U.S. patent application number 12/369693 was filed with the patent office on 2009-12-24 for surgical orientation device and method.
This patent application is currently assigned to Orthalign, Inc.. Invention is credited to Joseph F. Russial, A. Curt Stone.
Application Number | 20090318836 12/369693 |
Document ID | / |
Family ID | 34083197 |
Filed Date | 2009-12-24 |
United States Patent
Application |
20090318836 |
Kind Code |
A1 |
Stone; A. Curt ; et
al. |
December 24, 2009 |
SURGICAL ORIENTATION DEVICE AND METHOD
Abstract
A device for detecting and measuring a change in angular
position with respect to a reference plane is useful in surgical
procedures for orienting various instruments, prosthesis, and
implants with respect to anatomical landmarks. One embodiment of
the device uses three orthogonal rate sensors, along with
integrators and averagers, to determine angular position changes
using rate of change information. A display provides position
changes from a reference position. Various alignment guides are
useful with surgical instruments to obtain a reference plane.
Inventors: |
Stone; A. Curt; (Aspinwall,
PA) ; Russial; Joseph F.; (Pittsburgh, PA) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
Orthalign, Inc.
Laguna Beach
CA
|
Family ID: |
34083197 |
Appl. No.: |
12/369693 |
Filed: |
February 11, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10864085 |
Jun 9, 2004 |
|
|
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12369693 |
|
|
|
|
60476998 |
Jun 9, 2003 |
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Current U.S.
Class: |
600/595 |
Current CPC
Class: |
A61F 2250/0006 20130101;
A61B 2034/2051 20160201; A61B 5/1071 20130101; A61B 17/175
20130101; A61B 2017/00115 20130101; A61F 2002/4668 20130101; A61B
17/1778 20161101; A61F 2002/4632 20130101; A61F 2/34 20130101; A61B
2034/2048 20160201; A61F 2002/30538 20130101; A61F 2002/4687
20130101; A61F 2/4609 20130101; A61B 5/4504 20130101; A61F 2/4657
20130101; A61B 34/20 20160201 |
Class at
Publication: |
600/595 |
International
Class: |
A61B 5/11 20060101
A61B005/11 |
Claims
1. A method of determining angular position change comprising: a.
sensing the presence or absence of motion of a rate sensor; b.
sensing a rate of change of angular position with respect to a
reference using the rate sensor to provide an output that is a rate
signal proportional to the rate of change of angular position of
the rate sensor; c. averaging the output of the rate sensor in the
absence of motion of the rate sensor to provide an average signal
representative of the output of the rate sensor in the absence of
motion of the rate sensor; d. integrating the rate signal when
motion is sensed to provide an integral signal indicative of a
relative angular position experienced by the rate sensor; and e.
presenting the difference between the integral signal and the
average signal as indicative of the change of position of the rate
sensor.
2. The method of claim 1 wherein the integral signal is zeroed
before step d.
3. The method of claim 2 wherein the difference is presented as an
absolute position change occurring after zeroing the integral
signal.
4. The method of claim 1 wherein step e. further comprises
presenting the difference in a visually perceptible format.
5. The method of claim 1 wherein step e. further comprises
presenting the difference in an electronic format.
6. The method of claim 1 further comprising an additional step: a0.
automatically zeroing the integral signal upon initial startup.
7. The method of claim 1 further comprising an additional step: f.
continuing to integrate the rate signal for a predetermined period
of time after motion stops.
8. The method of claim 1 further comprising an additional step: b1.
detecting the presence of motion by determining when there is more
than a predetermined difference between the output of the rate
sensor and the average signal.
9. The method of claim 8 wherein step b1 further comprises
detecting the absence of motion by determining when there is less
than the predetermined difference between the output of the rate
sensor and the average signal.
10. The method of claim 1 further comprising the additional step
of: g. detecting an error condition when the integral signal
exceeds a predetermined maximum value.
11. The method of claim 1 wherein step a. includes providing an
indication of the direction of motion detected.
12. The method of claim 1 wherein step d. includes providing an
indication of the direction of motion detected.
13. The method of claim 1 wherein each of the steps are performed
for each of three mutually orthogonal dimensions.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/864,085 filed Jun. 9, 2004, which is hereby
incorporated by reference in its entirety, which claims benefit
under 35 U.S.C. .sctn. 119(e) to U.S. Provisional Application No.
60/476,998 filed Jun. 9, 2003, which is hereby incorporated by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to medical orientation and
positioning devices and in particular to a device for orienting
surgical instruments, implements, implants, prosthetics, and
anatomical structures.
[0004] 2. Description of the Related Art
[0005] Correct positioning of surgical instruments and implants,
used in a surgical procedure, with respect to the patient's anatomy
is often an important factor in achieving a successful outcome. In
certain orthopaedic implant procedures, such as totals hip
replacement (THR) or arthroplasty, total knee arthroplasty (TKA),
high tibial osteotomy (HTO), and total shoulder replacement (TSR),
for example, the optimal orientation of the surgical implant
enhances initial function and the long term operability of the
implant. A misaligned acetabular prosthetic socket, for example,
can lead to complications such as dislocation of the hip joint,
decreased joint motion, joint pain, and hastened failure of the
implant.
[0006] Obtaining satisfactory orientation and positioning of a
prosthetic implant is often a challenging task for orthopaedic
surgeons. Currently, one technique for orientation and positioning
is accomplished using purely mechanical instruments and procedures
based on anatomical landmarks. For example, the desired anteversion
for an acetabular cup prosthesis within an acetabulum is
accomplished by using external landmarks associated with a
patient's pelvis. These methods, however, are subject to
misalignment caused by variations in these external landmarks.
These variations can be caused, for example, by failing to orient
the patient's pelvis in the assumed neutral position on the
operating table. Other orientation and positioning techniques
involve sophisticated computer imaging systems, which are typically
expensive and complicated to use.
[0007] There is a need in the art for an improved device and method
for obtaining accurate orientation of surgical instruments and
implants during various orthopaedic repair and replacement
procedures. There is a further need for a device that is simple and
easy to operate.
SUMMARY OF THE INVENTION
[0008] The present invention, according to one embodiment is a
surgical instrument for assisting a surgeon in obtaining correct
orientation of an acetabular prosthetic socket in a patient's
acetabulum. The instrument includes a support shaft adapted for
supporting the acetabular prosthetic socket, a three-dimensional
electronic orientation device securely coupled to the support
shaft, and an acetabular alignment guide having at least three
arms, the arms having a length sufficient to each contact a rim of
the acetabulum.
[0009] According to another embodiment, the present invention is an
apparatus for measuring and providing an indication of angular
position with respect to a reference. The apparatus includes a rate
sensor initially positioned with respect to a reference and
operative to measure a rate of change of angular position with
respect to the reference and provide a rate signal proportional to
the rate of change of the angular position. It also includes an
integrator selectively connected to the rate sensor and operative
to integrate the rate signal and to provide an integral signal
indicative of the relative angular position of the rate sensor. It
further includes an averager selectively connected to the rate
sensor and operative to average the rate signal and to provide an
average signal indicative thereof. Finally, it includes a motion
detector connected to the rate sensor and operative to switch the
rate signal to (i) the averager when no motion is detected, and
(ii) the integrator when motion is detected.
