A method for judging whether the screw has penetrated the inner wall of the pedicle based on intraoperative X-ray

Abstract

The present invention claims a method for determining whether a screw penetrates the inner wall of a pedicle based on intraoperative X-rays, including the following process: obtaining an anteroposterior image and a lateral image of a screw in a patient's pedicle; measuring the distance from the screw head to the screw tail in the anteroposterior image and recording it as B, measuring the distance from the medial edge of the pedicle to the screw head and recording it as x; measuring the distance from the screw head to the screw tail in the lateral image and recording it as A, measuring the distance from the posterior edge of the pedicle to the screw head in the lateral image and recording it as a; obtaining a comparison value b by formula a / A=b / B; analyzing the distance x from the medial edge of the pedicle to the screw head in the anteroposterior image and the comparison value b to determine whether the screw penetrates the inner wall of the pedicle. In theory, when it is determined that the distance x from the medial edge of the pedicle to the screw head is greater than the comparison value b, it indicates that the screw penetrates the inner wall of the pedicle, and through actual case verification, it is concluded that b-x<0.97mm can be used to determine that the screw penetrates the inner wall of the pedicle. This allows doctors to adjust the position of the screw in time during surgery.

Description

Technical Field

[0001] The invention relates to the technical field of surgical operations, and more particularly to a method for judging whether a screw penetrates the inner wall of a pedicle based on intraoperative X-rays. Background Art

[0002] Pedicle screw technology is a three-column internal fixation method that passes through the posterior articular process of the spinal segment through the pedicle to the vertebral body. Since the 1970s, it has been widely used in spinal stability reconstruction surgery because it can provide strong stability support. At present, it is still considered the gold standard for thoracic and lumbar segmental fixation.

[0003] However, pedicle screw technology also has related surgical risks and complications. Among them, the most common and important complications are that the screw penetrates the inner wall of the pedicle and damages the nerve roots, dura mater or spinal cord in the spinal canal. According to literature reports, the probability of pedicle screws penetrating the pedicle ranges from 5-23%, of which the incidence of breaking through the inner wall of the pedicle is about 5.7%. Postoperative CT scanning to confirm the relationship between the pedicle screw and the pedicle is a reliable method to judge the accuracy of screw placement. However, if the screw position is poor after surgery, it is necessary to reoperate to adjust the screw, which is an unplanned reoperation, which brings additional harm and medical burden to the patient. Therefore, the best solution is to judge the screw position immediately during surgery and make timely corrections.

[0004] At present, intraoperative C-arm X-ray machines are commonly used to guide and judge the accuracy of screw placement, but C-arm X-ray machines can only provide anteroposterior and lateral planar images, and cannot accurately judge the positional relationship between the screw and the pedicle, and are completely dependent on the surgeon's empirical judgment. Intraoperative robot navigation systems and O-arm navigation systems are also used, which use three-dimensional image fitting to accurately observe the position of the screw. However, these require additional large instruments, are costly, and will significantly prolong the operation time and increase the patient's radiation dose.

[0005] Therefore, how to determine whether the screw has penetrated the inner wall of the pedicle only by X-ray is the technical problem to be solved by the present application. Summary of the invention

[0006] In view of the shortcomings of the prior art, on the one hand, the present invention proposes a method for judging whether a screw has penetrated the inner wall of the pedicle based on intraoperative X-ray. The distance between the screw and the inner wall of the pedicle is measured and calculated by the principle of "corresponding sides of similar triangles are proportional", thereby judging whether the screw has penetrated the inner wall of the pedicle.

[0007] The present invention provides a method for judging whether a screw has penetrated the inner wall of a pedicle based on intraoperative X-rays, and the technical solution is as follows:

[0008] A method based on intraoperative X-ray to determine whether the screw has penetrated the inner wall of the pedicle includes the following steps:

[0009] St10. Obtain anteroposterior and lateral images of the screws in the patient's pedicles.

[0010] St20. Measure the distance from the screw head to the screw tail in the AP image and record it as B. Measure the distance from the medial edge of the pedicle to the screw head in the AP image and record it as x.

[0011] St30. Measure the distance from the screw head to the screw tail in the lateral image and record it as A. Measure the distance from the posterior edge of the pedicle to the screw head in the lateral image and record it as a.

[0012] St40, obtain the comparison value b through the formula a / A=b / B.

[0013] St50, analyze the distance x from the medial edge of the pedicle to the screw head in the anteroposterior image and the comparison value b to determine whether the screw has penetrated the inner wall of the pedicle.

[0014] In a second aspect, a computer device is proposed, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, a method for determining whether a screw has penetrated the inner wall of a pedicle based on intraoperative X-rays is implemented.

