KR102581370B1 - Fracture fixation force finite element analysis method according to insertion angle of fibular allografts and system for thereof - Google Patents

Abstract

The present invention is a method of improving the fixation of the fractured bone and reducing side effects after the procedure. The present invention is a method of improving the insertion angle of the fibular graft used with a bone plate for joining the fracture site through finite element analysis to determine the optimal fibular graft insertion angle. This relates to a finite element analysis method for fracture fixation force according to the fibular graft insertion angle that can calculate conditions.

Description

Fracture fixation force finite element analysis method according to insertion angle of fibular allografts and system for the same {Fracture fixation force finite element analysis method according to insertion angle of fibular allografts and system for the same}

The present invention relates to determining the insertion angle of a fibular graft to improve fracture fixation, and more specifically, to determine the insertion angle of a fibular allograft used in conjunction with a bone plate for fracture site cementation through simulation of the insertion angle of various grafts to determine the fibula's stability when stressed. A finite element analysis method for fracture fixation according to the fibular graft insertion angle that can improve fixation and reduce post-procedure side effects by deriving the optimal graft insertion angle condition by applying finite element analysis to measure the stress of the plate and a system for the same. It's about.

A fracture is a condition in which the bone is partially or completely broken due to the action of a strong external force. Depending on the symptoms or area, if the fracture is severe or requires rapid healing, a long plate-shaped plate made of artificial metal is attached to the fracture site and then screwed. Internal fixation treatment is used by fastening to the bone.

Fractures of the proximal humerus, which occur frequently in the elderly and account for 15% of fractures in people over 50 years of age, can be treated with conventional fracture management, but if there is severe deformity, surgery is required.

To fix the broken bone, a fixation plate is used or a screw on the fixation plate (calcar screw) is used to support the inside of the calcaneus to treat proximal humerus fractures. If the fracture has progressed into 3 or 4 parts, an intramedullary (IM) nail is used. A ring is used, or an intramedullary fibular allograft (FA) is used with a fixation plate.

Additionally, if a problem occurs in the part supporting the medial part of the proximal humerus fracture, there is a possibility that varus deformity and subsequent subsidence may occur.

Many surgeries are being introduced to overcome postoperative complications such as varus collapse, and in these surgeries, fixation plates along with fibular allograft are used to strengthen medial support and prevent varus misalignment. At this time, the similarity between the diameters of the fibula and the proximal humerus improves stability, allowing complete filling of the inner part of the root canal.

Therefore, when a patient has varus deformity, it is more appropriate to use calcaneal screws, IM nailing, or fibular allograft on the plate rather than using a fixation plate alone, and vertical insertion of FA has been proposed to overcome varus collapse.

Vertically inserted fibular allografts showed a 1.72-fold increase in the failure load (critical point) of the construct and a 3.84-fold increase in initial stiffness in biomechanical studies, while studies using synthetic bone models also demonstrated a 5-fold decrease in intercycle motion and a 2-fold decrease in fragment movement. The effect is being verified, with the remaining plastic deformation decreasing by 2 times.

As such, most studies of fibular allografts have focused on vertical fixation of the graft in the intramedullary space, but there are few clear clinical trials supporting the long-term effectiveness of vertical insertion, and it has been reported that vertically applied fibular allografts can be used for 3-minute proximal fractures. There are also studies showing that oblique fibular allograft does not have a statistically significant effect on the complication rate when compared to the vertical insertion group.

Therefore, it is necessary to calculate the optimal insertion angle when inserting a fibular graft to reduce complications such as secondary varus collapse by simulating fibular graft insertion at an angle.

Republic of Korea Patent Publication No. 10-2017-0093133 (2017.08.14)

The present invention was created in response to the above-mentioned needs, and the purpose of the present invention is to improve the fixation of the fractured bone and reduce side effects after the procedure. A fibular graft used with a bone plate for joining the fracture site is provided. The purpose of this study is to provide a finite element analysis method for fracture fixation force according to the fibular graft insertion angle and a system for calculating the optimal fibular graft insertion angle condition through finite element analysis of insertion changes.

