Principles of Microsurgery

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Microsurgery uses the operating room microscope or high-powered loupe magnification to facilitate the microvascular surgical techniques used to anastomose small vessels and nerves. ^[1]  Microsurgical reconstruction is used for complex reconstructive surgery problems when other options (eg, primary closure, healing by secondary intention, skin grafting, and local or regional flap transfer) are not adequate.

The field of microsurgery began with the introduction of the operating microscope, when Jacobson and Suarez described the anastomosis of blood vessels. In the 1960s, as microsurgical techniques were perfected, increasing success was seen with digital artery repairs and finger replantation. This laid the foundation for microsurgical composite tissue transfer, which became popular in the 1970s. ^[2]

In the 1980s, an emphasis was placed on improved function with autologous tissue transplantation, which is exemplified in mandibular reconstructions for cancer. Composite grafts consisting of soft tissue and bone aided in stabilizing the mandible, assisted with mastication, and allowed reliable coverage during the postoperative period, when radiation usually was required. Today, microsurgical techniques have become an integral part of the armamentarium for plastic surgeons, allowing for soft-tissue coverage and function after trauma or oncologic resections.

Microsurgery may not be the best solution for all reconstructive dilemmas and usually is not the first choice in the reconstructive ladder. However, it can offer the reconstructive surgeon an important tool for achieving complex reconstruction by proceeding with free tissue transfer from distant sites. Free tissue transfer includes flaps such as the following:

In addition, specific tissue transfers such as neural grafts or vein grafts are also considered free tissue transfer. In specific cases, such as large defects of the face after tumor resection, free tissue transfer may be the best option for closure of the defect.

Reconstructive microsurgery has entered a stage where, because of continued developments in technology and a better understanding of the anatomy, anastomosis of very small vessels (0.3 mm) is possible. These highly challenging procedures are referred to in the literature as supermicrosurgery. They allow anastomosis of perforator flaps such as the medial plantar flap to perforator recipient vessels. ^[3]  Additional applications include complex digit reimplantation and lymphatic anastomosis.

Although microsurgery continues to develop, the basic principles of microsurgery remain the same:

This article outlines the basics of microsurgery, preoperative planning, specific operative techniques, and postoperative care. In addition, it describes some of the flaps most commonly used for microsurgical reconstruction.

Indications for tissue transfer utilizing microsurgical techniques include the following:

Finger reimplantation or transfer may represent another aspect of this technique. ^[4] Microsurgery may also be used as a new approach to achieve lymphatic drainage in cases of lymphedema. ^[5]

The specific indications for microsurgical reconstruction and the particular type of flap used depend on the type of tissue required and the size and location of the defect. Defects can be an isolated tissue type, such as soft-tissue defects on the dorsum of the hand, or some combination of skin, subcutaneous tissue, nerves, muscle, tendons, cartilage, bone, and mucosa.

Free flaps can be categorized into two different types of transplants: isolated and composite. Isolated tissue transplants include skin, fascia, muscle, nerve, or bone individually. The more common composite tissue transplant represents a more complex flap and provides more than one type of tissue. Such flaps include myocutaneous, osteocutaneous, or innervated myocutaneous flaps. ^[6]

Historically, reconstruction of a defect was based on a reconstructive ladder, with local and simple procedures being performed before more extensive procedures or distant tissue transfers. Today, the use of free tissue transfer is no longer seen as the apex of the reconstructive ladder. Instead, it is a generalized tool for complex or composite tissue transfers, for treating wounds with poor healing or inflow, and for situations in which postoperative radiation may play a factor in wound healing. (See Table 1 below.)

Table 1. Examples of Free Tissue Transfer (Open Table in a new window)

Defect Type

Tissue Defect

Common Flaps

Coverage of exposed structures

Open tibial fractures in distal third of leg

Latissimus dorsi muscle free flap; gracilis muscle free flap

Dead space

Obliteration of maxilla defect after maxillectomy for cancer

Rectus abdomin-s muscle free flap

Tissue defect

Breast reconstruction

Transverse rectus abdominus myocutaneous (TRAM) free flap; deep inferior epigastric perforator (DIEP) flap; superior gluteal artery perforator (SGAP) free flap

Bone and soft defect

Mandible reconstruction

Fibula osteocutaneous free flap

Bone and soft defect

Infraorbital and maxillary defect

Parascapular osteocutaneous free flap

Facial muscle denervation

Facial paralysis with muscular atrophy

Gracilis muscle free flap

Digital amputation

Thumb amputation

Great toe composite free flap

Digestive tract defect

Esophageal reconstruction

Jejunum free flap; anterior lateral thigh (ALT) free flap

Contraindications for microsurgical free tissue transfer fall into two categories: patient issues and surgical issues.

