METHOD AND DEVICE FOR BONE TISSUE GROWTH

Abstract: The invention relates to method and device for osseous tissue growth. In the method osseous tissue is uncovered by excising a flap of soft tissue over the site where the osseous tissue growth shall take place. A domed spacer is located at said site, and the flap is put back over the spacer which maintains a cavity between the flap and the osseous tissue. The device comprises a shape permanent domed spacer which is intended to be located over the uncovered portion of the osseous tissue in order to define said cavity over the surface of the osseous tissue.

Description: Method and device for bone tissue growth The invention relates to method and device for osseous tissue growth. In the method osseous tissue is uncovered by excising a flap of soft tissue over the site where the osseous tissue growth shall take place. A domed spacer is located at said site, and the flap is put back over the spacer which maintains a cavity between the flap and the osseous tissue . The device of the invention comprises a shape per¬ manent domed spacer to be located over the uncovered portion of the osseous tissue in order to define said cavity over the surface of the osseous tissue. O-A1-91/14404 discloses method and device for osseous tissue growth of the kind referred to above. In that case the spacer comprises a semi-spherical or truncated semi-spherical calot having a rounded base edge. The calot is perforated and is made of a tissue compatible and inert material, preferably titanium, but it can also be made of a ceramic material, steel, plastics, or hydroxyl apatite. The calot has a central opening and is attached by means of a screw which passes through the central opening and is screwed into a fixture implanted into the osseous tissue, after a portion of osseous tissue having been uncovered by excising a flap of soft tissue and periosteum. The calot is engaged at the base edge with the uncovered osseous tissue and then is covered by the flap. It is the intention that the cavity maintained around the implanted fixture betweeen the calot and the uncovered osseous tissue shall be filled with fresh osseous tissue, but in practice it has been found that there will not be obtained a complete filling of this cavity with osseous tissue. On the contrary there is obtained in said cavity growth of osseous tissue as well as connective tissue. DE-A1 42 23 153 discloses an implant for fastening a tooth prosthesis in the yaw. This device comprises a frame forming a latticed structure which is attached to the sur¬ face of uncovered osseous tissue by pointed pins on the frame being driven into the osseous tissue. The frame is covered by a membrane of porous polytetrafluoroethylene or another equivalent material, and this membrane engages at the outer peripheral portion thereof the surface of the uncovered osseous tissue. The frame comprises a central portion with a threaded bore therein for the attachment of a threaded elemen . The frame and the membrane located over the frame is covered by soft tissue. The purpose of this prior art device is that there shall take place inside the frame under the membrane a growth of osseous tissue for anchoring the frame in the yaw bone. O-A1-94/03121 discloses a surgical element and a method for selective tissue regeneration wherein a cavity in the osseous tissue is covered by a shape permanent element which tightly engages the surface of the osseous tissue around the cavity. The element is covered by soft tissue, and in the cavity thus separated from the soft tissue an osseous tissue growth takes place in order to fill the cavity. The tight engagement at the periphery of the element is provided in order to prevent connective tissue from growing in between the membrane and the surface of the osseous tissue, which could jeopardize the osseous tissue growth in the cavity. The purpose of the present invention is to provide method and device of the kind referred to above in order to produce osseous tissue growth on an osseous tissue surface without infiltration of soft tissue, and for this purpose method and device of the invention have obtained the characterizing features of claim 1 and claim 7, respectively. In order to explain the invention in more detail reference is made to the accompanying drawings in which FIG. 1 is a vertical cross sectional view of a domed spacer of a presently preferred embodiment, FIG. 2 is a vertical cross-sectional view of the spacer in FIG. 1 in implanted condition, and FIG. 3 is a vertical cross-sectional view of the domed spacer of another embodiment The spacer disclosed in FIG. 1 comprises a spherically curved calot 10 and a cylindrical base portion 11. A radially projecting circumferential flange 12 is provided on said base portion spaced above the base edge thereof. The spacer should be made of a tissue compatible material, and a suitable material is titanium. However, the