U.S. patent application number 11/063351 was filed with the patent office on 2006-03-16 for apparatus and method for cleaning a surgically prepared, concave bone surface.
Invention is credited to Clyde Ronald Pratt, William Ralph Pratt, Vineet Kumar Sarin.
Application Number | 20060058730 11/063351 |
Document ID | / |
Family ID | 36035071 |
Filed Date | 2006-03-16 |
United States Patent
Application |
20060058730 |
Kind Code |
A1 |
Pratt; William Ralph ; et
al. |
March 16, 2006 |
Apparatus and method for cleaning a surgically prepared, concave
bone surface
Abstract
An apparatus suitable for cleaning a surgically prepared bony
concavity includes a body portion adapted to supply pressurized
fluid (preferably carbon dioxide gas) to the concavity and aspirate
surface debris. The apparatus further comprises a head having an
orifice with a plane, circular rim having a diameter less than that
of the bony concavity. A method for cleaning a surgically prepared,
concave, generally hemispherical bony cavity includes the steps of:
covering a region of the hemispherical bony concavity with a
cleaning head; supplying a pressurized fluid to the region covered
by the cleaning head, and collecting the pressurized fluid from the
covered region with a surface debris aspirator coupled to the
cleaning head. A cleaning head having a generally circular orifice
substantially seals and encloses a spherical zone to be
cleaned.
Inventors: |
Pratt; William Ralph;
(Newbury Park, CA) ; Pratt; Clyde Ronald; (Somis,
CA) ; Sarin; Vineet Kumar; (Simi Valley, CA) |
Correspondence
Address: |
WILLIAM L. JOHNSON
P. O. BOX 1240
SOMIS
CA
93066-1240
US
|
Family ID: |
36035071 |
Appl. No.: |
11/063351 |
Filed: |
February 23, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10941313 |
Sep 15, 2004 |
|
|
|
11063351 |
Feb 23, 2005 |
|
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Current U.S.
Class: |
604/26 |
Current CPC
Class: |
A61F 2/4675 20130101;
A61F 2/38 20130101; A61M 1/85 20210501 |
Class at
Publication: |
604/026 |
International
Class: |
A61M 37/00 20060101
A61M037/00 |
Claims
1. A method for cleaning a surgically prepared, concave, generally
hemispherical bony concavity, comprising the steps of: covering a
region of said hemispherical bony concavity with a cleaning head;
supplying a pressurized fluid to said region covered by said
cleaning head; collecting said pressurized fluid from said covered
region with a surface debris aspirator coupled to said cleaning
head.
2. The method of claim 1, wherein the supplied pressurized fluid is
carbon dioxide (CO.sub.2) gas, said CO.sub.2 gas being suitable for
use on the surgically prepared working surface.
3. The method of claim 1, wherein said step of covering a portion
of said hemispherical bony concavity comprises: engaging said bony
concavity with a substantially circular, plane cleaning orifice of
said cleaning head.
4. The method of claim 3 wherein said circular, plane cleaning
orifice defines a plane at an angle between 30 and 60 degrees
relative to an elongated neck coupled to said cleaning head.
5. An apparatus suitable for cleaning a concave, surgically
prepared working surface, said apparatus comprising: means for
supplying pressurized fluid to the surgically prepared working
surface; at least one surface debris aspirator operatively coupled
to said pressurized fluid supply means; and means for confining the
supplied pressurized fluid to flow substantially across a portion
of the surgically prepared working surface; wherein said means for
confining the supplied pressurized fluid includes an orifice having
a plane, circular rim, capable of engaging a zone of said concave
surgically prepared surface.
6. The apparatus of claim 5, wherein the supplied pressurized fluid
is carbon dioxide (CO.sub.2) gas, said CO.sub.2 gas being suitable
for use on the surgically prepared working surface.
7. The apparatus of claim 5, wherein said orifice has a diameter
less than that of the concave surface.
8. The apparatus of claim 7, wherein said diameter of said orifice
is less than that of a human acetabular socket.
9. The apparatus of claim 8 wherein said confining means comprises
a cleaning head having a thickness dimension less than its
diameter.
