Patent Publication Number: US-11660127-B2

Title: Spinous process fixation system and methods thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is a continuation of U.S. patent application Ser. No. 17/497,453 filed on Oct. 8, 2021, which is a continuation of U.S. patent application Ser. No. 16/281,133 filed on Feb. 21, 2019 (published as U.S. Pat. Pub. No. 2019-0254721), which is a continuation of U.S. patent application Ser. No. 14/923,894 filed on Oct. 27, 2015, now U.S. Pat. No. 10,251,680, which is a continuation of U.S. patent application Ser. No. 13/799,364 filed on Mar. 13, 2013, now U.S. Pat. No. 9,198,697, the entire disclosures of all of which are incorporated herein by reference for all purposes. 
    
    
     FIELD OF THE INVENTION 
     This description relates to medical devices and systems and more particularly to a spinous process fixation system and methods thereof. In particular, in one or more implementations, this description relates to spinous process fusion devices that distract and/or immobilize the spinous processes of adjacent vertebrae. 
     BACKGROUND 
     A variety of medical devices and medical device systems may be implanted within a body of a patient to provide support to a portion or portions of the patient&#39;s body. For example, some medical devices may be implanted and coupled to backbones or portions of a spine of a patient and may be configured to provide support to the spinal bone structure of the patient. 
     Typically, weaknesses in the spine are corrected using devices that fuse one or more vertebrae together. It may be desirable to have an implantable device that provides for structural stability to adjacent vertebrae and to achieve supplemental fusion to treat weaknesses in the spine due to degenerative disc disease, spondylolisthesis, trauma (i.e., fracture or dislocation), tumor and/or other causes. 
     SUMMARY 
     According to one general aspect, an implantable device includes a barrel. The barrel has a first portion and a second portion. The implantable device includes a first plate having multiple projections extending from one side of the first plate, where the first plate is configured to movably couple to the first portion of the barrel. The implantable device includes a second plate having multiple projections extending from one side of the second plate, where the second plate is configured to movably couple to the second portion of the barrel. The barrel is configured to transition from a collapsed form having a first height to an expanded form having a second height, where the second height is greater than the first height. 
     Implementations may include one or more of the following features. For example, the barrel may include a frame, a first endplate having a curved shape and a second endplate having a curved shape. The first endplate and the second endplate may be coupled to the frame to form the barrel, where the barrel has a bulleted shape in both a lateral direction and a posterior direction. The barrel may include a frame, a first endplate, a second endplate, a first actuator having a split ramp inserted into the frame, a second actuator having a split ramp inserted into the frame and a central screw inserted through the first actuator and the second actuator, where the first actuator and the second actuator are configured to act on the first endplate and the second endplate in response to a rotation of the central screw. The barrel may include a first window and a second window, where the first window and the second window may be configured to receive graft packing material. The barrel may include a first endplate having a shaped groove and a second endplate having a shaped groove. 
     For example, in one implementation, the first portion and the second portion may be rails that extend from a same side of the barrel. For example, in another implementation, the first portion and the second portion may be rails that each extend from a different side of the barrel. 
     For example, the first plate and the second plate are each shaped in a lordotic profile. The first plate may include a bushing to enable the first plate to angulate about the bushing and the second plate may include a bushing to enable the second plate to angulate about the bushing. The first plate may be locked in position using a first set screw at any position within a range of motion for the first plate and the second plate may be locked in position using a second set screw at any position within a range of motion for the second plate. The first set screw may include a cup-shaped end to lock the first plate in position and the second set screw may include a cup-shaped end to lock the second plate in position. 
     In another general aspect, an implantable device includes a barrel having a first portion and a second portion, a first plate having multiple projections extending from one side of the first plate, where the first plate is configured to movably couple to the first portion of the barrel and to angulate about an axis of the first portion, and a second plate having multiple projections extending from one side of the second plate, where the second plate is configured to movably couple to the second portion of the barrel and to angulate about an axis of the second portion. The first plate and the second plate are each shaped in a lordotic profile. 
