U.S. patent application number 10/115446 was filed with the patent office on 2002-12-12 for internal cord fixation device.
Invention is credited to Dakin, Edward B., Lippincott, Albert L. III.
Application Number | 20020188297 10/115446 |
Document ID | / |
Family ID | 22583891 |
Filed Date | 2002-12-12 |
United States Patent
Application |
20020188297 |
Kind Code |
A1 |
Dakin, Edward B. ; et
al. |
December 12, 2002 |
Internal cord fixation device
Abstract
Methods and apparatuses for fixing a bone fragment or a bone
prosthesis onto a bone. To affix a bone fragment to the bone, an
internal fastener is attached from within the interior of the bone
to a bone fragment with a length of flexible, inelastic cord
extending within the bone interior and attached to the fastener and
passing outwardly through an opening in a second bone fragment. The
fastener and cord are so positioned as to draw respective fracture
surfaces together to reduce the fracture when the cord is pulled
outwardly of the opening in the second bone fragment. A second
fastener desirably is attached to the bone opening, this fastener
including an open bore to receive the cord and a lock to secure the
cord to this fastener and maintain the cord under tension.
Inventors: |
Dakin, Edward B.; (Lindsay,
CA) ; Lippincott, Albert L. III; (Prior Lake,
MN) |
Correspondence
Address: |
Fredrikson & Byron, P.A.
1100 International Centre
900 2nd Avenue South
Minneapolis
MN
55402-3397
US
|
Family ID: |
22583891 |
Appl. No.: |
10/115446 |
Filed: |
April 2, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10115446 |
Apr 2, 2002 |
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09162036 |
Sep 28, 1998 |
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6368326 |
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Current U.S.
Class: |
606/62 ; 606/103;
606/304; 606/313; 606/323; 606/327; 606/328; 606/60; 606/74;
606/916 |
Current CPC
Class: |
A61B 17/842 20130101;
Y10S 606/916 20130101; A61B 17/8861 20130101; A61B 17/683 20130101;
A61B 2017/044 20130101 |
Class at
Publication: |
606/72 ; 606/60;
606/73; 606/103 |
International
Class: |
A61B 017/58 |
Claims
I claim:
1. An orthopedic fixation system for fixing a bone to an element
which is a bone fragment or a prosthesis, comprising a length of
flexible, inelastic cord, a first fastener for attaching the cord
to said element; a second fastener for fastening the cord to the
bone, at least one of the fasteners having an opening through which
the cord may pass from the interior of the bone to the exterior to
enable said element to be securely mounted to the bone portion.
2. An orthopedic fixation system comprising a bone having an
exterior cortical portion and a non-cortical interior, an element
which is a prosthesis or a bone fragment, a length of inelastic,
flexible cord; a first fastener attaching the cord to said element,
a second fastener attaching the cord to the bone, the cord
extending from said first fastener within the interior of the bone
to the second fastener.
3 The orthopedic fixation system of claim 2 wherein at least one of
said fasteners includes an opening through which said cord passes
from the interior of the bone to the exterior, said at least one
fastener including a lock for locking the cord to the fastener
through which it passes.
4. The orthopedic fixation system of claim 3 wherein at least one
of said fasteners includes a threaded portion adapted to be screwed
into bone.
5. The orthopedic fixation system of claim 2 wherein said element
is a bone fragment resulting from a fracture of said bone, said
bone fragment and bone having mating fracture surfaces that are
prevented from separating by said cord extending between them.
6. The orthopedic fixation system of claim 5 wherein at least one
of said fasteners includes an elongated toggle portion adapted to
pass in a generally coaxial direction through a bore formed in said
bone or bone fragment and to assume a position generally normal to
said axis against an outer surface of said bone or bone
fragment.
7. The orthopedic fixation system of claim 5 wherein at least one
of said fasteners includes a threaded portion adapted to be screwed
into bone.
8. The orthopedic fixation system of claim 5 wherein at least one
of said fasteners includes a bone plate adapted to engage a bone
surface.
9. The orthopedic fixation system of claim 5 including a third
fastener fastenable to bone and having a surface within said
interior over which said cord may be movably trained to change the
direction of said cord between the first and second fasteners.
10. The orthopedic fixation system of claim 5 wherein at least one
of said fasteners includes an opening through which said cord
passes from the interior of the bone to the exterior, said at least
one fastener including a lock for locking the cord to the fastener
through which it passes.
11. The orthopedic fixation system of claim 10 wherein said opening
comprises a bore at least partially threaded and within which the
cord extends, and wherein said lock comprises a threaded member
threadingly received in the bore and capable of engaging said cord
to restrain cord movement.
12. The orthopedic fixation system of any one of claims 2-11
including a tensioning instrument adapted to contact the cord and
at least one of said fasteners to place the cord in tension by
drawing said cord outwardly through said fastener.
13. A bone fracture reduction system for reducing and promoting
healing of a bone fracture, comprising a bone normally having an
exterior cortical portion and a non-cortical interior, the bone
having bone fragments with generally confronting fracture surfaces,
an internal fastener attached from within said interior to a first
bone fragment, a length of flexible, inelastic cord extending
within said bone interior and attached to said internal fastener
and passing outwardly through an opening in a second bone fragment,
said internal fastener and cord being so positioned as to draw
respective fracture surfaces together to reduce said fracture upon
tensioning of the cord extending outwardly through said
opening.
14. The bone fracture reduction system of claim 13 including a lock
locking the cord to said second fragment.
15. The bone fracture reduction system of claim 14 wherein said
interior fastener includes a threaded portion screwed into said
cortical portion from within said bone interior.
16. The bone fracture reduction system of claim 13 wherein said
first bone fragment has an outer, cortical surface and wherein said
first fastener includes an elongated toggle supported against said
outer surface portion.
17. The bone fracture reduction system of claim 13 including an
external fastener attached to said second fragment and having a
hollow interior through which said cord extends.
18. The bone fracture reduction system of claim 17 wherein said
hollow interior of the second fastener is at least partially
threaded, and wherein said lock comprises a threaded member
threadingly received in said hollow interior, said cord being
operatively grasped between said threaded member and said hollow
interior to restrain cord movement within said second fastener.
19. The bone fracture reduction system of claim 17 wherein said
bone is a long bone having a medullary cavity, said internal
fastener being carried attached from within the medullary canal to
one of the bone fragments and said length of flexible, inelastic
cord extending from said internal fastener through said external
fastener across a fracture interface and more closely adjacent one
side of said medullary canal than the other side thereof, the bone
fracture reduction system including a second flexible, inelastic
cord and an external fastener attached to said second fragment and
through which said second cord extends, said second cord being
arranged on generally the opposite side of said medullary canal
from said first cord, whereupon said cords may be independently
adjusted so as to resist bending moments applied at the transverse
fracture site.
20. The bone fracture reduction system of claim 19 wherein said
internal fastener comprises a pair of fasteners each having
threaded portions threaded into said first bone fragment on
opposite sides of the medullary canal.