For the above purpose, the finite element analysis method for fracture fixation force according to the insertion angle of the fibular graft of the present invention includes first characteristic information including the name, shape, and structural strength of the bone, and second characteristic information including the shape and structural strength of the plate and screw. A database construction step of preparing information, third characteristic information including the shape and structural strength of the fibular graft, and graphic information including two-dimensional and three-dimensional images of the bone, plate, and fibular graft, and an image source for fracture representation; A modeling step of generating a three-dimensional bone model through a photographed image of the bone and corresponding graphic information; A basic setting step of setting the fracture location, the insertion location and angle of the fibula graft, the fixation location of the plate, and the arrangement of the screws in the three-dimensional bone model; An angle setting step of setting an insertion angle of the fibular graft when inserting a screw into a plate and inserting the fibular graft into the fracture site while supporting the three-dimensional bone model; External forces including load and rotational force according to the axis set to the three-dimensional bone model fixed with a plate are applied, respectively, according to the first characteristic information, second characteristic information, and third characteristic information and the set insertion angle of the fibula graft. A finite element analysis step to calculate the stress applied to the fibular graft and screw; An angle derivation step of deriving a stress graph of the fibular graft and screw for each fibular graft insertion angle according to the applied external force, and deriving and providing an insertion angle of the fibular graft in descending order of stress; It is characterized by consisting of.

At this time, the finite element analysis step is preferably performed by setting the coefficient of friction between the plate and the bone and between the fibular graft and the bone and defining the plate and screw as being perfectly combined.

In addition, in the angle setting step, it is preferable that the insertion angle of the fibula graft is set step by step from vertical to horizontal.

For the above purpose, the present invention's fracture fixation force finite element analysis system according to the fibular graft insertion angle includes first characteristic information including the name, shape, and structural strength of the bone, and second characteristic information including the shape and structural strength of the plate and screw. A database in which information, third characteristic information including the shape and structural strength of the fibular graft, and graphic information including two-dimensional and three-dimensional images of the bone, plate, and fibular graft, and an image source for fracture expression are stored and constructed; a modeling unit that generates a three-dimensional bone model through a photographed image of the bone and corresponding graphic information; a basic setting unit that sets the fracture location, the insertion location and angle of the fibula graft, the fixation location of the plate, and the arrangement of the screws in the three-dimensional bone model; An angle setting unit that inserts a screw into a plate and sets an insertion angle of the fibular graft when inserting the fibular graft into the fracture site while supporting the three-dimensional bone model; External forces including load and rotational force according to the axis set to the three-dimensional bone model fixed with a plate are applied, respectively, according to the first characteristic information, second characteristic information, and third characteristic information and the set insertion angle of the fibula graft. A finite element analysis unit that calculates the stress applied to the fibular graft and screw; An angle derivation unit that derives a stress graph of the fibular graft and screw for each fibular graft insertion angle according to the applied external force and derives and provides an insertion angle of the fibular graft in descending order of stress; It is characterized by consisting of.

At this time, the finite element analysis unit preferably sets friction coefficients between the plate and the bone and between the fibula graft and the bone, and defines the plate and screw as being perfectly combined.

In addition, it is preferable that the insertion angle of the fibular graft is set step by step from vertical to horizontal in the angle setting unit.

Through the present invention, it is possible to derive the optimal graft insertion angle condition in fibula allograft used with a bone plate for joining fracture areas, thereby improving bone fixation and reducing side effects after the procedure.

1 is a block diagram showing the configuration of the fracture fixation force finite element analysis method according to the present invention;
Figure 2 is a flowchart showing the fracture fixation force finite element analysis method according to the present invention;
Figure 3 is a conceptual diagram showing three-dimensional bone modeling according to the present invention;
Figure 4 is a conceptual diagram showing the fixation configuration of the proximal humerus fracture model according to standard surgical guidelines;
Figure 5 is a conceptual diagram showing the fibula insertion angle for finite element analysis of proximal humerus fractures according to the present invention;
Figure 6 is a conceptual diagram showing stress application to the humerus according to the present invention;
Figure 7 is a graph showing the stresses of the plate and fibula according to the experiment of the present invention;
Figure 8 is a diagram showing the maximum stress analysis of the plate according to the experiment of the present invention;
Figure 9 is a graph showing stiffness values under axial and shear loads according to experiments of the present invention;
Figure 10 is a graph showing the change in distance of the inner fracture gap under axial load according to the experiment of the present invention.

