Spring Ligament Complex and Posterior Tibial Tendon: MR Anatomy and Findings in Acquired Adult Flatfoot Deformity

The spring ligament complex is an important stabilizer of the medial ankle, together with the posterior tibial tendon (PTT) and the deltoid ligament complex. Lesions in these stabilizers result in acquired adult flatfoot deformity. The spring ligament complex includes three ligaments: the superomedial calcaneonavicular ligament, the medioplantar oblique calcaneonavicular ligament, and the inferoplantar longitudinal calcaneonavicular ligament. Normal MR imaging anatomy of the spring ligament complex and the PTT are described and illustrated in detail. Isolated lesions of the spring ligament complex are rare. In most cases, spring ligament complex lesions are secondary to PTT dysfunction. The best criteria for an injury of the clinically relevant superomedial calcaneonavicular ligament are increased signal on proton-density or T2-weighted sequences with thickening (> 5 mm), thinning (