Patent Description:
In about <NUM>, research surgeons began trying to capture the deviation of the APP in order to correct the acetabular cup intraoperatively back to a neutral position. This process spawned development of the first computer assisted hip surgery and was call "tilt adjustment". At present, only a small number of surgeons use a tilt adjustment or computers. Tilt adjustment surgeries have not been found to lower the complication of the acetabular cups dislocating, as this adjustment is a static adjustment in the supine position of the APP to the neutral position.

Approximately <NUM> years ago Lazennec began studying the functional motions of the spine-pelvis-hip complex with regards to hip replacement surgery, using terminology developed in the field of spinal surgery and defined a new paradigm for assessment of the acetabular cup in the sagittal plane. He used lateral images from a new low dose X-ray scanner called the EOS Imaging System (Paris, France) and measured the acetabular cup's position and behavior in different functional positions (i.e., standing upright and sitting upright inside the scanner). The lateral or sagittal plane measurement of the cup in space was defined and has come to be known as Anteinclination (AI) through the works of Dorr. In addition, a new constant measure relating this acetabular cup position to the position of the pelvis was created, and named the Sacroacetabular Angle (SAA) by Lazennec.

Lazennec did not develop his findings into a methodology to target components. Instead, Dorr used coronal targeting research to amass data on these sagittal plane parameters and publish ranges and means for AI and SAA. Dorr also characterized the aberrations of pelvic position and pelvic mobility that created the outlier pelvic behavior causing the mechanical risks for implant failure.

<CIT> teaches a method for aligning an acetabular cup insertion instrument by taking a single lateral view pre-operative digital x-ray of a standing patient's pelvis.

<CIT> teaches planning tool for Total Hip Arthroplasty. Images of musculoskeletal structure of a patient are displayed together and via co-registration and spatial transformations.

<NPL>, studied the post-operative interaction of skeletal mobility and sagittal acetabular component position.

The present invention leverages biomechanical properties of the spino-pelvic-femoral complex and provides methods for planning (including use of digital platforms), tracking, targeting, navigation, and placement (including assisted or robotic execution) in vivo of the acetabular cup of a total hip replacement (i.e., total hip arthroplasty). Specifically, methods are provided that permit an acetabular cup to be individually targeted based on sagittal parameters. These sagittal parameters link the cup to the pelvis with respect to both the tilt (i.e., pelvic position) and the mobility (i.e., pelvic excursion) thereby producing optimal Anteinclination (AI) and Sacroacetabular Angle (SAA) values. These goniometric ratios permit the methods of the present invention to track the acetabular cup in space and to execute the acetabular position with an individual target based on a patient's measurements with increased accuracy over the 20x20° Lewinnek zone. These methods of the present invention may be used to analyze preoperative studies, including X-rays, CT scans, and MRI scans to determine a recommended orientation of the acetabular cup on patient-by-patient basis. The methods of the present invention may also be used to provide intraoperative guidance as to the position of the implant by tracking anatomy and the implant in space and automating, in whole or in part, navigation equipment to place the acetabular cup.

The method of the present invention is defined in claim <NUM>. A non-transitory computer-readable medium according to the present invention is defined in claim <NUM>. Further improvements are subject to the dependent claims.

The drawings are for the purpose of illustrating examples, but it is understood that the inventions are not limited to the arrangements and instrumentalities shown in the drawings.

As used herein, "Anterior Pelvic Plane" ("APP") refers to the plane traditionally used to measure or normalize (level) the sagittal tilt of the pelvis with respect to the coronal (longitudinal) plane of the body. The APP is the plane defined by three points, the right and left Anterior Superior Iliac Spines and the pubis symphysis prominence.

As used herein, "Anteinclination" ("AI") or Sagittal Angle of Inclination ("SAI") refers to the lateral or sagittal plane measurement of the acetabular cup in space. AI consists of a line tangent to the face of the sagittal projection of the acetabular implant and the horizontal reference line (i.e., parallel to the ground). The conventional limits of this parameter range from <NUM>-<NUM> degrees in a standing position and ranges from <NUM>-<NUM> degrees in a seated position. The present invention contemplates an AI or SAI ranging from <NUM>-<NUM> degrees in the standing position and ranges from <NUM>-<NUM> degrees in the seated position. AI of the acetabular component is a <NUM>-dimensional measure based on a lateral X-ray film. AI represents the operative or sagittal plane anteversion of the acetabular cup (i.e., the angle between the longitudinal axis of the patient and the acetabular component axis as projected onto the sagittal plane), with a minor influence of operative inclination. In other words, AI is a direct measure of anteversion, but the AI value is a different number from the coronal plane value used by surgeons. The anteversion clinically used by surgeons is called the radiographic anteversion, which is the projection of anteversion measured on an anterior to posterior (AP) X-ray as the patient is lying supine on a table.

As used herein, "Sacral Slope" ("SS") refers to the angle between the horizontal reference line and the tangent line along the sacral promontory (also referred to as the sacral endplate) having normal standing ranges from <NUM>°-<NUM>°, sitting from <NUM>°-<NUM>° for Pelvic Incidence values between <NUM>°-<NUM>°.

As used herein, "dSS," when applied to the SS value, refers to a delta or numerical change when moving a pelvis and an implanted acetabular cup between two positions. The measurements are obtained when the pelvic sacral slope angle is measured in two positions, namely the standing position and the upright seated position.

As used herein, "SacroAcetabular Angle" ("SAA") refers to a constant measure relating the AI cup position to the position of the pelvis. The SAA is formed by the anterior extension of the line tangent to the sacral promontory and the anterior extension of the line tangent to the sagittal face of the acetabular cup (i.e., AI+SS). When dSS is <NUM> degrees, SAA is also equal to (<NUM>+PI)/<NUM>.

As used herein, "Pelvic Tilt" ("PT") refers to a positional parameter formed by the angle between the vertical reference line and a line connecting the center of the bicoxofemoral axis and the center of the S <NUM> promontory.

As used herein, "Pelvic Mobility" refers to pelvic excursion and is synonymous with dSS.

As used herein, "Pelvic Incidence" ("PI") refers to a morphologic constant parameter in the sagittal plane that categorizes pelvic construction, PI is equal to the sum of the Pelvic Tilt and Sacral Slope angles (i.e., PT+SS). PI is formed by the line connecting the center of the bicoxofemoral axis and the center of the S <NUM> promontory and a second line perpendicular to the S <NUM> promontory at the S <NUM> promontory's central point. The typical human range is <NUM>-<NUM> degrees with a mean of <NUM>-<NUM>, values under <NUM> and above <NUM> are rare.

As used herein, Pelvic Acetabular Angle ("PAA") refers to an angle that corresponds to (<NUM>-AI)+PT. This angle was first described, defined, and leveraged in the disclosed methodsby Dr. Bodner, the inventor.

As used herein, "Bodner's Triangle" refers to a triangle that has three angles, namely (i) the SAA, (ii) (<NUM>-PI) at the sacral apex, and (iii) the PAA. The three sides are formed by the extension of the SS line anteriorly and inferiorly intersecting with the extension of the AI line superiorly and anteriorly, with the third side the PT line connecting the hip center to the center of the S <NUM> endplate. Therefore, the geometric construct of Bodner's Triangle ties together the acetabular cup's spatial position to that of the pelvic construction and spatial position. Bodner's triangle is influenced in form, spatial orientation, and excursion by all by each angle that it comprises, namely PI, SS, PT, AI, and functionally by the excursion or mobility between positions that is defined as dSS.

