Patent Publication Number: US-2023149180-A1

Title: Expandable Implant with Deflectable Sequence of Segments

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of, and claims priority to and benefit under 35 U.S.C. § 120 to, prior copending U.S. application Ser. No. 16/952,891, filed Nov. 19, 2020, which is a divisional application of, and claims priority and benefit under 35 U.S.C. § 121 to, U.S. application Ser. No. 15/741,294, filed Jan. 2, 2018, now U.S. Pat. No. 10,842,641, which was the National Stage filing (under 35 U.S.C. § 371) of International Application No. PCT/IL2016/050762, filed Jul. 14, 2016, which claims priority to and benefit under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 62/192,084, filed Jul. 14, 2015, the entire contents of each of which are hereby incorporated by reference. 
    
    
     FIELD AND BACKGROUND OF THE INVENTION 
     The present invention relates to implants and, in particular, it concerns an expandable implant with a deflectable sequence of segments. 
     Various expanding implants are described in prior patents and patent publications commonly assigned with the present invention, which provide the most relevant background to the present invention. The publications mentioned herein are not to be considered prior art other than to the extent that they are defined as such by the applicable patent laws for the national phase of any application stemming from this international application. Such documents include: U.S. Pat. No. 9,005,291 B2; U.S. Pat. No. 9,017,413 B2; International Publication No. WO 2015/063719 A1; and International Publication No. WO 2016/063283 A1. 
     In general terms, these examples disclose various forms of an adjustable implant which includes a telescopic body with first and second portions in sliding engagement, and a deflectable linkage connected between the two portions of the base. The deflectable linkage is formed from at least two segments in pivotal interconnection so that adjustment of a length of the telescopic body causes a corresponding deflection of the deflectable linkage. Such implants find a range of applications, particularly where it is desired to insert an implant in a relatively low-profile state and subsequently expand the implant. Where a linkage with three segments is used, an intermediate segment is typically enlarged and provides a contact surface facing outwards such that adjustment of the implant can achieve tissue distraction. Where two segments are used, one of which is enlarged, the device can be used for adjusting an angular relationship between two facing regions of tissue. Such implants find particularly valuable applications in the field of spinal surgery, for example, for insertion into an intervertebral space to achieve axial distraction, lordotic correction and/or correction of scoliosis. 
     SUMMARY OF THE INVENTION 
     The present invention is an expandable implant with a deflectable sequence of segments. 
     According to the teachings of an embodiment of the present invention there is provided, an implant comprising: (a) a base; (b) a sequence of at least two segments including a first segment and a last segment, the first segment being pivotally linked to the base, adjacent segments of the sequence of segments being interconnected at pivotal connections; and (c) a bolt having a threaded shaft with a central axis and a head, the threaded shaft being engaged in a threaded channel of the base, wherein the last segment and the head define therebetween a spherical bearing such that rotation of the bolt about the central axis varies a degree of overlap between the base and the bolt, and causes deflection of the sequence of segments. 
     According to a further feature of an embodiment of the present invention, the sequence comprises only two segments. 
     According to a further feature of an embodiment of the present invention, a first of the two segments extends along a majority of a length of the sequence, and a second of the two segments extends along less than half of the length of the sequence. 
     According to a further feature of an embodiment of the present invention, the first segment and the second segment are interconnected at a pivot axis, and the pivot axis is located within a medial 50% of a length of the first segment. 
     According to a further feature of an embodiment of the present invention, the sequence includes three segments. 
     According to a further feature of an embodiment of the present invention, the three segments comprise a major intermediate segment and first and last linking segments. 
     According to a further feature of an embodiment of the present invention, there is also provided a gear-tooth engagement to preserve parallel orientation of the intermediate segment to the base. 
