| Objective:To investigate the distribution of plantar pressure after Swanson double-stem silicone implant arthroplasty of the first metatarsophalangeal joint, And to analysis the pre-and post-operative biomechanics of the feet by means of three-dimensional finite element.Laboratory proof was Provided for the structural and functional changes of Hallux Valgus before and after the operation.Methods:A Hallux Valgus patient without other foot deformities was selected in clinical. Computed Tomography scan was undertaken preoperatively. The data was imported into Ansys, a kind of software for three-dimensional finite element analysis. A preoperative finite element model of Hallux Valgus was established and arthroplasty based on the preoperative model were simulated. Static stress analysis were carried on preoperative and postoperative finite element modelsResult:1.By measuring the postoperative compared with the preoperative, HVA decreased from56.3°to9.2°and IMA from16.3°to9.8°2.Forefoot plantar pressure distribution of Hallux Valgus is quite different from that of normal feet. The stress distribution of the preoperative finite element model showed that pressure under the3-5metatarsal are maximum while that of the first metatarsal is minimum. The medial Forefoot plantar pressure is obviously less than anterolateral, the center of pressure shift anterolateral from the medial.3.The stress distribution of the preoperative finite element model showed that pressure under the3-5metatarsal are maximum while that of the first metatarsal is minimum. According to the postoperative model, pressure under1-2metatarsal are maximum. However pressure under the3-5metatarsal increased slightly after implant arthroplasty of the first metatarsophalangeal joint,but the stress value and amplification are less than the1-2metatarsal. This trend indicates that the center of pressure shift medially as normal.Conclusion: There are structural and biomechanical differences between Hallux Valgus and normal feet which can be embodied by the distribution of plantar pressure. After implant arthroplasty of the first metatarsophalangeal joint, the Hallux Valgus Angle and intermetatarsal Angle values are less than preoperative ones and the center of plantar pressure shifts medially. The three-dimensional finite element analysis showed that the Swanson silicon implant arthroplasty of the first metatarsophalangeal joint changed the plantar pressure distribution obviously and made the center of pressure shift medially as normal. |
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