CT scan of the placement of the femoral tunnel in combined anterior cruciate ligament and anterior lateral ligament reconstruction by a single femoral tunnel using the outside-in technique

Background: The main difficulty with this ALL reconstruction method is the placement of the femoral tunnel as isometrically as possible. The femoral insertion of the ALL is usually located one centimeter posteriorly and proximal to the lateral epicondyle, at the level of the Lemaire vessels. The purpose of our study was to evaluate the placement of the femoral tunnel in ligament reconstruction by combined ACL and ALL reconstruction with a single femoral tunnel using the outside-in technique. Our hypothesis was that a single femoral tunnel by outside-in technique would allow satisfactory placement of the femoral insertion of the ALL.. Methods: We conducted a retrospective bi-centric study of all patients who underwent combined ACL and ALL reconstruction surgery with a common outside-in femoral technique. A postoperative low-dose knee CT scan with multiplane reconstructions was performed after patient consent. After locating the top of the epicondyle on three-dimensional CT scan reconstructions, the distances between the top of the lateral epicondyle and the center of the femoral tunnel in the frontal and sagittal planes were measured. These measurements were taken by a surgeon and a radiologist. Results: 45 patients were included and the average age was 29 years (17-39). 30 patients had a CT scan. Analysis of the placement of the femoral tunnel showed that 10 tunnels were placed posteriorly and proximal to the top of the lateral epicondyle. Conclusion: This study did not confirm our hypothesis. Combined ACL and ALL reconstruction by a single tunnel did not provide access to the isometric point of the femoral insertion of the ALL in a reproducible manner, despite open intra-operative identification of this point. This study highlights the difficulty of locating the femoral isometric point with a standard outside-in femoral guide. Developing a specific femoral guide might be useful.