Navigation method and system for correcting the length of a hand drill guide pin during surgery

Abstract

The application discloses a navigation surgery hand drill guide needle length correction method and system, and belongs to the technical field of medical surgery navigation. The method is divided into two stages of preoperative modeling and intraoperative real-time calculation: the geometric models of the hand drill, the guide needle and the guide device are established and four key points are defined before operation; the key point coordinates are obtained in real time through an optical tracking device during operation, the guide needle is divided into two rigid sections and one deformation section; the deformation section is fitted by using a parameterized curve to restore the bending shape, the curve arc length is used as the real length of the deformation section to complete the correction; based on the total fixed length of the guide needle, the remaining penetration length is obtained by deducting the lengths of the three sections, and then the accurate spatial position of the guide needle head is calculated. The application does not need to increase additional hardware sensors, and can correct the navigation error caused by the bending of the guide needle only by relying on the existing navigation tracking information, has high calculation efficiency and is easy to integrate, can effectively improve the navigation precision and operation safety of the orthopedic implant surgery, and is suitable for various orthopedic navigation surgery scenes.

Description

Technical Field

[0001] This invention relates to the field of medical image-guided surgical navigation technology, and in particular to a method and system for correcting the length of a hand drill guide needle in navigation surgery. Background Technology

[0002] In image-guided orthopedic surgery, surgical navigation systems use optical tracking devices to spatially locate surgical instruments in real time. Combined with preoperative medical images, they provide doctors with visual guidance on the position, direction, and depth of instruments. This is a core technology for improving the precision of procedures such as screw implantation and drilling, and reducing surgical risks.

[0003] In orthopedic screw implantation surgeries such as spinal and trauma surgeries, a slender guide pin is typically inserted into the bone using a hand drill for positioning, and then the screw is implanted along the guide pin. Current surgical navigation systems generally simplify the guide pin into a rigid linear structure, estimating the spatial position of the guide pin tip by extending it in a straight line along the drill bit's axis. However, in actual surgery, the guide pin is a slender, flexible component. When the surgeon operates the hand drill, multiple factors such as the weight of the drill itself, the resistance of the bone during insertion, and the constraint of the guide tube opening cause the guide pin to undergo varying degrees of elastic bending deformation in the free section between the guide and the drill bit.

[0004] The navigation calculation method based on the assumption of a rigid straight line does not take into account the aforementioned bending deformation, resulting in a significant deviation between the needle position displayed on the navigation interface and the actual position. This directly affects the doctor's judgment of the needle insertion depth and direction, and poses a potential risk of damaging important tissues such as nerves and blood vessels.

[0005] Currently, there are three main solutions to this problem: the first is the rigid assumption model, which directly uses straight line extension to estimate the needle position, but the error is large; the second is the sensor addition scheme, which adds force sensors or deformation sensors to the guide needle, but the cost is high and it is difficult to apply clinically; the third is the experience estimation method, which relies on the doctor's experience to judge the degree of bending and lacks quantitative basis.

[0006] In summary, there is currently a lack of a method in this field that can quickly and accurately correct the bending length of the guide needle and calculate the true position of the needle tip without adding additional hardware and relying solely on existing navigation and tracking information. Summary of the Invention

[0007] The purpose of this invention is to provide a method and system for correcting the length of a hand drill guide needle in navigation surgery. It does not require any additional deformation sensors or hardware modifications. It can quantify and correct the bending deformation of the guide needle by utilizing the key point coordinates that can be obtained from the existing optical navigation system, accurately calculate the spatial position of the needle tip, improve the accuracy and safety of surgical navigation, and is easy to integrate into the existing navigation system.