10. The apparatus of claim 9, wherein said means for confining
comprises an elongated neck and a cleaning head opened by said
orifice; and wherein a plane defined by said plane, circular rim of
said orifice defines an angle in the range of 30 to 60 degrees
relative to said elongated neck.
11. The apparatus of claim 10 wherein said angle is substantially
equal to 45 degrees.
12. The apparatus of claim 9 wherein said cleaning head had a
thickness dimension less than half its diameter.
13. An apparatus suitable for cleaning a surgically prepared bony
surface of concave, generally hemispherical recess, said apparatus
comprising: a body portion adapted to supply pressurized fluid to
the surgically prepared working surface and aspirate surface debris
dislodged from the bony working surface; and a head portion adapted
to confine the supplied pressurized fluid to flow substantially
across the surgically prepared working surface to dislodge debris
therefrom when said head portion is in contact with the bony
working surface, said dislodged surface debris being aspirated by
said body portion; wherein said head portion has a generally
circular orifice having a diameter less than that of the concave,
generally hemispherical recess, thereby allowing said orifice to
substantially seal against the inside surface of said concave,
generally hemispherical recess.
14. The apparatus of claim 13, wherein the supplied pressurized
fluid is carbon dioxide (CO.sub.2) gas, said CO.sub.2 gas being
suitable for use on the surgically prepared working surface.
15. The apparatus of claim 13, wherein the supplied pressurized
CO.sub.2 gas flows at a rate suitable for cleaning the surgically
prepared working surface from debris.
16. The apparatus of claim 13, wherein said head portion is adapted
to confine the supplied pressurized fluid to flow over the
surgically prepared working surface to dislodge debris therefrom
when said head portion is in contact with the surgically prepared
working surface, said dislodged surface debris being aspirated by
said body portion.
17. The apparatus of claim 16, wherein the supplied pressurized
fluid is carbon dioxide (CO.sub.2) gas, said CO.sub.2 gas being
suitable for use on the surgically prepared working surface.
18. The apparatus of claim 17, wherein the supplied pressurized
CO.sub.2 gas flows at a rate suitable for cleaning the surgically
prepared working surface from debris.
19. The apparatus of claim 13, wherein said body portion includes
at least one pressurized fluid channel operatively coupled to at
least one fluid jet outlet.
20. The apparatus of claim 19, wherein said body portion further
includes at least one surface debris aspirator disposed in
operational proximity to said at least one fluid jet outlet.
21. The apparatus of claim 13, wherein said head portion includes
at least one partial partition between said at least one surface
debris aspirator and said at least one fluid jet outlet.
22. The apparatus of claim 21, wherein said surface debris
aspirator is disposed peripherally near a circular rim of said
orifice, and said at least one fluid jet outlet is disposed
generally near the center of the circle defined by the circular
orifice, so that fluid flows generally outward, sweeping debris
from the surgically prepared working surface.
23. The apparatus of claim 13 wherein said body portion comprises
an elongated neck, disposed at an angle to a plane defined by said
rim of said circular orifice.
24. The apparatus of claim 23 wherein said angle is in the range
from 30 to 60 degrees, inclusive.
25. The apparatus of claim 24 wherein said angle is substantially
equal to 45 degrees.
26. The apparatus of claim 13 wherein the diameter of said circular
orifice is less than the diameter of a human acetabular socket.
27. The apparatus of claim 13 wherein said head portion has a
thickness dimension less than its diameter
28. The apparatus of claim 27 wherein said head portion has a
thickness dimension less than half of its diameter.
29. The apparatus of claim 28 wherein said head portion has width
dimensions generally tapering in the direction away from the
orifice, to avoid interference from contacting the rim of an
acetabular socket.
30. The apparatus of claim 29, wherein said body portion further
includes at least one surface debris aspirator disposed in
operational proximity to said at least one fluid jet outlet.
31. The apparatus of claim 30, wherein said head portion includes a
rim configured to substantially follow the surgically prepared
working surface and at least one partition between said at least
one surface debris aspirator and said at least one fluid jet
outlet.
