U.S. patent application number 10/183092 was filed with the patent office on 2003-03-13 for methods for manufacturing skeletal implants.
Invention is credited to Morris, John W., Shimp, Lawrence A..
Application Number | 20030050699 10/183092 |
Document ID | / |
Family ID | 22632943 |
Filed Date | 2003-03-13 |
United States Patent
Application |
20030050699 |
Kind Code |
A1 |
Shimp, Lawrence A. ; et
al. |
March 13, 2003 |
Methods for manufacturing skeletal implants
Abstract
Instrumentation for manufacturing a bone dowel from human or
animal cadaveric bone and instrumentation for evaluating the
suitability of the bone and/or dowel for implant use after each
step of the manufacturing process is provided. Such instrumentation
for manufacturing a bone dowel includes a blanking or coring
apparatus, a milling apparatus a threading apparatus and a tapping
apparatus. A gauge is provided to inspect and determine the
suitability of the bone dowel at each step of the manufacturing
process. By inspecting the dowel being manufactured after each step
of the manufacturing process, time and effort which is needlessly
wasted during completion of the manufacturing of dowels which are
unsuitable for implant use (due to unsuitable bone and/or
inaccurate machining of bone) can be avoided. Instrumentation for
more accurately positioning bone and the partially manufactured
dowel into the instrumentation for machining the dowel is also
provided. Such instrumentation includes a gauge for positioning a
piece of bone in relation to the apparatus, and mounting blocks for
securing the partially manufactured dowel in relation to the
milling apparatus.
Inventors: |
Shimp, Lawrence A.;
(Morganville, NJ) ; Morris, John W.; (Beachwood,
NJ) |
Correspondence
Address: |
Peter G. DIlworth, Esq.
DILWORTH & BARRESE, LLP
333 Earle Ovington Blvd.
Uniondale
NY
11553
US
|
Family ID: |
22632943 |
Appl. No.: |
10/183092 |
Filed: |
June 27, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10183092 |
Jun 27, 2002 |
|
|
|
PCT/US01/00113 |
Jan 2, 2001 |
|
|
|
60173646 |
Dec 30, 1999 |
|
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|
Current U.S.
Class: |
623/17.11 ;
623/17.16; 623/23.63 |
Current CPC
Class: |
A61F 2/4455 20130101;
A61F 2002/4646 20130101; A61F 2002/4649 20130101; A61F 2/4657
20130101; A61B 17/32053 20130101; B23G 2210/12 20130101; B23B
47/281 20130101; B23G 1/48 20130101; B23B 47/28 20130101; A61F
2002/2839 20130101; A61F 2/3094 20130101; B23G 2210/08 20130101;
A61F 2002/4661 20130101; B23C 5/1054 20130101; A61B 2017/1602
20130101; A61B 2090/061 20160201; A61B 17/1637 20130101; A61F
2002/3085 20130101; A61F 2/442 20130101; A61F 2002/4658 20130101;
B23G 5/04 20130101; B23G 2200/10 20130101; A61F 2002/30616
20130101; A61F 2/468 20130101; A61F 2/4644 20130101; A61F 2002/4659
20130101 |
Class at
Publication: |
623/17.11 ;
623/23.63; 623/17.16 |
International
Class: |
A61F 002/44 |
Claims
1. A method for manufacturing a bone dowel from a bone shaft
defining a medullary canal, the method comprising the following
steps: a) coring a cylindrical dowel from the bone shaft such that
the medullary canal of the bone shaft forms a throughbore in the
dowel having an axis which is transverse to the longitudinal axis
of the dowel; b) performing an in-process inspection of wall
thickness of the dowel; c) rejecting the dowel if the dowel wall
thickness does not have at least predetermined dimensions suitable
for implant use; and d) forwarding the dowel for further machining
if the dowel has dimensions greater than the predetermined
dimensions suitable for implant use.
2. A method according to claim 1, wherein the step of performing an
in-process inspection of the wall thickness of the dowel includes
inspecting the sidewall thickness of the dowel.
3. A method according to claim 1 wherein the step of performing an
in-process inspection of the wall thickness of the dowel includes
inspecting the thickness of the top and bottom walls of the dowel.
