Orthopedic navigation system with sensorized devices

A low-cost and compact electronic device toolset is provided for orthopedic assisted navigation. The toolset comprises wireless sensorized devices that communicate directly with one another. A computer workstation is an optional component for further visualization. The sensorized devices are constructed with low-cost transducers and are self-powered. The toolset is disposable and incurs less hospital maintenance and overhead. As one example, the toolset reports anatomical alignment during a surgical workflow procedure. Other embodiments are disclosed.

BACKGROUND

The present disclosure relates generally to orthopedic medical devices, and more specifically to input pointing devices and assisted navigation surgical tools.

Input pointing devices permit pointing to a point of interest. Within a navigation system its utility is a function of the sensing technology. An optical camera system generally processes captured images to determine the pointed location. An electromagnetic system generally evaluates changes in magnetic field strength. An ultrasonic sensing system evaluates received ultrasonic waveforms.

As one example, an optical navigation system can be used for a knee replacement surgery. A total knee replacement is a surgical procedure whereby the diseased knee joint is replaced with artificial material and prosthetic components. The knee is a hinge which provides motion at the point where the femur meets the tibia. During a total knee replacement, the distal end of the femur bone is removed and replaced with a femoral component. The proximal end of the tibia is also removed and replaced with a tibial component. Depending on the condition of the kneecap portion of the knee joint, a button may also be added under the kneecap surface.

During total knee replacement surgery it is imperative that the bone cuts on the femur and tibia are made to result in proper alignment. The alignment ensures proper balance and straightness of the leg. The bone cuts can be made with use of physical guides and jigs, and more recently, by way of highly accurate computer assisted systems. Commercial CAS systems are based on specific sensing principles (e.g., active or passive optical or electromagnetic) where precise intra-operative orientation is provided by high-resolution imaging techniques (e.g., computed tomography (CT), magnetic resonance imaging (MRI)). These systems generally require the placement of fiducial markers, CT or MRI imaging, data transfer to the operating room (OR), and identification and registration of the fiducials. They are also sensitive to deviations in light intensity, contrast, and reflections. When performing these preparatory and practice steps, each platform has individual needs and a number of potential deficiencies influencing the accuracy of the system.

CAS platforms generally consist of three main parts: a computer workstation, a position interface (e.g., camera system) and a passive instrument pointer. The computer workstation is the hub between the position interface and the instrument pointer. It is generally positioned away from the surgical area yet close enough to track the instrument pointer. Although it requires minimal space in the Operating Room and is sufficiently mobile it is generally a capital expense that is maintained on-site. The instruments must be sterilized with each use and the sophisticated optical components are custom made.

DETAILED DESCRIPTION

A navigation system is herein disclosed that addresses the need for low cost, portable and disposable surgical tools. The navigation system comprises compact wireless sensorized devices that communicate directly with one another; no computer workstation is required there between, which is a departure from conventional computer assisted surgery. Constructed with low-cost ultrasonic transducers and self-powered electronic components the sensorized tools provide extended surgical use and can thereafter be disposed, thereby incurring less hospital support and overhead.

In one embodiment, the sensorized tools of the navigation system comprise a receiver for placement on a first cutting jig, a mounted wand for placement on a second cutting jig, and a second wand to register points of interest on a first and second bone with respect to the cutting jigs. The receiver and wands use ultrasonic sensing to track their relative location to one another and the cutting jigs; all of which are wireless. Based on the registered points of interest, the receiver can then assess and report parameters related to the orientation of the cutting jigs for achieving cutting alignment of the first and second bone. The receiver can communicate with a display system via a wireless connection to report and visually present alignment information in real-time.

FIG. 1depicts an exemplary embodiment of the navigation system100for use as an alignment tool in total knee replacement procedures. The navigation system100includes a receiver101, a mounting wand102and a hand-held wand103; the sensorized tools. The system can include the remote system108(e.g., laptop, mobile device, etc.) for presenting a graphical user interface (GUI)107. The GUI107allows the user to visualize a navigated workflow with the sensorized tools and that can be customized to the orthopedic procedure. One example of providing sensory feedback in a navigated workflow with the sensorized tools is disclosed in U.S. patent application Ser. No. 12/900,878 filed Oct. 8, 2010 entitled “Navigation System and User Interface For Directing a Control Action”, the entire contents of which are hereby incorporated by reference.

The receiver101can precisely track both wands102-103and report their position on the GUI107as part of the navigated workflow procedure. As will be discussed ahead, during the procedure, the receiver101is rigidly affixed to one component of a femoral cutting jig121for establishing cut angles on the distal femur and making corresponding femoral cuts. The mounting wand102can be rigidly affixed to one component of a tibial cutting jig123for establishing cut angles and making corresponding cuts on the proximal tibia. The wand103is used to register points of interest with the receiver101. The points of interest can be on a bone or on cutting jigs121-123used during surgery. The navigation system100reports real-time alignment of the cutting jigs121-123and bones by way of direct communication between the wands102-103and the receiver101; no computer workstation is required there between. The compact navigation system100assists the surgeon in establishing alignment of the cutting jigs112and bones and evaluating surgical process of bone alignment during and after surgery.

