Deltoid Ligament Insufficiency in Hindfoot Arthrodesis for Progressive Collapsing Foot Deformity: A Retrospective Analysis.

Abstract

In advanced stages of progressive collapsing foot deformity, attenuation of the deltoid ligament can contribute to valgus tilt of the talus within the ankle mortise. Hindfoot arthrodesis is the standard treatment for late-stage progressive collapsing foot deformity; however, unrecognized deltoid ligament insufficiency may predispose patients to postoperative tibiotalar valgus. To evaluate the accuracy of preoperative MRI in detecting deltoid ligament insufficiency in patients undergoing hindfoot arthrodesis for late-stage PCFD. 37 feet from 35 patients undergoing arthrodesis for advanced PCFD were reviewed. Preoperative MRI findings were compared to intraoperative valgus stress radiographs. Sensitivity, specificity, and odds ratio for MRI detecting deltoid incompetence were calculated. Deltoid ligament disruption occurred in 18.9% (7/37) of cases as confirmed by both MRI and intraoperative stress testing. 35.1% (13/37) had a negative MRI but a positive stress exam. An additional 10.8% (4/37) had MRI-positive findings unconfirmed by stress test. Overall, 54.1% (20/37) demonstrated deltoid ligament insufficiency in intraoperative stress examination. MRI identified deltoid tears in 29.7% (11/37) of cases, yielding a sensitivity of 63.6% and specificity of 50.0%. The odds ratio of a positive MRI predicting actual deltoid ligament insufficiency was 1.75. MRI as a standalone modality demonstrated limited accuracy in detecting functionally significant deltoid laxity. Functional deltoid incompetence should be considered in surgical planning, and adjunctive intraoperative assessments should be performed to confirm deltoid instability. Prospective studies are needed to determine the best method of reducing the incidence of postoperative tibiotalar valgus. Level III evidence.