Coverage of the Anterior Cruciate Ligament Femoral Footprint Using 3 Different Approaches in Single-Bundle Reconstruction

Abstract

Background:

Performing a single-bundle anterior cruciate ligament (ACL) reconstruction within the femoral footprint is important to obtain a functional graft and a stable knee.

Hypothesis:

There will be a significant difference in the ability of 3 ACL reconstruction techniques to reach and cover the native femoral footprint.

Study Design:

Controlled laboratory study.

Methods:

The percentage of the ACL footprint covered by the femoral tunnel was compared after 3 different techniques to target the footprint: transtibial (TT), inside-out/anteromedial (IO), and outside-in/transfemoral (OI). Fourteen cadaveric knee specimens with a mean age of 67.5 years were used. For each knee, the TT technique utilized a 7.5-mm offset guide, the IO technique was performed through an accessory anteromedial portal, and the OI technique was carried out through the femur from the external wall of the lateral condyle. Entry points in the footprint were spotted with markers, and orientations (sagittal and frontal) of each drill guide were noted. The distal femurs were sawed and scanned, and 3-dimensional image reconstructions were analyzed. The virtual drilled area (reamer diameter, 8 mm) depending on the entry point and the sagittal/frontal orientation of the drill guide was calculated and reported for each of the 3 techniques. The distance from the tunnel center to the ACL center, percentage of the femoral tunnel within the ACL footprint, and percentage of the ACL footprint covered by the tunnel were calculated and statistically compared (analysis of variance and t test).

Results:

The average distance to the native femoral footprint center was 6.8 ± 2.68 mm for the TT, 2.84 ± 1.26 mm for the IO, and 2.56 ± 1.39 mm for the OI techniques. Average percentages of the femoral tunnel within the ACL footprint were 32%, 76%, and 78%, and average percentages of the ACL footprint covered by the tunnel were 35%, 54%, and 47%, for the TT, IO, and OI techniques, respectively. No significant difference was observed between the IO and OI techniques (P = .11). The TT approach gave less satisfactory coverage on all testing criteria.

Conclusion:

The IO and OI techniques allowed for creation of a tunnel closest to the ACL femoral footprint center. Despite this fact and even if the average percentage of the drilled area included in the femoral footprint was close to 80% for these 2 techniques, the average percentage of the ACL footprint covered by the tunnels was <55% for all 3 techniques. Coverage of the ACL footprint depended on the entry point, orientation, and diameter of the drilling but also on the size of the footprint.

Clinical Relevance:

To improve the coverage of the native femoral footprint with a single-bundle graft, in addition to the entry point it may also be necessary to consider the orientation of the drilling to increase the dimensions of the area while respecting the anatomic constraints of the femoral bone and graft geometry.