**4.2 Tunnel enlargement**

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

Contemporary Anterior Cruciate Ligament Reconstruction 203

A B

at the desired depth. During drilling, the tibial tunnel is widened by the drill.

must be done in order to avoid extension deficit.

Fig. 6. Transtibial technique, femoral steps. A: An endofemoral guide wire is introduced through the tibial tunnel. The knee remains bent at 90 degree. The hook located at the proximal tip has variable offset with regard to the shaft of the aimer (X mm). An eyelet needle is drilled through the lateral femoral condyle. This drawing perfectly illustrates the fact one can't reach the center of the ACL femoral footprint with the transtibial technique. B: An endoscopic cannulated drill is passed on the on the guide wire drilling a femoral socket

(Fig. 6). A long guide wire with an eyelet is inserted with the help of the femoral guide, through the lateral femoral condyle, breaching the lateral cortex until it passes through the skin of the lateral side of the thigh. The femoral guide is removed keeping the guide wire in the condyle. Then, maintaining the knee at 90° of flexion, a cannulated endoscopic drill, which head is the cutting part and the shaft smaller, is threaded on the guide wire through the tibial tunnel, the intercondylar notch, the lateral femoral condyle at a depth which depends on graft type and fixation type. The diameter of the endoscopic drill is chosen according to the graft diameter. The eyelet of the guide wire is used to pull a loop suture through the tibial tunnel, the intercondylar notch and the tibial tunnel exiting on the lateral side of the thigh. The loop stitch is use do pull the graft until it settles in the femoral tunnel and fixed appropriately either with an interference screw, an Endobutton or with cross pins. Then the graft is put under Manual tension; the knee is cycled from full extension to full flexion at least 20 times. The length variation of the graft at the exit of the tibial tunnel is measured and the graft fixed in the tibia either with an interference screw or using extra cortical fixation: button or screw post and washer. The knee flexion at fixation depends on the graft length variation: the larger is the length variation, closer to extension the fixation

As the reader will notice the "clock-face" reference do determine the tunnel position is not used in this chapter. Although this reference has been widely accepted in the literature to describe femoral tunnel positioning it has generated more confusion than clarification (Fu, 2008; Van Eck et al., 2010). The "clock-face" system is based on radiographs of the knee in extension while ACL reconstruction is performed at 90 degree of flexion or more. Therefore
