Microsurgery: Free Tissue Transfer and Replantation
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MICROSURGERY: FREE TISSUE TRANSFER AND REPLANTATION John R Griffin MD and James F Thornton MD HISTORY In 1964 Nakayama and associates15 reported In the late 1890s and early 1900s surgeons began what is most likely the first clinical series of free- approximating blood vessels, both in laboratory ani- tissue microsurgical transfers. The authors brought mals and human patients, without the aid of magni- vascularized intestinal segments to the neck for cer- fication.1,2 In 1902 Alexis Carrel3 described the vical esophageal reconstruction in 21 patients. The technique of triangulation for blood vessel anasto- intestinal segments were attached by direct microvas- mosis and advocated end-to-side anastomosis for cular anastomoses in vessels 3–4mm diam. Sixteen blood vessels of disparate size. Nylen4 first used a patients had a functional esophagus on follow-up of monocular operating microscope for human ear- at least 1y. drum surgery in 1921. Soon after, his chief, Two separate articles in the mid-1960s described Holmgren, used a stereoscopic microscope for the successful experimental replantation of rabbit otolaryngologic procedures.5 ears and rhesus monkey digits.16,17 Komatsu and 18 In 1960 Jacobson and coworkers,6 working with Tamai used a surgical microscope to do the first laboratory animals, reported microsurgical anasto- successful replantation of a completely amputated moses with 100% patency in carotid arteries as digit in 1968. That same year Krizek and associ- 19 small as 1.4mm diameter. In 1965 Jacobson7 was ates reported the first successful series of experi- able to suture vessels 1mm diam with 100% patency mental free-flap transfers in a dog model. Also in 20 in laboratory animals. Jacobson emphasized the 1968 Cobbett transferred a great toe to the hand. importance of avoiding intimal trauma and precise In 1971 Antia and Buch21 reported successful intima–intima reapproximation. In 1966 Green free transfer of a superficial epigastric artery skin and colleagues8 used 9-0 nylon suture on rat aortas flap to the face. The authors anastomosed the (avg 1.3mm diam) and vena cavas (avg 2.7mm diam) superficial epigastric artery and vein to the com- and reported anastomotic patency in 37/40 animals mon carotid artery and internal jugular vein to repair at 21d. Acland9 in 1972 published a series showing a cheek defect. Also in 1971 McLean and Buncke22 95% patency in anastomosed rat superficial epigas- transferred the omentum to the scalp via microvas- tric arteries. Since Smith’s10 and Cobbett’s11 reviews cular anastomoses. In 1973 Daniel and Taylor23 of microsurgical instruments and techniques, suture and O’Brien and associates24 independently technology has progressed to 50mcm needles with reported the free tissue transfer of groin flaps for 12-0 suture. lower extremity reconstruction. In 1962 Malt and McKhann12 described the first Since the beginning of clinical microvascular sur- successful clinical replantations in 2 patients who gery in the early 1970s, donor sites for free tissue had arm amputations. In 1963 Chinese surgeons transfer have multiplied and microsurgical tools and successfully reattached a patient’s hand amputated techniques have been expanded and refined. As at the wrist. The radial and ulnar arteries were microsurgery became more prevalent and experi- anastomosed using short links of 2.5mm diam poly- ence with free tissue transfer mounted, the success ethylene tubes.13 Kleinert and Kasdan14 in 1963 rates of microvascular procedures also climbed, to described their experience with digital amputations >90% today (Table 1). Khouri’s25 survey of 9 and near amputations. They were unable to replant microsurgeons “clearly indicates that operative digits successfully, but did revascularize near- experience is the single most critical factor related amputated digits. They used loupe magnification to improved success rates. A major determinant and stressed the importance of using vein grafts if of success or failure is therefore operator related the vessel anastomosis was under tension. and, in a broader sense, technical.” SRPS Volume 10, Number 5, Part 2 TABLE 1 BASIC SCIENCE CONCEPTS Free Flap Success Rate and Learning Curve IN MICROSURGERY In addition to possessing the appropriate techni- cal skills, the microvascular surgeon should under- stand the mechanisms of vessel injury, repair, and regeneration; should be familiar with the processes of vasospasm and thrombosis and their pharmaco- logic control; and be aware of the effects of ischemia and hypoxia on revascularized tissue. Vessel Injury and Regeneration Microvascular anastomoses inevitably disturb the endothelium and subendothelium of the vessel walls. (Data from Khouri RK: Avoiding free flap