A new method to determine graft angles after knee ligament reconstruction

Variation in Graft Bending Angle During Range of Motion in Single-Bundle Posterior Cruciate Ligament Reconstruction: A 3-Dimensional Computed Tomography Analysis of 2 Techniques

PURPOSE

To compare variations in femoral graft bending angle during range of motion (ROM) of the knee between inside-out (IO) and retro-socket outside-in (OI) techniques in posterior cruciate ligament (PCL) reconstruction using in vivo 3-dimensional (3D) computed tomography analysis.

METHODS

Ten patients underwent PCL reconstruction by the IO technique (5 patients) or the retro-socket OI technique (5 patients) for suspensory femoral fixation. After PCL reconstruction, 3D computed tomography was performed in 0° extension and 90° flexion to reconstruct 3D femur and tibia bone models using Mimics software. Positions of femur and tibia at 30°, 45°, and 60° flexion were reproduced by determining the kinematic factors of anteroposterior translation, mediolateral translation, and internal-external rotation angle of each patient based on previously measured kinematic data. Variation in graft bending angle according to the flexion range of the knee was calculated by the difference in graft angulation measured at each flexion angle. The results were compared between the 2 techniques.

RESULTS

There was significant difference in variation of femoral graft bending angle between IO and retro-socket OI techniques from 0° to 90° flexion of the knee (P = .008). Significant difference was also noticed at 30° to 45° (P = .008), 45° to 60° (P = .008), and 60° to 90° (P = .016) ROM of the knee between the 2 groups.

CONCLUSIONS

The retro-socket OI technique resulted in less variation in femoral graft bending angle compared with the IO technique during knee ROM. We recommend the retro-socket OI technique for femoral tunnel placement to reduce the graft motion at the intra-articular femoral tunnel aperture.

CLINICAL RELEVANCE

The retro-socket OI technique produces significantly less variation in femoral graft bending angle when compared with the IO technique. Such reduction in variation of femoral graft bending angle might be related to lower stress at the femoral tunnel aperture.

Graft Bending Angle at the Intra-articular Femoral Tunnel Aperture After Single-Bundle Posterior Cruciate Ligament Reconstruction: Inside-Out Versus Outside-In Techniques

BACKGROUND

To date, no in vivo 3-dimensional computed tomography (3D-CT) studies have compared graft bending angles at the femoral tunnel aperture and femoral tunnel length in patients who underwent posterior cruciate ligament (PCL) reconstruction with outside-in (OI) and inside-out (IO) techniques.

PURPOSE/HYPOTHESIS

This study used in vivo 3D-CT analysis to compare graft bending angles at the femoral tunnel aperture and femoral tunnel lengths after OI and IO femoral drilling techniques in single-bundle PCL reconstruction. It was hypothesized that the graft bending angle at the femoral tunnel aperture would be less acute with the OI compared with the IO technique, with no difference in femoral tunnel lengths.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Immediate postoperative in vivo 3D-CT and curved planar reformation were used to assess the graft bending angles and femoral tunnel lengths in the sagittal, axial, and coronal planes in 67 patients who underwent single-bundle PCL reconstruction with the OI (n = 37) and IO (n = 30) techniques.

RESULTS

The mean graft bending angles on the sagittal and axial planes were 8.2° more acute (23.5° vs 15.3°, P = .011) and 5.3° more acute (49.0° vs 43.7°, P = .013), respectively, with the IO compared with the OI technique, but the difference in the coronal plane was not statistically significant (25.3° vs 24.8°, P = .623). Femoral tunnel length was similar in the 2 groups.

CONCLUSION

The graft bending angles in single-bundle PCL reconstruction were more acute in the sagittal and axial planes with the IO compared with the OI technique, but there was no difference in the coronal plane. In addition, femoral tunnel lengths did not differ significantly in patients who underwent OI and IO single-bundle PCL reconstructions. Although further biomechanical studies are needed to evaluate the effect on graft failure of a <10° difference in graft bending angle, the small magnitude of this difference would likely have little adverse effect on graft survival.

Optimal femoral tunnel positioning in posterior cruciate ligament reconstruction using outside-in drilling

PURPOSE

The goal of our study was to determine the precise femoral drill guide placement during reconstruction of the anterolateral bundle (ALB) of the posterior cruciate ligament (PCL) femoral footprint that would produce a minimum tunnel length of 25 mm, a maximum graft/femoral tunnel angle of 50°, and a minimum distance of 10 mm between the femoral socket and the subchondral bone of the weight-bearing surface of the medial femoral condyle.

METHODS

Using computer navigation, we used synthetic replicas of human femora to create a series of virtual femoral sockets. We then measured the bone tunnel length, angle of the femoral socket relative to the PCL footprint, and distance from the subchondral bone of the weight-bearing surface of the medial femoral condyle to the femoral socket at a series of guide pin sleeve positions. We positioned the guide pin using the following angle combinations: -20°, -10°, 0°, 10°, 20°, 30°, 40°, 50°, and 60° to a line perpendicular to the femoral axis in the coronal plane and -15°, 0°, 15°, 30°, 45°, and 60° to a line parallel to the transepicondylar axis in the axial plane. Using linear regression models, we determined the precise drill guide placement angles that would produce the optimal tunnel length, graft/femoral tunnel angle, and distance to the subchondral bone margin.

