A Novel and Low-Cost Modified Sternal Closure Technique in Open Heart Surgery

Objectives: Sternal dehiscence that may occur after an open heart surgery is a serious complication that may result in morbidity and mortality from pain in sternum and separation of wound lips to pulmonary dysfunction, superficial and deep mediastinal infection [1-4]. Sternal movement and instability may occur on the first day or weeks later after the surgery depending on the risk factors of the patient, sternal closure material or surgical technique. Sternal closure materials are being used more frequently and increase the costs [5]. We are presenting a study where we closed the sternum of 20 patients in our clinic with a novel technique using a standard steel wire. Methods: We closed the sternum of 40 patients who underwent open heart surgery in the cardiovascular surgery clinic at Yeditepe University Faculty of Medicine Hospital between January 2017-May 2018 with a new technique. Results: Patients were assessed at 1 week and 1 month in the early post-operative period and following discharge. Sternal instability, dehiscence or sternum superficial wound site infection or mediastinitis were not detected in the early period. None of the patients used a sternum corset in the post-operative period. Conclusion: Today, median sternotomy is still the most frequently used method in heart surgery routine despite the advancements in minimal invasive techniques. Sternal dehiscence may be seen at the rate of 0.2%-5% following open heart surgery [6-9]. We think that an excellent sternal fixation and stability is ensured with the technique we used without increasing the costs.


Introduction
Median sternotomy is the most common incision for cardiac surgery. It provides safety and easy exposure for surgeon. Following the cardiac surgery by median sternotomy, sternum is closed by surgical steel wires. However post-operative mechanical sternal dehiscence of sternum is still a frightening and devastating complication for both patients and surgeons. This may result ranging from increased postoperative pain to sternal wound infection and mediastinitis and readmissions in post-operative period.
Readmission rates for coronary artery bypass graft (CABG) surgery range from 15 to 21%. Readmissions result in increased hospital costs, but even more importantly, have been associated with increased morbidity and mortality. So, reducing readmissions following cardiac surgery should be major priority for whatever it takes [5]. There is a growing diversity of sternal wiring techniques, from single wire to more modified "figure of eight"-wires and cable closure techniques, even dynamic fixation plates have been discussed and used properly ( Figure 1). Most of the cardiac surgery patients are severe obese, diabetic, with obstructive pulmonary disease, are mostly smokers and old. After Cardiac surgery due to mechanical sternal dehiscence cause mediastinitis is a multifactorial disease with an incidence between 0.5 and 5%. The main independent risk factors are: obesity, diabetes, smoking, Chronic Obstructive Pulmonary Disease, use of pedicled internal thoracic artery and prolonged on-pump time [8][9][10][11].
Sternal complications were seen to be higher in patients undergoing bilateral pedicled IMA. Rather than conventional closure methods, closure methods such as sternal plating, sternal band have gained importance particularly in these patients. However, the most important problem at this point is the high cost of sternal closure products. With the modified technique we used in our study, sternum was closed with a steel wire used in routine practice without using a sternal closure product. Sternal dehiscence is mostly seen in lower 1/3 part of the sternum [2][3][4].
In our modified technique we use double steel wires for perfect stabilization for the inferior part of sternum. With this technique, 7064 excellent stabilization was ensured and dehiscence was avoided. Sternum corset was not used in any of the patient's post-operation. Sternal closing technique used in our study is reported to prevent cutting of sternal cortex as tension on sternum is applied on more balanced area, unlike to conventional sternal steel wires [10,11]. It provides better stabilization and perfect closing of inferior 1/3 part of sternum. The aim of this study is to present 20 patients on whom we used a sternal closure method which is quite practical and lowcost and just as effective.

