**9. University hospital Olomouc management of DSWI after cardiac surgery**

#### **9.1. Adopted treatment strategy for DSWI**

We retrospectively analyzed our experience with treatment strategies of DSWI since February 2002, when our department was established. A total of 100 patients fulfilling CDC criteria [5] for DSWI were enrolled until September 2011 with an overall incidence of DSWI of 1.36%. The results of 28 patients (March 2002-June 2004) primarily treated with closed chest irrigation using diluted iodine solution were compared with 76 patients (September 2004 to September 2009) treated with NPWT (VAC ATS™, KCI, St. Antonio, USA). A standardized protocol for first-line application of NPWT is depicted in Figure 1. Six patients from the interim period (June to September 2004) when closed irrigation and NPWT were combined were excluded from the analysis. Both groups had comparable demographic and perioperative characteris‐ tics, however, the NPWT arm had an insignificant trend towards advanced age, higher logistic EUROSCORE, more complex primary cardiac surgery. No difference in the rate of causative agent was found, with SA and CONS identified in almost 70% of cases. Escherichia coli (5.8%) and Pseudomonas species (7.2%) as leading Gram negative strains were cultivated. The time to presentation of DSWI was insignificant between groups (17.5±15.0 vs. 13.8±16.3, p=0.55) as well as readmission for late clinical presentation of DSWI (38.6% vs. 50%, p=0.12). Although the overall length of DSWI therapy was comparable (14.3±11.9 vs. 14.9±7.9 days, p=0.82), NPWT required more dressing changes (5.4±2.3 vs. 1.8±1.2, p<0.001), but was associated with substantially lower failure of primary therapy (5.1 vs. 39.2%, p<0.01) with closed chest irrigation. In-ICU stay was significantly shorter in the NPWT group (209.6±331.3 vs. 516.1±449.5 hours, p<0.001), nevertheless, shortened in-hospital stay (40.2±16.3 vs. 48.8±29.2 days, p=0.16) was insignificant in this group. Addressing mortality, 30-day and 1-year mortality was considerably lower in the NPWT arm (3.9 vs. 21.4%, p<0.05, 15.8 vs. 39.2%, p<0.05, respectively). A Kaplan-Meier 1 year-survival analysis is shown in Figure 2. The risk of major bleeding complications was comparable between groups, with 2 patients (3.6%) from the closed chest irrigation group having erosion of venous bypass graft and right ventricle (RV), and 3 patients (3.9%) from the NPWT group, including 1 debridement-related and 2 spontaneous injuries of the RV. Employment of local and advancement flaps for covering of residual defects was higher in the NPWT groups (65.7 vs. 17.8%, p<0.01). Our experience showed that NPWT is effective in the treatment of DSWI, compared with closed chest irrigation, leading to lower failure of primary therapy, ICU stay, and better short- and midsurvival of patients. We did not prove NPWT influenced length of in-hospital stay or risk of major bleeding, however, residual defects required more complex approach to assure sternal stability and covering defects [119,130].

#### **9.2. Sternal stabilization and management of residual bone defects**

for defects in the distal part of sternotomy wound or mobilized on either of the gastroepiploic vessels to cover full-length sternotomy defects [201-203]. Passing the omental flap subcutane‐ ously from the upper portion of the laparotomy bears up to a 21% risk of late herniation [202], thus, a better solution seems to create the transdiaphragmatical tunnel just right of the falciform ligament [204]. The risk of abdominal cavity infection is rare [205], but the traction on the gastroepiploic artery can cause motility disturbances of the stomach and duodenum [206], and one case of fatal cecum volvulus have been reported [207]. Laparoscopic harvesting seems to

Microsurgical free flaps can be used to cover sternal defects in particular situations. This technique, due to its duration and technical complexity, should serve as a last treatment option. The use of the tensor fascia lata myocutaneous flap, rectus abdominis myocutaneous flap and deep inferior epigastric artery fasciocutaneous flap for this indication have been reported [210]. As a donor vessel, the thoracoacromial, internal thoracic or cervical vessels can be used. The cephalic vein attached to the thoracoacromial or cervical arteries, can be used for lengthening

There are special requirements for care after flap surgery. In general, it is important to protect the blood circulation within the flap, maintaining both general and local hemodynamics. Vascular spasm must be prevented by using vasodilator drugs if possible. The elevated and transposed flap usually loses most of its physiological blood and lymphatic network and is dependent only on a small part of it, so varying degrees of edema are usually present. Large swelling of the tissue compresses the capillaries and decreases the blood flow in the flap, increasing the tension on the suture. Corticosteroids are used to prevent swelling for several days in most flap surgeries unless serious contraindications are present. The flap must be kept from topical pressure, particularly in places of passing vascular pedicle and in peripheral parts of the flap because of limited vascular competence. Undoubtedly, changes in body position influence the blood supply of the flap. Furthermore, stretching of the arms causes increased tension on the medial sternal suture. In the case of the pectoral and latissimus dorsi flap, the use of muscles of the shoulder girdle should be avoided. When using the rectus abdominis flap, the abdominal wall must be relaxed and supported with bandages for several weeks to prevent hernia formation. Finally, nutritional support with enteral feeding is essential for

**9. University hospital Olomouc management of DSWI after cardiac surgery**

We retrospectively analyzed our experience with treatment strategies of DSWI since February 2002, when our department was established. A total of 100 patients fulfilling CDC criteria [5]

be promising in reduction of access complications and pain [108,208,209].

