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Slipped Capital Femoral Epiphysis (SCFE)
- Progressive, posterior medial displacement (slipping) of the proximal femoral epiphysis
- Complicated by AVN and premature physis closure
http://www.raymondliumd.com/images/SCFE%20illustrated%20and%20cropped.jpg
Early Diagnosis:
- Allows best chance for intervention and good functional outcome
- Subtle and difficult with X-ray
- Classic teaching is Klein’s line
Klein’s Line on AP view
- A line drawn from the superior aspect of the femoral neck will not intersect the femoral head epiphysis
- Modified line
- >2mm difference in width lateral to line between each side
https://pedemmorsels.com/wp-content/uploads/2018/01/Slipped-Capital-Femoral-Epiphysis-3.png
Another virtual line may assist in diagnosis
S-sign
- The S-sign is a curvilinear line drawn on the inferior margin of the proximal femoral head neck junction along the proximal femoral physis.
- Discontinuity or an abrupt sharp turn are abnormal
Klein's line and S-sign
- A group of 20 orthopedic surgeons, radiologists, and pediatricians viewed 35 radiographs of SCFE using Klein's line on the AP view and the S-sign on frog-leg lateral view to make the diagnosis.
- Overall diagnostic accuracy was better with the S-sign than Klein's line, 92% vs 79%.
- Sensitivity of the S-sign was 89%, specificity 95%.
- Sensitivity of Klein's line was 68%, specificity 89%.
- Combined S-sign + Klein's line sensitivity was 96%, specificity 85%.
Consider adding both of these virtual lines/signs to your review of the pediatric hip plain film
References
Rebich et al., 2018. The S Sign: A New Radiographic Tool to Aid in the Diagnosis of Slipped Capital Femoral Epiphysis. J Emerg Med.