TINI SHAPE-MEMORY CLAMPS WITH OPTIMIZED STRUCTURE PARAMETERS

The different treatments of TiNi shape memory alloys applied as a mate rial for so-called TiNi clamps and their influence on substructure par ameters and deformation behaviour are discussed. The forces generated in fine-grained materials with higher dislocation density are stable a fter the cooling of the clamp to body temperature, which is a necessar y condition for stable fixation of bone fragments. The forces generate d and reversible strains depend on the substructure state and system s tiffness parameter. The ''yield point'' and the ''elastic moduli'' are modified by controling the B2/B19' interface mobility. The mechanical parameters obtained after annealing at 400 and 500 degrees C, respect ively, following the 15% cold-working reduction are optimal for the Ti Ni clamp design. The TiNi clamps with optimal properties have been use d in a total of 68 patients. The new TiNi clamps enhance the fixation of the bone fragments involved, helping to prevent redislocation and p rovide the ability for earlier active rehabilitation.