Medical Professional Publications

Modified Dunn Procedure Complication Rates are Higher for Stable Slipped Capital Femoral Epiphysis

Columbus, OH — May 2017

The modified Dunn procedure has proven successful for treating unstable slipped capital femoral epiphysis in pediatric patients. But a new study shows the procedure results in higher complication rates, including avascular necrosis (AVN) and postoperative instability, when used on stable slips.

The research emphasizes the findings of an international study that determined the postoperative hip instability rate has been low overall, but when the complication occurs, it leads to poor outcomes.

"So we're stepping back from a push nationally and internationally where we were doing this procedure on a lot of these kids," says Kevin Klingele, MD, chief of the Department of Orthopaedics at Nationwide Children’s Hospital and an author of the studies.

"As a center, we're much more selective now ... it's rare for us to do the procedure on a stable slip," says Dr. Klingele, who is also an adjunct assistant professor of Orthopaedic Surgery at The Ohio State University College of Medicine.

The studies are published in the Journal of Pediatric Orthopaedics and Clinical Orthopaedics and Related Research.

Children with a stable slip generally can limp into a physician's office; the epiphysis and the proximal femur move as one. Children with unstable slips can't bear weight even with crutches or a walker; the epiphysis shifts independently of the femoral neck region.

In the largest single-center study comparing modified Dunn outcomes, Dr. Klingele's team found that among children with stable slips, 29 percent suffered AVN and nearly 18 percent had hip instability. Among children with unstable slips, 6 percent of children suffered AVN. That rate is significantly lower than the rate reported at most other centers.

Records of children with stable and unstable slips at Nationwide Children's and seven pediatric surgical centers worldwide show 4 percent of children who had undergone the modified Dunn procedure suffered from postoperative hip instability. While a low rate overall, the authors call the complications "devastating." The majority of the patients developed degenerative joint disease. 

Despite the difference in mobility among patients, the degree of deformity is typically higher in stable slips. That, Dr. Klingele suggests, may be the main reason for the increased rate of hip instability and AVN.

"You have to do a lot more corrective work, which means putting the blood vessels on more stretch to get the femoral head back on," Dr. Klingele says. "Because of that, sometimes you have to shorten the femoral neck to ease the reduction, but that can alter the stability of the hip.”

For the small number of children with severe, stable slips requiring the modified Dunn procedure, Dr. Klingele's team has implemented new intraoperative and postoperative steps and protocols to reduce the risk of AVN and instability. The team is also performing a different procedure to increase patient safety and achieve good overall correction of the hip deformity.

References:

Davis RL, Samora WP, Persinger F, Klingele KE. Treatment of unstable versus stable slipped capital femoral epiphysis using the modified Dunn procedure.Journal of Pediatric Orthopaedics. 2017 March 21. [Epub ahead of print]

Upsani VV, Birke O, Klingele KE, Millis MB; International SCFE Study Group. Iatrogenic hip instability is a devastating complication after the modified Dunn procedure for severe slipped capital femoral epiphysis. Clinical Orthopaedics and Related Research. 2017 April; 475(4): 1229-1235.

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