JP7814032B2 - Template manufacturing method - Google Patents

Description

Article 30, paragraph 2 of the Patent Act applies. October 17, 2022. Published in the Abstracts of the 31st Annual Meeting of the Japanese Society of Spinal Instrumentation, page 83, SY4-4.

Article 30, Paragraph 2 of the Patent Act applied. Presented at the 31st Annual Meeting of the Japanese Society of Spinal Instrumentation on November 25, 2022.

The present invention relates to a method for manufacturing a template that is attached to each vertebra of the spinal column and is used prior to placing a rod configured as an implant material inside a patient's body, and that indicates the degree of curvature of the rod.

Conventionally, surgical treatments for stabilizing the spine involve making a large incision down the midline of the patient's back, inserting pedicle screws and rods through the incision, and attaching them to the spine to improve spinal stability or correct spinal deformities. In spinal deformity correction and fixation procedures, rods made of biocompatible materials such as titanium alloys and cobalt-chromium alloys are held in place by pedicle screws threaded into the pedicles, thereby correcting and fixing the spine. The rods are typically manually bent during surgery, using a surgical instrument such as a bender, just before being firmly attached to the pedicle screws. Furthermore, even before the rods are firmly attached to the pedicle screws (temporarily attached), the surgeon may manually fine-tune the curvature of the rod, if necessary.

The shape of the bent rod (rod curvature) largely determines the state of the spine after correction. Therefore, rod curvature is an important factor in spinal deformity correction and fixation surgery. In previous spinal deformity correction and fixation surgeries, the surgeon or surgical staff bent the straight rod appropriately using specialized surgical instruments during surgery. However, the degree of curvature of the entire rod, i.e., the direction and angle of the curvature, depended on the experience and intuition of the surgeon and other surgical staff, and could vary slightly depending on the surgeon or surgical staff, making it difficult to achieve the optimal correction for the patient. In other words, until now, there was no way to instruct the surgeon or surgical staff on the degree of curvature of the entire rod that would achieve the optimal correction for the patient before placing the rod inside the patient's body.

In recent years, minimally invasive surgery has been adopted, in which pedicle screws and rods are inserted percutaneously (through several small incisions) into the patient's back and fixed to each vertebra, stabilizing the spine. Compared to procedures requiring large back incisions, percutaneous spinal stabilization offers many advantages to patients, including reduced blood loss, shorter surgery times, and reduced surgical site infections. In such minimally invasive surgery, the aforementioned issue of rod curvature becomes more pronounced and becomes a major problem. This is because, just like in procedures requiring large back incisions, even in such minimally invasive surgery, the rods are bent appropriately by the surgeon and other surgical staff using specialized surgical instruments before being inserted into the patient's body. However, once the bent rods are inserted percutaneously, it is not easy to adjust the curvature of the rods.

In addition, procedures that involve large incisions in the patient's back involve releasing all of the muscles and ligaments attached to the vertebral tissue, opening the surgical field, and correcting the spinal alignment using a spinal stabilization system (including pedicle screws and rods). This places less stress on the rods, and the amount of deformation of the rods after placement is smaller than the amount of deformation before placement. In contrast, percutaneous procedures do not release the muscles and ligaments attached to the vertebral tissue, and instead correct the spinal alignment using a spinal stabilization system. This places more stress on the rods, and the amount of deformation after placement is greater than the amount of deformation before placement. For this reason, the experience and intuition gained from procedures that involve opening the patient's back about the degree of rod curvature before placement is completely useless in percutaneous procedures. Therefore, even in percutaneous procedures, the precise degree of rod curvature before placement becomes even more important.

Patent Document 1 discloses an instrument for bending surgical rods, which includes a handle that forms a receiving area for receiving a surgical rod, a lever that is rotatably connected to the handle, and a template rod holder that is configured to hold a template rod having a bent shape that can be used as a template for bending the surgical rod around a bending axis, and is attached to one of the handle and the lever at a position adjacent to the receiving area.

Special Publication No. 2021-519171

However, while the surgical rod bending instrument described in Patent Document 1 is equipped with a template rod holder for holding a template rod, this template rod is simply used to locally bend the surgical rod and does not instruct the surgeon or surgical staff on the overall curvature direction or exact angle of the surgical rod that will provide the optimal correction effect for each patient. In other words, the template rod described in Patent Document 1 does not instruct the surgeon or surgical staff on the optimal curvature of the entire surgical rod based on the patient's specific pelvic morphological angle (PI). Therefore, even if a surgical rod bent along the template rod is used to correct and fix a spinal deformity, it will be difficult to achieve the optimal correction effect for each patient.

In short, even with the template rod described in Patent Document 1, when performing spinal deformity correction and fixation surgery using a procedure that involves a large incision in the patient's back or a percutaneous procedure (minimally invasive surgery), it is difficult for the surgeon and other surgical staff to determine the degree of curvature of the rod, i.e., the precise direction and angle of curvature, that will provide the optimal correction effect for the patient when curving the rod before placing it inside the patient's body.

The present invention has been made in consideration of the above points, and aims to provide a method for manufacturing a template that instructs the surgical staff, including the surgeon, on the degree of rod curvature that will achieve the optimal correction effect for the patient before the template is placed inside the body, without relying on the experience or intuition of the surgical staff, including the surgeon.

For reference, the first aspect of the template is a template that is attached to each vertebra of the spine and is used when placing a rod configured as an implant material inside the patient's body, and is characterized in that, prior to placing the rod inside the body, the template instructs the surgical staff, including the surgeon, on the degree of curvature of the entire rod that corresponds to the morphological angle of the pelvis unique to the patient.
In the first aspect of this template , the template allows the surgeon and other surgical staff to learn the degree of curvature of the entire rod corresponding to the patient's specific morphological angle before the rod is placed inside the body. As a result, by correcting and fixing the spinal deformity with the rod curved according to the template, it is possible to obtain the optimal correction effect for the patient.

