Oblique lateral vertebral fusion cage

Abstract

To provide an oblique lateral vertebral fusion cage capable of preventing a medical accident that may occur in a patient.SOLUTION: The present invention provides an oblique lateral vertebral fusion cage enabling execution of a surgery even when there are a psoas muscle and a peritoneum along an operation route, which is performed in a direction inclined from a flank. The oblique lateral vertebral fusion cage has a curved shape as a whole so as to be stably seated in a space between vertebral bodies irrespective of a skill level of an operator.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an oblique lateral spinal fusion cage. More specifically, the present invention relates to an oblique lateral spinal fusion cage that enables surgery along a surgical path that is obliquely directed from the flank, despite the presence of the psoas muscle and the peritoneum.

Background Art

[0002] The vertebral column consists of 32 to 35 vertebrae that form the main body, and intervertebral discs between the vertebrae, that is, discs, and is the central part of the human body that connects the skull at the upper end and the pelvis at the lower end.

[0003] The vertebrae consist of 7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae, 5 sacral vertebrae, and 3 to 5 coccygeal vertebrae from top to bottom. In adults, however, the 5 sacral vertebrae fuse to form 1 sacrum, and the 3 to 5 coccygeal vertebrae fuse to form 1 coccyx.

[0004] As one of the treatment methods for treating severe spinal diseases over a long period, there is a method of spinal fusion. Such a spinal fusion surgery is a surgical method in which an intervertebral disc (disc) is removed, a cage for replacing it is inserted, and adjacent vertebral bodies are fused to each other.

[0005] When such spinal fusion surgery is performed on the lumbar spine, it can be classified into posterior lumbar interbody fusion (PLIF), transformational lumbar interbody fusion (TLIF), lateral lumbar interbody fusion (LLIF), oblique lumbar interbody fusion (OLIF), and anterior lumbar interbody fusion (ALIF), depending on the direction of cage insertion.

[0006] Posterior interbody fusion (PLIF) is a procedure in which an incision is made along the midline of the spine, the vertebral bodies are exposed, a portion of the posterior side of the vertebrae is removed, the disc is removed, and a PLIF cage is inserted.

[0007] Posterior interbody fusion (PLIF) is the longest-standing method of spinal fusion surgery and is an essential procedure when performing fusion of two or three segments. However, it has several drawbacks: a high possibility of adhesion to nerves, ligaments, and muscles during the surgical process, a large incision area, a long healing time, and, in some cases, significant long-term complications.

[0008] The PLIF cage consists of a pair of small cages positioned on both the left and right sides, making it the smallest cage used in all spinal fusion surgeries.

[0009] Posterior lumbar interbody fusion (TLIF) is a surgical procedure in which small incisions are made along both sides of the spinal muscles to expose the vertebral body as minimally as possible. The vertebral joint area is then removed in the direction of the nerve foramen, and the TLIF cage is inserted after removing the disc. This surgical technique has the advantages of less bleeding and shorter operating time, making it suitable for single-section surgery. However, if surgery on various areas is required, PLIF surgery must be performed. The TLIF cage is almost arc-shaped and is inserted into the vertebral body and rotated. The convex portion should face ventrally. The TLIF cage is larger than the PLIF cage, but its support area is smaller than that of the LLIF cage or ALIF cage described later.

[0010] Anterior interbody fusion (ALIF) has several advantages, such as faster surgical recovery and no need to worry about adhesions. However, it has the disadvantage of requiring a high level of skill because it involves making an anterior (ventral) incision and approaching the spine while avoiding internal organs. The ALIF cage has the advantage of having the largest support area of ​​all spinal fusion cages.

[0011] Paravertebral interbody fusion (LLIF) was developed to overcome the shortcomings of ALIF, PLIF, and TLIF. Because LLIF is performed through a flank incision, it has the advantage of being able to further widen the space between the vertebrae in the narrowed area compared to existing surgeries that involve an incision in the back, and also has the advantage of causing almost no damage to surrounding tissues. However, there are problems such as the presence of the psoas muscle and peritoneum around the surgical route, and if an error occurs during surgery, it can result in thigh muscle paralysis. The LLIF cage is smaller than the ALIF cage, but larger than the PLIF cage and TLIF cage.

