# Feasibility of Osseous Landmarks for ACL Reconstruction--A Macroscopic Anatomical Study
###### Abstract  
During knee arthroscopy, easy orientation is important, and possible landmarks include the lateral intercondylar ridge (LIR) and the lateral bifurcate ridge (LBR). The objective was to show the feasibility of the LIR and the LBR as landmarks of the femoral attachment of the anterior cruciate ligament (ACL) among subjects with different levels of training. Thirty-six formalin-phenol-fixed lower extremities were acquired for this prospective macroscopic anatomical study. All soft tissue apart from the ligaments was removed. The two bundles of the ACL and their origins were identified, marked and photographed. Photographs were taken in an arthroscopic setting. An orthopedic surgeon, an anatomist and a medical student identified the ridges. The LIR existed in 80.6% of samples, while the LBR existed in 13.8% of samples. A significant difference existed between the raters in correctly identifying the LIR (\(p<0.01\)). Due to its high frequency, the LIR seems more reliable than the LBR, especially as the LBR has the potential for false positive identification. Nevertheless, as these ridges are not easily discernible, the surgeon has to know the anatomy of the intercondylar notch perfectly to stand even a small chance of correctly placing drill holes in ACL reconstruction. New guidelines for more easily recognizing LIR and LBR arthroscopically are proposed.  
americ  
the ACL through individual placement of the graft at the respective osseous insertion. In this, the LBR thus represents an important landmark [21]. This procedure aims for a more stable and anatomically correct reconstruction, but is combined with a rather more complicated surgical procedure [21]. Even more complicated are revisions of double-bundle ACL reconstructions, as an additional set of tunnels have to be added to the already existing two femoral and tibial tunnels [22; 23].  
As the two bundles of the ACL cannot be discerned macroscopically with certainty without functional tests, we are especially in need of a reliable landmark for the correct positioning of the femoral tunnels. The LIR was overall found in 85 to 100% [5; 8; 13; 16; 17; 24; 25], and therefore was deemed as a reliable osseous landmark for arthroscopic ACL reconstruction. In contrast, reports of the frequency of the LBR vary substantially, ranging from 15 to 90% [5; 13; 16; 24; 26]. This would suggest that the LBR is highly variable, probably depending both on the study population and the investigators, and therefore is not a secure point of orientation during surgery.  
In reviewing the available existing literature, the abovementioned large range of incidence of the two osseous ridges was noted. Of course, there are several possible explanations for this, such as anatomical variability, study design or the kind of specimens and mode of dissection in anatomical studies. However, the question also arose as to whether the experience of the investigator could influence the correct identification of the LIR and the LBR.  
Therefore, the hypothesis for this study was that the correct identification of the two relevant ridges at the femoral insertion of the ACL correlates with the experience of the investigator and is therefore a tool for orientation during knee arthroscopy for experienced knee surgeons, and not for beginners.