     There is also provided according to an embodiment of the present invention, an implant comprising: (a) a base; (b) a sequence of at least two segments including a first segment and a last segment, the first segment being pivotally linked to the base, and the sequence of segments being sequentially pivotally linked; (c) a core rotatably mounted within a transverse bore through the last segment, the core having a socket; and (d) a bolt having a threaded shaft and a head, the bolt being engaged in the socket of the core with the threaded shaft projecting therefrom, the threaded shaft being engaged in a threaded channel of the base, such that rotation of the bolt changes a degree of overlap between the base and the bolt, and causes deflection of the sequence of segments. 
     According to a further feature of an embodiment of the present invention, the sequence includes only two segments comprising one major segment and one linking segment. 
     According to a further feature of an embodiment of the present invention, the sequence includes three segments. 
     According to a further feature of an embodiment of the present invention, the three segments comprise a major intermediate segment and first and last linking segments. 
     According to a further feature of an embodiment of the present invention, there is also provided a gear-tooth engagement to preserve parallel orientation of the intermediate segment to the base. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: 
         FIG.  1 A ,  FIG.  1 B , and  FIG.  1 C  are isometric views of an implant, constructed and operative according to an aspect of the present invention, shown in a low profile state, a partially expanded state and a fully expanded state, respectively; 
         FIG.  2 A ,  FIG.  2 B , and  FIG.  2 C  are longitudinal cross-sectional views taken through the implant as shown in  FIGS.  1 A- 1 C , respectively; 
         FIG.  3 A  is an isometric view of a further implant, constructed and operative according to an aspect of the present invention, shown in a low profile state; 
         FIG.  3 B  and  FIG.  3 C  are longitudinal cross-sectional views taken through the implant of  FIG.  3 A , shown in a low profile state and a partially expanded state, respectively; 
         FIG.  4 A  is an isometric view of a further implant, constructed and operative according to an aspect of the present invention, shown in a low profile state; 
         FIG.  4 B  and  FIG.  4 C  are longitudinal cross-sectional views taken through the implant of  FIG.  4 A , shown in a low profile state and a partially expanded state, respectively; 
         FIG.  5 A  is an isometric view of a further implant, constructed and operative according to an aspect of the present invention, shown in a low profile state; 
         FIG.  5 B  and  FIG.  5 C  are side views of the implant of  FIG.  5 A , shown in a low profile state and a partially expanded state, respectively; 
         FIG.  5 D  is a longitudinal cross-sectional view taken through the implant of  FIG.  5 C  in its partially expanded state; 
         FIG.  6 A  is a side view of a further implant, constructed and operative according to an aspect of the present invention, shown in a low profile state; 
         FIG.  6 B  and  FIG.  6 C  are isometric views of the implant of  FIG.  6 A , shown in a low profile state and a fully expanded state, respectively; 
         FIG.  7 A  and  FIG.  7 B  are longitudinal cross-sectional views taken through the implant of  FIG.  6 B  and  FIG.  6 C , shown in a low profile state and a fully expanded state, respectively; 
         FIG.  8    is a table containing schematic illustrations of applications employing the implant of  FIGS.  1 A- 2 C  in a range of intervertebral applications with expansion in a vertical (axial) direction, the implant being shown in a low-profile insertion configuration and an expanded configuration, respectively; 
         FIG.  9    is a table containing schematic illustrations of applications employing the implant of  FIGS.  1 A- 2 C  in a range of intervertebral applications with expansion in a transverse (lateral) direction, the implant being shown in a low-profile insertion configuration and an expanded configuration, respectively; 
         FIG.  10    is a table containing schematic illustrations of applications employing the implant of  FIGS.  3 A- 3 C  in a range of intervertebral applications with angular expansion in a vertical (axial) direction, the implant being shown in a low-profile insertion configuration and an expanded configuration, respectively; and 
         FIG.  11    is a table containing schematic illustrations of applications employing the implant of  FIGS.  3 A- 3 C  in a range of intervertebral applications with angular expansion in a transverse (lateral) direction, the implant being shown in a low-profile insertion configuration and an expanded configuration, respectively. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is an expandable implant with a deflectable sequence of segments. The principles and operation of implants according to the present invention may be better understood with reference to the drawings and the accompanying description. 
