Background: The spring ligament has been reported to be composed of
the inferior calcaneonavicular and superomedial calcaneonavicular ligaments.
We investigated the lower layer of the spring ligament fibrocartilage complex
under the fibrocartilaginous surface, identified three distinct structures,
and examined the morphology and running patterns of their fiber bundles.
Methods: Forty-eight cadaveric feet were examined. After ablation of
the ankle joint and extirpation of the talus, the surface cartilage of the
spring ligament fibrocartilage complex was carefully removed with forceps, and
the length, width, and thickness of the three components of the complex were
measured with calipers.
Results: The three components of the spring ligament complex are the
superomedial calcaneonavicular ligament, the inferior calcaneonavicular
ligament, and a structure that we termed the third ligament, which
comprises fibers running from the notch between the calcaneal facets to the
navicular tuberosity.
Conclusions: We demonstrated a third component of the spring
ligament; this component runs from the notch between the anterior and middle
calcaneal facets to the tubercle of the navicular in the lower layer of the
spring ligament complex, lying beneath the cartilaginous surface of the
complex.
Clinical Relevance: More accurate knowledge of the anatomy of the
spring ligament complex will enhance our understanding of its role in the
support of the head of the talus and, potentially, its critical interactions
with the posterior tibial tendon in this regard.