Static Versus Dynamic Musculoskeletal Ultrasound for Detection of Plantar Plate Pathology.

Musculoskeletal ultrasound (US) is a common modality used to examine plantar plate pathology. Comparison of the diagnostic accuracy of static versus dynamic ultrasound has not been previously published. The objective of this study was to prospectively compare the value of using preoperative static and dynamic ultrasound findings to diagnose plantar plate pathology using intraoperative inspection as the standard of reference. Patients attending a single foot and ankle specialty clinic from August 2012 to June 2013 with clinically suspected plantar plate pathology that was unresponsive to conservative care served as the study population. Static and dynamic ultrasound exams were performed by a single experienced rater and compared to intraoperative findings. The overall accuracy, sensitivity, specificity, positive predictive value and negative predictive value were determined for static and dynamic ultrasound exams. Thirty-six patients (45 lesser metatarsophalangeal joints) were included in this analysis. Of the 36 patients, 29 were females and 7 were males with average age of 57.9 ± 7.8 years (range, 38-73). There were 38 plantar plate tears (84.4%) noted on intraoperative examination. The accuracy, sensitivity, specificity, positive predictive value, and negative predictive value for the static US exam were 80.0%, 81.6%, 71.4%, 93.9%, and 41.7%, respectively. The same values for the dynamic US exam were 88.9%, 100%, 28.6%, 88.3%, and 100%, respectively. Static and dynamic ultrasound techniques are each highly sensitive methods for assessing plantar plate pathology. However, the sensitivity and accuracy of the exam is best when dynamic assessment of the plantar plate is employed. Caution should be used when relying solely on static images to diagnose subtle injuries in this area of the foot.

LEVELS OF EVIDENCE: Diagnostic Level II, Prospective.