The diagnosis of knee laxity is essentially clinical. Sometimes, the diagnosis is difficult requiring additional tests, especially MRI and dynamic X-rays like TELOS. This latter technique is expensive and requires specialized equipment and a skilled staff. The aim of this study is to validate the use of the lateral view of the X-ray of the knee with the quadriceps contracted as an alternative to the TELOS technique in the diagnosis of the anterior knee laxity. We conducted a prospective, inter- and intra-observer, comparative study on 40 acute ruptures of the anterior cruciate ligament (ACL), comparing the gathered data with the TELOS technique to those obtained from the knee radiography technique with and without quadriceps contraction. Performed by two different observers, the measurement of the anterior tibial translation on dynamic X-ray switch and without quadriceps contraction and the one with the TELOS was reliable and reproducible (ICC> 0.85). The differential values make possible to overcome measurement errors and also individual laxity. The value of the anterior tibial translation in the "intact ACL" group was significantly lower than the "ruptured ACL" group whether in absolute or differential values, and whatever the technique that has been used. For X-rays that are with and without quadriceps contraction, the differential average between the two knees was 10 millimeters (between 4 and 18mm), and this value was above or equal to 4 mm in 100% of cases. Cases were compared to other controls; the differential tibial translation on radiographs with and without quadriceps contraction was significant starting from 2 millimeters and very significant starting from 3 millimeters. The study of these data showed similar results and concluded that the X-ray of the knee with and without quadriceps contraction is a reliable and reproducible technique to objectify and quantify the degree of the anterior translation in ACL tears.
Keywords: Knee, ACL (Anterior cruciate ligament), Magnetic resonance imaging, Quadriceps muscle, dynamic radiography.
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