Abstract:
A translaminar screw is formed from a polymer material (such as PEEK, PLLA, PCL, carbon fiber PEEK, and the like) so that the screw does not come loose, even after an extended period of mobilization. Spinal implants, instrumentation, and methods relating to stabilization and/or fusion of a facet joint via trans-facet and intra-facet delivery of the implants are disclosed herein. The implant or screw functions as a sort of flexible mechanical staple and/or key that prevents sliding motion between the diarthroidal surfaces of the facet joint. The spinal implant includes an elongated member extending from a distal tip to a proximal end having a head formed thereon. The elongated member can further include a threaded portion. The implant member can be, for example, a polymer translaminar screw that is formed from one of a PEEK, PLLA, PCL, carbon fiber PEEK, or similar polymer or other relatively flexible material.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Application No. PCT/IB2014/000379, filed Mar. 17, 2014, which claims priority from U.S. Provisional Application No. 61/787,179, filed Mar. 15, 2013. The disclosures of both applications are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates to the general field of orthopedic surgical implants. In particular, this invention relates to an osteosynthesis/translaminar screw that is formed from a polymer material (such as, for example, PEEK (polyether ether ketone), PLLA (poly-l-lactide acid), PCL (polycaprolactone), carbon fiber PEEK, and the like) and can be used in the field of surgical spine treatment and other applications. 
         [0003]    The vertebrae in a patient&#39;s spinal column are linked to one another by intervertebral discs and facet joints. This three joint complex controls the movement of the vertebrae relative to one another. Each vertebra has a first pair of articulating surfaces located on the left side and a second pair of articulating surfaces located on the right side, and each pair includes a superior articular surface and an inferior articular surface. Together, the superior and inferior articular surfaces of the adjacent vertebrae form facet or zygapophyseal joints. Facet joints are synovial joints, which means that each joint is surrounded by a capsule of connective tissue and produces a fluid to nourish and lubricate the joint. The joint surfaces are coated with cartilage, allowing the joints to move or articulate relative to one another. Diseased, degenerated, impaired, or otherwise painful facet joints and/or discs can require surgery to restore function to the three joint complex. In the lumbar spine, for example, one form of treatment to stabilize the spine and to relieve pain involves fusion of the facet joint. 
         [0004]    Pedicles connect the vertebral body to the posterior elements. Each vertebra has two pedicles. A basic pedicle screw structure includes a threaded shaft portion having one or more slots provided on a head portion. Pedicle screws are screwed into the spine through the respective pedicles, and a rod is used to lock the pedicle screws in place to minimize relative motion. These rods are locked into place with the pedicle screws using a fastening screw, such as a set screw. 
         [0005]    Translaminar screw fixation on the lumbar spine, in context of spinal fusion and operative treatment of injuries, has been used for almost twenty five years. The principle of translaminar screw fixation consists of the use of osteosynthesis screws to lock the facet or zygapophyseal joints to prevent any possible movement between two vertebrae, with resulting immobilization of the two vertebrae. The screw enters on one side of the spinous process of the bone, extends through the mutual lamina, traverses the zygapophyseal joints (facet joints), and ends up in the base of transverse process of the lower vertebrae. 
         [0006]    This method of spinal fusion with translaminar fixation has been known to fail because the implants have been made out of stainless steel and/or titanium alloy materials. Such metallic screws can become loose when more than six weeks of mobilization is stimulated. Thus, there is a need for an improved implant for use with translaminar fixation and other spinal and/or orthopedic procedures. 
       SUMMARY OF THE INVENTION 
       [0007]    In accordance with this invention, when the translaminar screw is formed from a polymer material (such as PEEK, PLLA, PCL, carbon fiber PEEK, and the like), the screw does not come loose, even after an extended period of mobilization. This could be attributed to the fact that PEEK and other polymer materials have elastic modulus properties that are similar to bone. Alternatively, it may be the result because PEEK and other polymer materials, due to their elasticity, can deform and again re-form to the position together with bone leading to flexible stabilization of the joint. 
         [0008]    Spinal implants, instrumentation, and methods relating to stabilization and/or fusion of a facet joint via trans-facet and intra-facet delivery of the implants are disclosed herein. In general, the implant or screw functions as a sort of flexible mechanical staple and/or key that prevents sliding motion between the diarthroidal surfaces of the facet joint. 
