Laminoplasty plate

Abstract

A laminoplasty plate (10) comprises: a first fixing part (1) and a second fixing part (2) respectively fixed to a first cutting end part and a second cutting end part of a vertebral arch; and a spacer part (3) extending between the first fixing part (1) and the second fixing part (2). The first fixing part (1) includes: a first engagement part (4) and a second engagement part (4) that are disposed at an interval from each other and are disposed respectively on the posterior side and the anterior side of the first cutting end part; and a connection part (6) that connects the first engagement part (4) and the second engagement part (5) so as to be displaceable in a direction approaching each other.

Description

Laminoplasty Plates

[0001] The present invention relates to laminoplasty plates.

[0002] Plates for single-door laminoplasty have been known (see, for example, Patent Documents 1 and 2). Single-door laminoplasty is one of the treatment methods for spinal cord compression, such as cervical myelopathy. As shown in Figure 8, in single-door laminoplasty, one side of the vertebral arch A is cut, the cut ends B and C of the vertebral arch A are opened, and the vertebral arch A is fixed with a plate 10.

[0003] Patent No. 4482445 Patent No. 6302845

[0004] The plates in Patent Documents 1 and 2 have a pair of flanges that sandwich the ends of the vertebral arch in the anterior-posterior direction, and the distance between the pair of flanges is fixed. Because the size of the vertebral arch varies from person to person, the plate may not fit the size of the vertebral arch, resulting in a gap between the anterior flange and the anterior surface of the vertebral arch.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a bone plate for laminoplasty that is compatible with vertebral arches of various sizes.

[0006] One aspect of the present invention is a laminoplasty plate for fixing an enlarged vertebral arch between a first cutting end and a second cutting end, the laminoplasty plate comprising: a first fixing portion fixed to the first cutting end; a second fixing portion fixed to the second cutting end; and a spacer portion extending between the first fixing portion and the second fixing portion, the first fixing portion being spaced apart from each other and comprising first and second engaging portions respectively disposed on the rear and front sides of the first cutting end; and a connecting portion connecting the first engaging portion and the second engaging portion so that they can be displaced toward each other.

[0007] The present invention has the advantage of being adaptable to vertebral arches of various sizes.

[0008] 4A 。 FIG. 4B is a perspective view of a laminoplasty spacer according to the first embodiment. FIG. 4C is a side view of the spacer of FIG. 1A, viewed from the second fixing portion side in the left-right direction. FIG. 4D is a view explaining a method of using the spacer of FIG. 1A. FIG. 4E is a view explaining a method of using the spacer of FIG. 1A. FIG. 4F is a perspective view of another laminoplasty spacer according to the first embodiment. FIG. 4G is a perspective view of a laminoplasty spacer according to the second embodiment. FIG. 4H is a cross-sectional view of the spacer of FIG. 4A taken along line II. FIG. 4H is a view explaining a method of using the spacer of FIG. 4A. FIG. 4H is a cross-sectional view of another laminoplasty spacer according to the second embodiment. FIG. 4H is a perspective view of a laminoplasty spacer according to the third embodiment. FIG. 4I is a view explaining open-door laminoplasty. FIG. 4J is a view showing a first fixing portion of a conventional laminoplasty spacer fixed to a first cut end of a vertebral arch. FIG. 4J is a view from the posterior side of a plate placed on a vertebral arch, illustrating a step of fixing the first fixing portion of the spacer to the vertebral arch with a screw.

[0009] First Embodiment A laminoplasty plate according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 8 illustrates a single-door laminoplasty to which a laminoplasty plate 10 according to this embodiment is applied. Single-door laminoplasty is one of the treatment methods for diseases in which the spinal cord is compressed, such as cervical myelopathy. In single-door laminoplasty, one side of the vertebral arch A is cut, the area between the cut ends B and C is widened, and the widened vertebral arch A is fixed with the plate 10. This widens the spinal canal and relieves compression of the spinal cord. In FIG. 8, the dashed line indicates the cutting position.

[0010] As shown in FIGS. 1A and 1B, the plate 10 includes a first fixed portion 1, a second fixed portion 2, and a spacer portion 3 extending between the first fixed portion 1 and the second fixed portion 2.

