Abstract:
A multi-level polyaxial screw connection mechanism includes a bone fixation component and a head component directly connected to the bone fixation component. The head component includes a lower portion comprising at least one lower portion concave socket configured and an upper portion elevated compared with the lower portion. The upper portion comprises at least one upper portion concave socket configured and the lower portion(s) concave socket comprises a volume substantially equal to a volume of the upper portion(s) concave socket.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The embodiments herein generally relate to medical devices and assemblies, and more particularly to an orthopedic surgical implant assembly used in the field of surgical lumbar, thoracic, and cervical spine treatment. 
         [0003]    2. Description of the Related Art 
         [0004]    Surgical procedures treating spinal injuries are one of the most complex and challenging surgeries for both the patient and the surgeon. When there are various deformities, trauma, or fractures of the vertebra, surgeons may attempt to “fuse” them together by attaching screw-like devices into the pedicles of the spine and thereby connecting several vertebrae (typically two or more) using a semi-rigid rod. Due to the complexity of the human anatomy, however, the vertebra to be fused may not reside at the same elevation, or height, along a longitudinal axis within the human body. To reach multiple heights during the fusing procedure, most surgeons bend the rod or more rods (causing notches thereby reducing fatigue resistance) before placing them into two or more non-aligned pedicle screws in order to properly stabilize the pedicle screw assembly within the patient&#39;s body. 
         [0005]    Depending on the purpose of the spine surgery, indications, and patient size, surgeons may pre-operatively choose between different spinal systems with differing rod sizes sometimes causing delays in surgery while waiting for more adequate systems to be sterilized. Some surgeons prefer monoaxial screws for rigidity, while some sacrifice rigidity for surgical flexibility in screw placement. 
         [0006]    Additionally, conventional systems require several different components to be manipulated and assembled by the surgeon during a surgical procedure. Reducing the number of components in a screw assembly that are manipulated and assembled would simplify operating room logistics; the steps performed by the surgeon during the surgical procedure; and, ultimately, improve patient recovery time. 
       SUMMARY 
       [0007]    In view of the foregoing, an embodiment herein provides a multi-level bone fixation device comprising a bone fixation component; and a head component directly connected to the bone fixation component, wherein the head component comprises a lower portion comprising at least one lower portion concave socket configured therein; and an upper portion elevated compared with the lower portion, wherein the upper portion comprises at least one upper portion concave socket configured therein, wherein the at least one lower portion concave socket comprises a volume substantially equal to a volume of the at least one upper portion concave socket. 
         [0008]    Such an embodiment further provides that the bone fixation component may comprise any of a bone anchor and a bone screw. In addition, at least one lower portion concave socket may comprise two lower portion concave sockets configured at the same level. 
         [0009]    An assembly is also provided that comprises a first bone fixation device comprising a first bone fixation component; and a first head component directly connected to the first bone fixation component, wherein the first head component comprises a lower portion comprising a plurality of lower portion concave sockets configured therein; and an upper portion elevated compared with the lower portion, wherein the upper portion comprises at least one upper portion concave socket configured therein; at least one longitudinal member comprising at least one fastener channel bored therethrough and at least one outwardly protruding and expandable round bulbous body that connects to at least one of (i) the plurality of lower portion concave sockets and (ii) the at least one upper portion concave socket; and a second bone fixation device operatively connected to the at least one longitudinal member, wherein the second bone fixation device comprises a second bone fixation component; and a second head component directly connected to the second bone fixation component, wherein the second head component comprises at least one concave socket that receives a bulbous body. 