Hereinafter, the finite element analysis method for fracture fixation force according to the insertion angle of the fibular graft of the present invention will be described in detail with reference to the attached drawings.

Figure 1 is a block diagram showing the configuration of the fracture fixation force finite element analysis method according to the present invention, and Figure 2 is a flow chart showing the fracture fixation force finite element analysis method according to the present invention. The fracture fixation force finite element analysis method according to the present invention is finite. It is assumed that element analysis is performed through a program-based fracture fixation force finite element analysis system.

The first step (S 110) is to build the database 110, which includes first characteristic information including the name, shape, and structural strength of the bone, and second characteristic information including the shape and structural strength of the plate and screw. A database constructed by storing characteristic information, third characteristic information including the shape and structural strength of the fibular graft, and graphic information including two-dimensional and three-dimensional images of bones, plates, and fibular grafts, and image sources for fracture expression. (110) is constructed.

The database 110 is constructed by storing various information for finite element analysis when joining fractured bones using plates and fibula grafts, and provides more accurate finite element analysis data through continuous information update.

In the present invention, the database 110 basically categorizes and stores first characteristic information about the bone subject to fracture, second characteristic information about plates and screws, and third characteristic information and image sources about the fibula graft, Even if a fracture occurs, information related to bones not amenable to fracture treatment using a fibula graft can be excluded.

Specifically, the first characteristic information is basic information about bones, including the names of all bones in the human body that are subject to finite element analysis when joining fractures using plates and fibula grafts through the present invention, as well as the basic shape and form of the bones. This is information that includes the arrangement relationship, that is, the location of the bone in the human body, the arrangement structure of other adjacent bones, and the basic structural strength characteristics of the bone.

Basically, in the event of a fracture, the general information related to the bone that can be treated with a plate or fibula graft is set as default and stored, but the information is updated by adding information about artificial bones made of various materials, including factors that impede bone strength, including osteoporosis. This can be done.

The second characteristic information is information about the plate for which the screw insertion angle is designed and the screw inserted into it, including various types of plates and screws applied depending on the fracture site and location, and structural strength depending on the material of the plate and screw. This is information about characteristics.

The third characteristic information is basic information about the fibular graft and includes the arrangement structure and basic structural strength characteristics of the fibular graft used in the procedure.

The image source includes two-dimensional and three-dimensional image sources of the bone and plate where the fracture occurred, and in particular, the two-dimensional image includes image information for three-dimensional bone modeling through X-ray images, and the shape and basic structure of the bone. Contains information about intensity.

The various information stored in the database 110 is based on information obtained experimentally, including information already secured, but becomes more realistic as information collected in experiments or clinical sites is added and updated through analysis. We will provide support so that the analysis can be carried out.

The next step is the modeling step (S 120), where a 3D bone model is created using a photographed image of the bone and corresponding graphic information, which is obtained by photographing the patient's fracture using the image source stored in the database 110. This process is carried out through the modeling unit 120, which applies an algorithm that generates a 3D bone model through images.

The third is the basic setting step (S 130), which sets the fracture location, insertion location and angle of the fibula graft, fixation location of the plate, and placement of screws in the 3D bone model, and confirms this through a graphic interface. This is performed through the basic setting unit 130 configured to work.

That is, a bone plate suitable for the bone type and fracture location is selected and placed based on the second characteristic information stored in the database 110.

Figure 3 is a conceptual diagram showing the three-dimensional bone modeling according to the present invention, where 3(a) is a computed tomography image, 3(b) is an intact model before osteotomy, and 3(c) is an unstable medial column due to a rectangular osteotomy. Each bone model is shown.

In an embodiment of the present invention, a three-dimensional finite element model was created from a computed tomography (CT) scan (Aquilion prime, Canon Medical Systems, Japan) of a 73-year-old man with a humerus fracture. The CT protocol included a craniotomy-caudal helical scan completely including the scapula, and the scanning parameters used during scanning were tube voltage of 120 kvp, tube current of 250 mAs, rotation time of 0.6 s, slice collimator of 0.5 × 40 mm, slice of 3 mm. A thickness and pitch coefficient of 0.825 were used.