RESULTS

The results were consistent between small, medium, and large femora. We found that the optimal drilling angles for anatomic reconstruction of the femoral footprint of the ALB of the PCL were 0° to a line perpendicular to the femoral axis in the coronal plane and 15° to a line parallel to the transepicondylar axis in the horizontal or axial plane.

CONCLUSIONS

During outside-in drilling for PCL reconstruction, holding the guide pin sleeve at a position 0° to a line perpendicular to the femoral axis in the coronal plane and 15° to a line parallel to the transepicondylar axis in the horizontal or axial plane results in optimal bone tunnel length, graft/tunnel angle, and distance between the femoral socket and the subchondral bone of the weight-bearing surface of the medial femoral condyle.

CLINICAL RELEVANCE

We describe a precise femoral tunnel drill guide placement during outside-in PCL reconstruction that ensures an optimal femoral socket with a minimum bone tunnel length of 25 mm, maximum graft/femoral tunnel angle of 50°, and minimum distance of 10 mm between the subchondral bone of the weight-bearing surface of the medial femoral condyle and the femoral socket.

Graft tension of the posterior cruciate ligament using a finite element model

PURPOSE

The aim of the study was to analyse the change in length and tension of the reconstructed single-bundle posterior cruciate ligament (PCL) with three different femoral tunnels at different knee flexion angles by use of three-dimensional finite element method.

METHODS

The right knees of 12 male subjects were scanned with a high-resolution computed tomography scanner at four different knee flexion angles (0°, 45°, 90° and 135°). Three types of single-bundle PCL reconstruction were then conducted in a 90° flexion model: femoral tunnels were created in anterolateral (AL), central and posteromedial (PM) regions of the footprint. Length versus flexion curves and tension versus flexion curves were generated.

RESULTS

Between 0° and 90° of knee flexion, changes in length and tension in the PM grafts were not significant. Whereas the lengths and tension of the AL and central grafts significantly increased in the same flexion range. The length and tension of the PM grafts at 135° of knee flexion were significantly higher than those at 90° of knee flexion, whereas the AL and the central grafts showed only slight length changes beyond 90° of flexion. However, the tension of the AL graft increased significantly beyond 90° of flexion.

CONCLUSIONS

Changes in the graft length, and tension were generally affected by different femoral tunnels and knee flexion angles. In groups with the AL and PM single-bundle reconstruction, the graft tension increased beyond 90° of knee flexion when the graft is tensioned at 90° of flexion. These data suggest that final fixation angle at 90° for the AL or PM graft would induce graft overtension in high knee flexion of 135°. Whereas central graft which is fixed in 90° of flexion is desirable in terms of prevention of graft overtension. Because the graft tension within it was relatively constant beyond 90° of flexion.

Posterior cruciate ligament reconstruction by means of tibial tunnel: anatomical study on cadavers for tunnel positioning

OBJECTIVE

to determine the reference points for the exit of the tibial guidewire in relation to the posterior cortical bone of the tibia.

METHODS

sixteen knees from fresh cadavers were used for this study. Using a viewing device and a guide marked out in millimeters, three guidewires were passed through the tibia at 0, 10 and 15 mm distally in relation to the posterior crest of the tibia. Dissections were performed and the region of the center of the tibial insertion of the posterior cruciate ligament (PCL) was determined in each knee. The distances between the center of the tibial insertion of the PCL and the posterior tibial border (CB) and between the center of the tibial insertion of the PCL and wires 1, 2 and 3 (CW1, CW2 and CW3) were measured.

RESULTS

in the dissected knees, we found the center of the tibial insertion of the PCL at 1.09 ± 0.06 cm from the posterior tibial border. The distances between the wires 1, 2 and 3 and the center of the tibial insertion of the PCL were respectively 1.01 ± 0.08, 0.09 ± 0.05 and 0.5 ± 0.05 cm.

CONCLUSION

the guidewire exit point 10 mm distal in relation to the posterior crest of the tibia was the best position for attempting to reproduce the anatomical center of the PCL.

Femoral graft-tunnel angles in posterior cruciate ligament reconstruction: analysis with 3-dimensional models and cadaveric experiments

PURPOSE

The purpose of this study was to compare four graft-tunnel angles (GTA), the femoral GTA formed by three different femoral tunneling techniques (the outside-in, a modified inside-out technique in the posterior sag position with knee hyperflexion, and the conventional inside-out technique) and the tibia GTA in 3-dimensional (3D) knee flexion models, as well as to examine the influence of femoral tunneling techniques on the contact pressure between the intra-articular aperture of the femoral tunnel and the graft.