As one example, mechanical axis bone alignment is reported when the points of the femur head (A′), patella (B′) and ankle (C′) are positioned in a straight line. As will be explained ahead in more detail, the navigation system100intra-operatively assesses alignment of the femur and tibia bones during knee surgery by way of the rigidly attached receiver101and wand102. The navigation system100can also transmit alignment information to wireless devices (e.g., laptop, cell phone, net book) and upload the information to a server connected to electronic medical or health care records. The system100assesses and reports in real-time the position of these points, or other registered points, by way of the GUI107on the remote system108. It provides visual and auditory feedback related to cutting jig orientation and alignment, such as audible acknowledgements, haptic sensation (e.g., vibration, temperature), and graphical feedback (e.g., color coded line data).

FIG. 2shows one exemplary embodiment of the wand200and the receiver220, though, not all the components shown are required; fewer components can be used depending on required functionality. The receiver220and wand200and communication modes of operations there between are disclosed in U.S. patent application Ser. No. 12/900,662 entitled “Navigation Device Providing Sensory Feedback” filed Oct. 8, 2010; the entire contents of which are hereby incorporated by reference. Briefly, the current dimensions permit touchless tracking with sub millimeter spatial accuracy (<1 mm) up to approximately 2 m in distance. Either device and can be configured to support various functions (e.g, hand-held, mounted to object) and neither is limited to the dimensions described below.

The wand200is a hand-held device with a size dimension of approximately 10 cm in width, 2 cm depth, and an extendable length from 18 cm to 20 cm. As indicated above, the wand200can register points of interest (see points A, B, C), for example, along a contour of an object or surface, which can be shown in a user interface (see GUI107FIG. 1). As will be discussed ahead, the wand200and receiver220can communicate via ultrasonic, infrared and electromagnetic sensing to determine their relative location and orientation to one another. Other embodiments incorporating accelerometers provide further positional information.

The wand200includes sensors201-203and a wand tip207. The sensors can be ultrasonic transducers, Micro Electro Mechanical Element (MEMS) microphones, electromagnets, optical elements (e.g., infrared, laser), metallic objects or other transducers for converting or conveying a physical movement to an electric signal such as a voltage or current. They may be active elements in that they are self powered to transmit signals, or passive elements in that they are reflective or exhibit detectable magnetic properties.

In a preferred embodiment, the wand200comprises three ultrasonic transmitters201-203for each transmitting ultrasonic signals through the air, an electronic circuit (or controller)214for generating driver signals to the three ultrasonic transmitters201-203for generating the ultrasonic signals, an user interface218(e.g., button) that receives user input for performing short range positional measurement and alignment determination, a communications port216for relaying the user input and receiving timing information to control the electronic circuit214, and a battery218for powering the electronic circuit218and associated electronics on the wand200. The wand200may contain more or less than the number of components shown; certain component functionalities may be shared as integrated devices.

Additional transmitter sensors can be included to provide an over-determined system for three-dimensional sensing. As one example, each ultrasonic transducer can perform separate transmit and receive functions. One such example of an ultrasonic sensor is disclosed in U.S. Pat. No. 7,725,288 the entire contents of which are hereby incorporated by reference. The ultrasonic sensors can transmit pulse shaped waveforms in accordance with physical characteristics of a customized transducer for constructing and shaping waveforms.

The wand tip207identifies points of interest on a structure, for example, an assembly, object, instrument or jig in three-dimensional space but is not limited to these. The tip does not require sensors since its spatial location in three-dimensional space is established by the three ultrasonic transmitters201-203arranged at the cross ends. However, a sensor element can be integrated on the tip207to provide ultrasound capabilities (e.g., structure boundaries, depth, etc.) or contact based sensing. In such case, the tip207can be touch sensitive to registers points responsive to a physical action, for example, touching the tip to an anatomical or structural location. The tip can comprise a mechanical or actuated spring assembly for such purpose. In another arrangement it includes a capacitive touch tip or electrostatic assembly for registering touch. The wand tip207can include interchangeable, detachable or multi-headed stylus tips for permitting the wand tip to identify anatomical features while the transmitters201-203remain in line-of-sight with the receiver220(seeFIG. 1). These stylus tips may be right angled, curved, or otherwise contoured in fashion of a pick to point to difficult to touch locations. This permits the wand to be held in the hand to identify via the tip207, points of interest such as (anatomical) features on the structure, bone or jig.

The user interface218can include one or more buttons to permit handheld operation and use (e.g., on/off/reset button) and illumination elements to provide visual feedback. In one arrangement, a 8-state navigation press button209can communicate directives to further control or complement the user interface. It can be ergonomically located on a side of the wand to permit single handed use. The wand200may further include a haptic module with the user interface218. As an example, the haptic module may change (increase/decrease) vibration to signal improper or proper operation. The wand200includes material coverings for the transmitters201-202that are transparent to sound (e.g., ultrasound) and light (e.g., infrared) yet impervious to biological material such as water, blood or tissue. In one arrangement, a clear plastic membrane (or mesh) is stretched taught; it can vibrate under resonance with a transmitted frequency. The battery218can be charged via wireless energy charging (e.g., magnetic induction coils and super capacitors).

