The Relationship Between Lateral Femoral Anatomic Structures and the Femoral Tunnel Outlet in Anterior Cruciate Ligament Reconstruction Using the Transportal Technique: A 3-Dimensional Simulation Analysis

Influence of knee flexion angle on graft bending angle during anterior cruciate ligament reconstruction using the transportal technique

This study aimed to examine change in the graft bending angle (GBA) according to various knee flexion angles in creating femoral tunnel by the transportal technique in ACL reconstruction, and to reveal knee flexion angle minimizing GBA while maintaining stable femoral tunnel characteristics. Patients who underwent ACL reconstruction using the transportal technique between January 2017 and December 2018 were retrospectively reviewed. Patients were classified into three groups according to knee flexion angle when creating femoral tunnel (group 1: < 120° (n = 19); group 2: 120-129° (n = 32); group 3: ≥ 130° (n = 33). GBA was measured on three-dimensional knee model reconstructed from postoperative computed tomography images. The length of the femoral tunnel and posterior wall blow-out were also checked. There was significant difference of GBA between the groups (group 1 = 112.1°; group 2 = 106.4°; group 3 = 101.4°, p < 0.001). The knee flexion angle in creating femoral tunnel was negatively correlated with GBA (r = - 0.733, p < 0.001). Five patients in group 1 had short femoral tunnel. GBA was influenced by knee flexion angle in creating femoral tunnel and got more acute as the knee flexion angle increased. Considering length and risk of wall blow-out in femoral tunnel, and GBA, knee flexion angle between 120 and 130° could be recommended as appropriate angle to create optimal femoral tunnel in ACL reconstruction using the transportal technique.

Safe femoral tunnel drilling angles avoid injury to the medial and posteromedial femoral anatomic structures during single-bundle posterior cruciate ligament reconstruction with the inside-out technique

PURPOSE

To investigate the relationship between the medial and posteromedial femoral anatomic structures and the femoral tunnel exit produced by different tunnel orientations when creating the femoral tunnel for posterior cruciate ligament reconstruction (PCLR) using the inside-out (IO) technique and to estimate safe tunnel orientations to minimize the risk of iatrogenic injury to these structures.

METHODS

Eleven cadaveric knees were used. The medial and posteromedial aspects of each knee joint were dissected to reveal the "safe zone," which is a bony area that avoids the distribution or attachment of at-risk structures (MCL, PMC structures, and articular cartilage), while remaining 10 mm away from the articular cartilage. The hypothesis of this study was that by creating the femoral tunnel at specific angles using the IO technique, the tunnel outlet would be as close to the safe zone as possible, protecting the at-risk structures from damage. Femoral tunnels were drilled at 20 different angle combinations on each specimen: 0°, 15°, 30°, 45°, and 60° relative to a line parallel to the transepicondylar axis in the axial plane, as well as 15°, 30°, 45°, and 60° relative to a line parallel to the femoral axis in the coronal plane. The positional relationship between each tunnel exit and the safe zone was recorded, and the shortest distance between the exit center and the safe zone boundary was measured.

RESULTS

The risk of iatrogenic injury differed depending on the drilling orientation (χ² = 168.880, P < 0.001). Femoral drilling angle combinations of 45/45°, 45/60°, 60/30°, 60/45°, and 60/60° (axial/coronal) were considered relatively safer than other orientations (P < 0.05). The shortest distance between the tunnel exit and the safe zone boundary was negatively correlated with the angle in the axial plane (P < 0.001, r = - 0.810).

CONCLUSIONS

When creating the IO femoral tunnel for single-bundle PCL reconstruction, angle combinations of 45/45°, 45/60°, 60/30°, 60/45°, and 60/60° (axial/oblique coronal) could be utilized to prevent at-risk structures from being damaged. The drilling angles and the safe zone can be employed to optimize the femoral tunnel in PCLR.

Effect of Soft Tissue Interposition and Postoperative Suspensory Cortical Button Migration on Functional Outcomes and Ligamentization After Single-Bundle ACL Reconstruction

Background:

Soft tissue interposition between a suspensory cortical button and the lateral femoral condyle is the most common cause of postoperative suspensory cortical button migration in patients undergoing anterior cruciate ligament reconstruction (ACLR).

Purpose:

To investigate the effects of soft tissue interposition and suspensory cortical button migration after ACLR on functional outcomes and graft ligamentization.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Included were 249 patients who underwent single-bundle ACLR with hamstring tendon autografts. To measure soft tissue imposition, the patients were divided into 2 groups: those in whom the suspensory cortical button was in contact with (group 1) or at least 1 mm away from (group 2) the lateral femoral condyle on 1-day postoperative radiographs. To measure suspensory cortical button migration, the patients in group 2 were further divided into 2 subgroups: those with button migration (group M) and those without migration (group non-M) as observed on 12-month postoperative radiographs. Ligamentization was evaluated according to Howell classification (grades 1-4) on 12-month follow-up magnetic resonance imaging scans. Also recorded were preoperative and 24-month postoperative Lysholm and Tegner scores and 24-month postoperative arthrometer measurements for anterior knee laxity.

Results:

There was no significant difference between groups 1 and 2 or between groups M and non-M in terms of demographic characteristics or additional intra-articular pathologies detected intraoperatively. Normal anterior laxity (<3 mm) was detected in 83.7% of the patients postoperatively, and all patients showed statistically significant pre- to postoperative improvement on the Tegner (from 4.1 to 4.3) and Lysholm (from 44.0 to 89.2) scores (P < .05 for both). No significant difference in postoperative functional results or graft ligamentization was found between either the soft tissue interposition groups (groups 1 and 2) or the suspensory cortical button migration groups (groups M and non-M).

Conclusion:

Differences between patients in soft tissue interposition and suspensory cortical button migration did not significantly affect postoperative clinical or functional outcomes or graft ligamentization after single-bundle ACLR.

Anterior cruciate ligament reconstruction, can an anatomic femoral tunnel be achieved with the trans-tibial technique? Cadaveric study

Purpose

To evaluate the possibility to access the anatomic femoral insertion of the anterior cruciate ligament (ACL) through trans-tibial (TT) and trans-portal technique, for ACL reconstruction in an independent way. To register anatomical characteristics of the TT tunnels.

Methods

Ten formaldehyde preserved knee anatomic articular specimens were dissected. Femoral tunnels were confectioned reproducing the original topography of the ACL. First, the femoral tunnel was made with the independent trans-portal technique. Then, utilizing the tibial stump of the ACL and tibial guides at 45°, the TT tunnels were confectioned trying to match the previously made femoral tunnel by trans-portal technique.

Results

In all specimens, match between the TT tunnel with the independent trans-portal tunnel was achieved. Mean values for TT coronal angle was 53,0°, for transversal angle 43,3° and for distance from tunnel to joint line 2,55 cm. A horizontalization and medialization of the TT tunnels had to be made to adequately match with the femoral tunnel made by the independent trans-portal technique.

Conclusions

By macroscopic anatomic and independent means, an anatomic femoral tunnel was confectioned with the TT technique matching with the anatomic femoral tunnel made in an independent way. As clinical relevance, the present study allows to anatomically assess the possibility to perform an anatomic femoral tunnel through the TT technique.

Level of evidence

V