Patent Publication Number: US-2023157840-A1

Title: Spinal fusion device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present disclosure claims priority to U.S. provisional Application No. 63/109,663 filed on Nov. 4, 2020, which is incorporated by reference herein for all purposes. 
    
    
     BACKGROUND 
     Spine disorders often result in degeneration of the spinal disc in an intervertebral space between upper and lower vertebral bodies. Such a degenerated spinal disc may be treated by installing a fusion device into the intervertebral space and providing bone graft material through the installed fusion device to fuse the upper and lower vertebral bodies. While installing the fusion device, the fusion device may be susceptible to external forces applied thereto, which may result in structural failure of the fusion device. Facilitation of providing the bone graft material may be desirable to improve bone growth in fusing the upper and lower vertebral bodies. 
     SUMMARY 
     Embodiments of the present application relate to a fusion device and a process of using the fusion device to treat spinal disorders. 
     In an embodiment, a fusion device includes an actuator including a shaft, a receiver disposed posterior to the actuator and configured to be coupled to the shaft of the actuator, and a first plate and a second plate each slidably coupled to the actuator. The first and second plates are configured to move away from each other when the fusion device transitions from a first state to a second state. 
     In an embodiment, an implant includes an actuator including a hollow shaft, a receiver disposed posterior to the actuator and configured to be coupled to the hollow shaft of the actuator, a connector rotatably coupled to the receiver, and a first plate and a second plate each slidably coupled to the actuator and the connector. The first and second plates are configured to move away from each other when the fusion device transitions from a first state to a second state. The shaft has a through hole for delivering material therethrough, and the first state is a non-expanded state and the second state is an expanded state. 
     In an embodiment, a method of using a fusion device includes inserting a fusion device in a first state into a treatment region, transitioning the fusion device from the first state to a second state by inserting the hollow shaft of the actuator into the receiver, and injecting material through the channel of the fusion device to make the injected material flow out from the opening of the actuator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    and  FIG.  2    illustrate a fusion device in a first state (e.g., a non-expanded state) and a second state (e.g., an expanded state), respectively, according to an embodiment of the present disclosure 
         FIGS.  3 A,  3 B, and  3 C  illustrate a top view, a cross-sectional view, and a rear view of the fusion device of  FIG.  1    in the non-expanded state, according to an embodiment of the present disclosure. 
         FIGS.  4 A,  4 B, and  4 C  illustrate a top view, a cross-sectional view, and a rear view of the fusion device of  FIG.  2    in the expanded state, according to an embodiment of the present disclosure. 
         FIG.  5    illustrates an exploded view of the fusion device of  FIGS.  1  and  2    according to an embodiment of the present disclosure. 
         FIG.  6    illustrates a top view of an actuator of the fusion device of  FIGS.  1  and  2    according to an embodiment of the present disclosure. 
         FIG.  7    illustrates a fusion device locked in an expanded state using a set fastener according to an embodiment of the present disclosure. 
         FIGS.  8 A,  8 B, and  8 C  illustrate a perspective view, a side view, and a rear view of the set fastener of  FIG.  7    according to an embodiment of the present disclosure. 
         FIG.  9    illustrates an exploded view of a fusion device according to an embodiment of the present disclosure. 
         FIG.  10    illustrates an exploded view of a fusion device according to an embodiment of the present disclosure. 
         FIG.  11    is a flowchart illustrating a process of using a fusion device to treat spinal disorders according to an embodiment. 
         FIG.  12    illustrates an insertion tool used to insert a fusion device according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present application relate to a fusion device and a process of using the fusion device to treat spinal disorders. 
     In an embodiment, a fusion device (may also be referred to as, “implant” or “spinal device”) includes an actuator including a shaft, a receiver disposed posterior to the actuator and configured to be coupled to the shaft of the actuator, a connector rotatably coupled to the receiver, and a first plate and a second plate each slidably coupled to the actuator and the connector. The first and second plates may move away from each other when the fusion device transitions from a first state (e.g., a non-expanded state) to a second state (e.g., an expanded state). Since the receiver is disposed posterior to the actuator and have a threaded inner surface to which an outer threaded surface of the hollow shaft is coupled, the receiver may have a relatively long longitudinal length to ensure structural reliability of the fusing device. The shaft may be hollow depending on implementation. 
