NL1002343C1 - Re-sorbable inter-vertebral implant - Google Patents

Abstract

The implant or cage is used in posterior and/or anterior fusion of vertebrae in the human spinal column, so as to adjust the height between vertebrae. It can be so prepared that the natural carbonaceous apathy is replaced by artificial apathy, or the natural collagen by polyglyconate.

Description

A resorbable intervertebral implant.

The invention relates to an object called "cage" or "intervertebral implant" whose shape, dimensions and choice of material are such that it replaces the intervertebral disc in the back for a number of months, such that it initially completely at the restored original height absorbs forces between the two vertebrae, after which the implant is gradually resorbed and remodeled by the body: replaced by newly formed bodily bone tissue.

Current operative technique.

Back pain arises, among other things, because an intervertebral disc loses its properties such that the spine becomes unbalanced and nerves are pinched, causing the pain. This pain can be removed by rebalancing the spine.

A This is done as follows in the posterior (back) vertebral body fusion.

A.1. In the following, a segment of the back is considered consisting of the defective intervertebral disc with the vertebrae on either side. This segment is called a spine unit {wku).

A. 2. Operatively, holes are drilled in the wku into which screws are inserted.

A. 3. The wku is put back in the correct position.

A. 4. The defective intervertebral disc of the wku is removed and a non-absorbable spacer, here called cage, is placed in the space.

A. 5. Finally, autologous trabecular bone, usually from the iliac crest in shredded form, is placed on either side of the cage and / or posteriorly at the end of surgery.

A. 6. A fixation implant plate is connected with the screws to keep the wku in the correct position.

A. 7. The wound is closed.

A. 8. Insertion of the non-absorbable cage can also be done from the ventral side without the insertion of screws and fixation implant (anterior vertebral body fusion).

30 B. The essential points on which the now used "cage" has been designed are: B. 1. In a posterior vertebral body fusion, the forces between the vertebrae of the wku are absorbed in front by the cage and only 20% by the dorsal fixation material.

B. 2. The shape and dimensions of the “cage” are determined by the geometry of the vertebrae, the soft tissues on the spot, the surgical techniques for introducing the cage 1 0 02 3 4 3 2 and the forces applied there. on working.

B3. The current material of the “cage” has been chosen in such a way that it is biologically inert, biomechanically stable, creates a fusion of the wku and restores the original height of the intervertebral disc of the wku.

5 C. Disadvantages of the current cage.

C. 1. In principle, it is permanently present because it cannot be broken down by the surrounding tissues.

C. 2. Unexpected implant removal may be associated with high morbidity, especially after complete fusion.

10 C. 3. There is a risk of infection when the foreign material remains.

C. 4. It is not biomechanically adaptive while the local biomechanical ratios of wku to wku are different.

D. The surgical technique does not change.

E. The essential points on which the new cage is designed.

E. 1. The material is of such a composition that it is broken down and absorbed by the body through osteoclastic absorption and at the same time is replaced by newly formed body bone tissue (remodeling).

E. 2. The material does not need to be removed as it is completely absorbed and remodeled.

20 E. 3. There is no risk of infection after absorption and remodeling.

E. 4. Remodeling and resorption lead to a fusion with local adaptation of the biomechanical properties.

E. 5. The other advantages of the non-absorbable cage are retained, namely: E. 5.1. Keeping the wku at bay until bony fusion of the subsequent 25 vertebrae has occurred.

E. 5.2. Restoration of the local anatomical proportions of the wku.

E. 5.3. The possibility to insert the cage posterior as well as anterior.

F. The biomechanical characteristics.

F. 1. The choice of materials and dimensions of the cage are such that the initial biomechanical stability during resorption and remodeling is maintained until the fusion of the subsequent vertebrae is fully completed.

F. 2. The material has a modulus of elasticity initially of the same magnitude as that of the human bone, generally ranging from 5-30 Gpa. 35 It is by the above processes, mentioned in point E1, according to the law of 1002343 3

Wolff remodeled into bone with the local elastic modulus of the wku.

F. 3. Due to the tensile strength of 50 - 300 MPa, the walls of the cage can be made so thin that the resorption and remodeling is realized within the desired time.

5 F. 4. By dimensioning the tensile-strain curve between 2- 20 MJm-3, the desired biomechanical stability during resorption and remodeling can be obtained.

G. The material.

G. 1. The material consists of natural collagen and natural carbonate-like apatite, 10 which can be made usable as such, but also either removing the natural apatite and replacing it with artificially manufactured carbonate-like apatite or removing the natural collagen and replacing it with the plastic polyglyconate.

G. 2. The natural collagen and natural carbonate-like apaptite is extracted from natural bone, this bone having the biomechanical properties mentioned in part F.

G. 3. By removal of cellular components, the material is immunologically inert and has biomechanical properties at the values specified in Part F.

G.4. Less high value biomechanical properties can be obtained by removing the natural carbonate-like apatite and replacing it with the artificially manufactured carbonate-like apatite.

G. 5. Biomechanical properties with even lower values can be obtained by removing the natural collagen and replacing it with the plastic polyglyconate.

25 H. The dimensions.

H. 1. The dimensions are roughly a box shape with a length, width and thickness of 25 millimeters, 10 millimeters and 10 millimeters successively and depend in detail on the required distance between the spinal vertebrae of the wku.

H. 2. Recesses have been made in the vertical side surfaces and in the horizontal top and bottom surfaces allowing newly generated tissue to effect the fusion in the wku in the required time.

H. 3. The shape of the recesses and the dimensions depend in detail on the biomechanical requirements on site in the wku.

H. 4. The inclination between the horizontal top and bottom surfaces and their roughness 35 depend on the forces acting locally on the wku, the requirement being that the forces do not force the 1002343 4 cage between the vertebrae. .

The taper is determined by the height of the front and back side faces which have the following dimensions in millimeters in pairs: - lumbar 7 and 9, 9 and 11.11 and 13.13 and 15.5 - cervical 3 and 5, 5 and 7, - special 10 and 15.

H. 5. The shape of the vertical side surfaces is determined by the instrument with which the cage is introduced into the wku.

1002343

Claims (1)

CONCLUSION. A "cage" or "intervertebral implant" used in the posterior and / or anterior vertebral body fusion in the spinal unit of the human body to restore the height between the dorsal vertebrae characterized by being made of 5 natural bone with a high tensile strength and very high work under the tensile-elongation curve, optionally applied after preparation as such or in a state where either the natural carbonate-like apatite can be replaced by artificial carbonate-like apatite or the natural collagen by the plastic poly-glyconate, combines high strength and biomechanical stability with resorption-10 and remodeling characteristics for the human body, eliminating the drawbacks of a cage made from biomechanically inert materials while preserving the benefits 15 ......... .................. 1002343