Correlation between knee laxity and graft appearance on magnetic resonance imaging after double-bundle hamstring graft anterior cruciate ligament reconstruction.

BACKGROUND: In recent years, double-bundle (anteromedial bundle [AMB], posterolateral bundle [PLB]) anterior cruciate ligament reconstruction has developed into an accepted practical surgical procedure; therefore, its efficacy needs to be established. HYPOTHESIS: Multiple-sliced 2-dimensional magnetic resonance imaging allows evaluation of each bundle separately. Both bundles are important for knee stability, and each bundle has a role in the prevention of knee instability. Knee laxity testing will correlate with the magnetic resonance imaging appearance of the individual graft bundles. STUDY
DESIGN: Cohort study; Level of evidence, 2.
METHODS: A total of 97 double-bundle anterior cruciate ligament reconstructions were evaluated 1 year after surgery, including side-to-side difference of KT-2000 arthrometer and pivot shift test. T2-weighted 2-dimensional magnetic resonance images were captured in the middle plane of each bundle to express magnetic resonance signals of each bundle. The magnetic resonance signals were divided into 3 grades: grade I, low-intensity signal; grade II, high-intensity signal within 50%; and grade III, high-intensity signal greater than 50%.
RESULTS: Anterior laxity in AMB grade II (PLB I, 3.5 +/- 1.7 mm; PLB II, 4.5 +/- 1.9 mm) was significantly larger than in AMB grade I (PLB I, 1.9 +/- 1.7 mm; PLB II, 2.1 +/- 1.7 mm) with statistical difference (P = .025 in PLB I; P = .002 in PLB II). A positive rate in pivot shift test in PLB II (48%) was significantly larger than in PLB I (21%) with statistical difference (P = .031).
CONCLUSIONS: Varying magnetic resonance signals according to the bundle indicate role differences of each bundle in knee stability. These results imply that the AMB has a major role in preventing anterior translation of the tibia and the PLB has a major role in preventing anterolateral rotatory instability.