**1. Introduction**

196 Modern Arthroscopy

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The modern era of anterior cruciate ligament (ACL) reconstruction started in the early 1990's with the development of arthroscopic knee reconstruction procedures. Early on, graft fixation issues and, graft choice have been extensively debated. Then, the transtibial technique appeared (Rosenberg & Deffner, 1997; Chen et al., 2003). This was an easy and quick way to reconstruct the ACL which became soon adopted by most surgeons. However, the outcome was not always as good as expected (Freedman et al.,2003, Lewis et al., 2008) and with the re-discovery of the ACL anatomy and biomechanics, deep changes have been introduced in the way to reconstruct the ACL. This chapter reviews the main features related to ACL reconstruction and focus on the current state of the art in this field

#### **2. ACL anatomy**

The reader will find all the necessary details in the numerous articles which have been recently published in this field (Colombet et al.,2006; Edwards et al., 2006; Giron et al. 2006; Harner et al.,1999; Mochizuki et al., 2007; Petersen & Zantop, 2007; Purnell et al.,2008; Takahashi et al., 2006; Zantop et al., 2006,). We will summarize the main relevant points for surgical reconstruction of the ACL.

The ACL consists of at least two functional bundles, anteromedial (AMB) and posterolateral (PLB). The AMB is about twice long and big as compared to the PLB. The AM bundle is more sagitally oriented, limiting the anterior tibial translation while the more oblique PLB (Fig 1), limits the internal rotation of the tibia (Zantop et al.,2007).

Both bundles are parallel in full knee extension and, due to the location of their attachments, they cross each other when the knee bends. During knee flexion, the PLB shortens by more than 30%, while the AMB elongates by 15%. The PLB is tight when the knee is close to extension whereas the AMB is tensed when the knee bends. The range of length variation for the AMB varies between 1-3mm while the PLB exhibits a much widerrange, 4-7mm. In order to reproduce the ACL anatomy several studies have assessed and quantify the footprints.

Fig. 3.

Bernard.

**2.2 Tibial footprint** 

Contemporary Anterior Cruciate Ligament Reconstruction 199

ridge. The center of the femoral bundles can be also located using the quadrants method described by Bernard et al (Bernard et al, 1997). The position of the centers is illustrated on

It is larger than on the femoral side with a 17.6mm ± 2.1mm length and 12.7mm ± 2.8mm witdth. The distance between the bundle centers is 8.4 mm ± 0.4mm (Colombet et al., 2006). The most anterior point of the tibial footprint is located right behind the posterior edge of the anterior inter-meniscal ligament. The most posterior fibers of the footprint are located at 10.3mm ± 1.9mm in front of the retro eminence ridge which corresponds to the ridge limiting the anterior attachment of the posterior cruciate ligament on the tibia. The center of the ACL tibial footprint is thus located 20-22mm in front of the PCL attachment. The distribution and the surface area of the bundle attachments is variable (Colombet et al., 2006; Edwards et al.,

2007) and there is no visible ridge separating the bundles as on the femoral side.

Fig. 3. Location of the femoral bundle centers according to the quadrant's method of

Fig. 4. Position of the tibial bundle centers projected on the Staubli & Rauschning line. The

center of the ACL is located at 43% of the AP diameter

Fig. 1. ACL bundles. Solid line: anteromedial bundle (AM), dotted line; posterolateral bundle (PL)

#### **2.1 ACL femoral foot print**

In Western subjects, the length of the foot print is 18.3mm ± 2.3mm, the width 10.3mm ± 2.7mm (Colombet et al., 2006). The distance between the bundle centers is 8.2mm ± 1.2mm. In anatomic position, the most anterior fibers of the foot print are located behind the lateral intercondylar ridge (Fu & Jordan, 2007). There are no ACL fibers located in front of the lateral intercondylar ridge (Fig. 2). The most posterior fibers are located at 2-3mm from the lateral femoral condyle articular cartilage limit, following its curvature. The bifurcate ridge, perpendicular to the lateral intercondylar ridge separates the AMB from the PLB attachment.

Fig. 2. Three-dimensional CT view of the intercondylar notch in "endoscopic" position (femoral shaft horizontal). The ACL bundle attachment sites are shown in relation with the lateral intercondylar- and the bifurcate ridges.

On a lateral X-ray it is possible to locate the lateral intercondylar ridge (Farrow et al, 2008). When the femur is in the endoscopic position, i.e. horizontal, the ridge originates at the posterior part of the Blumensaat's line (80% from anterior) and the mean Blumensaat's-ridge angle is 75.5°. In this position, the whole ACL femoral footprint becomes posterior to the ridge. The center of the femoral bundles can be also located using the quadrants method described by Bernard et al (Bernard et al, 1997). The position of the centers is illustrated on Fig. 3.
