U.S. patent application number 12/459251 was filed with the patent office on 2009-10-29 for impulsive percussion instruments for endplate preparation.
Invention is credited to Loic Josse, Mingyan Liu.
Application Number | 20090270871 12/459251 |
Document ID | / |
Family ID | 34130376 |
Filed Date | 2009-10-29 |
United States Patent
Application |
20090270871 |
Kind Code |
A1 |
Liu; Mingyan ; et
al. |
October 29, 2009 |
Impulsive percussion instruments for endplate preparation
Abstract
A hand-held instrument, with a rotary power input to a camshaft,
has cam and follower arrangement to provide a reciprocating shaft
output. A cutter is provided on the output shaft. In one example,
rotating cam percussion is transmitted to the cutter by engaging
the cutter with the tissue to be cut, and pushing the instrument
forward toward the cutter. In another example, rotating cam
percussion is transmitted to the cutter by engaging the cutter with
the tissue to be cut, and pulling the instrument back toward the
user while maintaining engagement of the cutter with the tissue. In
both examples, the cutter remains in idle condition until an
axially directed load, forward in the one example, or backward on
the other example, is placed on the cutter by moving the instrument
forward or backward, respectively, while the camshaft is rotating.
A distractor with frame is used to spread and maintain space
between vertebral bodies, enabling entrance of the cutter.
Inventors: |
Liu; Mingyan; (Bourg La
Reine, FR) ; Josse; Loic; (Palaja, FR) |
Correspondence
Address: |
MEDTRONIC;Attn: Noreen Johnson - IP Legal Department
2600 Sofamor Danek Drive
MEMPHIS
TN
38132
US
|
Family ID: |
34130376 |
Appl. No.: |
12/459251 |
Filed: |
June 29, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10937159 |
Sep 9, 2004 |
7569057 |
|
|
12459251 |
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Current U.S.
Class: |
606/90 |
Current CPC
Class: |
A61B 17/1757 20130101;
A61B 2017/0256 20130101; A61B 17/1604 20130101; A61B 17/025
20130101; A61B 17/1671 20130101 |
Class at
Publication: |
606/90 |
International
Class: |
A61B 17/58 20060101
A61B017/58 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 11, 2003 |
EP |
03292241.1 |
Claims
1.-34. (canceled)
35. A surgical method for treating vertebral endplates, comprising:
selecting an elongate disc space keeper frame having two side
members and front, intermediate and rear cross members; engaging
with the frame a distractor having a wedge portion, head portion,
handle portion and a hook; receiving the front cross member of the
frame in a groove defined in a front tip of the wedge portion of
the distractor; receiving the intermediate cross member of the
frame in the hook on the distractor; and inserting the frame into
the intervertebral disc space from an anterior approach by
displacing the distractor.
36. The method of claim 35 and further comprising: removing the
distractor from the frame while leaving the distractor front cross
member and portions of the side members in the disc space to
maintain the disc space for insertion of cutter instruments adapted
for the preparation of vertebral endplates for receipt of an
interbody fusion device.
37. A combination distractor and disc space keeper for use in
spinal surgery, comprising: an elongate frame having two side
members and front, intermediate and rear cross members; and a
distractor having a wedge portion, head portion, handle portion and
a forward facing hook; the wedge portion of the distractor having a
tip at the front of the wedge portion and having a forward facing
groove in the tip; and the front cross member of the frame being
received in the groove in the tip of the wedge portion, and the
intermediate cross member of the frame being received in the hook
of the distractor.
38. The combination of claim 37 and wherein: the wedge portion of
the distractor is located between the frame side members.
39. The combination of claim 38 and wherein: the head portion of
the distractor is located between portions of the side members of
the frame.
40. The combination of claim 38 and wherein: portions of the wedge
portion are adjacent frontal portions of the side members and
diverge vertically in a rearward direction from a rounded tip to a
shoulder at the head portion.
41. The combination of claim 40 and wherein: the frontal portions
of the side members of the frame adjacent the wedge portion diverge
in a manner similar to the wedge portion from the front cross
member rearward.
42. The combination of claim 41 and wherein: the handle portion and
wedge portion and front cross member lie in a first plane; and the
side members have portions intermediate the frontal portions and
extending rearward from the frontal portions and away from the
first plane to the rear cross member in a second plane offset from
the first plane to admit a powered instrument to the space between
the planes upon separation of the distractor from the frame.
