U.S. patent application number 10/739216 was filed with the patent office on 2004-05-20 for endo-distractor.
This patent application is currently assigned to Synthes (U.S.A.). Invention is credited to Krenkel, Christian, Lixl, Georg.
Application Number | 20040097953 10/739216 |
Document ID | / |
Family ID | 4358050 |
Filed Date | 2004-05-20 |
United States Patent
Application |
20040097953 |
Kind Code |
A1 |
Krenkel, Christian ; et
al. |
May 20, 2004 |
Endo-distractor
Abstract
The invention relates to a device for the distraction of bones
or bone segments. The device comprises an anchoring screw having a
longitudinal axis, a screw tip, a screw end for rotatably driving
the anchoring screw, a threaded shank which adjoins the screw tip
and has a screw thread, and a screw shank adjoining the screw end;
and a distraction sleeve axially displaceable on the screw shank
including a rear end, a front end, a through-bore extending
coaxially therebetween, an external thread adjoining the front end,
and a coupler portion formed in the rear end for receiving a
driving tool. The anchoring screw comprises a collar positioned
between the threaded shank and the screw shank that radially
projects at least from the screw shank and which serves as an axial
stop for the front end of the distraction sleeve when the
distraction sleeve is positioned over the screw shank. The
through-bore has a boring section with an enlarged cross-section
which adjoins the rear end provided with a lateral surface and a
seal ring coaxially arranged between the lateral surface and the
screw shank.
Inventors: |
Krenkel, Christian;
(Salzburg, AT) ; Lixl, Georg; (Oberndorf,
AT) |
Correspondence
Address: |
JONES DAY
222 EAST 41ST STREET
NEW YORK
NY
10017
US
|
Assignee: |
Synthes (U.S.A.)
|
Family ID: |
4358050 |
Appl. No.: |
10/739216 |
Filed: |
December 17, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10739216 |
Dec 17, 2003 |
|
|
|
10230074 |
Aug 29, 2002 |
|
|
|
6666869 |
|
|
|
|
10230074 |
Aug 29, 2002 |
|
|
|
PCT/CH00/00117 |
Feb 29, 2000 |
|
|
|
Current U.S.
Class: |
606/105 ;
606/304; 606/312; 606/318; 606/328 |
Current CPC
Class: |
A61B 17/666 20130101;
A61C 8/0006 20130101 |
Class at
Publication: |
606/105 ;
606/073 |
International
Class: |
A61B 017/60 |
Claims
What is claimed is:
1. A device for the distraction of bones or bone segments
comprising: an anchoring screw having a threaded shank, a screw
shank and a longitudinal axis; a distraction sleeve extending
coaxially along the longitudinal axis; the distraction sleeve
having a first end, a second end and a through-bore extending from
the first end to the second end sized and dimensioned to receive
the screw shank; at least a portion of the first end of the
distraction sleeve comprises an external screw thread; a seal ring
sized and dimensioned to fit between the screw shank and the
distraction sleeve; a collar positioned between the threaded shank
and screw shank; and means for rotatably driving the anchoring
screw.
2. The device in claim 1 wherein the through-bore includes a boring
section with an enlarged cross-section which adjoins the second end
of the distraction sleeve, the boring section being provided with a
lateral surface, the seal ring being arranged between the lateral
surface and the screw shank.
3. The device in claim 1 wherein the second end of the distraction
sleeve includes coupling means for receiving a driving tool.
4. The device in claim 3 wherein the coupling means includes a
plurality of slots.
5. The device in claim 1 wherein the distraction sleeve is axially
displaceable on the screw shank.
6. The device in claim 4 wherein the collar radially projects from
the screw shank such that the collar acts as an axial stop for the
first end of the distraction sleeve when the distraction sleeve is
positioned over the screw shank.
7. The device in claim 1 wherein the threaded shank has a first
diameter; the screw shank has a second diameter and the collar has
a third diameter, the third diameter being larger than the first
and second diameter.
8. The device in claim 7 wherein the first diameter is larger than
the second diameter.
9. The device in claim 7 wherein the diameter of the threaded shank
is approximately 2.2 mm to approximately 3.5 mm and the diameter of
the screw shank is approximately 1.8 mm to approximately 2.5
mm.
10. The device in claim 7 wherein the diameter of the threaded
shank is approximately 2.7 mm and the diameter of the screw shank
is approximately 2.2 mm.
11. The device in claim 1 wherein the threaded shank further
includes a screw tip.
12. The device in claim 1, wherein the threaded shank has a
self-tapping screw thread.
13. The device in claim 1, wherein the threaded shank has a screw
thread with an asymmetrical thread profile.
14. The device of claim 13, wherein the screw thread includes
flanks directed towards a screw tip that form an angle of between
80 and 90 degrees with respect to the longitudinal axis.
