Abstract:
A spinal fusion system has at least one spinal rod including a longitudinal member having at least one hollow extending therethrough, and at least one rod fenestration that extends through the longitudinal member. There are at least two bone screws for attachment to a spine. Each bone screw includes a threaded shaft for location within the spine, and a head attached to the threaded shaft. The head is able to be used for attachment to a rod, and the head includes at least one fenestration. At least one spinal rod is attached to the respective heads of the bone screws.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a rod and method of insertion. In particular, the invention relates to a rod used for spinal fusion and therefore will be described in this context. However, it should be appreciated that the rod may be used for other surgical procedures, such as any fixation of two bone segments. 
       BACKGROUND OF THE INVENTION 
       [0002]    Posterior spinal fusion has been well understood over the decades and remains a common surgical procedure that is required to treat spinal pathologies, such as degenerative pathologies, deformity, tumours and traumatic fractures. The combination of metallic bone screws and associated rods has also been well described and adds to the biomechanical stability of the spinal level or levels being fused. Further, the use of metallic bone screws and associated rods adds to an increase in fusion rates. However, the addition of bone graft to the posterior spinal bone surfaces to achieve successful biological spinal fusion remains one of the key components to the surgical technique of posterior spinal fusion. 
         [0003]    Advances in minimally invasive surgical (MIS) techniques has improved patient morbidity outcomes, yet offers new challenges to surgeons to expose and to deliver bone graft to posterior bone surfaces of the spinal column, especially the transverse processes. Traditionally, bone graft of various types is added to the space between the transverse processes between two vertebrae that are being fused. This postero-lateral gutter space between the transverse processes can be difficult to reach and requires a degree of muscle stripping to expose this space. Percutaneous bone screw placement has also been popularised, yet offers a new challenge for the adequate exposure of the postero-lateral gutter for the application and delivery of bone graft materials. 
         [0004]    It is an object of the invention to overcome and/or alleviate one or more of the above disadvantages or provide the consumer with a useful or commercial choice. 
       SUMMARY OF THE INVENTION 
       [0005]    In one form, although not necessarily the only or broadest form, the invention resides in a spinal rod able to be used with any bone fixation device, the spinal rod comprising: 
         [0006]    a longitudinal member having at least one hollow extending therethrough. 
         [0007]    The longitudinal member is typically cylindrical in shape. The diameter of the longitudinal member may be the same or similar to the dimension of spinal rods currently on the market. However, it is envisaged that the longitudinal member may be of any suitable diameter and/or length. 
         [0008]    The longitudinal member may be made from a combination of segments. Each segment may be solid, hollow, or a combination thereof. 
         [0009]    The hollow may extend completely or partially through the longitudinal member. 
         [0010]    Preferably, the spinal rod comprises at least one fenestration. Normally there are a plurality of rod fenestrations that extend through the longitudinal member. 
         [0011]    Preferably, the longitudinal member is made from a material or materials that allow bone growth on the surface of the longitudinal member. More preferably, the longitudinal member will allow bone growth through the rod fenestrations and within the hollow of the longitudinal member. The material used may be titanium alloy, CrCo, 316L stainless steel, PEEK™, Nitinol, ceramic and any other polymer, metal or any material. The longitudinal member may be treated with a roughening process, such as blasting or hydroxyl-apatite coating, as to assist in permitting bone on-growth. 
         [0012]    The longitudinal member may be straight, pre-bent to a set arc or able to be bent at the time of the surgery. 
         [0013]    The longitudinal member may have an internal design structure that adds strength in a certain direction or plane. For example, the longitudinal member may include a ridged beam or strengthening ribs. 
         [0014]    It is preferable that the hollow of the longitudinal member is sized to permit the easy passage of bone graft material along the length of the longitudinal member. The internal diameter dimensions of the hollow may permit programmed bone graft flow. That is, the internal dimensions of the hollow member may or may not be uniform. It will be designed so as to optimise flow dynamics for the graft material. The hollow may permit passage of graft material to adjacent bony structures to encourage posterior spinal bone grafting between two spinal levels. 