[0010] The present invention, in yet another embodiment, is a
method of using an alignment instrument to align a prosthesis with
an implant site. The method includes providing the instrument with
a three dimensional measuring system capable of measuring angular
position changes from a reference position, locating the instrument
at a reference position with respect to the implant site using an
alignment guide to contact the implant site, zeroing the measuring
system while the alignment guide is in contact with the implant
site and in the reference position, replacing the alignment guide
with a prosthetic implant member, and positioning the instrument to
a desired angular orientation with respect to the reference
position using the measuring system to align the prosthesis with
the implant site.
[0011] While multiple embodiments are disclosed, still other
embodiments of the present invention will become apparent to those
skilled in the art from the following detailed description, which
shows and describes illustrative embodiments of the invention. As
will be realized, the invention is capable of modifications in
various obvious aspects, all without departing from the spirit and
scope of the present invention. Accordingly, the drawings and
detailed description are to be regarded as illustrative in nature
and not restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a perspective view of a surgical orientation
device, according to one embodiment of the present invention.
[0013] FIG. 2 is a simplified block diagram of the rate sensor,
system electronics, and display useful in the practice of the
present invention.
[0014] FIG. 3 is a more detailed block diagram of one channel of
three corresponding to the block diagram of FIG. 2.
[0015] FIG. 4 is a still more detailed block diagram of one channel
of the present invention, shown along with additional subsystems of
the present invention.
[0016] FIG. 5 is a key for FIGS. 6 and 7.
[0017] FIG. 6 is a detailed electrical schematic of ROLL, PITCH and
YAW sensors and associated integrator and averager circuitry,
useful in the practice of the present invention.
[0018] FIG. 7 is a detailed electrical schematic of overrange,
overrate, and motion detectors and associated circuitry useful in
the practice of the present invention.
[0019] FIG. 8 is a detailed electrical schematic of the additional
subsystems of FIG. 2.
[0020] FIG. 9 is a wiring diagram for certain parts of the present
invention.
[0021] FIG. 10 is a detailed electrical schematic of an analog to
digital converter and display for the ROLL channel of the present
invention.
[0022] FIG. 11 is a detailed electrical schematic of an analog to
digital converter and display for the PITCH channel of the present
invention.
[0023] FIG. 12 is a detailed electrical schematic of an analog to
digital converter and display for the YAW channel of the present
invention.
[0024] FIG. 13 is a simplified block diagram of an alternative
embodiment of the present invention.
[0025] FIG. 14 is a perspective view of an acetabular alignment
instrument for use in obtaining a desired orientation for a
prosthetic acetabular socket with respect to a patient's
acetabulum, according to one embodiment of the present
invention.
[0026] FIG. 15 is a plan view of the top or distal face of the
alignment guide shown in FIG. 14.
[0027] FIG. 16 shows a perspective view of an attachment base for
attaching the device to the support shaft 304, according to one
embodiment of the present invention.
[0028] FIG. 17 is a perspective view showing the instrument of FIG.
14 used to identify the plane of the acetabular rim.
[0029] FIG. 18 is a perspective view showing the instrument of FIG.
14 used for positioning an acetabular prosthetic socket.
[0030] FIGS. 19A and 19B are flow charts illustrating operation of
an alignment instrument for orientation of an acetabular prosthetic
socket.
[0031] FIG. 20 shows a femoral broaching instrument adapted for
aligning the femoral broach with the greater and lesser trochanter
of the proximal femur.
[0032] FIGS. 21A and 21B are top and side plan views of a femoral
alignment guide.
[0033] FIGS. 22A and 22B are a side plan view and a front plan view
of an implant instrument and alignment guide for identifying the
plane of the glenoid during a TSR procedure.
[0034] FIG. 23 is a flowchart describing the use of the alignment
guide of FIG. 22.
[0035] While the invention is amenable to various modifications and
alternative forms, specific embodiments have been shown by way of
example in the drawings and are described in detail below. The
intention, however, is not to limit the invention to the particular
embodiments described. On the contrary, the invention is intended
to cover all modifications, equivalents, and alternatives falling
within the scope of the invention as defined by the appended
claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0036] FIG. 1 is a perspective view of a surgical orientation
device 10, according to one embodiment of the present invention. As
shown in FIG. 1, the device 10 includes a housing 12, a power
switch 14, displays 18, a zero button 20, and indicator lights 22,
24, and 26. The housing 12 contains the electronic circuitry and
components necessary for device operation. The housing 12 may be
made from any material suitable for use within a surgical field or
patient treatment setting. The device 12 may be either disposable
or reusable.
[0037] The displays 18, in the embodiment shown in FIG. 1, include
a ROLL display 18a, a PITCH display 18b, and a YAW display 18c.
These displays 18 provide an indication of the angular orientation
of the device in three dimensions, which allow the device to
function as a three-dimensional goniometer. The displays 18 may be
a gauge of any type (e.g., analog meter, digital display, color
bar, and thermocouple meter), and may be integrated on the housing
or part of a separate, stand-alone device. The indicator lights
include a wait/ready or RUN indicator 22, a LOW BATTERY indicator
24, and an overrange or ERROR indicator 26. In one exemplary
embodiment, the indicator lights (e.g., LEDs) are integrated on the
housing, to indicate when a positional property of interest, such
as a angle, has been reached and/or not reached and/or
exceeded.
[0038] In one embodiment, the device 10 further includes attachment
straps 28 connected to the housing 12. The straps 28 are configured
to allow attachment of the device 10 to a surgical instrument,
implant, or prosthetic device. In one embodiment, the straps 28 are
replaced with clips adapted for coupling with one or more surgical
instruments. The device 10 may be transferable from instrument to
instrument within an implant system or systems, or may be dedicated
for use with one instrument. In one embodiment, further discussed
below, the device 10 may in addition or in the alternative include
sensors and displays for providing linear positioning information.
Also, the device 10 may include only one or two of the ROLL, PITCH,
and YAW displays 18 and the related circuitry.
[0039] In one embodiment, the device includes the sensors, further
described below, for providing position and orientation signals.
The sensor, for example, may be directly integrated into the body
of the housing 12 or mounted onto the body of the housing 12. The
sensors may be adhered to the housing 12, located inside the
housing 12, or fabricated directly on the surface of the housing
12, for example, by depositing a layer of silicon on the housing 12
by chemical vapor deposition (CVD) or sputtering, and then building
the devices in this silicon layer using techniques common to or
derived from the art of semiconductor or MEMS processing.
[0040] In another embodiment, the device 10 is adapted to receive
orientation and positioning signals from sensors located in an
external device. The device 10 may have receptacles for attachment
to such an external device through direct cable or wireless
communication capabilities such as RF and IR. In that embodiment,
such an external device is attached to the surgical instrument or
prosthetic, and the device 10 is used by the surgeon as an
interface. In one such embodiment, the sensor is connected, via
wireless and/or wired connections, to a computer or other
electronic instrument, which may record or display the sensor
measurements (e.g., temperature), and which may at least partially
control or evaluate the sensor. For example, an auxiliary computer
or other electronic instrument may at least partially control the
sensor by, for example, performing sensor calibration, performing
real-time statistical analysis on the data from the sensor, or
running error detection and correction algorithms on the data from
the sensor.