15. The device of claim 1, wherein the external screw thread of the
distraction sleeve has an asymmetrical thread profile.
16. The device of claim 15, wherein the external thread includes
flanks directed towards the second end that form an angle of
between 80 and 90 degrees with respect to the longitudinal
axis.
17. The device in claim 1, wherein the external screw thread formed
on the distraction sleeve is a left-hand thread.
18. The device of claim 1, wherein the external screw thread formed
on the distraction sleeve displays flattened, threaded tips.
19. The device of claim 1, wherein the external screw thread formed
on the distraction sleeve extends approximately one-half the length
of the distraction sleeve.
20. The device of claim 1, wherein the collar comprises a cone.
21. The device of claim 1, wherein the collar comprises a
spherically convex, tapered portion.
22. The device of claim 1, wherein the means for driving the
anchoring screw is arranged on a screw end of the screw shank.
23. The device of claim 1, wherein the means for rotatably driving
the anchoring screw do not radially protrude from the screw
shank.
24. The device of claim 1, wherein the means for driving the
anchoring screw includes a hexagon having external surfaces
arranged about the periphery of the screw shank.
25. The device of claim 1, wherein the screw shank further includes
a bore having an internal screw thread for threadedly receiving a
cover screw.
26. A device for the distraction of bones or bone segments
comprising: an anchoring screw having a longitudinal axis; the
screw including a threaded shank, a screw shank and a collar
disposed between the threaded shank and the screw shank; a
distraction sleeve having a first end, a second end and a
through-bore extending from the first end to the second end sized
and dimensioned to receive the screw shank such that the
distraction sleeve is axially displaceable on the screw shank; at
least a portion of the first end of the distraction sleeve
comprises an external screw thread; and a seal ring sized and
dimensioned to fit between the screw shank and the distraction
sleeve; wherein the screw shank includes a screw end having a
multi-sided configuration with external surfaces arranged about the
periphery of the screw shank for rotatably driving the anchoring
screw; wherein the collar radially projects from the screw shank
such that the collar acts as an axial stop for the first end of the
distraction sleeve when the distraction sleeve is positioned over
the screw shank.
27. The device in claim 26 wherein the through-bore includes a
boring section with an enlarged cross-section which adjoins the
second end of the distraction sleeve, the boring section being
provided with a lateral surface, the seal ring being arranged
between the lateral surface and the screw shank.
28. The device in claim 26 wherein the second end of the
distraction sleeve includes coupling means for receiving a driving
tool.
29. The device in claim 28 wherein the coupling means includes a
plurality of slots.
30. The device in claim 26 wherein the threaded shank has a first
diameter; the screw shank has a second diameter and the collar has
a third diameter, the third diameter being larger than the first
and second diameter.
31. The device in claim 30 wherein the first diameter is larger
than the second diameter.
32. The device in claim 30 wherein the diameter of the threaded
shank is approximately 2.2 mm to approximately 3.5 mm and the
diameter of the screw shank is approximately 1.8 mm to
approximately 2.5 mm.
33. The device in claim 30 wherein the diameter of the threaded
shank is approximately 2.7 mm and the diameter of the screw shank
is approximately 2.2 mm.
34. The device in claim 26 wherein the threaded shank further
includes a screw tip.
35. The device in claim 26, wherein the threaded shank has a
self-tapping screw thread.
36. The device in claim 26, wherein the threaded shank has a screw
thread with an asymmetrical thread profile.
37. The device of claim 36, wherein the screw thread includes
flanks directed towards a screw tip that form an angle of between
80 and 90 degrees with respect to the longitudinal axis.
38. The device of claim 26, wherein the external screw thread of
the distraction sleeve has an asymmetrical thread profile.
39. The device of claim 38, wherein the external thread includes
flanks directed towards the second end that form an angle of
between 80 and 90 degrees with respect to the longitudinal
axis.
40. The device in claim 26, wherein the external screw thread
formed on the distraction sleeve is a left-hand thread.
41. The device of claim 26, wherein the external screw thread
formed on the distraction sleeve displays flattened, threaded
tips.
42. The device of claim 26, wherein the external screw thread
formed on the distraction sleeve extends approximately one-half the
length of the distraction sleeve.
43. The device of claim 26, wherein the collar comprises a
cone.
44. The device of claim 26, wherein the collar comprises a
spherically convex, tapered portion.
45. The device of claim 26, wherein the screw shank further
includes a bore having an internal screw thread for threadedly
receiving a cover screw.
