This flat appearance was also noted in several previous papers.

In 1980, Welsh [10] describes that femoral ACL attachment “inserts into a broad flat area on the back of the lateral femoral condyle.” It inserts “not as a distinct cord but is splayed over a broad flattened area.”

In 2013, Mochizuki et al. [4] published a paper in which he evaluates anatomical appearance of fanlike extension fibers at the femoral ACL attachment site in 28 cadaveric knees. He distinguished between direct and indirect insertion, based on histological appearance. Direct insertion (midsubstance fibers) has a transitional cartilaginous zone through which ACL fibers attach to the bone. That kind of insertion is typical for areas with great tension applied. The indirect insertion is created by fanlike extension fibers which are directly attached to the bone (Fig. 15.2a, b).

The attachment of midsubstance fibers of ACL is in exact continuity of the posterior femoral cortex [7, 9] (Fig. 15.3a–c). Knowing that relationship, the surgeon may double check the position of his femoral tunnel: arthroscopically and intraoperatively with X-ray C-arm. However, one may not talk about tunnel placement without a context of graft and fixation choice (Fig. 15.4a–c). For example, the use of BPTB graft or even a hamstring graft with interference screw fixation allows to “push” the graft to the side of the tunnel. Therefore, if the graft is supposed to arise from the place where midsubstance ACL fibers have their direct attachment, the center of tunnel drilled should be a little “higher” (more toward ventral side).