This bone image was converted into a three-dimensional model using the Materialize Interactive Medical Image Control System (MIMICS) S/W (Ver.21, Materialize, Belgium), which is a rectangular osteotomy with a height of 6 mm at the surgical neck, resulting in an unstable medial side. It was used to simulate a proximal humerus fracture with a column.

Figure 4 is a conceptual diagram showing the fixation configuration of the proximal humerus fracture model according to standard surgical guidelines, where 4(a) is the fixation configuration of the proximal humerus fracture model according to standard surgical guidelines, and 4(b) is the locking plate model used in simulation. It represents.

Bone stock was simulated considering the state of normal bone without osteoporosis. The fixation plate was placed on the proximal humerus fracture model according to standard surgical guidelines, and the fibula model used a simulated bone model with a thickness of approximately 3.5 mm. The lengths of the fibula models were 60, 35, and 25 mm, respectively, and the inside of the cancellous bone was filled according to the angle supporting the inner part.

The locking plate model used was designed using Solidworks 2015 based on the standard product LCP Proximal Humerus Plates (PHILOS®). The length is 90 mm, the diameter of the three shaft holes is 3.5 mm, and the threads of the locking screws are omitted to simplify the model.

[Table 1] shows the physical properties of the bone model used in finite element analysis in the present invention.

Location Bone type Poisson’s ratio Elastic modulus (MPa) Density
(g/cm3) Humerus Cortical bone

0.3 13,800 0.83 Cancellous bone 1,380 0.64 Fracture site Cortical bone 15,200 0.85 Cancellous bones 1,520 0.31 Fibula Cortical bone 17,000 2.13

Finite element analysis in this embodiment was performed using ANSYS Workbench 19.2 (FEA, ANSYS Inc., U.S.). Linear elastic and isotropic material properties were assigned to all models and implant materials. The total number of elements in the finite element models ranged from 90,000 to 180,000, and the total number of nodes ranged from 70,000 to 160,000.

The elastic moduli of cortical bone and cancellous bone were assumed to be 13,800 MPa and 1,380 MPa, respectively, and the mineral densities of these bones were assumed to be 0.83 g/cm ³ and 0.64 g/cm ³ , respectively. The cortical and cancellous bone at the fracture site were assumed to have bone densities of 0.85 g/cm ³ and 0.31 g/cm ³ and elastic moduli of 15,200 MPa and 1,520 MPa, respectively.

The fibula was assumed to have only cortical bone, and the modulus of elasticity and bone density were set to 17,000 MPa and 2.13 g/cm ³ , respectively. The integrated Poisson's ratio is 0.3.

Next is the angle setting step (S 140), where a screw is inserted into the plate and the insertion angle of the fibular graft is set when inserting the fibular graft into the fracture position while supporting the three-dimensional bone model. Likewise, this is done through a graphic interface. This is performed through the angle setting unit 140, which is configured to check and set.

Figure 5 is a conceptual diagram showing the fibula insertion angle for finite element analysis of a proximal humerus fracture according to the present invention.

The contact motion of the plate and locking screw, locking screw, and bone interface was defined as fully fixed, with insufficient screws inserted into the plate, humerus, and fibula.

The friction coefficients between the plate and bone, and the fibula and bone were set to 0.08 and 0.2, respectively, and the fibula insertion angles were set at 30°, 50°, and perpendicular to the axis. The fibula was fixed using 1 to 4 screws depending on the angle.

The next finite element analysis step (S 150) applies external forces including load and rotational force along the axes set to the three-dimensional bone model fixed with a plate, and the data is transmitted to the database 110 through the finite element analysis unit 150. The stress applied to the fibular graft and screw is calculated according to the stored first characteristic information, second characteristic information, and third characteristic information and the set insertion angle of the fibular graft.

It is desirable to set the coefficient of friction between the plate and the bone and between the fibula graft and the bone, and define the plate and screw as fully combined before proceeding.

