Risk analysis of tunnel collision in combined anterior cruciate ligament and anterolateral ligament reconstructions

Optimal Anterolateral Ligament Tibial Tunnel Orientation to Prevent ACL Tunnel Collision and Saphenous Nerve Injury

Background

Collision risks between femoral tunnels during combined anterior cruciate ligament (ACL) and anterolateral ligament (ALL) reconstruction have been reported. However, studies on collision risks between tibial tunnels and optimal ALL tibial tunnel orientation are lacking.

Purpose

To analyze the optimal orientation of the ALL tibial tunnel to minimize collisions with the ACL tibial tunnel while preventing injury to the saphenous nerve in combined reconstruction.

Study Design

Descriptive laboratory study.

Methods

Preoperative magnetic resonance imaging (MRI) and postoperative computed tomography (CT) images of patients who underwent primary ACL reconstruction using the anteromedial portal technique were analyzed. Only patients with preoperative MRI scans including thin-cut images (<1 mm) were included for 3-dimensional (3D) reconstruction. Patients who underwent ALL reconstruction or had poorly 3D-reconstructed essential structures were excluded to ensure accurate reproduction of bony attachments and landmarks associated with ALL. Bony structures of the knee joint, including the proximal tibia with the actual ACL tibial tunnel, were reconstructed from the postoperative CT scans. The greater saphenous vein (GSV), which runs together with the saphenous nerve, was reconstructed from the preoperative MRI and subsequently transferred to the CT model, maintaining the appropriate positional relationship. Twelve orientations of the ALL tunnel (at 10° intervals, ranging from 0° to 20° anteriorly and from 0° to 30° distally) were simulated with the final 3D model, starting from the ALL tibial footprint (midpoint between the Gerdy tubercle and the fibular head, 10 mm distal to the joint line), to measure the distances between the ALL tunnel trajectory and other structures (ACL tibial tunnel, GSV) by each orientation.

Results

A total of 35 out of 304 patients were included in this study. An anteriorly oriented ALL tunnel decreased the minimum distance to the ACL tibial tunnel (MD-ACL) and increased minimum distance to the GSV (MD-GSV) (all P < .001). A distally oriented ALL tunnel increased MD-ACL and decreased MD-GSV (all P < .001). Optimal ALL tunnel orientation was 10° anterior to 30° distal (MD-ACL, 14.6 ± 4.0 mm; MD-GSV, 27.8 ± 12.4 mm) and 20° anterior to 30° distal (MD-ACL, 11.5 ± 3.6 mm; MD-GSV 43.6 ± 12.9 mm), considering both collisions with the ACL tunnel and the potential risk of injury to the saphenous nerve.

Conclusion

The optimal orientations of the ALL tibial tunnel to avoid collision with the ACL tibial tunnel and prevent saphenous nerve injury are 10° anterior to 30° distal and 20° anterior to 30° distal for far-cortex drilling techniques, starting from the midpoint between the Gerdy tubercle and the fibular head, 10 mm distal to the joint line.

Incidence of Convergence Between Distally and Anteriorly Oriented ALL Femoral Tunnels and ACL Femoral Tunnels in Combined ACL and ALL Reconstruction: 3-Dimensional Computed Tomography Analysis of 227 Patients

BACKGROUND

Adjusting the direction of the anterolateral ligament (ALL) femoral tunnel is suggested to avoid tunnel convergence during anterior cruciate ligament (ACL) reconstruction. Yet, there has been no in vivo clinical study reporting the effect of changing the direction of the ALL tunnel on the incidence of convergence with the ACL tunnel.

PURPOSE

To report the incidence of convergence between the ACL femoral tunnel and a distally and anteriorly directed ALL femoral tunnel and to determine a safe distal angle and anterior angle.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 227 patients undergoing concomitant ALL and anatomic single-bundle ACL reconstruction between January 2020 and December 2022 were retrospectively reviewed. The tunnel convergence rate, angular orientation of the tunnels, and distance between tunnels were obtained using postoperative computed tomography. The patients were grouped based on the direction of the ALL tunnel (transverse vs distal anterior) and the presence of tunnel convergence (convergence vs no convergence).