     In an embodiment, the actuator further includes an anterior portion slidably coupled to the first plate and the second plate, a posterior portion, and an opening disposed between the anterior portion and the posterior portion. The opening may be sufficiently great to facilitate injection of material for improving bone growth (or bone fusion) in a fusion process, and sufficiently small to ensure the structural reliability of the fusing device. 
     In an embodiment, the receiver is configured to receive a set fastener to substantially fix a position of a posterior end of the hollow shaft of the actuator, thereby locking the fusion device at a desired height. Since the set fastener and the receiver together may provide a robust locking mechanism for the hollow shaft, the position of the posterior end of the hollow shaft may be substantially fixed to maintain an expanded height of the actuator at a target value while ensuring the structural reliability of the fusion device. 
     In an embodiment, a method of using a fusion device includes inserting the fusion device in a non-expanded state into a treatment region, transitioning the fusion device from the non-expanded state to an expanded state by inserting a hollow shaft of the actuator into the receiver, and injecting material through a channel of the fusion device to make the injected material flow out from an opening of the actuator. In an embodiment, the injected material may be bone graft material, bone morphogenic protein, or other materials, or a combination thereof, that may be used to facilitate the fusing of the fusion device to the bone (hereinafter, referred to as “fusing material.”) 
     A detailed description of embodiments is provided below along with accompanying figures. The scope of this disclosure is limited only by the claims and encompasses numerous alternatives, modifications and equivalents. Although steps of various processes are presented in a given order, embodiments are not necessarily limited to being performed in the listed order. In some embodiments, certain operations may be performed simultaneously, in an order other than the described order, or not performed at all. 
     Numerous specific details are set forth in the following description. These details are provided to promote a thorough understanding of the scope of this disclosure by way of specific examples, and embodiments may be practiced according to the claims without some of these specific details. Accordingly, the specific embodiments of this disclosure are illustrative, and are not intended to be exclusive or limiting. For the purpose of clarity, technical material that is known in the technical fields related to this disclosure has not been described in detail so that the disclosure is not unnecessarily obscured. 
       FIG.  1    and  FIG.  2    illustrate a fusion device  10  in a first state (e.g., a non-expanded state) and a second state (e.g., an expanded state), respectively, according to an embodiment of the present disclosure.  FIGS.  3 A,  3 B, and  3 C  illustrate a top view, a cross-sectional view, and a rear view of the fusion device  10  in the non-expanded state, respectively, according to an embodiment of the present disclosure. For example, the cross-sectional view shown in  FIG.  3 B  of the fusion device  10  may be obtained by cutting the fusion device  10  along a line A-A′ shown in  FIG.  3 A .  FIGS.  4 A,  4 B, and  4 C  illustrate a top view, a cross-sectional view, and a rear view of the fusion device  10  in the expanded state, respectively, according to an embodiment of the present disclosure. For example, the cross-sectional view shown in  FIG.  4 B  of the fusion device  10  may be obtained by cutting the fusion device  10  along a line B-B′ shown in  FIG.  4 A .  FIG.  5    illustrates an exploded view of the fusion device  10  according to an embodiment of the present disclosure.  FIG.  6    illustrates a top view of an actuator  6  included in the fusion device  10  according to an embodiment of the present disclosure. 
     Referring to  FIGS.  5  and  6   , the fusion device  10  includes a first plate  2  (e.g., an upper plate), a second plate (e.g., a lower plate)  4 , an actuator  6 , a connector  12 , and a receiver  14 . A set fastener (or set screw)  52  (see  FIG.  7   ) may be inserted into the receiver  14  to lock the fusion device  10  at a given expanded state. 
     The actuator  6  may include an anterior portion  34 , first and second side portions  36   a  and  36   b , and a posterior portion  46 . In an embodiment, the anterior portion  34  of the actuator  6  may include a pair of upper grooves  62  slidably coupled to a pair of first grooves  18  of the first plate  2 , and a pair of lower grooves (not shown) slidably coupled to a pair of first grooves  58  of the second plate  4 . The anterior portion  34  may further include a through hole  48  through which a guide wire may be inserted. As explained below, the through hole may also be used to inject fusing material therethrough. 