[0041] In one embodiment, the device 10 includes communication
capabilities for interacting with other equipment, for example, a
computer generated image recreation system. It may, for example, be
incorporated for use with computer aided surgical navigation
systems, such as VectorVision available from BrainLab, Inc. of
Germany, OrthoPilot, available from Aesculap, Inc. of Germany,
HipNav, available from Casurgica, Inc., of Pittsburgh, Pa., and
Navitrack, available from Orthosoft-Centerpulse Orthopedics, of
Austin, Tex. In one such embodiment, data received from a sensor
may be used by the computer system to control and/or modify a
position of an implant. The computer or other electronic instrument
may be configured to activate the appropriate controls or devices
as necessary based on the data received from the sensor. Manual
adjustments may also be made in response to the data received from
the sensor. In another such embodiment, data from the sensor can be
used in a feedback loop with positioning elements (either directly,
via a computer or other electronic instrument, or by manual
control) to maintain a desired property, such as an orientation or
position.
[0042] Upon attachment of the device 10 to a surgical instrument,
an operator, such as a surgeon for example, can use the device 10
to obtain three-dimensional orientation information. This
combination of the device 10 with a surgical instrument is useful
for assisting surgical procedures wherein one anatomical part is
desirably aligned with another anatomical part. For example, when a
limb-to-torso joint replacement is to be performed (e.g., THR or
TSR), it is desirable to orient an implant (such as an acetabular
cup) with the anatomical part within which it is to be implanted
(such as the acetabulum) so that the implant will be properly
positioned. For THR, the acetabular cup is desirably aligned with
respect to the plane of the acetabulum. The present invention
allows a surgeon to establish a reference plane corresponding to
the plane of the acetabulum by positioning the device to physically
align the device with the plane of the acetabulum and then zeroing
the display when the device is aligned with the plane of the
acetabulum to establish the reference plane. From then on, the
device provides three dimensional angular information (ROLL, PITCH,
and YAW) to the surgeon as the device is moved angularly with
respect to the reference plane. FIGS. 2-13 show block diagrams and
schematics illustrating the circuitry of the device 10. FIGS. 14-20
illustrate alignment guides used for identifying the desired
reference plane, along with methods of using the present invention
in joint replacement procedures.
[0043] Referring to FIG. 2, position information is obtained using
an angular measurement and display system 30, preferably having
three RATE SENSOR blocks 32, 34, 36 which measure angular rate of
change and deliver respectively, ROLL, PITCH, and YAW information
to a SYSTEM ELECTRONICS block 38. The SYSTEM ELECTRONICS block
converts the angular rate of change into angular position
information and uses the DISPLAY block 40 to provide ROLL, PITCH,
and YAW information in a human readable form, and additionally or
alternatively, in electronic form for use by other systems, such as
a data logger (not shown). An optional block 41 is shown in FIG. 2
to illustrate the communication capabilities mentioned above. Block
41 represents a communication link which may be as simple as a
wire, or may include an interface which may be wired or wireless,
and may encompass electrical, acoustical (preferably ultrasonic),
radio frequency, or optical communication technologies, all of
which are considered to be within the term "electronic," as that
term is used herein. It is to be understood that block 41
represents an output with the angular orientation and (optionally)
linear position information made available in a machine-readable
(e.g., computer-compatible) format, while block 40 has a human
readable display of the output information in a visually
perceptible format.
[0044] Referring now to FIG. 3, a more detailed block diagram of
one channel, e.g., the ROLL channel 42, may be seen. It is to be
understood that the other two (PITCH and YAW) channels are
preferably identical to the ROLL channel 42. In FIG. 3, dashed line
38 encloses those blocks which form part of the SYSTEM ELECTRONICS
38 for the ROLL channel 42. Furthermore, it is to be understood
that DISPLAY 40 in FIG. 3 refers to the display function for this
channel, i.e., it includes a display of ROLL angular
information.
[0045] For this channel, the RATE SENSOR 32 is preferably a MEMS
(micro-electro-mechanical systems) device that provides angular
rate of change information to a SWITCH block 44 and a MOTION
DETECTOR AND DELAY block 46. SWITCH block 44 receives command
information from the MOTION DETECTOR AND DELAY block 46 and directs
the rate of change information to either an INTEGRATOR block 48 or
an AVERAGER block 50. A ZERO block 52 permits resetting the
INTEGRATOR 48 to a zero output in a manner to be described.
[0046] Referring now also to FIG. 4, a more detailed block diagram
54 shows additional details of one channel (with the ROLL channel
42 used as an example) along with additional supporting functions
of the SYSTEM ELECTRONICS 38. Each channel includes a MOTION
DETECTOR block 56 and a MOTION HOLD-ON DELAY block 58 within the
MOTION DETECTOR AND DELAY functional block 46 which controls the
operation of a relay type switch 60 in SWITCH functional block 44
to switch between INTEGRATE and AVERAGE functions.
[0047] An OVERRANGE DETECTOR block 62 monitors whether the output
of the INTEGRATOR block 48 reaches an OVERRANGE condition
(corresponding to an angular position beyond which the system 30 is
able to measure). An OVERRATE DETECTOR block 64 monitors the output
of RATE SENSOR block 32 and provides an ERROR indication if the
rate exceeds that which the system 30 is able to measure. Each of
the blocks 62 and 64 are coupled to an ERROR LATCH block 66 which
retains the ERROR condition (whether related to range or rate or
both) until reset by the ZERO block 52. A STARTUP CONTROL block 70
monitors a POWER SUPPLY block 72 and the MOTION HOLD-ON DELAY block
58 and provides a WAIT/READY signal at a RUN indicator 22. A LOW
BATTERY DETECTOR block 74 is connected to the POWER SUPPLY 72 and
controls a LOW BATTERY indicator 24.
[0048] Referring now to FIGS. 5, 6, and 7, FIG. 5 is a key to the
electrical circuit schematics shown in FIGS. 6 and 7, which are to
be understood to be joined at line 78. Dot dash line 80 separates
the ROLL channel 42 from a PITCH channel 84. Dot dash line 82
separates the PITCH channel 84 from a YAW channel 86. Since the
components and interconnections are the same for each of channels
42, 84, and 86, only ROLL channel 42 will be described, it being
understood that the same description applies to each of the other
channels, as well.
[0049] ROLL sensor 32 (and the PITCH. and YAW sensors) are each
preferably an ADXRS150 150 degree/second angular rate sensor
(gyroscope) on a single chip, in a MEMS technology, available from
Analog Devices, One Technology Way, P.O. Box 9106, Norwood, Mass.
02062-9106. It is to be understood that the ROLL, PITCH, and YAW
sensors are mounted in a conventional orthogonal 3-dimensional
(x-y-z) orientation. Each sensor produces an output voltage RATEOUT
that is proportional to the angular rate of rotation of that
respective sensor. The output voltage is nominally 2.5 volts for
zero rotation. The zero rotation output (or NULL) voltage varies
from device to device, and with time and with temperature. The
RATEOUT voltage varies above and below NULL for positive and
negative rotational movement, respectively. The RATEOUT scale
factor is typically 12.5 millivolts per degree per second with a
full scale corresponding to 150 degrees per second. The ROLL sensor
RATEOUT signal is also identified as a ROLL RATE signal. It is to
be understood that each sensor responds in one plane only, and
hence three separate sensors are mounted orthogonally to each other
to achieve response in all three conventional mutually
perpendicular (x, y, and z) axes.