The wand200can include a base attachment mechanism208for coupling to a structure, object or a jig. As one example, the mechanism can be a magnetic assembly with a fixed insert (e.g., square post head) to permit temporary detachment. As another example, it can be a magnetic ball and joint socket with latched increments. As yet another example, it can be a screw post o pin to an orthopedic screw. Other embodiments may permit sliding, translation, rotation, angling and lock-in attachment and release, and coupling to standard jigs by way of existing notches, ridges or holes.

The wand200can further include an amplifier213and the accelerometer217. The amplifier enhances the signal to noise ratio of transmitted or received signals. The accelerometer217identifies3and6axis tilt during motion and while stationary. The communications module216may include components (e.g., synchronous clocks, radio frequency ‘RF’ pulses, infrared ‘IR’ pulses, optical/acoustic pulse) for signaling to the receiver220(FIG. 2B). The controller214, can include a counter, a clock, or other analog or digital logic for controlling transmit and receive synchronization and sequencing of the sensor signals, accelerometer information, and other component data or status. The battery218powers the respective circuit logic and components. The infrared transmitter209pulses an infrared timing signal that can be synchronized with the transmitting of the ultrasonic signals (to the receiver).

The controller214can utilize computing technologies such as a microprocessor (uP) and/or digital signal processor (DSP) with associated storage memory108such a Flash, ROM, RAM, SRAM, DRAM or other like technologies for controlling operations of the aforementioned components of the device. The instructions may also reside, completely or at least partially, within other memory, and/or a processor during execution thereof by another processor or computer system. An Input/Output port permits portable exchange of information or data for example by way of Universal Serial Bus (USB). The electronic circuitry of the controller can comprise one or more Application Specific Integrated Circuit (ASIC) chips or Field Programmable Gate Arrays (FPGAs), for example, specific to a core signal processing algorithm. The controller can be an embedded platform running one or more modules of an operating system (OS). In one arrangement, the storage memory may store one or more sets of instructions (e.g., software) embodying any one or more of the methodologies or functions described herein.

The receiver220comprises a processor233for generating timing information, registering a pointing location of the wand200responsive to the user input, and determining short range positional measurement and alignment from three or more pointing locations of the wand200with respect to the receiver220. The receiver has size dimensions of approximately 2 cm width, 2 cm depth, and a length of 10 cm to 20 cm. It includes a communications interface238for transmitting the timing information to the wand200that in response transmits the first, second and third ultrasonic signals. The ultrasonic signals can be pulse shaped signals generated from a combination of amplitude modulation, frequency modulation, and phase modulation. Three microphones221-223each receive the first, second and third pulse shaped signals transmitted through the air. The receiver220shape can be configured from lineal as shown, or in more compact arrangements, such as a triangle shape. One example of a device for three-dimensional sensing is disclosed in U.S. patent application Ser. No. 11/683,410 entitled “Method and Device for Three-Dimensional Sensing” filed Mar. 7, 2007 the entire contents of which are hereby incorporated by reference.

The memory238stores the ultrasonics signals and can produce a history of ultrasonic signals or processed signals. It can also store wand tip positions, for example, responsive to a user pressing the button to register a location. The wireless communication interface (Input/Output)239wirelessly conveys the positional information and the short range alignment of the three or more pointing locations to a remote system. The remote system can be a computer, laptop or mobile device that displays the positional information and alignment information in real-time as described ahead. The battery powers the processor233and associated electronics on the receiver220. The receiver200may contain more or less than the number of components shown; certain component functionalities may be shared or therein integrated.

Additional ultrasonic sensors can be included to provide an over-determined system for three-dimensional sensing. The ultrasonic sensors can be MEMS microphones, receivers, ultrasonic transmitters or combination thereof. As one example, each ultrasonic transducer can perform separate transmit and receive functions. One such example of an ultrasonic sensor is disclosed in U.S. Pat. No. 7,414,705 the entire contents of which are hereby incorporated by reference. The receiver220can also include an attachment mechanism240for coupling to bone or a jig by way of the pin281. As one example, the mechanism240can be a magnetic assembly with a fixed insert (e.g., square post head) to permit temporary detachment. As another example, it can be a magnetic ball and joint socket with latched increments.

The receiver220can further include an amplifier232, the communications module238, an accelerometer, and processor233. The processor233can host software program modules such as a pulse shaper, a phase detector, a signal compressor, and other digital signal processor code utilities and packages. The amplifier232enhances the signal to noise of transmitted or received signals. The processor233can include a controller, counter, a clock, and other analog or digital logic for controlling transmit and receive synchronization and sequencing of the sensor signals, accelerometer information, and other component data or status. The accelerometer236identifies axial tilt (e.g., 3/6 axis) during motion and while stationary. The battery234powers the respective circuit logic and components. The receiver includes a photo diode241for detecting the infrared signal and establishing a transmit time of the ultrasonic signals to permit wireless infrared communication with the wand.