43. The combination of claim 42 and wherein: the departure of the
intermediate portions of the side members from the first plane to
the second plane is sufficient to admit a cutter instrument into
the space between the planes.
44. A combination distractor and disc space keeper for use in
spinal surgery, comprising: a distractor extending along a
longitudinal axis and including a wedge portion, an elongate shaft
portion, and a forward facing engagement portion, the wedge portion
having a distal tip and upper and lower surfaces that diverge away
from one another from the distal tip in a rearward direction toward
the shaft portion; an elongate frame having two side members
laterally offset from one another to define a housing space
therebetween, the frame including a transverse cross member between
the side members; and wherein the distractor and the frame are
removably assembled together with the wedge portion of the
distractor positioned within the housing space between the side
members of the frame and with the forward facing engagement portion
of the distractor engaged with the transverse cross member of the
frame.
45. The combination of claim 44, wherein the frame includes a front
transverse cross member and a rear transverse cross member each
extending between the side members.
46. The combination of claim 44, wherein the distal tip of the
wedge portion of the distractor has a forward facing transverse
groove; and wherein the frame includes a front transverse cross
member extending between the side members; and wherein the front
transverse cross member of the frame is received in the transverse
groove in the distal tip of the wedge portion when the wedge
portion is positioned within the housing space between the side
members of the frame.
47. The combination of claim 44, wherein the forward facing
engagement portion of the distractor comprises a forward facing
hook; and wherein the transverse cross member of the frame
comprises a transverse pin; and wherein the transverse pin is
received in the forward facing hook when the wedge portion of the
distractor is positioned within the housing space between the side
members of the frame.
48. The combination of claim 47, wherein the forward facing hook of
the distractor extends transversely from the shaft portion of the
distractor.
49. The combination of claim 44, wherein the distractor further
includes a head portion between the wedge portion and the shaft
portion, the distractor defining abutment shoulders at the
transition from the wedge portion to the head portion and extending
outward from the upper and lower surfaces of the wedge portion,
respectively.
50. The combination of claim 49, wherein the abutment shoulders
have an arcuate shape.
51. The combination of claim 44, further comprising a cutter
instrument having a cutting head sized for insertion into the
housing space between the side members of the frame and adapted for
preparation of vertebral endplates.
52. The combination of claim 44, wherein the wedge portion is
positioned adjacent frontal portions of the side members of the
frame; and wherein the frontal portions of the side members include
upper and lower frame surfaces that diverge in a manner similar to
the upper and lower surfaces of the wedge portion in the rearward
direction.
53. The combination of claim 44, wherein the side members have
frontal portions positioned adjacent the wedge portion of the
distractor and lying in a first plane, intermediate portions
extending rearward from the frontal portions away from the first
plate, and rear portions extending rearward from the intermediate
portions and lying in a second plane offset from the first plane,
the first and second planes spaced apart to admit a cutter
instrument in a space between the first and second planes upon
removal of the distractor from the frame.
54. The combination of claim 53, wherein the transverse cross
member of the frame is offset from the first plane.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present Application claims foreign priority benefits of
European Patent Application Number 03292241.1, filed Sep. 11, 2003,
the contents of which are hereby incorporated by reference.
BACKGROUND
[0002] This invention relates generally to surgery tools and more
particularly to power cutting instruments for vertebral endplate
preparation in spinal surgery.
[0003] Following removal of some disc materials during spinal
surgery, it is important to prepare the endplates of the vertebral
bodies for reception of inter-body implant materials. It is
desirable to provide devices and procedures for safer, more
controlled and more efficient disc space cleaning and endplate
preparation. The present invention is directed to providing an
additional option for surgeons for improvement in these
regards.
SUMMARY
[0004] In general, the present invention provides power-operated,
hand-held instruments adapted to reception of different types of
tissue treatment tools, and drives them in a reciprocating
motion.
[0005] Further, the invention provides for conversion from a rotary
input power source to a reciprocating source, and percussion action
in the forward direction in one embodiment, and percussion action
in the reverse direction in another embodiment. More specifically,
in one embodiment the invention enables use with treatment tools
expected to perform more effectively during a forward motion and,
in another embodiment, the invention enables use with treatment
tools expected to perform more effectively during a reverse motion.