32. The apparatus of claim 31, wherein said at least one partition
is sufficiently recessed from said rim to constrain the supplied
jet fluid to flow substantially tangentially relative to the
surgically prepared working surface when said rim is in contact
with the surgically prepared working surface, said constrained
tangential fluid flow sweeping debris from the surgically prepared
working surface via said at least one surface debris aspirator.
33. An apparatus for cleaning a surgically prepared, concave bone
surface, comprising: a pressurized fluid supply channel; an
aspiration channel; a cleaning head, including at least one
chamber, in communication with said aspiration channel and said
fluid supply channel; said chamber having a generally circular
orifice, the circular boundary of said orifice defining a boundary
capable of close engagement with a concave bone surface to
substantially close said chamber; said chamber arranged to create
an internal pressure gradient between said pressurized fluid supply
channel and said aspiration channel, and having a path for fluid
flow from said fluid supply channel to said aspiration channel;
wherein said fluid flow path for fluid flow includes at least one
region in which flow is constrained to flow across said concave
bone surface.
34. The apparatus of claim 33, wherein said fluid flow path
comprises at least one slot, whereby said fluid flow is channeled
into a sheet of flow.
35. The apparatus of claim 34, wherein said slot is defined between
said boundary surface and a partition which incompletely divides
said chamber.
36. The apparatus of claim 33 wherein said orifice is bounded by a
rim.
37. The apparatus of claim 21, wherein said pressurized fluid
supply channel is adapted to supply pressurized carbon dioxide gas.
Description
[0001] This application is a continuation-in-part of U.S.
application Ser. No. 10/941313 filed on Sep. 15, 2004 (inventors
Pratt, et al.) and claims priority to that application as to
material disclosed therein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to surgical
instruments, and more particularly to apparatus and method for
cleaning a surgically prepared working surface.
[0004] 2. Description of the Related Art
[0005] In traditional orthopedic surgery, bone is prepared to
receive a prosthetic implant by first cutting or sculpting the bone
with a manual or powered tool such as a saw, drill, or broach.
Next, the exposed bone is usually cleaned with a sterile saline
solution for lavage and irrigation. Finally, suction is applied to
remove debris. Often, surgical sponges are inserted into a cavity
or against the bone surface to absorb excess fluids.
[0006] Joint replacements are commonly but not necessarily secured
with the aid of "joint cement" or biocompatible adhesives. A
typical such cement is a polymethyl methacrylate. The success of
such adhesives is thought to depend in part on proper preparation
of the bone bed.
[0007] U.S. Pat. No. 5,037,437 to Matsen III (1991) discloses a
significant improvement in the art of preparing bone surface for
cemented joint replacement surgery. Matsen identified some of the
previously unrecognized shortcomings of traditional liquid flushing
lavage for preparation of the cancellous portions of an exposed
bone bed. Matsen's invention was based on the finding that dry
flowing gas directed at and into the sculpted bony bed effectively
prepares the bone for prosthetic implantation. When a bone cement
is also used, the use of gas increases the likelihood of strong
mechanical interdigitation of the bone cement with the bone. A
number of such advantages to the gas lavage technique are
identified in U.S. Pat. No. 5,037,437; the enumerated advantages
need not be repeated here. Additional advantages may exist which
have not been identified. Matsen also suggests that carbon dioxide
is especially well suited for use as the dry gas for bone lavage,
being demonstrated safe for use in the human body. As he notes,
"the very high diffusion coefficient of carbon dioxide causes it to
present a significantly lower risk of embolism as compared to the
use of nitrogen or oxygen." Moreover, carbon dioxide gas is
commonly available in hospital operating rooms, finding use in
laparascopic surgery, for example.
[0008] Since the publication of the Matsen patent, tools have
become available for preparing bony surfaces by sterile, dry gas
lavage, or lavage with sterile admixtures of gas and liquid. A
carbon dioxide lavage system is available, for example, from
Kinamed, Inc. in Camarillo, Calif. (marketed under the trade name
"CarboJet"). The use of carbon dioxide is believed to be more
effective than liquid debris removal because a compressed gas jet
creates strong, fluctuating pressure gradients, displacing debris
rapidly and thoroughly. This method is more effective at removing
fluid and fluid-suspended debris from the interstices of cancellous
bone.
