The bones of the skeleton not only give shape to the body, they transmit the forces necessary to move it. It is the muscles of the body which generate the forces necessary for this movement, and it is the tendons attached to the muscles which direct these forces into the bone. It is the joints of the skeleton, held by ligaments, which allow for its movement.
Portions of these musculo-
This lost function can be replaced, to some extent, by use of an external prosthesis or artificial limb but reconstruction attempts to build up the lost tissues within the body itself using a combination of artificial and natural substances. Most preferably, if possible, the tissues of the body itself are used.
Because the growth and healing of living tissue takes time the process of reconstruction of a limb or part of the body can be a long and tedious process. It takes a lot of determination and courage of the affected individual to undergo the numerous procedures which usually necessary to achieve restitution. Nevertheless, although the tissues are replaced, a reconstructed limb is not always exactly the same as the original one which was lost and the expectations for the ultimate result of the process must be realistic.
Reconstruction is carried out in several areas:
The skin covers the body and is usually the first structure to be lost in any injury. Part of its function is to protect the underlying tissues from drying out and from infection. If there is any significant muscle and bone loss it will be necessary to restore the skin cover to the area before any musculo-
If the skin loss is superficial it may be replaced by a ‘split skin graft’, taking a thin layer of normal skin from an unaffected area and placing it over the denuded area. The grafted skin attaches and covers the area in which it is placed and the ‘donor’ area from which it is obtained grows a new layer to replace it.
Thicker areas of skin loss require thicker skin grafts to replace them but, in order to maintain the nutrition and vitality of these thicker layers of skin it becomes necessary to transfer the skin along with its blood supply. In these cases the skin graft may be shifted to its new position trailing its blood vessels or, if the distance is too far, the blood vessels are reattached to others in the area by microvascular techniques.
Paralysed or lost muscle cannot be replaced as the body does not regenerate this type of tissue. What is done is to use another muscle in the region to replace the lost muscle function if this is necessary and is feasible. This is accomplished by detaching one end of a working muscle in the same region and inserting it into the bone in place of the damaged muscle. With training the replaced, or ‘transferred’, muscle will take over the lost function.
This procedure is undertaken if the lost muscle was responsible for an important function or if an imbalance of muscle power across a joint has occurred as this will lead to contracture of that joint .
Tendon transfers and grafting
Like muscle, tendons cannot be recreated by the body. If a tendon has to be replaced that of another muscle can be used and its tendon inserted in place of that which is lost. Alternatively a length of tendon can be taken from a muscle whose action is not too important and ‘grafted’ into the area of loss. Alternatively, for small areas of tendon or ligament loss, strips of fibrous fascia surrounding the muscles can be fashioned into a tendon substitute.
Tendons need to glide through tunnels of synovial tissue. To date there is no artificial substance which can perform this function. However, for short lengths, cords of various synthetic fibres can be used as a substitute for the ligaments around a joint.
Bone gives the basic form, structure and support to the body. Without it the muscles and tendons will not function effectively. It is, however, the one substance which the body can replace. The attempts therefore are to induce its formation by the body where it is lost. There are several techniques whereby this is attempted. The simplest technique is to place small portions of bone derived from the affected person’s skeleton and lay it down in the deficient area. At this site it acts as a scaffold on which the body generates and lays down normal bone. Where there is not enough of the individual’s bone available bone derived from other donor’s can be utilised.
In addition to natural bone various ‘bone substitute’ materials are sometimes used. These too act as a scaffold in which the body deposits its normal bone. The advantage of these substitutes is that their use can spare the individual another operation needed to obtain the bone but, on the other hand they do not always cause the new bone to be formed.
Chemical substances which stimulate the body to generate bone are sometimes used, usually along with bone inducing substances.. The best known example of this is BMP, or ‘bone morphogenic protein’. While effective in stimulating the body to produce bone they have, in the past, been difficult to obtain and tend to be expensive.
Perhaps the most remarkable innovation with regard to inducing bone formation and replacing lost bone in the limbs is the Ilizarov technique. This method causes new bone to be formed as a bone is lengthened by a method known as ‘callotaxis’.