This case demonstrates a patient who presented with chest discomfort post-bypass surgery and was found to have a small to moderate-sized hemopericardium as a result of a fractured sternotomy wire projecting posteriorly into the pericardial space resulting in a cardiac wound. In our patient, the fractured and posteriorly angulated sternal wire is thought to have been a result of his sternal instability. This case highlights the importance of evaluating patients with an unstable sternum who have recently undergone a sternotomy as this can lead to a sternal wire fracture and potential angulation. Although sternal wire fractures occasionally appear on post-operative follow-up chest roentgenograms, they are often thought of as nonspecific findings or even omitted from the final radiology report [3,4,5]. Findings of central sternal lucency and loss of sternal wire alignment raises the suspicion for sternal nonunion/dehiscence. Moreover, this radiologic findings, particularly in the context of an unstable sternum, may result in the fractured wire angulating and penetrating the pericardium causing serious cardiovascular injury.

Post-sternotomy hardware complications include sternal wire rotation, migration, displacement, rupture, and fracture [6]. The incidence of each of these complications has not been elucidated. The mechanism for wire-fracture is hypothesized to be multifactorial, with mechanical distortion during sternal closure and chemical erosion from contact with bodily fluids being the main contributing factors [3]. The breaking of sternal wires has the potential to cause serious complications, with the literature reporting cases of fractured fragmented wire embolizing to the lung [7] and migration and puncture of the wire fragments into the ascending aorta [8]. We present however, to the best of our knowledge, the first reported case of a direct sternal wire puncture into the pericardial space.

Other, more common sequelae of post-sternotomy hardware complications include sternal instability and sternal dehiscence, which when combined, have an estimated prevalence of 1–3% [9]. There are several patient-specific risk factors that can contribute to sternal dehiscence, including chronic obstructive pulmonary disease, obesity, trauma, and diabetes mellitus. In addition, certain operative and post-operative factors may also increase the risk of sternal dehiscence, such as prolonged time on pump, procedures involving the internal thoracic artery, repeat surgery, and prolonged post-procedure ventilation. [10]. Sternal dehiscence is usually evident clinically, but may be clinically occult in a small subset of patients [4]. In the modern day, surgeons often close sternotomies by placing wires in figure-of-8 fashion, as it increases the area of contact between the wire and the sternum and is associated with lower rates of wire loosening or fracturing [11]. In high risk patients, some surgeons augment their sternal closures with additional hardware such as plates or clips, though recent studies have shown that these often have little to no impact on post-operative morbidity [12, 13].

Treatment of sternal wire fractures, particularly in patients with an unstable sternum, is often left up to the individual surgeon, as the literature is limited to case reports only [7, 8]. Central sternal lucency and loss of sternal wire alignment on post-operative chest X-rays should alert the clinician of sternal malunion/dehiscence. We recommend that sternal wire fractures in this setting should be removed given the potential of angulation and penetration into the mediastinum. In our patient, after repairing the cardiac wound, the sternal bone was repaired using sternal plates.