21. The bone fracture reduction system of claim 19 wherein said
internal fastener comprises an elongated fastener adapted for
insertion and capture within the medullary canal of the first bone
fragment with said cords extending from said fastener adjacent
opposite sides of the intermedullary canal.
22. The bone fracture reduction system of claim 13 wherein said one
bone fragment has a bore extending through its cortical portion and
wherein said second fastener includes a plate adapted to engage the
outer surface of the cortical portion.
23. The bone fracture reduction system of claim 13 including a
third fastener fastened from the interior of said bone to a third
bone fragment and having a pulley surface over which said cord is
movably trained to change the direction of said cord within the
interior of said bone.
24. The bone fracture reduction system of claim 13 including a
plurality of internal fasteners attached from within said bone
interior to different ones of said bone fragments, said fasteners
and cord being so positioned as to draw respective fracture
surfaces of said bone fragments together to reduce said fracture
upon tensioning of the cord extending outwardly through said
opening.
25. The bone fracture reduction system of claim 23 wherein at least
one of said interior fasteners includes a pulley surface over which
said cord is movably trained to change the direction of said cord
within the interior of said bone.
26. The bone fracture reduction system of claim 23 wherein each of
said interior fasteners includes a pulley surface over which said
cord is movably trained to change the direction of said cord within
the interior of said bone.
27. Method for positioning fragments of a bone fracture with
respect to each other to reduce the fracture and promote healing of
a bone which normally has an exterior cortical portion and a
non-cortical interior, the bone fragments having confronting
fracture surfaces forming a fracture interface, the method
comprising attaching from within the interior of the bone to a
first bone fragment an internal fastener to which is attached a
length of flexible, inelastic cord, drawing said cord through a
bore formed in a second bone fragment to draw said fragments
together in a direction to relieve the fracture.
28. The method of claim 27 including the step of securing the cord
to said second bone fragment to restrain separation of the bone
fragments at the fracture interface.
29. The method of claim 27 including the step of determining the
direction of tensile force desired to draw said fracture surfaces
toward each other, and positioning said cord parallel to said
direction.
30. The method of claim 27 wherein said internal fastener has a
threaded end, the method including the step of screwing said
threaded end from the interior of said bone into a cortical portion
of said first bone segment.
31. The method of claim 27 wherein said internal fastener has an
elongated toggle portion, the method including the step of forming
a bore through said first bone fragment, and passing said toggle
from the interior of the bone through said bore to enable the
toggle to lie against a cortical outer surface of said first bone
fragment.
32. The method of claim 27 including the step of attaching to the
second bone fragment an external fastener through which the cord
can be drawn, and locking the cord to the latter fastener.
33. The method of claim 32 including the step of providing a
tensioning instrument having a first portion grasping said cord and
a second portion in contact with said external fastener, and
operating said instrument so as to separate said portions and to
place said cord in tension.
34. The method of claim 27 comprising attaching a plurality of
internal fasteners to different ones of a plurality of bone
fragments, said internal fasteners having attached to them said
length of flexible cord, said internal fasteners being so
positioned with respect to each other that when said cord is
tensioned, said fragments are drawn together in directions to
reduce the fracture.
35. The method of claim 34 wherein at least one of said interior
fasteners includes a pulley surface over which said cord is movably
trained to change the direction of said cord within the interior of
said bone, the method including the step of pulling said cord over
said pulley surface.
36. The method of claim 34 wherein each of said interior fasteners
includes a pulley surface over which said cord is movably trained
to change the direction of said cord within the interior of said
bone, the method including the step of pulling said cord over said
pulley surfaces.
37. Method for reducing a bone fracture in a bone having a cortical
exterior portion and a non-cortical interior, said fractured bone
having at least three bone fragments in which first and second
fragments have first mating fracture surfaces and second and third
bone fragments have second, different mating fracture surfaces, the
method comprising attaching one end of a length of flexible cord
from within the bone interior to the first bone fragment, attaching
a pulley bearing said cord to the second bone fragment, the other
end of said cord passing outwardly of the bone through an opening
in the third bone fragment, tensioning said cord to draw together
said mating fracture surfaces to relieve the fractures, and
securing said tensioned cord to said third bone fragment.
38. Method for reducing a bone fracture comprising at least two
pairs of bone fragments, a first pair of bone fragments having
first mating fracture surfaces and a second pair of bone fragments
having second, different mating fracture surfaces, and wherein one
bone fragment may be common to each of the first and second pairs,
the bone having an exterior cortical portion and an interior
non-cortical portion, the method comprising a. attaching one end of
a length of flexible cord from the interior of the bone to one
fragment of said first pair, said cord extending through an opening
in the other bone fragment of said first pair in a direction so
that when said cord is placed in tension, the first mating fracture
surfaces are drawn toward each other; b. attaching one end of a
second length of flexible cord from the interior of the bone to one
fragment of said second pair, said second length of cord extending
through an opening in the other bone fragment of said second pair
in a direction so that when said cord is placed in tension, the
second mating fracture surfaces are drawn toward each other; and c.
appropriately adjusting tension in said cords with respect to each
other to reduce the fracture surfaces.
39. The method of claim 38 including the step of securing the
tensioned cords to said other bone fragments.
40. Method for reducing a bone fracture of a bone having a cortical
exterior portion and a non-cortical interior, the fracture
comprising at least three bone fragments each having fracture
surfaces mating with fracture surfaces of the other fragments, the
method comprising: a. attaching from the interior of the bone to
each of two of said bone fragments a fastener having a pulley
surface over which is trained a length of flexible cord; b. drawing
said cord through an opening in a third bone fragment and
tensioning said cord to draw said fracture surfaces together; and
c. securing said cord to said third bone fragment to respect to
each other to reduce the fracture surfaces.
41. Method for reducing a bone fracture of an elongated bone having
a medullary canal and a generally transverse fracture dividing the
bone into first and second bone fragments, comprising a. attaching
from the interior of the bone to one of said bone fragments an
internal fastener from which extends at least two flexible,
inelastic cord lengths; b. drawing said cord lengths through
openings formed in said second bone fragment at spaced positions
along the interior of the medullary canal of that fragment so that
said cord lengths are spaced from one another within the medullary
canal at the fracture site; and c. securing said cords to said
second bone fragment to reduce the fracture surfaces, said spaced
cords resisting bending moments at the fracture site.
42. A bone fracture reduction system for use in reducing a fracture
of a long bone producing first and second bone fragments,
comprising an internal fastener adapted for insertion and capture
within the medullary canal of one bone fragment, a pair of
flexible, inelastic cords attached at laterally spaced points to
and extending from said internal fastener, and a pair of spaced
external fasteners attachable to the other of said bone fragments
and having openings through which said cords may respectively pass
on opposite sides of the medullary canal, whereby said cords may
traverse the fracture site within the medullary canal on opposite
sides thereof to resist bending moments at the fracture site.
Description
FIELD OF THE INVENTION
[0001] This invention pertains to the field of fixation devices for
bones.