[0012] Compared to such paravertebral interbody fusion (DLIF), an even safer and more effective surgical method is oblique lumbar interbody fusion (OLIF, or ATPO (anterior to psoas) fusion). This oblique lumbar interbody fusion has the advantage of allowing surgery between the fourth lumbar vertebra (L4) and the fifth lumbar vertebra (L5), where surgery is difficult with DLIF, due to the psoas muscle and peritoneum. Furthermore, it has a significantly lower risk of nerve damage, which is a problem with paravertebral interbody fusion.

[0013] Existing oblique lateral interbody fusion procedures utilize an LLIF cage rather than a separate cage. However, unlike paravertebral fusion, if the existing LLIF cage is used in oblique lateral interbody fusion, even a slight error by the surgeon could cause the LLIF cage to advance further along the insertion direction, potentially causing the distal end of the LLIF cage (the insertion end) to pass the vertebral body and damage a blood vessel or nerve on the opposite side of the insertion. [Prior art documents] [Patent Documents]

[0014] [Patent Document 1] US 2016-0310294A [Patent Document 2] US 9474624 [Patent Document 3] KR 1632908B [Overview of the project] [Problems that the invention aims to solve]

[0015] The objective of the present invention, devised to solve the aforementioned problems, is to provide an oblique lateral spinal fusion cage that can be stably placed in a desirable position within the intervertebral space during treatment, thereby preventing medical accidents. [Means for solving the problem]

[0016] To solve the aforementioned problems, the present invention provides an oblique lateral spinal fusion cage inserted between vertebral bodies, comprising: an anterior side portion; a posterior side portion formed at a distance from the anterior side portion; a medial side portion connected to the anterior side portion and the posterior side portion, where insertion between vertebral bodies begins; and an outer portion connected to the anterior side portion and the posterior side portion, where it is connected to the device at a position opposite to the medial side portion. including a lateral side portion), and at the central portions of the front side portion and the rear side portion, respectively including a front bending portion and a rear bending portion that are bent so that the center of curvature faces the front side, wherein the rear bending portion, the inner side portion, and the outer side are located in the cortical region of the vertebral body, and it is an oblique lateral spinal fusion cage.

[0017] In the front side portion, a front straight portion, which is a straight section, is formed between the inner side portion and the outer side portion with the front bending portion as the center. In the rear side portion, a rear straight portion, which is a straight section, is formed between the inner side portion and the outer side portion with the rear bending portion as the center.

[0018] Further, the radius of curvature R1 of the front bending portion is less than or equal to the radius of curvature R2 of the rear bending portion.

[0019] Further, when the maximum distance between the front straight portion and the rear straight portion is the straight portion width W1, the radius of curvature R2 of the rear bending portion is the same as the sum of the radius of curvature R1 of the front bending portion and the straight portion width W1.

[0020] Further, the inner side portion is formed in a round shape that protrudes substantially inward, and the magnitude of the radius of curvature R3 of the inner side portion is greater than or equal to the magnitude of the straight portion width W1.

[0021] Further, a transition portion is arranged between the inner side portion and the rear straight portion.

[0022] Further, the radius of curvature R4 of the transition portion is greater than the radius of curvature R3 of the inner side portion and less than the radius of curvature R2 of the rear side portion.

[0023] Further, the maximum height H1 of the rear side portion is less than or equal to the maximum height H2 of the front side portion.

[0024] Further, the front straight portion and the rear straight portion are symmetric with respect to both sides and inclined at the same angle about a virtual line connecting the rear portion and the inner portion.