         [0015]    The hollow of the longitudinal member may be pre-packed with graft material. 
         [0016]    The end of the hollow may be capped to act as a graft restrictor. Alternatively, the hollow may be open at both ends, closed at both ends or a combination thereof. 
         [0017]    The rod fenestrations may be of any suitable size and/or shape. The rod fenestrations typically are in fluid communication with the hollow. The rod fenestrations can be arranged posteriorly, anteriorly, medially and/or laterally 
         [0018]    The rod fenestrations may be preferentially placed to direct graft material into the posterior spinal lateral gutter and/or medially placed facet joint area or any area above/below or either side of the longitudinal member. 
         [0019]    The hollow and/or rod fenestrations could include a design feature or be made of a material that permits a particular flow of graft and/or fluid in a certain direction and/or speed. That is, the hollow and/or rod fenestrations may include channels, ridges, barriers or similar. A delivery port may be located on the longitudinal member. 
         [0020]    The delivery port may double as a rod fenestration. The delivery port may be located on any portion of the longitudinal member. Preferably, the delivery port is located at one end of the longitudinal member. 
         [0021]    A delivery tool for inserting graft material may be connected to the delivery port. The delivery tool may be hand driven, hydraulic, motorized or pneumatic. 
         [0022]    The hollow and fenestrated rods could include a design feature or be made of a material that permits a dynamic or a movable feature. A motion couple to a solid rod section could be included. A helical shape to a segment of the rod or a material choice, such as a memory metal alloy, could be included to permit some motion to permit a dynamic fusion or stabilization construct. 
         [0023]    In another form, the invention resides in a bone screw comprising: 
         [0024]    a threaded shaft for location to a spine; 
         [0025]    a screw head attached to the threaded shaft, the head able to be used for attachment to a rod; 
         [0000]    wherein the screw head includes at least one fenestration. 
         [0026]    The shape and size could be variable to regulate rate and direction of flow. 
         [0027]    The screw head fenestration could be on one side only or both sides of the screw head. The screw head could be treated to permit on-growth of bone. For example, the screw head could be acid treated to permit on-growth, roughened or could be hydroxy-apatite coated. 
         [0028]    The screw head may be made of titanium alloy, 316L stainless steel, chrome cobalt, Nitinol or any other suitable material. 
         [0029]    The screw head could be fixed or mobile to the shaft. 
         [0030]    In another form, the invention resides in a spinal fusion system comprising: 
         [0031]    at least one spinal rod comprising a longitudinal member having at least one hollow extending through the longitudinal member; and a plurality of rod fenestrations that extend through the longitudinal member; and 
         [0032]    at least two bone screws for attachment to a spine, each bone screw comprising a threaded shaft for location within the spine, a head attached to the threaded shaft, the head able to be used for attachment to a rod, the head including at least one fenestration; 
         [0033]    wherein at least one spinal rod is attached to the respective heads to the bone screws. 
         [0034]    Preferably, the rod fenestrations are aligned with screw head fenestrations to allow graft material to pass from the longitudinal member and through the screw head. 
         [0035]    In another form, the invention resides in a method of surgery including the steps of: 
         [0036]    attaching a spinal rod to at least one bone screw, the spinal rod comprising a longitudinal member having at least one hollow extending through the longitudinal member; and a plurality of rod fenestrations that extend through the longitudinal member; and 
         [0037]    injecting bone graft into the hollow of the longitudinal member. 
