The spinal cord dura mater reaction to nitinol and titanium alloy particles: a 1-year study in rabbits

Abstract

This investigation was undertaken to simulate in an animal model the particles released from a porous nitinol interbody fusion device and to evaluate its consequences on the dura mater, spinal cord and nerve roots, lymph nodes (abdominal para-aortic), and organs (kidneys, spleen, pancreas, liver, and lungs). Our objective was to evaluate the compatibility of the nitinol particles with the dura mater in comparison with titanium alloy. In spite of the great use of metallic devices in spine surgery, the proximity of the spinal cord to the devices raised concerns about the effect of the metal debris that might be released onto the neural tissue. Forty-five New Zealand white female rabbits were divided into three groups: nitinol (treated: N = 4 per implantation period), titanium (treated: N = 4 per implantation period), and sham rabbits (control: N = 1 per observation period). The nitinol and titanium alloy particles were implanted in the spinal canal on the dura mater at the lumbar level L2-L3. The rabbits were sacrificed at 1, 4, 12, 26, and 52 weeks. Histologic sections from the regional lymph nodes, organs, from remote and implantation sites, were analyzed for any abnormalities and inflammation. Regardless of the implantation time, both nitinol and titanium particles remained at the implantation site and clung to the spinal cord lining soft tissue of the dura mater. The inflammation was limited to the epidural space around the particles and then reduced from acute to mild chronic during the follow-up. The dura mater, subdural space, nerve roots, and the spinal cord were free of reaction. No particles or abnormalities were found either in the lymph nodes or in the organs. In contact with the dura, the nitinol elicits an inflammatory response similar to that of titanium. The tolerance of nitinol by a sensitive tissue such as the dura mater during the span of 1 year of implantation demonstrated the safety of nitinol and its potential use as an intervertebral fusion device.

Quantifying subtle but persistent peri-spine inflammation in vivo to submicron cobalt–chromium alloy particles

“…However, our results are consistent with past investigation of peri-spine implant debris such as magnesium particles [22], titanium particles [7] and PEEK particles [30,36]. These past in vivo investigations of spinal implant particles demonstrated that clinically relevant particles elicit chronic mild inflammatory reactions [5,7,17,29,30]. Similar to our results, TNF-a was previously identified as a locally elevated cytokine associated with debris and peri-posterolateral arthrodesis [7,38].…”

“…Reportedly, spinal implant debris elicits a macrophage-mediated response with increased levels of local pro-inflammatory cytokines, osteoclastogenesis and cellular apoptosis [8,13,29,40]. The results of this in vivo study support this and this response is both dose dependent and can persist over the long term.…”

“…(e.g., Guidance for Industry and FDA Staff-Class II Special Controls Guidance Document: Intervertebral Body Fusion DeviceDocument issued on: June 12, 2007, http://www.fda.gov/MedicalDevices/ DeviceRegulationandGuidance); (2) previous studies of spinal implant debris reactivity have used rabbit models, thus our results will be comparable to other biomaterials; and (3) a rabbit model has been previously validated as capable of demonstrating debris induced osteolysis and inflammation in the peri-spine [5,7,17,29,30,36].…”

“…2, 3). This severe reaction to Ni was unexpected because past investigation by Rhalmi et al [29] had previously shown that Nitinol particles (comprised of Ti with as high as 35 % Ni), were similarly non-reactive in perispine tissue when compared to pure Ti particles without Ni. The histopathology of Ni-treated animals (Fig.…”

The applications and research progresses of nickel–titanium shape memory alloy in reconstructive surgery

“…Up to now, many porous NiTi SMAs with different pore structures were developed by combustion synthesis or self-propagating high-temperature synthesis (SHS) [52]. A research [53] on porous nitinol interbody fusion device revealed that nitinol has perfect biocompatibility on the dura mater, spinal cord and nerve roots, lymph nodes (abdominal para-aortic), and organs (kidneys, spleen, pancreas, liver, and lungs). Liang et al [54] prepared porous microstructures on Nickel-Titanium (NiTi) alloy surfaces by linearly polarized femtosecond lasers with moving focal point at a certain speed.…”