Song Wu, Feng Wan, Yong-shun Gao, Zhe Zhang, Hong Zhao, Zhong-qi Cui, and Ji-yan Xie

Department of Cardiac Surgery, Peking University Third Hospital, Beijing 100191, China

DEEP sternal wound infection (DSWI) is a life- threatening complication after cardiac operations with an incidence of 0.4%-5.1%.1The asso- ciated mortality rate in the literature ranges from 10% to 47%.2,3Sternal wound complications accumulate an average of 20 additional hospital-stay days and incur a cost estimated 2.8 times that in cases with uncomplicated postoperative courses.4The treatment options in the past included closed suction and continuous irrigation. Current practices in the management of DSWI include early wound exploration, surgical debridement, vacuum-assisted closure therapy, flap coverage, and sternal plating.

In this study, we present our experience in treating 19 patients suffering from DSWI after median sternotomy, using adequate debridement followed by single-stage bilateral pectoralis major muscle flap transposition or plus rectus abdominis muscle flap transposition.

PATIENTS AND METHODS

Patient selection

Between January 2009 and December 2013, 19 patients with DSWI after a median sternotomy for cardiac surgery were admitted to the Department of Cardiac Surgery, Peking University Third Hospital. The selected patients included 14 males (73.7%) and 5 females (26.3%), aged from 18 to 78 (55±13) years. According to the Pairolero classification of infected median sternotomies, 3 patients (15.8%) were classified as type II, the other 16 (84.2%) as type III. The initial operations and demographic data are listed in Table 1. DSWI was diagnosed based on clinical examination (local infection signs, fistulas, and fever) and laboratory test results (leukocytosis and C-reactive protein increase).5Computed tomography revealed dehiscence or osteolysis of the sternum. The diagnosis was verified by microbiological examination and histological analysis in all cases. Staphylococci infection (52.6%) was the most common finding (Table 2). 8 patients (42.1%) had chronically unstable sternum. All of these patients had failed attempts of debridement and rewiring.

Procedure of muscle flap transposition

The mean time between open heart surgery and muscle flap plastic was 84±36 days. General anesthesia was practiced for all the 19 patients prior to surgery. The incision is made along the primary incision scar and extended to the upper and lower direction beyond the ends of the sternum. Necrotic skin and adjacent hyperplasic tissues of the fistulawere excised. Steel wires for sternal fixation were removed. All infected and necrotic tissue, bone and cartilage were resected. Infected costal cartilages were entirely debrided to bleeding rib. The base of the wound, consisting of the epicardium and great vessels, was left undisturbed. The wound was rinsed with hydrogen peroxide and repeatedly flushed with normal saline until fresh wound surface was indicated. The wound was then assessed for the amount of muscle tissue necessary for closure. The pectoralis major flap transposition was the first choice in our institute to minimize the mediastinal space.

Table 1. Characteristics of the 19 patients with DSWI

The reconstruction started by mobilizing the pectoral muscle and subcutaneous tissue from the chest wall to a distance of about 10 cm from the median line. The closure technique first involved elevation of the skin and subcutaneous tissues off of the anterior pectoralis major fascia to just lateral to the nipple line (Fig. 1). The pectoralis major muscle was elevated from its lower rib origins, from lateral to medial until the perforating intercostal vessels from the internal mammary were identified. The muscle flaps were then turned into the wound to cover the damage site. To obliterate the dead space, it was necessary to mobilize the opposite pectoralis muscle because a single pectoral muscle flap did not suffice. After complete mobilization of both pectoral muscles, the left flap was fixed to the resection line of the right sternum and cartilage using single stitches with absorbable suture. The right pectoral muscle was pulled to the left side to overlap the left pectoral muscle and sewn to the fascia of the left flap (Fig. 2).

