U.S. patent application number 12/825736 was filed with the patent office on 2010-12-30 for encapsulated force sensor for measuring a parameter of the muscular-skeletal system.
This patent application is currently assigned to OrthoSensor. Invention is credited to James Ellis, Marc Stein.
Application Number | 20100331737 12/825736 |
Document ID | / |
Family ID | 43379281 |
Filed Date | 2010-12-30 |
United States Patent
Application |
20100331737 |
Kind Code |
A1 |
Stein; Marc ; et
al. |
December 30, 2010 |
ENCAPSULATED FORCE SENSOR FOR MEASURING A PARAMETER OF THE
MUSCULAR-SKELETAL SYSTEM
Abstract
A sensing insert device (100) is disclosed for measuring a
parameter of the muscular-skeletal system. The sensing insert
device (100) can be temporary or permanent. Used intra-operatively,
the sensing insert device (100) comprises an insert dock (202) and
a sensing module (200). The sensing module (200) is a
self-contained encapsulated measurement device having at least one
contacting surface that couples to the muscular-skeletal system.
The insert dock (202) is a passive component made for different
prosthetic component manufacturers as well as for different size
prosthetic components. The sensing module (200) fits in an opening
or cavity of the insert dock (202). The intra-operative insert
device is substantially equal in dimension to an implanted final
insert. The sensing insert device (100) is also a permanent
prosthetic component. The sensing module (200) residing within the
sensing insert device and coupling to a bearing surface of the
insert.
Inventors: |
Stein; Marc; (Chandler,
AZ) ; Ellis; James; (Tempe, AZ) |
Correspondence
Address: |
Orthosensor, Inc.
1560 Sawgrass Corporate Pkwy, 4th Floor
Sunrise
FL
33323
US
|
Assignee: |
OrthoSensor
Sunrise
FL
|
Family ID: |
43379281 |
Appl. No.: |
12/825736 |
Filed: |
June 29, 2010 |
Related U.S. Patent Documents
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Application
Number |
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Patent Number |
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61221817 |
Jun 30, 2009 |
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61221761 |
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Current U.S.
Class: |
600/587 |
Current CPC
Class: |
A61B 8/15 20130101; A61B
5/4528 20130101; A61B 5/7239 20130101; A61B 5/4509 20130101; A61B
5/6878 20130101; A61B 5/6846 20130101 |
Class at
Publication: |
600/587 |
International
Class: |
A61B 5/103 20060101
A61B005/103 |
Claims
1. A sensing system for measurement of a parameter of the
muscular-skeletal system comprising: a trial insert having
dimensions substantially equal to the dimensions of a final insert;
a sensing module in the trial insert to measure the parameter.
2. The sensing system of claim 1 where the sensing module is placed
in a cavity of the trial insert.
3. The sensing system of claim 1 where the sensing module is
encapsulated to be hermetically sealed.
4. The sensing system of claim 2 where the trial insert comprises a
dock having a feature that operatively couples to a prosthetic
component where the dock includes an opening to receive the sensing
module.
5. The sensing system of claim 1 where the trial insert interfaces
with permanent prosthetic components.
6. The sensing system of claim 1 where the trial insert includes a
cover overlying a contacting surface of the sensing module.
7. The sensing system of claim 1 where the trial insert measures a
force, pressure, or load that is substantially equal to the force,
pressure, or load applied by the muscular-skeletal system to the
final insert when installed.
8. The sensing system of claim 1 where the sensing platform
comprises one or more sensing assemblages; electronic circuitry
operatively coupled to the one or more sensing assemblages to
measure the parameter; a power source coupled to the electronic
circuitry; a transmitter coupled to the electronic circuitry; an
antenna coupled to the transmitter; and an enclosure that
encapsulates the electronic circuitry, the power source, antenna,
transmitter, and the one or more sensing assemblages where a
transit time, frequency, or phase is measured by the sensing
platform.
8. (canceled)
9. The sensing system of claim 1 where the sensing module is
disposed of after surgery.
10. A prosthetic component with sensing capability for in-situ
measurement of the muscular-skeletal system comprising a final
insert having a bearing surface where a sensing module resides
within the final insert and where the sensing module includes a
contacting surface that couples to the bearing surface to measure
loading thereon.
11. The prosthetic component 10 where a capacitor in the sensing
module is inductively charged and where the capacitor powers the
sensing module to measure a parameter of the muscular-skeletal
system.
12. The prosthetic component of claim 11 where a transit time,
frequency, or phase is measured by the sensing module corresponding
to the parameter applied to the bearing surface of the final
insert.
13. The sensing system of claim 12 where the sensing platform
comprises one or more sensing assemblages; electronic circuitry
operatively coupled to the one or more sensing assemblages to
measure the parameter; a power source coupled to the electronic
circuitry; a transmitter coupled to the electronic circuitry; an
antenna coupled to the transmitter; and an enclosure that
encapsulates the electronic circuitry, the power source, and the
one or more sensing assemblages.
14. The sensing system of claim 13 where the sensing assemblage
comprises: a compressible waveguide; and at least one transducer to
emit an energy wave into the compressible waveguide and detect a
propagated energy wave.
15. The sensing system of claim 13 where the sensing assemblage
comprises a MEMS structure, a strain gauge, or a piezo-resistive
sensor.
16. The sensing system of claim 11 where the sensing module
measures position where the parameter is applied to the bearing
surface of the final insert.
17. A trial insert for knee reconstruction comprising: a dock
having an opening; and at least one sensing module placed in the
dock where the trial insert has dimensions substantially equal to a
final insert.
18. The trial insert of claim 17 further including a feature on the
dock for aligning and retaining the dock to a tibial prosthetic
component.
19. The trial insert of claim 17 where the at least one sensing
module couples to permanent femoral and tibial prosthetic
components during a measurement.
20. The trial insert of claim 17 where the sensing module has no
components extending into the surgical field.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority benefit of U.S.
provisional patent application Nos. 61/221,761, 61/221,767,
61/221,779, 61/221,788, 61/221,793, 61/221,801, 61/221,808,
61/221,817, 61/221,867, 61/221,874, 61/221,879, 61/221,881,
61/221,886, 61/221,889, 61/221,894, 61/221,901, 61/221,909,
61/221,916, 61/221,923, and 61/221,929 all filed 30 Jun. 2009; the
disclosures of which are hereby incorporated herein by reference in
their entirety.
FIELD
[0002] The present invention pertains generally to measurement of
physical parameters, and particularly to, but not exclusively to, a
hermetically encapsulated sensing module for communicating sensor
data and measurements in real-time.
BACKGROUND
[0003] The skeletal system of a mammal is subject to variations
among species. Further changes can occur due to environmental
factors, degradation through use, and aging. An orthopedic joint of
the skeletal system typically comprises two or more bones that move
in relation to one another. Movement is enabled by muscle tissue
and tendons attached to the skeletal system of the joint. Ligaments
hold and stabilize the one or more joint bones positionally.
Cartilage is a wear surface that prevents bone-to-bone contact,
distributes load, and lowers friction.
[0004] There has been substantial growth in the repair of the human
skeletal system. In general, orthopedic joints have evolved using
information from simulations, mechanical prototypes, and patient
data that is collected and used to initiate improved designs.
Similarly, the tools being used for orthopedic surgery have been
refined over the years but have not changed substantially. Thus,
the basic procedure for replacement of an orthopedic joint has been
standardized to meet the general needs of a wide distribution of
the population. Although the tools, procedure, and artificial joint
meet a general need, each replacement procedure is subject to
significant variation from patient to patient. The correction of
these individual variations relies on the skill of the surgeon to
adapt and fit the replacement joint using the available tools to
the specific circumstance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Various features of the system are set forth with
particularity in the appended claims. The embodiments herein, can
be understood by reference to the following description, taken in
conjunction with the accompanying drawings, in which:
[0006] FIG. 1 is a perspective view of a medical sensing platform
comprising an encapsulating enclosure in accordance with one
embodiment;
[0007] FIG. 2 is a perspective view of a medical sensing device
suitable for use as an bi-compartmental implant and comprising an
encapsulating enclosure in accordance with one embodiment;
[0008] FIG. 3 is an illustration of an application of sensing
insert device in accordance with an exemplary embodiment;
[0009] FIG. 4 is an illustration of a sensing insert device placed
in a joint of the muscular-skeletal system for measuring a
parameter in accordance with an exemplary embodiment;
[0010] FIG. 5 is an exemplary block diagram of the components of a
sensing module in accordance with an exemplary embodiment;
[0011] FIG. 6 is a cross sectional view of the sensing insert
device in further detail according to one embodiment as an
encapsulating enclosure;
[0012] FIG. 7 depicts high-level processing blocks of an
encapsulated force sensor in accordance with one embodiment;
[0013] FIG. 8 is a cross-sectional view of a layout architecture of
the sensing module in accordance with an exemplary embodiment;
[0014] FIG. 9 is a block diagram of a propagation tuned oscillator
(PTO) to maintain positive closed-loop feedback in accordance with
an exemplary embodiment;
[0015] FIG. 10 is a final insert device in accordance with an
exemplary embodiment;
[0016] FIG. 11 is a perspective view of the sensing modules in the
final insert in accordance with an exemplary embodiment; and
[0017] FIG. 12 is an illustration of the final insert installed in
a knee in accordance with an exemplary embodiment.
