Note: Descriptions are shown in the official language in which they were submitted.
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PROSTHESIS POSITIONING SYSTEMS AND METHODS
CROSS REFERENCE TO RELATED APPLICATIONS
[000li This application claims benefit of US patent application 14/585,056 and
US patent
application number 14/584, 656 and additionally claims benefit of both US
Patent Application No.
61/921,528 and US Patent Application No. 61/980,188, the contents of these
applications in their
entireties are hereby expressly incorporated by reference thereto for all
purposes.
FIELD OF THE INVENTION
[own] The present invention relates generally to orthopedic surgical systems
and procedures
employing a prosthetic implant for, and more specifically, but not
exclusively, to joint replacement
therapies such as total hip replacement including controlled installation and
positioning of the
prosthesis such as during replacement of a pelvic acetabulum with a prosthetic
implant.
BACKGROUND OF THE INVENTION
[Imo] The subject matter discussed in the background section should not be
assumed to be
prior art merely as a result of its mention in the background section.
Similarly, a problem mentioned
in the background section or associated with the subject matter of the
background section should not
be assumed to have been previously recognized in the prior art. The subject
matter in the background
section merely represents different approaches, which in and of themselves may
also be inventions.
[0004] Total hip replacement refers to a surgical procedure where a hip joint
is replaced
using a prosthetic implant. There are several different techniques that may be
used, but all include a
step of inserting an acetabular component into the acetabulum and positioning
it correctly in three
dimensions (along an X, Y, and Z axis).
[0005] In total hip replacement (THR) procedures there are advantages to
patient outcome
when the procedure is performed by a surgeon specializing in these procedures.
Patients of surgeons
who do not perform as many procedures can have increased risks of
complications, particularly of
complications arising from incorrect placement and positioning of the
acetabular component.
[0006] The incorrect placement and positioning may arise even when the surgeon
understood
and intended the acetabular component to be inserted and positioned correctly.
This is true because
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in some techniques, the tools for actually installing the acetabular component
are crude and provide
an imprecise, unpredictable coarse positioning outcome.
[0007] It is known in some techniques to employ automated and/or computer-
assisted
navigation tools, for example, x-ray fluoroscopy or computer guidance systems.
There are computer
assisted surgery techniques that can help the surgeon in determining the
correct orientation and
placement of the acetabular component. However, current technology provides
that at some point the
surgeon is required to employ a hammer/mallet to physically strike a pin or
alignment rod. The
amount of force applied and the location of the application of the force are
variables that have not
been controlled by these navigation tools. Thus even when the acetabular
component is properly
positioned and oriented, when actually impacting the acetabular component into
place the actual
location and orientation can differ from the intended optimum location and
orientation. In some
cases the tools used can be used to determine that there is, in fact, some
difference in the location
and/or orientation. However, once again the surgeon must employ an impacting
tool (e.g., the
hammer/mallet) to strike the pin or alignment rod to attempt an adjustment.
However the resulting
location and orientation of the acetabular component after the adjustment may
not be, in fact, the
desired location and/or orientation. The more familiar that the surgeon is
with the use and
application of these adjustment tools can reduce the risk to a patient from a
less preferred location or
orientation. In some circumstances, quite large impacting forces are applied
to the prosthesis by the
mallet striking the rod; these forces make fine tuning difficult at best and
there is risk of fracturing
and/or shattering the acetabulum during these impacting steps.
[0008] What is needed is a system and method for improving positioning of a
prosthesis,
particularly prostheses having a preferred orientation with respect to a frame
of reference of a
patient.
BRIEF SUMMARY OF THE INVENTION
[0009] Disclosed is a system and method for improving positioning of a
prosthesis,
particularly prostheses having a preferred orientation with respect to a frame
of reference of a
patient.
[0010] The following summary of the invention is provided to facilitate an
understanding of
some of technical features related to total hip replacement, and is not
intended to be a full description
of the present invention. A full appreciation of the various aspects of the
invention can be gained by
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taking the entire specification, claims, drawings, and abstract as a whole.
The present invention is
applicable to other surgical procedures, including replacement of other joints
replaced by a
prosthetic implant in addition to replacement of an acetabulum (hip socket)
with an acetabular
component (e.g., a cup). Use of pneumatic and electric motor implementations
have both achieved a
proof of concept development.
[00iii The disclosed concepts involve creation of a system/method/tool/gun
that vibrates an
attached prosthesis, e.g., an acetabular cup. The gun would be held in a
surgeon's hands and
deployed. It would use a vibratory energy to insert (not impact) and position
the cup into desired
alignment (using current intra-operation measurement systems, navigation,
fluoroscopy, and the
like).
[0012i In one embodiment, a first gun-like device is used for accurate
impaction of the
acetabular component at the desired location and orientation.
[0013i In another embodiment, a second gun-like device is used for fine-tuning
of the
orientation of the acetabular component, such as one installed by the first
gun-like device, by
traditional mallet and tamp, or by other methodology. However the second gun-
like device may be
used independently of the first gun-like device for adjusting an acetabular
component installed using
an alternate technique. Similarly the second gun-like device may be used
independently of the first
gun-like device, particularly when the initial installation is sufficiently
close to the desired location
and orientation. These embodiments are not necessarily limited to fine-tuning
as certain
embodiments permit complete re-orientation. Some implementations allow for
removal of an
installed prosthesis.
[0014i Another embodiment includes a third gun-like device that combines the
functions of
the first gun-like device and the second gun-like device. This embodiment
enables the surgeon to
accurately locate, insert, orient, and otherwise position the acetabular
component with the single
tool.
[0015] Another embodiment includes a fourth device that installs the
acetabular component
without use of the mallet and the rod, or use of alternatives to strike the
acetabular component for
impacting it into the acetabulum. This embodiment imparts a vibratory motion
to an installation rod
coupled to the acetabular component that enables low-force, impactless
installation and/or
positioning.
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[0016] A positioning device for an acetabular cup disposed in a bone, the
acetabular cup
including an outer shell having a sidewall defining an inner cavity and an
opening with the sidewall
having a periphery around the opening and with the acetabular cup having a
desired abduction angle
relative to the bone and a desired anteversion angle relative to the bone,
including a controller
including a trigger and a selector; a support having a proximal end and a
distal end opposite of the
proximal end, the support further having a longitudinal axis extending from
the proximal end to the
distal end with the proximal end coupled to the controller, the support
further having an adapter
coupled to the distal end with the adapter configured to secure the acetabular
cup; and a number N,
the number N, an integer greater than or equal to 2, of longitudinal actuators
coupled to the
controller and disposed around the support generally parallel to the
longitudinal axis, each the
actuator including an associated impact head arranged to strike a portion of
the periphery, each
impact head providing an impact strike to a different portion of the periphery
when the associated
actuator is selected and triggered; wherein each the impact strike adjusts one
of the angles relative to
the bone.
[0017j An installation device for an acetabular cup disposed in a pelvic bone,
the acetabular
cup including an outer shell having a sidewall defining an inner cavity and an
opening with the
sidewall having a periphery around the opening and with the acetabular cup
having a desired
installation depth relative to the bone, a desired abduction angle relative to
the bone, and a desired
anteversion angle relative to the bone, including a controller including a
trigger; a support having a
proximal end and a distal end opposite of said proximal end, said support
further having a
longitudinal axis extending from said proximal end to said distal end with
said proximal end coupled
to said controller, said support further having an adapter coupled to said
distal end with said adapter
configured to secure the acetabular cup; and an oscillator coupled to said
controller and to said
support, said oscillator configured to control an oscillation frequency and an
oscillation magnitude of
said support with said oscillation frequency and said oscillation magnitude
configured to install the
acetabular cup at the installation depth with the desired abduction angle and
the desired anteversion
angle without use of an impact force applied to the acetabular cup.
[0018j An installation system for a prosthesis configured to be implanted into
a portion of
bone at a desired implantation depth, the prosthesis including an attachment
system, including an
oscillation engine including a controller coupled to a vibratory machine
generating an original series
of pulses having a generation pattern, said generation pattern defining a
first duty cycle of said
original series of pulses; and a pulse transfer assembly having a proximal end
coupled to said
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oscillation engine and a distal end, spaced from said proximal end, coupled to
the prosthesis with
said pulse transfer assembly including a connector system at said proximal
end, said connector
system complementary to the attachment system and configured to secure and
rigidly hold the
prosthesis producing a secured prosthesis with said pulse transfer assembly
communicating an
installation series of pulses, responsive to said original series of pulses,
to said secured prosthesis
producing an applied series of pulses responsive to said installation series
of pulses; wherein said
applied series of pulses are configured to impart a vibratory motion to said
secured prosthesis
enabling an installation of said secured prosthesis into the portion of bone
to within 95% of the
desired implantation depth without a manual impact.
[0019] A method for installing an acetabular cup into a prepared socket in a
pelvic bone, the
acetabular cup including an outer shell having a sidewall defining an inner
cavity and an opening
with the sidewall having a periphery around the opening and with the
acetabular cup having a
desired installation depth relative to the bone, a desired abduction angle
relative to the bone, and a
desired anteversion angle relative to the bone, including (a) generating an
original series of pulses
from an oscillation engine; (b) communicating said original series of pulses
to the acetabular cup
producing a communicated series of pulses at said acetabular cup; (c)
vibrating, responsive to said
communicated series of pulses, the acetabular cup to produce a vibrating
acetabular cup having a
predetermined vibration pattern; and (d) inserting the vibrating acetabular
cup into the prepared
socket within a first predefined threshold of the installation depth with the
desired abduction angle
and the desired anteversion angle without use of an impact force applied to
the acetabular cup.
[0020] This method may further include (e) orienting the vibrating acetabular
cup within the
prepared socket within a second predetermined threshold of the desired
abduction angle and within
third predetermined threshold of the desired anteversion angle.
[0021i A method for inserting a prosthesis into a prepared location in a bone
of a patient at a
desired insertion depth wherein non-vibratory insertion forces for inserting
the prosthesis to the
desired insertion depth are in a first range, the method including (a)
vibrating the prosthesis using a
tool to produce a vibrating prosthesis having a predetermined vibration
pattern; and (b) inserting the
vibrating prosthesis into the prepared location to within a first
predetermined threshold of the desired
insertion depth using vibratory insertion forces in a second range, said
second range including a set
of values less than a lowest value of the first range.
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[0022] Any of the embodiments described herein may be used alone or together
with one
another in any combination. Inventions encompassed within this specification
may also include
embodiments that are only partially mentioned or alluded to or are not
mentioned or alluded to at all
in this brief summary or in the abstract. Although various embodiments of the
invention may have
been motivated by various deficiencies with the prior art, which may be
discussed or alluded to in
one or more places in the specification, the embodiments of the invention do
not necessarily address
any of these deficiencies. In other words, different embodiments of the
invention may address
different deficiencies that may be discussed in the specification. Some
embodiments may only
partially address some deficiencies or just one deficiency that may be
discussed in the specification,
and some embodiments may not address any of these deficiencies.
[0023j Other features, benefits, and advantages of the present invention will
be apparent
upon a review of the present disclosure, including the specification,
drawings, and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[oo24] The accompanying figures, in which like reference numerals refer to
identical or
functionally-similar elements throughout the separate views and which are
incorporated in and form
a part of the specification, further illustrate the present invention and,
together with the detailed
description of the invention, serve to explain the principles of the present
invention.
[0025j FIG. 1 illustrates a representative installation gun;
[0026j FIG. 2 illustrates a right-hand detail of the installation gun of FIG.