         [0010]    In such an assembly, the second head component of the second bone fixation device may also comprise a first level portion comprising a plurality of first level portion concave sockets configured therein; and a second level portion comprising an elevated surface compared with the first level portion, wherein the second level portion comprises at least one second level portion concave socket configured therein. In addition, the second head component of the second bone fixation device may comprise exactly one concave socket. Furthermore, such an assembly may further comprise at least one pin, wherein each pin engages within one fastener channel and contacts one bulbous body causing the one bulbous body to outwardly expand. Additionally, any of the first bone fixation device and the second bone fixation device in such an assembly may comprise any of a bone anchor and a bone screw. At least one lower portion concave socket of such an assembly may comprise two lower portion concave sockets configured at the same level. Moreover, at least one longitudinal member of such an assembly may comprise a multi-component member. Furthermore, at least one longitudinal member of such an assembly may comprise a telescoping member. 
         [0011]    An apparatus is also provide that comprises a pair of multi-level bone fixation devices each comprising a first bone fixation component; and a first head component directly connected to the first bone fixation component, wherein the first head component comprises a lower portion comprising a pair of lower portion concave sockets configured therein; and an upper portion elevated compared with the lower portion, wherein the upper portion comprises an upper portion concave socket configured therein; a pair of co-linear longitudinal members each comprising a first pair of fastener channels bored therethrough; and a first pair of outwardly protruding and expandable round bulbous bodies, wherein a first round bulbous body of each co-linear longitudinal member connects to one of the lower portion concave sockets; a pair of single-level bone fixation devices each comprising a second bone fixation component; and a second head component directly connected to the second bone fixation component, wherein the second head component comprises a concave socket configured therein; a transverse longitudinal member that is positioned transverse to the pair of co-linear longitudinal members, wherein the transverse longitudinal member comprises a second pair of fastener channels bored therethrough; and a second pair of outwardly protruding and expandable round bulbous bodies, wherein a first round bulbous body of the transverse longitudinal member connects to the upper portion concave socket; a plurality of pins engaging the first and second pair of fastener channels. 
         [0012]    In such an apparatus, each pin may engage a bulbous body causing the bulbous body to outwardly expand. Furthermore, any of the pair of multi-level bone fixation devices and the pair of single-level bone fixation devices in such an apparatus may comprise any of a bone anchor and a bone screw. Additionally, the pair of lower portion concave sockets may be configured at the same level in such an apparatus. The concave socket of each single-level bone fixation device of such an apparatus may be at the same level as the level of the pair of lower portion concave sockets. In addition, any of (i) the pair of co-linear longitudinal members and (ii) the transverse longitudinal member may comprise a multi-component member. Any of (i) the pair of co-linear longitudinal members and (ii) the transverse longitudinal member may also comprise a telescoping member. In such an apparatus, the first head component may be larger than the second head component. Moreover, all sockets may comprise identical volumes. 
         [0013]    These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which: 
           [0015]      FIG. 1  illustrates a perspective view of a multi-level screw connection assembly according to an embodiment described herein; 
           [0016]      FIG. 2  illustrates a perspective view of a multi-level fixation component according to an embodiment described herein; 
           [0017]      FIG. 3(A)  illustrates a perspective view of a longitudinal member according to a first embodiment described herein; 
           [0018]      FIG. 3(B)  illustrates a perspective view of a longitudinal member according to a second embodiment described herein; 
           [0019]      FIG. 3(C)  illustrates a perspective view of another longitudinal member according to a third embodiment described herein; 
           [0020]      FIG. 4  illustrates a cross-sectional view of a longitudinal member according to an embodiment described herein; 
           [0021]      FIG. 5  illustrates a bottom view of the bulbous end of a longitudinal member according to an embodiment described herein; 
           [0022]      FIG. 6(A)  illustrates a perspective view of a securing pin according to an embodiment described herein; 
           [0023]      FIG. 6(B)  illustrates a perspective view of a set screw according to an embodiment described herein; 
           [0024]      FIG. 6(C)  illustrates a top view of a set screw according to an embodiment described herein; and 
           [0025]      FIG. 7  illustrates a perspective view of two adjoining longitudinal members according to an embodiment described herein. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0026]    The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein. 
         [0027]    The embodiments herein provide an improved multi-level headless polyaxial screw device with fewer components than conventional systems. Referring now to the drawings and, more particularly to  FIGS. 1 through 7 , where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments. 
