Biomechanical Study And Clinical Significance Discussion Of Dynamic Memorial Stress

By the method of experimental biomechanics and computed biomechanics, the biomechanical foundation of Nitinol Patellar Concentrator (NT-PC) and Swan-like Memory-compressive Connector (SMC) was studied, which are made of nitinol and used for treating fractures and nonunion, and the clinical significance of three-dimensional fixation, dynamic memorial stress for treating fractures and nonunion was discussed. The study is divided into two relative independent parts: 1. Biomechanical Study and Clinical Significance Discussion of Nitinol Patellar Concentrator (NT-PC) for treating patellar fractures Methods: By electrometric method and three dimensional photoelasticity technique, the study was performed. Electrometric method: By pasting gauge, multiple times standardization, load-strain curve was got, then the continuously longitudinal memorial force of NT-PC was obtained by fixating the fresh patellar. Three-dimensional photoelasticity technique: By precision moulding, we got the epoxy resin three dimensional photoelasticity patellar model, then it was fixated by NT-PC, meanwhile an epoxy resin cirque was used to share the continuously memorial compress to guarantee the success of the experiment. By dividing layer, photographing and tracing, we used the iterative method to calculate the stress value of every internal node of the epoxy resin three dimensional photoelasticity patellar model, and 24 space component stress of 4 inspected nodes were divided by Leize polarizing microscope. The stress field of patellar fixated by NT-PC, tension band, circle wire was compared. Three-dimensional finite element analysis: The NT-PC and patellar was analyzed by ANSYS, which is authorized by international ISO 9001. The finite element was three dimension brick unit with 20 nodes, 8 faces. Defining degree of freedom was six. In NT-PC, 10483 units were divided and the number of nodes was 17959; In Patellar, 8775 units were divided and the number of nodes was 15847. The patellar model was loading according to the five converging directions of NT-PC, and the calculation under the law of conservation of space force. Fracture type, clinical results of 4023 cases patellar fractures fixated by NT-PC was analyzed. Results: Electrometric method: The continuously longitudinal memorial force of NT-PC was 13.67kg, which could initially centripetally converge the fractured patellar to its reductive position. Three-dimensional photoelasficity method: Stress value of 1262 nodes scattered in 12 layers which were obtained by photoelasticity method indicated that an overall stress field was yield when the Nitinol Patellar fixated the patellar, which was major in longitudinal and minor in transverse, the share stress was small, there was continuous fixated stress in the facies articularis and distal pole of patella. The initially, continuously memorial stress and the character of stress distribution mentioned above was the essence of NT-PC distinguished from tension band and circle wire. Three-dimensional finite element analysis: The NT-PC was come in for tension force on its internal face, and pressure force in its external face when it fixated the patellar. The maximum value was 1 95.8Mpa and ? 8Mpa, which was much less than its utmost stress and fatigue limit. The memory converging force of NT-PC was 134N, which was coincide with the results of electrometric method. The stress distributed on...