[0008] To achieve the above objectives, in a first aspect, the present invention provides a method for correcting the length of a hand drill guide in navigation surgery, which is applied to a surgical navigation system equipped with an optical tracking device, including a preoperative modeling stage and an intraoperative real-time calculation stage; The preoperative modeling stage includes: In the surgical navigation system, a geometric model of the hand drill, guide needle, and guide device is established, and four key points are defined: guide device exit point, guide device inlet point, drill bit point, and guide needle end point inside the drill bit. The intraoperative real-time calculation phase includes: S1. Obtain the three-dimensional spatial coordinates of the four key points in real time using an optical tracking device; S2. Divide the guide pin along its extension path into three segments: a first rigid segment located between the guide pin outlet point and the guide pin inlet point and constrained by the guide pin tube wall; a deformable segment located between the guide pin inlet point and the drill bit point and capable of elastic bending; and a second rigid segment located between the drill bit point and the guide pin end point and fixed by the drill bit. S3. Perform parametric curve fitting on the spatial path of the deformed segment, calculate the arc length of the fitted spatial curve, and use this to correct the length of the deformed segment. The arc length is then taken as the true length of the deformed segment. S4. Obtain the total fixed length of the guide needle, and subtract the length of the first rigid segment, the actual length of the deformable segment, and the length of the second rigid segment from the total fixed length to obtain the remaining insertion length outside the guide exit point; extend the remaining insertion length from the guide exit point to the bone side along the axis of the guide to calculate the three-dimensional spatial position of the guide needle tip.

[0009] Furthermore, in step S1, optical positioning trackers are installed on the hand drill and the guide respectively, and the three-dimensional spatial coordinates of four key points are collected in real time through the optical tracking device.

[0010] Furthermore, the three-dimensional coordinates of the end point of the guide needle are determined in the following way: based on the real-time axial direction of the drill bit obtained from the preoperative calibration, combined with the length of the guide needle inserted into the drill bit, the coordinates are calculated in reverse along the drill bit axis from the drill bit point.

[0011] Furthermore, in step S3, cubic Hermite interpolation, B-spline interpolation, or Bézier curve interpolation are used to perform parametric curve fitting on the spatial path of the deformed segment.

[0012] Furthermore, when using cubic Hermite interpolation, the endpoint tangent vectors of the cubic Hermite curve are constructed according to the following formula: ; ; in, Let be the starting tangent vector at the guide entrance point (B). Let be the endpoint tangent vector at drill bit point (C); , Let be the tangent vector scale factor, and = = That is, the scale factor value is equal to the straight-line distance between the guide inlet point (B) and the drill bit point (C).

[0013] Furthermore, the parametric equations for the cubic Hermite curve are: ; In the formula, are curve parameters and The four corresponding basis functions are as follows: 1; t; ; ; The actual length of the deformed segment is the arc length corresponding to the curve of that parameter.

[0014] Furthermore, in step S4, The formula for calculating the length of the first rigid segment is: ; The formula for calculating the length of the second rigid segment is:

[0015] in, , , , These are the three-dimensional coordinates of the guide exit point (A), guide inlet point (B), drill bit point (C), and guide pin end point (D), respectively. This is a function for calculating the distance between two points in space.

[0016] Furthermore, in step S4, The formula for calculating the remaining insertion length outside the guide exit point (A) is as follows: ; The formula for calculating the three-dimensional coordinates of the guide needle tip is: ; in, This is the actual length of the deformed segment; The total fixed length of the guide pin (3); It is the unit vector pointing from the guide entrance point (B) to the guide exit point (A).

[0017] Furthermore, after calculating the three-dimensional spatial position of the guide needle tip, it is output to the surgical navigation system for real-time display, thereby realizing the dynamic update of the real position of the guide needle (3).

[0018] In a second aspect, the present invention provides a surgical navigation system, including an optical tracking module, a memory, and a processor. The memory stores a computer program, and the processor executes the computer program to implement the hand drill guide length correction method in navigation surgery as described in the first aspect.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) No additional hardware equipment is required. The calculation can be completed based on the coordinates of four spatial points already obtained by the existing navigation system. It is easy to integrate into the existing system and has a low threshold for clinical implementation.

[0020] (2) Fitting the bent section of the guide needle according to mathematical modeling corrects the error of the straight line estimation, making it closer to the real physical state. The calculation process is fast and the calculation results are accurate, which can effectively improve the precision and safety of surgical operation.