46. A device for the distraction of bones or bone segments
comprising: a threaded shank having a screw tip on one end thereof
and a collar on the other end; a screw shank having an internally
threaded bore for receiving a cover screw on an end thereof, the
screw shank being coupled to the collar; a distraction sleeve
having a first end, a second end and a through-bore extending from
the first end to the second end sized and dimensioned to receive
the screw shank such that the distraction sleeve is axially
displaceable on the screw shank, at least a portion of the first
end of the distraction sleeve comprises an external screw thread,
at least a portion of the second end of the distraction sleeve has
an enlarged cross-section forming a boring section, a seal ring
sized and dimensioned to fit between the screw shank and the boring
section of the distraction sleeve; wherein the end of the screw
shank having the internally threaded bore has a multi-sided outer
configuration with external surfaces about the periphery of the
screw shank for receiving a driving tool; wherein the collar
radially projects from the screw shank such that the collar acts as
an axial stop for the first end of the distraction sleeve when the
distraction sleeve is positioned over the screw shank.
47. The device in claim 46 wherein the second end of the
distraction sleeve includes coupling means for receiving a driving
tool.
48. The device in claim 47 wherein the coupling means includes a
plurality of slots.
49. The device in claim 46 wherein the threaded shank has a first
diameter; the screw shank has a second diameter and the collar has
a third diameter, the third diameter being larger than the first
and second diameter.
50. The device in claim 49 wherein the first diameter is larger
than the second diameter.
51. The device in claim 49 wherein the diameter of the threaded
shank is approximately 2.2 mm to approximately 3.5 mm and the
diameter of the screw shank is approximately 1.8 mm to
approximately 2.5 mm.
52. The device in claim 49 wherein the diameter of the threaded
shank is approximately 2.7 mm and the diameter of the screw shank
is approximately 2.2 mm.
53. The device in claim 46, wherein the threaded shank has a
self-tapping screw thread.
54. The device in claim 46, wherein the threaded shank has a screw
thread with an asymmetrical thread profile.
55. The device of claim 54, wherein the screw thread includes
flanks directed towards a screw tip that form an angle of between
80 and 90 degrees with respect to the longitudinal axis.
56. The device of claim 46, wherein the external screw thread of
the distraction sleeve has an asymmetrical thread profile.
57. The device of claim 56, wherein the external thread includes
flanks directed towards the second end that form an angle of
between 80 and 90 degrees with respect to the longitudinal
axis.
58. The device in claim 46, wherein the external screw thread
formed on the distraction sleeve is a left-hand thread.
59. The device of claim 46, wherein the external screw thread
formed on the distraction sleeve displays flattened, threaded
tips.
60. The device of claim 46, wherein the external screw thread
formed on the distraction sleeve extends approximately one-half the
length of the distraction sleeve.
61. The device of claim 46, wherein the collar comprises a
cone.
62. The device of claim 46, wherein the collar comprises a
spherically convex, tapered portion.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of co-pending U.S. patent
application Ser. No. 10/230,074, filed on Aug. 29, 2002, which is a
continuation of the U.S. national stage designation of
International Patent Application PCT/CH00/00117, filed Feb. 29,
2000, the entire content of which is expressly incorporated herein
by reference thereto.
FIELD OF THE INVENTION
[0002] The present invention relates generally to an apparatus for
the distraction of bone or bone segments.
BACKGROUND OF THE INVENTION
[0003] In modern surgical operative technique, external or also
internal distractors are used to bring about a controlled
displacement of bone fragments relative to one another.
Endo-distractors are especially suitable for oral surgery, as they
allow to minimize the disturbance of the patient during the
distraction process which may often take several weeks.
[0004] Distractors are also used with toothless jaws in cases of
advanced atrophy of the mandible. Apart from the cosmetic aspect,
mandibular atrophy may also create difficulties for the
implantation of a set of artificial teeth. The absence of the
necessary bone substance may lead to a loosening of the implants or
even to a fracture of the mandible. A pathological atrophy of the
mandible is not only observed with old patients but may even occur
with a 40-year-old patient, in which case the decision in favor of
an operative intervention is greatly facilitated.
[0005] In order to rebuild the mandible, an osteotomy of the
mandible is realized in a horizontal direction. Subsequently, the
osteotomy gap is continuously increased. This distraction of the
osteotomy gap is carried out at a rate on the order of about 1/2 mm
per day. During the slowly advancing process of distraction,
osseous tissue is formed in the osteotomy gap. After completion of
the distraction, the osteotomy gap has to be maintained at the
right distance for a certain period of time.
