**8. Options in soft tissue defects reconstruction after DSWI in cardiac surgery**

There are a broad range of possibilities for managing sternal soft tissue defects caused by DSWI. In the case of minor defects, a direct suture with tissue undermining can be effective. In wide dehiscence, some type of flap transfer is needed and excessive bone and soft tissue loss are dependent on close co-operation between the cardiac and reconstructive surgeons. There are two crucial conditions influencing the reconstructive strategy. The first condition is the size of the defect, while the second is the vascular network, which would optimally remain uncompromised after primary surgery or previously failed reconstructions. Although various flaps and their modifications have been proposed, none have been found to be a reconstructive option for all defects [97,163,164], therefore Greig et al suggested a simple classification system to address the choice of flap based on the size and location of the post-sternotomy defect (Table 6) [165]. It is not possible, however, to follow this classification system because various factors and conditions influencing the result must be taken into the account.


**Table 6.** Classification of sternal wounds according to anatomical site (modified from Greig et al [165])

In 1976, Lee et al were the first to report on the use of a pedicled greater omentum to fulfill the large defect after total sternectomy [93]. In 1980, Jurkiewicz et al introduced the bilateral pectoralis turnover flap for the same indication. Although various muscle flaps, along with their modifications have been reported, there is still debate about using muscular versus cutaneous or fasciocutaneous flaps to cover difficult defects. It has been presumed that muscular flaps carry richer vascular networks, thus bringing a better blood supply to the defect, along with a higher antibiotic concentration. Recent studies, however, did not support this hypothesis and suggested that muscle flaps have no particular advantage over fasciocu‐ taneous flaps in terms of improving vascularity and eradicating infection [166,167]. Never‐ theless, there is still a reasonable argument for muscular flaps as additional muscle brings enough tissue for planed reconstruction.

cover the entire sternotomy defect, but this method requires secondary skin grafting from an islanddonor site [177].This techniquewas adoptedandmodifiedbyMolitor et al[178].The skin island is dissected, while the underlying muscle fascia and pectoralis major are elevated and completely released from their insertions to the humerus, sternocostal junctions and abdomi‐ nalmuscles.Thethoracoacromialvesselsarevisualizedandtheclavicularinsertionofthemuscle is released to achieve comfortable advancement of the flap to the defect. The secondary defect in the lateral thoracic wall is then sutured in the V-Y manner and no skin graft is needed [178].

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Finally, the pectoralis major musculocuteneous flap can be mobilized in a rotational manner when the skin-muscle flap is elevated based on the thoracoacromial pedicle and is rotated to

This flap is based on perforators of the internal mammary artery. Once the skin is elevated off of the anterior pectoralis fascia, the distal rib, proximal clavicular origin and humeral insertion of the muscle are divided. Then, the thoracoacromial pedicle is dissected and ligated, and the pectoralis major is elevated from lateral to medial until the perforating vessels from the internal thoracic artery are identified, and the muscle is then turned into the defect. To gain additional width of the narrowing humeral portion of the flap, fascial release incisions along the direction of the muscle fibers can be done. By this maneuver an average increase in flap width of 5.8 cm can be obtained [181]. Usually bilateral turnover muscle flaps are used [94,95]. The disadvan‐ tages of this flap include limitations in the distal parts of the sternum, need for wide skin undermining, dependence on an intact internal mammary artery, and an unfavorable aesthetic consequence including a missing anterior axillary line and parasternal subcutaneous tissue

This flap was first used in cardiac surgery by Jurkiewicz in the case of a pectoral turnover flap failing to cover the entire defect [94,95]. To cover the sternal defect, the rectus abdominis flap is used exclusively as a pedicled flap based on the superior epigastric artery [182]. Because this artery is the terminal branch of the internal thoracic artery, the flap cannot be used if the ipsilateral internal thoracic artery was used for bypass grafting. The functional consequences of using the rectus abdominis to reconstruct sternal defects were assessed by Netscher et al [169]. They found no significant differences in abdominal wall function between the groups of patients in whom the rectus muscle was used for reconstruction and the group without sternal wound complications. There is a higher associated risk of hernia (11%) or fascial weakness (42%) as was reported [103,183]. The rectus abdominis flap may be used as a

The rectus abdominis muscular flap may be dissected without the use of a skin island. The skin incision continues distally to the desired point according to the necessary flap length. The

muscular flap [94,184) or as a myocutaneous island flap [171,185].

the defect [179].

bulkiness [95].

