Ann Thorac Surg 2007;84:1012-1014
© 2007 The Society of Thoracic Surgeons
Case Reports
Corrosion of Pure Titanium Sternal Wire
Yasuko Tomizawa, MD, PhDa,*,
Takao Hanawa, PhDb
a Department of Cardiovascular Surgery, The Heart Institute of Japan, Tokyo Women’s Medical University, Tokyo, Japan
b Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan
Accepted for publication April 16, 2007.
* Address correspondence to Dr Tomizawa, Department of Cardiovascular Surgery, The Heart Institute of Japan, Tokyo Women’s Medical University, 8-1 Kawada, Shinjuku, Tokyo, 162-8666, Japan (Email: 4crnry{at}hij.twmu.ac.jp).
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Abstract
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Titanium and its alloys are considered reliable materials commonly used in heart surgeries. A patient had severe inflammation at the median sternotomy wound develop after open heart surgery. Sternal wires were removed and were found to be seriously corroded on most of the surface. Energy dispersive spectroscopy identified titanium as the only elemental component of the explanted wire with grade 2 purity, and the polarization curve showed satisfactory corrosion resistance similar to commercial pure titanium. Prolonged inflammation might have caused extensive corrosion of titanium in the present case.
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Introduction
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Many metals have been used in the medical field, and we have found implanted stainless steel sternal wires to be stable for decades with minimum corrosion [1]. Titanium and its alloys are considered reliable materials. They are strong, chemically stable, corrosion-resistant, and rarely sensitized. However we found that even when using sternal wires made of pure titanium, inflammation may cause total corrosion.
A 51-year-old man presented on 162 days after undergoing open heart surgery at our hospital because of severe inflammation with reddening, swelling, and pain at the median sternotomy wound. Three of six sternal wires had been removed at 4 months after surgery because of pain and redness, and all yielded negative bacteriological examinations. The three remaining wires were removed and their surfaces were examined by scanning electron microscopy with energy dispersive spectroscopy. Most of the surface was seriously corroded at the grain boundary (Figs 1A,
1B). Scratches along the direction of extrusion were found on most grains and small crevices, while slip lines were also observed on the grains. Scanning electron microscopic examination of the surface of an unused titanium wire from the same company showed scratches from extrusion (Fig 1C). Energy dispersive spectroscopy identified titanium as the only elemental component of the explanted wire with grade 2 purity (Fig 1D), and polarization curve showed satisfactory corrosion resistance similar to commercial pure titanium (Fig 1E).
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Fig 1. Examinations of titanium sternal wire. (A) Scanning electron microscopy of an explanted titanium sternal. Most of the surface is seriously corroded at the grain boundary. (B) Higher magnification of figure part A. Scratches along the direction of drawing (double-headed black arrow indicates drawing direction on the manufacturing process of the titanium wire) are found on most grains and small crevices, and slip lines (white arrowheads) formed during plastic deformation are also observed on the grains. (C) The surface of an unused titanium wire from the same company shows scratches from drawing (double-headed black arrow indicates drawing direction). (D) Energy dispersive spectroscopy identifies titanium as the only component of the explanted wire with grade 2 purity. (E) Polarization curve shows that the explanted wire maintains satisfactory corrosion resistance similar to commercially pure titanium. (E/V vs. SCE = potential voltage (E) versus saturated calomel electrode.)
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Comment
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The surface of titanium sternal wires removed from a patient has never been carefully investigated. Prolonged inflammation might have caused severe corrosion of titanium in the present case.
Titanium remains in a passive state after implantation, and many implantable medical devices are made of titanium. Pacemaker contact sensitivity is rare [2–5]. However, a patch test is not reliable to detect titanium sensitivity [4, 5]. An intra-cutaneous test with serum incubated with titanium and a lymphocyte stimulation test were positive in a case of pacemaker dermatitis [4].
Titanium corrodes by contact with active oxygen in vitro [6], and inflammation activates macrophages and generates active oxygen in vivo. In the 1970s it was noticed that the soft tissue had a tendency to discolor in the presence of titanium [7]. In hip replacement cases a tendency of discoloration due to titanium dissolution and local accumulation was observed, and microscopic examination of the blackened tissue showed cells containing black granules and titanium debris [8]. Histologic analyses of areas of titanium debris showed abundant macrophages, suggesting sensitization to titanium [8]. Some early titanium medical implants, such as hip replacements, possibly failed due to corrosion of the material [8]. In a case of granulomatous dermatitis after implantation of titanium-coated pacemaker, titanium was detected in the skin biopsy by electron probe microanalysis [3]. In that case, the titanium debris was probably derived from corrosion after inflammation.
In the present case, it is surprising that continuous inflammation was associated with corrosion of grade 2 pure titanium within several months in vivo. An amount of metal ions equivalent to the volume of corrosion should have been released into the tissue. The dissolved ions from the implants possibly accumulated in the internal organs. However, the effect of dissolved titanium ions on a human is still unknown.
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References
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- Tomizawa Y, Hanawa T, Kuroda D, Nishida H, Endo M. Corrosion of stainless steel sternal wire after long-term implantation J Artif Organs 2006;9:61-66.[Medline]
- Abdallah HI, Balsara RK, O’Riordan AC. Pacemaker contact sensitivity: clinical recognition and management Ann Thorac Surg 1994;57:1017-1018.[Abstract/Free Full Text]
- Viraben R, Boulinguez S, Alba C. Granulomatous dermatitis after implantation of a titanium-containing pacemaker Contact Dermatitis 1995;33:437.[Medline]
- Yamauchi R, Morita A, Tsuji T. Pacemaker dermatitis from titanium Contact Dermatitis 2000;42:52-53.[Medline]
- Peters MS, Schroeter AL, van Hale HM, Broadbent JC. Pacemaker contact sensitivity Contact Dermatitis 1984;11:214-218.[Medline]
- Mu Y, Kobayashi T, Sumita M, Yamamoto A, Hanawa T. Metal ion release from titanium with active oxygen species generated by rat macrophages in vitro J Biomed Mater Res 2000;49:238-243.[Medline]
- Williams DF. Titanium as a metal for implantationPart 2: biological properties and clinical applications. J Med Eng Technol 1977;1:266-270.[Medline]
- Lalor PA, Revell PA, Gray AB, Wright S, Railton GT, Freeman MA. Sensitivity to titaniumA cause of implant failure?. J Bone Joint Surg Br 1991;73:25-28.[Medline]
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Abstract
Introduction
