Method for determining intervertebral implant device parameters for an intervertebral implant device for spinal fusion surgery - Patents.com

Abstract

1. A method for determining intervertebral implant device parameters, comprising: a) obtaining a three-dimensional image of a patient's spine (10); b) calculating a three-dimensional model of the spine (20); c) acquiring (30) at least one two-dimensional image of the spine; d) performing a first sagittal balance of the three-dimensional model to calculate spinopelvic parameters (50); e) determining (60) intervertebral device parameters corresponding to the intervertebral device to be used; f) applying (70) the intervertebral device parameters to the three-dimensional model of the spine, thus obtaining a corrected three-dimensional model of the spine; g) comparing (80) the corrected three-dimensional model of the spine with the two-dimensional image and performing a second sagittal balance to obtain corrected spinopelvic parameters; h) comparing the corrected parameters to predetermined values ​​to determine if the desired balanced spine has been achieved (90); i) if not, repeating steps e)-h).

Description

[Technical field]

[0001] The present invention relates to a method for determining intervertebral implant device parameters of an intervertebral implant device for spinal fusion surgery. [Background technology]

[0002] Spinal fusion is a surgical procedure that permanently connects two or more vertebrae of the spine, thus eliminating motion between the vertebrae and stabilizing the patient's vertebral segments.

[0003] Spinal fusion is a procedure in which a cage is placed in the patient's spine. The cage acts as a spacer between the affected vertebrae, allowing bone to grow between them and eventually become part of the spine.

[0004] Intervertebral cages are placed between two adjacent vertebrae after removing the disc that normally occupies this space. Spinal cages can be made of metal, polymer, ceramic, or a fusion of various materials.

[0005] The cage has a central cavity which is filled with a material to promote bone growth, or with the patient's own bone harvested, for example from the hip joint, during the same surgery as the fusion.

[0006] Intervertebral cages are intended to improve stability and balance of the treated spinal segment while simultaneously relieving pain and restoring function.

[0007] Cage selection for intervertebral fusion procedures is commonly performed intraoperatively based on simple mechanical trials. These trials allow for basic geometric analysis of form and fit, but do not allow for consideration of many important factors, such as sagittal balance, facet interference, foraminal height, and implant endplate contact.

[0008] Currently, the technology does not provide tools for planning, prior to surgery, the characteristics of the cage or other implant device that will be used to achieve the desired correction of an injured spine. Summary of the Invention

[0009] Therefore, there is a need to have the ability to plan spinal surgery by determining the physical and constructional characteristics of the device to be implanted to achieve the desired correction of spinal defects, thus overcoming the problems of the prior art.

[0010] These and other objects are fully achieved by a method for determining intervertebral implant device parameters of an intervertebral implant device for spinal fusion surgery having the features defined in independent claim 1 and by a system for determining intervertebral implant device parameters of an intervertebral implant device for spinal fusion surgery having the features defined in claim 10.

[0011] Preferred embodiments of the invention are defined in the dependent claims, the subject matter of which is understood to form an integral or integral part of this description. [Brief description of the drawings]

[0012] Further characteristics and advantages of the invention will become apparent from the following description, given purely as a non-limiting example, with reference to the accompanying drawings, in which: [Figure 1] FIG. 2 shows a block diagram of the steps of a method for determining intervertebral implant device parameters of an intervertebral implant device for spinal fusion surgery according to the present invention. [Diagram 2] 1 illustrates a system for determining intervertebral implant device parameters of an intervertebral implant device for spinal fusion surgery according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Briefly, the method for determining intervertebral implant device parameters of an intervertebral implant device for spinal fusion surgery according to the present invention involves a patient-specific analysis of the effects of three-dimensional reconstructed vertebral motion and the interaction of the implant device with the patient's anatomy based on a three-dimensional scan, e.g., a CT scan or an MRI scan, of the patient's spine.

[0014] Taking into account implant devices such as cages of various heights and lordotic / kyphotic angles that are inserted into the intervertebral disc space and affect the geometric relationship of the two vertebrae, e.g., distance, translation, rotation, angle (lordotic / kyphotic), the amount of correction is prescribed based on an analysis of sagittal balance.

[0015] Therefore, the optimal device to be implanted can be selected by considering the device design, length, height, width, and lordosis, while considering various factors such as sagittal balance, foraminal height / indirect decompression, facet interference due to intervertebral motion, and implant / vertebral endplate contact.

[0016] If a CT scan is performed, bone density at the implant endplate contact site using Hounsfield values ​​is also available within the CT scan information.