**8.7. Microsurgical flaps**

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successful healing.

**9.1. Adopted treatment strategy for DSWI**

the donor vessel (arterio-venous loop) [210,211].

**8.8. Specifics of care after flap surgery in cardiac surgery**

Non-complicated sternal dehiscence following DSWI that is not associated with considerable bone loss can be stabilized with transverse titanium plates (Titanium Sternal Fixation system™, Synthes, Switzerland) at our department. Plates are applied on the anterior surface of the ribcage to achieve sufficient stability of the chest wall while minimizing the risk of an iatrogenic injury to the heart. From January 2008 to September 2012 we performed 31 sternal wall reconstructions using the Titanium Sternal Fixation system™. In four cases, osteosynthesis was applied to treat a sterile mechanical dehiscence of the median sternotomy, while 27 other chest osteosyntheses were performed after DSWI when wound bed decontamination was achieved with NPWT. In the postoperative period, 2 patients (7.4%) needed to be operatively revised due to bleeding from pectoral flap advancement; in 3 cases (11.1%) the plates needed

**Figure 1.** The first-line application protocol of NPWT for treatment of DSWI

to be removed for soft tissue healing complications post-reconstruction. Nevertheless, removal could be postponed until satisfactory healing of the sternal bones was achieved. One patient (3.7%) had to be drained for iatrogenic pneumothorax. We also retrospectively analyzed 21 patients with post-DSWI sternal dehiscence from January 2005 to January 2010, comparing 11 patients with re-cerclage wiring and 10 patients with titanium plate osteosynthesis. DSWI was managed with the same protocol of NPWT prior to reconstruction mentioned above [119]. Plating was accompanied by a lower risk of therapy failure (1% vs. 1.85%), shorter in-hospital stay (22 vs. 59%), and reduction in costs ((€8,243 vs. €33,365) (unpublished data).

treating large sternal defects in the same way as a total or near-total sternectomy and fixed properly with titanium plate system ensures chest cage stability. An allogenous bone trans‐ plant doesn´t contain any vital bone marrow cells, which eliminates difficulties in immunogenetic acceptance of the graft by a patient; it represents a biological tissue transfer, which even under conditions of maximum precautions represents a minor risk for transmission of viral or bacterial infections. An allogenous graft must meet legislative criteria from the Czech Republic and the European Association of Tissue Banks [161,162]. Prior to graft harvesting, each donor is cross-checked for registration within the National Registry for organ donation refusal. All deceased donors treated for infectious disease, sepsis, malignant tumors, or systemic and autoimmune diseases at the time of death are withdrawn from the donor list. Donor blood serum samples are tested for antibodies and HIV types 1 and 2, hepatitis B surface

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**Figure 2.** 1-year Kaplan-Meier survival analysis comparing NPWT with conventional therapy (CONV)

In cases of minor sternal bone loss, we use an autologous bone graft harvested from the patient ´s own iliac crest. The graft is preferably prepared as bi-cortical. There is a limit to the extent of bone tissue that can be solved through this method. Fixation of the bone graft and chest stabilization is done in the manner described above. From 2009 to 2012 we used this method in 2 patients. In both cases the wounds healed successfully and the sternal wall regained full stability. Both sternal defects represented partial loss of bone tissue from 6 to 8 cm in length.

Based on this experience, we decided to apply a novel approach for the treatment of massive bone loss after DSWI, by supplying the bone defect with an allogenous bone graft. It allows

**Figure 2.** 1-year Kaplan-Meier survival analysis comparing NPWT with conventional therapy (CONV)

to be removed for soft tissue healing complications post-reconstruction. Nevertheless, removal could be postponed until satisfactory healing of the sternal bones was achieved. One patient (3.7%) had to be drained for iatrogenic pneumothorax. We also retrospectively analyzed 21 patients with post-DSWI sternal dehiscence from January 2005 to January 2010, comparing 11 patients with re-cerclage wiring and 10 patients with titanium plate osteosynthesis. DSWI was managed with the same protocol of NPWT prior to reconstruction mentioned above [119]. Plating was accompanied by a lower risk of therapy failure (1% vs. 1.85%), shorter in-hospital

In cases of minor sternal bone loss, we use an autologous bone graft harvested from the patient ´s own iliac crest. The graft is preferably prepared as bi-cortical. There is a limit to the extent of bone tissue that can be solved through this method. Fixation of the bone graft and chest stabilization is done in the manner described above. From 2009 to 2012 we used this method in 2 patients. In both cases the wounds healed successfully and the sternal wall regained full stability. Both sternal defects represented partial loss of bone tissue from 6 to

Based on this experience, we decided to apply a novel approach for the treatment of massive bone loss after DSWI, by supplying the bone defect with an allogenous bone graft. It allows

stay (22 vs. 59%), and reduction in costs ((€8,243 vs. €33,365) (unpublished data).