[0025] Further, when the maximum length of the obliquely lateral spinal fusion cage is L and the maximum distance between the front straight portion and the rear straight portion is the straight portion width W1, the maximum length satisfies the following relational expression (1) among the straight portion width and the radii of curvature of the inner portion and the outer portion:

[0026]

Equation

[0027] Further, the inclination angle (B°) with respect to the longitudinal direction based on the maximum length L of the obliquely lateral spinal fusion cage is obtained from the following relational expression (2) when 12 ≦ w1 ≦ 30 and 30 ≦ L ≦ 90:

[0028]

Equation

Advantages of the Invention

[0029] When inserting the obliquely lateral spinal fusion cage according to the present invention, it can be placed at a desired position in the intervertebral space without depending on skill. That is, the obliquely lateral spinal fusion cage has a self-centering function of finding a desired position by itself, and the inner portion of the obliquely lateral spinal fusion cage can prevent damage to blood vessels or nerves.

Brief Description of the Drawings

[0030] [Figure 1] FIG. 1 is a perspective view of an obliquely lateral spinal fusion cage according to Embodiment 1 of the present invention. [Figure 2] FIG. 2 is a plan view and a side view of the obliquely lateral spinal fusion cage of FIG. 1. [Figure 3] FIG. 3 is a schematic view showing an insertion process of the obliquely lateral spinal fusion cage of FIG. 1. [Figure 4] This is a perspective view of the lowest height state of the oblique lateral spinal fusion cage according to Embodiment 2 of the present invention. [Figure 5] Figure 4 shows a plan view and a side view of the oblique lateral spinal fusion cage. [Figure 6] Figure 4 is a perspective view of the oblique lateral spinal fusion cage at its highest point. [Figure 7] Figure 6 shows a plan view and a side view of the oblique lateral spinal fusion cage. [Figure 8] Figure 4 is a schematic diagram showing the insertion process of the oblique lateral spinal fusion cage. [Modes for carrying out the invention]

[0031] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. When assigning reference numerals to the components in each of the following drawings, the same reference numerals will be used for identical components as much as possible, even if they are shown in other drawings, and detailed descriptions of known functions and configurations that would unnecessarily obscure the gist of the present invention will be omitted.

[0032] The directions are defined below. In Figures 3 and 8, P represents the posterior direction, which is the back side of the human body, and A represents the anterior direction, which is the ventral side of the human body. M represents the medial direction, relative to the surgical route, and L represents the lateral direction, relative to the surgical route. Furthermore, in the cage itself, the side furthest from the insertion instruments 20 and 30 is the distal direction, and the side closer to the insertion instruments 20 and 30 is the proximal direction. In other words, in the cage, the side from which insertion begins is the distal direction, and the opposite side is the proximal direction. The following explanation will be based on the directions described above.

[0033] Referring to Figures 1 to 3, an oblique lateral spinal fusion cage 100 according to Embodiment 1 of the present invention will be described. As illustrated in Figures 1 and 2, the oblique lateral spinal fusion cage 100 basically has a window into which bone graft can be inserted, and broadly speaking comprises an anterior side portion, a posterior side portion formed at a distance from the anterior side portion, a medial side portion 104 connected to the anterior and posterior side portions and into which insertion between the vertebral bodies begins, and a lateral side portion 102 connected to the anterior and posterior side portions and into which insertion device 20 is connected at a position opposite to the medial side portion 104.

[0034] The oblique lateral spinal fusion cage 100 may be made from a polymeric substance harmless to the human body, such as polyether ether ketone (PEEK), or it may be made by bonding segments of such polymeric material with segments of metal material. In this case, the metal used may be a metal material harmless to the human body, such as titanium or stainless steel. It goes without saying that it is also possible to make the entire body out of metal.

[0035] Furthermore, in the oblique lateral spinal fusion cage 100, a bridge 120 is used to enhance mechanical strength and ensure that the bone graft material inserted into the internal window remains stable and does not leak out. In addition, an instrument mounting portion 122 for connection with the insertion instrument 20 is formed in the outer portion 102. In Embodiment 1, the instrument mounting portion 122 is represented as a hole with a threaded wire, but is not limited to that.

