U.S. patent number 3,866,607 [Application Number 05/387,177] was granted by the patent office on 1975-02-18 for bone fracture compression device and method of usage.
This patent grant is currently assigned to Environmental Sciences Corporation. Invention is credited to Alan K. Forsythe, Charles J. Green.
United States Patent |
3,866,607 |
Forsythe , et al. |
February 18, 1975 |
BONE FRACTURE COMPRESSION DEVICE AND METHOD OF USAGE
Abstract
Apparatus and method for applying controlled compressive forces
to a bone fracture via a bone fracture plate is described. Means
are provided for applying a predetermined compressive force to the
fracture situs. The method comprises the steps of firmly fastening
one end of a bone plate to one segment of a fractured bone adjacent
the fracture, placing a bone engaging screw through a longitudinal
slot in the bone plate adjacent the second bone fragment, drawing
the bone segments firmly together by use of the compression device
of this invention to exert a predetermined compression force across
the bone fracture, inserting a second bone engaging screw through
the bone plate to firmly attach the bone plate to the second bone
segment and finally tightening the first placed bone engaging screw
in the second bone.
Inventors: |
Forsythe; Alan K. (Vashon,
WA), Green; Charles J. (Vashon, WA) |
Assignee: |
Environmental Sciences
Corporation (Vienna, VA)
|
Family
ID: |
23528807 |
Appl.
No.: |
05/387,177 |
Filed: |
August 9, 1973 |
Current U.S.
Class: |
606/105; 606/86B;
606/282 |
Current CPC
Class: |
A61B
17/8019 (20130101) |
Current International
Class: |
A61B
17/68 (20060101); A61B 17/80 (20060101); A61f
005/04 () |
Field of
Search: |
;128/92R,92D,92B,92EC,92BC,83 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Yasko; J.
Attorney, Agent or Firm: Christensen, O'Connor, Garrison
& Havelka
Claims
1. An orthopedic apparatus for compression of a bone fracture and
extramedulary fixation of a rigid bone plate thereon said bone
plate adapted to be positioned in contact with the surface of a
fractured bone, aligned parallel to the axis of said bone and
overlapping a fracture therein, said plate having at least two bone
screw receiving apertures positioned in each overlapping portion
thereof whereby at least two bone screws may enter each segment of
said fractured bone, one of said apertures comprising an elongate
slot adapted for situation adjacent a fracture in said bone and
having means to receive a plate engaging pin means adjacent said
slot; said apparatus comprising:
a frame means including a bone plate engaging flange means having a
depending pin means adapted for engagement with said bone
plate;
a threaded member extending upwardly from said flange means and
journalled into said frame means, the end of said threaded member
opposite said flange means extending beyond said frame means and
carrying means for indicating torque applied thereto;
cam means having external guiding cam surfaces thereon in threaded
engagement with said threaded member and adapted to translate along
said threaded member in response to rotation thereof; and,
a movable subassembly carried by said frame having cam follower
means drivingly interengaged with said guiding cam surfaces and
adapted for translation substantially parallel to said flange means
upon movement of said cam means, said movable subassembly including
hook means for engaging a bone screw positioned in said elongate
slot whereby rotation of said threaded member causes said pin and
said hook means to move with respect to each other, the force
necessary to effect such movement being shown by
2. The apparatus of claim 1 wherein said cam follower means
comprises a
3. The apparatus of claim 1 wherein said pin means and said
threaded member
4. The apparatus of claim 1 wherein said frame means and said
movable subassembly carry indicia to indicate the relative position
therebetween.
5. The apparatus of claim 1 wherein said pin means and said hook
means are operatively positioned on said bone plate with the bone
fracture site
6. The apparatus of claim 1 wherein said pin means and said hook
means are
7. The apparatus of claim 1 where said pin means and said plate
have cooperating interlocking means restraining disengagement
thereof whenever force is applied between said pin means and said
hook means.
Description
BACKGROUND OF THE INVENTION
This invention relates to apparatus and method for emplacing a bone
fracture compression plate and further relates to a novel method of
applying a predetermined compression to a bone fracture site
spanned by a bone plate.