The pelvic morphological angle (PI) is an angle specific to each patient, and anatomically normal sagittal alignment (vertebral arrangement) of the spine is established based on this morphological angle. In other words, differences in the morphological angle result in different kyphosis angles of the thoracic spine and lordosis angles of the lumbar spine, resulting in the thoracic and lumbar vertebrae being balanced in the sagittal plane depending on the morphology of the pelvis.

In the first aspect of this template , the template can teach the optimal rod shape corresponding to the morphological angle of the pelvis unique to each patient, i.e., the rod shape having the optimal curvature, so that by correcting and fixing the spinal deformity using the rod having the optimal curvature taught by the template without relying on the experience or intuition of the surgical staff, including the surgeon, it is possible to approach normal spinal alignment, that is, to obtain the optimal correction effect for each patient. In short, in the first aspect of this template , the surgical staff, including the surgeon, can curve the rod according to the optimal rod shape corresponding to the morphological angle unique to each patient based on the template, thereby realizing semi-customized treatment for each patient.

In addition, the templates must be prepared appropriately for different patient approaches (such as procedures involving a large incision in the patient's back or percutaneous procedures), different rod materials (such as titanium or cobalt-chromium alloy), and different rod outer diameters.

A second aspect of the template is the first aspect, characterized in that the template has a display section that displays the rod shape showing the degree of curvature of the entire rod in two dimensions.
In the second aspect of the template , the surgical staff, including the surgeon, can easily bend the rod to conform to the rod shape shown on the display section of the template.

A third aspect of the template is the second aspect, characterized in that the template is formed by providing the display portion on a surface of a plate material.
In the third aspect of this template , a display unit is provided on the surface of the plate, i.e., the upper surface and/or the lower surface, and this plate can be easily brought into the operating room, making it easy to handle.

A fourth aspect of the template is the second aspect, characterized in that the display unit displays an inflection point of the rod shape.
In the fourth aspect of this template , the position of the inflection point (the inflection point that is the boundary between lumbar lordosis and thoracic kyphosis) can be grasped as one of the indicators for sagittal plane correction by rod fixation for spinal deformity when the rod is curved using the template, allowing the surgeon to imagine the corrected position of the patient after surgery.

A fifth aspect of the template is the first aspect, characterized in that the template is made of a temporary rod that has been bent in two or three dimensions to change the degree of curvature of the entire rod.
The fifth aspect of the template is particularly effective when the degree of curvature of the entire rod (rod shape) is three-dimensional.

The invention of claim 1 relating to the method for manufacturing a template is a method for instructing surgical staff, including an operator, on the degree of curvature of a rod, which is attached to each vertebra of the spine and configured as an implant material , when the rod is bent before being placed inside a patient's body, and the method includes a rod shape acquisition step of acquiring data on the shape of the rod bent when placed inside the body and the shape of the rod bent before being placed inside the body based on many past cases, a morphological angle classification step of classifying the many rod shapes bent when placed inside the body acquired in the rod shape acquisition step into groups according to the morphological angle of the pelvis unique to the patient, and a method for classifying the many rod shapes classified in the morphological angle classification step into groups according to the morphological angle of the pelvis. and a rod deformation amount calculation step of calculating the deformation amount of the rod for each morphological angle by comparing the rod shape acquired in the rod shape acquisition step for the same patient, the rod shape curved when placed in the body, with the rod shape bent before being placed in the body, and calculating the deformation amount of the rod for each morphological angle. The method is characterized by including: an approximate rod shape acquisition step of calculating an approximate curve for each morphological angle of the pelvis based on the shape of the pelvis, for each morphological angle, and acquiring a single rod shape having the curve; a rod deformation amount calculation step of calculating the deformation amount of the rod for each morphological angle by adding the deformation amount calculated for each morphological angle by the rod deformation amount calculation step to the rod shape for each morphological angle acquired in the approximate rod shape acquisition step, to derive a rod shape having an optimal curvature for each morphological angle, and manufacturing a template based on the rod shape .
In the invention of claim 1 , it is possible to derive the optimal rod shape, i.e., the rod shape with the optimal curvature, for each pelvic morphological angle specific to a patient, and to manufacture a template that teaches the degree of curvature of the entire rod corresponding to the morphological angle. As a result , by correcting and fixing the spinal deformity using the rod taught by the template, it is possible to obtain the optimal correction effect for each patient without relying on the experience or intuition of the surgical staff, including the surgeon.

In addition, depending on the degree of flexibility in correcting each patient's spinal deformity and the surgical environment, for example, the surgical environment after placing an LIF cage between vertebral bodies, even if the morphological angle is approximately the same for each patient, the amount of deformation of the rod may differ significantly when comparing the curved rod shape while placed in the body with the shape of the rod bent before being placed in the body.

In consideration of these circumstances, the invention of claim 1 particularly comprises a rod deformation amount calculation process in which the rod shape curved when placed in the body, acquired in the rod shape acquisition process, is compared with the rod shape bent before being placed in the body, and the deformation amount is calculated for each morphological angle; and a template manufacturing process in which the deformation amount calculated for each morphological angle in the rod deformation amount calculation process is added to the rod shape for each morphological angle acquired in the approximate rod shape acquisition process to derive an optimal rod shape for each morphological angle, and a template is manufactured based on the rod shape, thereby improving the accuracy of obtaining a rod shape with an optimal curvature for each patient.