         [0009]    In the preferred embodiment, the spinal implant includes an elongated member extending from a distal tip to a proximal end having a head formed thereon. The elongated member can further include a threaded portion. The implant member can be, for example, a polymer translaminar screw that is formed from one of a PEEK, PLLA, PCL, carbon fiber PEEK, or similar polymer or other relatively flexible material. 
         [0010]    Various aspects of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a rear elevational view of a portion of a spine showing a conventional pedicle screw stabilization structure. 
           [0012]      FIG. 2  is a side elevational view of the spine and the conventional pedicle screw stabilization structure illustrated in  FIG. 1 . 
           [0013]      FIG. 3  is a rear elevational view of a portion of a spine showing a conventional translaminar screw fixation technique developed by Friedrich Magerl. 
           [0014]      FIG. 4  is a side elevational view of the spine and the conventional translaminar screw fixation illustrated in  FIG. 3 . 
           [0015]      FIG. 5  is a perspective view of a first embodiment of a translaminar screw in accordance with this invention. 
           [0016]      FIG. 6  is a side elevational view of the first embodiment of the translaminar screw illustrated in  FIG. 5 . 
           [0017]      FIG. 7  is a sectional elevational view of the first embodiment of the translaminar screw illustrated in  FIGS. 5 and 6 . 
           [0018]      FIG. 8  is a perspective view of a second embodiment of a translaminar screw in accordance with this invention. 
           [0019]      FIG. 9  is a side elevational view of the second embodiment of the translaminar screw illustrated in  FIG. 8 . 
           [0020]      FIG. 10  is a sectional elevational view of the second embodiment of the translaminar screw illustrated in  FIGS. 8 and 9 . 
           [0021]      FIG. 11  is a perspective view of a third embodiment of a translaminar screw in accordance with this invention. 
           [0022]      FIG. 12  is a side elevational view of the third embodiment of the translaminar screw illustrated in  FIG. 11 . 
           [0023]      FIG. 13  is a sectional elevational view of the third embodiment of the translaminar screw illustrated in  FIGS. 11 and 12 . 
           [0024]      FIG. 14  is a perspective view of a fourth embodiment of a translaminar screw in accordance with this invention. 
           [0025]      FIG. 15  is a side elevational view of the fourth embodiment of the translaminar screw illustrated in  FIG. 14 . 
           [0026]      FIG. 16  is a sectional elevational view of the fourth embodiment of the translaminar screw illustrated in  FIGS. 14 and 15 . 
           [0027]      FIG. 17  is a perspective view of a first embodiment of a working cannula in accordance with this invention. 
           [0028]      FIG. 18  is a sectional elevational view of the first embodiment of the working cannula illustrated in  FIG. 17 . 
           [0029]      FIG. 19  is a perspective view of a first embodiment of a trocar in accordance with this invention. 
           [0030]      FIG. 20  is a side elevational view of the first embodiment of the trocar illustrated in  FIG. 19 . 
           [0031]      FIG. 21  is a perspective view of an assembly of the working cannula illustrated in  FIGS. 17 and 18  and the trocar illustrated in  FIGS. 19 and 20 . 
           [0032]      FIG. 22  is a side elevational view of the assembly of the working cannula and trocar assembly illustrated in  FIG. 21 . 
           [0033]      FIG. 23  is a perspective view of an insertion trocar in accordance with this invention. 
           [0034]      FIG. 24  is a sectional elevational view of the insertion trocar illustrated in  FIG. 23 . 
           [0035]      FIG. 25  is an enlarged perspective view of an end of the insertion trocar illustrated in  FIGS. 23 and 24 . 
           [0036]      FIG. 26  is a perspective view of an assembly of the working cannula illustrated in  FIGS. 17 and 18  and the insertion trocar illustrated in  FIGS. 23 ,  24 , and  25 . 
           [0037]      FIG. 27  is a sectional elevational view of the trocar assembly illustrated in  FIG. 26 . 
           [0038]      FIG. 28  is a perspective view of an assembly of the trocar assembly illustrated in  FIGS. 26 and 27  including a Kirschner wire. 
           [0039]      FIG. 29  is an enlarged perspective view of an end of the trocar assembly and the Kirschner wire illustrated in  FIG. 28 . 
           [0040]      FIG. 30  is a perspective view of a translaminar screw driver assembly in accordance with this invention. 
           [0041]      FIG. 31  is a perspective view of a screw driver shaft for the translaminar screw driver assembly illustrated in  FIG. 30 . 
           [0042]      FIG. 32  is an enlarged perspective view of an end of the screw driver shaft illustrated in  FIG. 31 . 
           [0043]      FIG. 33  is a side elevational view of a drill bit in accordance with this invention. 
           [0044]      FIGS. 34 through 40  illustrate a method for performing a minimal invasive surgical technique for placement of a translaminar screw on a spine in accordance with this invention. 
           [0045]      FIG. 41  illustrates how translaminar screws in accordance with this invention can be used in the cervical spine to facilitate fusion of C1 and C2 vertebrae. 
