Planning methods for hip joint reconstruction

Abstract

A method of planning hip arthroplasty for a subject is described, the method comprising: receiving at least one image of the subject while the subject is in an upright position, the image being obtained substantially from a sagittal plane; calculating at least one spinopelvic metric from the at least one image; and calculating a hip arthroplasty risk profile for the subject based on the calculated spinopelvic metric. A method of determining an acetabular cup orientation angle range for an acetabular cup implant in the subject is further described, and a computer-implemented method of determining an orientation angle range for an acetabular cup implant in the subject is further described.

Description

Technical Field

[0001] The present invention relates to a method for planning hip joint formation. In other examples, the present invention relates to a method for determining an orientation angle range of an acetabular cup.

Background Art

[0002] Hip joint formation is a surgical procedure in which an artificial device is implanted into a subject to replace the hip joint. The artificial device usually mimics the natural spherical hip joint by a femoral head that rotates within an acetabular cup.

Summary of the Invention

Problems to be Solved by the Invention

[0003] In some cases, the subject experiences hip joint pain, dislocation, or unsatisfactory function after surgery. This can lead to ongoing problems and may, in some cases, require reconsideration of the surgery.

[0004] The surgeon may strive to place the acetabular cup within an angle range generally considered to produce acceptable results. However, even within this range, the subject may experience problems such as pain or dislocation. Means for Solving the Invention

[0005] According to one example, a method for planning hip joint formation for a subject is provided, which includes: Receiving at least one image of the subject obtained substantially from the sagittal plane when the subject is in a standing position; Calculating at least one spinal pelvic metric from the at least one image; Calculating the characteristics of the risk in the hip joint formation of the subject based on the calculated spinal pelvic metric, and including.

[0006] According to another example, a method for determining an orientation angle range of an acetabular cup implant for a subject is provided, which includes: The process involves receiving at least one image of the subject obtained substantially from the sagittal plane while the subject is standing; before Twist Receiving an angular range; To receive the tilt angle range; Calculated spinal-pelvic metrics, received before Twist Based on the angular range and the received inclination angle range, the orientation angle range of the acetabular cup for the subject's acetabular cup implant is determined, Includes.

[0007] In another example, a computer-aided method is provided for determining the orientation angle range for a subject's acetabular cup implant, which is: before Twist Receiving an angular range; To receive the tilt angle range; To receive the spinal and pelvic metrics of the subject; This includes determining the orientation angle range of the acetabular cup for the acetabular cup implant in the subject.

[0008] Embodiments may be carried out in accordance with any one of dependent claims 2-14, 16-23, or 24-27.

[0009] It should be understood that the terms “comprise” and “comprising” may have either an exclusive or inclusive meaning under different jurisdictions. For the purposes of this specification, unless otherwise specified, these terms are intended to have an inclusive meaning. That is, these terms are to be understood as encompassing the enumerated components used for direct quotations and for quotations of other unspecified components or elements.

[0010] Reference to any document herein that forms part of the common general knowledge or prior art that can be formally combined with other documents is not permitted.

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the general description of the invention given above and the detailed description of the embodiments below, serve to explain the principles of the invention.

Brief Description of the Drawings

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[0013] The methods described herein utilize patient-specific information to assess risk for a particular patient and determine the optimal orientation of an acetabular cup. The inventors have found that patient-specific pelvic spinal metrics are associated with the likelihood that an arthroplasty recipient will experience adverse outcomes such as dislocations in the future. The inventors have also found that patient-specific pelvic spinal metrics may impose additional constraints in the optimal placement orientation for an acetabular cup, in addition to universal (i.e., not patient-specific) orientation constraints that a surgeon may otherwise work with. This additional patient-specific constraint may indicate a narrower range in the particularly suitable acetabular cup orientation for the patient of interest. The size of this narrower range can be another indicator of risk.

[0014] Pelvic spinal metrics can be obtained from images of a patient in a standing position in one or more sagittal planes. The terms "sagittal plane" and the description of images taken in the sagittal plane are not intended to require exact compliance with the orientation or position of the nominal sagittal plane in the subject. Due to skeletal differences, inaccuracies in the subject's posture during imaging, and other factors, this is rarely achievable. In fact, this terminology generally refers to images taken from the side of the patient, and generally the image plane is aligned with a plane passing through the front and back of the subject.