     Referring now to the drawings, a first aspect of the present invention is referred to firstly in terms generic to the various embodiments of an implant  100 ,  200 ,  300  and  400  illustrated in  FIGS.  1 A- 5 D . Specifically, these figures each show an implant  100 ,  200 ,  300  or  400  having a base  10 , and a sequence of at least two segments including a first segment  12  and a last segment  14 . First segment  12  is pivotally linked to base  10 , for example, via a hinge pin  16  or other pivotal interconnection. Adjacent segments of the sequence of segments are interconnected at pivotal connections  18 . A bolt  20  has a threaded shaft  22  and a head  24 . Threaded shaft  22  is engaged in a threaded channel  26  of base  10  so that rotation of bolt  20  about a central axis of threaded shaft  22  varies a degree of overlap between base  10  and bolt  20 . Last segment  14  and head  24  define therebetween a spherical bearing  28 . Rotation of bolt  20  thus varies a distance between spherical bearing  28  and hinge pin  16 , thereby causing deflection of the sequence of segments. 
     The term “spherical bearing” is used herein to refer to a bearing in which the contact surfaces presented by last segment  14  for abutment of head  24  of bolt  20  correspond to partial spherical surfaces, thereby facilitating both a rotating motion of bolt  20  about its central axis and a pivotal motion of last segment  14  about a center of the “sphere” in all rotational positions of the bolt. Most preferably, the complementary surfaces of head  24  are also partial spherical surfaces in order to distribute loading over an extended contact region, rather than just along a line of contact. Most preferably, the partial-spherical bearing surfaces of last segment  14  correspond to two strips of a cylindrical surface on either side of a slot sized to allow the shaft of the bolt to extend therebetween. 
     The use of a bolt with spherical bearings provides a particularly elegant implementation of an expandable implant, typically reducing the number of components of the implant compared to a similar implant with a telescopic base and a separate adjustment mechanism and/or locking mechanism. 
     The term “segment” as used herein refers to a rigid structure which bridges between two pivotal connections, and may extend beyond those connections. Each segment may be a single central structure, or may be a forked structure which extends on either side of another segment. In some cases, the function of a single “segment” is provided by a pair of parallel arms which are not directly interconnected. Any such structures which bridge between the same two pivot axes and move together are referred to herein as a single segment. 
     The various pivotal connections, including pivotal connection  16  between base  10  and first segment  12  and pivotal connections  18  between adjacent segments, may be implemented in any desired manner, whether by use of a separate hinge pin which engages apertures in both elements, or by formation of an integral pin or other engagement features in one of the elements which engages an aperture in the other. A single pin may traverse the center of the implant, or the engagement may be bilateral, with separate pins on each side of the implant. 
     Depending upon the intended application and deployment location, the implants of the present invention are typically formed with various openings, for example, to allow filling with material for promoting bone growth and/or for ingrowth of bone or other tissue such as for osteo-integration. The locations, orientations and size of the various openings or windows will be readily chosen by a person having ordinary skill in the art according to the details of the intended application. 
     Similarly, the implants typically include various features for facilitating manipulation of the implant by an implant holder device, as exemplified by projecting pins  40  illustrated in certain embodiments below. 
     Turning now to the specific exemplary embodiments of this aspect of the present invention,  FIGS.  1 A- 2 C  illustrate an implant  100  in which the sequence of segments includes three segments, one of which is a major intermediate segment  130  which is pivotally linked to first and last segments  12  and  14 , which are implemented as linking segments. In this context, a “major segment” refers to a segment which extends along a length of at least 50% of the total length of the implant in its collapsed state, and more typically, in excess of 70%, and most preferably in excess of 80%. The term “linking segment” is used to refer to segments which each extend no more than about 55% of the length of the implant in its collapsed state, and most preferably no more than about 50%. Additionally, the “major segment” typically extends in both directions at least about 10% of its length beyond the location of pivotal connections  18  whereas the “linking segments” typically extend less than 10% of their respective lengths beyond the locations of pivotal connections  18 . 
