What’s the Diagnosis – Case 156
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What’s the Diagnosis – Case 156
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What’s the Diagnosis – Case 156
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Findings Just based on the limited images made available, there has been an interval change of the lateral condyle from the older to the current radiograph. This is confirmed on the MRI image showing an indentation along the anterior to middle surface of the lateral condyle.
What’s the Diagnosis – Case 156
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What’s the Diagnosis – Case 156
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Diagnosis: Deep Lateral Femoral Notch Sign Indicating ACL Disruption In the following slides I will show the ACL disruption on MR imaging, but I wanted to focus on the radiographic findings which frequently go overlooked. The lateral femoral condyle has a notch which is almost always seen at the junction of the middle and anterior portion of the condyle. The medial condyle has a notch further anteriorly which is not as consistently seen on radiographs. In the setting of an ACL injury with anterior translation, the impaction at the lateral aspect of the knee occurs at the posterior aspect of the proximal tibia (often difficult to see on radiographs) and at the notch of the lateral condyle described above. This area of the lateral condyle is technically called the sulcus terminalis as it represents the interface of the trochlear sulcus and the remainder of the condyle. The lateral condyle should be smooth as shown in the comparison case with the green outline. If there is an impaction of the lateral condyle that represents a deep lateral femoral notch sign. An impaction of 1.5mm has a positive predictive value (PPV)of over 96%. This sign does however have a low sensitivity of 15 to 20%. Decreasing the depth of the impaction to 1mm leaves a high PPV but raises the sensitivity to almost 40%. The more important point is the identification of this area of impaction is extremely helpful in identifying an ACL tear. Agreed, most individuals will obtain an MRI for confirmation but in a more emergent/ER setting having this information just based on the radiographs (especially when an exam may be challenging at best) can be of great benefit.
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References The lateral femoral notch sign: a reliable diagnostic measurement in acute anterior cruciate ligament injury. Prabath C. A. M. Lodewijks, Diyar Delawi,Thomas L. Bollen, Gawein R. Dijkhuis, Nienke Wolterbeek, Jacco A. C. Zijl. Knee Surg Sports Traumatol Arthrosc. 2019; 27(2): 659–664. Published online 2018 Oct 13. doi: 10.1007/s00167-018-5214-x Lateral femoral notch sign (knee). Dr Yuranga Weerakkody, Dr Charlie ChiaTsong Hsu et al. radiopaedia.org
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