           [0046]      FIGS. 42 and 43  illustrate how translaminar screws in accordance with this invention can be used for fixation of the odontoid peg fracture, which is a fracture of the C2 vertebra. 
           [0047]      FIGS. 44 and 45  illustrate how translaminar screws in accordance with this invention can be used for fixation of a sacroiliac joint. 
           [0048]      FIG. 46  shows an alignment sensor attached to a biopsy needle or a cannula that allows a surgeon to achieve the correct anatomical trajectory based on a pre-operative planning study. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0049]      FIGS. 1 and 2  illustrate a conventional pedicle screw stabilization structure that is formed from a stainless steel or titanium alloy material, along with a portion of a spine showing a pedicle screw stabilization structure.  FIGS. 3 and 4  illustrate a portion of a spine showing a conventional translaminar screw fixation technique developed by Fritz Magerl. 
         [0050]      FIGS. 5 ,  6 , and  7  illustrate a first embodiment of a cannulated translaminar screw, indicated generally at  10 , in accordance with this invention. In this first embodiment of the invention, the screw  10  includes a head portion  11 , a non-threaded portion  12 , and a threaded portion  13 . As best shown in  FIG. 5 , the head portion  11  of the screw  10  has an outer surface and an inner driving structure. In the illustrated embodiment, the outer surface of the head portion  11  is generally hexagonal in shape and the inner driving structure is generally star-shaped, although any other shapes may be provided. In the illustrated embodiment, the size of the head portion  11  of the screw  10  is somewhat larger than the size of the non-threaded portion  12 . Thus, the outer surface of the screw  10  is stepped from the head portion  11  to the non-threaded portion  12 . Also, in the illustrated embodiment, the diameter of the non-threaded portion  12  is somewhat larger than the diameter of the threaded portion  13 . Thus, the outer surface of the screw  10  is tapered from the non-threaded portion  12  to the threaded portion  13 . The thread provided on the threaded portion  13  of the screw  10  can having any desired shape or configuration including, for example, a single lead, a double lead, or a quad lead. A passageway  14  is formed through the screw  10  from the head portion  11  through the non-threaded portion  12  to the threaded portion  13  for a purpose that will be explained below. The entire screw  10  is formed from a polymer material such as, for example, PEEK, PLLA, PCL, carbon fiber PEEK, and the like, and can be used as a translaminar screw in the field of surgical spine treatment and for other applications. 
         [0051]      FIGS. 8 ,  9 , and  10  illustrate a second embodiment of a cannulated translaminar screw, indicated generally at  20 , in accordance with this invention. In this second embodiment of the invention, the screw  20  includes a head portion  21 , a non-threaded portion  22 , and a threaded portion  23 . As best shown in  FIG. 8 , the head portion  21  of the screw  20  has an outer surface and an inner driving structure. In the illustrated embodiment, the outer surface of the head portion  21  is generally hexagonal in shape and the inner driving structure is generally star-shaped, although any other shapes may be provided. In the illustrated embodiment, the size of the head portion  21  of the screw  20  is approximately the same size as the size of the non-threaded portion  22 . Thus, the outer surface of the screw  20  is essentially flush with the head portion  21  to the non-threaded portion  22 . Also, in the illustrated embodiment, the diameter of the non-threaded portion  22  is somewhat larger than the diameter of the threaded portion  23 . Thus, the outer surface of the screw  20  is tapered from the non-threaded portion  22  to the threaded portion  23 . The thread provided on the threaded portion  23  of the screw  20  can having any desired shape or configuration including, for example, a single lead, a double lead, or a quad lead. A passageway  24  is formed through the screw  20  from the head portion  21  through the non-threaded portion  22  to the threaded portion  23  for a purpose that will be explained below. The entire screw  20  is formed from a polymer material such as, for example, PEEK, PLLA, PCL, carbon fiber PEEK, and the like, and can be used as a translaminar screw in the field of surgical spine treatment and for other applications. 
         [0052]      FIGS. 11 ,  12 , and  13  illustrate a third embodiment of a cannulated translaminar screw, indicated generally at  30 , in accordance with this invention. In this third embodiment of the invention, the screw  30  includes a head portion  31  and a threaded portion  33 . As best shown in  FIG. 11 , the head portion  31  of the screw  30  has an outer surface and an inner driving structure. In the illustrated embodiment, the outer surface of the head portion  31  is generally hexagonal in shape and the inner driving structure is generally star-shaped, although any other shapes may be provided. In the illustrated embodiment, the size of the head portion  31  of the screw  30  is approximately the same size as the size of the non-threaded portion  32 . Thus, the outer surface of the screw  30  is essentially flush with the head portion  31  to the non-threaded portion  32 . Also, in the illustrated embodiment, the thread provided on the threaded portion  33  of the screw  30  can having any desired shape or configuration including, for example, a single lead, a double lead, or a quad lead. A passageway  34  is formed through the screw  20  from the head portion  31  to the threaded portion  33  for a purpose that will be explained below. The entire screw  30  is formed from a polymer material such as, for example, PEEK, PLLA, PCL, carbon fiber PEEK, and the like, and can be used as a translaminar screw in the field of surgical spine treatment and for other applications. 