BACKGROUND OF THE INVENTION
[0002] Simple fractures of bones are readily treated by bringing
the fracture surfaces together and holding them in the desired
orientation with respect to one another through the use of splints,
casts and the like. Bones in general have dense outer, strong
cortical portions and interior, non-cortical portions that may
include cancellous bone.
[0003] Comminuted fractures and fractures involving the breakage of
a bone into numerous bone fragments are more difficult to deal with
since one must attempt to reposition each bone fragment in an
orientation relative to each other bone fragment so that the
fragments may knit together properly. For this purpose, physicians
have often used metal plates that attach to the outer cortical
surfaces of the bones and which utilize bone screws to hold the
bone fragments in position.
[0004] Another method involves the use of cerclage procedures in
which a wire is, in effect, wrapped about a broken bone to hold the
fragments in place, the cerclage wire occasionally penetrating
through the bone. Reference is made to Johnson et al., U.S. Pat.
No. 4,146,022. Yet another method taught in Berger, U.S. Pat. No.
5,658,310, involves anchoring the balloon portion of a balloon
catheter in the medullary cavity at one end of a long bone having a
transverse fracture, and stretching the remaining portion of the
elastic catheter across the fracture interface within the bone to
maintain the fracture interface in compression. It would appear
that unless the elastic catheter traverses the precise center of
the bone at the fracture site (which may be difficult to
accomplish, considering the bowed or curved nature of most bones),
compressive forces will be uneven across the fracture site. That
is, the compressive forces on the side of the bone nearest the
catheter will be greater than the compressive forces on the
opposite side of the bone, generating an unwanted bending moment
across the fracture site.
[0005] Surgical procedures used to mount bone plates and cerclage
elements to a bone often require supportive tissue that is normally
joined to the bone to be cut from the bony tissue to enable direct
visual access to the bone. With cerclage procedures, one must
entirely encircle a bone in order to hold the bony parts
together.
[0006] Procedures using bone plates and cerclage elements often
tend to interrupt blood flow to the damaged bone fragments, and
thus hinder the healing process. Moreover, the use of bone plates
and cerclage elements, particularly the former, can lead to stress
shielding of the fracture site. It is well known (Wolff's law) that
bone growth is stimulated when stress is applied. However,
continuous, excessive pressure applied to a bone may cause unwanted
resorption of bone at the pressure site. In order to promote
healing of bone fractures, the fracture surfaces that are brought
together during reduction of the fracture should be subject to
cyclic or periodic compressive forces so as to stimulate the growth
of new bone across the fracture interface without causing bone
resorption. When a fracture interface is immobilized, as by a cast,
the bone material that is deposited at the fracture interface may
have a collagen fiber matrix that is random rather than aligned
with the fiber matrix of bone on either side of the fracture, the
healed fracture interface being weaker in tension than bone on
either side of the interface.
[0007] Some bone fractures result in the production of many bone
fragments, and proper reduction of the fracture requires the
fragments to be carefully reassembled next to each other with their
fracture surfaces in contact. Bone screws and bone plate devices
commonly are used for this purpose. Using bone screw techniques,
two bone fragments may be joined together, and these two fragments
as a unit may be moved into approximation with a third fragment and
joined to it, and so on. Fragments that are thus joined together by
rigid screws cannot move with respect to other fragments, and
mismatching of the fracture surfaces as the first several fragments
are joined together can have a compounding effect, causing
mal-union or non-union of fracture surfaces and resulting in far
less than perfect bone fragment assembly and healing.
SUMMARY OF THE INVENTION
[0008] The invention involves an orthopedic fixation system for
fixing a bone to an element which is a bone fragment or a
prosthesis. The system includes a length of flexible, inelastic
cord, a first fastener for attaching the cord to the element; and a
second fastener for fastening the cord to the bone. At least one of
the fasteners has an opening through which the cord may pass from
the interior of the bone to the exterior to enable the element to
be securely mounted to the bone.
[0009] In one embodiment, the invention involves a fracture relief
system in which bone fragments are brought together by internal,
inelastic flexible cords to counter forces tending to widen the
fracture interfaces when the bone is stressed through normal,
though often restricted, physical activity of a patient. Movement
of fracture surfaces away from each other thus is prevented, but
the flexible, inelastic cords do not restrict the transfer of
compressive stress from one fragment to another across fracture
interfaces during physical activity. That is, the cords do not
prevent the bone fragments forming a fracture interface from
converging slightly to enable stress transfer. Due to their
inelastic nature, the flexible cords do not maintain the fracture
interface in compression during rest, and thus resorption of bone
due to excessive constant compressive force is largely avoided.
[0010] In another embodiment, the invention relates to a bone
fracture reduction system for positioning bone fragments with
respect to each other to reduce a fracture and promote healing. The
system comprises a flexible, inelastic cord having an end portion,
a fastener attached to the end portion of the cord and adapted for
attachment to a bone fragment in a direction generally coaxial to
the axis of the end portion, and a second fastener attachable to
the other bone fragment and having an opening through which the
cord can be drawn to place the cord in tension. The second fastener
includes a lock for locking the cord to the second fastener to
restrain separation of the bone fragments.
[0011] In a further embodiment, the invention provides a bone
fracture reduction system for reducing and promoting healing of a
bone fracture. The fracture reduction system comprises a fractured
bone normally having an exterior cortical portion and a
non-cortical interior, the bone having bone fragments with
confronting fracture surfaces. An internal fastener is attached
from within the bone interior to a first bone fragment with a
length of flexible, inelastic cord extending within the bone
interior and attached to said fastener and passing outwardly
through an opening in a second bone fragment. The fastener and cord
are so positioned as to draw respective fracture surfaces together
to reduce the fracture upon tensioning of the cord extending
outwardly through said opening. A second, external fastener
desirably is attached to the bone opening, this fastener including
an open bore to receive the cord and a lock to secure the cord to
this fastener.
[0012] The invention also relates to a method for positioning
fragments of a bone fracture with respect to each other to reduce
the fracture and promote healing of a bone which normally has an
exterior cortical portion and a non-cortical interior, the bone
fragments having confronting fracture surfaces forming a fracture
interface. The method comprises attaching from within the interior
of the bone to a first bone fragment an internal fastener to which
is attached a length of flexible, inelastic cord, and drawing the
cord through an opening formed in a second bone fragment to draw
the fragments together in a direction to reduce the fracture. The
cord preferably is secured to the second bone fragment to maintain
the bone fragments in a predetermined position to transfer
compressive loads through the fracture interface during physical
activity. Desirably, the method includes the step of determining
the direction of tensile force desired to draw the fracture
surfaces together, and positioning the cord approximately parallel
to that direction. A tensioning instrument may be provided, the
instrument having a first end portion grasping the cord that
protrudes outwardly from the second bone fragment and a second end
portion in contact with the external fastener, the method including
the step of operating the instrument so as to separate said end
portions and thus place the cord in tension to draw the bone
fragments into the desired position.