DETAILED DESCRIPTION
[0018] Embodiments of the invention are broadly directed to
measurement of physical parameters, and more particularly, to
real-time measurement and communication of load, force, pressure,
displacement, density, viscosity, or localized temperature by
sensing structures or assemblies encapsulated within hermetic or
non-hermetic modules or devices. Many parameters of interest within
physical systems or bodies can be measured by evaluating changes in
the transit time of energy waves or pulses having the property that
their propagation velocity is affected by physical changes in a
medium of propagation. Alternatively, piezo-resistive sensing, MEMS
sensing, strain gauge sensing can also be incorporated into the
sensing assembly. The physical parameter or parameters of interest
include, but are not limited to, measurement of load, force,
pressure, displacement, density, viscosity, localized temperature.
The sensing platforms that include the sensing assemblies can be
placed on or within a body, instrument, appliance, vehicle,
equipment, or other physical system.
[0019] In all of the examples illustrated and discussed herein, any
specific materials, temperatures, times, energies, etc. for process
steps or specific structure implementations should be interpreted
to illustrative only and non-limiting. Processes, techniques,
apparatus, and materials as known by one of ordinary skill in the
art may not be discussed in detail but are intended to be part of
an enabling description where appropriate.
[0020] Note that similar reference numerals and letters refer to
similar items in the following figures. In some cases, numbers from
prior illustrations will not be placed on subsequent figures for
purposes of clarity. In general, it should be assumed that
structures not identified in a figure are the same as previous
prior figures.
[0021] One embodiment is a sensing platform that employs a
combination of two or more load bearing surfaces incorporating
features for contacting external objects. The sensing assembly
comprises one or more transducers, a compressible energy
propagating structure media, and spring or springs or other means
of elastic support, to measure force or pressure external to the
sensing platform or displacement produced by contact with an
external object. In a non-limiting example, the sensing platform
measures load. A position of the center or focal point (or locus or
centroid) of the applied load, force, pressure, or external contact
on the load bearing or contacting surface or surfaces of the
sensing platform can also be determined. The centroid or barycenter
is considered the average of all points, weighted by the local
density. In fluid mechanics, the force density has the physical
dimensions of force per unit volume
[0022] Force, pressure, displacement, density, or viscosity is
measured by controlled compression or displacement of the
compressible energy propagating structure or structures or media.
The compression or displacement of the compressible energy
propagating structure or structures or media is accurately
controlled by the action of the spring or springs or other means of
elastic support positioned in conjunction with the compressible
energy propagating structure or structures or media between the
contacting surfaces. Changes in compression or displacement of the
compressible energy propagating structure or structures or media
alter their physical length and may be detected by changes in
transit time of energy pulses or waves propagating therein. The
center or focal point (or locus or centroid) of the applied force,
pressure, displacement, density, or viscosity on the load bearing
or contacting surfaces may be determined by combining measurements
taken with a combination of assemblages of energy transducers and
compressible energy propagating structure or structures or media.
For clarity, the remainder of the description focuses on a specific
form of energy and medium of propagation. Ultrasound energy pulses
or waves, the emission of ultrasound pulses or waves by ultrasound
resonators or transducers, transmitted through ultrasound
waveguides, and detected by ultrasound resonators or transducers
will be used in the following discussion and examples of
embodiments of the present invention as examples of energy pulses,
waves, and propagation structures and media.
[0023] FIG. 1 is a perspective view of a medical sensing platform
comprising an encapsulating enclosure in accordance with one
embodiment. In general, parameters of the muscular-skeletal system
can be measured with a sensing module 200 that in one embodiment is
an integral part of a complete sensing insert device 100. The
sensing module 200 is a self-contained sensor within an
encapsulating enclosure that integrates sensing assemblages, an
electronic assemblage that couples to the sensing assemblages, a
power source, signal processing, and wireless communication. All
components required for the measurement are contained in the
sensing module 200. The sensing module 200 has at least one
contacting surface for coupling to the muscular-skeletal system. A
parameter of the muscular-skeletal system is applied to the contact
surfaces to be measured by the one or more sensing assemblages
therein. As will be disclosed in further detail herein, the sensing
module 200 is part of a system that allows intra-operative and
post-operative sensing of a joint of the muscular-skeletal system.
More specifically, sensing module 200 is placed within a temporary
or permanent prosthetic component that has a similar form factor as
the passive prosthetic component currently being used. This has a
benefit of rapid adoption because the sensing platform is inserted
identically to the commonly used passive component but can provide
much needed quantitative measurements with little or no procedural
changes.
[0024] As shown, the sensing insert device 100 comprises an insert
dock 202 and the sensing module 200. Sensing insert device 100 is a
non-permanent or temporary measurement device that is used
intra-operatively to provide quantitative data related to the
installation of prosthetic components such as in joint replacement
surgery. The combination of the insert dock 202 and sensing module
202 has a form factor substantially equal to a final insert device.
The final insert device can be a passive component or sensored
incorporating sensing module 200. The substantially equal form
factor of sensing insert device 100 means that there are no
extraneous structures in the surgical field that can interfere with
the procedure. For example, a final insert device is designed to
mimic the function of the natural component it is replacing. The
final insert device allows natural movement of the
muscular-skeletal system and does not interfere with ligaments,
tendons, tissue, muscles, and other components of the
muscular-skeletal system. Similarly, sensing insert device 100
allows exposure of the surgical field around the joint by having
the similar form factor as the final insert thereby allowing the
surgeon to make adjustments during the installation in a natural
setting with quantitative measurements to support the
modifications.
[0025] In one embodiment, insert dock 202 is an adaptor. Insert
dock 202 is made in different sizes. In general, prosthetic
components are manufactured in different sizes to accommodate
variation in the muscular-skeletal system from person to person. In
the example, the size of insert dock 202 is chosen to mate with the
selected prosthetic implant components. In particular, a feature
204 aligns with and retains insert dock 202 in a fixed position to
a prosthetic or natural component of the muscular-skeletal system.
The insert dock 202 is a passive component having an opening for
receiving sensing module 200. The opening is positioned to place
the contacting surfaces in a proper orientation to measure the
parameter when used in conjunction with other prosthetic
components. The insert dock 202 as an adaptor can be manufactured
at low cost. Moreover, insert dock 202 can be formed for adapting
to different prosthetic manufacturers thereby increasing system
flexibility. This allows a standard sensing module 200 to be
provided but customized for appropriate size and dimensions through
dock 202 for the specific application and manufacturer
component.
[0026] The one or more sensing assemblages within sensing module
200 couple to the contacting surfaces of sensing module 200 for
receiving the applied parameter of the muscular-skeletal system. In
one embodiment, a sensing assemblage comprises one or more energy
transducers coupled to an elastic structure. The elastic structure
allows the propagation of energy waves. The forms of energy
propagated through the elastic energy propagating structures may
include, but is not limited to, sound, ultrasound, or
electromagnetic radiation including radio frequency, infrared, or
light. A change in the parameter applied to the contacting surfaces
results in a change a dimension of the elastic structure. The
dimension of the elastic structure can be measured precisely using
continuous wave, pulsed, or pulsed echo measurement. The dimension
and material properties of the elastic structure have a known
relationship to the parameter being measured. Thus, the dimension
is precisely measured and converted to the parameter. Other factors
such as movement or acceleration can be taken into account in the
calculation. As an example, a force, pressure, or load applied to
the one or more contacting surfaces of sensing module 200 is used
to illustrate a parameter measurement hereinbelow. It should be
noted that this is for illustration purposes and that the sensing
module 200 can be used to measure other parameters.
[0027] As will be shown ahead, the encapsulating enclosure can
serve in a first embodiment as a trial implant for orthopedic
surgical procedures, namely, for determining load forces on
prosthetic components and the musculoskeletal system. In a second
embodiment, the encapsulating enclosure can be placed within a
permanent prosthetic component for long term monitoring. The
encapsulating enclosure supports and protects internal mechanical
and electronic components from external physical, mechanical,
chemical, and electrical, and electromagnetic intrusion that might
compromise sensing or communication operations of the module or
device. The integration of the internal components is designed to
minimize adverse physical, mechanical, electrical, and ultrasonic
interactions that might compromise sensing or communication
operations of the module or device.
[0028] FIG. 2 is a perspective view of a medical sensing device
suitable for use as a bi-compartmental implant and comprising an
encapsulating enclosure in accordance with one embodiment. As
shown, the load sensing insert device 100 comprises two sensing
modules 200. Each sensing module 200 is a self-contained
encapsulated enclosure that can make individual or coordinated
parameter measurements. For example, the sensing insert device 100
can be used to assess load forces on a bi-compartmental knee joint
implant. In particular, both sensing modules 200 can individually,
or in combination, report applied loading forces. Bi-compartmental
sensing provides the benefit of providing quantitative measurement
to balance each compartment in relation to one another.
[0029] Similar to that described above, insert dock 202 is an
adaptor having two openings instead of one. Insert dock 202 can be
made in different sizes to accommodated different sized prosthetic
components and different manufacturers. The insert dock 202 with
two openings is a passive component for receiving two separate
sensing modules 200. The opening is positioned to place the
contacting surfaces in a proper orientation to measure the
parameter when used in conjunction with other prosthetic
components. In general, encapsulated enclosures can be positioned
on or within, or engaged with, or attached or affixed to or within,
a wide range of physical systems including, but not limited to
instruments, appliances, vehicles, equipments, or other physical
systems as well as animal and human bodies, for sensing and
communicating the parameter or parameters of interest in real time.
