high that it could happen. More severe slips may require further repositioning of the hip.

After surgery, patients are allowed to walk with crutches, only putting some of their weight on the affected leg. Patients who have both hips treated generally need to use a wheelchair for the first couple of weeks after surgery.

After Surgery

When SCFE is detected and treated early, most kids do well. They will likely receive physical therapy to strengthen the hip and leg muscles, and will continue to have follow-up X-rays to monitor the condition. But in most mild cases, further surgery is not needed.

Kids with unstable SCFE, however, do have a greater chance of developing other problems, 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 realign the hips as they grow.

Of course, there's no way to prevent SCFE in every child. But one thing parents can do to lessen the risk is to encourage kids to keep their weight in a healthy range. Maintaining a healthy weight can go a long way in sparing kids' bones and joints from the excess wear and tear that can weaken and damage them. So if you need help figuring out how to get your child started on a safe diet and exercise plan, talk to your doctor.

Reviewed by: Alfred Atanda Jr., MD
Date reviewed: February 2010