[0015] By assessing a patient's risk at an individual level, the patient can be classified into risk levels. This can provide more comprehensive pre-operative imaging and analysis in the preparation for surgery to higher-risk patients, while such extensive pre-operative procedures are not necessary for lower-risk patients. This can improve efficiency and outcomes by reducing overall costs and directing resources to the patients who most need them.

[0016] By taking into account patient-specific constraints in the placement and orientation of the acetabular cup, the placement angle can be better adjusted for each individual patient. This can lead to improved surgical outcomes.

[0017] Figure 1 illustrates an exemplary method 10 for assessing the risks associated with anticipated hip dysplasia. Method 10 includes receiving an image of the subject. This image is taken in the sagittal plane of the subject 11. This image may be one of various preferred types of images. This image may include a depiction of the subject's skeletal structure, such as the spine, pelvis, and femur. In one example, the image is a radiographic image. Alternatively, the image may be obtained by other forms of radiographic imaging, such as gamma radiography, or by ultrasound imaging or other preferred techniques capable of imaging bone. In other examples, if the orientation and / or position of the bone can be inferred from the image, it may be possible to use other imaging techniques that do not directly image the bone.

[0018] Based on the images, one or more spinal-pelvic metrics are calculated.12 Spinal-pelvic metrics relate to the geometric features of the skeletal structure, including the spine, pelvis, and femur. Spinal-pelvic metrics can be used as indicators of the subject's kinematics and balance. These metrics may include, for example, lumbar lordosis (LL), pelvic incidence angle (PI), pelvic tilt (PT), sacral tilt (SS), acetabular anterior tilt (AI), and pelvic-femoral angle (PFA), as set out in the table below.

[0019] [Table 1]

[0020] These metrics are illustrated in Figures 4 and 5. Figure 4 is an X-ray image of a standing subject taken in the sagittal plane. Figure 5 is an X-ray image of a seated subject taken in the sagittal plane. These metrics are based on the arrangement of the spine 41, pelvis 42, and femur 43 in each posture.

[0021] Metrics can be measured based on anatomical landmarks. These landmarks can be identified based on user input. For example, a user can examine an image on a computer device and place markers on relevant landmarks. Alternatively, these landmarks can be automatically located using computer software. The computer software may include object recognition and labeling algorithms that identify landmarks and calculate metrics. The computer software may be an artificial intelligence system. In one example, the artificial intelligence system is based on a machine learning model. The machine learning model is trained on a dataset of specific surgeons to learn the surgeons' preferences or techniques.

[0022] Combinations of these metrics can be used to construct other metrics for use in risk assessment method 10. For example, sagittal balance is defined by PI-LL. As shown in Figure 11, patients who experienced anterior or posterior dislocation after arthroplasty tended to have higher PI-LL values ​​than patients who did not experience dislocation. In this graph, bar 101 shows the frequency of dislocation (or absence of dislocation) as a function of PI-LL. Furthermore, the same metric can be measured in different postures. Combinations of the values ​​of that metric in different postures can be used as metrics for risk assessment. For example, the difference in LL values ​​(ΔLL) between standing and sitting postures can be useful for determining stability or instability.

[0023] The risk characteristics of a subject in hip arthroplasty are then calculated from the following metrics.13 As mentioned above, metrics can be used individually or in combination to determine risk characteristics. Risk characteristics may take the form of a range of values ​​representing the importance of the risk, or they may make up separate risk classifications such as "low risk" or "high risk." Risk characteristics may be used on their own as markers indicating that a subject is at particular risk of a poor surgical outcome. In one example, an unstable metric is used to classify patients as high-risk or low-risk. The unstable metric can be sagittal balance (PI-LL). In one example, the risk classification is based on subjects with PI-LL values ​​that are significantly greater than 0°, greater than approximately 2°, or greater than approximately 10°. Subjects with PI-LL in these ranges can be classified as high-risk. These subjects may have an increased risk of suffering dislocation after hip arthroplasty. Another unstable metric that may be used is ΔLL. Risk classification can be based on subjects with ΔLL values ​​significantly lower than 40° or lower than approximately 29°. Subjects with ΔLL in these ranges can be classified as high risk. Another metric that may be used is PFA. Very large or very small PFA values ​​may indicate a risk due to difficulty in placing the acetabular cup in a favorable orientation. For example, if a combined sagittal index (CSI) postoperatively is required to be within a specific range, it may be difficult to place the acetabular cup in an orientation that would bring the postoperative CSI within the required range when the PFA is very large or very small. CSI is described in more detail with reference to Figure 2.

