The kinematic effect of tunnel orientation and position, during ACL reconstruction, has been only recently related to the control of rotational instability.

This paper presents a detailed computer-assisted in vitro evaluation of two different femoral tunnel orientations with the same tunnel position, at 10.30 ‘o clock, during the intervention of ACL reconstruction with double bundle technique. Results highlighted better kinematic performances of the horizontal tunnel, with respect to the vertical one, in controlling antero-posterior (AP) laxities at 30°, and internal-external (IE) laxities.

Elongations of anterior and posterior bundles of reconstructed ACL, for both reconstruction, decreased during PROM respectively by 20% and 40%. Total length of the graft varied during PROM, mainly due to graft elongation during tests, graft length on horizontal tunnel varied from 237 to 213mm while graft length on vertical tunnel varied from 257 to 233mm. Kinematic tests showed a better performance of horizontal tunnel in the control of IE rotations at 30° and 90° and of the Lachman test with respect to the vertical one. Stability was restored with both reconstructions.