Three-dimensional Magnetic Resonance Imaging of the Anterolateral Ligament of the Knee: An Evaluation of Intact and Anterior Cruciate Ligament-Deficient Knees From the Scientific Anterior Cruciate Ligament Network International (SANTI) Study Group.

PURPOSE: To determine the visualization rate of the anterolateral ligament (ALL) in uninjured and anterior cruciate ligament (ACL)-deficient knees using 3-dimensional (3D) magnetic resonance imaging (MRI) and to characterize the spectrum of ALL injury observed in ACL-deficient knees, as well as determine the interobserver and intraobserver reliability of a 3D MRI classification of ALL injury. METHODS: A total of 100 knees (60 ACL deficient and 40 uninjured) underwent 3D MRI. The ALL was evaluated by 2 blinded orthopaedic surgeons. The ALL was classified as follows: type A, continuous, clearly defined low-signal band; type B, warping, thinning, or iso-signal changes; and type C, without clear continuity. The comparison between imaging performed early after ACL injury (<1 month) and delayed imaging (>1 month) was evaluated, as was intraobserver and interobserver reliability. RESULTS: Complete visualization of the ALL was achieved in all uninjured knees. In the ACL-deficient group, 24 knees underwent early imaging, with 87.5% showing evidence of ALL injury (3 normal, or type A, knees [12.5%], 18 type B [75.0%], and 3 type C [12.5%]). The remaining 36 knees underwent delayed imaging, with 55.6% showing evidence of injury (16 type A [44.4%], 18 type B [50.0%], and 2 type C [5.6%]). The difference in the rate of injury between the 2 groups was significant (P = .03). Multivariate analysis showed that the delay from ACL injury to MRI was the only factor (negatively) associated with the rate of injury to the ALL. Interobserver reliability and intraobserver reliability of the classification of ALL type were good (κ = 0.86 and κ = 0.93, respectively). CONCLUSIONS: Three-dimensional MRI allows full visualization of the ALL in all normal knees. The rate of injury to the ALL in acutely ACL-injured knees identified on 3D MRI is higher than previous reports using standard MRI techniques. This rate is significantly higher than the rate of injury to the ALL identified on delayed imaging of ACL-injured knees. LEVEL OF EVIDENCE: Level IV, diagnostic, case-control study.

[Visualization of Anterolateral Ligament of the Knee Using 3D Reconstructed Variable Refocus Flip Angle-Turbo Spin Echo T2 Weighted Image].

Anterolateral ligament (ALL) is one of the lateral structures in the knee that contributes to the internal rotational stability of tibia. ALL has been referred to in some recent reports to re-emphasize its importance. We visualized the ALL on 3D-MRI in 32 knees of 27 healthy volunteers (23 male knees, 4 female knees; mean age: 37 years). 3D-MRIs were performed using 1.5-T scanner [T(2) weighted image (WI), SPACE: Sampling Perfection with Application optimized Contrast using different flip angle Evolutions] in the knee extended positions. The visualization rate of the ALL, the mean angle to the lateral collateral ligament (LCL), and the width and the thickness of the ALL at the joint level were investigated. The visualization rate was 100%. The mean angle to the LCL was 10.6 degrees. The mean width and the mean thickness of the ALL were 6.4 mm and 1.0 mm, respectively. The ALL is a very thin ligament with a somewhat oblique course between the lateral femoral epicondyle and the mid-third area of lateral tibial condyle. Therefore, the slice thickness and the slice angle can easily affect the ALL visualization. 3D-MRI enables acquiring thin-slice imaging data over a relatively short time, and arbitrary sections aligned with the course of the ALL can later be selected.