[0024] As an alternative or addition, use the previous metric. Twist These metrics can be used in combination with other data, such as angles and inclination angles, to determine risk characteristics. The metrics can also be used as input to determine specific arthroplasty parameters, such as the preferred acetabular cup orientation angle range. This will be explained in more detail with reference to Figure 2.

[0025] Figure 2 presents a method for determining the orientation angle range of the acetabular cup implantation. Method 20 can be used on its own or in combination with the method in Figure 1.

[0026] Before describing the method in Figure 2 in detail, the relevant angles will be explained with reference to Figures 6 and 7.

[0027] Figure 6 shows an X-ray image of a subject with a hip prosthesis 64. The image is coronal (i.e., taken from the front or back of the subject). The prosthesis 64 includes a femoral head 63 and an acetabular cup 61. Together, they form a ball-and-socket joint that mimics a natural hip joint. The acetabular cup 61 has a circular rim 61. The rim 62 is shown as an ellipse in the coronal image of Figure 6 because, in this example, it is positioned at an angle to the coronal plane. The base of the prosthesis 64 is placed in the subject's femur 43, and the acetabular cup 61 is placed in the subject's pelvis 42. The angles of the two commonly used acetabular cups are shown in the inclination and anterior view of the radiograph. Twist The cup inclination is the angle between the surface of the rim 62 and the cross-section of the subject (horizontal 66 in Figure 6) when projected onto the coronal plane. Similarly, the cup inclination can be defined as the angle between the longitudinal axis of the subject (vertical in Figure 6) and the acetabular axis when projected onto the coronal plane. The acetabular axis is the axis that passes through the center of the acetabular cup and is perpendicular to the surface of the rim 62. Twist This is the angle between the circular rim surface and the line perpendicular to the coronal surface. Similarly, the front of the cup Twist This can be defined as the angle between the acetabular axis and the coronal plane. This is calculated from the eccentricity measured in the image of the rim, based on the recognition that the rim is an actual circle, for example, based on the relative sizes of the major and minor axes in the elliptical image of the rim. In this example, the inclination of the cup is 40.5°, and the front of the cup Twist It is 26°.

[0028] Figure 7 is an X-ray image of the subject in Figure 6, taken in the sagittal plane. This image shows the forward tilt of the cup, which is the angle between the horizontal line 72 and the straight line 71. The straight line 71 is placed along or parallel to the major axis (i.e., principal axis) of the image of the rim 62 in the sagittal plane. Similarly, the front of the cup Twist When projected in the sagittal plane, this can be defined as the angle between the subject's longitudinal axis (perpendicular in Figure 7) and the acetabular axis. In this example, the anterior tilt is 39.6°.

[0029] When a surgeon plans hip replacement, they usually... Twist The coronal plane angle and inclination angle are considered. In detail, specific ranges in these angles are generally considered to be "safe" and have a low risk of adverse outcomes (such as dislocation). However, the surgeon may... Twist And some judgment or personal preference may be exercised regarding a specific range of inclination. However, some patients may still experience adverse outcomes due to a specific placement in the patient's skeletal structure when the acetabular cup is positioned within those angular ranges. One criterion for the likelihood of a patient suffering adverse outcomes is the combined sagittal index (CSI). This is defined as the sum of the PFA and the anterior inclination of the acetabular cup, i.e., CSI = PFA + AI(cup). The inventors have identified several pre- Twist And the slope values ​​have been found to result in CSI values ​​outside the optimal range. Because before Twist And the inclination is related to AI. In particular, the inventors believe that these are related as follows:

[0030]

number

[0031] This relationship is shown in the graphs of Figures 8 and 9. In Figure 8, line 81 is before a certain value. Twist These represent curves. The slope and forward slope are plotted on the X and Y axes, respectively. In Figure 9, line 91 represents a curve with a constant slope value. These are plotted on the X and Y axes, respectively. Twist The forward slope is plotted separately.

