Anatomical relationship between insertion sites, tunnel placement, and lateral meniscus anterior horn injury during single and double bundle anterior cruciate ligament reconstructions: A comparative macroscopic and histopathological evaluation in cadavers

Abstract Purpose The influence of tunnel extension outside the anatomical anterior cruciate ligament (ACL) insertion in single-bundle (SB) or double-bundle (DB) ACL reconstruction is unclear. This study aimed to investigate the anatomical relationship between ACL insertion and tunnel extension in SB and DB ACL reconstruction, and the impact of tibial tunnel extension to the insertion of anterior horn of lateral meniscus in terms of injury. Methods Forty-six paired cadaver knees (mean age, 82.7 ± 10.7 years) were used. Right and left knees were used for SB (10 mm) and DB tunnel reaming (6 mm for the anteromedial and posterolateral bundles). Tibial and femoral tunnels were created to aim at the center of the ACL insertion by arthroscopic visualization. The relationship between tunnel extension and ACL insertion was evaluated macroscopically, and there ratio in two groups were compared by chi-square test. Further, the relative risk for meniscus injury based on tunnel placement was estimated. Coronal section of tibia and parallel section to Blumensaat line in femur were prepared to evaluate the relationship among tunnel position, ACL insertion, and anterior horn of the meniscus histologically. Results Tibial tunnel extension out of the ACL insertion was observed macroscopically in 9 (39.1%) knees of the SB group, and 3 (13.0%) of the DB group (p = 0.045). In femoral tunnels, extension out of the ACL insertion was seen in 8 (34.8%) knees of the SB group and 1 (4.3%) of the DB group (p = 0.011). Partial injuries of the lateral meniscus anterior horn (LMAH) were observed in 5 (21.7%) knees of the SB group and 1 (4.3%) knee of the DB group (p = 0.091). The relative risk for LMAH injury was calculated as 5.0 (odds ratio, 6.1). Microscopically, SB tunnels appeared to expand out of ACL insertion, both in the femur and tibia. Conclusions The incidence of tunnel extension out of the ACL insertion in femur and tibia were higher with SB than with DB reconstruction. Furthermore, injury rate of the LMAH in the DB group was lower.