FR2738477A1 - IMPROVEMENT ON IMPLANTABLE PLATES IN MAXILLOFACIAL SURGERY - Google Patents

Abstract

Maxillofacial osteosynthesis plate, having the shape of a substantially planar strip, having, in various locations, holes or eyelets (1) arranged to receive the heads of fixing screws, two consecutive eyelets being separated by an elongated portion , called "bridge" (3, 7), and having a first face intended to be applied against the cortical bone, and a second face (5), opposite to the first and having seat means receiving the screw heads, characterized in that said two faces have different surface states, namely, for said first face, a rough surface state, and, for said second face (5), a smooth surface state.

Description

The present invention relates to a perfec-

  implantation of plates implantable in maxillary surgery

  facial. In maxillofacial surgery, osteosynthesis plates or blades are used, intended to remain

  temporarily or permanently established and present

  both generally in the form of straight or angled blades, with or without branching, and provided with holes in the form of eyelets, arranged to receive screw heads, and preferably having, for this purpose, spherical bearing surfaces. These plates have eyelets which are generally separated by elongated portions

say "bridges".

  These blades must be resistant, malleable

  they can be deformed at the convenience of the surgeon, and well supported by the patient. We realize

  therefore generally high purity titanium blades.

  As for the screws, for reasons of resistance to

  breaking, are made of titanium alloy.

  In the event of maxillary or facial fractures, the surgeon uses a suitable approach and frees up a suitable surface of the cortex

  bone, on either side of the fracture line.

  After having carried out a rigorous reduction of the fracture, he keeps the plate applied against the fracture and proceeds to drill the pilot holes using the holes in the plate as guides. he

  then proceed to tighten the titanium screws which immobilize

  definitely read the plate. The plate, remaining in place, is then, little by little, more or less integrated into

1 bone.

  The known plates however have a

  a number of drawbacks. They are quite difficult

  to immobilize them during drilling and screwing gestures. They incorporate more or less well into the bone and overlying structures and can facilitate

formation of infectious foci.

  The present invention proposes to remedy

  to these disadvantages and to provide a plate of osteosyn-

  improved thesis which is easier to set up, which adapts better to the tissues concerned and which, consequently, simplifies the operative gesture and facilitates

osteosynthesis.

  The subject of the invention is an osteo-plaque

  maxillofacial synthesis, preferably made of titanium, having the shape of a substantially flat strip, having, in various locations, holes or eyelets arranged to receive heads of fixing screws, two

  consecutive eyelets being separated by an elongated portion

  gée, called "bridge", and having a first face intended to be applied against the cortical bone, and a second face, opposite to the first and presenting seat means receiving the screw heads, characterized in that said two faces have different surface states, namely, for said first face, a rough surface state, and, for said second

face, a smooth surface finish.

  By rough surface state is meant a surface state whose roughness is sensitive to the touch, and preferably having a roughness coefficient Ra at least equal to 5 and preferably between 5 and 7,

for example of the order of 6.

  By smooth surface state is meant a surface state similar to that of existing plates, by

example a state called polish-buffer.

  Preferably, the rough surface finish was obtained by alumina corundum, that is to say by a process of spraying small alumina beads, the alumina having the advantage of being perfectly biocompatible . It is understood that one can however use other means to achieve a rough surface state, which can consist of simple roughness due to the deformation of the metal surface, or on the contrary by

  obtaining a rough coating by corundum.

  Preferably, the plates according to the invention are made of high purity titanium. The properties of the plates according to the invention can be further improved by producing them in a non-alloy grade titanium.

1 (according to ASTM F67).

  Clinical studies have shown that the plates according to the invention have advantages

important.

  During the installation, a good grip is immediately obtained on the bone surface which has been cleared by the surgeon and the risk of slipping is avoided.

  during delicate drilling operations.

  It is found that the attachment between the bone and the first rough face of the plate promotes bone regrowth and micro-vascularization, which tends to

  also reduce the risk of infection.

  On the other hand, the second face distant from the face in contact with the bone surface, delays or prevents unwanted and reduced bone integration

  therefore the risk of fibrosis in the above plans

  underlying. In the long run, it is believed that bone consolidation is also improved, because the strong adhesion between the first face and the underlying bone prevents or reduces micro-movements of the bone parts on the

and across the fracture line.

  Other advantages and characteristics of

  the invention will appear on reading the description

  following, made with the aid of nonlimiting examples, and referring to the appended drawing in which: FIG. 1 represents a top view of a plate according to a first embodiment of the invention,

  - Figure 2 shows a cross-section

  dirty of this plate at the axis of one of the holes, - Figure 3 shows a top view of a plate according to a variant of the invention, - Figure 4 shows a plate according to a

another variant of the invention.

