External fixing device for bone surgery

An external fixing device for bone surgery, particularly dento-maxillo-facial surgery, includes at least a rigid rod having a portion of constant cross-section and rectilinear axis. A spacer element, such as a lip spacer, is fixed to a rod at a distance from the extremities of the portion substantially perpendicularly to the axis of the rod portion. At least one moving element is associated to the portion to freely slide along the latter. There is provided in the moving element and opening of which the axis is substantially parallel to the axis of the rod portion, which opening provides a passage for a bone trepanation tool. An immobilizer is provided on the element to immobilize it with respect to the rod portion.

BACKGROUND OF THE INVENTION 
The present invention relates to an external fixing device for bone 
surgery, particularly dento-maxillo-facial surgery, and especially to a 
device for carrying out trepanation, allowing implants to be positioned. 
The invention aims to provide an external fixing device of the 
above-mentioned kind, which can be equipped with various fittings allowing 
one to carry out with a very high precision all the necessary trepanations 
for positioning implants whatever the kind of the latter may be. 
SUMMARY OF THE INVENTION 
To this end, according to the invention, this external fixing device 
comprises one or more undeformable rods serving, in particular, as a 
handle of the fixing device and presenting a portion of constant 
cross-section and of rectilinear axis. The device further includes a 
spacer element, such as a lip retractor, intended to bear on a first face 
of the bone to be trepaned and which is fixed to the rod at a distance 
from the extremities of said portion of the rod and substantially 
perpendicularly to the axis of said rod portion, one or more moving 
elements associated with the above-mentioned rod portion in order to be 
able to freely slide along this portion so as to rest either on the mucosa 
covering a second face of the bone, opposite to the first face with which 
the spacer element cooperates, or on a protection plate for this mucosa, 
or with this second face of the bone in which an opening is provided, this 
opening having an axis substantially parallel to the axis of the rod 
portion, this opening being intended to allow the passage of a tool for 
trepaning the bone, such as a bur. And the device further includes means 
provided on said element in order to immobilize it in a selected position 
with respect to said rod portion. 
According to an embodiment of the invention, the fixing device comprises a 
moving support for a trepanation tool such as a bur-holder angle-shaped 
piece arranged to freely slide along said rod portion opposite to the 
spacer element with respect to the moving element, means arranged to 
immobilize the moving support with respect to the rod in a selected 
position, means for containing the bur-holder angle-shaped piece, and 
means for immobilizing it with respect to the moving support in order that 
the bur and the opening provided in the moving element are coaxial. 
According to an advantageous embodiment of the invention, the external 
fixing device comprises a moving member provided for supporting a guide 
for the trepanation tool in order that this guide and the opening of the 
spacer element are coaxial, this member freely sliding onto the rod 
portion opposite to the moving element with respect to the spacer element 
and presenting means arranged to immobilize it on the rod portion in a 
selected position. 
According to a particularly advantageous embodiment of the invention, the 
fixing device comprises, on the one hand, a moving support for a 
trepanation tool, such as a manual bur-holder piece, this support being 
arranged to freely slide along the rod portion, opposite to the spacer 
element with respect to the moving member, means arranged to immobilize 
this support in a selected position with respect to the rod portion, and 
means arranged to immobilize the trepanation tool in order that its axis 
coincides with the axis of the opening of the spacer element. The fixing 
device of this embodiment further includes a moving support for one or 
more trepanation tools, such as a bur, this support being arranged to 
freely slide along the rod portion in the portion of the latter, which is 
comprised between the spacer element and the moving element, means 
arranged to immobilize the support in a selected position with respect to 
the rod portion and means for immobilizing the trepanation tool in the 
support in order that its axis is transverse to the axis of the opening 
existing in the spacer element.

DETAILED DESCRIPTION 
The external fixing device 1 according to the invention and such as shown 
in the drawings is more particularly intended to allow trepanations to be 
made easily and in an extremely precise manner in dento-maxillo-facial 
surgery in order to position implants. 
In its most simplified embodiment, such as is shown in FIGS. 1 and 2, the 
external fixing device 1 comprises, for example, for positioning single 
implants of the rod type, either one undeformable rod 2 (FIG. 1) or two 
parallel undeformable rods 2 and 2' (FIG. 2), the end 3 of which can, in 
particular serve as a handle of the fixing device and which each present a 
portion 4 of constant and rectilinear cross-section. On this portion 4 of 
the rod 2 or of the rods 2 and 2', a spacer element such as a lip spacer 5 
is fixed at a distance from the extremities of said portion 4, which 
spacer element is intended to bear on a first face 6 of the bone to be 
trepaned 7, the latter being schematically shown in dot-and-dash line on 
FIG. 1, the spacer element extending substantially perpendicularly to the 
axis 8 of the rod portion 4. This rod also bears a moving element 9 which 
freely slides along the axis 8 to rest either on the mucosa covering the 
face 11 of the bone opposite to the face 6 or on a protection plate 12 for 
the mucosa, such as shown in dot-and-dash line in FIG. 1, or on the face 
11 of the bone. This element 9 is provided with an opening 13 of which the 
axis is parallel to the axis 8 and which allows the passage of a 
trepanation tool 14 (FIG. 3), such as a bur, and with one or more set 
screws 15' provided to immobilize this element 9 in a selected position 
with respect to the portion 4 of the rod 2 or of parallel rods 2 and 2'. 
