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Technique of Muscle Flap Harvest for Intrathoracic Use

      The technique of muscle transposition is a powerful tool in the armamentarium of the thoracic surgeon. Pedicled thoracic myoplasty, a simple and robust technique to bring vascularized tissue into the chest cavity, is performed to address space issues or to buttress closure of the bronchus or esophagus. The ability of the thoracic surgeon to successfully complete these procedures without consultant involvement is important; the myoplasty is often a key or integral component of the planned thoracic operation, or in other cases the need for muscle transposition may present itself unexpectedly.
      The use of muscle transposition to treat the persistent intrathoracic space typically occurs in the setting of postsurgical empyema (with or without ongoing parenchymal air leak), or in combination with high-risk anatomic pulmonary resection. In the latter case, the transposed muscle is employed in a prophylactic fashion to minimize postoperative infectious or air leak complications. The muscle flap may also be used as a well-vascularized tissue buttress, applied to bronchial stumps, esophageal anastomoses, or esophageal repairs.
      We discuss the technique of harvesting and transposition of the three flaps most commonly used at our institution: latissimus dorsi, pectoralis major, and intercostal muscle. The first two muscles may be used both for space issues and to buttress airway or esophageal closure, whereas the intercostal flap is used primarily for buttressing. Use of the serratus anterior muscle for intrathoracic myoplasty results in a flared or “winged” scapula, poorly tolerated in this typically debilitated patient population, and thus, is rarely employed at our institution.

