Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to a fixation device
permitting the orientation of the part held, ~hich device is more
specifically used in the field of external bone fixation
appliances.
For the reduction of bone fractures, for example, a
technique of fixlng pins in the bone was in fact developed long
ago, which pins are either extended in the neighboring bone or are
secured in an external fixation device including a ~rame in order
to hold the fractured segments in place.
Frame appliances comprising arcuate cradle elements are
known, such as the ones described in Switzerland Patent 630,798.
The sectional shape of such an arcuate element has also
been analyzed, and preEerence given to a form which permits the
realization of numerous and extensive possibilities for mounting
pins as well as frame rods or other connecting parts or members.
The elements of which such external fixation means are
composed must be designed with two aims. ~Firstly, they must be as
simple as possible to facilitate the surgeon's work during the
operation while permitting a wlde r~ange of posslble pasltionings.
Secondly, they must afford a thoroughly rigid and secure fixation,
so that the reduction of the fracture will not be compromised
during convalescence.
There are known positioning and securing devices
comprising jaws clamping a part, the contacting surfaces of the
jaws and of the part to be clamped therewith being realized so as
to be somewhat roughened, for example as obtained by sandblasting.
These devices are generally satisfactory, but with time the rough
surfaces wear smooth and the roughness is lost. As the surfaces
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in contact become smoother, the clamping becomes le5s and less
effective.
Securing devices have al.so been proposed that comprise
planar surfaces with grooves. Such planar surfaces commonly clamp
a cylinder or a sphere of plastic material. Alternatively,
grooves may likewise be provided on the part having a rounded
portion to be clamped. Such a device is described, for example,
in PCT World Patent Application No. 83/02554. This device gives
good results, but the plastic part deteriorates quickly so that
its service life lS relatively short.
The present invention provides a system comprising a
part to be positioned and secured~and a device for positioning and
securing said part, said device comprising two jaws arranged to be
pressed against each other to clamp said part, wherein at least
one element selected from the g~roup consisting of said part and
said jaws comprises at least one region, the cross section of
which is circularj wherein said at least one region has a
succession of facets with polygonally-shaped boundaries regularly
arrayed over at least a portion of~said at~least one reglon,
wherein adjacent facets meet at obtuse angles and wherein the
boundaries between adjacent facets are sharp edges and sharp
points.
The invention also provides a device for positioning and
; securing at least one part having a rounded portion, said device
comprising two members which are adapted to be disposed facing one
another and which firmly clamp said part between said members
wherein said members are capable of being pressed together by at
least two screws whose centerline are not strictly parallel, so
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that upon tightening oE said screws at least one of said members
flexes so as to more firmly secure the rounded portion of said
part.
The part preferably also includes a central bore
intended to receive a rod or pin. It may be divided into two
portions along the axis oE the central borej or it may be an
integral part with a tube extending from the sphere, either on
only one side or on both sides thereof.
Moreover, the part to be clamped may take the form of a
cylinder or a truncated cone having at least one segment or region
provided with facets. The cylinder to be clamped may also include
a central bore perpendicular to its axis intended to receive a pin
or rod and to be divided into two parts along the axis of the
central bore.
The succession of facets is provided on a harder
material than the material of the jaws clamping the faceted areas.
These materials may be, respectively, tempered steel and
untempered steel, or steel and a light metal, or light metal ~ ;
alloys of different hardnesses, or aIloys and plastic materials.
~0 The accompanying drawings, by way of example,~show
several embodiments and modifications of a device for positioning
and securing a part according to the invention.