[0009] Although surgical gas lavage nozzles are available, typical
nozzles must be used in concert with surgical suction tools.
Simultaneous manipulation and coordination of both gas supply and
suction is difficult. Flow of the gas is not well controlled or
confined to the bony surface. Both suction and gas jet must be
constantly moved in a drying pattern to effectively clean and dry
the bony surface. The difficulty of this technique in increased in
surgical situations that permit only limited access or interfere
with the surgeon's freedom of motion. As one example, in hip
replacement surgery it is usual to prepare the acetabular cup by
mechanical reaming or grinding into a generally hemispherical,
concave shape, suitable for receiving an acetabular implant
component. Before gluing the component into place, it is desirable
to treat the acetabular surface by gas lavage. However, efficient,
simultaneous suction and drying of a small, concave, generally
hemispherical cup presents is awkward with conventional tools. No
gas lavage tool is available that is specifically adapted to
efficiently clean and dry a concave cup (an acetabular cup, for
example).
[0010] For these and other reasons, a need persists for specially
adapted lavage devices and methods which can better access specific
bony surfaces, and which more efficiently and conveniently prepare
the surfaces to receive cement or implants. Any time saved in the
operating room is of great value (medically and economically) to
both surgeon and patient.
SUMMARY OF THE INVENTION
[0011] In accordance with one aspect of the invention, an apparatus
suitable for cleaning a concave bony surface includes: a body
portion adapted to supply pressurized fluid to the surgically
prepared working surface and aspirate debris dislodged from the
bony working surface; and a head portion adapted to confine the
supplied pressurized fluid to flow substantially across the
surgically prepared working surface to dislodge debris therefrom
when the head portion is in contact with the bony working surface.
The head portion has a generally circular orifice having a diameter
less than that of the concave, generally hemispherical recess to be
cleaned, thereby allowing the orifice to substantially seal against
the inside surface of the hemispherical recess.
[0012] According to another aspect of the invention, a method for
cleaning a surgically prepared, concave, generally hemispherical
bony cavity includes the steps of: covering a region of the
hemispherical bony concavity with a cleaning head; supplying a
pressurized fluid to the region covered by the cleaning head, and
collecting the pressurized fluid from the covered region with a
surface debris aspirator coupled to the cleaning head. A cleaning
head having a generally circular orifice substantially seals and
encloses a spherical zone to be cleaned.
[0013] These and other aspects of the invention will become
apparent from a review of the accompanying drawings and the
following detailed description of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The present invention is generally shown by way of reference
to the accompanying drawings in which:
[0015] FIG. 1 is a side elevation view (with some system elements
indicated schematically) of an apparatus and system suitable for
cleaning a surgically prepared working surface in accordance with
the present invention;
[0016] FIG. 2 is a perspective view of the cleaning head of the
apparatus of FIG. 1;
[0017] FIG. 3 is a plan view from below of the cleaning head of
FIG. 2;
[0018] FIG. 4 is a sectional view taken along section line 4 in
FIG. 3;
[0019] FIG. 5 is a sectional view taken along the section line 5 in
FIG. 3;
[0020] FIG. 6 is a sectional view taken along the section 6 line in
FIG. 3;
[0021] FIG. 7 is an perspective view of the apparatus of the
invention disposed in working relation to a concave bony surface,
with the bony body and the apparatus partially cut away to better
visualize the relationship between the apparatus and the bone;
and
[0022] FIG. 8 is a sectional view of the apparatus of the invention
in working relation to a concave bony surface, with both the
apparatus and bone shown in cross section along the same sectioning
plane as that of FIG. 4, also showing presumed fluid flow
lines.
DETAILED DESCRIPTION OF THE INVENTION
[0023] Some embodiments of the invention will be described in
detail with reference to the related drawings of FIGS. 1-8.
Additional embodiments, features and/or advantages of the invention
will become apparent from the ensuing description or may be learned
by practicing the invention. In the figures, the drawings are not
to scale with like numerals referring to like features throughout
both the drawings and the description.
