**8. Development of anatomic double-bundle ACL reconstruction**

Anatomic ACL reconstruction is defined as the functional restoration of the ACL to its native dimensions, collagen orientation, and insertion sites (Van Eck et al., 2010). The concept and development of double-bundle ACL reconstruction comes from the rediscovery of the ACL bundles anatomy and biomechanics of ACL reconstruction. Several studies have shown that rotational control of the tibia as well as anterior tibial translation were much improved when the PLB was reconstructed in addition to the AMB (Colombet et al., 2007; Kanaya et al., 2009; Markolf et al., 2009; Sbihi et al., 2004; Yagi et al., 2002; Zaffagnini et al., 2008; Zantop et al., 2007).

Already in his original transtibial technique, T Rosenberg was mentioning the possibility to reconstruct 2 bundles, if the femoral footprint size was big enough, by drilling 2 sockets in the femur and one tunnel in the tibia. This idea was further developed in Japan (Hara et al., 2000; Hamada et al., 2001; Mae et al., 2001;Munetta et al., 1999), then in France (Franceschi et al, 2002; Bellier et al., 2004 ) and finally in the USA. While few authors persisted in the use of transtibial technique (Yasuda et al., 2004), it appeared rapidly to most surgeons that double bundle ACL reconstruction which necessitates drilling 2 femoral sockets and 2 tibial tunnels could be only performed either with transportal technique or two-incision technique.

**8.1** Following is a brief summary of the principles of anatomic double-bundle ACL reconstruction technique. We will describe transportal technique with four tunnels, which is the most widely used. Few surgeons are using alternative techniques like two-incision- (Aglietti et al., 2005) or modified transtibial technique (Yasuda et al., 2004). Most of the authors use autogenous hamstring tendons. Usually the AMB is reconstructed with a double-stranded semitendinosus tendon, while the gracilis is used for the PLB. According to their size or length, tendons can be doubled, tripled or even quadruple-stranded. Allografts are used mostly in the USA. In Western patients, with autogenous hamstrings, the average AMB diameter is 7mm (6-9mm) and PLB 6mm (5-7mm). Most of the authors use Endobutton® CL for the femoral fixation. Others are using interference screws. On the tibial side, various fixation methods have be described: interference screws, plate and screw, screw post and washer. As femoral tunnels are drilled independently one may start either by drilling tibial- or femoral tunnels.

#### **8.1.1 Femoral tunnels**

The femoral footprint is visualized through an AM portal and carefully identified according to the landmarks previously described (Cha et al., 2005). Identifying the intercondylar ridge is a key issue and fluoroscopy may help. Through an accessory AM portal two sockets are drilled through the center of each bundle attachment with the knee bent at least at 110° of flexion (Basdekis et al., 2008; Basdekis et al., 2009; Hoshino et al., 2009). Specific instruments allow proper positioning of the tunnels, keeping a 2-3 mm bone bridge (Fig. 11) between them in order to insure independent fixation of each bundle (Bellier et al., 2004; Christel et

Contemporary Anterior Cruciate Ligament Reconstruction 211

As for single-bundle ACL, several authors have shown tunnel position is highly critical for proper tension and bundles efficacy (Forsythe et al., 2010; Giron et al., 2007, Nishimoto et al., 2009; Silva et al., 2010). Unfortunately most of the publications related to double-bundle ACL reconstruction outcome do not document the position of the tunnels. In order to document tunnel position after surgery, 3-dimensional CT scan is the method of choice (Basdekis et al., 2009a; Forsythe B et al., 2010; Saharsrabudhe et al., 2010). Accordingly, if many publications relate to double-bundle ACL reconstruction, it is hard to distinguish between those which perform anatomical reconstruction, i.e. with tunnels drilled within the ACL footprints, and those with non-anatomical reconstructions where tunnels are drilled

Fig. 12. Three-dimensional CT scan views of the tunnels after double-bundle AC reconstruction. A: femoral sockets, B: intra-articular aperture of the tibial tunnels.

A B

A B

Fig. 13. Intra-articular view of a double bundle ACL graft. The AMB is reconstructed with a double-stranded semitendinosus while the PLB is reconstructed with a double stranded gracilis. A: grafts viewed through the AL portal, B: grafts viewed through an AM portal

outside the ACL footprints.

al., 2005; Christel et al., 2008 a-c). Three-dimensional CT studies (Fig 12 A) have validated the accuracy of the instruments (Basdekis et al., 2009a). The resulting cortical bone bridge separating the tunnel apertures remains stable with time (Hantes et al., 2010). When the knee is at 90° of flexion, PLB tunnel is located in front and lower compared to AMB tunnel. The axis going through the center of both tunnels should make a 30° angle with the long axis of the femur.

Fig. 11. Double bundle ACL reconstruction, left knee, drilling of the femoral sockets. The lateral wall of the intercondylar notch is viewed from medial. A: the centers of both bundles are marked. A guide wire is inserted through the center of the AMB, knee bent at 110 degree. B: the AM socket is drilled at a diameter equal to the bundle graft. C: both sockets are drilled, knee views from medial at 90 degree of flexion. D: there is a 2mm bone bridge between the 2 sockets.