[0011] The plate 10 has a left-right direction X, a front-back direction Y, and a top-bottom direction Z, which respectively correspond approximately to the left-right direction X', the front-back direction Y', and the top-bottom direction Z' (see FIG. 8) of the vertebra V. Hereinafter, one side and the other side in the left-right direction X, which respectively correspond approximately to the inside (midline) and outside (opposite the midline) of the vertebra V, will be referred to as the "inside" and the "outside," one side and the other side in the front-back direction Y, which respectively correspond approximately to the front and back sides of the vertebra V, will be referred to as the "front side" and the "back side," and one side and the other side in the top-bottom direction Z, which respectively correspond approximately to the top and bottom sides of the vertebra V, will be referred to as the "upper side" and the "lower side."

[0012] The plate 10 is made of a single member, and the first fixing portion 1, the second fixing portion 2, and the spacer portion 3 are seamlessly connected to each other. The plate 10 is made of a material that is strong and biocompatible and is generally used for bone fixation plates, for example, a metal such as a titanium alloy or a resin such as PEEK.

[0013] The first fixing part 1 and the second fixing part 2 are the inner and outer parts of the plate 10, respectively. The first fixing part 1 is fixed to the inner first cut end part B, and the second fixing part 2 is fixed to the outer second cut end part C. After dilation, the cut ends B and C are arranged at positions spaced apart from each other in the left-right direction X' and the front-back direction Y'. Corresponding to this arrangement of the cut ends B and C, the first fixing part 1 and the second fixing part 2 are arranged at positions spaced apart from each other in the left-right direction X and the front-back direction Y, and the first fixing part 1 is offset rearward from the second fixing part 2.

[0014] The spacer portion 3 is a portion that is arranged between the cut ends B and C to ensure space between the cut ends B and C, and connects the outer end of the first fixing portion 1 and the inner end of the second fixing portion 2.

[0015] When viewed in the vertical direction Z, the first fixing portion 1 is approximately C-shaped or U-shaped with an open interior, and is provided with a pair of engaging portions 4, 5 arranged at a distance d from each other in the front-to-rear direction Y, and a connecting portion 6 connecting the outer ends of the pair of engaging portions 4, 5.

[0016] The first engagement portion 4 and the second engagement portion 5 are flat plates extending in the left-right direction X and have contact surfaces 4a, 5a facing each other in the anterior-posterior direction Y. The first engagement portion 4 is positioned posterior to the first cutting end B, with the contact surface 4a contacting the posterior surface of the first cutting end B. The second engagement portion 5 is positioned anterior to the first cutting end B, with the contact surface 5a contacting the anterior surface of the first cutting end B. Since the thickness of the vertebral arch A varies from person to person, the distance d is designed to be sufficiently large relative to the thickness of the vertebral arch A, taking into account the variation in the thickness of the vertebral arch A. The first engagement portion 4 has one or more screw holes 71 penetrating the first engagement portion 4 in the anterior-posterior direction Y. Although the number of screw holes 71 is one in FIGS. 1A and 1B , two or more screw holes may be used.

[0017] The connecting portion 6 has a deforming portion (plastically deforming portion) 61 that is plastically deformed in response to a compressive force F in the front-rear direction Y. The deforming portion 61 comprises at least a portion of the connecting portion 6, and the plastic deformation of the deforming portion 61 displaces the first engaging portion 4 and the second engaging portion 5 in a direction toward each other. The deforming portion 61 that is plastically deformed by the compressive force F does not spontaneously return to its original shape, but maintains its deformed shape. Therefore, the deforming portion 61 constitutes a return prevention means that prevents the first engaging portion 4 and the second engaging portion 5 from displacing in the opposite direction (a direction away from each other) after being displaced in a direction toward each other.

[0018] 1A and 1B, the deformation portion 61 has an annular shape when viewed in the left-right direction X, and the upper and lower portions 6a, 6b of the deformation portion 61 are bent in a direction that protrudes outward in the up-down direction Z. The upper portion 6a and the lower portion 6b are plastically bent in a direction that protrudes further outward in the up-down direction Z (see arrow D) by a compressive force F in the front-back direction Y, whereby the deformation portion 61 is easily compressively deformed in the front-back direction Y.

[0019] The connecting portion 6 may have a pair of pressurized surfaces 8a, 8b as a structure for making it easier for a user, such as a doctor, to apply a compressive force F to the deforming portion 61. The pair of pressurized surfaces 8a, 8b are provided on the rear and front sides of the deforming portion 61, with the rear pressurized surface 8a facing backward and the front pressurized surface 8b facing forward. In the example of Figures 1A and 1B, the pressurized surfaces 8a, 8b are made up of the rear and front surfaces of the annular deforming portion 61 and are flat surfaces perpendicular or approximately perpendicular to the front-to-rear direction Y.