[0024] The following description is not to be taken in a limiting
sense, but is made merely for the purpose of describing the general
principles of the invention.
[0025] The acetabular cup of the human hip is a concave, generally
hemispherical recess in the pelvis. In a hip replacement surgery,
this cavity is typically reamed or otherwise mechanically prepared
to receive a cup-like acetabular prosthetic component. After
hollowing the acetabular cup to the desired shape and dimension, it
is desirable to apply a fluid lavage, preferably in the view of the
inventors a carbon dioxide gas lavage. Such lavage better prepares
the acetabular cup to receive cement and bond effectively with the
prosthetic cup component.
[0026] FIG. 1 shows the apparatus or tool in accordance with the
invention, generally referred to by reference numeral 10. The
embodiment of FIG. 1 is particularly well adapted for cleaning a
substantially hemispherical, concave bony surface, such as is
presented by a surgically prepared acetabular socket. The tool 10
includes a generally disk-like cleaning head 11 having a generally
circular orifice 12, situated on the underside of the head and with
the opening facing downward. Preferably, the head 11 is mounted on
or depends from an elongated extension neck 14. In one embodiment,
the neck 14 includes one or more through passages used to supply
pressurized fluid and/or to provide an aspiration pathway.
Alternatively, pressurized fluid and vacuum for aspiration could be
otherwise supplied to the head via hoses or tubes.
[0027] Preferably, a rim 15 of the orifice 12 lies upon and defines
a plane disposed obliquely or at an angle a to the long axis X of
the elongated neck, so that a normal to the plane of the rim is
neither parallel to nor perpendicular the long axis or dimension of
the neck 14. In an embodiment in which the neck 14 includes fluid
channels, hose couplings are provided near the rearward end of the
neck: a pressurized gas hose connection 16 and a vacuum hose
connection 18 are shown. Optionally, these connections could be
integrated into a trigger type control grip (not shown) which
facilitates control of the application/disconnection of both gas
and suction, via a simple trigger operated valve. However
controlled, fluid (preferably carbon dioxide gas or an admixture of
same with liquid) is controllably supplied under pressure from
pressurized fluid supply 20 to gas connection 16 via a hose 21.
Similarly, suction is controllably supplied from vacuum source 22
via hose 24 to the vacuum hose connection 18.
[0028] The head 11 is shown in more detail the view of FIG. 2. The
orifice 12 is preferably bounded by a planar, generally circular
lip or rim 15. In the embodiment shown, the rim forms a
substantially circular perimeter around the orifice 12. The orifice
12 opens into a partitioned internal cavity 28 having at least one
inner chamber 30 and at least one outer chamber 32. The
aforementioned inner and outer chambers are incompletely isolated
from each other by at least one internal partition 34.
[0029] Further details are more easily seen in FIG. 3 (plan from
below) and in the sectional views of FIGS. 4, 5 and 6. At least one
hidden, internal gas channel 36 connects the inner chamber 30 to a
pressurized fluid supply passage 38, and thus allow the inner
chamber to communicate with the pressurized fluid supply 20. In the
embodiment shown, the communication occurs via an internal channel
contained in the neck 14; in other embodiments, communication could
be directly through a pressurized fluid hose coupled to the head.
The inner chamber, communicating passages, and pressurized fluid
supply together make up a pressurized fluid supply apparatus.
Similarly, a vacuum channel 40 (visible in FIGS. 4 and 6) connects
the at least one outer chamber 32 to an aspiration connection 18,
allowing the one or more outer chambers to communicate with the
vacuum source supply 22. The outer chamber or chambers, vacuum
channel(s), vacuum connections, and vacuum source together make up
an aspirator. The pressurized fluid chamber and supply channel are
seen best in FIGS. 4 and 5; the vacuum channels are better seen in
FIGS. 4 and 6.
[0030] Pressurized fluid (preferably carbon dioxide) is supplied
from a channel 36, which in some embodiments is contained within
the neck 14. The pressurized fluid flows into the inner chamber 30.
In one embodiment as shown, the inner chamber 30 takes the form of
a long narrow slot, arranged diametrically across the circular
orifice and substantially running through the center of the circle.