[0050] The variation in sensor NULL voltage and the requirement to
accurately process small rates of rotation make it desirable to
establish an automatically self adjusting NULL reference. When the
system is not physically rotating about any of the three x, y, z
axes, the RATEOUT signal is connected through SWITCH block 44 to a
low pass filter to produce an averaged representation of the
RATEOUT voltage. This is the NULL voltage and it adjusts over time
to sensor variations. When angular motion is detected in one or
more of the three x, y, z axes, the SWITCH block (in response to an
INTEGRATE signal [on line 140] from block 58, see FIG. 8) the
RATEOUT signal is switched from the AVERAGER 50 to the INTEGRATOR
48.
[0051] At this time, since the input to the AVERAGER 50 is open
circuited, the AVERAGER circuit 50 then enters a "hold" mode and
retains the most recent previous NULL voltage, using that NULL
voltage as a reference throughout the duration of the motion. The
ROLL channel 42 NULL voltage is buffered by an operational
amplifier 88 and delivered as a ROLL S/H signal. The operational
amplifier integrated circuits 88 in the INTEGRATOR and AVERAGER
circuits 48 and 50 are preferably AD8606 type op amps, available
from Analog Devices. AVERAGER circuit 50 uses a low pass filter
made up of a 2 MEG ohm resistor 90 and a 0.47 microfarad capacitor
92, resulting in a time constant of one second, which has been
found to work well. However, it is to be understood that other part
values and other time constants may be used, while still remaining
within the scope of the present invention. The capacitor 92
preferably has a low leakage and low dissipation factor.
[0052] Angular position is the time integral of rotation rate. When
motion is detected, the SWITCH block transfers the RATEOUT signal
to the INTEGRATOR circuit 48 to compute angular position. The
output of the ROLL INTEGRATOR 48 is available as a ROLL INT signal.
INTEGRATOR circuit 48 uses a 2.7 MEG ohm resistor 94 and a 0.47
microfarad capacitor 96 to perform the integration. The reference
for the integration is the no-motion NULL voltage for that channel.
The capacitor 96 preferably has low leakage and a low dissipation
factor. The integrating resistor 94 in conjunction with capacitor
96 provides a full scale range of over +120 degrees.
[0053] The INTEGRATOR 48 is reset to zero by discharging the
capacitor 96. When the ZERO button 20 is depressed, relay 116 is
energized by the ZERO signal on terminal 118 (see FIG. 8). The
relay 116 discharges capacitor 96 through a 10 ohm resistor 120 to
limit the discharge current.
[0054] Referring now most particularly to FIG. 7, in ROLL channel
42, integrated circuit comparators 98 are preferably LM393 type low
power, low offset voltage comparators, available from National
Semiconductor Corporation, 2900 Semiconductor Drive, P.O. Box
58090, Santa Clara, Calif., 95052-8090. If the sensor 32 is rotated
too fast, the sensor output will saturate and the display would be
incorrect. Similarly if the sensor is rotated through too great an
angle, the integrator will saturate and the display would be
incorrect. OVERRATE and OVERRANGE detectors 64 and 62 are provided
to warn the operator in the event of the occurrence of either or
both of these errors. There are three OVERRATE detectors and three
OVERRANGE detectors, one pair for each of axes x, y, z,
corresponding to ROLL, PITCH, and YAW channels 42, 84, and 86. Each
channel has a window comparator circuit for each of the OVERRANGE
and OVERRATE detectors. The comparators 98 in the OVERRATE circuit
64 provide the OVERRATE signal on a terminal 100, and the
comparators 98 in the OVERRANGE circuit 62 provide the OVERRANGE
signal on a terminal 102. Comparators 98 in circuit 64 monitor and
compare the ROLL RATEOUT signal to a fixed level, and comparators
98 in circuit 62 compare the output of the ROLL INTEGRATOR circuit
48 to a fixed level. When the RATEOUT signal exceeds a
predetermined level, either positive or negative, the window
comparator made up of comparators 98 in the OVERRATE circuit 64
determines that the system is in an OVERRATE error condition. The
threshold is set to approximately 150 degrees per second by a tap
on the voltage divider string 122.
[0055] The output of the ROLL INTEGRATOR circuit 48 is sent to
another window comparator made up of integrated circuit comparators
98 in the ROLL portion or channel of OVERRANGE circuit 62. When the
INTEGRATOR circuit output (ROLL INT) exceeds a predetermined
threshold, the ROLL channel portion of circuit 62 determines that
the system is in an OVERRANGE error condition. The threshold is set
at approximately 120 degrees by a tap on the voltage divider string
122. The twelve comparators in circuits 62 and 64 have open
collector outputs. The six OVERRATE outputs (including the ROLL
OVERATE output at terminal 100) together with the six OVERRANGE
outputs (including the ROLL OVERRANGE output at terminal 102) are
connected together. Both terminals 100 and 102 (i.e., all twelve
comparator outputs) are connected to terminal 104 in the ERROR
LATCH circuit 66 (see FIG. 8) and form the OVER signal. The OVER
signal goes LOW whenever any one of the twelve comparators senses
an error condition. Terminal 104 receives the OVER signal as an
active LOW signal setting a type 74HC74 D type flip flop 150,
available from Fairchild Semiconductor Corporation, 82 Running Hill
Road, South Portland, Me. 04106. The flip-flop 150 is configured as
a SET-RESET memory element. The "Q" output drives the ERROR
indicator 26, which is preferably a red LED. The flip-flop 150 is
reset by the ZERO signal on terminal 118.
[0056] Comparators 98 in the MOTION DETECTOR circuit 56 compare the
output of the ROLL rate sensor 32 to a fixed level and provide a
MOTION signal representative of whether the ROLL rate sensor 32 has
experienced motion or not. When rotational motion is detected, the
RATEOUT signal deviates from the NULL or no-motion voltage. The
RATEOUT signal is sent to a "window" comparator made up of
comparators 98 in the MOTION DETECTOR circuit 56. When the RATEOUT
signal deviates from the NULL voltage by a predetermined amount or
threshold (either positive or negative) the window comparator
detects rotational motion. A threshold of one degree per second has
been found to be preferable, but it is to be understood to be
within the scope of the present invention to use other values, in
the alternative.
[0057] A tap on a voltage divider string 122 sets the ROLL
comparator MOTION thresholds. The divider 122 is connected between
+5A 124 and circuit common 126, with the center point connected to
the NULL voltage (ROLL S/H) line 128. This provides that the
thresholds are referenced to the NULL voltage and compensates for
drift and device-to-device variations in the NULL voltage. The
MOTION signal appears on terminal 106 in MOTION DETECTOR circuit 56
and is connected to corresponding MOTION terminal 106 in the MOTION
HOLD-ON DELAY circuit 58 (see FIG. 8). Each of circuits 56, 62, and
64 are provided with a pair of comparators 98 in the ROLL channel
42 so as to provide a bipolar (+/-) comparator function. All six
MOTION comparators (including ROLL channel comparators 98) in
channels 42, 84 and 86 have open collector outputs which are
connected together via MOTION terminal or line 106. It is to be
understood that the signal on MOTION line 106 will go to a LOW
state whenever any one of the six comparators senses motion.