SUMMARY OF THE INVENTION
[0006] The present invention is directed to a device for the
distraction of bones or bone segments comprising an anchoring screw
having a longitudinal axis, a threaded shank, a screw shank, and a
screw end provided with means for rotatably driving the anchoring
screw, as well as a distraction sleeve axially displaceable along
the screw shaft extending coaxially along the longitudinal axis and
is provided with a rear end, a front end, a circular cylindrical,
through-bore, an external screw thread adjoining the front end, and
a coupling means formed on the rear end for receiving a driving
tool. In addition, the anchoring screw comprises a collar located
between the threaded shank and the non-threaded shank and
projecting radially at least over the non-threaded shank so as to
serve as an axial stop for the front end of the distraction sleeve
that is slid over the screw shank. The through-bore comprises a
boring section with an enlarged cross-section in which a seal ring
is coaxially arranged between the lateral surface of the boring
section and the screw shank.
[0007] In one embodiment of the device, the collar is shaped in the
form of a cone which leads to the screw shaft. Thus, the contact
surface between said cone and the front end of the distraction
sleeve is minimized, which has the advantageous result that in
spite of the axial load existing between the anchoring screw and
the distraction sleeve, the anchoring screw remains easily
rotatable about the longitudinal axis. Alternatively, the
transition segment may also be spherically convex.
[0008] The device according to the invention comprises in addition,
a cover screw which may be screwed into a bore formed on the screw
end and provided with an internal screw thread. The cover screw
forms the mechanical seal of the distractor in the oral cavity and,
in addition, secures the anchoring screw in its position relative
to the distraction sleeve.
[0009] In another embodiment, the collar comprises a spherically
convex, tapered portion which leads to the screw shank. Also, the
boring section can have an inner cone which leads to the
through-bore. In another embodiment, the screw thread may be
self-tapping, or the screw thread can have an asymmetrical thread
profile. Also, the screw thread may include flanks directed towards
the screw tip that form an angle of between 80 and 90 degrees with
respect to the longitudinal axis.
[0010] Also, the external thread may have an asymmetrical thread
profile, and the external thread may include flanks directed
towards the rear end that form an angle of between 80 and 90
degrees with respect to the longitudinal axis, and the thread
profile of the external thread may have flattened, threaded tips.
In one embodiment, the means for rotatably driving the anchoring
screw do not radially protrude from the screw shank.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Preferred features of the present invention are disclosed in
the accompanying drawings, wherein similar reference characters
denote similar elements throughout the several views, and
wherein:
[0012] FIG. 1 is a longitudinal section of the preferred embodiment
of the device according to one embodiment of the present
invention;
[0013] FIG. 2 is a sectional view of a mandible at the beginning of
the distraction process, including a device according to the
invention inserted therein;
[0014] FIG. 3 is a sectional view of a mandible during the
distraction process, including a device according to the invention
inserted therein; and
[0015] FIG. 4 is a sectional view of a mandible during the
distraction process, including two devices according to the
invention inserted therein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] For convenience, the same or equivalent elements in the
various embodiments of the invention illustrated in the drawings
have been identified with the same reference numerals. Further, in
the description that follows, any reference to either orientation
or direction is intended primarily for the convenience of
description and is not intended in any way to limit the scope of
the present invention thereto.
[0017] FIG. 1 shows one preferred embodiment of the distraction
device according to the invention. The distraction device comprises
an anchoring screw 2 having a longitudinal axis 1 as well as a
distraction sleeve 3 extending coaxially along longitudinal axis 1,
a seal ring 4, and a cover screw 5. The anchoring screw 2 is
circular cylindrical and includes a threaded shank 7 which adjoins
a rounded screw tip 6 and has a screw thread 8 that extends over
approximately half of the anchoring screw 2 and is provided with an
outside diameter d.sub.a. Threaded shank 7 is adjoined respectively
by a collar 10 and a circular cylindrical screw shank 11 with a
diameter d.sub.11 which are axially arranged in the mentioned order
in the direction of the screw end 9. The screw thread 8 is
asymmetrically shaped, forming an angle of 87 degrees between the
flanks of the screw thread directed towards the screw tip 6 and the
longitudinal axis 1. Facing the threaded shank 7, the collar 10 has
a circular cylindrical section 12 with a diameter d.sub.12.
Diameter d.sub.12 is superior to outside diameter d.sub.a and
superior to diameter d.sub.11 of the screw shank 11. Facing the
screw shank 11, collar 10 comprises a transition segment or cone 13
which leads in a conically tapered manner from section 12 to screw
shank 11. Depending on the type of seal ring 4 used, the transition
segment between the boring segment with enlarged cross-section and
the through-bore of the distraction sleeve may be shaped either in
the form of a plan surface or of an inner cone leading to the
through-bore. Thus, a suitable axial contact surface for the seal
ring 4 may be obtained.