If these pectoralis major muscle flaps could not reach the lowest portion of the wound which was below the xiphoid process, the rectus abdominis muscle was used for closing this area. The midline incision was extended to just above the umbilicus. The abdominal wall skin on the side selected for the muscle flap was elevated to the lateral margin of the rectus sheath. The rectus sheath was then divided over the mid-portion of the rectus abdominis muscle, which was divided at the level of the umbilicus and elevated by detachment from the rectus sheath. The superior deep epigastric vascular pedicle which enters its lower surface from beneath the costal margin was preserved. The rectus abdominis muscle flap can be turned up into the lower section of the wound (Fig. 3). The anterior rectus sheath was closed with non-absorbable sutures. The opposing pectoral muscles were sutured firmly together. The sternum was not rewired. The skin and subcutaneous tissues were closed over the muscle flaps usually without need for skin grafts. Subcutaneous drains were placed on each side. After insertion of mediastinal and subcutaneous drains, subcutis and skin were closed by single stitches. Drainage tubes were connected to the negative pressure generator for drainage of hematocele and effusion. Postoperative antibiotics were administered according to microbiological testing of secretions. Sutures were removed 12 days after the operation. Drainage tubes were usually removed when output was less than 20 ml/d. Follow-up was conducted through clinic visits and telephone interview every 3 months, lasting over 12 months. The patients were cautioned against resistive exercises or activities that put stress on the suture line or central chest for at least 6 weeks.

Figure 1. The photo showing mobilizing the pectoral muscle and subcutaneous tissue from the chest wall.

Figure 2. The left pectoral muscle flap was fixed to the resection line of the right sternum and cartilage using single stitches with absorbable suture.

Figure 3. The rectus abdominis muscle flap was turned up into the lower section of the wound.

RESULTS

There were no intraoperative deaths. The 30-day perioperative mortality rate was zero with overall one-year survival of 89.5%. 2 patients (10.5%) died after discharge, one from renal failure and the other from multi-organ failure that was not directly related to sternal wound infection. In 15 patients (78.9%), bilateral pectoral muscle flaps were mobilized sufficiently to cover and stabilize the defect imposed by wound debridement, while the other 4 patients (21.1%) needed bilateral pectoral muscle plus rectus abdominis muscle flaps because in these cases the pectoralis major muscle flaps could not reach the lowest portion of the wound. 17 patients (89.5%) were discharged after their wounds had healed. Hematoma occurred in 3 patients (15.8%), all cured by needle aspiration and compression bandaging for 2-4 times. 2 patients (10.5%) suffered from subcutaneous wound infection after discharge, which was treated with local wound care. 17 patients (89.5%) were examined at follow-up 12 months after discharge (Table 2), all found healed and with stable sternum.

DISCUSSION

Post-sternotomy DSWI is a rare but potentially life-threatening complication of cardiac surgery. Its incidence (about 1%) has remained unchanged although profound efforts have been directed towards identifying and eliminating its causes and risk factors. Risk factors for the development of DSWIs after median sternotomy include diabetes, obesity, chronic obstructive pulmonary disease, osteoporosis, cigarette smoking, bilateral harvesting of the internal mammary artery, reoperation, prolonged intensive care unit stay, and use of assist devices. Additional surgical risk factors have been reported, such as increased operation time and perfusion time, use of an intra-aortic balloon pump, postoperative bleeding, sternal rewiring, extensive electrocautery, shaving with razors, administration of prophylactic antibiotics >60 minutes prior to incision, improper antibiotic dose adjustments, inadequate skin preparation in obese patients, and the use of bone wax.2-6

During the development of modern cardiac surgery, a number of wound-healing strategies have been establishedfor the treatment of DSWI, primarily consisting of early wound exploration and debridement. There are now a multitude of treatment options available for DSWI closure, including closed suction antibiotic catheter irrigation systems, vacuum-assisted closure (VAC), the omental transposition, the pectoralis major muscle turnover flap, the rectus abdominis muscle flap, the latissimus dorsi muscle flap, and various combinations of the above.7At present, there is little consensus regarding the most appropriate surgical approach to DSWI following open-heart surgery.

