Material and Methods:
This retrospective study was approved by the local ethics committee and have been performed in accordance with the ethical standards laid down in Declaration of Helsinki. Between December 2009 and January 2020, a total of 21,357 median sternotomies were performed, with an incidence of NISD of 1.32% (283/21,357). The incidence of infectious sternal dehiscence during the same period was 2.1% (432/21,357). Sternal instability was determined at hospital and was defined as the presence of mobility when pressing both sternal halves separately. Treatment failure was defined as the need for reintervention for sternal closure.
Institutional protective measures against major wound infection and sternal dehiscence included: a bath with chlorhexidine soap the night before the operation, surgical site antisepsis with 10% povidone-iodine solution, whole body shaving two days before the operation, antibiotic prophylaxis with 1 g cefazolin (2 g in patients >80 kg), and use of a chest brace and activity restriction for 6 to 8 weeks after the surgery. Bone wax was not used during the procedures. Sternal closure included the placement of 6–8 stainless steel wire U-sutures one-by-one, without crossing.
We considered three principal categories for the classification of sternal wound complications: mechanical NISD, sternal dehiscence with superficial wound sternal infection, and sternal dehiscence with deep sternal wound infection [5]. Patients who experienced infectious complications of the sternal wound after sternotomy (n=432) were excluded from the study. Of 283 patients with NISD who underwent refixation, we mainly studied 34 cases who received TRNC treatment. We divided these 34 cases into two groups: patients who had a previous Robicsek repair before TRNC treatment (group A, n=11) and patients who had been directly referred to TRCN treatment (group B, n= 23). In addition, we compared the results of those who underwent TRCN treatment (group B, n=23) with all 260 patients who underwent Robicsek repair (group C, n=260) as the first sternal refixation procedure (Figure1). Demographic, preoperative, intraoperative and postoperative parameters were analyzed.
Nitinol thermoreactive clips (IAWA Bioscience Engineering Company, Jiangsu, China) were used. Operation time was defined as the time interval between the introduction of anesthesia and the end of the surgical procedure. Routine preoperative echocardiography examinations were performed. All patients were cultured for infection at the time of reoperation and received standard antibiotic prophylaxis, which included 24-hour administration of a first-generation cephalosporin. Before repair treatment, all cultures were verified to be negative for infective microorganisms. Computerized data of the patients were reviewed for reassessment of those in whom refixation was performed.
High-risk patients were defined as those having three or more risk factors, including comorbidities and surgical complications which predisposed them to sternal dehiscence. All reported comorbidities were established by attending physicians.
Comorbidities included: severe or morbid obesity (body mass index >35 kg/m2), old age (> 75 years), chronic obstructive pulmonary disease (COPD) (forced expiratory volume less than 70% in 1 second, and/or need for bronchodilatatory therapy for more than 6 months), congestive heart failure (New York Heart Association functional classes III-IV), peripheral vascular disease (Fontaine classification stages IIB-IV), chest irradiation, diabetes (insulin dependent or non-insulin dependent therapy longer than 12 months), severe osteoporosis (therapy for more than 6 months), chronic steroid use (therapy more than 6 months), renal insufficiency (creatinine >2 mg/dL), and prolonged ventilation (more than 7 days) [6].
Surgical complications included: use of bilateral internal mammary artery grafts, cardio-pulmonary bypass run longer than 5 hours, an asymmetric off-center sternotomy, transverse fractures of the sternum, rewiring for post-operative bleeding, and repeated sternal reopening [7].
Out of 283 patients with NISD; 260 underwent Robicsek repair, of which 17 were reported as high-risk patients. Of these 17 high-risk patients, 11 still had sternal instability after Robicsek treatment. There was no reported failure in the remaining Robicsek cases. Failed cases were referred to the thoracic surgery clinic for TRNC treatment.
The Robicsek method consists of placing continuous wire sutures parasternally. First, substernal tissues or adhesions were dissected. Each half of the sternum was fastened by continuous parasternal wire sutures. The suture began at the upper end of the sternum and passed down to the xiphoid process, alternating anteriorly and posteriorly between the costal cartilages. The suturing was then reversed toward the cranial direction, passing through the cartilages posteriorly where it had been anterior, and vice versa. At the upper end of the first rib, adequate reinforcement was provided and the two ends of the suture were tied together. Stainless steel wires were placed parasternally. The first wire was then passed through the manubrium through the second intercostal space and twisted to form a ring. The second wire was placed through the second and third intercostal spaces in an interlocking fashion until the end of the sternum was reached. The interlocking created a chain on both sides of the sternum [8]. The Robicsek technique was performed in the cardiovascular surgery clinic.
The TRNC method includes placement of nitinol clips either with or without the dissection of the substernal tissues. The pectoral muscle was completely bilaterally mobilized from the thoracic wall to facilitate approximation. Granulation tissues at both sternal ends were carefully removed and the bone tissue was exposed. Using electrocautery, parasternal holes were opened through the intercostal muscles close to the parasternal edges. When dissection of the substernal tissues or adhesions was required, they were dissected close to the costochondral junction using a right angle instrument. Both hemi-sternums were joined and stabilized with two Backhaus forceps. The sternal horizontal diameters were measured with the sizing tool provided, and appropriately-sized nitinol clips were used. The clips were put into refrigerated (<5° C) sterile saline solution. They became forgeable in minutes and were adequately enlarged by bending. The clips were inserted into the parasternal holes, from superior to inferior direction, and at least four horizontal placements were made for each patient. The clips were then heated with warm water (>45° C). After the clips resumed their original shapes and regained stiffness, the forceps were removed. The TRNCs were placed at the intercostal spaces without using steel wires. Pectoral muscle flaps were closed at the midline using absorbable sutures. Small suction drains were left in the central defect and under both pectoral muscle flaps and the substernum. The TRNC technique was performed at the thoracic surgery clinic (Figure 2). In both reoperations, mediastinal tissue and fluid cultures were collected in patients with suspected infections.
All statistical analyses were performed using SPSS version 21.0 software (SPSS, Inc., Chicago, IL, USA). Continuous parameters are presented as mean standard deviations. Categorical data are presented as numbers and percentages, and proportions between the two groups were compared using the chi-square test or Fisher’s exact test. The Mann–Whitney U test was used for comparison of nonparametric variables, and the independent samples t test was used for comparison of parametric variables. A p value <0.05 was considered significant.