As used herein, "electrically coupled" refers to coupling using a conductor, such as a wire or a conductible trace, as well as inductive, magnetic and wireless couplings.

As used herein, "sagittal feedback" includes biomechanical values such the pelvic incidence (PI), the sacral slope (SS), the pelvic tilt (PT), the delta (dSS) of the sacral slope (SS), the pelvic femoral angle (PFA), the leg length, a hip offset, a hip center of rotation, and a femoral version.

Embodiments of the preoperative templating apparatus, navigation devices and methods described herein can be used to determine a spatial position and orientation of the acetabular component and provide intraoperative guidance or control as to the spatial position and orientation of the acetabular component by tracking patient anatomy and the acetabular component in real-time. The disclosed example preoperative templating apparatus, navigation devices and methods also beneficially obtain and provide on a display sagittal feedback detailing or illustrating the acetabular component's position and may also be used to determine a coronal position based on the obtained sagittal feedback consisting of the AI, SAA, all obtainable from the SS measured in the standing and sitting positions.

<FIG> is a block diagram showing an operating environment <NUM> that includes or involves, for example, preoperative templating apparatus <NUM> or navigation device <NUM>. Method <NUM> in <FIG> described below shows an embodiment of a method that can be implemented within this operating environment <NUM>.

<FIG> is a block diagram illustrating an example of a computing device <NUM>, according to an example implementation, that is configured to interface with operating environment <NUM>, either directly or indirectly. The computing device <NUM> may be used to perform functions of the method shown in <FIG> and described below. In particular, computing device <NUM> can be configured to perform one or more functions, including determining a spatial position and orientation of the acetabular component and providing intraoperative guidance or control as to the spatial position and orientation of the acetabular component by tracking patient anatomy and the acetabular component in real-time, for example, as well as, obtaining and providing on a display sagittal feedback detailing or illustrating the acetabular component's position and determining a coronal position based on the obtained sagittal feedback. The computing device <NUM> has a processor(s) <NUM>, and also a communication interface <NUM>, data storage <NUM>, an output interface <NUM>, and a display <NUM> each connected to a communication bus <NUM>. The computing device <NUM> may also include hardware to enable communication within the computing device <NUM> and between the computing device <NUM> and other devices (e.g. not shown). The hardware may include transmitters, receivers, and antennas, for example.

The communication interface <NUM> may be a wireless interface and/or one or more wired interfaces that allow for both short-range communication and long-range communication to one or more networks <NUM> or to one or more remote computing devices <NUM> (e.g., a tablet 216a, a personal computer 216b, a laptop computer 216c and a mobile computing device 216d, for example). Such wireless interfaces may provide for communication under one or more wireless communication protocols, such as Bluetooth, WiFi (e.g., an institute of electrical and electronic engineers (IEEE) <NUM> protocol), Long-Term Evolution (LTE), cellular communications, near-field communication (NFC), and/or other wireless communication protocols. Such wired interfaces may include Ethernet interface, a Universal Serial Bus (USB) interface, or similar interface to communicate via a wire, a twisted pair of wires, a coaxial cable, an optical link, a fiber-optic link, or other physical connection to a wired network. Thus, the communication interface <NUM> may be configured to receive input data from one or more devices, and may also be configured to send output data to other devices.

The communication interface <NUM> may also include a user-input device, such as a keyboard, a keypad, a touch screen, a touch pad, a computer mouse, a track ball and/or other similar devices, for example.

The data storage <NUM> may include or take the form of one or more computer-readable storage media that can be read or accessed by the processor(s) <NUM>. The computer-readable storage media can include volatile and/or non-volatile storage components, such as optical, magnetic, organic or other memory or disc storage, which can be integrated in whole or in part with the processor(s) <NUM>. The data storage <NUM> is considered non-transitory computer readable media. In some examples, the data storage <NUM> can be implemented using a single physical device (e.g., one optical, magnetic, organic or other memory or disc storage unit), while in other examples, the data storage <NUM> can be implemented using two or more physical devices.

The data storage <NUM> thus is a non-transitory computer readable storage medium, and executable instructions <NUM> are stored thereon. The instructions <NUM> include computer executable code. When the instructions <NUM> are executed by the processor(s) <NUM>, the processor(s) <NUM> are caused to perform functions. Such functions include, but are not limited to, determining a spatial position and orientation of the acetabular component and providing intraoperative guidance or control as to the spatial position and orientation of the acetabular component by tracking patient anatomy and the acetabular component in real-time, for example, as well as, obtaining and providing on a display sagittal feedback detailing or illustrating the acetabular component's position and determining a coronal position based on the obtained sagittal feedback.

The processor(s) <NUM> may be a general-purpose processor or a special purpose processor (e.g., digital signal processors, application specific integrated circuits, etc.). The processor(s) <NUM> may receive inputs from the communication interface <NUM>, and process the inputs to generate outputs that are stored in the data storage <NUM> and output to the display <NUM>. The processor(s) <NUM> can be configured to execute the executable instructions <NUM> (e.g., computer-readable program instructions) that are stored in the data storage <NUM> and are executable to provide the functionality of the computing device <NUM> described herein.

The output interface <NUM> outputs information to the display <NUM> or to other components as well. Thus, the output interface <NUM> may be similar to the communication interface <NUM> and can be a wireless interface (e.g., transmitter) or a wired interface as well. The output interface <NUM> may send commands to one or more controllable devices, for example.

The computing device <NUM> shown in <FIG> may also be representative of a local computing device 200a in operating environment <NUM>, for example, in communication with rinse station apparatus <NUM>. This local computing device 200a may perform one or more of the steps of the method <NUM> described below, may receive input from a user and/or may send image data and user input to computing device <NUM> to perform all or some of the steps of method <NUM>. In addition, in one optional example embodiment, the preoperative templating apparatus or navigation device <NUM> may be utilized to perform method <NUM>.

Method <NUM> shown in <FIG> presents an example of a method that could be used with the computing device <NUM> of <FIG>, for example. Further, devices or systems may be used or configured to perform logical functions presented in <FIG>. In some instances, components of the devices and/or systems may be configured to perform the functions such that the components are configured and structured with hardware and/or software to enable such performance. Components of the devices and/or systems may be arranged to be adapted to, capable of, or suited for performing the functions, such as when operated in a specific manner. Method <NUM> may include one or more operations, functions, or actions as illustrated by one or more of blocks <NUM>-<NUM>. Although the blocks are illustrated in a sequential order, some of these blocks may also be performed in parallel, and/or in a different order than those described herein. Also, the various blocks may be combined into fewer blocks, divided into additional blocks, and/or removed based upon the desired implementation.

It should be understood that for this and other processes and methods disclosed herein, flowcharts show functionality and operation of one possible implementation of the present examples. In this regard, each block may represent a module, a segment, or a portion of program code, which includes one or more instructions executable by a processor for implementing specific logical functions or steps in the process. The program code may be stored on any type of computer readable medium or data storage, for example, such as a storage device including a disk or hard drive. Further, the program code can be encoded on a computer-readable storage media in a machine-readable format, or on other non-transitory media or articles of manufacture. The computer readable medium may include non-transitory computer readable medium or memory, for example, such as computer-readable media that stores data for short periods of time such as register memory, processor cache and Random Access Memory (RAM). The computer readable medium may also include non-transitory media, such as secondary or persistent long term storage, like read only memory (ROM), optical or magnetic disks, compact-disc read only memory (CD-ROM), for example. The computer readable media may also be any other volatile or non-volatile storage systems. The computer readable medium may be considered a tangible computer readable storage medium, for example.

