Note: Descriptions are shown in the official language in which they were submitted.
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F.3011
AUXILIARY DEVICE FOR OSTEOSYNTHESIS
BAC~GROUND OF THE lNv~N-LLON
The invention relates to an orthopedic appliance, often
referred to as an external fixator, for stabilized
maintenance of spaced portions of a bone fracture and for
the selective and progressive incremental adjustment thereof
in the course of osteosynthesis, i.e., bone healing at the
fracture. The invention has particular use in application
to small bone fractures, as of the hand or foot.
From German Patent DE-3,701,533 C2 (and its correspond-
ing U.S. Patent No. 4,988,349), a fixator of the character
indicated is known wherein a short central spacer has
flexible connection at its respective ends, via twin ball
joints, to separate arms which can be so selectively clamped
as to provide a wide range of universal angular setting
between the two arms, thereby providing a wide range of
adjustment for bone-fastener units that anchor bone screws
or pins via selectively adjustable fixation of such units to
~he respective arms. The de3ign permits swivel and height
adjustment of the bone-fastener units via individually
locked ball joints at the central spacer, thereby creating
added freedom of adjustment over a widened overall angular
range. Thus, even very complex bone positions and their
~ine adjustment can be controlled by the surgeon.
When applying an external fixator in the area of the
hand and of individual fingers, the surgeon also needs a
maximum range of adjustment of single elements in relation
to each other. At the ~ame time, however, the structural
elements should be kept small enough so that they will
interfere to a minimum degree with movements of the hand,
for example. The flxator of said pa~ent has serious
limitations in such a small-bone context.
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BRIEF ~TATEMENT OF THE LNv~NLION
It i6 the object of the invention to provide an
improved auxiliary device for osteosynthesis, namely, an
external-fixator construction (i) wherein overall dimensions
may be kept to a minimum, (ii~ wherein basic design can be
simple without impairing reliable releasably locked
performance of the various structural elements, (iii)
wherein a wide range of angle adjustability can be available
with simplified locking, (iv) wherein multiple bone screws
or pins can also be readily and adjustably clamped to the
respective ends of the fixator with simplified locking, and
(v) wherein substantially improved applicability can be
- achieved Eor ~mall-bone fixation.
= The invention achieves this object with a reduced-scale
and ~implified construction (a) wherein each of two bone-
screw clamping units utilizes a single clamp which can in
one operation effectively establish fixed retentlon of a
plurality of bone screws or pins, (b) wherein the respective
clamping units are adjustably lockable in desired position
along ball-jointed end arms (carrier rods), and (c) wherein
a single operation i9 effective to clamp two centrally
spaced ball joints, within a wide range of universally
flexible articulated connections.
More specifically, each of the bone-screw clamping
units comprises plural (i.e., at ieast two) flat plates in
ace-to-face adjacency, with plural spaced sets of aligned
bores that are sized to receive an inserted bone screw or
pin. These plates may be of rectangular, square or oval
configuration, and they are characterized by spaced sets of
transversely aligned bores, each set being adapted for
insertional assembly to the shank of a bone screw or pin.
~ach clamping unit must comprise at least two such plates in
face-to-face adjacency, and the selective actuation into and
out of securely and accurately locked engagement to one or
more bone screws or pins is determined by rotation of an
eccentric bolt, thus shifting one with respect to the other
of the plates. Preferably, each clamping unit consists of a
plate-like body which is locally slit to divide its
thickness dimension into two spaced plates, accommodating a
40' shiftable central plate therebetween. The aligned bores of
each set extend transversely through the body plates and the
shiftable plate, and the eccentric bolt is journalled in the
body plates, wlth its eccentric surface effectively
journalled in the central, shiftable plate. One or more
first sets of aligned holes are normal to the plates; other
S sets are preferably canted from the normal, and are
convergently aligned for externally projected geometric
intersection with a corresponding projection of one or more
of the first sets, thus for example ensuring that convergent
operative ends of bone pins can be brought into very close
relation to each other at bone engagement.
