Avoiding Screwhead Impingement in Slipped Capital Femoral Epiphysis

Children who haven't completed growing can develop a problem called slipped capital femoral epiphysis (SCFE). The growth center of the hip (the capital femoral epiphysis) slips backwards on the top of the femur (the thighbone).

The standard treatment for this problem is to use a screw to hold the epiphysis in place until growth is completed. The screw is usually placed perpendicular (at a right angle) to the physis. This keeps the screw from going into the joint while giving maximum stability of the slipped epiphysis.

In this report, surgeons address a problem that can occur in cases of moderate-to-severe SCFE. The problem is called screw impingement. The head of the screw can bump up against the rim of the acetabulum (hip socket). This happens when the leg is flexed or bent.

The patient must rotate the hip outward to avoid impingement. The result is limited hip motion, pain, and an altered gait (walking) pattern. Over time, the cartilage around the joint gets worn away or can tear causing more problems.

Through a series of X-rays and diagrams, the authors show how changing the placement of the screw can make a difference. An imaginary line drawn down along the neck of the femur is called the intertrochanteric line. The screw is still placed perpendicular, but should be advanced past this line on the lateral side. This avoids a prominent screw head that can cause impingement.

The authors use diagrams to show surgeons where the at risk zone is located. They suggest using the alternative fixation with the screwhead resting lateral to the intertrochanteric line to avoid impingement. The screw must still be located in the center of the femoral head. Only moderate-to-severe SCFE requires this kind of change in screw placement.