Radiographic Identification of the Deltoid Ligament Complex of the Medial Ankle

Abstract

Background: An injury to the deltoid ligament complex of the ankle can require surgical intervention in cases of chronic instability. There is an absence of data describing medial ankle ligament anatomy on standard radiographic views. Purpose: To quantitatively describe the anatomic origins and insertions of the individual ligamentous bands of the superficial and deep deltoid on standard lateral and mortise radiographic views with reference to osseous landmarks and anatomic axes. Study Design: Descriptive laboratory study. Methods: Twelve nonpaired, fresh-frozen cadaveric foot and ankle specimens were utilized. Specimens were dissected free of all overlying soft tissue to identify individual ligamentous bands of the superficial and deep deltoid ligaments and to isolate their distinct origins and insertions. Footprint centers were identified on standard lateral and mortise radiographs by 2-mm stainless steel spheres embedded at the level of the cortical bone. Distances to osseous landmarks were measured independently by 2 blinded reviewers to calculate mean distances and evaluate reliability and repeatability measures using intraclass correlation coefficients. Results: Varying subsets of the 4 superficial deltoid bands including the tibionavicular (12/12), tibiospring (12/12), tibiocalcaneal (9/12), and superficial posterior tibiotalar (9/12) ligaments were found across specimens. On the lateral view, the tibionavicular ligament was the most anterior and attached 7.6 ± 1.9 mm superior and anterior to the inferior tip of the medial malleolus. The tibiospring ligament attached 12.1 ± 2.2 mm superior and anterior to the inferior tip of the medial malleolus and attached to the spring ligament, which coursed from its origin 12.3 ± 1.6 mm anterior and slightly inferior to the posterior point of the sustentaculum tali to its insertion on the navicular tuberosity. The tibiocalcaneal ligament and superficial posterior tibiotalar ligament were found posteriorly in the majority of specimens. Two constituents of the deep deltoid, including the deep anterior tibiotalar (11/12) and deep posterior tibiotalar (12/12) ligaments, were found in the majority of specimens. The deep posterior was larger and coursed from the tibia, 8.1 ± 2.2 mm posterior and superior to the inferior tip of the medial malleolus, to its attachment on the talus, 15.5 ± 2.4 mm superior and anterior to the posterior inferior point of the talus on the lateral view. Conclusion: Quantitative radiographic relationships describing the anatomic origins and insertions of the individual superficial and deep deltoid constituents were defined with excellent reliability and reproducibility. Clinical Relevance: Radiographic parameters will augment current anatomic data by assisting with preoperative planning, intraoperative guidance, and postoperative assessment. These radiographic guidelines will facilitate the development of novel anatomic reconstructions and allow surgeons to plan the locations of reconstruction tunnels.