Description
[0001] This application claims priority from U.S. provisional
application Serial No. 60/173,646, filed Dec. 30, 1999, which is
incorporated herein by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure relates generally to methods and
instrumentation for manufacturing an implant, and more particularly
to methods and instrumentation for manufacturing and inspecting an
intervertebral implant formed from cadaveric human or animal
bone.
[0004] 2. Background to Related Art
[0005] Intervertebral implants which are formed from cadaveric
human or animal bone ("bone") are well known in the art.
Intervertebral implants formed of bone having a threaded dowel
configuration, i.e., cylindrical, are also well known. The
manufacturing or machining of a threaded intervertebral bone dowel
is an involved process which includes at least a drilling or coring
step, a milling step, a tapping step and a threading step. Due to
the anatomical limitations of bone, each of the manufacturing steps
must be precisely performed to produce a dowel having the requisite
dimensions suitable for implant use. Typically, the entire
manufacturing process is performed before the dowel is evaluated or
inspected for suitability for implant use. Thus, where donor bone
is not suitable for dowel manufacture or the donor bone has been
improperly machined, much time and effort is needlessly wasted in
performing additional manufacturing steps on a dowel which will
never be useable as an implant.
[0006] Accordingly, a continuing need exists for methods and
instrumentation for precisely manufacturing a bone dowel from a
bone and for quickly identifying unsuitable bone early in the
machining process to avoid undue waste of time and effort.
SUMMARY
[0007] In accordance with the present disclosure, instrumentation
for manufacturing a bone dowel from human or animal cadaveric bone
and instrumentation for evaluating the suitability of the bone
and/or dowel for implant use after each step of the manufacturing
process is provided. Such instrumentation for manufacturing a bone
dowel includes a blanking or coring apparatus, a milling apparatus,
a threading apparatus and a tapping apparatus. A series of gauges
are provided to inspect and determine the suitability of the bone
dowel at each step of the manufacturing process. By inspecting the
dowel being manufactured after each step of the manufacturing
process, time and effort which is needlessly wasted during
completion of the manufacturing of dowels which are unsuitable for
implant use (due to unsuitable bone and/or inaccurate machining of
bone) can be avoided.
[0008] Instrumentation for more accurately positioning bone and the
partially manufactured dowel into the instrumentation for machining
the dowel is also provided. Such instrumentation includes a gauge
for positioning a piece of bone in relation to the coring
apparatus, and mounting blocks for securing the partially
manufactured dowel in relation to the milling, threading and
tapping apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Preferred embodiments of the presently disclosed
instrumentation for manufacturing and evaluating intervertebral
implants are described herein with reference to the drawings,
wherein:
[0010] FIG. 1 is a perspective of one preferred embodiment of the
presently disclosed blanking or coring apparatus;
[0011] FIG. 1A is a perspective view of the presently disclosed
Shimp gauge;
[0012] FIG. 2 is a perspective view of a bone dowel formed by the
coring apparatus shown in FIG. 1;
[0013] FIG. 3 is a perspective view with parts separated of a
holding block of the presently disclosed dowel milling
apparatus;
[0014] FIG. 4 is a perspective view of the holding block shown in
FIG. 3 in the assembled condition;
[0015] FIG. 5 is a side view of the holding block shown in FIG.
3;
[0016] FIG. 6 is a perspective view of one preferred embodiment of
the presently disclosed milling apparatus;
[0017] FIG. 7 is a perspective view of the bone dowel formed by the
milling apparatus shown in FIG. 6;
[0018] FIG. 8 is a perspective view of the slot milling bit of the
milling apparatus shown in FIG. 6;
[0019] FIG. 9 is a perspective view of the support blocks of the
second adjustment vise of the coring apparatus shown in FIG. 1;
[0020] FIG. 10 is a side view of the support block shown in FIG.