Table 2. Pairolero classification, pathogens, and follow-up results of the 19 patients with DSWI

VAC is a recent technical innovation in wound care with a growing number of applications. Several papers have reported excellent outcomes with the use of VAC in DSWI.8-10However, bacteremia, wound deeper than 4 cm, bony exposure, and sternal instability are strong predictors of VAC failure.11Complications associated with VAC use include a possible increased risk of bleeding and potential damage to underlying tissues, in particular the rare complication of right ventricular rupture.12The duration of VAC therapy has been an issue of debate.13

An adequate wound debridement followed by a wound closure with well vascularized flaps has recently been recommended for DSWI treatment. However, clinical researches more than often conclude that omental flap transposition has disadvantages, for instance, additional surgical trauma and possible flap-related complications such as pain, weakness, hernia, necrosis and the potential for infectious spread from one cavity to the other. Therefore omental flaps are often the second option after pectoralis.14,15

Muscle flap transposition is commonly applied for DSWI treatment because muscle flaps are readily available and it is a simple procedure. Pectoralis major flap transposition is now the first choice to minimize the mediastinal space. Advantages of this procedure for DSWI are as follows: (1) it is applicable for management of DSWI following any type of heart surgery, and considered the most effective modality for reconstruction to treat DSWI since it does not incur new incisions. (2) It can be applied to any post-cardiac surgical patient for its not requiring an intact internal mammary artery. The pectoralis major muscle is vascularized by the perforating branch of the internal mammary artery and the muscular branch of the thoracoacromial artery. (3) The bilateral pectoralis major flaps are large enough to fill the deepest space of the mediastinum. Moreover, being adjacent to the sternum, it is ready to be separated and transferred, thus an optimal option for treating DSWI. (4) The pectoralis major muscle is ductile and its flaps can be separated without affecting the activity of the ipsilateral upper limb. Additionally, normal pulmonary function can be restored.7,16

In this study, all the 19 patients treated with single-stage bilateral pectoralis major flaps transposition after sternal debridement have survived the operation. Most patients healed primarily and the sternum became quite stable in a few weeks. There was no significant functional loss from use of pectoralis major muscles. Use of the rectus abdominis muscle did not cause hernia or abdominal wall weakness. Intraoperative and perioperative bleeding was the frequent problem. It was well managed with meticulous control of vessels during muscle flap development and infusion of fresh whole blood or appropriate blood components. The most common postoperative complication was hematoma (3/19, 15.8%), occurring in the first 3 patients within 48 hours after the flap transposition. We paid more attention to stop bleeding during operation, ensured the smooth drainage, and applied compression bandaging on the wound after operation. As a result, there was no hematoma in the following 16 patients. The favorable outcomes may resulted from the following factors: (1) adequate debridement of dead bones, granulation, steel wires, suture residues and foreign substances to eliminate infection sources, and extensive resection of infected sternum and costal cartilage to prevent recurrence; (2) employment of a single-stage muscle flap transposition, which results in immediate chest stabilization and early extubation, reducing the length of hospital stay;17(3) the damaged sites following debridement were filled with bilateral pectoralis major muscle flaps to obliterate dead space, and the muscle flaps and skin flaps were fixed and sutured to the extent that the possibilities of infection by residues of suture or foreign substances were eliminated. Additionally, normal pulmonary function was restored, as supported by the results of previous studies.18,19In 4 cases in this study, when pectoralis major muscle flaps could not reach the lowest portion of the wound or there was significant open wound below the xiphoid, we used flaps of rectus abdominis muscle to close these lower portion of the wound. This method avoids opening another compartment and laparotomy. Outcomes of the 4 patients supported the use of unilateral rectus abdominis muscle as auxiliary muscle flap of pectoralis major muscle to cover the lower portion of the sternotomy wound. In none of our patients were omental flaps required.

In conclusion, we treated 19 DSWI patients with single-stage pectoralis major flap transposition or plus rectus abdominis muscle after early diagnosis and adequate wound debridement. Our results present favorable outcomes during hospital stay and in mid-term to long-term follow-up. However, prevention is more important than treatment. Patients with recognized risk factors for DSWI require more careful intraoperative monitoring and posto- perative wound care. Various broad-spectrum antibiotic regimens need to be evaluated further for their prophylactic efficacy in patients exposed to extensive surgical and intravascular intervention. To minimize the risk of bacteremia related to various monitoring and therapeutic interventions, operating room, central supply, and intensive care unit sterilization policies should be reviewed regularly. Though limited by the small sample size, this study supports the feasibility and efficacy of single-stage pectoralis major flap transposition or plus rectus abdominis muscle in treatment for DSWI.