     Implementations may include one or more of the following features. For example, the first plate may be configured to angulate up to about 25 degrees about the axis of the first portion and the second plate may be configured to angulate up to about 25 degrees about the axis of the second portion. In one implementation, the first portion and the second portion may be rails that extend from a same side of the barrel. In another implementation, the first portion and the second portion may be rails that each extend from a different side of the barrel. 
     For example, the barrel may be configured to transition from a collapsed form having a first height to an expanded form having a second height, where the second height is greater than the first height. The first plate may be locked in position using a first set screw at any position within a range of motion for the first plate, where the first set screw has a cup-shaped end, and the second plate may be locked in position using a second set screw at any position within a range of motion for the second plate, where the second set screw has a cup-shaped end. 
     In another general aspect, a method includes inserting a barrel of an implantable device into an interspinous space. The implantable medical device includes the barrel having a first portion and a second portion, a first plate having multiple projections extending from one side of the first plate and a second plate having multiple projections extending from one side of the second plate. The method includes expanding the barrel from a collapsed form having a first height to an expanded form having a second height, where the second height is greater than the first height, moving the first plate on the first portion to engage a spinous process and moving the second plate on the second portion to engage the spinous process. 
     Implementations may include one or more of the following features. For example, the method may include engaging set screws in the first plate and the second plate to lock the first plate and the second plate in position. The method may include positioning the first plate to a desired angle with respect to the first portion, positioning the second plate to a desired angle with respect to the second portion and engaging set screws in the first plate and the second plate to lock the first plate and the second plate in position. 
     In another general space, an implantable device may include a barrel, the barrel having an upper portion and a lower portion. The implantable device may further include an actuator assembly disposed in the barrel, the actuator assembly comprising a front ramped actuator in engagement with the barrel, a rear ramped actuator in engagement with the barrel, and a central screw that extends from the rear ramped actuator through the front ramped actuator. The implantable device may further include a first plate having multiple projections extending from one side of the first plate, the first plate comprising a first portion that extends from the upper portion and a second portion that extends form the lower portion. The implantable device may further include a second plate having multiple projections extending from one side of the second plate, the second plate configured to be received on the central screw. The barrel may be configured to transition from a collapsed form having a first height to an expanded form having a second height and wherein the second height is greater than the first height. 
     In another general aspect, a method may include implanting a medical device in a patient, the method comprising: inserting a barrel of the device between adjacent spinous process, the medical device comprising a first plate disposed on one end of the barrel; rotating a central screw disposed in the barrel to cause the barrel to expand from a collapsed form having a first height to an expanded form having a second height; and ratcheting a second plate onto the central screw such that the first plate and the second plate engage the adjacent spinous process, the second plate being free to rotate about its center within a range of motion. 
     The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a medical device according to an example implementation. 
         FIG.  2    is a top view of the medical device of  FIG.  1   . 
         FIG.  3    is a front view of the medical device of  FIG.  1   . 
         FIG.  4    is a side view of the medical device of  FIG.  1   . 
         FIG.  5    is a perspective view of a medical device according to an example implementation. 
         FIG.  6    is a top view of the medical device of  FIG.  5   . 
         FIG.  7    is a front view of the medical device of  FIG.  5   . 
         FIG.  8    is a side view of the medical device of  FIG.  5   . 
         FIG.  9    is a perspective view of a medical device according to an example implementation. 
         FIG.  10    is a top view of the medical device of  FIG.  9   . 
         FIG.  11    is a front view of the medical device of  FIG.  9   . 
         FIG.  12    is a side view of the medical device of  FIG.  9   . 
         FIG.  13    is a perspective view of a medical device according to an example implementation. 
         FIG.  14    is a top view of the medical device of  FIG.  13   . 
         FIG.  15    is a front view of the medical device of  FIG.  13   . 