In addition, each block in <FIG>, and within other processes and methods disclosed herein, may represent circuitry that is wired to perform the specific logical functions in the process. Alternative implementations are included within the scope of the examples of the present invention in which functions may be executed out of order from that shown or discussed, including substantially concurrent or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art.

In the sagittal plane there are two fundamental relationships between five parameters that link the acetabulum to the pelvic orientation. The first relationship is for the pelvic rotational changes inherent in the pelvis's construction, namely pelvic incidence (PI) corresponds to pelvic tilt (PT) in combination with sacral slope (SS). The second relationship is between the acetabular cup and the pelvis as they both rotate in space such that sacroacetabular angle (SAA) corresponds to anteinclination (AI) in combination with sacral slope (SS). PI and SAA are fixed constants over any position while PT, SS and AI are reciprocal parameters that change on a <NUM>:<NUM> ratio as the pelvis assumes different positions. PI and SAA share the SS parameter which allows the various parameters to be related to each other, for example, PI-PT=SAA-AI that expresses the pelvic parameters on the left and acetabular parameters on the right.

Additionally, these equations are applicable when the parameters are measured in different functional positions, and may be applied to the data that exists for measures taken with the patient standing and seated prior to surgery. Spinal surgeons use the PI relationship to assist in correcting spinal deformities but this has only been applied to the standing position, and these parameters have not been managed over different positions. For example, moving a pelvis and acetabular cup between the two positions creates a delta or numerical change(dSS) when applied to the SS value. The pelvis and the acetabular cup move together as the acetabular cup is firmly fixed into the acetabulum, a part of the pelvis. The methods of the present invention contemplate superimposing the components of the PI and SAA relationships on a lateral rendering, as shown in <FIG>, thereby illustrating new angular relationships not previously known or utilized.

The technical effect of the methods leveraging the ratios between these angular parameters is to determine the degree to which changes in one parameter affect another parameter and how different amounts of mobility affect the acetabular-cup related parameters. With respect to the pelvis, spine surgeons have described that as PI changes <NUM> degrees, SS changes approximately <NUM> degrees and PT <NUM> degrees. The present invention includes methods that determined a refined ratio, starting at PI of <NUM>, SS of <NUM>, and PT of <NUM> degrees, every <NUM>-degree rise in the constant PI of the pelvis causes a <NUM> degree rise in the SS, and a <NUM> degree rise in the PT, that is, the inherent ratio between PI:SS:PT is <NUM>:<NUM>:<NUM>. These unique geometric relationships are SS=<NUM>+<NUM>. 666PI and PT=-<NUM>+<NUM>. Therefore a PI of <NUM> degrees in a normal individual will have a standing SS of <NUM> degrees, and a PT of <NUM> degrees; likewise, a PI of <NUM> degrees yields a standing SS of <NUM> degrees and a PT of <NUM> degrees. PT and SS values change from this normal relationship in people as they age and with disease but for every degree of change in SS, PT will change <NUM> degree in the opposite direction, in individuals these parameters are reciprocal.

Leveraging the effects of pelvic position and mobility in the methods of the present invention advantageously permit a determination of AI and SAA and a determination of the acetabular cup's spatial position and angular relationship to the pelvis. Further, the methods of the invention utilize the parameters of Bodner's Triangle, including the previously unrecognized angle referred to as the Pelvic Acetabular Angle PAA, in two new relationships to improve biomechanical position between the acetabular cup and pelvic position and mobility.

For example, the first relationship is SAA+PAA = PI+<NUM>. This is analogous to SS+PT = PI, but includes measurements related to the position of the acetabular cup. Experimental results have shown that when pelvic motion measured (dSS) is <NUM> degrees then SAA = PAA and Bodner's Triangle is an isosceles triangle. This relationship geometrically links the acetabular cup to a known dSS. In prior work, a sagittal relationship for dSS to cup position and mobility has been determined using Stefl et al data for mean and ranges for AI and SAA, which confirmed this new relationship was nearly identical to past clinical data calculations and revealed the exact ratios between parameters. As such, for any PI value when dSS is <NUM> degrees, the SAA = (PI+<NUM>)/<NUM> and also equals SS+AI, which works at any dSS. This triangular relationship also dictates that, similar to positional parameters in the other relationships, SAA and PAA are reciprocal. If SAA changes in one direction, PAA must change the same amount in the other direction as the apex angle <NUM>-PI never changes and the <NUM> angles of a triangle add to <NUM> degrees. So PAA at dSS of <NUM> degrees = SAA= (PI+<NUM>)/<NUM> as well as the definition for any dSS, (<NUM>-AI)+PT.

The geometric effects were determined when this triangle moved in space over differing mobility dSS. The effect of changing SS and PT that define the pelvic position from the norm given by the <NUM>:<NUM>:<NUM> gear ratio of the pelvic construction was also determined. These master ratios became (<NUM>:<NUM>:<NUM>:-<NUM>:<NUM>)/(<NUM>:<NUM>) for (PI:SS:PT:AI:SAA)/(PAA:dSS). This means that when two normal patients present one with a PI of <NUM> and a second with a PI of <NUM>, the first patient's numbers will be SS <NUM>, PT <NUM>, AI <NUM>, SAA <NUM>, and the second patient's numbers will be SS <NUM>, PT <NUM>, AI <NUM>, SAA <NUM>. However, they move in differing directions, when SS decreases and PT increases, AI increases but SAA decreases, when SS increases and PT decreases, AI decreases and SAA increases. The mobility ratio, that is, when a patient's measured dSS is not <NUM> degrees but rather any other number, for every degree divergent from <NUM> both the AI stand and the SAA change <NUM> degrees in the opposite direction, stiffness raising AI stand and SAA while lowering AI sit and PAA. For example, when dSS is <NUM> degrees, SAA goes up <NUM> degrees, AI goes up <NUM> degrees, PAA goes down <NUM> degrees. If dSS goes to <NUM> degrees, SAA and AI stand each go up <NUM> degrees, while AI sit and PAA each goes down <NUM> degrees. The inherent relationship of the acetabular cup to the pelvic position and to the mobility of the pelvis are all linear relationships that are leveraged by the methods of the present invention to tailor the acetabular cup position. The AI is the only parameter surgically determined in the whole system to either match the pelvis or to safely diverge from the pelvic machinery using the clinical limits defined in Stefl's work.