**Figure 1.** The first-line application protocol of NPWT for treatment of DSWI

8 cm in length.

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treating large sternal defects in the same way as a total or near-total sternectomy and fixed properly with titanium plate system ensures chest cage stability. An allogenous bone trans‐ plant doesn´t contain any vital bone marrow cells, which eliminates difficulties in immunogenetic acceptance of the graft by a patient; it represents a biological tissue transfer, which even under conditions of maximum precautions represents a minor risk for transmission of viral or bacterial infections. An allogenous graft must meet legislative criteria from the Czech Republic and the European Association of Tissue Banks [161,162]. Prior to graft harvesting, each donor is cross-checked for registration within the National Registry for organ donation refusal. All deceased donors treated for infectious disease, sepsis, malignant tumors, or systemic and autoimmune diseases at the time of death are withdrawn from the donor list. Donor blood serum samples are tested for antibodies and HIV types 1 and 2, hepatitis B surface antigen (HbsAg), hepatitis C antibodies (anti-HCV), and HTLV I and II antibodies. Harvest of a sternal bone graft is performed under strictly sterile conditions by a team from the National Tissue Center in Brno. The graft is harvested under sterile conditions and stored in the freezer at −80°C. Prior to its clinical use, the graft is thawed at 4-6°C for 12 hours, soaked with a 1% gentamicin solution, prepared for its final shape, and stored in the freezer again at −80°C. If bacterial sampling is negative, the graft is thawed for 12 hours before transplantation, and submerged in a bath with 1% neomycin solution immediately before surgery.

Inherent surgical technique is modified by a more aggressive debridement of residual chest bone or ribs (1-2 cm safety line). Afterwards, the bone graft is adjusted to the size of the bone defect and fixed with plates anchored by self-cutting or self-drilling cortical screws. An uneven surface and tiny bone deficiency can be filled in with a spongy bone which is prepared from another graft provided by the tissue bank (femoral or tibial graft source). Residual soft tissue defect is covered with monolateral or bilateral pectoral muscle flap transfer. Within the postoperative period, it is strongly recommended to avoid excessive coughing or any rough mechanical strain on the sternal wall. Intravenous antibiotics are administered for at least three weeks after the reconstruction. Between January 2010 and September 2012, we performed six reconstructions of the sternal wall using an allogenous bone graft. We used a cadaveric sternum in four cases (Figure 3), and due to a lack of allografts, we had to use a calva bone in one patient (Figure 4) and a split femoral diaphysis in one patient. Successful healing after the reconstruction was achieved in five cases (83%), while one patient required additional treatment for partial skin necrosis. One obese female experienced flap failure and died from multiple organ failure. Follow-up of the other patients at 3, 6 and 12 months after reconstruc‐ tion proved stability of the chest wall. A radio-isotope scan using technetium as a tracer of autologous leukocytes (Technetium-HMPAO) carried out at 3, 6 and 12 months after the reconstruction showed a high level of healing activity within the area of the allogenous bone implant, and further chest wall stability with allograft union was confirmed through 3D-CT evaluation done 5 to 7 months after the reconstruction (unpublished data).

**Figure 4.** Cadaveric calva bone allograft in large bone defect repair and CT reconstruction showing the bone re-union

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In a group of 76 consecutive patients primarily treated with NPWT for DSWI from September 2004 to September 2011, 19 residual defects (25%) were closed by direct suture, and 57 patients (75%) underwent flap transfer to achieve reliable tension-free suture. All but 2 patients (2.7 %) underwent sternal stabilization with re-cerclage (61.8%) or transverse plates with or without bone graft (35.5%). Local fasciocutaneous advancement was used in 12 patients (21.1%), bilateral pectoralis advancement flap in 35 patients (61.2%), monolateral pectoralis flap with V-Y skin island in 7 patients (12.3%), bipedicled pectoral and rectus abdominis flap in 1 patient (1.7%), and vertical rectus abdominis flap in 2 patients (3.5%). We faced 2 flap failures (3.5%) and one whole monolateral pectoralis flap with V-Y skin island was lost due to vascular pedicle thrombosis, with 50% of the mass of the VRAM flap needing to be removed for flap necrosis. Minor healing complications requiring further local wound care were noted in 15 cases (26.3%). While the bilateral pectoralis advancement flap is a technique used by cardiac surgeons, other flaps used for covering larger residual soft tissue defects are utilized by plastic surgeon. The pectoral major flap with V-Y skin island is the first choice (Figure 5). When the defect is wide and deep, or in a female patient with large breasts, the VRAM pedicled flap is considered. If these two options fail or are not accessible, the latissimus dorsi pedicled flap is the next choice,

**9.3. Reconstruction of residual soft tissue defects**

and as a last resort, the microsurgical transfer is taken into account.