         [0053]      FIGS. 14 ,  15 , and  16  illustrate a fourth embodiment of a cannulated translaminar screw, indicated generally at  40 , in accordance with this invention. In this fourth embodiment of the invention, the screw  40  includes a head portion  41 , a non-threaded portion  42 , and a threaded portion  43 . As best shown in  FIG. 14 , the head portion  41  of the screw  40  has an outer surface and an inner driving structure. In the illustrated embodiment, the outer surface of the head portion  41  is generally hexagonal in shape and the inner driving structure is generally star-shaped, although any other shapes may be provided. In the illustrated embodiment, the size of the head portion  41  of the screw  40  is approximately the same size as the size of the non-threaded portion  42 . Thus, the outer surface of the screw  40  is essentially flush with the head portion  41  to the non-threaded portion  42 . Also, in the illustrated embodiment, the non-threaded portion  42  is provided within an intermediate region of the threaded portion  43 . The thread provided on the threaded portion  43  of the screw  40  can having any desired shape or configuration including, for example, a single lead, a double lead, or a quad lead. A passageway  44  is formed through the screw  40  from the head portion  41  through the non-threaded portion  42  to the threaded portion  43  for a purpose that will be explained below. The entire screw  40  is formed from a polymer material such as, for example, PEEK, PLLA, PCL, carbon fiber PEEK, and the like, and can be used as a translaminar screw in the field of surgical spine treatment and for other applications. 
         [0054]      FIGS. 17 and 18  illustrate a first embodiment of a working cannula, indicated generally at  50 , in accordance with this invention. In the illustrated embodiment, the working cannula  50  includes a handle portion  51 , a cannula portion  52 , and a sharp tip  53 . As best shown in  FIG. 18 , the cannula portion  52  is tapered from the handle portion  51  to the tip portion  53 , although such is not required. A passageway  54  is formed through the working cannula  50  from the handle portion  51  through the cannula portion  52  to the sharp tip  53  for a purpose that will be explained below. The cannula portion  52  of the working cannula  50  can vary in length from about 100 mm to about 200 mm and is preferably about 120 mm. The overall length of the working cannula  50  can also vary, but is preferably about 150 mm. The cannula portion  52  defines an inner diameter that can vary with the size of the translaminar screw used therewith, as will be described below. For example, the inner diameter of the cannula portion  52  can be about 7 mm ID when a translaminar screw or other implant of about 4.5 mm is used. 
         [0055]      FIGS. 19 and 20  illustrate a first embodiment of a trocar, indicated generally at  60 , in accordance with this invention. In the illustrated embodiment, the trocar  60  includes a handle portion  61  and a shaft portion  62  that terminates in a sharp tip  63 . A passageway (not shown) is formed through the shaft portion  62  from the handle portion  61  to the sharp tip  63  to accommodate the passage of a conventional Kirschner wire  64  (see  FIGS. 21 and 22 ) therethrough.  FIGS. 21 and 22  illustrate the assembly of the working cannula  50  illustrated in  FIGS. 17 and 18  and the trocar  60  illustrated in  FIGS. 19 and 20 . As shown therein, the shaft portion  62  of the trocar  60  can be inserted through the cannula portion  52  of the working cannula  50  such that the sharp tip  63  of the trocar  60  extends from the sharp tip  53  of the working cannula  50 . The Kirschner wire  64  is shown in use with the assembly of the working cannula  50  and the trocar  60 . 
