[An experimental study and preliminary clinical report of shape-memory sawtooth-arm embracing internal fixator].

ABSTRACT

The sawtooth-arm internal embracing fixator is made of Nickel-Titanium shape memory alloy and consists of 3 components body, arms and sawteeth. In cross section a 2/3 circumference is constructed by body and arms of the fixator. The free ends of the arms which exceed the semi-circle are bent more medially so that it can match the requirement of fixation of long tubular bone whose cross section is not a regular circle. The embracing fixator has two types the cylinder type is for use in the middle part and the cone type is either for the proximal or distal 1/3 of the shaft of long tubular bone. The animal experimental studies and in vitro mechanical tests demonstrated that the embracing fixator possesses good anti-bending and anti-torsion effects, and its resisting compression effect was much lower than that of bone plate. These characteristics are beneficial for enhancing fracture healing, reducing post fixation osteoporosis and providing a new, simple and effective method for the treatment of long tubular bone fracture. The fixator has already been used in the treatment of fractures of femur, humerus, radius and ulna with good results.