material may also be a resorbable material such as ali¬ phatic polyester. The spacer should be shape permanent, which in the present case means that it can but must not be rigid; it can be of such nature that the shape thereof can be changed and that the spacer then maintains the shape imparted to it for the time required for the osseous tissue to grow under the spacer and to fill out the cavity defined by it. Finally, the spacer should be non-perforated in order to form an impermeable barrier but it is also pos¬ sible to have a spacer which is at least partly perforated the perforation being dimensioned to allow cells from surrounding tissue to grow through the spacer but only with some delay. It is not necessary that the spacer is symme- trical around the axis thereof; it can also have oval or elongated shape but for working the method of the invention as it now will be described by using the spacer according to Fig. 1 the spacer should be symmetrical about the axis thereof as described. When the method of the invention is applied, FIG. 2, a flap 13 is excised, comprising periosteum and connective tissue, from osseous tissue 14 so that the surface 15 thereof is uncovered. By means of a trephine cutter a circular groove 16 is made in the surface of the osseous tissue said groove being dimensioned such that the cylindrical base portion 11 can be received therein with flange 12 engaging the surface of the osseous tissue as disclosed in Fig. 2. The spacer can have tight fit in the groove to be kept in place and to sealingly engage one or the other side surface of the groove. Also, a sealing element can be provided between flange 12 and the osseous tissue surface 15. In this connection it is essential that the spacer has a completely tight fit against the osseous tissue surface 15. When the spacer is mounted in this way it is covered by flap 13 being placed over the spacer and sutured to surrounding soft tissue. Under the spacer there is now defined a cavity over the uncovered osseous tissue surface, said cavity being completely sealed towards the surroundings, and in said cavity growth of osseous tissue will take place so that the cavity under the spacer will be completely filled with osseous tissue 17. EXAMPLE On a rabbit a central incision was made down to the bone surface of the skull of the rabbit and a flap of connective tissue and periosteum was raised in order to uncover the skull bone at each side of the incision. A spacer according to FIG. 1 made of titanium and having an inner diameter of 4.5 mm and an inner height of 3.0 mm was mounted to the skull bone by forming a 0.6 mm circular groove therein by means of a trephine cutter having an inner diameter of 5.0 mm. The spacer was fitted at the base portion 11 thereof into the groove with tight fit therein due to the different inner diameters of the trephine cutter and base portion 11. Due to the tight engagement between the inside of the base portion and the inner bonding wall of the groove the spacer was reliably fixed on the skull bone and then, the flap was put back over the spacer and sutured to surrounding soft tissue. After a healing period of three months the rabbit was sacrificed and histological cross sections through the skull bone with the spacer in its place were examined. These examinations revealed that the cavity under the spacer was completely filled with osseous tissue without any signs of growth of tissue of other kinds thereinto. This proves that the use of a spacer which is completely sealed, has sufficient rigidity and stability and in a reliable way is attached to and sealed against the osseous tissue at the periphery thereof provides a predictable osseous tissue growth in spaces externally of the skeleton surface. Even if the spacer used in the experiment accounted for above was completely sealed it has been found that the osseous tissue growth can be further stimulated and thus considerably accelerated by calot 10 being perforated at least partly. However, such perforation must be dimensioned in such way that nutrition flow through the perforation is allowed, growth of cells from soft tissue at the same time being retarded. It would also be possible to stimulate the osseus tissue growth by mechanically penetrating the sur¬ face of the osseous tissue in order to facilitate migration of bone forming cells into the cavity defined by the spacer. In the embodiment of the spacer of the invention disclosed in FIG. 3 the spacer comprising a spherically curved calot 10' is provided with a gasket 18 of soft material e.g. silicon rubber, at the base edge, the edge portion being received by a groove in the gasket. A screw 19 is passed through a central opening in the spacer the head of said screw being countersunk in the spacer, and by screwing this screw into the osseous tissue the spacer can be attached to the osseous tissue with gasket 18 pressed tightly against the surface of the osseous tissue.