Such tools have preferred performance directions, forward or
reverse. The invention further comprises treatment tool
configurations particularly suitable to the direction and type of
cutting action sought. For tools that perform well in either
direction, either of the embodiments of the invention may be used.
The invention further provides a distractor and keeper arrangement
for maintaining distracted disc space height during endplate
preparation, the keeper being shaped for convenient use with the
powered instruments according to the present invention.
BRIEF DESCRIPTION OF THE FIGURES
[0006] FIG. 1 is an elevation view of a percussion instrument
according to one embodiment of the present invention.
[0007] FIG. 1A is a perspective view of the embodiment shown in
FIG. 1 and showing, schematically, an example of an air powered
rotary motor and air supply line from a foot pedal operated
compressor.
[0008] FIG. 2 is a partial section through it taken at line 2-2 in
FIG. 1 and viewed in the direction of the arrows.
[0009] FIG. 2A is a perspective view of the instrument with a
quarter section.
[0010] FIG. 2B is an enlarged perspective view of the proximal end
portion of FIG. 2.
[0011] FIG. 3 is a left-hand end view thereof.
[0012] FIG. 4 is an enlarged elevation view of the camshaft
thereof.
[0013] FIG. 5 is a section taken at line 5-5 in FIG. 4 and viewed
in the direction of the arrows and showing a square cam
cross-section.
[0014] FIG. 6 is an enlarged sectional view of the spring guide and
seat member of FIG. 2.
[0015] FIG. 7 is an enlarged elevation view of one type of
cutter-shaft combination of the embodiment of FIGS. 1 and 2 but on
a larger scale, and with a portion broken out to conserve space in
the drawing.
[0016] FIG. 8 is a section taken at line 8-8 in FIG. 7 and viewed
in the direction of the arrows.
[0017] FIG. 9 is an enlarged view of the shaft guide and spring
chamber.
[0018] FIG. 10 is a left-hand end view thereof.
[0019] FIG. 11 is a sectional view of the end closure ring for the
spring chamber.
[0020] FIG. 12 is a fragmentary elevation view of the proximal end
portion of the instrument body of FIG. 1 but on a larger scale and
without the end cap and internal parts.
[0021] FIG. 13 is a left-hand end view thereof.
[0022] FIG. 14 is an elevation view of a second embodiment of the
present invention featuring reversed percussion movements (pull
back impacts).
[0023] FIG. 15 is a view, partially in section taken at line 15-15
in FIG. 14, and viewed in the direction of the arrows.
[0024] FIG. 16 is an enlarged elevation view of the camshaft.
[0025] FIG. 17 is an end view of the camshaft.
[0026] FIG. 18 is a top (overhead) view of the cutter drive
shaft.
[0027] FIG. 19 is a view of the version of reversed percussion
cutter shaft as shown in FIGS. 14 and 15, but with a portion of the
length thereof broken away to conserve space in the drawing.
[0028] FIG. 20 is an axial view of the camshaft end bearing.
[0029] FIG. 21 is a cross section at line 21-21 in FIG. 20 and
viewed in the direction of the arrows.
[0030] FIG. 22 is an inside face view of the proximal end cap
usable in the FIG. 2 and FIG. 15 embodiments of the invention.
[0031] FIG. 23 is a section taken at line 23-23 in FIG. 22 and
viewed in the direction of the arrows.
[0032] FIG. 24 is a top (overhead) view of a combination distractor
and distractor blade housing used to establish and maintain the
desired disc space during use of the instruments of FIGS. 1-23.
[0033] FIG. 25 is a section taken at line 25-25 in FIG. 24 and
viewed in the direction of the arrows and showing application into
the disc space.
[0034] FIG. 26 is a top (overhead) view of the distractor itself
with a portion broken away from the middle to conserve space in the
drawing.
[0035] FIG. 27 is a section taken at line 27-27 in FIG. 26 and
viewed in the direction of the arrows.
[0036] FIG. 28 is a left-hand end view thereof.
[0037] FIG. 29 is a top (overhead) view of the distractor blade
housing which serves also as the disc space keeper.
[0038] FIG. 30 is a section view taken at line 30-30 in FIG. 29 and
viewed in the direction of the arrows.
[0039] FIG. 31 is a left-hand view thereof.
[0040] FIG. 32 is a right-hand view thereof.