The communications module238can include components (e.g., synchronous clocks, radio frequency ‘RF’ pulses, infrared ‘IR’ pulses, optical/acoustic pulse) for local signaling (to wand102). It can also include network and data components (e.g., Bluetooth, ZigBee, Wi-Fi, GPSK, FSK, USB, RS232, IR, etc.) for wireless communications with a remote device (e.g., laptop, computer, etc.). Although external communication via the network and data components is herein contemplate, it should be noted that the receiver220can include a user interface237to permit standalone operation. As one example, it can include 3 LED lights224to show three or more wand tip pointing location alignment status. The user interface237may also include a touch screen or other interface display with its own GUI for reporting positional information and alignment.

The processor233can utilize computing technologies such as a microprocessor (uP) and/or digital signal processor (DSP) with associated storage memory108such a Flash, ROM, RAM, SRAM, DRAM or other like technologies for controlling operations of the aforementioned components of the terminal device. The instructions may also reside, completely or at least partially, within other memory, and/or a processor during execution thereof by another processor or computer system. An Input/Output port permits portable exchange of information or data for example by way of Universal Serial Bus (USB). The electronic circuitry of the controller can comprise one or more Application Specific Integrated Circuit (ASIC) chips or Field Programmable Gate Arrays (FPGAs), for example, specific to a core signal processing algorithm or control logic. The processor can be an embedded platform running one or more modules of an operating system (OS). In one arrangement, the storage memory238may store one or more sets of instructions (e.g., software) embodying any one or more of the methodologies or functions described herein.

In a first arrangement, the receiver220is wired via a tethered electrical connection (e.g., wire) to the wand200. That is, the communications port of the wand200is physically wired to the communications interface of the receiver220for receiving timing information. The timing information from the receiver220tells the wand200when to transmit and includes optional parameters that can be applied to pulse shaping. The processor on the receiver220employs this timing information to establish Time of Flight measurements in the case of ultrasonic signaling with respect to a reference time base.

In a second arrangement, the receiver220is communicatively coupled to the wand200via a wireless signaling connection. A signaling protocol is disclosed in U.S. patent application Ser. No. 12/900,662 entitled “Navigation Device Providing Sensory Feedback” filed Oct. 8, 2010; the entire contents of which are hereby incorporated by reference. An infrared transmitter209on the wand200transmits an infrared timing signal with each transmitted pulse shaped signal. It pulses an infrared timing signal that is synchronized with the transmitting of the ultrasonic signals to the receiver. The receiver302can include a photo diode241for determining when the infrared timing signal is received. In this case the communications port of the wand200is wirelessly coupled to the communications interface of the receiver220by way of the infrared transmitter and the photo diode for relaying the timing information to within microsecond accuracy (˜1 mm resolution). The processor on the receiver220employs this infrared timing information to establish the first, second and third Time of Flight measurements with respect to a reference transmit time.

FIG. 3depicts an exemplary illustration using the wand103to register anatomical features on the bone. During registration, one of the wand tips207(seeFIG. 2) is touched to the distal bone center, to register that location with the receiver101. The remote system108visually shows the movement of the wand103in 3D with respect to the receiver101and the registered points. The wand103and the receiver101can communicate via a local communications protocol (e.g. optical/ultrasonic pulsing) apart from the network communication (e.g., Bluetooth, Wi-Fi) between the receiver101and the remote system108. In a master-slave configuration, the wand103serves as the slave to inform the receiver101of the points of interest, and the receiver101serves as the master for communication of the alignment information to the remote system108.

FIG. 4depicts a high-level exemplary workflow400for a sensory assisted surgical procedure according to one embodiment. Briefly, the workflow400is directed to a total knee replacement surgery. During the workflow, the surgeon desires to obtain a neutral mechanical axis. This is defined as a straight line extending from the patients femoral head, through the center of the knee to the center of the ankle (see line ABC,FIG. 1). The proper knee joint alignment is critical for a patient's knee function and performance.

The navigation system100assists the surgeon in making navigated knee replacements an easy and successful procedure. It visually guides the surgeon towards proper alignment and making bone cuts to achieve a neutral mechanical axis. The workflow400can be practiced with more or less than the number of steps shown and is not limited to the order shown. The workflow400can also be modified to include additional steps such as performing a combined balance and alignment evaluation during insert trialing as will be discussed ahead. Completion of the workflow steps during surgical operation may be on the order of 8-7 minutes. Briefly, low-level method steps401-409of the workflow are described ahead inFIG. 8A. Low-level method steps410-413of the workflow are described ahead inFIG. 8B.

FIG. 8depicts the low-level portion of the workflow steps401-409of workflow400ofFIG. 4. At step801, setup information and patient data is provided to a first GUI page for commencing the workflow400. It can be input to the remote system108which in the present embodiment hosts the GUI107. The GUI107hosts the customized workflow400for the total knee replacement procedure. An example of a navigated workflow is disclosed in U.S. patent application Ser. No. 12/900,878, the entire contents of which are hereby incorporated by reference. The patients name and surgery information can be entered into the GUI107. It also documents a time in and time out to confirm the patient with the procedure.