Figure 6 is a conceptual diagram showing stress application to the humerus according to the present invention, showing the distal portion of the humerus being fixed and axial and torsional forces applied to the model. The stability of the fracture site was assessed by the change in distance of the medial fracture gap.

An axial force of 500 N, oriented vertically in the coronal and sagittal planes, was distributed to the proximal humeral head.

To simulate rotation, a torque of 10 Nm was applied to the proximal humeral head around the humeral axis. After fixing the load value and load direction, the entire experiment was repeated five times by changing the load range.

In an embodiment of the present invention, the purpose was to compare the integrated stability, stress performance, and stability of the fracture site when using four fibula insertion angles immediately after surgery. To evaluate the force conditions, the von Mises stress distribution for the implant and fibula were compared. The maximum stress was determined.

To compare the integrated stability of various bone-implant structures, the structural stiffness was determined, and the stability of the fracture site was evaluated under axial loading by changing the medial fracture gap.

Statistical analysis was performed on the evaluation results using SPSS (version 25.0; SPSS Inc, Chicago, IL) software.

The Kolmogorov-Smirnov test was used to analyze normal distribution and the Bartlett test was used to analyze statistical homogeneity. The stability of the fracture site was determined using an independent two-sample t-test, and the level of statistical significance was defined as p <.05.

The next angle derivation step (S 160) derives a stress graph of the fibular graft and screw for each angle of fibular graft insertion according to the external force applied through the finite element analysis step (S 150), and inserts the fibular graft in order of stress. This step of deriving and providing an angle is performed through the angle deriving unit 160, which can output a design plan of a plate to which the derived screw insertion angle is applied along with a graph.

As a result of statistical analysis, looking at von Mises stresses, FIG. 7 shows a graph showing the stresses of the plate and fibula according to the experiment of the present invention.

When axial loading was applied to the humerus fracture model, the stress on the plate was minimal when the axis was perpendicular (horizontal application of the graft).

On the other hand, when the graft did not contact the fracture, the maximum stress was observed regardless of load (p <.001). Additionally, it was observed that the maximum stress occurred when the graft was inserted into the plate at 30 degrees during shear loading. However, the angle of application of the graft did not have a significant effect on the stress when the graft touched the fracture. On the other hand, the stress during axial loading was found to be minimum in the vertical state of the axis.

Significant differences in the von Mises stress of the fibula were found when the graft was inserted at 30°, 50° along the axis, and in axial orthogonal conditions under axial and shear loading (p <.05). When shear loading was applied, the maximum stress was applied to the graft when inserted horizontally (axial perpendicular condition).

Figure 8 is a diagram showing the maximum stress analysis of the plate according to the experiment of the present invention.

When an axial load was applied to the fracture model (except in the axial normal state, where the stress was uniformly applied), the stress results were concentrated at the fracture site, particularly the fibula-screw joint, one of the plate-screw joints.

However, under shear loading, stresses were generally found to be concentrated in the shaft portion of the plate, and the stress on the fibula was found to be indirectly related to the junction between the FA and the fracture.

As this area increased, the stress decreased, confirming that the stress on the FA depended on the contact surface area between the fracture and the graft and not on the graft insertion angle.

Looking at stability, Figure 9 is a graph showing stiffness values under axial and shear loads according to experiments of the present invention, where 11(a) shows the axial load and 11(b) shows the stiffness values under shear load, respectively.

The stiffness of the model showed the greatest decrease in the absence of FA (p <.001). In particular, when the graft was applied horizontally (vertical axis condition), the stiffness reached its maximum (p <.05).

Statistically, axial loading resulted in the highest stiffness when the graft was applied horizontally. The difference in stiffness due to different application methods was statically significant (p <.001).

However, under shear loading, there was no significant difference depending on the application method of the graft, except for the axial perpendicular condition. The stiffness in the vertical axis state was significantly higher than in the other three conditions (p <.001).

Next, looking at the stability of the fracture site, Figure 10 shows a graph showing the change in distance of the inner fracture gap under axial load according to the experiment of the present invention.