         FIG.  16    is a side view of the medical device of  FIG.  13   . 
         FIG.  17    is a perspective view of a medical device according to an example implementation. 
         FIG.  18    is a top view of the medical device of  FIG.  17   . 
         FIG.  19    is a front view of the medical device of  FIG.  17   . 
         FIG.  20    is a side view of the medical device of  FIG.  17   . 
         FIG.  21    is a top view of a medical device according to an example implementation. 
         FIG.  22    is a side view of the medical device of  FIG.  21   . 
         FIG.  23    is a detailed view of the inset A of  FIG.  22   . 
         FIGS.  24 - 27    are side views of a plate of a medical device according to an example implementation. 
         FIG.  28    is top view of a barrel of a medical device according to an example implementation. 
         FIG.  29    is an exploded front view of a barrel of a medical device according to an example implementation. 
         FIG.  30    is an exploded top view of a barrel of a medical device according to an example implementation. 
         FIG.  31    is a perspective view of a medical device according to an example implementation. 
         FIG.  32    is a top view of the medical device of  FIG.  31   . 
         FIG.  33    is a front view of the medical device of  FIG.  31   . 
         FIG.  34    is a side view of the medical device of  FIG.  31   . 
         FIG.  35    is a perspective view of a medical device according to an example implementation. 
         FIG.  36    is a top view of the medical device of  FIG.  35   . 
         FIG.  37    is a front view of the medical device of  FIG.  35   . 
         FIG.  38    is a side view of the medical device of  FIG.  35   . 
         FIG.  39    is a perspective view of a medical device according to an example implementation. 
         FIG.  40    is a top view of the medical device of  FIG.  39   . 
         FIG.  41    is a front view of the medical device of  FIG.  39   . 
         FIG.  42    is a side view of the medical device of  FIG.  39   . 
         FIG.  43    is a perspective view of a medical device according to an example implementation. 
         FIG.  44    is a top view of the medical device of  FIG.  43   . 
         FIG.  45    is a front view of the medical device of  FIG.  43   . 
         FIG.  46    is a side view of the medical device of  FIG.  43   . 
         FIG.  47    is an exploded top view of a barrel of a medical device according to an example implementation. 
         FIG.  48    is a flow chart illustrating an exemplary method including the medical device of  FIG.  1   . 
         FIG.  49    is a perspective view of a medical device according to one implementation. 
         FIG.  50    is an exploded view of the medical device of  FIG.  49    with the locking plate removed according to one implementation. 
         FIG.  51    is a side view of the medical device of  FIG.  50   . 
         FIG.  52    is a front view of the medical device of  FIG.  50   . 
         FIG.  53    is a rear view of the medical device of  FIG.  50   . 
         FIG.  54    is a top view of the medical device of  FIG.  50   . 
         FIG.  55    is a side view of the medical device of  FIG.  49    with the locking plate removed according to one example implementation. 
         FIG.  56    is a front view of the medical device of  FIG.  55   . 
         FIG.  57    is a rear view of the medical device of  FIG.  55   . 
         FIG.  58    is a top view of the medical device of  FIG.  55   . 
         FIGS.  59 - 62    illustrate assembly of an expandable central barrel of a medical device according to one example implementation. 
         FIGS.  63 - 65    illustrate assembly of the spikes for the medical device of  FIGS.  59 - 62   . 
         FIG.  66    is a side view of a locking plate for a medical device according to one example implementation. 
         FIG.  67    is a front view of the locking plate of  FIG.  66   . 
         FIG.  68    is a cross-sectional view of a trunion assembly for a medical device according to one example implementation. 
         FIG.  69    is a front view of the trunion assembly of  FIG.  68   . 
         FIG.  70    is cross-sectional view of a tube that can be used to release the pawls of the trunion assembly of  FIG.  68    according to one example implementation. 
         FIGS.  71 - 73    illustrate assembly of a locking plate for a medical device according to one example implementation. 