At step802the sterilized components (sensorized tools) of the navigation system100are opened, activated and calibrated. This includes: receiver101, mounted wand102and hand-held wand103(hereinafter system components). The calibration is a short procedure where the system components are validated for user requirement accuracy. At step803the system components broadcast their activation. The GUI107indicates (e.g., visual, auditory, and/or haptic) that the system components are on and operational according to specification.

After the patient is prepped for surgery the GUI107transitions to a femur registration page with information to provide visual guidance. The knee is opened with a longitudinal incision to expose the knee joint. Retractors are applied to protect soft tissue. At step804a Femur Pin281is placed in the distal femur. The receiver101is mounted to the femur pin281(in or out of incision). As an example of affixing, a screw post can include a detachable magnetic assembly to temporarily couple the receiver101to the bone. Other affixing means are herein contemplated. The receiver board is angled medially the receiver101to allow line-of-sight to the mounted wand102.

The GUI transitions to a tibia registration page. At step808a tibial pin (like pin281) is pinned in the proximal tibia or midway on the tibia. The mounted wand102is mounted to the tibial pin to be line-of-sight with the receiver101. Similar mounting mechanisms can be included to ensure a rigid attachment of the mounted wand102to tibial pin.

At step806the other hand-held Wand103(hereinafter Wand) is temporarily mounted to a stationary (overhead) stand and angled towards the receiver101(SeeFIG. 1). Wand103serves as a reference location for the receiver101when the receiver101is moving, as will be seen ahead. The Wand103can be placed within close proximity of the receiver101, for example, within 2 meters, and out of the way of the mechanics of the procedure.

In the next step807, the tibia is moved through a first range of motion (ROM1) from extension (straight leg) to flexion (knee bent ˜90 degrees) to ensure the receiver101and mounted wand102remain sufficiently in line-of-sight; approximately −60 to 60 degrees face-to-face incident angles. The GUI107confirms local line of sight between the receiver101and mounted wand102at step808. The GUI can provide sensory feedback to visually indicate line-of-site conditions, for example, turning red or green accordingly.

Next, the GUI107transitions to a femoral Identification (ID) page. It instructs the surgeon to place the hip in flexion and apply gentle femoral rotation. This motion is applied at step809to allow the receiver101to identify the femoral head (e.g., hip joint). One example of determining the femur head center is disclosed in U.S. patent application Ser. No. 12/900,955 filed Oct. 8, 2010 entitled “Orthopedic Method and System for Mapping an Anatomical Pivot Point, the entire contents of which are included by reference in entirety. Another is based on pivot point determination in U.S. Pat. No. 7,788,607, the entire contents of which are hereby incorporated by reference. The GUI107visually confirms this second range of motion (ROM) at step810, for example, by indicating a green status for line-of-sight. Line of sight is approximately ±60 degrees conical for certain user requirement precision, but can approach up to +90 degrees otherwise. It indicates a red status when the ROM is outside the line-of-sight. At step811GUI107informs the surgeon when the femoral head is registered and located within accuracy—it shows data collection, timestamp, and check points. The femur head establishes a first point for mechanical axis alignment (seeFIG. 1, point A of line ABC).

Once the GUI107confirms femur head identification, the wand103is removed from the stationary (overhead) stand at step812. It is thereafter used to register the anatomical landmarks during the workflow procedure. At step813, the GUI instructs the surgeon to register distal femoral center with Wand tip207. The GUI also indicate if the Wand103falls out of the line-of-sight and/or requires surgeon to re-register landmarks. The following points are registered:Lowest points on distal femoral condyles (medial and lateral)EpicondylesAnterior cortex of distal femurPosterior femoral condyles (PFC) (medial and lateral).
At step814, the GUI instructs the surgeon to use the wand103to register the following tibial landmarks:Center of tibia (base of ACL)Deepest points on proximal medial and lateral tibial plateau
At step818, the GUI instructs the surgeon to use the wand103to register the following ankle landmarks:Medial malleolusLateral malleolus

During the registration above, the GUI visually shows the registered points on the display in 3D, but is not limited to only the registration of these points. It also displays the desired mechanical axis of the leg for the leg in extension case (seeFIG. 1, line ABC).

At step816, dynamic knee data and leg information is captured related to the patient's current leg alignment and knee flexion. This information is recorded and reported. The knee flexion is specified by an angle indicating the amount of hyperextension through full bending of the knee (flexion). This angle can be between −10 to +120 degrees depending on the patient's condition. The GUI107instructs the surgeon to place the knee in extension and hold the leg steady to register the extension angle and mechanical axis. The knee is them moved through a full ROM1while the receiver101collects flexion data through minimum to maximum range. The GUI107tracks and reports the femur and tibia during ROM1as shown inFIG. 6A.

