Anti-shifting system for spinal arthrodesis bar

Details Anti-shifting system for spinal arthrodesis bar Anti-shifting system for spinal arthrodesis bar

1998-01-08

1999-11-16

Buiz, Michael

Surgery

Instruments

Orthopedic instrumentation

A61B 1756

Patent

active

059849231

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to the surgical stabilisation of the spine.
2. The Prior Art
The principle of stabilisation of algesic spine by means of vertebral arthrodesis has been known to orthopaedic-surgeons for many years. Arthrodesis is achieved after perfect immobilisation of the vertebrae by means of a rigid frame which acts as a support to the pathological spine. This frame is constituted of plates, or non distorsion bars, placed in situ, firmly fixed to the spine using screws or hooks.
If a bar is used, these screws include a threaded rod which is intended to be set into a vertebra, and an extra-osseous head tulip-shaped and slotted to the diameter of the said bar. The bar is bolted to the screw by means of a point screw or a vice. However, no matter how tight the point screw or the vice, the permanent stress which the spine undergoes finally causes the bar to shift in its support.
To limit this drawback, special surface structures of the bar have been suggested (serrated surface structure, cross-hatched surface structure EP 0348 272), or the use of special locking rings has been advocated (FR 83 07450/2545350). Nonetheless, about 7% of failures occur, due to the shifting of the bars in their fixing members.


SUMMARY OF THE INVENTION

It is an object of the invention to provide an anti-shifting device in which the above-mentioned drawbacks, i.e. the shifting of the linking bars on the means of fixation to the vertebrae, are avoided.
The concept of the present invention consists in increasing the diameter of the bar at defined intervals with bosses, like double-convex lenses (1') or washers (1) to be fitted inside the tulip-shaped head of the means of fixation, preventing any shifting.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a spinal stabilizing frame according to the invention;
FIG. 1' shows a spinal stabilizing frame with linking bars;
FIG. 2 shows a spinal stabilizing frame with an anti-shifting boss;
FIG. 3 shows a means of fixation;
FIG. 3' shows another means of fixation;
FIG. 4 shows a further means of fixation;
FIG. 5 shows a spinal stabilizing frame with spherical anti-shifting bosses;
FIG. 6 shows another embodiment with spherical anti-shifting bosses;
FIG. 7 shows another embodiment with spherical anti-shifting bosses;
FIG. 8 shows two spinal stabilizers joined together;
FIG. 9 shows a spinal stabilizer frame having a threaded bar at one end;
FIG. 10 shows a spinal stabilizer frame having a threaded bar at two ends;
FIG. 11 shows a linking bar having a cylindrical part with cross tapping in its center;
FIG. 12 shows another linking bar having a cylindrical part with cross tapping in its center;
FIG. 13 shows another embodiment of a linking bar with a threaded attachment;
FIG. 14 shows a linking bar with a threaded end and an attachable arm;
FIG. 15 shows two anti-shifting bosses in the form of a double-convex lens;
FIG. 15' shows the two bosses of FIG. 15 fitted into a single cavity;
FIG. 16 shows two bosses in the form of a concave sphere into which a double-convex lens is fitted;
FIG. 17 shows two linking bars with two double-convex lenses on both sides of a fixation means;
FIG. 18 shows a top view of a linking bar coupled to a fixation means;
FIG. 19 shows a front view of a linking bar coupled to a fixation means; and
FIG. 20 shows a side view of a linking bar coupled to a fixation means.


DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

According to a preferred embodiment, these bosses having the form of spheres (2) are integral with the linking bar and perfectly congruent with the cavity of the means of fixation (3) [profile view] and (3') [top view], these being closed by the plug (4). Thus, in its simplest form, the linking bar has the form of a small dumb-bell (5), the predefined length of which is adapted to the morphology of the spine. Different sizes are required, with spaces between the spheres ranging from 15 to 35 mm, in steps of 1 to 5 mm. A slight extension (6) of the linking bar after the sphere improves resistanc

REFERENCES:
patent: 5176680 (1993-01-01), Vignaud et al.
patent: 5437669 (1995-08-01), Yuan et al.
patent: 5536268 (1996-07-01), Griss
patent: 5540688 (1996-07-01), Navas

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