         FIG.  74    is a side view showing rotation of a locking plate for a medical device according to one example implantation. 
         FIG.  75    is a perspective view showing angulation of the spike assembly of the locking plate of  FIG.  74   . 
     
    
    
     DETAILED DESCRIPTION 
     Detailed implementations of the present invention are disclosed herein; however, it is to be understood that the disclosed implementations are merely examples of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting, but rather to provide an understandable description of the invention. 
     The terms “a” or “an,” as used herein, are defined as one or more than one. The term “another,” as used herein, is defined as at least a second or more. The terms “including” and/or “having”, as used herein, are defined as comprising (i.e., open transition). 
     The devices and methods described herein are generally directed to medical devices that can be used to support, stabilize and/or replace anatomical structures within a body of a patient. In some implementations, the devices and methods described herein are configured to provide support to a spine or back of a patient, including providing support between two vertebrae in the spine or back of the patient. In other implementations, other portions of the body of the patient can be supported by the devices described herein. 
     The medical devices described herein may be implanted within a body of a patient to assist in maintaining normal physiologic motion in the spine of the patient. 
     The term patient may be used hereafter for a person who benefits from the medical device or the methods disclosed in the present invention. For example, the patient may be a person whose body receives the medical device disclosed by the present invention in a surgical treatment. For example, in some embodiments, the patient may be a human female, human male, or any other mammal. 
     This document describes implementations of an implantable medical device that may be used as a posterior, non-pedicle supplemental fixation device for use in the non-cervical spine. The medical device may be used as an interspinous fusion device. The medical device may be implanted with or without the removal of the supraspinous ligament. In one or more implementations, the supraspinous ligament may be preserved. The medical device may be attached firmly to the spinous processes above and below an interspinous space. The medical device may immobilize a lumbar motion segment posteriorly with no other devices implanted. The medical device may withstand compressive, torsional and shear loads seen in the lumbar spine. The medical device may be used to achieve supplemental fusion and to treat conditions of the spine such as, for example, degenerative disc disease, spondylolisthesis, trauma (i.e., fracture or dislocation), tumor and/or other conditions. 
     This document describes implementations of an implantable medical device, where the medical device may include an expandable central barrel with polyetheretheketone (PEEK) bone contacting endplates, with two spiked plates attached to the central barrel. For example, the two spiked plate may be held together on posterior rails. By way of further example, one of the spiked plates may be on one end of the expandable central barrel (e.g., integrally formed with the central barrel) with another one of the spiked plates being attached after the barrel is inserted into the interspinous space to clamp the device in place. The plates may include projections (e.g., spikes) that bite into the spinous process to clamp the device in place. Each of the plates may angulate to conform to the patient anatomy. The plates may be locked with a set screw and may have a lordotic profile to match the lumbar anatomy. The expandable barrel may provide interspinous distraction, off-loading the spikes on the plate and reducing the chances of breaking the spinous process. The barrel may be sized to fit into the interspinous space without resistance, and then expanded. The barrel may include a graft window (e.g., anteriorly and posteriorly) which may be packed with graft material after expansion. In some embodiments, the barrel includes a graft window anteriorly and posteriorly and can be packed with the graft material using the posterior window. The PEEK endplates may include anatomically-shaped grooves for optimal bone contact and fit. 
       FIGS.  1 - 4    illustrate a medical device  10  according to one example implementation. The medical device  10  may be implanted in a patient and referred to as a spinous process fusion device.  FIG.  1    is a perspective view of the medical device  10  with a barrel illustrated in a collapsed or contracted position and the plates in a separated position relative to one another.  FIGS.  2 - 4    illustrate a top view, front view and side view, respectively, of the medical device  10  of  FIG.  1   , which illustrates the barrel in the collapsed or contracted position. 