In the drawings:
Figure 1 is a perspeative view of a positioning and
securing device intended to be placed on a circular arcuate cradle
element (shown in dotted lines) and holding a guide sleeve
(likewise shown in dotted lines) including a tubular portion
ssuing from a central sphere;
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Figure 2 is an exploded perspective view o the elements
shown in Figure l;
Figure 3 is a side elevation view of the device .
previously shown, except that in this case a sleeve having a
tubular portion extending to either side of the central sphere is
shown;
Figure 4 is a sectional view taken along line IV-IV in
Figure 3;
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FIG. 5 is a side elevation view of a spherical
sleeve;
FIGS. 6A and 6s are sectional views of the sleeve
of FIG. 5, in different embodiments;
FIG. 7 is a side view of a modification of the
sleeve;
FIG. 8 is an enlarged view of the central portion
of the sleeve of FIG. 3, showing facets regularly
arrayed over ~he surface of the spherical portion;
FIG. 9 is a further enlarged view of a small
portion o the surface of the sleeve represented in ;
FIG, 8, showing the facets in detail, in a first :
embodiment having planar facets;
FIG. 10 is a sectional view taken along line X-X
in FIG. 9, showing also a portion of the;jaw;
FIG. 11 is a sectional view taken along line XI-XI
in FIG. 9, likewise including a portion of the jaw;
FIG. 12 is similar to FIG.~;10, but in a second:
embodiment having concave :facets;
FIG. 13 is a perspective view of a positioning and
securing device intended to receive transfixing pins;
FIG. 14 is a side view of the device of FIG. 1~3 :
intended to position and:secure a connecting bar,~with :
the upper portion of the jaws shown partially in ~ .
section; and : ~-
FIG. 15 is a side view of a modification of the
part shown in FIG. 14.
The positioning and securing device shown in FIGS.
1 to 4 comprises principally two fixation screws 10 and
20 intended to pass through an upper member 30 and a
lower member 40 and then cooperate with a shackle 50,
all serving to permit the positioning and the fixation
of a sleeve 60 as well as the clamping of the assembly
to an arcua~e element 70.
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It should irst be noted that the centerlines 11
and 21 of the fixation screws 10 and 20 are not
parallel, but form an angle of about 10 for a reason to
be e~plalned below.~
The screws lO and 20 have large heads 12 and 22 to
facilitate their placement and manual tightening before
they are firmly tightened with a suitable tool when the
system is in place. The depicted screws have square
heads 12 and 22, but obviously any other head shape may
be adopted without departing from the scope of the
present invention.
Moreover, the screws~10 and 20 include was~hers 13
and 23 each presenting a plane face 14`,~24 intended to
bear against t~he corresponding~screw head 12~,~22;, as
well as a spheri~cal portion 15~, 25 on the opposed ace,~
the function~of~which will be stated~below. It is to
be noted that the washers~13~ and 2~3~are~engaged~with~
the screws 10~ ~and 2 0 once and~for all, and~then turned
in at their~base into~recesses 16 and 26 ~in the sc~rews
lO and 20. Thus the washers~ 13~and~23;remain~integral
with the screws 10 and~;20 during operations~such~as
assemblin~ or ster~ilisation. ~In FIG. 2, washer~13~ is~
shown against the screw~head~12 to reveal the recess
16, whereas washer 23 is substantially within~the~lower~
portion of th~ recess 26.
The screws lO and~ 20 further comprise a threade~d
length 17 and 27, respectively, intended to fit into a
corresponding tapped hole, as will be seen~below.
The screws~10 and ~20~and t~heir washers 13 a~nd 23
are typical~ly made of stainless steel, which affords
parts that are re~sistant~and suitable for steriliza~
tion.
The upper member 30 includes two passages 31 and
32~on the centerllnes 11 and 21 for the screws 10 and
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20, with the upper portion of the passages being
countersunk at 33 and 34 to cooperate with the
spherical ~ace 15 or 25 of the washers 13 and 23. The
concavities 33 and 34 may be either spherical or
conical. To avoid any risk of cracking, the surfaces
of the spherical portions 15 and 25 of the washers, as
well as those of the recesses 33 and 34, should be
highly polished.
The bottom face of the member 30 further includes
a socket 35 centered between the passages 31 and 32, as
is seen in FIG. 4. The socket 35 is provided with a
central recess 36, the use of which will be explained
below.
