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Magnetic resonance imaging (MRI) of the ankle (Figure 1) demonstrated a thickened structure with increased signal in the medial side of the ankle just deep to the posterior tibialis tendon. It courses from the sustentaculum tali of the calcaneus inferiorly and curves around the talar head acting as a sling for the talus and attaches to the medial aspect of the navicular. This structure represents the superomedial calcaneonavicular portion of the spring ligament complex. In addition, increased signal is noted continuing superiorly from the navicular to the medial malleolus of the tibia compatible with the tibiospring ligament, a superficial portion of the deltoid ligament. The posterior tibial tendon is seen coursing just superficial to the spring ligament and is normal in signal and morphology. These findings are compatible with an isolated injury to the spring ligament and the tibiospring ligament. The patient's condition improved with conservative treatment (ie, immobilization in an ankle brace), and surgical repair was not indicated.
The spring ligament complex provides support for the talar head and is one of the static stabilizers of the medial longitudinal arch of the foot along with the plantar fascia and plantar ligaments. These static stabilizers work in conjunction with the main dynamic stabilizer - die posterior tibial tendon. The spring ligament most often is abnormal in posterior tibial tendon pathology resulting in an acquired flat foot deformity.1-2 Isolated spring ligament injury is rare and has been reported in few case reports.3,4
ANATOMY
The spring ligament complex is composed of tihree separate ligaments mat connect me calcaneus to me navicular. Taniguchi et al,5 in a recent comprehensive study, detailed the anatomy of the spring ligament based on me dissection of 48 cadaveric feet.
The largest portion of the spring ligament complex and me portion most frequenfly injured is me superomedial calcaneonavicular ligament (Figure 2). It originates from me middle articular facet of the calcaneus and sustentaculum tali, and attaches to the medial portion of me navicular near the talar articular surface. The deep surface of die ligament is smootii, lined by fibrocartilage, and articulates with the talus forming a sling for me talar head.5 The tibiospring ligament (Figure 2B) attaches to the superomedial calcaneonavicular ligament and continues superiorly to die medial malleolus forming a portion...