Rationale for Proper Arthroscopic Tunnel Placement in Anterior Cruciate Ligament Reconstruction

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Abstract

Correct tunnel placement is critical to the success of anterior cruciate ligament (ACL) reconstruction. In the revision setting this is more difficult as anatomic landmarks may be distorted or missing and secondary landmarks may be necessary. Native anatomy was not well replicated by early ACL reconstruction procedures and consequently did not optimally restore stability. The over-the-top position placed a nonanatomic graft too anteriorly on the tibia and too proximally on the femur with graft of supraphysiological length. This resulted in vertical grafts with a propensity to impinge, lengthen, and become lax. Notchplasty was a method of reducing impingement of grafts and is less often indicated with anatomic graft positioning. Trans-tibial drilling and clockface tunnel positioning are falling out of favor as graft positioning more closely replicates native anatomy, and more precise anatomic landmarks are used to guide graft positioning through the anteromedial portal. Current recommendations for femoral tunnel positioning are now the center of the femoral ACL origin at 1.7 mm proximal to the bifurcate ridge and 6.1 mm posterior to the intercondylar ridge. Recommendations for the tibial tunnel are the center of the tibial insertion at 7.5 mm medial to the anterior horn of the lateral meniscus, 7.9 mm lateral to the medial plateau cartilage border, and 13 mm anterior to the retroeminence ridge. Radiographically the tibial tunnel is 41% from anterior on the Amis and Jakob line and 47% from the medial side. A thorough knowledge of relevant anatomy and rationale for anatomic placement are necessary to ensure consistent optimal graft placement in revision ACL reconstructions.

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