The Development And Biomechanical Study Of NiTi Shape Memory Alloy Four-corner Arthrodesis Concentrator

Objective: The anatomic parameters of the four bones (capitatum, lunate, triquetrum and hamate) were measured with vernier caliper. According to the measured results of the four bones and the characteristics of Nitinol, a special internal fixator for four-corner arthrodesis, NiTi shape memory alloy four-corner arthrodesis concentrator (NT-FCAC) was designed. In order to provide the biomechanical proofs for clinical application, the biomechanical characteristics of NT-FCAC were tested with 858-Material Test System (858-MTS). Methods: Firstly, 45 carpal specimens of adult cadaver were anatomized. The ligaments of dorsal and palmar of wrist were preserved. Trapezium, trapezoid and scaphoid were excised. According to the invariable bony marks, the distances between four bones (capitatum—lunate, hamate—lunate, lunate —triquetrum , capitatum—triquetrum, hamate—triquetrum and capitatum—hamate) were measured with vernier caliper. Secondly, the anatomical shapes of four bones (capitatum, lunate, triquetrum and hamate) were observed after they were separated. Thirdly, the parameters (width, length, thickness) of the four bones were measured with vemier caliper. According to the measured datum and anatomic features of the four bones (capitatum, lunate, triquetrum and hamate), a special internal fixator—NiTi shape memory alloy four-corner arthrodesis concentrator (NT-FCAC) was designed with Nitinol. Fourthly, the four-corner arthrodesises were carried out in 32 carpal specimens of the four bones (capitatum, lunate, triquetrum and hamate) in vitro, 16 specimens of the four bones (capitatum, lunate, triquetrum and hamate) were fixed with NT-FCAC, and the others were fixed with K-wires. Finally, the fixed strengths of the NT-FCAC groups and the K-wires groups were tested with 858-MTS, two fixators were fatigued with 20 —200N cycling pulling load(1HZ) by 858-MTS, and the deformations of them were observed. The stresses were measured after the three dimensional finite elements of NT-FCAC were loaded. The biomechanical...