MATERIALS AND METHODS

Twelve cadaveric knees were tested. Computed tomography scans were performed at different knee flexion angles (0°, 45°, 90°, and 120°). Femoral and tibial GTAs were measured at different knee flexion angles on the 3D knee models. Using pressure sensitive films, stress on the graft of the angulation of the femoral tunnel aperture was measured in posterior cruciate ligament reconstructed cadaveric knees.

RESULTS

Between 45° and 120° of knee flexion, there were no significant differences between the outside-in and modified inside-out techniques. However, the femoral GTA for the conventional inside-out technique was significantly less than that for the other two techniques (p<0.001). In cadaveric experiments using pressure-sensitive film, the maximum contact pressure for the modified inside-out and outside-in technique was significantly lower than that for the conventional inside-out technique (p=0.024 and p=0.017).

CONCLUSION

The conventional inside-out technique results in a significantly lesser GTA and higher stress at the intra-articular aperture of the femoral tunnel than the outside-in technique. However, the results for the modified inside-out technique are similar to those for the outside-in technique.

Comparison of the clinical results of three posterior cruciate ligament reconstruction techniques

BACKGROUND

Despite its technical complexity, arthroscopic tibial inlay reconstruction of the posterior cruciate ligament has biomechanical advantages over transtibial procedures. The purpose of this study was to compare the clinical results of arthroscopic tibial inlay single-bundle and double-bundle techniques with those of the conventional transtibial single-bundle technique.

METHODS

We evaluated twenty-nine patients treated with primary posterior cruciate ligament reconstruction and followed for longer than two years. Eight patients were treated with a transtibial single-bundle procedure; eleven, with an arthroscopic inlay single-bundle procedure; and ten, with an arthroscopic inlay double-bundle procedure. An Achilles tendon allograft was used in all cases. Each patient was evaluated on the basis of the Lysholm knee score, the mean side-to-side difference in tibial translation as measured on Telos stress radiographs, and the side-to-side difference in the range of motion of the knee.

RESULTS

The mean side-to-side difference (and standard deviation) in posterior tibial translation differed significantly between the arthroscopic tibial inlay double-bundle group (3.6 +/- 1.43 mm) and the transtibial single-bundle group (5.6 +/- 2.00 mm) (p = 0.023), although there was no significant difference between the arthroscopic inlay single-bundle group (4.7 +/- 1.62 mm) and the transtibial group (p = 0.374). The mean range of motion and Lysholm scores were similar among the three groups.

CONCLUSIONS

Despite its technical difficulty, the arthroscopic tibial inlay double-bundle technique is our preferred method of reconstruction of the posterior cruciate ligament because it stabilizes posterior tibial translation better than do the other two methods.

Clinical comparison of anteromedial versus anterolateral tibial tunnel direction for transtibial posterior cruciate ligament reconstruction: 2 to 8 years' follow-up

BACKGROUND

It has been suggested that transtibial posterior cruciate ligament reconstruction may be compromised by graft abrasion at the "killer turn," where the graft emerges from the tibia. In 1998, one of the authors suggested that beginning the tibial tunnel anterolaterally rather than anteromedially would reduce the killer turn and possibly improve the results of posterior cruciate ligament reconstruction.

PURPOSE

This article is intended to present the clinical results of single-bundle transtibial posterior cruciate ligament reconstruction, comparing cases in which the tibial tunnel was begun anteromedially with cases in which the tunnel was begun anterolaterally.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

The authors retrospectively studied 23 patients (group I) using the anteromedial tibial tunnel technique from April 1998 to August 2003 and 37 patients (group II) using the anterolateral tibial tunnel technique from February 1998 to August 2003. The average follow-up period was 58.6 months in group I and 56.9 months in group II. The minimum follow-up period was 24 months in each group. All revision cases and patients with general laxity were excluded.

RESULTS

The mean side-to-side difference of posterior tibial translation by Telos stress radiography was 3.98 +/- 1.27 mm (range, 1.80-7.80 mm) in group I and 2.87 +/- 1.25 mm (range, 1.43-6.82 mm) in group II, which was a statistically significant difference (P < .01). The final mean Lysholm knee score was 88.6 +/- 7.10 points (range, 77-98 points) in group I and 88.4 +/- 6.44 points (range, 78-98 points) in group II, which was not a statistically significant difference (P = .4358). According to the final International Knee Documentation Committee (IKDC) evaluation in group I, 30.4% (7 of 23) were normal (A), 60.9% (14 of 23) were nearly normal (B), and 8.7% (2 of 23) were abnormal (C). In group II, 24.3% (9 of 37) were normal (A), 73.0% (27 of 37) were nearly normal (B), and 2.7% (1 of 37) were abnormal (C) (P = .467). With respect to the mean side-to-side difference of range of motion, there was no statistically significant difference (P = .1697). The mean was 4.7 degrees +/- 2.38 degrees (range, 2 degrees -10 degrees ) in group I and 4.0 degrees +/- 1.73 degrees (range, 0 degrees -8 degrees ) in group II.

CONCLUSION

The anterolateral tibial tunnel technique is preferred to the anteromedial technique in terms of the objective results; however, clinical results as judged by Lysholm and IKDC scores are not significantly correlated to these results.