Similar to that described above, insert dock 202 as an adaptor can
be manufactured at low cost providing design flexibility and
allowing rapid adoption of quantitative measurement.
[0030] FIG. 3 is an illustration of an application of sensing
insert device 100 in accordance with an exemplary embodiment. The
illustration shows the device 100 measuring a force, pressure, or
load applied by the muscular-skeletal system. In the illustration,
device 100 can collect load data for real-time viewing of the load
forces over various applied loads and angles of flexion. The
sensing insert device 100 can measure the level and distribution of
load at various points on the prosthetic component and transmits
the measured load data by way data communication to a receiver
station 110 for permitting visualization. This can aid the surgeon
in making any adjustments needed to achieve optimal joint
balancing.
[0031] In general, device 100 has at least one contacting surface
that couples to the muscular-skeletal system. As shown, a first and
a second contacting surface respectively couple to a femoral
prosthetic component 104 and a tibial prosthetic component 106.
Device 100 is designed to be used in the normal flow of an
orthopedic surgical procedure without special procedures,
equipment, or components. Typically, one or more natural components
of the muscular-skeletal system are replaced when joint
functionality substantially reduces a patient quality of life. A
joint replacement is a common procedure in later life because it is
prone to wear over time, can be damaged during physical activity,
or by accident.
[0032] A joint of the muscular-skeletal system provides movement of
bones in relation to one another that can comprise angular and
rotational motion. The joint can be subjected to loading and torque
throughout the range of motion. The joint typically comprises two
bones that move in relation to one another with a low friction
flexible connective tissue such as cartilage between the bones.
Natural lubricant in the joint in conjunction with the cartilage
aid in joint movement. Sensing insert device 100 mimics the natural
structure between the bones of the joint. Insert device 100 has a
contacting surface on which a bone or a prosthetic component can
moveably couple. A knee joint is disclosed for illustrative
purposes but sensing insert device 100 is applicable to other
joints of the muscular-skeletal system. For example, the hip,
spine, and shoulder have similar structures comprising two or more
bones that move in relation to one another. In general, insert
device 100 can be used between two or more bones allowing movement
of the bones during measurement or maintaining the bones in a fixed
position.
[0033] The load sensor insert device 100 and the receiver station
110 forms a communication system for conveying data via secure
wireless transmission within a broadcasting range over short
distances on the order of a few meters to protect against any form
of unauthorized or accidental query. A combination of cyclic
redundancy checks and a high repetition rate of transmission during
data capture permits discarding of corrupted data without
materially affecting display of data
[0034] In the illustration, a surgical procedure is performed to
place a femoral prosthetic component 104 onto a prepared distal end
of the femur 102. Similarly, a tibial prosthetic component 106 is
placed to a prepared proximal end of the tibia 108. The tibial
prosthetic component 106 can be a tray or plate affixed to a
planarized proximal end of the tibia 108. The sensing insert device
100 is a third prosthetic component that is placed between the
plate of the tibial prosthetic component 106 and the femoral
prosthetic component 104. The three prosthetic components enable
the prostheses to emulate the functioning of a natural knee joint.
In one embodiment, sensing insert device 100 is used during surgery
and replaced with a final insert after quantitative measurements
are taken to ensure optimal fit, balance, and loading of the
prosthesis.
[0035] In one embodiment, sensing insert device 100 is a mechanical
replica of a final insert. In other words, sensing insert device
100 has substantially equal dimensions to the final insert. The
substantially equal dimensions ensure that the final insert when
placed in the reconstructed joint will have similar loading and
balance as that measured by sensing insert device 100 during the
trial phase of the surgery. Moreover, passive trial inserts are
commonly used during surgery to determine the appropriate final
insert. Thus, the procedure remains the same. It can measure loads
at various points (or locations) on the femoral prosthetic
component 104 and transmit the measured data to a receiving station
110 by way of an integrated loop antenna. The receiving station 110
can include data processing, storage, or display, or combination
thereof and provide real time graphical representation of the level
and distribution of the load.
[0036] As one example, the sensing insert device 100 can measure
forces (Fx, Fy, and Fz) with corresponding locations and torques
(e.g. Tx, Ty, and Tz) on the femoral prosthetic component 104 and
the tibial prosthetic component 106. It can then transmit this data
to the receiving station 110 to provide real-time visualization for
assisting the surgeon in identifying any adjustments needed to
achieve optimal joint balancing.
[0037] FIG. 4 is an illustration of a sensing insert device 100
placed in a joint of the muscular-skeletal system for measuring a
parameter in accordance with an exemplary embodiment. In
particular, sensing insert device 100 is placed in contact between
a femur 102 and a tibia 108 for measuring a parameter. In the
example, a force, pressure, or load is being measured. The device
100 in this example can intra-operatively assess a load on
prosthetic components during the surgical procedure. As mentioned
previously, sensing insert device 100 collects data for real-time
viewing of the load forces over various applied loads and angles of
flexion. It can measure the level and distribution of load at
various points on the prosthetic component and transmit the
measured load data by way data communication to a receiver station
110 for permitting visualization. This can aid the surgeon in
making any adjustments needed to achieve optimal joint
balancing.
[0038] A proximal end of tibia 108 is prepared to receive tibial
prosthetic component 106. Tibial prosthetic component 106 is a
support structure that is fastened to the proximal end of the tibia
and is usually made of a metal or metal alloy. The tibial
prosthetic component 106 also retains the insert in a fixed
position with respect to tibia 108. Similarly, a distal end of
femur 102 is prepared to receive femoral prosthetic component 104.
The femoral prosthetic component 104 is generally shaped to have an
outer condylar articulating surface. The preparation of femur 102
and tibia 108 is aligned to the mechanical axis of the leg. The
sensing insert device 100 provides a concave or flat surface
against which the outer condylar articulating surface of the
femoral prosthetic component 104 rides relative to the tibia
prosthetic component 106. In particular, the top surface of the
sensing module 200 faces the condylar articulating surface of the
femoral prosthetic component 104, and the bottom surface of the
insert dock 202 faces the top surface of the tibial prosthetic
component 106.
[0039] A final insert is subsequently fitted between femoral
prosthetic component 104 and tibial prosthetic component 106 that
has a bearing surface that couples to femoral component 104
allowing the leg a natural range of motion. The final insert is has
a wear surface that is typically made of a low friction polymer
material. Ideally, the prosthesis has an appropriate loading,
alignment, and balance that mimics the natural leg and maximizes
the life of the artificial components.
[0040] The sensing insert device 100 is used to measure, adjust,
and test the reconstructed joint prior to installing the final
insert. As mentioned previously, the sensing insert device 100 is
placed between the femur 102 and tibia 108. The condyle surface of
femoral component 104 contacts a major surface of device 100. The
major surface of device 100 approximates a surface of a final
insert. Tibial prosthetic component 106 can include a cavity or
tray on the major surface that receives and retains an insert dock
202 and a sensing module 200 during a measurement process. It
should be noted that sensing insert device 100 is coupled to and
provides measurement data in conjunction with permanent prosthetic
components. In other words, the permanent prosthetic components are
the installed components of the patient.
[0041] Insert dock 202 is provided in different sizes and shapes.
Insert dock 202 can comprise many different sizes and shapes to
interface appropriately with different manufacturer prosthetic
components. Prosthetic components are made in different sizes to
accommodate anatomical differences over a wide population range.
Insert dock 202 is designed for different prosthetic sizes within
the same manufacturer. In at least one embodiment, multiple docks
of different dimensions are provided for a surgery. For example,
the thickness of the final insert is determined by the surgical
cuts to the muscular-skeletal system and measurements provided by
sensing module 200. The surgeon may try two insert docks 202 of
different thicknesses before making a final decision. In one
embodiment, sensing insert device 100 selected by the surgeon has
substantially equal dimensions to the final insert used. In
general, insert dock 202 allows standardization on a single sensing
module 200 for different prosthetic platforms. Thus, the sensing
module 200 is common to the different insert docks 202 allowing
improved quality, reliability, and performance.
[0042] In one embodiment, one or more insert docks 202 are used to
determine an appropriate thickness that yields an optimal loading.
In general, the absolute loading over the range of motion is kept
within a predetermined range. Soft tissue tensioning can be used to
adjust the absolute loading. The knee balance can also be adjusted
within a predetermined range if a total knee reconstruction is
being performed and a sensing module 202 is used in each
compartment. Tibial prosthetic component 106 and device 100 have a
combined thickness that represents a combined thickness of tibial
prosthetic component 106 and a final (or chronic) insert of the
knee joint. Thus, the final insert thickness or depth is chosen
based on the trial performed using device 100. Typically, the final
insert thickness is identical to the device 100 to maintain the
measured loading and balance. In one embodiment, sensing module 200
and insert docks 202 are disposed of after surgery. Alternatively,
the sensing module 200 and insert docks 202 can be cleaned,
sterilized, and packaged for reuse.
[0043] The prosthesis incorporating device 100 emulates the
function of a natural knee joint. Device 100 can measure loads or
other parameters at various points throughout the range of motion.
