In early flexion
of the anterior orientation of the patella tendon results in an anterior
tibal translocation force. The anterior displacement is constrained
by the ACL.
The Active Drawer Test
BioMechanics
In early flexion
of the anterior orientation of the patella tendon results in an anterior
tibal translocation force. The anterior displacement is constrained
by the ACL.
As the knee flexion
increases the patella tendon orientation becomes posterior, resulting in
a posterior translocation force.
In Vitro Study of Quadriceps ACL Interaction
The cadaver limb
is mounted and a flexion load is applied which is resisted by the quadriceps
pull.
The tibial femoral
position is documented using visual grid system
The ACL is cut and the flexion angles where the tibial femoral relationship
is altered is noted.
The normal tibial-femoral relationship is reestablished with an ACL
substitute cable.
With the femur oriented horizontally, the tension in the ACL cable to
maintain the tibia-femoral relationship ion an anatomic position is presented
as a ratio of cable tension divided by limb load times 1000 at several
positions of flexion. The added weight was located 16 inches distal
to the origin of the MCL. Seven specimens were studied using 0 to
15 lbs. of limb load. The linear regression line indicates the mean
flexion angle where the ACL was unloaded is 51 degrees.
20º Active Quadriceps Drawer
Anterior tibial
translocation with quadriceps contraction to lift the leg may be measured
with a Knee Ligament ARTHROMETER®.
If the examiner extends the knee by lifting the foot, the proximal tibia
does not move anteriorly in relation to the femur. However, when
the patient contracts the quadriceps to lift the leg, the tibia translocated
anteriorly. Read the dial as the heel lifts off the table.
The translocation in 408 normal volunteers was 4 mm. The side to
side difference in the normal population and 118 ACL deficit patients is
noted below.
90º Active Quadriceps Test
With the knee in a 90º of flexion, contraction of the quadriceps
in the normal knee results in 0 to 2 mm of posterior tibial displacement.
In a PCL deficit knee there is a posterior tibial sag and quadriceps contraction brings the tibia anterior. The Knee Ligament ARTHROMETER® may be used to measure the 90º active quadriceps drawer.
Summary
1. There is a consistent interaction between the quadriceps muscle and the cruciate ligaments which depends on the knee flexion angle.
2. 20º Active Quadriceps Drawer.
A quadriceps contraction with the knee at 20º of flexion displaces the tibia forward.
The ACL constrains tibial displacement.
3. 90º Active Quadriceps Drawer.
A quadriceps contraction in the normal knee at 90º of flexion displaces the tibia posterior.
In a PCL deficit knee with a posterior tibia sag, the quadriceps contraction pulls the tibia anterior.
4. The Active Drawer Tests may be measures with a Knee Ligament Arthrometer®
Prepared for the 50th Annual Meeting of the American Academy
of Orthopaedic Surgeons
From the Departments of Orthopedic Surgery: Kaiser Hospital,
San Diego; University of California, San Diego; Donald Sharp Rehabilitation
Center, San Diego
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