[0018] In one embodiment, the external screw thread formed on the
distraction sleeve is preferably realized as a left-hand thread. In
one embodiment, the screw thread is in the form of a self-tapping
screw thread which may be provided with one or several cutting
grooves. The outside diameter of the screw thread may be in a range
of between 2.2 mm and 3.5 mm, but is preferably about 2.7 mm. The
thread profile is preferably asymmetrical, and the flanks of the
screw thread directed towards the screw tip preferably forming an
angle of between 80 and 90 degrees relative to the longitudinal
axis. Thus, the pressure load may be transmitted in a substantially
axial manner to the cancellous bone. The diameter of the screw
shank may be in a range of between 1.8 mm and 2.5 mm, but is
preferably about 2.2 mm. The means for driving the anchoring screw
preferably does not radially project from the screw shank and may,
for example, consist of surfaces evenly arranged in a polygonal
pattern on the periphery of the screw shank so as to form
preferably a square or a hexagon.
[0019] Means 14 for driving the anchoring screw 2 are arranged on
screw shank 11 in the area of screw end 9. In one embodiment,
driving means 14 are in the form of a hexagon consisting of six
surfaces 15 regularly arranged about the periphery of the screw
shank 11. Screw end 9 is provided with a bore 16 extending
coaxially to the longitudinal axis 1 and provided with an internal
screw thread 17.
[0020] The distraction sleeve 3 is shaped in the form of a hollow
cylinder extending coaxially along longitudinal axis 1 and has a
front end 19, a rear end 20, and a length L extending parallel to
longitudinal axis 1. The distraction sleeve 3 comprises an external
screw thread 23 beginning on the front end 19 and extending over
half of the length L. The sleeve segment 24 that adjoins the rear
end 20 has an enlarged diameter and is provided with four slots 25
arranged on the rear end 20 and extending orthogonally relative to
one another so as to serve as a coupling means 26 for receiving a
screwing-in or driving tool. A continuous boring or through-bore 21
extends coaxially to the longitudinal axis 1 and is of circular
cylindrical shape and has a diameter that permits the distraction
sleeve 3 to be axially displaced along the screw shank 11.
Beginning from the rear end 20, through-bore 21 has a boring
section 22 with an enlarged cross-section which penetrates to a
depth T, the boring section 22 conically leading to the
through-bore 21 with half a cone angle of 60 degrees and the depth
T being dimensioned in such a way that the boring section 22 does
not extend over the entire sleeve segment 24. The distraction
sleeve 3 may be slid over the screw shank 11 from the screw end 9
until its front end 19 abuts on the cone 13, the distraction sleeve
3 remaining freely rotatable on the screw shank 11 about the
longitudinal axis 1 and the rear end 20 projecting over the screw
end 9.
[0021] The external screw thread formed in the distraction sleeve
may equally be advantageously provided with an asymmetrical thread
profile, the flanks of the screw thread directed towards the rear
end forming an angle of between 80 and 90 degrees relative to the
longitudinal axis. Here again, a substantially axial transmission
of the pressure load to the bone may be obtained.
[0022] Between lateral surface 27 of the boring section 22 and the
screw shank 11, seal ring 4 is arranged which ensures a tight
sealing between the oral cavity and the mandible.
[0023] The distraction sleeve has many functions, including but not
limited to: abutment for lifting the upper osteotomy segment;
gingiva former in view of the implant to be subsequently inserted;
provide protected access to the internal screw, permitting to turn
said screw; providing sealing possibility by means of kneaded wax
due to the countersinking of the internal screw (a difference in
level of 0.5 mm between the upper edge of the distraction sleeve
and the end of the anchoring screw may be provided to lodge the
bead of kneaded wax); and as a sleeve for receiving O-rings
ensuring a tight sealing of the bone against saliva and
bacteria.
[0024] In addition, the distraction device comprises a cover screw
5 which includes a threaded portion 28 which may be screwed into
the internal screw thread 17 formed in the screw end 9 until the
screw head 30 abuts on the rear end 20 of the distraction sleeve 3.
The cover screw seals the dead space of the distraction sleeve, it
has a function similar to that of a gingiva former and offers some
degree of support for a temporary prosthesis.
[0025] The distractor device may be used for many applications,
including but not limited to the distraction of the alveolar
processes of the mandible extending over a large surface,
distraction of the alveolar processes of the maxilla extending over
a large surface, local distraction of the alveolar crest, cheekbone
distraction, chin augmentation distraction, augmentation
distraction of the border of the mandible, distraction of the
mandibular neck, bone transport in cases of deficiencies in the
ramus of the mandible in combination with a functionally dynamic
bridging plate, as well as in other osseous parts of the body, such
as finger distractions.
[0026] The distraction device may be used as an endo-distraction
implant in at least the following two basic modes of application,
each mode of application showing two different types which may be
mutually combined:
[0027] In one mode of application (mode A), the distraction device
may be used when the osteotomy fragment is situated distally
relative to the skin or the mucous membrane and provided with the
bone thread for receiving the anchoring screw forms the stationary
part, whereas the osteotomy fragment facing the skin or the mucous
membrane and lodging the distraction sleeve forms the mobile part
that is displaced relative to the stationary, principal fragment
during the distraction treatment. This mode of application may be
used, for example, for distractions of the alveolar processes of
the maxilla and the mandible extending over a large surface, for
local distractions of the alveolar crest, distractions of the
cheekbone, distractions of the mandibular neck, and for other
osseous regions of the body, such as finger distractions.
