Is Second Metatarsal Protrusion Related to Metatarsophalangeal Plantar Plate Rupture?

Abstract

<b>OBJECTIVE.</b> The purpose of this study was to determine whether the relative length of protrusion of the second metatarsal, measured on MRI and weight-bearing foot radiography, predicts the diagnosis of second metatarsophalangeal (MTP) joint plantar plate (PP) tear on MRI. <b>MATERIALS AND METHODS.</b> We retrospectively evaluated 166 consecutive patients (211 feet). Patients had undergone weight-bearing foot radiography and forefoot MRI. Using the Coughlin method, two independent observers measured second meta-tarsal protrusion length on radiography and MRI. MRI findings were classified as normal PP, complete PP tear, or degenerative or partial PP tear. <b>RESULTS.</b> Patients had a mean age of 47 ± 14.6 (SD) years, and 131 (78.9%) were women. MRI measurements were highly correlated with radiographic measurements (<i>r</i> = 0.882; 95% CI, 0.866-0.898; <i>p</i> < 0.001). A significant correlation was found between length of protrusion and cases classified as either normal PP or PP tear. Patients with a normal PP had a mean protrusion length of 4.11 ± 1.35 mm on radiographs and 2.61 ± 1.31 mm on MR images, whereas those with a PP tear had a mean protrusion length of 4.75 ± 1.53 and 3.05 ± 1.34 mm, respectively. ROC curve analysis showed that protrusion length cutoff values of 5.47 mm measured on radiographs and 3.17 mm on MR images were correlated with MTP PP tear. <b>CONCLUSION.</b> We identified a linear correlation between second metatarsal protrusion measured on MRI and that measured on radiography, with values about 35% higher for the latter. Our study showed an association between length of protrusion of the second metatarsal and PP rupture and identified a cutoff value for the second meta-tarsal overlength that is associated with these tears.