Each of the clamping units is freely positionable along
and is releasably securable to its carrier rod, and the
inner erd of each carrier rod terminates in a ball, which is
the means of universal ball-joint connection to a central
coupling or frame member. A single adju3tment at this
central frame member provides simultaneous releasably
locking action of the frame member to the ball of each of
the carrier rods, the locking action being fully contained
within the frame member. The frame member and the clamping
wedge structure by which both ball joints can be releasably
~ locked require a minimum of structural thickness and bulk,
-- thereby enabling the overall fixator to present minimum
inconvenience or handicap to a small-bone region such as the
hand.
For stretching or compressive ac~ion on bone in the
course of healing while held by the fixator, one or both of
the carrier rods has external threads, and a nut engaged to
such threads may be incrementally rotated in small steps and
in abutment with the body of one of the clamping units.
This nut may be peripherally graduated with angle-marking
indicia to enable the surgeon to note how much he has
incrementally compressed or stretched the fixation span,
from time-to-time in the coursè of bone healing.
DETl~Il,ED DESCRIPTION
The invention will be described for illustrative
embodiments, in conjunction with the accompanying drawings,
in which:
Fig. 1 is a partially exploded view in perspective of
- an external fixator of the invention;
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6~538-1124
Fig. 2 is an enlarged view in longitudinal section
through longitudinally connected components of the fixator of
Fig. l;
Fig. 3 is a sectional view taken at 3-3 of Fig. 2;
Flg. 4 is a view similar to Fig. 1, for a second
embodiment of the invention;
Fig. 5 is a view similar to Fig. 2, for the embodiment
of Fig. 4; and
Fig. 6 is a sectional view taken at 6-6 of Fig. 5.
In Figs. 1 to 3 of the drawings, an auxiliary device or
external fixator of the lnvention is seen to comprise two like
clamping units 1 and 2, respectively adapted to carry bone
fasteners 4, 5 which may be bone pins or bone screws engaged to
the clamping Lnit 2.
Each o the clamping units 1 (2) is freely positionable
along one of two carrier rods 7 (8), and each of the carrier rods
features a ball 9 (10), by which ad~acent but spaced ends of the
carrier rods are connected and retained in assembled relation to
a central box-like annular frame 11, thus establishing a twin
ball-joint assembly 3. While unlocked, each of the two carrler
rods 7, 8 can be swivelled in any desired dlrection, so that rods
7, 8 can be oriented as desired for adaptation to the curvature
of the bones to be immobilized by the fixator.
Specifically, ea~h o the opposed walls 21 of frame 11
iæ formed with a ball-seating surface which flares in the inward
direction, and wedge-loading plates 27, 28, are interposed
between the respective balls 9, 10 and an ad~ustable wedge
mechanism 20, 22. As shown, this mechanism comprises a wedge
element 22 with opposed flats which converge inwardly and act on
corresponding flats of the respective plates 27, 28, wherein such
coaction is designed to occur primarlly in the reglon defined by
and below the geometrical line between the centers of balls 9,
10. The other part of the mechanlsm is in axially retained
relation to the frame 11 and comprises an ad~ustment element at
A
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20992~0
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rotatable jacking element 20 having an external socket for Allen-
head wrench access. ~lements 20, 22 have threaded formations and
coaction, enabling wedge element 22 to drive plates 27, 28
laterally for selective clamping action against balls 9, 10 of
their carrier rods 7, 8. As shown, the inner end of wedge
element 22 is reduced and externally threaded, engaging the
threaded bore of the inner end of element 20. Also, as shown,
the inwardly projecting end of element 20 iB frusto-conical and
~onvergent to termination at or just short of the geometrical
line between ball centers; and this frusto-conical formation
engages in correspondingly sloped areas of upper regions of
plates 27, 28, so that the conical engagements and the wedge-flat
engagements each contribute to ball-~oint locking, respectively
above and below the geometrical line between ball centers.