[0028] In another mode of application (Mode B), the device is used
as a distraction device in which the osteotomy fragment situated
distally relative to the skin or the mucous membrane and provided
with the bone thread for receiving the anchoring screw forms the
mobile part, whereas the osteotomy fragment facing the skin or the
mucous membrane and lodging the distraction sleeve forms the
stationary part which pushes away the mobile bone part with the
bone thread during the distraction treatment. This mode of
application is used, for example, for chin augmentation
distractions, augmentation distractions of the border of the
mandible, bone transport in cases of deficiencies in the ramus of
the mandible in combination with a functionally dynamic bridging
plate, and for other osseous parts of the body.
[0029] In this regard, the distractor device may be used as an
endo-distraction implant in which the distraction sleeve including
a stop for the anchoring screw is an implant screwed into the bone
and thus rigidly connected to the osteotomy segment. This implant
type may be used, for example, for distractions of the alveolar
processes of the maxilla and the mandible extending over a large
surface and for local distractions of the alveolar processes.
[0030] Also, the distractor device may be used as an
endo-distraction implant in which the abutment including a stop for
the anchoring screw is stabilized straight or at various different
angles relative to the bone, as required, by means of small
miniature plates using specially designed screws. This implant type
may be used, for example, for cheekbone distractions, for chin
augmentation distractions, augmentation distractions of the border
of the mandible, distractions of the mandibular neck, and bone
transport in cases of deficiencies in the ramus of the mandible in
combination with a functionally dynamic bridging plate.
[0031] FIGS. 2 and 3 illustrate a distraction process through the
example of a mandible 33 having undergone osteotomy and presenting
an osteotomy gap 32. The drawings show in particular a distraction
process according to Mode A in which the alveolar process is
displaced in the cranial direction. As described above, the
anchoring screws 2 of the endo-distractors are passed through the
cranial bone segment 34 and through the osteotomy gap 32 and are
then inserted into the caudal bone segment 35. The anchoring screws
2 are screwed into the caudal bone segment 35 until their threaded
tips 6 protrude from the opposite side thereof. The excessive
length corresponds to the amount of distraction to be obtained for
the osteotomy gap. The distraction sleeves 3 are inserted into the
cranial bone segment 34 and prevent the anchoring screws 2 from
moving in the cranial direction. As the anchoring screw 2 is
screwed backwards, the cranial bone segment 34 is lifted in the
cranial direction by the action of the distraction sleeve 3, while
the caudal bone segment 35 remains stationary.
[0032] FIG. 4 illustrates the distraction process according to Mode
B through the example of a mandible 33 that has undergone
osteotomy. In this example the distraction results in a
displacement of the chin in the caudal direction.
[0033] One skilled in the art may appreciate that when the
distractor device is used, the distraction force is preferably
applied in the center of gravity of the distraction so that the
distraction device is preferably exclusively exposed to axial
pressure and not to any flexural strain, which facilitates an
endo-distraction device having small dimensions. Also, the
distraction occurring subsequent to an osteotomy may begin
horizontally offset, representing at the same time a horizontal
displacement osteotomy, and the offset may be carried out in a
controlled manner. The distraction following the osteotomy may also
be carried out in different directions, depending on the angle
relative to the osteotomy plane selected for the bore designed to
receive the endo-distractor, which allows for corrective measures
in cases of a defective relation of the crests of the maxilla and
the mandible as a preparation for a prosthetic appliance to be
placed subsequently.
[0034] Furthermore, it should be recognized that the distraction
sleeve, together with its cover screw, may serve to stabilize a
temporary prosthesis during the retention period of several months
and may assume a function comparable to that of a dental implant.
In this regard, putting load on the endo-distractor and, as a
consequence, on the freshly distracted bone at an early stage
provides a great deal of functional stimuli and thus may lead to an
accelerated bone formation in the distraction area. Also, since the
screw thread of the distraction sleeve is counter-rotating it is
secured against being screwed off in the course of the distraction.
After the removal of the distraction sleeve, the left-hand thread
of the latter leaves behind a left-hand thread formed in the bone.