1;
[0027j FIG. 3 illustrates a left-hand detail of the installation gun of FIG. 1
and generally
when combined with FIG. 2 produces the illustration of FIG. 1;
[0028j FIG. 4 illustrates a second representative installation system;
[0029j FIG. 5 illustrates a disassembly of the second representative
installation system of
FIG. 4;
[0030j FIG. 6 illustrates a first disassembly view of the pulse transfer
assembly of the
installation system of FIG. 4;
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[0031] FIG 7 illustrates a second disassembly view of the pulse transfer
assembly of the
installation system of FIG. 4;
[0032] FIG. 8 illustrates a third representative installation system;
[0033] FIG. 9 illustrates a disassembly view of the third representative
installation system of
FIG. 8;
[0034] FIG. 10 illustrates a schematic side section representation of an
acetabular cup
mispositioned into a pelvis;
[0035] FIG. 11 illustrates a conventional use of a mallet and tamp to apply an
orientation-
altering force to an unencoded and mispositioned acetabular cup, such as that
illustrated in FIG. 10;
[00361 FIG. 12¨FIG 14 illustrate a reference frame used in THR surgery
including an
acetabular prosthesis installed into a pelvis including identified orthogonal
axes;
[0037] FIG. 12 illustrates the reference frame and the orthogonal axes;
[00381 FIG. 13 illustrates the orthogonal axes with an associated frontal
plane and a
transverse plane; and
[0039] FIG. 14 illustrates a different perspective view of the orthogonal axes
with the
associated frontal plane and a transverse plane; and
[0040] FIG. 15 illustrates an encoded prosthesis including a set of pure
points;
[0041i FIG. 16 illustrates a positioning of an encoded prosthesis;
[0042] FIG. 17 illustrates an automated positioning of an encoded prosthesis;
[0043] FIG. 18 illustrates a schematic representation of an embodiment of a
positioning gun
configured for prosthesis adjustment;
[0044] FIG. 19¨FIG. 21 illustrate a detailed schematic of an embodiment of a
positioning
gun configured for prosthesis adjustment;
[0045] FIG. 19 illustrates a representative positioning gun;
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[0046] FIG. 20 illustrates a left-hand detail of the positioning gun of FIG.
19;
[0047] FIG. 21 illustrates a right-hand detail of the positioning gun of 19
and generally when
combined with FIG. 20 produces the illustration of FIG. 19;
[0048] FIG. 22¨FIG. 24 illustrate use of an impact ring for positioning an
installed
prosthesis;
[0049] FIG. 22 illustrates an initial condition of the pre-positioned
installed prosthesis with
respect to an impact ring installed on a positioning system;
[0050] FIG. 23 illustrates an intermediate condition of the pre-positioned
installed prosthesis
with respect to the impact ring installed on a positioning system; and
[0051] FIG. 24 illustrates a final condition having a positioned installed
prosthesis with
respect to the impact ring installed on a positioning system; and
[0052] FIG. 25 illustrates an embodiment of a positioning system employing an
impact ring;
[0053] FIG. 26 illustrates an evolution of one version of a positioning system
employing an
impact ring, such as illustrated in FIG. 25, to another version of a
positioning system employing an
impact ring;
[0054] FIG. 27¨FIG. 34 illustrate alternate embodiments for a positioning
systems
employing an impact ring model;
[0055] FIG. 27¨FIG. 28 illustrate a first alternate embodiment for a
positioning system;
[0056] FIG. 27 illustrates a side view of the first alternate embodiment; and
[0057] FIG. 28 illustrates a top view of the first alternate embodiment; and
[0058] FIG. 29¨FIG. 30 illustrate a second alternate embodiment for a
positioning system;
[0059] FIG. 29 illustrates a side view of the second alternate embodiment; and
[0060] FIG. 30 illustrates a top view of the second alternate embodiment; and
[0061] FIG. 31¨FIG. 32 illustrate a third alternate embodiment for a
positioning system;
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[0062] FIG. 31 illustrates a side view of the third alternate embodiment; and
[0063] FIG. 32 illustrates a top view of the third alternate embodiment; and
[0064] FIG. 33 illustrates a side view of a fourth alternate embodiment for a
positioning
system; and
[0065] FIG. 34 illustrates a side view of a fifth alternate embodiment for a
positioning
system.
DETAILED DESCRIPTION OF THE INVENTION
[oo66] Embodiments of the present invention provide a system and method for
improving
positioning of a prosthesis, particularly prostheses having a preferred
orientation with respect to a
frame of reference of a patient. The following description is presented to
enable one of ordinary skill
in the art to make and use the invention and is provided in the context of a
patent application and its
requirements.
[0067] Various modifications to the preferred embodiment and the generic
principles and
features described herein will be readily apparent to those skilled in the
art. Thus, the present
invention is not intended to be limited to the embodiment shown but is to be
accorded the widest
scope consistent with the principles and features described herein.
[00681 Definitions
[0069] Unless otherwise defined, all terms (including technical and scientific
terms) used
herein have the same meaning as commonly understood by one of ordinary skill
in the art to which
this general inventive concept belongs. It will be further understood that
terms, such as those defined
in commonly used dictionaries, should be interpreted as having a meaning that
is consistent with
their meaning in the context of the relevant art and the present disclosure,
and will not be interpreted
in an idealized or overly formal sense unless expressly so defined herein.
[0070] The following definitions apply to some of the aspects described with
respect to some
embodiments of the invention. These definitions may likewise be expanded upon
herein.
[0071] As used herein, the term "or" includes "and/or" and the term "and/or"
includes any
and all combinations of one or more of the associated listed items.
Expressions such as "at least one
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of," when preceding a list of elements, modify the entire list of elements and
do not modify the
individual elements of the list.
[0072] As used herein, the singular terms "a," "an," and "the" include plural
referents unless
the context clearly dictates otherwise. Thus, for example, reference to an
object can include multiple
objects unless the context clearly dictates otherwise.
[0073] Also, as used in the description herein and throughout the claims that
follow, the
meaning of "in" includes "in" and "on" unless the context clearly dictates
otherwise. It will be
understood that when an element is referred to as being "on" another element,
it can be directly on
the other element or intervening elements may be present therebetween. In
contrast, when an
element is referred to as being "directly on" another element, there are no
intervening elements
present.
[0074] As used herein, the term "set" refers to a collection of one or more
objects. Thus, for
example, a set of objects can include a single object or multiple objects.
Objects of a set also can be
referred to as members of the set. Objects of a set can be the same or
different. In some instances,
objects of a set can share one or more common properties.
[0075] As used herein, the term "adjacent" refers to being near or adjoining.
Adjacent
objects can be spaced apart from one another or can be in actual or direct
contact with one another.
In some instances, adjacent objects can be coupled to one another or can be
formed integrally with
one another.
[0076] As used herein, the terms "connect," "connected," and "connecting"
refer to a direct
attachment or link. Connected objects have no or no substantial intermediary
object or set of objects,
as the context indicates.
[0077] As used herein, the terms "couple," "coupled," and "coupling" refer to
an operational
connection or linking. Coupled objects can be directly connected to one
another or can be indirectly
connected to one another, such as via an intermediary set of objects.
[0078] As used herein, the terms "substantially" and "substantial" refer to a
considerable
degree or extent. When used in conjunction with an event or circumstance, the
terms can refer to
instances in which the event or circumstance occurs precisely as well as
instances in which the event
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or circumstance occurs to a close approximation, such as accounting for
typical tolerance levels or
variability of the embodiments described herein.
[0079] As used herein, the terms "optional" and "optionally" mean that the
subsequently
described event or circumstance may or may not occur and that the description
includes instances
where the event or circumstance occurs and instances in which it does not.
[0080] As used herein, the term "bone" means rigid connective tissue that
constitute part of a
vertebral skeleton, including mineralized osseous tissue, particularly in the
context of a living patient
undergoing a prosthesis implant into a portion of cortical bone. A living
patient, and a surgeon for
the patient, both have significant interests in reducing attendant risks of
conventional implanting
techniques including fracturing/shattering the bone and improper installation
and positioning of the
prosthesis within the framework of the patient's skeletal system and
operation.
[0081i As used herein, the term "size" refers to a characteristic dimension of
an object. Thus,
for example, a size of an object that is spherical can refer to a diameter of
the object. In the case of
an object that is non-spherical, a size of the non-spherical object can refer
to a diameter of a
corresponding spherical object, where the corresponding spherical object
exhibits or has a particular
set of derivable or measurable properties that are substantially the same as
those of the non-spherical
object. Thus, for example, a size of a non-spherical object can refer to a
diameter of a corresponding
spherical object that exhibits light scattering or other properties that are
substantially the same as
those of the non-spherical object. Alternatively, or in conjunction, a size of
a non-spherical object
can refer to an average of various orthogonal dimensions of the object. Thus,
for example, a size of
an object that is a spheroidal can refer to an average of a major axis and a
minor axis of the object.
When referring to a set of objects as having a particular size, it is
contemplated that the objects can
have a distribution of sizes around the particular size. Thus, as used herein,
a size of a set of objects
can refer to a typical size of a distribution of sizes, such as an average
size, a median size, or a peak
size.
[0082] As used herein, mallet or hammer refers to an orthopedic device made of
stainless
steel or other dense material having a weight generally a carpenter's hammer
and a stonemason's
lump hammer.
[0083] As used herein, an impact force for impacting an acetabular component
(e.g., an
acetabular cup prosthesis) includes forces from striking an impact rod
multiple times with the
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orthopedic device that are generally similar to the forces that may be used to
drive a three inch nail
into a piece of lumber using the carpenter's hammer by striking the nail
approximately a half-dozen
times to completely seat the nail. Without limiting the preceding definition,
a representative value in
some instances includes a force of approximately 10 lbs/square inch.
[0084] The following description relates to improvements in a wide-range of
prostheses
installations into live bones of patients of surgeons. The following
discussion focuses primarily on
total hip replacement (THR) in which an acetabular cup prosthesis is installed
into the pelvis of the
patient. This cup is complementary to a ball and stem (i.e., a femoral
prosthesis) installed into an end
of a femur engaging the acetabulum undergoing repair.
[0085] As noted in the background, the surgeon prepares the surface of the
hipbone which
includes attachment of the acetabular prosthesis to the pelvis.
Conventionally, this attachment
includes a manual implantation in which a mallet is used to strike a tamp that
contacts some part of
the acetabular prosthesis. Repeatedly striking the tamp drives the acetabular
prosthesis into the
acetabulum. Irrespective of whether current tools of computer navigation,
fluoroscopy, robotics (and
other intra-operative measuring tools) have been used, it is extremely
unlikely that the acetabular
prosthesis will be in the correct orientation once it has been seated to the
proper depth by the series
of hammer strikes. After manual implantation in this way, the surgeon then may
apply a series of
adjusting strikes around a perimeter of the acetabular prosthesis to attempt
to adjust to the desired
orientation. Currently such post-impaction result is accepted as many surgeons
believe that post-
impaction adjustment creates an unpredictable and unreliable change which does
not therefore
warrant any attempts for post-impaction adjustment.