[0021] (3) It has a wide range of applications and can be widely used in various surgical navigation systems involving guide pin implantation, such as orthopedics, trauma, and spine.

[0022] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0023] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same parts in the exemplary embodiments of the invention.

[0024] Figure 1 A flowchart of a method for correcting the length of a hand drill guide pin in navigation surgery according to Embodiment 1 of the present invention is shown.

[0025] Figure 2 A schematic diagram illustrating the segmented modeling principle of the hand drill guide length correction method in navigation surgery according to Embodiment 1 of the present invention is shown.

[0026] Explanation of reference numerals in the attached figures: 1. Guide; 2. Hand drill; 3. Guide pin; 4. Skeleton; A. Guide exit point; B. Guide inlet point; C. Drill bit point; D. Guide pin end point. Detailed Implementation

[0027] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0028] Example 1

[0029] like Figure 1 and 2 As shown in the figure, this disclosure provides a method for correcting the length of a hand drill guide in navigation surgery. It is implemented by a surgical navigation system equipped with an optical tracking device. The overall process is divided into two stages: preoperative modeling and intraoperative real-time calculation. The specific implementation process is as follows.

[0030] I. Preoperative modeling stage: S01. Establishing the geometric model and coordinate system. Three-dimensional geometric models of the hand drill 2, guide needle 3, and guide device 1 are established in the surgical navigation system. The calibration mapping between the optical tracking coordinate system, the instrument local coordinate system, and the medical image coordinate system is completed. This calibration process is a standard technique in this field and will not be elaborated here. This method defines four key points: guide device exit point A is the center of the end face of guide device 1 near bone 4, i.e., the position where guide needle 3 exits the guide device; guide device entry point B is the center of the end face of guide device 1 near hand drill 2, i.e., the position where guide needle 3 enters the guide device; drill bit point C is the center of the end face of the chuck at the front of hand drill 2, i.e., the position where guide needle 3 exits the drill bit; and guide needle end point D is the tail end of guide needle 3 located inside the drill bit.

[0031] S02. Determine the calculation rules for the guide pin tip point. The guide pin tip point D cannot be directly tracked by optical equipment. Its calculation rules are as follows: Based on the real-time axial direction of the drill bit obtained from the preoperative calibration, combined with the length of the guide pin inserted into the drill bit measured during the operation, the three-dimensional coordinates of point D are calculated by extending backward along the drill bit axis from drill bit point C into the drill bit.

[0032] S03. Establish a benchmark rigid model. Define the guide pin 3 as a rigid straight component in an ideal, non-bending state, and establish a benchmark calculation model based on straight line extension as an error comparison reference.

[0033] S04. Preset bending fitting method. The free segment between the guide inlet point B and the drill bit point C is determined as the deformation segment, and its bending shape is fitted using a parametric space curve. In this embodiment, the cubic Hermite interpolation method is preferred.

[0034] II. Intraoperative Real-Time Calculation Phase: S1. Real-time acquisition of key point coordinates: Optical positioning targets are installed on the hand drill 2 and the guide 1 respectively, and both are placed within the field of view of the optical tracking device. The optical tracking device acquires the three-dimensional spatial coordinates of the guide exit point A, the guide entry point B, and the drill bit point C in real time. At the same time, combined with the real-time drill bit posture and insertion length, the three-dimensional coordinates of the guide pin end point D are calculated. The four points along the extension direction of the guide pin, from farthest to near, are: guide pin end point D, drill bit point C, guide entry point B, and guide exit point A.

[0035] S2. Three-segment division of the guide pin: Based on physical constraint characteristics, the entire guide pin 3 is divided into three segments along its extension path: The first rigid segment L1 corresponds to the guide pin part from the guide outlet point A to the guide inlet point B. This segment is constrained by the rigid tube wall of the guide pin 1 and always maintains a straight shape; The deformation segment L2 corresponds to the guide pin part from the guide inlet point B to the drill bit point C. This segment has no external rigid constraint and will undergo elastic bending under the action of the weight of the hand drill and the resistance of the needle insertion, which is the correction object of this method; The second rigid segment L3 corresponds to the guide pin part from the drill bit point C to the guide pin end point D. This segment is held and fixed by the hand drill chuck and always maintains a straight shape.