[0032] Figure 10 shows the frequency of posterior and anterior hip dislocations after arthroplasty as a function of standing CSI. Bar 101 represents the number of patients who experienced (or did not experience) each type of dislocation. As can be seen, patients who experienced anterior dislocations tended to have higher CSI values ​​than patients who did not experience dislocations, and patients who experienced posterior dislocations tended to have lower CSI values ​​than patients who did not experience dislocations.

[0033] Figure 12 shows the tilt of the patient's cup and the front of the cup. Twist This is a scatter plot. Values ​​for specific patients are represented by dots 121, and shaded according to their CSI values. Also shown is the overall allowable slope angle and front Twist The box-shaped outline of region 122 corresponds to the "safe" value of the angle. Region 122 is defined by the lower limit 124a and upper limit 124b of the inclination, and the front Twist The boundary is defined by the lower limit 123a and the upper limit 123b. As mentioned, there are several patients within region 122 with CSI values ​​less than 200° or greater than 245°.

[0034] In method 20 shown in Figure 2, an image of the subject in the sagittal plane is received 21. The image in the sagittal plane may be the one described with reference to Figure 1.

[0035] Based on the images, one or more spinal-pelvic metrics are calculated.22 This metric can indicate the expected instability of the subject after surgery. For method 20, one preferred metric is PFA. This can be particularly useful in imposing constraints on the optimal acetabular cup placement angle.

[0036] Method 20 is, Twist This also includes receiving an angle range.23 These angles may be predetermined or based on the surgeon's judgment or preference, and may be considered suitable for setting the acetabular cup. Twist It can represent an angular range. In one example, this range may be a median around 20°. In another example, a range of 20°±10° (i.e., 10-30°) may be received.

[0037] This method also includes receiving the tilt angle range.24 Twist When angles are used, they may be predetermined or based on the surgeon's judgment or preference. They represent a range of inclination angles considered suitable for placing the acetabular cup. In one example, this range may be a median of approximately 40°. In another example, it may be a range of 40°+10° (i.e., 30-50°).

[0038] Spinal pelvic metrics, anterior Twist Based on the angular range and the tilt angular range, the orientation angular range of the acetabular cup is determined.25 In one example, the angular range of the acetabular cup is the received TwistThe range and inclination range of the acetabular cup, when positioned in the subject, is the angle at which the subject's CSI falls within an acceptable range. In one example, the acceptable range of CSI is 200°±10° and 245°±10° in a standing position. The acceptable range of CSI may be determined based on experimental data, computer simulations / modeling, or other investigations. The acceptable range may also be determined based on the surgeon's skill level, preferences, or judgment. The acceptable range may also be based on the level of risk tolerance or avoidance. Using the subject's measured PFA, a range of AI (cup) values ​​that leads to an acceptable CSI can be determined. The determined acetabular cup orientation angle can be an angle that aligns with the determined range of AI (cup) values ​​that leads to an acceptable CSI. In particular, the AI ​​range may be selected based on the following formula: CSI = PFA + ΔPFA + AI (cups) Here, ΔPFA is the expected change in PFA after hip plasty, thereby classifying CSI into a range of 200°±10° to 245°±10°. ΔPFA can be clinically established preoperatively, usually within the range of 2-10°. ΔPFA can also be given as a fixed value, such as 5°.

[0039] As this relationship shows, the PFA value of a particular subject imposes constraints on the optimal AI value. When determining the preferred angular range of the acetabular cup, the output angle is subject to this constraint, as well as the received previous Twist This can be defined as an angle that satisfies the angle range and the inclination angle range.