     The medical device  10  includes a first plate  12 , a second plate  14  and an expandable central barrel (also referred to as a barrel)  16 . The barrel  16  is illustrated in a collapsed state. The barrel  16  includes a first portion  18  (e.g., a first rail  18 ) and a second portion  20  (e.g., a second rail  20 ). The first rail  18  and the second rail  20  also may be referred to as the rails  18  and  20 . The first rail  18  and the second rail  20  may be integrally formed with the barrel  16 . The first rail  18  and the second rail  20  also may be referred to as posterior rails. The first plate  12  and the second plate  14  (also referred to as the plates  12  and  14 ) may be secured to the barrel  16  by coupling the first plate  12  to the first rail  18  and the second plate  14  to the second rail  20 . The first plate  12  and the second plate  14  each may include a bushing  22  (e.g., a spherical bushing) assembled into the plates  12  and  14 , where the plates  12  and  14  slide on the respective rails  18  and  20  through the bushing  22  and are secured using a set screw  24 . As discussed in more detail below, each plate  12  and  14  may move laterally along its respective rail  18  and  20  to engage spinous processes of adjacent vertebra above and below the interspinous space.  FIGS.  1 - 4    illustrate the plates  12  and  14  in a separated position with respect to one another. Also, as discussed in more detail below, each plate  12  and  14  may angulate through a range of degrees with respect to the rails  18  and  20  to better conform to patient anatomy when implanted in a patient. 
     In other example implementations (not shown), the first portion  18  and the second portion  20  may be grooves on the barrel  16 . In this example, the first plate  12  and the second plate  14  each may include a projection (e.g., a rail) that is movably inserted into the corresponding groove on the barrel  16 . This example implementation may function in the same way as described above and below, other than the structure of the rails may be implemented on the plates  12  and  14 , which are then received in the first portion  18  and the second portion  20  of the barrel  16 , where the first portion  18  and the second portion  20  are grooves on the barrel  16 . 
     The first plate  12  may include an upper portion  26  and a lower portion  28 . The second plate  14  may include an upper portion  30  and a lower portion  32 . The plates  12  and  14  may include multiple projections  34  (e.g., spikes) on both the upper portions  26  and  30  and the lower portions  28  and  32 . While the term spikes may be used for the projections  34  other types of projections may be used that may have a more tapered point or rounded point or other type of ending to the projection. The spikes  34  may be used to attach firmly and bite into the spinous processes above and below an interspinous space. The spikes  34  may be integrally formed with the plates  12  and  14  or the spikes  34  may be separate components that are secured to the plates  12  and  14 . The spikes  34  may be pyramid shaped with a base portion secured or integrally formed on the plates  12  and  14 . The sides of the spikes  34  may extend from the base to form a point in the shape of a pyramid. In other example implementations, the spikes  34  may be formed into other shapes that rise to a point to enable the spike to engage the spinous process. As discussed above, the end of the spikes  34  may include tips other than a point such as, for example, rounded tip, a square tip or other-shaped tip. 
     The plates  12  and  14  and the spikes  34  may be made of titanium. In other implementations, the plates  12  and  14  and the spikes  34  may be made of other biocompatible materials. 
     The example illustration of the medical device  10  includes four (4) spikes  34  on each portion  26 ,  28 ,  30  and  32  of the plates  12  and  14 . In other example implementations, fewer or more spikes  34  may be included. In one example implementation, the spikes  34  on opposing portions (i.e., upper portions  26  and  30  and lower portions  28  and  32 ) may be aligned across from one another. In other example implementations, the spikes  34  on opposing portions may be offset from one another. 
     The first plate  12  and the second plate  14  may be shaped in a lordotic profile to match the lumbar anatomy. With respect to the first plate  12 , the upper portion  26  is connected to the lower portion  28  by a central portion  36 . The upper portion  26 , the lower portion  28  and the central portion  36  may be integrally formed as a single plate component. The central portion  36  includes an open side (e.g., a C-shaped opening) to receive the bushing  22  and an opening (e.g., a hole) to receive the set screw  24 , as illustrated in more detail in  FIGS.  24 - 27   . In other example implementations, the first plate  12  and the second plate  14  may be other shapes suitable for a particular application. 