The invention relating to the template manufacturing method of claim 2 is the invention of claim 1 , further comprising, between the morphological angle classification step and the approximate rod shape acquisition step, a rod length classification step of classifying, at each morphological angle, the multiple rod shapes classified into groups for each morphological angle of the pelvis, into groups for each of a plurality of set total lengths of the rod, based on the multiple rod shapes classified into groups for each morphological angle of the pelvis, and the approximate rod shape acquisition step is characterized in that an approximate curve is calculated based on the multiple rod shapes classified into groups for each rod total length at each morphological angle acquired in the morphological angle classification step and the rod length classification step, and a single rod shape having the curve is acquired.
In the invention of claim 2 , in the rod length classification step, the rod shapes are obtained by classifying the rods into groups according to rod length at each morphological angle, so that the accuracy can be further improved to obtain the optimal rod shape for each patient.

A third aspect of the present invention relates to a template manufacturing method according to the first aspect of the present invention, wherein the deformation amount includes a difference in lumbar lordosis angle.
In the invention of claim 3 , the amount of deformation can be calculated with high accuracy by calculating at least the difference in the lumbar lordosis angle (LL) on the lumbar side from the inflection point of the rod.

The invention relating to the template manufacturing method of claim 4 is the invention described in claim 1 , characterized in that in the template manufacturing process, when the configuration angle is in the range of 40° to 49°, multiple rod shapes having optimal curvatures are set, and also when the configuration angle is in the range of 50° to 59°, multiple rod shapes having optimal curvatures are set.
In the invention of claim 4 , a rod shape with an optimal curvature can be selected taking into consideration the degree of hardness or softness in correcting each patient's spinal deformity, and special surgical environments, such as the surgical environment after installing an LIF cage between adjacent vertebrae. This also makes it possible to improve the accuracy in obtaining the optimal rod shape for each patient.

The reference template can teach the surgical staff, including the surgeon, the degree of rod curvature that will provide the optimal correction effect for the patient before the rod is placed inside the body, without relying on the experience or intuition of the surgical staff, including the surgeon. Furthermore, the template manufacturing method of the present invention can derive rod shapes with optimal curvatures for each morphological angle of the patient's pelvis based on many past cases, and can manufacture templates based on these rod shapes.

FIG. 1 is a schematic diagram illustrating a percutaneous spinal stabilization system. FIG. 2 is a plan view of a display section on the top surface of a plate material used in the template according to this embodiment, on which the shapes of the rods are displayed. FIG. 3 is a plan view of a display portion on the underside of the plate material used in the template according to this embodiment, on which the shapes of the rods are displayed. FIG. 4 is a perspective view of a temporary rod, which is a template according to another embodiment. FIG. 5 is a diagram showing the balance of the spine on the sagittal plane. FIG. 6 is an enlarged view of part A in FIG. FIG. 7 is a flow diagram showing a method for manufacturing a template according to an embodiment of the present invention. Figure 8(a) shows a number of rod shapes that were classified into a morphological angle range of 30° to 39° in the morphological angle classification process from a large number of data on rod shapes bent while placed inside the body, and were also classified by total rod length in the rod length classification process, and (b) shows a single rod shape (central axis line) that has an approximate curve (average curve) calculated from the large number of classified rod shapes. FIG. 9 is a diagram showing angle parameters from the thoracic vertebra T10 to the sacrum S of the spine. FIG. 10 is a diagram showing the shape of a rod having a morphological angle (PI) of 40° to 49° and a total length of 305 mm, acquired through the rod shape acquisition step, morphological angle classification step, rod length classification step, and approximate rod shape acquisition step. FIG. 11 shows the T10-L1 kyphosis angle, lumbar lordosis angle (LL), and lower lumbar lordosis angle (LLL) for each morphological angle (PI) obtained through the rod shape acquisition process, morphological angle classification process, rod length classification process, and approximate rod shape acquisition process. Figure 12 shows the lumbar lordosis angle of the rod shape (patient) after placement in the body obtained in the rod shape acquisition process, the patient's corrected target lumbar lordosis angle, the deformation amount obtained in the rod deformation amount calculation process, and the final rod shape lumbar lordosis angle obtained in the template manufacturing process for patterns 1 to 6. FIG. 13 shows the central axes of the rod shapes finally calculated and derived for patterns 1 to 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.
As shown in Figure 1, a percutaneous spinal stabilization system 1, which corrects and stabilizes spinal deformities by percutaneously approaching a patient from behind, is used in various surgical treatments for adult spinal deformities, such as degenerative kyphoscoliosis, lumbar spondylolisthesis, and dislocated spinal tumors. The percutaneous spinal stabilization system 1 includes multiple pedicle screws 2 that are screwed into the vertebral bodies via the pedicles of each vertebra in the spine, and rods 3 that are arranged along the craniocaudal direction of the spine and connected to the heads 2A of each pedicle screw 2, thereby correcting, fixing, and stabilizing spinal deformities. In this embodiment, the pedicle screws 2 and rods 3 are made of titanium.

The percutaneous spinal stabilization system 1 shown in Figure 1 corrects and stabilizes spinal deformities by inserting pedicle screws 2 and rods 3 into the patient's body percutaneously (through several small incisions) from the back and fixing them to each vertebra. The percutaneous spinal stabilization system 1 shown in Figure 1 is equipped with LIF cages 4 interposed between adjacent lumbar vertebrae. The LIF cages 4 are used in lateral lumbar interbody fusion (LLIF). In Figure 1, three LIF cages 4 are interposed. The rods 3, which are components of the percutaneous spinal stabilization system 1, are bent before being placed percutaneously in the body to achieve optimal correction for the patient. This bending is performed by staff, including the surgeon, based on the shape of each rod shown on the display section 12 of the template 10 (described below). A dedicated surgical instrument, such as a plate bender, is used to appropriately bend the rods 3. In this embodiment, the pedicle screw 2, rod 3, and LIF cage 4 correspond to the implant material.

