**2.2 Tibial footprint**

198 Modern Arthroscopy

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

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

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

lateral intercondylar- and the bifurcate ridges.

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.

bundle (PL)

**2.1 ACL femoral foot print** 

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 Bernard.

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

Contemporary Anterior Cruciate Ligament Reconstruction 201

Most studies which have reported results of ACL reconstruction show no significant difference in residual anterior laxity, functional results and International Knee Documentation Committee (IKDC) scores regardless the autograft which is used (Aune et al., 2001; Beynnon et al., 2002; Freedman et al., 2003; Maletis et al., 2007; Yunes et al., 2001)

Allografts avoid harvesting tendons with their drawbacks, i.e anterior knee pain or numbness. In countries where legal issues are important, especially the United States (USA),

**3.2.1** Currently, three kinds of allografts are available: chemically treated, irradiated and/or fresh frozen. Due to their poor mechanical properties, chemically treated or irradiated allografts are gradually abandoned (Krych et al., 2008). Currently, fresh frozen allografts are the most widely used. Tissue banks insure the proper donor selection as well as bacterial and viral screening. With the current infection control protocols, the incidence of viral or bacterial contamination is null. Graft quality is an issue and donor age must be known. Thus

**3.2.2** Fresh frozen tibialis anterior or posterior tendons, Achilles' tendon with bone plug and BPTB are the most widely used. The outcome is similar to autografts (Foster et al., 2010) however, allografts have significantly lower normal stability rates than autografts (Bach et

Most of the US authors do not recommend the use of allografts in young and high demanding athletes. Also the use of allografts add a significant cost to the procedure (c.a. \$ 3,000 in the USA). Thus, for the authors, the use of allografts which lead to inferior results

**4.1** Composite grafts with bone plugs are commonly fixed in the tunnels either with absorbable or metal interference screws.. This method provides the highest strength and rigidity. However there is concern that a too rigid construct may alter the full range of knee motion and some surgeons prefer suspensory fixation with sutures tied on post or buttons or buttons with build in tissue loops. Soft tissue grafts fixation relies on numerous different methods: interference screws, suspensory devices, cross pins. On the femoral side suspensory devices with build in tissue loop, like the Endobutton® Continuous Loop provides the strongest and stiffest fixation. With hamstring grafts, graft slippage at the tibial

Following ACL reconstruction, tunnel enlargement occurs regardless the graft choice and the fixation system (L'Insalata et al., 1997). This is an early phenomenon which occurs during the first-three post operative months. Biomechanical (bungee cord and wiper windshield effects) as well as biological factors (local cytokine release) may account for this enlargement (Wilson et al., 2004). Until now, one important factor might have been underestimated: the graft positioning. With anatomic placement of the ACL grafts tunnel

fixation site may occur explaining the slight increase in laxity compared to BTB.

allografts became the graft of choice for ACL reconstruction.

compared to autografts at an increased cost remains questionable

the choice of the tissue bank is critical.

al.,2005; Prodromos et al., 2007).

**4. Graft fixation issues** 

**4.2 Tunnel enlargement** 

enlargement is less (Chhabra et al., 2006).

**3.2 Allografts** 

On lateral X rays it is possible to locate the various centers of the tibial ACL foot print. Using the Stäubli and Rauschning technique (Fig. 4), the footprint center is located at 43 % of the antero-posterior diameter of the tibia (Stäubli & Rauschning, 1994) while the center of the AMB is located at 36% and the center of the PLB at 52% (Colombet et al., 2006).