9;
[0021] FIG. 11 is a backside view of the support block shown in
FIG. 9;
[0022] FIGS. 12a-12c are perspective, front and side views of one
embodiment of the presently disclosed wall thickness GO/NO GO
gauge;
[0023] FIG. 13 is a perspective view of one embodiment of the
presently disclosed slot width GO/NO GO gauge;
[0024] FIG. 14 is a perspective view of one embodiment of the
presently disclosed outer diameter and length gauge;
[0025] FIG. 15 is a perspective view of one embodiment of the
presently disclosed pilot hole gauge;
[0026] FIG. 16 is a perspective view with parts separated of one
embodiment of the presently disclosed drilling holding block;
[0027] FIG. 17 is a perspective view of the bone dowel after the
pilot hole has been drilled and tapped;
[0028] FIG. 18 is a perspective of the holding block shown in FIG.
16 in the assembled condition;
[0029] FIG. 19 is a perspective view of one embodiment of the
presently disclosed tapping holding block;
[0030] FIG. 20 is a perspective view of the presently disclosed
dowel threading tool;
[0031] FIG. 21 is a perspective view of a presently disclosed dowel
thread gauge; and
[0032] FIG. 22 is a perspective view of a threaded bone dowel after
the outer surface has been threaded using the dowel threading tool
shown in FIG. 20.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0033] The embodiment of the methods and apparatus disclosed herein
are discussed in terms of skeletal implantation and related
instrumentation. It is contemplated that the present methods and
apparatus for manufacturing implants find application in spinal
implantation procedures whereby a fusion implant is placed into a
receiving bed formed in an intervertebral space.
[0034] In one particular embodiment in accordance with the
principles of the present disclosure, a procedure is described for
machining and inspecting fusion implants including threaded
cortical dowels. It is contemplated that the procedure may include
processes such as coring a dowel, milling a dowel, tapping a dowel
and threading a dowel. These processes are described in greater
detail below.
[0035] Referring now in detail to the drawings wherein like
reference numerals identify similar or like components throughout
the several views, FIG. 1 illustrates aspects of a process for
coring a bone dowel using a dowel coring apparatus 10.
CORING OF A DOWEL
[0036] A pneumatic dowel blanking or coring apparatus 10 is
prepared and set up for operation prior to the coring process by
connecting an air supply line 12 of dowel coring apparatus 10 to an
air supply. The dowel coring apparatus 10 includes a drill press
11. Typically, an air pressure of 100 psi and above is utilized to
drive a dowel cutter 24, although coring apparatus using lesser
pressures may also be used. Dowel coring apparatus 10 is also
attached to a water supply (not shown) for irrigation.
[0037] A bone shaft 14 is selected for producing the threaded
cortical dowels. Bone shaft 14 is preferably a long bone shaft,
i.e., the shaft of a femur, ulna, radius, tibia or fibula, although
other bone may also be used. A cortical shaft portion 16 of bone
shaft 14 includes a medullary canal 18 which is examined to
determine the appropriate size dowel cutter to be used. The dowel
cutter includes a hollow cylindrical bit which must be greater in
diameter than the medullary canal of bone shaft 14. It is
contemplated that dowel cutter sizes such as, for example, 6 mm, 8
mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, etc., may be used.
[0038] After the appropriate size dowel cutter 24 is selected, it
is secured to dowel coring apparatus 10. Dowel cutter 24 is secured
to shaft 26 of dowel coring apparatus 10 in a known manner and
includes an annular serrated edge 14. Dowel cutter 24 is configured
to penetrate bone shaft 14 to blank a dowel.
[0039] Bone shaft 14 is placed into a vise assembly 28 of dowel
coring apparatus 10 so that a targeted portion of shaft 14 may be
blanked to produce the dowel. A first adjustment vise 30 positions
bone shaft 14 along at least one axis so that canal 18 is centered
with dowel cutter 24. First adjustment vise 30 is manipulated by
knob 31 to adjust positioning of bone shaft 14 relative to dowel
cutter 24.
