Ligament structures in the tarsal sinus and canal.

BACKGROUND: The concrete anatomy and functional characteristics of the subtalar ligaments have been a matter of debate that some believe has hampered the progress of clinical ligament reconstruction.

METHODS: In 32 fresh-frozen cadaver feet, the course of the inferior extensor retinaculum (IER) and other subtalar ligaments was carefully measured and photographed both from the portal of the tarsal sinus and from a posterior view.

RESULTS: The IER inserted inside the tarsal sinus and canal by means of 3 roots: a lateral, an intermediate, and a medial one. These roots, along with the tarsal canal, divided the subtalar space into 3 parts. In front of the IER and inside the tarsal sinus, the thick cervical ligament (CL) lay at a 45-degree angle to the calcaneus. Behind the IER and inside the posterior capsule, in most cases (25 of 32 specimens), the posterior capsular ligament (PCaL) lay directly in front of the posterior talocalcaneal facet. Inside the tarsal canal, the fan-shaped medial root of the IER spread from outside upper lateral to lower medial, and the interosseous talocalcaneal ligament (ITCL) ran from upper medial to lower lateral; fibers of these 2 ligaments blended tightly together to form a V-shaped ligament complex. Just anterior to this complex in some cases (20 of 32 specimens), a short narrow upright ligament, the tarsal canal ligament (TCL), was located behind the middle talocalcaneal joint.

CONCLUSION: The results of this study show that the CL is the primary ligament in the tarsal sinus and that the ITCL is a thin single band rather than a strong bilaminar ligament located inside the tarsal canal. Instead, the medial root of the IER is the primary ligamentous structure in the tarsal canal.

CLINICAL RELEVANCE: The anatomical description provided here may provide a more accurate theoretical foundation for clinical subtalar stability restoration.