6.4. Perineural response to NiTi

The present study is the first to report neural and perineural responses to NiTi. Some NiTi applications intended to be used in contact with the central or peripheral nervous system have been suggested and further systems might be developed in the future (Iwabuchi et al. 1975). Also, the osteosynthesis material intended for use in cranial surgery must not cause any harmful effects on brain tissue.

In the present study, a total of 16 implants were in very close contact with peripheral nervous tissue (Figure 5-6 A3- 4, B2-4, C2-3). Nine of these were NiTi implants. No signs of necrosis, prolonged inflammation or irritation, accumulation of a specific cell type, cells with phagocytosed material, foreign particles or abnormal connective tissue response were seen in the perineural tissue with any of the tested materials. There was no edema, irritation, glial hyperplasia or inflammatory reaction in the nerve itself. Very few giant cells, PMNs, plasma or mast cells could be found in the area between the nerve and the encapsulating membrane of the implant.

In conclusion, the observed neural and perineural responses were clearly non-toxic and non-irritating with Nitinol at 26 weeks follow-up. More studies are needed before application made of NiTi is intend to use inside the neural tissue