The incidence of cardiovascular disease is currently on the rise and the corresponding direct cardiac surgery is widely performed, with a concomitant increase in the number of cases of sternal osteomyelitis after cardiac surgery. Most of these complications are difficult to resolve and clinically challenging to treat. In this article, we refer to the relevant literature and summarize the current management of such complications.
1. Incidence.
According to statistics, the incidence of subcutaneous infection of the sternotomy after direct intracardiac surgery is 0.4-8%. Subcutaneous infections that are not effectively treated can progress to sternal infections and mediastinitis and may lead to sepsis, cardiac incisional infections, or even cardiac rupture, and may lead to surgical failure due to secondary infection of the artificial material used to repair the heart. The mortality rate of mediastinitis has been reported in the literature to be 25.7% to 52%. When the inflammation invades the sternum and causes chronic osteomyelitis, the disability rate and hospitalization time are greatly increased, which consumes medical resources. Therefore, patients with incisional infections after direct cardiac surgery should be given high priority. The incisional complications after direct cardiac surgery are clinically more common, especially after surgery for congenital heart disease, 2.2% after valve replacement and 1.9%-8.5% after coronary artery bypass surgery, including 1.1% for those who take the saphenous vein, 2.3% for those who take the unilateral internal thoracic artery, and up to 8.5% for those who take the bilateral internal thoracic artery.
2. Causes of sternal osteomyelitis.
(1) diabetes mellitus: diabetes mellitus can lead to microangiopathy and immune function decline, microangiopathy can cause microcirculatory disorders, tissue hypoxia, and thus prone to infection.
(2) Internal mammary artery grafting: Internal mammary artery grafting is often performed in cardiac surgery, which will reduce the blood supply to the ipsilateral sternum by more than 90%, thus affecting postoperative sternal healing and predisposing the sternum to necrosis and infection.
(3) Surgery time: surgery time is directly proportional to poor sternal healing, and prolonged surgery will increase the chance of intraoperative contamination, and prolonged extracorporeal circulation can weaken the body’s defense mechanism and increase the chance of postoperative infection.
(4) Hematoma: incomplete intraoperative hemostasis and poor postoperative drainage make blood accumulation behind the sternum easy to cause osteomyelitis to occur.
(5) Soft tissue injury: too frequent application of electric knife and excessive power can cause skin and subcutaneous tissue damage, poor skin healing, and infection from superficial to deep sternal osteomyelitis.
(6) Poor sternal fixation: the sternal wire is not firmly fixed, and the relative activities of the sternum affect its healing.
(7) Other: the patient’s advanced age, poor physical condition, poor nutritional status, etc. will increase the chance of postoperative sternal infection.
3.Clinical manifestations.
Some scholars have statistics that early sternal fracture mostly occurs 9 to 23 days after extracorporeal circulation surgery, with an average of (14±3.23) days. The clinical manifestations of early fracture are: ① blood and fluid oozing from the wound, increased cough, respiratory effort and shortness of breath; ② abnormal activity of the sternum during physical examination; ③ a series of changes such as increased heart rate, blood pressure and decreased oxygen saturation.
When the inflammation involves the sternum, sternal necrosis and septic osteomyelitis appear, and in severe cases, pathological fracture of the sternum occurs, and the effect of drug exchange and systemic application of antibiotics is poor. Patients with chronic sternal osteomyelitis have a long course of disease, often visible skin ulcerated surface, sinus tracts, local long-term recurrent infection, necrosis, pus flow, and persistent.
4.Treatment methods.
(1) Conservative treatment.
In the early stage of sternal infection, when the infection is more limited and the necrotic tissue is less, it is possible to insist on changing the medication, keeping the wound clean, promoting the growth of fresh granulation, and if necessary, to be sutured in the second stage when the wound is fresh. carriage of bacteria. Krabatsch et al. studied 34 patients with poor sternal wound healing after direct intracardiac surgery via median sternal incision, and found that the majority of patients were treated on postoperative day 1, day 4, and day 12 by injecting contrast through the flushing drain and taking chest radiographs. Most patients had a significantly smaller postoperative retrosternal cavity on postoperative days 4 and 12 compared to the preoperative period. Posterior sternal irrigation and drainage can reduce the size of the posterior sternal pus cavity, a process that can be observed by flushing and draining the contrast and determining the need for continued flushing based on the size of the pus cavity as shown on the radiographs. It should be noted, however, that the infected cavity is not suitable for imaging if it is connected to the pleural cavity.