This thread, together with the right-hand thread formed in the
lower bone segment, simultaneously has the function of a pilot bore
for the implant to be placed in the course of the same surgical
intervention once the endo-distractor has been removed. These
threaded bores therefore represent at the same time the pilot bores
for receiving the dental implant to be subsequently inserted. The
osseous left-hand thread of the hollow implant, after the cutting
of a right-hand thread for a dental implant, results in a reliable,
new bone thread providing a good primary seat for the dental
implant. The two counter-rotating threads cross at different
positions, depending on the difference in their respective thread
pitches. All types of dental implants can be used, no matter what
kind of screw thread they may have, and the surgeon is not limited
to a particular type of implant to be used for the prosthetic
treatment.
[0035] With the aid of the distraction device, the following
exemplary surgical technique for the distraction of the mandible
may be realized: the mandible is split horizontally using accesses
that avoid excessive soft-tissue damage (osteotomy). Depending on
the situation, any number of distractor devices or endo-distractors
may be used. The anchoring screws of the endo-distractors are
passed through the cranial bone segment and the osteotomy gap and
are then inserted into the caudal bone segment. The anchoring
screws are screwed into the caudal bone segment until their
threaded tips protrude from the opposite side thereof. The
excessive length corresponds to the amount of distraction to be
obtained for the osteotomy gap. The distraction sleeves are
inserted into the cranial bone segment and prevent the anchoring
screws from moving in the cranial direction.
[0036] The actual distraction process takes place during several
days or weeks and in most cases is carried out by the patient
himself. The patient turns back the anchoring screw by about 1/2 mm
per day. As the distraction sleeve prevents the anchoring screw
from being screwed out in the cranial direction, the cranial bone
segment is lifted in the cranial direction by means of the
distraction sleeve. Advantageously, this surgical technique may be
realized with relatively unsophisticated technical equipment and
the implants have a small volume.
[0037] Also, the distractor device allows vertical distraction of
the alveolar processes of the maxilla and the mandible according to
the Salzburg concept. It is of particular advantage if prior to the
insertion of the implants the alveolar process can be "rebuilt" to
its initial height. Preferably, the distance between the toothless
alveolar processes of the maxilla and the mandible corresponds
again to the height of natural teeth and the implant structures are
low and therefore resistant. Also, preferably there are no recesses
under the implants which are difficult to clean, and after
completion of the distraction, the mandible has recovered its
normal height and width and is capable of receiving long and stable
implants, without running the risk of a spontaneous fracture.
[0038] As described above, the endo-distraction implant includes an
abutment (with axial and radial function) for the anchoring screw
and is integrated into a distraction sleeve inserted into the outer
bone segment which does not need to have an internal screw thread
and keeps the anchoring screw sealed tightly against bacteria and
saliva by means of O-rings during the entire distraction and
retention period. Also, the anchoring screw is inserted directly in
a threaded bore tapped into the osseous substance of the bone
segment situated on the opposite side of the osteotomy gap. A
secure guidance and directional stability of the distraction
process is preferably ensured by the threaded bore formed in the
cortical bone. The distraction preferably occurs in the central
part of the bone and preferably no part of the osteotomy line is
covered on the outside by metal, which is an ideal condition for
callus formation. The spare length of the anchoring screw
corresponding to the extent of distraction required is preferably
hidden deep in the soft tissues on the side opposite to the side on
which the device is readjusted and, for this reason, preferably
does not entail any negative effect on the patient.
[0039] One exemplary method of implantation involves first planning
for the operation, for instance by observing surgical instructions
concerning the distraction of the anterior mandible, providing
anesthesia, performing preparations, drafting and following a
surgical drawing, electing a type of incision, measuring, and
planning of the horizontal osteotomy. Next the horizontal osteotomy
is performed and bores are drilled for receiving the implant and
tapped. Tapping may be done for example by 2.times. tapping of a
left-hand thread (4.0 mm) in the upper segment such as by means of
a ratchet and with sufficient cooling the threads and until all the
bone chips have been removed from the bone threads. Next the
implants are screwed in, for example by using an adequate crown
spanner and the ratchet, the two distraction sleeves are screwed
completely into the two threads formed in the upper segment. In
doing so, attention must be paid that the two O-rings placed within
the distraction sleeve will not get lost, as they ensure that
saliva, food residues, and germs are prevented from reaching the
bone. The implant is then secured and osteoplasty may be performed
followed by wound closure, an early postoperative period, a
distraction period, a retention period, and finally, once the
ossification has been completed satisfactorily insertion of the
dental implants. For the prosthetic structures the following
implant systems may be used: Ankylos implants; Bonefit implants;
Frialit II implants; Br.ang.nemark implants, among others
[0040] It will be appreciated that use of the longest implants
available may be desirable, as long implants are apt to reach also
the caudal osteotomy fragment, i.e. to bridge the distraction gap,
which is necessary in order to counteract he tendency towards
shrinking of the newly formed bone substance. In order to remove
the inventive endo-distraction implants, a simple section of the
crest of the mandible is performed, directly laying open the
implant region. Positional records relating to the insertion of the
implants are helpful for finding the location of the lateral
implants at a safe distance from the mental nerve. First, the outer
implants are inserted in the usual manner. Drilled bone chips
occurring during the insertion of these implants are carefully
harvested using the bone aspirator and temporarily stored in a cell
nutrient solution. Subsequently, the distraction sleeves are
screwed out clockwise (left-hand thread) using the crown spanner
and the ratchet, after which the anchoring screws are screwed out
anti-clockwise (right-hand thread) by means of their specific
spanner. The following step consists in the bone preparation for
the two mesial implants, great care being taken to temporarily
store every bone fragment which can be harvested in a cell nutrient
solution. In case of dehiscences occurring in the region between
the inserted implants and the bone, these are carefully curetted
and filled up with bone chips and bone meal. A semi-permeable
membrane placed over the implant prevents bone resorption and the
ingrowth of connective tissue. After the mobilization of the mucous
membranes, these are closed in two layers using slowly resorbable
sutures. The sutures are removed two weeks after the implantation.