[0086] In most cases, any and all surgeons including an inexperienced surgeon
may not be
able to achieve the desired orientation of the acetabular prosthesis in the
pelvis by conventional
solutions due to unpredictability of the orientation changes responsive to
these adjusting strikes. As
noted above, it is most common for any surgeon to avoid post-impaction
adjustment as most
surgeons understand that they do not have a reliable system or method for
improving any particular
orientation and could easily introduce more/greater error. The computer
navigation systems,
fluoroscopy, and other measuring tools are able to provide the surgeon with
information about the
current orientation of the prosthesis (in real time) during an operation and
after the prosthesis has
been installed and its deviation from the desired orientation, but the
navigation systems (and others)
do not protect against torsional forces created by the implanting/positioning
strikes. The prosthesis
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will find its own position in the acetabulum based on the axial and torsional
forces created by the
blows of the mallet. Even those navigation systems used with robotic systems
(e.g., MAKO) that
attempt to secure an implant in the desired orientation prior to impaction are
not guaranteed to result
in the installation of the implant at the desired orientation because the
actual implanting forces are
applied by a surgeon swinging a mallet to manually strike the tamp.
[0087] A Behzadi Medical Device (BMD) is herein described and enabled that
eliminates
this crude method (i.e., mallet, tamp, and surgeon-applied mechanical
implanting force) of the
prosthesis (e.g., the acetabular cup). A surgeon using the BMD is able to
insert the prosthesis exactly
where desired with proper force, finesse, and accuracy. Depending upon
implementation details, the
installation includes insertion of the prosthesis into patient bone, within a
desired threshold of
metrics for insertion depth and location) and may also include, when
appropriate and/or desired,
positioning at a desired orientation with the desired threshold further
including metrics for insertion
orientation). The use of the BMD reduces risks of fracturing and/or shattering
the bone receiving the
prosthesis and allows for rapid, efficient, and accurate (atraumatic)
installation of the prosthesis. The
BMD provides a viable interface for computer navigation assistance (also
useable with all
intraoperative measuring tools including fluoroscopy) during the installation
as a lighter more
responsive touch may be used.
[0088] The BMD encompasses many different embodiments for installation and/or
positioning of a prosthesis and may be adapted for a wide range of prostheses
in addition to
installation and/or positioning of an acetabular prosthesis during THR.
[0089] FIG. 1 illustrates a representative installation gun 100; FIG. 2
illustrates a right-hand
detail of the installation gun 100; and FIG. 3 illustrates a left-hand detail
of installation gun of 100
and generally when combined with FIG. 2 produces the illustration of FIG. 1.
Installation gun 100 is
represented as operable using pneumatics, though other implementations may use
other mechanisms
for creating a desired vibratory motion of prosthesis to be installed.
[0090] Installation gun 100 is used to control precisely one or both of (i)
insertion, and (ii)
abduction and anteversion angles of a prosthetic component. Installation gun
100 preferably allows
both installation of an acetabular cup into an acetabulum at a desired depth
and orientation of the cup
for both abduction and anteversion to desired values. The following reference
numbers in Table I
refer to elements identified in FIG. 1¨FIG. 3:
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[0091] TABLE I: Device 100 Elements
102 Middle guide housing
104 Klip
106 Kuciste
108 CILINDAR
110 Cjev
112 Poklopac
114 54 mm acetabular cup
116 Body
118 Valve
120 Bottom cap
122 Upper guide housing
124 Handle cam
126 DIN 3771 6 x 1,8 - N -NBR 70
128 Main Air Inlet - Input Tube
130 Trigger
132 Trigger pin
134 DIN 3771 6 x 1,8 - N -NBR 70
136 MirrorAR15 ¨ Hand Grip 1
138 Crossover Tube
140 9657K103 compression spring
142 Elongate tube
144 Lower guide housing
146 Primary adapter
148 Housing
[0092] Installation gun 100 includes a controller with a handle supporting an
elongate tube
142 that terminates in adapter 146 that engages cup 114. Operation of trigger
130 initiates a motion
of elongate tube 142. This motion is referred to herein as an installation
force and/or installation
motion that is much less than the impact force used in a conventional
replacement process. An
exterior housing 148 allows the operator to hold and position prosthesis 114
while elongate tube 142
moves within. Some embodiments may include a handle or other grip in addition
to or in lieu of
housing 148 that allows the operator to hold and operate installation gun 100
without interfering
with the mechanism that provides a direct transfer of installation motion to
prosthesis 114. The
illustrated embodiment includes prosthesis 114 held securely by adapter 146
allowing a tilting and/or
rotation of gun 100 about any axis to be reflected in the position/orientation
of the secured
prosthesis.
[0093] The installation motion includes constant, cyclic, periodic, and/or
random motion
(amplitude and/or frequency) that allows the operator to install cup 114 into
the desired position
(depth and orientation) without application of an impact force. There may be
continuous movement
or oscillations in one or more of six degrees of freedom including
translation(s) and/or rotation(s) of
adapter 146 about the X, Y, Z axes (e.g., oscillating translation(s) and/or
oscillating/continuous
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rotation(s) which could be different for different axes such as translating
back and forth in the
direction of the longitudinal axis of the central support while rotating
continuously around the
longitudinal axis). This installation motion may include continuous or
intermittent very high
frequency movements and oscillations of small amplitude that allow the
operator to easily install the
prosthetic component in the desired location, and preferably also to allow the
operator to also set the
desired angles for abduction and anteversion.
[0094] In some implementations, the controller includes a stored program
processing system
that includes a processing unit that executes instructions retrieved from
memory. Those instructions
could control the selection of the motion parameters autonomously to achieve
desired values for
depth, abduction and anteversion entered into by the surgeon or by a computer
aided medical
computing system such as the computer navigation system. Alternatively those
instructions could be
used to supplement manual operation to aid or suggest selection of the motion
parameters.
[0095] For more automated systems, consistent and unvarying motion parameters
are not
required and it may be that a varying dynamic adjustment of the motion
parameters better conform
to an adjustment profile of the cup installed into the acetabulum and status
of the installation. An
adjustment profile is a characterization of the relative ease by which depth,
abduction and
anteversion angles may be adjusted in positive and negative directions. In
some situations these
values may not be the same and the installation gun could be enhanced to
adjust for these
differences. For example, a unit of force applied to pure positive anteversion
may adjust anteversion
in the positive direction by a first unit of distance while under the same
conditions that unit of force
applied to pure negative anteversion may adjust anteversion in the negative
direction by a second
unit of distance different from the first unit. And these differences may vary
as a function of the
magnitude of the actual angle(s). For example, as the anteversion increases it
may be that the same
unit of force results in a different responsive change in the actual distance
adjusted. The adjustment
profile when used helps the operator when selecting the actuators and the
impact force(s) to be
applied. Using a feedback system of the current real-time depth and
orientation enables the
adjustment profile to dynamically select/modify the motion parameters
appropriately during
different phases of the installation. One set of motion parameters may be used
when primarily setting
the depth of the implant and then another set used when the desired depth is
achieved so that fine
tuning of the abduction and anteversion angles is accomplished more
efficiently, all without use of
impact forces in setting the depth and/or angle adjustment(s).
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[0096] This device better enables computer navigation as the
installation/adjustment forces
are reduced as compared to the impacting method. This makes the required
forces more compatible
with computer navigation systems used in medical procedures which do not have
the capabilities or
control systems in place to actually provide impacting forces for seating the
prosthetic component.
And without that, the computer is at best relegated to a role of providing
after-the-fact assessments
of the consequences of the surgeon's manual strikes of the orthopedic mallet.
(Also provides
information before and during the impaction. It is a problem that the very act
of impaction
introduces variability and error in positioning and alignment of the
prosthesis.
[0097] FIG. 4 illustrates a second representative installation system 400
including a pulse
transfer assembly 405 and an oscillation engine 410; FIG. 5 illustrates a
disassembly of second
representative installation system 400; FIG. 6 illustrates a first disassembly
view of pulse transfer
assembly 405; and FIG 7 illustrates a second disassembly view of pulse
transfer assembly 405 of
installation system 400.
[0098] Installation system 400 is designed for installing a prosthesis that,
in turn, is
configured to be implanted into a portion of bone at a desired implantation
depth. The prosthesis
includes some type of attachment system (e.g., one or more threaded inserts,
mechanical coupler,
link, or the like) allowing the prosthesis to be securely and rigidly held by
an object such that a
translation and/or a rotation of the object about any axis results in a direct
corresponding translation
and/or rotation of the secured prosthesis.
[0099] Oscillation engine 410 includes a controller coupled to a vibratory
machine that
generates an original series of pulses having a generation pattern. This
generation pattern defines a
first duty cycle of the original series of pulses including one or more of a
first pulse amplitude, a first
pulse direction, a first pulse duration, and a first pulse time window. This
is not to suggest that the
amplitude, direction, duration, or pulse time window for each pulse of the
original pulse series are
uniform with respect to each other. Pulse direction may include motion having
any of six degrees of
freedom ¨ translation along one or more of any axis of three orthogonal axes
and/or rotation about
one or more of these three axes. Oscillation engine 410 includes an electric
motor powered by
energy from a battery, though other motors and energy sources may be used.
[MOM Pulse transfer assembly 405 includes a proximal end 415 coupled to
oscillation
engine 410 and a distal end 420, spaced from proximal end 420, coupled to the
prosthesis using a
connector system 425. Pulse transfer assembly 405 receives the original series
of pulses from
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oscillation engine 410 and produces, responsive to the original series of
pulses, an installation series
of pulses having an installation pattern. Similar to the generation pattern,
the installation pattern
defines a second duty cycle of the installation series of pulses including a
second pulse amplitude, a
second pulse direction, a second pulse duration, and a second pulse time
window. Again, this is not
to suggest that the amplitude, direction, duration, or pulse time window for
each pulse of the
installation pulse series are uniform with respect to each other. Pulse
direction may include motion
having any of six degrees of freedom ¨ translation along one or more of any
axis of three orthogonal
axes and/or rotation about one or more of these three axes.
[Mu For some embodiments of pulse transfer assembly 405, the installation
series of
pulses will be strongly linked to the original series and there will be a
close match, if not identical
match, between the two series. Some embodiments may include a more complex
pulse transfer
assembly 405 that produces an installation series that is more different, or
very different, from the
original series.
[0102] Connector system 425 (e.g., one or more threaded studs complementary to
the
threaded inserts of the prosthesis, or other complementary mechanical coupling
system) is disposed
at proximal end 420. Connector system 425 is configured to secure and rigidly
hold the prosthesis. In
this way, the attached prosthesis becomes a secured prosthesis when engaged
with connector system
425.
[0103] Pulse transfer assembly 405 communicates the installation series of
pulses to the
secured prosthesis and produces an applied series of pulses that are
responsive to the installation
series of pulses. Similar to the generation pattern and the installation
pattern, the applied pattern
defines a third duty cycle of the applied series of pulses including a third
pulse amplitude, a third
pulse direction, a third pulse duration, and a third pulse time window. Again,
this is not to suggest
that the amplitude, direction, duration, or pulse time window for each pulse
of the applied pulse
series are uniform with respect to each other. Pulse direction may include
motion having any of six
degrees of freedom ¨ translation along one or more of any axis of three
orthogonal axes and/or
rotation about one or more of these three axes.
[0104] For some embodiments of pulse transfer assembly 405, the applied series
of pulses
will be strongly linked to the original series and/or the installation series
and there will be a close, if
not identical, match between the series. Some embodiments may include a more
complex pulse
transfer assembly 405 that produces an applied series that is more different,
or very different, from
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the original series and/or the installation series. In some embodiments, for
example one or more
components may be integrated together (for example, integrating oscillation
engine 410 with pulse
transfer assembly 405) so that the first series and the second series, if they
exist independently are
nearly identical if not identical).