Data from device 100 is transmitted to a receiving station 110 via
wired or wireless communications. In a first embodiment, device 100
is a disposable system. Device 100 can be disposed of after using
the sensing insert device 100 to optimally fit the joint implant.
Device 100 is a low cost disposable system that reduces capital
costs, operating costs, facilitates rapid adoption of quantitative
measurement, and initiates evidentiary based orthopedic medicine.
In a second embodiment, a methodology can be put in place to clean
and sterilize device 100 for reuse. In a third embodiment, device
100 can be incorporated in a tool instead of being a component of
the replacement joint. The tool can be disposable or be cleaned and
sterilized for reuse. In a fourth embodiment, device 100 can be a
permanent component of the replacement joint. Device 100 can be
used to provide both short term and long term post-operative data
on the implanted joint. In a fifth embodiment, device 100 can be
coupled to the muscular-skeletal system. In all of the embodiments,
receiving station 110 can include data processing, storage, or
display, or combination thereof and provide real time graphical
representation of the level and distribution of the load. Receiving
station 110 can record and provide accounting information of device
100 to an appropriate authority.
[0044] The sensing insert device 100, in one embodiment, comprises
a load sensing platform 121, an accelerometer 122, and sensing
assemblies 123. This permits the sensing device 100 to assess a
total load on the prosthetic components when it is being moved. The
system accounts for forces due to gravity and motion. In one
embodiment, load sensing platform 121 includes two or more load
bearing surfaces, at least one energy transducer, at least one
compressible energy propagating structure, and at least one member
for elastic support. The accelerometer 122 can measure
acceleration. Acceleration can occur when the load sensing device
100 is moved or put in motion. Accelerometer 122 can sense
orientation, vibration, and impact. In another embodiment, the
femoral component 104 can similarly include an accelerometer 127,
which by way of a communication interface to the sensing insert
device 100, can provide reference position and acceleration data to
determine an exact angular relationship between the femur and
tibia. The sensing assemblies 123 can reveal changes in length or
compression of the energy propagating structure or structures by
way of the energy transducer or transducers. Together the load
sensing platform 121, accelerometer 122 (and in certain cases
accelerometer 127), and sensing assemblies 123 measure force or
pressure external to the load sensing platform or displacement
produced by contact with the prosthetic components.
[0045] In at least one exemplary embodiment, an energy pulse is
directed within one or more waveguides in device 100 by way of
pulse mode operations and pulse shaping. The waveguide is a conduit
that directs the energy pulse in a predetermined direction. The
energy pulse is typically confined within the waveguide. In one
embodiment, the waveguide comprises a polymer material. For
example, urethane or polyethylene are polymers suitable for forming
a waveguide. The polymer waveguide can be compressed and has little
or no hysteresis in the system. Alternatively, the energy pulse can
be directed through the muscular-skeletal system. In one
embodiment, the energy pulse is directed through bone of the
muscular-skeletal system to measure bone density. A transit time of
an energy pulse is related to the material properties of a medium
through which it traverses. This relationship is used to generate
accurate measurements of parameters such as distance, weight,
strain, pressure, wear, vibration, viscosity, and density to name
but a few.
[0046] Incorporating data from the accelerometer 122 with data from
the other sensing components 121 and 123 assures accurate
measurement of the applied load, force, pressure, or displacement
by enabling computation of adjustments to offset this external
motion. This capability can be required in situations wherein the
body, instrument, appliance, vehicle, equipment, or other physical
system, is itself operating or moving during sensing of load,
pressure, or displacement. This capability can also be required in
situations wherein the body, instrument, appliance, vehicle,
equipment, or other physical system, is causing the portion of the
body, instrument, appliance, vehicle, equipment, or other physical
system being measured to be in motion during sensing of load,
pressure, or displacement.
[0047] The accelerometer 122 can operate singly, as an integrated
unit with the load sensing platform 121, and/or as an integrated
unit with the sensing assemblies 123. Integrating one or more
accelerometers 122 within the sensing assemblages 123 to determine
position, attitude, movement, or acceleration of sensing
assemblages 123 enables augmentation of presentation of data to
accurately identify, but not limited to, orientation or spatial
distribution of load, force, pressure, displacement, density, or
viscosity, or localized temperature by controlling the load and
position sensing assemblages to measure the parameter or parameters
of interest relative to specific orientation, alignment, direction,
or position as well as movement, rotation, or acceleration along
any axis or combination of axes. Measurement of the parameter or
parameters of interest may also be made relative to the earth's
surface and thus enable computation and presentation of spatial
distributions of the measured parameter or parameters relative to
this frame of reference.
[0048] In one embodiment, the accelerometer 122 includes direct
current (DC) sensitivity to measure static gravitational pull with
load and position sensing assemblages to enable capture of, but not
limited to, distributions of load, force, pressure, displacement,
movement, rotation, or acceleration by controlling the sensing
assemblages to measure the parameter or parameters of interest
relative to orientations with respect to the earths surface or
center and thus enable computation and presentation of spatial
distributions of the measured parameter or parameters relative to
this frame of reference.
[0049] Embodiments of device 100 are broadly directed to
measurement of physical parameters, and more particularly, to
evaluating changes in the transit time of a pulsed energy wave
propagating through a medium. In-situ measurements during
orthopedic joint implant surgery would be of substantial benefit to
verify an implant is in balance and under appropriate loading or
tension. In one embodiment, the instrument is similar to and
operates familiarly with other instruments currently used by
surgeons. This will increase acceptance and reduce the adoption
cycle for a new technology. The measurements will allow the surgeon
to ensure that the implanted components are installed within
predetermined ranges that maximize the working life of the joint
prosthesis and reduce costly revisions. Providing quantitative
measurement and assessment of the procedure using real-time data
will produce results that are more consistent. A further issue is
that there is little or no implant data generated from the implant
surgery, post-operatively, and long term. Device 100 can provide
implant status data to the orthopedic manufacturers and surgeons.
Moreover, data generated by direct measurement of the implanted
joint itself would greatly improve the knowledge of implanted joint
operation and joint wear thereby leading to improved design and
materials.
[0050] As mentioned previously, device 100 can be used for other
joint surgeries; it is not limited to knee replacement implant or
implants. Moreover, device 100 is not limited to trial
measurements. Device 100 can be incorporated into the final joint
system to provide data post-operatively to determine if the
implanted joint is functioning correctly. Early determination of a
problem using device 100 can reduce catastrophic failure of the
joint by bringing awareness to a problem that the patient cannot
detect. The problem can often be rectified with a minimal invasive
procedure at lower cost and stress to the patient. Similarly,
longer term monitoring of the joint can determine wear or
misalignment that if detected early can be adjusted for optimal
life or replacement of a wear surface with minimal surgery thereby
extending the life of the implant. In general, device 100 can be
shaped such that it can be placed or engaged or affixed to or
within load bearing surfaces used in many orthopedic applications
(or used in any orthopedic application) related to the
musculoskeletal system, joints, and tools associated therewith.
Device 100 can provide information on a combination of one or more
performance parameters of interest such as wear, stress,
kinematics, kinetics, fixation strength, ligament balance,
anatomical fit and balance.
[0051] FIG. 5 is an exemplary block diagram of the components of a
sensing module 200 in accordance with an exemplary embodiment. It
should be noted that the sensing module could comprise more or less
than the number of components shown. As illustrated, the sensing
module includes one or more sensing assemblages 303, a transceiver
320, an energy storage 330, electronic circuitry 307, one or more
mechanical supports 315 (e.g., springs), and an accelerometer 302.
In the non-limiting example, an applied compressive force can be
measured by the sensing module.
[0052] The sensing assemblage 303 can be positioned, engaged,
attached, or affixed to the contact surfaces 306. Mechanical
supports 315 serve to provide proper balancing of contact surfaces
306. In at least one exemplary embodiment, contact surfaces 306 are
load-bearing surfaces. In general, the propagation structure 305 is
subject to the parameter being measured. Surfaces 306 can move and
tilt with changes in applied load; actions which can be transferred
to the sensing assemblages 303 and measured by the electronic
circuitry 307. The electronic circuitry 307 measures physical
changes in the sensing assemblage 303 to determine parameters of
interest, for example a level, distribution and direction of forces
acting on the contact surfaces 306. In general, the sensing module
is powered by the energy storage 330.
[0053] As one example, the sensing assemblage 303 can comprise an
elastic or compressible propagation structure 305 between a
transducer 304 and a transducer 314. In the current example,
transducer 304 can be an ultrasound (or ultrasonic) resonator, and
the elastic or compressible propagation structure 305 can be an
ultrasound (or ultrasonic) waveguide (or waveguides). The
electronic circuitry 307 is electrically coupled to the sensing
assemblages 303 and translates changes in the length (or
compression or extension) of the sensing assemblages 303 to
parameters of interest, such as force. It measures a change in the
length of the propagation structure 305 (e.g., waveguide)
responsive to an applied force and converts this change into
electrical signals which can be transmitted via the transceiver 320
to convey a level and a direction of the applied force. In other
arrangements herein contemplated, the sensing assemblage 303 may
require only a single transducer. In yet other arrangements, the
sensing assemblage 303 can include piezoelectric, capacitive,
optical or temperature sensors or transducers to measure the
compression or displacement. It is not limited to ultrasonic
transducers and waveguides.