PRIOR ART
In the treatment of bone fractures a bone engaging plate is
frequently used, especially in the veterinary medicine practice in
which a plurality of bone screws are inserted through apertures in
the plate after the plate has been placed adjacent the bone
spanning the fracture area. The plate serves to rigidly hold the
proximal and distal bone segments in the appropriate position for
healing by natural body process. In one device long-known to the
prior art the bone plate has an elongated slot for slidably
receiving the shank of one of several bone screws. A compression
unit is utilized to draw the proximal and distal bone segments
together and is utilized by inserting one of the bone screws
positioned in the proximal segment of the fractured bone through a
first element of the compression device, thus, anchoring it with
respect to the bone plate and to the proximal segment of the
fractured bone. A moveable portion of the compression device is
inserted into a special countersunk head end of a specially
designed bone screw inserted into the slotted screw-receiving
aperture in the distal bone segment engaging portion of the bone
plate. The compression device is then drawn together by rotation of
a threaded shaft member standing between the two above-mentioned
portions of the compression device, thus drawing together the
distal and proximal segments of bone. The structure of this device
requires the usage of a separate wrench to accomplish a sufficient
compression across the fracture interface.
After the distal and proximal segments of bone are drawn together,
several additional screws are then placed in the distal portion of
the fractured bone through the bone plate and tightened into place.
The compression unit is removed by removing the bone screw holding
it in place and then returning the bone screw to its operative
position. The special screw utilized in the elongate slot screw
aperture is removed and replaced by an ordinary bone screw. A
substantial amount of the surgeon's time is thus consumed by the
need to emplace and remove special screws during the attachment and
removal of the compression device. The need to use a separate
wrench to operate the compression device has been found to be a
source of delay during a bone setting operation since the wrench is
easily misplaced.
Another well-known compression device and method requires the usage
of a longer special type of anchor screw inserted through the
bottom of the compression device through the slotted aperture of
the bone plate and then into the bone segment opposite the segment
to which the plate is attached. This special screw must be replaced
by an ordinary bone screw after compression of the fracture site.
This system utilizes a hook means which engages one of the bone
screw apertures adjacent the end of the proximal segment of the
fractured bone. When the tightening is completed, additional screws
are inserted into the distal portion of bone to hold the plate in
place for removal of the compression device. This system, in
addition to suffering from the need to emplace and replace
specialized anchor screws and requiring the use of a wrench element
to tighten the compression device, additionally requires the usage
of a bone plate having preferably six or more bone screw apertures
therein so that the proximal and distal elements of the bone may be
held in alignment during the compression of the fracture.
Still another compression device, similar to that just described,
is mounted directly on the bone with an anchor screw. This type of
device is utilized in a method in which the bone plate, positioned
to span the fracture, is secured to the distal bone segment with
several screws. The device is then anchored with a bone screw on
the proximal bone segment a predetermined distance from the end of
the bone plate. The hook means of the device is then made to engage
the end screw hole in the plate. The screw jack mechanism of the
device is then made to apply compressive force at the fracture site
by drawing the plate and attached distal bone segment toward the
proximal segment. When desired compression is achieved, a screw is
installed through the plate into the proximal bone segment to
maintain compression while the device is disengaged from the plate.
A screw is then installed in the end screw hole to complete the
installation. The anchor screw securing the device is then removed
and the assembly is removed from the bone. The obvious drawback to
this method is the additional bone damage inflicted by the
temporarily installed device anchoring screw.
The need in each of the known prior art bone plate compression
systems and devices to use specially formed bone screws in the bone
for the purpose of compressing the fracture and then replacement by
ordinary bone screws is a time consuming operation. In addition the
holding power of the screws is decreased due to the repeated
insertion and removal of the screws in the bone structure. The
prior art devices also require the usage of a special wrench
separate from the compression device. The wrench, being separable
from the compression unit, is inconvenient and may become misplaced
resulting in valuable time lost in finding the wrench or seeking a
replacement.
Further, no compression device of the prior art has any means other
than experience or natural feel for determining the amount of force
actually applied to the fracture site, even though compression
force has a significant effect on rapidity and effectiveness of
healing. Excessive force can cause pressure necrosis and prevent
healing while too little force will retard healing and may permit
refracture.