         [0038]    The method may further include one or more of the follow steps including: 
         [0039]    setting the bone screw in a spine, each bone screw comprising a threaded shaft for location within the spine, a head attached to the threaded shaft, the head able to be used for attachment to a rod, the head including at least one fenestration; wherein the shaft is rotated so that the fenestration in the head is in a desired location; 
         [0040]    rotating the rod with respect to the bone screw such that a rod fenestration is located adjacent a screw head fenestration. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0041]    Embodiments of the invention will be described with reference to the accompanying drawings in which: 
           [0042]      FIG. 1A  is an end view of a spinal rod according to a first embodiment of the invention; 
           [0043]      FIG. 1B  is a perspective view of a spinal rod according to  FIG. 1A ; 
           [0044]      FIG. 2A  is an end view of a spinal rod according to a second embodiment of the invention; 
           [0045]      FIG. 2B  is a perspective view of a spinal rod according to  FIG. 2A ; 
           [0046]      FIG. 3A  is a perspective view of a spinal rod according to a third embodiment of the invention; 
           [0047]      FIG. 3B  is a side sectional view of a spinal rod according to  FIG. 3A ; 
           [0048]      FIG. 4A  is a perspective view of a spinal rod according to a fourth embodiment of the invention; 
           [0049]      FIG. 4B  is a side sectional view of a spinal rod according to  FIG. 4A ; 
           [0050]      FIG. 5A  is a perspective view of a spinal rod according to a fifth embodiment of the invention; 
           [0051]      FIG. 5B  is a side sectional view of a spinal rod according to  FIG. 5A ; 
           [0052]      FIG. 6A  is a perspective view of a spinal rod according to a sixth embodiment of the invention; 
           [0053]      FIG. 6B  is a side sectional view of the spinal rod of  FIG. 6A  attached to two bone screws; 
           [0054]      FIG. 7A  is a perspective view of a spinal rod according to a seventh embodiment of the invention; 
           [0055]      FIG. 7B  is a side sectional view of the spinal rod of  FIG. 7A  attached to two bone screws; 
           [0056]      FIG. 8A  is a perspective view of a spinal rod according to a eighth embodiment of the invention; 
           [0057]      FIG. 8B  is a perspective view of the spinal rod of  FIG. 8A  attached to two bone screws with graft material located within the spinal rod; 
           [0058]      FIG. 9A  is a perspective view of a spinal rod according to a ninth embodiment of the invention; 
           [0059]      FIG. 9B  is a perspective view of the spinal rod of  FIG. 9A  attached to two bone screws with graft material located within the spinal rod; 
           [0060]      FIG. 10A  is a perspective view of a spinal rod according to a tenth embodiment of the invention; 
           [0061]      FIG. 10B  is a perspective view of the spinal rod of  FIG. 10A  attached to two bone screws with graft material located within the spinal rod; 
           [0062]      FIG. 11A  is a perspective view of a spinal rod according to a eleventh embodiment of the invention; 
           [0063]      FIG. 11B  is a perspective view of the spinal rod of  FIG. 11A  attached to two bone screws with graft material located within the spinal rod; 
           [0064]      FIG. 12  is a perspective view of a spinal rod attached to two bone screws with graft material being introduced through a pipe; 
           [0065]      FIG. 13  is a perspective view of a spinal rod attached to two bone screws with graft material being introduced through a locking cap; 
           [0066]      FIG. 14  is a perspective view of a spinal rod attached to two bone screws with graft material being introduced through a pipe; 
           [0067]      FIG. 15A  is a perspective view of a delivery tool according to an embodiment of the invention; 
           [0068]      FIG. 15B  is a perspective view of the delivery tool of  FIG. 15A  in use in the delivery graft material in the hollow of a spinal rod; 
           [0069]      FIG. 16A  is a perspective view of a further delivery tool adjacent an associated spinal rod according to an embodiment of the invention; and 
           [0070]      FIG. 16B  is a perspective view of the delivery tool of  FIG. 16A  in use in the delivery graft material in the hollow of a spinal rod shown in  FIG. 16A . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0071]      FIGS. 1A and 1B  shows a perspective view of a spinal rod  10  for use in spinal surgery, especially with respect to spinal fusion. The spinal rod  10  is formed from a longitudinal member  11  made of titanium. However, it should be appreciated that other materials may be used. Two hollows  12  extend through the length of the longitudinal member  11 . The two hollows  12  are semi-circular in transverse cross section. 
