Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Implant or insert
Patent
1995-02-02
1997-04-08
Michl, Paul R.
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Implant or insert
424423, 424602, A61F 228
Patent
active
056185499
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to the field of treatment of certain bone diseases.
It is known that bone is a continuously regenerated tissue. Schematically, osteoblasts secrete an inorganic matrix consisting mainly of hydroxyapatite and the osteoblast surrounded by this inorganic matrix converts into an osteocyte. In parallel, specialized cells, such as osteoclasts break down the inorganic matrix. In healthy bone, the space thus liberated is reoccupied by osteoblasts and so on.
It is important to retain a balance between osteogenesis and osseous resorption so that the bone can fulfil its function in the skeleton.
BACKGROUND
A number of diseases are known which are associated with demineralization or mineralization disorders of bone. The most well-known disease is without doubt osteoporosis, in which the regeneration of the bone tissue is imbalanced because the breakdown of the bone matrix by the osteoclasts becomes predominant. The activity of the osteoblasts is greatly decreased and, as the disease progresses, the inorganic matrix is present in an insufficient quantity to allow activity of the osteoblasts to develop normally. The result of this is that the reconstruction of the bone matrix is interrupted or, in any case, insufficient to maintain the conditions necessary for the osteogenesis process. The number, thickness and relative volume of the bone-tissue bridges in the spongy bone are reduced. The density of the bone decreases, which leads to greater mechanical fragility. This results in bone fractures due to impact or falling (especially fractures of the femur, of the wrists or of the humerus) or else vertebral compressions under the pressure exerted by the weight of the body. Repairing such fractures may become difficult because of the small mass of bone available for repair. It is known, in particular, that fractures of the neck of the femur in the elderly suffering from osteoporosis can lead to death in approximately 20% of cases.
Other diseases are accompanied by demineralization or weak mineralization or a mineralization defect of the bone. This is the case, in particular, of Paget's disease, fibrous dysplasias and osteodystrophies caused, in particular, by certain renal insufficiencies. In addition, demineralization of the jaw bone may be the cause of certain periodontal diseases.
Until now, the treatments of demineralization diseases of the bone, in particular osteoporosis, comprise oral supply of calcium, optionally in association with vitamin D, or the administration of oestrogens, optionally in combination with progestogens. These treatments can arrest the breakdown process, but without allowing remineralization by regeneration of the interstitial bone tissue.
The administration of fluorides, also orally, stimulates the osteoblast activity and can lead to an increase in the bone mass by 5 to 10% per year in responsive patients (approximately 60% of cases). However, treatment using fluorides has the drawback of some degree of cumulative toxicity, with the appearance of bone microfractures which can cause significant amounts of pain.
SUMMARY OF THE INVENTION
It has now been discovered that it is possible to reinitiate remineralization of the bone by locally supplying calcium in the form of a biocompatible and bioabsorbable salt.
It has been observed that the local application, within the bone, of a calcium salt makes it possible to reinitiate a process of remineralization and regeneration of the interstitial bone tissue with, in particular, increase of the bone density (and therefore the solidity of the bone), whereas oral supply of calcium does not make it possible to reinitiate the process of reconstruction of the resorbed bone spans. In addition, by virtue of this local treatment, remineralization is particularly rapid. It should be noted that the remineralization process extends throughout the bone and is not limited to the part which is in contact with the region where the calcium salt is implanted.
The use has already been described of various calcium salts, and i
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Cirotteau Yves
Patat Jean-Louis
Howard Sharon
Inoteb
Michl Paul R.
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