Microsurgery Essentials





Key Words

free flap, free tissue transfer, microscope, skin flap, fasciocutaneous flap, muscle flap

 




Synopsis


Microsurgical techniques are performed with an operating microscope and specialized instruments. They are useful when a skin graft or local flap(s) cannot adequately achieve reconstruction and in replantation surgery or nerve repair. The goal of microsurgical procedures is to restore form and function that is lost as a result of trauma, cancer, or congenital deficiency. Although it can be more complex than conventional surgery, microsurgery can often be the best solution to major reconstructive challenges.




Clinical Issues


Microsurgery is a technique with wide-ranging applications in reconstructive surgery. It has three essential components:



  • 1.

    Magnification with a surgical microscope is used for a portion of the procedure.


  • 2.

    Specialized precision instruments are used under the microscope.


  • 3.

    Specific operating techniques are applied while using the instruments and microscope. These techniques are learned clinically and in the laboratory with time spent under the microscope.



Microsurgery techniques are primarily used to repair (coapt) small blood vessels and nerves. Microvascular anastomosis and microneural coaptation can be aids for reconstruction of tissue after trauma, cancer, and congenital deficiencies. Two of the main procedures performed with microsurgery are free tissue transfer (also known as a free flap) and replantation surgery. Free flaps are aids to reconstruction of wounds after trauma or cancer extirpation. They can also be used to reconstruct some congenital deficiencies. Indeed, the utility of microsurgery is its applicability to a wide array of surgical challenges.


Typical applications of microsurgery are:




  • Management of complex wounds, especially those with exposed vital structures and bone



  • Repair of nerves



  • Repair of blood vessels



  • Replantation of amputated body parts

This chapter will focus on the essentials for the indications, planning, and achieving successful outcomes in microsurgery—the prerequisites that are fundamental. Specific flaps will be outlined in Chapter 2.8 , Common Free Flaps.


Definitions


Free Flap


The terms free flap, free tissue transfer, and microvascular transplant can be used interchangeably for tissue that is isolated on a vascular pedicle and transplanted from one part of the body to another. A graft, on the other hand, relies on tissue from the recipient area to supply nutrition and vascular ingrowth over time. A free flap requires microsurgical vascular repair for blood supply. There are numerous free flaps and applications of free flaps for reconstruction.


Replantation


Replantation is the permanent reattachment of a body part that has become severed.


Operating Microscope


An operating microscope consists of separate binocular fields, one for the surgeon and one for the assistant.


Microsurgery is certainly more complex than conventional surgery and is often considered to be at the top of the reconstructive ladder. It requires detailed planning, flap selection, and careful intra-operative and post-operative patient management. In wound management, microsurgery is often applied when a skin graft, or local flap(s), cannot adequately (or best) achieve reconstruction. A classic application is an open wound on the distal one-third of the leg with a fracture or exposed bone. Local flaps are sparse, small, and unreliable in this area, and a skin graft cannot adequately take directly on bone. A microsurgical free flap represents the best solution. Another example is soft tissue loss on the forearm with exposed bone and/or tendon. If a local flap is not available, a free flap can cover exposed structures and be a good bed for tendon transfer or grafting if necessary. Skin grafts do not provide an adequate bed for a tendon transfer or grafting. A third example is a head-and-neck defect with exposed bone or vital structures after trauma or cancer extirpation. Skin grafts are not a good choice for coverage of vital structure in the head and neck, and if local flaps are not available or large enough, a free flap can safely and effectively cover bone and vital structures. Furthermore, a free flap with bone can reconstruct skeletal loss such as resection of the mandible.




Clinical Issues


Microsurgery is a technique with wide-ranging applications in reconstructive surgery. It has three essential components:



  • 1.

    Magnification with a surgical microscope is used for a portion of the procedure.


  • 2.

    Specialized precision instruments are used under the microscope.


  • 3.

    Specific operating techniques are applied while using the instruments and microscope. These techniques are learned clinically and in the laboratory with time spent under the microscope.



Microsurgery techniques are primarily used to repair (coapt) small blood vessels and nerves. Microvascular anastomosis and microneural coaptation can be aids for reconstruction of tissue after trauma, cancer, and congenital deficiencies. Two of the main procedures performed with microsurgery are free tissue transfer (also known as a free flap) and replantation surgery. Free flaps are aids to reconstruction of wounds after trauma or cancer extirpation. They can also be used to reconstruct some congenital deficiencies. Indeed, the utility of microsurgery is its applicability to a wide array of surgical challenges.


Typical applications of microsurgery are:




  • Management of complex wounds, especially those with exposed vital structures and bone



  • Repair of nerves



  • Repair of blood vessels



  • Replantation of amputated body parts

This chapter will focus on the essentials for the indications, planning, and achieving successful outcomes in microsurgery—the prerequisites that are fundamental. Specific flaps will be outlined in Chapter 2.8 , Common Free Flaps.


Definitions


Free Flap


The terms free flap, free tissue transfer, and microvascular transplant can be used interchangeably for tissue that is isolated on a vascular pedicle and transplanted from one part of the body to another. A graft, on the other hand, relies on tissue from the recipient area to supply nutrition and vascular ingrowth over time. A free flap requires microsurgical vascular repair for blood supply. There are numerous free flaps and applications of free flaps for reconstruction.


Replantation


Replantation is the permanent reattachment of a body part that has become severed.


Operating Microscope


An operating microscope consists of separate binocular fields, one for the surgeon and one for the assistant.