RESULTS

The overall tunnel convergence rate was 53.3% (121/227 patients). Tunnel convergence was observed less frequently in the distal anterior group (33.7%) than in the transverse group (65.2%) (P < .001). The no convergence group showed an ALL tunnel oriented more distally (20.2°± 11.1°) and anteriorly (19.5°± 10.2°) compared with the convergence group (8.7°± 6.5° and 6.9°± 5.3°, respectively) (P = .005 and P = .008, respectively). There were no cases of tunnel convergence for ALL tunnels >24.3° distally and >25.5° anteriorly. There was no difference in the angle of the ACL femoral tunnel between all groups.

CONCLUSION

A distally and anteriorly directed ALL femoral tunnel reduced the incidence of convergence with the ACL femoral tunnel. A distal angle >24.3° and an anterior angle >25.5° of an ALL tunnel are suggested to safely avoid convergence with the ACL tunnel.

Lateral Extra-Articular Tenodesis Staple Risks Penetration of Anterior Cruciate Ligament Reconstruction Tunnel

Purpose

To identify the risk of anterior cruciate ligament (ACL) femoral tunnel penetration with the use of a staple for lateral extra-articular tenodesis (LET) graft fixation and to determine whether this varied between 2 different techniques for ACL femoral tunnel drilling.

Methods

Twenty paired, fresh-frozen, cadaver knees underwent ACL reconstruction with a LET. Left and right knees were randomized to ACL reconstruction with femoral tunnel creation by use of either a rigid guide pin and reamer through the accessory anteromedial portal or by the use of a flexible guide pin and reamer through the anteromedial portal. Immediately after tunnel creation, the LET was performed and fixated with a small Richard's staple. Fluoroscopy was used to obtain a lateral view of the knee to determine staple position, and visualization of the ACL femoral tunnel was performed with the arthroscope to investigate penetration of the staple into the femoral tunnel. The Fisher exact test was conducted to determine whether there was any difference in tunnel penetration between tunnel creation techniques.

Results

The staple was noted to penetrate the ACL femoral tunnel in 8 of 20 (40%) extremities. When stratified by tunnel creation technique, the Richards staple violated 5 of 10 (50%) of the tunnels made via the rigid reaming technique compared with 3 of 10 (30%) of those created with a flexible guide pin and reamer (P = .65).

Conclusions

A high incidence of femoral tunnel violation is seen with lateral extra-articular tenodesis staple fixation.

Level of Evidence

Level IV, controlled laboratory study.

Clinical Relevance

The risk of penetrating the ACL femoral tunnel with a staple for LET graft fixation is not well understood. Yet, the integrity of the femoral tunnel is important for the success of ACL reconstruction. Surgeons can use the information in this study to consider adjustments to operative technique, sequence, or fixation devices used when performing ACL reconstruction with concomitant LET to avoid the potential for disruption of ACL graft fixation.

The orientation of the ALL femoral tunnel to minimize collision with the ACL tunnel depends on the need or not of far-cortex drilling

PURPOSE

To (1) evaluate the optimal drill orientation of the anterolateral ligament (ALL) femoral tunnel to minimize collision with the anterior cruciate ligament (ACL) femoral tunnel during anatomical ACL reconstruction according to the need for far-cortex drilling and (2) investigate the geometric factors that affect tunnel collision secondary to drill orientation of the ALL femoral tunnel.

METHODS

A three-dimensional femoral model of patients who underwent anatomical single-bundle ACL reconstruction between 2015 and 2016 was constructed, and the geometric factors were evaluated. Virtual ALL femoral tunnels were created to simulate 45 drilling conditions. For each condition, whether the virtual ALL femoral tunnel and its trajectory violated the femoral cortex and the minimum distance between tunnels was investigated.

RESULTS

Thirty-nine subjects were included. Overall violation rates of the femoral cortex by the ALL tunnels and its trajectories were 11.1% (195 of 1755 conditions) and 40.7% (714 of 1755 conditions), respectively. A drilling angle of axial 0° and coronal - 40° showed the longest minimum distance between tunnels without femoral cortex violation by the ALL tunnel (6.3 ± 4.0 mm; collision rate 2.6% [1 of 39 subjects]). With simultaneous consideration of the ALL tunnel's trajectory representing far-cortex drilling, a drill angle of axial 40° and coronal 10° showed the longest minimum distance between tunnels without femoral cortex violation (0.6 ± 3.9 mm; collision rate 38.5% [15 of 39 subjects]). For surgical techniques requiring far-cortex drilling, regression analyses were performed on geometric factors that could affect tunnel collision, which revealed that the sagittal inclination angle of the ACL and the distance between the ACL femoral tunnel's outlet and ALL's femoral attachment were associated with tunnel collision.