Next, the GUI107transitions to a femoral resection and instrumented cutting jig page. The knee is placed in flexion. During this step, the tibial wand102may be temporarily removed from the tibial pin if it is in the way, but remounted in a later step ahead. At step817, the wand103is then mounted to the femoral cutting jig (seeFIG. 1,121).FIG. 6Bshows one example of a wand coupled to a cutting jig component602although other embodiments are herein contemplated. In the current example, the component602can be coupled to cutting jig121ofFIG. 1. This permits the receiver101to track translation and orientation of the cutting jig component602for establishing femoral cutting angles as shown in step818to make femoral cuts. During navigation of the cutting jig602, the GUI displays the following:Distal femur and registered femoral featuresTracking of the Femoral Cutting JigCutting planes with depth of cut to each registered distal condyles.Flexion/extension angle of cutting plane relative to femoral mechanical axis, andVarus-valgus angle of cutting plane relative to femoral mechanical axis.

At step819, the Femoral Cutting Jig121is positioned and navigated in view of the GUI and pinned securely to the distal femur for the desired cutting plane. The distal end of the femur is then cut. The Femoral Cutting Jig121is then unpinned and placed bottom flat surface on the cut distal femoral surface to verify cut accuracy; that is, it is laid against the cut. The GUI107report distal femural cut accuracy based on the positioning of the wand102mounted (sensorized) cutting jig121.

The GUI then transitions to the tibial resection and instrumented cutting jig page. The wand102is then removed from the femoral cutting jig121and attached to the tibial cutting jig123at step820. During this time, the other mounted wand103may be remounted to the tibial pin281if it was previously removed. This permits the receiver101to track translation and orientation of the cutting jig123for establishing tibial cutting angles as shown in step821to make tibial cuts. The GUI displays the following:Tibia and registered tibial featuresTibial Cutting Jig on the DisplayCutting plane with depth of cut to lowest points on medial and lateral tibial plateau.Varus-valgus angle of cutting plane relative to Tibial mechanical axis, andanterior/posterior slope relative to the tibial mechanical axis.

At step822, the Tibial Cutting Jig123is positioned and navigated in view of the GUI and pinned securely to the tibia for the desired cutting plane. The proximal end of the tibia is then cut. Bony or meniscal remnants are removed from the cut area. The Tibial Cutting Jig123is then unpinned and placed bottom flat surface on the cut proximal tibial surface to verify cut accuracy; it is laid against the cut. The GUI107report proximal tibial cut accuracy based on the positioning of the wand102mounted (sensorized) cutting jig123.

FIG. 8Bdepicts the low-level portion of the workflow steps410-413of workflow400ofFIG. 4and continues fromFIG. 8Aabove. At shown in step823, upon completion of the tibial cut, the knee is extended with an extension block to assess extension gap and confirm gap resection. The extension gap is a volumetric void between the distal femur end and the proximal tibia end; a portion of the void was created due to the cutting of the femur bone end and the tibial bone end which had partially occupied that region prior to cutting.

The GUI107at step824displays the measured gap distances and varus/valgus alignment. These measurements can be verified by the navigation system100in addition to the extension block. The gap distance is a function of knee flexion and indicates the flexibility and strength of the medial and lateral knee tendons. The gap distance in extension (leg straight) can differ from the gap distance in flexion (leg bent) by a few millimeters. It also provides an indication of a permitted level of soft tissue release for achieving proper balance and alignment which is performed in step828. The gap distance is also assessed in order to determine appropriate chamfer cutting angles on the distal femur and proximal tibia and trial insert sizes.

The GUI107then transitions to a femoral Anterior-Posterior (AP) and chamfer cuts page. The knee is placed in flexion. At step826, the wand103is mounted to a 4in1 cutting block; a sophisticated jig that provides four different cutting angles in one block. The AP position and rotary position of the 4in1 cutting block is then defined in view of the GUI107. The GUI shows the location and orientation of the (sensorized) 4in1 block relative to the cutting planes and registered anatomical features. At step827, the 4in1 block is positioned and navigated in view of the GUI107and pinned securely for the desired cutting plane. The AP cut is made and thereafter the chamfer cuts are made on the distal femur end as shown in step828. Upon making the first series of cuts, a tensioning device is then applied off the tibia at step829to distract the knee joint to cause the ligaments to rotate the femur until it is parallel to the cut tibial plateau (Ligament Tensioning technique). The 4in1 block is then positioned and navigated in view of the GUI107with the incorporated AP positioning. The 4in1 block is pinned securely for the desired cutting plane and the final AP and chamfer cuts are made at step830.