[0040] A second adjustment vise 32 secures and stabilizes bone
shaft 14 in position for coring. Second adjustment vise 32 includes
support blocks 31a and 31b and inserts 34a and 34b. One insert is
supported on each support block. Each support block is rotatably
secured to vise 32 and each insert is vertically adjustable in
relation to a respective support block to facilitate securement of
the irregular shape of bone shaft portion 16 within vise 32. Second
adjustment vise 32 is manipulated by rotating knob 33 to advance
insert 34a towards insert 34b to clamp shaft portion 16
therebetween. It is contemplated that the components of the first
and second adjustment vises may be movable by motorized means.
Referring to FIGS. 9-11, inserts 34a and 34b have angled cavities
36 configured to receive bone shaft 14. It is contemplated that
angled cavities 36 may have alternate angular configurations or may
comprise other geometric configurations such as, for example,
elliptical, parabolic, etc.
[0041] As illustrated in FIG. 1A, a shimp gauge 38 can be employed
for properly aligning dowel cutter 24 with bone shaft 14. Shimp
gauge 38 includes flexible walls 39a and 39b which are positioned
on opposite sides of and snap onto dowel cutter 24. Gauge 38
includes a cross hair 40 for aligning dowel cutter 24 with the
center of the medullary canal 18 of bone shaft 14. More
specifically, with gauge 38 positioned about dowel cutter 24, knob
31 can be turned to adjust the position of bone shaft 14 with
respect to dowel cutter 24. Bone shaft 14 should be positioned such
that cross hair 40 is aligned with and positioned in front of the
medullary canal at bone shaft 14. A window cavity 42 is formed
about cross hair 40 and allows for a visual determination of the
adequacy of thickness of cortical shaft portion 16, i.e., the
cortical thickness of bone shaft 14 should cover the space between
cross hair 40 and the edge 42' of window 42. To assist in
visualization of canal 18 during subsequent cuts, it is suggested
to remove bone shaft 14 from vise assembly 28 and saw off the
previously cut end of cortical shaft portion 16.
[0042] Referring back to FIG. 1, during operation, the air and
water supplies connected to dowel coring apparatus 10 are
activated. As a safety feature, the air and water supplies are
activated only after dowel cutter 24 is installed. A handle 44 of
dowel coring apparatus 10 is manipulated, such as, for example, by
gradually being pulled down in the direction indicated by arrow
"A", until dowel cutter 24, which is rotating, passes through bone
shaft 14. Handle 44 is thereafter released. It is contemplated that
manipulation of handle 44 should be performed slowly because
cutting too fast may result in off-center drilling, resulting in
possible damage to the bone dowel. It is further contemplated that
the components of the dowel coring apparatus may be movable by
motorized means.
[0043] Referring to FIG. 2, a bone dowel 46 is produced and is
disposed within dowel cutter 24. Bone dowel 46, which comprises a
cylindrical bone blank having a throughbore defined by medullary
canal 18, may be removed from dowel cutter 24 by hand or by the use
of compressed air.
[0044] Referring to FIGS. 12A-12C, an in process check of the
sidewall thickness of bone dowel 46 is performed to determine the
adequacy thereof. Bone dowel 46 is rinsed in water to remove loose
bone particles from its exterior and medullary canal 18. The
cortical sidewall thickness of bone dowel 46 is checked using a
gauge, such as the universal Wall Thickness Go/No Go gauge 48.
Using a gauge end 50, which is suitably marked, e.g., "wall",
medullary canal 18 of bone dowel 46 is positioned about post 52
such that the thinnest portion of the bone wall defined between
medullary canal 18 and the outer circumference of bone dowel 46 is
permitted to freely fall between gauge post 52 and sidewall 54 of
gauge 48. Bone dowel 46 should not be forced or pushed between
gauge post 52 and sidewall 54, as a false measurement for adequacy
of the bone dowel may be taken. If the dowel falls to the bottom of
post 52, the bone wall is too thin, and the bone dowel is rejected.
This adequacy procedure is repeated for the opposite side of canal
18. If the bone dowel wall is unacceptable, i.e., rejected, bone
shaft 14 should be rechecked for centering and/or a different size,
i.e., larger, dowel cutter should be used. It is contemplated that
reassessment of the suitability of the donor for bone dowel
production may be reconsidered. If bone dowel 46 is acceptable,
proceed in the manufacturing method.