**8.2. The rectus abdominis flap**

*8.2.1. Rectus abdominis muscular flap*

*8.1.2. Pectoral muscle turnover flap*

#### **8.1. The pectoralis major flap**

The pectoralis major provides many qualities that make it a suitable flap choice for covering sternal defects including close proximity to the sternotomy, triple blood supply (the thora‐ coacromial artery, perforating branches of the internal thoracic artery and the lateral thoracic artery), and versatility of the flap as either the thoracoacromial or internal thoracic artery vascular axis may be used separately to nourish the flap [168]. Netcher et al did not show an adverse influence of the pectoral muscle transposition on pulmonary function [169], moreover, pain and loss of strength appeared to be related more to sternal instability rather than to the muscle transposition. Additionally, Cohen et al reported an improvement of spirometric parameters (forced vital capacity and standardized forced expiratory volume in 1 second) before and after pectoral flap transfer, thus supporting the crucial role of the flap in chest stabilization [170].

#### *8.1.1. Pectoral muscle advancement flap*

The pectoral muscle advancement flap is based on the thoracoacromial pedicle and is consid‐ ered to be the best muscular reconstructive option in this area due to its technical simplicity, versatility, and low risk of flap loss (<3%). There is, however, some risk of skin island necrosis or partial necrosis (≈30%) [171, 172]. Dissection and elevation of the flap begins along the median line of the costal grid until reaching the relatively avascular plane under the muscle. Undermining then proceeds by blunt dissection laterally as necessary to achieve approxima‐ tion of the bilateral flaps at the median line without tension. The thoracoacromial vascular pedicle is visible at the dorsal plane of the muscle. The humeral and clavicular insertion of the muscle can be released if needed. If the distal portion of the sternum is exposed, dissection continues distally under the anterior sheet of the rectus abdominis which then becomes part of the flap [164]. Though the flap is elevated mostly in a myocutaneous fashion [73,163,164,173,174], Brutus et al reported on the use of a pectoral muscle flap released from skin for covering the entire sternal defect [175]. Completely dissected and freed from all of its origins, the pectoral muscle was advanced medially on the skeletonized vascular pedicle to cover the full length of the sternal defect. Separating the skin from the muscle can jeopardize the cutaneous blood supply and increase risk of skin necrosis. This technique included the release of humeral insertion from a short skin counter incision [175].

If the defect is wide, it may be difficult to achieve tension-free suturing in the midline. A modification of the advancement flap with a skin relaxing incision has been reported [176]. Majure et al proposed shifting the skin island over the pectoralis muscle in the V-Y manner to

cover the entire sternotomy defect, but this method requires secondary skin grafting from an islanddonor site [177].This techniquewas adoptedandmodifiedbyMolitor et al[178].The skin island is dissected, while the underlying muscle fascia and pectoralis major are elevated and completely released from their insertions to the humerus, sternocostal junctions and abdomi‐ nalmuscles.Thethoracoacromialvesselsarevisualizedandtheclavicularinsertionofthemuscle is released to achieve comfortable advancement of the flap to the defect. The secondary defect in the lateral thoracic wall is then sutured in the V-Y manner and no skin graft is needed [178].

Finally, the pectoralis major musculocuteneous flap can be mobilized in a rotational manner when the skin-muscle flap is elevated based on the thoracoacromial pedicle and is rotated to the defect [179].