[0054] The accelerometer 302 can measure acceleration and static
gravitational pull. Accelerometer 302 can be single-axis and
multi-axis accelerometer structures that detect magnitude and
direction of the acceleration as a vector quantity. Accelerometer
302 can also be used to sense orientation, vibration, impact and
shock. The electronic circuitry 307 in conjunction with the
accelerometer 302 and sensing assemblies 303 can measure parameters
of interest (e.g., distributions of load, force, pressure,
displacement, movement, rotation, torque and acceleration) relative
to orientations of the sensing module with respect to a reference
point. In such an arrangement, spatial distributions of the
measured parameters relative to a chosen frame of reference can be
computed and presented for real-time display.
[0055] The transceiver 320 comprises a transmitter 309 and an
antenna 310 to permit wireless operation and telemetry functions.
In various embodiments, the antenna 310 can be configured by design
as an integrated loop antenna. As will be explained ahead, the
integrated loop antenna is configured at various layers and
locations on the electronic substrate with electrical components
and by way of electronic control circuitry to conduct efficiently
at low power levels. Once initiated the transceiver 320 can
broadcast the parameters of interest in real-time. The telemetry
data can be received and decoded with various receivers, or with a
custom receiver. The wireless operation can eliminate distortion
of, or limitations on, measurements caused by the potential for
physical interference by, or limitations imposed by, wiring and
cables connecting the sensing module with a power source or with
associated data collection, storage, display equipment, and data
processing equipment.
[0056] The transceiver 320 receives power from the energy storage
330 and can operate at low power over various radio frequencies by
way of efficient power management schemes, for example,
incorporated within the electronic circuitry 307. As one example,
the transceiver 320 can transmit data at selected frequencies in a
chosen mode of emission by way of the antenna 310. The selected
frequencies can include, but are not limited to, ISM bands
recognized in International Telecommunication Union regions 1, 2
and 3. A chosen mode of emission can be, but is not limited to,
Gaussian Frequency Shift Keying, (GFSK), Amplitude Shift Keying
(ASK), Phase Shift Keying (PSK), Minimum Shift Keying (MSK),
Frequency Modulation (FM), Amplitude Modulation (AM), or other
versions of frequency or amplitude modulation (e.g., binary,
coherent, quadrature, etc.).
[0057] The antenna 310 can be integrated with components of the
sensing module to provide the radio frequency transmission. The
substrate for the antenna 310 and electrical connections with the
electronic circuitry 307 can further include a matching network.
This level of integration of the antenna and electronics enables
reductions in the size and cost of wireless equipment. Potential
applications may include, but are not limited to any type of
short-range handheld, wearable, or other portable communication
equipment where compact antennas are commonly used. This includes
disposable modules or devices as well as reusable modules or
devices and modules or devices for long-term use.
[0058] The energy storage 330 provides power to electronic
components of the sensing module. It can be charged by wired energy
transfer, short-distance wireless energy transfer or a combination
thereof. External power sources can include, but are not limited
to, a battery or batteries, an alternating current power supply, a
radio frequency receiver, an electromagnetic induction coil, a
photoelectric cell or cells, a thermocouple or thermocouples, or an
ultrasound transducer or transducers. By way of the energy storage
330, the sensing module can be operated with a single charge until
the internal energy is drained. It can be recharged periodically to
enable continuous operation. The energy storage 330 can utilize
common power management technologies such as replaceable batteries,
supply regulation technologies, and charging system technologies
for supplying energy to the components of the sensing module to
facilitate wireless applications.
[0059] The energy storage 330 minimizes additional sources of
energy radiation required to power the sensing module during
measurement operations. In one embodiment, as illustrated, the
energy storage 330 can include a capacitive energy storage device
308 and an induction coil 311. External source of charging power
can be coupled wirelessly to the capacitive energy storage device
308 through the electromagnetic induction coil or coils 311 by way
of inductive charging. The charging operation can be controlled by
power management systems designed into, or with, the electronic
circuitry 307. As one example, during operation of electronic
circuitry 307, power can be transferred from capacitive energy
storage device 308 by way of efficient step-up and step-down
voltage conversion circuitry. This conserves operating power of
circuit blocks at a minimum voltage level to support the required
level of performance.
[0060] In one configuration, the energy storage 330 can further
serve to communicate downlink data to the transceiver 320 during a
recharging operation. For instance, downlink control data can be
modulated onto the energy source signal and thereafter demodulated
from the induction coil 311 by way of electronic control circuitry
307. This can serve as a more efficient way for receiving downlink
data instead of configuring the transceiver 320 for both uplink and
downlink operation. As one example, downlink data can include
updated control parameters that the sensing module uses when making
a measurement, such as external positional information, or for
recalibration purposes, such as spring biasing. It can also be used
to download a serial number or other identification data.
[0061] The electronic circuitry 307 manages and controls various
operations of the components of the sensing module, such as
sensing, power management, telemetry, and acceleration sensing. It
can include analog circuits, digital circuits, integrated circuits,
discrete components, or any combination thereof. In one
arrangement, it can be partitioned among integrated circuits and
discrete components to minimize power consumption without
compromising performance. Partitioning functions between digital
and analog circuit enhances design flexibility and facilitates
minimizing power consumption without sacrificing functionality or
performance. Accordingly, the electronic circuitry 307 can comprise
one or more Application Specific Integrated Circuit (ASIC) chips,
for example, specific to a core signal processing algorithm.
[0062] In another arrangement, the electronic circuitry can
comprise a controller such as a programmable processor, a Digital
Signal Processor (DSP), a microcontroller, or a microprocessor,
with associated storage memory and logic. The controller can
utilize computing technologies with associated storage memory such
a Flash, ROM, RAM, SRAM, DRAM or other like technologies for
controlling operations of the aforementioned components of the
sensing module. In one arrangement, the storage memory may store
one or more sets of instructions (e.g., software) embodying any one
or more of the methodologies or functions described herein. The
instructions may also reside, completely or at least partially,
within other memory, and/or a processor during execution thereof by
another processor or computer system.
[0063] FIG. 6 is a cross sectional view of the sensing insert
device 100 in further detail according to one embodiment as an
encapsulating enclosure. As shown, the sensing insert device 100
comprises the sensing module 200 and the insert dock 202. The
insert dock 202 in this embodiment provides a concave surface. In a
first configuration, the insert dock 202 can further include an
insert cover 704 to seal in the sensing module 200. The insert
cover 704 couples to a contacting surface of sensing module 200. In
a second configuration, the insert cover 704 may be absent, and the
sensing module 200 alone is sealed.
[0064] In either configuration, the sensing module 200 can be
hermetically sealed to form the encapsulating enclosure. The
sensing module 200 and insert dock 202 are sterilized in sealed
packages that are opened within the surgical field prior to use.
The sensing module 200 is placed through an opening into a cavity
of insert dock 202. The insert cover 704 can overlie sensing module
200. In one embodiment, the sensing insert device 100 is used
intra-operatively to measure parameters related to prosthetic
implantation during surgery. The sensing insert device 100
comprising insert dock 202 and sensing module 200 adds flexibility
by simplifying customization for different manufacturers.
Alternatively, the sensing insert device 100 can be formed as a
single measurement device where the sensing module 200 is
incorporated in an encapsulating enclosure and cannot be removed.
The sensing module 200 fits within or at a boundary of dock 202. No
components extend out in the surgical area because all measurement
circuitry is contained and resides within sensing module 200. This
enclosure permits the sensing module 200 to measure parameters of
interest within a wide range of applications including, but not
limited to, applications within adverse and harsh environments,
long-term applications, or medical applications. It can also be
constructed in a wide range of sizes from very compact to large as
required to fit the application. The hermetic sealing facilitates
real time measurement and communication of physiological parameters
within animal or human bodies including, but not limited to,
loading within individual joints, bone density, movement, fluid
motion, various parameters of interstitial fluids including, but
not limited to, viscosity, pressure, and localized temperature with
applications throughout the vascular, lymph, respiratory, and
digestive systems, as well as within or affecting muscles, bones,
joints, and soft tissue areas.
[0065] In the first configuration, the encapsulating enclosure
comprises a unitary main body 242 and load bearing or contact
surfaces 243 that can be, but are not limited to, dissimilar
materials combined to form a hermetic or non-hermetic module or
device. The components of the encapsulating structure can also
consist of, but are not limited to, bio-compatible materials. In
the second configuration, the encapsulating enclosure comprises the
insert dock 202, the sensing module 200, and the insert cover 704.
For medical applications, the encapsulating enclosure is hermetic.
The encapsulating enclosure can comprise biocompatible materials,
for example, but not limited to, polycarbonate, steel, silicon,
neoprene, and similar materials.
[0066] Polycarbonate is an example material that fulfills the
molding and hermetic requirements for the unitary main body.
Polycarbonate and steel are examples of materials that fulfill the
interface and hermetic requirements for the load bearing or
contacting surfaces. In the example of combining separate
components of polycarbonate and steel to construct an encapsulating
enclosure, silicon, silicon adhesive, and neoprene are examples of
materials that fulfill the sealing and flexibility requirements for
interfacing the polycarbonate and steel components.
[0067] The sensing module 200 can also be incorporated into, but
not limited to, handheld instruments, such as one that might be
commonly used for evaluation of the flexion-extension gap; or a
final, chronically implanted prosthetic implants, such as a tibial
bearing or insert; as well as many other in vivo or external
applications enabled by the flexibility to encapsulate the wireless
load sensing module within a wide range of shapes and sizes. This
wireless load sensing module or device may also have a wide range
of non-medical and applications as well as medical
applications.