The securing member 30 is further provided with
lateral relieved regions 37 and 38 on either side of
the socket 35 to permit angular orientation of the
tubular extensions 61 and 62 of the sleeve 60 shown in
FIG. 3.
The lower member 40 faces the upper member 30
described above. It is similarly provided with two
passages 41 and 42 on the centerlines ll and 21 of the
screws 10 and 20, a socket 43 with a central recess 44,
and two lateral relieved regions 45 and 46, all of
these features being visible either in perspective in
FIG. 2 or in the side view of FIG. 3.
In its lower portion the member 40 further
comprises a support extension 47 and a~jaw 48
presenting an inclined face 49, which are visible in
FIG. 3 especially.
The extension 47 serves as a support surface for
the face 51 of the shackle 50, in which tapped holes 52
and 53 are provided on the centerlines 11 and 21 to
accommodate the threads 17 and 27 of screws 10 and 20.
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In the embodiment being described, where the
device is mounted on an arcuate member o~ cross section
,
71 formed of two triangles joined by a web (~see FIG~.
l)j th~ shackle 50 is provided with~an inclined jaw 54,
with the arcuate member 70 intended to be held between
the jaw 4B~ of the lower clamp member 40 and~said ]aw~
54. ~ ~
As has just been~noted, the embodimen~ being
descr1b~d~relates to a device~intended;to be mounted on
an arcuate member. ~For this reason the~elements 30, 40 ~ ;
and 50 have a~slight curvature, seen especially in FIG.
4, which~matches the curvature~of~the arcuate element
on which the~device~is~moun~ted~ Need1es~s to~say~ in
other embodiments the~cl~amping~elements~3~0`;and~4~0,~as
well as the~shaok1e~50~;~if~presen~t),~wi11~be~f1at and
not curved.
Moreover, the~pos1tian1ng and~secur1ng devicé~here~
represented is intended~to~be clamped on~the outside of
the arcua~te member, but without departing from the~
~scope of~the~present invention one~could~of coursé~
likewise~make~a device~intended to~be placed;o: the~
~inside of the~arcuate~memb~er,~
The clamping elem0nts 3~0~and 40 as~wel~l as the
shackle 50 are~typically~ma~de~of~light alloy,~but~could; ;~
alternatively~be made of~a~synthetic material~suitable
for~sterilization.
As for~the spher~ical sleeve 60 intended to be
gr~ipped between elements~30 and~40,~ it~may include two
tubular exten~s~ions 61 and 62, as shown in FIG. 3,
dispos~ed on~either side of the sphere ~6~3. In the
modification of FIGS~. l and~2, only one lateral
extension 6~4 is provided, the central bore 65 of which
serves to guide a frame rod or other connecting piece
or~member;. ~ ~ ~
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In the modification detailed in FIG. 5, the sleeve
consists wholly of a spherical portion 63. Note the
small facets in this fiqure which, although present,
are not shown in FIGS. 1 and 2 for clarity of
presentation.
The sleeve of FIGS. 5 and 6 consists of two shells
66 and 67, each of which includes a trough 68 ar 69.
These troughs are dimensioned to clasp a fixation rod
or a transcutaneous pin placed in the central-passage
65 and secure it against movement in its longitudinal
direction as well as in rotation.
In the modiflcation of FIG. 6A, the trough 68
formed in each half shell 66 or 67 has the cross
sectional shape of a semicircle.
Alternativel~, the trough 69 may have a cross
section in the form of a regular *rapezoid, in which the
inclined sides form an angle greater than or equal to
7 with the perpendicular to the two other sides, as is
seen in FIG. 6B. The exterior of the spherical sleeve
63 represented in FIG. 7 consists of hexagonal facets;
needless to say, the use of other polygons is llkewise
contemplated.
FIG. 8 depicts the central portion of the sleeve
60 shown in~FIG. 3 having tubular extensions 61 and 62
disposed on either side of the sphere 63, said central
portion being much enlarged. Note the succession of
small facets 81, regularly spaced and disposed upon the
surface of the sleeve.
