The occurrence rate and character of anterior horn of lateral meniscus (AHLM) injury in anatomical single bundle anterior cruciate ligament reconstruction were assessed in 100 females. The occurrence rate of AHLM injury was 15%. The injury group had significantly shorter distance of the slope of the medial intercondylar ridge and greater lateral meniscal extrusion compared with the intact group.
The risk of iatrogenic anterior horn of lateral meniscus (AHLM) injury in anterior cruciate ligament (ACL) reconstruction was reported in many cadaveric studies. However, the occurrence of AHLM injury in individuals with small skeletons like Asian people is unknown. The purpose of the study was to investigate the occurrence rate and the character of AHLM injury in anatomical single bundle ACL reconstruction.
Between April 2011 and February 2018, 100 female patients underwent anatomical single bundle ACL reconstruction. All surgeries were performed using hamstring autograft. A round tibial tunnel was created at the anatomical insertion of the ACL, and was determined to be 7.0 to 9.0 mm depending on the graft diameter. Using computerized tomography scan taken 1 week after surgery, we retrospectively assessed the anatomical relationship between predicted AHLM insertion and the tibial tunnel, and divided the patients into partial AHLM injury and intact groups. As bone landmarks for grouping, we measured the distance from the apex to the bottom of the slope of medial intercondylar ridge (SMIR) and the insertion of AHLM. We defined the AHLM injury index by dividing the distance of AHLM insertion by SMIR, with less than 40% of AHLM injury index defined as AHLM injury. Height, body weight, body mass index (BMI), the length between bone landmarks, size of tibial tunnel, and the change in amount of lateral meniscal extrusion (LME) between preoperative and 6 months postoperative MRI were compared between the two groups. The data were analyzed using the Mann-Whitney U test, and the level of significance was set at a=0.05.
Fifteen of 100 patients (15%) had suspected partial AHLM injury by CT scan. The mean ages of the injury and intact groups were 23.7±13.3 and 24.7±12.5. In the injury group, the distance from the apex to the bottom of the SMIR was significantly shorter compared with the intact group (15.1±1.9 vs 16.9±1.4 mm: P<0.05); the change in LME was significantly greater than that in the intact group (0.9±0.6 vs 0.3±0.5 mm: P=0.001). Tibial tunnel diameter in the 15 injury group patients was 7.0 mm in 1 case, 8.0 mm in 7 cases, 8.5 mm in 4 cases, and 9.0 mm in 3 cases. There were no significant differences between the two groups in other assessment measurements (height [cm] 158.3±5.8 vs 159.8±5.9, P=0.41; body weight [kg] 57.8±9.1 vs 56.3±8.8, P=0.56; BMI 22.9±2.9 vs 21.9±2.7, P=0.07; tibial tunnel [mm] 8.2±0.4 vs 8.0±0.6, P=0.38).
AHLM injury in anatomical single bundle ACL reconstruction was suspected in 15 of 100 females. In the injury group, the distance from the apex to the bottom of the SMIR was significantly shorter and the change in LME was significantly greater than those in the intact group. In cases of patients with small skeletons, surgeons should be aware that AHLM injury will occur if the tunnel deviates even a little.