[0041] FIG. 33 is an enlarged perspective view of the cutter
illustrated in the FIGS. 1, 2, 7 and 8 illustrations.
[0042] FIG. 34 is a perspective view of another type of cutter.
[0043] FIG. 35 is an elevation view of the cutter and shaft for the
cutter of FIG. 34, with a portion broken away to conserve space in
the drawing.
[0044] FIG. 36 is a perspective view of another embodiment of
cutter useful in the FIG. 1 embodiment of the invention.
[0045] FIG. 37 is an enlarged overhead view of the complete cutter
and shaft for the cutter of FIG. 36 with a portion broken away to
conserve space in the drawing.
[0046] FIG. 38 is an end view thereof.
[0047] FIG. 39 is a section therethrough taken at line 39-39 in
FIG. 37 and viewed in the direction of the arrows.
[0048] FIG. 40 is a perspective view of another cutter useful with
the FIG. 1 embodiment of the invention.
[0049] FIG. 41 is a perspective view of still another cutter
similar to that of FIG. 33 but narrower.
[0050] FIG. 42 is a perspective view of the cutter shown in the
illustrations of FIGS. 14, 15 and 19 for the pull-back embodiment
of the invention.
[0051] FIG. 43 is an elevation view of another embodiment of the
cutter and shaft used with the pull-back embodiment of the
invention of FIGS. 14 and 15.
[0052] FIG. 44 is a section therethrough taken at line 44-44 in
FIG. 43 and viewed in the direction of the arrows.
DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0053] For the purposes of promoting an understanding of the
principles of the invention, reference will now be made to the
embodiments illustrated in the drawings and specific language will
be used to describe the same. It will nevertheless be understood
that no limitation of the scope of the invention is hereby
intended, such alterations and further modifications in the
illustrated devices, and such further applications of the
principles of the invention as illustrated herein being
contemplated as would normally occur to one skilled in the art to
which the invention relates.
Forward Percussion Embodiment
[0054] Referring now to the drawings in detail, particularly FIGS.
1-3, 12 and 13, the instrument has a one-piece elongated body 11
having a cam housing portion 12, a spring chamber portion 13, guide
barrel portion 14, and end cap 16. A camshaft 17 is received in the
cam housing portion.
[0055] A cutter-shaft 21 is received in the guide barrel and has a
shaft portion with proximal end 22 and a cutter portion with distal
end 23. A spring housing 26 (FIGS. 2, 9 and 10) is received in the
bore 27 of the spring chamber portion of the body 11. As best shown
in FIGS. 9 and 10, this spring housing has one end wall 29 with a
central aperture 31 which receives and guides the proximal end
portion of the cutter shaft 21. Housing 26 has stop tabs 32 and 33
at the end wall and which are received in grooves 34 and 36 (FIG.
13, and dashed lines in FIG. 1). These grooves extend
longitudinally forward from the proximal end 37 (FIGS. 1 and 12) of
the body, and end at plane 35 as shown in FIG. 1. They provide
abutments to prevent movement of the housing 26 in the direction of
arrow 78, beyond the location shown in FIG. 2. Also, the tabs 32
and 33 in grooves 34 and 36, respectively, prevent rotational
movement of the spring housing within the body 11.
[0056] The hole 31 in the proximal end wall 29 serves as a proximal
end bearing for the cutter shaft 21. Forward portions of the shaft
21 are slidably received and guided by contact of the outer wall of
the shaft with the inner wall of the guide barrel portion 14 of the
body 1.
[0057] A spring guide and end stop 38 (FIGS. 2 and 6) is slidably
received on the proximal end portion of the shaft 21. Its outer rim
39 is slidably received in the bore 41 (FIG. 9) of the housing 26.
A coil spring 42 (FIG. 2) is received around the stepped-down
portion 43 of the member 38. The shoulder 44 at the step from the
cylindrical surface 39 to the cylindrical surface 43 serves as a
seat for the distal end of the spring 42. The inside face 46 of the
end wall 29 of the housing 26 serves as a spring seat for the
proximal end of spring 42.
