Validity of indirect Ultrasound Findings in Acute Anterior Cruciate Ligament Ruptures

Oct 16

Validity of indirect Ultrasound Findings in Acute Anterior Cruciate Ligament Ruptures

Researchers at Emory University in Atlanta, Georgia are concerned about the validity of physical examinations of ACL tears in acute care settings. This article investigates ultrasound findings in acute ACL ruptures, which have historically been poorly diagnosed in acute care settings, such as the emergency room. The significance of this evidence-based inquiry will off-set the high risk of further cartilage damage in misdiagnosed patients and expedite the return-to-play clearance in recovering athletes. 

Magnetic Resonance Imaging (MRI) has long been the standard used to diagnose ACL ruptures. Ultrasound (US) coupled with functional testing is increasingly being used  to objectively evaluate ACL injuries due to limited accessibility and high cost associated with MRIs. Moreover, researchers Mautner et al translate the US findings of 3 indirect signs of ACL ruptures to clinical acute care settings compared to MRIs and arthroscopic findings. The three indirect US signs of ACL rupture include the widely studied femoral notch sign, the PCL wave sign and the capsular protrusion sign, which has only been described once in literature. 

Patients age 16-50 who reported an ACL injury within 6 weeks of the clinical study contributed to a group of seventy-four patients recruited to participate; however, five patients were excluded.  The study group included 16 control patients and only 53 patients with ACL injuries. All patients accepted into the clinical study underwent US examination by a single examiner. The US examination was performed over the posterior aspect of the knee, noting the 3 indirect US signs of an ACL rupture, first examined in a transverse plane to assess the ACL femoral insertion, then longitudinally to assess the PCL and posterior capsule. 

Of the 3 signs, the femoral intercondylar notch sign has been the most studied.  It is commonly understood that the femoral notch sign disappears over time, yet, the literature does not support the resolve of the femoral notch sign within the first 10 weeks after injury.  Mautner et al intentionally excluded chronic ACL tears and included subjects who sustained injury within 6 weeks of the study. Even so, 52% of patients underwent US examination within 2 weeks of injury. Conversely, in the ACL group, only 33% had an isolated ACL tear, whereas, most patients had additional soft tissue derangement with respect to the knee joint. Thus, the limitations of this study may have contributed to a potential confounding variable. 

Researchers concluded that US cannot replace MRI, but it may help sports medicine professionals in acute care settings diagnose and treat acute knee injuries and decrease the number of underdiagnosed ACL tears with a non-invasive, cost-effective clinical method. Congratulations to TOBI Faculty Dr. Ken Mautner and his team of researchers on their success in being published in the Journal of Ultrasound in Medicine, and having their research recognized by the American Institute of Ultrasound in Medicine. Follow the link to read the full article


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