Other arrangements are possible: for example, the pressurized fluid
supply could be through a central, axial bore, while the vacuum
chamber could be an annular cylinder, coaxial with the central bore
and incompletely separated from the inner chamber by a cylindrical
partition.
[0031] The inner chamber 30 (slot) is incompletely isolated from
the outer, vacuum chamber 32. At least one partition (two shown: 34
and 42) is disposed between inner and outer chambers. At least one
of said partitions 42 terminates in a shoulder 46. The extent of
the partition 42 is predetermined to maintain a small.
predetermined clearance between the shoulder 46 and a working
surface (a concave bony surface), defining a relatively narrow slot
through which gas can flow from the inner chamber to the outward
chamber (thus from pressure toward vacuum). In one embodiment the
shoulder 46 is a straight wall, recessed below the plane defined by
the circular rim 15. In other embodiments the shoulder 46 could be
slightly convex, and may, near center, extend slightly below the
plane of the circular rim; in such an embodiment the necessary
clearance for fluid flow is provided by the concave curvature of
the bony surface to be cleaned. Preferably, the pressurized fluid
is constrained to flow across the bony surface to be cleaned, there
being no other significant pathways of fluid communication between
the pressurized source 20 and the vacuum 22.
[0032] It is advantageous that the rim 15 of the orifice 12 is
generally adapted to substantially seal against a concave,
generally hemispherical bony surface. The circular orifice in
accordance with the invention, having a diameter less than that of
the hemispherical concavity to be cleaned, is well adapted to seal
to the hemispherical, concave surface. A satisfactory seal can be
obtained from a variety of positions and orientations within the
concave surface; and the tool can be actively repositioned by
manipulating the neck 14, for example by revolving the neck within
a cone, in pattern similar to the precession of a child's spinning
top. Note that for a fixed rim dimension, a seal can be obtained
for any size hemispherical concavity, provided that the diameter of
the circular rim is less than that of a great circle of the
hemispherical concavity.
[0033] The sectional view of FIG. 6 shows the at least one outer or
vacuum chamber 32 and associated passages. Note that in the
embodiment shown the vacuum chamber includes two compartments 32,
which communicate through the transverse passage 38. When the
pressurized fluid source 20 and vacuum source 22 are actively
coupled to the head, the fluid flows from the inner chamber 30,
over the shoulders 46, and into the dual chambers 32; thereafter
the fluid, along with debris and tissues, are sucked through the
outlet tube 17, into the vacuum line 24, and are ultimately
collected in the suction source or aspirator chamber 22 (shown in
FIG. 1).
[0034] The sections of FIGS. 4, 5, and 6 clearly show one
arrangement by which the pressurized and vacuum passages may be
arranged without interference with one another. Other arrangements
are possible.
[0035] The figures also illustrate that the tool can suitably be
manufactured from two distinct body parts: a lower component 52 and
an upper component 54 (visible in FIG. 2) which are mated under
pressure from at least one screw 56. In the simple embodiment
shown, two such screws pass through bores in the upper component 54
and engage threaded bores in the lower component 52, allowing
simple assembly of the two components. The dual components
facilitate manufacture because the hidden fluid and suction
passages and chambers can be readily machined in the separate
components, then the components assembled to enclose hidden
passages as shown. The neck 14 can be inserted tightly or otherwise
bonded to the head 11. Similarly, outlet tube 17 can be inserted
into a hole bored in the upper body component 54.
[0036] The entire head 11 can suitably be machined or otherwise
formed from a solid such as aluminum or stainless steel, which are
capable of enduring repeated autoclaving for sterilization.
Alternatively, polymers or other materials could be used. In some
embodiments the tool may be disposable, thereby avoiding the need
for sterilization by the hospital.
[0037] FIGS. 7 (perspective) and 8 (cross-section) show how the
tool 10 can be used to prepare the bony surfaces of an acetabular
cup to receive an implant component. The figure assumes that the
bone is previously prepared to a generally hemispherical, concave
surface. The bony concavity 60 is shown partially cut away in FIG.
