Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction: Kinematics and Knee Flexion Angle–Graft Tension Relation

Knee simulator with mounted specimen. A constant force was applied to the quadriceps and hamstring muscle groups during testing. After the anatomic DB-ACLR, the tibial side of each graft was held with custom-made tensioning devices that allowed precise and separate tensioning of each bundle. For kinematic testing, anterior and posterior loads were applied to the tibia by use of an eyelet inserted into an anchor in the tibial tubercle. Application of a posterior load is shown.

Calculating rotational displacement. The yellow outline represents the position of the tibial plateau in the unloaded state as viewed from above. The red and blue outlines represent the position of the tibial plateau in the intact and ACL-deficient knee, respectively, in response to the combined rotatory load. The red and blue arrows represent the measured arc of overall rotational displacement in the intact and ACL-deficient specimens, respectively. The red and blue points represent the points about which the tibial plateau rotated relative to the femur in the intact and ACL-deficient knee, respectively, in response to the combined rotatory load.

Anatomic DB-ACLR. (A) Placement of tibial guidewires as viewed from anterolateral portal. (B) Position of femoral tunnels with knee at 90° of flexion as viewed from AM portal. (C) Completed DB-ACLR with knee at 90° of flexion as viewed from anterolateral portal.

Technique for quantification of tunnel positions by use of lateral radiographs. (A) Lateral radiograph with all 4 guidewires in place showing positions of planned tunnels for each bundle. (B) Lateral radiograph with guide bolts in femoral tunnels after reaming. (C) The position of each femoral tunnel was defined in terms of the percentage distance in each axis with the posterior end of the Blumensaat line defined as 0%, with “a” being the distance on the x-axis (along the Blumensaat line) and “b” being the distance on the y-axis of the grid. (D) The position of each tibial tunnel was expressed as a percentage of the maximum tibial sagittal diameter with the anterior-most point defined as 0%.

Dynamic testing setup. Custom-made tensioning devices that allowed precise and separate tensioning of each bundle were used to hold the tibial side of each graft. Each tensioning device included a load cell (LSB200; Futek) that dynamically measured the tension in each bundle as the knee was brought through range of motion.

Knee flexion angle–bundle tension relation during dynamic testing. For the 20/20 protocol, the bundle tensions intersect at 23°. The AM and PL bundle tensions were statistically equivalent throughout knee range of motion. In contrast, for the 45/15 protocol, the AM bundle tension was higher than the PL bundle tension for the entire flexion-extension arc, and the difference was statistically significant throughout knee range of motion.