An enlarged detail of the facets 81 is presented
in FIG. 9, which shows that the facets 81 are inscribed
in adjacent circles 82, with each set of circles having
at its center another circle of the same diameter
intersecting the other four circles so as to define
sharp edges 83 as well as the corners 84 of the facets
81. Preferably, the circles 82 are of such a size that
the corners 84 of a single facet are inscribed in an
angle of about 10 from the center of the sphere 63.
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The cross sectional view of FIG. 10, alon~ the
line X-X in FIG. 9, is taken so as to intersect all the
common corners 84 of successive facets in a row of
facëts -81. Thus each corner 84 is a point that will
come into contact wlth the sockets 35 and 43 of
clàmping members 30 and 40.
The cross sectional view of FIG. 11, along XI-XI
in FIG. 9, is taken so as to intersect the sharp edges
83 perpendicularly.
Whereas in FIGS. 9 to 11, corresponding to a first
embodiment, the facets are planes, in the modification
of FIG. 12 (which corresponds to FIG. ll) the facets 81
are curved. As a result, sharper vertices 84 are
obtained which are hence more effectiveIy secured in
the sockets i5 and 43 of the jaws 30 and 40.
Furthermore, it will be clear to those skilled in
the art that the facets may be of other polygonal
shapes. The purpose of the presence of the facets,
planar or curved, may~be stated as being to create
sharp edges or points between the facets, permitting a
firm grip with the jaws. ~;-
The~ sleeve part 60 is in general intended to be
traversed by and to retain pins or rods of from 2 to
8 mm. in diameter. Hence the spherical portlon 63
will typically be from 15 to 20 mm. in diameter.
As a general rule, the jaws 30 and 40 will be made
of a material having a lower hardness than the material
of the sleeve 60. Thus the enclosure formed by the
jaws will be more elastic than the portion 63 of the
sleeve. On that basis, a large number of materials may
be chosen. For example, the sleeve 60 may be of
tempered steel and the jaws of untempered steel. ;~
AlternativelY~ a steel sleeve may be associated with
jaws of light alloy, or a sleeve of light alloy wlth -~
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jaws having a lower hardness, for example of plastic
material.
The use of the positi.oning and securing device
represented in FIGS. 1 to 4 will now be described in
detail.
In each case, the type of sleeve 60 required in
the assembly will first be determined, whether a sleeve
with two lateral extensions 61 and 62 (see FIG. 3), or
a sleeve with one extension 64 IFIG. 2), or a simple
spherical sleeve, possibly composed of two
hemispherical shells 66 and 67 (FIG. 5).
The diameter of the central bore 65 will be chosen
according to the pieces to be assembled.
The assembly will then be mounted directly on the
arcuate element, without of course yet firmly
tightening the screws 10 and 20 in the corresponding
tapped holes 52 and 53 of piece 50, and the spherical
part 60 as well as the arcuate element 70 are disposed
according to requirements.
One now appreciates the function of the lateral
clearances 37 and 38 of member 30, and 45 and 46 of
member 40, which allow the tubular portions 64, or 61 `
and 62, to be oriented, unrestricted by the members 30
and 40, within a range of angular orientation of up to
about 40.
When the proper positioning has been attained, the
screws 10 and 20 can be tightened so as to lock the
assembly, which mav of course be unlocked subsequently
at any time to permit any adjustment.
Upon recalling that the centerlines 11 and 21
are not strictly parallel, but form a mutual angle of `~
about 10, it will be appreciated how the invention
affords àn improved security, both of the sleeve and
of the arcuate member, since the tightening of the
screws can flex the clamping members 30 and 40.
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The deformation due to ~he flexure of members 30
and/or 40 is compensated for by the play of the washers
13 and 23, whose spherical portion 15 or 25 rests in
the spherical or conical sockets 33 and 34. These
washers serve to augment clasping while reducing
friction. In practice, the spherical portions 15 and
25 of the washers should be dimensioned so that contact
with the corresponding socket occurs approximately at
the center of the~rounded portion.