         [0072]    Four rod fenestrations  13  extend through the longitudinal member  11 . The rod fenestrations  13  are elliptical in shape. However, it should be appreciated that the shape and size of the rod fenestrations  13  may be varied according to design requirements. Two rod fenestrations  13  are located on one side of the longitudinal member  11  with the other two rod fenestrations  13  being located on the opposite side of the longitudinal member  11 . Two rod fenestrations  13  are fluidly connected to one of the two hollows  12  whilst the other two rod fenestrations  13  are fluidly connected to the other of the two hollows  12 . 
         [0073]      FIGS. 2A and 2B  show a second embodiment of a spinal rod  10 . In this embodiment, there are again two rod fenestrations  13 . However, each of these rod fenestrations  13  are fluidly connected to the two hollows  12 . 
         [0074]      FIGS. 3A and 3B  show a third embodiment of a spinal rod  10 . In this embodiment, the longitudinal member  11  has three individual compartments  14 . Each of these compartments  14  has a hollow  12 , a circular rod fenestration  13  and an elliptical rod fenestration  13 . One of the compartments  14  has an open end whilst the other compartments are enclosed. 
         [0075]      FIGS. 4A and 4B  show a fourth embodiment of a spinal rod  10 . In this embodiment, there are four circular rod fenestrations  13 . Flow restrictors  16  are located within the single hollow  12 . One end of the hollow  12  is also semi-circular in transverse cross-section to vary flow. 
         [0076]      FIGS. 5A and 5B  show a fifth embodiment of a spinal rod  10 . In this embodiment, there is a single hollow  12  and five rod fenestrations  13 . Four rod fenestrations  13  are located on one side of the longitudinal member  11  with the other rod fenestration  13  diametrically opposed. A flow control device  17 , in the form of a barb, is located adjacent each of the four rod fenestrations  13 . Each of the barbs face toward the fifth rod fenestration  13 . 
         [0077]      FIG. 6A  shows a sixth embodiment of a spinal rod  10 . The spinal rod  10  again has a hollow  12  extending through the longitudinal member  11  with four rod fenestrations  13  extending through the longitudinal member  11 . A helical channel  18  extends through the centre of the longitudinal member  11  to make for easier bending of the longitudinal member  11 . 
         [0078]      FIG. 6B  shows the spinal rod  10 , shown in  FIG. 6A , attached to two bone screws  20 . Each bone screw  20  includes a threaded shaft  21  and a screw head  22 . Two screw head fenestrations  23  are located on each screw head  22 . The spinal rod  10  is attached to the screw head  22  using locking caps  24  as is standard practice in the art. 
         [0079]      FIG. 7A  shows a seventh embodiment of a spinal rod  10 . In this embodiment, there are four rod fenestrations  13  that extend through the longitudinal member  11 . Again, a single hollow  12  also extends through the longitudinal member  11 . The longitudinal member  11  is narrower in some portions than other to simply bending of the longitudinal member  11 . 
         [0080]      FIG. 7B  shows the spinal rod  10  shown in  FIG. 7A  attached to two bone screws  20 . The bone screws  20  shown in  FIG. 7A  are the same as the bone screws  20  shown in  FIG. 6B . 
         [0081]    In use, bone screws  20  are located within spinal vertebrae using open or minimally invasive surgical techniques. A degree of stripping of the adjacent transverse processes is then conducted using a long handle elevator. 
         [0082]    A variety of different bone screws  20  that have or may not have screw head fenestrations  23  in lateral wall of screw head  22  may be used. Lateral screw head fenestration/s may be used if graft material flow is required down and laterally onto adjacent transverse process. Medial screw head fenestration/s can be used if there is a facet joint milled bony facet defect or a facet cage that requires filling. 