Eesh of the carrier rods 7, 8 may be externally
threaded but, as shown, only rod 8 is threaded, for operative
engagement by the internal threads 19 of a nut 18. Also shown is
a preference that carrier rods be milled with opposing flats, for
smoothly keyed reception in a conforming guide-bore formation in
the body of each of the clamping units 1, 2. In Fig. 3, the
section shown for carrier rod 8 reveals the proportions of the
milled flats, and the described threads will be understood to be
limited to the diametrically opposed rounded ends of the rod
section, between the milled flats. Not only do the milled flats
and the conforming con~ours of the guide bore in the clamping-
unit body account for smoothly ad~ustable positioning of the
clamping unit 2 along its carrier rod 8, but the lower flat
presents an optimum ~urface for engagement by a set screw 26, to
lock the clamping unit in a desired location along its rod 8.
Similarly, carrier rod 7 is engaged by set screw 25. In
addition, the nut 18 ls incrementally ad~ustable when abutted to
clamping unit 2, as in Fig. 2, to effect an incrementally
ad~usted ~acking shift of the clamping unit 2 in the
longitudinally outward direction, thus incrementally stretching
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2Q99240 60538-ll24
an afflicted bone in the course of healing a fracture. And it
will be understood that lf nut 18 is assembled to its carrier rod
8 so as to abut the outer end of the body of clamping unit 2, it
is al60 possible to effect an incremental longitudinal
compression of the involved fracture. As shown, nut 18 is
circumferentially inscribed with angularly spaced indicia and/or
local sockets 29, to facilitate angular indexing and entry of
data for a succession of different stretching or compressional
adjustments of the position of clamping unit 2, in the course of
a given prescription for healing the involved bone fracture.
As shown, each of the clamping units 1, 2 comprises a
---~ generally prismatic body 30 having progressively reduced length,
width and thlcknesæ dimensions L, W, T, respectively. The length
dimension L iæ oriented for transverse offæet of an upper bone-
screw/bone-pin clamping region C, with respect to a lower
carrier-rod guidance region, which extends through the full width
dimension W of body 30. The offset clamping reglon is
characterized by a slot 24 which is central of the thickness
dimension T, thereby defining two flat plate formations 12, 15
which are integral features of body 30. As shown, the depth of
slot 24 substantially matches the width dimension W, so that the
confronting flat inner ~urfaces of plate formations 12, 15 are
substantially square, and a separate plate 14 of slightly reduced
area is slidably fitted in slot 24, for face-to-face engagement
with plate for~ations 12, 15. First spaced sets of aligned bores
23 are drilled in the composite of elements 12, 14, 15 on
alignments normal to the flat plate surfaces, the same being
adapted to receive and correspondingly locate one or more
inserted bone-pin/bone-screw shanks, as at 31, 31'; and second
spaced sets of aligned bores are drilled in the composite of
elements 12, 14, 15 on alignments that are canted from normal to
the flat plate surfaces, the same being adapted to receive and
correspondingly locate one or more inserted bone-pin/bone-screw
shanks 32, 32'. The spacings between sets of aligned bores are
2099240
` 60538-1124
substantially equal, wlth each set fully contalned by the
composlte of elements 12, 14, 15; and the centers of the
respective elements 12, 14, 15 are bored for development of an
eccentrlcally driven shifting displacement of the central plate
14 via a rotary pin or bolt 34 that i8 journalled ln plate
formations 12, 14. Specifically, pin 34 has an enlarged head
(with an Allen-head socket) ~ournalled in plate formation 15, a
central eccentric 16 of lesser dlameter journalled in the
shlftable plate 14, and a further-reduced other end ~ournalled in
plate formation 12, with snap-rlng retentlon agalnst the outer
surface of plate formation 12. The throw of eccentric action is
more than enough to releasably yet securely blnd one or more
inserted bone-pin/bone-screw shanks to each of the clamping unit~
1, 2, merely upon a slngle Allen-wrench actuatlon of the involved
rotatable bolt or pin 34.
A preference is indicated, by dashed lines 31", 32" in
Fig. 1, that the canting of at least one of the aligned sets of
_- bores in the composite 12, 14, 15 shall be such as to converge
with the normal orientation of at least another one of the
allgned sets of bores as to involve bore axis pro~ection for
geometric intersection at a point 35 that ls offset from the
clamping-unit body 30. With this arrangement, it is clear that
bone plns at 31', 32' can be set as closely together as desired
at bone engagement, merely by selecting the extent to which their
shanks are inserted through aligned bores in the composite 12,
14, 15, prior to eccentrically driven clamping of pins 31', 32'
by a single wrenched partial turn of pin 34.