[0013] A plurality of internal fasteners may be fastened to
different ones of a plurality of bone fragments, the internal
fasteners having attached to them the length of flexible inelastic
cord. The internal fasteners are so positioned with respect to each
other that when the cord is tensioned, the bone fragments are drawn
together in directions to properly join their respective fracture
surfaces. As desired, one or more of the interior fasteners may
include a pulley surface, such as that provided by an eyelet, over
which the cord is movably trained to change the direction of the
cord within the interior of the bone, the method including the step
of pulling the cord over the pulley surface to tension the cord and
properly position the bone fragments with respect to each
other.
[0014] The flexible, inelastic cord system and methods of the
invention may be employed to mount prosthetic devices to bone, such
as acetabular cups to the acetabulum, bone plates to long bones,
etc. Speaking broadly, a length of flexible, inelastic cord may be
fastened at one end to a bone of a patient, the cord extending
within the bone to a prosthesis which is to be held to the bone.
For example, in the case of an acetabular cup, several cords may be
employed that extend generally radially outwardly of the cup within
the pelvis to maintain the acetabular cup in position.
BRIEF DESCRIPTION OF THE DRAWING
[0015] FIG. 1 is a partial cross sectional view of a fractured bone
to which a cord fracture fixation device of the invention is being
applied to reduce the fracture;
[0016] FIG. 2 is an exploded view, in partial cross section, of a
device of the invention shown in FIG. 1;
[0017] FIG. 3 is a partially exploded view, in partial cross
section, of the device shown in FIG. 2;
[0018] FIG. 4 is a partially exploded view, in partial cross
section, of a modification of the device shown in FIG. 3;
[0019] FIG. 5 is a partially exploded view, in partial cross
section, of another modification of the device shown in FIG. 3;
[0020] FIG. 6A is a view in partial cross section, of a fastener of
the invention having a pulley surface;
[0021] FIG. 6B is an exploded view of another fastener useful in
the invention;
[0022] FIG. 7 is a perspective view, partially broken away, of a
step in the installation of the pulley attachment element of FIG.
6A;
[0023] FIG. 8 is a partial cross sectional view of a fractured bone
to which several cord fracture fixation devices are being applied
to reduce the fracture;
[0024] FIG. 9A is a broken away cross sectional view of an elbow
olecranon fracture to which a fracture fixation device of the
invention is being applied;
[0025] FIG. 9B is a broken-away, cross sectional view taken along
line 9B-9B of FIG. 9A;
[0026] FIG. 10 is an end-on cross sectional view of a fractured
bone to which a fracture fixation device of the invention has been
applied;
[0027] FIG. 11A is a side view of a bone plate shown also in FIGS.
9A and B;
[0028] FIG. 11B is a top view of the plate of FIG. 11A;
[0029] FIG. 11C is a cross sectional view taken along line 11C-11C
of FIG. 11B;
[0030] FIG. 12A is a schematic representation of the pelvis,
showing the location of a fracture in the ilium to be reduced by a
method of the invention;
[0031] FIG. 12B is a cross sectional view of the pelvis of FIG. 12A
showing a step in the reduction of the fracture; and
[0032] FIG. 12C is a cross sectional view of the pelvis of 12A
showing the reduced bone.
[0033] FIG. 13A is a schematic perspective view of a portion of the
pelvis showing an acetabular cup prosthesis held in position by a
cord system of the invention;
[0034] FIG. 13B is a partially broken away side view of the
prosthesis shown in FIG. 13A;
[0035] FIGS. 14A, B and C are schematic representations of the
distal end portion of the humerus showing different steps in the
placement of a cord system of the invention;
[0036] FIG. 14D shows a toggle type cord fixation system employed
in the humerus mounted on a flexible installation rod and shown
during insertion of the toggle;
[0037] FIG. 14E is a perspective view of a toggle of the type shown
also in FIG. 14D; and
[0038] FIG. 14F is a schematic view, in partial cross section, of
the humerus showing a fracture relieved through the use of the
toggle and cords shown in FIGS. 14A-14E.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] As used herein, "cord" refers to any of a variety of
materials that are strong in tension, inelastic, flexible, and
biocompatible. If desired, the cord can be made of an organic
suture material, or may be made from bioabsorbable materials such
as poly (lactic acid). Preferably, however, the cord is made of a
metal wire, preferably in the form of a metal wire braid for
improved flexibility. Stainless steel is an appropriate and
preferred material. The cords are sufficiently flexible so that
they substantially straighten within the bone interior when placed
under sufficient tension to draw bone fragments together, that is,
under a tension of about 5 or more newtons. The cords may be made
of a single material or composite, or may include sections of
different materials chosen for their particular properties such as
strength, flexibility, and radiopacity to enable the cords to be
readily visualized by fluoroscopy.
[0040] The cords are sufficiently flexible as to exhibit
substantially no axial compressive strength; that is, strength to
resist axially applied compressive forces. The cords may be
sufficiently stiff as to enable cord ends to be threaded through
the eyelets of pulley-like fasteners and the like, but not
sufficiently stiff to prevent bone fragments joined by a cord from
converging, as is the case with, for example, bone screws or rigid
pins such as Steinman pins.
[0041] The cords also are inelastic. "Inelastic", as used herein,
means that when a cord is placed in sufficient tension to draw bone
fragments together, i.e., under tensile forces ranging generally
from about 5 to about 800 newtons, the cord stretches elastically
only a very small amount if at all, so that the internal cord
lengths extending from one bone fragment to another within a bone
are under essentially no tension after the fragments have been
properly anastomatized. Preferably, the cords demonstrate elastic
recovery at body temperature of no more than about 10% upon release
of a stretching force of 800 newtons.
[0042] As a result, the fracture interfaces are not stressed in
compression by the cords when a patient is at rest, compression
stress instead being applied intermittently through physical
activity.
[0043] Referring first to FIG. 1, which illustrates a simple
version of the invention, a fractured bone 10 is shown in schematic
form as having a cortical portion 12 and an interior portion 14
that is non-cortical. "Cortical" bone refers to the hard, dense,
outer shell of a bone that bears stress in normal physical
activities. The interior or non-cortical portion of some bones may
simply be hollow, or may have interconnected trebeculae of
cancellous bone. The cortical shell portion of bones typically
ranges in thickness from about 2 to about 10 mm. As shown in FIG.
1, the bone has been broken into two bone fragments 16, 18. The
fracture surfaces of these bone fragments are shown at 16.1 and
18.1, respectively.
[0044] In the cortical bone portion 12 of fragment 18, there is
placed a screw-type internal fastener 20, the designation
"internal" referring to the fact that the fastener is attached to
the bone fragment 18 from within the non-cortical interior of the
bone. A flexible cord 22 attached to the fastener 20 extends across
the interior of the bone as shown. Another screw-type fastener 24
is attached to the cortical portion of the other bone fragment 16.