[0105j The applied series of pulses are designed to impart a vibratory motion
to the secured
prosthesis that enable an installation of the secured prosthesis into the
portion of bone to within 95%
of the desired implantation depth without a manual impact. That is, in
operation, the original pulses
from oscillation engine 410 propagate through pulse transfer assembly 405
(with implementation-
depending varying levels of fidelity) to produce the vibratory motion to the
prosthesis secured to
connector system 425. In a first implementation, the vibratory motion allows
implanting without
manual impacts on the prosthesis and in a second mode an orientation of the
implanted secured
prosthesis may be adjusted by rotations of installation system 400 while the
vibratory motion is
active, also without manual impact. In some implementations, the pulse
generation may produce
different vibratory motions optimized for these different modes.
[0106j Installation system 400 includes an optional sensor 430 (e.g., a flex
sensor or the like)
to provide a measurement (e.g., quantitative and/or qualitative) of the
installation pulse pattern
communicated by pulse transfer assembly 405. This measurement may be used as
part of a manual
or computerized feedback system to aid in installation of a prosthesis. For
example, in some
implementations, the desired applied pulse pattern of the applied series of
pulses (e.g., the
vibrational motion of the prosthesis) may be a function of a particular
installation pulse pattern,
which can be measured and set through sensor 430. In addition to, or
alternatively, other sensors
may aid the surgeon or an automated installation system operating installation
system 400, such as a
bone density sensor or other mechanism to characterize the bone receiving the
prosthesis to establish
a desired applied pulse pattern for optimal installation.
[0107j The disassembled views of FIG. 6 and FIG. 7 detail a particular
implementation of
pulse transfer assembly 405, it being understood that there are many possible
ways of creating and
communicating an applied pulse pattern responsive to a series of generation
pulses from an
oscillation engine. The illustrated structure of FIG. 6 and FIG. 7 generate
primarily
longitudinal/axial pulses in response to primarily longitudinal/axial
generation pulses from
oscillation engine 410.
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[0108] Pulse transfer assembly 405 includes an outer housing 435 containing an
upper
transfer assembly 640, a lower transfer assembly 645 and a central assembly
650. Central assembly
650 includes a double anvil 655 that couples upper transfer assembly 640 to
lower transfer assembly
645. Outer housing 635 and central assembly 650 each include a port allowing
sensor 630 to be
inserted into central assembly 650 between an end of double anvil 655 and one
of the upper/lower
transfer assemblies.
[0109] Upper transfer assembly 640 and lower transfer assembly 645 each
include a support
660 coupled to outer housing 435 by a pair of connectors. A transfer rod 665
is moveably disposed
through an axial aperture in each support 660, with each transfer rod 665
including a head at one end
configured to strike an end of double anvil 655 and a coupling structure at a
second end. A
compression spring 670 is disposed on each transfer rod 665 between support
660 and the head. The
coupling structure of upper transfer assembly 640 cooperates with oscillation
engine 410 to receive
the generated pulse series. The coupling structure of lower transfer assembly
645 includes connector
system 425 for securing the prosthesis. Some embodiments may include an
adapter, not shown, that
adapts connector system 425 to a particular prosthesis, different adapters
allowing use of pulse
transfer assembly 405 with different prosthesis.
[OHO] Central assembly 650 includes a support 675 coupled to outer housing 435
by a
connector and receives double anvil 655 which moves freely within support 675.
The heads of the
upper transfer assembly and the lower transfer assembly are disposed within
support 675 and
arranged to strike corresponding ends of double anvil 655 during pulse
generation.
[Om In operation, oscillation engine 410 generates pulses that are transferred
via pulse
transfer assembly 405 to the prosthesis secured by connector system 425. The
pulse transfer
assembly 405, via upper transfer assembly 640, receives the generated pulses
using transfer rod 665.
Transfer rod 665 of upper transfer assembly 640 moves within support 660 of
upper transfer
assembly 640 to communicate pulses to double anvil 655 moving within support
675. Double anvil
655, in turn, communicates pulses to transfer rod 665 of lower transfer
assembly 645 to produce
vibratory motion of a prosthesis secured to connector system 425. Transfer
rods 665 move, in this
illustrated embodiment, primarily longitudinally/axially within outer housing
435 (a longitudinal
axis defined as extending between proximate end 415 and distal end 420. In
this way, the surgeon
may use outer housing 435 as a hand hold when installing and/or positioning
the vibrating
prosthesis.
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[0112] The use of discrete transfer portions (e.g., upper, central, and lower
transfer
assemblies) for pulse transfer assembly 405 allows a form of loose coupling
between oscillation
engine 410 and a secured prosthesis. In this way pulses from oscillation
engine 410 are converted
into a vibratory motion of the prosthesis as it is urged into the bone during
operation. Some
embodiments may provide a stronger coupling by directly securing one component
to another, or
substituting a single component for a pair of components.
[0113] FIG. 8 illustrates a third representative installation system 800; and
FIG. 9 illustrates
a disassembly view of third representative installation system 800.
[0114i The embodiments of FIG. 4¨FIG. 8 have demonstrated insertion of a
prosthetic cup
into a bone substitute substrate with ease and a greatly reduced force as
compared to use of a mallet
and tamp, especially as no impaction was required. While the insertion was
taking place and
vibrational motion was present at the prosthesis, the prosthesis could be
positioned with relative ease
by torqueing on a handle/outer housing to an exact desired alignment/position.
The insertion force is
variable and ranges between 20 to 800 pounds of force. Importantly the
potential for use of
significantly smaller forces in application of the prosthesis (in this case
the acetabular prosthesis) in
bone substrate with the present invention is demonstrated to be achievable.
[0115] Similarly to installation system 100 and installation system 400,
installation system
800 is used to control precisely one or both of (i) installation and (ii)
abduction and anteversion
angles of a prosthetic component. Installation system 800 preferably allows
both installation of an
acetabular cup into an acetabulum at a desired depth and orientation of the
cup for both abduction
and anteversion to desired values. The following reference numbers in Table II
refer to elements
identified in FIG. 8¨FIG. 9:
[0116] TABLE II: Device 800 Elements
802 Air Inlet
804 Trigger
806 Needle Valve
808 Valve Body
810 Throttle Cap
812 Piston
814 Cylinder
816 Driver
818 Needle Block
820 Needles
822 Suspension Springs
824 Anvil
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826 Nozzle
828 Connector Rod
830 Prosthesis (e.g., acetabular cup)
[0117] Installation system 800 includes a controller with a handle supporting
an elongate rod
that terminates in a connector system that engages prosthesis 830. Operation
of trigger 804 initiates a
motion of the elongate rod. This motion is referred to herein as an
installation force and/or
installation motion that is much less than the impact force used in a
conventional replacement
process. An exterior housing allows the operator to hold and position
prosthesis 830 while the
elongate rod moves within. Some embodiments may include a handle or other grip
in addition to or
in lieu of the housing that allows the surgeon operator to hold and operate
installation system 800
without interfering with the mechanism that provides a direct transfer of
installation motion. The
illustrated embodiment includes prosthesis 830 held securely allowing a
tilting and/or rotation of
installation system about any axis to be reflected in the position/orientation
of the secured prosthesis.
[0118j The actuator is pneumatically operated oscillation device that provides
the impact and
vibration action this device uses to set the socket (it being understand that
alternative motive systems
may be used in addition to, or alternatively to, a pneumatic system).
Alternatives including
mechanical and/or electromechanical systems, motors, and/or engines. The
actuator includes air inlet
port 802, trigger 804, needle valve 806, cylinder 814, and piston 812.
[0119j Air is introduced through inlet port 802 and as trigger 804 is squeezed
needle valve
806 admits air into the cylinder 814 pushing piston 812 to an opposing end of
cylinder 814. At the
opposite end piston 812 opens a port allowing the air to be admitted and
pushing the piston 812 back
to the original position.
[0120j This action provides the motive power for operation of the device and
functions in
this embodiment at up to 70 Hz. The frequency can be adjusted by trigger 804
and an available air
pressure at air inlet port 802.
[0121] As piston 812 impacts driver 816, driver 816 impacts needles 820 of
needle block
818. Needles 820 strike anvil 824 which is directly connected to prosthesis
830 via connecting rod
828.
[0122j Suspension springs 822 provide a flexibility to apply more or less
total force. This
flexibility allows force to be applied equally around prosthesis 830 or more
force to one side of
prosthesis 830 in order to locate prosthesis 830 at an optimum/desired
orientation. Installation
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system 800 illustrates a BMD having a more strongly coupled pulse transfer
system between an
oscillation engine and prosthesis 830.
[0123] The nature and type of coupling of pulse communications between the
oscillation
engine and the prosthesis may be varied in several different ways. For
example, in some
implementations, needles 820 of needle block 818 are independently moveable
and respond
differently to piston 812 motion. In other implementations, the needles may be
fused together or
otherwise integrated together, while in other implementations needles 820 and
needle block 818 may
be replaced by an alternative cylinder structure.
[0124] As illustrated, while both embodiments provide for a primarily
longitudinal
implementation, installation system 800 includes a design feature intended to
allow the
inserting/vibratory force to be "steered" by applying forces to be
concentrated on one side or another
of the prosthesis. Implementations that produce a randomized vibrational
motion, including "lateral"
motion components in addition to, or in lieu of, the primarily longitudinal
vibrational motion of the
disclosed embodiments may be helpful for installation of prosthesis in a wide
range of applications
including THR surgery.
[0125] Installation system 400 and installation system 800 included an
oscillation engine
producing pulses at approximately 60 Hz. System 400 operated at 60 Hz while
system 800 was
capable of operating at 48 to 68 Hz. In testing, approximately 4 seconds of
operation resulted in a
desired insertion and alignment of the prosthesis (meaning about 240 cycles of
the oscillation
engine). Conventional surgery using a mallet striking a tamp to impact the cup
into place is generally
complete after 10 blows of the mallet/hammer.
[0126] Experimental
[0127] Both system 400 and system 800 were tested in a bone substitute
substrate with a
standard Zimmer acetabular cup using standard technique of under reaming a
prepared surface by 1
mm and inserting a cup that was one millimeter larger. The substrate was
chosen as the best option
available to us to study this concept, namely a dense foam material. It was
recognized that certain
properties of bone would not be represented here (e.g. an ability of the
substrate to stretch before
failure).
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[0128] Both versions demonstrated easy insertion and positioning of the
prosthetic cup
within the chosen substrate. We were able to move the cup in the substrate
with relative ease. There
was no requirement for a mallet or hammer for application of a large impact.
These experiments
demonstrated that the prosthetic cups could be inserted in bone substitute
substrates with
significantly less force and more control than what could be done with blows
of a hammer or mallet.
We surmise that the same phenomena can be reproduced in human bone. We
envision the prosthetic
cup being inserted with ease with very little force.
[0129] Additionally we believe that simultaneously, while the cup is being
inserted, the
position of the cup can be adjusted under direct visualization with any intra-
operative measurement
system (navigation, fluoroscopy, etc.). This invention provides a system that
allows insertion of a
prosthetic component with NON-traumatic force (insertion) as opposed to
traumatic force
(impaction).
[0130] Experimental configuration ¨ System 400
[0131] Oscillation engine 410 included a Craftsman G2 Hammerhead nailer used
to drive
fairly large framing nails into wood in confined spaces by applying a series
of small impacts very
rapidly in contrast to application of few large impacts.
