US 20090318836 A1
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.
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
3. The method of
4. The method of
5. The method of
6. The method of
a0. automatically zeroing the integral signal upon initial startup.
7. The method of
f. continuing to integrate the rate signal for a predetermined period of time after motion stops.
8. The method of
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
10. The method of
g. detecting an error condition when the integral signal exceeds a predetermined maximum value.
11. The method of
12. The method of
13. The method of
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. § 119(e) to U.S. Provisional Application No. 60/476,998 filed Jun. 9, 2003, which is hereby incorporated by reference in its entirety.
1. Field of the Invention
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.
2. Description of the Related Art
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.
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.
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.
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.
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.
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.
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.
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.
The displays 18, in the embodiment shown in
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.
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.
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.
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.
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.
Referring now to
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.
Referring now also to
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.
Referring now to
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.
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
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.
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.
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
Referring now most particularly to
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
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.
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
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.
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.
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.
Referring now again to
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.
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.
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.
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.
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.
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
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.
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.
Referring now to
Referring now to
Referring now to
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.
Referring now to
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.
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.
As shown in
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.
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).
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 18 a indicates “25” and the PITCH display 18 b and YAW display 18 c indicate zero. Next the prosthetic socket 362 is secured to the acetabulum 354 (block 386).
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.
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 18 a 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.
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.
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.
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.
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.