7 to render the head 11 visible. The head 11 of the tool is placed
within the hemispherical concavity 60 of the acetabular cup. It
should be apparent that the diameter of the head 11 must be less
than that of the hemispherical concavity of the acetabular cup, and
preferably is chosen to be substantially less than that of the cup.
Thanks to a known property of spherical geometry, the plane,
circular rim 15 of the tool is guaranteed to closely fit a
hemispherical concavity such a the acetabular cup (the intersection
of a plane and a sphere always defines a circle). A close seal is
desirable, but some leakage is tolerable. Having the head 11
engaged with the bony surface 60, the surgeon activates the sources
of pressurized gas and suction, and moves the tool 10 in a wobbling
pattern by both rotating and tilting the neck 14, in a generally
conical pattern. By this means, the rim of the tool wanders around
a plurality of intersecting circles, to completely clean the bony
surface. When the surface is clean (and dry), the surgeon removes
the tool and applies the cement in accordance with medical
practice.
[0038] When the head is actively engaged with the surface to be
cleaned, the rim engages and encloses a region of the concave
surface. Geometrically speaking, the enclosed region is
substantially a spherical "zone" and more specifically a "zone of
one base": a surface formed by two parallel planes cutting a
sphere, where one of the planes is a tangent to the sphere. See The
Penguin Dictionary of Mathematics, J. Daintich and R. D. Nelson
(Penguin, 1989).
[0039] Flow lines in FIG. 8 show the presumed direction of gas flow
when the device is activated in engagement with a bony surface. The
bony surface can be visualized as surface 60, but here is shown cut
away, to better visualize the assumed gas flow in the tool. The
extent of the rim or other boundary of the orifice defines a
boundary surface for the orifice. The figure assumes that the
orifice is fully engaged with concave bony surface 60, by placing
with slight pressure the rim 15 flush to the concave bony surface.
Thus engaged, circular rim 15 in contact with concave bony surface,
the cavity and bone surface together define a substantially
enclosed volume or chamber having a pressurized gas source 30
inwardly disposed, and a vacuum or suction 32 more outwardly
situated in the head, incompletely separated by partition 34. More
generally described, the apparatus thus engaged defines a
substantially closed volume having on at least one side a bony
surface. When actively coupled to the pressurized gas source and
the vacuum source, the volume develops a pressure gradient
substantially across the bony surface. The fluid is thus
constrained to flow substantially across the surgically prepared
surface 60. Most preferably, in at least some region the gradient
is substantially tangential to the surface to be cleaned. Thus, the
fluid is constrained to flow across the surface to be cleaned, at
least in some region.
[0040] In a preferred embodiment, the at least one partition 34
constricts or pinches the gas flow, visualized by flow arrows 54 in
the figure. Flow between the partition 34 and the bony surface is
pinched or constricted as the gas passes through the narrow
clearance between partition and bone. Thus, across the narrow
shoulder 46 of partition 34 the flow has increased velocity and
decreased pressure due to "Bernoulli's principle" or "venturi
effect". Applicants find that the lowered pressure and increased
velocity in this pinched channel is efficacious to draw debris and
liquid (such as blood) from the interstices of a porous bony
surface, which effect is observed to occur with unexpected
efficiency. The constricted channel defined between the sill of
partition 34 and the bone surface should preferably be less than 10
millimeters, more preferably less than 5 mm, and most preferably
even less than three millimeters at the narrowest point.
[0041] The entire cleaning process occurs within a closed volume
defined by the combination of the cavity and bony surface in close
fitted relationship. In addition to increasing the cleaning
efficiency, the closed system also reduces splattering and controls
the aerosolization of biological materials (such as blood, fat and
marrow).
[0042] The inventors presently believe that the preferred
pressurized gas for use in the invention is carbon dioxide
(CO.sub.2). Some of the reasons for this conclusion are set forth
in the Matsen patent, referenced above in the "Background of the
Invention". However, the invention could be modified to employ
other pressurized gases, or an admixture of liquid and gas. In
order to take full advantage of the "Bernoulli effect" in passing
through the constricted channel, a compressible fluid such as a gas
or gas mixture is greatly preferred. In some embodiments, a mixture
of compressed gas and incompressible fluid is used. Such mixtures
allow the density of the fluid to be varied controllably to improve
cleaning efficiency yet control unwanted tissue damage or creation
of emboli.
