Anterolateral knee ligament may have little impact on anterior knee laxity when ilio-tibial band is preserved.
The anatomy of the antero-lateral ligament (ALL) of the knee has been described on anatomic preparation, suggesting that this ligament might be a restraint of knee anterior drawer. However, experimental results showed conflicting results about the impact of the ALL on knee stability. The goal of the study was to measure the changes in the anterior knee laxity according to the status of the antero-lateral ligament (ALL) and of the anterior cruciate ligament (ACL). We hypothesized that section of the ALL will significantly increase the anterior tibia translation.
Material And Methods
5 pairs of fresh frozen gross specimens were analyzed. The knee was positioned at 20° of flexion on a special splint. An increasing calibrated postero-anterior force was applied; the anterior tibia translation was measured by a navigation system for each applied force. Three settings were used for each knee: intact ACL and ALL, section of the ACL or ALL (randomly assigned to each knee of a pair), section of both ACL and ALL. The reference for each knee was the measurement by intact knee. The primary criterion was the anterior tibia translation at 250 N. Secondary criteria was the stiffness of the knee in anterior translation (slope of the curve force vs anterior laxity). The paired increase of anterior tibia translation was calculated for each situation. The results were compared between all couples of situations with a Mann-Whitney test at a 0.05 level of significance. Similar process was performed for stiffness.
The mean anterior tibia translation at 250 N was 5.3 ± 2.8 mm for intact knees. There was no significant difference between right (4.8 ± 3.2 mm) and left (5.8 ± 2.5 mm) knees. The mean paired increase was 1.2 mm after isolated ALL section, 9.0 mm after isolated ACL section, and 6.1 mm after combined ALL and ACL section. There was no significant increase after isolated ALL section. There was a significant increase after isolated ACL section. There was no significant increase after additional ALL section by ACL deficient knees.
The mean knee stiffness in anterior translation for intact knees was 0.015 ± 0.02 N/mm. The mean paired increase was 0.01 N/mm after isolated ALL section, 0.038 N/mm after isolated ACL section, and 0.021 N/mm after combined ALL and ACL section. There was no significant increase after isolated ALL section. There was a significant increase after isolated ACL section. There was no significant difference after additional ALL section by ACL deficient knees.
The main result of this study is that section of the ALL did not impact anterior laxity and stiffness of the knee in comparison to normal knee, neither isolated or by ACL deficient knee.?The expected role of ALL in controlling anterior knee laxity could not be confirmed. We suggest that preservation of the iliotibial band may be a major explanation for these conflicting results.
We suggest that the potential influence of the ALL on knee stability should be further investigated before performing routine ALL reconstruction. ALL may have little impact on anterior tibia translation when ilio-tibial band is preserved.