      Operative Technique

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      Figure 1Latissimus dorsi (LD) is the largest chest wall muscle and is a versatile flap that is easily harvested through a standard incision. The only relative contraindication to using this muscle is if it has been divided during previous thoracotomy. LD is supplied by the thoracodorsal neurovascular bundle. Its proximal insertion is on the intertubercular groove of the humerus and distally to the spine (T7 to L5), iliac crest, and sacrum. It can fill as much as 30% of the intrathoracic volume. The pedicled LD as described can be easily applied to apical and mid-intrathoracic spaces but is less useful for a basilar space. It may be harvested based on its distal vascular (perforating) blood supply to reach a basilar space by dividing the proximal neurovascular bundle (not described here). A standard skin incision for thoracotomy is created as pictured here. a. = artery; m. = muscle.
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      Figure 2Cautery is used to dissect through the subcutaneous fat without injuring the LD. Once the LD is reached, skin flaps are raised superiorly, inferiorly along the anterior border, and posteriorly nearly to the spine.
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      Figure 3The anterior border of the LD is then identified and retracted outward. The undersurface of the LD is separated from the underlying serratus muscle using electrocautery. There will be small perforators to the LD that can be divided with cautery. Care must be taken to avoid injury to the long thoracic neurovascular bundle, which lies on the surface of the serratus muscle. n. = nerve.
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      Figure 4As one progresses superiorly toward the thoracodorsal artery, blunt dissection can be combined with cautery to avoid injury to the pedicle. This superior portion of the dissection can be completed after the muscle is divided distally. The latissimus is then divided posteriorly and inferiorly until it is on a pedicle from the thoracodorsal bundle and the humerus. a. = artery.
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      Figure 5(A) Further proximal dissection can now be performed with ease, identifying the thoracodorsal bundle in doing so. It is important to avoid skeletonizing the neurovascular pedicle, increasing the possibility of injury to the vascular structures and perhaps loss of the entire flap. The proximal humeral attachment is preserved until the surgeon is ready to place the flap within the intrathoracic space. The muscle may be tucked under the superior skin flap for transposition later in the procedure, and thoracotomy at desired location is begun. Once the intrathoracic portion of the case is otherwise complete, the LD is then detached from the humerus, again taking great care to avoid injury to the thoracodorsal bundle. Assessment of the mobilized flap assures the surgeon of the viability of the muscle, particularly at the distal (inferior) extent. A counterincision in the second or third intercostal space anterior to the lateral border of the scapula is used for entry of the muscle into the thoracic cavity. (B) The distal end of the muscle is fed through the counterincision until only the cut end is sticking through the opening. Care must be taken to avoid torsion of the vascular pedicle during this step. We often will use two or three tacking sutures between the proximal end of the muscle and the adjacent intercostal muscle to assure torsion of the pedicle will not occur. A small, flexible (Jackson–Pratt or Blake) drain is placed in the original extrathoracic bed of the transposed muscle for postoperative use to avoid subcutaneous seroma formation. a. = artery; m. = muscle; v. = vein.
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      Figure 6The LD spreads out like a fan across the apex of the chest and its distal portion is attached to the bronchial stump if present. It is anchored to all four aspects of the bronchial stump using four horizontal mattress absorbable sutures.
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      Figure 7The pectoralis major (PM) is the second largest chest wall muscle. Similar to the LD, it can be used for both space and buttressing functions and is best suited for apical spaces. It may be used when the LD has been damaged by previous thoracotomy. The PM is dependent on the thoracoacromial bundle, with the arterial supply arising mid-clavicle from the subclavian artery. When performing concomitant posterolateral thoracotomy, an anterior axillary counterincision is made to harvest the pectoralis major muscle. When harvested as an isolated flap, the infraclavicular incision is preferred. The thoracoacromial bundle enters superolaterally to the deep aspect of the pectoralis major muscle. a. = artery.
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      Figure 8Skin flaps are raised overlying the PM all the way to the sternum medially, clavicle superiorly, and inframammary line inferiorly. The pectoralis major is then detached at the sternal, costal, and clavicular borders. It is freed from the underlying pectoralis minor from the inframammary border upward until the thoracoacromial bundle is identified and preserved. The pectoralis insertion to the humerus is preserved until the muscle is ready for intrathoracic entry but may be divided easily through the same infraclavicular incision. Similar to the latissimus, the pectoralis muscle is brought into the chest via a small incision in the second or third interspace, located from the mid-clavicular to mid-axillary line. A flexible (Jackson–Pratt or Blake) drain is used in the bed of the transposed PM to avoid seroma formation.
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      Figure 9(A, B) The intercostal muscle (ICM) flap is easily harvested and may be used as a buttress for esophageal repair or bronchial stump closure. The flap must be harvested before placing a rib spreader. The interspace used to enter the chest is typically chosen, although depending on the use of the flap, another intercostal space may be easily used. The intercostal muscle and neurovascular pedicle are separated from the inferior (caudad) rib using a periosteal elevator. The ICM is then freed from the underside of the superior (cephalad) rib taking great care to preserve the intercostal neurovascular bundle, again using a periosteal elevator (A). The elevator is preferred over cautery to avoid thermal injury to the pedicle (B). The intercostal muscle is then divided as far anteriorly (near costochondral cartilage) as possible. a. = artery; m. = muscle; n. = nerve; v. = vein.
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      Figure 10The mobilized ICM flap may be preserved within the chest while the rest of the case is performed. Following lobectomy/pneumonectomy, the intercostal muscle is positioned within the chest from its origin posteriorly and should lie dependently along the chest wall on its pathway to the bronchial stump. Assessment of muscle flap viability may be performed at this point. It is anchored to all four sides of the bronchial stump using absorbable horizontal mattress suture. Care should be taken to avoid torsion of the flap. After completion of the buttressing, any tension leading to the flap being “suspended in the air” within the chest could lead to flap avulsion on residual lung inflation.

      Summary

      The additional impact of muscle transposition on the postoperative care of the thoracic surgical patient is negligible. The subcutaneous drain is maintained until drainage is minimal to avoid seroma formation. Early mobility and range of motion of the ipsilateral upper extremity is encouraged, with a gradual increase to full use over 4 to 6 weeks. Most patients report the return of full range of motion and nearly complete strength following large muscle (LD and PM) transposition, with only mild weakness in adduction and medial rotation of the upper extremity.
      Intrathoracic muscle transposition is a versatile and easily mastered procedure, applicable to a variety of clinical situations. The use of a muscle flap to buttress an esophageal or bronchial closure can minimize postoperative morbidity, particularly in the difficult or complex case. In the setting of a persistent, infected pleural space, selective intrathoracic myoplasty may lead to eradication of the space with surprisingly minimal impact on upper extremity motion or strength. A basic knowledge of the techniques described above is essential to the busy thoracic surgeon.