Anatomic and MRI study of the subtalar ligamentous support.

The diagnosis of subtalar instability remains difficult both clinically and radiographically. The authors present an anatomic and MRI study of the subtalar ligamentous support. The anatomic study has consisted in dissections and sections of cryoconserved hindfeet (15 cases) which precises the organisation of ligamentous bundles in the lateral (sinus tarsi) and central (canalis tarsi) subtalar compartments, mainly represented by the trilayered inferior extensor retinaculum, the cervical talo-calcaneal ligament and the interosseous talo-calcaneal ligament. MRI study (1.5 tesla) of anatomic specimens was performed according to defined types of sections: sagittal, coronal, coronal oblique, axial transverse. The correlations of anatomic and MRI sections allowed a precise interpretation of the subtalar ligamentous support as anatomically described. A complementary clinical MRI study was performed which allowed the validation of "the inversion test": this test optimizes the visualization of the different ligamentous structures. Relative to the difficulties of conventional imaging procedures, MRI appears of clinical relevance in the diagnosis of subtalar instabilities. This technique allows direct visualization of ligaments (or their rupture) and therefore a better evaluation of subtalar involvement in ankle sprain. This paper present a functional concept in MRI articular ligamentous restraints concern.