U.S. patent application number 11/810180 was filed with the patent office on 2007-10-11 for implant for osteosynthesis.
This patent application is currently assigned to Stryker Trauma GmbH. Invention is credited to Ronald Prager, Nils Zander.
Application Number | 20070239164 11/810180 |
Document ID | / |
Family ID | 7979329 |
Filed Date | 2007-10-11 |
United States Patent
Application |
20070239164 |
Kind Code |
A1 |
Prager; Ronald ; et
al. |
October 11, 2007 |
Implant for osteosynthesis
Abstract
An implant for osteosynthesis, for example a bone nail, has an
implant body which has at least one bore with a threaded portion
and a bone screw which engages the thread when it is threaded into
a bone for the fixation of the implant body. The threaded bore has
an annular groove the diameter of which is larger than the thread
outer diameter, and which receives a ring of a deformable material
with an inner diameter which is smaller than the outer diameter of
the thread of the bone screw so that the ring extends partially
into the bore.
Inventors: |
Prager; Ronald; (Bovenau,
DE) ; Zander; Nils; (Eckenfoerde, DE) |
Correspondence
Address: |
LERNER, DAVID, LITTENBERG,;KRUMHOLZ & MENTLIK
600 SOUTH AVENUE WEST
WESTFIELD
NJ
07090
US
|
Assignee: |
Stryker Trauma GmbH
Schonkirchen
DE
|
Family ID: |
7979329 |
Appl. No.: |
11/810180 |
Filed: |
June 5, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10755815 |
Jan 12, 2004 |
7247157 |
|
|
11810180 |
Jun 5, 2007 |
|
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Current U.S.
Class: |
606/71 |
Current CPC
Class: |
A61B 17/74 20130101;
A61B 17/72 20130101; A61B 17/7241 20130101; A61B 2017/8655
20130101 |
Class at
Publication: |
606/073 |
International
Class: |
A61B 17/58 20060101
A61B017/58 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 23, 2003 |
DE |
20300987.8 |
Claims
1. An implant for osteosynthesis, comprising a bone nail having a
body which has at least one bore with a threaded portion and a bone
screw which engages the threaded portion when it is threaded into a
bone for the fixation of the implant body, wherein the bore has an
annular groove and a ring made of a material which can be deformed
by the threads of the bone screw for insertion into the groove, the
ring having an inner diameter which is smaller than the major
diameter of the thread of the bone screw.
2. The implant as set forth in claim 1 wherein the bore has a screw
inlet end and a screw outlet end and the annular groove is disposed
adjacent to the outlet end.
3. The implant as set forth in claim 2 wherein a bore portion
between the annular groove and the outlet end is non-threaded.
4. The implant as set forth in claim 3 further including a
non-threaded bore portion adjacent to the inlet end.
5. The implant as set forth in claim 4 wherein the non-threaded
portions are of a diameter which is slightly larger than the major
diameter of the bore thread.
6. The implant as set forth in claim 1 wherein the annular groove
is rectangular in cross-section.
7. The implant as set forth in claim 1 wherein the ring is formed
from a resiliently yielding plastic.
8. The implant as set forth in claim 1 wherein the ring is split
and ends of the split ring are spaced from each other when it is in
a relaxed state.
9. The implant as set forth in claim 8 wherein the ends of the ring
are at an oblique angle and have the same angle of inclination.
10. The implant as set forth in claim 1 wherein a ring inner
diameter has edges which have a chamfer.
11. The implant as set forth in claim 1 wherein the ring has a
width which is slightly smaller than a width of the annular
groove.
12. The implant as set forth in claim 11 wherein an outer diameter
of the ring, when in a relaxed state, is slightly larger than a
maximum diameter of the annular groove.
13. The implant as set forth in claim 1 wherein the bone nail is an
interlocking nail.
14. The implant as set forth in claim 1 wherein the nail is a
humeral nail, a proximal end of which has a plurality of
cross-bores, the cross-bores each extending along an axis which are
offset from each other in a circumferential direction.
15. A bone fracture fixation device comprising: a bone nail having
a body extending along a longitudinal axis and having at least one
bore extending in a direction transverse to said axis, said bore
having an inner diameter surface with an annular groove formed
therearound, said groove having one side open to said bore; and a
split plastic ring mounted in said groove having an inner portion
extending from said one side of said groove into said bore; and a
bone screw having a threaded portion with a major diameter
engageable with the inner portion of said ring upon insertion into
said bore the split plastic ring having a minimum outer diameter
greater than the inner bore diameter.
16. The fracture fixation device as set forth in claim 15 wherein
said bore is threaded.
17. The fracture fixation device as set forth in claim 16 wherein
the annular groove is rectangular in cross-section and extends
perpendicular to a central axis of said bore.
18. The fracture fixation device as set forth in claim 15 wherein
the ring is split and ends of the split ring are spaced from each
other when it is in a relaxed state.