     This three-segment embodiment is typically configured to generate roughly parallel expansion in the sense that a lower surface of the base and an upper surface of the major segment are initially roughly parallel (subject to modification for conforming to anatomical feature with which they are to fit and/or bone purchasing features or the like) and undergo a roughly linear (parallel) expansion so that the angle between the outward facing surfaces does not significantly change as they move apart. As a result, this embodiment and variations thereof are highly suited to various tissue extraction and expansion applications, including but not limited to, intervertebral height restoration as part of a fusion procedure, or vertebral body height restoration as part of a kyoplasty procedure. It can also be used to advantage for in-plane expansion as an implant with a low-profile insertion state which is subsequently expandable. A subset of possible applications for vertical and in-plane expansion are illustrated schematically in the tables of  FIGS.  8  and  9   , for a range of different approach modalities and applications. 
     In certain cases, implant  100  may advantageously include additional features for helping to maintain a parallel orientation of the intermediate segment relative to the base. In the case illustrated here, first and last segments  12  and  14  are formed with a gear-tooth engagement configuration  132  to preserve parallel orientation of the intermediate segment to the base. Further details of this solution may be found in the description of the aforementioned International Publication No. WO 2016/063283 A1. 
     Turning now to  FIGS.  3 A- 3 C and  4 A- 4 C , these illustrate two further implants  200  and  300  that correspond to the generic description above, but in these cases implemented with a sequence of segments including only two segments, namely, first segment  12  and last segment  14 , that are directly pivotally attached at pivotal connection  18 . Preferably, a first of the two segments is a “major segment” extending along a majority of the length of the sequence, and a second of the two segments is a “linking segment”, preferably extending along less than half of the length of the sequence. Pivot axis  18  between the two segments is most preferably located within a medial 50% of a length of the major segment, i.e., at a location between 25% and 75% of the length of the segment from one of the ends. 
     In the case of implant  200 , last segment  14  is the major segment while first segment  12  is the linking segment. As a result, the functionality of implant  200  is to provide angular opening between the lower surface of the base and the upper surface of the major segment where the opening occurs primarily through a separation of the contact surfaces at the distal end of the device. This configuration would be particularly suitable, for example, for restoration of a lordotic angle between adjacent vertebral bodies where the implant is inserted from a posterior (e.g., PLIF or TLIF) approach to generate increased separation in an anterior region of the intervertebral space, or for correction of scoliosis where increased elevation is required at the side furthest from the insertion opening. 
     In the case of implant  300 , first segment  12  is the major segment while last segment  14  is the linking segment. In this non-limiting example, first segment  12  is formed from a forked portion of structure similar to last segment  14  rigidly integrated (welded or integrally formed) with an extended contact surface portion  12 ′. As a result, the functionality of implant  300  is to provide angular opening between the lower surface of the base and the upper surface of the major segment where the opening occurs primarily through a separation of the contact surfaces at the proximal end of the device. This configuration would be particularly suitable, for example, for restoration of a lordotic angle between adjacent vertebral bodies where the implant is inserted from an anterior approach to generate increased separation in an anterior region of the intervertebral space, or for correction of scoliosis where increased elevation is required at the side closest to the insertion opening. 
     These embodiments can also be used for in-plane expansion. A subset of possible applications for vertical and in-plane angular expansion are illustrated schematically in the tables of  FIGS.  10  and  11   , for a range of different approach modalities and applications. 