     The first and side portions  36   a  and  36   b  of the actuator  6  may couple the anterior portion  34  and the posterior portion  46 , such that a posterior end of the anterior portion  34 , inner side surfaces of the first and second side portions  36   a  and  36   b , and an anterior end of the posterior portion  46  define an opening  70 . Each of the first and second side portions  36   a  and  36   b  may have an upper ramp surface  44  and a lower ramp surface  82  that are slidably coupled to a ramp surface  42  of the first plate  2  and a ramp surface  84  of the second plate  4 , respectively. 
     The posterior portion  46  of the actuator  6  may include a first wedge (e.g., an upper wedge)  86  and a second wedge (e.g., a lower wedge)  88  that are slidably coupled to the first and second plates  2  and  4 , respectively. For example, the upper wedge  86  of the posterior portion  46  may include a pair of upper grooves  48  that are slidably coupled to a pair of grooves  20  of the first plate  2 . 
     The posterior portion  46  may further include a hollow shaft  32  that extends in a longitudinal direction along a centerline CL of the fusion device  10 . In an embodiment, the hollow shaft  32  has a threaded outer surface  90  to be coupled to an inner surface  74  of the receiver  14 . For example, the outer surface  90  of the hollow shaft  32  may have a male thread and the inner surface  74  of the receiver  14  may have a female thread. However, embodiments of the present disclosure are not limited thereto. 
     The receiver  14  may include a first portion  38 . The first portion  38  of the receiver  14  may have the inner surface  74  coupled to the outer surface  90  of the hollow shaft  32  and an outer surface  76  rotatably coupled to a through hole  30  of the connector  12 . Since the receiver  14  may be disposed posterior to the actuator  6  and have the threaded inner surface  74  to which the outer threaded surface  90  of the hollow shaft  32  is coupled, the receiver  14  may have a relatively long length in the longitudinal direction. For example, referring to  FIG.  3 B  illustrating the fusion device  10  in the non-expanded state, a longitudinal length L R  of the receiver  14  along the centerline CL may be in a range from 25% to 45% of a longitudinal length L FD  of the fusion device  10  along the centerline CL. When the longitudinal length L R  of the receiver  48  is shorter than 25% of the longitudinal length L FD  of the fusion device  10 , the hollow shaft  32  of the actuator  6  may not be inserted into the receiver  14  with a sufficient depth to ensure the structural reliability of the fusion device  10 . When the longitudinal length L R  of the receiver  48  exceeds 45% of the longitudinal length L FD  of the fusion device  10 , a size of the opening  70  of the actuator  6  may be reduced to such a degree that the size is not sufficiently large to facilitate injection of fusing material, as will be described below in more detail. In an embodiment, the longitudinal length L R  of the receiver  14  along the centerline CL is at least 30% of the longitudinal length L FD  of the fusion device  10  along the centerline CL. In another embodiment, the longitudinal length L R  of the receiver  14  along the centerline CL is at least 35% of the longitudinal length L FD  of the fusion device  10  along the centerline CL. In yet another embodiment, the longitudinal length L R  of the receiver  14  along the centerline CL is at least 40% of the longitudinal length L FD  of the fusion device  10  along the centerline CL. 
     The receiver  14  may further include a second portion  40  disposed posterior to the first portion  38 . The second portion  40  of the receiver  14  may have an inner surface  78  with a cross-sectional shape matching that of an end of a driving tool for rotating the receiver  14 . In an embodiment, the second portion  40  may have a polygon shape with a size (e.g., a distance between opposite sides of the polygon shape) greater than a size (e.g., a major diameter of the internal thread) of the inner surface  74  of the first portion  38 . 
     After the fusion device  10  has been placed in a treatment region (e.g., a damaged intervertebral disc space), the insertion driver may be inserted into the second portion  40  of the receiver  14  to rotate the receiver  14  in a given rotational direction, thereby causing the actuator  6  to move along the centerline CL in a posterior direction to increase a length of a portion of the hollow shaft  32  inserted into the first portion  38  of the receiver  14 . As a result, the actuator  6  drives the first and second plates  2  and  4  away from the centerline CL of the fusion device  10 , leading to the expanded state of the fusion device  10  shown in  FIGS.  2  and  4 A- 4 C . For example, the length of the inserted portion of the hollow shaft  32  may be adjusted until an expanded height (e.g., a height H EXP  between a bottom surface of the second plate  4  and an upper surface of the first plate  2  in  FIG.  4 B ) of the actuator  6  reaches a desired height. 
