Many children with unilateral slipped capital femoral epiphysis actually have bilateral disease.
MRI evaluation identifies warning signs of pre-slip in the contralateral, “normal” hip of children who were receiving treatment for unilateral slipped capital femoral epiphysis (SCFE), according to a new study lead by a team of orthopedic surgeons and radiologists at Nationwide Children’s Hospital.
The prospective study was published in the Journal of Children’s Orthopaedics.
“There has always been a debate as to what to do with the hip that is not slipped at the time of presentation,” says Kevin Klingele, MD, chief of Orthopaedic Surgery at Nationwide Children’s and senior author of the study. “Many studies suggest a high percentage of children will have sequential slips in the other hip within 12 to 18 months from presentation.”
The ability to identify hips at risk for sequential SCFE using MRI would help surgeons avoid unnecessary prophylactic pinning while indicating which hips do need prophylactic treatment.
The researchers hypothesized that MRI findings could diagnose contralateral pre-slip and help to predict subsequent, contralateral SCFE in patients who present with unilateral SCFE. To test this hypothesis and to compare MRI prediction with previously described SCFE prediction methods, the team designed a prospective, surgeon-blinded study, in which no treatment decisions were made based on the MRI findings.
A total of 33 patients participated in the study, and 29 (87.8%) patients had complete clinical and radiographic follow-up. All patients had preoperative anteroposterior and frog-leg lateral pelvis radiographs and contralateral hip MRI within a week of presentation.
The team found that 67% of patients who subsequently had a slip in the contralateral hip also had MRI findings consistent with pre-slip at the time of original presentation. Based on slip grading, 82% of sequential SCFE were mild in severity. A combination of the MRI findings with the presence of an open triradiate cartilage was the best overall predictor of subsequent slip (sensitivity 80%, specificity 100%, PPV 100%, NPV 96.6%).
Other predictive methods alone did not perform as well. Posterior sloping angle of more than 14.5° predicted 9.1% (sensitivity; specificity 81.4%, PPV 11.1%, NPV 77.8%) of sequential slips. Modified Oxford Bone Score predicted 45.5% (sensitivity; specificity 93%, PPV 62.5%, NPV 87%) of sequential slips. An open triradiate cartilage occurred in 72.2% of patients with sequential slips (sensitivity; specificity 81.4%, PPV 50%, and NPV 92.1%). Abnormal MRI findings alone predicted 80% of subsequent slips (sensitivity; specificity 92.9%, PPV 66.7%, NPV 96.3%).
While MRI costs may increase the initial cost of treatment for SCFE, the authors argue that these costs would be offset by preventing future hospital admissions and treatments.
“This has been a very useful tool to us. It’s become a routine part of our preoperative evaluation of these kids, and it’s shown that a significant amount of kids who end up with so-called sequential disease actually have asymptomatic, bilateral disease at the time of presentation,” says Klingele. “It’s best to save the children from future operations, and if we have a good way of predicting contralateral disease, we’re really not prophylactically pinning; we’re pinning subclinical pre-slips, and it makes sense that this should be the standard of care.”
Balch Samora J, Adler B, Druhan S, Brown SA, Erickson J, Samora WP, Klingele KE. MRI in idiopathic, stable, slipped capital femoral epiphysis: evaluation of contralateral pre-slip. Journal of Children’s Orthopaedics. 2018 Oct 1; 12(5):454-460.