Contraindications associated with the patient include any condition that may place his or her life in danger or significantly increase the probability of postoperative flap loss. The time required to harvest and insert a flap is relatively long. Therefore, any medical condition that inhibits the patient’s ability to withstand prolonged anesthesia (eg, severe respiratory disease) is an absolute contraindication. Microsurgical free tissue transfer is absolutely contraindicated in patients who have the following:

Age alone is not a risk factor in the success or failure of free flaps when preexisting medical conditions are not taken into account. ^[7] However, peripheral vascular disease and renal disease are strong predictors of reconstructive failure and patient morbidity and mortality. ^{[8, 9]}

Relative contraindications include any condition that increases the risk of intraoperative or postoperative complications. Common conditions that are not contraindications but can increase the risk of complications include the following:

In general, a thorough review of the patient’s medical history and current conditions is critical in formulating a treatment algorithm and determining optimal timing of surgery.

Tobacco use has been shown to affect cutaneous blood flow, wound healing, and survival of pedicled flaps. The overall effect of cigarette smoke is to promote a thrombogenic state through vasoconstriction of the microvasculature. Surprisingly, the current literature has failed to show any damaging effects of cigarette smoke on free tissue transfer. ^{[10, 11]}

Surgical issues include the lack of a properly trained surgeon or surgical team. In current practice, this usually is not an issue, because microsurgery is now common and forms a major part of most plastic surgery training programs.

Other surgical issues include limited resources that might inhibit the staff from properly caring for the patient intraoperatively or postoperatively or the lack of access to specialized microsurgical instruments.

Vessel injury and regeneration occur through the following steps:

The first step in healing of a fresh arterial or venous anastomosis is the formation of a platelet plug. With intimal injury, exposed collagen triggers platelet adhesion. Platelets aggregate and activate fibrinogen, which adheres to platelets and links them together to form a plug. Fibrinogen is converted to fibrin, strengthening the platelet plug. If the vessel walls are not damaged and the anastomosis is secure, the platelet plug gradually disappears over the first 3-5 days, with the pseudointima forming by day 5. New endothelium covers the anastomotic site 1-2 weeks later.

The critical period of thrombus formation in the anastomosis is the first 3-5 days of healing. ^[12]  The underlying theme of microvascular free flap failures is a result of endothelial disruption with exposure of subendothelial collagen and formation of a platelet plug. If platelet aggregation reaches a critical mass, it will trigger a cascade of events leading to eventual thrombus formation in the vessel.

Skin, subcutaneous tissue, muscle, and bone have different ischemic tolerances. Skin and subcutaneous tissue are relatively resistant to anoxia and can tolerate warm ischemia for 4-6 hours and cold ischemia for as long as 12 hours. ^{[12, 13]}  Skeletal muscle is less tolerant to ischemia than skin is. Muscle can tolerate warm ischemia for as long as 2 hours; irreversible damage to the microcirculation begins at 6 hours, even under cold ischemia. ^{[14, 15]}  Bone is more resistant to anoxia and can tolerate up to 24 hours of cold ischemia. ^[16]

Mathes and Nahai ^[17] classified flaps as either random or axial on the basis of blood supply. A random flap is perfused by random small blood vessels without a proper name (eg, local bilobed flap). An axial flap is based on a known, named blood vessel or set of blood vessels. Mathes and Nahai classified these flaps as follows:

Shenaq SM, Klebuc MJ, Vargo D. Free-tissue transfer with the aid of loupe magnification: experience with 251 procedures. Plast Reconstr Surg. 1995 Feb. 95(2):261-9. [Medline].

Barbary S, Dap F, Dautel G. Finger replantation: surgical technique and indications. Chir Main. 2013 Dec. 32 (6):363-72. [Medline].

Koshima I, Nanba Y, Tsutsui T, et al. Medial plantar perforator flaps with supermicrosurgery. Clin Plast Surg. 2003 Jul. 30(3):447-55, vii. [Medline].

Adani R, Woo SH. Microsurgical thumb repair and reconstruction. J Hand Surg Eur Vol. 2017 Aug 1. 1753193417723310. [Medline].

Campisi C, Eretta C, Pertile D, et al. Microsurgery for treatment of peripheral lymphedema: long-term outcome and future perspectives. Microsurgery. 2007. 27(4):333-8. [Medline].

Kotsougiani D, Platte J, Bigdeli AK, Hoener B, Kremer T, Kneser U, et al. Evaluation of 389 patients following free-flap lower extremity reconstruction with respect to secondary refinement procedures. Microsurgery. 2017 Aug 31. [Medline].

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Moran SL, Illig KA, Green RM, Serletti JM. Free-tissue transfer in patients with peripheral vascular disease: a 10-year experience. Plast Reconstr Surg. 2002 Mar. 109(3):999-1006. [Medline].

Moran SL, Salgado CJ, Serletti JM. Free tissue transfer in patients with renal disease. Plast Reconstr Surg. 2004 Jun. 113(7):2006-11. [Medline].