[0020] The plate 10 may have openings 9a and 9b to make it easier to place a pressure tool on the pressure-receiving surfaces 8a and 8b. The first opening 9a is adjacent to the rear side of the first pressure-receiving surface 8a, and the first pressure-receiving surface 8a forms part of the inner surface of the first opening 9a. The second opening 9b is adjacent to the front side of the second pressure-receiving surface 8b, and the second pressure-receiving surface 8b forms part of the inner surface of the second opening 9b. A user can apply a compressive force F to the pressure-receiving surfaces 8a and 8b using a tool inserted into the openings 9a and 9b, easily compressing and deforming the deformation portion 61.

[0021] The second fixing portion 2 is flat and extends in the left-right direction X, and has a contact surface 2a on its front side. The second fixing portion 2 is disposed on the rear side of the second cut end C, and the contact surface 2a is brought into contact with the rear surface of the second cut end C. The second fixing portion 2 has one or more screw holes 72 that penetrate the second fixing portion 2 in the front-rear direction Y. Although the number of screw holes 72 is two in FIGS. 1A and 1B , there may be only one or three or more.

[0022] The first fixation part 1 preferably further includes a stopper part 11 that prevents the first fixation part 1 from moving relative to the vertebral arch A in a direction along the surface of the vertebral arch A. As shown in Figures 1A and 1B, an example of the stopper part 11 is a protrusion provided on the first engagement part 4 and protruding from the contact surface 4a. The protrusion 11 has a sharp tip and can bite into the surface of the vertebral arch A. To reliably prevent rotation of the vertebral arch A, which will be described later, it is preferable that multiple protrusions 11 be arranged at intervals around the circumferential direction of the screw hole 71.

[0023] The first fixing portion 1 and the second fixing portion 2 may further have abutment portions 1a, 2b against which the cut end of the vertebral arch A abuts. The first abutment portion 1a is provided at the outer end of at least one of the contact surfaces 4a, 5a and protrudes in the anterior-posterior direction Y from at least one of the contact surfaces 4a, 5a. In the example of Figures 1A and 1B, the first abutment portion 1a is formed from the inner surface of the connecting portion 6. The second abutment portion 2b is provided at the inner end of the contact surface 2a and protrudes in the anterior-posterior direction Y from the contact surface 2a.

[0024] Next, we will explain how to use the plate 10. After cutting one side of the vertebral arch A and widening the space between the cut ends B and C, as shown in Figure 2A, the first cut end B is placed between the pair of engaging portions 4 and 5, and a compressive force F is applied to the connecting portion 6 using any tool 40. Due to the compressive deformation of the deforming portion 61, the pair of engaging portions 4 and 5 are displaced in directions that bring them closer to each other.

[0025] 2B , the deforming portion 61 is compressed and deformed until the contact surfaces 4 a and 5 a respectively come into contact with the rear and front surfaces of the first cut end B. As a result, the protrusion 11 bites into the rear surface of the first cut end B, and the protrusion 11 prevents relative movement between the first fixing portion 1 and the first cut end B in a direction along the surface of the first cut end B.

[0026] Next, a screw (not shown) is inserted into the first cut end B through the screw hole 71, and the first fixing part 1 is fixed to the first cut end B. Meanwhile, the second fixing part 2 is disposed on the rear surface of the second cut end C, and a screw (not shown) is inserted into the second cut end C through the screw hole 72, and the second fixing part 2 is fixed to the second cut end C.

[0027] Before fixation with the screws, the cut ends of the vertebral arch A may be abutted against the abutment portions 1 a and 2 b, respectively, to position the plate 10 relative to the cut ends B and C. This allows the distance between the cut ends B and C to be determined to a predetermined distance determined by the dimensions of the spacer portion 3.

[0028] As described above, according to this embodiment, the distance d between the pair of engaging portions 4, 5 of the first fixation portion 1 can be reduced by compressive deformation of the connecting portion 6. Therefore, the distance d can be adjusted according to the thickness of the vertebral arch A, allowing the plate 10 to be adapted to vertebral arches A of various sizes. This also allows the second engaging portion 5 to be positioned so that it contacts the anterior surface of the first cut end B. As shown in FIG. 9 , in a conventional plate in which the distance between the pair of engaging portions 4′, 5′ is fixed, the dimensions of the first fixation portion 1′ may not be adapted to the vertebral arch A, resulting in a gap between the second engaging portion 5′ and the anterior surface of the first cut end B. Because the spinal cord is present in front of the vertebral arch A, such an arrangement of the second engaging portion 5′ is not preferable.