From the foregoing, a second relationship is observed such that when dSS=<NUM> degrees and SAA and PAA each = (<NUM>+PI)/<NUM>, then for SAA=(<NUM>+PI)/<NUM>=AI+SS, and for PAA = (<NUM>+PI)/<NUM> = (<NUM>-AI)+PT. In addition, PAA+(AI-PT)=<NUM> or <NUM>-(AI-PT)=PAA. Known normative data for PI:SS:PT at dSS <NUM> degrees can then be utilized to create "master values" for the acetabular cup AI and SAA that look like this: PI <NUM>, SS <NUM>, PT <NUM>, AI stand/sit <NUM>/<NUM>, SAA/PAA <NUM>, (AI-PT) <NUM>. For PI <NUM>, SS <NUM>, PT <NUM>, AI stand/sit <NUM>/<NUM>, SAA/PAA <NUM>, (AI-PT) <NUM>. This can be done for any presenting PI. The last parameter, (AI-PT) is the positional and mobility dependent quotient that is utilized in the derived relationship; PI + (AI-PT) = SAA, which is defined as the unifying governing relationship bridging the acetabular and pelvic parameters. (AI-PT) changes by the same ratio as SAA/PAA, that is, when PI increases by <NUM>°, (AI-PT) decreases by <NUM>°, the same as PAA and reciprocally to SAA in any cup calculation. Both solutions, Bodner's triangle using presenting standing SS data with a single mobility correction and the AI-PT relationship requiring two corrections, one from normative pelvic position and the second for alteration in dSS mobility from <NUM> degrees to arrive at the geometrically optimal cup AI, SAA, and PAA, may be employed. The following methods of the present invention leverage biomechanical behavior of the pelvis and the acetabular cup in the lateral plane permitting determination of sagittal plane coordinates for a given patient's acetabular cup and also permit a determination of when the acetabular cup should not be placed in concert with aberrant spinopelvic behavior. For example, disease and degeneration within the spine-pelvis-hip system may not be compatible with known methods for acetabular cup placement. Compensatory mechanisms are involuntarily used by the body to keep gravity balanced standing and allow sitting to occur. These mechanisms may lead the pelvis to an unfavorable spatial position and/or aberrant mobility between postures that are beyond a safe position for the acetabular cup implant. The methods of the present invention include adjusted cup positions for such mechanical situations in the sagittal plane. The resulting positional- (tilt), and mobility-derived coordinates may be used (i) to advise or guide surgeons in selection of the location and orientation for the acetabular cup placement, (ii) to track these parameters in space for surgeons in real-time, (iii) to perform biplanar conversion to the coronal plane that surgeons inherently understand, and (iv) link these coordinates to robotic execution devices to navigate the acetabular cup.

In a pre-operative patient evaluation, X-rays are obtained to observe standing and seated lateral views from the L1 lumbar vertebra to the upper fifth of the femur, a standing anteroposterior ("AP") pelvis view, both an AP and lateral view of the hip and a modified Budin view for estimation of femoral stem version. In addition to or alternatively, transverse CT scans or MRI images may be obtained to observe one or more of these views. The patient is also evaluated to assess hip range of motion, including flexion, extension, contractures, internal rotation and external rotation. Biomechanical values from measurements derived from these X-rays include pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), delta (dSS) of the sacral slope (SS), pelvic femoral angle (PFA), leg length, hip offset and center of rotation, and femoral version.

Referring now to <FIG>, a method <NUM> is illustrated using the preoperative templating apparatus <NUM> or navigation device <NUM> and computing device of <FIG>. Method <NUM> includes, at block <NUM>, a processor determining a sagittal acetabular cup position in the form of a standing Anteinclination (AI), a seated AI and a SacroAcetabular Angle (SAA) based on at least one of (i) a standing sacral slope (SS) of a first patient relative to a normative SS, (ii) a delta of the sacral slope (dSS) of the first patient between a standing position of the first patient and an upright seated position of the first patient, (iii) a femoral version of the first patient, when the femoral version corresponds to a femoral version outlier position, and (iv) a pelvic femoral angle (PFA) of the first patient that corresponds to a PFA outlier position in at least one of a standing position, an upright seated position, or a delta between the standing position and the upright seated position. Then, at block <NUM>, the processor determines a coronal acetabular cup position in the form of a supine coronal anteversion and at least one of a supine or a standing coronal inclination and anteversion based on the sagittal acetabular cup position. Next, at block <NUM>, the processor determines a post-operative standing AI and a post-operative seated AI based on at least the coronal acetabular cup position.

The post-operative standing AI and the post-operative seated AI determined using the methods of the present invention may be utilized to manually place the acetabular cup in the first patient. For example, a surgeon may prepare and place the acetabular cup and stem with a handheld device and confirm the acetabular cup position based on computer feedback. Alternatively, robotics may utilize the post-operative standing AI and the post-operative seated AI for placement of the acetabular cup. For example, a navigation device with a tracking sensor may be linked to a mechanical arm that moves based on a pre-planned trajectory and desired coronal or sagittal position of the acetabular cup. The post-operative standing AI and the post-operative seated AI, once converted to coronal anteversion could also be used for acetabular and femur preparation, by inclusion of femoral considerations for planning appropriate combined anteversion and mobility.

In one optional embodiment, the method <NUM> includes the processor sending at least one of the sagittal acetabular cup position and the coronal acetabular cup position to a remote processor electrically coupled to at least one of a preoperative templating apparatus or a navigation device. In one embodiment, the processor is electrically coupled to at least one of a preoperative templating apparatus or a navigation device.

In another embodiment, the method <NUM> includes the processor receiving a plurality of biomechanical values including a pelvic incidence (PI), the sacral slope (SS), a pelvic tilt (PT), the delta of the sacral slope (dSS), the pelvic femoral angle (PFA), a leg length, a hip offset, a hip center of rotation, and the femoral version based on images of the first patient. In a further embodiment, the processor receiving the plurality of biomechanical values comprising the pelvic incidence (PI), the sacral slope (SS), the pelvic tilt (PT), the delta of the sacral slope (dSS), the pelvic femoral angle (PFA), the leg length, the hip offset, the hip center of rotation, and the femoral version based on the images of the first patient includes the processor receiving one or more digitized voice commands that include one or more of the plurality of biomechanical values. In another embodiment, the processor is electrically coupled to an audio-digital converter configured to digitize the one or more voice commands.

In an alternative embodiment, the method <NUM> includes the processor receiving the plurality of biomechanical values comprising the pelvic incidence (PI), the sacral slope (SS), the pelvic tilt (PT), the delta of the sacral slope (dSS), the pelvic femoral angle (PFA), the leg length, the hip offset, the hip center of rotation, and the femoral version based on the images of the first patient includes the processor receiving one or more signals from a user input module. And the one or more signals include one or more of the plurality of biomechanical values.

In another optional embodiment, the method <NUM> includes the processor determining or receiving a plurality of biomechanical values comprising a pelvic incidence (PI), the standing sacral slope (SS), a pelvic tilt (PT), the delta of the sacral slope (dSS), the pelvic femoral angle (PFA), a leg length, a hip offset, a hip center of rotation, and the femoral version based on one or more images including the first patient showing a standing lateral view from an L1 lumbar vertebra to an upper fifth of a femur, a seated lateral view from the L1 lumbar vertebra to the upper fifth of the femur, a standing anteroposterior (AP) pelvis view, an AP view of a hip, a lateral view of the hip and a modified Budin view.

In still another optional embodiment, the method <NUM> includes providing, via at least one of a display or an audio-digital converter, intraoperative guidance or control of a navigation device based on at least one of the sagittal acetabular cup position and the coronal acetabular cup position. In a further embodiment, determining the post-operative standing AI and the post-operative seated AI based on at least the coronal acetabular cup position includes the processor tracking anatomy of the first patient and the acetabular cup in real-time. And a plurality of sensors are coupled to one or more of the acetabular cup, the anatomy of the first patient and the navigation device and the plurality of sensors are electrically coupled to the processor. In another optional embodiment, the audio-digital converter is configured to permit two-way communication between a surgeon and the processor.