Patients and Method
We closed the sternum of 40 patients who underwent open heart surgery at the cardiovascular surgery clinic at Yeditepe University Faculty of Medicine Hospital between January 2017-May 2018 with a new technique (28 males, 12 females; mean age: 53,8). Sternum upper zone was closed with the routine Figure-8 method after the open heart surgery. In the middle and lower zone of the sternum, 2 of the 4 steel wires, which were close to each other, were first fixed the same side of the sternum, and then the sternum was fixed with the wires on the opposite site. Therefore, a strong inseparableness was created in the middle and lower zone of the sternum. Patients with renal failure or who had a cerebrovascular event were excluded from the study.
Surgery was performed through a median sternotomy. Following sternotomy, the IMAs were exposed using a sternal retractor and the left IMA was harvested first. When a single LIMA was used, it was harvested in pedicled fashion. When BIMA were used, they were both harvested in skeletonized fashion. After that cardiopulmonary bypass established selective venous cannulation through vena cava superior and vena cava inferior and ascending aortic cannulation in mitral valve patients. CABG patients after median sternotomy right atrial and asendan aorta cannulation was performed. Blood cardioplegia was used in the initial and Intermittent cold cardioplegia thereafter. Hypothermic cardiopulmonary bypass was started with rectal temperature lowered to 30°C or 32°C. An intravenous second-generation cephalosporin antibiotic was administered intraoperatively and for 48 hours postoperatively for prophylaxis against infection. Patients were followed up for a mean of 2,6 days in intensive care. They were then taken into the general ward and discharged after a mean of 7.2 days. The patients were assessed in terms of operative mortality, intensive care and hospitalization length, incision site pain, Mediastinitis, post-operative healing complications and reoperation (Table 1).

Statistics Analysis
No statistical tests were used. Data was expressed as mean ± standard deviation.

Results
Patients were assessed at 1 week and 1 month in the early post-operative period and following discharge. Sternal instability, dehiscence or sternum superficial wound site infection or mediastinitis were not detected in the early period. None of the patients used a sternum corset in the post-operative period.

Discussion
Due to an aging population and increasing number of comorbidities, the operative risk has risen over the years. In the last decades, studies reported an improvement in cardiac surgery techniques, perioperative and postoperative management. As a result, despite the trend towards a worsening surgical risk profile, the combined morbidity and mortality rate remained unchanged. The prevalence of multimorbid patients undergoing cardiac surgery is progressively increasing. As a result of this cardiac surgeons are performing a growing number of sternotomies in high-risk patients. This phenomenon is the consequence of an aging population and an increase in comorbidity [9][10][11][12][13][14][15][16][17][18][19].
Closing of sternum is the most important factor for sternal dehiscence. During sternal closing done by conventional approach using steel wires 5/0 or 6/0, bone cortex erosion, fracture and consequently sternal dehiscence can occur due to compression of steel wires. Sternal dehiscence may lead to respiratory dysfunction, infection, increased pain and re-exploration [20]. The frightening complication of post-operative mechanical sternal dehiscence is the infection starting with the separation of wound lips and subsequently spreading to the lower layers and sternum and resulting in mediastinitis. Considering that the starting point is sternal dehiscence, it comes to mind how important the right sternal closure is.
Mediastinitis is a devastating complication, which can lead to prolonged hospitalization, high hospital costs, high associated morbidity and even mortality. It is important to focus not only on efficient aseptic preoperative preparations and surgical techniques but even more on postoperative prevention techniques. With increasing evidence that patients who received bilateral internal mammary artery (BIMA) grafts have better long-term outcomes than those receiving single internal mammary artery (SIMA) grafts. BIMA grafting is increasingly adopted as the routine. Since the technique employed for harvesting the internal mammary artery (IMA) varies, the incidence of sternal wound complications (SWCs) varies from 1.5% to 6.9%. With the conventional wide-pedicled dissection of the BIMAs, sternal infection rates of 1.7% to 6

Conclusion
We think that the modified technique we used in this study with routine sternum steel wires provides a more durable and stable sternal closure compared to the conventional sternal closure in the middle and lower zone of the sternum. Also, a robust fixation was created in the sternum without using sternal closure products such as sternal plating, sternum screw etc. which are high cost. Given the sternum improvement problems especially in patients who are diabetic, obese or using BITA, this result is promising. The small number of patients is the most important limitation of this study. Also, the follow-up of patients until 1 month after the operation is another limitation in terms of medium-and long-term outcomes.

Scientific Responsibility Statement
The authors declare that they are responsible for the article's scientific content including study design, data collection, analysis and interpretation, writing, some of the main line, or all of the preparation and scientific review of the contents and approval of the final version of the article.

Animal and Human Rights Statement
All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. No animal or human studies were carried out by the authors for this article.