[0029] Furthermore, according to this embodiment, the engaging portions 4, 5, once displaced by the plastic deformation of the deforming portion 61, are held at the displaced position without subsequently displacing in the opposite direction. Therefore, no additional work is required to hold the engaging portions 4, 5 at the displaced position, which simplifies the procedure.

[0030] Furthermore, according to this embodiment, the stopper portion 11 provided on the first engagement portion 4 prevents relative movement between the first engagement portion 4 and the first cut end B. This prevents rotation of the vertebral arch A due to torque T when the screw is inserted into the first cut end B. As shown in Figure 10, when the screw 12 is inserted, torque T is transmitted from the rotating screw 12 to the first cut end B. To facilitate the expansion of the vertebral arch A, a hinge portion H is formed at the base of the other side of the vertebral arch A, and the vertebral arch A is likely to rotate around the hinge portion H. Rotation of the vertebral arch A is undesirable because it places a load on the hinge portion H.

[0031] FIG. 3 shows another example of the plate 10 according to this embodiment. In the plate 10 shown in FIG. 3, the deforming portion 61 is thin and bent in a direction that protrudes outward. The rear end of the deforming portion 61 is connected to the outer end of the first engagement portion 4 via a first connecting portion 62, and the front end of the deforming portion 61 is connected to the outer end of the second engagement portion 5 via a second connecting portion 63. When a compressive force F is applied in the front-rear direction Y, the deforming portion 61 further bends and is compressed and deformed in the front-rear direction Y, thereby displacing the first engagement portion 4 and the second engagement portion 5 toward each other. The first engagement portion 4 has two screw holes 71 arranged in the left-right direction X, and a plurality of protrusions 11 are provided around each screw hole 71.

[0032] Second Embodiment Next, a laminoplasty plate according to a second embodiment of the present invention will be described. In this embodiment, features different from those of the first embodiment will be described, and features common to the first embodiment will be denoted by the same reference numerals and will not be described again. As shown in Figures 4A and 4B , a laminoplasty plate 20 according to this embodiment includes a first fixing portion 21 fixed to the first cutting end B, a second fixing portion 2 fixed to the second cutting end C, and a spacer portion 3 extending between the first fixing portion 21 and the second fixing portion 2.

[0033] The first fixing portion 21 includes a pair of engaging portions 24, 25 spaced apart from each other in the front-rear direction Y by a distance d, and a connecting portion 26 connecting outer ends of the pair of engaging portions 24, 25. The first engaging portion 24 and the second engaging portion 25 are flat plates extending in the left-right direction X and have contact surfaces 24a, 25a facing each other in the front-rear direction Y. The first engaging portion 24 is disposed rearward of the first cut end portion B, and the contact surface 24a contacts the rear surface of the first cut end portion B. The second engaging portion 25 is disposed frontward of the first cut end portion B, and the contact surface 25a contacts the front surface of the first cut end portion B.

[0034] The engaging portions 24 and 25 are formed from separate members, and the connecting portion 26 is formed from a movement mechanism that supports the engaging portions 24 and 25 so that they can move toward each other. Specifically, the connecting portion 26 has a first portion 27a fixed to the outer end of the first engaging portion 24, a second portion 27b fixed to the outer end of the second engaging portion 25, and a screw (screw mechanism) 28 that connects the first portion 27a and the second portion 27b. In this embodiment, the first engaging portion 24 and the first portion 27a are formed from a single member, and the second engaging portion 25, the second portion 27b, the spacer portion 3, and the second fixing portion 2 are formed from a single member.

[0035] The screw 28 has a screw shaft 28a and a head 28b with a diameter larger than that of the screw shaft 28a. The first portion 27a has a through hole (screw mechanism) 27c through which the screw shaft 28a passes in the front-rear direction Y, and the second portion 27b has a screw hole (screw mechanism) 27d that extends in the front-rear direction Y and to which the screw shaft 28a is fastened. The through hole 27c has a diameter smaller than that of the head 28b. By screwing the screw 28 into the screw hole 27d, the head 28b presses against the first portion 27a, displacing the first engagement portion 24 in a direction approaching the second engagement portion 25. The first portion 27a may have a countersunk hole to accommodate the head 28b.