Fastener 24 may be termed an "external" fastener because it is
attached to the bone fragment 16 from the exterior of the bone
rather than the interior. Fastener 24 has a hollow bore through
which the cord 22 passes to the exterior of the bone. A
hand-operated cord tensioning instrument 26, which bears against
the fastener 24 and also which pulls the cord 22, is used to
tension the cord. A commercially available instrument of this type,
commonly known as a Hall tensioning instrument, is described in
Hall, U.S. Pat. No. 4,050,464, the teachings of which are
incorporated herein by reference.
[0045] Fasteners 20 and 24 are so positioned that when the cord
between them is placed in tension, the fracture surfaces 16.1, 18.1
will be brought together at a fracture interface with the interface
being maintained under compression as long as the cord 22 is
maintained in tension. The external fastener 24 is provided with a
locking device 28 in the form of a screw that is received in a
threaded bore in the fastener 24 and which, in this embodiment,
clenches the cord between the fastener and screw to hold it in
place. The tensioning instrument 26 is operated until the cord 22
between the fasteners is straightened and the fracture surfaces of
the fragments are properly joined. While moderate cord tension is
maintained, the locking screw 28 is inserted in the fastener 24 to
clamp the cord in place. Slight further movement of the fragments
toward each other relieves the tension in the cords, and the cords
thereafter serve to prevent separation of the fracture surfaces as
a patient engages in normal (although likely initially restricted)
physical activity while freely permitting stress transfer across
the fracture interfaces. Inasmuch as the newly formed bone at the
fracture interface is subjected to stresses normally borne by that
bone, the resulting collagen fiber matrix having the correct
alignment and providing a strong union between bone fragments.
[0046] It is of importance to properly locate the fasteners 20, 24
so that the resulting direction of the cord 22 is such as to reduce
the fracture and maintain the bone fragments in the proper position
for healing. A variety of devices and instruments may be employed
to properly place the fasteners. Internal fastener 20 can generally
be placed where needed because the fracture site itself is open and
accessible to the surgeon.
[0047] The procedure associated with FIG. 1 involves the steps of
gaining access from the interior of the bone to the desired
position for the fastener 20, drilling a small pilot hole through
the cortical bone at this location from the bone interior,
providing the fastener 20 with cord attached, and threading the
fastener into the pilot hole, the fastener cutting its own threads.
If the site for the fastener 20 cannot be readily accessed, an
access hole can be drilled into the opposite side of the bone
across from the desired site and the site may be accessed through
this hole with the cord being drawn downwardly (in FIG. 1) through
the hole formed for the external fastener 24. Although the
fasteners 20, 24 in FIG. 1 and the fasteners described below are
illustrated as having an elongated portion (threaded in FIG. 1)
that extends approximately perpendicular to the surface of the
bone, the fasteners may be attached at such other angles to the
bone surface as may be appropriate to allow the force vector of the
cord to parallel the axis of the fastener.
[0048] As described in greater detail below, one may employ a
flexible, elongated tool to reach into the bone interior to
properly place the fastener. A guide wire may first be placed in
the bone interior with the tip of the wire adjacent the position of
the desired internal fastener. The elongated tool may have a hollow
interior to enable it to slide over the guide wire and into the
proper position, following which the tool may be operated to
perform the needed drilling and fastener replacement procedures.
Fluoroscopy may be employed to aid the surgeon in this
procedure.
[0049] The surgical procedures involved in the present invention
are particularly beneficial for several reasons. First, through
careful placement of the fasteners, the desired force vectors may
be obtained to pull two or more bone fragments together and affect
proper union of their respective fracture surfaces. Second,
placement of the fasteners is a fairly simple technique and does
not require substantial tissue division or removal of supportive
tissue (i.e., muscle, tendon) from a bone.
[0050] FIGS. 2 and 3 show the fastener and cord structure described
above in connection with FIG. 1. The cord 22 may have an enlarged
end portion 22.1 which may be a crimped-on sleeve, a welded-on
collar, etc. The cord 22 is inserted in a hollow bore 20.1 formed
through the fastener 20, the enlarged end 22.1 of the cord coming
to rest within an enlarged distal end portion 20.2 of the bore. The
proximal end 20.3 of the internal fastener 20 is provided with an
appropriate shape, such as a hexagonal perimeter or recess, to
enable it to be turned by an appropriate tool such as a hollow,
flexible nut driver as shown in FIG. 7 or an Allen wrench, or by
some other means.
[0051] Internal fastener 20 desirably has self-cutting threads 20.4
of a design commonly utilized for bone screws. The cord and the
fasteners must be sufficiently strong, of course, to bear the
expected tensile stress to be placed on the cord. The external
fastener 24 in FIGS. 2 through 5 has similar thread-cutting threads
24.2, and a generally hexagonal head or other appropriate shaped
proximal end 24.1 to receive a tool such as the nut-driver of FIG.
7, the tool preferably having a hollow interior through which may
pass the cord 22.
[0052] As shown best in FIG. 2, the exterior fastener 24 has an
interior bore 24.3 sized to slidingly receive the cord 22. At the
proximal end of this fastener, the bore has a widened, proximally
open portion with interior threads 24.4 sized to threadingly
receive the threads 28.1 of a locking screw 28. The threaded bore
24.4 has one or more, preferably four, circumferentially spaced,
axially extending slots 24.5 that are sufficiently wide to permit
the cable to pass into them as shown in FIGS. 3-5. Locking screw 28
is formed with a rounded distally facing nose 28.2 configured to
come into contact with the cord when the cord extends through the
slot 24.5, as shown in FIG. 3, the cord being pinched between the
nose 28.2 and the interior of the fastener 24 to lock the cord in
place. In the event the cord must be re-tensioned to adjust the
position of a bone fragment, the locking screw 28 can be backed out
readily from the fastener 24, the cord re-tensioned as needed, and
the locking screw 28 repositioned in the fastener.
[0053] Several different internal fasteners are shown in FIGS. 4
and 5. FIG. 4 illustrates a fastener 20.5 in the form of a toggle,
the fastener having an elongated, axially slotted shank 20.6
carrying at its distal end a pair of elongated arms 20.8 capable of
swinging from the folded position shown in dashed lines in FIG. 4
to the fully extended position shown in solid lines in FIG. 4, the
arms being pivotally attached to the shank by a pivot pin 20.7. In
use, the internal fastener 20.5 is passed from the interior of the
bone through a hole formed in a bone fragment until the arms 20.8
clear the hole, following which the arms may move into the position
shown in solid lines in FIG. 4 to contact the outer surface of the
bone and thus anchor itself to the bone.
[0054] FIG. 4 also shows, as the exterior fastener, a dynamic
compression plate 24.5 of known design, the plate having a ramped
orifice 24.6. Within the orifice is received a complementary shaped
insert 24.7 having an aperture 24.8 threaded to receive the locking
screw 28. Cord 22 extends through the aperture 24.8, and the
locking screw locks the cord to the insert.
