I think that I know a technology for rebuilding a severed limb. I would like to discuss why it is not used in practice. Here is the brief description of the technology. The source is my web-site http://www.freetextbooks.narod.ru/rsharipov/e17.htm.
Upon limb amputation, if it is not at a joint, a fragment of the limb remains, which is called a stump. This sump comprises a fragment of the bone (or bones).
It is known that bones can be elongated. The Ilizarov apparatus is used for this purpose (see Ilizarov apparatus). Elongation of a bone (or bones) fragment within the stump is the first step of the technology being described. Along with the bone elongation soft tissues are also elongated, including muscles. This process is stimulated by mechanical tension that arises when bones are elongated. Additionally physical loading (exercises) and plastic surgery methods can be used.
The stump bone (or bones) should be elongated to a length exceeding their natural length in a healthy organ. For instance, if a hand is amputated below the elbow, the ulna-bone and the spoke-bone should be elongated to their initial lengths plus the palm length and plus the length of the wrist joint. Then the procedure of the bone splitting follows. The elongated ulna-bone and spoke-bone are split at their ends into two parts. Between their parts a film is placed that prevents their consolidation into a single bone. A structure similar to a slingshot or a fork arises. If necessary, upon healing, each half of the ulna-bone or the spoke-bone is again split into two parts. As a result a structure roughly resembling a palm, but having no mobility arises.
Bones fracturing and forming a limb.
Let's continue considering the above example. The next step of the technology is fracturing the structure roughly resembling a palm into small fragments whose number is equal to the number of bones in a natural palm. In this step part of the bone tissue can be milled into sawdust and placed into a reticulate titanium corset. In such a corset it will be supplied with blood and will integrate into a solid bone of a desired shape.
Forming joints and tendons.
Forming joints and tendons is a separate step. One can use artificial joints. Endoprostheses for joints are available now. The other option is to form joints by means of the cartilage tissue autotransplantation. As we noted above, muscles are elongated along with bones. The ends of elongated muscles should be cut and used for producing small muscles moving the palm and fingers. Tendons can be produced by autotransplantation.
Sensibility and mobility.
Nerve tissue can regenerate. When elongating the bones and soft tissues of a stump, nerves are elongated as well. But for making the formed limb sensible and mobile neurosurgical operations can also be used.