Introduction

Millions of individuals each year sustain major trauma, have tumors surgically excised or are born with congenital defects that require complex reconstructive surgeries to repair the resulting large tissue defects. Conventional management of such tissue deficiencies with prosthetic rehabilitation or surgical reconstruction (with autologous tissues) may not achieve optimal outcomes. Current surgical procedures are limited by available tissues for reconstruction, morbidity from extensive surgery, prolonged rehabilitation and costs of multiple surgeries. For such complex injuries not amenable to conventional reconstruction, composite tissue allotransplantation can achieve near perfect primary restoration of tissue defects with improved functional and aesthetic outcomes. Composite tissue allotransplantation is among the newest of transplant areas and combines the time-tested techniques of reconstructive microsurgery with the immunologic principles of transplantation. The overall goal of composite tissue allotransplantation is to improve the quality of life of patients who have significant tissue defects.

Upper extremity transplants are vascularized composite tissue allografts because they are modules of distinct tissues, including skin, muscle, ligament, tendon, nerve, blood vessel, bone, joint and cartilage, bone marrow, and lymph nodes.¹ In the United States alone, the numbers of extremity amputations are estimated to be around 1 285 000 per year.² In 2005, there were approximately 1.6 million people living with limb loss, in the US.³ Of these, nearly 540 000 individuals had upper extremity amputations – 34 000 individuals had major limb loss. Even if 1% of those with major upper limb loss were deemed candidates for hand transplantation, this would entail over 300 procedures. However, only 50 patients have undergone upper extremity allotransplantation in the world over the past 12 years. The reason for this disparity in numbers has largely been due to skepticism of the immunological feasibility⁴ and concern for immunosuppression-related complications in upper extremity allotransplantation.⁵ Despite their obvious advantages, the adverse effects of prolonged immunosuppression necessary for graft survival have limited the routine clinical use of these procedures. These risks include infection, cancer, and metabolic derangement and greatly affect recipient quality of life, alter the risk profile and jeopardize the potential benefits of upper extremity transplantation. Notably, unlike in solid organs, clinical success is dictated not only by graft acceptance and survival but also by nerve regeneration, which determines ultimate functional outcomes. Novel strategies such as cellular and biologic therapies that integrate the concepts of immune regulation with those of nerve regeneration have shown promising results in small and large animal models. Clinical translation of these insights to upper extremity reconstructive transplantation could further minimize the need of immunosuppression and optimize functional outcomes; enabling greater feasibility and wider application of these procedures as an option for upper extremity amputees.

Evolution of upper extremity allotransplantation

Historical development and milestones

The earliest accounts of organ transplantation date to the Chinese physician Pien Chi’ao, who in 500 bce performed a dual-heart transplant on warriors Gong Hu and Qi Ying.⁶ The Sušruta Samhita, a surgical treatise written by the Indian surgeon Sušruta who lived around 480 bce describes in detail the techniques of rhinoplasty and pedicled autografts from the forehead, neck, and cheek to restore mutilating injuries of the nose and ear.⁷^–⁹ About 870 years later, the patron saints Cosmos and Damian are credited with performing the first limb allotransplantation.¹⁰^–¹³ Legend has it that around the year 348, they successfully transplanted the right leg of a dead Moor onto the Roman deacon, Justinian after amputating his cancerous/gangrenous leg (Fig. 38.1). A 15th century fresco in the St. Julius Basilica in Milan shows St. Julius replanting the amputated thumb of a man.¹⁴ In his book written in the 16th century, De curtorum chirurigia per insitionem (“On the surgery of mutilation by grafting”), the Italian surgeon Gaspare Tagliacozzi, from Bologna described a method of nasal and aural allo-reconstruction, where he used skin from the inner aspect of the arm from a slave to reconstruct the nose of a wealthy patient who injured it during a sword fight.¹⁵^–¹⁷ In his book, Tagliacozzi discusses the practical difficulty in binding two persons (referring to tissue rejection) to one another for a sufficient length of time.

Fig. 38.1 St. Cosmas and Damian perform the first human extremity allotransplantation. Per mythology, Christian Roman deacon, Justinian, had a malignant growth on his leg and fell asleep while praying for a cure in the Church of Cosmas and Damian in Rome. In his dreams, the saints amputated the diseased limb and transplanted the leg of a Moor, brought to the church for burial. The patient awoke and gratefully observed a now healthy leg, though black in color.

(Reproduction with permission from Württembergisches Landesmuseum, Stuttgart.)

It took another 300 years before these “practical difficulties” in transplantation began to be elucidated. During this time, advancements in antisepsis, anesthesia, hemostasis, organ preservation and, most importantly, microvascular surgery led to the rapid progress of reconstructive microsurgery. Alexis Carrell in 1902 described the surgical technique of vascular anastomosis, thus laying the foundation for conventional vascular surgery.¹⁸ Carrell successfully obtained the revascularization of experimental organ allografts,^19,²⁰ but failed to achieve permanent graft acceptance. Carrell attributed this “organ failure” to vascular complications because he had no knowledge of the process of rejection. In 1932 and 1937, the first attempts at skin grafting were performed between identical twins.^21,²² Again, no mention was made of rejection. In 1944, Hall published the first detailed theoretical account of cadaveric donor upper extremity transplantation (at the mid-humeral level).²³ In this protocol, he describes the need for an experienced surgical team in a well-equipped hospital to perform the procedure, and includes descriptions of organ preservation, osteosynthesis, and vascular anastomoses. Potential complications related to thrombosis and infections are discussed, but, again, no reference is made to the occurrence of rejection. Strikingly, Hall was not aware that Sir Peter Brian Medawar, a young zoologist in Britain, and Thomas Gibson, a plastic surgeon, had made the historic discovery of the immunologic phenomenon of skin allograft rejection in the very same year (1944).²⁴ The challenge of skin transplantation led to the exploration of new frontiers in organ transplants. In 1954, a plastic surgeon, Joseph E. Murray with his team members, John P. Merrill, and J. Hartwell Harrison in Boston, performed the first successful human kidney transplantation between identical twins.^25,²⁶ This was followed in 1957, by the first clinical attempt at allotransplantation of an en bloc composite digital flexor tendon mechanism by a plastic surgeon Erle E. Peacock, Jr.^27,²⁸ Indeed, it was Peacock who coined the term “composite tissue allograft” to differentiate these transplants that were composed of modules of multiple tissues unlike solid organs.²⁹

Our understanding of the immunologic behavior of allografts lagged behind technical developments in surgery. It is only the knowledge gained from landmark discoveries in the past century ³⁰^–³⁸ that facilitated the manipulation or suppression of the immune response, allowing successful prolongation of graft survival. After Medawar’s demonstration that rejection was an immunologic event, the next logical question was: Why not prevent this phenomenon by suppressing the immune system? In the 1950s, corticosteroids and irradiation were used for immunosuppression.^39,⁴⁰ In the 1960s, the anti-metabolites 6-mercaptopurine and its derivative azathioprine were introduced, along with agents such as antilymphocyte globulin. These drugs were used either alone^41,⁴² or in combination with corticosteroids.⁴³^–⁴⁵ Graft survival improved but was still dismal because these drugs acted indiscriminately and were associated with severe organ specific and systemic adverse effects.

In 1964, the first hand transplantation was performed using pharmacologic immunosuppression.⁴⁶^–⁴⁸ Dr Gilbert in Guayaquil, Ecuador, transplanted the right forearm of a 28-year-old sailor who had lost his limb at the wrist level caused by a hand-grenade explosion the previous day. The donor was a laborer who had died of hematemesis (with gastric bleeding) a few hours earlier. The recipient was given heparin, dextran, and a broad-spectrum antibiotic after the surgery and was maintained on a combination regimen of prednisone and 6-mercaptopurine. 6-mercaptopurine was replaced 24 h later by azathioprine. These drugs can be considered primitive according to present day standards, and signs of acute allograft rejection occurred after two and half weeks. The patient was then moved to Peter Bent Brigham Hospital in Boston, where at 3 weeks, aggressive rejection set in, and the forearm had to be re-amputated 4 cm above the wrist level. Unfortunately, the advanced state of necrosis prevented any histopathologic evaluation of the graft. This bold and pioneering attempt at hand transplantation laid the foundation to the successful attempts yet to come.

