Utility of the FABS MRI sequence in the evaluation of distal biceps pathology

Objective The flexed elbow, abducted shoulder, forearm supinated (FABS) position has been described as a method of imaging the distal biceps tendon on its long axis. The purpose of this study is to evaluate whether obtaining additional MR imaging in the FABS position changes the radiologist’s assessment of the distal biceps tendon compared with traditional sequences only. Materials and methods Blinded review of 46 elbow MRIs when viewed without (−F) and with (+F) FABS sequences available was performed by two independent readers. The biceps tendon was graded in each case using a 0–3 scale, and a confidence level of 0–10 was assigned. −F and +F reads were compared. Reads were also compared with the surgical reference standard when available, 12 patients. Results Pooled intra rater reliability was 0.800 (0.714, 0.886) between the −F and +F groups. Pooled mean confidence was 7.163 (1.252) for the −F group and 8.370 (1.264) for the +F group ( p < 0.001). Pooled diagnostic accuracy was 0.651 (0.420, 0.882) for the −F group and 0.615 (0.456, 0.875) for the +F group compared with the surgical reference standard. Conclusion The FABS sequence changed the radiologist’s impression of the distal biceps tendon in the minority of cases and did not significantly change diagnostic accuracy. We do not recommend its use in the majority of cases. In challenging cases of high-grade partial vs complete tendon tear, FABS may be helpful to identify subtle residual tendon fibers.