**4.1 Composite tissue transplantation**

When body structures composed of multiple tissues derived from ectoderm and endoderm is transplanted then the procedure is named composite tissue allotransplantation. Such transplants are also known as " vascular composite allografts". The concept of composite tissue transplantation includes hand, face, larynx, joint, abdominal wall transplantations. This type of transplant has a life-changing nature, as the main goal is to restore reduced or completely lost functions and to increase

the quality of life. Unlike solid organ transplants, nerve regeneration must occur in the transplant to restore sensory and motor functions.

The first hand transplant was tried in Ecuador in 1964 with failure. The failure was believed to be associated with inadequate immunosuppression [9]. Dubernard and his coworkers transplanted the right distal forearm and hand from a deceased donor to a 48- year- old male patient who had had a traumatic amputation of the distal third of his right forearm. Motor and sensory recovery were evaluated as excellent six months postoperatively and no serious signs of rejection were observed [10].

The same group performed surgical intervention involving bone fixation, arterial and venous anastomosis, nerve suturing, tendon, and muscle joining in a 33-year old, bilateral forearm amputated patient. They applied physical therapy, electrostimulation, and occupational therapy in the postoperative period. In the postoperative 15th month, they observed satisfactory sensory and motor improvement as well as improvement in the quality of life. This procedure was the first human double-hand transplantation with satisfactory results [11]. It is generally believed that bilateral below-elbow amputation is the most accepted indication for hand transplantation.

In a study comparing the functional and psychosocial outcomes of hand transplantation and prosthesis options, upper extremity functions were globally evaluated with ARAT [Action Research Arm Test] and SHAP [Southampton Hand Assessment Procedure]. The study revealed that functional results are not significantly different. The advantages of transplantation are that it provides sensory and self-perception in addition to providing motor activity. Complications due to immunosuppression pose a disadvantage in transplantation. However, if immunosuppression is well tolerated, regeneration of an organ with its like is naturally an advantage. In bilateral below-elbow amputees, it is understood that the benefit is greater when the acquisition of motor and sensory functions is compared with the risks of immunosuppression. Unilateral amputees can compensate for many functional deficits by using healthy limbs and prostheses. Also, In addition, there is no need for a long-term rehabilitation program after prosthesis implantation, as in transplantation. For these reasons, the prosthesis option is a priority in patients with unilateral below-elbow amputees [12].