In 1976, another major breakthrough in transplantation came with the discovery of the immunosuppressive properties of the calcineurin inhibitor cyclosporine A.^49,⁵⁰ In 1978, cyclosporine was first used clinically in organ⁵¹ as well as bone marrow transplantation with remarkable results. The FDA approved cyclosporine A in 1983. Cyclosporine A, along with agents like anti-CD3 antibody (OKT3, introduced in 1981),⁵² effectively reduced reliance on high-dose steroids for the prevention of rejection. The calcineurin inhibitor tacrolimus (FK 506) was discovered in 1987,⁵³ clinical trials were conducted in 1989,⁵⁴ and FDA approval came in 1994. Tacrolimus led to dramatic improvements in solid organ transplantation,⁵⁵^–⁵⁸ allowing highly immunogenic grafts such as the small bowel to be transplanted.⁵⁹^–⁶¹ The success of the calcineurin inhibitors cyclosporine A and tacrolimus made them the cornerstone drugs of the modern era of transplantation.⁶² The 1990s saw the introduction of novel drugs such as the antimetabolite mycophenolate mofetil⁶³ (MMF, approved by FDA in 1995) and rapamycin⁶⁴ (sirolimus, discovered in 1976 but FDA approved only in 1999). Combining these drugs with a calcineurin inhibitor⁶⁵^–⁶⁸ significantly reduced acute rejection and improved solid organ graft survival with a reduction in adverse effects.

Immunology of composite tissue allografts

Much knowledge concerning the immunologic aspects of composite tissue allografts has been gained from studies in small and large animal models. Animal research has confirmed that each tissue in a composite tissue allograft has its own distinct degree of antigenicity and is rejected by different mechanisms. This is because each of the component tissues is characterized by different antigen expression and presentation mechanisms.⁶⁹ The components of a composite tissue allograft express different amounts of major histocompatibility complex (MHC) antigens and tissue-specific antigens, which are primarily responsible for the elicitation of the recipient’s cellular mediated response.⁷⁰ Antigen recognition and targeting by the recipient immune system also differ among the allograft tissue elements owing to their different vascular and lymphatic supply. Altogether, these facts explain a pattern of differential rejection observed in whole limb transplanted allografts. For example, transplanted muscle elicits mainly a cell-mediated immune response, whereas skin elicits both cellular and humoral responses.⁷¹ In general, skin and bone marrow appear to reject earlier and more aggressively than muscle, bone, cartilage or tendon. The knowledge of relative antigenicity can lead to the development of strategies intended to decrease the antigenicity of a specific component. In addition, a better understanding of this relative antigenicity of allograft components enables the concept of tailored immunosuppression, targeting only specific cellular and humoral components of rejection. This would limit the amount of immunosuppression used and the consequent related complications of opportunistic infections and malignancies. Thus, it is logical to presume that to prevent rejection; the most effective immunosuppressive strategy would be a combination of agents that affect different pathways of the immune response through different mechanisms.⁷² Ideally, this combination of drugs must be selective, specific, and synergistic, free of toxic reactions, easy to administer, and inexpensive. Most of the information regarding potential immunosuppressive regimens has been derived from small animal (rat) and large animal (porcine, canine, and primate) composite tissue allograft models.

Experimental background and scientific basis

In early rodent limb transplant studies (pre-cyclosporine A era), recipients treated with various combinations of immunosuppressive doses of 6-mercaptopurine or its derivative azathioprine and prednisone all died from drug-induced side-effects before the onset of macroscopic signs of rejection.⁷³ Even high doses of cyclosporine A did not improve limb or animal survival.⁷⁴^–⁷⁸ The incidence of side-effects and morbidity/mortality was significant. Indeed, cyclosporine A monotherapy has been uniformly unsuccessful in prolonging composite tissue allograft survival not only in small animal but also in nonhuman primate models, which have been considered to be representative of the human immune system and the best predictors of success in clinical trials.⁷⁹ Remarkably, composite tissue allograft rejection in nonhuman primates cannot be prevented unless trough levels of cyclosporine A are 3–4 times the level achieved in human solid organ transplantation resulting in peri-transplant infections and malignancies.⁸⁰^–⁸³

None of the above-mentioned studies attempted to combine a calcineurin inhibitor and an antimetabolite drug (such as mycophenolate mofetil) with or without steroids. None of the above studies could consistently demonstrate long-term limb allograft survival. In 1996, Benhaim and colleagues demonstrated that a combination of cyclosporine with mycophenolate mofetil could successfully prolong rat hind limb allograft survival.⁸⁴ For the first time, predictable long-term, functional limb allograft survival was achieved. Using a similar regimen, the only large animal model that demonstrated long-term survival of fully mismatched composite tissue allografts was the swine model.^85,⁸⁶ It should be noted that like the non-human primate, swine and humans share immunological similarities. These include the structure of MHC and the expression of MHC class II antigens (on endothelial cells, epithelial cells, and dendritic cells).⁸⁷ Therefore, there was sufficient sound evidence in both a small (rodent)^88,⁸⁹ and large animal composite tissue allograft model,^85,⁸⁶ implying that the experimental basis of human extremity composite tissue allotransplantation was feasible.⁹⁰

The success in rodent and swine models did not translate to primate studies. This was because modern combination immunosuppression (tacrolimus or cyclosporine A with mycophenolate mofetil ± steroids) has never been tested in a non-human primate composite tissue allograft model.⁷⁹ However, given the marked success of the early hand transplant experience (95% graft survival with 100% 1- and 2-year patient survival) using standard combination therapy, the lack of a pre-clinical primate model may now only be semi-relevant.

