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    Automated anterior tibial translation test with consideration of medial rotation for objective precise assessment of the ACL

    Genourob's LDA® Method is integrated in the core of the GNRB, which is a medical device designed to automate the anterior drawer test (Lachman Test). It applies anterior tibial translation on the tibia and allows users to objectively evaluate the state and performance of the anterior cruciate ligament (ACL) by providing compliance curves (=opposite of stiffness curves), hence evaluating knee stability

    In addition to this technique of use of the LDA® Method for ACL analysis by the GNRB can be added an option called the Rotab. This option enables the users to evaluate the induced medial rotation of the tibia provoked by the anterior tibial translation of the GNRB (see video below) to study the posterior-lateral bundle of the ACL. An electronic goniometer integrated in the boot of the Rotab option is what makes the measuring of the tibial rotation possible.

    GNRB Rotab video: automated anterior drawer test with medial rotation data

    GNRB Rotab arthrometer using LDA® Method

    Innovations of measurement with GNRB Rotab :

    • Perform an objective, precise and rigorous automated Lachman Test.
    • Increase the accuracy and reproducibility of tests.
    • Rotab Option: More precise evaluation of partial lesions compared to GNRB.
    • Compare and document the results over time.
    • Allow great patient/doctor communication.
    • Move from manual test to an automated quality.

    Dynamic ACL test with medial rotation data

    Running dynamic tests on the anterior cruciate ligament with devices such as the GNRB Rotab permits medical practitioners to evaluate the state of the ACL with greater precision than the GNRB during the pre-surgery phase and also to do a follow-up of the ACL graft during post-surgery phase. The image showing Graph 1 and its Table Chart show the results obtained by the GNRB Rotab.

    Dynamic tests allow doctors to have three valuable parameters:

    - The tibia displacement differential (Δ134).

    - The slope of the compliance curves of both knees (ΔP2).

    - The rotation differential between both knees (Diff Rot. Final).

    The data collected by these three parameters are essential and make the GNRB Rotab unique of a kind as it is the only device currently present on the market that objectively evaluates knee stability.

    For each push, 50 values of tibia displacement are registered at a 0,1 of a mm. After each test, the data on the ACL is immediately saved on the computer that is provided with the GNRB Rotab arthrometers. Selection and comparison of specific results is possible and can easily be done.

    Calculation of displacement differential at 134N, slopes of the curves and medial rotation differential between both knees is automatically done by the means of the dynamic elongation curves created during the tests to compare both knees.

    What is new compared to other arthrometers?

    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 (Study of Bercovy and Weber).

    Most of the devices that are nowadays used to analyze the state of the ACL do the tests while applying a single pressure force at 134N. These experiments are considered like static tests.

    The KT 1000 is a product that resembles in many ways the GNRB and was used for generations by doctors all over the world because it was one of the first devices allowing the analysis of the ACL with objective results. Its technology was based on the drawer test also known as the lachman test.

    Then came the KT 2000 when computers started making their appearances in hospitals. The KT 2000 was indeed a simple replica of the KT 1000 but compared to its predecessor, exporting of the results on a computer was possible.

    Today, Genourob's products continue analyzing the ACL while applying anterior tibial translation but innovation is present in the way we gather results. All the tests done by our products are dynamic (different forces applied on the tibia) and this therefore enables to draw compliance curves (=opposite of the stiffness curves). Analysis consequently becomes more interesting because studying the slope of the compliance curves in addition to the displacement differential turn out to be possible ultimately leading medical practitioners in obtaining valuable information on knee stability and on the state of the ACL.

    Besides, adding the Rotab option on the GNRB allows doctors to collect additional information on the posterior-lateral bundle of the ACL by analyzing the medial tibial rotation provoked by the anterior translation applied on the tibia.

    KT1000/KT2000 and other devices present on the market nowadays were indeed only designed to study the tibia displacement at a certain force and this can in some cases be misleading.

    Simple ACL Test

    1) Positioning of the patient: The patient's leg is placed on the GNRB Rotab and a knee-cup is placed over the patella of his knee. This cup is than tightened so that the patella is pushed against the femur therefore preventing them from any kind of movement. During the process, the foot is also locked in the boot so that the patient has no way of doing any vertical movement with his foot. In addition, a sensor is than placed on the tibial tuberosity (top of the tibia) to collect data on displacement of the tibia. 

    2) Testing: A cup located under the calf starts applying controlled forces on the calf which creates a translation movement of the tibia, the anterior tibial translation. During this movement, the sensor located over the anterior tibial tuberosity collects data on the displacement of the top of the tibia and the electronic goniometer located in the boot harvests the data on the tibial rotation. Since the patella/femur and the foot are locked in position, these parameters ultimately provide data on the state and performance of the anterior cruciate ligament (ACL) and its posterior-lateral bundle as it is put in stress.

    3) Data collection: the displacement and tibial rotation data collected are immediately saved on the computer database and easily comprehensible through force/displacement curves also known as compliance curves (=opposite of stiffness curves).

    Therefore, overall check-up of the ACL state and performance is easily and quickly done. Since the forces applied on the knee are controlled (forces applied between 100N and 200N), the tests can be done during the pre-surgery phase to diagnose the state of the anterior cruciate ligament and during the post-surgery phase to follow the state and performance of the ACL graft (very useful since rehab after ACL reconstruction surgery takes several months).

    In the case that the posterior-lateral bundle has been torn does not assure its braking function, measures done with GNRB Rotab will show an increase in medial tibial rotation, hence indicating the posterior-lateral bundle of the ACL is torn.

    Please find below a video showing how a test is done with the GNRB Rotab.

    GNRB Rotab - Patient Positioning Tutorial

    As preoperatively than postoperative, the combination of three calculated differentials allows an accurate evaluation of the ligament function.

    During the test of anterior tibia translation, the software registers the traditional parameters of displacement and slope, but also calculates the differential of the induced medial rotation for precise knee ACL analysis.

    GNRB Rotab summary: simple quick and precise tests for ACL assessment

    GNRB with Rotab option for precise ACL analysis

    GNRB with Rotab option for precise ACL analysis

    1 - Fixation of ankle and thigh.

    2 - Positioning of tibia displacement sensor.

    3 – Automatic application of adapted forward push.

    4 – Synthesis, comparison and immediate calculation of measurements of both knees by LDA® software.

    5 – Tests require a knee flexion of 30°, with the use of Genourob's accessory, the LDA® Couch.

    If you want more information, please feel free to download the "Automated Dynamic Laximetry" document below: