Effect of Scan Plane and Arthrography on Visibility and Interobserver Agreement of the Equine Distal Sesamoidean Impar Ligament on Magnetic Resonance Images

Abstract In magnetic resonance imaging (MRI) examinations, moderate to severe changes of the distal sesamoidean impar ligament (DSIL) were found in horses with lameness localized to their feet. Histologic abnormalities were detected more commonly in lame horses. Because of its heterogeneity and small thickness, evaluation of the DSIL in MRI can be challenging. The aim of the study was to determine the optimal sequence and the ideal transverse perpendicular angle for visualization of the DSIL before and after arthrography of the distal interphalangeal joint (DIPJ). Twenty-five cadaver forelimbs were examined with low-field MRI. Sagittal, frontal, and three different angled transverse planes were obtained before and after arthrography of the DIPJ. All planes were acquired in T1w (weighted) Gradient Recall Echo (GRE), T2∗w GRE, T2w Fast Spin Echo (FSE), and Short Tau Inversion Recovery (STIR) FSE and visualization of the DSIL was scored by two observers. Visualization of the DSIL was best on sagittal T2w FSE and STIR FSE images. All transverse planes were inferior compared with sagittal sequences. After arthrography of the DIPJ, visualization of the DSIL origin improved in sagittal T2w FSE sequences, and agreement between observers increased for sagittal T2w FSE and STIR FSE images. Sagittal T2w FSE and STIR FSE images allowed good visualization of the DSIL in low-field MRI. Visualization of the DSIL did not improve for altered angled transverse sequences but increased with arthrography of the DIPJ. Subjective influence between different observers was found but decreased with DIPJ arthrography.