Magnetic resonance and cadaveric findings of the incidence of plantaris tendon.

A retrospective review of 63 Magnetic Resonance Image studies (yielding 86 ankles) was conducted to find the incidence of the plantaris tendon. Radiographically, the plantaris tendon was visualized 62.8% of the time. Surgical confirmation of this tendon during 18 achilles surgeries yielded 13 "true positives" and 4 "true negatives". Sensitivity was 92.8%; specificity and positive predictive value was 100%, respectively. As a comparison, forty cadaveric specimens were evaluated as well, with the incidence of the plantaris found to be 97.5%. These findings may be useful when considering MRIs as a screening tool for the presence of plantaris tendon. When axial images were 4 mm or less, the plantaris tendon was more easily visualized. A Chi-squared test examining for differences of axial sections greater than 4 mm was not significant. (P=0.2). This is important if one is to use MRI to screen for the plantaris (for graft purposes).