### *8.1.2. Pectoral muscle turnover flap*

cutaneous or fasciocutaneous flaps to cover difficult defects. It has been presumed that muscular flaps carry richer vascular networks, thus bringing a better blood supply to the defect, along with a higher antibiotic concentration. Recent studies, however, did not support this hypothesis and suggested that muscle flaps have no particular advantage over fasciocu‐ taneous flaps in terms of improving vascularity and eradicating infection [166,167]. Never‐ theless, there is still a reasonable argument for muscular flaps as additional muscle brings

The pectoralis major provides many qualities that make it a suitable flap choice for covering sternal defects including close proximity to the sternotomy, triple blood supply (the thora‐ coacromial artery, perforating branches of the internal thoracic artery and the lateral thoracic artery), and versatility of the flap as either the thoracoacromial or internal thoracic artery vascular axis may be used separately to nourish the flap [168]. Netcher et al did not show an adverse influence of the pectoral muscle transposition on pulmonary function [169], moreover, pain and loss of strength appeared to be related more to sternal instability rather than to the muscle transposition. Additionally, Cohen et al reported an improvement of spirometric parameters (forced vital capacity and standardized forced expiratory volume in 1 second) before and after pectoral flap transfer, thus supporting the crucial role of the flap in chest

The pectoral muscle advancement flap is based on the thoracoacromial pedicle and is consid‐ ered to be the best muscular reconstructive option in this area due to its technical simplicity, versatility, and low risk of flap loss (<3%). There is, however, some risk of skin island necrosis or partial necrosis (≈30%) [171, 172]. Dissection and elevation of the flap begins along the median line of the costal grid until reaching the relatively avascular plane under the muscle. Undermining then proceeds by blunt dissection laterally as necessary to achieve approxima‐ tion of the bilateral flaps at the median line without tension. The thoracoacromial vascular pedicle is visible at the dorsal plane of the muscle. The humeral and clavicular insertion of the muscle can be released if needed. If the distal portion of the sternum is exposed, dissection continues distally under the anterior sheet of the rectus abdominis which then becomes part of the flap [164]. Though the flap is elevated mostly in a myocutaneous fashion [73,163,164,173,174], Brutus et al reported on the use of a pectoral muscle flap released from skin for covering the entire sternal defect [175]. Completely dissected and freed from all of its origins, the pectoral muscle was advanced medially on the skeletonized vascular pedicle to cover the full length of the sternal defect. Separating the skin from the muscle can jeopardize the cutaneous blood supply and increase risk of skin necrosis. This technique included the

If the defect is wide, it may be difficult to achieve tension-free suturing in the midline. A modification of the advancement flap with a skin relaxing incision has been reported [176]. Majure et al proposed shifting the skin island over the pectoralis muscle in the V-Y manner to

release of humeral insertion from a short skin counter incision [175].

enough tissue for planed reconstruction.

**8.1. The pectoralis major flap**

508 Artery Bypass

stabilization [170].

*8.1.1. Pectoral muscle advancement flap*

This flap is based on perforators of the internal mammary artery. Once the skin is elevated off of the anterior pectoralis fascia, the distal rib, proximal clavicular origin and humeral insertion of the muscle are divided. Then, the thoracoacromial pedicle is dissected and ligated, and the pectoralis major is elevated from lateral to medial until the perforating vessels from the internal thoracic artery are identified, and the muscle is then turned into the defect. To gain additional width of the narrowing humeral portion of the flap, fascial release incisions along the direction of the muscle fibers can be done. By this maneuver an average increase in flap width of 5.8 cm can be obtained [181]. Usually bilateral turnover muscle flaps are used [94,95]. The disadvan‐ tages of this flap include limitations in the distal parts of the sternum, need for wide skin undermining, dependence on an intact internal mammary artery, and an unfavorable aesthetic consequence including a missing anterior axillary line and parasternal subcutaneous tissue bulkiness [95].

