MR in the evaluation of new anterior cruciate ligament and tibial tunnel position: correlation with clinical and functional features.

PURPOSE: This study aimed to evaluate correlations between the position of the tibial tunnel, its alignment with the ligament-screw system, presence of intratunnel fluid, position of the tibial tunnel with respect to the Blumensaat line and clinical knee stability in patients who underwent arthroscopic reconstruction of the anterior cruciate ligament (ACL), by using magnetic resonance (MR) imaging. MATERIALS AND METHODS: Forty-eight patients (40 men, eight women; mean age, 31 years) underwent arthroscopic reconstruction of the ACL using double-strand semitendinosus and gracilis tendons. The new ACL was fixed to the tibial tunnel using Bio-Intrafix (Mitek). All patients underwent MR imaging 12 months after surgery and clinical evaluation at 6 and 12 months using the International Knee Documentation Committee (IKDC) scoring system. MR imaging and clinical features were correlated using the Mann-Whitney U test for continuous variables and Fisher's exact test for categorical variables. RESULTS: Forty-one patients were clinically stable (groups A and B according to the IKDC test) and seven were unstable (group C). Mean values of tibial tunnel position in clinically unstable vs stable patients were, respectively, -3.6 ±3.8 mm vs. -2.8±3.8 mm in relation to the Blumensaat line (p=0.5712) and 77.3°±11.3 vs. 72.5°±5.5 as concerned the angle measured on the coronal view of the new ACL (p=0.3248); fluid was present in the tibial tunnel in 42.9% and 9.8% of cases, respectively (p=0.2104). MR imaging showed misalignment of ligament screw and tibial tunnel in 57.1% of patients in group C and in 12.2% in groups A and B (p=0.017). CONCLUSIONS: Misalignment of the ligament-screw system and the tibial tunnel and the presence of fluid in the tibial tunnel appear to be directly correlated with clinical instability.