Femoral Bone Tunnel Placement (Arthroscopically and with Fluoroscopy)

Abstract

Anatomic placement of the femoral tunnel is critical to the success and clinical outcome of anterior cruciate ligament (ACL) reconstruction [1–11]. Anatomic single-bundle ACL reconstruction is defined as a single-bundle ACL reconstruction in which the femoral and tibial bone tunnels are positioned at the center of the native ACL femoral and tibial attachment sites [1, 3, 12, 13]. Nonanatomic ACL tunnel placement is the most common technical error leading to recurrent instability and a failed ACL reconstruction [2, 4–7, 9–11]. Proper placement of the ACL femoral tunnel is especially important because the length and tension of the ACL replacement graft is most influenced by the position of the ACL femoral tunnel [14–18]. Malposition of the ACL femoral tunnel can cause excessive tightening or loosening of the ACL graft, which may result in a loss of motion and or patholaxity of the knee [2, 4–11, 15–18]. Proper placement of the femoral tunnel during ACL reconstruction is therefore a critical part of the surgical procedure. A working knowledge of the anatomy of the ACL femoral attachment site is important to ensure anatomic placement of the ACL femoral tunnel. The anatomy of the ACL has been discussed in greater detail elsewhere in this book. To summarize, the ACL femoral attachment site is oval in appearance and is located along the lower third of the inner wall of the lateral femoral condyle [13, 14, 19–26]. The ACL femoral attachment site is defined by two bony ridges, the lateral intercondylar and the lateral bifurcate ridges [13, 20, 22–24, 26, 27] (Fig. 19.1). The lateral intercondylar ridge is an important anatomic landmark since the native ACL always attaches inferior (arthroscopic description) or posterior (anatomic description) to the lateral intercondylar ridge [3, 20, 22–24, 26–28] (Fig. 19.1). The lateral intercondylar ridge can be identified arthroscopically in 88 % of subacute and chronic ACL-deficient knees and therefore is a consistent anatomic landmark to assist the knee surgeon with placement of the ACL femoral tunnel [29]. The lateral bifurcate ridge which can be identified arthroscopically in 48 % of subacute and chronic knees runs perpendicular to the lateral intercondylar ridge and divides the ACL femoral attachment site into the attachment site areas for the posterolateral (PL) and anteromedial (AM) bundles [3, 12, 13, 20, 22, 24, 26] (Fig. 19.1). The center of the ACL femoral attachment site is 1.7 mm deep or proximal to the bifurcate ridge and 7.3–8.5 mm superior or anterior to the inferior or posterior articular cartilage margin of the lateral femoral condyle [8, 21, 23, 28]. For anatomic single-bundle ACL reconstruction, the center of the ACL femoral attachment site is chosen as the position for the ACL femoral tunnel [1, 3, 5, 12, 13, 30–32]. Biomechanical and clinical studies have demonstrated that ACL reconstruction using a replacement graft placed at the center of the ACL femoral and tibial attachment sites is more effective at controlling anterior tibial translation and the combined motions of anterior tibial translation and internal tibial rotation (simulated pivot shift test) and restores knee kinematics more closely to that of the normal knee compared to “isometric” ACL femoral tunnel placement, other anatomic ACL tunnel placements, or techniques that have traditionally restored predominantly the AM bundle fibers [1, 6, 30–38].