Referring now also to FIG. 8, and more particularly, to circuit 58,
when the MOTION signal on terminal 106 goes LOW, a 1 microfarad
capacitor 130 will discharge through a 14.8K ohm resistor 132
causing a comparator 134 to deliver a HIGH output on line 136. This
turns on an IRFD 110 type FET transistor 138 which pulls the
INTEGRATE line 140 LOW. The IRFD 110 type FET transistor is
available from International Rectifier at 233 Kansas St. El
Segundo, Calif. 90245 USA
[0058] Comparator 134 is preferably a type LM393. When the
INTEGRATE line 140 goes LOW, the relay 60 in SWITCH block 44
transfers the system from "average" mode to "integrate" mode. A
pair of 143 K ohm resistors 142 and 144 set the threshold voltage
for comparator 134 and a 100 K ohm resistor 146 provides
hysteresis.
[0059] When the angular movement stops, the RATEOUT signal returns
to the NULL voltage. The window comparators return to the
open-collector state, allowing the capacitor 130 to slowly charge
through a 1 MEG ohm resistor 148. The system 30 remains in the
"integrate" mode until capacitor 130 charges sufficiently to switch
comparator 134, which is approximately 0.7 seconds. This allows the
system 30 to register any small movements the operator may make at
the end of a gross movement. Such small movements may not otherwise
be enough to activate the MOTION DETECTOR circuit 56.
[0060] After the 0.7 second delay, comparator 134 switches and the
INTEGRATE line goes HIGH, terminating the "integrate" mode. At this
point the relay 60 releases and the mechanical shock of the release
is sensed by at least one of the sensors causing a noise output on
one or more RATEOUT lines. This noise output can be large enough to
retrigger the MOTION DETECTOR circuit 56, resulting in continuous
cycling of relay 60. Such undesirable cycling is prevented by
resistor 132 delaying discharge of capacitor 130 until the
transient noise caused by the relay release has passed.
Alternatively, relay 60 may be shock mounted.
[0061] Referring now again to FIG. 8, the STARTUP CONTROL circuit
70, POWER SUPPLY circuit 72, and LOW BATTERY DETECTOR circuit 74
may be seen. The STARTUP CONTROL circuit 70 has four functions. It
generates a master reset pulse to initialize the system at power
on. It provides a three minute warm-up period for the sensors. It
enforces the requirement that the sensors not be moving for 10
seconds at the end of the warm-up period (to set the "no-motion"
reference). It also gives the user feedback about the system status
via the WAIT/READY status of the RUN indicator 22.
[0062] An LM 393 type comparator 172 generates a master reset
pulse. The pulse is active LOW, with a pulse width of approximately
0.6 seconds, determined by a 1 microfarad capacitor 174 and a 475K
ohm resistor 176. The pulse width is selected to be long enough to
fully discharge a 10 microfarad capacitor 178 (through a diode 180
and a 1K ohm resistor 182) and at least partially discharge a 390
microfarad capacitor 184 (through a diode 186 and a 1K ohm resistor
188). The discharge of capacitors 178 and 184 is necessary to
handle the situation where the system 30 is turned OFF and then
immediately turned ON again. A 1N5817 type diode 190 protects
comparator 172 and quickly discharges capacitor 174 on power down.
A 15.0K ohm resistor 192 and a 34.8K ohm resistor 194 provide the
reference voltage for comparator 172, and a 475K ohm resistor 196
provides hysteresis.
[0063] The master reset pulse also clears a WAIT/READY flip flop
198, which is preferably a 74HC74 type D flip flop. Flip flop 198
is cleared during the warm-up or WAIT period and is SET when the
system 30 enters the READY state. Flip flop 198 drives the RUN
indicator 22, which is preferably a yellow/green two color LED
driven differentially by the Q and Q-not outputs at pins 5 and 6 of
the device 198. Indicator 22 is preferably illuminated YELLOW
during the WAIT or warm-up period, and switches to a GREEN
illumination when the system enters the READY mode. A 392 ohm
resistor 200 provides current limiting for the RUN indicator
22.
[0064] A 10K ohm resistor 202 connected to the Q output (pin 5) of
flip flop 198 provides an input to the FET transistor 138 which
serves as a relay driver for relay 60. When the system is in the
WAIT mode or warm-up period, the input provided through resistor
202 forces the system to the AVERAGE mode by connecting the sensors
to the AVERAGER amplifiers, since the Q output remains LOW during
the warm-up period.
[0065] An LM 393 comparator 204 is the warm-up timer. A 221K ohm
resistor 206 and capacitor 184 set the duration of the warm-up
period. At the end of the warm-up period, the output (at pin 7) of
comparator 204 goes to an open collector condition. This clocks the
WAIT/READY flip flop 198 into the READY state, provided that 10
seconds have elapsed with no motion at the end of the warm-up
period.
[0066] The 10 second "no-motion" requirement is enforced by a 10
second timer, which uses an LM 393 type comparator 208. The 10
second timer monitors the MOTION signal on line 106 (buffered
through another LM 393 type comparator 210). If any of the sensors
detect motion, capacitor 178 will be held discharged by comparator
210 acting through a diode 212 and a 475 ohm resistor 214. When
none of the sensors detect motion, capacitor 178 will begin to
charge through a 1.00 MEG ohm resistor 216. If no motion is
detected for 10 seconds, the output (at pin 1) of comparator 208
will go to an OPEN condition, releasing the CLOCK input (at pin 3)
of flip flop 198. The result is that the WAIT/READY flip flop is
SET only after both the warm-up period has elapsed, and the system
30 has not detected motion for 10 seconds.
[0067] The POWER SUPPLY circuit 72 utilizes two integrated circuit
voltage regulators 110 preferably LM2931 type, available from
National Semiconductor Corporation. Regulators 110 and 112 each
provide regulated +5 volts DC power to the various circuits shown.
Regulator 110 provides power to digital circuits in system 30
(indicated by "+5D") and regulator 112 provides power to the analog
circuits (particularly amplifiers 88, as indicated by "+5A). The
sensors, (including ROLL sensor 32) require both analog and digital
power. Separate analog and digital circuit common paths or "ground"
traces are used to segregate analog and digital power supply
currents, with the exception that only the analog ground is taken
to the printed circuit board(s) (not shown) on which the sensors
are mounted, because the digital currents are low in the sensors. A
9 volt battery 272 (see FIG. 9) provides power to the regulators
110, 112 and also to various other components and subcircuits, such
as comparators 98 and A/D converter 114 (shown in FIG. 10). A diode
152 protects against reverse battery polarity.
[0068] An LM393 type comparator 154 is used for the LOW BATTERY
DETECTOR 74. When the battery voltage drops below approximately 6.8
volts, comparator 154 switches, driving the signal on the BATLOW 2
terminal 156 LOW, turning on the BATTERY LOW indicator 24, which is
preferably a red LED. The LED is supplied through a 392 ohm
resistor 158. A precision voltage reference diode 160 sets a
reference voltage at the "-" input (pin 2) of comparator 154 to 1.2
volts. A 100K ohm resistor 162 and a 21.5K ohm resistor 164 set the
voltage at the "+" input (pin 3) of comparator 154 to 1.2 volts
when the battery voltage is 6.8 volts. A 10 microfarad capacitor
166 delays the rise of the reference voltage at pin 2 of comparator
154 to force the comparator output voltage at the BATLOW 2 terminal
156 HIGH at power on. A diode 168 and a 57.6K ohm resistor 170
provide hysteresis to lock the output 156 in a LOW state once a low
battery condition is detected. This prevents the BATTERY LOW
indicator 24 from cycling ON and OFF in response to changing
current demands on the battery 272, causing the battery voltage to
fluctuate above and below 6.8 volts.