[0068] The sensing module 200 can also be used in non-medical
applications that require measurement of, but not limited to, load,
force, pressure, or movement of portions of physical systems, or
load, force, pressure placed upon, or movement of, physical systems
or bodies themselves, or load, force, pressure, or movement caused
by external objects in the environment of the physical systems or
bodies, or combinations of these parameters. The sensing module 200
can be ported to applications where the following attributes are
preferred: measurement of parameters of interest in real time,
communication of measured values in real time, exemplary accuracy
and precision of measurements, or a wide range of sizes of the
sensing and communication module or device to fit requirements of
applications or harsh environments within which the measurement
data is captured, or any combination of these attributes.
[0069] FIG. 7 depicts high-level processing blocks of an
encapsulated force sensor 600 in accordance with one embodiment.
The blocks are operatively coupled together within the encapsulated
enclosure of the sensing module 200 and together form an
encapsulated force sensor 600. An ASIC or application specific
integrated circuit is used to minimize the form factor by
incorporating most of the circuitry on a single die. The
encapsulated force sensor 600 comprises the hermetic seal 623 and
may include more or less than the number of high-level processing
blocks shown. In one embodiment, a temporary test interconnect or
text tab 625 can be used during set-up, calibration or testing that
can be removed after all testing, calibration, and programming is
complete.
[0070] Load sensing platform block A is responsible for detecting
and supporting load requirements. Compact low-power energy source
block B is responsible for powering components of the sensing
module 200. In one embodiment, low-power energy source block B
includes a super-capacitor that can be charged in a short period of
time prior to surgery. The super-capacitor can be charged by
inductive coupling. The stored charge on the super-capacitor is
sufficient to power encapsulated force sensor 600 for the duration
of the surgery. The output voltage of the super capacitor can be
regulated. Integrated position and load sensing block C is
responsible for interpreting load and position measurements.
High-Precision sensing block D is responsible for sensing precise
load measurements such as level and distribution of force. It
permits reliable measurement of the load across the entire range of
flexion of the knee joint. Short-range telemetry block E is
responsible for transmitting load and position measurements to a
receiving system.
[0071] Notably, the encapsulating force sensor 600 supports and
protects the specialized mechanical and electronic components from
external physical, mechanical, chemical, and electrical, and
electromagnetic intrusion that might compromise sensing or
communication operations of the module or device. The encapsulating
force sensor 600 also supports internal mechanical and electronic
components and minimizes adverse physical, mechanical, electrical,
and ultrasonic interactions that might compromise sensing or
communication operations of the module or device.
[0072] The housing electrically insulates the internal electronic,
sensing, and communication components. The encapsulating force
sensor 600 eliminates parasitic paths that might conduct ultrasonic
energy and compromise excitation and detection of ultrasound waves
within the sensing assemblages during sensing operations. A
temporary bi-directional electrical interconnect assures a high
level of electrical observation and controllability of the
electronic assembly within the encapsulating force sensor 600. The
temporary interconnect also provides a high level of electrical
observation of the sensing subsystem, including the transducers,
waveguides, and mechanical spring or elastic assembly.
[0073] The encapsulating force sensor 600 has a compact size
permitting it to fit for example within a trial insert to measure
the level and incidence of the load on subsequent implanted
prosthetic devices. It can be constructed using standard components
and manufacturing processes. Manufacturing carriers or fixtures can
be designed to emulate the final encapsulating enclosure of the
sensing module 200. Calibration data can be obtained during the
manufacturing processing thus enabling capture of accurate
calibration data. These calibration parameters can be stored within
the memory circuits integrated into the electronics assemblage of
the sensing module 200. Testability and calibration further assures
the quality and reliability of the encapsulated enclosure.
[0074] Examples of a wide range of potential medical applications
can include, but are not limited to, implantable devices, modules
within implantable devices, intra-operative implants or modules
within intra-operative implants or trial inserts, modules within
inserted or ingested devices, modules within wearable devices,
modules within handheld devices, modules within instruments,
appliances, equipment, or accessories of all of these, or
disposables within implants, trial inserts, inserted or ingested
devices, wearable devices, handheld devices, instruments,
appliances, equipment, or accessories to these devices,
instruments, appliances, or equipment.
[0075] FIG. 8 is a cross-sectional view of a layout architecture of
the sensing module 200 in accordance with an exemplary embodiment.
The blocks are operatively coupled together within the encapsulated
enclosure of the sensing module 200 and together form an
encapsulated force sensor 900. The encapsulated force sensor 900
illustrates an exemplary load sensing platform block A of the
encapsulating force sensor 600 according to one embodiment. In
general, the sensors overlie the electronics within the assembly to
achieve the form factor required for implanting. It comprises a top
steel plate 904 coupled to a lower printed circuit board (PCB) 918
by way of spring retainer 906, disc spring 908, and spring post
914. The load sensing platform block A is biased with springs or
other means of elastic support to accurately maintain a required
distance between the load bearing or contact surfaces such as top
cover 902 and to minimize hysteresis due to material properties of
waveguide 910.
[0076] Ultrasound waveguide 910 is coupled to the top cover 902. A
force applied to the top cover 902 compresses waveguide 910. Lower
piezo 924 and upper piezo 912 are piezo-electric transducers
respectively coupled to waveguide 910 at a first and second
location. In one embodiment, the transducers are ultrasonic
transducers. Waveguide 910 is a compressible propagating medium for
ultrasonic energy waves. The transducers emit energy waves and
detect propagated energy waves in waveguide 910. Electronic
circuitry is coupled to lower piezo 924 and upper piezo 912 to
measure transit time, frequency, or phase of the propagated energy
waves. The transit time, frequency, or phase of energy waves
propagating between the first and second locations of waveguide 910
can be precisely measured and therefore the length of the
ultrasound waveguide 910. The length of waveguide 910 is calculated
by a known function relating material properties of the waveguide
910 to the parameter being measured. In the example, a force,
pressure, or load is calculated from the measured length of
waveguide 910. More than one waveguide 910 can be coupled to top
cover 902 to measure the parameter value and the position where the
parameter is applied to cover 902. For example, the magnitude and
position of the loading on the contacting surface of sensing module
200 applied by femur 102 and tibia 108 to sensing module 200 can be
measured and displayed. Multiple springs or other means of elastic
support coupled with multiple sensing assemblages attached between
the load bearing surfaces enable accurate translation of the extent
and location of the center or focal point (or locus or centroid) of
the load.
[0077] The encapsulated force sensor 900 can accurately and
repeatedly measure one pound changes in load with changes in length
of a waveguide comprising 2.5 microns. The maximum change in the
present implementation is specified at less than 5.0 microns. This
assures that the size of the sensing module 200 throughout all
measurements remains within the required dimension (e.g., distance)
of the insert between the load bearing surfaces of the prosthetic
components.
[0078] An exemplary level of control of the compression or
displacement of the waveguides 910 with changes in load, force,
pressure, or displacement is achieved by positioning the spring or
springs 908 or other means of elastic support, including the
waveguides 910 themselves, between the load bearing contact
surfaces to minimize any tendency of the load bearing contact
surfaces to cantilever. Cantilevering can compromise the accuracy
of the inclination of the load bearing contact surface whenever
load, force, pressure, or displacement is applied to any point near
a periphery of the load bearing contact surfaces. In one
embodiment, springs 908 are disc springs. The spring 908 is held in
a predetermined location by spring post 914 and spring retainer
904.
[0079] The walls of the unitary main body 957 include a small gap
to enable the steel plate 904 to move. The hermetic seal is also
flexible to allow the steel plate 904 of the force sensor 904 to
slide up and down, like a piston, for distances on the order of a
hundred microns without compromising integrity of the seal. The
hermetic seal completes manufacturing, sterilization, and packaging
processes without compromising ability to meet regulatory
requirements for hermeticity. The level of hermeticity is
sufficient to assure functionality and biocompatibility over the
lifetime of the device. Implant devices with total implant time
less than 24 hours may have less stringent regulatory requirements
for hermeticity. Unbiased electrical circuitry is less susceptible
to damage from moisture. The electronics in one embodiment are only
powered during actual usage. In another embodiment, the
encapsulated force sensor 900 employs low duty cycles to serve as a
measurement-on-demand device to efficiently perform at low total
operating time when the electronics are powered on.
[0080] FIG. 9 is a block diagram 1000 of a propagation tuned
oscillator (PTO) 4 to maintain positive closed-loop feedback in
accordance with an exemplary embodiment. The measurement system
includes a sensing assemblage 1 and propagation tuned oscillator
(PTO) 4 that detects energy waves 2 in one or more waveguides 3 of
the sensing assemblage 1. In one embodiment, energy waves 2 are
ultrasound waves. A pulse 11 is generated in response to the
detection of energy waves 2 to initiate a propagation of a new
energy wave in waveguide 3. It should be noted that ultrasound
energy pulses or waves, the emission of ultrasound pulses or waves
by ultrasound resonators or transducers, transmitted through
ultrasound waveguides, and detected by ultrasound resonators or
transducers are used merely as examples of energy pulses, waves,
and propagation structures and media. Other embodiments herein
contemplated can utilize other wave forms, such as, light.