[0055] Illustrated in FIG. 5 is an internal fastener 20.9 having a
body carrying a pair of spring-loaded arms 30. Arms 30 are capable
of being elastically pressed inwardly against the body 30.1 of the
fastener to enable the fastener to be received through a bore
formed in a bone fragment, the arms 30 springing outwardly into
contact with the walls of the bore to anchor the fastener in place.
Various other fasteners of the types used to anchor sutures, such
as the well known "fishhook" types, may be used.
[0056] As described in greater detail below, the internal fastener
may have an internally extending eyelet or ring to provide a
pulley-like surface over which the cord may be trained. With
reference particularly to FIGS. 6A and 7, fastener 32 is provided
with a body 32.1 having self-tapping threads adapted to screw into
cortical bone (into which is first preferably drilled a small pilot
hole) and a hexagonal head 32.2. The fastener includes a swivel
body 32.3 that carries an eyelet 32.4 and that is attached to the
threaded body 32.1 by means of a swivel mounting shown best in FIG.
6A. As illustrated, the threaded body 32.1 may have a hollow
interior within which is rotatably mounted the swivel body with the
latter having a flared end engaging the threaded body and
preventing the swivel body from escaping.
[0057] Referring now to FIG. 7, a tool for mounting the threaded
internal fasteners of the invention is shown generally at 34. The
tool includes a distal end 34.1 having a hexagonally shaped recess
to encounter the hexagonally shaped head portion of the fasteners,
but Allen wrench configurations (in which the tool has a solid
hexagonal end portion and the fastener head has a hexagonal recess)
and various other tool/fastener shape configurations may be used as
well. The tool includes an elongated body portion 34.2 and handle
portion 34.3 which may be conveniently knurled, as shown.
Desirably, the tool is hollow so that a cord 22 can pass entirely
through the tool, through the eyelet 32.4 of the fastener 32, and
back through the handle of the tool. In this fashion, when the tool
is rotated about its axis to thread the threaded body 32.1 into
cortical bone, the proximally extending eyelet 32.4 may remain
substantially rotationally stationary to avoid twisting the cord.
If desired, the distally open end 34.1 of the tool may have an
axially extending, distally open slot such as that shown at 34.4
through which the cord 22 may extend when fasteners of the type
shown in FIGS. 1-3 are threaded into bone. As mentioned above, the
hollow interior of the tool may be employed to follow over a
previously placed guide wire.
[0058] FIGS. 8-10 illustrate various ways in which the devices of
the invention may be employed. Referring first to FIG. 8, an
elongated bone 10 is shown as having been broken into three bone
fragments 36, 38 and 40. Cord systems of the type shown in FIGS.
1-3 are mounted at solid, unbroken end portions of the bones, the
cords being shown as 42 and 44. A series of small bone plates 46,
each having a curved bottom surface to fit against the exterior of
the bone, are provided. Each of the bone plates has a central bore
46.1 for receiving an external fastener 24 and has one or more
bores 46.2 extending within the bone plate generally parallel to
the axis of the bone and capable of slidably receiving the cords
42, 44. One fracture 38.1 is reduced through the use of the cords
42.1, 42.2, and the other fracture 38.2 is reduced through the use
of cords 42.3 and 42.4. Note that the latter cords each have
proximal ends passing through a single external fastener 24. The
cords 42, 44 extend laterally through the bores 46.2 in the bone
plates, the cords being appropriately manipulated to properly bring
together the fracture surfaces of the bone fragments. Cords 42, 44
may be locked to the end-most bone plates and to such other plates
as may be desired through use of such locking devices as are
typified in FIGS. 11A-11C; that is, a threaded bore such as that
designated as 56.7 in these figures may be formed in the bone
plates of FIG. 8 at an angle to and intersecting the cord-receiving
bores 46.2. A set screw 46.3 or the like may be threaded into the
threaded bore to engage the cord and lock it to the plate.
[0059] FIGS. 9A and 9B show the reduction of an olecranon fracture
of the type that might result from trauma to the ulna by a fall on
the outstretched hand, i.e., by the severely tensioned triceps. It
is important here to reduce the fracture by drawing the bone
fragments together and maintaining the fragments in proper
alignment during healing, the fracture interface resisting
separation under the force of the triceps. Here, an internal
fastener 32 of the type shown in FIGS. 6A and 7 is placed from
within the interior of the bone into the bone fragment 48, as shown
in FIG. 9A. A second interior fastener 50 is placed distally from
the fracture site within the ulna, as shown in the drawing, the
vector between the fasteners 32, 50 denoting the direction of the
resulting tensile forces that will be placed on the cord 52
extending between them. The fastener 50 may, if desired, include a
pulley surface of the tape provided by the eyelet 32.4 of the
fastener 32 in FIG. 9A, or may be of a different design such as the
type shown in FIG. 6B. The latter fastener comprises a ring 50.1 to
be received against the surface of the bone 54, and a bone screw
50.2 having a ring-contacting wide head such as the hexagonal head
shown at 50.3, the threaded portion of the screw 50.2 being sized
to pass through the ring 50.1 and into a pilot hole 54.1 formed in
the bone to securely fasten the fastener 50 to the bone. Cords 52,
52.1 are attached to the fastener by a crimp such as shown at 50.4
or by other means.
[0060] Fractures of such bones as the olecranon and the patella can
result from extremely high tensile forces that are generated, in
the case of the olecranon, by the triceps muscle, and, in the case
of the patella, by the quadriceps muscle group. Reduction of
fractures in these bones in the past has been accomplished through
the use of external wires in what has become known as a "figure of
eight" technique, the wires being trained around the ends of pins
protruding from the bone fragments and the wires themselves laying
against the outer bone surface. This external fixation technique
has many of the drawbacks associated with cerclage techniques in
that placement of the wires requires exposure of substantial
exterior bone surface areas with associated loss of connective and
supportive tissue. The use of extensive external wire structures
can be largely avoided or eliminated in accordance with the present
invention.
[0061] Referring again to FIG. 9A, the cord 52 extends from the
fastener 50 through the eyelet 32.4 of the fastener 32 and thence
out through an opening formed in the bone. If desired, the fastener
50 can be attached by utilizing screw fasteners having
self-drilling and self-tapering screw portions, as shown in FIG. 7.
An elongated tool having a right-angled drill adapter can be
employed to attach the fastener to the bone. The cord 52.1
similarly is drawn out through the opening formed in the bone. An
exterior fastener of the type described in connection with FIGS.
1-3 may be employed at the opening of the bone, the cords 52, 52.1
passing outwardly through the fastener. After suitable tension has
been applied to the cords, the cords can be secured to the fastener
in the manner described above. If desired, the external fastener
may include a bone plate 56 as shown. Preferably, two generally
parallel but transversely spaced cord systems are employed, as
shown in FIG. 9B.