[0058] The right-hand end portion 47 of housing 26 is internally
threaded at 48 and receives end closure ring 49 (FIG. 11) which is
screwed into the housing 26. This prevents the member 38 and spring
therewith, from sliding out of the assembly when one cutter shaft
is removed and replaced by another one having a different type of
cutter. Normally, however, a screw 51 (FIGS. 1 and 2) is screwed
into the body 11 and extends through an elongated hole 52 in the
shaft 21. This screw normally retains the shaft 21 in the body. The
length of hole 52 in the axial direction permits a range of shaft
reciprocation from engagement with low points on the cam surface to
slightly beyond the maximum height of the cam surface. To change
cutters, the screw must be removed and then the shaft 21 can be
dropped or pulled out from the distal end 53 of the guide barrel 14
followed by installation of the replacement cutter shaft.
[0059] Referring now more particularly to FIGS. 4 and 5 along with
FIG. 2, the camshaft 17 is generally cylindrical about the axis 56
and has cylindrical flanges 57 and 58 which abut flanged bushings
59 and 61 received in upper and lower, rearwardly opening yokes 62
in the cam housing portion of the body 11 (FIGS. 1 and 12).
Similarly, end cap 16 (FIGS. 22 and 23) has yoke portions which
receive the bushings 59 and 61 when the end cap is fastened to the
body with the four screws 66 (FIG. 3). The bushings 59 and 61 can
be engaged by the outboard faces of the flanges 57 and 58 of the
camshaft, so they provide location and thrust bearings for the
camshaft as well as radial bearings for the smooth cylindrical
surfaces 67 and 68 (FIG. 4) of the camshaft. It is seen that the
yokes 62 of the body and 64 of the end cap 16, capture the bushings
59 and 61 and thereby capture the cam shaft in the assembly for
centering the camshaft axis 56 colinear with the axes of bushings
59 and 61, when the end cap is secured in place by the screws
66.
[0060] The cam surface itself shown generally at 71 in FIGS. 4 and
5, is square shaped, having four low areas 72 and four high points
73. Other cam surface profiles may also be used. One example is
shown in dotted lines in FIG. 5 in the form of a hexagon. It is the
square cam shape which is shown in FIG. 2, with the shaft end 22
(rounded as shown in FIG. 8) engaging a low point on the cam and
serving as the cam follower surface. Normally, however, spring 42
urges the spring seat 44 on member 38 (FIG. 6) to the right (in the
direction of arrow 78). Abutting engagement of the wall 76 of
member 38 with the annular shoulder 77 (FIGS. 7 and 8) of the
cutter shaft 21 urges the shaft in the outward direction of arrow
78 (FIG. 2) to an extent limited by the engagement of the proximal
end 79 of hole 52 with the stop screw 51. Therefore, in this normal
rest position of the cutter shaft, the proximal end 22 thereof will
be located, as shown by the dotted line 22R (FIG. 2), spaced away
from the circular path of the high points of the cam.
[0061] Since this is a power operated instrument, converting rotary
motion to reciprocating motion, the cam shaft has flat surfaces 81
for reception of a coupler, and a circular notch 82 for reception
of a spring clip or clamp of a coupler from an external rotary
power source. This may be any of a variety of power sources such
as, electric, hydraulic or more likely an air or nitrogen powered
turbine motor 85 (FIG. 1A) coupled to the camshaft. Air may be
supplied through tubing 85A from a compressor 85B with speed
control pedal 85C. Any other available source of air or other gas
with pressure and/or volume control may be used.
Operation
Forward Percussion Embodiment
[0062] As an example of the operation of this embodiment of the
invention, the user may select the treatment tool to be used,
insert it in the barrel 14 and install the screw 51. The tissue
treatment tool referred to above and hereinafter is referred to
broadly hereinafter as a cutter, and this term is intended to
include tools which chisel, file, shape, rasp, polish, broach or
otherwise perform the intended effect on or with the body tissue
treated.
[0063] Before or after installation of the cutter shaft, the user
may connect the power source to the camshaft. After positioning the
distal end 23 of the cutter at the endplate treatment site and
engaging the tissue to be treated, the user may apply force in the
forward direction of arrow 78, which is the forward cutting
direction of the cutters to be used with this embodiment of the
invention. The forward force will compress the spring 42 and move
the cam surface toward the shaft end (the cam follower surface) 22.
