Femoral Tunnels in Anatomical ACL Reconstruction: Techniques Inside Out X Outside In

Objective: To 
observe the accuracy and the advantages and disadvantages of the femoral 
tunnels made by the two techniques. Materials and Methods: We randomly summoned 
nineteen patients undergoing anatomic ACL reconstruction in a single band 
technique by the same surgeon: Ten by group II (GII) and nine by Group I (GI). GI: drilling in the technical in-out. 
GII: drilling the technique out-in. The patients underwent a CT scan with three-dimensional 
reconstruction of the distal femur. Was applied the technique of quadrants 
described by Bernard and Hertel and optimized for position by Forsythe and 
observed in the femoral tunnel: the accuracy of the joint entry; posterior 
cortical thickness in that point; emergency lateral distance to the lateral 
epicondyle and the overall length. Results: The coordinates of the distances 
obtained average was very close, with no statistical difference comparable to 
that obtained by Bernard and Hertel and Forsythe. The distance from the tunnel 
exit to the lateral epicondyle obtained average 1.46 cm in GI and 0.47 cm in 
GII, with a significant statistical difference. The thickness of the posterior 
cortex was 3.9 mm in GI and 5.4 mm in GII, with no statistical difference. The 
length averaged was 3.07 cm in GI and GII in 2.94 cm, with no statistical 
difference. Conclusions: Both techniques allow well placed tunnels, with no 
statistical difference. In the technique in-out the tunnel exit is closer to 
the lateral epicondyle. The thickness of the posterior cortex is similar. The 
length of the femoral tunnel is similar and around 3 cm.


Introduction
The demand for greater stability and precision in the anterior cruciate ligament (ACL) reconstruction has increasingly used the technique called anatômica [1]- [6]. This technique returns after decades of dominance isometric transtibial technique, which usually results in a higher tunnel entrance and with a more vertical position of the graft in the sagittal and coronal aspects, reducing rotacional [7] [8] stability. On the anatomical technique, the femoral tunnel can be made in two main ways: through the anteromedial portal or in the outside-in way (two incisions).
Freddie Fu popularized the anatomic ACL reconstruction with preparation of the femoral tunnel with the drill from the arthroscopic anteromedial portal [9] [10]. Chambat popularized the technique of the femoral drill on from the outside in way, with an additional lateral incision [11].
Bernard and Hertel [12] developed the quadrant method to analyze the profile of the RX tunnel entrance precision in the lateral femoral condyle. Later, Forsythe [13] in cadaver study adapted this method to the study with computed tomography with a three-dimensional reconstruction, as in Figure 1. Albuquerque [14] also in an experimental study in cadaver, makes measurements of the thickness of the posterior cortex in the tunnel entrance and the distance from the emergence of the guide wire to the lateral epicondyle, analyzing the safety of tunnels on the possibility of breaking its back wall and injury of the lateral ligaments.

Objective
To observe the accuracy and the possible advantages and disadvantages of femoral

Materials and Methods
Were randomly summoned nineteen patients undergoing anatomic ACL reconstruction in a single band technique by the same surgeon made for at least 2 years, ten by the technique of the group l and nine by the group ll. After completing the consent form, patients underwent computed tomography with three-dimensional reconstruction of the distal femur.  The statistical t test was applied, considering statistically significant P less than or equal to 0.05.

Results
The results are shown in Table 1.

Discussion
The distance was very close to average in the 2 groups, respectively 25.3% and 24.5%, with no significant difference. However, there was a higher standard deviation in group II showing greater uniformity in l group. This may be due to the fact that the group l the tunnel was made starting at inside and in outside in group 2 and the emergence usually is less accurate. Also, the progressive extension of the tunnel was done in this case guided by direct visualization, with a guide wire in an even larger tunnel, which increases the possibility of variability. The same was found in the distance b, with averages of 32.6% and 29.6% and higher standard deviation in group II, with no statistical difference by applying the same observations above.
Group 1 approached more with the results obtained for Forsythe [13], which was originally made for the two bands ACL but in the case of single band, the reconstruction is considered rebuilding the anteromedial ACL bundle. Forsythe results to the distance a was an average of 21.7%, ranging from 18.9% to 25.7% in experimental environment and going straight in the insertion of still intact out of your range we had one case in group 1 and 2 patients in group II.
Compared with the studies of Bernard and Hertel [12], the distance is still very similar because they found an average of 24.8%. The distance b is a little less similar, they obtained 28.5%.
In the distance from the tunnel exit to the lateral epicondyle, we obtained av- In the group II, the greater thickness of the posterior cortex and the screw placed inwardly theoretically tolerate higher interference screws of diameters with less danger of breaking up the walls. In fact in our cases in Group I, was used absorbable interference screw thick on average 2 mm below the tunnel diameter and ll group of 1 mm above the tunnel diameter. The use of larger diameter screws beyond the tunnel entrance angle to the ACL reconstructed be higher in group II should lead to a lower chance of graft loosening after surgery.
The size of the femoral tunnel averaged 3.07 cm in group 1 and 2.94 cm in group II, nearly equal, with no statistical difference, but with higher standard deviation in group II. Greater than 25 mm interference screws protrude may be internal or external, may primarily in the II group, cause friction on the external structures such as the lateral collateral ligament, for example. The type fastening systems with tie buttons which require some free tunnel space for the system, grafting may not leave enough for successful integration because of lack of long tunnel, and in group II, can cause the same type of the lateral ligaments friction, as mentioned above.

Conclusions
1) The two techniques allow well-placed tunnels, with no statistical differences, but with greater variability in out-in technique.
2) In the technique out-in the tunnel entrance is closest to the lateral epicondyle, exposing more to injury the structures located in that region.
3) The thickness of the posterior cortex is something greater in the out-in technique which, combined with the fixing from outside to inside, allows greater security to not break the tunnel in the use of interference screws.
4) The length of the femoral tunnel is similarly obtained and about 3 cm, making it less desirable to use interference screws larger than 25 mm and limiting the use of other fastening systems.