19. The fracture fixation device as set forth in claim 18 wherein
the ends of the ring are at an oblique angle and have the same
angle of inclination.
20. The fracture fixation device as set forth in claim 15 wherein
the inner portion of said ring has edges which have a chamfer.
21. The fracture fixation device as set forth in claim 15 wherein
an outer diameter of the ring, when in a relaxed state, is slightly
larger than a maximum diameter of the annular groove.
22. The implant as set forth in claim 15 further including a
non-threaded bore portion adjacent to the inlet end.
23. The implant as set forth in claim 22 wherein the non-threaded
portions are of a diameter which is slightly larger than the outer
diameter of the bore thread.
24. The implant as set forth in claim 15 wherein the implant is a
bone nail.
25. An implant for osteosynthesis, comprising a bone nail having a
body which has at least one bore with a threaded portion and a bone
screw which engages the threaded portion when it is threaded into a
bone for the fixation of the implant body, wherein the bore has an
annular groove the diameter of which is larger than a major
diameter of the thread and a ring of a deformable material for
insertion into the groove, the ring having an inner diameter which
is smaller than the major diameter of the thread of the bone screw
wherein the nail is a humeral nail, a proximal end of which has a
plurality of cross-bores, the cross-bores each extending along an
axis which are offset from each other in a circumferential
direction.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 10/755,815, filed on Jan. 12, 2004, the disclosure of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] It is generally known to fix plates to bone by means of bone
screws for the repair of bone fractures. Further, it is well known
to configure bone screws for use with so-called interlocking nails
for the care of fractures of tubular bones. Interlocking nails have
cross-bores for the reception of bone screws or interlocking screws
at both the distal and proximal nail ends. It is known to provide
the bores with a thread for the reception of a bone screw. In most
cases, the thread is a so-called cortical thread, i.e. a thread
corresponding to the thread of the bone screw. This thread has the
advantage that it impedes the postoperative migration of the bone
screws.
[0003] It is known to configure nails for the repair of humeral
fractures as interlocking nails and to provide several cross-bores
in the proximal portion of the interlocking nail which are offset
from each other in the circumferential direction and extend
obliquely to the axis of the nail, if required. A nail having
oblique cross-bores is shown in U.S. Pat. No. 5,472,444. The
emigration of interlocking screws is critical and, thus, is a
particular problem in a humeral fracture.
SUMMARY OF THE INVENTION
[0004] It is one object of the invention to provide an implant for
osteosynthesis that efficiently prevents the postoperative
migration of bone screws.
[0005] In the inventive implant, the threaded bore has an annular
groove the diameter of which is larger than the thread outer
diameter, and which receives a ring of a deformable material with
an inner diameter which is smaller than the outer diameter of the
thread of the bone screw. Thus, the ring has a portion which
extends into the threaded bore.
[0006] According to the invention, the ring is preferably made of a
plastic material, e.g. polyethylene. After insertion into the
annular groove the ring blocks some portion of the thread
cross-section and, while the bone screw is turned in, the ring is
deformed so as to produce a frictional engagement between the bone
screw, the ring and the annular groove, that prevents the bone
screw from turning out by itself.
[0007] Moreover, the ring centers the bone screw in the threaded
bore so that an increased angular stability of the bone screw is
achieved in the implant as compared to that of the non-secured
design.
[0008] The bores in the implant usually have an inlet end and an
outlet end. According to an aspect of the invention, the annular
groove is disposed adjacent to the outlet end. According to another
aspect of the invention, the bore portion between the outlet end
and annular groove preferably is non-threaded. According to an
aspect of the invention, the bore portion adjacent to the inlet end
is also non-threaded. The arrangement of the ring at the outlet
side of the through bore ensures that the screw is already in a
threaded engagement when it strikes the ring. Here, the mostly
conical tip of the bone screw urges the ring into the groove before
the ring of the bone screw undergoes deformation. This ensures that
the interlocking screw does not force the ring out of the bore.
[0009] According to another aspect of the invention, the annular
groove is rectangular in cross-section with the ring exhibiting a
complementary cross-section. However, it is preferred that the
width of the ring be somewhat smaller than the width of the annular
groove. This allows easier insertion of the ring into the annular
groove. Also, this creates a clearance for an axial deformation of
the ring.
[0010] According to another aspect of the invention, the ring is
split and the ends of the ring are at a distance from each other
when the ring is in a relaxed state. During its insertion, the ring
may be slightly contracted radially to enable it to be inserted
into the annular groove without a problem. Preferably, the two
inside edges of the ring are chamfered to prevent the ring from
being forced out of the groove. Basically, it would be sufficient
to chamfer the edge facing the inlet end, but since it is desired
that the orientation in which the ring is inserted into the groove
does not matter it is preferred to form both inner edges with a
chamfer.