[0132] The bone substitute was 15 pound density urethane foam to represent the
pelvic
acetabulum. It was shaped with a standard cutting tool commonly used to clean
up a patient's
damaged acetabulum. A 54 mm cup and a 53 mm cutter were used in testing.
[0133] In one test, the cup was inserted using a mallet and tamp, with
impaction complete
after 7 strikes. Re-orientation of the cup was required by further strikes on
an periphery of the cup
after impaction to achieve a desired orientation. It was qualitatively
determined that the feel and
insertion were consistent with impaction into bone.
[0134] An embodiment of system 400 was used in lieu of the mallet and tamp
method.
Several insertions were performed, with the insertions found to be much more
gradual; allowing the
cup to be guided into position (depth and orientation during insertion). Final
corrective positioning is
easily achievable using lateral hand pressure to rotate the cup within the
substrate while power was
applied to the oscillation engine.
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[0135] Further testing using the sensor included general static load detection
done to
determine the static (non-impact) load to push the cup into the prepared
socket model. This provided
a baseline for comparison to the impact load testing. The prosthesis was
provided above a prepared
socket with a screw mounted to the cup to transmit a force applied from a
bench vise. The handle of
the vice was turned to apply an even force to compress the cup into the socket
until the cup was fully
seated. The cup began to move into the socket at about an insertion force of
¨200 pounds and
gradually increased as diameter of cup inserted into socket increased to a
maximum of 375 pounds
which remained constant until the cup was fully seated.
[0136i Installation system 400 was next used to install the cup into a
similarly prepared
socket. Five tests were done, using different frame rates and setup
procedures, to determine how to
get the most meaningful results. All tests used a 54 mm acetabular Cup. The
oscillation engine ran at
an indicated 60 impacts/second. The first two tests were done at 2,000
frames/second, which wasn't
fast enough to capture all the impact events, but helped with designing the
proper setup. Test 3 used
the oscillation engine in an already used socket, 4,000 frames per second.
Test 4 used the oscillation
engine in an unused foam socket at 53 mm, 4,000 frames per second.
[0137] Test 3: In already compacted socket, the cup was pulsed using the
oscillation engine
and the pulse transfer assembly. Recorded strikes between 500 and 800 lbs,
with an average
recorded pulse duration .8 ms.
[0138] Test 4: Into an unused 53 mm socket, the cup was pulsed using the
oscillation engine
and the pulse transfer assembly. Recorded impacts between 250 and 800 lbs, and
an average
recorded pulse duration .8 ms. Insertion completed in 3.37 seconds, 202 impact
hits.
[0139] Test 5: Into an unused 53 mm socket, the cup was inserted with standard
hammer (for
reference). Recorded impacts between 500 and 800 lbs, and an average recorded
pulse duration 22.0
ms. Insertion completed in 4 seconds using 10 impact hits for a total pressure
time of 220 ms. This
test was performed rapidly to complete it in 5 seconds for good comparability
with tests 3 and 4 used
240 hits in 4 seconds, with a single hit duration of 0.8 ms, for a total
pressure time of 192 ms.
[0140i In non-rigorous comparison testing without a direct comparison between
system 400
and system 800, generally it appears that the forces used for installation
using system 800 were
lower than system 400 by a factor of 10. This suggests that there are certain
optimizing
characteristics for operation of an installation system. There are questions
such as to how low these
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forces can be modulated and still allow easy insertion of the prosthetic cup
in this model and in
bone. What is the lowest force required for insertion of a prosthetic cup in
to this substrate using the
disclosed concepts? What is the lowest force required for insertion of a
prosthetic cup into hard bone
using the these concepts? And what is the lowest force required for insertion
of a prosthetic cup into
soft and osteoporotic bone using these concepts? These are the questions that
can be addressed in
future phase of implementations of the present invention.
[0141] Additionally, basic studies can further be conducted to correlate a
density and a
porosity of bone at various ages (e.g., through a cadaver study) with an
appropriate force range and
vibratory motion pattern required to insert a cup using the present invention.
For example a surgeon
will be able to insert sensing equipment in patient bone, or use other
evaluative procedures,
(preoperative planning or while performing the procedure for example) to asses
porosity and density
of bone. Once known, the density or other bone characteristic is used to set
an appropriate vibratory
pattern including a force range on an installation system, and thus use a
minimal required force to
insert and/or position the prosthesis.
[0142] BMD is a "must have" device for all medical device companies and
surgeons.
Without BMD the Implantation problem is not addressed, regardless of the
recent advances in
technologies in hip replacement surgery (i.e.; Navigation, Fluoroscopy,
MAKO/robotics,
accelerometers/gyro meters, etc.). Acetabular component (cup) positioning
remains the biggest
problem in hip replacement surgery. Implantation is the final step where error
is introduced into the
system and heretofore no attention has been brought to this problem. Current
technologies have
brought significant awareness to the position of the implants within the
pelvis during surgery, prior
to impaction. However, these techniques do not assist in the final step of
implantation.
[0143] In FIG. 1¨FIG. 9, and the discussion above, BMD embodiments addressing
various
installation implementations (including installation and positioning) have
been illustrated and
described. In many of the disclosed embodiments, there is no requirement for
post-installation
positioning of the prosthesis as the prosthesis is precisely inserted and
aligned as desired. In FIG.
10¨FIG. 34 there are illustrated a set of systems and methods to address
prosthesis mal-alignment
AFTER the prosthesis has been implanted without attendant correct alignment
irrespective of the
system or method that has implanted the prosthesis. As noted herein, some
implementations of the
systems and methods disclosed with respect to FIG. 1¨FIG. 9 may also be used
to "float" a
previously installed prosthesis to allow correct positioning, such as may be
the case where a decision
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is made to change a desired alignment for the installed prosthesis. Float, in
this context for the
purposes of this invention refers to removal and/or reduction of forces
inhibiting a re-orienting of an
inserted and mispositioned prosthesis (e.g., static frictional forces) to
allow the surgeon to properly
orient the prosthesis.
[0144] The systems of methods of FIG. 12¨FIG 34 when realized as a positioning
BMD
were conceptualized and intended to be used with the navigational systems that
provide real time
information during the surgical procedure such as those now available; as well
as other variety of
real-time monitoring systems such as (fluoroscopy and
accelerometers/gyrometers).
[0145] FIG. 10 illustrates a schematic side section representation of an
acetabular cup C
mispositioned into a portion of a pelvis P. Misposition, in this context,
refers to an inserted
prosthesis that has a preferred orientation before attaining that preferred
orientation. FIG. 11
illustrates a conventional use of a mallet M and tamp T to apply an
orientation-altering force to an
unencoded and mispositioned acetabular cup C, such as that illustrated in FIG.
10. Typically, no
matter how well the position of the patient's pelvis, the operating room
table, and the prosthetic
components are monitored in surgery (navigation), during the implantation
process, cup C ends up in
a less than desired position (i.e., mispositioned). This condition often
occurs due to a lack of control
of the forces created by the uneven blows of mallet M on impacting tamp T.
Currently, when a
surgeon desires to change the alignment of an already impacted cup C, various
locations on an edge
of cup C are struck using tamp T and mallet M.
[0146i A problem with this solution is that the surgeon has no a priori idea
how any
particular impact on the cup will change the specific alignment of cup C. For
example, while the
surgeon knows that when a general part of cup C is tamped (e.g., a "front")
this will change varying
degrees of anteversion, this action will also inadvertently produce some
unwanted change amount of
abduction or adduction depending on where this impact was made (above or below
the equator). It
is quite accurate to state that when the surgeon uses tamp T and mallet M to
correct the position of
an already implanted cup C, that the surgeon does not know precisely the
location and direction to
achieve the desired orientation with complete precision.
[0147] Positioning BMDs are a result of an insight/invention devised to
provide a solution to
this particular problem: How the surgeon correct the misposition of an already
implanted cup C with
some measure of accuracy? The goals here were to (1) provide a map or a way to
use current
technology to define, quantify, digitize, and encode an already implanted
prosthetic cup C; and (2) to
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provide a tool that could produce measurable, reliable, and predictable
changes to the position of cup
C.
[0148] FIG. 12¨FIG 14 illustrate a reference frame used in THR surgery
including an
acetabular prosthesis (e.g., cup C) installed into a pelvis P including
identified X-Y-Z orthogonal
axes. FIG. 12 illustrates the reference frame and the orthogonal axes; FIG. 13
illustrates the
orthogonal axes with an associated frontal plane F and a transverse plane T;
and FIG. 14 illustrates a
different perspective view of the orthogonal axes with the associated frontal
plane F and transverse
plane T.
[0149] In an operating room employing a navigation system, the reference frame
is
established in which the location of the patient on the operating room table
is mapped. Frontal plane
F and transverse plane T are set to pass through the acetabulum and,
consequently, the inserted cup
C. It is with respect to this reference frame that any particular desired
orientation (e.g., a particular
amount or range of abduction and anteversion). In conventional procedures, a
range is typically
specified because of challenges in achieving a particular amount. In some
implementations, a
different reference frame may be used, however there will typically be a way
to remap such a
different reference frame to the reference frame described herein.
[0150i Pure Points:
[0151] Pure Points on the implanted cup are determined using mathematical
calculations
within the reference frame as defined below. Given facts: Frontal plane F is
constructed by the X and
Z axis and transverse plane T is constructed by the X and Y axis.
[0152] A pure abduction point on an edge of an inserted acetabular cup is a
spot defined by a
highest point on frontal plane F on the positive side of the Z-axis when the
cup is transposed on
frontal plane F.
[0153] A pure adduction point on the edge of the cup is a spot defined by the
lowest point on
frontal plane F on the negative side of the Z-axis, when the cup is transposed
on frontal plane F.
[0154] A pure anteversion point on the edge of the cup is a spot defined by
the highest point
on the Y-axis of transverse plane T in the positive direction.
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[0155] A pure retroversion point on the edge of the cup is a spot defined by
the lowest point
on the Y-axis of transverse plane T in the negative direction.
[0156j These pure points were conceived to create a map of the edge of an
installed cup for
use with a positioning BMD system or tool. Once these four essential points
are defined and encoded
(actual and/or virtual encoding) on the edge of the cup with navigation
software, the additional
points in between can be quantified with trigonometric calculations. Virtual
encoding in this context
refers to determination and mapping of the pure points in the reference frame
for an installed cup
and does not require any tangible indicia to be applied. In some
implementations of the present
invention, there may be ways to directly communicate these pure points to the
surgeon in real-time
such as by various visual cues. Other implementations may provide indirect
communication of the
pure points during use and operation of the systems and methods.
[0157j FIG. 15 illustrates an encoded prosthesis 1500 including a set of pure
points. This set
includes: a pure adduction point 1505, a pure abduction point 1510, a pure
anteversion point 1515,
and a pure retroversion point 1520. Intermediate points between adjacent pure
points produce some
amount of both associated points, as may be determined from trigonometric
calculations.
[0158] FIG. 16 illustrates a manual positioning system 1600 for encoded
prosthesis 1500
using mallet M and tamp T. The edge of cup 1500 is now encoded with
information (i.e., it is
digitized and quantified in the reference frame). The surgeon now has a type
of map and sense of
how to manipulate an inserted and mispositioned encoded cup 1500 to produce
the desired
orientation. The surgeon knows the pure points and understands that any impact
on an edge of cup
1500 between pure abduction and pure anteversion (e.g., 30 degrees in front of
pure abduction 1605)
will produce both abduction and anteversion motion. Based on trigonometric
calculations , the
surgeon now anticipates a higher increase in abduction than anteversion. The
contribution of
impacted force towards each of these planes can now be quantified allowing the
surgeon to
accurately, precisely, efficiently, and predictably achieve a specific desired
orientation.