In another embodiment, the method <NUM> includes the display providing images showing a spatial position and an orientation of the acetabular cup in real-time. In a further embodiment, the method includes the processor determining an orientation of a femoral component.

In still another optional embodiment, the method <NUM> includes the processor registering anatomy of the first patient to an OR table. In a further embodiment, the processor synchronizes the registered anatomy of the first patient to a treatment path of a robotic arm of a navigation device and to at least one of the sagittal acetabular cup position and the coronal acetabular cup position.

In another embodiment, the method <NUM> includes a localization device confirming a plurality of placement parameters in a plurality of planes after implanting an acetabular cup in the first patient. In a further embodiment, the method <NUM> includes a localization device measuring changes in a post-operative state relative to a pre-operative state after implanting an acetabular cup in the first patient.

In yet another embodiment, the method <NUM> includes the processor determining at least one recommendation for a type of implant, a treatment plan or a surgical tip based on historical data from a plurality of patients. The historical data includes a plurality of coronal acetabular cup positions, a plurality of coronal or sagittal biomechanical values and measured changes in a post-operative state relative to a pre-operative state. The method also includes at least one of a display or audio-digital converter providing the at least one determined recommendation to a surgeon.

In one optional embodiment, the method includes the processor storing data associated with the first patient. The data includes the coronal acetabular cup position, a plurality of coronal or sagittal biomechanical values and measured changes in a post-operative state relative to a pre-operative state.

As discussed above, a non-transitory computer-readable medium having stored thereon program instructions that upon execution by a processor may be used to cause performance of any of the functions of the foregoing methods of the present invention.

As one example, a non-transitory computer-readable medium having stored thereon program instructions that upon execution by a processor, cause performance of methods that include the processor determining a sagittal acetabular cup position in the form of a standing Anteinclination (AI), a seated AI and a SacroAcetabular Angle (SAA) based on at least one of (i) a standing sacral slope (SS) of a first patient relative to a normative SS, (ii) a delta of the sacral slope (dSS) of the first patient between a standing position of the first patient and an upright seated position of the first patient, (iii) a femoral version of the first patient, when the femoral version corresponds to a femoral version outlier position, and (iv) a pelvic femoral angle (PFA) of the first patient that corresponds to a PFA outlier position in at least one of the standing position, the upright seated position, or a delta between the standing position and the upright seated position. The processor then determines a coronal acetabular cup position in the form of a supine coronal anteversion and at least one of a supine or a standing coronal inclination based on the sagittal acetabular cup position. Next, the processor determines a post-operative standing AI and a post-operative seated AI based on at least the coronal acetabular cup position.

A <NUM> year old male with a height of <NUM> (<NUM>'<NUM>") and a weight of <NUM> (<NUM> lbs) presents with an arthritic L hip. The patient has normal motion with a small flexion joint contracture. His X-ray data are as follows; pelvic incidence PI is <NUM>, stand/sit Sacral Slope SS is <NUM>/<NUM> such that his dSS is <NUM> degrees, stand/sit PFA is <NUM>/<NUM> such that his dPFA is <NUM>, Lumbar stand/sit lordosis is <NUM>/<NUM> such that dLL is <NUM>. In this example, a preoperative X-ray evaluation of his femoral anteversion is not available. Note that in alternative scenarios, transverse CT scans or MRI imaging may be used to obtain sagittal and/or coronal data. Lumbar lordosis and dLL are used to evaluate spinal stiffness but are not ultimately utilized to determine acetabular cup position.

To determine acetabular cup position in the sagittal plane, example methods of the present invention determine three values. The first determination is the normal cup position or architectural cup position for any patient with a pelvic incidence PI of <NUM>. The second determination is the pelvic tilt PT adjustment (i.e., the adjustment for the standing deviation of this patient from that of the standing norm). The third determination is the dSS (i.e., the adjustment to that cup position based on the patient's pelvic mobility value).

The methods to derive these values are described in the invention above. In addition, the relationships PI = SS+PT and SAA = SS+AI can be rewritten as PI+(AI-PT) = SAA, where pelvic incidence PI and sacroacetabular angle SAA are constant values. Pelvic tilt PT adjustment and pelvic mobility dSS adjustment determine values for AI (and thus SAA). For any given patient, the measured pelvic incidence PI is fixed, but at the time of surgical presentation the pelvic tilt PT value may or may not be significantly different from the normative pelvic tilt PT value associated with that pelvic incidence PI. To determine a patient's anteinclination AI based on the foregoing relationships, a determination of the patient's SS or PT relative to the normative value for their pelvic incidence PI must be made to arrive at the tilt adjusted anteinclination AI (and SAA value). Then the tilt adjusted anteinclination AI must be further adjusted to account for the mobility difference dSS from the normative <NUM> degrees. For every degree the pelvic tilt PT diverges from the normative pelvic tilt PT value, the anteinclination AI is adjusted <NUM> degrees in the same positive or negative direction. Thus, if PT increases, then AI increases and vice versa. The resulting adjusted anteinclination AI is then adjusted a second time to account for the difference in mobility from <NUM> degrees, such that AI is increased <NUM> degrees for every degree of dSS divergence less than the normative <NUM> degrees and decreased <NUM> degrees for every degree of dSS divergence greater than <NUM> degrees. Using this twice adjusted AI and subtracting PT and then adding PI will result in the SAA value to determine optimal mechanical acetabular cup position.

The methods of the present invention were used to determine the architectural relationships between pelvic incidence PI, sacral slope SS, and pelvic tilt PT. For example, a ratio was determined such that starting at the PT intercept or <NUM>-point, and pelvic incidence PI at <NUM> degrees, every <NUM> degree rise in pelvic incidence PI creates a <NUM> degree rise in sacral slope SS and <NUM> degree rise in pelvic tilt PT. In another example, for every <NUM> degree rise in pelvic incidence PI, sacral slope SS rises <NUM> degrees and pelvic tilt PT rises <NUM> degrees, a <NUM>:<NUM>:<NUM> ratio for PI:SS:PT. This determination permits a normative value to be determined for a given patient's pelvic incidence PI. These relationships are SS=<NUM>+<NUM>. 666PI and PT=-<NUM>+<NUM>.

In addition, the mean pelvic incidence PI is typically considered to be about <NUM> degrees that corresponds to a sacral slope SS of about <NUM> degrees and a pelvic tilt PT of <NUM> degrees. Utilizing the ratio determined using the methods of the present invention, a pelvic incidence PI of <NUM> degrees has a sacral slope SS of <NUM> degrees and pelvic tilt PT of <NUM> degrees. The result is a table of normative values for pelvic incidence PI, sacral slope SS and pelvic tilt PT based on this <NUM>:<NUM>:<NUM> ratio provided in <FIG>. PI appears to describe a sinusoidal rise over run relationship between the distance between the center of the hip and the center of S1, where the hypotenuse of a constructed right triangle may be described as <NUM>/tan(<NUM>-PT). As PI increases the ratio of horizontal offset between hip and sacral centers increases with respect to the vertical distance between the two points. These physical changes all occur to provide a fixed ratio <NUM>:<NUM>:<NUM> between PI, SS, and PT such that for every <NUM> degrees PI changes, the SS angle changes <NUM> degrees and the PT changes <NUM> degree. With a <NUM> intercept for PT at <NUM> degrees of PI and SS, a determination can be made for absolute geometric normative values for any pelvis, the ratio of SS/PT giving a relative postural efficiency ratio between differing PI angles.