[0036] The first portion 27a will not move in the opposite direction (the direction away from the second portion 27b) unless the screw 28 is rotated in the direction of removing it from the screw hole 27d. Therefore, the screw mechanisms 27c, 27d, and 28 constitute return prevention means that prevents the first engaging portion 24 from being displaced in the opposite direction (the direction away from the second engaging portion 25) after being displaced in the direction toward the second engaging portion 25 by screwing in the screw 28.

[0037] The first fixing portion 21 preferably further has a stopper portion 11, for example, a protrusion protruding from the contact surface 24a. The fixing portions 21 and 2 may further have abutting portions 21a and 2b against which the cut ends of the vertebral arch A abut. In the example of Figures 4A and 4B, the first abutting portion 21a is formed from the inner surface of the second portion 27b.

[0038] Next, a method of using the plate 20 will be described. After cutting one side of the vertebral arch A and widening the space between the cut ends B and C, as shown in Fig. 5A, the first cut end B is placed between the pair of engaging portions 24 and 25, and a screw 28 is screwed into the screw hole 27d using a tool such as a screwdriver. The head portion 28b, which moves forward, presses the first portion 27a, displacing the first engaging portion 24 in a direction approaching the second engaging portion 25. As shown in Fig. 5B, the screw 28 is screwed in until the contact surfaces 24a and 25a come into contact with the posterior and anterior surfaces of the first cut end B, respectively.

[0039] Next, similarly to the first embodiment, the first fixing part 21 is fixed to the first cut end part B by a screw. In addition, the second fixing part 2 is disposed on the rear surface of the second cut end part C and fixed to the second cut end part C by a screw.

[0040] As described above, according to this embodiment, the first engagement portion 24 is movable in the anterior-posterior direction Y relative to the second engagement portion 25, and the distance d can be reduced by tightening the screw 28. Therefore, the distance d can be adjusted according to the thickness of the vertebral arch A, and the plate 20 can be adapted to vertebral arches A of various sizes. This also allows the second engagement portion 25 to be positioned so as to contact the anterior surface of the first cutting end B.

[0041] Furthermore, according to this embodiment, the first engagement portion 24, which has been displaced toward the second engagement portion 25 by the screw 28 being threaded, is maintained in the displaced position without subsequently displacing in the opposite direction. Therefore, no additional work is required to maintain the first engagement portion 24 in the displaced position, simplifying the procedure. Furthermore, according to this embodiment, the stopper portion 11 provided on the first engagement portion 24 can prevent rotation of the vertebral arch A when the screw is inserted into the first cut end B.

[0042] FIG. 6 shows another example of the plate 20 according to this embodiment. In the plate 20 shown in FIG. 6 , the connecting portion 26 has a ratchet mechanism 29 between a first portion 27 a and a second portion 27 b. The first portion 27 a is connected to the second portion 27 b via the ratchet mechanism 29 so as to be movable in the front-rear direction Y. The ratchet mechanism 29 limits movement of the first portion 27 a relative to the second portion 27 b only in the direction toward the second portion 27 b. Specifically, the ratchet mechanism 29 has a pawl 29 a provided on the first portion 27 a and a plurality of grooves 29 b provided on the outer surface of the second portion 27 b, into which the pawl 29 a fits. The grooves 29 b are arranged in the front-rear direction Y and have a shape that allows the pawl 29 a to move forward and prevents the pawl 29 a from moving backward.

[0043] With this type of connection portion 26, after the first cut end B is placed between the pair of engagement portions 24, 25, the first portion 27a or the first engagement portion 24 can be pushed to displace the first engagement portion 24 in a direction toward the second engagement portion 25 until the contact surfaces 24a, 25a respectively contact the rear and front surfaces of the first cut end B. Furthermore, the ratchet mechanism 29 prevents the first engagement portion 24, which has been displaced in a direction toward the second engagement portion 25, from moving in the opposite direction, and the first engagement portion 24 is held in the displaced position.