[0036] The most distinctive feature of the oblique lateral spinal fusion cage 100 is that it includes an anterior flexed portion 108 and a posterior flexed portion 106, respectively, at the center of the anterior and posterior portions, which are bent so that the center of curvature faces anteriorly. As a result, the posterior flexed portion 106, the medial portion, and the lateral portion are located in the cortical region of the vertebral body. In other words, the oblique lateral spinal fusion cage 100 has a curved shape so that the center of curvature is located anteriorly overall. Therefore, it can be rotated while being inserted from the flank side, and as a result, if the posterior flexed portion 106 is located at the center of the posterior cortical bone 14 on the posterior side of the vertebral body, the oblique lateral spinal fusion cage 100 is placed in the desired position. In particular, when the oblique lateral spinal fusion cage 100 is inserted, its width is the width of the straight section W1, which will be described later, but after being placed, as shown in Figure 2, the maximum width in the AP direction becomes W2, which is considerably wider than W1.

[0037] As a result, the narrow oblique lateral spinal fusion cage 100 has a larger support area compared to the straight cage. This will be explained in more detail below.

[0038] Furthermore, in the front portion, with the front bend portion 108 as the center, a straight section, the front straight sections 114 and 116, may be formed between the inner portion 104 and the outer portion 102, and in the rear portion, with the rear bend portion 106 as the center, a straight section, the rear straight sections 110 and 112, may be formed between the inner portion 104 and the outer portion 102.

[0039] Therefore, the front portion includes the front bent portion 108 and the front straight portions 114 and 116, and the rear portion includes the rear bent portion 106 and the rear straight portions 110 and 112.

[0040] The anterior straight sections 114, 116 and the posterior straight sections 110, 112 facilitate insertion after the medial section 104 has been inserted through the surgical route. That is, when force is applied to the insertion instrument 20 or an impact is applied with a hammer (not shown) or the like to push the oblique lateral spinal fusion cage 100 into the space between the vertebral bodies 10, these sections help to allow insertion in a linear direction.

[0041] Furthermore, it is desirable that the radius of curvature R1 of the anterior flexed portion 108 be less than or equal to the radius of curvature R2 of the posterior flexed portion 106. That is, when inserting the oblique lateral spinal fusion cage 100 into the space between the vertebral bodies 10, in particular when rotating the oblique lateral spinal fusion cage 100 with the posterior flexed portion 106 and the anterior flexed portion 108 inserted, it is desirable to insert the anterior portion more than the posterior portion to increase the amount of rotation, so the radius of curvature R1 of the anterior flexed portion 108 must be smaller than the radius of curvature R2 of the posterior flexed portion 106.

[0042] In this case, when the maximum distance between the front straight sections 114, 116 and the rear straight sections 110, 112 is defined as the width of the straight section W1, the radius of curvature R2 of the rear bent section 106 can be set to be the same as the sum of the radius of curvature R1 of the front bent section 108 and the width of the straight section W1. In other words, if the rear section passes through approximately the width of the straight section W1 more than the front section, the amount of rotation of the oblique lateral spinal fusion cage 100 described above is considered sufficient. Here, W1 is 12 mm to 30 mm, preferably, considering the size of a typical vertebral body. The radius can be set to 18mm or 24mm. R2 can then be set to 30-100mm, preferably 40-85mm.

[0043] Furthermore, the inner portion 104 is also formed in a rounded shape that substantially protrudes inward. This is to facilitate insertion when the oblique lateral spinal fusion cage 100 is first inserted, and the radius of curvature R3 of the inner portion 104 is greater than or equal to the width W1 of the straight portion. In other words, the inner portion 104 is most convex in the form of a semicircle with a diameter equal to the width W1 of the straight portion, but it can also be formed to be even more gently curved.