  Referring first to Figures 1 and 2, we see a plate according to the invention made of unalloyed titanium grade 1. The dimensions of the plate,

  in millimeters, appear in the figure.

  The plate is made in the form of a rectilinear stamped strip having four holes or eyelets 1 made in circular enlargements of the plate. Two of the eyelets are arranged at the two ends of the plate and two other eyelets are in the intermediate position, being separated from each other by a bridge of great length 2. There are thus produced two groups of eyelets 1, two eyelets of a group being each time separated from a short bridge 3, the two groups being separated from each other by a long bridge 7 intended to overlap the line of bone fracture. It is preferred that the inter-axes between the two eyelets of a group of eyelets are standardized, in order to be able to cooperate with suitable tools. We see, in Figure 2, that each eyelet i has, at the level

  of a first face 4 of the plate, a cylindrical passage

  that the, while on the side of the second face 5 of the plate, the passage la continues with a flared passage in the form of a spherical bowl forming a seat intended to receive the lower part, also spherical of a titanium screw head , which, in a known manner, ensures excellent reception of the screw head while allowing an angular difference between the axis of the screw and the axis of the eyelet. The plate according to the invention also has two lateral faces 6, perpendicular to the first and

second sides 4.5.

  As can be seen, the plates according to the invention can advantageously have bridges 3, 7 of different lengths. However, for this same plate according to the invention, it is desirable that the different bridges have an identical or similar rigidity, so that the plate has a uniform rigidity. This is obtained by adapting the width of the bridges 7 of great length to those of the bridges 3 of short length. In other words, the bridges 7 of great length have a greater width than that of the bridges 3 of short length, giving the former the desired rigidity close to or identical to that of the bridges of short length. Preferably the ratio of the lengths of bridges 7 and 3 is between 1 and 2, while the ratio of the widths of these bridges is between 0.8

and 1.5.

  In the example of a plate in FIG. 1, long bridges have been made, the distance between the axes of the eyelets placed at the ends is 13 mm, while the distance between the axes of the eyelets placed at the ends of the bridges small dimension is 7 mm, the ratio between these two distances being 1.8. For such a plate, the width of long bridges and that of short bridges are

  2.5 and 2 mm respectively, the ratio being 1.25.

  In accordance with the invention, the face 4 is made rough, preferably over its entire surface, by alumina corning. In the example shown, the

  roughness coefficient Ra is 6.3.

  Preferably, without this being obligatory.

  re, the side faces 6 are made rough from the

same way.

  The free face 5 is, for its part, left

smooth and polished.

  The installation of the plate according to the invention

  is done, for example, as follows.

  In the case of a fracture of the maxilla

  superior, the surgeon uses an endo-

  buccal and incise the mucosa transversely to the fracture line. It clears the periosteum by careful roaring to free the cortical bone surface. After reduction of the fracture, he applies a plate according to the invention and deforms it thanks to its malleability, if necessary, to adapt it to the local curvature. He then applies the plate in position, transverse to the fracture line, the risks of slipping being at this time significantly reduced due to the contact of the rough face 4 with

  the cortical bone. This allows it to drill conveniently.

  the pilot holes by passing the forest through the eyelet concerned. He finally proceeds to the screwing

  screws and then to the wound facing.

Claims (9)

  1. Maxillofacial osteosynthesis plate,   having the shape of a substantially flat strip, presented   both, at various locations, holes or eyelets (1) arranged to receive heads of fixing screws, two   consecutive eyelets being separated by an elongated portion   gée, known as "bridge" (3,7), and having a first face (4) intended to be applied against the cortical bone, and a second face (5), opposite to the first and presenting seat means receiving the heads quote,   characterized in that said two faces (4,5) present   try different surface states, namely, for said first face (4), a rough surface state, and,   for said second face (5), a smooth surface state.   2. Plate according to claim 1, character-   in that said first face (4) has a roughness coefficient Ra at least equal to 5 and of preferably between 5 and 7.   3. Plate according to claim 2, character-   laughed at in that the roughness coefficient Ka is around 6.   4. Plate according to one of claims 1 &   3, characterized in that the rough surface finish has been   obtained by corundum with alumina.   5. Plate according to one of claims 1 to   3, characterized in that its lateral faces (6) are also rough.   6. Plate according to one of claims 1 to   5, characterized in that it is carried out entitane no-   ally grade 1 (according to ASTM F67).   7. Plate according to one of claims 1 &   6, characterized in that the elongated portions, or bridges, separating the eyelets between them, have different lengths and widths such that the plate has   uniform rigidity over its entire length.   8. Plate according to claim, charac-   because the relationship between the lengths of the bridges   is between 1 and 2, and in particular of the order of 1.8.   9. Plate according to claim 8, characterized in that the ratio between the widths of the bridges is between 0.8 and 1.5 and in particular of the order of 1.25.