AJSM 2016

Over the past decade, there has been an increasing emphasis on anatomic anterior cruciate ligament (ACL) reconstruction to best restore knee kinematics after an ACL tear. Although studies have shown that the position, size and shape of the ACL insertion site are variable, anatomic single-and double-bundle ACL reconstructions have both shown improved outcomes, especially when performed using an individualized technique. However, recent investigations of anatomic ACL reconstruction have highlighted concern over iatrogenic injuries of anterior meniscal root insertions caused by reaming of tibial bone tunnels, specifically the anterolateral meniscal root (ALMR) insertion.

While many studies have investigated the significance of the ACL and potential reconstruction techniques, the complex relationship between the tibial ACL and the lateral meniscus has become a recent area of focus. The ALMR insertion has been described to attach underneath the lateral portion of the ACL insertion with a disorganized fiber network connecting the 2 insertions. An investigation of ACL reconstruction tunnel reaming demonstrated that iatrogenic injuries of the ALMR insertion area occurred in two-thirds of sample groups and that the average area of injuries was at least 25% of the original ALMR insertion area, likely because of this intricate relationship. More importantly, damage to the ALMR insertion caused by tunnel reaming was found to significantly decrease its ultimate failure load. Although variability in tibial ACL tunnel placement has been reported to be relatively consistent between surgeons, with 90% of tibial tunnels within applied literature- based guidelines, these studies of iatrogenic injuries suggest that even well-placed anatomic tunnels may disrupt the ALMR insertion. Because the lateral meniscus has been reported to be an important secondary stabilizer of the knee, particularly during pivot-shift loading,19 the demonstrated risk of iatrogenic injuries to the ALMR insertion during ACL reconstruction may pose a threat to overall knee integrity after this procedure.

While these studies begin to describe the complex relationship and the risk of ACL reconstruction on the ALMR insertion, further investigation of how the 2 insertions interact is necessary to understand and define the 3-dimensional relationship between these 2 structures. To further understand the quantitative anatomy of the insertion relationship, LaPrade reported that, on average, 41% of the ACL insertion area and 63% of the ALMR insertion area overlapped with one another. Microscopic studies of the tibial insertion site have been previously conducted to investigate quantities of fibrocartilaginous zones to relate biomechanical properties of the insertion however, the authors are unaware of any study that has microscopically evaluated the fibrocartilaginous insertion of the tibial insertion with respect to the ALMR insertion, particularly in the sagittal and coronal planes.

Therefore, the purpose of this study was to investigate the microstructural relationship between the tibial ACL and ALMR insertions using scanning electron microscopy (SEM) in the coronal and sagittal planes. It was hypothesized that a significant portion of the ACL would overlap the ALMR insertion in both the coronal and sagittal planes.

Full Article: Overlap Between Anterior Cruciate Ligament and Anterolateral Meniscal Root Insertions

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