### **8.2. The rectus abdominis flap**

This flap was first used in cardiac surgery by Jurkiewicz in the case of a pectoral turnover flap failing to cover the entire defect [94,95]. To cover the sternal defect, the rectus abdominis flap is used exclusively as a pedicled flap based on the superior epigastric artery [182]. Because this artery is the terminal branch of the internal thoracic artery, the flap cannot be used if the ipsilateral internal thoracic artery was used for bypass grafting. The functional consequences of using the rectus abdominis to reconstruct sternal defects were assessed by Netscher et al [169]. They found no significant differences in abdominal wall function between the groups of patients in whom the rectus muscle was used for reconstruction and the group without sternal wound complications. There is a higher associated risk of hernia (11%) or fascial weakness (42%) as was reported [103,183]. The rectus abdominis flap may be used as a muscular flap [94,184) or as a myocutaneous island flap [171,185].

### *8.2.1. Rectus abdominis muscular flap*

The rectus abdominis muscular flap may be dissected without the use of a skin island. The skin incision continues distally to the desired point according to the necessary flap length. The skin is undermined over the rectus fascia to expose the muscle. Then, the rectus anterior sheet is divided and the muscle is dissected and mobilized. The distal pedicle inferior epigastric vessels are ligated and divided. The muscle is then turned to the defect. The exposed muscle and pedicle is covered either by skin suture or grafting [95].

shoulder girdle strength, such as paralytic patients in a wheelchair or walker dependent patients, may endorse strength difficulties after muscle harvesting as well as tennis and golf players or those whose profession involves overhead tasks [187]. Up to 50% of patients may

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Usually the muscle from the non-dominant side is used. The arc of rotation and position of the skin island is assessed and marked. The skin component is predominantly oriented perpendic‐ ular to the muscle fibers near the vertebral column, but a longitudinal course from the medial axillary line to the medial caudal dorsum is also possible. The flap is dissected using the whole muscle up to the pedicle. Thoracodorsal vessels are skeletonized and humeral muscle inser‐ tion is divided, allowing an additional 4-10 cm of flap advancement. Then the flap is trans‐ posed to the defect through a subcutaneous tunnel superficial to the pectoralis major [188,189].

Obese female patients with large breasts are at higher risk of sternal dehiscence due to the infero-lateral tension of the breasts, especially on the distal third of the sternotomy [72].This instability results from the greater protrusion of the lower thorax and abdomen during respiration, greater dimensions of the lower versus the upper thorax, the concentration of forces from the attachment of the ribs, and the reduced thickness of the lower sternum [72]. Therefore a special bandage, supporting bra, or other garment is used to release the tension resulting from large breasts. The technique of covering the sternal dehiscence with a bilateral pectoral muscle advancement flap with simultaneous breast reduction has been reported [190-192]. Large breasts carry an enormous amount of relatively well vascularized tissue that can potentially be used to cover the sternal defect [193,194]. The vascular supply of the breast is basically the same as the pectoral muscle. There is, however, a unique vascular network inside the breast gland, known as Würinger´s septum. Uygur et al reported a method of covering a large distal sternum defect with bilateral fasciocutaneous V-Y flaps from the breasts [193]. These flaps were anatomically based on the Würinger´s septum [193,195]. Another method has been suggested by Hamdi et al [196]. They performed a septum-based therapeutic mammoplasty on two patients. The principle of this technique is to reduce breast mass with

harvesting of a large fasciocutaneous flap from the inferomedial part of the breast

vascular pedicles of the breast [197,198].

**8.6. Omentum**

Another possibility for utilizing the breasts to cover the sternal defect is a Cyclops´ flap. In this technique the whole breast is transposed to the central or even contralateral chest defect, so that the areola is centralized. The breast flap in this case is based on the lateral and central

The greater omentum is a well-vascularized tissue with plentiful lymphatic drainage and angiogenic activity [93,98,199]. Its size can be up to 36x46 cm and is reliable to cover large defects. It is difficult, however, to predict the flap size preoperatively because the greater omentum volume has no direct correlation with the patient's habitus [200]. The omentum can be transposed to the defect in various ways such as, pedicled on both gastroepiploic arteries

complain of localized numbness at the harvesting area [172].