1. Juhl AA, Koudahl V, Damsgaard TE. Deep sternal wound infection after open heart surgery–reconstructive options. Scand Cardiovasc J 2012; 46:254-61.

2. Gummert JF, Barten MJ, Hans C, et al. Mediastinitis and cardiac surgery–an updated risk factor analysis in 10,373 consecutive adult patients. Thorac Cardiovasc Surg 2002; 50:87-91.

3. Losanoff JE, Richman BW, Jones JW. Disruption and infection of median sternotomy: a comprehensive review. Eur J Cardiothorac Surg 2002; 21:831-9.

4. Pairolero PC, Arnold PG. Management of infected median sternotomy wounds. Ann Thorac Surg 1986; 42:1-2.

5. van Wingerden JJ, Lapid O, Boonstra PW, et al. Muscle flaps or omental flap in the management of deep sternal wound infection. Interact Cardiovasc Thorac Surg 2011; 13:179-87.

6. El Oakley RM, Wright JE. Postoperative mediastinitis: classification and management. Ann Thorac Surg 1996; 61:1030-6.

7. Singh K, Anderson E, Harper JG. Overview and management of sternal wound infection. Semin Plast Surg 2011; 25: 25-33.

8. Tang AT, Ohri SK, Haw MP. Novel application of vacuum assisted closure technique to the treatment of sternotomy wound infection. Eur J Cardiothorac Surg 2000; 17:482-4.

9. Cayci C, Russo M, Cheema FH, et al. Risk analysis of deep sternal wound infections and their impact on long-term survival: a propensity analysis. Ann Plast Surg 2008; 61: 294-301.

10. Baillot R, Cloutier D, Montalin L, et al. Impact of deep sternal wound infection management with vacuum-assisted closure therapy followed by sternal osteosynthesis: a 15-year review of 23,499 sternotomies. Eur J Cardiothorac Surg 2010; 37:880-7.

11. Gdalevitch P, Afilalo J, Lee C. Predictors of vacuum- assisted closure failure of sternotomy wounds. J Plast Reconstr Aesthet Surg 2010; 63:180-3.

12. Mokhtari A, Petzina R, Gustafsson L, et al. Sternal stability at different negative pressures during vacuum- assisted closure therapy. Ann Thorac Surg 2006; 82: 1063-7.

13. Schroeyers P, Wellens F, Degrieck I, et al. Aggressive primary treatment for poststernotomy acute mediastinitis: our experience with omental- and muscle flaps surgery. Eur J Cardiothorac Surg 2001; 20:743-6.

14. Sj?gren J, Malmsj? M, Gustafsson R, et al. Poststernotomy mediastinitis: a review of conventional surgical treatments, vacuum-assisted closure therapy and presentation of the Lund University Hospital mediastinitis algorithm. Eur J Cardiothorac Surg 2006; 30:898-905.

15. Reade CC, Meadows WM Jr, Bower CE, et al. Laparoscopic omental harvest for flap coverage in complex mediastinitis. Am Surg 2003; 69:1072-6.

16. Stump A, Bedri M, Goldberg NH, et al. Omental trans- position flap for sternal wound reconstruction in diabetic patients. Ann Plast Surg 2010; 65:206-10.

17. Jeevanandam V, Smith CR, Rose EA, et al. Single-stage management of sternal wound infections. J Thorac Cardiovasc Surg 1990; 99:256-62.

18. Cohen M, Yaniv Y, Weiss J, et al. Median sternotomy wound complication: the effect of reconstruction on lung function. Ann Plast Surg 1997; 39:36-43.

19. Klesius AA, Dzemali O, Simon A, et al. Successful treatment of deep sternal infections following open heart surgery by bilateral pectoralis major flaps. Eur J Cardio- thorac Surg 2004; 25:218-23.