     Once expanded to reach the desired height, fusing material may be provided to the fusion device  10 . For example, an injecting device (not shown) may be inserted into the receiver  14  to inject the fusing material through the through hole  92  of the hollow shaft  32 , and the injected fusing material may flow out from the opening  70  of the actuator  6 . In an embodiment, the opening  70  of the actuator  6  may be sufficiently great to facilitate the injection of the fusing material, thereby improving the bone growth in the fusion process. In addition, the opening  70  of the actuator  6  may be sufficiently small to ensure the structural reliability of the actuator  60 . For example, referring to  FIG.  6    illustrating a top view of the actuator  6 , when the opening  70  may have a first length L 1  in a longitudinal direction of the actuator  6  and a second length L 2  in a direction perpendicular to the longitudinal direction, the first length L 1  of the opening  70  may be in a range from 15% to 30% of a total length L 3  of the actuator  6  in the longitudinal direction, and the second length L 2  of the opening  70  may be in a range from 50% to 70% of a total length L 4  of the actuator  6  in the direction perpendicular to the longitudinal direction. In an embodiment, the first length L 1  of the opening  70  is at least 20% (e.g., about 22%) of a total length L 3  of the actuator  6  in the longitudinal direction, and the second length L 2  of the opening  70  is at least 58% (e.g., about 60%) of a total length L 4  of the actuator  6  in the direction perpendicular to the longitudinal direction. In another embodiment, the first length L 1  of the opening  70  is at least 25% of a total length L 3  of the actuator  6  in the longitudinal direction, and the second length L 2  of the opening  70  is at least 63% of a total length L 4  of the actuator  6  in the direction perpendicular to the longitudinal direction. 
     Once the injection of the fusing material has been complete, a set fastener (e.g., the set fastener  52  in  FIG.  7   ) may be inserted into the receiver  14 . For example, referring to  FIG.  7   , the set fastener  52  may be inserted until an anterior end of the set fastener  52  contacts a posterior end of the hollow shaft  32 . Since the set fastener  52  and the receiver  14  together may provide a robust locking mechanism for the hollow shaft  32 , the position of the posterior end of the hollow shaft  32  may be substantially fixed to maintain the expanded height of the actuator  6  at the desired height while ensuring the structural reliability of the fusion device  10 . In an embodiment, the set fastener  52  may have a threaded outer surface to be inserted into the receiver  14 . For example, referring to  FIGS.  7  and  8 A to  8 C , the set fastener  52  may have a threaded outer surface  75  to be coupled to the inner surface  74  of the receiver  14 . 
       FIG.  9    illustrates an exploded view of a fusion device  100  according to an embodiment of the present disclosure. The fusion device  100  includes a first plate  102 , a second plate  104 , an actuator  106 , a connector  112 , and a receiver  114 , and one or more pins  111 . Descriptions on structural and functional features of the fusion device  100  similar to those of the fusion device  10  in  FIGS.  1  to  6    may be omitted for the interest of brevity. 
     The fusion device  100  in  FIG.  9    differs from the fusion device  10  in  FIGS.  1  to  6    in that the first plate  102  and the second plate  104  of the fusion device  100  have different structures from each other, whereas the first plate  2  and second plate  4  of the fusion device  10  have substantially the same structure. For example, the first plate  102  of the fusion device  100  has a side portion  113  slidably coupled to a first recess  117  of the second plate  104 . The fusion device  100  in  FIG.  9    also differs from the fusion device  10  in  FIGS.  1  to  6    in that the connector  112  of the fusion device  100  includes a side portion  115  slidably coupled to the side portion  113  of the first plate  102  and a second recess  119  of the second plate  104 . In addition, the fusion device  100  in  FIG.  9    differs from the fusion device  10  in  FIGS.  1  to  6    in that the pins  111  are received by the connector  112  to engage a neck  121  of the receiver  114 , thereby retaining the receiver  114  within the connector  112  while allowing the receiver  114  to rotate for expanding the fusion device  100 . 
       FIG.  10    illustrates an exploded view of a fusion device  200  according to an embodiment of the present disclosure. The fusion device  200  includes a first plate  202 , a second plate  204 , an actuator  206 , a connector  212 , and a receiver  214 , and one or more pins  211 . Descriptions on structural and functional features of the fusion device  200  similar to those of the fusion device  10  in  FIGS.  1  to  6    may be omitted for the interest of brevity. 
