Is Second Metatarsal Protrusion Related to Metatarsophalangeal Plantar Plate Rupture?

OBJECTIVE. 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. MATERIALS AND METHODS. 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. RESULTS. 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 (r = 0.882; 95% CI, 0.866-0.898; p < 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. CONCLUSION. 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.

Lesser metatarsophalangeal joint instability: prospective evaluation and repair of plantar plate and capsular insufficiency.

BACKGROUND: Anatomical dissection of the second metatarsophalangeal (MTP) joint suggests that the plantar plate is the major stabilizing structure of the joint due to its central location and multiple important attachments. Many surgical procedures have been recommended when conservative treatment has failed, but some have had limited clinical success. The aim of our prospective study was to show the results obtained in the treatment of a group of patients with plantar plate tears by direct repair through a dorsal approach combined with a Weil metatarsal osteotomy with a minimum followup of 12 months. METHODS: We prospectively treated 28 patients (55 MTP joints) with lesser MTP joint instability, but only 22 patients (40 MTP joints) were treated by the direct repair of the plantar plate and were included in the study. All of them had initial complaints of acute forefoot pain with the subsequent development of deformity and instability of the MTP joints. All patients were evaluated clinically, radiographically, (plain radiographs and MRI exam), and by MTP joint arthroscopy. With this data, a direct correlation between the clinical staging and the anatomical grading for plantar plate dysfunction of each patient was determined RESULTS: The plantar plate of the second MTP joint was the most commonly affected joint (63%), and Grade III type tear (transverse and/or longitudinal extension tear) was the most frequent type. With the surgical treatment, we were able to markedly improve the parameters studied (pain, medial or dorsomedial deviation of the toe, joint stability, muscle balance, and joint congruence) to acceptable levels, The AOFAS score improved substantially from an average of 52 points preoperatively to 92 points postoperatively. CONCLUSION: The direct plantar plate repair combined with a Weil osteotomy and lateral soft tissue reefing can restore the normal alignment of the MTP joint. We have demonstrated that the anatomic repair of the plantar plate can correct the deviation of the affected toe (medial, dorsal, dorsomedial or dorsolateral), which lead to diminished pain with improved functional scores.