CONCLUSION

The optimal drill orientations of the ALL femoral tunnel to minimize collision with the ACL femoral tunnel were axial 0° and coronal - 40° for surgical techniques not requiring far-cortex drilling and axial 40° and coronal 10° for techniques requiring far-cortex drilling. For techniques requiring far-cortex drilling, additional adjustment for orientation of the ACL femoral tunnel is required to reduce the risk of tunnel collision. Therefore, an individualized surgical strategy should be applied according to the graft fixation method of the ALL femoral tunnel.

How to Avoid Knee Tunnel Convergence When Performing a Modified Lemaire Extra-Articular Tenodesis

There has been a significant increase in the number of anterior cruciate ligament (ACL) reconstruction (ACLR) procedures being performed with a lateral extra-articular procedure (LEAP). However, tunnel convergence in combined ACLR and LEAP techniques has been described and can lead to damage to the graft or graft failure. This technical note describes how to avoid knee tunnel convergence when performing a modified Lemaire extra-articular tenodesis using a knotless suture anchor.

Optimal Combination of Femoral Tunnel Orientation in Anterior Cruciate Ligament Reconstruction Using an Inside-out Femoral Technique Combined With an Anterolateral Extra-articular Reconstruction

BACKGROUND

The optimal orientation of the anterolateral extra-articular reconstruction (ALLR) femoral tunnel to avoid collision with the anterior cruciate ligament reconstruction (ACLR) femoral tunnel is not clearly defined in the literature.

PURPOSE

To define the optimal combination of orientations of the ALLR femoral tunnel and the ACLR femoral tunnel using an inside-out technique to minimize risk of collision between these tunnels.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Three-dimensional reconstruction of magnetic resonance imaging scans of 40 knees after an isolated ACLR with an inside-out femoral technique was used to assess the collision risk between ACLR and virtual ALLR tunnels. The optimal ACLR tunnel orientation was defined as having the safest distance from the ALLR tunnel. A second collision analysis was performed on all patients presenting with an optimal orientation of the ACLR tunnel to then define the optimal ALLR tunnel orientation. The potential for trochlear damage was also studied. A collision risk of 0% to 5% was considered acceptable and referred to as "low risk."

RESULTS

The only ALLR tunnel orientation presenting a low risk of collision with the ACLR tunnel was with an axial angle of 40° anteriorly and a coronal angle of 0°. This orientation presented a 48% risk of trochlear damage with the guide wire of the ALLR tunnel. The more posterior the orientation of the ACLR, the larger the distance from the ALLR tunnel. Among the 22 patients presenting with an optimal ACLR tunnel (alpha angle superior to 40°), the ALLR tunnels aimed with 1 of these 3 orientations presented a low risk of tunnel collision and trochlear damage: 40° axial and 10° coronal, 35° axial and 5° coronal, or 30° axial and 0° coronal.

CONCLUSION/CLINICAL RELEVANCE

To minimize risk of tunnel collision or trochlear damage when combining an inside-out ACLR with an ALLR, the ACLR tunnel should be performed with a posterior orientation (alpha angle >40°), and the ALLR tunnel should be aimed with 1 of 3 orientations: 40° axial and 10° coronal, 35° axial and 5° coronal, or 30° axial and 0° coronal.

Bone Staples Provide Favorable Primary Stability in Cortical Fixation of Tendon Grafts for Medial Collateral Ligament Reconstruction: A Biomechanical Study

Background:

The use of the interference screw (IFS) for the cortical fixation of tendon grafts in knee ligament reconstruction may lead to converging tunnels in the multiligament reconstruction setting. It is unknown whether alternative techniques using modern suture anchor (SA) or bone staple (BS) fixation provide sufficient primary stability.

Purpose:

To assess the primary stability of cortical fixation of tendon grafts for medial collateral ligament (MCL) reconstruction using modern SA and BS methods in comparison with IFS fixation.