Claims: CLAIMS 1. Method for osseous tissue growth wherein the osseous tissue is uncovered by excising a flap of soft tissue over the site where the osseous tissue growth shall take place, a domed spacer is positioned at said site, and the flap is put back over the spacer which maintains a cavity between the flap and the osseous tissue, characterized in that the spacer retarding or preventing penetration of cells is sealingly applied to the osseous tissue at the periphery thereof. 2. Method as in claim 1, characterized in that a groove is made in the osseous tissue, corresponding to the shape of the base surface of the spacer, and that the spacer at a base edge portion thereof is countersunk into the groove. 3. Method as in claim 2, characterized in that the spacer at a radial outside flange is engaged with the surface of the osseous tissue. 4. Method as in claim 3, characterized in that the flange is sealed against the surface of osseous tissue. 5. Method as in claim 1, characterized in that the spacer at a gasket along the base edge thereof is pressed against the surface of the osseous tissue. 6. Method as in claim 5, characterized in that the pressure is provided by a screw connection between the spacer and the osseous tissue. 7. Shape permanent spacer to be placed over an uncovered portion of osseous tissue to define a cavity over the surface of the osseous tissue, characterized in that the spacer is impermeable or has restricted permeability to cells to retard cell growth into the cavity and at the base edge of the spacer can be engaged with the osseous tissue complete sealing being provided between the osseous tissue and the spacer. 8. Spacer as in claim 7, characterized in that the spacer is perforated to at least some part to allow retarded cell growth thereinto. 9. Spacer as in claim 7 or 8, characterized in that a portion of the spacer adjacent the base edge is defined by surfaces perpendicular to the base plane. 10. Spacer as in claim 9, characterized in that an outwardly projecting flange is provided above the base edge spaced therefrom. 11. Spacer as in claim 7 or 8, characterized in that a soft gasket is provided along the base edge, which can be engaged with the surface of the osseous tissue, and that means are provided for attaching the spacer to the osseous tissue the gasket being pressed against the surface of the osseous tissue. AMENDED CLAIMS [received by the International Bureau on 27 March 1996(27.03.96) original claims 1-11 replaced by amended claims 1-9 (2 pages)] 1. Method for osseous .."issue growth wherein the osseous tissue is uncovered by excising a flap of soft tissue over the site where the osseous tissue growth shall take place, a domed spacer retarding or preventing penetration of cells is positioned at said site, said spacer being engaged with the osseous tissue at the periphery thereof, and the flap is put back over the spacer which maintains a cavity between the flap and the osseous tissue, characterized in that a groove is made in the osseous tissue, corresponding to the shape of the base surface of the spacer, and that the spacer at a base edge portion thereof is countersunk into the groove. 2. Method as in claim 1, characterized in that the spacer at a radial outside flange is engaged with the surface of the osseous tissue. 3. Method as in claim 2, characterized in that the flange is sealed against the surface of osseous tissue. 4. Method as in claim 1, characterized in that the spacer at a gasket along the base edge thereof is pressed against the surface of the osseous tissue. 5. Method as in claim 4, characterized in that the pressure is provided by a screw connection between the spacer and the osseous tissue. 6. Shape permanent spacer which is impermeable or has restricted permeability to cells to retard cell growth therethrough, to be placed over an uncovered portion of osseous tissue sealingly engaging the osseous tissue at the base edge thereof, to define a cavity over the surface of the osseous tissue, characterized in that a portion of the spacer adjacent the base edge is defined by surfaces perpendicular to the base plane. 7. Spacer as in claim 6, characterized in that an outwardly projecting flange is provided above the base edge spaced therefrom. 8. Spacer as in claim 6, characterized in that the spacer is perforated to at least some part to allow retarded cell growth therethrough. 9. Spacer as in claim 1, characterized in that a soft gasket is provided along the base edge, which can be engaged with the surface of the osseous tissue, and that means are provided for attaching the spacer to the osseous tissue the gasket being pressed against the surface of the osseous tissue.

Inventors: LUNDGREN DAN, LUNDGREN, DAN
Applicants: GUIDOR AB, LUNDGREN DAN, LUNDGREN, DAN
Application year: 1995
Main classification: A61C8
IPC codes: A61B17, A61C8, A61F2