The main muscles of the back when considering posterior trunk reconstruction are the paired latissimus dorsi, the trapezius, the paired paraspinal muscles (erector spinae), and the paired serratus anterior and posterior. The latissimus dorsi muscles are the largest muscles in the body and span the lower and mid back from their origin on the posterior iliac crest and thoracolumbar fascia, passing cranially from T12 to T7 vertebrae just over the scapula tip and inserting on the anterior humerus. The latissimus is a real workhorse flap for reconstruction and this is the case for both anterior and posterior trunk defect reconstruction.1 In the midline, cranially the trapezius is the most superficial muscle of the posterior trunk commencing at the nuchal fold of the occiput and passing inferiorly to T12 spinous process and inserting along the scapulae. Caudally, it overlaps the latissimus dorsi medially between T7 and T12. When raising a latissimus muscle flap, one should carefully identify the inferior tip and lower border as it passes over the latissimus to avoid damage to this muscle. The erector spinae run parallel to the spine and function to stabilize and extend the vertebrae. They are made up of three distinct muscle bellies—spinalis, longissimus, and iliocostalis—travelling the length of the spine. Along the medial posterior trunk, the paraspinous muscles are immediately deep to the latissimus dorsi, except in the T10–L1 location, where the serratus posterior inferior muscle fibers may be found sandwiched between them and latissimus dorsi.1,2 There are anterior and posterior serratus muscles. The serratus posterior has two components (superior and inferior) and is located in the thoracolumbar region at the level of C7–L2 where it passes from the spinous processes of the vertebrae to the ribs. It helps to stabilize the vertebral column and to elevate and depress the ribs. The serratus anterior originates from the 1st to 9th or 10th ribs on the lateral chest wall and inserts on the medial border of the scapula. It acts to pull the scapula onto the thorax. The lower part of this muscle can be used for reconstruction in its own right, either free or pedicled, or used as part of a composite muscle flap with latissimus (Fig. 63.1).3
Reconstruction of the lateral posterior trunk is most commonly required after wide local excision of cutaneous or soft tissue malignancies. Defects can range from small to large and lateral posterior trunk reconstruction adheres to the standard reconstructive principles of plastic surgery in terms of replacing tissue in a like for like fashion. Where primary closure is not possible and there is a well-vascularized bed, which is often the case, the wound can be closed with a skin graft. Alternatively, the lateral posterior trunk is well suited to local flap or regional flap options of which there are many where there are larger defects. As a result, the need for free tissue transfer is rarely necessary compared with other sites such as the limbs or head and neck. The major challenge of undertaking free tissue transfer in this anatomic area, when needed, is the relative paucity of recipient vessels. If a free flap is required, a vein graft or arteriovenous loop is often needed to achieve sufficient reach to appropriate vessels. Finding a suitable donor site should not be a problem as the usual free flap choices may be used. Likewise, positioning the patient is standard operating practice as either a lateral or prone position may be used. The position of the microscope should be just as simple to set up as with any Trachea Thyroid gland Carotid sheath Sympathetic trunk (chain) Vertebral artery C5 nerve root Nuchal ligament Erector spinae muscles Trapezius muscle Levator scapulae muscle Scalene muscles Longus colli muscle Deep (investing) fascia Sternocleidomastoid muscle Platysma muscle Pretracheal fascia Strap muscles C6 Cervical (C6) Thoracic (T8) Lumbar (L3) A Sternum Lung Pleura Intercostal muscles Serratus anterior muscle Latissimus dorsi muscle Rhomboid muscle Trapezius muscle Erector spinae muscles Head of rib Tip of scapula T8 Ribs Thoracic B Fig. 63.1 Cross-sectional musculoskeletal anatomy at the cervical, thoracic, and lumbar levels. Erector spinae muscles Rectus abdominus muscle External oblique muscle Internal oblique muscle Transversus abdominus muscle Peritoneum Inferior vena cava Latissimus dorsi muscle Quadratus lumborum muscle Psoas major muscle Lumbodorsal fascia Aorta Ureter L3 Lumbar C other case, and a dual team approach should still be possible with most donor site flaps, especially those from the contralateral side.1–6
Patients will occasionally be referred for plastic surgery following spinal surgery with dehisced or infected wounds overlying hardware. The usual principles of performing thorough debridement and reconstructing tissue apply. For this debridement a dual specialty approach is generally advised. During the debridement it is important to remove all nonviable soft tissue and unincorporated bone graft. In this scenario, however, the usual principles of removing metalwork cannot be followed as this may leave patients with an unstable spine. Only if the hardware is broken, loose, or chronically infected, should it be removed and replaced. If hardware is removed, it should be replaced at the same sitting by the spinal team. The debridement should ideally be performed in a single stage, but where necessary, wounds can and should be temporized. Use of drains and/or negative pressure dressings is normal practice in posterior trunk reconstruction. However, care should be taken when there may be a dural leak as negative pressure would be contraindicated in this case.1–5
This scenario is not uncommon in clinical practice. A key component of the debridement is to remove all necrotic tissue and the prominent bone before reconstruction as the bony prominences with thin soft tissue coverage are often a contributory factor in the wound healing problem. In this scenario, a robust local muscle flap option is preferred and the trapezius works well for such defects due to its close proximity to the defect and reliable blood supply. The trapezius flap is supplied by the descending branch of the transverse cervical artery. The midline part of the trapezius can be harvested with a skin paddle to close defect of this size with the donor site closing directly and the flap tunneling to the defect or with elevation of skin flaps to join the two wounds together. Because the donor is away from the wound, the woody nature of the wound edge tissue has less relevance in this scenario. The muscle is ideal for filling the defect, especially in the presence of previous infection and the skin will provide a robust cover. The latissimus dorsi flap as an alternative may reach but would be a second choice. The keystone island flap can work well on the back but in this instance, it would probably fail to move sufficiently due to the woody nature of the tissues, nor would it fill the defect depth adequately. The lumbar perforator flap would not reach this defect, nor would a pectoralis major flap. The pectoralis major flap would also involve turning the patient half way through the procedure. The lumbar perforator flap is indicated for more distal wounds and the pectoralis major for anterior trunk or head and neck wounds.1–3
The paraspinous muscle flaps are considered the first-line option for reconstruction of smaller thoracic or lumbar midline regions. When used in this setting, the paraspinous muscle flaps should be released from their lateral fascial attachments to allow for medial advancement. The muscle bellies can be imbricated into the wound and obliterate dead space with the use of a Lembert suture technique.1–3 The latissimus dorsi can be used as either an advancement flap on the main pedicle or as a reverse flap on its segmental vessel supply. Alternative options also include the omentum or a lumbar perforator fasciocutaneous flap. The omentum can be isolated on the right or left gastroepiploic vessels and tunneled through the diaphragm or retroperitoneum to fill dead space and protect hardware along the thoracic spine. A transpelvic vertical rectus abdominis myocutaneous (VRAM) flap is an option for lower defects involving the sacrum where anterior and posterior approaches are combined. Gluteal flaps, either V-Y or rotational, can also be useful for lower lumbar or sacral defect coverage.
6. Arkudas A, Horch RE, Regus S, et al. Retrospective cohort study of combined approach for trunk reconstruction using arteriovenous loops and free flaps. J Plast Reconstr Aesthet Surg 2018;71(3):394–401