It is therefore an object of this invention to provide a bone
fracture compression device and method which eliminates the need
for special bone screws for operation but rather uses only the
ordinary bone screws which remain at the fracture site upon
completion of the emplacement of the bone compression plate.
It is a second object of this invention to provide a bone fracture
compression device for use with bone compression plates which is
self-contained and does not require use of a separate wrench or
other adjusting means.
It is another object of this invention to provide a bone
compression device which provides the surgeon with a direct
indication of compression applied to the fracture.
SUMMARY OF THE INVENTION
A bone fracture compression method which permits the surgeon to
accurately control the amount of compression placed upon the
fracture line between the distal and proximal bone segments of a
bone fracture is described herein. The device is utilized with a
bone compression plate having means to engage a first portion of
the device and having a longitudinal elongate slot adapted to
slidably receive a bone engaging screw. Additional bone screw
receiving apertures are positioned in the bone plate for
emplacement of bone engaging screws in distal and proximal bone
fracture segments. A depending hook means attached to a second
portion of the compression device is adapted to engage the
bone-engaging screw positioned in the elongate slot. The device
includes means to cause relative motion between the first and
second portions including means to measure the amount of force
exerted in such movement. The above-described bone compression
plate attached by two or more bone engaging screws to a distal
segment of a fractured bone and by a single screw through the
elongate slot into a proximal segment of the fractured bone may be
used to draw the bone segments together into compressive contact
with the above-described bone compression device. Force measuring
means to indicate the force applied between the two portions of the
bone compression device provides the surgeon with a direct
indication of the amount of compressive force applied to the
fracture site. Upon achieving the desired compressive force at the
fracture site, at least one additional bone engaging screw is
inserted through a bone screw receiving aperture in the compression
plate and into the proximal end segment of the bone fracture. The
bone compression device is then removed from the bone plate simply
by releasing the pressure applied between the protruding portion
and the hook means and lifting the device out of engagement with
the bone plate. The bone plate remains in place with the applied
compressive force across the fracture site remaining for proper
healing of the bone. The bone screw residing in the elongate slot
in the bone compression plate is then tightened and the incision
repaired by well known surgical techniques. By using the bone
compression device and the method taught herein it is unnecessary
to use bone screws having a specially formed head or other special
bone-engaging means but rather the ordinary typical bone screws
widely utilized by surgeons are suitable for use with this
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects and advantages of this invention will become
evident with a reading of the ensuing description of the preferred
embodiment which makes reference to the accompanying drawings in
which:
FIG. 1 is an isometric view of a compression device used in
orthopedic surgery for repair of bone fractures by internal
fixation.
FIG. 2 is an exploded isometric view of the device illustrated in
FIG. 1 and includes an illustration of a typical bone plate with
which the device is used.
FIG. 3 is a cross-sectional view of the device taken along lines
3--3 of FIG. 6, illustrating the interface between the drive
portion and the slidable output portion.
FIG. 4 is a side elevation view of a compression device positioned
on a bone compression plate prior to fracture compression.
FIG. 5 is a partial cross-section illustrating the manner in which
the drive shaft pin extension engages the bone plate.
FIG. 6 is a side elevation view partly in section, of the
compression device positioned on a bone compression plate after
fracture compression on the bone ends of the fracture.
FIG. 7 is a cross-sectional view of a completed bone compression
plate installation prepared according to the teachings of this
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The Figures illustrate a compression device 10 used during
orthopedic surgery in the repair of bone fractures by internal
fixation and the method in which the compression device 10 in
conjunction with a bone plate 76 is used. The compression device 10
functions to draw bone segments 100 and 104 into engagement at
fracture site 98 and permanently fasten the bone segments together
in compression to promote repair and healing of the fracture. The
device applies a measurable compressive force at the fracture and
holds the fracture under the desired compressive force until bone
plate installation can be completed by the surgeon. The compression
of the bone segments at the fracture is then maintained by the bone
plate 76 to promote healing. The device is reliably simple and is
reusable. Its simplicity allows easy assembly and disassembly for
cleaning and sterilization purposes.