[0036] S3. Deformation Segment Length Correction Calculation: Parametric curve fitting is performed on the spatial path of the deformation segment, and the arc length of the fitted curve is calculated as the true length of the deformation segment to complete the length correction. This embodiment uses cubic Hermite interpolation to construct the spatial curve of the deformation segment. The specific process is as follows: First, construct the endpoint tangent vector. Taking the guide inlet point B as the starting point of the curve, the axial direction of the first rigid segment is taken as the direction of the starting tangent vector; taking the drill bit point C as the ending point of the curve, the axial direction of the second rigid segment is taken as the direction of the ending tangent vector.

[0037] Starting point tangent vector Tangent vector to the endpoint The calculation formula is: ; ; In the formula, , The tangent vector scaling factor is the same for both vectors in this embodiment; both are the straight-line distance between the two endpoints of the deformed segment. = = This method of value selection allows the scale of the fitted curve to match the physical dimensions, ensuring the accuracy of the reproduction of the bending shape.

[0038] Second, construct a cubic Hermite curve. Based on endpoint positions and tangent vector constraints, construct parameters. cubic Hermite parameter curves: ; The four corresponding cubic Hermite basis functions are: 1; t; ; ; Third, calculate the arc length of the curve. Differentiate the parametric curve described above and integrate it over the parameter domain [0,1] to obtain the true arc length of the curve, which is the true length of the deformed segment L2: ; In engineering implementation, the Gaussian numerical integration method can be used to solve the problem quickly, ensuring real-time computational efficiency.

[0039] S4. Calculate the position of the guide needle tip: Both the first rigid segment L1 and the second rigid segment L3 are calculated directly using the Euclidean distance between the two points.

[0040] The formula for the length of the first rigid segment L1 is: In the formula, The three-dimensional coordinates of the guide exit point A are: The three-dimensional coordinates of the guide entrance point B are: This is a function for calculating the distance between two points in space.

[0041] The formula for the length of the second rigid segment L3 is: In the formula, Let C be the three-dimensional coordinates of the drill bit point. Let D be the three-dimensional coordinates of the end point D of the guide needle.

[0042] Let the total fixed length of the guide pin be L, which is an inherent parameter of the guide pin and is entered into the navigation system preoperatively. After deducting the three segments, the remaining guide pin length piercing the bone lateral to the guide exit point A is: ; Extending the remaining length from guide outlet point A toward the bone along the guide axis, the three-dimensional coordinates of the guide needle tip are obtained: ; In the formula, This is the unit vector pointing from point B to point A, which is the axial unit vector of the guide.

[0043] As a preferred implementation, after calculating the position of the guide needle, a navigation display update step is performed: the calculated three-dimensional coordinates of the guide needle are mapped to the medical image coordinate system, and the real shape and position of the guide needle are updated and displayed in real time in the navigation interface, providing doctors with precise guidance on needle insertion depth and direction.

[0044] In other alternative embodiments, curve fitting of the deformed segment can also employ other parametric curve methods such as B-spline interpolation and Bézier curve interpolation, all of which fall within the protection scope of this invention.

[0045] Example 2

[0046] This disclosure provides a surgical navigation system, including an optical tracking module, a memory, and a processor. The memory stores a computer program, and the processor executes the computer program to implement the hand drill guide length correction method in navigation surgery described in Embodiment 1.