     Similarly to the first plate  12 , the second plate  14  includes a central portion  38  that connects the upper portion  30  to the lower portion  32 . The upper portion  30 , the lower portion  32  and the central portion  38  may be integrally formed as a single plate component. The central portion  38  include an open side (e.g., a C-shaped opening) to receive the bushing  22  and an opening (e.g., a hole) to receive the set screw  24 , as illustrated in more detail in  FIGS.  24 - 27   . The set screw  24  is used to lock the plates  12  and  14  in an angular position at any position within their range of angular motion. 
     The central barrel  16  is an expandable barrel that may be in a collapsed position for insertion into a patient in the interspinous space without resistance and then expanded up to the barrel&#39;s maximum height. In one example implementation, the maximum expanded height of the barrel may be about 4 mm greater than the collapsed height. 
     The central barrel  16  includes a first endplate  40  and a second endplate  42  (also referred to as endplates  40  and  42 ), as best viewed in  FIG.  3   . Each of the endplates  40  and  42  includes a respective groove  44  and  46 . The grooves  44  and  46  may be anatomically-shaped grooves optimal bone contact and fit in the patient. The endplates  40  and  42  may be PEEK bone contacting endplates. The barrel  16  may be bullet-shaped on both ends in the lateral and posterior directions to facilitate insertion into a patient. The expandable barrel  16  may provide interspinous distraction and may offload the forces of the spikes  34  on the plates  12  and  14  to reduce the chances of breaking a spinous process. The barrel  16  may be inserted, laterally or posteriorly, in a smaller height and then expanded to provide distraction, eliminating forces on the spinous process and potential frustration for a surgeon performing the implantation. 
     The barrel  16  includes a first window  48  (e.g., also referred to as an opening or an anterior window) and a second window  50  (e.g., also referred to as an opening or a posterior window). The first window  48  and the second window  50  may be used as graft windows for the packing of bone graft material following the insertion and placement of the medical device  10  in a patient. In one implementation, after the barrel  16  has been expanded, the barrel  16  may be packed with bone graft using the second window  50 . In this manner, graft containment areas accessed by the windows  48  and  50  may provide for a larger grafting area and may be packed after expansion of the barrel  16 . 
     Referring to  FIGS.  5 - 8   , an example implementation of the medical device  10  of  FIGS.  1 - 4    is illustrated with the barrel  16  shown in an expanded state and the plates  12  and  14  shown in a separated position with respect to one another. That is, the plates  12  and  14  are each positioned towards an outer end of the rails  18  and  20 . The barrel  16  expands and contracts by expanding and contracting the endplates  40  and  42  in a direction towards the upper  26  and  30  and lower portions  28  and  32  of the sides  12  and  14 , respectively. The mechanism to expand and contract the barrel  16  is illustrated in more detail in  FIGS.  28 - 30    below. 
     In general, a central screw  52  is rotated to actuate two independent internal actuators. The actuators include split ramps that raise and lower the endplates  40  and  42  when the central screw  52  is rotated.  FIGS.  7  and  8    provide views that illustrate the barrel  16  in a fully expanded state. As discussed above, the barrel  16  may be expanded after insertion into the interspinous space. After expansion, the barrel  16  may be packed with bone graft material using the window  50 . Prior to expansion, some bone graft material may be packed into the barrel  16  using the window  48 . 
     Referring to  FIGS.  9 - 12   , an example implementation of the medical device  10  of  FIGS.  1 - 4    is illustrated with the barrel  16  shown in a collapsed state and the plates  12  and  14  shown in a closed position. That is, the plates  12  and  14  have been traversed along the rails  18  and  20  towards one another. The plates  12  and  14  may slide along the rails  18  and  20  and may be secured in position at any point along the rails  18  and  20  using the set screw  24 . When the plates  12  and  14  are slid together along the rails  18  and  20 , the spikes  34  on the plates  12  and  14  may engage and clamp (or bite into) the spinous process. In this manner, the spikes  34  on the upper portions  26  and  30  may clamp together and into one spinous process and the spikes  34  on the lower portions  28  and  32  may clamp together and into an adjacent spinout process. 