If the camshaft is rotating, percussion action will begin as soon
as the shaft end is touched by the high points of the rotating cam,
and reciprocating action of the cutter will begin. The speed of
such action can be controlled by speed control of the power source,
whether by a motor at the instrument (as shown in FIG. 1A), or
through a cable or hose and foot control or whatever speed control
is desired or available. The percussion impact will depend on how
much force the user applies in the direction of arrow 78, as the
spring 38 is compressed by increasing force and thereby permits the
end of the shaft 22 to project farther into the path of the cam
surface as the cam surface moves about the rotational axis 56 of
the camshaft.
[0064] From the foregoing discussion, it can be recognized that
cutter shafts other than shaft 21 shown specifically in FIGS. 1, 2,
7 and 8, may be used in the practice of the present invention.
Examples are different types of chisels, shavers and rasps to
decorticate the endplate from the disc materials and the cartilage
layer. Some are shown in FIGS. 34, 35, 36-39, 40 and 41. It is only
necessary to remove the screw 51 and drop or pull cutter shaft 21,
select a cutter shaft having a different distal end cutter (the
shaft portion from the cutter to the proximal end 22 being of the
same configuration as shown in FIGS. 7 and 8), and insert the
proximal end of the cutter shaft through the distal end of the
barrel 14 and through the bore and spring seat member 38 and into
the bore 31 of the housing 26. Of course, it is preferable to have
the power source turned off or disconnected from the camshaft
during the cutter shaft installation to avoid the risk of having
the proximal end 22 struck by the cam and driving the tool back out
of the barrel before the limit screw has been installed. Such event
might otherwise occur, depending upon whether the cutter shaft is
pushed in with enough force to compress the spring 42.
Reverse Percussion Embodiment
[0065] This embodiment is discussed with reference to FIGS. 14
through 23, although it will be seen that several of the components
described above with reference to the first (forward percussion)
embodiment also are used in the reversed percussion embodiment. In
this second embodiment of the invention illustrated in FIGS. 14
through 23, some of the components are very similar to those in the
first described embodiment. For example, the body 86 has a cam
housing portion 87, a spring housing 88 and a guide barrel portion
89. The body 86 is very similar to the body 11 of the first
embodiment, and the end cap 91 is virtually identical to the end
cap 16 of the first embodiment.
[0066] Referring particularly to FIGS. 14-23, and in contrast to
the direction of percussion impulse from the cam in the first
embodiment, the direction of impulse from the cam in this second
embodiment is in the reverse direction so that it pulls the cutter
edge 93 in the rearward direction of arrow 92. For that purpose,
there is a cam shaft 94 mounted for rotation in the cam housing
portion 87 of the body. It operates a cutter drive shaft 96
slidably received in the guide barrel portion 89. Its proximal end
portion 97 is associated with the camshaft, while its distal end
portion 98 receives a proximal end portion 99 of a cutter shaft
having the cutter 93 at its distal end.
[0067] Referring now to FIGS. 16 and 17 along with FIG. 15, the
camshaft 74 is mounted in the body in bushings 101 and 102 which
are received and located in the housing in essentially the same way
as are bushings 59 and 61 described above with reference to the
first embodiment. The camshaft itself has a smooth cylindrical
surface at 103 receiving radial bearing support by bushing 102. It
also has a cylindrical flange 104 having outer face 106 engaging
bushing 102 for thrust bearing support. The outer end portion of
the camshaft has a pair of diametrically opposed flat surfaces 108
on the otherwise cylindrical surface 103 which provide
anti-rotation cooperation with a connector of a rotary power source
in the same manner as for the first described embodiment. Likewise,
it has a stem with annular groove 109 and head 111 to cooperate
with the power source connector and retain it in place.
Accordingly, the drive for this camshaft is like that for the first
embodiment.
[0068] In this embodiment, the cam surface itself is shown at 112
as a square, having four high points 113 and four flat surfaces
114, the center of each flat 114, as in the square cam of the first
embodiment, being a low point in the cam travel. The cam can have
other cross sectional shapes as mentioned above. One of several
possible shapes could be hexagonal as designated by the dash line
116 in FIG. 17. At the end face 117 of the cam 112, there is a step
inward to a hexagonal post 118 non-rotatably received in bearing
119 (FIGS. 20 and 21) and secured to the bearing by a socket head
screw 121 screwed into the end of the camshaft. The hexagonal post
118 on the camshaft is received in the hexagonal aperture 122 of
the bearing 119 which is rotatably received in bushing 101. Thus,
the cylindrical surface 123 of the bearing 119 rotating in the
bushing 101 provides radial bearing support for the camshaft, and
the circular face 124 of the bearing 119 slidingly engaging the
lower face of bushing 101 provides thrust bearing support for the
camshaft.