A temporary prosthetic appliance can be made one week after the
insertion of the implants at the earliest. Attention must be paid
to ensure that the centric occlusion is absolutely correct and that
the prostheses are repeatedly padded in short intervals.
[0041] It will be appreciated that when using the distractor
device, the oral vestibule does not need to undergo a second
surgical intervention which would otherwise be necessary to remove
parts of the implant. In addition, the initially drilled bores can
be used for the insertion of the final dental implant, which may be
carried out under local anesthesia in a simple manner easily
acceptable for the patient. Also, the part of the endo-distraction
implant to be worked on is preferably located at the same height
relative to the surface of the skin or the mucous membrane, so that
the temporary prostheses can be made at an early stage, and as a
result, the number of implant parts may be reduced from at least
three to no more than two. The distraction may be started in a
controlled manner even with an offset relative to the osteotomy
plane and by using different bore angles, the distraction may take
place at various angles of inclination, depending on the specific
requirements. The implant may be completely removed in a very easy
manner by simply screwing out the distraction sleeve and the
anchoring screw, and once the implant has been removed, the final
dental implant may immediately be inserted using any of the
commercially available implant systems, so that no further surgical
intervention will be necessary.
[0042] It will also be appreciated that during the insertion
process, no parts undergo mechanical deformation, so that any
damage of an implant, which might otherwise occur during adaptation
works even before the implant is used, can eliminated, and if in
the course of a surgical intervention the application of a
distraction device has failed, the distraction device may simply be
inserted at another location.
[0043] If two distraction devices according to the invention are
required in order to prevent twisting and to obtain a better
distribution of the distraction forces, the two endo-distraction
implants may be inserted parallel to each other at a wide or narrow
distance. When inserted at a wide distance the daily distraction
may be by an equal amount on both sides and may be achieved by
turning on both devices in an exactly identical manner by means of
a spanner (a mark on the spanner is necessary). Alternatively, the
two devices may be inserted at a narrow distance to each other and
be manipulated by means of an attachment which simultaneously
rotates the two threaded rods by an identical angle of rotation in
the same direction of rotation, thus causing a parallel
distraction. An attachment of this type works with three serially
interlocked gears the middle one of which being in engagement, by
its axis, with the spanner, whereas the two outer gears drive the
threaded rods by means of their axes.
[0044] One skilled in the art will further appreciate, that the
left-hand thread of the hollow implant provides additional security
while the right-hand thread of the threaded rod is used during the
distraction. Should the hollow implant have become slightly
loosened within the bone thread of the upper osteotomy segment,
said implant is tightened again by the torque of the threaded rod
as said threaded rod is screwed out. Generally, one and the same
device may be used as an all-purpose device for the most diverse
areas of application, and there is no necessity of further surgery
for the removal of the device, as this intervention coincides with
the insertion of the dental implants and, in addition, provides the
bores required for the dental implants. Also, tight sealing of the
bone against saliva and bacteria is provided on the distraction
site. No unnaturally shaped parts are required, either in the oral
cavity nor outside in the area of the face, so that no
disfigurement occurs and the patient feels no embarrassment in
pursuing such activities as eating, speaking, or mouth hygiene.
Also, the endo-distractor according to the invention has the
external shape of a single-tooth implant and is capable of
providing support even during the retention period, similar to a
tooth or a dental implant. As a result, the endo-distractor
according to the invention is small but efficient as to the
distraction length it allows, it acts in the centre of the bone in
the structurally most favorable region, and the component parts are
exclusively exposed to axial, compressive and tensile stress
(absence of any lateral shear forces and flexural stresses that are
typical of many other known devices), which ensures the greatest
possible protection against fractures due to material fatigue.
* * * * *