Methods for determining pedicle base circumference, pedicle isthmus and center of the pedicle isthmus for pedicle screw or instrument placement in spinal surgery

Detailed description of the invention

This application claims the priority of US Provisional Patent Application No. 60 / 761,365 (filed January 24, 2006).

[Technical field to which the invention belongs] The present invention generally relates to the field of spinal cord surgery and is a computerized method for the accurate placement of screws for pedicles or internal fixation instruments for pedicles in spinal cord surgery. , Or how it is automated. More specifically, it relates to a method for determining the periphery of the pedicle, the pedicle isthmus, and the center of the pedicle isthmus.

[Background of invention] Placing screws on the human spine is a routine surgical procedure that allows the performance of multiple spinal cord surgeries. Screws are usually inserted into the pedicles of the patient's lumbar and sacral vertebrae. Because of its biomechanical advantages over other fixation forms, the surgeon installs a pedicle screw in the spine to dilate the spine.

However, near the spine, where many life-sustaining structures and organs are present, especially in the cervical and thoracic vertebrae, for surgically injured wounds that ultimately lead to significant morbidity and / or mortality. Almost tolerant. For this reason, most studies focusing on the placement of screws for pedicles have focused on improving the accuracy of holding screws in the bone (intrabone) environment.

The image guide system has been improved to further improve user convenience to help the surgeon install the screw correctly. Important figures for installing a screw for the pedicle in the human spine are the diameter, length, insertion path, and actual installation location of the screw. To date, many image-guided systems have enabled manual measurements of the above numbers, improving the surgeon's manual operation in screw installation.

However, to date, there have been systems that automatically measure the ideal diameter, length, and insertion path of the pedicle screw for accurate placement of the pedicle screw. Absent. The present invention provides the automated function similar to the computer-controlled flight function used by pilots operating airplanes, and the screw for the pedicle can be used in either incision or percutaneous techniques. Allows installation.

The invention described in U.S. Patent Application Publication No. 2004/0240715 (published December 2, 2004) relates to methods and computer systems for determining the location of screws for pedicles in spinal surgery. .. In the disclosed method, in order to determine the optimal screw insertion path, first establish the minimum diameter of the pedicle, then use the optimal insertion path for each pedicle to determine the maximum diameter of the screw and the maximum diameter of the screw. Establish the maximum length. In the above method, the data of the two-dimensional cross-sectional slice is superposed on the appropriate three-dimensional data using the linear least squares solution, and the solution that minimizes the width in the cross section in the entire pedicle is obtained. Be done.

The disadvantage of the method is that the abnormal insertion path is determined, especially the distorted pedicle structure is determined to have a screw with a maximum diameter and length smaller than ideal, and as a result, the screw is a living body for the pedicle. The structure is mechanically inferior.

In contrast, the new improvements of the invention use the center point of the smallest cross-sectional area (gorge) and in circumscribed regions in each direction facing each other, as described in more detail below. On the other hand, by extending the normal with a computer and determining a suitable insertion route, the insertion route to the pedicle is always arranged concentrically with the pedicle. A new modification of the invention allows each determination of the maximum diameter and length of the screw for intraosseous placement.

U.S. Patent Application Publication No. 2005/0192575 (September 1, 2005) discusses a methodology for determining the diameter, length, and insertion path of a screw for an ideal pedicle. The interface where the arch root is connected to the vertebral body is described. This boundary surface represents the periphery of the pedicle (B). The area around the pedicle (B) is identified by X-ray imaging in the axial direction as a circle like the cortical density observed on the lateral surface of the head of the vertebral body.

The most important feature around the pedicle is different from the pedicle isthmus (the narrowest area X in the pedicle), but occasionally the same. The pedicle isthmus is a rate-determining step for maximizing the diameter of the screw for the pedicle without causing damage to the cortical wall. To maximize the diameter of the pedicle screw inside any pedicle, the pedicle isthmus must be determined. Subsequently, the determination of the center of the pedicle isthmus allows the determination of the ideal insertion path, which allows the placement of concentric screws for the pedicle along the ideal insertion path.

The present application is intended for new improvements that determine the peri-vertebral arch, the pedicle isthmus, and the center of the pedicle isthmus.

[Gist of the invention] According to the method of the present invention, a suitable method is used to obtain a continuous stacked image of any surface of the vertebral body. Each of these images is then reconstructed to obtain an accurate 3D image of the vertebral body. The periphery of the pedicle and the isthmus of the pedicle are represented as a three-dimensional image and a two-dimensional image.

Once an accurate three-dimensional image of the vertebral body is obtained, it is then segmented by cross section for visualization to obtain the exodermis surface structure. Next, each front line in the series is tangentially drawn along the exodermis surface structure. Next, each second line in the series is drawn so as to be arranged in the vertebral body at right angles to each of the first lines, which are tangent lines arranged on the surface of the exodermis.

In the area of the pedicle and the area of the boundary that transitions from the pedicle to the vertebral body, each second line defines the structure around the pedicle and the pedicle isthmus. Specifically, the periphery of the pedicle is defined as a region where the second lines adjacent to each other are not linear with each other and have the maximum angle that does not harmonize with each other. The vertebral arch is defined as the region where the second lines facing each other are most parallel to each other. Each tiny point on the surface of the exodermis is utilized for the installation of each first line tangent on the surface of the exodermis and each second orthogonal line corresponding to each of the first lines described above.

Once the pedicle is defined, the center of the pedicle needs to be defined to allow concentric insertion pathway determination and construction of the pedicle columnar structure. .. Most pedicles have an elliptical or irregular shape, but most pedicles are conceptually considered columnar. Thus, accurate determination of the center of the pedicle is important.

