From the Guidelines
MRI is the most appropriate imaging study for suspected Anterior Cruciate Ligament (ACL) tear.
Reasons for Choosing MRI
- MRI has many distinct advantages for the evaluation of the injured knee in the setting of negative radiographs, allowing for earlier surgical intervention by obtaining a more accurate diagnosis 1.
- MRI can diagnose the patterns and severity of bone marrow contusions that frequently have an association with the specific mechanisms of injury and can predict associated soft-tissue injuries 1.
- MRI facilitates diagnosis of the anterolateral ligament injuries that have frequent association with ACL injuries and anterolateral knee instability 1.
- MRI is proven helpful in detection and characterization of posterolateral corner injuries, which can be associated with the ACL ruptures and, if missed, may lead to considerable morbidity 1.
Comparison with Other Imaging Studies
- CT may be performed as the next imaging study for the evaluation of suspected radiographically occult knee fractures, but it is not as sensitive as MRI for detecting soft-tissue injuries such as ACL tears 1.
- Bone scan with SPECT or SPECT/CT is not the next best imaging study to evaluate for radiographically occult fractures and/or internal derangement, and has lower sensitivity, specificity, and accuracy than MRI in evaluating meniscal injuries 1.
Clinical Considerations
- In patients with acute knee trauma, MRI can change management from surgical to conservative in up to 48% of patients presenting with a locked knee 1.
- MRI can help in preoperative planning, particularly with a growing interest in ligament preservation technique 1.
From the Research
Imaging Study for Suspected Anterior Cruciate Ligament (ACL) Tear
- The recommended imaging study for suspected ACL tear is Magnetic Resonance Imaging (MRI) 2, 3, 4, 5, 6.
- MRI has been shown to have high accuracy in diagnosing ACL injuries, with sensitivity and specificity rates of 95.45% and 91.67%, respectively 2.
- MRI is also effective in diagnosing partial and complete ACL tears, with accuracy rates of 94.74% and 92.86%, respectively 2.
- The use of MRI in diagnosing ACL injuries has been supported by multiple studies, which have demonstrated its high accuracy and reliability compared to arthroscopy 2, 4, 6.
- MRI signs of ACL injury can be categorized into primary and secondary signs, including interruption of ACL continuity, thickening and edema, and abnormal walking, as well as indirect signs such as posterior cruciate ligament index and Notch sign 2, 5.
- The diagnostic accuracy of MRI in evaluating ACL tear has been reported to be 92.0% accurate, with 97.4% sensitivity, 75.0% specificity, 92.5% positive predictive values, and 90.0% negative predictive values 6.