[0040] Figures 13 and 14 show nomograms of two different subjects A (Figure 13) and B (Figure 14). These nomograms show the results in a single plot. Twist It shows inclination and anterior inclination, which is useful for determining a suitable orientation angle for acetabular cup placement, and at the same time, a satisfactory anterior inclination. Twist This can be a constraint on the incline and forward incline. Line 133 is an incline curve of a constant value. TwistThe values ​​are measured along the X-axis, and the forward tilt value is measured along the Y-axis.

[0041] These drawings show shaded region 134 of the slope value, which corresponds to the range of the received slope value. This range is between the lower limit 135a and the upper limit 135b. In this example, the range is 30 to 50°. Shaded region 131 is the received previous Twist This corresponds to the angular range. This range is between the lower limit 132 and the upper limit 132b. In this example, the range is 5 to 25°. In Figures 13 and 14, ranges 131 and 134 are the same for subjects A and B, because they are not based on measurements of the subjects.

[0042] Furthermore, Figure 13 shows a shaded region 136, which corresponds to the range of anterior tilt (AI) values ​​determined for subject A. This range is determined based on the spinal-pelvic metrics of subject A, as described above. The range 136 is between the lower limit 137a and the upper limit 137b. In this example, the range is approximately 0 to 44°. Region 138 in Figure 13 corresponds to the range of acetabular cup orientation angles that satisfies all constraints and is suitable for acetabular cup placement. For subject A, this region 138 is formed from the overlap of regions 134, 131, and 136. Note that this region is subject-specific because region 136 is based on the spinal-pelvic metrics of a particular subject. Point 139 corresponds to a specific combination of cup orientation angles within range 138 that may be considered suitable for acetabular cup placement with a low probability of malfunction. In the method shown in Figure 2, the determined range of acetabular values ​​may correspond to region 138 for subject A.

[0043] In Figure 14, region 141 corresponds to the range of determined anterior tilt values ​​for subject B. This region 141 is between the lower limit 142a and the upper limit 142b. In this example, the range for subject B is 15 to 40°. Region 143 corresponds to the range of acetabular cup orientation angles that satisfy all constraints and are suitable for acetabular cup placement. For subject B, this region is formed from the overlap of regions 134, 131, and 141. Note that this region is smaller than region 138 in Figure 13. Point 144 corresponds to a specific combination of cup orientation angles suitable for acetabular cup placement for subject B.

[0044] In some cases, slope and / or front Twist The preferred angular range may be small, based on the spinal-pelvic metrics in a particular subject. Any size within these ranges may be used to determine the subject's risk characteristics. For example, a subject with one or more small ranges may be classified as higher risk than a subject with no small ranges. In one example, the tilt or anterior of the acetabular cup. Twist If either or both of the determined ranges are 10° or less, the subject is classified as high-risk. In this example, if both ranges are greater than 10°, the subject may be classified as low-risk. The size of the range used to classify risk may vary depending on factors such as the risk threshold of a particular surgeon, or by taking into account other risk factors of the subject. Risk characteristics may also be proportional to the size of the range, accompanied by multiple individual risk characteristics or risk characteristics on a continuous scale.

[0045] Depending on the risk profile, accurate 3D planning may be recommended for patients in preparation for surgery. This may only be recommended for subjects characterized as high risk. This may involve generating a 3D model of the patient's hip bone from CT or MRI scans. Alternatively, these may be reconstructed from coronal and sagittal X-ray data. During 3D planning, software may be used to create subject-specific anterior plans.Twist And the slope range is the patient-specific pre-calculated above. Twist and inclination range; acetabular cup and stem front Twist A combination of; or before maximizing the range of motion of the hip joint. Twist If the user customizes the cup angle in the software, which can be calculated based on a more optimized combination of angle and tilt angle, the software can provide a warning when the angle exceeds any of the above ranges.

[0046] On the other hand, if the subjects are characterized as low-risk, standard 2D templating may be recommended.

[0047] Figure 3 shows a computer-aided method for determining the orientation angle range of the acetabular cup. In this method, the computer device is used to determine the orientation angle range of the acetabular cup. Twist The computer device also receives an angle range 31, which may be predetermined or based on the surgeon's preference as described above. The computer device also receives a tilt angle range 32, which may also be predetermined or based on the surgeon's judgment or preference. The computer device also receives one or more spinal-pelvic metrics related to the subject 33. Based on this information, the computer device determines the orientation range of the acetabular cup 34. This can be done by the procedure detailed above.