[0011] The outer diameter of the ring, when in a relaxed state, is
slightly larger than the diameter of the annular groove. This
causes the ring to be retained by itself in the groove, i.e. also
during transport and while the implant is handled before the bone
screw is turned in.
[0012] The invention is applicable to any implants that are
inserted in combination with bone screws. The invention is
specifically preferred for use with an intramedullary implant, e.g.
a bone nail, preferably an interlocking nail. It is particularly
preferred to apply it to a humeral nail, the proximal end of which
has three or more cross-bores the axes of which are offset from
each other in a circumferential direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The invention will be described in more detail below with
reference to an embodiment shown in the drawings.
[0014] FIG. 1 shows a cross-section of the proximal end of the
humeral nail with securing rings according to the invention in a
perspective view;
[0015] FIG. 2 shows a longitudinal section through a humeral nail
with a threaded bore, a groove and a securing ring according to the
invention;
[0016] FIG. 3 shows the front view of a securing ring of FIG. 1 or
2; and
[0017] FIG. 4 shows a section through the ring of FIG. 3 along the
line 4-4.
DETAILED DESCRIPTION
[0018] Referring to FIG. 1 there is shown a humeral nail 10 having
four offset cross-bores and having a longitudinally sectioned
proximal portion 12. As can be seen, the preferred proximal portion
12 is provided with four cross-bores 14, 16, 18 and 20 which, in
the preferred embodiment are offset from each other in the axial
and circumferential directions and are at an angle from the
longitudinal axis 21 of nail 10. In the preferred embodiment, bores
14, 16, 18 and 20 are configured as threaded bores. FIG. 1 further
shows that bores 14, 18 and 20 receive a securing ring 22, 24 and
26, respectively. If desired, bore 16 can also include a securing
ring. These rings serve for securing an interlocking screw 28 which
has a head 30 and a shank 32 with thread 34. In the preferred
embodiment thread 34 is a cortical thread which is useful in
ensuring a fixed seating in the bone without unnecessarily imposing
a stress on the bone. The preferred thread 34 is a flat thread
which threadably engages the thread in the threaded bores 14, 16,
18 and 20.
[0019] FIG. 2 illustrates a single threaded bore, e.g. the threaded
bore 14. This bore is typical of the other threaded bores of the
preferred embodiment. Bore 14 has an inlet end 36 and an outlet end
39. Therefore, during use conical tip 38 of interlocking screw 28
shown in FIG. 1 is introduced into the inlet end 36 which has an
inlet conical taper or countersink 40 as can be seen at end 36. In
the preferred embodiment, countersink 40 is joined by a
non-threaded bore portion 42. This is followed by threaded portion
44. Portion 44 has at its end formed therein an annular groove 46
of a rectangular cross-section in which securing ring 22 is
received. Again, in the preferred embodiment, non-threaded portion
48 is located towards outlet end 39. As can be seen the width of
ring 22 is somewhat smaller than the width of annular groove
46.
[0020] Preferred ring 22 is illustrated in somewhat more detail in
FIGS. 3 and 4. As can be seen in the preferred embodiment, ring 22
is split and ends 50, 52 are provided with a slope at an angle of
45.degree. are spaced a certain distance from each other. The
inside edges of ring 22 are provided with chamfer 54 and 56,
respectively. The outer diameter of ring 22, when in a relaxed
state, is slightly larger than the diameter of annular groove 46.
In the preferred embodiment, the inner diameter of the ring is
smaller than the outer or major diameter of threaded portion 34,
but is larger than the inner or minor diameter of threaded portion
34 of screw 28.
[0021] While being inserted, ring 22 is somewhat compressed
circumferentially so that it can be readily introduced into annular
groove 46. After insertion into groove 46, ring 22 will relax and
expand to a small extent after insertion, but not up to its fully
expanded diameter in the relaxed state. This results in the ring
being retained in the annular groove 46 to a fairly reliable
degree.
[0022] When an interlocking screw 28 is introduced into bore 14
from inlet end 36, threads 44 and 34 engage each other before
thread 34 interacts with securing ring 22. Conical tip 38 of
interlocking screw 28 initially urges securing ring 22 radially
outwardly before thread 34 interacts with securing ring 22 so that
forcing ring 22 out of the bore is avoided. The ring, which is made
of an elastic plastic material, is deformed accordingly and
frictional engagement is produced between thread 34 and ring 22 and
between ring 22 and annular groove 46, the result obtained being
that screw 28 is efficiently secured in bore 34.
[0023] Although the invention herein has been described with
reference to particular embodiments, it is to be understood that
these embodiments are merely illustrative of the principles and
applications of the present invention. It is therefore to be
understood that numerous modifications may be made to the
illustrative embodiments and that other arrangements may be devised
without departing from the spirit and scope of the present
invention as defined by the appended claims.
* * * * *