[0069] FIG. 8 also includes the details of the ZERO block or
circuit 52. A CD4093 type NAND Schmitt Trigger integrated circuit
has a NAND gate 218 driving an IRFD 110 type FET transistor 220
which energizes relay 116 for the ZERO function (see FIG. 6). One
input (at pin 9) of NAND gate 218 is connected to the Q output (at
pin 5) of the WAIT/READY flip flop 198. This holds the system 30 in
the ZERO state or condition during the warm-up period. When the
system enters the READY mode, the ZERO condition is cleared and the
INTEGRATOR circuit 48 is enabled. Manual ZERO is accomplished by
closing a ZERO switch 224 (see FIG. 9) which is connected between
circuit common ("GND") and an input at pin 8 on NAND gate 218.
Pushing the ZERO button closes switch 224, connecting the pin 8
input of NAND gate 218 to circuit common, at which time NAND gate
218 turns on transistor 220. When the switch 224 is released, it
opens, allowing a 0.33 microfarad capacitor 228 to charge through a
750K ohm resistor 230, producing a ZERO pulse of at least 250
milliseconds.
[0070] When the system 30 detects motion, the user is given visual
feedback by flickering the RUN indicator 22 with GREEN
illumination. NAND gates 232 and 234 (also type CD4093) form a
square wave oscillator with a period of about 50 milliseconds. When
motion is detected, the oscillator is enabled by comparator 134
releasing the input at pin 1 of gate 232 to go HIGH. The oscillator
output (at pin 4 of gate 234) drives an IRFD 110 type FET
transistor 236. When transistor 236 is ON, it increases the current
in the RUN indicator LED 22 by providing a path to circuit common
through a 392 ohm resistor 238. The transistor 236 is turned ON and
OFF every 50 milliseconds while the system senses motion, providing
a visually perceptible feedback or indication to the user that the
system 30 is sensing motion.
[0071] Referring now to FIG. 9, a wiring diagram for connection of
various parts to the STARTUP CONTROL 70 and ZERO block 52 of system
30 may be seen. It is to be understood that the connections shown
correspond to the lowermost connections on the right hand side of
FIG. 8. A power switch 14 may be used to provide ON-OFF control of
the system 30. Battery 272 is preferably a 9 volt battery. The ZERO
switch 224 is preferably a normally OFF, momentary ON, spring
return pushbutton type switch.
[0072] Referring now to FIG. 10, a portion 240 of the DISPLAY block
40 for the ROLL channel 42 may be seen. The output of the ROLL
INTEGRATOR block and circuit 48 is provided on a ROLL INT terminal
or line 242. The output of the ROLL AVERAGER block and circuit 50
is provided on a ROLL S/H terminal or line 244. The ROLL INT and
ROLL S/H signals are provided to the analog to digital converter
integrated circuit 114 which is preferably a TC7106 type 31/2 digit
A/D converter, available from Microchip Technology, Inc., 2355 West
Chandler Blvd., Chandler, Ariz. 85224-6199. The A/D converter 114
contains all the circuitry necessary for analog to digital
conversion and also provides decoded outputs for a 31/2 digit LCD
display. The ROLL S/H signal is provided to the (-) analog input
and the ROLL INT signal is provided to the (+) input of the A/D
converter 114. The A/D inputs are thus seen to be connected
differentially between the NULL reference voltage and the
INTEGRATOR output. The A/D converter is preferably scaled to
display the output in mechanical degrees of rotation. The least
significant digit output provides tenths of degrees and is not
used. The three most significant digit outputs provide "degrees,
tens of degrees, and 100 degrees" respectively. The digital decoded
outputs from the A/D converter are connected to a visually
perceptible digital display 18a, preferably a S401C39TR type LCD
display available from Lumex, Inc. of 290 East Helen Road,
Palatine, Ill. 60067. The digital display 18a simultaneously
displays degrees, tens of degrees, 100 degrees, and either a
positive or negative sign to indicate direction of rotation from
the ZERO condition or position. A 10K ohm potentiometer 248
provides a single system calibration adjustment for the ROLL
channel 42.
[0073] Referring now to FIGS. 11 and 12, it may be seen that the
PITCH and YAW portions 250 and 260 the DISPLAY block 40 are
essentially identical to the' ROLL portion 240, each with their own
A/D converters 252 and 262 and LCD displays 18b and 18c,
respectively. It is to be understood that DISPLAY block 40 include
the ROLL, PITCH, and YAW displays 18a, 18b, and 18c, and in this
embodiment also includes A/D converters 114, 252, and 262.
[0074] It is to be understood that the ROLL, PITCH, and YAW data
(either in analog or digital form) may be delivered to other
circuitry and systems (not shown) in addition to (or as an
alternative to) the DISPLAY block 40. For example, the digital data
representing the final ROLL, PITCH, and YAW angle selected with
respect to the reference plane may be recorded by a data logger
(not shown) if desired. Furthermore, it is to be understood that
data may be provided in serial form as well as in parallel form,
using conventional circuitry to produce serial digital data from
either the analog values or parallel digital values.
[0075] Referring now to FIG. 13, an alternative embodiment of the
present invention may be seen in a software block diagram 280. In
this embodiment, rate sensor 32 has an output that is immediately
converted to digital form by an A/D converter 282 (which may be the
same or different than A/D converter 114. The A/D converter output
is then provided to a microprocessor-based system 284 which
delivers the ROLL, PITCH and YAW information to a DISPLAY 286 which
may be the same or different than display 40. This embodiment may
also provide the ROLL, PITCH and YAW information to other circuitry
or systems (not shown).
[0076] In the embodiment of the present invention including
accelerometers, the device 10 can be utilized independently or in
conjunction with gyroscopes or other sensors to provide three
dimensional positional orientation with or without angular change
for applications such as osteotomies, placing screws in the
pedicle, bone cuts/preparation during total joint arthroplasties,
disc replacement, and position of tunnels for ligament and tendon
repairs. One sensor useful as an accelerometer, either in
combination with the gyroscopic sensors, or independently, is an
Analog Devices type ADXL103 accelerometer, which may be used in
place of device 32 to detect linear acceleration which is then
integrated to obtain linear position (which may be replicated in
three orthogonal channels along x, y and z axes). With the ADXL103
type devices, it is believed preferable to include the motion
sensing and averaging aspects shown and described herein, to remove
device-to-device errors, as is done with the gyroscopic type rate
sensors. It is to be understood that if an accelerometer is used to
obtain linear position information, two integrations (from
acceleration to velocity to position) are needed.
[0077] In another embodiment, the device 10 further includes
additional sensors such as temperature, ultrasonic, and pressure
sensors, for measuring properties of biological tissue and other
materials used in the practice of medicine or surgery, including
determining the hardness, rigidity, and/or density of materials,
and/or determining the flow and/or viscosity of substances in the
materials, and/or determining the temperature of tissues or
substances within materials. Specifically these additional sensors
can, for example, identify the margins between cortical and
cancellous bone, determine the thickness of cancellous bone,
monitor temperature of cement for fixating implants, and
differentiate between nucleus pulposis and annulus of a spinal
disc. Also, these sensors can identify cracks/fractures in bone
during placement of implants such as pedicle screw placement, screw
fixation in bone, femoral implant during THA, and identify
tissue-nerve margins to determine proximity of nerves.