[0015] In a third aspect, a computer-readable storage medium is proposed, on which a computer program is stored. When the computer program is executed by a processor, the steps of a method for determining whether a screw has penetrated the inner wall of a pedicle based on intraoperative X-rays are implemented.

[0016] In summary, the above technical solution has the following beneficial effects: during the operation, a C-arm X-ray machine is used to collect the anteroposterior and lateral images of the screws in the patient's pedicles, and the comparison value b and the distance x from the inner edge of the pedicle to the screw head are calculated in real time to compare. In theory, when it is judged that the distance x from the inner edge of the pedicle to the screw head is greater than the comparison value b, it means that the screw has penetrated the inner wall of the pedicle. Through actual case verification, we have concluded that bx<0.97mm can be used to judge that the screw has penetrated the inner wall of the pedicle. This allows doctors to adjust the position of the screw in time during the operation to avoid surgical failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of measuring and calculating the distance between the screw and the inner wall of the pedicle using the principle of "corresponding sides of similar triangles are proportional";

[0018] Figure 2 This is a flow chart of a method for determining whether a screw has penetrated the inner wall of a pedicle based on intraoperative X-rays;

[0019] Figure 3 To measure the lateral and anteroposterior X-ray images Figure 1 Schematic diagram of the midline segments A, B, a, x;

[0020] Figure 4 This is a schematic diagram of CT measurement of the distance between the pedicle screw and the inner wall of the pedicle;

[0021] Figure 5 Schematic diagram of the linear correlation between X-ray measurement value (y=bx) and CT measurement value (Y);

[0022] Figure 6 The ROC curve diagram for predicting the penetration of the inner wall of the pedicle screw by the y value;

[0023] Figure 7 Flowchart for determination of cutoff values. DETAILED DESCRIPTION

[0024] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] like Figure 1 As shown, the principle of the method of the present application is as follows: after the operation, a postoperative CT cross section is used to demonstrate how to use the principle of "corresponding sides of similar triangles are proportional" to measure and calculate the distance between the screw and the inner wall of the pedicle. Figure 1 As shown in the figure: draw a tangent to the posterior edge of the vertebral body, and draw a perpendicular line through the head of the pedicle screw to intersect this tangent, forming a right triangle 1, and the two right-angled sides of this triangle are recorded as a and b. Extend a, and draw a parallel line to b through the tail of the screw, intersecting with the extended line to form another right triangle 2, and the right-angled sides of triangle 2 are recorded as A and B. It can be seen from the figure that: a / A=b / B. In line segment b, the distance from the inner wall of the pedicle to line segment A is recorded as x. b-x is the distance from the screw to the inner wall of the pedicle. If this value is greater than 0, it means that the screw has not penetrated the inner wall and is in a good position. If the value is less than 0, it means that the screw has penetrated the inner wall of the pedicle. Because CT cannot be used for cross-sectional (horizontal) scanning during surgery, the more accurate ones are intraoperative orthopedic robot navigation systems and O-arm navigation, but the price of these devices ranges from several million to tens of millions. Under normal circumstances, only X-ray machines can be used to obtain pedicle anteroposterior images (coronal plane) and lateral images (sagittal plane) during surgery.

[0026] like Figure 2 As shown in FIG. 1 , a method for determining whether a screw has penetrated the inner wall of a pedicle based on intraoperative X-rays includes the following steps:

[0027] St10. Obtain anteroposterior and lateral images of the screws in the patient's pedicles.

[0028] St20. Measure the distance from the screw head to the screw tail in the AP image and record it as B. Measure the distance from the medial edge of the pedicle to the screw head in the AP image and record it as x.

[0029] St30. Measure the distance from the screw head to the screw tail in the lateral image and record it as A. Measure the distance from the posterior edge of the pedicle to the screw head in the lateral image and record it as a.

[0030] St40, obtain the comparison value b through the formula a / A=b / B.

[0031] St50, analyze the distance x from the medial edge of the pedicle to the screw head in the anteroposterior image and the comparison value b to determine whether the screw has penetrated the inner wall of the pedicle.

[0032] During the operation, a C-arm X-ray machine was used to collect the anteroposterior and lateral images of the screws in the patient's pedicles, and the comparison value b was calculated in real time to compare the distance x from the inner edge of the pedicle to the screw head. Theoretically, when the distance x from the inner edge of the pedicle to the screw head is greater than the comparison value b, it means that the screw has penetrated the inner wall of the pedicle. Through actual case verification, we concluded that bx < 0.97mm can be used to determine that the screw has penetrated the inner wall of the pedicle. This allows doctors to adjust the position of the screw in time during surgery to avoid surgical failure.