[0045] Referring again to FIGS. 12A-12C, an in process check of
cortical face wall thickness may be checked using the universal
Wall Thickness Go/No Go gauge 48. Using gauge end 56, which is
suitably marked, e.g., "Face", medullary canal 18 of bone dowel 46
is positioned onto post 58 with one end of dowel 46 positioned
against face wall 60 of gauge 48 at its thinnest point. Bone dowel
46 is permitted to freely fall between gauge post 58 and face wall
60. For the reasons discussed above, bone dowel 46 should not be
forced or pushed between gauge post 58 and face wall 60. If bone
dowel 46 falls to the bottom of post 58, it is rejected, i.e., the
wall thickness is insufficient for dowel use. If the face wall
thickness of bone dowel 46 is unacceptable, bone dowel 46 is
rejected and placement of bone shaft 14 in dowel coring apparatus
10 should be checked. If the bone dowel is rejected, the
suitability of the donor bone for bone dowel production may be
reconsidered. If bone dowel 46 is acceptable, proceed in the
manufacturing method.
[0046] Referring to FIG. 14, an in process check of the outside
diameter and length of bone dowel 46 is performed to determine the
adequacy thereof Bone dowel 46 is placed in an appropriate outside
diameter and length Go/No Go gauge 62. Bone dowel 46 is inserted
into the No Go end 64 of gauge 62. If bone dowel 46 is acceptable
(does not fit in No-Go end 64) proceed to check bone dowel 46 in
the Go end 66 of gauge 62 by inserting bone dowel 46 into the Go
end 66 of gauge 62 so that a slot of bone dowel 46 mates on a gauge
boss 68 and medullary canal 18 is visible in window 70. If bone
dowel 46 fits in the Go end 66 of gauge 62, the outside diameter is
acceptable. If the outside diameter is acceptable, the length of
bone dowel 46 can be checked by viewing length marker 72 to
determine if the length falls within an acceptable range. If the
length is acceptable, bone dowel 46 is acceptable. If bone dowel 46
fails, bone dowel 46 is rejected and dowel coring apparatus 10
should be checked. If the diameter of bone dowel 46 is acceptable,
but the length is too long, bone dowel 46 is cut to a proper length
and rechecked. If the length of bone dowel 46 is too short, bone
dowel 46 is rejected.
[0047] The results of the above mentioned in-process checking
procedures may be recorded on an attached log or the like.
MILLING OF SLOT AND FACE
[0048] Referring to FIGS. 3-8, a dowel milling apparatus 74 is
prepared and set up for operation during the manufacturing process
by connecting an air supply 75 to dowel milling apparatus 74 (FIG.
6). Typically, a pressure of 100 psi and above is utilized,
although milling apparatus requiring lower air pressures may also
be used. A water supply (not shown) is connected to dowel milling
apparatus 74 for irrigation.
[0049] Referring to FIGS. 6 and 8, a face and slot milling bit 76
is secured to dowel milling apparatus 74. As a safety feature, air
supply 75 should not be connected to apparatus 74 until the bit is
secured to the dowel milling apparatus 74. Moreover, the water
supply should only be turned on when using dowel milling apparatus
74.
[0050] Referring to FIGS. 3-5, bone dowel 46 is inserted into an
appropriately sized holding block 78. Bone dowel 46 is positioned
in holding block 78 such that canal 18 is visible through block
window 80 and the slot is milled approximately perpendicular to
canal 18. The depth of bone dowel 46 as seated in block 78 is set
with use of a guide 82 attached to block 78, as shown in FIG. 5.
Set screws 84 are tightened so that block 78 holds bone dowel 46
securely in place. Up to three bone dowels can be placed into
holding block 78 at one time. It is contemplated that holding block
78 may be alternately configured to hold a single or multiple
number of bone dowels.
[0051] Referring back to FIG. 6, holding block 78 is inserted into
a pre-centered vise 86 positioned on dowel milling apparatus 74 and
vise 86 is secured.