[0078] FIG. 14 shows an acetabular alignment instrument 300 for use
in obtaining a desired orientation for a prosthetic acetabular
socket with respect to a patient's acetabulum, according to one
embodiment of the present invention. The use of such an instrument
for orthopaedic hip procedures, such as THR, is well known in the
art. One such instrument, for example, is disclosed in U.S. Pat.
No. 6,743,235, which is hereby incorporated by reference. The
instrument 300 can be any instrument known for the placement and
orientation of acetabular components, including the preparation
instruments for THR procedures.
[0079] As shown in FIG. 14, the instrument 300 includes a handle
302, a prosthetic support shaft 304, an orientation shaft 306, the
surgical orientation device 10, and an anatomic benchmark alignment
guide 308. As shown, the surgical orientation device 10 is securely
attached to the support shaft 304, such that the device 10 moves in
concert with the support shaft 304. As further shown in FIG. 14,
the orientation shaft 306 includes an orientation guide 310, which
may be used by a surgeon for manually orienting an implant or
prosthetic. In one embodiment, the instrument 300 does not include
an orientation guide 310. The support shaft 304 has external
threads 314 at a distal end. The threads 314 are adapted to mate
with corresponding internal threads 316 on the alignment guide 308,
such that the alignment guide is releasably attachable to the
support shaft 304.
[0080] FIG. 15 is a plan view of the top or distal face of the
alignment guide 308. As shown, the alignment guide 308 includes a
body portion 318 and wings or arms 320a, 320b, and 320c, which are
disposed generally in the same plane. The body portion 318 includes
internal threads 316 for mating with the support shaft 304. In one
embodiment, the arms 320 secured at points 320 degrees apart around
the circumference of the body portion 318 by pivots 324a, 324b, and
324c. The pivots 324 allow for slight in-plane rotation of the arms
320 where necessary, for example to avoid contact with an
anatomical aberration as the lip of the acetabulum. In another
embodiment, the arms 320 are fixed to the body portion 318 such
that they cannot pivot. In a further embodiment, the pivots 324 are
located at any point along the arms 320.
[0081] As further shown, the arms 320 include an inner arm 326 and
an outer arm 328, which are coupled to each other such that the
outer arms 328 can telescope or extend with respect to the inner
arms 326. This telescoping action allows the surgeon to adjust the
length of the arms 320, based on the diameter of a particular
patient's acetabulum. In another embodiment, the arms 320 are made
from a unitary piece and thus are not amenable to a length
adjustment. The distal ends of the arms 320 define an outer
diameter of the alignment guide 308. The arms 320, in one
embodiment, have a length of from about 40 to about 70 mm, with
each arm 320 having the same length. The length of the arms is
driven by the diameter of a particular patient's acetabulum, such
that the outer diameter of the alignment guide is slightly larger
(e.g., 1-3 mm) than the diameter of the acetabulum. In various
exemplary embodiments, the arms 320 have a length of 48, 52, 56,
60, or 64 mm. In one embodiment, the arms 320 have a width of from
about 2 to about 5 mm and a thickness of from about 1 to about 3
mm. In one exemplary embodiment, the arms have a width of about 3.5
mm and a thickness of about 2 mm.
[0082] FIG. 16 shows a perspective view of an attachment base 332
for attaching the device 10 to the support shaft 304. As shown in
FIG. 16, the attachment base 332 includes a body 334 and a brace
336. The body 332 is dimensioned to generally mate with the
dimensions of the housing 12 of the device 10. In one embodiment,
the body 334 includes mounting tabs 338 for mating with the housing
12 and fixing the position of the device 10 with respect to the
attachment base 332. In one embodiment, the body 334 includes a
groove 339 shaped to mate with the outer surface of the support
shaft 304. This configuration increases the surface contact between
the attachment bases 332 and the support shaft 304, which enhances
fixation of the two components. In one embodiment, the body 334
includes holes 340 for accepting a fastener, such as string, wire,
spring wire, a strap, a hook and loop fastener, or any other
fastener. The fastener is used to fix the body 334 to the support
shaft 304. The brace 336 includes a curve 342 configured to accept
the outer surface of the orientation shaft 306. The attachment base
332 is attached to the instrument 300 by placing the body 334 on
the support shaft 304 and the curve 342 of the brace 336 against
the orientation shaft 306. In this position, the brace 336 resists
rotation of the attachment base 332 around the circumference of the
support shaft 304.
[0083] FIG. 17 shows the instrument 300 during use. As shown, the
instrument 300 is in contact with a portion of the pelvic bone 350.
Specifically, the alignment guide 308 is contacting the acetabular
rim 352 of the acetabulum 354. As shown, the arms 320 have a length
sufficient to reach the acetabular rim 352. As shown in FIG. 18,
the support shaft 304 is also adapted to mate with a ball support
360, which is used to support an acetabular prosthetic socket
362.
[0084] FIG. 19 is a flowchart illustrating an acetabular alignment
process 370 for using the alignment instrument 300 to orient an
acetabular prosthetic socket 362. As shown, the process 370
includes powering on the device using the power switch 14 and
attaching the device to the shaft of the alignment instrument 300
(block 372). The alignment guide 308, having the appropriate
diameter, is then attached to the end of the support shaft 304
(block 374). After preparation of the surgical site according to
standard procedures, the instrument 300 is placed into the surgical
site, such that the alignment guide 308 is resting on the rim 352
of the acetabulum 354 (block 376). In one embodiment, the center of
the alignment guide 308 is generally aligned with the center of the
acetabulum 354 and the arms are place on the rim 352 of the
acetabulum 354, as follows. A first arm is placed on the most
superior point of the acetabulum, a second arm is positioned at the
lowest point of the acetabular sulcus of the ischium, and a third
arm is positioned at the saddle point at the confluence between the
illiopubic eminence and the superior pubic ramus. In the absence of
a significant acetabular rim, the above anatomic landmarks may be
used to identify the plane of the acetabulum.
[0085] According to one embodiment, as described above, the arms
320 are adjusted in length by the surgeon using a telescoping
action. In another embodiment, the surgeon may need to pivot the
arms 320 to avoid an osteophyte or other surface aberration on the
rim 352 of the acetabulum 354. Once the alignment guide 308 is
correctly positioned on the rim 352 of the acetabulum, the surgeon
depresses the zero button 20 to set the reference plane (block
378).
[0086] After zeroing the device 10, the surgeon removes the
instrument 300 from the surgical patient's body. The alignment
guide is then removed and the ball support 360 and prosthetic
socket 362 are attached to the support shaft 304 (block 380). The
surgeon then places the prosthetic socket 362 into the acetabulum
354 using the instrument 300 (block 382). The surgeon then
manipulates the orientation of the prosthetic socket 362 in the
acetabulum 354 using the instrument 300, until the device 10
indicates the desired orientation (block 384). In one embodiment,
for example, the surgeon manipulates the instrument 300 until the
displays 18 on the device indicate an anteversion of 25 degrees. In
this embodiment, the ROLL display 18a indicates "25" and the PITCH
display 18b and YAW display 18c indicate zero. Next the prosthetic
socket 362 is secured to the acetabulum 354 (block 386).
