- femoral tunnel
- tibial tunnel:
- isometric placement of ACL refers to the concept that a full range of knee can be achieved w/o causing long-term ligament deformation;
- isometry can not exist because, during ROM, there is no one point on femur that maintains a fixed distance from a single point on tibia;
- elongation always will occur;
- placement of graft as closely as possible to centers of tibial & femoral attachments of anterior medial band results in least amount of strain (least
change in length of ACL during complete ROM of knee);
- many researchers have tried to determine which bundle regions of ACL are most isometric;
- bone patellar bone grafts attempted replacement of anteromedial band of ACL, which is most nearly isometric portion of the normal structure;
- of note, most surgeons feel that it is more important to replace the more non-isometric posterolateral band;
- ACL graft should pull up into the tibial tunnel by about 2-3 mm with extension when fixed on the femoral side;
- this represents the closest reconstitution of the ACL's "physiometry";
- a graft that tightens (pulls up into tibial tunnel) w/ flexion will have a much higher likelyhood of failure and usually indicates a femoral tunnel too far anterior in notch.
- Graft Fixation:
Testing for isometry during reconstruction of the anterior cruciate ligament. Anatomical and biomechanical considerations.
Effect of the Angle of the Femoral and Tibial Tunnels in the Coronal Plane and Incremental Excision of the Posterior Cruciate Ligament on Tension of an Anterior Cruciate Ligament Graft: An in Vitro Study.