         [0056]      FIGS. 23 ,  24 , and  25  illustrate a second embodiment of a trocar, indicated generally at  70 , in accordance with this invention. In the illustrated embodiment, the trocar  70  includes a caged handle portion  71  and a shaft portion  72  that terminates in a sharp tip  73 . A passageway  74  is formed through the shaft portion  72  from the caged handle portion  71  to the sharp tip  73  to accommodate the passage of a conventional Kirschner wire  74  (see  FIGS. 28 and 29 ) therethrough.  FIGS. 26 through 29  illustrate the assembly of the working cannula illustrated in  FIGS. 17 and 18  and the trocar  70  illustrated in  FIGS. 23 ,  24 , and  25 . As shown therein, the shaft portion  72  of the trocar  70  can be inserted through the cannula portion  52  of the working cannula  50  such that the sharp tip  73  of the trocar  70  extends from the sharp tip  53  of the working cannula  50 . The Kirschner wire  74  is shown in use with the assembly of the working cannula  50  and the trocar  70 . The caged handle portion  71  of the trocar  70  is provided to facilitate the attachment of an inclinometer (see  95  in  FIG. 46 ) thereto for use during a surgical procedure. As will be explained further below, the inclinometer  95  is, of itself, conventional in the art and is adapted to generate an indication of the slope, tilt, angle, elevation, or depression of the trocar  70  relative to a reference line defined (in this instance) by gravity. Thus, the assembly of the working cannula  50  and the trocar  60  or  70  can be properly and accurately positioned for and during use. Teeth provided at the tip of the trocar  70  (best shown in  FIG. 25 ) allow for proper grip into the bone. This part can be used as a blunt dissection tool and to prevent tissue from entering into the working cannula  50  during use. 
         [0057]    In use, the trocar  70  slides into the working cannula  50  and can be locked into place to prevent sliding and rotation during surgery. One or more Kirschner wires can then be inserted into the trocar  70 . For example, a relatively thick Kirschner wire can provides stability to a relatively thin Kirschner wire when it is inserted into the bone. The Kirschner wires may have diamond tipped ends (see  FIG. 29 ) to provide proper grip and accurate placement into the bone. 
         [0058]      FIG. 30  illustrates a translaminar screwdriver assembly, indicated generally at  80 , in accordance with this invention. In the illustrated embodiment, the screwdriver assembly  80  includes a handle portion  81  and a shaft portion  82  that terminates in a driver tip  83 . The handle portion  81  is preferably relative large to facilitate grasping and applying rotational force by a user. The shaft portion  82  of the screwdriver assembly  80  can be of any desired length. The driver tip  83  of the screwdriver assembly  80  is shaped to be complementary to the inner driving structures of the head portions of the translaminar screws described above. As a result, a translaminar screw can be inserted through the cannula portion  52  of the working cannula  50  and rotatably driven into the bone by the screwdriver assembly  80 . If desired, the driver tip  83  of the screwdriver assembly  80  may be provided with one of more splits  83   a  (three are shown in the illustrated embodiment) that allow the driver tip  83  to frictionally engage the outer surface of the head portion of the translaminar screw being driven into the bone. A passageway  84  may be formed through the screwdriver assembly  80  from the handle portion  81  through the shaft portion  82  to the driver tip  83  to accommodate a Kirschner wire (not shown) for facilitating alignment. 
         [0059]      FIG. 33  is a side elevational view of a drill bit, indicated generally at  90 , that can be used for surgery in accordance with this invention. In the illustrated embodiment, the drill bit  90  includes an engagement portion  91 , a shaft portion  92 , a relatively large diameter drill portion  93 , and a relatively small diameter portion  94 . The engagement portion  91  is provided to facilitate the connection of the drill  90  with a source of rotational power (not shown). The relatively large diameter drill portion  93  is provided to create a cavity for larger diameter portion of the translaminar screw (such as the non-threaded portion  12  of the translaminar screw  10  illustrated in  FIGS. 5 ,  6 , and  7 ), while the relatively small diameter portion  94  is provided to create a cavity for smaller diameter portion of the translaminar screw (such as the threaded portion  13  of the translaminar screw  10  illustrated in  FIGS. 5 ,  6 , and  7 ). 
         [0060]      FIGS. 33 through 40  illustrate a method for performing a minimal invasive surgical technique for placement of a translaminar screw in accordance with this invention. Surgical preplanning can be done using a conventional CT scan using simple and conventional software. As shown in these drawings, the desired angulation of the translaminar screw can be calculated. Thereafter, the inclination angle can be calculated. These calculations allows the surgery to be planned with minimal opportunity for error during the minimal invasive spine surgery placement of the translaminar screw. This angulation preplanning is then transferred as marking on the skin as shown in  FIG. 40 . 
         [0061]    Many other applications of this polymer osteosynthesis screw (formed from PEEK, PEAK, or carbon fiber) are within the scope of this invention. For example, as shown in  FIG. 41 , these screws can be used in the cervical spine to do fusion of C1 and C2 vertebrae.  FIGS. 42 and 43  show how these screws can be used for fixation of the odontoid peg fracture with is fracture of the C2 vertebra.  FIGS. 44 and 45  show how these screws can be used for fixation of a sacroiliac joint. The screw can also be used for many other orthopedic application, such as wrist joint stability and ankle joint stability, as it would allow the joint to be stabilized while, at the same time, allowing function movement, thereby preventing fusion from occurring. The screw can also be used for osteoporotic fixation of various orthopedic fractures and surgical procedure with low quality bone. 