[0081] The sensing assemblage 1 comprises transducer 5, transducer
6, and a waveguide 3 (or energy propagating structure). In a
non-limiting example, sensing assemblage 1 is affixed to load
bearing or contacting surfaces 8. External forces applied to the
contacting surfaces 8 compress the waveguide 3 and change the
length of the waveguide 3. Under compression, transducers 5 and 6
will also be moved closer together. The change in distance affects
the transit time 7 of energy waves 2 transmitted and received
between transducers 5 and 6. The propagation tuned oscillator 4 in
response to these physical changes will detect each energy wave
sooner (e.g. shorter transit time) and initiate the propagation of
new energy waves associated with the shorter transit time. As will
be explained below, this is accomplished by way of PTO 4 in
conjunction with the pulse generator 10, the mode control 12, and
the phase detector 14.
[0082] Notably, changes in the waveguide 3 (energy propagating
structure or structures) alter the propagation properties of the
medium of propagation (e.g. transit time 7). The energy wave can be
a continuous wave or a pulsed energy wave. A pulsed energy wave
approach reduces power dissipation allowing for a temporary power
source such as a battery or capacitor to power the system during
the course of operation. In at least one exemplary embodiment, a
continuous wave energy wave or a pulsed energy wave is provided by
transducer 5 to a first surface of waveguide 3. Transducer 5
generates energy waves 2 that are coupled into waveguide 3. In a
non-limiting example, transducer 5 is a piezo-electric device
capable of transmitting and receiving acoustic signals in the
ultrasonic frequency range.
[0083] Transducer 6 is coupled to a second surface of waveguide 3
to receive the propagated pulsed signal and generates a
corresponding electrical signal. The electrical signal output by
transducer 6 is coupled to phase detector 14. In general, phase
detector 14 compares the timing of a selected point on the waveform
of the detected energy wave with respect to the timing of the same
point on the waveform of other propagated energy waves. In a first
embodiment, phase detector 14 can be a zero-crossing receiver. In a
second embodiment, phase detector 14 can be an edge-detect
receiver. In the example where sensing assemblage 1 is compressed,
the detection of the propagated energy waves 2 occurs earlier (due
to the length/distance reduction of waveguide 3) than a signal
prior to external forces being applied to contacting surfaces.
Pulse generator 10 generates a new pulse in response to detection
of the propagated energy waves 2 by phase detector 14. The new
pulse is provided to transducer 5 to initiate a new energy wave
sequence. Thus, each energy wave sequence is an individual event of
energy wave propagation, energy wave detection, and energy wave
emission that maintains energy waves 2 propagating in waveguide
3.
[0084] The transit time 7 of a propagated energy wave is the time
it takes an energy wave to propagate from the first surface of
waveguide 3 to the second surface. There is delay associated with
each circuit described above. Typically, the total delay of the
circuitry is significantly less than the propagation time of an
energy wave through waveguide 3. In addition, under equilibrium
conditions variations in circuit delay are minimal. Multiple pulse
to pulse timings can be used to generate an average time period
when change in external forces occur relatively slowly in relation
to the pulsed signal propagation time such as in a physiologic or
mechanical system. The digital counter 20 in conjunction with
electronic components counts the number of propagated energy waves
to determine a corresponding change in the length of the waveguide
3. These changes in length change in direct proportion to the
external force thus enabling the conversion of changes in parameter
or parameters of interest into electrical signals.
[0085] The block diagram 1000 further includes counting and timing
circuitry. More specifically, the timing, counting, and clock
circuitry comprises a digital timer 20, a digital timer 22, a
digital clock 24, and a data register 26. The digital clock 24
provides a clock signal to digital counter 20 and digital timer 22
during a measurement sequence. The digital counter 20 is coupled to
the propagation tuned oscillator 4. Digital timer 22 is coupled to
data register 26. Digital timer 20, digital timer, 22, digital
clock 24 and data register 26 capture transit time 7 of energy
waves 2 emitted by ultrasound resonator or transducer 5, propagated
through waveguide 3, and detected by or ultrasound resonator or
transducer 5 or 6 depending on the mode of the measurement of the
physical parameters of interest applied to surfaces 8. The
operation of the timing and counting circuitry is disclosed in more
detail hereinbelow.
[0086] The measurement data can be analyzed to achieve accurate,
repeatable, high precision and high resolution measurements. This
method enables the setting of the level of precision or resolution
of captured data to optimize trade-offs between measurement
resolution versus frequency, including the bandwidth of the sensing
and data processing operations, thus enabling a sensing module or
device to operate at its optimal operating point without
compromising resolution of the measurements. This is achieved by
the accumulation of multiple cycles of excitation and transit time
instead of averaging transit time of multiple individual excitation
and transit cycles. The result is accurate, repeatable, high
precision and high resolution measurements of parameters of
interest in physical systems.
[0087] In at least one exemplary embodiment, propagation tuned
oscillator 4 in conjunction with one or more sensing assemblages 1
are used to take measurements on a muscular-skeletal system. In a
non-limiting example, sensing assemblage 1 is placed between a
femoral prosthetic component and tibial prosthetic component to
provide measured load information that aids in the installation of
an artificial knee joint. Sensing assemblage 1 can also be a
permanent component or a muscular-skeletal joint or artificial
muscular-skeletal joint to monitor joint function. The measurements
can be made in extension and in flexion. In the example, assemblage
1 is used to measure the condyle loading to determine if it falls
within a predetermined range and location. Based on the
measurement, the surgeon can select the thickness of the insert
such that the measured loading and incidence with the final insert
in place will fall within the predetermined range. Soft tissue
tensioning can be used by a surgeon to further optimize the force
or pressure. Similarly, two assemblages 1 can be used to measure
both condyles simultaneously or multiplexed. The difference in
loading (e.g. balance) between condyles can be measured. Soft
tissue tensioning can be used to reduce the force on the condyle
having the higher measured loading to reduce the measured pressure
difference between condyles.
[0088] One method of operation holds the number of energy waves
propagating through waveguide 3 as a constant integer number. A
time period of an energy wave corresponds to energy wave
periodicity. A stable time period is one in which the time period
changes very little over a number of energy waves. This occurs when
conditions that affect sensing assemblage 1 stay consistent or
constant. Holding the number of energy waves propagating through
waveguide 3 to an integer number is a constraint that forces a
change in the time between pulses when the length of waveguide 3
changes. The resulting change in time period of each energy wave
corresponds to a change in aggregate energy wave time period that
is captured using digital counter 20 as a measurement of changes in
external forces or conditions applied to contacting surfaces 8.
[0089] A further method of operation according to one embodiment is
described hereinbelow for energy waves 2 propagating from
transducer 5 and received by transducer 6. In at least one
exemplary embodiment, energy waves 2 is an ultrasonic energy wave.
Transducers 5 and 6 are piezo-electric resonator transducers.
Although not described, wave propagation can occur in the opposite
direction being initiated by transducer 6 and received by
transducer 5. Furthermore, detecting ultrasound resonator
transducer 6 can be a separate ultrasound resonator as shown or
transducer 5 can be used solely depending on the selected mode of
propagation (e.g. reflective sensing). Changes in external forces
or conditions applied to contacting surfaces 8 affect the
propagation characteristics of waveguide 3 and alter transit time
7. As mentioned previously, propagation tuned oscillator 4 holds
constant an integer number of energy waves 2 propagating through
waveguide 3 (e.g. an integer number of pulsed energy wave time
periods) thereby controlling the repetition rate. As noted above,
once PTO 4 stabilizes, the digital counter 20 digitizes the
repetition rate of pulsed energy waves, for example, by way of
edge-detection, as will be explained hereinbelow in more
detail.
[0090] In an alternate embodiment, the repetition rate of pulsed
energy waves 2 emitted by transducer 5 can be controlled by pulse
generator 10. The operation remains similar where the parameter to
be measured corresponds to the measurement of the transit time 7 of
pulsed energy waves 2 within waveguide 3. It should be noted that
an individual ultrasonic pulse can comprise one or more energy
waves with a damping wave shape. The energy wave shape is
determined by the electrical and mechanical parameters of pulse
generator 10, interface material or materials, where required, and
ultrasound resonator or transducer 5. The frequency of the energy
waves within individual pulses is determined by the response of the
emitting ultrasound resonator 4 to excitation by an electrical
pulse 11. The mode of the propagation of the pulsed energy waves 2
through waveguide 3 is controlled by mode control circuitry 12
(e.g., reflectance or uni-directional). The detecting ultrasound
resonator or transducer may either be a separate ultrasound
resonator or transducer 6 or the emitting resonator or transducer 5
depending on the selected mode of propagation (reflectance or
unidirectional).
[0091] In general, accurate measurement of physical parameters is
achieved at an equilibrium point having the property that an
integer number of pulses are propagating through the energy
propagating structure at any point in time. Measurement of changes
in the "time-of-flight" or transit time of ultrasound energy waves
within a waveguide of known length can be achieved by modulating
the repetition rate of the ultrasound energy waves as a function of
changes in distance or velocity through the medium of propagation,
or a combination of changes in distance and velocity, caused by
changes in the parameter or parameters of interest.