[0159j FIG. 17 illustrates a positioning system 1700 having a positioning BMD
1705 orient
an inserted and mispositioned encoded prosthesis 1500. Positioning BMD 1705
was conceived as a
tool that a surgeon S would apply it to an already implanted cup, and simply
"dial in" a desired
alignment 1710. A purely automated positioning BMD incorporated into a
computer navigation
system 1715 would do the rest, correcting a position of an inserted and
mispositioned cup to the
desired alignment, (essentially completely automating this corrective process,
eliminating surgeon
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error and unpredictability). An early positioning BMD, represented by
positioning BMD 1705
includes twelve actuators evenly distributed around a 360 degree cup periphery
(each actuator thus
separated by 30 degrees around the edge of the cup).
[0160i BMD 1705, in cooperation with encoded cup 1500 and the above described
additions
to the navigation software, surgeon S now proceeds with a digitized and
"encoded" cup (pure points
on the cup's edge are defined in by the reference frame in the operating room
space). Surgeon S
proximates (i.e., attaches, contacts, or otherwise uses BMD 1705 to control an
orientation of cup
1500) positioning BMD 1705 to inserted cup 1500, such as with an adaptor
specific to this prosthesis
as BMD 1705 may be used in some cases for other prostheses), and dials in the
desired alignment
1710 for cup 1500 (for this example, 40 degrees abduction and 20 degrees
anteversion is desired
with the inserted and malpositioned cup initially at 50 degrees abduction and
30 degrees
anteversion). Computer navigation system 1715 then calculates the point on the
cup that is most
likely to produce the desired change as any force impacted on the cup now
produces a predictable
increase/decrease in abduction/anteversion which is now quantified by
navigation system 1715.
Navigation system 1715 then chooses an actuator of BMD 1705 that corresponds
to that point on the
cup, impacting on that calculated point. After the corrective impact, a re-
measurement of the cup's
position would have to be done and made available to navigation system 1715 so
that the new
position is known. The cup has now a new alignment. This process is repeated
until the desired
alignment of the implanted cup is achieved. Computer navigation system 1715
continues this process
through a feedback loop mechanism until the position of the cup is exactly the
same as that which
was dialed in by surgeon S.
[Mu FIG. 18 illustrates a schematic representation of an embodiment of
positioning system
1800 using a positioning BMD 1805 configured for correcting inserted and
malpositioned
prostheses. While system 1700 was conceived as a purely automated optimal
solution, other systems
may also be implemented that include some manual and/or semi-automated steps.
System 1700 was
created to eliminate surgeon error, automate the process of cup implantation,
relieve surgeon anxiety
and reassure patients that a better and more comprehensive system is available
for the procedure of
total hip replacement surgery. With system 1700, regardless of surgeon
experience a "perfect cup
placement" could be achieved. Regardless of which hospital a patient elected
for the THR
procedures, the patient would leave having "a perfect cup" result. This idea
was developed to
eliminate the problem of hip dislocations, wear, impingement, readmissions and
reoperations and
waste.
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[0162] System 1800 is a simpler implementation using a different embodiment
for
positioning BMD 1805 that includes four orthogonal actuators that surgeon S
may align with the
pure points. Surgeon S could then manually direct and individually fire the
actuators to change the
cup alignment to achieve the desired result with computer navigation system
1715 providing results
of each intermediate operation.
[01631 FIG. 19¨FIG. 21 illustrate a detailed schematic of an embodiment of a
positioning
gun 1900 configured for prosthesis adjustment which is an implementation of
BMD 1805. FIG. 19
illustrates a representative positioning gun 1900; FIG. 20 illustrates a left-
hand detail of positioning
gun 1900; and FIG. 21 illustrates a right-hand detail of positioning gun 1900
and generally when
combined with FIG. 20 produces the illustration of FIG. 19.
[0164j Positioning gun 1900 is used to control precisely abduction and
anteversion angles of
a prosthetic component, in this case, an acetabular cup installed into an
acetabulum. The following
reference numbers in Table III refers to elements identified in FIG. 19¨FIG.
21:
[0165] TABLE III: Device 1900 Elements
1902 Acetabular cup (not shown)
1904 Hand grip
1906 Body
1908 Valve
1910 Bottom Cap
1912 Handle Cam
1914 DIN 3771 6 x 1,8 - N -NBR 70 (0-ring)
1916 Input Tube
1918 Trigger
1920 9657K312
1922 Grip guide housing
1924 MirrorAR15 ¨ Hand Grip 1
1926 Dial Valve Body
1928 Dial Valve cap
1930 Dial Valve guide
1932 Knob
1934 Middle Guide housing
1936 Lower Guide housing
1938 Primary adapter right side
1940 Airtube
1942 Lower Guide end point
1944 Primary adapter left side
1946 1561T480
1948 Cup clamp
1950 Cup piston lock
1952 FINDEVA FAL 18 pneumatic knocker
1954 FINDEVA FAL 18 pneumatic knocker ram
1956 Spring cap
1958 9657K265
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[0166] Positioning gun 1900 essentially includes a handle/grip control for a
set of elongate
longitudinal actuators arranged around a central support. An adapter attached
to the central support
mounts to and releasably engages the prosthetic to be adjusted. This adapter
allows relative motion
between the central support and the cup and provides as many degrees of
freedom as necessary or
desirable to enable the features implemented by the device (not all
implementations will include all
features). This embodiment includes two degrees of freedom for rotation about
each of two
perpendicular axes.
[0167] In one implementation, the adapter allows appropriate freedom of motion
permitting
the cup to move in positive and negative anteversion and abduction angles. The
set of elongate
longitudinal actuators include four actuators that are equally distributed
around the central support at
ninety degree angles relative to each adjacent actuator. These actuators
include an actuator head that
strikes a portion of rim periphery of the acetabular shell to impart a
controllable and variable
longitudinal impact at a precise location on the edge. Preferably the four
actuators are each aligned
with one of the four pure anteversion and abduction points (i.e., locations
where application of the
longitudinal impact alters only one of anteversion or abduction).
[0168] To simplify the discussion, the controller is pneumatically or
electronically powered
and provides an ability to control a magnitude and/or frequency of the
longitudinal actuators
independent from each other. A dial on at the end of the controller may select
a particular one
actuator for operation in response to actuation of the trigger. The trigger
results in application of the
longitudinal impact at the desired point on the edge of the cup, and when
implemented as described,
each actuator will control only one of the four pure points so the acetabular
cup will move either
positive anteversion, negative anteversion, positive abduction, or negative
abduction with any single
actuator.
[0169] The control may be manual which includes the operator selecting a
particular set of
one or more actuators and triggers them for operation. The triggering causes
one or more of a series
of impacts to strike specific locations along the rim to adjust the angle to a
desired value. The one or
more impacts may have a constant or variable magnitude. Such as each trigger
operation causes the
set of actuators to strike the rim at the selected location(s) with a desired
magnitude (that may be
predetermined or adjusted by the operator). Or each trigger operation may
cause a series of strikes,
each with the same or different (e.g., increasing magnitude ranging between
preset limits of a low
value to a high value). The number of strikes may be preset or continue as
long as the operator
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maintains the trigger operation. For example, the operator may engage the
trigger and the actuator(s)
continue until the trigger is released. Some implementations may include a
trigger that allows the
operator to control the magnitude of the impacts from the set of actuators,
such as a light pull
causing strikes of a certain force and a greater pull on the trigger resulting
in strikes of a greater
magnitude.
[WO] In some implementations, the controller includes a stored program
processing system
that includes a processing unit that executes instructions retrieved from
memory. Those instructions
could control the selection of the set of actuators and/or triggering
autonomously to achieve values
for abduction and anteversion entered into by the surgeon or by a computer
aided medicine
computing system such as the computer navigation system. Alternatively those
instructions could be
used to supplement manual operation to aid or suggest selection of the
actuator set and/or triggering
force(s) (not all actuators of a set require that they strike the rim with the
same magnitude).
[Wm Thus the resulting impact(s) from operation of any single actuator of the
set of
selected actuators may be one or more equal strength impacts, a set of
periodic impacts that continue
until the trigger is released, or any other combination of constant or
variable amplitude and/or
frequency impacts.
[0172] As described, the four pure adjustment points are mapped out and
identified in
advance so that the operator may align the actuators appropriately during
preparation. In some
systems, it may be the case that the four points have NOT been mapped out in
advance. In such
circumstance, the computer navigation system may respond to a first
longitudinal impact to map out
the four points. After mapping, the actuators may be appropriately
repositioned. In some
implementations, the adapter may provide a rotational freedom of motion to
allow the actuators to be
rotated about a longitudinal axis of the central support so that the actuators
are all appropriately
aligned with the pure locations. After that, the operator may manually select
a particular actuator for
operation to adjust anteversion and abduction appropriately and independently.
[0173] In some implementations, it may be desirable to use feedback from the
navigation
system to determine how multiple simultaneous actuators all operating
simultaneously on the cup
can adjust the orientation to the desired anteversion and abduction. For
example, when one actuator
may move anteversion 2 units in the appropriate direction while also adding
one undesired unit of
abduction, the computer navigation system may use multiple actuators at the
same time to apply the
appropriate adjustment while cancelling out the undesired adjustment.
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[0174] While a system employing four actuators is described above, other
embodiments may
include other numbers of longitudinal actuators, such as N number of
actuators, N = 1 to 24
actuators, most preferably evenly distributed around a periphery of the edge
of acetabular cup (e.g.,
for 24 cups, each actuator would be 15 degrees separated from an adjacent
actuator).
[0175] For more automated systems, even distribution of the actuators about
the central
support are not required and it may be that asymmetric arrangements better
conform to an
adjustment profile of the cup installed into the acetabulum. An adjustment
profile is a
characterization of the relative ease by which abduction and anteversion
angles may be adjusted in
positive and negative directions. In some situations these values may not be
the same and the
positioning gun could be enhanced to adjust for these differences. For
example, a unit of force
applied to pure positive anteversion may adjust anteversion in the positive
direction by a first unit of
distance while under the same conditions that unit of force applied to pure
negative anteversion may
adjust anteversion in the negative direction by a second unit of distance
different from the first unit.
And these differences may vary as a function of the magnitude of the actual
angle(s). For example,
as the anteversion increases it may be that the same unit of force results in
a different responsive
change in the actual distance adjusted. The adjustment profile when used helps
the operator when
selecting the actuators and the impact force(s) to be applied.
[0176] In some implementations, a constraint of system 1800 is that surgeon S
wait for
current orientation information of cup 1500 in between actuations of
positioning BMD 1805 may
discourage some surgeons from considering its use despite the many benefits
for the patient,
surgeon, and facility. A solution to a problem of requiring remeasurement in-
between actuations
could further promote adoption of embodiments of a positioning BMD. One such
solution includes
transferring the encoding information from the prosthesis to the positioning
BMD. This paradigm
allows the information, regarding the desired position of the cup, to be held
and maintained on the
gun, at all times, eliminating any need to re-measure the position of the cup
after every corrective
impact. This includes additionally mapping the encoded information of the
positioning BMD into the
reference frame that includes the operating room and the prosthesis.