     Turning now to  FIGS.  5 A- 5 D , it should be noted that implementations of the present invention may be configured to employ bolt  20  to expand the implant when increasing overlap with base  10 , as illustrated above, or when decreasing overlap with base  10 . By way of example, implant  400  is conceptually and functionally similar to implant  200  in that it employs a two-segment sequence in which last segment  14  is a major segment and first segment  12  is a linking segment. In this case, pivot  16  is located closer to head  24  of bolt  20  than pivot  18 , and spherical bearing  28  is configured to oppose extensional forces of bolt head  24 , i.e., that push last segment  14  along the axial direction of the bolt away from base  10 . This together with an initial offset of pivot  18  above pivot  16  results in a pivotal opening motion of major segment  14  as bolt  20  is actuated by rotation about its central axis to recede from base  10 . 
     It should be noted that this alternative form of actuation, as the bolt withdraws from base  10 , may equally be implemented in any of the other configurations described herein, as will be clear to a person having ordinary skill in the art. 
     Turning now to  FIGS.  6 A- 7 B , in the embodiments of the invention presented thus far, the combined motions of rotation of bolt  20  and pivoting of last segment  14  relative to the head of the bolt are accommodated by use of a spherical bearing. These drawings illustrate an implant  500  with an alternative configuration for accommodating such motion. 
     Specifically,  FIGS.  6 A- 7 B  illustrate schematically an implant  500  that is generally similar to implant  200  described above, with equivalent components labeled similarly. Thus implant  500  has a base  10 , a sequence of at least two segments including a first segment  12  and a last segment  14 , where first segment  12  is pivotally linked to base  10  at pivot axis  16 , and the sequence of segments are pivotally linked at  18 . In this case, the sequence employs only two independent segments, providing angular adjustment functionality similar to that of implant  200 , although forms such as implants  100 ,  300  and  400  can also be implemented according to the principles of this embodiment. 
     Implant  500  differs from implant  200  primarily in the form of interconnection between bolt  20  and last segment  14 . In this case, pivotal motion of last segment  14  relative to bolt  20  is accommodated by a core  502  that is rotatably mounted within a transverse bore through last segment  14 . Core  502 , which is typically cylindrical, has a socket  504  for receiving the head of bolt  20 . Specifically, threaded shaft  22  of bolt  20  passes through an aperture formed in core  502  and head  24  is seated in socket  504  of core  502  so that threaded shaft  22  projects from the core and head  24  is rotatably within socket  504 . Threaded shaft  22  is engaged in a threaded channel  26  of base  10 . Bolt  20  is seated in core  502  so as to be rotatable about its central axis, while the entire core can rotate relative to last segment  14  to accommodate the required pivotal motion of last segment  14  relative to the head of the bolt. Thus, rotation of bolt  20  changes a degree of overlap between base  10  and bolt  20 , thereby causing deflection of the sequence of segments. 
     This alternative mechanism may be used to implement each of the variant embodiments and features described above, whether for parallel motion or angular opening at either the distal or proximal end, and for all of the various applications described herein. 
     The use of the various implants of the present invention will now be self-evident to a person having ordinary skill in the art on the basis of the implant structure and various applications described herein above. In general terms, after preparation of the deployment volume, the implant is inserted into the body in its collapsed, closed state using a suitable implant holder tool (not shown) until correctly positioned within the target volume. An adjustment tool, for example with a hex-key tip or other screwdriver configuration designed to complement the form of head  24  of bolt  20  is engaged with the head and used to turn the bolt until a desired degree of expansion is achieved. The adjustment tool is typically removed, and where applicable, a quantity of biocompatible filler material is introduced into the implant. The holder is then released and withdrawn, and any required subsequent stages of the procedure are performed. 
     To the extent that the appended claims have been drafted without multiple dependencies, this has been done only to accommodate formal requirements in jurisdictions which do not allow such multiple dependencies. It should be noted that all possible combinations of features which would be implied by rendering the claims multiply dependent are explicitly envisaged and should be considered part of the invention. 
     It will be appreciated that the above descriptions are intended only to serve as examples, and that many other embodiments are possible within the scope of the present invention as defined in the appended claims.