[0033] like Figure 3 Shown: An example of an X-ray image of a patient undergoing L4 / 5 lumbar fusion and internal fixation surgery. Figure 3 In a, the distance from the screw head to the screw tail is measured on the X-ray anteroposterior image, which corresponds to Figure 1 The length of line segment B in ; Figure 3 b Measure the distance from the medial edge of the bilateral pedicles of L4 and L5 to the screw head, corresponding to Figure 1 The length of the line segment x in triangle 1; Figure 3 The distance from the screw head to the screw tail in the lateral image in c is measured, which corresponds to Figure 1 The length of the midline segment A; Figure 3 In d, the distance from the posterior edge of the vertebral body to the nail head was measured in the lateral image, which corresponds to Figure 1 The length of line segment a; on the right side we measured the lengths of line segments A, B, a, and x; from the above, according to the formula a / A=b / B, the length of line segment b can be calculated; thus the value of b-x is calculated, and the relationship between the screw and the medial wall of the pedicle is determined according to the positive or negative value of b-x or the size of b and x.

[0034] St11. Obtain the frontal and lateral images of the screws in the patient's pedicles using an X-ray machine.

[0035] C-arm X-ray machine is a device commonly used to determine the accuracy of pedicle screw placement. Of course, other devices that can obtain anteroposterior and lateral images of screws in the patient's pedicles can also use the method of this application.

[0036] St51. Calculate the difference between the comparison value b and the distance x from the inner edge of the pedicle to the screw head, record it as the calculated value y, and preset the cutoff value; when it is judged that the calculated value y is greater than the cutoff value, it is judged that the screw has not penetrated the inner wall of the pedicle; when it is judged that the calculated value y is less than the cutoff value, it is judged that the screw has penetrated the inner wall of the pedicle.

[0037] We preliminarily screened and collected imaging data of patients who underwent thoracolumbar pedicle screw fixation surgery in our hospital from 2014 to 2020, with a total of 650 conventional-sized screws, including X-ray anteroposterior images, lateral images, and CT images of each patient after surgery; 59 (9.08%) pedicle medial walls were perforated on CT. Based on X-ray measurements, y<0 means that the screws perforated the inner wall, totaling 40, with a sensitivity of 52.54% and a specificity of 98.48%. However, since the anterior segment of the pedicle screw is conical, it is not an ideal rectangular segment in the measurement, which results in the measured values ​​a and A increasing by the same value compared to the actual value, thereby increasing the value of a / A. According to a / A=b / B, the calculated value of b also increases, y=bx, and the final y value is slightly greater than the actual value. Since this error value is difficult to overcome in the measurement design, there is a cutoff value greater than 0, so that when the calculated value y is greater than the cutoff value, it is judged that the screw has not penetrated the inner wall of the pedicle; when the calculated value y is less than the cutoff value, it is judged that the screw has penetrated the inner wall of the pedicle.

[0038] The cutoff value is obtained by the following process:

[0039] St60 and CT scan were used to verify whether the screws penetrated the inner wall of the pedicle, and the cutoff value was determined according to the ROC curve.

[0040] like Figure 4-Figure 6 As shown in the figure, at present, the gold standard for judging whether the pedicle screw has penetrated the inner wall of the pedicle is CT plain scan; therefore, we used postoperative CT to verify this measurement method; we used CT coronal images to adjust the image brightness to reduce metal artifacts until the screw diameter in the CT image was close to the actual screw diameter; then we used the movement trajectory of the screw image at different levels ( Figure 3 The bright white shadow in a) finds the plane with the shortest distance between the screw and the inner wall of the pedicle, and measures the distance between the inner wall of the pedicle and the screw; this is recorded as the verification value Y (e.g. Figure 3b). The consistency and linear correlation between the verification value Y and the calculated value y can represent the accuracy of the measurement method. The ROC curve was used to determine the cutoff value of y. The results showed that the optimal cutoff value for conventional screws was 0.97, that is, if the y value was less than 0.97 mm, it was considered that the screw had penetrated the inner wall. The AUC was 0.95, which had a strong predictive power, with a corresponding sensitivity of 89.83% and a specificity of 88.49%.

[0041] Specifically, the cutoff value is 0.97 mm.

[0042] like Figure 7 As shown, CT scan includes the following processes:

[0043] St61. Calculate the difference between the distance x from the medial edge of the pedicle to the screw head and the comparison value b, and record it as the calculated value y.

[0044] St62, after surgery, the corresponding patients were scanned on the coronal plane by CT to obtain the layer with the shortest distance between the screw and the inner wall of the pedicle, so as to measure the distance between the inner wall of the pedicle and the screw, and record it as the verification value Y.

