Tibial insertions of the anterior cruciate ligament and the anterior horn of the lateral meniscus: A histological and computed tomographic study

Abstract Background A positional relationship between the anterior cruciate ligament (ACL) and the anterior horn of the lateral meniscus (AHLM) has not previously been a topic of interest in the literature because the AHLM is already known to be obviously adjacent to the ACL and is assumed as a lateral border. The objective of this study was to investigate the positional anatomic relationship between the ACL and AHLM by histological evaluation of sequential slices and computed tomography (CT) of the tibial insertion sites. Hypothesis/Purpose. The ACL has a specific positional relationship with the AHLM and there is an identifiable distinct bony border between them. The position of the AHLM could be an important and useful landmark for accurate tibial tunnel positioning in anatomical ACL reconstruction. Study Design. Descriptive laboratory study. Methods Twelve ACL-intact knees from embalmed cadavers were used in this study. Six knees were sectioned into four slices for histologic examination in the coronal planes parallel to the AHLM alignment. Before sectioning, these knees were subjected to three-dimensional (3-D) volume-rendering CT. Each of the four slices demonstrated the insertion area of the ACL relative to the position of the AHLM. Each histologic slice was compared with the corresponding CT image. Only histological examination in the sagittal planes was performed in the other six knees. Results The ACL fibres were broadly attached at the region anterior to the AHLM. However, the ACL and AHLM shared a clear border identifiable on the coronal CT images and appeared as a prominence of the bony ridge on the 3-D CT images. No dense ACL fibres were attached to the region posterior to the AHLM. Based on the histological data, the geometry of the ACL tibial insertion was L-shaped along the AHLM. Conclusion The ACL and AHLM have a specific positional relationship not only in the mediolateral direction but also anteroposteriorly. The AHLM serves not only as a lateral border, but also as a useful reference in an anterioposterior direction for tunnel positioning in ACL reconstruction. Specifically, the ACL fibres were found to be broadly attached onto the bony surface in the region anterior to the AHLM and there was no firm attachment of the ACL in the region posterior to the AHLM on the tibial side, which is useful in avoiding posterior tunnel placement.