[0017] Furthermore, the planned information can be used in intraoperative monitors to check whether the surgical procedure is being performed as planned or to identify deviations between the planned and actual foraminal heights.

[0018] FIG. 1 shows a block diagram of the steps of the method for determining intervertebral implant device parameters of an intervertebral implant device for spinal fusion surgery according to the present invention.

[0019] In a first step 10, a three-dimensional scan image, for example an MRI or CT image, of the patient's spine is obtained.

[0020] In a further step 20, a three-dimensional model of at least one vertebra is created in a manner known per se from the scanned image of the spine in step 10. In one embodiment of the invention, a three-dimensional virtual complete model of the spine is obtained, in particular as a juxtaposition of a number of individual specific vertebrae. Advantageously, a three-dimensional image of the lower limbs of the spine (sacrum and / or pelvis) is added to the complete model of the spine.

[0021] In a third step 30, at least one two-dimensional x-ray image, preferably a lateral and / or anterior-posterior (sagittal) x-ray image, of the patient's spine is acquired, the two-dimensional image including a plurality of vertebrae.

[0022] If only limited 3D scan information is available, then in the next step 40, matching of the 2D and 3D images is performed: 3D reconstructed vertebral / sacrum / pelvis images are selected from a predefined database of patient-specific 3D vertebrae, which have a predetermined correspondence with the vertebral images of the 2D x-ray images of step 30, and then they are combined to obtain a reconstructed model of the spine that combines the 2D x-ray images and the 3D information of the levels where information is available.

[0023] In step 40, the reconstructed three-dimensional images of the vertebrae from the database are matched to the two-dimensional images of the vertebrae from the x-ray image acquisition, for example using a DDR (Digital Reconstruction Imaging) algorithm, in order to obtain a three-dimensional virtual reconstruction model of the patient's spine.

[0024] At this point, changes in intervertebral position and potential interactions between the implant and the patient's anatomy are analyzed.

[0025] In step 50, using either x-ray images or a three-dimensional model of the spine (full or reconstructed), a first sagittal balance analysis is performed to calculate the patient's spinopelvic parameters, such as pelvic incident, sacral tilt, pelvic tilt, lumbar lordosis, thoracic kyphosis, and sagittal longitudinal axis.

[0026] Advantageously, additional information, such as an analysis of the disc height of previous patients, or an analysis of the disc height relative to healthy levels above and below the index level, is taken into account to better predict the amount of distraction likely and the resulting implant height and lordosis relative to the index level.

[0027] The values ​​of the spino-pelvic parameters are used in a further step 60 to analyze the relations and movements between the different vertebrae of the three-dimensional model of the spine, e.g. the lordotic or kyphotic corrections that must be applied to various positions of the spine in order to finally obtain a balanced spine. This makes it possible to determine, in a manner known per se, intervertebral device parameters such as facet interference, endplate contact, bone mineral density, optimal shape (design, length, height, width, lordotic, kyphotic) of intervertebral devices such as cages to be used in the surgery in order to obtain the desired balanced spine.

[0028] These intervertebral device parameters should match commercially available components since the surgeon will select the device that will be used in the spinal fusion procedure that best matches the intervertebral device parameters calculated above.

[0029] In a further step 70, the intervertebral device parameters are applied, in a manner known per se, to a three-dimensional model of the spine (full or reconstructed), thus obtaining a corrected three-dimensional model of the spine.

[0030] In step 80, the corrected 3D model of the spine is aligned with the 2D x-ray image to ensure that the defined correction is present in the x-ray image and in the 3D model, updating, if necessary, the sagittal balance analysis performed in step 50. A second sagittal balance analysis is performed, thus obtaining corrected spinopelvic parameters (which have been corrected with respect to the spinopelvic parameters calculated in step 50 thanks to the intervertebral devices of the 3D model of the spine). If the lordosis of the segments defined in step 50 does not change in the 3D model, the spinopelvic parameters remain identical to those previously calculated.

[0031] In step 90, the corrected spinopelvic parameters are compared to predetermined range values ​​reported in the literature to determine whether the desired balanced spine has been achieved.

[0032] In the positive case, i.e., if the corrected spinopelvic parameters are within such range values, the above determined intervertebral device parameters may be used to design a corresponding intervertebral device to be applied to the patient's spine during a subsequent surgical procedure.

[0033] If not, steps 60-90 are repeated until the correct intervertebral device parameters are obtained.