In the external fixing device shown in FIG. 1, the portion 4 of the rod 2 
and the opening 13 provided in the moving element 9 have such a 
cross-section that the element 9 is motionless in rotation around the axis 
8 of the portion 4 of the rod 2. This element 9 is advantageously arranged 
on the portion 4 of the rod 2 in a removable manner in order that the 
element can be replaced by another element 9 which is more appropriate to 
the trepanation to be made. 
In the embodiment of the external fixing device 1 shown in FIG. 2, the 
moving element 9 presents on its face 15 turned to the spacer element 5, 
some studs 16 the points of which are intended to penetrate either into 
the bone 5 (FIG. 1), or into the plate 12 protecting the mucosa 10 (FIG. 
1) in order to substantially immobilize the element 9 and accordingly the 
external fixing device 1 with respect to said bone 7 or to the protection 
plate 12. 
As shown in FIG. 3, the spacer element 5 advantageously comprises on its 
face 17 turned to the moving element 9 and still to reinforce the 
immobilization of the fixing device 1 with respect to the bone 7, two 
fixed plates 18 fitting together with the spacer element 5 along two lines 
19 which are substantially parallel to the plane passing through the axis 
of the rods 2 and 2' and regularly diverging from one another with respect 
to a tracing plane 20 which is parallel to the plane passing through the 
axes of said rods, these plates 18 resting on the bone 7 on both sides of 
the face 6 of the latter, with which the spacer element 5 cooperates. 
Also as shown as well by FIG. 3 as by FIGS. 2, 4 and 5, in order to allow 
the precise positioning of implants, necessitating trepanation of the bone 
7 from faces 6 and 11 of the latter, the spacer element 5 has an opening 
21 which is coaxial with the opening 13 of the moving element 9, this 
opening 21 allowing the passage of a trepanation tool such as the bur 22 
(see FIG. 4). 
In order to ensure a perfect guiding of the bur or trepan 22 when the 
latter is driven manually, the spacer element 5 comprises, from its face 
23 (FIG. 4), a cavity 24 which is coaxial to its opening and arranged in 
order to receive, so as to immobilize it, the extremity 25 of a guide 26 
coaxial to same opening 21 and through which the bur 22 passes. This guide 
26 is advantageously supported, as shown in FIGS. 4 and 5, by means of a 
moving member 27 which freely slides onto the portion 4 of the rods 2 and 
2', opposite to the moving element 9 with respect to the spacer element 5, 
set screws 28 being provided to immobilize this member 27 with respect to 
the rods 2 and 2' when the extremity 25 of the guide 26 is located in the 
cavity 23 provided in the spacer element 5. This guide 26 is arranged on 
the moving member 27 so that its position is controllable along a 
direction parallel to the axis of the portion 4 of the rods 2 and 2' and 
is advantageously comprised of a tube into which the bur or trepan 22 is 
inserted so that its axis coincides with the axis of the tube, the latter 
being threaded externally and cooperating with a threaded hole 29 which is 
provided in the member 27 and is coaxial to the openings 13 and 21, the 
precise control of the guide 26 with respect to the member 27 being made 
by rotating the threaded tube forming this guide around its axis, the 
threads of the tube and of the threaded hole being such that the tube 
remains motionless in rotation around its axis as long as it is not 
positively controlled in rotation. 
In order that the bur or trepan 14 is perfectly guided through the opening 
13 of the moving element 9, the external fixing device 1 comprises, as 
shown by FIGS. 3 to 5, a moving support 30 for the tool 14 which is borne 
by a bur-holder angle-shaped piece 31 which is arranged to freely slide 
along portions 4 of rods 2 and 2', opposite to the spacer element 5 with 
respect to the moving element 9. Set screws 32 and 33 are provided, on the 
one hand, for immobilizing the bur-holder angle-shaped piece 31 in the 
cavity 34 of the support 30 so that the bur or trepan 14 and the opening 
13 of the moving element 9 are coaxial and, on the other hand, for 
immobilizing, when desired, the support 30 in a selected position with 
respect to the rods 2. 
When it is desired to mechanically guide the bur or trepan 22, one can 
provide on the fixing device 1, as shown in FIGS. 4 and 5, a moving 
support 35 for a manual bur-holder piece 36 which is arranged to freely 
slide along the rods 2 and 2', opposite to the spacer element 5 with 
respect to the moving member 27. Set screws 37 and 38 are provided in 
order to immobilize, when desired and in a selected position, the moving 
support 35 with respect to the rods 2 and 2' and to immobilize the manual 
piece 36 so that the bur or trepan 22 has its axis coinciding with the 
axis of the opening 21 provided in the spacer element 5 and with the axis 
of the guide 26. 