The main structural feature of the device 10, as shown in FIGS. 2,
4, and 5 includes the frame 12 which provides the fixture upon
which function components are mounted, spaced and otherwise
interrelated. The adjustment linkage through which the device 10 is
operated includes a threaded shaft 14, slide block 16, torque
spring 18, and knurled knob 20. A cam means such as the slide block
16 is internally threaded and receives the threaded shaft 14. The
shaft 14 is rotatably mounted in the frame 12 at the upper shaft
bearing 13 with the lower shaft bearing provided at the interface
with pin extension 22. The pin extension 22 is press fit into an
opening 15 in the base portion of the frame 12 and has on the
uppermost end a radial flange 23 which seats against the frame 12
and a bearing segment 25 which is crowned by a convex bearing
surface 27. A recess 29 in the lower end of the threaded shaft 14
rotatably seats over the bearing segment 25 such that the flat
innermost face of the recess rests on the convex bearing surface 27
thereby providing a low-friction bearing interface at the point of
tangency. The shaft 14 is restrained from longitudinal movement by
a snap ring 17 on the upper end and the statically mounted pin
extention 22 engaging the recess 29 in the shaft on the lower end.
An unthreaded segment 24 of shaft 14 protrudes from the top of the
frame. An enlarged portion 26 of segment 24 provides a bearing
surface 32 engaging a corresponding bearing surface 37 on the
underside of knurled knob 20. The mounting tang 28 of the torque
spring 18 is inserted through a hole 33 situated in shaft 14. The
slide block 16 is threaded on the shaft 14 and slidably engages a
face 30 of the frame 12 which prevents the block from rotating as
the shaft is turned. Thus, as the shaft 14 is rotated clockwise the
block 16 is forced to progress upwardly along the shaft threads in
sliding engagement with face 30. Conversely, as the shaft 14 is
rotated counterclockwise, the block 16 is forced to recede along
the threads of the shaft.
Rotation is imparted to the threaded shaft by the knurled knob 20
via the torque spring 18 which is statically affixed to the shaft
as previously described. The knob 20 is mounted for relative
rotation on shaft 14 such that bearing surface 37 rests in sliding
engagement upon bearing surface 32. The end tang 34 of the torque
spring 18 engages a notch 36 in flange 38 inside the knob 20. A
screw 40 inserted through Torque index plate 42 is positioned at
the extreme upper end of shaft 14 and is held in place by screw 40
inserted into threaded hole 44 in the end of shaft 14. The screw
14, utilizing plate 42 as a washer, retains the knob 20 on the
shaft 14 while allowing the knob 20 to rotate freely on the
unthreaded shaft segment 24 within the limitations imposed by the
torque spring 18. The torque index plate 42, on the other hand, is
statically mounted on the end of the shaft 14 by the screw 40.
Thus, torque applied to shaft 14 is shown by the relative angular
deflection between knurled knob 20 and torque index plate 42.
Indicia 46 on the torque index plate and scribe 48 on knurled knob
20 permit observation of the torque applied to shaft 14.
A subassembly formed by two slide plates 50 and 52, a spacer block
54, a hook fixture 56 and fasteners 58 is slidably mounted on the
frame 12. The slide plates 50 and 52 reside on either side of the
frame 12 between flange surfaces 60 and 62 at the top and bottom of
the frame. Fasteners 58 secure plates 50 and 52 to each other with
the spacer block 54 and hook fixture 56 between them. Note that
pins 64 on the spacer block 54 and the flanges 66 on the hook
fixture 56 fix the positions of the respective pieces relative to
the slide plates 50 and 52 when assembled. The cardinal features of
the slidable subassembly are the diagonal grooves 68 in the
interior surfaces of the slide plates 50 and 52. As is best shown
in FIG. 3, the external guiding cam surfaces in the form of ridges
70 on the sides of the slide block 16 slidably engage and reside in
the grooves 68 and provide the interface through which the drive
force is transmitted from the threaded shaft 14 to the slidable
subassembly.
