A Simple Technique to Manage Sternal Wound Dehiscence

Introduction

Since Shoemaker first performed midline sternotomy in an elective cardiac operation in 1953, midline sternotomy has become the most common approach for most cardiac surgical operations, as this is easy to perform, causes less pain, and provides good exposure. However, complications of this approach, such as deep sternal wound infection, fragmented sternum, paramedian sternotomy (1), and non-union lead to significant risks of morbidity and mortality. Surgeons use various methods and techniques to deal with these complications (2), including: closed suction antibiotic catheter irrigation systems (3) , vacuum-assisted closure (4), omental transposition (5), unilateral or bilateral pectoralis major muscle turnover flap in mediastinitis (6), pectoralis major muscle transposition for infected sternotomy wounds (7), pedicle pectoralis major muscle rotation advancement flap (8, 9, 10), bilateral myocutaneous pectoralis major muscle flaps (11), rectus abdominus muscle flap (12), pectoralis major-rectus abdominis bi-pedicle muscle flap (13), latissimus dorsi muscle flap (14), microsurgical free flap (15), primary sternal closure with titanium plate fixation (16), one-step radical sternal debridement and muscle flap(s) reconstruction (17), and various combinations of the above. Bilateral myocutaneous pectoralis major muscle flaps have been used as a single-stage management of deep sternal wound infections without re-approximation of sternal edges or with osteo-synthesis (18, 19, 20).

The authors have used bilateral pectoralis major myocutaneous flaps based on the thoraco-acromial pedicle to manage sternal wound dehiscence in 42 patients from 2003 – 2019. These patients were originally operated on by various cardiac surgeons. This procedure can easily be done by a cardiac surgeon without the involvement of the plastic surgeons. The authors detach the left and right pectoralis muscles from their sternal origin as well as free the deep surface of pectoral muscle from the chest wall attachments. This technique eliminates the oppositely directed dragging forces on two halves of the sternum by right and left pectoralis muscle contraction. Hence, this technique removes all kinds of pull on two halves of the sternum. This will allow the two halves of the bone to remain in contact and ultimately heal. Pectoralis muscles of both sides suture together, therefore when they contract, they pull each other, rather than pull the bone. The upper limbs movements remain unaffected. 

There were two cohorts of patients.

1. Patients had sterile non-union of the sternum, as seen in the first part of this video. The authors also used this technique for fragmented sternum and para-median sternotomy.
2. Patients who had fragmented sternum secondary to deep sternal wound infection, as seen in the second part of this video.

The authors used similar techniques for both groups. 

1. Sterile non-union of the sternum (as seen in the first part of the video)

The patient in this video underwent CABG at the age of 44 due to stenosis of the left main stem, LAD, and right coronary artery. The left internal mammary artery and great saphenous veins were used to do three grafts. Following closure of the skin, the patient went into ventricular fibrillation that required compression of the chest, and the chest was reopened. Two additional grafts attached to distal LAD and obtuse marginal arteries. His postoperative recovery was uneventful and he was discharged in stable condition. Two months later, he was reviewed in the clinic. His sternum was examined, and was stable, and the wound healed completely. Four years later, he noticed pain and discomfort in his sternum. A CT scan showed complete non-union of the sternum with the gap measuring up to 1.4 cm inferiorly and broken sternal wires. There was no evidence of osteomyelitis or bony destruction. He was first treated by removal of the sternal wires and fixation of the sternum with five sternal plates and 18 screws. 
Initially he feels better, however, four months later he had a fall and the sternal plates displaced. Pain and discomfort recurred. Therefore, he was taken to the operation theater and the sternal plates were removed. Unfortunately, sternal discomfort and pain was persist, and non-union returned.

He had a background of late presentation of non-union of the sternum and a failed attempt of fixation of the sternum with screw and plates, due to a fall. In addition, the sternum was firmly adhered to the front of the heart with five patent grafts. Therefore, the authors decided to use this technique of pectoralis muscles flaps to support his sternum and eliminate the oppositely directed dragging forces on two halves of the sternum, by right and left pectoralis muscle contraction. His postoperative recovery remained uneventful and he did not complain of pain or discomfort anymore. The authors removed Redivac drains on the fifth postoperative day, and then he was discharged on the same day.

      2. Patients who had a fragmented sternum secondary to deep sternal wound infection (as seen in the second part of the video).

Patients who had deep sternal wound infection were initially managed with wound debridement followed by VAC (Vacuum Assisted Closure) therapy until the infection was well controlled and the wound looked healthy. During the VAC therapy, the authors assessed the sternum and identified those sternums that were fractured or weak and hence unlikely to give a satisfactory fixation with standard steel wires.

