Finite Element Analysis And Clinical Application Of NiTi Shape Memory Alloy Four-corner Arthrodesis Concentrator

[Objective] 1.To evaluate the biomechanical properties of NiTi shape memory alloy four-corner arthrodesis concentrator (NTMA-FCAC) by the method of finite element analysis and provide theoretical data for clinical application.2.To evaluate the results of NTMA-FCAC for carpal collapse.[Methods] 1.With the structure analysis function of Ansys 10.0,the models of NTMA-FCAC were built.Under the same loading condition as the arthrodesis concentrator devices encountering in fatigue test, the models were stricted and laoded.Through structure analysis, the strain/stress distributions in it,compression and tension stiffness were processed.2.We reviewed,retrospectively 13 patients who underwent scaphoid excision with four-corner arthrodesis (capitate, lunate, triquetrum and hamate) using NTMA-FCAC for carpal collapse from September 2008 to December 2010. There were nine males and four females, with an average age of 37 years (range,21-61 years). Eight patients had SNAC, four perilunate dislocations and one SLAC. The injury mechanisms included four traffic accidents, four falls from a height, four crashes and one sprain. Nine cases injured their right wrists and the remaining four left wrists. Objective measurements included grip strength and range of the wrist. Radiographs were performed in all patients. Patients were subjectively surveyed using visual analogus scales for wrist pain. The results were evaluated according to the Krimmer wrist scores.[Results] 1.The result showed that in addition to several stress-bearing areas located in the junctional zones between body and arms. The stress distribution of other parts are even. The stiffness of two models are similar. Within the scope of certain the NTMA-FCAC can satisfy wrist functional exercise postoperatively.2.The mean follow-up time was 26.5 months (range,6 months-3 years).. Clinical evaluation yielded a mean grip strength of 33±6kg (80.8% of opposite side). The mean range of the wrist reached over 53% of the healthy side. Non-union and wound infection were not seen. At preoperative and postoperative, mean pain scores were 4.5±1.0 and 1.3±1.0(non-stress); 7.0±1.4 and 2.6±1.3 (stress). There were remarkable differences statistically between them. The mean vale of Krimmer wrist score was 79.[Conclusion] The result showed the newly-improved NTMA-FCAC had excellent biomechanics properties.It can meet clinical application. Four-corner arthrodesis using NTMA-FCAC is an effective method to treat carpal collapse for preserving a majority of wrist function.