[0048] A computer device can be any suitable computer device having one or more interfaces, memory, and processing circuits for receiving and outputting information. In one example, the computer device is a mobile phone. A computer implementation can be implemented by a computer device that operates according to a set of instructions that constitute a computer program. A computer program may take the form of a mobile phone application.

[0049] A computer program may include instructions to carry out the procedure outlined above. In detail, this can be done using the methods described with reference to Figures 1 and 2.

[0050] Figures 15 and 16 summarize one exemplary method 150 from arthroplasty recommendation to 2D or 3D templating. First, it is decided that the patient requests whole hip arthroplasty 151. Coronal radiographs are taken 152, and the surgeon determines the angular range of the coronal cup 153. The angular range of the coronal cup is determined by specific prior arthroplasty, as detailed previously. Twist The range and inclination range are also measured. Sagittal X-rays are also taken.154 Landmarks on the sagittal X-rays are labeled,155 and used to measure the sagittal spinal-pelvic metric, as detailed earlier.156 The cup angle and metric are passed on to the dislocation risk classification step,160 which is shown in more detail in Figure 16. If the subject is classified as low risk, 2D templating is performed.157 If the subject is classified as high risk, 3D templating is performed.158

[0051] Risk classification 160 can be based on the procedure detailed previously. Specifically, the surgeon's coronal cup angle 153 and the subject's sagittal measurement 156 are used and cross-referenced using a nomogram 161, as detailed previously. The safe zone of the acetabular cup angle is then determined as the area that satisfies all constraints 162. The determined acetabular cup angle range (previous Twist The size of each of the (and slope) is compared to a threshold, which in this case is 10°. If both ranges are greater than 10°, the subject is classified as low risk164. If one or both ranges are less than 10°, the subject is classified as high risk165. Other thresholds may be used, such as 20°, 15°, or 5°. Thresholds may be set based on experimental data, computer simulations / modeling, or other research. Thresholds may also be set based on the surgeon's skill level, preferences, or judgment. Thresholds may also be based on the level of risk tolerance or avoidance.

[0052] The present invention has been illustrated by the description of its embodiments, and those embodiments have been described in detail, but the applicant does not intend to limit or restrict the scope of the appended claims in any way by such details. Additional advantages and modifications will readily come to mind for those skilled in the art. Thus, the present invention in a broader sense is not limited to specific details, representative apparatus and methods, or the exemplary examples shown and described. Accordingly, developments from these details may be made without departing from the spirit or scope of the applicant's overall inventive concept.

Claims

1. A computer-based method for evaluating the risks associated with hip augmentation for a subject, The computer receives at least one image of the subject obtained from the sagittal plane while the subject is standing, The computer calculates at least one spinal-pelvic metric from at least one of the images, and the spinal-pelvic metric includes at least the pelvis-femur angle and anterior tilt. The computer determines the risk classification of the subject in hip joint reconstruction by calculating a postoperative standing composite sagittal index from at least the pelvic-femoral angle and the anterior tilt, based on at least one calculated metric of the spinal-pelvis. The risk classification for hip joint reconstruction in the aforementioned subjects is high if the postoperative standing composite sagittal index is less than 190° or if the postoperative standing composite sagittal index exceeds 255°. A method for assessing risks associated with hip grafting in a given population.

2. The process involves receiving at least one image obtained from the sagittal plane while the subject is seated, Calculating at least one metric of the spinal pelvis from at least one of the aforementioned images, Includes, A method for evaluating the risk associated with hip joint formation for a subject, according to claim 1, wherein the risk classification of the subject in hip joint formation is further based on at least one image obtained from the sagittal plane when the subject is standing and at least one image obtained from the sagittal plane when the subject is sitting.

3. A method for assessing the risk associated with hip augmentation for a subject, according to claim 1 or 2, further comprising indicating one or more orientations for an acetabular cup implant based on at least one calculated spinal-pelvic metric, and determining the subject's risk classification for hip augmentation, further based on one or more orientations for an acetabular cup implant.