Microsurgery is certainly more complex than conventional surgery and is often considered to be at the top of the reconstructive ladder. It requires detailed planning, flap selection, and careful intra-operative and post-operative patient management. In wound management, microsurgery is often applied when a skin graft, or local flap(s), cannot adequately (or best) achieve reconstruction. A classic application is an open wound on the distal one-third of the leg with a fracture or exposed bone. Local flaps are sparse, small, and unreliable in this area, and a skin graft cannot adequately take directly on bone. A microsurgical free flap represents the best solution. Another example is soft tissue loss on the forearm with exposed bone and/or tendon. If a local flap is not available, a free flap can cover exposed structures and be a good bed for tendon transfer or grafting if necessary. Skin grafts do not provide an adequate bed for a tendon transfer or grafting. A third example is a head-and-neck defect with exposed bone or vital structures after trauma or cancer extirpation. Skin grafts are not a good choice for coverage of vital structure in the head and neck, and if local flaps are not available or large enough, a free flap can safely and effectively cover bone and vital structures. Furthermore, a free flap with bone can reconstruct skeletal loss such as resection of the mandible.




Management


Flap Selection


When presented with a patient in need of reconstruction, there are numerous potential free flap donor sites available to reconstruct a plethora of defects, both large and small. The vast majority of wounds can be reconstructed with just a few flaps. Workhorse flaps include the latissimus, radial forearm, rectus, anterolateral thigh, and the fibula. However, many more flaps are available. Flap selection should consider the size of the defect and potential dead space, loss of adjacent structures (such as bone, tendon, and nerve), pedicle length, size and location of the recipient vessels, and possible necessity for future revision surgery. Skin, fasciocutaneous, fascia, muscle, or bone flaps are selected based on the potential of their attributes to satisfy the needs of the recipient area.


Skin and Fasciocutaneous Flaps


Skin and fasciocutaneous flaps such as the radial forearm flap, lateral arm flap, anterolateral thigh flap, and the deep inferior epigastric artery flap (DIEP) have broad utility. They can be used to cover exposed vital structures or for contour restoration such as in breast reconstruction.


Skin flaps contain skin and subcutaneous fat along with a vascular pedicle, whereas a fasciocutaneous flap contains the underlying fascia and skin along with the vascular pedicle. A radial forearm flap, for instance, is usually harvested as a fascial flap; the underlying antebrachial fascia is kept in continuity with the pedicle and skin. A DIEP flap is harvested with skin and a vascular pedicle and no fascia by dissecting the perforators to the skin through the fascia and leaving rectus fascia behind.


Skin and fasciocutaneous flaps have many features that make them well suited to reconstruction of various defects. They are indicated to:




  • Reconstruct complex wounds involving skin loss



  • Reconstruct complex wounds involving mucosal loss



  • Provide sensate coverage if harvested with a nerve



  • Provide coverage of exposed vital structures

In considering these flaps, the quality and thickness of donor skin is evaluated by inspection and physical examination ( Fig. 2.7.1 ). Color match can be assessed for a head-and-neck reconstruction, a pinch test serves to evaluate the thickness of the donor tissue, and Doppler examination can outline a central perforator for help in flap design. The fact that skin is removed means the donor area will be closed under some tension. In case of excess tension, skin grafting of the donor site may be required.


FIG. 2.7.1


(A) An anterolateral thigh flap was used to reconstruct a dorsal arm wound. This represents poor flap selection. The donor site in the patient was quite thick, and the resulting reconstruction is excessively bulky. In addition, the flap required skin grafting to close the thick edge of the flap that could not be inset. (B) A radial forearm flap was used to cover a wound of exposed cranial bone after craniotomy bone flap plate infection and removal. The area was radiated, and local tissue was not a good option. (C) The flap has good contour, and the pedicle could reach the superficial temporal artery and facial vein. This represents good flap selection.


Muscle Flaps


Muscle flaps such as the latissimus, partial latissimus, rectus, and gracilis flaps can also reconstruct a large variety of wounds ( Fig. 2.7.2A–C ). Muscle flaps have several excellent attributes. They have high flow and infection fighting ability. They are supple and can obliterate dead space. They can be elevated at a later date for secondary surgery. They can also be taken with their nerve to create functional muscle reconstructions ( Fig. 2.7.2D–F ).




FIG. 2.7.2


(A) A large forearm wound with exposed bone and necrotic tendon. (B) The wound was debrided, and a latissimus muscle was used to cover the defect. A meshed split-thickness skin graft was placed on the muscle. (C) The muscle atrophied and had good contour. It can be elevated for later bone grafting (as in this case) or for tendon transfer or grafting. (D) A full-thickness loss of the lower lip and orbicularis muscle after necrotizing infection. (E) A functional gracilis muscle was used to reconstruct the orbicularis by innervating to the marginal mandibular nerve while bilateral facial artery musculomucosal flaps were used for lip vermilion. (F) The patient after 1 year has good oral competence and excellent aesthetic outcome.


Muscle can be taken with skin paddle, or without a skin paddle and simply be skin grafted. The skin paddle can aid in visual monitoring of the flap, whereas a muscle with skin graft is more difficult to assess for vascular compromise. However, the skin paddle can increase the thickness of the flap construct.


Disadvantages of muscle flaps include the potential for hernia formation or bulging (rectus flap) and the need for split-thickness skin grafting in most cases. Donor loss of the entire latissimus can produce back asymmetry that is visible in the fit patient, but it does not produce any significant donor site functional loss. Muscle flaps can be bulky but do atrophy with time.


Bone Flaps


Free vascularized bone flaps can be harvested from several areas including the fibula ( Fig. 2.7.3 ), iliac crest, lateral scapula, medial femoral condyle, and lateral arm. Bone flaps can be used when a large defect of bone requires reconstruction and/or when conventional bone grafting has failed due to poor blood supply. They can be taken with an overlying skin paddle.


Dec 24, 2019 | Posted by in Reconstructive surgery | Comments Off on Microsurgery Essentials
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