In the axis perpendicular condition, micromotion at the fracture site was significantly lower than in other conditions (p <.05). When the distance change of the medial fracture gap (amplitude of distance) was compared numerically, the axis perpendicular state showed the lowest value. This was 3.14 to 4.17 times lower than that observed with other graft application methods (p <.05).

Axial perpendicular conditions provided the highest stability to the fracture site among all graft application methods (p <.001).

The rights of the present invention are not limited to the embodiments described above but are defined by the claims, and those skilled in the art can make various changes and modifications within the scope of the claims. This is self-evident.

101: bone 102: plate
103: screw 104: fibula graft
110: database 120: modeling department
130: Basic setting unit 140: Angle setting unit
150: Finite element analysis unit 160: Angle derivation unit

Claims (6)

In the fracture fixation force finite element analysis system,
First characteristic information including the name and shape of the bone and the elastic modulus and structural strength of cortical and cancellous bone; second characteristic information including the shape and structural strength of the plate and screw; the shape of the fibula graft assuming only cortical bone; and A database 110 in which third characteristic information including structural strength, graphic information including two-dimensional and three-dimensional images of bones, plates, and fibula grafts, and image sources for fracture expression are stored and constructed;
A modeling unit 120 that generates a three-dimensional bone model through a photographed image of the bone and corresponding graphic information;
A basic setting unit 130 that sets the insertion position and angle of the fibula graft to fill the inside of the cancellous bone according to the fracture position and the angle supporting the inner part in the three-dimensional bone model, and the fixation position of the plate and arrangement of screws. ;
An angle setting unit 140 that inserts a screw into a plate and supports the three-dimensional bone model while gradually setting the insertion angle of the fibula graft at the fracture site from vertical to horizontal;
The friction coefficient between the plate and the bone and between the fibula graft and the bone is set, the plate and the screw are defined as fully coupled, and external forces including load and rotational force along the axis set on the three-dimensional bone model fixed with the plate are applied, respectively. However, a finite element analysis unit 150 that calculates the stress applied to the fibular graft and screw according to the first characteristic information, second characteristic information, and third characteristic information and the set insertion angle of the fibular graft;
An angle derivation unit 160 that derives a stress graph of the fibular graft and screw for each fibular graft insertion angle according to the applied external force and derives and provides an insertion angle of the fibular graft in descending order of stress. A finite element analysis system for fracture fixation force according to the fibular graft insertion angle, characterized in that it consists of.
delete delete In the fracture fixation force finite element analysis method performed through a fracture fixation force finite element analysis system according to the fibular graft insertion angle,
First characteristic information including the name and shape of the bone and the elastic modulus and structural strength of cortical and cancellous bone; second characteristic information including the shape and structural strength of the plate and screw; the shape of the fibula graft assuming only cortical bone; and A database construction step (S 110) of preparing third characteristic information including structural strength, graphic information including two-dimensional and three-dimensional images of bones, plates, and fibula grafts, and image sources for fracture expression;
A modeling step (S 120) of generating a three-dimensional bone model through a photographed image of the bone and corresponding graphic information;
A basic setting step (S 130) of setting the insertion position and angle of the fibular graft to fill the inside of the cancellous bone according to the fracture position and the angle supporting the inner part in the three-dimensional bone model, and the fixation position of the plate and arrangement of screws );
An angle setting step (S 140) of gradually setting the insertion angle of the fibular graft from vertical to horizontal when inserting the fibular graft into the fracture site while inserting a screw into the plate and supporting the three-dimensional bone model;
The friction coefficient between the plate and the bone and between the fibula graft and the bone is set, the plate and the screw are defined as fully coupled, and external forces including load and rotational force along the axis set on the three-dimensional bone model fixed with the plate are applied, respectively. However, a finite element analysis step (S 150) of calculating the stress applied to the fibular graft and screw according to the first characteristic information, second characteristic information, and third characteristic information and the set insertion angle of the fibular graft;
An angle derivation step (S 160) of deriving a stress graph of the fibular graft and screw for each fibular graft insertion angle according to the applied external force and deriving and providing an insertion angle of the fibular graft in descending order of stress; A finite element analysis method for fracture fixation force according to the fibular graft insertion angle, characterized in that it consists of. delete delete