         [0028]      FIG. 1  illustrates an embodiment of a multi-level polyaxial screw connection assembly  1 . In one embodiment, multi-level connection system  1  includes multi-level fixation components  2   a ,  2   b , a plurality of securing pins  3 , single-level fixation components  5   a ,  5   b ,  7   a ,  7   b , longitudinal members  4 ,  6   a ,  6   b ,  8   a ,  8   b  and a plurality of securing channels  9 . As shown in  FIG. 1 , multi-level fixation components  2   a ,  2   b  are joined by longitudinal member  4 . Multi-level fixation component  2   a  is attached and secured to bone (not shown) at a first height (or level), while multi-level fixation component  2   b  is attached and secured to bone (not shown) at a second height (or level). Consequently, multi-level fixation components  2   a ,  2   b  are secured to bone at different heights, with respect to one another, to accommodate variation in human anatomy. Additionally, multi-level fixation component  2   a  is adjacent to fixation components  5   a ,  5   b  and connected thereto by longitudinal members  6   a ,  6   b , respectively, via securing pins  3  mounted into securing channels  9  (described in further detail below). Multi-level fixation component  2   b  is adjacent to fixation components  7   a ,  7   b  and connected thereto by longitudinal members  8   a ,  8   b  via securing pins  3  mounted into securing channels  9  (described in further detail below). In the configuration shown in  FIG. 1 , fixation components  5   a ,  5   b  are secured to bone (not shown) at the same height as multi-level fixation component  2   a  and fixation components  7   a ,  7   b  are secured to bone (not shown) at the same height at multi-level fixation component  2   b . The configuration of the different components shown in  FIG. 1 , however, is one of many possible embodiments of the herein. Based on what is shown in  FIG. 1  and discussed below, those skilled in the art could readily implement alternative configurations without undue experimentation and the embodiments herein are not limited to the configuration shown in  FIG. 1 . 
         [0029]      FIG. 2 , with reference to  FIG. 1 , is a perspective view of a multi-level fixation component  2   a ,  2   b . In the embodiment shown, multi-level fixation component  2   a ,  2   b  includes upper portion  11 , first socket  12 , second socket  13 , lateral socket  14 , lower portion  15 , threads  16 , and tip  17 .  FIG. 2  shows upper portion  11  of multi-level fixation component  2   a ,  2   b  having three female spherical sockets: first socket  12 , second socket  13 , and lateral socket  14 . Each socket  12 ,  13 ,  14  is configured to allow a longitudinal member  4 ,  6   a ,  6   b ,  8   a ,  8   b  to pivot freely but not to disassemble once a bulbous body (described below) is inserted and engaged within the respective socket  12 ,  13 ,  14 . In one embodiment of multi-level fixation component  2   a ,  2   b , the maximum angulation for each socket is 25 degrees/side, but the medial correction/travel of a longitudinal member (not shown) is 3.2 mm/side, which is nearly 50% more than what most conventional screws offer. 
         [0030]    Situated below upper portion  11 , lower portion  15  includes threads  16  to engage different biological matter. While lower portion  15  is illustrated as a bone screw, those skilled in the art would understand that other types of fixation components could be utilized (such as a bone anchor) in accordance with the embodiments herein. The threads  16  of multi-level fixation component  2   a ,  2   b  may be a multiple lead thread to allow faster insertion into a bone. Threads  16  may also be tapered on the minor diameter while cylindrical on the major diameter to allow a new “bite” with every turn and to accommodate more thread depth towards the bottom of multi-level fixation component  2   a ,  2   b  for the cancellous bone. For example, threads  16  may be double lead, which provides greater surface contact with the bone, but drives at 4 mm/revolution. Lower portion  15  also includes a tapered tip  17  to assist engagement of multi-level fixation component  2   a ,  2   b  into different biological matter. 