[0044] The radius of curvature R1 of the anterior part and the radius of curvature R2 of the posterior part can be determined empirically as follows. That is, when the maximum length of the oblique lateral spinal fusion cage 100 is L, and the maximum distance between the anterior straight sections 114, 116 and the posterior straight sections 110, 112 is the straight section width W1, the relationship between the maximum length, the straight section width, and the radii of curvature between the medial and lateral parts satisfies the following equation 1. Here, L is determined to be 30 to 90 mm, preferably 40 to 65 mm:

[0045]

number

[0046] A transition section 118 may be positioned between the medial section 104 and the posterior straight section 110. The transition section 118 is initially inserted into the medial section 104, and as it advances, it comes into contact with the oblique lateral vertebral fusion cage 100 in the posterior cortical bone 14, facilitating rotation. For this purpose, it is desirable that the radius of curvature R4 of the transition section 118 be larger than the radius of curvature R3 of the medial section and smaller than the radius of curvature R2 of the posterior section.

[0047] Furthermore, it is desirable that the maximum height H1 of the posterior portion be less than or equal to the maximum height H2 of the anterior portion. The spine as a whole exhibits alternating lordosis and kyphosis, with the lumbar region having a lordotic shape. Therefore, to accommodate this, the posterior portion must be formed to be lower in height than the anterior portion. Moreover, if such a height difference between the posterior and anterior portions forms a lordosis angle (A°), then when the oblique lateral spinal fusion cage 100 is inserted using the insertion device 20, applying force will cause the oblique lateral spinal fusion cage 100 to be biased posteriorly, like a wedge.

[0048] Furthermore, the anterior straight sections 114, 116 and the posterior straight sections 110, 112 are formed to be inclined at the same angle symmetrically on both sides, with respect to a virtual line (AP line) connecting the posterior and anterior sections. This design offers ease of insertion, and after insertion is complete, the oblique lateral spinal fusion cage 100 is symmetrically positioned around the AP line, resulting in anatomical stability.

[0049] Furthermore, the inclination angle (B°) of the oblique lateral spinal fusion cage 100 with respect to its maximum length L is obtained from the following formula 2 when 12 ≤ w1 ≤ 30 and 30 ≤ L ≤ 90:

[0050]

number

[0051] The aforementioned inclination angle (B°) not only determines the shape of the oblique lateral spinal fusion cage 100, but also determines the direction in which it is initially inserted into the vertebral body 10. The inclination angle (B°) shown in Figures 3 and 8 is 15°, and is generally determined to be between 8° and 45°.

[0052] Next, the insertion process will be explained with reference to Figure 3. First, as shown in Figure 3(a), the insertion device 20 is connected to the oblique lateral spinal fusion cage 100 and inserted so that the insertion angle is the inclination angle (B°). At this time, the inclination angle (C1°) that the insertion device 20 makes with the ML line is not adjusted separately, but is determined by the direction in which the device attachment portion 122 of the oblique lateral spinal fusion cage 100 is formed.

[0053] Then, as shown in Figures 3(b) and 3(c), the oblique lateral spinal fusion cage 100 is rotated while being continuously inserted into the space between the vertebral bodies 10. This rotation is also performed by pushing the insertion device 20 to the rear. At this time, as described above, the transition portion 118 connected to the medial portion 104 will contact the posterior cortical bone 14 and guide the rotation of the oblique lateral spinal fusion cage 100.

[0054] Finally, once insertion is complete, the oblique lateral spinal fusion cage 100 is positioned so as shown in Figure 3(d), tilted at the same angle on both sides around the AP line. As a result, the medial portion 104 is located on the medial cortical bone 12, the lateral portion 102 is located on the lateral cortical bone 16, and the posterior flex portion 106 is located on the posterior cortical bone 14.

[0055] Next, the oblique lateral spinal fusion cage 200 according to Embodiment 2 of the present invention will be described using Figures 4 to 8. The oblique lateral spinal fusion cage 200 has the same shape as the oblique lateral spinal fusion cage 100 of Embodiment 1, except that it is an expandable cage with adjustable height. Although they have different reference numerals, the same components will not be described.