The methods of the present invention were then used to determine how this ratio impacted placement of an implanted acetabular cup whose sagittal values are known as AI and SAA. Specifically, Bodner's triangle permits this determination.

For example, the correlation between the position of the pelvis and hip are reflected by the relationships: PI = PT+SS and SS+AI = SAA. These two relationships share a common value, namely sacral slope SS. In addition, sacroacetabular angle SAA ties the position of the acetabular cup to the pelvis. The present invention recognizes for the first time a Pelvic Acetabular Angle PAA that creates a new relationship between the position of the acetabular cup and the pelvis to create Bodner's triangle. Bodner's triangle has three angles that correspond to the sacroacetabular angle SAA, the pelvic acetabular angle PAA and at the sacral apex ninety degrees minus pelvic incidence (<NUM>-PI). The angles of Bodner's triangle tie the position of the acetabular cup to sacral slope SS, to pelvic tilt PT, and to pelvic incidence PI. The anteinclination AI describes an angle with one limb measuring above the horizontal reference line, this same line is shared with both the sacroacetabular angle SAA and pelvic acetabular angle PAA. These lines are spatially identical and all three lines are created by the surgeon at the moment of acetabular cup placement (i.e., impaction) into the acetabulum of the pelvis. Once the sacroacetabular angle SAA and pelvic acetabular angle PAA are established, they become fixed constants and do not change. Only the anteinclination AI changes by the same number of degrees that the pelvis rotates between positions, the same amount as pelvis tilt, PT, and reciprocally to the SS amount, <NUM>: <NUM> ratios. As such, the position of the acetabular cup is correlated to the position of the hip via the relationship demonstrated in Bodner's triangle.

There is a condition in which Bodner's triangle becomes an isosceles, meaning that SAA = PAA. As this triangle consists of <NUM> constants, this means that these values will remain the same in both the standing and seated positions for a given patient. Bodner's triangle assumes this isosceles form when dSS is <NUM> degrees, and sacroacetabular angle SAA, which always is equal to SS+AI, becomes equal to (PI+<NUM>)/<NUM>. By substituting (PI+<NUM>)/<NUM> for SS+AI, the result is that AI is the only remaining value to determine. This determination may be made based on pelvic incidence PI values for any sacral slope SS associated with pelvic incidence PI, which will provide the sacroacetabular angle SAA and therefore anteinclination AI.

Turning to the patient in the present example, the patient has a pelvic incidence PI of <NUM> degrees. As a result, in a healthy scenario the patient would typically have a sacral slope SS of <NUM> degrees and a pelvic tilt PT of <NUM> degrees. Then assuming he had <NUM> degrees of mobility, his sacroacetabular angle SAA would be (<NUM>+<NUM>)/<NUM> = <NUM> making his standing anteinclination AI <NUM>-<NUM> = <NUM>. And if the patient had a dSS of <NUM> degrees, his seated anteinclination AI would be <NUM>+<NUM> = <NUM>. The foregoing would be the standard baseline values for the patient.

However, the patient presented with a sacral slope of <NUM> degrees, rather than <NUM> degrees, and his dSS is <NUM> degrees, not <NUM> degrees. In order to determine the acetabular cup angle in view of the present sacral slope SS and to permit <NUM> degrees of pelvic mobility, the ratio for PI:SS:PT determined by the methods of the present invention may be used. Here, a pelvic incidence PI of <NUM> degrees has a norm sacral slope SS of <NUM> degrees, a sacroacetabular angle SAA of <NUM> degrees and anteinclination AI of <NUM> degrees. The standing sacral slope SS provides a tilt adjusted standing anteinclination AI, regardless of the pelvic incidence PI, here <NUM> degrees.

Bodner's triangle, once established via acetabular cup placement (i.e., impaction), moves in space between the standing and seated positions, and the acetabular cup moves exactly the same angular amount and direction. However, the amount of pelvic mobility, as measured by dSS, has an effect on a determination of the preferred angle of the acetabular cup. A <NUM> degree change between the standing and seated positions does not require any alteration to the tilt adjusted acetabular cup position. But for every degree that dSS deviates from the normative <NUM> degrees of pelvic mobility both anteinclination AI and sacroacetabular angle SAA move <NUM> degrees. For example, when dSS is lower than <NUM> degrees, sacroacetabular angle SAA and anteinclination AI increase by <NUM>, and when dSS is above <NUM> degrees, sacroacetabular angle SAA and anteinclination AI decrease by <NUM>.

Taking into account the patient's pelvic mobility dSS of <NUM> degrees, <NUM>-<NUM> = <NUM>, such that the patient is <NUM> degrees stiffer than the norm. Applying the methods of the present invention, the patient's anteinclination AI and sacroacetabular angle SAA are increased <NUM> degrees. Further, based on the patient's actual measured values as presented above, his final mechanical acetabular cup position is based upon <NUM>+<NUM>=<NUM> standing anteinclination AI and his seated anteinclination AI is <NUM>+<NUM> = <NUM>. His sacroacetabular angle SAA value is determined to be <NUM>+<NUM> = <NUM>. Thus, for every degree that sacral slope SS decreases or pelvic tilt PT increases from the pelvic incidence PI normative value, the anteinclination AI increases <NUM> degrees and sacroacetabular angle SAA decreases <NUM> degrees. The change in the sacroacetabular angle SAA is determined by PI+(AI-PT) = SAA. And parameter (AI-PT) will decrease <NUM> degrees even as anteinclination AI goes up <NUM> degrees, because pelvic tilt PT is subtracted and PT moves in the same direction as the anteinclination AI moves. Once again, when the pelvis rolls back <NUM> degree, the pelvic tilt PT will increase <NUM> degree from the normative value, the anteinclination AI (i.e., the acetabular cup anteversion) increases <NUM> degrees and the parameter (AI-PT) becomes (<NUM>-<NUM>) = -<NUM> which reflects the change to the sacroacetabular angle SAA value.

Based on the foregoing, the patient has a mechanical plan for placement of his acetabular cup, with a sacroacetabular angle SAA of <NUM> degrees and stand/sit anteinclination AI <NUM>/<NUM>. Most patients do not change their standing sacral slope SS postoperatively. As such, the approach during surgery is to place an acetabular cup using lateral plane fluoroscopy guidance creating an sacroacetabular angle SAA of <NUM> degrees on the OR table. The patient's coronal values are then determined in order to use fluoroscopic control to view coronal inclination that is measured as an angle. The methods of the present invention are used to target the acetabular cup's anteversion based on the sacroacetabular angle SAA and the coronal inclination by converting sagittal values to coronal values.

