Autograft
Autografting is the most widely performed method of orthopaedic transplantation. It involves moving bone, cartilage cells, or tendon (all three on occasion) from one part of the body to another. The commonest reason for doing so is when a fracture has failed to unite, when bone cells are taken from the pelvis, or elsewhere, and moved to the fracture site. The fresh bone cells attempt to give the old ones a kick start.
The problem with autografting is simply volume. The surgeon is limited in the quantity of tissue he can remove. One obviously cannot remove an entire pelvis - a few dessert spoonfuls of bone is all one is likely to obtain. There is thus a limit to the size of defect that can be filled with autograft bone. The donor site can also be more painful than the recipient area after surgery.
However, despite the difficulties, autograft tissue is undoubtedly the best choice, if enough can be obtained. There is no problem with an immune response, or disease transmission, or compatibility. Sometimes autograft bone is mixed with other forms of tissue, be it allograft or xenograft to make sufficient volume.
In recent years autografting techniques have been used in the management of articular cartilage (gristle) defects, for example the athlete in whom a fragment of gristle has peeled off the inside of the knee, giving rise to locking, or pain, or instability. By leaving such an irregular surface within the joint it is almost assured that osteoarthritis (OA) will ensue. Many different techniques have been described to fill such defects - carbon fibre pads, microfracture, simple debridement, drilling, etc. Autografting is also possible. For example a surgeon can take cartilage cells from the chest of a patient and move them down to the knee (or elsewhere) of a patient.
Chondrocyte culture is another technique. Here cartilage cells are taken from the knee joint at arthroscopy and sent to a laboratory for culture. This involves taking out relatively few cells, but using the laboratory to encourage the cells to multiply enormously. When a sufficient number has been obtained, the cells are reinserted into the patient.
Mosaicplasty is a further method. This involves coring out small cylinders of bone and cartilage cells and moving the cylinders from one part of a joint to another. For example, there are certain areas within the knee where the articular cartilage has limited function. These areas can be used as donor sites, the cylinders being moved to fill defects found on the essential, weight-bearing portions of the joint. The donor defect can be left as it is, or filled with a plug of hydroxyapatite.
Long term results for all these techniques, particularly chondrocyte culture and mosaicplasty, are still awaited. However, they do look encouraging. What is certain is that to leave a large articular cartilage defect alone is not a happy state for a joint, particularly a weight-bearing one