- See: Notchplasty:
- Discussion:
- most common error is non isometric anterior tunnel placement within intercondylar notch rather than at its normal posterior insertion;
- ACL graft should pull up into the tibial tunnel by about 2mm with extension when fixed on the femoral side;
- this represents the closest reconstitution of the ACL's "physiometry"; (see: isometry);
- a graft that tightens (pulls up into the tibial tunnel) with flexion will have a much higher likelyhood of
failure and usually indicates a femoral tunnel too far anterior in the notch;
- tunnel positioning:
- anterior graft placement (relative to normal anatomical insertion of ACL) results in high strain on graft as knee is flexed;
- this restricts flexion of knee if graft remains intact, or it may elongate graft if the range of motion is restored;
- posterior placement or distal to normal site of attachment results in excessive tightening of the graft when knee is extended;
- consider whether there is an interplay between posterior graft placement and appropriate graft tension;
- with a posteriorly positioned femoral tunnel consider final tibial graft fixation in full extension rather
than 30 deg flexion, since positioning in 30 deg flexion at the time of final fixation may result in
excessive graft tension when the knee is position in full extension;
- over the top position:
- over the top repair tensioned in extension will provide support in terminal extension but may slacken at greater flexion angles;
- grafts that pass thru femoral tunnels develop more internal pressure at femoral attachment site than those passed over top because
of sharp edge of the tunnel;
- some create a trough in the femur to bring graft closer to anatomical position, or they fix graft in place w/ knee in full extension;
- lateral tunnel placement:
- w/ a right knee, place the tunnel at about the 9:30 to 10 o’clock position;
- allows the femoral attachment point to overlap the anterolateral and posteromedial bundles insertion site
- in the report by MJ Strobel et al., the authors report a case of a painful reflex extension loss due to femoral malplacement of an ACL
graft in a female high-level athlete;
- graft was placed on the femoral site in the high noon position combined with a slight medial tibial tunnel placement;
- resulting anterior-posterior cruciate ligament impingement near extension caused a persistent functional extension deficit of 20°;
- under anesthesia, the extension loss diminished, and thus it was hypothesized that the ACL-PCL impingement during
extension activates a proprioceptive reflex leading to a functional extension loss while the patient is awake.
- references:
- Reflex extension loss after ACL reconstruction due to femoral high noon graft placement. MJ. Strobel, MD. April 2001 Vol 17 No 4
- Knee stability and graft function following ACL reconstruction: Comparison between 11 and 10 o'clock femoral tunnel placement.
- Knee stability and graft function after anterior cruciate ligament reconstruction: a comparison of a lateral and an anatomical femoral tunnel placement.
- Native Anterior Cruciate Ligament Obliquity Versus Anterior Cruciate Ligament Graft Obliquity. An Observational Study Using Navigated Measurements
- Surgical Technique:
-
one incision technique:
-
two incision technique:
-
open technique:
- Complications:
- 30 yo male who presented for revision ACL reconstruction;
- (his medical history and operative note were not available for review);
- the obvious teaching points are that both the femoral and tibial tunnels were placed far to anterior;
- another example of how not to perform an ACL reconstruction:
Anterior cruciate ligament reconstruction with patellar tendon: an ex vivo study of wear related damage and failure at the femoral tunnel.
BK Graf et al. Am. J. Sports Med. Vol 22. p 131. 1994.
Anterior cruciate ligament replacements: a mechanical study of femoral attachment location, flexion angle at tensioning, and initial tension.
DE Bylski-Austrow et al. J. Orthop Res. Vol 8. p 522. 1990.
Varying Femoral Tunnels Between the Anatomical Footprint and Isometric Positions.
ACL graft can replicate the normal ligament's tension curve.
Effects of notchplasty and femoral tunnel position on excursion patterns of an anterior cruciate ligament graft.
Effects of femoral tunnel placement on knee laxity and forces in an anterior cruciate ligament graft.
Editorial: The Lateral Intercondylar Ridge—A Key to Anatomic Anterior Cruciate Ligament Reconstruction
Morphology of the Femoral Intercondylar Notch
Does the position of the femoral tunnel affect the laxity or clinical outcome of ACL-reconstructed knee? A clinical, prospective, randomized, double-blind study.