     The fusion device  200  in  FIG.  10    differs from the fusion device  10  in  FIGS.  1  to  6    in that the actuator  206  of the fusion device  200  includes a side upper portion  237  and a side lower portion  231  each extending in an oblique direction with respect to a longitudinal direction of the actuator  206 , and that the first plate  202  and the second plate  204  include recesses  233  and  235  slidably coupled to the side upper and lower portions  237  and  231 , respectively. In addition, the fusion device  200  in  FIG.  10    differs from the fusion device  10  in  FIGS.  1  to  6    in that the pins  211  functions to engage a neck  221  of the receiver  214 , thereby retaining the receiver  214  within the connector  212  while allowing the receiver  214  to rotate for expanding the fusion device  200 . 
       FIG.  11    is a flowchart illustrating a process of using a fusion device (e.g., the fusion device  10  in  FIGS.  1  to  6   ) to treat spinal disorders according to an embodiment. In an embodiment, such treatment may be a Posterior Lumbar Interbody Fusion (PLIF) surgery. 
     At S 1110 , the fusion device in a first state (e.g., the non-expanded state) may be attached to an insertion tool. In an embodiment, such an insertion tool may include a pair of prongs to be inserted into corresponding holes (e.g., side holes  79  of the connector  12  in  FIG.  5   ) of the fusion device for attaching the fusion device to the insertion tool.  FIG.  12    illustrates an insertion tool  77  according to an embodiment of the present disclosure. For example, the insertion tool  77  may include a sleeve  85  and an inserter body having a pair of prongs  83  and passing through the sleeve  85 . The insertion tool  77  may be coupled to an injecting device  87  used to inject fusing material as will be described below in more detail. 
     At S 1120 , the fusion device in the first state may be inserted into a treatment region (e.g., a damaged intervertebral disc space) using the insertion tool. In an embodiment, a portion of the insertion tool may be removed and the remaining portion of the insertion tool may be coupled with a structure suitable for applying an external force thereon. For example, the structure may have a posterior end having a relatively large cross-sectional area onto which a hammer strikes to exert the external force. 
     At S 1130 , the fusion device may transition from the first state to a second state (e.g., the expanded state). In an embodiment, a portion (e.g., the hollow shaft  32  in  FIGS.  4 B and  5   ) of an actuator (e.g., the actuator  6  in  FIGS.  4 B and  5   ) may be inserted into the receiver by a given distance to adjust a height (e.g., the expanded height H EXP  in  FIG.  4 B ) of the fusion device to a desired height (or target value). For example, a driving tool may be inserted into a receiver (e.g., the receiver  14  in  FIGS.  1  to  6   ) to rotate the receiver in a given rotational direction, thereby driving first and second plates (e.g., the upper and lower plates  2  and  4  in  FIGS.  1  to  6   ) away from each other until the adjusted height of the fusion device reaches the target value. 
     At S 1140 , material may be provided to the fusion device. In an embodiment, an injecting device (e.g., the injecting device  87  in  FIG.  12   ) may be inserted into the receiver to inject fusing material into a channel (e.g., the through hole  92  of the hollow shaft  32  in  FIG.  4 B ). Such a channel may be used to deliver the fusing material therethrough and be exposed to an opening (e.g., the opening  70  of the actuator  6  in  FIG.  6   ), and thus the injected material through the channel may flow out from the opening. 
     At S 1150 , a set fastener (e.g., the set fastener  52  in  FIG.  7   ) may be inserted into the receiver. In an embodiment, the set fastener may have a threaded outer surface (e.g., the threaded outer surface  75  in  FIGS.  8 B ) to be coupled to a threaded inner surface (e.g., the inner surface  74  in  FIG.  7   ) of the receiver, leading to a robust locking mechanism for a portion (e.g., the hollow shaft  32  of the actuator  6  inserted into the receiver  14  in  FIG.  4 B ) of the actuator inserted into the receiver. In an embodiment, the fusion device may be locked in a desired height without the set fastener, in which case step S 1150  may be performed optionally. 
     Aspects of the present disclosure have been described in conjunction with the specific embodiments thereof that are proposed as examples. Numerous alternatives, modifications, and variations to the embodiments as set forth herein may be made without departing from the scope of the claims set forth below. Accordingly, embodiments as set forth herein are intended to be illustrative and not limiting.