**8.5. Breast flap**

## *8.2.2. Rectus abdominis musculocutaneous flap*

Themyocutaneous flapcanhaveaskinislandorientedverticallyalongtheusedmuscle(VRAMvertical rectus abdominis muscle flap), or horizontally, as well as perpendicular to the muscle distal to the umbilicus (TRAM-transverse rectus abdominis muscle flap). The transverse orientationpermits harvest of a larger skinpaddle.Dissection ofthe VRAMstarts with marking the skin island over the used muscle. The skin component should be placed medially near the umbilicus to include important periumbilical perforators. The skin island is cut and the skin overlying the muscle is undermined above the muscle fascia. Then, the rectus sheet is divided bilaterallyattheedgesofthemuscleandthemuscleisdissectedandmobilized.Thedistalpedicle inferiorepigastricvesselsareligatedanddivided.Theflapisthenturnedtothedefect.TheTRAM is marked transversely under the umbilicus and skin island which can involve the entire area between the umbilicus and symphysis bilaterally. The flap is dissected in the similar way as the VRAM flap, but the mobilization of the skin island continues away from the muscle pedicle crossing the midline to the contralateral side [171,185]. Care must be taken to avoid pedicle compression passed through the subcutaneous tunnel to the sternal defect.

#### **8.3. Combined pectoral muscle — Rectus abdominis muscle flap**

For full length sternal defects, a combined pectoralis major and rectus abdominis flap (Pec-Rec flap) was proposed [186]. The flap is predominantly created on the left side, but can occasional‐ ly be bilateral. The skin overlying the pectoral muscle is elevated up to the mid-axillary line laterallyandfromtheclavicletotheinferiorcostallineinaverticaldirection.Thepectoralmuscle iselevatedwhilepreservingthethoracoacromialvessels.Themuscleisdetachedfromitshumeral insertion and medially from one third of the clavicle. Dissection of the flap continues distally while elevating the thoracoepigastric fascial attachments from the chest wall between the pectoralis major and the rectus abdominis. Distal to the fascia, the anterior sheet of the rectus abdominis is incisedmediallyandlaterallyandthemuscleismobilizedfromtheposteriorfascia. The muscular connections of the rectus abdominis to the distal ribs are detached as the last step of flap harvesting. The superior epigastric artery can be preserved or it can be divided close to the muscle if necessary for better medial transposition of the flap [186].

### **8.4. The latissimus dorsi muscle flap**

The latissimus dorsi flap is based on a thoracodorsal artery that has not been jeopardized by previous cardiac surgery. Moreover, a large flap can be harvested (the main surface area of muscle is 105 cm2 for women and 192 cm2 for men) [187]. The main disadvantages of this flap include the need for a lateral decubital position during flap harvesting that can endanger patients with large sternal bone defect and sternal instability and shoulder functional limita‐ tion followed latissimus dorsi muscle harvesting. Patients who are dependent on their shoulder girdle strength, such as paralytic patients in a wheelchair or walker dependent patients, may endorse strength difficulties after muscle harvesting as well as tennis and golf players or those whose profession involves overhead tasks [187]. Up to 50% of patients may complain of localized numbness at the harvesting area [172].

Usually the muscle from the non-dominant side is used. The arc of rotation and position of the skin island is assessed and marked. The skin component is predominantly oriented perpendic‐ ular to the muscle fibers near the vertebral column, but a longitudinal course from the medial axillary line to the medial caudal dorsum is also possible. The flap is dissected using the whole muscle up to the pedicle. Thoracodorsal vessels are skeletonized and humeral muscle inser‐ tion is divided, allowing an additional 4-10 cm of flap advancement. Then the flap is trans‐ posed to the defect through a subcutaneous tunnel superficial to the pectoralis major [188,189].
