The purpose of the study was to characterize the detailed MR anatomy in cadavers and the MR characteristics of the spring ligament complex in asymptomatic subjects.

First, the spring ligament complex was analyzed with high resolution MR imaging of five cadaveric feet and correlation to anatomic dissection was performed. Second, MR examinations of 78 asymptomatic subjects (41 women, 37 men; at least seven women and seven men for each decade from 20 to 70, range 23-83 years, mean 48 years ) were analyzed by two experienced musculoskeletal radiologists. For all three parts, the visibility, the optimal imaging plane, the signal characteristics and the thickness were evaluated.

In cadaveric feet, MR imaging enabled the differentiation of all three ligament parts. The superomedial CNL was visible in all asymptomatic subjects, the medioplantar oblique ligament was seen in 60 (77%) subjects and the inferior longitudinal CNL in 71 (91%) subjects. The superomedial CNL showed a mean thickness of 3.2 mm (range 2-5 mm), was best seen on oblique axial (60%) or coronal plane (40%) with intermediate signal on T1-weighted images (99%) and low signal on T2-weighted images (96%). The medioplantar oblique ligament showed a mean thickness of 2.8 mm (range 1-5 mm), was best seen on oblique axial images (95%) with a typical striated appearance on both T1- and T2-weighted images (82%). The short inferoplantar longitudinal CNL was the thickest ligament with a mean thickness of 4.0 mm (range 2-6 mm). It was best seen on coronal images (69%) with intermediate signal on T1-weighted images (93%) and variable signal on T2-weighted images. Women had a significant thinner superomedial (mean 3.3mm vs 3.5mm, p=0.015, Mann-Whitney- U test) and inferior longitudinal CNL (mean 3.8mm vs 4.2mm, p=0.02) than men. Ligament thickness did not show any correlation to age.

The superomedial and inferior longitudinal CNL are the thickest portions of the spring ligament complex. Both are consistently (>90%) well visible on MR imaging with an intermediate signal on T1-weighted images. The medioplantar oblique ligament is thinner, less consistently (~75%) seen and shows a typical striated appearance.