The sagittal-to-coronal conversion is conducted by superimposing the sagittal coordinates over mobility-dependent coronal coordinates published by Dr. Depending on the patient, these mobility-dependent coronal coordinates are in the form of a 10x10 degree window for normal mobility, a 5x5 degree window for stiff mobility and a 5x8 degree window for hypermobility. This conversion accounts for <NUM>-<NUM> degrees of coronal inclination and <NUM>-<NUM> degrees of anteversion. The conversion exceeded <NUM> degrees supine anteversion to account for cases of very stiff, very high pelvic incidence PI and high standing sacral slope SS such that coronal anteversion will need to go closer to <NUM> degrees. The angle at which the sagittal coordinates are overlaid relative to the coronal plane will have some effect on the conversion angle, but a reasonable estimation of this value may be utilized. Machine learning methods of the present invention permits a processor in the system to learn from acetabular cup placement outcomes to improve the sagittal-to-coronal conversion over time. The methods of the present invention have been clinically confirmed with about <NUM> procedures.

With the sagittal conversion values, anteversion AI can be determined a priori without resort to Bodner's triangle thereby providing an optimal sacroacetabular angle SAA value. For example, the relationship PI+(AI-PT) = SAA can be used based on the pelvis mobility dSS value from the sagittal values determined and measured above. With respect to the patient of the present example, his pelvic incidence PI is <NUM> degrees and his measured PT is <NUM> degrees more than his normative PT value. His tilt adjusted anteinclination AI adds <NUM> x <NUM> = <NUM> degrees to his normative anteinclination AI value of <NUM> degrees resulting in a final tilt adjusted AI of <NUM>+<NUM>=<NUM> degrees. And his pelvic mobility adjustment to both AI and SAA is <NUM> x (<NUM>-<NUM>) = <NUM> giving a final standing anteinclination AI of <NUM>+<NUM>=<NUM> and SAA of <NUM>+<NUM> (his measured preoperative standing SS) = <NUM>. The foregoing values are based on conversion ratios, rather than Bodner's triangle, as an alternative implementation of the methods of the present invention.

Turning to Bodner's triangle, SAA-(AI-PT) = PI and the complement is PAA+(AI-PT) = <NUM>. The same conversion ratios disclosed above can be used to determine anteinclination AI and pelvic acetabular angle PAA. In addition, the sacroacetabular angle SAA can be determined by (<NUM>+PI)-PAA = SAA.

In view of the foregoing, there are six parameters to consider when determining the normative values based on pelvic incidence PI, and then adjusted to determine individual acetabular cup position when the patient's pelvic position and mobility have deviated from architectural values in standing to sitting. The first set is the morphologic ratios as PI changes from one value to another, these ratios are PI:SS:PT:AI:SAA=<NUM>:<NUM>:<NUM>:<NUM>:<NUM>, with the sixth parameter the dSS mobility correction of <NUM> With the above ratios a complete set of normative values may be tabulated. When an individual patient presents with altered values for hip replacement, tilt adjusted cup position may be determined from the normative data by these individual conversion ratios, SS:PT:AI:SAA:dSS=<NUM>:<NUM>:<NUM>:<NUM>:<NUM>. The former set may be used to illustrate the change in cup values between patients when pelvic incidence PI increases by <NUM> degree, then PI(+<NUM>)+[AI(-<NUM>)-PT(<NUM>)]=SAA or <NUM>+(-<NUM>) = +<NUM> which means as pelvic incidence PI increases by one degree, the quotient (AI-PT) decreases <NUM> degrees resulting in a sacroacetabular angle SAA increase of <NUM> degrees, namely the effect of a change to pelvic incidence PI on acetabular cup position and sacroacetabular angle SAA. For an individual patient with a fixed pelvic incidence PI and changing sacral slope SS and pelvic tilt PT, the same relationship has a different solution, it becomes PI(+<NUM>)+[AI(<NUM>)-PT(<NUM>)] = SAA. In other words, for each degree pelvic tilt PT increases, anteinclination AI increases <NUM> degrees and sacroacetabular angle SAA decreases <NUM> degrees. This represents the tilt adjustment ratios before the <NUM> degree mobility correction (that is, deviation from the <NUM> degree norm) is applied to the anteinclination AI and sacroacetabular angle SAA values.

The overall spinopelvic balance of the hip replacement's acetabular cup position can be described by the relationship of the sacroacetabular angle SAA to the pelvic acetabular angle PAA, SAA:PAA. When the relationship of the acetabular cup to both the SS (SAA) and the PT (PAA) is equal the system is balanced. That is SAA = PAA and that occurs when SAA and PAA are both equal to (PI+<NUM>)/<NUM>. A perfectly balanced system is not always achievable for a given patient and the best possible outcome may be skewed towards the SAA where a patient has stiff mobility or a persistent rotated-forward pelvic position. For the typical Caucasian patient with a pelvic incidence PI of <NUM> degrees, the balanced SAA and PAA are both <NUM> degrees, i.e., (<NUM>+<NUM>)/<NUM>. Therefore <NUM>:<NUM> describes a balanced SAA:PAA ratio (a harmonious spinopelvic balance) for a hip replacement in a normal patient with a pelvic incidence PI of <NUM>. From the previous ratios, this occurs when dSS=<NUM> degrees or when the effect of an alteration in pelvic position is countered by an alteration due to mobility. Stiffness is countered by decreased sacral slope SS, whereas increased dSS mobility is countered by an increased sacral slope SS. The clinically normal pelvic mobility in patients presenting for THA is <NUM> degrees stand to sit such that the SAA:PAA ratio for a typical patient with a PI of <NUM> and <NUM> degrees mobility become <NUM>:<NUM>. These are the values for SAA and PAA derived from relationships and determinations based on Bodner's triangle, when the pelvic incidence PI is <NUM> and the dSS is <NUM>. The patient in the present example with a pelvic incidence PI of <NUM> has a SAA:PAA ratio of <NUM>:<NUM>. As such, he is significantly off the balanced SAA:PAA ratio of <NUM>/<NUM>, because he is stiffer but there is a much greater effect from his lowered standing sacral slope SS that effectively decreases the SAA and increases the PAA.

In summary, conditions that increase SAA and lower PAA are decreasing dSS mobility (pelvic stiffness, and increasing pelvic tilt position forward (i.e., raising sacral slope SS and decreasing pelvic tilt PT). Conditions that lower SAA and increase PAA are increasing dSS mobility and increasing pelvic spatial position backward (i.e., decreasing sacral slope SS and increasing pelvic tilt PT). Conditions that increase both SAA and PAA thereby increase pelvic incidence PI, whereas conditions that lower both SAA and PAA thereby decrease pelvic incidence PI. In other words, the sacroacetabular angle SAA increases and pelvic acetabular angle PAA decreases, when pelvic mobility decreases and the pelvis tilts forward. The sacroacetabular angle SAA decreases and pelvic acetabular angle PAA increases, when pelvic mobility increases and the pelvis tilts backwards.

The patient in the present example has a compromised standing posture. Specifically, his pelvis is significantly tilted (rotated) posteriorly driving his sacroacetabular angle SAA down. But the decreased pelvic mobility, which raises the sacroacetabular angle SAA, does not compensate enough to restore absolute balance where SAA=PAA. As a result, his optimal acetabular cup position is skewed to the pelvic tilt PT side, the PAA side that is higher than his sacral slope side, the SAA side. As a result, the SAA:PAA ratio permits determination of an acetabular cup's spatial relationship relative to the individual patient's deteriorating hip and spine alignment.

