The serial changes of static anterior tibial subluxation on MRI after double-bundle anterior cruciate ligament reconstruction

OBJECTIVES: Static anterior tibial subluxation after an anterior cruciate ligament (ACL) injury highlights the abnormal relationship between the tibia and femur in patients with ACL insufficiency. One of the aims of ACL reconstruction is to restore the normal tibiofemoral relationship. However, several studies indicated that an abnormal tibiofemoral relationship remained after single-bundle (SB) ACL reconstruction. The purpose of this study was to determine the serial changes of static relationship between tibia and femur in patient who had double-bundle ACL reconstruction with acute and chronic injuries. METHODS: Thirty five patients who underwent double-bundle ACL reconstruction between January 1 to July 31, 2017 were included in this prospective study and divided two groups: the acute ACL injury group and the chronic ACL injury group (more than 6 month after injury). All participants underwent preoperative and postoperative magnetic resonance imaging (MRI) at 3 weeks, 3, 6 and 12 months. Anterior tibial subluxation (ATS) of the medial and lateral compartments relative to the femoral condyles were measured on MRI. RESULTS: There were no significant differences in the age and KT side to side difference between both groups (Table 1). The ATS measurements are shown in table 2. In lateral compartment, the ATS in the acute ACL injury group was 5.3mm before surgery, while it was -0.31mm, 3.4mm, 3.5mm and 4.9mm at 3 weeks, 3, 6, 12months after surgery, respectively. The ATS in the chronic ACL injury group was 6.7mm before surgery, while it was 0.47mm, 3.9mm, 4.6mm and 5.9mm at 3 weeks, 3, 6, 12months after surgery, respectively. No significant difference was found between 2 groups. In medial compartment, the ATS in the acute ACL injury group was 1.8mm before surgery, while it was -1.6mm, 0.28mm, 0.93mm and 2.1mm at 3 weeks, 3, 6, 12months after surgery, respectively. The ATS in the chronic ACL injury group was 2.5mm before surgery, while it was -1.4mm, 1.6mm, 1.7mm and 3.0mm at 3 weeks, 3, 6, 12months after surgery, respectively. No significant difference was found between 2 groups. CONCLUSION: In both of lateral and medial compartment, the ATS was not significant different between acute and chronic ACL injuries before surgery. In lateral compartment, at 3 weeks, 3months and 6months after surgery, ATS was significantly less than before surgery in both groups. At 12 months, ATS was not significant different from before surgery in both groups. In medial compartment, at 3 weeks, ATS were significantly less than before surgery in both groups. After 3 months, ATS was not significant different from before surgery in both groups. The ATS was not significant different between acute and chronic ACL injuries in the same period after surgery.