**10. The anatomic single bundle ACL reconstruction**

Taking into account technical difficulties for drilling 4 independent tunnels with consistent bone bridges and the renewed knowledge of ACL anatomy, anatomic single bundle ACL reconstruction was a logic development. The basis for this technique is to drill the femoral tunnel in the center of the femoral foot print, between the centers of both bundles, behind the intercondylar ridge, in such way that it includes part of both AMB and PLB fibers (Ho et al., 2009; Rue et al., 2008; Shino et al., 2008, Steiner, 2009; van Eck et al., 2011; Yamamoto et al., 2004).

## **10.1 Technical principles**

In order to perform an optimal anatomic single-bundle ACL reconstruction the transportal technique must be used. As stated before, with the lens from the medial side it is easy to identify the femoral ACL stump, the intercondylar ridge and the centers of the AMB and PLB. The center of the anatomic femoral tunnel is located in at mid distance from the bundle centers. It can be drilled right in the middle of the footprint and will contain 50% of AMB fibers and 50% of PLB fibers. I can also be drilled more proximally to contain more AMB fibers or more distally, containing more PLB fibers. However a single tunnel in the middle of the foot print will contain less fiber than 2 tunnels drilled in the center of each bundle

Contemporary Anterior Cruciate Ligament Reconstruction 215

Currently, only few published papers deal with comparison of the outcome of anatomic single- with anatomic double-bundle (Gobbi et al., 2011; Park et al., 2010; Song et al., 2009). On the clinical stand point these studies show no statistical differences between the objective and subjective outcomes of the two techniques. Thus it seems that reconstructing the ACL with anatomic single-bundle technique is a valid option with improved results compared to single-bundle transtibial. Further publications and longer follow-up should confirm these

There is still much to learn about ACL reconstruction. The old transtibial technique which does not reconstruct the ACL where it is attached has progressively evolved toward anatomical ACL reconstruction. Currently anatomic single- and double-bundle ACL reconstruction are well established and well described. However, if the outcome of these techniques has considerably improved with regard to the transtibial technique, the results are still far to be perfect. There are still small percentages of fair results for which improvements have to be made. Only long term results will tell if the restoration of ACL anatomy is going to decrease knee joint degeneration which remains the major issue of long

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**10.2 Outcome of anatomic single-bundle ACL** 

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**11. Conclusion** 

**12. References** 

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attachment. On the tibial side the tunnel is drilled in the center of the ACL foot print, slightly medial. As the femoral tunnel is much lower than with the transtibial technique, the resulting graft has a more oblique orientation and is able to resist anterior tibial translation and tibial internal rotation (Fig. 14).

Fig. 13. Femoral socket for single bundle anatomic reconstruction. A: the lateral wall of the intercondylar notch has been gently cleaned with a curette to locate the lateral intercondylar ridge (arrows). B: position of a 9mm socket, right behind the intercondylar ridge. C: the socket aperture is positioned in such a way that it overlaps 50% of the PLB- and 50% of the AMB attachment sites. A,B, and C views are taken from the medial side. D: view of the socket from the AL portal.

Fig. 14. Comparison of the obliquity of an anatomic single bundle ACL (A) with a native ACL (B). Note the similarity in orientation of both reconstructed and native ACL.

## **10.2 Outcome of anatomic single-bundle ACL**

Currently, only few published papers deal with comparison of the outcome of anatomic single- with anatomic double-bundle (Gobbi et al., 2011; Park et al., 2010; Song et al., 2009). On the clinical stand point these studies show no statistical differences between the objective and subjective outcomes of the two techniques. Thus it seems that reconstructing the ACL with anatomic single-bundle technique is a valid option with improved results compared to single-bundle transtibial. Further publications and longer follow-up should confirm these preliminary results.