**8.1.2** On the tibial side, the AMB tunnel starts along the medial side of the tibial tubercle and opens in the center of the AMB footprint. The PLB tunnel starts more medially, in front of the anterior edge of the medial collateral ligament. Specific instrumentation allows drilling the PLB tunnel through the center of the PLB footprint, 8-9mm behind and slightly lateral to the AMB aperture, saving a 2-3mm bone bridge between the two tunnels (Christel et al., 2005; Christel et al., 2008 a-c). Three-dimensional CT studies (Fig.12B) have validated the accuracy of the instruments (Saharsrabudhe et al., 2010). The diameters of the tunnels correspond to the graft diameters.

al., 2005; Christel et al., 2008 a-c). Three-dimensional CT studies (Fig 12 A) have validated the accuracy of the instruments (Basdekis et al., 2009a). The resulting cortical bone bridge separating the tunnel apertures remains stable with time (Hantes et al., 2010). When the knee is at 90° of flexion, PLB tunnel is located in front and lower compared to AMB tunnel. The axis going through the center of both tunnels should make a 30° angle with the long

A B

 C D

Fig. 11. Double bundle ACL reconstruction, left knee, drilling of the femoral sockets. The lateral wall of the intercondylar notch is viewed from medial. A: the centers of both bundles are marked. A guide wire is inserted through the center of the AMB, knee bent at 110 degree. B: the AM socket is drilled at a diameter equal to the bundle graft. C: both sockets are drilled, knee views from medial at 90 degree of flexion. D: there is a 2mm bone bridge

**8.1.2** On the tibial side, the AMB tunnel starts along the medial side of the tibial tubercle and opens in the center of the AMB footprint. The PLB tunnel starts more medially, in front of the anterior edge of the medial collateral ligament. Specific instrumentation allows drilling the PLB tunnel through the center of the PLB footprint, 8-9mm behind and slightly lateral to the AMB aperture, saving a 2-3mm bone bridge between the two tunnels (Christel et al., 2005; Christel et al., 2008 a-c). Three-dimensional CT studies (Fig.12B) have validated the accuracy of the instruments (Saharsrabudhe et al., 2010). The diameters of the tunnels

axis of the femur.

between the 2 sockets.

correspond to the graft diameters.

Fig. 12. Three-dimensional CT scan views of the tunnels after double-bundle AC reconstruction. A: femoral sockets, B: intra-articular aperture of the tibial tunnels.

As for single-bundle ACL, several authors have shown tunnel position is highly critical for proper tension and bundles efficacy (Forsythe et al., 2010; Giron et al., 2007, Nishimoto et al., 2009; Silva et al., 2010). Unfortunately most of the publications related to double-bundle ACL reconstruction outcome do not document the position of the tunnels. In order to document tunnel position after surgery, 3-dimensional CT scan is the method of choice (Basdekis et al., 2009a; Forsythe B et al., 2010; Saharsrabudhe et al., 2010). Accordingly, if many publications relate to double-bundle ACL reconstruction, it is hard to distinguish between those which perform anatomical reconstruction, i.e. with tunnels drilled within the ACL footprints, and those with non-anatomical reconstructions where tunnels are drilled outside the ACL footprints.

Fig. 13. Intra-articular view of a double bundle ACL graft. The AMB is reconstructed with a double-stranded semitendinosus while the PLB is reconstructed with a double stranded gracilis. A: grafts viewed through the AL portal, B: grafts viewed through an AM portal

A B

Contemporary Anterior Cruciate Ligament Reconstruction 213

Two outcome measures were reported (in a manner permitting meta-analysis) in at least 3 of 4 trials: KT-1000 arthrometer and pivot-shift testing. On average, KT-1000 arthrometer sideto-side difference was 0.52 mm closer to normal in patients treated with double-bundle reconstruction. This difference is demonstrated to be clinically insignificant. The odds of a normal or nearly normal pivot shift is higher in the patients treated with double-bundle ACL reconstruction than in those treated with single bundle. However, this finding is not statistically significant because the 95% confidence intervals include 0. The authors concluded double-bundle reconstruction does not result in clinically significant differences in KT-1000 arthrometer or pivot shift testing. One may argue the authors grouped together normal and nearly normal knees, while the goal of ACL surgery is to restore a normal knee. When considering the figures of this study and separating normal- from nearly normal knees it appears that following single-bundle (293 patients) 63.5 % of them had no pivot shift while following double bundle (318 patients), 87.7% had no pivot shift (p<0.001). In fact all the single-bundle versus double-bundle studies have compared anatomic with nonanatomic reconstructions. Single bundle technique was based on a transtibial approach (with a femoral tunnel almost entirely located outside the ACL footprint) while, double-

If one wish to maintain a sufficient graft size (7mm for AMB and 6mm for PLB), small ACL footprints (less than 14mm long) do not allow drilling independent tunnels with a sufficient bone bridge in between. In this case single bundle reconstruction must be used. Also narrow intercondylar notch is a severe limitation as it does not leave enough space for the graft. The concept of anatomic double bundle ACL reconstruction was further applied to partial tears of the ACL when one bundle only has been ruptured. In these particular cases it has been proposed to reconstruct only the damaged bundle, performing an ACL augmentation

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

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

bundle tunnels were located within the ACL footprints.