[0092] It should be noted that ultrasound energy pulses or waves,
the emission of ultrasound pulses or waves by ultrasound resonators
or transducers, transmitted through ultrasound waveguides, and
detected by ultrasound resonators or transducers are used merely as
examples of energy pulses, waves, and propagation structures and
media. Other embodiments herein contemplated can utilize other wave
forms, such as, light. Furthermore, the velocity of ultrasound
waves within a medium may be higher than in air. With the present
dimensions of the initial embodiment of a propagation tuned
oscillator the waveguide is approximately three wavelengths long at
the frequency of operation.
[0093] Measurement by propagation tuned oscillator 4 and sensing
assemblage 1 enables high sensitivity and high signal-to-noise
ratio. The time-based measurements are largely insensitive to most
sources of error that may influence voltage or current driven
sensing methods and devices. The resulting changes in the transit
time of operation correspond to frequency, which can be measured
rapidly, and with high resolution. This achieves the required
measurement accuracy and precision thus capturing changes in the
physical parameters of interest and enabling analysis of their
dynamic and static behavior.
[0094] These measurements may be implemented with an integrated
wireless sensing module or device having an encapsulating structure
that supports sensors and load bearing or contacting surfaces and
an electronic assemblage that integrates a power supply, sensing
elements, energy transducer or transducers and elastic energy
propagating structure or structures, biasing spring or springs or
other form of elastic members, an accelerometer, antennas and
electronic circuitry that processes measurement data as well as
controls all operations of ultrasound generation, propagation, and
detection and wireless communications. The electronics assemblage
also supports testability and calibration features that assure the
quality, accuracy, and reliability of the completed wireless
sensing module or device.
[0095] The level of accuracy and resolution achieved by the
integration of energy transducers and an energy propagating
structure or structures coupled with the electronic components of
the propagation tuned oscillator enables the construction of, but
is not limited to, compact ultra low power modules or devices for
monitoring or measuring the parameters of interest. The flexibility
to construct sensing modules or devices over a wide range of sizes
enables sensing modules to be tailored to fit a wide range of
applications such that the sensing module or device may be engaged
with, or placed, attached, or affixed to, on, or within a body,
instrument, appliance, vehicle, equipment, or other physical system
and monitor or collect data on physical parameters of interest
without disturbing the operation of the body, instrument,
appliance, vehicle, equipment, or physical system.
[0096] FIG. 10 is a final insert 1102 in accordance with an
exemplary embodiment. In the example, the final insert 1102 is a
prosthetic component for a total knee reconstruction. Insert 1102
comprises two bearing surfaces that couple to the condyles of a
femur or femoral prosthetic component. A bottom surface of insert
1102 couples to a tibial implant. The final insert 1102 is an
active device for measuring a parameter of the muscular-skeletal
system. A sensing module 1104 as disclosed hereinabove underlies
each bearing surface of insert 1102. In one embodiment, a
contacting surface of insert 1102 couples to the bearing surface.
The final insert 1102 is a permanent or quasi-permanent member of
the joint prosthesis that provides long term post-operative sensing
of the joint. Quasi-permanent refers to the fact that insert 1102
has a wear surface that has a finite life time that could need
replacing depending on a number of factors such as life style,
physical shape, and length of use. Final insert 1102 replaces a
passive insert that has no sensing capability. In one embodiment,
an external device proximally located to the knee prosthetics can
inductively charge the sensing module 1104. A super capacitor is
charged in sensing module 1104 that powers the sensor and circuitry
to perform the one or more measurements.
[0097] FIG. 11 is a perspective view of sensing modules 1104 in
final insert 1102 in accordance with an exemplary embodiment. Final
insert 1102 is shown being separated in two halves via a horizontal
cut to show sensing modules 1104. Final insert 1102 is used in a
total knee reconstruction where both knee compartments are
replaced. A single sensing module 1104 would be used for a partial
reconstruction. Bearing surfaces 1204 couple to a femoral
prosthetic component (not shown) such that the articulating
surfaces allow movement of the muscular-skeletal system. In the
example, a bottom surface 1206 of the final insert 1102 aligns and
couples to a tibial prosthetic component. In the example, the
bottom surface 1206 is a support surface that retains insert 1102
in a fixed position relative to a mechanical axis of the leg.
Furthermore, the bottom surface 1206 and a surface of the tibial
prosthetic component are non-articulating.
[0098] Sensing modules 1104 underlie bearing surfaces 1204. A
parameter of the muscular-skeletal system is applied to the bearing
surface 1204 and couples through the material of final insert 1102
to contacting surfaces 1202 of sensing modules 1104. The bearing
surfaces 1204 are typically a high strength polymer such as ultra
high molecular weight polyethylene. In a non-limiting example, a
force, pressure, or load is the parameter measured by sensing
module 1104. Sensing module 1104 can measure parameter magnitude
and the location where the parameter is applied. Sensing module
1104 can have a surface that mirrors or replicates the surface of
bearing surfaces 1204.
[0099] In one embodiment, the final insert 1102 can be precision
molded in two or more pieces that allow the positioning and
insertion of sensing module 1104. As shown, the final insert is
formed in two halves. The upper half includes the bearing surfaces
1204. The insert can be formed of a composite material. The
composite material will at least include the bearing surface
material and a second material that is attached or bonded together.
A cavity is formed in predetermined locations that receive sensing
modules 1104. The cavities correspond to bearing surfaces 1104 for
each compartment of the knee. The sensing modules 1104 are placed
in each cavity. The halves of final insert 1102 are then fastened
together whereby the contacting surface 1202 operatively couples to
a corresponding bearing surface 1204. The contact surfaces 1202
have a relational position to bearing surfaces 1104 allowing
position detection where the parameter is applied. The halves of
final insert 1102 can be mechanically fastened, attached by
adhesive, thermally bonded or connected by other method such that
halves will not separate under all operating conditions. The
fastening process can also form a seal that isolates sensing
modules 1104 from the external environment.
[0100] FIG. 12 is an illustration of the final insert 1102
installed in a knee in accordance with an exemplary embodiment. In
the example, a femoral prosthetic component 1210 is coupled to a
prepared 1214 femur. Similarly, a tibial prosthetic component 1212
is coupled to a prepared tibia 1216. The preparation includes
alignment of the prosthetic components to a mechanical axis. The
insert is placed between the tibial prosthetic component 1212 and
femoral prosthetic component 1210. The artificial condyles of
femoral prosthetic component 1210 articulate with a bearing surface
of final insert 1102 that allows movement of the leg.
[0101] As disclosed above, final insert 1102 includes a sensing
module that can transmit data to a processor 1208. The processor
can be in a tool, equipment, computer, display, or other device. As
shown, the processor is in a notebook computer. Receiver circuitry
is coupled to processor 1208 that can communicate with the sensing
module. Typically, the receiver circuitry is placed in close
proximity to final insert 1102 to receive the short-range
transmission. In one embodiment, the sensing module can only
transmit data. In a second embodiment, the sensing module can have
two-way communication between the sensing module and processor
1208.
[0102] The loading, balance, and position can be adjusted during
surgery within predetermined quantitatively measured ranges through
surgical techniques and adjustments using data from a trial insert
and final insert 1102. Both the trial and final inserts include the
sensing module to provide measured data to processor 1208 for
display. The final insert 1102 is also used to monitor the
reconstructed joint long term. The data can be used by the patient
and health care providers to ensure that the joint is functioning
properly during rehabilitation and as the patient returns to an
active normal lifestyle. Conversely, the patient or health care
provider is notified when the measured parameters are out of
specification. This provides early detection of a problem that can
be resolved with minimal stress to the patient. The data from final
insert 1102 can be displayed on a screen in real time using data
from the embedded sensing module. In one embodiment, a handheld
device is used to receive data from final insert 1102. The handheld
device can be held in proximity to the knee allowing a strong
signal to be obtained for reception of the data.
[0103] In general, final insert 1102 is an example of a sensor
system that can be integrated into prosthetic components. The form
factor of the sensing assemblages, layout architecture, electronic
circuitry, and housing allow it to fit in one or more prosthetic
components. Moreover, it is a self-contained device that performs
the measurement without extraneous devices. The sensing module can
also be placed in femoral prosthetic component 1210 or tibial
prosthetic component 1212 to measure a parameter of interest. Data
generated by the device can be sent to a database for analysis.
[0104] Artificial components for other joint replacement surgeries
have a similar operational form as the knee joint example. The
joint typically comprises two or more bones with a cartilaginous
surface as a bearing surface that allows joint movement. The
cartilage also acts to absorb loading on the joint and prevents
bone-to-bone contact. Reconstruction of the hip, spine, shoulder,
and other joints have similar functioning insert structures having
at least one bearing surface. Like the knee joint, these other
insert structures typically comprise a polymer material. The
polymer material is formed for a particular joint structure. For
example, the hip insert is formed in a cup shape that is fitted
into the pelvis. In general, the size and thickness of these other
joint inserts allow the integration of the sensing module. It
should be noted that the sensing module disclosed herein
contemplates use in both trial inserts and permanent inserts for
the other joints of the muscular-skeletal system thereby providing
quantitative parameter measurements during and post surgery.
[0105] While the present invention has been described with
reference to particular embodiments, those skilled in the art will
recognize that many changes may be made thereto without departing
from the spirit and scope of the present invention. Each of these
embodiments and obvious variations thereof is contemplated as
falling within the spirit and scope of the invention.
* * * * *