[0056] As illustrated in Figures 4 to 7, the oblique lateral spinal fusion cage 200 basically has an upper plate 201 and a lower plate 203, with an outer portion 202 and an inner portion 204 located between the upper plate 201 and the lower plate 203. A fixing screw 224 integrally connected to the inner portion 204 and a drive screw 226 that penetrates the outer portion 202 and is supported so as to be rotatable are located in a straight line. Therefore, as the drive screw 226 rotates and connects with the fixing screw 224, the distance between the outer portion 202 and the inner portion 204 is reduced, and as a result, the height of the upper plate 201 and the lower plate 203 can be changed. Rails (not shown) are formed between the outer portion 202, the inner portion 204, the upper plate 201 and the lower plate 203 for mutual movement.

[0057] However, in order to restrain the vertical movement of the upper plate 201 and the lower plate 203, an upper guide 205 may be formed on the upper plate 201 and a lower guide 207 may be formed on the lower plate 203.

[0058] It is identical to Embodiment 1 in that it has a window into which bone graft material can be inserted, and broadly speaking includes an anterior portion, a posterior portion formed at a distance from the anterior portion, an inner portion 104 connected to the anterior portion and the posterior portion and in which insertion between the vertebral bodies begins, and an outer portion 102 connected to the anterior portion and the posterior portion and in which insertion device 20 is connected at a position opposite to the inner portion 104.

[0059] The oblique lateral spinal fusion cage 200 is basically made of metal, such as titanium or stainless steel, or of a polymeric substance harmless to the human body, such as polyether ether ketone (PEEK), or it is also possible to use different metals and polymeric substances for each component.

[0060] Furthermore, the outer portion 202 has a device mounting portion 222 for connecting with the insertion device 30. In Embodiment 2, the device mounting portion 222 is represented by the shape of a tool groove formed on the head portion of the drive screw 226, but is not limited thereto. Although not shown, the insertion device 30 may further include a gripper or the like for a secure connection with the oblique lateral spinal fusion cage 200.

[0061] The oblique lateral spinal fusion cage 200 also includes an anterior bend portion 208 and a posterior bend portion 206 at the center of the anterior and posterior portions, respectively, which are bent so that the center of curvature faces anteriorly.

[0062] Furthermore, in the anterior portion, with the anterior bend portion 208 as the center, anterior straight sections 214 and 216 are formed between the inner portion 204 and the outer portion 202, and in the posterior portion, with the posterior bend portion 206 as the center, posterior straight sections 210 and 212 are formed between the inner portion 204 and the outer portion 202, which is the same as the oblique lateral spinal fusion cage 100 of Example 1.

[0063] Furthermore, a transition section 218 may be provided between the inner section 204 and the rear straight section 210.

[0064] Furthermore, the fact that the maximum height H1 of the posterior portion is less than or equal to the maximum height H2 of the anterior portion is the same as in the oblique lateral spinal fusion cage 100 of Example 1.

[0065] Next, the insertion process will be explained with reference to Figure 8. First, as shown in Figure 8(a), the insertion device 30 is connected to the oblique lateral spinal fusion cage 200 and inserted so that the insertion angle is the inclination angle (B°). At this time, the inclination angle (C2°) that the insertion device 30 makes with the ML line is not adjusted separately, but is determined by the direction in which the device attachment portion 222 of the oblique lateral spinal fusion cage 200 is formed.

[0066] Then, as shown in Figures 8(b) and 8(c), the oblique lateral spinal fusion cage 200 is rotated while being continuously inserted into the space between the vertebral bodies 10. This rotation is also performed by pushing the insertion device 30 to the rear. At this time, as described above, the transition portion 218 connected to the medial portion 204 will guide the rotation of the oblique lateral spinal fusion cage 200 while making contact with the posterior cortical bone 14.