4. A method for assessing the risk associated with hip joint formation for a subject according to any one of claims 1 to 3, wherein at least one of the spinal-pelvic metrics is one or more from the group consisting of sagittal index, sacral inclination, pelvic-femoral angle, lumbar lordosis, and overall sagittal balance.

5. A method for evaluating the risk associated with hip joint formation for a subject according to any one of claims 1 to 4, further comprising determining a range of acetabular tilt or anteversion angles, wherein the subject's risk classification for hip joint formation is high when the determined range of acetabular tilt or anteversion angles is less than 20°.

6. A method for evaluating the risk associated with hip joint formation for a subject, according to claim 5, wherein the risk classification of the subject in hip joint formation is high when the determined acetabular tilt angle or anteversion angle range is less than 10°.

7. A method for assessing the risk associated with hip formation for a subject according to any one of claims 1 to 6, wherein at least one of the spinal-pelvic metrics is calculated using anatomical landmarks received from the user.

8. A method for assessing the risk associated with hip joint formation for a subject according to any one of claims 1 to 7, wherein at least one of the spinal-pelvic metrics is calculated using anatomical landmarks, and the method comprises locating the anatomical landmarks.

9. A method for determining the orientation angle range of an acetabular cup for a subject's acetabular cup implant, performed by computer, The computer receives at least one image of the subject obtained from the sagittal plane while the subject is standing, The computer calculates at least one metric of the spine and pelvis from at least one of the images, The aforementioned computer receives the range of anteversion angles, The aforementioned computer receives the tilt angle range, The computer includes determining an acetabular cup orientation angle range for the subject's acetabular cup implant based on the calculated at least one metric of the spinal pelvis, the received anteversion angle range, and the received tilt angle range. The acetabular cup orientation angle range is determined such that the calculated postoperative combined standing sagittal index is 190° or more and less than 255°. A method for determining the orientation angle range of an acetabular cup for a patient's acetabular cup implant.

10. A method for determining the orientation angle range of an acetabular cup for a subject's acetabular cup implant, according to claim 9, wherein at least one metric of the spinal pelvis is calculated using anatomical landmarks received from the user.

11. A method for determining the orientation angle range of an acetabular cup for an acetabular cup implant in a subject, according to claim 9 or 10, wherein at least one of the spinal-pelvic metrics comprises one or more from the group consisting of sagittal index, sacral inclination, pelvic-femoral angle, lumbar lordosis, and overall sagittal balance.

12. A method for determining an acetabular cup orientation angle range for an acetabular cup implant in a subject, according to any one of claims 9 to 11, wherein at least one metric of the spinal pelvis is calculated using anatomical landmarks, and the method comprises locating the anatomical landmarks.

13. A method for determining the orientation angle range of an acetabular cup for an acetabular cup implant in a subject, according to any one of claims 9 to 12, wherein the orientation angle range of the acetabular cup is determined to be such that the calculated postoperative standing composite sagittal index is greater than 200° and less than 250°.

14. A computer-aided method for determining the orientation angle range for an acetabular cup implant in a subject, The aforementioned computer receives the range of anteversion angles, The aforementioned computer receives the tilt angle range, The computer receives a metric for at least one spinal pelvis of the subject, The computer includes determining an orientation angle range for the acetabular cup for the subject's acetabular cup implant based on at least one metric of the spinal pelvis, the received anteversion angle range, and the received tilt angle range. The orientation angle range of the acetabular cup is determined such that the calculated postoperative standing composite sagittal index is 190° or more and less than 255°. A computer-aided method for determining the orientation angle range for acetabular cup implants in subjects.

15. A computer-aided method for determining an orientation angle range for a subject's acetabular cup implant, according to claim 14, wherein the spinal pelvic metrics include one or more from the group consisting of sagittal index, sacral inclination, pelvic-femoral angle, lumbar lordosis, and overall sagittal balance.

16. A computer-aided method for determining an orientation angle range for an acetabular cup implant in a subject, according to claim 14 or 15, wherein the orientation angle range of the acetabular cup is determined to be such that the calculated postoperative standing composite sagittal index is greater than 200° and less than 250°.

Images