         [0031]    Additionally, as indicated in  FIG. 1 , each single-level fixation component  5   a ,  5   b ,  7   a ,  7   b  also includes an upper portion  41  and a lower portion  42 . However, unlike multi-level fixation component  2   a ,  2   b , the single-level fixation components comprise only a single socket  43  in the upper portion  41  thereof. The features described above for lower portion  15  of multi-level fixation component  2   a ,  2   b , however, are similar for the lower portion of the single-level fixation components  5   a ,  5   b ,  7   a ,  7   b.    
         [0032]      FIG. 3(A) , with reference to  FIGS. 1 and 2 , provides a front perspective view of an embodiment of longitudinal members  4 ,  8   a ,  8   b .  FIG. 3(B) , with reference to  FIGS. 1 and 2 , provides a front perspective view of an embodiment of longitudinal members  6   a ,  6   b . Longitudinal members  4 ,  6   a ,  6   b ,  8   a ,  8   b  each include a first body  22  and a bulbous body  26  directly connected to the first body  22 . Bored into first body  22  is securing channel  32 , shown with threading etched into its inner perimeter. Furthermore, bulbous body  26  includes a plurality of slotted flanges  34  that allow bulbous body  26  to expand when engaged within a female socket  12 ,  13 ,  14 ,  43  of either a single-level fixation component  5   a ,  5   b ,  7   a ,  7   b  or a multi-level fixation component  2   a ,  2   b , respectively, at any allowable angle once securing pin  3  (shown in  FIG. 6(A) ) is urged through the securing channel  32  and causing the bulbous body  26  to expand. Since the bulbous body  26  is pivoting inside a female socket  12 ,  13 ,  14 ,  43 , connection assembly  1  is allowed to be inserted deeper into the bone without having the bone or anatomy prematurely limit the range of angulations of longitudinal member  20 . 
         [0033]      FIG. 3(C) , with reference to  FIGS. 1 and 2 , provides a front perspective view of another embodiment of a longitudinal member  20 , which may be used to connect to the fixation components  2   a ,  2   b ,  5   a ,  5   b ,  7   a ,  7   b . In  FIG. 3(C) , longitudinal member  20  includes a first body  22   a , an elongated body  24 , and a bulbous body  26  that is directly connected to the first body  22   a . Bored in first body  22   a  are a plurality of channels including elongation channel  28 , optional setting channel  30 , and securing channel  32 . As shown, elongation channel  28  has a smooth bore while both setting channel  30  and securing channel  32  each have threads etched into an inner perimeter therein. Additionally, bulbous body  26  includes a plurality of slotted flanges  34  that allow bulbous body  26  to expand when engaged within a female socket  12 ,  13 ,  14 ,  43  of either a single-level fixation component  5   a ,  5   b ,  7   a ,  7   b  or a multi-level fixation component  2   a ,  2   b , respectively, at any allowable angle once securing pin  3  (shown in  FIG. 6(A) ) is urged through the securing channel  32  and causing the bulbous body  26  to expand. Since longitudinal member  20  is pivoting inside a female socket  12 ,  13 ,  14 ,  43 , connection assembly  1  is allowed to be inserted deeper into the bone without having the bone or anatomy prematurely limit the range of angulations of longitudinal member  20 . 
         [0034]    Elongation channel  28  is preferably configured as a substantially horizontal bore (i.e., with respect to the longitudinal axis of the first body  22   a  and elongated body  24 ) through the first body  22   a  and terminates at the securing channel  32 . Setting channel  30  is a substantially vertical bore (i.e., with respect to the longitudinal axis of the first body  22   a  and elongated body  24 ) through the first body  22   a  and terminates at elongation channel  28 . Furthermore, securing channel  32  is also a substantially vertical bore (i.e., with respect to the longitudinal axis of the first body  22   a  and elongated body  24 ), and is configured through first body  22   a  and bulbous body  26 . 
