Background: In an attempt to improve the accuracy and reproducibility of tunnel positioning, radiographs are being analyzed in an attempt to recreate the native anatomy of the ACL. Understanding the native ACL radiographic anatomy is an essential prerequisite to understand the relevance of postoperative tunnel position.
Questions/purposes: We performed a systematic review of the literature to delineate the radiographic location of the native ACL femoral and tibial footprints.
Methods: A search was performed in March 2014 in PubMed, the Cochrane Collaboration Library, and EMBASE to identify all studies that evaluated the native anterior cruciate ligament (ACL) anatomy on radiographs. Various measurement methods were used in each study, and averages were obtained of the data from studies with the same measurement methods.
Results: Fifteen papers were identified (which included data on 177 femora and 207 tibiae in total). Evaluation of the femoral footprint using the quadrant method on lateral knee radiographs showed that the average percent distance location of the anteromedial (AM) bundle and posterolateral (PL) bundle was 22.8% (95% confidence interval (CI) 16.59-28.90) and 32.5% (95% CI 27.71-37.26) from the posterior condyle, respectively, and 23.2% (95% CI 19.52-26.94) and 50.0% (95% CI 46.16-53.76) from Blumensaat's line, respectively. Using the Amis and Jacob method, the tibial footprint on the lateral knee radiograph average percent distances was 35.1% (95% CI 34.46-35.72) for the center of the AM bundle and 47.3% (95% CI 41.69-52.95) for the center of the PL bundle of the ACL. The femoral and tibial ACL footprints on the anteroposterior (AP) views of the knee were not well delineated by these studies.
Conclusion: The information presented in this systematic review offers surgeons another important tool for accurate ACL footprint identification.
Keywords: anatomy; anterior cruciate ligament; footprint; radiograph; systematic review.