[0069] Referring now particularly to FIGS. 15 and 18, the cutter
drive shaft 96 for the cutter shaft has a cam follower end portion
97 configured for following the cam 112. It is illustrated in the
form of an elongate hole 126 with straight parallel sidewalls 127
and 128 and a semi-circular end wall 129 having a radius equal to
half the distance between the sidewalls 127 and 128 and centered at
131. This radius is slightly greater than the distance
diametrically across the high points 113 of the cam and is centered
on the cam axis 130. The follower end portion 97 framing the hole
126 has a shoulder 133. A spring 134 (FIG. 15) is a compression
spring having a right-hand end 136 bearing on wall 137 of the
spring chamber portion of the body 86. The left-hand end of the
spring abuttingly engages the shoulder 133 of the follower end
portion of the shaft 96. Therefore, the spring normally pushes the
shaft 96 to the left in the direction of arrow 92.
[0070] An elongate hole 141 through shaft 96 receives travel limit
screw 142, which is screwed into the instrument body 86. When the
instrument is idle, the spring 134 moves the drive shaft 96 to the
left until the right-hand end 143 of the hole 141 engages and is
stopped by the screw 142. This is the normal rest position of the
shaft and places it such that the center 131 of the curved surface
129 of the cam shaft frame hole 126 is spaced slightly outboard of
the circle defined by the four high points of the cam when the
camshaft is rotated.
[0071] The left-hand end wall 146 of the cam follower portion 97 is
provided with extra thickness resulting in a bulge 147 at the
longitudinal axis 148 of the cutter drive shaft 96 and serves as
the cam follower surface of cutter drive shaft 96.
[0072] This embodiment of the invention can be provided with a
variety of cutters of various configurations and types useful,
particularly when pulled toward the surgeon. Some examples are
different types of curettes, scrapers and pull shavers. One example
is the cutter shaft 99 shown in elevation view in FIG. 19 and
partially shown in FIGS. 14 and 42 and shown partially in section
in FIG. 15. This cutter shaft 99 has a cylindrical body portion 151
slidably received on the inside bore of the barrel 89 of the
instrument. A stem portion 152 of the tool has less diameter than
the body portion 151 and is slidably received in a bore 153 in the
distal end portion of the cutter drive shaft 96. The barrel 89 of
the instrument has an elongate hole 154 at one location in the
wall. A hole 156 (FIG. 18) in cutter drive shaft 96 is normally
aligned or in registry with the hole 154 in the housing when the
cutter drive shaft is in rest position dictated by the engagement
of the stop screw 142 with the end wall 143 of hole 141 in the
cutter drive shaft. This is under the urging of the spring 134. So
when the cutter shaft is installed in the direction of arrow 92
into the open end 157 of the instrument body, it can be advanced to
the left so that the cutter stem 152 received in bore 153 has the
threaded hole 158 of the cutter stem 152 located in registry or
lined up with the hole 156 in the cutter drive shaft 96. Then screw
159 can be inserted through the hole 154 in the guide barrel 89 and
screwed into the cutter shaft hole 158 to fasten the cutter shaft
99 to the cutter drive shaft 96. The screw head is stopped so that
it resides in the hole 156 in the cutter drive shaft, retaining the
cutter shaft in place but recessed slightly from the inside wall of
the barrel 89 to avoid interference with reciprocation of the
cutter shaft. Besides, the hole 154 in the wall 89 is long enough
that the screw can move forward and backward in the direction of
arrow 92 within the hole 154 during reciprocation of the drive
shaft 96. With this arrangement, the cutter shaft 99 can be readily
removed from the guide barrel by simply removing screw 159 and
pulling the cutter shaft out of the barrel. Another cutter shaft
with a different configuration of the cutter portion but with the
same configuration otherwise, can then be inserted through the end
157 in the direction of arrow 92. When the anchor hole 158 thereof
is lined up with the hole 154, the screw 159 is installed to fix
the new cutter shaft to the drive shaft 96 in preparation for using
the new cutter.
