Anatomical study of the positioning of guide wires for the reconstruction of the two bands of the anterior cruciate ligament using transtibial technique

PURPOSE: To determine whether it is possible and the difficulty of anatomical placement of guide wires for reconstruction of the two bands of the anterior cruciate ligament using transtibial technique and to measure the angle and positioning of the anatomic tibial guide wires for this technique. METHODS: Ten cadaver knees were dissected and a guide wire was positioned in the center of origin and insertion of each band. Were collected measurements of the distance from: 1) the entry point of the guide wire on tibial tuberosity; 2) the medial end of the tibia; 3) the tibial articular surface. Were also measured the medial and caudal angles of the guide wires. RESULTS: For the anteromedial band the medial angle was 19±5o and the caudal was 44±4o.The distances were 20±2 mm from anterior tuberosity, 26±5 mm from the tibial plateau and 25±5 mm from the medial end of the tibia. For the posterolateral band the medial angle was 26±5o and the caudal one was 36±8°. The distances were 31±6 mm for the anterior tuberosity, 24±4 mm for the tibial plateau and 17±7 mm from the end of the tibia. CONCLUSIONS: It is possible to position the guide wires of the two bands to reconstruct the anterior cruciate ligament using transtibial technique. The parameters for the proper positioning of the guide wire from anteromedial band is caudal angle of 44o with entry point 20 mm from anterior tuberosity; for the posterolateral band the caudal angle is 36o; from the tibial tuberosity the distance is 31 mm. This technique is difficult to perform leaving its questionable reproducibility.


Introduction
Since the 80s, the arthroscopic reconstruction of the ruptured anterior cruciate ligament (ACL) became the gold standard of treatment for this injury 1 .Although the reconstruction is done with a single band, anatomical studies show that the ACL consists of two bands, one anteromedial and one posterolateral 2,3 .

Despite excellent results with ACL reconstruction
technique by a single band 2 , long-term studies show 15% to 30% of residual rotational instability, persistence and progression to rebound osteoarthritis in 40% of cases when this technique is used [4][5][6][7] .
One of the techniques which aim to improve the shortcomings of conventional reconstruction is the rebuilding of the two bands of the ACL 8 .This reconstruction can be done basically in two ways: 1 -first drilling tunnels in the tibia and then doing the same one femoral site, through tibia, known as reconstruction or transtibial monotunel 8 ; 2) to drill the tunnel of the femur and tibia independently of each other, ie, the two tunnels are drilled cortical external to internal, also called outside-in or double incision 9 .
Transtibial reconstruction is the most performed, but it adds a difficulty to the procedure.The articular tibial tunnel outlet, anatomically well positioned, is not enough for a proper positioning of the graft.The perforating angles must also be correct to allow proper preparation of the femoral tunnel, because the second drilling is through the tunnel previously done 10 .There are many studies to define the location and angles of guide wires suitable for construction of tunnels for the ACL transtibial technique of dual-band 8,10,11 .
The aim of this study was: 1) to determine whether it is possible and the difficulty of anatomical placement of guide wires for reconstruction of the two bands of the anterior cruciate ligament using transtibial technique and 2) to measure the angle and positioning of the anatomic tibial guide wires for this technique.

Methods
The study was conducted on the Department of Anatomy of Federal University of Parana, Curitiba-PR, Brazil during April and May of 2011.
Ten dissected cadaver knees were randomly chosen without distinction of sex and age.They were numbered from 1 to 10 according to the chronological sequence of dissection.For measurements of the distances between the points of interest as well as the angles, were used needles, caliper rule, steel wires with two millimeters in diameter, a battery puncher and two paintbrushes for color demarcations.
Were identified during the dissection, the anterior cruciate ligament (ACL) and its two bands, the anteromedial and posterolateral, as shown in Figure 1.Length of the tunnel (Figure 2).To determine the length of the tibial tunnel, was used a caliper rule to measure the difference in total length of the guide wire by measuring the outside wire, when it was getting off the tibial plateau.The angles of interest were: 1.
Caudal angle -the angle of the guide wire (Fam or FPL) with the plane of the tibial plateau (axial)

2.
Medial angle -guide wire angle (Fam or FPL) in the sagittal plane (Figure 3).To obtain the value of the medial angle was necessary to establish a triangle formed by the guide wires (Fam or FPL), with another wire placed at the tibial tuberosity and parallel to the axial and sagittal planes (Figure 4).To obtain the value of the caudal angle was necessary to establish a triangle formed by the guide wires (Fam or FPL), with another wire placed parallel to the tibial plateau (axial) (Figure 5).A triangle was formed by two wires and an imaginary line joining the two 10 cm of its acute angle (Figure 5).The length of the third line determines the angle of the guide wire by trigonometry.
These data were extracted with the help of AutoCAD ® software for the determination of the angles (Figure 6).