The GUI107then transitions to an insert trialing page which guides the surgeon through selecting trial inserts. At step831, the femoral and tibial implant trials with tibial insert trial are inserted. During this procedure, a load sensing insert device can also be embedded within the tibial trial insert to assess balance.FIG. 6Cillustrates an exemplary relationship among such components of a prosthetic knee implant: the sensing module611, the femoral prosthetic component614, tibial prosthetic (tray or plate) component616, and the tibial insert dock612. The Load Sensing Insert Device611provides a concave surface against which the outer condylar articulating surface of the femoral prosthetic component614rides relative to the tibia prosthetic component616. Examples of a load sensing insert sensing module are described in ORTHO-01US, U.S. patent application Ser. No. 12/825,638 entitled “SYSTEM AND METHOD FOR ORTHOPEDIC LOAD SENSING INSERT DEVICE”, ORTHO-07US, U.S. patent application Ser. No. 12/825,724 entitled “WIRELESS SENSING MODULE FOR SENSING A PARAMETER OF THE MUSCULAR-SKELETAL SYSTEM”, ORTHO-10US, U.S. patent application Ser. No. 12/825,770 entitled “INTEGRATED SENSOR FOR MEDICAL APPLICATIONS”, ORTHO-27US, U.S. patent application Ser. No. 12/826,329 entitled “SENSING MODULE FOR ORTHOPEDIC LOAD SENSING INSERT DEVICE” all filed Jun. 29, 2010; the entire contents of each which are hereby incorporated by reference herein. In such a configuration, the navigation system100reports combined balance and alignment information by way of the GUI107.

At step832, the knee is removed through a third range of motion (ROM3) to assess implant stability, slipping and proper fit. During the ROM3, the GUI107displays the knee with extension angle and mechanical axis as shown in step833. It also displays combined balance and alignment information when the sensing insert device800above (seeFIG. 8) is included therein. The GUI107reports knee flexion, balance and alignment while the knee is moved through maximal flexion through extension to hyperextension as permitted. During ROM3, the knee may be subluxed posteriorally in flexion in view of the GUI107to define any posterior instability. At step834, the patella is cut and trialed. The femur bone and tibia are then prepped for implant and cemented in at step838and the final poly is inserted. The knee is moved through a final Range of Motion in view of the GUI displaying the extension angle and mechanical axis to validate balance and alignment as shown in step836.

FIG. 7shows alignment along a mechanical axis of a leg for normal and abnormal conditions. In extension, the femur721and tibia722of the leg are aligned along the mechanical axis (MA). The MA is approximately θ˜=6 degrees728from the vertical (V) at the ankle; and approximately 18-18 degrees from the vertical (V) at the knee (Q-angle) for a straight leg in standing position. As illustrated in the center subplot, a varus deformity is an outward angulation of the distal segment of a bone or joint with an alignment angle (or error) described by −Φ727. As illustrated in the right subplot a valgus deformity is a term for the inward angulation of the distal segment of a bone or joint with an alignment angle (or error) described by +Φ727. The system100reports the alignment angle Φ727between the first line741and the second line742as part of the positional location (information). The first line741is defined by the first point A′ (registered at a first time) and a second point B′ (registered at a second time). The second line742is defined by the pointing location of the Wand200at the second point B′ and a third point C′ at a third time. The system100can include multiple points for determining alignment and is not limited to a 3-point profile.

As previously indicated the receiver200itself can display alignment information or report the information to remote system to provide visualization. As one example, the LED lights224on the Receiver302illuminate in accordance with a detected alignment. A single multi-color LED will turn green for perfect alignment (0°), turn yellow if less than 2°, and turn red if alignment is off by 3° or more. With single color LEDS, a varus condition will illuminate the corresponding medial (inside) LED, a valgus condition will illuminate the corresponding lateral (outside) LED, and an alignment less than 1° will show all LEDS green. Other illumination patterns are herein contemplated and are not limited to those described. Similarly, the GUI307can report alignment information via text representation of the alignment error or by color coding displayed line segments.

For example, referring toFIG. 8, a communication network800for alignment detection and reporting is shown. Briefly, the communication network800broadens the data connectivity of the navigation system100shown inFIG. 1to other devices or services. For instance, the alignment detection and reporting aspects of the navigation system100can be communicatively coupled to the communications network800and any other associated systems or services.

As one example, the navigation system100can share its parameters of interest (e.g., angles, alignment, displacement, movement, orientation, rotation, and acceleration) with remote services or providers, for instance, to analyze or report on surgical status or outcome. This data can be shared for example with a service provider to monitor progress or with plan administrators for surgical monitoring purposes or efficacy studies. The communication network800can further be tied to an Electronic Medical Records (EMR) system to implement health information technology practices. In other embodiments, the communication network800can be communicatively coupled to HIS Hospital Information System, HIT Hospital Information Technology and HIM Hospital Information Management, EHR Electronic Health Record, CPOE Computerized Physician Order Entry, and CDSS Computerized Decision Support Systems. This provides the ability of different information technology systems and software applications to communicate, to exchange data accurately, effectively, and consistently, and to use the exchanged data.

The communications network800can provide wired or wireless connectivity over a Local Area Network (LAN)801, a Wireless Local Area Network (WLAN)808, a Cellular Network814, and/or other radio frequency (RF) system (seeFIG. 4). The LAN801and WLAN808can be communicatively coupled to the Internet820, for example, through a central office. The central office can house common network switching equipment for distributing telecommunication services. Telecommunication services can include traditional POTS (Plain Old Telephone Service) and broadband services such as cable, HDTV, DSL, VoIP (Voice over Internet Protocol), IPTV (Internet Protocol Television), Internet services, and so on.

