Background: Ligamentous and capsular insufficiency of the second metatarsophalangeal joint has been surgically treated for over two decades, mainly with indirect surgical repairs, which stabilize adjacent soft tissue and shorten or decompress the osseous structures. While ligamentous insufficiency has been described and recognized, degeneration of the plantar plate and tears of the capsule have rarely been documented. The purpose of this study was to document and describe the presence and pattern of plantar plate tears in specimens with crossover second toe deformities, and based on this, to develop an anatomical grading system to assist in the assessment and treatment of this condition.
Methods: Sixteen below-knee cadaveric specimens with a clinical diagnosis of a second crossover toe deformity were examined, and dissected by removing the metatarsal head. The pathologic findings of plantar plate and capsular pathology, as well as ligamentous disruption, were observed and recorded. Demographics of the specimens were recorded, and simulated weightbearing radiographs were obtained prior to dissection so that pertinent angular measurements could be obtained.
Results: Demographics demonstrated a high percentage of female specimens, and a typically older population that has been reported for this condition. Radiographic findings documented a high percentage of hallux valgus and hallux rigidus deformities. The MTP-2 and MTP-3 angles were divergent consistent with a crossover toe deformity. We consistently found transverse tears in the plantar plate region immediately proximal to the capsular insertion on the base of the proximal phalanx. With increasing deformity, wider distal transverse tears extending from lateral to medial were found. Midsubstance tears, collateral ligament tears, and complete disruption of the plantar plate were found in more severe deformities.
Conclusion: In this largest series of cadaveric dissections of crossover second toe deformities, we describe the types and extent of plantar plate tears associated with increasing deformity of the second ray. We present, based on these findings, an anatomic grading system to describe the progressive anatomic changes in the plantar plate.