Results
In all cases it was possible to reach the anatomical position by the transtibial technique.In some it was technically difficult and required the passage of the guide wire numerous times, especially for the FPL.
The distance measurements of the guide wire to anatomical landmarks and the caudal and medial angles of the anteromedial band, are shown in Table 1 and the posterolateral band in Table 2.

Discussion
Nowadays the importance of reconstruction of the ACL two bands is always in discussed 12 .One of the barriers to reconstruction with two bands is the difficulty in its performance, especially by the transtibial technique.For some, the transtibial technique cannot reproduce the correct anatomy of the ACL 13 .For them the only way to reconstruct the ACL with two bands in its original anatomical position, is drilling tunnels independently 9 .
There are studies that show the possibility of reconstructing the anatomy of the ACL by a double band for the transtibial technique, as well as the present study 8,14 .
The fact that some authors got the opportunity to reproduce the technique of anatomical reconstruction of the ACL via the transtibial 8,14 shows that it is possible to do it, even taking into account the fact that others have failed 13 .But it is questionable the reproducibility of the technique, because in some cases was very difficult to reproduce the anatomy in laboratories; certainly, in the surgical environment would increase these difficulties.
The wires in the anteromedial band measured 20 mm medial to the tibial tuberosity, 25 mm in tibial plateau and with caudal angulation of 46 o .This shows how the tunnel must be superficial in the joint surface to reach the anatomical position.
The posterolateral tunnel will be more superficial, due to the fact it is closer to the plateau (24 mm) and in minor caudal angle (36 o ).
Seibold 16 found by MRI enlargement in 100% of cases and communication between the tunnels in 41% one year after surgery.This high rate of communication underlines the close anatomical relationship between the two tibial tunnels.This could cause difficulties in a possible revisional surgery.The data in this study, showing the proximity of the guide wires, corroborates the conclusion of these authors.
In a published anatomical dissection of 50 knees to determine areas of positioning of the two tibial tunnels, was noted significant anatomical variation and the impossibility to locate the tunnel in the center of insertion of each band, because there was not enough space for its realization 15 .They recommended that the anteromedial tunnel respect a "security zone" of 2 mm from the anterior edge of the remaining stump of the ligament to prevent impingement of the femur.To prepare the posterolateral tunnel is necessary to take special precautions in not cause damage to the posterior horn of the lateral meniscus.
The reconstruction with double band is more difficult when the femoral tunnels are created from the tibial tunnel, carrying greater possibility of error.Facing this problem, to ensure the correct position to the neoligament, femoral anatomical references can be recommended for making femoral bands tunnel in posterolateral and anteromedial position, or a browser can be used 8 .
Based on the results of this research, it was possible to reproduce the optimal placement of guide wires for the construction of ACL anteromedial and posterolateral tunnels bands via transtibia.For the anteromedial band the angle was 19±5 o , the caudal angle was 44±4 o .The distances of anatomical points were 20±2 mm from anterior tuberosity, 26±5 mm from the tibial plateau and 25±5 mm from the medial end of the tibia.
For the posteriolateral band the angle was 26±5 o , the caudal angle was 36±8 o .The distances of anatomical points were 31±6 mm from anterior tuberosity, 24±4 mm from the tibial plateau and 17±7 mm from the end of the tibia.For the anteromedial band, there were no technical difficulties in obtaining an optimal placement.However, for the positioning of the guide wire in the posterolateral band, great difficulties were encountered due to their entry point to be very medial in tibia.

Conclusions
It is possible to position the guide wires of the two bands to reconstruct the anterior cruciate ligament using transtibial technique.The parameters for the proper positioning of the guide wire from anteromedial band is caudal angle of 44º with entry point 20 mm from anterior tuberosity; for the posterolateral band the caudal angle is 36º; from the tibial tuberosity the distance is 31 mm.This technique is difficult to perform leaving its questionable reproducibility.

FIGURE 2 -
FIGURE 2 -Distance from the entry point of the tunnel to the tibial tuberosity (AT-C); distance from entry point to the medial end of the tibia (C-EM); distance from the tibial articular surface to the point of entry (Plateau-C).

FIGURE 3 -
FIGURE 3 -Reproduction of medial and caudal angles.

FIGURE 4 -
FIGURE 4 -Method to measure the medial angle.

FIGURE 5 -
FIGURE 5 -Method to measure the caudal angle.

TABLE 1 -TABLE 2 -
Results of measurements of the guide wire of the anteromedial band (n=10).Note: AT-C = entry point of the tunnel to the tibial tuberosity; C-IN = end entry point of the medial tibial; Plateau-C = entry point of the tibial articular surface; COMP = length of the tibial tunnel; Â caudal = caudal angle; Â medial = medial angle; SD = standard deviation Results of measurements of the guide wire of the posterolateral band (n=10).Note: AT-C = entry point of the tunnel to the tibial tuberosity; C-IN = end entry point of the medial tibial; Plateau-C = entry point of the tibial articular surface; COMP = length of the tibial tunnel; Â caudal = caudal angle; Â medial = medial angle; SD = standard deviation