Porous titanium‐nickel for intervertebral fusion in a sheep model: Part 2. Surface analysis and nickel release assessment

Abstract

Porous titanium-nickel (PTN) devices represent an alternative to traditional cage implants. PTN materials possess an interconnecting network of pores with capillarity properties that may promote bone ingrowth, long-term fixation, and intervertebral fusion without the need for bone grafting. However, their considerable surface area and nickel content may elicit concerns over sensitization potential. Therefore, PTN surface corrosion and nickel release resistance must be carefully studied. To evaluate this possibility, a PTN interbody fusion device (IFD) was compared to a conventional nonporous cage made of TiAlV, a well-known biocompatible biomaterial, in a sheep model. PTN and TiAlV IFDs were inserted at two non-contiguous lumbar sites for 3, 6, and 12 months postsurgery. Their surface was then evaluated by scanning electron microscopy (SEM) combined with backscattered electron analysis (BSE). No evidence of surface corrosion was observed either pre- or postimplantation, regardless of device type. Dosage of nickel ions was also performed with the use of inductively coupled plasma-mass spectrometry (ICP-MS). Blood nickel levels were observed to be within acceptable levels at all postinstrumentation times. Nickel content in PTN-adjacent tissue, as well as in detoxification and remote organs, was equivalent both in PTN-treated and control sheep. Therefore, porous titanium-nickel demonstrated resistance to both in vivo surface corrosion and nickel ion release and compared very well with a conventional titanium implant in the course of a 12-month sheep study.

The Potential of Powder Metallurgy for the Fabrication of Biomaterials on the Basis of Nickel‐Titanium: A Case Study with a Staple Showing Shape Memory Behaviour

“…[6,7] Additionally, a mold insert of high quality and low surface roughness is necessary for injection molding. [8] For complete form filling and damage free demolding in combination with decreasing size of the molded parts, tailored binders are used for feedstock production. [9] Besides a tool concept for molding and damage free demolding, the debinding and sintering strategy is important to establish the complete process.…”

“…An extensive in vivo study showed that it compared well to a titanium implant in a 12-month sheep implantation experiment. [8] Microstructurally, shape memory behaviour is based on a diffusionless and reversible phase transformation between the low-temperature martensite and the high-temperature austenite phases. The transformation is characterized by the phase transformation temperatures (PTTs) with a start, a peak and a finish temperature (abbreviations M s , M p and M f for the transformation to martensite, A s , A p and A f for the reverse transformation to austenite).…”

Critical overview of Nitinol surfaces and their modifications for medical applications

“…In her dissertation, however, Bogdanski [6] mentioned the possibility of Nitinol surface enrichment with Ni, but this possibility was not explored. Since the Ni release induced by Nitinol surfaces in the studies discussed was three orders of magnitude higher than the natural Ni level in the human basal serum, from 1 to 6 ng ml À1 [108], we took the liberty of analyzing this case in more detail.…”

Tensile deformation of NiTi wires

“…7 Biomedical researchers have thoroughly examined the corrosion resistance, 8 -13 soft-tissue cellular biocompatibility, 14 -20 hard-tissue cellular biocompatibility, [21][22][23][24][25] and Ni release from NiTi. [25][26][27] These studies have generally demonstrated that NiTi possesses a high degree of biocompatibility relative to alternative implant materials. Considerably less work has been published in biomedical materials journals on fundamental structure-mechanical property relationships in NiTi.…”