It is also clear that by having the ball ~olnts fully
contalned by the box-like frame 11, the clamplng units 1, 2 have
a great range of adjustable posltlonlng on thelr respective
carrler rods, up to a point of virtual ad~acency to the ball ends
by which they are connected to the double-ball ~oint assembly
within frame 11. Still further, it will be noted that all
external features of the described fixator assembly are
209924Q . 60538-ll24
reallzable (i) with minimum mass of component parts, (ii) within
the same minimum thickness T as described for each of the
clamping unlts 1, 2, and (iii) with a single actuator to perform
multiple releasable clamp settings at units 1, 2 and 3 of the
assembly.
Compact assembly of the central double-ball joint unit
3 within frame 11 is achievable via fixed retention of the
reduced end of a carrier rod in a local radially inward bore or
socket of its ball, the same being transversely pinned into
permanent assembly after each ball is in place within frame 11.
Preferably, the reduced carrier-rod end is threaded, and the
local radially inward bore of the ball is tapped for threaded
carrier-rod engagement.
In the drawings, the capacity is shown for each of the
clamping units 1, 2 to accommodate four pins 5, wherein the lower
pair of spaced parallel bores will accommodate pins that are
parallel to each other and normal to the clamp plates 12, 14, 15,
and wherein the upper pair of spaced parallel bores will
accommodate pins that are parallel to each other but inclined
from the normal, for yeo~etric axis intersectlon, as at 35 in
Fig. 1. As a practical matter, however, the four sets of aligned
bores in the plates 12, 14, 15 of each clamp are not needed at
any given time, in that two bone~screw pins 5 or the like are
generally all that are needed for a given use of the structure.
Thus, the surgeon has choices: to use his two pins via the lower
pair of parallel sets of bores that are normal to plates 12, 14,
15; or to use his two pins via the upper pair of parallel sets of
bores that are inclined from the normal to plates 12, 14, 15; or
to use his two pins via one of the lower and one of the upper
sets of aligned bores, thus releasably clamping hi6 two pins for
a predetermined angular relation of the two pins. In all cases,
a single rotary actuation of the eccentric drive 34 wlll
establish a positive locking ~am of plate 14 against both of the
two pins, regardless of the aligned bores in which they have been
2~992~0 60538-1124
inserted.
In the embodiment of Figs. 4 to 6, the same double
ball jolnt assembly 3 descrlbed for Figs. 1 to 3 serves two
clamping units 101, 102* each of which is embodied in a clamping-
unit body 130 of generally L-shape, whereby to enable plural pin~
4, 5 clamped by units 101, 102 to be set at very close proximity,
as when external fixation is needed for small-bone fracture
repair. The generally L-shape of each body 130 is seen to have a
base end of width W and thickness T for selectively clamped
longitudinal mounting on one of the carrier rods 7 (8), but the
length dimension L' of each body 130 exceeds the dimension L of
Figs. 1 to 3, in order that each clamping unit 101, 102 may
safely clear interference with the ball-joint assembly 3, for a
wide range of angular settings of the carrier rods 7 (8). The
generally L-shape of each body 130 enables each clamping unlt
101, 102 to be at axial offset W' from lts base end; preferably,
the axial offset W' exceeds one half the axial width W" of the
ball-joint frame 11, thereby enabling such freedom of carrier-rod
angular ad~ustment as to permit clamping units 101, 102 to abut,
even for a clamped angularly canted orientation of the respective
bodies 130. In all cases, pin positloning in the clamping unlts
101, 102 is as described for unlts 1, 2 of Figs. 1 to 3.
* In Figs. 4 to 6, parts of the clamping units 101, 102
corresponding to parts of the clamping unlts 1, 2 of
Figs. 1 to 3 have been given the same numbers, in the
100 series, adopted for the clamping-unit designa~ions
101, 102.
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