         [0035]    Longitudinal member  20  also has threads  35  etched into first body  22   a , configured to mate with threads embedded in securing pin  3  (as described below). Setting channel  30  is similarly configured with threads etched into first body  22  and are configured to mate with threads embedded on a set screw  53  (shown in  FIG. 6(B) ). Longitudinal member  20  may connect with another similarly configured longitudinal member  20  such that the elongated body  24  of the second longitudinal member is seated within elongation channel  28  of the first longitudinal member with a set screw  53  being inserted in setting channel  30  to lock the two longitudinal members together once the proper alignment is selected by the surgeon. 
         [0036]      FIG. 4 , with reference to  FIGS. 1 through 3(C) , illustrates a cross-sectional view of longitudinal members  4 ,  8   a ,  8   b . Longitudinal members  6   a ,  6   b , while not shown in  FIG. 4 , have a similar cross-section.  FIG. 4  shows securing channel  32  is bored through both first body  22  and bulbous body  26 . In addition,  FIG. 4  shows securing channel  32  is etched with threads  35 . While not shown, threads  35  are configured to mate with securing pin  3  (shown in  FIG. 6(A) ). 
         [0037]      FIG. 5 , with reference to  FIGS. 1 through 4 , illustrates the bottom view of any of the longitudinal members  4 ,  6   a ,  6   b ,  8   a ,  8   b ,  20 , and is shown to include bulbous body  26  directly connected to first body  22 ,  22   a . As shown in  FIG. 5 , longitudinal members  4 ,  6   a ,  6   b ,  8   a ,  8   b ,  20  include the expandable bulbous (or generally spherical) male body  26  for engaging a concave female socket  12 ,  13 ,  14 ,  43  of either a single-level fixation component  5   a ,  5   b ,  7   a ,  7   b  or a multi-level fixation component  2   a ,  2   b , respectively. A plurality of axially spaced slots  36  are cut into bulbous body  26  forming a plurality of flanges  34 , which expand once securing pin  3  (shown in  FIG. 6(A) ) is forced through securing channel  32  of first body  22 ,  22   a  and cause the flanges  34  to outwardly project and expand. As a consequence, bulbous body  26  expands into the female socket  12 ,  13 ,  14 ,  43  of either a single-level fixation component  5   a ,  5   b ,  7   a ,  7   b  or a multi-level fixation component  2   a ,  2   b , respectively, at any allowable angle and thereby securing longitudinal members  4 ,  6   a ,  6   b ,  8   a ,  8   b ,  20  to either a single-level fixation component  5   a ,  5   b ,  7   a ,  7   b  or a multi-level fixation component  2   a ,  2   b.    
         [0038]      FIG. 6(A) , with reference to  FIGS. 1 through 5 , illustrates a perspective view of securing pin  3 . As shown, securing pin  3  includes an upper fastening portion  45  and a lower tip portion  50 . Upper fastening portion  45  further includes fastening socket  46 , pin head  47 , threads  48 , and connecting ring  49 . As shown, fastening socket  46  is a hexagonal shape. Those skilled in the art would recognize that other configurations are possible—for example, fastening socket  46  may be square or any other polygonal shape or may be a linear slit or cross-slit in pin head  47 . Threading  48  is embedded around an outer perimeter of upper fastening portion  45  and is configured to engage threads  35  etched into the inner perimeter of securing channel  32  of the longitudinal members  4 ,  6   a ,  6   b ,  8   a ,  8   b ,  20 . Connecting ring  49  is coupled to both the upper fastening portion  45  and lower tip portion  50 . When upper fastening portion  45  and lower tip portion  50  are composed of different materials (as described in further detail below), connecting ring  49  provides additional strength in the coupling thereof. 