As previously described, turning the knurled knob 20 as shown in
FIG. 4 drives the threaded shaft 14 via the torque spring 18
causing the rotationally captive slide block 16 to move upwardly or
downwardly along the threads of the shaft 14. This movement of the
slide block 16 along the threaded shaft 14 causes the side surfaces
of the ridges 70 on the block 16 to bear against the sides of the
grooves 68 in the slide plates 50 and 52. As the block 16 is
elevated or lowered by rotation of the shaft 14, the ridges 70
impart a force to the surfaces of the grooves 68 at an angle
causing the slidable subassembly to be laterally displaced relative
to the frame 12 as indicated by the dotted line 80 in FIG. 4. This
movement subsequently changes the spacing between pin extension 22
and hook 72 which is the essential mechanical output of the device
as will be described in detail later in this text.
The type of drive arrangement just described is specifically
advantageous in this application since counterforces exerted about
pin extension 22 and hook 72 cannot displace the slidable
subassembly once the desired positioning of the pin and hook has
been achieved. It should be noted that an incremented scale 74 is
provided on the top surface of the spacer block 54 allowing the
surgeon to visually monitor the exact relative position of the pin
22 and hook 72.
Operation of the device 10 by clockwise rotation of the knurled
knob 20 causes relative movement between the pin extension 22 and
the hook 72 of the hook fixture 56. This mechanical arrangement is
advantageously applied to a bone plate 76 and its bone engaging
fasteners 82, 84, 86 and 88 as are shown in FIGS. 2, 4 and 6. The
bone plate 76 is a common device used in orthopedic surgery and is
well-known to those skilled in the art. The bone plate is designed
to span a bone fracture 98 and hold the bone ends 102 and 103
rigidly together for healing by installation of screws through the
plate and bone. The bone plate used with the preferred embodiment
of the invention is substantially of standard design; however, it
bears one modification. A double diameter hole 90 has been added to
the plate 76 to receive the pin extension 22. The hole 90 and
annularly grooved pin extension 22 are shown in cross-section in
FIGS. 4, 5, and 6. The groove 92 on the pin engages the collar 94
formed by the small diameter portion of the hole 90 effectively
locking the pin in the hole when the device is in use.
During orthopedic surgery, after the incision is made and the site
of the bone fracture is exposed, a bone plate 76 of appropriate
size and type is selected. Although the bone plate illustrated in
FIG. 4 indicates four screw holes including the elongated slot 96,
bone plates containing more than four holes are commonly used in
situations in which a longer span of bone is desired to insure
rigid and secure bone engagement. The present invention is designed
to operate with any plate selected that has been modified by
addition of the double diameter hole 90. FIG. 4 also illustrates a
fracture 98 in an essentially rectilinear bone section; however,
the compression device may be used in plate instalations on
curvilinear bone sections requiring the bone plate to be moderately
altered longitudinally to conform to the curvature of the bone.
Screws to be employed with the bone plate are selected using a
depth gauge and exercising care to insure that the screw length is
just sufficient to traverse both cortices. In compression plating
of bone fractures, bone screws employed are preferably of the
precision type, consisting of buttress threads to obtain maximum
holding power. The screws can be self-tapping with radially fluted
points or the holes can be prethreaded with a bone tapper to
minimize bone destruction around the threads during insertion of
the screws.
Once the bone plate 76 and required screws have been selected, the
plate is positioned over the site of the fracture 98 such that the
end of the plate upon which the elongated screw slot 96 is situated
is positioned toward the distal bone section 100. The plate is
positioned longitudinally with the fracture 98 approximately
centered between the inboard end of the elongated hole 96 and the
next adjacent screw hold toward the proximal end. Thus positioned,
holes 106 and 108 are drilled in the proximal bone section 104
through the openings in the plate 76 using a drill and drill guide.
The screws 82 and 84 are installed and tightened in the holes,
thereby securing the plate 76 to the proximal bone section 104. The
fractured end 103 of the distal bone section 100 is then positioned
adjacent the fractured end 102 of the proximal bone section 104.
Using the drill and drill guide, a pilot hole 112 is drilled in the
distal bone section 100 through the elongated screw hole 96 in the
plate 76 at a point near the outboard end 110 of the hole. A screw
86 is then installed in the pilot hole 112 and tightened down so
that it is snug but not tight in the elongated hole 96 of the plate
76. At this point, the compression device 10 is positioned on the
plate 76 such that the annularly grooved pin extension 22,
protruding from the underside of the frame 12, engages the hole 90
in the plate. The knob 20 is then rotated clockwise until the hook
72 engages the countersunk head of the screw 86 on the side away
from the fracture 98. A slight clockwise turn of the knob 20
positively engages the hook 72 with the screw head.