Operation
Reverse Percussion Embodiment
[0073] As mentioned above, the surgeon can run the cam constantly
if desired, or can start it and stop it at the beginning and end of
a cutting operation. Depending upon the power source available, the
speed of rotation may be varied and thus, the speed of the cutter
strokes would vary. A reciprocating action begins when the surgeon
has engaged the cutter with the surface to be treated and pulls the
instrument in the direction of arrow 92 with the cutter edge 93
engaging the surface to be prepared. The force of impact between
the cutter edge 93 and material to be cut, is determined largely by
the force with which the instrument is pulled in the direction of
arrow 92, which thereby compresses the spring 134 and enables the
cam engaging follower surface 147 of the cam follower to impinge on
the path of rotation of the high points of the cam. The rate of
impulses depends upon the speed of the camshaft as determined by
the surgeon.
[0074] It can be understood that some cutters may be useful and
which can treat the tissue in a useful way regardless of whether
the cutter is driven in the forward or reverse direction. Such
cutters can be used in either the forward or reverse percussion
type instrument described above, if the proximal end portion of the
cutter shaft is shaped and located to work with the cam and
follower arrangement provided in the instrument. One example is a
cutter as shown in FIGS. 34 and 35. With the shaft as shown in
those figures, the cutter will work with the forward percussion
instrument. If the shaft is made as shown in FIGS. 43 and 44, the
cutter will work with the reverse percussion instrument.
Disc Height Maintenance
[0075] Referring now to FIGS. 24-30, there is shown apparatus used
according to the present invention to facilitate use of either of
the two previously described embodiments. Referring first to FIGS.
24 and 25, a combination distractor and disc space keeper is shown.
As shown specifically in FIGS. 26-28, the illustrated distractor
171 includes a handle portion 172, shaft portion 173, head portion
174, and wedge portion 176. A forwardly opening hook 177 is fixed
atop the shaft portion near the head portion. The wedge portion has
a transverse groove 178 at the tip. Abutments 179 are provided at
the transition from tip portion to head portion and are slightly
arcuate in shape, as shown in FIG. 26. The upper and lower surfaces
of the tip portion converge at a five degree total angle, half
above and half below a plane containing the axis 181 of the shaft
and handle portions. Referring particularly to FIGS. 29-32, a
distractor blade housing 186 and which serves as the disc space
keeper, is made in the form of a frame and includes parallel side
members 187, a rear cross member 188, an intermediate cross member
189 serving as a hinge pin, and a front cross member 191.
[0076] In the use of this device, and after the removal of the disc
from the space between vertebral bodies shown schematically at 191
and 192 in FIGS. 24 and 25, the distractor 171 is assembled with
the blade housing 186 by inserting the wedge portion between the
housing side members and moving it forward to engagement of the
groove 178 of the distractor tip with the front cross member 191 of
the blade housing and simultaneously receiving the hinge pin 189 in
the hook 177, as shown in FIG. 25. Then, approaching from the
anterior side of the spine, the space from which the disc material
has been previously removed is approached in the direction of the
arrow 193, and the handle 172 is pushed in that direction to open
up the space to approximately eight or ten millimeters, or to such
other extent as desired, and by hammer or other impulses on the
handle end 194, if needed. After the desired disc height is
established in this manner, the distractor handle is pulled out in
the direction of arrow 196, while the blade housing 186 remains in
place and maintains the disc height as desired, thus serving as the
disc space keeper. Because of the offset between the plane 197
(FIG. 30) containing the frame cross member 191, and the parallel
plane 198 containing the axis of the rear cross member 188, there
is ample room for entry and manipulation of a cutter in the space
between the vertebral bodies and entry of the percussion instrument
in the space between the plane 197 and the pivot pin 189 and rear
cross member 188 of the keeper frame.
[0077] While the views in FIGS. 24 and 25 show the combination with
the hook 177 of the distractor and the rear cross member 188 of the
keeper above the axis 181 of the distractor, the assembly can be
used with the orientation inverted relative to that shown in FIG.
25. As with the cutting instruments themselves, the orientation
will depend upon the preferences of the surgeon.
[0078] The preferred material for the larger components is
stainless steel; however, the used of other materials suitable for
the intended functions are also contemplated as falling within the
scope of the invention.
[0079] While the invention has been illustrated and described in
detail in the drawings and foregoing description, the same is to be
considered as illustrative and not restrictive in character, it
being understood that all changes and modifications that come
within the spirit of the invention are desired to be protected.
* * * * *