[0087] In other embodiments, the device 10 is used on other
acetabular instruments to identify the orientation of the
instrument with respect to a previously set plane of the
acetabulum. When the implant is in the neutral position the
information provided by the device may, for example, be in the form
of angular measurements to identify information such as rotation,
abduction and version angles. In the embodiment of the present
invention that includes accelerometers or other sensors for
providing linear positioning information, the device 10 also
provides information on position changes in linear dimensions to
identify properties such as depth of insertion and changes in
center of rotation. The instrument 300, including the device 10 is
capable of sub-millimeter and sub-degree accuracy to monitor the
position and angle with reference to the pelvis. It can provide
continuous measurements of cup abduction and flexion angles. These
angles may be provided during placement of the preparation
instruments, the insertion of the implant, after it is placed and,
if needed, after placement of supplementary screws.
[0088] FIG. 20 shows a femoral implant instrument 400 for aligning
the femoral implant with the greater and lesser trochanter of the
proximal femur. The instrument 400 may be, for example, a femoral
implant insertion instrument, a femoral rasp, or a femoral
broaching instrument. As shown in FIG. 20, the instrument 400
includes a handle 404, a rasp or broach 408, a femoral alignment
guide 430, and the device 10. The instrument 400 is used to clear
and shape the cancellous bone surrounding the canal of the proximal
femur 414. The broach 408 is releasably coupled to the handle 404,
such that the surgeon can readily change the broach 408 to one of a
different size. The broach 408 is shown in FIG. 20 with the cutting
segment embedded in the femur 414. In one embodiment, the
instrument 400 is a femoral broaching instrument such as Broach
Handle #4700-RH02, available from Wright Medical Technology, Inc.
of Arlington, Tenn. In other embodiments, the broach 408 is any
other rasp or broach known in the art. As shown, the guide 430 is
placed on the body 404 at the desired reference point and attached
using the locking mechanism 432. As further explained below, the
surgeon may use the guide 430 by aligning it with the greater
trochanter 418 and the lesser trochanter 422 at a proximal end of
the femur 414.
[0089] FIGS. 21A and 21B are top and side plan views of a femoral
alignment guide 430. As shown, the guide 430 includes a mounting
ring 432, a lesser trochanter alignment arm 434, and a greater
trochanter alignment arm 436. The alignment arms 434 and 436 extend
in generally opposing directions from the mounting ring 432. As
shown in FIG. 21B, the alignment arms 434 and 436 include angles
ends 438 and 440, respectively. The angled ends 438 and 440 are
usable by the surgeon to align the guide 430 with respect to the
patient's anatomy. The mounting ring 432 includes a locking screw
442 for securing the guide 430 to the instrument 400. In one
exemplary embodiment, the greater trochanter alignment arm 436 has
a length (l.sub.2) of about 40 percent of a length of the lesser
trochanter alignment arm 434. In one embodiment, the lesser
trochanter alignment arm 434 has a length (l.sub.1) of between
about 85 and about 105 mm. In one embodiment, the alignment arm 434
has a length (l.sub.1) of about 95 mm. In one embodiment, the
mounting ring 432 has an internal diameter (.beta.) of between
about 35 and 45 mm. The specific dimensions of the alignment guide
will depend upon the size of the handle 404 and the patient's
proximal femur 414.
[0090] The femoral alignment guide 430 is used to align the femoral
implant by referencing the lesser and greater trochanter of the
proximal end of the femur. The guide 430 can also be used to mark
the lesser or greater trochanter, or any other point marked by the
surgeon, to fix the predetermined/measured angle of the preparation
instruments or implant. The surgeon may then move the femur without
disrupting his measurement of the chosen anteversion. In one
embodiment, the guide 430 is attached to a femoral broaching
instrument. The guide 430 is placed at the desired angle and the
device 20 is set to zero. For example, the guide 430, in one
embodiment, is generally aligned with a center of the greater
trochanter 418 and the lesser trochanter 422. The surgeon then
turns the instrument 400 to the desired anteversion (e.g., 10
degrees), by using the ROLL display 18a of the device 10. The
surgeon then loosens the guide 430, rotates it such that the arms
434 and 436 are again generally aligned with the greater trochanter
418 and the lesser trochanter 422, and secures the guide 430 to the
handle 404. The surgeon then drives the instrument 400 into the
canal at this orientation and repeats this procedure with a larger
broach 408, as needed, using the guide 430 to achieve the desired
alignment.
[0091] The present invention is also useful in assisting a surgeon
with a TSR procedure. In a shoulder replacement, one of the steps
is placing a glenoid implant into the glenoid of the patient's
scapula. One such glenoid implant is described in U.S. Pat. No.
6,679,916, which is hereby incorporated by reference. Another step
of the TSR procedure is placement of the humeral implant. The
device 10 of the present invention is useful for assisting a
surgeon in achieving proper orientation of the glenoid implant with
respect to the glenoid vault and for achieving proper orientation
of the humeral implant. The device 10, for example, can be attached
to a T-handle or a drill commonly used by the surgeon with the
glenoid planer. The device 10, in further embodiment, can be
attached to a tapered reamer used for reaming the humeral canal or
to a humeral head cutting guide.
[0092] FIG. 22A shows a side plan view of a glenoid implant
insertion instrument 500 for use in orientation of a glenoid
implant. As shown, the insertion instrument 500 includes a shaft
504 and an alignment guide 510. FIG. 22B shows a front plan view of
the alignment guide 510. As shown, the alignment guide 510 includes
an upper arm 512, a lower arm 514, an anterior arm 516, and a
posterior arm 518, which are attached to a hub 520. The arms are
sized such that they span the glenoid rim for a particular
patient.
[0093] FIG. 23 is a flowchart illustrating a glenoid implant
alignment process 550 for using the implant insertion instrument
500 to orient a glenoid implant. As shown, the process 550 includes
securely attaching the device 10 to the shaft of an implant
insertion instrument 500 or glenoid planing instrument (block 554).
The alignment guide 510 is attached to the end of the instrument
where the glenoid implant is normally attached (block 556). The
guide 510 is placed on the rim of the glenoid, such that the upper
arm is placed at the most superior position of the rim, and the
anterior and posterior arms are generally aligned in the center of
the superior/posterior glenoid (block 558). Again, the arms may be
adjusted to avoid significant osteophytes. The "zero" switch is
then depressed to set the displays 18 on the device 10 to zero,
which sets the reference plane (block 560). The alignment guide 510
is removed and the glenoid implant is attached to the insertion
instrument 500 (block 562). Finally, the surgeon uses the displays
18 on the device 10 to achieve desired orientation and/or
positioning of the glenoid implant (block 564). The surgeon then
fixes the glenoid implant in the desired location.
[0094] In yet another embodiment, the device 10 is used by a
surgeon to facilitate TKA. For TKA, the device 10 may be affixed to
the initial guides commonly used by surgeons, to enable more
accurate alignment than that provided by the existing guides. In
various exemplary embodiments, the device 10 can be affixed to the
cutting blocks to provide more accurate rotational alignment,
varus/valgus alignment, and level of resection. The device 10 can
also be affixed to any other instruments known in the art and
commonly employed in a TKA procedure.
[0095] With respect the instruments described above, which include
sensors for providing orientation and/or position information, the
sensors may include a sensor configured to make a measurement
related to the at least one property at multiple locations on or in
the instrument or implant. According to one embodiment, the sensor
includes a plurality or an array of sensors to measure one or more
properties over multiple points, angles, distance, areas, or any
combination thereof.
[0096] Various modifications and additions can be made to the
exemplary embodiments discussed without departing from the scope of
the present invention. Accordingly, the scope of the present
invention is intended to embrace all such alternatives,
modifications, and variations as fall within the scope of the
claims, together with all equivalents thereof.
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