**Figure 5.** Technique of unilateral pectoral muscle flap advancement with V-Y skin island

**Figure 3.** Cadaveric sternal allograft and its use for large residual bone defect

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**Figure 4.** Cadaveric calva bone allograft in large bone defect repair and CT reconstruction showing the bone re-union

#### **9.3. Reconstruction of residual soft tissue defects**

antigen (HbsAg), hepatitis C antibodies (anti-HCV), and HTLV I and II antibodies. Harvest of a sternal bone graft is performed under strictly sterile conditions by a team from the National Tissue Center in Brno. The graft is harvested under sterile conditions and stored in the freezer at −80°C. Prior to its clinical use, the graft is thawed at 4-6°C for 12 hours, soaked with a 1% gentamicin solution, prepared for its final shape, and stored in the freezer again at −80°C. If bacterial sampling is negative, the graft is thawed for 12 hours before transplantation, and

Inherent surgical technique is modified by a more aggressive debridement of residual chest bone or ribs (1-2 cm safety line). Afterwards, the bone graft is adjusted to the size of the bone defect and fixed with plates anchored by self-cutting or self-drilling cortical screws. An uneven surface and tiny bone deficiency can be filled in with a spongy bone which is prepared from another graft provided by the tissue bank (femoral or tibial graft source). Residual soft tissue defect is covered with monolateral or bilateral pectoral muscle flap transfer. Within the postoperative period, it is strongly recommended to avoid excessive coughing or any rough mechanical strain on the sternal wall. Intravenous antibiotics are administered for at least three weeks after the reconstruction. Between January 2010 and September 2012, we performed six reconstructions of the sternal wall using an allogenous bone graft. We used a cadaveric sternum in four cases (Figure 3), and due to a lack of allografts, we had to use a calva bone in one patient (Figure 4) and a split femoral diaphysis in one patient. Successful healing after the reconstruction was achieved in five cases (83%), while one patient required additional treatment for partial skin necrosis. One obese female experienced flap failure and died from multiple organ failure. Follow-up of the other patients at 3, 6 and 12 months after reconstruc‐ tion proved stability of the chest wall. A radio-isotope scan using technetium as a tracer of autologous leukocytes (Technetium-HMPAO) carried out at 3, 6 and 12 months after the reconstruction showed a high level of healing activity within the area of the allogenous bone implant, and further chest wall stability with allograft union was confirmed through 3D-CT

submerged in a bath with 1% neomycin solution immediately before surgery.

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evaluation done 5 to 7 months after the reconstruction (unpublished data).

**Figure 3.** Cadaveric sternal allograft and its use for large residual bone defect

In a group of 76 consecutive patients primarily treated with NPWT for DSWI from September 2004 to September 2011, 19 residual defects (25%) were closed by direct suture, and 57 patients (75%) underwent flap transfer to achieve reliable tension-free suture. All but 2 patients (2.7 %) underwent sternal stabilization with re-cerclage (61.8%) or transverse plates with or without bone graft (35.5%). Local fasciocutaneous advancement was used in 12 patients (21.1%), bilateral pectoralis advancement flap in 35 patients (61.2%), monolateral pectoralis flap with V-Y skin island in 7 patients (12.3%), bipedicled pectoral and rectus abdominis flap in 1 patient (1.7%), and vertical rectus abdominis flap in 2 patients (3.5%). We faced 2 flap failures (3.5%) and one whole monolateral pectoralis flap with V-Y skin island was lost due to vascular pedicle thrombosis, with 50% of the mass of the VRAM flap needing to be removed for flap necrosis. Minor healing complications requiring further local wound care were noted in 15 cases (26.3%). While the bilateral pectoralis advancement flap is a technique used by cardiac surgeons, other flaps used for covering larger residual soft tissue defects are utilized by plastic surgeon. The pectoral major flap with V-Y skin island is the first choice (Figure 5). When the defect is wide and deep, or in a female patient with large breasts, the VRAM pedicled flap is considered. If these two options fail or are not accessible, the latissimus dorsi pedicled flap is the next choice, and as a last resort, the microsurgical transfer is taken into account.

**Figure 5.** Technique of unilateral pectoral muscle flap advancement with V-Y skin island