Chang LD, Buncke G, Slezak S, Buncke HJ. Cigarette smoking, plastic surgery, and microsurgery. J Reconstr Microsurg. 1996 Oct. 12(7):467-74. [Medline].

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Hayhurst JW, O’Brien BM. An experimental study of microvascular technique, patency rates and related factors. Br J Plast Surg. 1975 Apr. 28(2):128-32. [Medline].

Serafin D, Lesesne CB, Mullen RY, Georgiade NG. Transcutaneous PO2 monitoring for assessing viability and predicting survival of skin flaps: experimental and clinical correlations. J Microsurg. 1981 Mar. 2(3):165-78. [Medline].

Eriksson E, Anderson WA, Replogle RL. Effects of prolonged ischemia on muscle microcirculation in the cat. Surg Forum. 1974. 25(0):254-5. [Medline].

Thomason PR, Matzke HA. Effects of ischemia on the hind limb of the rat. Am J Phys Med. 1975 Jun. 54(3):113-31. [Medline].

Berggren A, Weiland AJ, Dorfman H. The effect of prolonged ischemia time on osteocyte and osteoblast survival in composite bone grafts revascularized by microvascular anastomoses. Plast Reconstr Surg. 1982 Feb. 69(2):290-8. [Medline].

Mathes SJ, Nahai F. Classification of the vascular anatomy of muscles: experimental and clinical correlation. Plast Reconstr Surg. 1981 Feb. 67(2):177-87. [Medline].

Zavlin D, Jubbal KT, Ellsworth WA 4th, Spiegel AJ. Breast reconstruction with DIEP and SIEA flaps in patients with prior abdominal liposuction. Microsurgery. 2017 Aug 26. [Medline].

Connolly TM, Sweeny L, Greene B, Morlandt A, Carroll WR, Rosenthal EL. Reconstruction of midface defects with the osteocutaneous radial forearm flap: Evaluation of long term outcomes including patient reported quality of life. Microsurgery. 2017 Aug 26. [Medline].

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Defect Type

Tissue Defect

Common Flaps

Coverage of exposed structures

Open tibial fractures in distal third of leg

Latissimus dorsi muscle free flap; gracilis muscle free flap

Dead space

Obliteration of maxilla defect after maxillectomy for cancer

Rectus abdomin-s muscle free flap

Tissue defect

Breast reconstruction

Transverse rectus abdominus myocutaneous (TRAM) free flap; deep inferior epigastric perforator (DIEP) flap; superior gluteal artery perforator (SGAP) free flap

Bone and soft defect

Mandible reconstruction

Fibula osteocutaneous free flap

Bone and soft defect

Infraorbital and maxillary defect

Parascapular osteocutaneous free flap

Facial muscle denervation

Facial paralysis with muscular atrophy

Gracilis muscle free flap

Digital amputation

Thumb amputation

Great toe composite free flap

Digestive tract defect

Esophageal reconstruction

Jejunum free flap; anterior lateral thigh (ALT) free flap

Brian A Janz, MD Assistant Professor, Department of Orthopedic Surgery, Division of Plastic Surgery, Ohio State University Medical Center

Brian A Janz, MD is a member of the following medical societies: American College of Surgeons

Disclosure: Nothing to disclose.

Jonathan C Yang, MD Arizona Center for Hand Surgery

Jonathan C Yang, MD is a member of the following medical societies: American Society for Surgery of the Hand

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Wayne Karl Stadelmann, MD Stadelmann Plastic Surgery, PC

Wayne Karl Stadelmann, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Surgeons, American Society of Plastic Surgeons, New Hampshire Medical Society, Northeastern Society of Plastic Surgeons, Phi Beta Kappa

Disclosure: Nothing to disclose.

Jorge I de la Torre, MD, FACS Professor of Surgery and Physical Medicine and Rehabilitation, Chief, Division of Plastic Surgery, Residency Program Director, University of Alabama at Birmingham School of Medicine; Director, Center for Advanced Surgical Aesthetics

Jorge I de la Torre, MD, FACS is a member of the following medical societies: American Burn Association, American College of Surgeons, American Medical Association, American Society for Laser Medicine and Surgery, American Society of Maxillofacial Surgeons, American Society of Plastic Surgeons, American Society for Reconstructive Microsurgery, Association for Academic Surgery, Medical Association of the State of Alabama

Disclosure: Nothing to disclose.

Geoffrey L Robb, MD, FACS Chair, Professor, Department of Plastic Surgery, University of Texas MD Anderson Cancer Center

Geoffrey L Robb, MD, FACS is a member of the following medical societies: Alpha Omega Alpha, American Society of Plastic Surgeons, American College of Surgeons, American Society of Maxillofacial Surgeons, American Society for Reconstructive Microsurgery, Texas Society of Plastic Surgeons

Disclosure: Nothing to disclose.

The authors and editors of eMedicine gratefully acknowledge the contributions of previous author James Chang, MD to the development and writing of this article.

Principles of Microsurgery

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