Next, the relationship of the acetabular cup's position to the femur is determined to satisfy the parameter known as combined anteversion. The coronal cup anteversion is accepted as measured by an ellipse methodology on the AP X-ray and adding the same to the femoral anteversion as estimated visually at the time of surgery or by matching the femur to a preoperative CT scan and using navigation to arrive at a number. Femoral version is based on the relationship of the position of the center of the head of the femoral component to the longitudinal axis of the femur, an angle is determined from the posterior condylar line of the knee (essentially creating an internal horizontal reference line) and the deviation of the neck of the femoral component to this reference line. This angle is added to the acetabular cup's coronal anteversion to achieve a <NUM>-<NUM> degree range between the femoral version and the cup's coronal version (typically men range from <NUM>-<NUM> and women range from <NUM>-<NUM>). The femoral version typically ranges from <NUM>-<NUM> and typically the cup coronal anteversion range is from <NUM>-<NUM>. If femoral version is below <NUM> degrees or above <NUM> degrees, the femoral version is best changed, which is difficult with the preferred uncemented press fit femoral components. The intraoperative result is that surgeons who use combined anteversion as a guide may elect to modify acetabular cup version from the mechanical plan described above and permit the femoral stem implant find its unaltered seating.

A second correction may be applied to outlier femoral mobility, a measure different from femoral cup version. This is measured as another sagittal parameter as the femur moves in the sagittal plane. The value is Pelvic Femoral Angle (PFA) by Dorr and Sacro Femoral Angle (SFA) by spine surgeons. Outliers are typically associated with; <NUM>) stiffness of the pelvis as PFA has been found to increase <NUM> degrees for every degree loss of dSS leading to an increased delta PFA and <NUM>) elevated PT standing, associated with a high standing PFA and a low sitting PT, associated with a low sitting PFA. The sagittal parameter defined as predicting functional safe cup placement is called Combined Sagittal Index (CSI) and is measured as the sum of AI+PFA = CSI. CSI is a position and PI-dependent value. The CSI has both standing and sitting values ranging between an upper limit to avoid a high standing CSI value that could result in an anterior dislocation and a lower limit to avoid a low sitting CSI value that could result in a posterior dislocation. Low pelvic incidence PI patients are particularly prone to a low sitting CSI value. To account for this, the methods of the present invention, adjust anteinclination AI upwards on a sliding scale, depending on how low the PFA is below the <NUM> degree normal value. Likewise, if a patient is above <NUM> standing CSI value, the methods of the present invention, adjust the anteinclination AI downward on a sliding scale. This adjustment is optional, but not required, for acetabular cup placement. PFA outliers are associated with stiffness frequently and the targeting corrections for stiffness can solve most of the issues. Insuring a proper or increased coronal offset and leg length resolves the rest.

Finally, values corresponding to the determined acetabular cup values may be further modified based on the natural anatomical depth and version of the patient's acetabulum. For example, a patient may present with a mismatch between the determined position for the acetabular cup and the depth of the cup that the acetabulum can accept without the cup extending out of the socket of the acetabulum.

In addition, in one optional embodiment, the relationships described herein, including the sagittal-to-coronal conversion will be provided in a tangible computer readable media with instructions for execution on one or more processors for a preoperative templating apparatus and/or an intraoperative navigation system. In toto, all this targeting information may then be confirmed in a computer simulation defining a "Range of Motion to Impingement" sequence using sagittal and coronal biplanar positions simultaneously.

There is only one tilt-adjusted acetabular cup position for any presenting standing sacral slope SS regardless of the pelvic incidence PI. In other words, acetabular cup position is not dependent on the construction of the pelvis with regards to pelvic incidence PI. Instead, acetabular cup position depends on the presenting pelvic position as measure by sacral slope SS as described here or by pelvic tilt PT based on the relationship PAA+(AI-PT)=<NUM>. The result is that the patient from Example <NUM> above and the patient in the present Example <NUM> both have an acetabular cup positioned in the same orientation, but the balance between the acetabular cup and the pelvis as determined by the values of sacral slope SS and pelvic tilt PT in relation to their respective pelvic incidence PI will be different.

For example, a female that has a pelvic incidence PI of <NUM> degrees, when she was <NUM> years old, also has a standing sacral slope SS of <NUM> with a pelvic tilt PT of <NUM> degrees, which is a normal distribution. At age <NUM>, the same female now has a standing sacral slope SS of <NUM> degrees and a pelvic tilt PT of <NUM> degrees, and her tilt adjusted intraoperative cup position will be based on her current sacral slope SS of <NUM>. A second patient presents with a pelvic incidence PI of <NUM> degrees but also has a presenting standing sacral slope SS of <NUM> degrees and a pelvic tilt PT of <NUM> degrees. Both of these patient's tilt adjusted standing cup positions will be the same, since the cup position is based on their presenting standing sacral slope SS of <NUM> degrees. Both patients will have a tilt adjusted cup anteinclination AI of <NUM> degrees standing and their sacroacetabular angle SAA will be <NUM> degrees. When a patient's dSS is determined, an adjustment to this standing anteinclination AI position can be applied to determine the sitting anteinclination AI, and to similarly adjust the sacroacetabular angle SAA to arrive at the tilt & mobility-dependent mechanical acetabular-sided cup position. In this example if patient <NUM> has a dSS of <NUM> degrees, her AI standing is changed to <NUM> and sitting becomes <NUM> with an SAA of <NUM> if patient <NUM> has dSS of <NUM> degrees, her standing AI drops to <NUM> and sitting becomes <NUM> with an SAA of <NUM>.

Claim 1:
A method, comprising:
receiving, via a processor, a plurality of biomechanical values comprising a pelvic incidence, PI, a sacral slope, SS, a pelvic tilt, PT, a delta of the sacral slope, dSS, a pelvic femoral angle, PFA, a leg length, a hip offset, a hip center of rotation, and a femoral version based on images of a first patient;
determining (<NUM>), via a processor, a sagittal acetabular cup position in the form of a standing Anteinclination, AI, a seated AI and a SacroAcetabular Angle, SAA, based on at least one of (i) the standing sacral slope of the first patient relative to a normative SS, (ii) the delta of the sacral slope of the first patient between a standing position of the first patient and an upright seated position of the first patient, (iii) the femoral version of the first patient, when the femoral version corresponds to a femoral version outlier position, and (iv) the pelvic femoral angle of the first patient that corresponds to a PFA outlier position in at least one of the standing position, the upright seated position, or a delta between the standing position and the upright seated position, wherein Pelvic Acetabular Angle, PAA, refers to an angle that corresponds to (<NUM>-AI)+PT, wherein one or more of the following relationships is used to determine the standing AI, the seated AI, and the SAA
(i) SAA + PAA =PI+ <NUM>;
(ii) a master ratio of (<NUM>:<NUM>:<NUM>:-<NUM>:<NUM>)/(<NUM>:<NUM>) for (PI:SS:PT:AI:SAA)/(PAA:dSS); and
(iii) PI + (AI-PT) = SAA;
determining (<NUM>), via the processor, a coronal acetabular cup position in the form of a supine coronal anteversion and at least one of a supine or a standing coronal inclination and anteversion based on the sagittal acetabular cup position; and
determining (<NUM>), via a processor, a post-operative standing AI and a post-operative seated AI based on at least the coronal acetabular cup position.