Tibial insertion of the anterior cruciate ligament and anterior horn of the lateral meniscus share the lateral slope of the medial intercondylar ridge: A computed tomography study in a young, healthy population.

Background: The central intercondylar ridge (CIR) is an anatomical bony landmark that bisects the slope of the medial intercondylar ridge (MIR) between the tibial insertion of the anterior cruciate ligament (ACL) and anterior horn of lateral meniscus (AHLM) and was recently revealed by computed tomography (CT) evaluation corresponding to histologic slices of cadaveric knees. The purpose of this study was to clarify the shape and size of ACL and AHLM tibial insertion in young, healthy knees using the new bony landmark (CIR) and previously reported landmarks.

Methods: The contralateral healthy knees in 34 ACL-reconstructed patients (18 male patients, 16 female patients, mean age: 24.0 years) were scanned by CT. In the reconstructed coronal/sagittal images, bony landmarks of ACL (anterior: anterior ridge, posterior: blood vessel in tubercle fossa, medial: MIR, lateral: CIR) and AHLM (medial: CIR, lateral: bottom of the slope) were plotted for evaluation. The length of sagittal slices and the width in five coronal slices of the insertion were measured.

Results: The ACL insertion consistently showed a boot-like-shape adjacent to the square shape of AHLM on three-dimensional imaging. The mean ACL sagittal length was 14.5 ± 1.9 mm, while the mean ACL widths (in mm) from anterior to posterior were 12.7 ± 2.7, 8.1 ± 1.9, 7.9 ± 2.0, 7.5 ± 1.5, and 7.2 ± 1.6, which was highly correlated with the tibial plateau size.

Conclusions: The boot-like-shape of the ACL tibial footprint insertion shared the slope of MIR with the rectangular shape of AHLM in young, healthy knees. This study may provide useful information for safe tibial tunnel creation at the time of ACL reconstruction.