         [0083]    The facet joint may be milled medially, if required, and a facet cage inserted as necessary. Decompression of neural structures is also performed if necessary. A transforaminal lumbar interbody fusion (TLIF) and/or posterior lumbar interbody fusion (PLIF) is performed if required. 
         [0084]    A spinal rod  10  may be selected based on its appropriate length, number of rod fenestrations  13  and position of rod fenestrations  13 . The spinal rod  10  is then located between screw head(s)  22  on each side of the spine. The spinal rod  10  is rotated to a desired position in order to locate the rod fenestrations  13  in the most advantageous position. For example, a rod fenestration  13  may be positioned adjacent a screw head fenestration  23 . Locking caps  24  are then used to fasten the spinal rod  10  to the bone screw  20 .  FIGS. 8A to 11A  show different spinal rods  10  whilst  FIGS. 8B to 11B  show the different spinal rods  10  connected to bone screws  20  with graft material flowing from the spinal rods  20 . 
         [0085]    A delivery tool  30  (for MIS particularly), is fluidly coupled to the hollow. The delivery tool  30  may be directly attached to the hollow  12  using a pipe  31  (or hose or nozzle) as shown in  FIG. 12  or accessed through the locking cap  24  shown in  FIG. 13  or accessed through a rod fenestration  13  as shown in  FIG. 14 . The delivery tool  30  is used to deliver graft material into the hollow  12  and may be shaped to deliver graft material in different directions as shown in  FIGS. 15A and 15B . Alternately, a bone morphogenic protein sponge graft or autograft can be placed in the hollow  12  before insertion to the screw heads  22 . 
         [0086]    The delivery tool  30  is then used to inject bone graft material to each side (i.e. right and left). The position of graft material can then be determined with fluoroscopy (if graft material is radio-opaque). Additional graft material can be added as is required. The surgical technique is then completed by closing the wound of patient in the usual fashion. 
         [0087]    It should be appreciated that the delivery tool  30  can be modified, shown in  FIGS. 16A and 16B , to provide a more controlled release of graft material into an associated spinal rod  10 . In this embodiment, the delivery tool  30  includes an elongate pipe  31  which is non-cylindrical. Further, outlet holes  32  are located adjacent the end of the pipe  31  as opposed to at the end of the pipe  31 . The associated spinal rod  10  includes hollow  12  which is also non-cylindrical and substantially matches the transverse cross section of the pipe  31 . 
         [0088]    In use, the pipe  31  is inserted into the hollow  12  passed the last fenestration  13 . As the pipe  31  is withdrawn from the hollow, graft material is fed through the pipe  31  and through specific fenestrations  13 . Due to the matching transverse cross sectional shape of the pipe  31  and the hollow  12 , the outlet holes  32  of the pipe align with the fenestrations  13  as the pipe  31  is withdrawn from the hollow  12 . This arrangement enables a controlled release of graft material that would otherwise not be possible. 
         [0089]    Essentially, the surgical technique above surrounds an attempt to achieve a posterior spinal fusion anywhere from the occiput level (base of skull) to sacrum or pelvic level. The hollow spinal rod can be used at any level in the spine as listed above and that can be used in conjunction with a bone screw or lateral mass screw. 
         [0090]    The surgical technique uses a hollow spinal rod that has rod fenestrations to permit the passage of bone graft material (most likely injectable bone graft forms), into the spinal rod when in situ and thus allow flow of graft material onto adjacent bone surfaces such as the transverse processes, the lamina and the facet joints. Similarly, the screw head fenestrations in the screw head also allow the flow of graft material onto adjacent bone surfaces such as the transverse processes, the lamina and the facet joints. 
         [0091]    It should be appreciated that various other changes and modifications may be made to the embodiments described without departing from the spirit or scope of the invention.