Extensive experience with organ transplantation has provided us with valuable information about the immunologic consequences of organ allografting and the efficacy and toxicity of immunosuppressive drugs. The field of transplantation evolved from transplanted kidneys ⁹¹ and hearts^92,⁹³ to livers,⁹⁴ lungs,⁹⁵ pancreas,⁹⁶ small bowel,⁹⁷ multiple abdominal viscera,⁹⁸ bone marrow,⁹⁹ and, most recently, composite tissue allografts.^100,¹⁰¹ The initial results of graft and patient survival after organ transplantation in the 1960s were poor. Editorials in major clinical journals,¹⁰² including the New England Journal of Medicine,¹⁰³^–¹⁰⁵ questioned the feasibility and ethical basis of these procedures. There was great concern for the adverse effects of chronic immunosuppression, especially the risk of opportunistic infections and malignancies. During the next four decades, because of the improvements in immunosuppression and in the management of post-transplant complications, this pessimism abated. Remarkably, however, attempts at hand transplantation,^106,¹⁰⁷ after three decades of quiescence since the first attempt in Ecuador,^46,⁴⁷ met with vigorous opposition. Paradoxically, most of the criticism came from hand surgeons.¹⁰⁸^–¹¹⁴ They argued that the risks of immunosuppressive therapy were justifiable in potentially life-saving organ transplants, but not in quality-of-life-enhancing transplants such as hand transplants. Furthermore, many hand surgeons thought that the immunological, ethical,^115,¹¹⁶ and psychological¹¹⁷ issues associated with hand transplantation needed to be addressed.¹¹⁸

The rationale for proceeding with clinical trials of hand transplantation using modern immunosuppression, has been based on scientific progress on several fronts: (1) the availability of novel immunosuppressive drugs that have improved efficacy and lower risk profiles; (2) improved prophylaxis and treatment of opportunistic fungal or viral infections (such as Pneumocystis carinii and Cytomegalovirus); 3) improved therapies for post-transplant malignancies (such as rituximab for post-transplant lymphoproliferative disorder, PTLD); (4) better expertise with drug dosing and fine-tuning of immunosuppressive drug combinations based on years of experience with solid organ transplantation, and, most importantly (5) all individual component tissues of the hand, including skin, muscle, tendons, vessels, nerve, bone and joint, were successfully transplanted in humans before the modern era of hand transplantation.¹¹⁹

Chronology of clinical upper extremity allotransplantation

In September 1991, the first conference on composite tissue allotransplantation was held in Washington, DC to “determine the clinical feasibility of transplanting limbs in patients with limb loss” and the “direction in which clinically oriented limb transplantation research should head.”¹²⁰ In November 1997, the 1st International Symposium on Composite Tissue Allotransplantation was convened in Louisville, Kentucky to discuss the “scientific, clinical and ethical barriers standing in the way of performing the first human hand transplant.” International experts at the meeting predicted that limb allotransplantation was not far from “becoming a clinical reality.”¹²¹ Within the next 22 months; 34 years after the first hand transplant,^46,⁴⁷ surgeons in Lyon, France, performed the world’s second unilateral hand transplant in September, 1998.^106,^107,^122,¹²³ In January 1999, the first unilateral hand transplant in the United States was performed in Louisville, Kentucky.^124,¹²⁵

Following these attempts, over the past 12 years, seven centers in Europe, five centers in China and five centers in the US have performed over 70 upper extremity allotransplantations. These were predominantly wrist to mid-forearm amputations, except for two partial hand grafts in China, one partial hand graft in the US, and two cases of above elbow transplantation. The first American patient has the longest surviving transplant, at 12 years, in January 2011.^126,¹²⁷

Experience with upper extremity allotransplantation

Program, patient, procedural and protocol-related considerations

Program establishment and implementation

Starting a hand transplant program poses tremendous challenges.^128,¹²⁹ Solid organ transplantation and hand replantation are time-tested procedures and are now the standard of care. Hand transplantation is the amalgamation of the scientific principles of reconstructive surgery and the concepts of organ transplantation. Thus, for any hand transplant program to be successful, it must be collaboration between a multidisciplinary team comprised among others of a core group of hand (plastic or orthopedic) and transplant surgeons. The transplant process is well established but is bound by tight regulation. This is not well known to most outside the field and often comes as a surprise to reconstructive plastic/hand surgeons who wish to start a hand program. The logistics of upper extremity allotransplantation can often be overwhelming and challenging for a new program. This is where the experience of the solid organ transplant members of the group helps in negotiating through the process. Such a joint effort can overcome the challenges that are inherent in a complex therapeutic option that integrates multiple specialties during the planning, procedural, and post-transplant phases.