[0044] Third Embodiment Next, a laminoplasty plate according to a third embodiment of the present invention will be described. In this embodiment, only the components different from those of the first embodiment will be described, and components common to those of the first embodiment will be denoted by the same reference numerals and will not be described again. As shown in FIG. 7 , a laminoplasty plate 30 according to this embodiment includes a first fixing portion 31 fixed to the first cutting end B, a second fixing portion 2 fixed to the second cutting end C, and a spacer portion 3 extending between the first fixing portion 31 and the second fixing portion 2. The plate 30 is composed of a single member, and the first fixing portion 31, the second fixing portion 2, and the spacer portion 3 are seamlessly connected to each other.

[0045] The first fixing portion 31 is approximately C-shaped or U-shaped with an open interior when viewed in the vertical direction Z, and is provided with a pair of engaging portions 34, 35 arranged at a distance d from each other in the front-to-rear direction Y, and a connecting portion 36 connecting the outer ends of the pair of engaging portions 34, 35.

[0046] The first engaging portion 34 and the second engaging portion 35 are flat plates extending in the left-right direction X and have contact surfaces 34a, 35a facing each other in the front-rear direction Y. The first engaging portion 34 is disposed rearward of the first cut end B, and the contact surface 34a contacts the rear surface of the first cut end B. The second engaging portion 35 is disposed frontward of the first cut end B, and the contact surface 35a contacts the front surface of the first cut end B.

[0047] The connecting portion 36 has a generally C-shaped or U-shaped leaf spring shape with an open interior when viewed in the vertical direction Z, and includes a deformation portion (elastic deformation portion) 37 and linking portions 38 a, 38 b. The rear end of the deformation portion 37 is connected to the outer end of the first engaging portion 34 via the first linking portion 38 a, and the front end of the deformation portion 37 is connected to the outer end of the second engaging portion 25 via the second linking portion 38 b.

[0048] The deformation portion 37 is elastically deformable in the front-rear direction Y by an external force F' acting on the engagement portions 34, 35, and the elastic deformation of the deformation portion 37 displaces the first engagement portion 34 and the second engagement portion 35 in directions separating them from each other. The external force F' is a force in the direction separating the engagement portions 34, 35 from each other. In the example of FIG. 7 , the deformation portion 37 is thin-plate shaped and bent in a direction protruding outward. The deformation portion 37 is elastically deformed in a direction expanding in the front-rear direction Y by the external force F'.

[0049] When the deforming portion 37 is released from the external force F' after elastic deformation, it attempts to return to its original shape due to its own elastic force, causing the first engaging portion 34 and the second engaging portion 35 to displace toward each other. At this time, the engaging portions 34, 35 will not displace in the opposite direction (away from each other) unless the external force F' that resists the elastic force acts again. Therefore, the deforming portion 37 constitutes a return prevention means that prevents the pair of engaging portions 34, 35 from displacing in the opposite direction after displacing toward each other.

[0050] 7 shows the plate 30 when the deformed portion 37 is in a natural state without the application of an external force. In the natural state, the pair of engaging portions 34, 35 are arranged parallel to each other, and the distance d is designed to be a size that enables the pair of engaging portions 34, 35 to grip vertebral arches A of various thicknesses.

[0051] The first fixing portion 31 preferably further has a stopper portion 11, for example, a protrusion protruding from the contact surface 34a. The fixing portions 31 and 2 may further have abutting portions 31a and 31b against which the cut ends of the vertebral arch A abut, respectively.

[0052] Next, we will explain how to use the plate 30. After cutting one side of the vertebral arch A and widening the space between the cut ends B and C, an external force F' elastically deforms the deforming portion 37, opening the pair of engaging portions 34, 35, and positioning the first cut end B between the pair of engaging portions 34, 35. Next, the external force F' is released, and the pair of engaging portions 34, 35 are displaced toward each other by the elastic force of the deforming portion 37 until the contact surfaces 34a, 35a come into contact with the posterior and anterior surfaces of the first cut end B, respectively.

[0053] Next, similarly to the first embodiment, the first fixing part 31 is fixed to the first cut end part B by a screw. In addition, the second fixing part 2 is disposed on the rear surface of the second cut end part C and fixed to the second cut end part C by a screw.

[0054] As described above, according to this embodiment, the distance d between the pair of engaging portions 34, 35 of the first fixing portion 31 can be expanded or contracted by elastic deformation of the deforming portion 37. Therefore, the distance d can be adjusted according to the thickness of the vertebral arch A, making it possible to adapt the plate 30 to vertebral arches A of various sizes. This also allows the second engaging portion 35 to be positioned so as to contact the anterior surface of the first cut end B.