In order to allow a precise positioning of implants with cross-locking or 
of transverse fixing screws of the external fixing device cooperating with 
the bone, the external fixing device 1 advantageously comprises, as shown 
in FIG. 5, a moving support 39 having openings 40 for burs or trepans (not 
shown), the axes of which are parallel and located in a plane which is 
perpendicular to the axes of the rods 2 and 2'. The trepans guided in the 
openings 40 allow to carry out some trepanations which, when the openings 
are joined together, allow to position bladed elements which immobilize 
the implants. The support 39 which is arranged between the elements 5 and 
9, bears set screws 41 and 42 allowing one on the one hand, to immobilize 
the support in a selected position with respect to the rods 2 and 2' and, 
on the other hand, to immobilize, when desired, the trepans in the 
openings 40. 
Except for the spacer element 5, which is fixed to the rods 2 and 2', all 
the other elements 9, 27, 30, 35 and 39 are advantageously removably 
assembled to rods 2 and 2', so that they can be used together or 
separately according to the trepanations to be carried out. 
The external fixing device according to the invention and shown in FIGS. 6 
and 7 is more particularly a variant of the fixing device of FIG. 5, but 
from which the moving member 27 has been omitted. In some cases, this 
member can constitute a constraint for the lips retraction, and wherein 
the moving support 39 has been replaced by a moving support 55 intended to 
receive the support 35 of the trepan or of the bur 22, in order to carry 
out trepanations along a direction perpendicular or transverse to the 
plane passing by the axes of the rods 2 and 2'. 
In this latter embodiment, the spacer element 5, in order to improve its 
insertion with respect to the bone 7, is bent and made of two parts 46, 
47, which are substantially planar and substantially perpendicular to the 
axes 8 of the rods 2 and 2', these parts being united by a slanting 
section 48, the part 47 which is the most remote from the axes 8 and is 
intended to be located in front of the bone, being located at a lower 
level than the part 46. This part 47 is arranged to support a moulding 44 
of the bone portion on which the spacer element must bear, such as the 
moulding made from information obtained by means of a scanner. Fixing 
means 45 for this moulding, which is removable and different for each case 
of trepanation, are arranged so that this moulding can follow the bone 
portion it reproduces so as to totally immobilize the external fixing 
device with respect to the bone when the latter is pinched between the 
moulding fixed to the spacer element 5 and the above-mentioned moving 
element 9. In such a case, any risk of inopportune movement of the fixing 
device during a trepanation is prevented. 
So as to precisely guide the trepanation tool, the guide 26 which was fixed 
to this member 27 in the embodiment of FIG. 5, is threaded and directly 
fixed on the spacer element 5 in the opening 21 which is internally 
threaded. 
In order to precisely guide a tool, analogous to the above-mentioned tool 
31, the opening 13 of the moving element 9 is also advantageously provided 
with a tubular guide 49 which is coaxial to said opening 13, the threaded 
end of which is screwed into said opening 13 which is internally threaded. 
So as to allow the external fixing device to be completely immobilized with 
respect to the bone, this device comprises a binding piece 50 arranged 
between the spacer element 5 and the moving element 9. This piece is 
parallel to the axis 8 of rods 2 and 2' and is arranged so as to allow, on 
the one hand, the control of the spacing between the spacer element 5 and 
the moving element 9 and, on the other hand, the total immobilization of 
both of these elements on the bone. 
The binding piece 50 comprises an elongated hole 51 which is parallel to 
the above-mentioned axes 8 and which is intended to form a passage, for 
example, for the trepanation tool 22, as hereinafter explained. 
The moving support 35 of this external fixing device bearing the 
trepanation tool 22 comprises a sleeve 52 arranged to receive and 
immobilize the tool 22, this sleeve freely sliding into the moving 
support, means 38 being provided on the latter and arranged to allow this 
immobilization of the sleeve 52 with respect to the moving support 35 when 
the fixing device is handled and transported. 
The moving support 35 and the sleeve 52 each advantageously present a 
fixing lug 53 for one end of an interchangeable spring 54 the axis of 
which is substantially parallel to the axis of the sleeve, this spring 
which is selected according to the characteristics of the bone, allowing 
the sleeve to automatically progress into the support 35 for the 
trepanation. 
This external fixing device also comprises a moving support 55 arranged to 
freely slide along the rods 2 and 2' near the spacer element 5 opposite to 
the moving element 9. Means 56 are arranged to immobilize the support 55 
on the rods 2 and 2' in a selected position. Two bars 57 and 57', 
analogous to rods 2 and 2', are fixed to the support 55 perpendicularly to 
the latter. On these bars 57 and 57', the moving support 35 for a 
trepanation tool can be slid and be immobilized, as shown by FIG. 7, when 
the tool is used for a trepanation through the above-mentioned elongated 
hole. 
It is to be understood that the invention is in no way limited to the 
described embodiments and that many changes can be made thereto without 
departing from the scope of the present patent.