Anatomic double-bundle ACL reconstruction restricts knee extension in knees with hyperextension

Double-bundle ACL reconstruction has been demonstrated to be at least as effective as single-bundle reconstruction in terms of restoring knee rotational and translational stability. Until now, the influence on knees with hyperextension has not been evaluated. It was the purpose of this study to evaluate whether double-bundle ACL reconstruction restricts extension in hyperextendable knees.

Hamstring tendon reconstructions of 10 human cadaveric knees with the ability of hyperextension (age: 48 ± 14 years) were performed as single bundle (SB) on one side and double bundle (DB) on the other side. A surgical navigation system (BrainLab, Germany) was used to assess the kinematics of each knee at the intact and reconstructed state. A difference with regard to the anterior-to-posterior translation (AP) and rotational stability at 30° of knee flexion, 90° of flexion and the hyperextension capability of each specimen was analysed.

The difference in AP translation before and after the reconstruction was not significantly different in 30° and 90° of flexion (n.s). Both single- and double-bundle reconstructions restored the preoperative kinematics at 30° and 90° of knee flexion (n.s). The knee extension was 4° ± 1.8° with the intact ACL and 4° ± 1.7° after reconstruction in the SB group (n.s). The knee extension was 5° of hyperextension ± 1.1° with the intact ACL and 0° ± 0.4° after reconstruction in the DB group; the limitation of the extension was significantly larger in this group (p = 0.013).

Both single- and double-bundle ACL reconstruction techniques are capable of restoring knee anteroposterior and rotational stability. Double-bundle reconstructions significantly reduce knee extension in knees with hyperextension capability. Care must be taken when using double-bundle techniques in patients with knee hyperextension as this procedure may limit the knee extension after double-bundle ACL reconstruction.