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    ACL TEST - MEDIAL ROTATION

    Automated anterior drawer test for ACL assessment - GNRB Rotab

    The GNRB Rotab was created for doctors’ whose intention was to study the anterior cruciate ligament with more precision than the GNRB. The option indeed measures the medial rotation that occurs on the tibia while applying an anterior translation. This medical device permits the analysis of the ACL and its posterior-lateral bundle.

    GNRB Rotab video - Anterior cruciate ligament (ACL) assessment with medial rotation

    GNRB Rotab - Automated Anterior Drawer Test for ACL analysis with consideration of medial rotation

    The GNRB Rotab is nowadays the most precise arthrometer capable of objectively evaluating knee stability because of the dynamic tests it does. It is also the only one able to evaluate the medial rotation resulting from anterior translation. User friendliness, reproducibility and precision are words that best describe the GNRB Rotab.

    The medial rotation evaluation added to the LDA® Method for ACL analysis is an integral part of the GNRB Rotab and it is what makes the GNRB Rotab the greatest innovation for functional analysis of the ACL instability. The results provided after running tests are shown under the form of a graph with compliance curves (=opposite of the stiffness curves) accompanied by a table chart. This makes the tests easy to understand and to reproduce.

    Innovation: Analysing the slopes of the laximetry curves.

    Graph 1 shows the results obtained after performing tests on both knees of a same patient with the GNRB Rotab. The graph shows the compliance curves (=opposite of stiffness curves) obtained after applying several forces on the tibia of the patient to perform an anterior tibial translation with consideration of medial rotation.

    This is called a dynamic analysis because calculation of the displacements of the tibia is done while applying different forces which put the anterior cruciate ligament under stress. Therefore, the bigger the displacement differential, the higher the chances of an ACL tear.

    So far, this is what other arthrometers (Laximetres) have been doing for the past 40 years and it is against this background that Genourob created the GNRB, the first automated tibial translation arthrometer for dynamic assessment of the anterior cruciate ligament.

    Click on the title below to learn more about dynamic assessment of the ACL.

    Example of an anterior cruciate ligament test using the GNRB Rotab

    Graph Results of two patients

    Graph Results of two patients

    The graphs above show the GNRB Rotab's precision concerning the functional analysis of the anterior cruciate ligament instability. The tests shown above are dynamic. They indeed show different forces applied on the tibia associated with different tibial displacements and this has proven to be more effective in the study of Bercovy and Weber for objectively evaluating the state of the ACL and knee stability.

    So far, only measuring the differential of laxity without consideration of the slopes of the lines does not allow a comprehensive analysis of the ligament state. Ironically, this is what most arthrometers created nowadays do.

    Only studying the displacement differential (doing a static analysis) for analyzing knee ligaments can sometimes lead to false diagnosis and does not give any objective result on knee stability. Both graphs shown above undeniably prove this by comparing two different patients' results.

    Patient 1: No instability in both knees Patient 2: Instability in left knee
    • Displacement Differential = 1.5 mm
    • Curve slope = Parrallel Curves
    • Displacement Differential = 1.5 mm
    • Curve slope = Divergent Curves

    The tables chart above resumes the analysis done between on Patient 1 and 2: The only difference resides in the fact that the slope of the curves do not behave alike for both patients.

    This example purely states the efficiency of running dynamics tests against static tests on the knee. Considering the slope differential between both compliance (=opposite of stiffness) curves on behalf of the displacement differential and the medial rotation differential between both knees ultimately leads to a much more precise analysis of the state and performance of the anterior cruciate ligament of the knee.

    The GNRB Rotab is therefore nowadays the best arthrometer (Laximeter) for evaluating the state of the ACL following ACL injuries. Besides, it is also very useful after anterior cruciate ligament surgery as is allows the doctors to follow the behavior of the graft over time. Today's surgical techniques indeed need a lot of time for recovering; therefore GNRB Rotab is also very useful during anterior cruciate ligament rehabilitation (ACL Rehab).

    How to run a test on the anterior cruciate ligament (ACL) with the GNRB Rotab

    GNRB Rotab - Patient Positioning Tutorial

    To run a precise diagnosis on the ACL of a patient using Genourob's GNRB Rotab, it is required to follow these steps:

    1) Position the patient on the GNRB Rotab.

    2) Run the tests on both legs.

    3) Read the results on the graph and its table chart.

    1) Position the patient of the GNRB Rotab


    Patient positioning is the first step to run tests on the anterior cruciate ligament (ACL) of the patient. His leg should be in a 30-40° flexion for optimal anterior cruciate ligament (PCL) testing. This can easily be done with a LDA® Couch which is an accessory especially designed for our products and patient comfort.

    Patient positioning is the first step to run tests of the anterior cruciate ligament (ACL) of the patient. First, two separate marks shall be placed with a pencil on the apex of the patella and the anterior tibial tuberosity. The leg of the patient shall then be placed on the GNRB with the mark of the apex of the patella being located in the hole of the knee cup. The objective here is to block the patella against the femur so that when tests are run, the femur/patella stay locked in position while the tibia undergoes anterior translation. Following this, the foot is to be locked in the Rotab boot which is equipped with a sensor calculating the medial rotation resulting from the anterior drawer test induced by the GNRB. A displacement sensor is then placed on the anterior tibial tuberosity to measure the tibial translation.

    2) Run the tests


    Once patient positioning is achieved, a patient file is to be created on the computer that is provided with the GNRB and the tests shall begin. As soon as a push force is chosen (134, 150, 200 N...), the user can choose to run the tests:

    The cup located under the calf starts applying the force on the tibia leading to an anterior translation. When the chosen force is detected, the cup under the calf stops and goes back to its initial position. This ultimately makes the displacement sensor move upwards/downwards calculating the displacement of the tibia against the force applied. Additionally, the Rotab boot also measures the Medial Rotation resulting from the anterior tibial translation. The data collected is then stored in a table chart with a graph.

    Repeat this on the other knee.

    3) Results:


    When the tests are done, the user will find in the results tab the data collected from these tests. They are under the form of a graph showing the compliance curves (=opposite of the stiffness curves) accompanied by a table chart showing the numerical values.

    GNRB main characteristics for optimal ACL assessment

    • Device using LDA® Method applying anterior anterior tibial translation (Lachman's Test) for anterior cruciate ligament and knee stability objective evaluation
    • Dynamic and none-invasive tests
    • Medial rotation calculus
    • Automatic tibial displacement differential and compliance curves slope differential calculation
    • Registration of the patellar fixation force and patient foot / Base of the machine distance for reproducibility
    • Delivery with PC and LDA® Software
    • Thrust force from 1 to 200 N
    • Patient data automatically saved, results exportable as xls. files, pdf. format for great communication
    • Dimensions : 845 x 270 x 400mm / 15kg

    GNRB additionnal options

    • The last main option available is the GNRB Radio: This option was designed to analyze the anterior cruciate ligament associated with X-ray technology. This device is indeed made of materials especially adapted to X-technology.
    • Finally, other remaining accessories available are the LDA®Couch which provides the patient with great comfort and is specially designed for our products, the biofeedback option that allows controlling of the hamstring muscular activity, the LDA®Trolley for storage of the GNRB and the printer for printing the results.