Transverse Fixation Device for Ensuring a Rigid Transverse Connection Between Two Rods of a Spinal Osteosynthesis System

The present invention relates to a fixation element for a transverse fixation device designed to ensure a rigid connection between two rods of a spinal osteosynthesis system, and to the transverse fixation device equipped with these elements.

It is known that in spinal osteosynthesis using the COTREL-DUBOUSSET technique, use is made of a transverse connection device (known by the abbreviation DTT) consisting of a fixed hook provided with a threaded rod, and of three free hooks which make it possible to bring together or space apart two knurled rods, by means of nuts and screws.

This system, necessary in order to guarantee the stability of the osteosynthesis equipment in the form of a frame, has the following disadvantages:

the time needed for its positioning is relatively long,

its positioning is quite difficult,

its torsional and flexural strength is relatively low.

The aim of the invention is therefore to overcome these disadvantages.

According to the invention, the fixation element consists of a hook designed so as to be able to cover, in a sliding manner, a rigid transverse bar and equipped with means for locking on said bar. This hook is made up of a body and two blades which are spaced apart by a distance of a width corresponding to that of the bar. A span for the hook to bear on the bar is made on the body between the blades, which blades extend on each side of the bar when the hook straddles the latter.

According to one feature of the invention, the two blades are curved in a radius of curvature corresponding to that of the rods, and thus designed so as to enclose the latter.

According to another characteristic, the span is planar in order to be able to bear on a planar surface of a bar of rectangular cross-section, the two blades extending parallel to one another on both sides of the said span.

The transverse fixation device, to which the invention also relates, comprises in combination a rigid bar of suitable length, and a pair of elements for fixation of the bar on the rods, such as mentioned hereinabove, being capable of being fixed in an adjustable manner at a chosen position on the bar.

This equipment is simplified compared to the equipment previously used and can therefore be positioned by the surgeon more quickly and more simply. In addition, it has a much greater torsional and flexural strength on account of the bar whose cross-section is considerable and constant over its entire length.

The invention will now be described with reference to the attached drawings which illustrate an embodiment thereof by way of a non-limiting example.

FIG. 1 is an exploded perspective view of an embodiment of the transverse fixation device according to the invention.

FIG. 2 is a perspective view, on an enlarged scale compared to FIG. 1, of one of the fixation elements of the device.

FIG. 3 is an exploded perspective view, at a different angle from FIGS. 1 and 2, of one of the hooks of the device, and of its plug for locking on the rod enclosed by this hook.

FIG. 4 is a perspective view of the device in FIGS. 1 to 3 when assembled, viewed from under the hooks, from the direction of the rods of the device.

FIG. 5 is a partial elevation view of the bar of the device in FIGS. 1 to 4 straddled by a hook.

FIG. 6 is a perspective view of the transverse connection device according to FIGS. 1 to 5, positioned on a spinal segment.

The drawings show a transverse fixation device designed to ensure a rigid transverse connection between two rods 1 and 2 of a spinal osteosynthesis system which is to be positioned on a spinal segment S, which is shown partially in FIG. 6.

This device comprises, on the one hand, a rigid bar 3, cut to a suitable length, slightly greater than the space between the two rods 1 and 2, and a pair of fixation elements 4 which can be fixed in an adjustable manner at a chosen position on the bar 3. The latter has a suitable cross-section, for example rectangular.

Each element 4 consists of a hook designed so as to be able to cover the bar 3 in a sliding manner. To this end, each hook 4 comprises a body 5 and two blades 6 extending parallel to one another and separated by a distance d (FIG. 3) whose width corresponds to that of one of the surfaces 3a of the bar 3 of rectangular cross-section, in order to be able to straddle the bar by extending on both sides of the latter. The two blades 6 are curved in a radius of curvature corresponding to that of the knurled rods 1 and 2, in order to be able to enclose the latter in their bearing surfaces 6a, for example over slightly more than a half circumference.

Formed between the base of the two blades 6 and on the body 5 is a span 7 for the bearing of a surface 3a of the bar 3, this span 7 constituting the base of the seat of the bar in the hook 4. The span 7 extends from one end of the body 5 to the other, and in its central zone it is interrupted by a tapped hole 8 (FIGS. 1 and 3) formed in the body 5. A threaded plug 9 is designed to be able to be screwed into the corresponding tapped hole 8, in such a way that, at the end of screwing, it comes to bear on the surface 3a of the bar 3 placed in abutment on the span 7 and to lock the bar 3 by means of clamping between the plug 9 and the rod 1 (or 2). The surface for the bearing of the plug 9 on the bar 3 is planar or may optionally be provided with catching means, such as a point. In each plug 9, a profiled orifice 11 is made, for example a hexagonal socket, designed to receive a tool (not shown) for screwing of the plug 9.

In order to position the device which has just been described, the surgeon places the bar 3 on the rods 1, 2 and then fits the two hooks 4 by making them straddle the bar 3 in order to enclose the rods 1, 2. Depending on the assembly chosen, the hooks 4 are placed either for spacing the rods 1 and 2 (FIG. 6), or for bringing together these rods. In the spacing position, the blades 6 are oriented in opposite directions to one another, their base being situated between the rods 1 and 2. In contrast, in the position of bringing together, the hooks 4 are placed in such a way that their blades 6 are oriented towards one another, their base being situated to the outside of the rods 1 and 2.

The fixation of the bar 3 on the rods 1 and 2 is therefore carried out after the surgeon has spaced apart or brought together the two hooks 4, the center distance being maintained by tightening the screws or plugs 9 for locking the hooks 4 in their chosen position on the bar 3. The latter is then fixed relative to the two rods 1 and 2 and ensures the cohesion or stability of the osteosynthesis system, with great torsional and flexural strength.

The invention is not limited to the embodiment described and can comprise alternative embodiments. Thus, if desired, the cross-section of the bar 3 could be other than rectangular, and the plugs or screws 9 for locking of the hooks 4 can be replaced by any equivalent means.