     As illustrated in  FIGS.  9 - 12   , the spikes  34  on one plate are aligned to mate at a same point with the spikes  34  on an opposing plate. In other example implementations, the spikes  34  on one plate may be offset in relation to the spikes  34  on an opposing plate. 
     Referring to  FIGS.  13 - 16   , an example implementation of the medical device  10  of  FIGS.  1 - 4    is illustrated with the barrel  16  shown in an expanded state and the plates  12  and  14  shown in a closed position. In this manner, this illustrates the medical device  10  in a state after insertion into the patient such that the plates  12  and  14  have been traversed along the rails  18  and  20  to clamp on the spinous process of adjacent vertebrae and the barrel  16  has been expanded using the central screw  52 . 
     Referring to  FIGS.  17 - 23   , an example implementation of the medical device  10  of  FIGS.  1 - 4    is illustrated with the barrel  16  shown in an expanded state and the plates  12  and  14  shown in an open or separated position and in an angulated configuration. As discussed above, the plates  12  and  14  may rotate angularly with respect to the rails  18  and  20 . The plates  12  and  14  may pivot around the bushing  22  and may be locked in place using the set screw  24 . In one example implementation, the plates  12  and  14  may have a range of motion of about 25 degrees offset with respect to the rails  18  and  20 . The angulation of the plates  12  and  14  enables each plate to conform independently to the anatomy of the particular patient. Each plate  12  and  14  may be pivoted and locked at any position in their range of motion independent of the other plate. 
     In  FIGS.  22  and  23   , a side view ( FIG.  22   ) and a detailed view of inset A ( FIG.  23   ) illustrate that the plates  12  and  14  are locked using the set screw  24 . The rails  18  and  20  may be C-shaped or curved and include a groove area  60 . The set screw  24  may include a curved, cup-shaped design on the tip  62 . The curved tip  62  penetrates through the opening in the rail  14  and through the bushing  22  to engage the groove area  62  of the rail  20  to secure and lock the plate  14  in place. The curved tip  62  maximizes the surface contact with the groove area  62  of the rail  20  when the plate  14  pivots through its range of motion.  FIGS.  24 - 27    below also illustrate the curved (or cup-shaped or bulleted) tip  62  of the set screw  24 . 
     Referring to  FIGS.  24 - 27   , the assembly of the plates  12  and  14  is illustrated. In these example figures, plate  14  is referenced for illustrative purposes. The plate  14  may be assembled by placing the bushing  22  into the plate initially offset by 90 degrees from its final position. As described above, the bushing  22  may be a spherical bushing that is shaped to be positioned on and traverse the rail  20  on the barrel  16 . The bushing  22  may include a slot  64  or opening in the back of the bushing to receive the set screw  24 . 
     Once the bushing  22  has been inserted into the plate  14  ( FIG.  25   ), the bushing  22  is rotated 90 degrees into its final position in the plate  14  ( FIG.  26   ). Then, the set screw  24  having the curved tip  62  may be inserted through the opening in the back of the plate  14  through the slot  64  in the bushing  22 . The set screw  24  serves to prevent the bushing  22  from rotating back out of the plate  14 . 
     Referring to  FIGS.  28 - 30   , the barrel  16  and assembly of the barrel  16  is illustrated in detail. As discussed above, the barrel  16  includes a first endplate  40  and a second endplate  42 . The endplates  40  and  42  may be PEEK endplates. The barrel  16  includes a central screw  52  having a first thread portion  66  and a second thread portion  68 . The barrel  16  includes a frame  65 , a first actuator  70  and a second actuator  72  (also referred to as the actuators  70  and  72 ) and two assembly pins (not shown). In one example implementation, the frame  65 , the actuators  70  and  72  and the central screw  52  may be made of titanium. In other example implementations, the components may be made of other biocompatible materials. 
