[The effect of the tibial tunnel fixation level on the results of cyclic loading in anterior cruciate ligament reconstruction].

Abstract

This study was designed to compare the biomechanical characteristics of non-anatomic (far from joint) and anatomic (close to joint) levels of tibial tunnel fixation with soft tissue graft using a soft tissue interference screw in anterior cruciate ligament (ACL) reconstruction. Twelve bovine tibiae and digital extensor tendons were divided into two homogeneously equal groups after removing soft tissues. Tibial tunnels were prepared with a 7-mm drill with the use of an ACL guide adjusted to 45 degrees . Each tunnel was then dilated to 9 mm in 0.5 mm increments. Digital extensor tendons were fixed at non-anatomic (group I) or anatomic (group II) tibial tunnel levels with a soft tissue metal interference screw, 9 x 30 mm in size. All the specimens were cycled 500 times from 50 to 250 N with 1 Hz frequency in a servo-hydraulic testing machine followed by ultimate load at-failure testing at a rate of 20 mm/min. Statistical analyses were made using the Mann-Whitney U-test. The mean screw insertion torque values were 8.2+/-2.4 Nm and 7.8+/-2.3 Nm in groups I and II, respectively (p=0.88). The mean values of graft displacement (1.9+/-0.75 mm versus 2.2+/-1.2 mm, p=0.63) and stiffness (132.72+/-10.93 N/mm versus 125.14+/-15.93 N/mm, p=0.63) did not differ significantly. The biomechanical properties of ACL reconstruction with soft tissue graft fixation using a soft tissue interference screw are not influenced by the level of tibial tunnel fixation.