Okay I just came back from the Children’s Hospital where our son goes for check-ups on his hip. He has slipped capital femoral epiphysis. I overheard two other parents talking about their children getting a positive test from Dr. Drehmann. There’s no Dr. Drehmann at that hospital so I Googled his name. Turns out he’s been dead awhile. What in the world are they talking about?

You are correct. Dr. G. Drehmann, a German physician first described what he called Drehmann’s sign back in 1903. Dr. G. Drehmann has since passed but another physician by the name of F. Drehman has since reviewed the first Dr. Drehmann’s finding and suggested that a positive Drehmann’s sign is a sign of femoroacetabular (hip) impingement.

Impingement refers to some portion of the soft tissue around the hip socket getting pinched or compressed. Femoroacetabular tells us the impingement is occurring where the femur (thigh bone) meets the acetabulum (hip socket). With SCFE, the growth center of the hip (the capital femoral epiphysis) actually slips backwards on the top of the femur (the thighbone). The altered shape of the femoral head can contribute to impingement.

Surgery to correct SCFE often changes the shape, position, and angle of the proximal (upper end) femur. With only minimal surgical remodeling of the hip, there can be a larger angle called the alpha angle. And the larger the alpha-angle, the greater the chance of impingement occurring even after corrective surgery.

Here’s how the test is done. With the patient lying supine (on his or her back), the examiner bends the patient’s leg up toward the belly button. If the leg automatically rotates outward (external rotation) and moves away from the body (abduction), there is a positive Drehmann sign. These are the movements the body makes in order to avoid hip impingement.

Sounds like one of the physicians at the hospital where you take your son is testing his or her patients after surgery for the presence of the Drehmann sign. Children with a positive Drehmann’s are more likely to report hip pain and a limp when walking. A positive Drehmann’s sign is direct confirmation of impingement.

Some experts suggest that Drehmann’s sign should be tested after surgery to correct slipped capital femoral epiphysis (SCFE). Even a mildly positive sign is an indication of hip impingement that should be treated. Eliminating impingement will help prevent the development of osteoarthritis later.