[0043] In the preferred embodiment, the pressurized gas is provided
from a relatively more central position and the vacuum applied to
the relatively more outside or peripheral portion of the cleaning
head. This principle can be followed using a slot and chamber
geometry as shown in the figures, or a coaxial, annular arrangement
as also mentioned above. Specifically, the pressurized fluid could
be supplied through an axial, inner cylindrical chamber or passage,
and the vacuum could be applied to an outer annular ring or shell,
in a generally coaxial, cylindrical geometry. Using the outer
portion for vacuum allocates a larger aperture to the aspiration
circuit, which prevents clogging from debris and tissue. However,
in some embodiments the arrangement could be reversed if desired
(applying pressure from the outer region, vacuum through a central
camber).
[0044] It is very beneficial, in accordance with the invention,
that the plane of the circular rim 15 be angled with respect to the
elongated neck 14. An angle a of between 30 and 60 degrees is
preferred. An angle of substantially 45 degrees is most preferred.
In no event should the neck and orifice facing be either a parallel
or perpendicular, because this would make access extremely
difficult to a hemispherical concavity. In some embodiments, the
coupling between the cleaning head and the neck could be made
pivotable in one or more directions, to facilitate manipulation of
the device into or within a socket. Flexible or articulable fluid
channels could be substituted for the fixed passages illustrated in
the drawings. The attachment point between the neck and the head
could be shifted. Said attachment point could be more or less
offset. Bent, flexible, pivotable, jointed, or articulated necks
could be employed.
[0045] It is greatly preferred that the head 11 have a thickness
dimension that is less than its diameter, and preferably less than
half of its diameter. This facilitates insertion of the head into
the bony concavity and allows manipulation within the concavity. It
is also most preferable that the head 11 has width dimensions
generally tapering in the direction away from the orifice, to avoid
interference from contacting the rim of an acetabular socket.
[0046] In one embodiment, an apparatus substantially as described
above is sterilized and packaged in a hermetically sealed,
disposable package for the convenience of the surgeon. In such an
embodiment, the cleaning tool (not including the vacuum and
pressurized fluid sources) is preferably manufactured of a
disposable material. Alternatively, if not disposable, the device
should be capable of withstanding repeated sterilization
procedures.
[0047] A person skilled in the art would undoubtedly recognize that
other components and/or configurations may be utilized in the
above-described embodiments. Moreover, all terms should be
interpreted in the broadest possible manner consistent with the
context. In particular, the terms "comprises" and "comprising"
should be interpreted as referring to elements, components, or
steps in a non-exclusive manner, indicating that the referenced
elements, components, or steps may be present, or utilized, or
combined with other elements, components, or steps that are not
expressly referenced.
[0048] While the invention has been described in detail with
regards to several embodiments, it should be appreciated that
various modifications and/or variations may be made in the
invention without departing from the scope or spirit of the
invention. In this regard it is important to note that practicing
the invention is not limited to the applications described
hereinabove. Many other applications and/or alterations may be
utilized provided that such other applications and/or alterations
do not depart from the intended purpose of the invention. For
example, the head, orifice, and rim may be shaped to fit contours
other than planar surfaces. In some embodiments, admixtures of gas
and liquid may be used in place of a carbon dioxide gas. Various
control valves and pressure regulation apparatus may be added to
the cleaning head or to its supply lines. The body may comprise
primarily gas and suction lines. The cleaning head may have
multiple pressure chambers and/or multiple vacuum chambers; the
head could be rotatable; Other such variations could be devised. A
skirt can be added to or substituted for the rim around the
cleaning orifice. A flexible or conformable skirt could be
used.
[0049] Also, features illustrated or described as part of one
embodiment can be used in another embodiment to provide yet another
embodiment such that the features are not limited to the exemplary
embodiments described hereinabove. Thus, it is intended that the
invention cover all such embodiments and variations as long as such
embodiments and variations come within the scope of the appended
claims and their equivalents.
* * * * *