The template 10 according to an embodiment of the present invention will now be described with reference to Figures 2 and 3. The template 10 according to this embodiment instructs the surgical staff, including the surgeon, on the degree of overall curvature of the rod 3 prior to placing the rod 3 inside the patient's body. Specifically, the template 10 according to this embodiment instructs the surgical staff, including the surgeon, on the degree of overall curvature of the rod 3 corresponding to the patient's specific pelvic morphological angle (PI) (described in detail below) prior to placing the rod 3 inside the patient's body. The template 10 according to this embodiment includes a display unit 12 on the surface of a thin plate 11, i.e., on the upper surface (see Figure 2) and lower surface (see Figure 3) of the plate 11, that displays the rod shape for each morphological angle (PI) (for each of patterns 1 to 6 shown in Figure 12, described in detail below) that can achieve the optimal correction effect for the patient. The rod shape for each morphological angle (PI) (for each of patterns 1 to 6 shown in Figure 12, described in detail below) represents the overall curvature of the rod 3 in two dimensions. Plate material 11 is made of metal, synthetic resin, etc. However, plate material 11 is not limited to these materials as long as it is sterilizable.

Specifically, the display section 12 of the template 10 (the upper and lower surfaces of the plate material 11) displays rod shapes for each configuration angle (PI) described in detail below, i.e., patterns 1 to 6 (45°, 50°, 55°, 60°, 65°, and 70°, which correspond to the lumbar lordosis angle (LL) in the final rod shape shown in FIG. 12 ), with the rods having the same overall length (285 mm in FIGS. 2 and 3 ) and outer diameter (5.5 mm in FIGS. 2 and 3 ). These rod shapes for patterns 1 to 6 are displayed based on the finally calculated rod axis shown in FIG. 13 . As shown in FIG. 2 , the upper surface of the display section 12 of the template 10 displays, from top to bottom, rod shapes for a configuration angle (PI) range of 30° to 39° (Pattern 1), a configuration angle (PI) range of 40° to 49° (Pattern 2), and a configuration angle (PI) range of 50° to 59° (Pattern 3). On the other hand, as shown in Figure 3, the bottom surface of the template 10, which is the display unit 12, displays, from top to bottom, rod shapes with a configuration angle (PI) in the range of 40° to 49° (pattern 4), rod shapes with a configuration angle (PI) in the range of 50° to 59° (pattern 5), and rod shapes with a configuration angle (PI) in the range of 60° or more (pattern 6).

In addition, each rod shape displayed on the display unit 12 shows the position of the thoracic vertebra (T10) to the sacrum (S2) of the spine when the rod 3 is placed inside the body, three 1/4 reference lines for the total length of the rod 3, the position of the apex, and the position of the inflection point (IP). The display unit 12 also displays the total length and outer diameter of the rod 3. It is known that the inflection point (IP) of the rod shape, i.e., the inflection point (IP) that marks the boundary between lumbar lordosis and thoracic kyphosis, is located closer to the head the greater the patient's morphological angle (PI), and similarly, the position of the apex vertebra of the lumbar lordosis is located closer to the head the greater the morphological angle (PI).

Knowing the location of the inflection point and apical vertebra, which serve as indicators for sagittal plane correction using rod fixation, helps the surgeon visualize the patient's postoperative correction position. Furthermore, if the inflection point is located more cranially than necessary (more cranial than thoracic vertebra T12), it is known to be associated with postoperative collapse of the non-fixed vertebrae above the fused vertebrae and loss of correction (technically referred to as PJK or PJF (Proximal Junctional Kyphosis/Failure)). Therefore, understanding the location of the inflection point and apical vertebra is an important factor in determining the appropriate corrective fixation position. Furthermore, the position of the three 1/4 reference lines relative to the entire length of the rod 3 is the position at which the rod 3 is supported by a dedicated surgical instrument, such as a plate bender, when bending the rod 3 to conform to its shape. The aforementioned template 10 is available in four lengths for the rod 3: 285 mm, 295 mm, 305 mm, and 320 mm, as described below. Therefore, a total of four templates are prepared, one for each length of the rod 3.

In the template 10 according to this embodiment, the rod shapes for patterns 1 to 6 are displayed as display units 12 on the top and bottom surfaces of the plate 11. However, the rod shapes for patterns 1 to 6 may be displayed as display units 12 on either one surface (the top surface) of the plate 11. In addition, in the template 10 according to this embodiment, the rod shapes are displayed as lines on the top and bottom surfaces of the plate 11. However, recesses having a width approximately equal to the rod diameter may be formed along the rod shapes. In this embodiment, after bending the rod 3, the rod 3 can be fitted into the recess of the taught rod shape to confirm the degree of bending. As shown in FIG. 4, a template 10A according to another embodiment may be constructed using a temporary rod 15 that has been bent in three dimensions in advance to determine the degree of curvature of the entire rod 3.

Next, a method for manufacturing a template 10 according to an embodiment of the present invention will be described. This method for manufacturing the template 10 will be described in detail, particularly the method for deriving the rod shape for each morphological angle (PI) displayed on the display unit 12 of the template 10 shown in Figures 2 and 3, i.e., for each of patterns 1 to 6, as described in detail below. In this embodiment, the method for deriving the rod shape for each of patterns 1 to 6 described below uses a titanium rod 3 with an outer diameter of 5.5 mm. Based on numerous past cases, the display unit 12 of the template 10 derives and displays a rod shape with the optimal curvature for each patient-specific pelvic morphological angle (PI). As previously mentioned, the pelvic morphological angle (PI) shown in Figures 5 and 6 is a patient-specific angle, and an anatomically normal sagittal alignment (vertebral arrangement) of the spine is established based on this morphological angle (PI). In other words, differences in the morphological angle (PI) result in different kyphosis angles (TK) of the thoracic spine and different lordosis angles (LL) of the lumbar spine, resulting in the thoracic and lumbar vertebrae being balanced in the sagittal plane depending on the morphology of the pelvis.