[0177] FIG. 22¨FIG. 24 illustrate use of an impact ring 2200 for positioning
an installed
prosthesis (e.g., an acetabular cup C); FIG. 22 illustrates an initial
condition of the pre-positioned
installed prosthesis C with respect to impact ring 2200 installed on a
positioning system; FIG. 23
illustrates an intermediate condition of the pre-positioned installed
prosthesis C with respect to
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impact ring 2200 installed on a positioning system; and FIG. 24 illustrates a
final condition having a
positioned installed prosthesis C with respect to impact ring 2200 installed
on a positioning system.
Impact ring 2200 holds the desired orientation in the reference frame and by
using a positioning
BMD associated with impact ring 2200 operating on prosthesis C, the
positioning BMD achieves the
desired orientation when cup C conforms to the desired orientation established
by impact ring 2200
as illustrated in FIG. 24.
[0178] FIG. 25 illustrates an embodiment of a positioning system 2500
employing a
positioning BMD 2505 including an impact ring 2510. System 2500 employs
computer navigation
system 1715 in this case to provide information to BMD 2500 for setting impact
ring 2510 to
properly orient cup C in pelvis P. BMD 2505 basically transfers positional
information previously
encoded on the edge of the cup C using navigation system 1715 to impact ring
2510. Impact ring
2510 has an orientation relative to handle 2515 that may be adjusted (e.g., by
servo motors or the
like) to set a desired orientation within the reference frame of the operating
room by use of
navigation system 1715.
[0179] A position/plane of impact ring 2510 is measured and calibrated in the
reference
frame (similarly to how the plane of the implanted cup and the pelvic bone is
calibrated and known
in the reference frame for the non-impact ring versions of a positioning BMD).
A position of the
BMD 2505 axes in this reference frame is also calibrated and known. BMD 2505
is proximated to
the already implanted and malpositioned cup within the acetabulum, such as an
attachment using an
adaptor. The desired plane for impact ring 2510 is chosen and provided to
navigation system 1715
and corresponds to the ultimate angle of abduction and anteversion that the
surgeon desires for the
implanted cup after the procedure. The following method for "dialing in" the
desired plane is
suggested. (Axes of BMD 2505 and impact ring 2510 are maintained in a neutral
position (referred
to herein as a double orthogonal position). For comfort of the surgeon, BMD
2505 is allowed to
swivel within a specified cone (e.g., a thirty degree cone ¨ other cone sizes
are possible) while
impact ring 2510 maintains the desired orientation as the angle between handle
2515 and impact ring
2510 changes to reflect the swiveling. BMD 2505 is swiveled around until the
desired plane for
impact ring 2510 in the reference frame of the operating room is established
by navigation system
1715. This plane in the reference space is then registered by navigation
system 1715, and will be set
in the navigation system as the desired angle of abduction and anteversion for
cup C. At that point
the surgeon can move and swivel the gun in whatever position is comfortable
for him/her during the
procedure. BMD 2505 will then continuously make adjustments to maintain impact
ring 2510
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coplanar with the "desired plane". At this point no matter how the surgeon
moves BMD 2505 in this
30 degree cone in space the mechanisms on BMD 2505 will make the automatic
necessary
adjustments to keep impact ring 2510 coplanar with the "desired plane" (e.g.,
40 degrees abduction
and 20 degrees anteversion). Once impact ring 2510 has been set to the desired
plane, a tilt of handle
2515 by 5 degrees in one direction is countered by a corresponding five degree
tilt of impact ring
2510 in an opposing direction to maintain impact ring 2510 at the desired
plane.
[0180i The feedback loop system works in the following manner. Navigation
system 1715
continuously and in real time measures the position and orientation of BMD
2505. Any positional
change an axis of BMD 2505 (for example within this 30 degree cone) is
measured by computer
navigation system 1715 and relayed to microprocessor included with BMD 2505 as
part of a stored
program computing system implemented by BMD 2505 when using a control
mechanism (e.g.,
servo motors coupled to impact ring 2510) to maintain impact ring 2510 in the
desired plane using
information from navigation system 1715. The microprocessor uses this
information to compute an
error between the "actual position" of BMD 2505 and the "desired position" of
BMD 2505. The
microprocessor converts this two dimensional special error into two one
dimensional angular
corrections and sends new commands to the control mechanism which will then
make corrections to
the position of impact ring 2510, moving it to the desired plane. The control
mechanism, in
addition, has an internal circuitry that is capable of maintaining a feedback
loop mechanism, which
functions to maintain the desired plane during swivels or other motions of BMD
2505 during
operation. In this fashion, the BMD 2505 maintains impact ring 2510 position
so that it is coplanar
with the desired plane within the reference frame. BMD 2505 then strikes cup C
with impact ring
2510 repeatedly until the mal-aligned cup is corrected to the desired position
(i.e. 40 abduction and
20 anteversion in this example) at which point impact ring 2510 and the
implanted cup become co-
planer as illustrated in FIG. 24.
[Mu In other words, BMD 2505 functions as follows: BMD 2505 includes a
microprocessor (circuit board) and one or more servos on board. These servos
control the position
of impact ring 2510 in the reference frame at all times. The BMD 2505 is
attached to implanted cup
C via an adaptor. BMD 2505 can swivel around a cone of 30 degrees while
maintaining impact ring
2510 in the desired orientation as the servos compensate and adjust an
orientation of impact ring
2510 to counter this swiveling motion. The surgeon moves BMD 2505 until the
positioning is
comfortable as the surgeon is going to use the device to impact the ring to re-
orient cup C. BMD
2505 is moved around until the "desired plane" for the impact ring is found
and registered in the
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reference frame (i.e. 40 abduction and 20 anteversion for this example) by
navigation system 1715.
The surgeon then moves BMD 2505 however desired and impact ring 2510 is
automatically
corrected to be the same as the "desired plane" at all times, regardless of
how BMD 2505 is swiveled
around. The surgeon then fires rapidly a repeating mechanical hammer that is
coupled to impact
ring 2510 rapidly causing the impact ring to hit on mal-aligned cup C until
cup C and impact ring
2510 become coplanar, at which time the implanted cup's alignment has been
corrected to the
desired plane/alignment.
[01821 Some implementations with proper reconfiguring of current navigation
systems will
allow the desired plane (e.g., 40 degrees abduction and 20 degrees
anteversion) to be calculated in
the operating room reference frame space simply by knowing the plane of the
acetabulum in the
operating room space is (e.g., abduction 50 degrees , anteversion 10 degrees).
Suggested
methodology is through construction of a double orthogonal to the measured
plane of the acetabulum
in the operating room space. A change in the double orthogonal results in a
change in the plane of
the acetabulum. A positioning BMD could then know what this plane is without
having its impact
ring registered and calibrated by the navigation system.
[0183] FIG. 26 illustrates an evolution of one version of a positioning BMD
2505 employing
an impact ring 2510, such as illustrated in FIG. 25, to another version of a
positioning BMD 2605
employing an impact ring 2610. During testing and evaluation of BMD 2505, it
was discovered the
impact ring positioning system (e.g., the servo motors) are required to have
strength and stiffness as
strikes of impact ring 2510 on the inserted cup are transferred to the servos.
BMD 2605 includes a
stiffer impact ring positioning system to allow the same real-time maintenance
of the desired plane
for impact ring 2610 while resisting problems associated with servo control.
For example, worm
gear or other microprocessor-controllable motor solution that provides a
sufficient stiffness to allow
portions of an impact ring to strike the mispositioned cup. The more
misaligned an impact ring and
cup are, the greater the angular differences are between the impact ring and
the cup which can result
in greater torsional/rotation response of the impact ring when striking the
installed cup.
[0184] While BMD 2505 provided excellent information about the desired plane
and was
responsive to swiveling motion during use, it did not have the desired level
of stiffness to hold the
desired plane for the impact ring when striking the cup for repositioning.
This is partially due to the
observation that the impact ring does not provide a clean focus energy
transfer mechanism due to the
misalignment of the desired plane with the mispositioned cup and that the
impact ring may be driven
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at the center while impacts are offset to an edge causing rotational stresses
on the impact ring
positioning system. While alternatives to the servos in BMD 2505, such as the
direct current worm
gear motor of BMD 2605 may improve stiffness, a drawback remains in the
relatively inefficient
energy transfer exists.
[0185] FIG. 27¨FIG. 34 illustrate alternate embodiments for a positioning
systems
employing an impact ring model. FIG. 27¨FIG. 28 illustrate a first alternate
embodiment for a
positioning system 2700; FIG. 27 illustrates a side view of the first
alternate embodiment; and FIG.
28 illustrates a top view of the first alternate embodiment. Positioning
system 2700 includes a
positioning BMD 2705 having N number of actuators 2710 (N being an integer of
3 or more) are
used to define a virtual impact ring using ends of the actuators (ends of
three or more actuators
define the desired plane). A prosthesis C is rotationally coupled to BMD 2705
using a pivot joint
2715. In this way, operation of a trigger 2720 causes all the actuators to
strike prosthesis C
concurrently at a peripheral edge. The actuators strike prosthesis C in the
desired plane and more
efficiently transfer repositioning energy to the edges of the cup. A computer
navigation system is
used to set the virtual impact ring.
[01861 FIG. 29¨FIG. 30 illustrate a second alternate embodiment for a
positioning system
2900; FIG. 29 illustrates a side view of the second alternate embodiment; and
FIG. 30 illustrates a
top view of the second alternate embodiment. Positioning system 2900 includes
a positioning BMD
2905 having a single repositionable actuator 2910 used to define a virtual
impact ring using an end
of the actuator. A prosthesis C is rotationally coupled to BMD 2905 using a
pivot joint 2915. In this
way, operation of a trigger 2920 rotates actuator 2910 around a central
support 2925 to locate
actuator 2910 at the desired location around the periphery of cup C and then
causes actuator 2910 to
strike prosthesis C at a peripheral edge. Actuator 2910 strikes prosthesis C
at the desired location to
achieve the desired plane and more efficiently transfer repositioning energy
to the edges of the cup.
A computer navigation system is used to set the virtual impact ring. As
actuator 2910 rotates about
support 2925, a longitudinal extent of its end shortens or lengthens such that
the end traces out a
virtual impact ring having the desired plane over the course of an entire
rotation about the support.
[0187] FIG. 31¨FIG. 32 illustrate a third alternate embodiment for a
positioning system
3100. FIG. 31 illustrates a side view of the third alternate embodiment; and
FIG. 32 illustrates a top
view of the third alternate embodiment. System 3100 includes a positioning BMD
3105 that
conceptually combines BMD 1805 with BMD 2605. The actuators of BMD 1805 are
very efficient
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in energy transfer (they transferred energy similar to mallet/tamp with
minimal leakage). This was a
desirable trait selected for this design. The impact ring of BMD 2605 was
attractive in that the ideal
position of the cup in the operating room reference frame space was always
known and maintained
by the positioning BMD.
[0188] With BMD 3105 the desired orientation information is now transferred
back to the
device itself. The position of a virtual impact ring is controlled by a
special virtual impact ring
controller having four (or more, for example 4-24) actuators 3110. The
controlling unit that includes
a microprocessor 3115, a motor driver 3120 with a rotatory encoder, a DC motor
3125, and worm
gear 3130. This controlling unit would then maintain the position of virtual
impact ring at all times
in the operating room reference frame space. The virtual impact ring is
defined by a plane created
by the tips of the actuators (four in BMD 3105).