[0034] The process according to the invention is performed by a system of the type shown in Figure 2, which comprises a workstation 200 of known type having a processing subsystem 210, a display device 220, a keyboard 230, a pointing device (mouse) 240 and provisions for connecting to a local area network (network bus) 250. Alternatively, the processing system may be distributed (not shown) having a processing subsystem and local or remote peripheral input / output devices.

[0035] The workstation 200 or distributed system is configured to process computing programs and processing groups or modules stored on a disk or accessible over a network and suitable for displaying the described processes and displaying the results on the device 220. The described solutions are considered to be well known to those skilled in the art and are therefore not described here as they are not relevant for the purposes and understanding of the present invention.

[0036] Obviously, the principles, embodiments and manufacturing details of the invention, which remain the same, can be significantly modified from what has been described and illustrated purely as non-limiting examples, without departing from the scope of protection of the invention as defined in the appended claims.

Claims

1. 1. A method for determining intervertebral implant device parameters for an intervertebral implant device for spinal fusion surgery, comprising: a) acquiring a three-dimensional image of a patient's spine (10); b) calculating (20) a three-dimensional model of the spine based on such three-dimensional images of the spine; c) acquiring (30) at least one two-dimensional image of the spine; d) performing a first sagittal balance of the three-dimensional model of the spine to calculate spinopelvic parameters (50); e) determining (60) intervertebral device parameters corresponding to intervertebral devices to be used to obtain a desired balanced spine for the patient based on the values ​​of the spino-pelvic parameters; f) applying (70) the intervertebral device parameters to the three-dimensional model of the spine, thus obtaining a corrected three-dimensional model of the spine; g) comparing (80) the corrected three-dimensional model of the spine with the two-dimensional image and performing a second sagittal balance, thus obtaining corrected spinopelvic parameters; h) comparing the corrected spinopelvic parameters with predetermined range values ​​to determine if the desired balanced spine has been achieved (90); i) if not, repeating steps e)-h).

2. The method of claim 1 , wherein the three-dimensional image of the spine comprises an MRI image or a CT image.

3. The method for determining intervertebral implant device parameters according to claim 1 or 2, wherein said at least one two-dimensional image consists of a lateral x-ray image and / or an anterior-posterior x-ray image.

4. 4. The method of determining intervertebral implant device parameters according to claim 1, wherein the step of calculating (20) a three-dimensional model of the spine comprises a step of matching (40) the two-dimensional image and the three-dimensional image.

5. 5. The method of claim 4, wherein the step of matching the two-dimensional image with the three-dimensional image includes the step of selecting a three-dimensional reconstructed image of a vertebra from a predefined database, the selected image having a predetermined correspondence with an image of the vertebra in the two-dimensional image, and the step of matching includes the step of then combining the reconstructed image of the vertebra with the two-dimensional image to obtain a reconstructed three-dimensional model of the spine.

6. 6. The method of claim 5, wherein said step of combining said reconstructed image and said two-dimensional image of the vertebrae includes applying a DDR (Digital Reconstruction) algorithm.

7. 7. The method of claim 1, wherein the spinopelvic parameters include pelvic incident, sacral tilt, pelvic tilt, lumbar lordosis, thoracic kyphosis, and sagittal longitudinal axis.

8. The method of determining intervertebral implant device parameters according to any one of claims 1 to 7, wherein the intervertebral device parameters include facet interference, endplate contact, bone mineral density, and geometry of the intervertebral device.

9. 9. The method of claim 8, wherein the geometry includes the design, length, height, width, lordosis and kyphosis of the intervertebral device.

10. 1. A system for determining intervertebral implant device parameters for an intervertebral implant device for spinal fusion surgery, comprising: a workstation (200) having a processing subsystem (210), the processing subsystem (210) comprising: a) obtaining a three-dimensional image of a patient's spine (10); b) calculating (20) a three-dimensional model of the spine based on such three-dimensional images of the spine; c) acquiring (30) at least one two-dimensional image of the spine; d) performing a first sagittal balance of the three-dimensional model of the spine to calculate spinopelvic parameters (50); e) determining (60) intervertebral device parameters corresponding to intervertebral devices to be used to obtain a desired balanced spine for the patient based on the values ​​of the spinopelvic parameters; f) applying (70) the intervertebral device parameters to the three-dimensional model of the spine, thus obtaining a corrected three-dimensional model of the spine; g) comparing (80) the corrected three-dimensional model of the spine with the two-dimensional image and performing a second sagittal balance, thus obtaining corrected spinopelvic parameters; h) comparing the corrected spinopelvic parameters to predetermined range values ​​to determine if the desired balanced spine has been achieved (90); i) if not, repeating steps e)-h).

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