Shape Memory Alloy for Orthopedic Surgery

NiTi shape memory alloy (SMA) can be used as biomaterial due to its good biocompatibility, unique shape memory effect and superelasticity. Successful applications of NiTi SMA as medical devices used in dentistry, orthopedics and radiation in China were introduced. However, the conventional solid NiTi SMAs can't be used a s hard tissue replacement implants as they have a too higher modulus to match with that of the tissue to be replaced. By controlling the porosity and pore size, modulus and yield stress of porous NiTi SMA can be adjusted to match that of the hard tissue, such as bone. Also, the cellular structure allows the ingrowth of bone tissue and is favorable for the fixation of the implants and for the transport of body fluids. Porous N iTi SMA fabricated by self-propagation high temperature synthesis method was proposed, and the effect of process parameters, such as powder size, preheating temperature on the porosity, pore size and phase composition was investigated.

BioFix for bone fracture

Biofix using in Ti-Nickel shape memory alloy has great potential as a fracture fixation device in orthopeadic , Neurosurgical and plastic surgery due to unique thermal shape memory effects, superelasticity and high damping properties.

Device Description

The BioFix is a cerclage positioning ring fabricated from Nitinol Shape Memory Alloy (SMA), and consists of single or double rings, and is intended to achieve compression in fixation of bones in the hand, foot, and tibia. Nitinol can change is configuration (shape) based on temperature. At ice-water, the material is pliant and the rings can be opened. This allows for easy positioning around the fracture. After the ring has reached body temperature, the ring closes inward to its original shape. This inward deflection causes ring retention and compression across the osteomy or arthrodesis site. By virtual of the Nitinol SMA properties, this inward closing is kept in place until removed by the surgeon.

Instructions for Use

The Biofix was prepared by cooling the TiNi SMA alloy in ice-cold saline. The reduction in temperature initiated a conversion into a martensitic phase state. Once cooled, the fixator was malleable and easy to deform. The fixator size was determined either preoperatively from radiological film or intraoperatively by direct measurement. An appropriately sized bone fixator was selected and applied to the reduced fracture site. Immediately thereafter, warm saline was irrigated over the TiNi SMA fixator , causing contraction of the fixator to its original shape. Fastening of the fracture site was enhanced.

Indications for Use

The BioFix is indicated for general-purpose orthopedic repairs. This includes such procedures as long bone fractures, bone grafting, and reinforcement of bone

TiNi shape memory bone stapler (BRM-SH system) is more effective and easy in application to some fractures than cerclage. This double ring might be more effective and auxiliary to IM nail system in spiral fracture to split fracture occurred during hip stem insertion.