| Objective: To study the the effect of the hyperextension of the second metatarsophalangeal (MP) joint and the relation with the plantar plate by measuring the orbit change of the MP joint when the plantar plate was migrated to eliminate the hyperextension of the MP joint. Then observe the tension, the histological change and the range of motion of the plantar plate, providing clinical anatomical basis.Methods: 1. Twenty-one preserved human second toes were obtained from amputated feet, dissected the second toes to observe the orbit change of the MP when the plantar plate was migrated, measure the tension and the range of motion of the plantar plate, Angle of the extension of MP joint was observed in the load 2N when the plantar plate was migrated and fixed in the periosteum of metatarsal bone, compared with the angle of the MP joint at the same load before operation. Then measure the length, the width and the thickness of the plantar plate.2. A series of 10 healthy chickens, the plantar plates of their right second toe were migrated and fixed in the periosteum of metatarsal bone, then the legs were immobilized with plaster for 6 weeks, at the end of tenth week, the chickens were sacrificed and specimens taken. The plantar plate was observed macroscopically and histiologically, compared with the plantar plate of the left second toe.Results: 1. The extension angle of the MP joint before separated from the foot is 62. 75±4. 74~0, the flexion angle is 38. 61±2. 45~0, the extension angle of the MP joint increased 15. 88±4. 51~0 and to 78. 63±4. 49~0 when the second toe was separated from the foot, the flexion angle increased 3. 28±3. 80~0 and to 41. 89±3. 59~0, there are significant difference(P＜0. 05). The length in our plantar plate samples is 19. 16±1. 63mm, the width is 7. 73±0. 73 mm—11. 59±0. 93mm, the thickness is 1. 88±0. 27mm—4. 71±0. 28mm.2. The extension angle of the MP joint decreased 62. 28±3. 62~0 and to 16. 35±2. 65~0 when the plantar plate was migrated, there is significant difference(P＜0. 01), the flexion angle is 41. 33±2. 61~0, there is no significant difference(P＞0. 05).3. The tension of the plantar plate is 217. 5±18. 3g, the range of motion of the plantar plate is 3. 53±0. 40mm when the flexion angle of the MP joint is 20. At the same load of 2N, the extension angle of the MP joint is 54. 15±3. 500 before operation, it decreased 48. 55±3. 70~0 and to 5. 61±1. 13~0 after operation, there is significant difference(P＜0. 05).4. The collagen fibers run in a longitudinal direction oblique bundles interspersed at regular intervals. Fibroblasts are seen scattered throughout the plantar plate. The arrangement of collagen fibers and fibroblasts of the operated specimens is normal,. It means there is no obviously histological change of the plantar plate 10 weeks later after operation.Conclusion: There is an anatomical feature of hyperextension with the second MP joint, we can eliminate the hyperextension of the MP joint by migrating the plantar plate in toe-hand transfer. The passive orbit of the MP joint after operation is the extension angle is 16. 35±2. 65~0, the flexion angle is 41. 33±2. 61~0. The tension of the plantar plate is 217. 5±18. 3g, the range of motion of the plantar plate is 3. 53±0. 40mm, and there is no obviously histological change of the plantar plate after operation.
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