Sonography of the superomedial part of the spring ligament complex of the foot: a study of cadavers and asymptomatic volunteers

Objective To evaluate the ability of high-resolution sonography for assessing the thickness and echogenicity of the superomedial part of the normal spring ligament in the foot in cadavers and asymptomatic volunteers. Materials and methods The superomedial part of the normal spring ligament of four cadaveric feet was imaged with a high-resolution linear array transducer. Upon localization, the ligament was injected with 0.1% methylene blue with sonographic guidance. A posteromedial approach was used to dissect the feet immediately following injection to confirm accurate identification of the ligament. The bilateral ligaments in 40 asymptomatic adult volunteers were subsequently imaged. Results Surgical dissection confirmed the accurate injection of methylene blue into all four cadaveric ligaments. The superomedial part of the normal spring ligament was identified bilaterally in all of the 40 asymptomatic volunteers, with a mean thickness of 3 mm in longitudinal short axes. The ligament was echogenic relative to surrounding fat, and it was thinner in women. Differences in ligament measurements with respect to age, sex, side (left vs. right) and foot dominance were not significant. The volunteers' height, weight and body mass index had a weakly positive correlation with ligament thickness. Conclusion High-resolution ultrasound can be used to identify and measure the thickness of the superomedial part of the normal spring ligament. The provided baseline measurements for the normal ligament could prove valuable when assessing the abnormal ligament.