[0062] It will be understood that as the cord 52 is tensioned, the
bone fragment 48 will be pulled to the right into contact with the
ulna to reduce the fracture. Fastener 32 acts as a pulley; as the
externally extending portion of cord 52 is pulled, some mechanical
advantage is obtained to reduce the fracture. If desired, only the
cord 52 need be employed in this procedure to reduce the fracture
and to maintain the fracture interface in position. It will be
observed that in this event, the cord will exert force on the bone
plate 56 in the direction of the fastener 32, and to counteract
this force, the cord 52.1 may be employed to provide a
counteracting, substantially balancing force vector. It will be
noted that the cords 52, 52.1 together are positioned to counter
the force exerted by the triceps, shown as T in FIG. 9A.
[0063] The bone plate 56 shown in FIGS. 9A and 9B is also
illustrated in greater detail in FIGS. 11A, 11B and 11C. The plate
56 may be made of plastic or steel or other biocompatable, rigid
material, and includes a top 56.1, a bottom 56.2 which is slightly
concave in order to fit more closely the convex surface of bone
such as the ulna as shown in FIGS. 9A and 9B, identical side walls
56.3 and identical end walls 56.4 tapered so as to avoid trauma to
overlying soft tissue. Cord-receiving bores 56.5, 56.6 are formed
at an acute angle to the top and bottom walls 56.1, 56.2, as
illustrated best in FIGS. 11A and 11C. These bores intersect
intermediate the top and bottom walls, and threaded bores 56.7 are
formed in the side walls 56.3 and extend toward each other so as to
intersect the bores 56.5, 56.6 at their point of intersection. The
threaded bores 56.7 are so oriented as to receive a set screw (not
shown) which, when fully inserted, engages cords passing through
the bores 56.5, 56.6 to lock them in place.
[0064] FIG. 10 further illustrates the use of pulley-like fasteners
within a bone. This figure shows a bone end-on, the bone having
been broken into three fragments 58, 60, 62. Internal fasteners of
the type shown at 32 in FIGS. 6A and 7 are placed from the interior
of the bone into each of bone fragments 60, 62 with the cord 64
extending through the pulley-like eyelets of these fasteners. Both
ends of the cord are drawn out of the bone through an external
fastener 24 of the type shown in FIGS. 1-3, the latter being
carried by bone fragment 58. The internal fasteners 32 and the
external fastener 24 are so positioned that when the ends of the
cord that extend outwardly through the external fastener are placed
in tension and are then secured to the fastener 24 through the
locking screw 28, the fragments are urged together to properly
reduce the fracture and to prevent the fracture surfaces from
separating. It should be understood that the pulley surfaces of the
fasteners 32 enable slight movement of the cord 64 as stress is
applied to balance any tensile forces in the cords and thus avoid
unwanted shifting of one bone fragment with respect to another due
to unequal loading.
[0065] Note also in connection with FIG. 10 that the vector of the
resultant force applied to each bone fragment is not parallel to
the direction of the cords, but rather depends for each fragment
upon the angle between the cord segments leading to that fragment
and the tension in each cord segment. Assuming that the tension in
each of the three cord segments fracture reduction occurs is
approximately the same, the vector of the resultant force acting on
each fastener approximately bisects the angle between the cord
segments leading to that fastener, and knowledge of this
relationship may aid the surgeon in proper placement of the
fasteners.
[0066] FIGS. 12A, 12B and 12C show steps in the reduction of a
fracture of the ilium of the pelvis, the fracture being designated
generally as 66. It is desired here to run a flexible, inelastic
cord of the invention from within the pelvis to cortical bone on
the far side of the fracture, fastening the cord to the cortical
bone, the cord thus running past the fracture site and exiting the
pelvis on the near side of the fracture site. Referring to FIG.
12B, installation of the cord and internal fastener is facilitated
through the use of an external drill mechanism 68 as illustrated in
this figure, and comprising a hand grip 68.1, a rotatable handle
68.2, a chuck 68.3, and a gear mechanism (not shown) that causes
the chuck to rotate about its axis in response to turning of the
handle 68.2. The drill may be of the type marketed by DePuy as its
Modified Pease Bone Drill, Model 2079-00. A flexible cable 68.4 is
provided, the cable being of known design and torsionally stiff so
that rotation of the cable at its end where attached to the chuck
68.3 results in rotation of the cable at its distal end 68.5. An
internal fastener of the type shown in FIG. 3 is shown at 70, and
is provided with a hexagonal head which is inserted within a
hexagonal end of the flexible cable 68.4 such that as the cable is
rotated about its axis, the threaded fastener 70 is threaded into
cortical bone with the cord (not shown) extending from the fastener
through the hollow interior of the flexible cable 68.4 such that
when the fastener 70 has been suitably fastened to cortical bone,
the flexible cable can be withdrawn from the pelvis leaving behind
it the flexible, inelastic cord within the bone.
[0067] The cord in FIG. 12C is designated 72, and extends from the
internal fastener 70 across the fracture 66, around the bends in
the ilium, and exits the pelvis through an external fastener of the
type described above and designated 74. Although only one such cord
is shown in the drawing, a plurality of such cords, extending in
the necessary directions to reduce the fracture, may be employed.
The cord 72 is placed under tension to reduce the fracture, and
then is secured in the external fastener 74 in the manner described
above to prevent the fracture interface from reopening.
[0068] FIG. 13A shows use of the cord system of the invention for
fixation of a prosthetic acetabular cup to the acetabulum of a
patient. Designated 80 in FIG. 13A is a prosthetic acetabular cup,
commonly comprising a cup-shaped metal jacket 82 formed of titanium
or other biocompatible metal, and an inner cup 84 having a
generally hemispherical cavity in it to receive the ball of the
femur. The outer surface of the metal jacket 82 may have threads or
spikes or other surface configurations enabling it to grip tightly
to the bony acetabulum once the latter has been surgically shaped
to receive the prosthesis. In accordance with the invention, the
generally cup-shaped metal jacket 82 is provided with a series of
apertures 86 (FIG. 13B) which may be threaded to receive lock nuts
88, the threaded apertures and lock nuts themselves forming an
external fastener as generally referred to above. Internal
fasteners 90 are attached from within the pelvic bone to the
cortical bone thereof in the manner described above in connection
with FIGS. 12B and 12C, the flexible, inelastic cords 92 extending
within the pelvis back through the apertures 86 in the acetabular
cup prosthesis. Desirably, 3 or 4, or more, such cords are
employed, extending preferably generally radially outwardly from
the cup in a variety of different directions. The ends of the cords
are individually suitably tensioned to properly position the
acetabular cup prosthesis 80, the ends of the cords extending into
the jacket then being locked in place through the use of the
locking screws 88. The polymeric inner cup 84 is then placed in the
jacket. The purpose of the flexible, inelastic cords 92 is to hold
the acetabular prosthesis in place and, as needed, to repair
fractures in the pelvis as well.
[0069] Referring now to FIGS. 14A-D, these figures depict how the
flexible, inelastic cords of the invention may be used to reduce
fracture of a long bone such as the humerus. A fractured humerus is
designated 96 and includes a medullar canal 98 bounded by cortical
bone 100. The fracture site is shown best in FIGS. 14D and 14F, the
fracture interface being designated 102. At its distal end, on
either side of the olecranon, the humerus has thin walled portions
through which are drilled holes 104, 106 for introduction of a cord
system of the invention.