Upon further rotation of knob 20 the device applies compressive
force between the hole 90 in the bone plate 76 which is integrally
attached to the proximal bone section 104 and the head of the screw
86 which is embedded into the distal bone section 100. The hook 72
engaging the screw 86 is physically moved closer to the pin 22
engaging the hole 90 in the plate 76 by further turning the knob 20
in a clockwise direction. Thus, the bone ends are drawn together.
As the bone ends 102 and 103 meet, as shown in FIG. 6, a
compressive force is applied at the fracture 98 through the action
of the device. The compressive force is proportional to the
torsional force applied to the threaded drive shaft 14 by knob 20
via the torque spring 18. This force is translated via the torque
meter mechanism into a measurable value expressed on the
incremented scale on plate 42 as related to the scribe on the knob
20. The surgeon may fine adjust the force at the fracture by
monitoring the torque meter. It should be noted that compression of
the bone fragments is helpful since it allows the fracture to heal
by direct bone formation and obviates the slower cartilaginous
phase of callus formation.
As noted above, the drive mechanism of the device is so designed
that it effectively nullifies counter-compressive forces at the
fracture during installation. The tendency of the bone ends to pull
apart and relax the compressive force set by the surgeon, as would
be translated into counter-compressive forces at the pin extension
22 and hook 72, are not readily translatable into a torsional force
which could rotate the threaded shaft 14 and knob 20. Once the
device has been set to a particular compressive force level at the
fracture by the surgeon, the device will maintain that level
unattended.
With the device maintaining the desired compressive force at the
fracture 98, a hole 114 is drilled in the distal bone segment 100
through the remaining screw hole 116 in the bone plate 76. A screw
88 is installed in the hole 114 and firmly tightened. This screw
will maintain the compressive force at the fracture while the
device 10 is released and removed from the bone plate. The device
is removed from the bone plate 76 by turning the knob 20 in a
counterclockwise direction until the hook 72 is free of the head of
screw 86. At this point the device can be lifted to allow pin
extension 22 to be disengaged from the hole 90 in the plate. With
the compression device removed, the screw 86 in the elongated hole
96 in the plate is tightened to complete the fixation of the bone
ends. The completed bone plate installation is illustrated in FIG.
7. The incision is then sutured to complete the operation.
It will be appreciated by those skilled in the art that an improved
bone fracture compression device and method of usage achieving the
above-mentioned and related objectives may be embodied in variant
forms within the framework of the inventive concepts. However, the
illustrated embodiment is considered to be of optimum form and
design so as to achieve these various objectives in a degree which
is unique. Thus, while the invention broadly embraces the concept
of applying a measured force to the fracture site of a bone
fracture by applying compressive forces between a bone plate
attached to one segment of the fractured bone and to a bone screw
loosely inserted into a slotted aperture in the bone plate and
thence into the second bone segment with subsequent insertion and
tightening of a sufficient number of bone screws adjacent the
fracture site so as to apply and maintain the desired compressive
force across the fracture, it will be recognized that the
application of forces across the fracture site may be accomplished
by variant forms of the applicant's invention within the scope and
intent of the disclosure set forth above. It should be noted that
various means of attachment for the bone compression device to the
bone compression plate may be utilized and that while compression
has been applied across the fracture site by drawing a bone screw
positioned in the elongate slot of the compression plate toward a
fixed point located across the fracture situs, the concepts of this
invention may be accomplished by apparatus in which the bone screw
positioned in the elongate slot is forced away from the adjacent
end of the compression plate by a suitably configured bone
compression device having means to indicate applied force. It
should also be noted that while the knurled knob carrying the
torque indicating means is positioned on a shaft oriented
perpendicular to the bone compression plate, the apparatus would
work equally well with the shaft means oriented parallel to the
plate, in threaded engagement with the frame and slidable
subassembly. Thus, while a specific preferred embodiment has been
described in detail, it will be apparent to one skilled in the art
that various modifications may be made to the apparatus and method
disclosed above while remaining well within the scope and spirit of
the invention.
* * * * *