The communication network800can utilize common computing and communications technologies to support circuit-switched and/or packet-switched communications. Each of the standards for Internet820and other packet switched network transmission (e.g., TCP/IP, UDP/IP, HTML, HTTP, RTP, MMS, SMS) represent examples of the state of the art. Such standards are periodically superseded by faster or more efficient equivalents having essentially the same functions. Accordingly, replacement standards and protocols having the same functions are considered equivalent.

The cellular network814can support voice and data services over a number of access technologies such as GSM-CPRS, EDGE, CDMA, UMTS, WiMAX, 2G, 3G, 4G, WAP, software defined radio (SDR), and other known technologies. The cellular network814can be coupled to base receiver810under a frequency-reuse plan for communicating with mobile devices802.

The base receiver810, in turn, can connect the mobile device802to the Internet820over a packet switched link. The internet820can support application services and service layers for distributing data from the load sensing system100to the mobile device802. The mobile device802can also connect to other communication devices through the Internet820using a wireless communication channel.

The mobile device802can also connect to the Internet820over the WLAN808. Wireless Local Access Networks (WLANs) provide wireless access within a local geographical area. WLANs are typically composed of a cluster of Access Points (APs)804also known as base stations. The navigation system100can communicate with other WLAN stations such as laptop803within the base station area. In typical WLAN implementations, the physical layer uses a variety of technologies such as 802.11b or 802.11g WLAN technologies. The physical layer may use infrared, frequency hopping spread spectrum in the 2.4 GHz Band, direct sequence spread spectrum in the 2.4 GHz Band, or other access technologies, for example, in the 8.8 GHz ISM band or higher ISM bands (e.g., 24 GHz, etc).

By way of the communication network800, the navigation system100can establish connections with a remote server830on the network and with other mobile devices for exchanging data. The remote server830can have access to a database840that is stored locally or remotely and which can contain application specific data. The remote server830can also host application services directly, or over the internet820.

FIG. 8Bshows one embodiment of a communication environment850operating via the communication network800for managing smart implant products, services and applications. A smart implant for example can identify alignment, joint movement, bone density, load forces and temperature data and the other parameters of interest herein previously described. This information can be conveyed via wireless services, for example, over a telecommunication network to event service providers. The event services can include orthopedic implant and patient event services for time critical, secure, and reliable messaging and reporting. This information is related to monitoring services responsible for medical reporting, patient/doctor and consulting offices, and research services, including medical device and pharmaceutical companies.

The computer system900may include a processor902(e.g., a central processing unit (CPU), a graphics processing unit (GPU, or both), a main memory904and a static memory906, which communicate with each other via a bus908. The computer system900may further include a video display unit910(e.g., a liquid crystal display (LCD), a flat panel, a solid state display, or a cathode ray tube (CRT)). The computer system900may include an input device912(e.g., a keyboard), a cursor control device914(e.g., a mouse), a disk drive unit916, a signal generation device918(e.g., a speaker or remote control) and a network interface device920.

The disk drive unit916may include a machine-readable medium922on which is stored one or more sets of instructions (e.g., software924) embodying any one or more of the methodologies or functions described herein, including those methods illustrated above. The instructions924may also reside, completely or at least partially, within the main memory904, the static memory906, and/or within the processor902during execution thereof by the computer system900. The main memory904and the processor902also may constitute machine-readable media.

The present disclosure contemplates a machine readable medium containing instructions924, or that which receives and executes instructions924from a propagated signal so that a device connected to a network environment926can send or receive voice, video or data, and to communicate over the network926using the instructions924. The instructions924may further be transmitted or received over a network926via the network interface device920.

The term “machine-readable medium” shall accordingly be taken to include, but not be limited to: solid-state memories such as a memory card or other package that houses one or more read-only (non-volatile) memories, random access memories, or other re-writable (volatile) memories; magneto-optical or optical medium such as a disk or tape; and carrier wave signals such as a signal embodying computer instructions in a transmission medium; and/or a digital file attachment to e-mail or other self-contained information archive or set of archives is considered a distribution medium equivalent to a tangible storage medium. Accordingly, the disclosure is considered to include any one or more of a machine-readable medium or a distribution medium, as listed herein and including art-recognized equivalents and successor media, in which the software implementations herein are stored.

These are but a few examples of embodiments and modifications that can be applied to the present disclosure without departing from the scope of the claims stated below. Accordingly, the reader is directed to the claims section for a fuller understanding of the breadth and scope of the present disclosure.

Where applicable, the present embodiments of the invention can be realized in hardware, software or a combination of hardware and software. Any kind of computer system or other apparatus adapted for carrying out the methods described herein are suitable. A typical combination of hardware and software can be a mobile communications device with a computer program that, when being loaded and executed, can control the mobile communications device such that it carries out the methods described herein. Portions of the present method and system may also be embedded in a computer program product, which comprises all the features enabling the implementation of the methods described herein and which when loaded in a computer system, is able to carry out these methods.

While the preferred embodiments of the invention have been illustrated and described, it will be clear that the embodiments of the invention are not so limited. Numerous modifications, changes, variations, substitutions and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present embodiments of the invention as defined by the appended claims.