Incidental Finding of Plantar Plate Pathology on Routine Magnetic Resonance Imaging of the Foot and Ankle

We hypothesized that there would be a comparable and high incidence of an incidental torn plantar plate on routine magnetic resonance imaging (MRI) in asymptomatic patients.

We included adult patients undergoing a foot MRI from 2019 to 2020. Based on the documented reason for MRI, patients were divided into symptomatic and asymptomatic. A separate musculoskeletal radiologist re-evaluated MRI images. Findings were categorized as "torn vs intact." We also used the anatomical grading system (AGS).

We reviewed 218 records, including 165 asymptomatic and 53 symptomatic patients. The chance of finding a plantar plate (PP) tear on MRI of symptomatic patients was 28% (21% in PP2, 5.7% in PP3, 5.7% in PP4, and 2% in PP5), while PP tear in asymptomatic patients was only apparent in 2% of MRIs (1.5% in PP2, 0 in PP3, 0 in PP4, and 0.6% in PP5). Cohen's kappa coefficient was 0.92, showing excellent agreement between the radiologists. Odds calculation revealed that the chance of finding a torn PP in an asymptomatic patient is 2.5%. In comparison, the chance of finding an intact PP in a symptomatic patient is 72%, showing 2.5 times more likely to find an intact PP than a torn PP in symptomatic individuals.

Interestingly, there was a low rate of abnormal PP appearance on MRI in both symptomatic and asymptomatic patients, which suggests that the chance of finding a false-positive PP tear in an asymptomatic patient is minimal and probably negligible.

Level IV diagnostic.