There were a total of 42 patients of sternal wound dehiscence in the above two groups of patients; 3 patients had sterile non-union, while others had a deep sternal wound infection. In 13 patients of this cohort, BIMA (bilateral internal mammary artery) was used; these 13 patients represent 2.7% of patients with BIMA. All these patients had excellent recovery with only minimal analgesic requirement. One patient required evacuation of a sub pectoral-flap hematoma. Most patients were discharged within five days of the procedure. 

Operative Steps

1. Make a midline incision to expose the sternum or remove the VAC dressing if it is in situ.
2. Debride all visible debris from the mediastinum and sternum. Use curette to clear the sternal edges from excessive granulation tissues and freshen the edges to facilitate better healing.

Fixation of the Sternum

The authors can use either of the following techniques for fixation of the sternum:
      a) Tighten up all the sternal wires if they were not already removed as part of the initial management with VAC therapy.
      b) In this video, the authors used number 5 Ethibond interrupted sutures that passed through partial thickness of the bone to reduce and fix the sternal edges. They used this technique if the posterior surface of the sternum stuck with the front of the heart due to adhesions; in addition, he had five grafts.
      c) Alternative technique: mobilize the sternum from the surface of the heart on both sides by 2-3 cm. Do this step only if it is possible to fix the sternum with steel wires through a few suitable areas. Assess the sternum to identify any suitable strong parts that can hold sternal wires. Pass steel wires through these suitable areas and very gently fix the sternal edge by gently tightening the wires. Please do not tighten too much, otherwise the wires will cut through the bone.

Pectoralis Muscle Flaps

1. Detach the left pectoralis muscle from its sternal origin by using diathermy. Start from the midline at the sternal edge, from medial to lateral, and free the deep surface of pectoral muscle from the chest wall attachments. Pass your hand underneath the pectoral muscle and confirm that the muscle has completely detached from the chest wall.
2. Do not raise the subcutaneous flaps off the surface of the muscle. Avoid dividing the muscles’ attachments on the rectus abdominis and external oblique inferiorly.
3. Secure the meticulous hemostasis and very carefully check the surface of the chest wall and deep surface of the pectoral muscle, otherwise a hematoma will develop.
4. Repeat the same process for the right pectoralis muscle.
5. Use three size 18 gauge high negative pressure drains (Redivac drains) - one retrosternal (if any space) and one on each side between the chest wall and pectoralis muscle.
6. Suture the two pectoral muscles together using the following technique.

            a. Use number one PDS
            b. All sutures should be interrupted and everted; please take 1.5 to 2 cm muscle tissue bites on both sites to avoid cutting through the muscle.
            c. Although placing and tying each stitch individually is time-consuming, this technique keeps the wound together even if one suture fails.
            d. Suture knots must be buried deep inside (everted sutures), otherwise superficial knots will cause skin irritation. 

Extra Sutures and Skin Closure

1. Excise the wound edges with a sharp knife all around the wound. Don’t use diathermy except for focal bleeders.
2. To provide extra support and strength, apply horizontal mattress interrupted sutures with number 2 zero prolene, as see in the video. Tie these sutures but keep them a little bit lose, as soft tissues swell up postoperatively. Make sure that they are not very tight and not strangulating the tissues. Placing and tying these sutures individually is time-consuming, but this technique keeps the wound together even if any other suture fails.
3. Suture skin edges together using either of the following techniques:
   a. Close the skin with absorbable Monocryl continuous subcuticular sutures, or
   b. Simple skin clips. 

Tips & Pitfalls

• If wound infection was the cause of the sternum dehiscence, then first manage the sternal wound infection by wound debridement and VAC therapy until the wound is infection-free and looks healthy.
• If there is no additional risk of damaging the heart/grafts, an attempt should be made to mobilize the sternal remnants from the surface of the right ventricle to allow for the placement of a few steel wires. 
• If it is difficult or you are unable to mobilize the sternum from the surface of the heart, 

            a. then just pass the steel wires through the outer pole of the sternum over a few suitable areas. Very gently fix the sternal edge by gently tightening the wires. OR
            b. Use Ethibond number 5 (as seen in the video) or PDS number 1 sutures to approximate the sternal edges, either interrupted or continuous sutures through periosteum and outer pole of the sternum OR
            c. Leave the sternum un-sutured.

• Wash the wound with normal saline and antiseptic.
• Avoid excessive use of diathermy at the wound edges; simply excise the wound edge with sharp knife.
• Keep the high negative pressure drains (Redivac drains) for 4-5 days to avoid serous collection underneath the pectoral muscles, as these drains create a gentle vacuum that reduces the potential space underneath the muscles.

Acknowledgements:
Thank you to Maaz A. Khan, Saad A Khan, and Zabreen Ahmed for video narration and thank you to Dr Hatem Elshora for photographs.

References 

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Disclosure

Furqan Raheel, Amit Sirivastawa, Johan D Bence and Victor Zlocha currently work at Glenfield Hospital, University Hospitals of Leicester NHS Trust, Leicester, United Kingdom.

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