Radiographic Anatomy of the Lateral Ankle Ligament Complex: A Cadaveric Study

Abstract

Background: When lateral ankle sprains progress into chronic lateral ankle instability (CLAI), restoring precise anatomic relationships of the lateral ankle ligament complex (LALC) surgically is complex. This study quantifies the radiographic relationships between the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and prominent osseous landmarks visible under fluoroscopy to assist in perioperative practices for minimally invasive surgery for CLAI.

Methods: Ten fresh frozen ankle specimens were dissected to expose the LALC and prepared by threading a radiopaque filament through the ligamentous footprints of the ATFL and CFL. Fluoroscopic images were digitally analyzed to define dimensional characteristics of the ATFL and CFL. Directional measurements of the ligamentous footprints relative to the lateral process of the talus and the apex of the posterior facet of the calcaneus were calculated.

Results: Dimensional measurements of the ATFL were a mean length of 9.3 mm, fibular footprint of 9.4 mm, and talar footprint of 9.1 mm. Dimensional measurements of the CFL were a mean length of 19.4 mm, fibular footprint of 8.2 mm, and calcaneal footprint of 7.3 mm. From the radiographic apparent tip of the lateral process of the talus, the fibular attachment of the ATFL was found 13.3 mm superior and 4.4 mm posterior, whereas the talar attachment was found 11.5 mm superior and 4.8 mm anterior. From the radiographic apparent posterior apex of the posterior facet of the calcaneus, the fibular attachment of the CFL was found 0.2 mm inferior and 6.8 mm anterior, whereas the calcaneal attachment was found 14.3 mm inferior and 5.9 mm posterior.

Conclusion: The ATFL and CFL were radiographically analyzed using radiopaque filaments to outline the ligamentous footprints in their native locations. These ligaments were also localized with reference to 2 prominent osseous landmarks. These findings may assist in perioperative practices for keyhole incision placement and arthroscopic guidance. Perfect lateral ankle joint imaging with talar domes superimposed is required to be able to do this.

Clinical relevance: Radiographic evaluation of the ATFL and CFL with reference to prominent osseous landmarks identified under fluoroscopy may assist in perioperative practices for minimally invasive surgery to address CLAI for keyhole incision placement and arthroscopic guidance.

Keywords: anatomic landmarks; ankle instability; ankle lateral ligaments; anterior talofibular ligament; calcaneofibular ligament; fluoroscopy; minimally invasive surgery.

Graphical abstract

Figure 1.

Representative anatomical diagram of specimen preparation demonstrating RAY-TEC filaments (dashed lines) weaved into footprints of (A) ATFL and (B) CFL. Image courtesy of Complete Anatomy (3D4Medical).

Figure 2.

Gross anatomic dissection images. (A) Untrimmed RAY-TEC filaments weaved into the bony attachment sites of the ATFL and CFL footprints. (B) Trimmed RAY-TEC filaments ready for radiographic imaging. (F) Fibula. (T) Talus. (C) Calcaneus.

Figure 3.

Dimensional measurements for ATFL and CFL. (A) Original radiograph highlighting RAY-TEC wire at the ligamentous footprints on the fibula, talus, and calcaneus. (B) Demonstration of image analysis performed to define ligament dimensions: (a) ATFL length, (b) ATFL fibular footprint, (c) ATFL talar footprint, (d) CFL length, (e) CFL fibular footprint, (f) CFL calcaneal footprint, (g) length-standard depth gauge at 10 mm.

Figure 4.

Directional measurement vectors used to find the relative distance from the lateral talar process to the (A) fibular and (B) talar attachments of the ATFL and from the apex of the posterior facet of the calcaneus to the fibular (C) and calcaneal (D) attachments of the CFL. The lateral process of the talus and the apex of the posterior facet of the calcaneus are illustrated with red boxes. [See online article for color figure.]

Figure 5.

Directional measurements for ATFL and CFL in reference to respective bony prominences. (A) Directional measurements for fibular (b) and talar (c) footprints of the ATFL in reference to the lateral talar process (a). (B) Directional measurements for fibular (e) and calcaneal (f) footprints of the CFL in reference to the posterior calcaneal facet (d), and length-standard depth gauge at 10 mm (g).