**9. Anatomic double bundle reconstruction limitations** 

(Borbon CA et al., 2011; Serrano-Fernandez JM et al., 2010).

al., 2004).

**10.1 Technical principles** 

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


#### **8.2 Outcome of anatomic double-bundle ACL reconstruction 8.2.1 Review study**

Table 2. Summary of the main studies comparing the outcome of single-bundle (SB) with anatomic double-bundle (A2B) ACL reconstruction. N is the number of patients in the study groups. Mean KT 1000 arthrometer results are given for a 134N load. Positive pivot shift test corresponds to pivot shift glide or more. All studies have at least a 2-year minimum follow up.

The above table summarizes 15 comparative studies, 6 level 1, 7 level 2, 2 level 3, all with follow up > 2 years and effective follow up, single-bundle 96.2 %, anatomic double-bundle 93.4 %. There is total number of 455 single-bundle patients and, 520 anatomic doublebundle. There is no statistical difference regarding the KT 1000 outcome. However, there is clearly less residual pivot shift after anatomic double-bundle reconstruction (12% vs 33%).

#### **8.2.2 Meta-analysis**

Meredick et al. (Meredick et al., 2008) have conducted a meta-analysis where they systematically identified randomized controlled trials (RCTs) comparing single-bundle versus doublebundle ACL reconstruction.

Yasuda et al, 2006 2 SB 24 2.8 50

Jarvela, 2007 1 SB 52 1.8 36

Muneta et al, 2007 1 SB 34 2.4 41.2

Asagumo et al, 2007 3 SB 52 1.9 19.2

Kondo et al, 2008 2 SB 157 2.5 49

Siebold et al, 2008 1 SB 35 1.6 31.4

Streich et al, 2008 1 SB 25 0.94 25

Kim et al, 2009 3 SB 28 2.6 11

Aglietti et al, 2010 1 SB 35 2.1 26

Table 2. Summary of the main studies comparing the outcome of single-bundle (SB) with anatomic double-bundle (A2B) ACL reconstruction. N is the number of patients in the study groups. Mean KT 1000 arthrometer results are given for a 134N load. Positive pivot shift test corresponds to pivot shift glide or more. All studies have at least a 2-year minimum follow

The above table summarizes 15 comparative studies, 6 level 1, 7 level 2, 2 level 3, all with follow up > 2 years and effective follow up, single-bundle 96.2 %, anatomic double-bundle 93.4 %. There is total number of 455 single-bundle patients and, 520 anatomic doublebundle. There is no statistical difference regarding the KT 1000 outcome. However, there is clearly less residual pivot shift after anatomic double-bundle reconstruction (12% vs 33%).

Meredick et al. (Meredick et al., 2008) have conducted a meta-analysis where they systematically identified randomized controlled trials (RCTs) comparing single-bundle

evidence Technique N KT 134 N(mm) Pivot shift

SB AM 20 1.9 35 SB PL 20 1.7 20 A2B 20 1.9 15

SB 25 2.4 42 2B transtibial 25 1.6 24 2B 2-incision 25 1.4 16

A 2B 24 1.1 12.5

A2B 25 1.4 3.3

A2B 105 1.4 14.7

A2B 71 1.7 12.7

A2B 171 1.2 19

A2B 35 1.0 0.04

A2B 24 1.1 24

A2B 31 1.8 0

A2B 35 1.2 14

%> glide

**8.2 Outcome of anatomic double-bundle ACL reconstruction** 

Level of

**8.2.1 Review study** 

up.

**8.2.2 Meta-analysis** 

versus doublebundle ACL reconstruction.

Authors Year of publication

Yagi et al, 2007 2

Aglietti et al, 2007 2

Two outcome measures were reported (in a manner permitting meta-analysis) in at least 3 of 4 trials: KT-1000 arthrometer and pivot-shift testing. On average, KT-1000 arthrometer sideto-side difference was 0.52 mm closer to normal in patients treated with double-bundle reconstruction. This difference is demonstrated to be clinically insignificant. The odds of a normal or nearly normal pivot shift is higher in the patients treated with double-bundle ACL reconstruction than in those treated with single bundle. However, this finding is not statistically significant because the 95% confidence intervals include 0. The authors concluded double-bundle reconstruction does not result in clinically significant differences in KT-1000 arthrometer or pivot shift testing. One may argue the authors grouped together normal and nearly normal knees, while the goal of ACL surgery is to restore a normal knee. When considering the figures of this study and separating normal- from nearly normal knees it appears that following single-bundle (293 patients) 63.5 % of them had no pivot shift while following double bundle (318 patients), 87.7% had no pivot shift (p<0.001). In fact all the single-bundle versus double-bundle studies have compared anatomic with nonanatomic reconstructions. Single bundle technique was based on a transtibial approach (with a femoral tunnel almost entirely located outside the ACL footprint) while, doublebundle tunnels were located within the ACL footprints.