To explain in more detail, the manufacturing method of the template 10 according to this embodiment, as shown in Figure 7, involves carrying out the following steps in this order: rod shape acquisition process S1 → morphology angle classification process S2 → rod length classification process S3 → approximate rod shape acquisition process S4 → rod deformation amount calculation process S5 → template manufacturing process S6. First, in the rod shape acquisition process S1, data is acquired based on numerous past cases of the rod shape curved while placed inside the body and the rod shape bent before being placed inside the body.

In the rod shape acquisition process S1, data on the shape of the rod bent before placement inside the body is first acquired. Specifically, an image of the rod 3 bent before placement is loaded into CAD (Computer Aided Design). Next, multiple plots are manually made at predetermined intervals along the central axis of the rod 3 loaded into CAD. Next, the coordinates of each of the multiple plots are measured, and an approximation curve (cubic equation) is calculated based on these coordinates. Next, the rod shape (two-dimensional) is calculated using this approximation curve as the central axis. Next, the coordinates of the inflection points are calculated for each of the many bent rod shapes stored as data.

Next, in the rod shape acquisition step S1, data on the curved rod shape when placed inside the body is acquired. Specifically, an X-ray image of the pedicle screw 2 including the rod 3 attached to the patient's spine is loaded into CAD. Next, multiple central positions of the connection between the rod 3 and the head 2A of the pedicle screw 2, specifically the overlapping portion of the rod 3 and the head 2A of the pedicle screw 2, are manually plotted (the same number as the pedicle screw 2). Next, the coordinates of each of the multiple plots are measured, and an approximate curve (cubic equation) is calculated based on these coordinates. Next, the rod shape (two-dimensional) is calculated with the approximate curve as the central axis. Next, the coordinates of the inflection points are calculated for each of the numerous rod shapes after placement inside the body that have been accumulated as data.

Next, the morphological angle classification step S2 is performed. In the morphological angle classification step S2, the numerous rod shapes curved while placed inside the body, acquired in the rod shape acquisition step S1, are classified into groups based on the patient's specific pelvic morphological angle (PI). The pelvic morphological angle (PI) is set to four types, for example, 30° to 39°, 40° to 49°, 50° to 59°, and 60° or greater. Next, the rod length classification step S3 is performed. In the rod length classification step S3, the morphological angles (PI) (the four types mentioned above) are classified into groups based on the set total length of the rod 3. The total length of the rod 3 is set to four types, for example, 285 mm, 295 mm, 305 mm, and 320 mm. Note that in this embodiment, the total length of the rod 3 is set to four types: 285 mm, 295 mm, 305 mm, and 320 mm, but is not limited to these four types.

The method for classifying rods by length will now be described in detail. Specifically, the rod shapes obtained from X-ray images are obtained by plotting multiple connection points between the rod 3 and the head 2A of each pedicle screw 2. The appropriate rod shapes are calculated so that the overall length of each rod 3 matches the set overall length of each rod 3. For example, if the overall length of the rod shape obtained from the X-ray image is approximately 275 mm, the rod shape is appropriately scaled using a similarity ratio to obtain total lengths of 285 mm, 295 mm, 305 mm, and 320 mm, respectively. Furthermore, if the overall length of the rod shape obtained from the X-ray image is approximately 300 mm, the rod shape is appropriately scaled using a similarity ratio to obtain total lengths of 285 mm, 295 mm, 305 mm, and 320 mm, respectively, and the rod shapes are calculated to obtain total lengths of 285 mm, 295 mm, 305 mm, and 320 mm, respectively. In this way, all rod shapes obtained from X-ray images are appropriately scaled using a similarity ratio to have four different total lengths: 285 mm, 295 mm, 305 mm, and 320 mm, and all rod shapes obtained from X-ray images are classified into four different total lengths.

The numerous rod shapes curved while placed inside the body, acquired in the rod shape acquisition step S1, are classified into four types based on the morphological angle (PI) and four types based on the total length of the rod 3, for a total of 16 types. Note that Figure 8(a) illustrates numerous rod shapes (central axes) acquired from X-ray images, classified into four total lengths of the rod 3 (285 mm, 295 mm, 305 mm, 320 mm) within the morphological angle (PI) range of 30° to 39°.

Next, the approximate rod shape acquisition process S4 is carried out. In the approximate rod shape acquisition process S4, an approximate curve (average curve) for each of the 16 types of rod shapes is calculated based on the numerous rod shapes (central axes) classified into 16 types acquired in the rod shape acquisition process S1, morphological angle classification process S2, and rod length classification process S3, and a single rod shape having this curve is acquired for each of the 16 types. Figure 8(b) illustrates a single rod shape (central axis) based on numerous rod shapes (central axes) classified into four total lengths of rod 3 (285 mm, 295 mm, 305 mm, 320 mm) in the morphological angle (PI) range of 30° to 39°. In short, a single rod shape is derived for each of the 16 types through the rod shape acquisition process S1, morphological angle classification process S2, rod length classification process S3, and approximate rod shape acquisition process S4.

Figure 10 shows rod shapes, for example, with a morphological angle (PI) of 40° to 49° and a total length of 305 mm, obtained through the rod shape acquisition process S1, morphological angle classification process S2, rod length classification process S3, and approximate rod shape acquisition process S4. The coordinates (positions) of the inflection points are calculated for each of the 16 types of rod shapes calculated. Furthermore, for each of the 16 types of rod shapes calculated, the T10-L1 kyphosis angle, lumbar lordosis angle (LL), and lower lumbar lordosis angle (LLL), etc., are calculated using a specific calculation method based on X-ray images. Therefore, Figure 11 shows the T10-L1 kyphosis angle, lumbar lordosis angle (LL), lower lumbar lordosis angle (LLL), and inflection point positions for the rod shape for each morphological angle (PI) acquired through the rod shape acquisition process S1, morphological angle classification process S2, rod length classification process S3, and approximate rod shape acquisition process S4. Note that in the approximate rod shape acquisition process S4, a total of 16 types of rod shapes are calculated for each morphological angle (PI) and each rod length, but the T10-L1 kyphosis angle, lumbar lordosis angle (LL), lower lumbar lordosis angle (LLL), and inflection point positions for each morphological angle (PI) are constant regardless of the rod length (4 types).

