With more ACL primary reconstructions being performed each year and increasing activity levels in the aging populartion, graft failure after ACL reconstruction will likely become a more frequent problem.

Graft failure is not limited to a physical graft re-tear.  Patient complaints of instability must be considered independently from laxity on the physcial examination.  Inadequate muscle function, pain, or loss of motion are separate issues from the integrity of the graft and may not be improved after revision surgery.

Etiology of recurrent instability is multifactorial.  Early phase recurrent instability occurs < 6 months post-operatively.  Reasons for failure can be poor surgical technique, loss of graft fixation, failure of graft incorporation, a premature return to high risk activites, and an overly agressive rehabilitation program.

Technical errors that can cause early phase failure are:
  • Incorrect tunnel postion on femur, tibia, or both
  • Poor graft quality or fixation
  • Inadequate tensioning

Failure of the surgeon to replicate native ACL anatomical insertion sites with tunnel placement.  This can lead to increased graft stresses and eventual attenuation of the graft.

A femoral tunnel placed vertically may restore anterior to posterior stability; however, it usually does not allow for proper rotational stability.



The position of both the femoral and tibial tunnels is responsible for the graft forces.  Not just one or the other. 

 Some issues with regards to tunnel placement are:

  • A femoral tunnel placed too anteriorly will cause an excessive graft tension in flexion.
  • A femoral tunnel placed too posteriorly, will cause an excessive graft tension in extension.
  • A tibial tunnel placed too posteriorly, will cause a Posterior Cruciate Ligament (PCL) impingement with a loss of flexion or graft attenuation.
  • A tibial tunnel is placed to anteriorly, will cause intercondylar notch impingement with the graft.
Unrecognized injury in the posterolateral or posteromedial structures may result in increased stresses in ACL graft resulting in early attenuation and graft failure.

The medial meniscus acts as an important secondary restraint on tibal translation.  Loss of medial meniscus leads to increased forces in the reconstructed graft and may lead to attenuation and failure



Late phase recurrent instability occurs > 6 months post-operatively.  Traumatic re-injury is the most common mode of late failure.  Poor tunnel location and other ligamentous or meniscal deficiency may also be present with late failures.  Athletes are not bullet-proof from an ACL re-rupture.  Risks of re-rupture in this stage depends upon their return to high risk sports and age (usually < 25) and decreases in older populations.

Other causes of ACL reconstruction failure include loss of motion and infection.  Loss of motion can range from a small loss of terminal knee extension or flexion to global arthrofibrosis.  Surgical factors affection range of motion after reconstruction is performing the surgery in an acute setting.  By not regaining full range of motion prior to surgery, you are decreasing potential results post-operatively.  Prolonged immobilization, non-anatomical graft placement, and graft over tensioning are also complications with loss of motion.  Other factors include RSD and indolent infection.

In regards to musculature, extensor mechanism dysfuction through quadriceps inhibition may be manifest as complaints of instability occurs in patients following ACL reconstruction.  Other complaints may include loss of patellar mobility, anterior knee pain, and patellar or quadriceps tendonitis.

The surgeon must recognize factors related to patient failure so a decision can be made as to whether a revision procedure is necessary and what chances exist for the patient to have success.

The above information was taken from Dr. Lowe's presentation titled "Revision ACL Reconstruction:  Strategies to Improve Results" from the Edward T. Smith Lectureship 2010, University of Texas Medical School, Houston, Texas.