 Hello, everyone. I'll be presenting a paper on utility of indirect science of ACL tier in MRI of the knee. A retrospective study on 30 patients with partial or complete ACL tier. I'm Dr. Chakshu Bhattra, final year PG, SGT Medical College Hospital and Research Institute Guru Ram. The aims and objectives are to determine the sensitivity of secondary science of ACL tier in both partial and complete ACL tiers. With science should be used as an adjunct to add confidence to the diagnosis of ACL tier and should be looked for in doubtful cases or in direct non visualization of ACL due to adjacent edema or error in image acquisition. The study is a retrospective study including 30 patients 22 with a full thickness ACL tier and eight with a partial thickness ACL tier. The MRI knee examination of all patients was done using a 1.5 Tesla MRI machine in the department of radio diagnosis at City Medical College Hospital Guru Ram. Most operative cases and patients with any underlying bony fractures or intra-articular inflict infections were excluded from the study. Patients of all ages and both sexes were included in the study. anterior cruciate ligament is the most commonly injured ligament of the knee. It is intra capsular but extra synovial. It is composed of two bundles and anterior medial bundle and a posterior lateral bundle. Attachments are to the inner aspect of little femoral condyle and intra-condyler eminence of tibia. The primary role of ACL is to provide stability to the knee joint. It resists anterior translocation and internal rotation of tibia over the femur. It also limits hyperextension of the knee. ACL injury is associated with anterior lateral instability of the knee joint. By image ACL, the clinical examination depends on the ability to demonstrate anterior tibial motion relative to a fixed femur in tests like latchman test, anterior drawer test and pivot shifts test. However, these tests have very low sensitivity and specificity and are difficult to perform because of pain and guarding sensation in the patient. MRI is the main imaging modality used to visualize ACL injury. It can diagnose ACL sprain, partial tear, complete tear, site of the tear, cognitive of fibres and evaluation of ACL graft reconstruction with the detailed anatomical details of the surrounding structures. The direct signs of ACL tear are discontinuity of the fibres which can be focal or diffuse, a T2 high signal intensity either in class substance or as a surrounding mass. An abnormal contour of the ACL, it could be wavy or making a more than 15 degrees angle to the plumen site's line. These direct signs are usually sufficient and have both high sensitivity and specificity for accurate diagnosis of ACL tear. However, pitfalls have been identified on direct ACL imaging. A line is drawn along the roof of the intercondyler notch of femur and another line is drawn along the posterior fibres of the ACL. The angle made between these two lines is known as the ACL plumen site angle. In an abnormal plumen site angle, the tip of the triangle is pointed downwards and the angle is more than 15 degrees. Then it is known as an abnormal ACL plumen site angle which is an indicator of ACL tear. Some pitfalls and direct ACL imaging are discontinuity with gap formation is not always visible. Locating a tear, grading a tear is sometimes difficult due to adjacent hemorrhage and edema. A tear may not give a detailed image of ACL near its insertion site as it is ACL is short, thin and angulated. And most common is the indirect scanning techniques, especially the oblique sagittal images by the radiology technicians. Indirect or secondary signs have immense importance in such cases. The secondary signs which are included in the study are bony contusions, complete a tear or a grade two signal in the medial meniscus, anterior translation of tibia, uncovered posterior horn of lateral meniscus, hyper intensity in the tibia, pericruciate fat pad, a very particular tendon sign, other signs like PCL buckling sign, associated cigars fracture, associated joint diffusions have also been mentioned. ACL tear is associated with medial collateral ligament injury and medial meniscus tear. This is termed as the unhappy dried up or don't know. Bony contusions are most common in the posterior femoral condyle and the posterior lateral aspect of the intercondyline notch of tibia. Contusions in both these areas are highly specific for ACL tear. Complete tear of ACL is when the signal intensity reaches one of its articular surfaces. This is a grade two C signal in the posterior horn of medial meniscus, and this is a vertical tear in the anterior horn of medial meniscus. Anterior translation of tibia is the radiological analog of anterior drawer sign. A line is drawn along the most posterior part of the tibia and the most posterior part of the femoral. The distance between these two lines, if it is more than 5 mm, the anterior translation of tibia test is said to be positive. As in this case it is 9.5 mm. Pericruciate fat pad is one of the fat pads located in the intercondyline notch of tibia. It is intimately related to both the cruciate ligaments. A hyper intensity in the pericruciate fat pad is one of the secondary signs of ACL tear. As we can see in the sagittal images, a PD fat sat image shows a hyper intense signal in the pericruciate fat pad. The posterior horn of lateral meniscus is not attached to the lateral-palletal ligament and is inherently more mobile than the posterior horn of the medial meniscus. The uncovered posterior horn of lateral meniscus sign is said to be positive if a tangent line drawn along the posterior margin of the tibia intersects the posterior horn of the lateral meniscus. In our study, we included 22 patients with a full-thickness tibial condyle. In our study, we included 22 patients with a full-thickness tibial condyle. If the tibia becomes concave in its superior surface, then the PCL is said to have buckled. In our study, we included 22 patients with a full-thickness tear in which bony contusions were associated with 72.7%. Signal in the medial meniscus is 45.5%. Capsular sign 40.9%, anterior translation of tibia 45.5%, lateral capsular sign 13.6% as MRI is not sensitive to depth sigon fracture. Uncovered posterior horn of lateral meniscus in 45.5%, pericruciate fat pad intensity in 90.9%, associated joint diffusion in 95.5%. Similar, we are the figures in a half-thickness tear. Bony contusions were associated in 72. As we can see in these pie charts, the variable amount of the presence of secondary signs in both as in full thickness, the partial thickness tear also shows the frequency of the associated signs in a variable degree. Hence, we came to the conclusion that secondary signs of ACL tear described in literature were found to have variable sensitivity on MR images. The presence of bony contusions, pericruciate fat pad hyper intensity and joint diffusion were found to have a high sensitivity for both full thickness and partial thickness ACL tears. Pericruciate fat pad signal and joint diffusion are nonspecific findings. Therefore, these can be used to suspect an underlying ACL abnormality to facilitate the scanning in a pd fat sets a vital sequence, or as a follow-up scan to rule out any ACL injury in cases of adjacent edema or hammerage. Rest of the indirect signs had moderate sensitivity in both full thickness and partial thickness ACL tears. The presence of these secondary signs increases the confidence of the diagnosis. In almost all cases of ACL tear, these secondary signs are present in different combinations. Hence, together as a whole, they can significantly indicate an underlying ACL tear or even a sprain. However, rarely ACL tear can even present with no indirect signs. Therefore, these secondary signs should be used as an adjunct to direct signs of ACL tear and not alone in diagnosing ACL injury. These are my references. Thank you.