[0052] Dowel milling apparatus 74 is activated by activating the
water and air supplies. A handle 88 is manipulated to feed block 78
throughface and slot milling bit 76 in the forward and reverse
directions. It is contemplated that bone dowel 46 should only pass
through face and slot milling bit 76 forwards and reverse once. It
is further contemplated that bone dowel 46 should not have reverse
movement until face and slot milling bit 76 is completely clear of
the last bone dowel in block 78. It is envisioned that prior to
stopping dowel milling apparatus 74, face and slot milling bit 76
is clear of bone dowel 46. Dowel milling apparatus 74 is
deactivated and holding block 78 is removed from vise 86.
[0053] Referring to FIG. 7, after the milling step described above,
bone dowel 46 has a milled slot 90 and smooth face 91. Slot 90 is
oriented substantially perpendicular to medullary canal 18. Bone
dowel 46 may be removed from block 78.
[0054] Referring to FIG. 13, an in process check of the slot width
is performed using the universal Slot Width Go/No Go Gauge 102. Go
side 104 of gauge 102 is inserted into slot 90 of bone dowel 46 so
that it extends through the entire length of slot 90. If gauge 102
extends through the entire slot, it is acceptable. If it does not
extend through the entire slot, bone dowel 46 is rejected. If bone
dowel 46 is acceptable, proceed to check a No Go side 106 in the
same manner. No Go side 106 should not fit into slot 90. Thus, if
it does, slot 90 is too wide and bone dowel 46 is rejected. If No
Go side 106 does not fit into slot 90, it is acceptable. If slot 90
is rejected, milling apparatus 74 should be checked. If bone dowel
46 is acceptable, proceed in the manufacturing process as
follows.
[0055] Referring to FIG. 16, bone dowel 46 is placed in a holding
block 92 for drilling and tapping an insertion tool engaging bore
95. Bone dowel 46 is positioned with milled slot 90 on top. Up to
three bone dowels can be placed into holding block 92 at one time.
It is contemplated that holding block 92 may be alternately
configured to hold a single or multiple number of bone dowels.
Referring to FIG. 17, holding block 92 includes a drill centering
device 93 having a guide bore 97 to facilitate proper positioning
of a pilot hole drill bit 94 for drilling hole 95 in bone dowel
46.
[0056] Drill centering device 93 includes a drill guide 96 which
defines guide bore 97 and cooperates with pilot hole drill bit 94
for drilling pilot hole 95. Pilot hole drill bit 94 is secured to
an electric drill or the like. Manual activation of pilot hole
drill bit 94 is also contemplated.
[0057] Pilot hole drill bit 94 is inserted through guide bore 97 to
drill pilot hole 95. Drill bit 94 is rotated clockwise until drill
bit 94 is observed through a holding block window (not shown)
inside canal 18 of bone dowel 46 and drill bit 94 turns freely.
Pilot hole drill bit 94 is removed by rotating drill bit 94 counter
clockwise. Pilot hole drill bit 94 should not be advanced such as
to engage the opposite wall of canal 18.
[0058] Referring to FIG. 15, an in process check of pilot hole 95
of bone dowel 46 is performed to determine the adequacy of the
inner diameter thereof. To accomplish this, pilot hole 95 is
visually checked to ensure that it is approximately centered and
that it passes into canal 18. Next, the inner diameter of pilot
hole 95 is checked with Pilot Hole Pin Gauge 97. To accomplish
this, end 98 of gauge 97 is inserted into pilot hole 95. Insertion
should not be forced. If end 98 extends though pilot hole 95 and
into canal 18, the diameter of pilot hole 95 is too large and bone
dowel 46 is not acceptable. If pilot hole 95 does not extend into
canal 18, it can be drilled through using a hand held tool and
rechecked for proper inner diameter, as discussed above.
[0059] Referring to FIG. 19, pilot hole 95 is now threaded. To
accomplish this, a tap centering device 101 is secured to mounting
block 92. Tap centering device 101 is similar to drill centering
device 93 except that guide bore 97' is larger than guide bore 97
to allow passage of tap 99. A tap 99 is inserted through guide bore
97' of device 101 to thread pilot hole 95 of bone dowel 46. Tap 99
is removed after this is accomplished by manually twisting tap 99
counter clockwise from guide bore 97'. It is contemplated that tap
99 may be operated by motorized means. It is further contemplated
that tap 99 should not be inserted so far as to engage the opposite
wall of canal 18.