[0067] Finally, once insertion is complete, the oblique lateral spinal fusion cage 200 is positioned so as to be tilted at the same angle on both sides, centered on the AP line, as shown in Figure 8(d). As a result, the medial portion 204 is located on the medial cortical bone 12, the lateral portion 202 is located on the lateral cortical bone 16, and the posterior flex portion 206 is located on the posterior cortical bone 14.

[0068] Furthermore, since the oblique lateral spinal fusion cage 200 of Example 2 is an inflatable cage, it is initially at its lowest height, as shown in Figure 5, upon insertion. However, by rotating the drive screw 226, the distance between the upper plate 201 and the lower plate 203 changes, as described above, and the height can be changed as shown in Figure 7.

[0069] As described above, the invention has been explained with reference to preferred embodiments, but those skilled in the art will understand that the invention can be modified and altered in various ways, as long as they do not deviate from the spirit and scope of the invention as described in the claims. [Industrial applicability]

[0070] The oblique lateral spinal fusion cage of this invention can be stably placed in the intervertebral space regardless of the practitioner's skill level, preventing potential medical accidents to the patient. Furthermore, because such stable placement is guaranteed, it can replace other methods of spinal fusion surgery by simply training the practitioner. Therefore, it is expected to have the potential to increase market share.

Claims

1. In an oblique lateral vertebral fusion cage inserted obliquely from the flank to the ventral side between the vertebral bodies, Front side and, A rear portion formed at a distance from the aforementioned front portion, The anterior portion and the posterior portion are connected, and the medial portion is inserted between the vertebral bodies, It includes an outer part that is connected to the front part and the rear part, and is coupled to the device at a position opposite to the inner part, The central part of the anterior part and the central part of the posterior part each include an anterior and posterior bends, respectively, which are bent so that the center of curvature is located anteriorly, so that the posterior bend, the medial part, and the lateral part are located in the cortical region of the vertebral body. The oblique lateral spinal fusion cage is characterized in that the posterior flexion portion is located in the posterior cortical region of the vertebral body.

2. In the front portion, a straight section is formed between the inner portion and the outer portion, centered on the front bent portion. In the rear portion, a straight section is formed between the inner portion and the outer portion, centered on the rear bend. The oblique lateral spinal fusion cage according to claim 1, characterized in that the front straight section and the rear straight section are symmetrical and inclined at the same angle around an imaginary line connecting the center of the rear section and the center of the front section.

3. The oblique lateral spinal fusion cage according to claim 1, characterized in that the radius of curvature R1 of the anterior flexed portion is less than or equal to the radius of curvature R2 of the posterior flexed portion.

4. The oblique lateral spinal fusion cage according to claim 2, characterized in that when the width between the front straight section and the rear straight section, which are parallel to each other, is defined as the width of the straight section W1, the radius of curvature R2 of the rear bent section is the same as the sum of the radius of curvature R1 of the front bent section and the width of the straight section W1.

5. The oblique lateral spinal fusion cage according to claim 4, characterized in that the inner portion is formed in a rounded shape that protrudes inward, and the radius of curvature R3 of the inner portion is greater than or equal to the width W1 of the straight portion.

6. The oblique lateral spinal fusion cage according to claim 5, characterized in that a transition portion is provided between the inner portion and the posterior straight portion.

7. The oblique lateral spinal fusion cage according to claim 6, characterized in that the radius of curvature R4 of the transition portion is greater than the radius of curvature R3 of the inner portion and smaller than the radius of curvature R2 of the posterior portion.

8. The oblique lateral spinal fusion cage according to claim 1, characterized in that the maximum height H1 of the posterior portion is less than or equal to the maximum height H2 of the anterior portion.

9. The oblique lateral spinal fusion cage according to claim 4 is characterized in that, when the maximum length of the oblique lateral spinal fusion cage is L, and the width between the anterior straight section and the posterior straight section, which are parallel to each other, is W1, the relationship between the maximum length L, the straight section width W1, the radius of curvature R1 of the anterior bend, and the radius of curvature R2 of the posterior bend satisfies the following equation 1: [Math 1] 。

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