POSTERIOR DRAWER TEST (AUTOMATED)

Automated posterior tibial translation test for objective assessment of the PCL

The LDA® Method is integrated in the GNRB PCL. This option provided to the GNRB laximeter allows medical practitioners to apply posterior tibial translation destined to the analysis of the posterior cruciate ligament (PCL) in addition to the evaluation of the state and performance of the anterior cruciate ligament (ACL).

The following section focuses on how the PCL can be analyzed using LDA® Method but it should be noted that when equipped with a GNRB PCL, ACL assessment is still available with anterior tibial translation.

GNRB PCL video: Automated Posterior Drawer Test

GNRB PCL Arthrometer using LDA® Method

INNOVATIONS of measurement with GNRB PCL

Perform an objective, precise and rigorous automated Lachman Test.
Increase the accuracy and reproducibility of tests.
Compare and document the results over time.
Allow great patient/doctor communication.
Move from manual test to an automated quality.

Dynamic PCL tests for optimal results

Graph 1 with its tables chart

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

Dynamic tests allow doctors to have two valuable parameters:

- The tibia displacement differential (Δ134).

- The slope of the compliance curves of each knee (ΔP2).

The data collected by these two parameters are essential and make the GNRB PCL 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 PCL is immediately saved on the computer that is provided with the GNRB PCL arthrometers. Selection and comparison of specific results is possible and can easily be done.

Calculation of displacement differential at 134N and slopes of the curves is automatically done.

What is new compared to other arthrometers?

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 was used during a long time 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.

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 PCL test

1) Positioning of the patient: The patient's leg is placed on the GNRB PCL so that his knee is at 45° of flexion 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 locked in position so that the patient has no way of doing any vertical movement with his leg. The PCL option is then placed under the tibial tuberosity (top of the tibia) and tightened around the tibia. This module is placed there as it will apply posterior tibial translation on the tibia. Following this, the displacement sensor of the GNRB PCL shall be placed on the tibial tuberosity in order to collect data on the tibial displacement.

2) Testing: The PCL option placed under the tibial tuberosity starts applying controlled forces on the top of the tibia which creates a translation movement of the tibia, the posterior tibial translation. While applying this movement, the sensor located over the tibial tuberosity collects data on the displacement of the top of the tibia since the patella/femur and the foot are locked in position ultimately giving data on the state and performance of the posterior cruciate ligament (PCL) as it is put in stress.

3) Data collection: The displacement data collected is 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 PCL 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 posterior cruciate ligament and during the post-surgery phase to follow the state and performance of the PCL graft (very useful since rehab after PCL reconstruction surgery takes several months).

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

Test parameters

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