[0189] The tip of the four actuators are calibrated to allow the computer
navigation system to
know the position of the "virtual impact ring" in the operating room reference
frame space. BMD
3105 is attached to an implanted cup C with an adaptor. The desired alignment
is input by the
surgeon into the computer navigation system. The computer navigation system
provides
information/commands to BMD 3105. The "controlling unit" of BMD 3105 maintains
the position
of the virtual impact ring in the operating room reference frame space, and
then fires the four
actuators 3110 in unison responsive to operation of a trigger 3135 hitting on
a peripheral edge 3140
of the implanted cup C until the virtual impact ring (the tips of four
actuators) and the implanted cup
C are co-planer, achieving the desired correction.
[0190i FIG. 33 illustrates a side view of a fourth alternate embodiment for a
positioning
system 3300 combining aspects of BMD 2505 and BMD 2905. System 3300 includes a
positioning
BMD 3305 that has a single repositionable actuator 3310 that strikes an
mispositioned implanted cup
C at a particular point on the edge to achieve a desired plane. The particular
point is identified by an
impact ring 3315 that is controlled by a servo 3320. In this case, servo 3320
is not part of the
impacting construct as its function in this mode is to hold and define the
desired plane. Impact ring
3315 is a slotted ring that serves to define the desired plane in the
operating room frame of reference
space. Single actuator 3310 rotates to the indicated position (which is the
point of contact of the
slotted ring with the implanted cup C) and impacts repeatedly on the edge of
cup on this point until
the slotted ring and the implanted cup C are co-planer. Servo 3320 and slotted
impact ring 3315
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provide the positional information on BMD 3305 and actuator 3310 provides
focused high efficiency
impacts on the edge of cup C to provide the desired change in cup alignment.
[Mu FIG. 34 illustrates a side view of a fifth alternate embodiment for a
positioning
system 3400 including a positioning BMD similar to BMD 1805 employing 12
actuators 3405 (with
a 30 degree uniformly-spaced arcuate separation around a 360 cup periphery).
The information for
BMD 1805 was preferably encoded on the cup's edge using the computer
navigation system. A
potential drawback of BMD 1805 with some implementations was that there was
not a mechanism to
quickly measure a cup orientation after an impact and provide feedback to the
computer navigation
system. For some users, this measurement and feedback of information to the
computer navigation
system had to occur rapidly to allow the navigation system and the positioning
BMD to perform
multiple and rapid corrective hits on the cup through a feedback loop
mechanism.
[01921 System 3400 reduces this problem by using three (or more) of the
actuators as "plane
calibrators" 3410. These actuators would serve both as impacting actuators and
as plane calibrators.
Much in the same way that the tips of the actuators in some embodiments were
calibrated to define a
'virtual impact ring', the tips of these three special actuators 3410 are
encoded and used to define a
plane. So after each corrective hit is made by system 3400, the three
actuators 3410 descend (slide
down) and touch the edge of the cup at different locations (the position of
which has just been
adjusted). A new plane NP is defined. The position of this plane is conveyed
back to the computer
navigation system. The computer navigation system now calculates the
difference between the new
cup position and the desired cup position, (what has been dialed in by the
surgeon). The computer
then provides a new command based the new positional information it has just
been given. A point
on the cup is calculated to provide the desired change in alignment, the
corresponding actuator 3405
fires to make another incremental change in the cup position. The position of
the cup C is again
measured by the sliding (plane calibrating) actuators 3410. The process is
repeated until the desired
alignment of the cup C is achieved (i.e., NP matches desired plane within the
desired threshold).
Ideally in the future the changes in the position of the cup can be measured
with a light or laser
system, obviating a need for the "sliding plane calibrating actuators" 3410.
This change would allow
more rapid measurement and acquisition of the cup's new position, relaying the
information more
rapidly to the navigation system. This allows system 3400 to make the
necessary corrective hits very
rapidly to obtain the desired cup alignment.
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[0193] When tool such as the positioning BMD is developed, surgeons in general
would be
much more likely to adopt computer navigation for hip replacement surgery. In
the US no more than
10% of surgeons use computer navigation systems for THR surgery. Improvements
to this adoption
is likely to occur for the following two reasons:
[0194] 1. The surgeon is now assured that the extra time spent in the
operating room
will translate into a very meaningful difference: a perfect cup position. All
surgeons will be happy
to add an 1/2 hour to their operation for this simple goal.
[0195] 2. Hip replacement surgery with navigation usually moves at a slower
pace due
to the fact that the surgeon continues to check the position of the
instruments in relation to the pelvis.
The surgeon will now be free to move more rapidly during the operation when it
is known that at the
end of the operation a reliable and effective tool is available to modify and
correct the final position
of the acetabular implant, in an automated and accurate fashion.
[0196j BMD allows all real time information technologies to utilize (a tool)
to precisely and
accurately implant the acetabular component (cup) within the pelvic
acetabulum. BMD device
coupled with use of navigation technology and fluoroscopy and (other novel
measuring devices) is
the only device that will allow surgeons from all walks of life, (low
volume/high volume) to perform
a perfect hip replacement with respect to acetabular component (cup)
placement. With the use of
BMD, surgeons can feel confident that they are doing a good job with
acetabular component
positioning, achieving the "perfect cup" every time. Hence the BMD concept
eliminates the most
common cause of complications in hip replacement surgery which has forever
plagued the surgeon,
the patients and the society in general.
[0197j It is known to use ultrasound devices in connection with some aspects
of THR,
primarily for implant removal (as some components may be installed using a
cement that may be
softened using ultrasound energy). There may be some suggestion that some
ultrasonic devices that
employ "ultrasound" energy could be used to insert a prosthesis for final fit,
but it is in the context of
a femoral component and it is believed that these devices are not presently
actually used in the
process). Some embodiments of BMD, in contrast, can simply be a vibratory
device (non ultrasonic),
most likely it will not be ultrasonic, and is more profound than simply an
implantation device as it is
most preferably a positioning device for the acetabular component in THR.
Further, there is a
discussion that ultrasound devices may be used to prepare bones for implanting
a prosthesis. BMD
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does not address preparation of the bone as this is not a primary thrust of
this aspect of the present
invention. Some implementations of BMD may include a similar or related
feature.
[0198j Some embodiments BMD include devices that concern themselves with
proper
installation and positioning of the prosthesis (e.g., an acetabular component)
at the time of
implanting of the prosthesis. Very specifically, it uses some form of
vibratory energy coupled with a
variety of "real time measurement systems" to POSITION the cup in a perfect
alignment with
minimal use of force. A prosthesis, such as for example, an acetabular cup,
resists insertion. Once
inserted, the cup resists changes to the inserted orientation. The BMDs of the
present invention
produce an insertion vibratory motion of a secured prosthesis that reduces the
forces resisting
insertion. In some implementations, the BMD may produce a positioning
vibratory motion that
reduces the forces resisting changes to the orientation. There are some
implementations that produce
both types of motion, either as a single vibratory profile or alternative
profiles. In the present context
for purposes of the present invention, the vibratory motion is characterized
as "floating" the
prosthesis as the prosthesis can become much simpler to insert and/or re-
orient while the desired
vibratory motion is available to the prosthesis. Some embodiments are
described as producing
vibrating prosthesis with a predetermined vibration pattern. In some
implementations, the
predetermined vibration pattern is predictable and largely completely defined
in advance. In other
implementations, the predetermined vibration pattern includes randomized
vibratory motion in one
or more motion freedoms of the available degrees of freedom (up to six degrees
of freedom). That is,
whichever translation or rotational freedom of motion is defined for the
vibrating prosthesis, any of
them may have an intentional randomness component, varying from large to
small. In some cases
the randomness component in any particular motion may be large and in some
cases predominate the
motion. In other cases the randomness component may be relatively small as to
be barely detectable.
[0199j In the discussion herein, in addition to pure points defined for
rotations of pure
abduction, pure adduction, pure anteversion, and pure retroversion, in some
implementations there
are actuators that strike an inserted prosthesis at other locations
intermediate a pair of pure points as
described herein. These non-pure point strikes rotate the inserted prosthesis
by a relative
predetermined combination of abduction and retroversion (based on
trigonometric contributions and
degree of variation from the adjacent pure points). In this context, it is
understood that the rotations
may include negative values for abduction and/or anteversion, also referred to
herein as adduction
and retroversion, respectively. Also, for pure points, a quantity for one of
the rotations is zero.
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[0200] The system and methods above has been described in general terms as an
aid to
understanding details of preferred embodiments of the present invention. In
the description herein,
numerous specific details are provided, such as examples of components and/or
methods, to provide
a thorough understanding of embodiments of the present invention. Some
features and benefits of
the present invention are realized in such modes and are not required in every
case. One skilled in
the relevant art will recognize, however, that an embodiment of the invention
can be practiced
without one or more of the specific details, or with other apparatus, systems,
assemblies, methods,
components, materials, parts, and/or the like. In other instances, well-known
structures, materials, or
operations are not specifically shown or described in detail to avoid
obscuring aspects of
embodiments of the present invention.
[0201] Reference throughout this specification to "one embodiment", "an
embodiment", or
"a specific embodiment" means that a particular feature, structure, or
characteristic described in
connection with the embodiment is included in at least one embodiment of the
present invention and
not necessarily in all embodiments. Thus, respective appearances of the
phrases "in one
embodiment", "in an embodiment", or "in a specific embodiment" in various
places throughout this
specification are not necessarily referring to the same embodiment.
Furthermore, the particular
features, structures, or characteristics of any specific embodiment of the
present invention may be
combined in any suitable manner with one or more other embodiments. It is to
be understood that
other variations and modifications of the embodiments of the present invention
described and
illustrated herein are possible in light of the teachings herein and are to be
considered as part of the
spirit and scope of the present invention.
[0202] It will also be appreciated that one or more of the elements depicted
in the
drawings/figures can also be implemented in a more separated or integrated
manner, or even
removed or rendered as inoperable in certain cases, as is useful in accordance
with a particular
application.
[0203] Additionally, any signal arrows in the drawings/Figures should be
considered only as
exemplary, and not limiting, unless otherwise specifically noted. Combinations
of components or
steps will also be considered as being noted, where terminology is foreseen as
rendering the ability
to separate or combine is unclear.
[0204] The foregoing description of illustrated embodiments of the present
invention,
including what is described in the Abstract, is not intended to be exhaustive
or to limit the invention
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to the precise forms disclosed herein. While specific embodiments of, and
examples for, the
invention are described herein for illustrative purposes only, various
equivalent modifications are
possible within the spirit and scope of the present invention, as those
skilled in the relevant art will
recognize and appreciate. As indicated, these modifications may be made to the
present invention in
light of the foregoing description of illustrated embodiments of the present
invention and are to be
included within the spirit and scope of the present invention.
[0205] Thus, while the present invention has been described herein with
reference to
particular embodiments thereof, a latitude of modification, various changes
and substitutions are
intended in the foregoing disclosures, and it will be appreciated that in some
instances some features
of embodiments of the invention will be employed without a corresponding use
of other features
without departing from the scope and spirit of the invention as set forth.
Therefore, many
modifications may be made to adapt a particular situation or material to the
essential scope and spirit
of the present invention. It is intended that the invention not be limited to
the particular terms used in
following claims and/or to the particular embodiment disclosed as the best
mode contemplated for
carrying out this invention, but that the invention will include any and all
embodiments and
equivalents falling within the scope of the appended claims. Thus, the scope
of the invention is to be
determined solely by the appended claims.
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