[0047] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for correcting the length of a hand drill guide pin in navigation surgery, applied to a surgical navigation system equipped with an optical tracking device, characterized in that... This includes the preoperative modeling stage and the intraoperative real-time calculation stage; The preoperative modeling stage includes: In the surgical navigation system, a geometric model of the hand drill (2), guide needle (3) and guide (1) is established, and four key points are defined as the guide exit point (A), guide entry point (B), drill bit point (C), and guide needle end point inside the drill bit (D). The intraoperative real-time calculation phase includes: S1. Obtain the three-dimensional spatial coordinates of the four key points in real time using an optical tracking device; S2. Divide the guide pin (3) into three segments along its extension path: the first rigid segment located between the guide outlet point (A) and the guide inlet point (B) and constrained by the guide (1) tube wall; the deformable segment located between the guide inlet point (B) and the drill bit point (C) and capable of elastic bending; and the second rigid segment located between the drill bit point (C) and the guide pin end point (D) and fixed by the drill bit. S3. Perform parametric curve fitting on the spatial path of the deformed segment, calculate the arc length of the fitted spatial curve, and use this to correct the length of the deformed segment. The arc length is then taken as the true length of the deformed segment. S4. Obtain the total fixed length of the guide needle (3), and subtract the length of the first rigid segment, the actual length of the deformed segment, and the length of the second rigid segment from the total fixed length to obtain the remaining insertion length outside the guide outlet point (A); extend the remaining insertion length from the guide outlet point (A) to the bone (4) along the axis of the guide (1) to calculate the three-dimensional spatial position of the guide needle tip.

2. The method for correcting the length of the hand drill guide pin in navigation surgery according to claim 1, characterized in that, In step S1, optical positioning trackers are installed on the hand drill (2) and the guide (1) respectively, and the three-dimensional spatial coordinates of four key points are collected in real time through the optical tracking device.

3. The method for correcting the length of the hand drill guide pin in navigation surgery according to claim 1, characterized in that, The three-dimensional coordinates of the end point (D) of the guide needle are determined in the following way: based on the real-time axial direction of the drill bit obtained from the preoperative calibration, combined with the length of the guide needle (3) inserted into the drill bit, the coordinates are calculated in reverse along the axial direction of the drill bit from the drill bit point (C).

4. The method for correcting the length of the hand drill guide pin in navigation surgery according to claim 1, characterized in that, In step S3, cubic Hermite interpolation, B-spline interpolation, or Bézier curve interpolation are used to perform parametric curve fitting on the spatial path of the deformed segment.

5. The method for correcting the length of the hand drill guide pin in navigation surgery according to claim 4, characterized in that, When using cubic Hermite interpolation, the endpoint tangent vectors of the cubic Hermite curve are constructed according to the following formula: ； ； in, Let be the starting tangent vector at the guide entrance point (B). Let be the endpoint tangent vector at drill bit point (C); , Let be the tangent vector scale factor, and = = That is, the scale factor value is equal to the straight-line distance between the guide inlet point (B) and the drill bit point (C).

6. The method for correcting the length of the hand drill guide pin in navigation surgery according to claim 5, characterized in that, The parametric equations for the cubic Hermite curve are: ； In the formula, are curve parameters and The four corresponding basis functions are as follows: 1； t； ； ； The actual length of the deformed segment is the arc length corresponding to the curve of that parameter.

7. The method for correcting the length of the hand drill guide pin in navigation surgery according to claim 1, characterized in that, In step S4 The formula for calculating the length of the first rigid segment is: ; The formula for calculating the length of the second rigid segment is: in, , , , These are the three-dimensional coordinates of the guide exit point (A), guide inlet point (B), drill bit point (C), and guide pin end point (D), respectively. This is a function for calculating the distance between two points in space.

8. The method for correcting the length of the hand drill guide pin in navigation surgery according to claim 7, characterized in that, In step S4 The formula for calculating the remaining insertion length outside the guide exit point (A) is as follows: ； The formula for calculating the three-dimensional coordinates of the guide needle tip is: ； in, This is the actual length of the deformed segment; The total fixed length of the guide pin (3); It is the unit vector pointing from the guide entrance point (B) to the guide exit point (A).

9. The method for correcting the length of the hand drill guide pin in navigation surgery according to claim 1, characterized in that, After calculating the three-dimensional spatial position of the guide needle tip, it is output to the surgical navigation system for real-time display, so as to realize the dynamic update of the real position of the guide needle (3).

10. A surgical navigation system, characterized in that, It includes an optical tracking module, a memory, and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the hand drill guide length correction method in navigation surgery as described in any one of claims 1 to 9.

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