(2) Rectus abdominis myocutaneous flap transfer repair.
Zhang Shaoming, Tao Hongwei et al. advocate that for patients with long duration of infection and severe sternal destruction, a one-stage debridement and repair with rectus abdominis muscle flap transfer should be performed. The scope of debridement should include most of the sternum and some of the ribs, and the thoracic wound should be repaired with a rectus abdominis muscle flap. For patients who have not been treated with several times of debridement and drainage, the duration of the disease is more than 4 months. Since a thick fiber plate has been formed locally, the sternum and ribs can still play a certain role as a scaffold after removal of the sternum and ribs, thus not affecting the respiratory function. The rectus abdominis muscle flap has good blood supply and can be sutured without tension when repairing chest wounds, thus ensuring good wound healing and better postoperative integrity and extension. The rectus abdominis muscle flap can ensure sufficient length and width, thus allowing the physician to thoroughly remove infected necrotic tissues without excessive concern for oversized wounds that cannot be repaired.
(3) Pectoralis major myocutaneous flap transfer repair.
This method involves filling the blood-rich pectoralis major muscle into the sternal defect site to increase the local resistance to infection, supplemented with effective antibiotics, which can achieve a one-time cure. The blood supply of the pectoralis major muscle comes from the penetrating branch of the internal thoracic artery on the one hand and from the myocardial branch of the thoracic-shoulder artery on the other hand, so it is rich in blood flow. In the treatment of osteomyelitis, in addition to thorough debridement, a blood-rich tissue should be provided for the cavity remaining after debridement to improve its ability to resist infection. The pectoralis major muscle is directly adjacent to the sternum, which is rich in blood flow, easy to peel and easy to transfer. Since only a portion of the pectoralis major muscle is applied intraoperatively, it has little effect on the ipsilateral upper limb. When the pectoralis major muscle flap with tip is used for transfer repair, only the corresponding segment of the pectoralis major muscle can be free according to the site of the residual cavity, and the flap only needs to be free for a short distance to fill the residual cavity without tension, without making another incision, with small trauma and good blood flow, and the length and size are appropriate to fill the residual cavity without tension; the tip of the pectoralis major muscle flap should be slightly wider than the length of the residual cavity to prevent ischemia of the muscle flap, and at the same time, the residual cavity can be filled more satisfactorily. It is also possible to free the flap to the anterior axillary line on both sides after complete excision of the sternal necrotic tissue, with the flap depth reaching the surface of the pectoralis major muscle. According to the site of sternal defect, the distal end of the proposed muscle flap is cut off, leaving the tip adjacent to the defect site, and the dead cavity is eliminated after filling the sternal defect area with the muscle flap. erez et al. had treated 9 cases of deep sternal wound infection in pediatric patients with sternomastoid muscle flap, and all 6 neonates were cured. The pectoralis major muscle flap not only promotes rapid wound healing, but also protects the life of critically ill children and rarely causes growth disorders.
(4) Transfer of the latissimus dorsi muscle flap for repair.
Dejesus applied the latissimus dorsi muscle flap to treat nine cases of infected sternal dehiscence, and he proposed that the anatomical advantages of the latissimus dorsi muscle flap are that it does not destroy the lateral circulation of the sternum and parasternal tissues, which is conducive to wound healing; its muscle tissue is large, has good blood flow, and has sufficient length to fill the residual cavity or cover the sternum; in addition, its free retrieval is easier and the time required for surgery is short. However, the disadvantage is the need for intraoperative position change. Taken together, the latissimus dorsi muscle flap is simple, safe and reliable as a means of treating infection in the median sternal incision.
(5) Large omental graft transfer repair.
The greater omentum has physiological functions such as anti-infection, immunity, re-vascularization, resorption and establishment of collateral circulation, and is rich in blood flow and easy to cut. when the greater omentum is removed from the abdominal cavity and transferred, it can rapidly adhere to the repaired tissue and become one, rapidly establishing collateral circulation and improving the blood supply to the ischemic tissue. belcher et al. reported 12 cases of applying the greater omentum graft to treat sternal after coronary artery bypass grafting Belcher et al. reported the results of 12 cases of infected sternal dehiscence after coronary artery bypass grafting, and concluded that severe sternal infection should be treated by early and complete debridement of necrotic tissue and direct closure of the incision with a large omental graft, which can reduce the recurrence of postoperative complications and shorten the hospital stay, and the procedure is simple and safe. d’Udekem et al [23] treated 14 patients with severe mediastinitis with complete debridement and large omental graft, and postoperative sedation of antibiotics for at least 4 weeks. antibiotics for a minimum of 4 weeks. There were no surgical deaths, a mean postoperative hospital stay of 31 (20-154) days, and no recurrence of infection at a mean follow-up of 20 months. Because of the high recurrence rate of infection and morbidity and mortality after debridement and mediastinal irrigation and drainage, most scholars advocate the application of appropriate muscle flap or large omental flap graft for treatment in one phase.