[0070] The holes 104, 106 may be formed through the use of a drill
of the type described above, the drill having a flexible shaft
shown schematically as 108 in FIG. 14A. The elongated bores formed
by the drill 108 converge at a point spaced proximally from the
olecranon, and further movement of the flexible drill shaft
upwardly (proximally) within the medullary canal 98 serves to
remove some of the tissue in the canal to make way for the cord
system. It is desired, once the cord system is in place, that a
pair of spaced cords traverse the fracture site within the
medullary canal, each cord exiting at one of the holes 104, 106.
For ease in placement of the cord system, each of the cords may
initially exit through hole 106, with one of the cords thereafter
being drawn downwardly through hole 104. This may be accomplished
as shown in FIGS. 14B and 14C. A wire 110 having a loop at one end
is inserted through the hole 104, the loop then being snared by a
hook-shaped end of a snare wire 112 that is inserted through the
other hole 106. The snare wire then can be removed and
discarded.
[0071] Through the hole 106 is introduced a flexible, hollow
introducer tube 114 carrying within it a toggle 116, the toggle
being of the type shown best in FIGS. 14C through 14F. Turning to
these figures, the toggle is shown as having an extended
orientation in which it is received in the tube 114 (FIG. 14C) and
in which it is eventually deployed in the medullary canal (FIG.
14F), and an articulated orientation (FIG. 14F) permitting it to be
moved within the close confines of the medullary canal during
placement of the toggle.
[0072] Referring to FIG. 14E, the toggle mechanism typified in the
drawing has a body formed of a pair of parallel, spaced, elongated
body strips 118 joined at their ends by transverse pins 120. Two
pairs of parallel gripping arms 122 are provided, the arms of each
pair being spaced and joined at their ends by a rod 124, and it is
to these rods extending between the arms 122 of each pair that the
ends of the cords 130, 132 are respectively attached through the
use of eyelet connectors 126. The pins 120 that join the body
strips 118 also pass outwardly through holes formed in the gripping
arms intermediate their ends so that the gripping arms can pivot
about the pins between extended and articulated orientations. Each
gripping arm has an end 128 opposite the ends joined by the rods
124 that is serrated or otherwise configured for gripping to
bone.
[0073] To properly position the toggle, a pair of flexible push
rods 140, 142 are provided within the introducer tube 114, each
push rod extending outwardly of the introducer tube as shown in
FIG. 14D and being attached to manually graspable rings 144 that
permit the push rods to move axially and also rotationally. The
push rods may have transverse grooves, as shown at 146 in FIG. 14E,
adjacent their ends, the grooves being sized to receive the
transverse pins 120. The grooves may be disengaged from the pins
120 simply by rotating the push rods through 90 degrees. One thus
may position the toggle as desired within the medullary canal
through relative axial movement of the push rods 140, 142, and once
the body of the toggle is in its desired location, the push rods
may be rotated to disengage them from the toggle so that they can
be removed. Moreover, once the body of the toggle has been oriented
as desired, and optionally before removal of the push rods, tension
is placed on the cords 130, 132, causing the arms 122 to pivot in
the direction of the arrow A in FIG. 14E to cause the ends 128 of
the arms to extend outwardly of the toggle body as shown best in
FIG. 14F into gripping contact with bone on each side of the
medullary canal.
[0074] Returning now to FIG. 14C, the flexible introducer tube 114,
including within it the toggle 116 to which are connected the pair
of flexible cords 130, 132, is pushed upwardly through the
medullaryy canal to a point at which anchoring of the cords is
desired, this, in FIG. 14D, being near the head of the humerus
where the medullary canal becomes wider. The toggle 116 is then
held in place within the medullary canal by the push rods 140, 142
attached to the transverse pins 120 of the toggle body, and the
flexible tube 114 is then withdrawn slightly to expose the toggle
within the medullary canal. By appropriate axial movement of the
push rods, the toggle arms ends 128 are deployed outwardly into
contact with the bone. Once approximate deployment of the toggle
has been accomplished, the flexible tube 114 may be removed
distally through the hole 106. Further manipulation of the push
rods with respect to each other and to the bone may be required to
achieve proper orientation of the toggle within the medullary
canal. A 90 degree twist of each push rod frees it from the toggle
and enables the push rods to be individually removed from the
medullary canal. Of course, in this and other procedures described
herein, fluoroscopy is used to insure proper placement of elements
of the cord system.
[0075] At this point, it will be noted that both of the flexible,
inelastic cords 130, 132 exit from the hole 106. The wire 110 with
formed loop is now attached to one of the cords, cord 130 in this
example, and pulling the wire 110 from the hole 104 draws the
fastened cord 130 outwardly through the hole 104.
[0076] FIG. 14F shows the flexible, inelastic cord system in place
in the humerus, the toggle device 116 being firmly anchored near
the head of the humerus, the flexible, inelastic cords 130, 132
extending in a spaced orientation downwardly through the medullary
canal with cord 130 exiting from the medullary canal through the
hole 104 and cord 132 exiting from the other hole 106. External
fasteners of the type described above in connection with FIG. 2 and
designated 134 are screwed into the holes 104, 106 with the cords
extending through these fasteners. By suitably pulling on the cords
130, 132 from the distal end of the humerus, one may bring together
the fracture surfaces as desired. By spacing the cords from one
another, the possibility of placing one side of the bone in tension
and the other in compression is largely avoided. Once the bones
have been appropriate located, the locking screws 136 are screwed
into the ends of the fasteners 134, locking the cords in place.
Because the cords are inelastic, any tension remaining in the cords
after attachment of the locking screws 136 is quickly lost.
[0077] The invention is particularly adapted for use in situations
in which a bone has been fractured into a number of fragments that
need to be carefully brought back into alignment, with compression
being generated at the fracture interfaces during physical activity
to promote fracture healing. The use of external splints, casts,
bandages, cerclage elements, and the like to reduce fractures in
badly fractured bones is quite difficult. Exterior pressure must be
used to force bones into the correct position and continued
adequate compression of all or most of the fracture interfaces is
difficult to attain. Through the use of the invention, in which
fasteners are placed into bone fragments from the interior of the
bone, with flexible cords being employed within the bone, to pull,
rather than push, the fragments into place, the force vectors
needed for proper fracture reduction and interface compression can
be readily chosen at the time of surgery. When many bone fragments
are involved, a surgeon may find it desirable to lead two, three or
more cords out of the opening formed in one fragment with the
interior ends of the cords attached to the variety of fragments via
internal fasteners, the surgeon then operating the cords
independently of each other to move the bone fragments into the
desired position using fluoroscopy as needed to visualize the cords
and proper placement of the bone fragments. The use of a cord
having a degree of radiopacity aids visualization of the cord.
[0078] While a preferred embodiment of the present invention has
been described, it should be understood that various changes,
adaptations and modifications may be made therein without departing
from the spirit of the invention and the scope of the appended
claims.
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