Integration osseuse du titanium nickel poreux pour une arthrodese intervertebrale

Back pain affects about three quarters of the human population and is considered a major problem of public health. There are various back pains as well as multiple causes. Most back pains are benign, but some such as those caused by a degeneration of the intervertebral discs often require a medical or surgical treatment. If symptoms recur after surgery, it's very often necessary to proceed with an intervertebral arthrodesis which stabilizes the adjacent vertebrae at the intervertebral discs degenerated space. Among the different techniques of fusion, cages occupy the first place and, this technique has not ceased to improve.

This work consisted in evaluating in vivo, the effectiveness of a new metal cage manufactured out of porous Titanium-Nickel, called Actipore . Its performance was compared with a control cage, made of pure titanium, called BAK. The animal model used was the sheep. Both types of cages were implanted in each sheep. From one sheep to the next, the two types of implant occupied alternatively the lumbar intervertebral levels L2–L3 and L4–L5 so that they were subjected to the same mechanical loads. Sheeps (not operated) without implants served as sham controls. The sheeps were sacrificed by groups of seven (six with implants and one control) at three and six months. A third group of five sheeps (four with implants and one control) were sacrificed at twelve months.

After sacrifice, side and back-front radiological view of the spine were performed to evaluate the positioning of the cages and to observe changes in the adjacent tissues. Computerised tomodensitometry of the vertebrae was used to quantify the density of the adjacent bone structure that could be affected by the presence of the cage. The osseointegration of both cages was evaluated on histological slices of cages and adjacent tissues using both qualitative (macro and microscopic) and quantitative (histomorphometry) observations. The results indicated that the Actipore used at that time, in spite of a low mechanical strength, had performed better than the BAK. A rigorous statistical analysis of these results made it possible to confirm this observation. The performance of the two implants seemed to be influenced by the biofunctionnality which is related to the structure and the shape of the cage. The biocompatibility of two implants seemed however comparable.