         [0062]    Additionally, the screws of this invention may be used in transforaminal lumbar interbody fusion (TLIF) surgeries, anterior lumbar interbody fusion (ALIF) surgeries, extreme lateral interbody fusion (XLIF) surgeries, and other surgical procedures. Similarly, the screws of this invention may also be used in nucleus replacement, total disc replacement, and annular repair surgical procedures. 
         [0063]      FIG. 46  shows an alignment sensor, such as a conventional inclinometer  95 , that is attached the caged handle portion  71  of the trocar  70  for use during a surgical procedure. The inclinometer  95  is, as mentioned above, conventional in the art and is adapted to generate an indication of the slope, tilt, angle, elevation, or depression of the trocar  70  relative to a reference with respect to gravity. Thus, the assembly of the working cannula  50  and the trocar  60  or  70  can be properly and accurately positioned for and during use. The inclinometer  95  can alternatively be attached to a biopsy needle or other device that allows a surgeon to achieve the correct anatomical trajectory based on a preoperative planning study. It is very helpful during spine and orthopedic surgeries, mainly the minimally invasive and percutaneous ones, to avoid misplaced implants and the associated consequences. For example, it can be indicated to guide the placement of pedicle screws, transfacet screws, and translaminar facet screws in procedures that are commonly performed around the world. The goal of the illustrated alignment sensor is to achieve the lateral angle of a fluoroscopy guided surgery with accuracy. 
         [0064]    Two other parameters that are important for a percutaneous placement (the caudal angle and the distance away from the midline) are also achieved during the preoperative planning study and drawn at the patient skin. One advantage of this new device is to allow a free hand navigation surgery without the necessity of a new skin incision to place the other techniques hardware and the easy way to handle it. The new device can be attached to all biopsy needle designs available on the market or adapted to customized ones or cannulas. The new alignment sensor is a very simple technological solution based on electronic components currently available, thus reducing its cost of manufacturing. The only simple orientation for the surgeon is to keep the patient position parallel to the operating surgery floor, avoiding an incorrect angle trajectory. Another big advantage of this device is to reduce the increased radiation exposure time for surgeons and patients, during minimally invasive and percutaneous surgery. 
         [0065]    The illustrated alignment sensor  95  is an inclinometer to use for in a surgical application. The inclinometer is capable of measure an angle between +90° and −90° from the referential ground plane (lateral angle). The measured angle assists the surgeon to introduce and position a needle during a surgical procedure that demands precise lateral angle positioning. Despite the rotation on its perpendicular axis, the inclinometer will continually show the lateral angle referred to ground plane. The inclinometer can remain off while not in use and will turn on its display when tapped consistently in its radial direction, like hitting a coin in a table. Once turned on it will remain in this state, showing the measured angle on display, while it has internal power to do so and while the absolute measured angle is greater than 10°. If the inclinometer is positioned below absolute 10° for fifteen seconds or other predetermined period of time, it will turn off and wait for another initialization with a radial tap. 
         [0066]    Although it can be applied to other type of surgeries, its first application is in spine soft fusion procedures, when the cannula that orients all the procedure is precisely positioned. In order to the readings be accurate with the necessary angle, the floor of the surgical room must be parallel to the earth&#39;s ground plane and the patient&#39;s back must be positioned in parallel with earth&#39;s ground plane as well. 
         [0067]    The inclinometer  95  can have an elliptical coin form factor that accommodates an easily readable luminous display with 2.1 digits for positive angles or −1.1 digits for negative angles above −10°, or −2 digits for negative angles below −10°. It can also have an interchangeable clip that adjusts and grips in the cannula in order to keep the inclinometer in an orthogonal angle in reference to the cannula extension (then the measured angle corresponds to the lateral angle of the cannula itself in reference to the earth&#39;s ground plane). It could have distinct body colors and formats. 
         [0068]    The sensing element can be a 3-axis micro electromechanical system accelerometer, which is capable to sense the vector of gravity. Desired features for this implementation include:
       3-axis;   small size;   low full scale (between 2 g and 5 g) with high sensitivity;   low noise;   low power consumption;   wide range of work voltage, to operate directly from the battery;   good long term stability.       
 