Donor and recipient selection

The overall success of composite tissue transplantation relies on many factors. One could argue that it is the technical expertise of the team and effective postoperative care of the recipient that plays a significant role in transplant outcomes. However, it is the proper evaluation, selection and management of donors and potential recipients that is probably more important. Decades of experience with solid organs have allowed us to establish criteria for donor and recipient selection. In a novel field like hand transplantation, parameters for inclusion and exclusion of donors and recipients have not yet been conclusively defined nor standardized.^130,¹³¹ Tables 38.1 and 38.2 highlight the general selection criteria in upper extremity transplantation and compares them to those of solid organ transplantation. Patients below the age of 18 are not considered to be adults, and, therefore, there are issues of informed consent in an experimental procedure. Furthermore, pediatric patients are more likely to develop immunosuppressive related complications like PTLD, than adults.¹³² Patients over the age of 65 are excluded because of increased immunosuppression-related complications; limited years of potential gain from the transplant, and decreased nerve regeneration. Medical screening of recipients includes a complete medical history and physical examination; routine laboratory studies; blood typing and cross-matching; human leucocyte antigen (HLA) typing; testing for panel-reactive antibodies; and serology for Epstein–Barr virus, cytomegalovirus, HIV, and viral hepatitis. Other tests include radiography (to plan for osteosynthesis), angiography (to exclude abnormal vascular patterns), electromyography, nerve conduction velocity, and functional magnetic resonance imaging (fMRI).

Table 38.1 Donor considerations in upper extremity transplantation versus solid organ transplantation

Upper extremity transplantation	Solid organ transplantation
Demographic and phenotypic characteristics	Organs from older/marginal donors may be considered. No other demographic or phenotypic exclusions
Skin color, tone, and texture match
Limb size and dimension (bone length and diameter match)
Age, sex, race and ethnicity match if possible
Donors must be deceased (brain death declared)	Donors may be deceased or living-related in particular organ transplants
Donor limb dissection and procurement must not interfere with organ recovery. Limb usually prepped first, perfused under isolated tourniquet, dissected after cross clamp and retrieved in sequence with heart and lung recovery. This minimizes overall ischemia time	Organs are dissected and procured in order of importance or in tandem by multiple teams. Sensitivity of organ to ischemia may be a consideration in timing or recovery
Donor family consent includes a discussion of cosmetic prosthesis for open casket funerals	No such consideration
History of malignancy (recent or remote) may be an exclusion	Donors with some malignancies (CNS tumors) may be considered
Paralysis of ischemia or traumatic origin, inherited peripheral neuropathy, infectious, post infectious or inflammatory neuropathy, toxic neuropathy (i.e., heavy metal poisoning, drug toxicity, industrial agent exposure) or mixed connective tissue disease, severe deforming rheumatoid or osteoarthritis in the limb may be exclusions	No such consideration

Table 38.2 Recipient considerations in upper extremity transplantation versus solid organ transplantation

Upper extremity transplantation	Solid organ transplantation
Subjects can be of any race, color, ethnicity in good health	Subjects usually have extensive co-morbidity
Age range for eligibility is variable but usually over 18 years and under 65 years	Age range is broader and related to organ failure or need for organ replacement
Subjects with congenital defects (e.g., transverse arrest) are currently not candidates due to the unknowns related to lack of pre-existing cortical recognition	Congenital (structural/genetic/metabolic) organ defects are candidates
Blindness is an exclusion in some programs due to complicated rehabilitation and lack of visual feedback that is critical for functional recovery	Blindness is not an exclusion
Rigorous psychosocial assessment mandatory to determine motivation for transplantation, emotional and cognitive preparedness for the procedure, body image adaptation, level of realistic expectations regarding post-transplant outcomes, anticipated comfort with the transplant, personality organization/risk of regression, history of medication compliance/substance abuse, potential for compliance, and social support system/family structure	Psychosocial screening performed but not rigorous or as exhaustive in nature
Use or attempted use of prostheses prior to transplant is a suggested requirement	No such consideration