[0055] Furthermore, according to this embodiment, the pair of engaging portions 34, 35, which are displaced toward each other by elastic force, are maintained in the displaced position without subsequently displacing in the opposite direction. Therefore, no additional work is required to maintain the pair of engaging portions 34, 35 in the displaced position, simplifying the procedure. Furthermore, according to this embodiment, the stopper portion 11 provided on the first engaging portion 34 can prevent rotation of the vertebral arch A when inserting the screw into the first cut end B.

[0056] In each of the above embodiments, the stopper portion 11 is a protrusion, but instead of or in addition to this, other means capable of preventing movement of the first fixing portion 1, 21, 31 relative to the first cut end portion B may be used. For example, the stopper portion 11 may be provided on the contact surface 4a and have a structure, such as a concave-convex structure, that increases friction between the surface of the cut end portion B and the contact surface 4a. The stopper portion 11 may also be provided on the second engaging portion 5, 25, 35.

[0057] In each of the above embodiments, the connecting portion has a return prevention means, but alternatively, it may not have a return prevention means. For example, the connecting portion may hold the first engaging portion and the second engaging portion so that they can move relatively in both the forward and backward directions Y. In this case, the user may use any means to hold the first engaging portion and the second engaging portion in their displaced positions. This configuration also allows for adaptation to vertebral arches A of various sizes.

[0058] Although the embodiments and modifications of the present invention have been described above in detail with reference to the drawings, the specific configuration of the present invention is not limited to the above embodiments and modifications, and various design changes are possible within the scope of the present invention. For example, in the first embodiment, the deformation portion 61 is configured as a part of the connection portion 6, but instead, it may be configured as the entire connection portion 6. In other words, the entire connection portion 6 may plastically deform in response to the compressive force F. In the third embodiment, the connection portion 36 may have a structure other than a leaf spring, and may have any elastic member such as a spring as the elastic deformation portion 37.

[0059] 10, 20, 30 Laminoplasty plate 1, 21, 31 First fixing portion 2, 22, 32 Second fixing portion 3, 23, 33 Spacer portion 4, 24, 34 First engaging portion 5, 25, 35 Second engaging portion 6 Connection portion 26 Connection portion (moving mechanism) 27a First portion (moving mechanism) 27b Second portion (moving mechanism) 27d Screw hole (screw mechanism) 27c Through hole (screw mechanism) 28 Screw (moving mechanism, screw mechanism) 29 Ratchet mechanism 61 Plastic deformation portion (return prevention means) 71, 72 Screw hole 11 Protrusion (stopper portion)

Claims

1. A laminoplasty plate for fixing an enlarged vertebral arch between a first cutting end and a second cutting end, comprising: a first fixing portion fixed to the first cutting end; a second fixing portion fixed to the second cutting end; and a spacer portion extending between the first fixing portion and the second fixing portion, wherein the first fixing portion comprises: a first engaging portion and a second engaging portion spaced apart from each other and respectively positioned on the posterior and anterior sides of the first cutting end; and a connecting portion connecting the first engaging portion and the second engaging portion so that they can be displaced toward each other.

2. The laminoplasty plate of claim 1, wherein said connecting portion has a return prevention means for preventing said first engaging portion and said second engaging portion from displacing in the opposite direction after being displaced in the direction toward each other.

3. A laminoplasty plate according to claim 2, wherein said connecting portion has a plastically deformable portion that is plastically deformed by the compressive force in the direction of approaching each other, and said return prevention means comprises said plastically deformable portion.

4. A laminoplasty plate as described in claim 2, wherein the connecting portion has a movement mechanism that supports the first engaging portion and the second engaging portion so that they can move toward each other, and the movement mechanism has a screw mechanism or a ratchet mechanism as the return prevention means.

5. A laminoplasty plate as described in claim 2, wherein the connecting portion has an elastically deformable portion connecting the first engaging portion and the second engaging portion, the elastically deformable portion being elastically deformable in a direction in which the first engaging portion and the second engaging portion move away from each other, and the return prevention means is comprised of the elastically deformable portion.

6. A laminoplasty plate as claimed in claim 1, wherein the first engagement portion has a screw hole and a stopper portion that prevents movement of the first engagement portion relative to the first cutting end in a direction along the surface of the first cutting end, and preferably the stopper portion has a plurality of protrusions that are spaced apart in the circumferential direction of the screw hole.

Images