Next, the rod deformation calculation step S5 is performed. In the rod deformation calculation step S5, the rod shape curved while placed in the body of the same patient, acquired in the rod shape acquisition step S1, is compared with the rod shape bent before placement in the body to calculate the deformation amount of the rod 3 for each morphological angle (PI). Specifically, the rod shape curved while placed in the body in the X-ray image of the same patient acquired in the rod shape acquisition step S1 and the rod shape bent before placement in the body (drawn in the diagram) are superimposed on the CAD so that their inflection points coincide. Next, the difference in the lumbar lordosis angle (LL) (see Figure 9) is calculated as the deformation amount between the rod shape curved while placed in the body in the X-ray image and the rod shape bent before placement in the body. This deformation amount is shown in Figure 12. This deformation amount varies between 5° and 15° as a difference in lumbar lordosis angle (LL) for each morphological angle (PI), i.e., for patterns 1 to 6 in Figure 12.

Next, the template manufacturing process S6 is carried out. In the template manufacturing process S6, the deformation amount (difference in lumbar lordosis angle (LL)) calculated for each morphological angle (PI) in the rod deformation amount calculation process S5 is added to the single rod shape calculated for each morphological angle (PI) (and for each rod length) acquired in the approximate rod shape acquisition process S4 to derive a rod shape for each morphological angle (PI) (and for each rod length), and the template 10 is manufactured based on that rod shape. For more details, referring to Figure 12, in pattern 1 (morphological angle (PI): 30°-39°), the deformation amount is 10°, so the lumbar lordosis angle (LL) of 35° after the target patient correction is added, resulting in a lumbar lordosis angle (LL) of 45° for the final rod shape. Then, for all rod shapes acquired in the approximate rod shape acquisition step S4, with total lengths of 285 mm, 295 mm, 305 mm, and 320 mm in the morphological angle (PI) range of 30° to 39°, the lumbar lordosis angle (LL) is set to 45°. For pattern 1 (morphological angle (PI): 30° to 39°), the inflection point of the final rod shape is at the position of the second lumbar vertebra (L2).

Furthermore, in pattern 2 (morphological angle (PI): 40°-49°), the deformation amount is 5°, so the deformation amount of 5° is added to the lumbar lordosis angle (LL) of 45° after the target patient correction, to set the lumbar lordosis angle (LL) of the final rod shape to 50°. Then, for all rod shapes with total lengths of 285 mm, 295 mm, 305 mm, and 320 mm in the morphological angle (PI): range of 40°-49° obtained in the approximate rod shape acquisition process S4, the lumbar lordosis angle (LL) is set to 50°. Furthermore, in pattern 4 (morphological angle (PI): 40°-49°), the deformation amount is 15°, so the deformation amount of 15° is added to the lumbar lordosis angle (LL) of 45° after the target patient correction, to set the lumbar lordosis angle (LL) of the final rod shape to 60°. Then, for all rod shapes acquired in the approximate rod shape acquisition step S4, with total lengths of 285 mm, 295 mm, 305 mm, and 320 mm in the morphological angle (PI) range of 40° to 49°, the lumbar lordosis angle (LL) is set to 60°. For patterns 2 and 4 (morphological angle (PI): 40° to 49°), the inflection point of the final rod shape is at the position of the first lumbar vertebra (L1).

In addition, in patterns 2 and 4, the amount of deformation differs between 5° and 15° at the same configuration angle (PI): 40° to 49°, so the lumbar lordosis angle (LL°) of the final rod shape is set to 50° or 60°. However, this is set appropriately taking into consideration the degree of flexibility in correcting each patient's spinal deformity and the circumstances of the surgical environment, for example, the surgical environment after placing the LIF cage 4 between the vertebral bodies. Therefore, if, for example, pattern 2 or 4, which has a configuration angle (PI): range of 40° to 49°, is determined to be too rigid (difficult to correct) for correcting the patient's spinal deformity, the final rod shape of pattern 4 is adopted.

Furthermore, in pattern 3 (morphological angle (PI): 50°-59°), the deformation amount is 5°, so the deformation amount of 5° is added to the lumbar lordosis angle (LL) of 50° after the target patient correction, resulting in a lumbar lordosis angle (LL) of 55° for the final rod shape. Then, for all rod shapes with total lengths of 285 mm, 295 mm, 305 mm, and 320 mm in the morphological angle (PI): 50°-59° range obtained in the approximate rod shape acquisition process S4, the lumbar lordosis angle (LL) is set to 55°. Furthermore, in pattern 5 (morphological angle (PI): 50°-59°), the deformation amount is 10° (or 15°), so the deformation amount of 10° (or 15°) is added to the lumbar lordosis angle (LL) of 55° (or 50°) after the target patient correction, resulting in a lumbar lordosis angle (LL) of 65° for the final rod shape. Then, for all rod shapes acquired in the approximate rod shape acquisition step S4, with total lengths of 285 mm, 295 mm, 305 mm, and 320 mm in the morphological angle (PI) range of 50° to 59°, the lumbar lordosis angle (LL) is set to 65°. For patterns 3 and 5 (morphological angle (PI): 50° to 59°), the inflection point of the final rod shape is at the position of the first lumbar vertebra (L1).