[0060] Bone dowel 46 can now be removed from holding block 92. Bone
dowel 46 is rinsed in water to remove loose bone particles from its
exterior and medullary canal 18. Referring to FIG. 18, bone dowel
46 now includes internally threaded pilot hole 95. Referring again
to FIG. 15, an end 100 of gauge 97 may be used to check the
adequacy of the threads of pilot hole 95.
[0061] An in-process check of the cortical face wall thickness of
bone dowel 46 may be conducted using the universal wall thickness
Go/No Go gauge 48, similar to that described above with regard to
FIGS. 12a-12c. If the face wall thickness of bone dowel 46 is
unacceptable, reject bone dowel 46 and recheck slot and face
milling bit 76 and placement in holding block 78. Also reassess the
suitability of the donor bone being used for dowel production. If
acceptable, proceed in the manufacturing process.
THREADING
[0062] Referring to FIGS. 20 and 21, bone dowel 46 can now be
externally threaded. A threading tool 108 is prepared and set up
for operation during the manufacturing process. A water supply (not
shown) is connected to threading tool 108 for irrigation. It is
contemplated that the water supply should be activated only when
threading tool 108 is in use. It is further contemplated that
threading tool 108 may be configured for a variety of different
size bone dowels, such as, for example, 14 mm, 16 mm, 18 mm, 20 mm,
etc. Bone dowel 46 is positioned onto a loading shelf 110 within
threading tool 108 through a window 112 formed in tool 108.
Threading tool 108 includes a plurality of circumferentially spaced
inserts 114 having teeth for engaging and threading the exterior
cylindrical surface of bone dowel 46. A driver 116 engages the
slotted end of bone dowel 46 to drive bone dowel 46 through
threading tool 108 to form the threads on the exterior of bone
dowel 46. Bone dowel 46 is placed onto driver 116 such that a tang
118 located at an end of driver 116 engages slot 90 of bone dowel
46.
[0063] Tang 118 is configured to engage slot 90 of bone dowel 46 to
manually advance bone dowel 46 through tool 108 by turning a handle
120 clockwise. When bone dowel 46 has passed entirely through
threading tool 108, it will discharge from tool 108 into a cradle
or the like (not shown) positioned at one end of tool 108. Bone
dowel 46 should not be backed through threads 114 of tool 108 once
it has passed through initially, nor should bone dowel 46 be run
through twice. Referring to FIG. 21, bone dowel 46 now includes
external threads 122.
[0064] Referring to FIG. 22, an in process check of threads 122 of
bone dowel 46 is performed to determine the adequacy thereof. To
accomplish this, dowel threads 122 are checked using thread check
gauge 124 which includes verifying threads 126. Verifying threads
126 are aligned with dowel threads 122 and threads 122 of bone
dowel 46 are visually checked for gaps, unevenness, and improper
fit. If gauge 124 fits threads 122 without gaps and unevenness,
threads 122 are acceptable. If threads 122 are unacceptable, bone
dowel 46 is rejected and threading tool 108 is inspected for
quality and adjusted. If threads 122 are acceptable, proceed in the
manufacturing process as follows:
[0065] An in-process check of the outside diameter and length of
bone dowel 46 may be conducted using outside diameter and length
gauge 62, similar to that described above with regard to FIG. 14.
After completion of the above method, each acceptable bone dowel 46
is sterility tested, measured and packaged for use.
[0066] It will be understood that various modifications may be made
to the embodiments disclosed herein. For example, the double sided
gauges shown in FIGS. 14-17 can be formed as two separate gauges.
The gauges may also be provided in a kit for forming bone dowels
having any desired dimensions. Moreover, the coring and milling
apparatus can be electrically, hydraulically, or pneumatically
actuated apparatus. Therefore, the above description should not be
construed as limiting but exemplifications of the various
embodiments. One skilled in the art will envision other
modifications within the scope and spirit of the claims appended
hereto.
* * * * *