New S-Sign for SCFE + Klein’s Line
July 11, 2018
Written by Clay Smith
Spoon Feed
Combining Klein’s line for the AP view and the new S-sign for the frog-leg lateral view increased the diagnostic accuracy for detecting slipped capital femoral epiphysis (SCFE).
Why does this matter?
SCFE may be subtle on radiographs. Early detection allows children the best chance for surgery and functional recovery. Classically, Klein’s line is taught. The S-sign adds another tool to Klein’s line to increase diagnostic yield of x-ray.
Klein’s line and S-sign
A heterogeneous 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. They found the 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%. Take a look and review Klein’s line for the AP view and the new S-sign for the frog-leg lateral.
Another Spoonful
CORE EM and Ped EM Morsels both have great posts to learn more about SCFE.
From cited article. AP pelvis view. “Klein’s line is abnormal when the line passes lateral to the epiphysis of the proximal femur.” Left side is abnormal.
From cited article. Frog-leg lateral view. “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 a sharp turn are abnormal. Left side is abnormal.
From cited article. Frog-leg lateral view. Can you spot the abnormality here?
Source
The S Sign: A New Radiographic Tool to Aid in the Diagnosis of Slipped Capital Femoral Epiphysis. J Emerg Med. 2018 Jun;54(6):835-843. doi: 10.1016/j.jemermed.2018.01.023. Epub 2018 Mar 15.
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Reviewed by Thomas Davis