What is an autograft / allograft / graft?

Bone or tissue transplanted from one part of the body to another part in the same person is called an autograft.
Bone or other tissue transplanted from one person to another is called an allograft.
The term "graft" is used to refer to both autografts and allografts.

What is a tissue bank?

A tissue bank is a facility that is capable of providing on demand, a spectrum of fresh or preserved biological tissues for transplantation. These tissues must be of predictable clinical function and free from transmissible disease. A Tissue Bank thus engages in the retrieval, processing, preservation, storage and/or distribution of donated tissue.

Ideally, the best replacement tissue following trauma, disease or surgery, is the patient's own tissue. However, using banked tissues has certain advantages. They eliminate the risks and the expense of the additional incision necessary for acquiring an autograft. They also avoid the creation of a permanent defect in the tissue recovery site which sometimes could give rise to major complications. Further, since allografts do not damage normal structures they provide the surgeon with a variety and quantity of tissue which otherwise may not be available. This is especially so in children who do not have enough tissue to meet their surgical needs and in patients who are already medically compromised.

The use of tissues from the TMH Tissue Bank also results in a considerable saving as the grafts are available for a nominal processing fee which is a fraction of the cost of imported grafts. In addition, hospital and medical expenses are brought down with the use of banked tissues due to reduced surgical time, faster recovery and a shorter hospital stay.

The use of biological dressings like amnion reduces pain and hastens healing. It also avoids frequent changes of dressings and reduces analgesic and antibiotic use thereby contributing to the financial saving.

Tissues such as bone, cartilage, ligaments, tendons, fascia lata (the thin covering of the muscles), heart valves, blood vessels, skin and amnion are currently being banked the world over.

Bone may be morsellised (broken into smaller bits) and used to fill cavities in a patient’s bone or may be used as a long segment to replace deceased or damaged bone. It may help to correct deformities, provide structural support and strengthen weakened bone as in patients with osteoarthritis and those needing total knee or hip replacement. In some patients it may prevent the amputation of a limb. 

Tendons and ligaments may be used to reconstruct damaged ones thus strengthening the joint and assisting the patient in walking and running.

Cryopreserved fascia lata can be used as a replacement for dura mater in neurosurgeries, as a supportive covering or for reconstructive repair.

Skin and amnion may be life-saving for critically burned patients. Amnion can be used to help restore sight in certain conditions. Banked skin can also be used for hernia repair, reconstruction of the bladder and pelvic floor, as well as to provide skin cover in surgeries when the patient’s own tissues are inadequate as in breast reconstruction following mastectomy.

Heart valve allografts are used to replace or repair damaged ones and offer the chance of an active life for many, especially children.  They offer certain advantages over mechanical and porcine valve substitutes and do not require the use of postoperative anticoagulants which are associated with a substantial risk of spontaneous bleeding and embolism.  Saphenous and femoral veins from the legs are used in cardiac by-pass surgery for patients who have suffered cardiovascular (heart) disease.

Allografts may be obtained either from living or deceased donors. Donated amnion, the membrane which is expelled along with the baby at birth, is recovered after deliveries. Donated bone can be obtained after surgical procedures like hip or total knee replacement for osteoarthritis. A variety of tissues can be recovered after death from a donor after the necessary screening, and written consent from the next-of-kin.

In order to render the allografts safe, the donors are screened for infectious diseases and diseases of unknown origin. The donor’s blood is tested for HIV/AIDS, Hepatitis B and C, and Syphilis.  If any of these tests prove to be positive the donated tissue is not used. In addition, at the TMH Tissue Bank the tissues are subjected to heat and chemical treatment to further reduce the risk of disease transmission, and finally sterilised with ionising radiation. Although there is some theoretical risk for disease transmission as is the case also in blood donation, the use of allografts that have undergone donor screening, serological testing, processing and irradiation has a significantly reduced risk.

At the TMH Tissue Bank donated tissue is cleaned of blood and in the case of bone the soft tissue and bone marrow is removed. The tissues are then subjected to heat and chemical treatment and then stored in -80ºC freezers. They are finally freeze-dried to remove 95% of their water content, double packed in a sterile environment and sterilised by exposing them to gamma radiation. These grafts are available in ready-to-use packs that have a shelf life of 3 years. They can be conveniently stored at room temperature and even mailed. Sometimes bone is irradiated in the frozen state without freeze-drying. Such bone must be stored at    -80ºC.

Tissues like amnion and skin that are used as biological dressings are for the most part used externally and are temporary covers. As healing takes place they peel off on their own.

Bone allografts are usually effective, facilitating the formation of new bone and reducing the percentage of repeat procedures. However, there are cases where the grafts do not perform as expected. This can be due to a variety of reasons which include the patient's age, lifestyle, primary medical condition, the time taken for surgery, and the number of surgical procedures already performed. Allograft struts are known to have the potential problem of non-union and fracture, as incorporation is slow, often taking up to a year. The situation could be aggravated with postoperative radiation and chemotherapy. According to the literature, the risk of post-operative infection in patients who will require an allograft is between 4% and 13.2%. In a preliminary study done at the TMH which was published in an international journal, the infection rate using our bone grafts was within this range.

Are there any problems of rejection of the graft as in the case of organ transplants ?

There are no problems of rejection as the transplantation antigen is destroyed during processing. Tissue typing is therefore not necessary, and anti-rejection drugs are not required to be used in the recipient of the allografts.

Is it safe to use radiation for the sterilisation of allografts?

Radiation sterilisation is a simple and safe process. It involves the exposure of the tissues to gamma radiation from a Cobalt-60 source, for a predetermined time so as to receive a prescribed dose. It has been established as an efficient and convenient technique for achieving a high level of sterility in medical supplies, medicinal products, in vitro diagnostic products and food products and its use has been extended to the sterilisation of grafts. Tissues sterilised in this way do not become radioactive and are completely safe.

If you are a non-profit organisation why do you charge for tissues?

The donation and banking of tissues has significant costs associated with it. The fee charged covers the cost of the resources and infrastructure necessary for retrieval of tissues (recovery team salaries, operating room time, supplies, transportation, etc.), tests to ensure the tissue's safety, processing and quality control, research to develop more effective grafts, and awareness campaigns to promote tissue donation and utilisation.