         [0039]    Securing pin  3  may also comprise a multi-part assembly. For example, the upper fastening portion  45  of securing pin  3  may comprise titanium and the lower tip portion  50  of the securing pin  3  may comprise a ceramic material. Additionally, the lower tip portion  50  may comprise a mechanically harder material than the upper fastening portion  45 . In such a configuration, longitudinal members  4 ,  6   a ,  6   b ,  8   a ,  8   b ,  20  and either a single-level fixation component  5   a ,  5   b ,  7   a ,  7   b  or a multi-level fixation component  2   a ,  2   b  may optionally comprise a first material, and the lower tip portion  50  of the pin  3  may comprise a material having a higher material hardness and compressive yield strength than the first material. Moreover, connection assembly  1  may further comprise a wear resistant ceramic coating (not shown) over longitudinal members  4 ,  6   a ,  6   b ,  8   a ,  8   b ,  20  and either a single-level fixation component  5   a ,  5   b ,  7   a ,  7   b  or a multi-level fixation component  2   a ,  2   b.    
         [0040]    Connection assembly  1  can also be used as a dynamic rod system to complement artificial discs. According to this aspect of the embodiments herein, the outside of the bulbous body  26  and an inner spherical surface of female sockets  12 ,  13 ,  14 ,  43  are coated with a wear resistant ceramic coating. In this scenario, the securing pin  3  is not digging into the socket and in fact is configured at a shorter length than some of the other embodiments. This allows some motion instead of rigid fixation and shares the load with the artificial disc disallowing excessive forces being applied to the artificial disc and increasing its functional life. For example, this occurs as a result of the ceramic coating, which may be used in the embodiments herein. As such, the bulbous body  26  of longitudinal members  4 ,  6   a ,  6   b ,  8   a ,  8   b ,  20  and the female sockets  12 ,  13 ,  14 ,  43  has a lower friction and higher wear resistance characteristics, thus improving the overall movement characteristics of connection assembly  1 . 
         [0041]      FIG. 6(B) , with reference to  FIGS. 1 through 6(A) , illustrates a set screw  53  used in accordance with the embodiments herein. The set screw  53  is dimensioned and configured to engage the setting channel  30  of the longitudinal member  20 . The set screw  53  is used to secure a corresponding elongated body  24  of another longitudinal member  20 , which connects inside elongated channel  28  to link two longitudinal members  20  together. Once the elongated body  24  of another longitudinal member  20  is positioned inside the elongation channel  28  and is in a desired position, the set screw  53  is inserted into the setting channel  30  such that the set screw  53  engages the elongated body  24  of another longitudinal member  20  and fixes it into a static position. Accordingly, set screw  53  is embedded with thread  54 , which are configured to mate with threads etched in setting channel  30  (shown in  FIG. 3(C) ). In addition, set screw  53  also includes socket  54   a  to assist in engaging the set screw  53  with the setting channel  30 . As shown, socket  54   a  is a hexagonal shape. Those skilled in the art would recognize that other configurations are possible—for example, socket  54   a  may be square or any other polygonal shape or may be a linear slit or cross-slit across set screw  53 . 
         [0042]      FIG. 7 , with reference to  FIGS. 1 through 6(B)  illustrates a second embodiment of a longitudinal member system  55 . Longitudinal member system  55  includes two adjoining longitudinal members  60 ,  65  connected together. The elongation system includes male longitudinal member  60  and female longitudinal member  65 . As shown, male longitudinal member  60  includes securing channel  62  positioned through the member  60  and through connected bulbous body  63 , which then connects to either a single-level fixation component  5   a ,  5   b ,  7   a ,  7   b  or a multi-level fixation component  2   a ,  2   b  via a securing pin  3 . Female longitudinal member  65  includes an elongation channel  66  and securing channel  67  positioned through the member  65  and through connected bulbous body  68 , which then connects to either a single-level fixation component  5   a ,  5   b ,  7   a ,  7   b  or a multi-level fixation component  2   a ,  2   b  via a securing pin  3 . Also shown in  FIG. 7  is elongated member  64  of male longitudinal member  60  engaged with the elongation channel  66  of female longitudinal member  65 . While not shown in  FIG. 7 , a corresponding setting channel and set screw may be incorporated with member  65  in a manner consistent with the embodiments shown in  FIGS. 1 through 6(C) . 
         [0043]    The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.