In addition, in patterns 3 and 5, the amount of deformation differs between 5° and 10° (15°) at the same configuration angle (PI): 50° to 59°, so the lumbar lordosis angle (LL) of the final rod shape is set to 55° or 65°. However, this is set appropriately taking into consideration the degree of flexibility in correcting each patient's spinal deformity and the circumstances of the surgical environment, for example, the surgical environment after placing the LIF cage 4 between the vertebral bodies. Therefore, if, for example, pattern 3 or 5, which has a configuration angle (PI): in the range of 50° to 59°, is judged to be too rigid (difficult to correct) for correcting the patient's spinal deformity, then the final rod shape of pattern 5 is adopted.

Furthermore, in pattern 6 (morphological angle (PI): 60° or more), the deformation amount is 10°, so the lumbar lordosis angle (LL) of the final rod shape is set to 70° by adding the deformation amount of 10° to the lumbar lordosis angle (LL) of 60° after the target patient correction. Then, for all rod shapes with total lengths of 285 mm, 295 mm, 305 mm, and 320 mm at a morphological angle (PI): 60° or more obtained in the approximate rod shape acquisition process S4, the lumbar lordosis angle (LL) is set to 70°. In pattern 6 (morphological angle (PI): 60° or more), the inflection point of the final rod shape is the position of the first lumbar vertebra (L1). Figure 13 shows the final calculated and derived rod shapes (central axes) for all rod shapes with total lengths of 285 mm, 295 mm, 305 mm, and 320 mm in patterns 1 to 6. In this embodiment, for patterns 1 to 6, the lumbar lordosis angle (LL) of all 16 types of rod shapes (effectively 4 types due to differences in morphological angle (PI)) calculated in the approximate rod shape acquisition step S4, i.e., the values (values for patterns 1 to 6) in the column for lumbar lordosis angle LL (°) of rod shape (patient) after placement in the body in Figure 12, are reference values and are not directly taken into consideration when calculating the final rod shape.

Next, in the template manufacturing process S6, the template 10 is manufactured based on the final calculated and derived rod shapes as described above. That is, in the template manufacturing process S6, the final calculated and derived rod shapes along the central axis for each of patterns 1 to 6 shown in FIG. 13 are displayed on the display units 12 on the surfaces of the plate material 11, i.e., the upper and lower surfaces, to manufacture the template 10. The detailed display format has been described above, so a detailed explanation will be omitted here.

In this embodiment, in the rod deformation amount calculation step S5, the deformation amount of the rod 3 obtained by comparing the curved rod shape in an X-ray image while placed inside the body with the shape of the rod bent before being placed inside the body on CAD is calculated as the difference in the lumbar lordosis angle (LL). However, to improve the accuracy of the deformation amount, the deformation amount may be calculated taking into account the difference in the lumbar lordosis angle (LL) and the difference in the T10-L1 kyphosis angle on the thoracic side from the inflection point of the rod 3. Furthermore, although the difference in the lumbar lordosis angle (LL) and the difference in the T10-L1 kyphosis angle are used as evaluation indices for the deformation amount in this embodiment, other evaluation indices may also be used.

In addition, the manufacturing method of the template 10 according to this embodiment includes the rod length classification step S3, which is the best mode from the perspective of handling (sales strategy, etc.), but the rod length classification step S3 is not necessarily included in the process of setting the final rod shape. That is, the T10-L1 kyphosis angle, lumbar lordosis angle (LL), and lower lumbar lordosis angle (LLL) for each morphological angle (PI) calculated in the approximate rod shape acquisition step S4 are constant regardless of the rod length (four types). Furthermore, when setting the final rod shape in the template manufacturing step S6, the lumbar lordosis angle (LL) is different for each of patterns 1 to 6 (different morphological angles (PI)), and rod length is not involved. Therefore, the rod length classification step S3 is not necessarily included. In other words, the final rod shapes in FIGS. 12 and 13 may be appropriately scaled using a similarity ratio to correspond to the set rod length, and a rod shape may be derived for each set rod length.

The template 10 according to this embodiment, as described above, can teach the surgeon and other surgical staff the degree of curvature of the entire rod that corresponds to the patient's specific pelvic morphological angle (PI) before the rod 3 is placed inside the body. This makes it possible to achieve optimal correction effects for each patient by correcting and fixing spinal deformities using the rod 3 with the optimal curvature taught by the template 10 according to this embodiment, without relying on the experience or intuition of the surgeon and other surgical staff.

The template 10 according to this embodiment also includes a display unit 12 that displays the rod shape, showing the degree of curvature of the entire rod in two dimensions. This allows the surgeon and other surgical staff to easily bend the rod 3 to conform to the rod shape shown on the display unit 12 of the template 10.

Furthermore, the template 10 according to this embodiment has a display unit 12 provided on the surface of the plate 11, i.e., on the top and/or bottom surface. This allows the plate 11 to be easily brought into the operating room, making it easier to handle. Furthermore, if the plate 11 is made of sterilizable synthetic resin, it can be made lighter, making it even easier to handle.

Furthermore, the display unit 12 of the template 10 according to this embodiment displays inflection points for the rod shape, which shows the degree of curvature of the entire rod in two dimensions. This allows the position of the inflection points to be grasped as one of the indicators for sagittal plane correction of spinal deformity by rod fixation in the rod 3 curved using the template 10 according to this embodiment, making it possible to visualize the corrected position of the patient after surgery.

Furthermore, the template 10 according to this embodiment is ideal for instructing surgical staff, including surgeons, on the degree of curvature of the rod 3 used in the percutaneous spinal stabilization system 1. In other words, the load on the rod 3 differs between percutaneous procedures (minimally invasive surgery) and procedures involving a large back incision, resulting in a different amount of deformation of the rod 3. Therefore, it is not possible to instruct the curvature of the rod 3 that corresponds to procedures involving a large back incision. However, even in procedures involving a large back incision, the manufacturing method for the template 10 according to this embodiment can be adopted, and analysis results equivalent to those shown in Figure 12 can be obtained to derive the final rod shape and manufacture the template 10. This template 10 is intended solely to instruct the curvature of the rod 3 that corresponds to procedures involving a back incision, and not to instruct the curvature of the rod 3 that corresponds to percutaneous procedures.