failure. Clin Plast Surg Exposure of the underlying subendothelium to the 19:773, 1992.) bloodstream results in platelet aggregation, which is the first step in the formation of a thrombotic plug. O’Brien26 reviews the strides made in microvas- Among the multiple connective tissue compo- cular surgery during the 1970s and ‘80s and looks nents of the blood vessel wall, collagen stimulates to the future for new applications of microsurgery. the greatest amount of platelet clumping. Weinstein 30 Several new areas of microsurgical interest have and associates effectively showed the blood ves- evolved over the last 15 years. In 2000 sel injury and repair processes through scanning Whitworthm and Pickford27 reported good results electron microscopy (SEM) of anastomoses. Full- at 30 years for the patient with the first toe-to- thickness sutures that afforded intimal continuity thumb transfer. Clinicians continue to refine tech- provoked the least amount of anastomotic bleeding niques for salvage of severely injured upper and platelet aggregates. “Far worse damage” was extremities, including the scenario of failed seen with partial-thickness bites of the vessel wall replantation. Functional free muscle transfer is an than with properly placed full-thickness sutures. In active area of research, with new applications still a separate study using SEM, Harashina and col- 31 being discovered. leagues noted no difference in patency (94%) of 1mm rat femoral vessels anastomosed with either The first human-to-human hand transplants were adventitial or full-thickness sutures. performed 17 years ago.28 Today plastic and ortho- During healing of the vessel wall, a pseudointima pedic surgeons express concern about this proce- forms within the first 5 days.31 Approximately 1–2 dure and raise the issues of poor sensory return, weeks after injury new endothelium covers the anas- acute or chronic rejection, systemic complications tomotic site. At the time of anastomosis a layer of of immunosuppressive therapy, and loss of the trans- platelet covers the denuded endothelium of the 29 plant. vessel wall. This layer of platelet cells will not As the results of surgery became more predict- progress to fibrin deposition and thrombosis if it is able and the number of available free flaps grew, not exposed to the media and the lumen is not efforts shifted to minimizing donor site morbidity. injured. Over the next 24–72 hours the platelets Clinical applications and choices of perforator flaps gradually disappear. Platelets show little affinity for continue to change. In the hands of experienced exposed surfaces of sutures within the vessel operators, loupe magnification now appears to be lumen.30,31 The disappearance of platelets within as effective as the operating microscope in certain the lumen and the formation of pseudointima cor- cases. Free flap selection in specific defects is relate well with previous clinical and experimental becoming more standardized, and technologic observations and lead to the conclusion that the innovations in anastomotic techniques and devices critical period of thrombus formation in the anasto- hold promise for the future of microsurgery. mosis is in the first 3–5 days.32,33 2 SRPS Volume 10, Number 5, Part 2 The mechanism of endothelial regeneration concentrations of the drug in these patients was depends on the presence or absence of mechani- well below toxic levels, suggesting that most of the cal injury to the subendothelial structures. If the topically applied lidocaine is not fully absorbed. endothelial layer alone is damaged, it is reconsti- Nevertheless, the standard pharmacology references tuted from surrounding cells and regeneration is list the maximum safe dose of injectable lidocaine complete in 7–10 days. With damage of the as ≤750mg in the average adult patient. Ohta and underlying subendothelial structures, media and others39 showed experimentally that xylocaine has adventitia, there is regeneration of damaged epi- its optimum spasmolytic and antispasmodic effects thelium by migration and differentiation of at a concentration of 20%. Clinically, 2% lidocaine myoendothelial cells from the cut vessel ends.34 The also has a beneficial effect on moist vessels. remaining layers of the vessel wall regenerate via Injury to the endothelium from microvascular proliferation of fibroblasts with collagen deposition clips is directly related to clip pressure.40 Weinstein and myointimal thickening at the anastomotic site.35 and colleagues30 note that curved or angled clips The elastic and muscular elements of the vessel wall cause more damage than flat clips. Closing pres- fail to regenerate to the same degree as the endo- sures of vascular clips should remain <30gm/mm2 thelium, and these layers do not return to their to minimize damage to vessels.41 O’Brien