The Apex of the Deep Cartilage: A Landmark and New Technique to Help Identify Femoral Tunnel Placement in Anterior Cruciate Ligament Reconstruction

Abstract

The purpose of this study was to evaluate the apex of the deep cartilage (ADC) as a landmark to help guide femoral tunnel placement during anatomic single-bundle anterior cruciate ligament (ACL) reconstruction. Our secondary purpose was to assess whether or not the endoscopic transtibial femoral offset drill guide could reach the center of the ACL's femoral footprint. Eight formalin-injected cadaveric knees were dissected and the center of the ACL femoral footprints identified. The ADC was selected as an easily identifiable landmark during arthroscopy and was used to reference the position of the ACL femoral footprint with the knee flexed at 90°. Next, a 7-mm transtibial femoral ACL drill guide was used to engage the posterior aspect of the lateral condyle at the level of the femoral footprint. This position was marked, and the distance from the center of the femoral footprint was recorded for each specimen. Descriptive statistics were used to report our measurements. The median high and shallow measurements were 3 mm (range, 1 to 4 mm) and 12 mm (range, 11 to 17 mm), respectively. The femoral offset guide never reached the center of the femoral footprint in all specimens; the median distance between the 2 measurements was 4.5 mm (range, 2 to 9 mm). If the anatomy is difficult to delineate at the time of reconstruction, our study suggests using the ADC as a landmark to guide anatomic placement. The dissection of 8 cadavers showed that the center of the ACL femoral footprint had a median position of 3 mm high and 12 mm shallow to the ADC. We also showed that the transtibial femoral offset guide did not reach the center of the ACL footprint on all specimens and should therefore not be used for anatomic ACL reconstruction. Current commercially available transtibial femoral offset guides cannot reach the center of the ACL's femoral footprint and therefore should not be used. Alternative techniques, such as referencing from the ADC through an anteromedial (AM) portal, are recommended.