         [0076]    The processing is made by a microcontroller unit (MCU) which runs a firmware that gives all the described functionality from the data collected from the sensing element. This MCU gives flexibility and adaptability to the design and thanks to a arithmetic unit capable of run the vectorial math and a set of integrated peripherals it allows the design of a very compact design. The desired MCU features in this design can include:
       small size;   low power consumption when processing;   extremely low power consumption while standing-by;   32 KB of internal non-volatile memory (FLASH) for program and configuration;   8 KB of internal data SRAM;   capability to run emulated floating-point operations with power and time efficiency, which a low-power 32-bit 12 Mhz MCU core with one-cycle multiplier should be able to do;   direct interface to selected MEMS accelerometer;   battery monitoring interface;   display drive capability;   wake-up from power-down mode through an interrupt pin;   timer;   no pin conflicts.       
 
         [0089]    The main floating-point operation can be defined by the equation: 
         [0000]    
       
         
           
             θ 
             = 
             
               
                 tan 
                 
                   - 
                   1 
                 
               
               ( 
               
                 
                   A 
                   
                     X 
                     , 
                     OUT 
                   
                 
                 
                   
                     
                       A 
                       
                         Y 
                         , 
                         OUT 
                       
                       2 
                     
                     + 
                     
                       A 
                       
                         Z 
                         , 
                         OUT 
                       
                       2 
                     
                   
                 
               
               ) 
             
           
         
       
       
         
           
             where: 
             θ=measured angle 
             tan −1 =arctangent operation 
             A X,OUT =value read in X-axis 
             A Y,OUT =value read in Y-axis 
             A Z,OUT =value read in Z-axis 
           
         
       
     
         [0096]    The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiments. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.