Potential risk of sternal wires

Objective: To understand the potential fracture mechanism of sternal wires, we collected extracted stainless steel sternal wires from patients with sternal dehiscence or chronic persistent postoperative sternal pain syndrome following open-heart operations. Surface alterations and fractured ends of sternal wires were inspected and analyzed. Methods: In sternal dehiscence group, twelve fractured and 18 non-fractured wires were extracted from 7 patients with mean implantation interval of 13.2±4.2 days (range 8-20 days). In chronic pain syndrome group, twenty-eight sternal wires with mean implantation period of 84±32 (range 26-312) months were retrieved from 10 patients. Extracted wires were cleaned and fibrotic tissues were removed. Irregularities and surface alternation were assayed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). Propagation of crack was also examined at the cross section. Results: In the sternal dehiscence group, all examined wires showed the presence of severe transversal cracks and crevice corrosion. In chronic pain syndrome group, all examined explants showed external and internal damages. Larger and irregularly shaped surfaces pits were observed in 70% of the explants. Vast regions of decay and cracks were found in several areas. EDAX examination revealed the deterioration and diminished nickel concentration in the corroded regions. Conclusions: The synergic effect of stress, poor wire quality, and hostile environment of body fluid could be the precursor of material failure for the sternal dehiscence. Severity of progressive corrosion of stainless steel sternal wires is a function of the implantation time. The adjacent tissue reaction and inflammation due to the released nickel would induce chronic persistent postoperative sternal pain syndrome after implantation. Cell-induced electrochemical corrosion and active cellular destruction of surfaces are well-known mechanisms and must be investigated for their roles in the corrosion of suture wires.