The method of the present invention utilizes the cross-sectional area defined by the pedicle isthmus, and then each second orthogonal line orthogonal to each other extending from the skin surface to the center of the cross-sectional area from each minimal point. Identifies as the intersection of two lines derived from each center of. The method of the present invention makes it possible to determine the center of the pedicle isthmus regardless of the pedicle structure.

[Explanation of Preferred Embodiments of the Present Invention] [Embodiment 1. Determining the area around the pedicle and the pedicle isthmus] Based on the method of the present invention, for the vertebral body 10, a series of stacked images of any plane was obtained by any suitable method. Each of these images was then reconstructed to obtain an accurate 3D image of the vertebral body 10. Peripheral vertebral root B and pedicle pedicle X are represented as three-dimensional and two-dimensional images as schematically shown in FIGS. 1A and 1B.

Once an accurate three-dimensional image of the vertebral body 10 is obtained, it is fragmented into cross sections for visualization to obtain the exodermis structure. Next, each of the series of front lines T is drawn tangentially along the outer cortex surface 12 from the point of contact of the outer cortex surface 12. Next, each of the series of second lines P is located inside the vertebral body 10, orthogonal to each first line T drawn along the exodermis surface 12, and the first line T and the exodermis cortex. Each is drawn so as to extend from the contacts on the surface 12. As a line drawing of each of the first line T and each of the second line P, as shown in FIG. 2, two lines each of the first tangent line T and the second line P orthogonal to the first tangent line T. Only is shown as a concrete example.

In the boundary region to the pedicle 14 and its vertebral body 10, each second line P in the series defined the pedicle circumference B and the pedicle X. Specifically, in the vertebral root periphery B, in each second line P orthogonal to the corresponding first line T, each second line P adjacent to each other has a maximum angle A (non-linear with each other). Or it is defined as an area that does not match).

On the other hand, the pedicle X is defined as the region where the second lines P facing each other are most parallel to each other. Each tiny point on the surface of the exodermis was used for the installation of each tangent first line T and correspondingly orthogonal second lines P. FIG. 3 shows a schematic diagram illustrating the above method for defining the vertebral root periphery B and the vertebral arch isthmus X.

Next, the points on each of the numerous cross-sections (TS1, TS2, TS3 ...) that define the pedicle perimeter B and pedicle X are shown in FIGS. 4A, 4B and 4C. , Collated to determine the structural three-dimensional position of the pedicle circumference B and vertebral arch isthmus X. 4B and 4C show the cross section TS2 passing through the center of the pedicle 14. In addition, FIGS. 4B and 4C show points related to the cross section and the cross section TS2 of the coronal surface, respectively.

[Embodiment 2. Determining the center of the vertebral arch gorge] Once the pedicle X is defined, the center C of the pedicle is always defined. The determination of the center C is necessary to enable the determination of the concentric insertion path and the construction of the pedicle columnar structure. Many pedicles have an elliptical or irregular shape, but most pedicles are conceptualized as cylindrical. As mentioned above, determining the center of each of these pedicles is of utmost importance.

A new and improved method of the invention utilizes the cross-sectional region defined by the pedicle X, followed by each other from each of the micropoints, as shown in FIGS. 5A, 5B, and 5C. With respect to the first line derived from each center of each orthogonal second orthogonal line P, that is, passing through each center of each second orthogonal line P parallel to each other, and each second orthogonal line P parallel to each other. The point at the intersection of the two first and second lines with the second line passing through the center of each of the other second orthogonal lines P, which are orthogonal to each other and parallel to each other, is the cross-sectional area. Identified as the center C of. The method of the present invention can determine the center of the pedicle isthmus, regardless of various different pedicle structures, as shown in FIGS. 5A, 5B, and 5C.

Each method of the present invention, as is readily understood, is to place the screw for the pedicle along the ideal insertion path concentrically with the center of the pedicle isthmus, around the pedicle, It provides a simple and reliable method for determining the pedicle and the center of the pedicle. Each method of the present invention is effective for the use of a computer or the like or any suitable method such as manual imaging from each two-dimensional cross section.

On the other hand, the present invention is described in the most practical and preferred embodiment currently conceivable. It should be understood that the present invention is not limited to each of the disclosed embodiments. The present invention is also intended to cover the spirit of the appended claims and the scope of various modifications and equivalent modifications within that scope.

<figref num="1A">It is a schematic diagram of the image of the vertebral body in the sagittal plane.</figref><figref num="1B">It is a schematic diagram of the image of the vertebral body in the transverse direction.</figref><figref num="2">It is a schematic diagram of the vertebral body shown in FIG. 1B.</figref><figref num="3">It is a schematic view which shows the vertebral arch which is a part of the vertebral body shown in FIG. 2, and shows each minimal tangent line of the surface and each line orthogonal to each other shown in FIG.</figref><figref num="4A">It is a schematic diagram in the sagittal plane of the vertebral body showing the position of the pedicle circumference and the pedicle isthmus determined according to the method of the present invention.</figref><figref num="4B">It is a schematic diagram in the cross section of the vertebral body showing the position of the vertebral arch circumference and the vertebral arch isthmus determined according to the method of the present invention.</figref><figref num="4C">It is a schematic view from the coronal part side of the vertebral body which shows the position of the vertebral pedicle periphery and the pedicle pedicle isthmus determined according to the method of this invention.</figref><figref num="5A">It is a schematic diagram of the cross section of the pedicle isthmus which showed the center of the pedicle was determined according to the method of this invention.</figref><figref num="5B">It is a schematic diagram of the cross section of the vertebral arch gorge which showed the center of the pedicle isthmus having an irregular shape determined according to the method of this invention.</figref><figref num="5C">It is a schematic diagram of the cross section of the vertebral arch gorge which shows the center of the vertebral canal part which has an irregular shape different from FIG.</figref>