Furthermore, the template 10A according to another embodiment is constructed from a temporary rod 15 that has been bent in three dimensions to match the degree of curvature of the entire rod. This makes it particularly effective when the degree of curvature of the entire rod (rod shape) is three-dimensional.

On the other hand, with the manufacturing method of the template 10 according to this embodiment described above, a rod shape with the optimal curvature is derived for each patient's specific pelvic morphological angle (PI) based on numerous past cases, and the template 10 is manufactured based on this rod shape. This allows even those with little experience in percutaneous surgical procedures to obtain the optimal correction effect for each patient by correcting and fixing the spinal deformity using the rod 3 with the optimal curvature taught by the template 10, without relying on the experience or intuition of the surgical staff, including the surgeon.

Furthermore, the manufacturing method for the template 10 according to this embodiment particularly includes a rod deformation amount calculation step S5, and the calculation results in this rod deformation amount calculation step S5 are reflected in the final rod shape in the template manufacturing step S6. This makes it possible to obtain an optimal rod shape for each patient (even if the morphological angle (PI) is the same) depending on the degree of stiffness or softness with respect to the correction of each patient's spinal deformity and the surgical environment, for example, the surgical environment after the LIF cage 4 has been placed between the vertebral bodies.

Furthermore, the manufacturing method for the template 10 according to this embodiment includes a rod length classification process S3, in which rod shapes are obtained by classifying the rods into groups according to rod length at each morphological angle (PI), thereby further improving the accuracy of obtaining the optimal rod shape for each patient.

Furthermore, in the manufacturing method of the template 10 according to this embodiment, in the template manufacturing step S6, when the patient-specific morphological angle (PI) is in the range of 40° to 49°, two types of rod shapes with optimal curvatures are set. Also, when the morphological angle (PI) is in the range of 50° to 59°, two types of rod shapes with optimal curvatures are set. This makes it possible to select the optimal rod shape for each patient, even if the patient-specific morphological angle (PI) is the same, based on the degree of flexibility in correcting the spinal deformity of each patient, as well as the special surgical environment, such as the surgical environment after the LIF cage 4 has been placed between the vertebrae. This also improves the accuracy with which the optimal rod shape can be obtained for each patient.

The template 10 according to this embodiment described above is applicable to percutaneous procedures in which the rod 3 is made of titanium and has an outer diameter of 5.5 mm. However, the template 10 must be prepared appropriately depending on the approach to the patient and the material and outer diameter of the rod 3 to be used.

Furthermore, the template 10 according to the present embodiment described above is used to instruct the surgical staff, including the surgeon, on the degree of curvature of the entire rod corresponding to the patient's specific pelvic morphological angle (PI) prior to placing the rod 3 of the percutaneous spinal stabilization system 1 inside the body. However, the template 10 according to the present embodiment may also be used as an educational tool for doctors and surgical staff with little experience in percutaneous spinal deformity correction and fixation surgery, particularly for educating them on the degree of curvature of the rod 3 before surgery, for example, in surgical treatment of adult spinal deformity, etc., using the percutaneous spinal stabilization system 1.

3 Rod, 10, 10A Template, 11 Plate, 12 Display, 15 Temporary Rod

Claims (4)

A method for manufacturing a template that instructs a surgical staff member, including a surgeon, on the degree of curvature when a rod that is attached to each vertebra of the spine and configured as an implant material is bent before being placed inside a patient's body, comprising:
a rod shape acquisition step for acquiring data on the shape of the rod bent when placed in the body and the shape of the rod bent before being placed in the body, based on many past cases;
a morphological angle classification step of classifying the shapes of the rods curved when placed in the body, which are acquired in the rod shape acquisition step, into groups according to the morphological angles of the pelvis specific to the patient;
an approximate rod shape acquisition step of calculating an approximate curve for each pelvic morphological angle based on the multiple rod shapes classified into groups for each pelvic morphological angle in the morphological angle classification step, and acquiring a single rod shape having the curve;
a rod deformation amount calculation step of comparing the rod shape curved when placed in the body of the same patient, acquired in the rod shape acquisition step, with the rod shape bent before being placed in the body, and calculating the deformation amount of the rod for each morphological angle;
a template manufacturing step of adding the deformation amount calculated for each configuration angle in the rod deformation amount calculation step to the rod shape for each configuration angle acquired in the approximate rod shape acquisition step to derive a rod shape having an optimal curvature for each configuration angle, and manufacturing a template based on the rod shape;
A method for manufacturing a template, comprising: Between the morphological angle classification step and the approximate rod shape acquisition step, a rod length classification step is provided for classifying the rods into a plurality of groups for each set total length at each morphological angle based on the many rod shapes classified into groups for each pelvis morphological angle,
2. The method for manufacturing a template according to claim 1, characterized in that in the approximate rod shape acquisition process, an approximate curve is calculated based on a large number of rod shapes classified into groups based on the total length of the rod at each morphological angle acquired in the morphological angle classification process and the rod length classification process, and a single rod shape having the curve is acquired. The method for manufacturing a template according to claim 1 , wherein the deformation amount includes a difference in a lumbar lordosis angle. In the template manufacturing process,
In the range of the configuration angle of 40° to 49°, a plurality of rod shapes having optimal curvatures are set,
The template manufacturing method according to claim 1 , further comprising the step of setting a plurality of rod shapes having optimum curvatures even when the configuration angle is in the range of 50° to 59°.