Imaging Appearance of the Normal and Partially Torn Ligamentum Teres on Hip MR Arthrography

Abstract

The purpose of this study was to evaluate the MR arthrographic appearance of the normal and partially torn ligament teres and to determine if there are imaging criteria for diagnosing partial tears of the ligamentum teres. One hundred sixteen patients underwent preoperative MR arthrography and hip arthroscopy. Each MR examination was evaluated independently by two musculoskeletal radiologists for the following: size and width of the ligamentum teres in the proximal, mid, and distal thirds of the ligamentum teres; overall length of the ligamentum; number of bundles (1-3); signal intensity (SI) within the ligamentum teres (low, intermediate, high); ligamentum teres fibers (normal, attenuated, thickened, wavy); ligamentum teres integrity (not torn, degenerated, frayed, partial tear); and femoral head edema at the ligamentum teres origin. Statistical analysis was performed using the Kruskal-Wallis rank sum test and Fisher exact test. Twelve of 116 (10%) subjects had partial ligamentum teres tears. One hundred four subjects had an intact ligamentum teres. The average size and width of the intact ligamentum teres was 12.6 × 4.38, 14.9 × 3.5, and 14.3 × 2.7 mm for proximal, mid, and distal, respectively, with an overall length 27.7 mm. It was most common to visualize two bundles in the proximal portion of the normal ligamentum teres (61 and 64/116). Low, intermediate, and high SI was common on all pulse sequences in normal and partially torn ligamentum teres for both readers (p = 0.33-0.84). For reader 1, there was no statistical difference between ligamentum teres fiber appearance in partial tears (p = 0.20). In contrast, reader 2 found partial tears associated with attenuated and wavy appearance (p = 0.003). Reader 1 diagnosed five of 12 (42%), and reader 2 diagnosed eight of 12 (67%) of the partial ligamentum teres tears (p = 0.47 and p = 0.0004). Edema of the femoral ligamentum teres origin was not associated with partial tears (p = 0.33-0.86). Retrospective review revealed that six partial tears had intra substance linear high SI on T2 images and peripheral irregularity, whereas four other tears had high SI within the ligamentum teres fibers without peripheral irregularity. The intact and partially torn ligamentum teres can have similar imaging findings on MR arthrography, making the diagnosis of partial ligamentum teres tears difficult. High SI within the substance of the fibers and irregularity suggest partial tearing; however, further research is warranted.