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    THE LDA® METHOD - OBJECTIVE KNEE JOINT LAXITY TEST

    How to assess knee ligament damage: LDA® Method

    The LDA® Method is an innovative patented technique created by company Genourob destined to the assessment of knee ligamentous laxity. It provides precise evaluation of the knee ligamentous structures by applying automated and controlled tibial translation (GNRB) or rotation (ROTAM). The LDA® Method, which stands for Automated Dynamic Laximetry (Laximétrie Dynamique Automatisée in French) Method, is a new approach to the measurement of knee laxity (aka. Laximetry) that is done through dynamic tests and with results under the form of compliance curves (=opposite of stiffness curve).

    Example of a test using LDA® Method

    Graph 1

    Graph 1

    The Graph 1 shows an example of tests run on both legs of a patient using the LDA® Method while applying anterior tibial translation.

    How does LDA® Method work?

    It is quite simple: The femur is locked in position while different forces are applied on the tibia. Both curves drawn on graph 1 represent the compliance (=opposite of stiffness) of the ligament that is measured.

    Green curve: Healthy Knee

    Red curve: Pathological Knee

    The dynamic tests performed on each knee are done with a precision of 0.1 mm and offer a wide range of results such as the tibia/femur displacement differential and the slope of the curves.

    This eventually leads to making a precise diagnostic of the state of knee ligaments (displacement differential) and knee stability (slope of the curves).

    Innovation: analyzing the slopes of the laximetry curves.

    Graph 2: Patient 1 (Left Graph) and Graph 3: Patient 2 (Right Graph)

    Graph 2: Patient 1 (Left Graph) and Graph 3: Patient 2 (Right Graph)

    So far, only measuring the differential of knee laxity without consideration of the slopes of the lines does not allow a comprehensive analysis of the ligament state and this has been proven by the study of Bercovy and Weber in 1995. 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 information on knee stability. The graph 2 undeniably proves this by comparing two different patients' results.

    Patient 1 results are represented by the graph 2 and Patient 2 results are represented by graph 3.

    Patient 1: No instability in both knees

    Patient 2: Instability in left knee

    • Displacement Differential = 1.5 mm
    • Curve slope = Parallel Curves
    • Displacement Differential = 1.5 mm
    • Curve slope = Divergent Curves

    The tables chart above resumes the analysis done between graph 2 and 3: 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 and performance of the ligamentous structures of the knee.

    Use of LDA® Method

    Nowadays, the LDA® Method is used in various ways to allow orthopaedic surgeons, sports doctors, radiologists and physiotherapy analyzing the state and performance of the different knee ligaments in the pre-surgery and post-surgery phase of a patient's management.

    The ligamentous structures that are analyzed using the LDA® Method include:

    • Analysis of the ACL with medial rotation consideration using an automated version of the anterior drawer test (Lachman Test) integrated in the GNRB Rotab.

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