It should also be noted that the recesses 36 and
44 of the clamping members 30 and 40, respectively,
serve to increase the elasticity of members 30 and 40
and hence enhance the clamping, since they allow for
duplication of the fulcrum on the sphérical portion of
the sleeve.
FIGS. 13 to 15 depict a second embodiment of a
positioning and securing device, likewise used in an
external fixation apparatus. This device consists
chiefly of;a fixation assembly 100 and a positioning
and clamping member 110.
The fixation assembly 100 is~ intended to be clamped
upon several~transfixing pins~by means of screws 101
and 102, and for this purpose the~jaws 103 and 104
define passages~lO5 intended to c~l~amp~the transfixing
pins (not shown in the drawings).
This fixatlon assembly`100 for tr~ansfixing pins
further comprises a cylindrical portion 106 having an ~ ~ -
internal circular groove (not shown), intended to
cooperate with the clamping member 110.
For this purpose, the member 110 comprises two
clamp parts lll and 112 whose lower portions have feet
113 and 114 adapted to be engaged in the inner circular
groove of cylinder 106. The clamp parts 111 and 112
are traversed at their upper end by a threaded rod 115
engaged with a wing nut 116. Parts 11l and 112 retain
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a sleeve 120 consisting of two circular pieces 121 and
122 (FIG. 14) which retain themselves a rod 123 in a
bore common to the two pieces 121 and 122. As in the
preceding version, this bore may be polygonal in cra5s
section.
When pieces 111 and 112 are tightened under the
action of the nut 116, feet 113 and 114 will~bear
firmlv against the groove in portion 106 and prevent
rotation of the upper assembly 110. The clamp parts ~ -
lll, 112 have circular surfaces 117, 118 placed facing
one another, against which~the circular surfaces 123,
124 of the cyllndrical pieces 121 and 122 will come to
bear. These surfaces 123, 124~present rows of
rectangular facets forming sharp~edges between them. `
In the embodiment of FIG. 14, thè rows of facets are
arrayed along spherical segments or zones dividing thé
domes of the Iateral~portions of the~pieces 121, 122.
In this case the fac~ets are planar~facets made of a~
harder material than the~material forming parts 111,
112.
In~the modiflcatlon of FIG.~ l5, parts;11l, ~1~12~are
included again~having~;the same~configuration as the
parts in FIG. 14, except that the inner surfaces~ll7, ;~
118 have the~form of a trunca~ted conlcal bore. The
circular pieces~ 121, 122 intended to clamp the rod I23
likewise have truncated conical lateral portions 125,
126, which present a succession of rectangular facets ~ ;
arrayed along the;generatrices of the truncated conical
portions. The facets form sharp edges between them
which will come to bear against the corresponding -~
smooth portions, having the shape of a truncated cone,
of the parts~;Ill, 112. As in the previous embodiments
or modifications, the pieces 121, 122 will be made o a
harder material than the parts 111, 112.
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The embodiments and modifications described herein
propose a positioning and securing means for~a part
with the aid of jaws affording a ar better
effecti-veness of clamping than anything known to date
in the prior art. This effective clamping is obtained
by providing a succession of plane or curved facets on
the part to be clamped, arranged over areas of the part
to be clamped in such a~manner that adjacent facets
form sharp edges or points~between them. The part to
be clamped and secured comprising~the facets is made of
a harder materiaI than that of the jaws. This enables
the sharp edges or points formed by the facets to~
produce elastic deformations in the jaws, thereby ~ ~
providing an especially ~effective clamping effect. It
will be clear to those ~skilled in the art that the
facets mav instead be~provlded~on~the ~jaws, and~in~that
case~the~jaws~would be: made;of~a~hard~er~material than
that provided for the part to be clamped. ~ ~
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