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Studies ACL: Anterior cruciate ligament
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    ACL INJURY/TEAR ASSESSMENT

    Automated anterior drawer test for ACL assessment - GNRB

    The anterior cruciate ligament (ACL) was for Genourob the first knee ligament intended to be studied using the GNRB. This arthrometer (aka. laximeter) has quickly become the reference in the orthopaedic field for studying the state of the ACL by applying an automated Lachman Test.

    GNRB Video - Anterior cruciate ligament (ACL) assessment

    GNRB - Automated lachman test for ACL assessment

    Presently, it is the device that provides the best precision in regards of knee ACL laxity assessement and it is the only arthrometer (aka. laximeter) able to objectively evaluate knee stability because of the dynamic tests it runs. User friendliness has also been taken into account while designing this arthrometer leading to several parameters and sensors being installed in order guide the users while running dynamic tests. Because of these parameters and sensors, precise test reproducibility has also become an attribute of the GNRB.

    The LDA® Method is an integral part of the GNRB and it is perhaps what makes this device leader on the market for ACL analysis. 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, to reproduce and it allows an evaluation with accurate figures of ligament laxity of the knee and more precisely knee stability.

    Example of an anterior cruciate ligament assessment using the GNRB

    Graph 1

    Graph 1

    Graph 1 shows the results obtained after performing tests on both knees of a patient with the GNRB. 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.

    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 anterior cruciate ligament tear.

    So far, this is what other arthrometers (Laximeters) 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 Genourob's knee joint ACL laxity assessment technique.

    Innovation: Analysing the slopes of the laximetry curves.

    Graph Results of two patients

    Graph Results of two patients

    The graphs above show the GNRB's precision regarding the functional analysis of the anterior cruciate ligament. The tests shown above are dynamic. Why? Because they 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 (displacement differential) 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 between both knees ultimately leads to a much more precise analysis of the state of the ACL present in the knee.

    The GNRB is therefore nowadays the most advanced arthrometer (Laximetre) for evaluating the state of the anterior cruciate ligament following knee injuries. Besides, it is also the only device capable of assessing ACL laxity after surgery thanks to its controlled tibial translation. Doctors are therefore able to follow the behaviour of the ACL graft over time which is the key to guarantee knee stability. Today's surgical techniques indeed require a lot of time of recovering therefore making the GNRB indispensable  during anterior cruciate ligament rehabilitation (ACL Rehab).

    How to run tests on the anterior cruciate ligament (ACL) with the GNRB

    GNRB - Patient Positioning Tutorial

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

    1) Position the patient on the GNRB.

    2) Run the tests on both legs.

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

    1) Position the patient on the GNRB


    Patient positioning is the first step to run tests on 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 to avoid any vertical movements and a displacement sensor in placed on the anterior tibial tuberosity.

    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. 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 tibial translation (Lachman's Test) for ACL and knee stability objective evaluation
    • Dynamic and none-invasive tests
    • 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

    • Over time, Genourob created several options that could be added to the GNRB such as the PCL option dedicated to analyzing the knee cruciate ligament, the posterior cruciate ligament (PCL).
    • GNRB Rotab is also available and was created to analyze the ACL with more precision by taking into account the calculation of the medial rotation that occurs when applying anterior tibial translation.
    • The last main option available is the GNRB Radio: This option was designed to analyze the ACL associated with X-ray technology. The GNRB Radio 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.