Study Design:

Controlled laboratory study.

Methods:

Cortical tendon graft fixation was performed in a porcine knee model at the tibial insertion area of the MCL using 3 different techniques: IFS (n = 10), SA (n = 10), and BS (n = 10). Specimens were mounted in a materials testing machine, and cyclic loading for 1000 cycles at up to 100 N was applied to the tendon graft, followed by load-to-failure testing. Statistical analysis was performed using 1-way analysis of variance.

Results:

There were no statistical differences in elongation during cyclic loading or peak failure load during load-to-failure testing between BS (mean ± standard deviation: 3.4 ± 1.0 mm and 376 ± 120 N, respectively) and IFS fixation (3.9 ± 1.2 mm and 313 ± 99.5 N, respectively). SA fixation was found to have significantly more elongation during cyclic loading (6.4 ± 0.9 mm; P < .0001) compared with BS and IFS fixation and lower peak failure load during ultimate failure testing (228 ± 49.0 N; P < .01) compared with BS fixation.

Conclusion:

BS and IFS fixation provided comparable primary stability in the cortical fixation of tendon grafts in MCL reconstruction, whereas a single SA fixation led to increased elongation with physiologic loads. However, load to failure of all 3 fixation techniques exceeded the loads expected to occur in the native MCL.

Clinical Relevance:

The use of BS as a reliable alternative to IFS fixation for peripheral ligament reconstruction in knee surgery can help to avoid the conflict of converging tunnels.

Safe Femoral Fixation Depth and Orientation for Lateral Extra-Articular Tenodesis in Anterior Cruciate Ligament Reconstruction

Background:

Patients who undergo anterior cruciate ligament (ACL) reconstruction (ACLR) can have a persistent postoperative pivot shift. Performing lateral extra-articular tenodesis (LET) concurrently has been proposed to address this; however, LET femoral fixation may interfere with the ACLR femoral tunnel, which could damage the ACL graft or its fixation.

Purpose:

To evaluate the safe maximum implant or tunnel depth for a modified Lemaire LET when combined with ACLR anteromedial portal femoral tunnel drilling and to validate the safe LET drilling angles to avoid conflict with the ACLR femoral tunnel.

Study Design:

Descriptive laboratory study.

Methods:

Twelve fresh-frozen cadaveric knees were used. With each knee at 120° of flexion, an ACLR femoral tunnel in the anteromedial bundle position was created arthroscopically via the anteromedial portal using a 5-mm offset guide, a guide wire, and an 8-mm reamer, which was left in situ. A modified Lemaire LET was performed using a 1 cm-wide iliotibial band strip harvested with the distal attachment intact, to be fixed in the femur. The desired LET fixation point was identified with an external aperture 10 mm proximal and 5 mm posterior to the fibular collateral ligament’s femoral attachment, and a 2.4-mm guide wire was drilled, aiming at 0°, 10°, 20°, or 30° anteriorly in the axial plane and at 0°, 10°, or 20° proximally in the coronal plane (12 different drilling angle combinations). The relationship between the LET drilling guide wire and the ACLR femoral tunnel reamer was recorded for each combination. When a collision with the femoral tunnel was recorded, the LET wire depth was measured.

Results:

Collision with the ACLR femoral tunnel occurred at a mean LET wire depth of 23.6 mm (range, 15-33 mm). No correlation existed between LET wire depth and LET drilling orientation (r = 0.066; P = .67). Drilling angle in the axial plane was significantly associated with the occurrence of tunnel conflict (P < .001). However, no such association was detected when comparing the drilling angle in the coronal plane (P = .267).

Conclusion:

Conflict of LET femoral fixation with the ACLR femoral tunnel using anteromedial portal drilling occurred at a mean depth of 23.6 mm but also at a depth as little as 15 mm, which is shorter than most implants. When longer implants or tunnels are used, the orientation should be directed at least 30° anteriorly in the axial plane to minimize the risk of tunnel conflict, bearing in mind the risk of joint violation.

Clinical Relevance:

This study provides important information for surgeons performing LET in combination with ACLR anteromedial portal femoral tunnel drilling regarding safe femoral implant or tunnel length and orientation.