5. Comparison of various methods.
For patients with mild infection and early course of disease, closed flush drainage method can be applied and the symptoms of infection can be controlled and cured. However, sometimes only the sternum and subpectoral infected areas are simply treated with incision, scratching and drainage, which still cannot be cured, and the treatment time is prolonged and the patient suffers greatly. Liu Wei et al. also reported that for chronic sternal infections despite insisting on open drug exchange for 3 months, no improvement was eventually seen. In cases of recurrent chronic infections, the inflammation is often confined to a particular segment of the sternum, and performing simple flushing and dressing changes requires long-term dressing changes, which is painful and prone to the formation of sinus tracts and more long-term failure to heal. Therefore, surgical debridement + myocutaneous flap transfer repair is the treatment of choice for recurrent infections, especially in cases where treatment with closed flush drainage has failed. The following three conditions are necessary for surgical treatment to achieve one-stage healing.
(1) Thorough removal of lesions and foreign bodies such as dead bone, granulation tissue, wires and threads to achieve no source of infection and make the surgical area relatively sterile.
(2) The defective area after removal of the lesion needs to be filled with transferred muscle flap to eliminate the dead cavity so that there is no accumulation of blood and fluid in the trauma after surgery to avoid re-infection.
(3) The flap should be sutured and fixed carefully so that no threads or foreign bodies remain in the wound as much as possible to avoid the formation of a hidden risk of reinfection.
It was learned through follow-up that in patients with sternal osteomyelitis treated with muscle flap transfer repair, the wounds healed in 15-20 days, no recurrence of sternal osteomyelitis or costochondritis was seen, the pain symptoms disappeared or improved significantly, and the early local, although mildly elevated, muscle atrophy and elevation disappeared after 3 months with good results. In patients with concomitant sternal osteomyelitis, treatment with a viable greater omentum or muscle flap can improve the cure rate of sternal infection and decrease the mortality rate to less than 10%. In the case of myoflap, Yellin et al. suggested that for patients with late detection of infection, complex trauma, and severe sternal destruction, a staged procedure should be used, i.e., a first-stage debridement with open wound, followed by a second-stage tissue flap transplantation when the infection is controlled. 98.0% of patients with mediastinitis were cured within 6 weeks, with a 4.0% mortality rate within 30 days. Szerafin et al. concluded that early mediastinal infection can be successfully cured by debridement and irrigation and drainage after early diagnosis, but if the patient delays surgery for other reasons or if the sternum is extensively infected or conservative treatment fails, the patient should be treated with a viable muscle flap. They summarized treatment options for 70 patients with mediastinitis after cardiac surgery and analyzed them for comparison. The results showed that the rates of recurrent infection and death in the “soft tissue flap” group were (14.0%, 6/43) and (11.6%, 5/43), respectively, which were lower than those in the “flush and drain” group (38.5%, 10/26) and (15.4%, 4/26). 4/26) were lower.
Each type of soft tissue flap has its own advantages and disadvantages in practice: the application of the greater omentum transfer to repair and fill the residual cavity formed by infection requires opening the abdominal cavity to free the greater omentum, which is more complicated, traumatic and has more complications. Although it is easier to remove the latissimus dorsi muscle, it is necessary to change the position during the operation, which increases the tediousness of the operation. For example, some patients after coronary artery bypass grafting cannot use both sides at the same time, because for such patients, the left internal thoracic artery is free as the graft vessel, and in order not to affect the blood flow of the left sternum, only the right pectoralis major muscle can be used, and the rectus abdominis muscle flap can easily cause weakness of the abdominal wall and incisional hernia after excision, and the abdominal wall needs to be reinforced with polypropylene mesh if necessary.
For different patients, appropriate soft tissue flaps need to be selected according to the actual situation to repair the tissue defects formed after complete removal of necrotic tissue.