[0045] The verification value Y can be used to determine whether the calculated value y is accurate, so as to obtain the cutoff value through the ROC curve. The accuracy of the judgment method can also be verified by the conformity rate and linear correlation of the calculated value y and the verification value Y. We preliminarily screened and collected the imaging data of patients who underwent thoracolumbar pedicle screw fixation surgery in our hospital from 2014 to 2020, totaling 650 pedicle screws; these included postoperative X-ray anteroposterior images, lateral images, and CT images of each patient; this measurement was completed by two observers, and there was good consistency between the two observers, as shown in Table 1. We conducted a correlation analysis on the X-ray calculated value y and the verification value Y of the CT measurement result, which showed that the two were significantly positively correlated; the correlation coefficient r=0.81 (strong correlation); p<0.01, such as Figure 4 shown.

[0046] Table 1. Inter-observer and intra-group agreement

[0047]

[0048] St63. When performing a plain scan of the coronal plane using CT, adjust the brightness of the image obtained by CT until the screw diameter in the CT image is close to the actual screw diameter. Adjust the image brightness to reduce metal artifacts until the screw diameter in the CT image is close to the actual screw diameter, thereby improving the accuracy of the verification value Y.

[0049] In summary, through this measurement method and data analysis, it is concluded that when y is less than 0.97 mm, the pedicle screw is judged to have penetrated the inner wall. This method can use the conventional intraoperative C-arm X-ray machine fluoroscopic images to achieve instant and accurate judgment of the safety and accuracy of pedicle screw placement during surgery. There is no need for large and high-cost instruments such as intraoperative navigation robots and O-arms. Based on this principle, image analysis software can be further developed, such as installing application software to scan images in mobile phones or adding image analysis functions to C-arm X-ray machines to automatically analyze intraoperative fluoroscopic images, thereby increasing convenience and reducing manual measurement errors.

[0050] A computer device includes a memory and a processor. The memory stores a computer program. When the processor executes the computer program, the steps of a method for judging whether a screw has penetrated the inner wall of a pedicle based on intraoperative X-ray are implemented.

[0051] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a method for determining whether a screw has penetrated the inner wall of a pedicle based on intraoperative X-rays.

[0052] The above are only preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by the processor, a method for determining whether a screw has penetrated the inner wall of a pedicle based on intraoperative X-rays is implemented, comprising the following process: Obtain anteroposterior and lateral images of the screws in the patient's pedicles; The distance from the screw head to the screw tail in the anteroposterior image was measured and recorded as B, and the distance from the medial edge of the pedicle to the screw head in the anteroposterior image was measured and recorded as x; The distance from the screw head to the screw tail in the lateral image was measured and recorded as A, and the distance from the posterior edge of the pedicle to the screw head in the lateral image was measured and recorded as a; The comparison value b is obtained by the formula a / A=b / B; Analyze the distance x from the medial edge of the pedicle to the screw head in the anteroposterior image and the comparison value b to determine whether the screw has penetrated the inner wall of the pedicle; Calculate the difference between the comparison value b and the distance x from the medial edge of the pedicle to the screw head, record it as the calculated value y, and preset the cutoff value; When the calculated value y is greater than the cutoff value, it is determined that the screw has not penetrated the inner wall of the pedicle; when the calculated value y is less than the cutoff value, it is determined that the screw has penetrated the inner wall of the pedicle.

2. A computer-readable storage medium according to claim 1, characterized in that: The anteroposterior and lateral images of the screws in the patient's pedicles were obtained by X-ray machine.

3. A computer-readable storage medium according to claim 1, characterized in that: CT scan was used to verify whether the screws penetrated the inner wall of the pedicle, and the cutoff value was determined according to the ROC curve.

4. A computer-readable storage medium according to claim 1, characterized in that: The cutoff value is 0.97 mm.

5. A computer-readable storage medium according to claim 3, characterized in that: CT scan includes the following steps: Calculate the difference between the distance x from the medial edge of the pedicle to the screw head and the comparison value b, and record it as the calculated value y; After surgery, the corresponding patients underwent a plain scan of the coronal plane using CT to obtain the layer with the shortest distance between the screw and the inner wall of the pedicle, thereby measuring the distance between the inner wall of the pedicle and the screw, and recording it as the verification value Y.

6. A computer-readable storage medium according to claim 5, characterized in that: When the coronal plane is scanned by CT, the brightness of the image acquired by CT is adjusted until the screw diameter in the CT image is close to the actual screw diameter.

7. A computer device comprising a memory and a processor, characterized in that: The memory is a computer-readable storage medium according to any one of claims 1 to 6, and the processor implements a method for determining whether a screw has penetrated the inner wall of a pedicle based on intraoperative X-rays when executing a computer program.

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