     Each of the actuators  70  and  72  may include split ramps  74  and  76  to accommodate the curved shape of the barrel  16 . The barrel  16  is curved shaped and may be bulleted (or egg-shaped) on each end to allow for easier insertion into the interspinous space. The curved shape of the barrel  16  may provide maximum graft packing volume. 
     The actuators  70  and  72  may be loosely assembled into the frame  65  of the barrel  16  and the  74  and  76  placed over the actuators  70  and  72 . The central screw  52  may be inserted into the actuators  70  and  72  and timed so that the actuators have specific spacing per rotation of the screw  52 . Once the screw  52  is fully inserted, two pins (not shown) are pressed into the frame  65  posteriorly to capture the screw  52  to prevent its disassembly. 
     The rotation of the screw  52  causes the actuators  70  and  72  to rotate and the ramps  74  and  76  on the actuators  70  and  72  to push against the endplates  40  and  42 , causing the endplates  40  and  42  to expand from a collapsed position. A counter rotation of the screw  52  causes the actuators  70  and  72  to rotate and the ramps  74  and  76  on the actuators  70  and  72  to recede from pushing against the endplates  40  and  42 , causing the endplates  40  and  42  to collapses from an expanded state. 
       FIGS.  31 - 34    illustrate a medical device  100  according to an example implementation. Similarly to the medical device  10 , the medical device  100  may be implanted in a patient and referred to as a spinous process fusion device. Like reference numbers between the  FIGS.  1 - 30    and  FIGS.  31 - 34   , and other figures below describing medical device  100 , refer to the same or similar components and features between the two medical devices. The medical device  100  may have the same features and functionality as the medical device  10 . 
     The medical device  100  includes a first plate  12  and a second plate  14 . The medical device  100  includes a barrel  116 . In the example of  FIGS.  31 - 34   , the barrel  116  includes rails  118  and  120  that each extend from a different side of the barrel  116  instead of extending from a same side like the rails  18  and  20  from the barrel  16  in medical device  10 . The barrel  116  is essentially rotated 90 degrees compared to the barrel  16 . In other aspects, the barrel  116  is an expandable barrel and has the same functionality as the barrel  16 . The barrel  116  may be inserted laterally into a patient in the interspinous space. The barrel  116  may be inserted at a smaller height (or in a collapsed state) and then expanded to provide distraction and to eliminate the forces on the spinous process and frustration for the surgeon. 
     In  FIGS.  31 - 34   , the medical device  100  illustrates the plates  12  and  14  in an open state and the barrel  116  in a collapsed state. In this manner, the medical device  100  may inserted into a patient and then the barrel  116  expanded. 
     Referring to  FIGS.  35 - 38   , the medical device  100  is illustrated with the barrel  116  in an expanded state. In one example implementation, the expanded barrel height for the barrel  116  may be about 7 mm greater than the collapsed height. The sides  12  and  14  are illustrated in an open state. The barrel  116  may be expanded from a collapsed state to an expanded state using the central screw  152 . Similarly, the barrel  116  may be collapsed from an expanded state to a collapsed state using the central screw  152 . 
     Referring to  FIGS.  39 - 42   , the medical device  100  is illustrated with the barrel  116  in an expanded state and the plates  12  and  14  in a closed position. As discussed above with respect to the medical device  10 , the plates  12  and  14  on the medical device  100  also may traverse the rails  118  and  120  of the barrel between an open position and a closed position. In the closed position, the plates  12  and  14  are designed to clamp and bite into the spinous process, as discussed above in detail. 
     Referring to  FIGS.  43 - 46   , the medical device  100  is illustrated with the barrel  116  in an expanded state and the plates  12  and  14  in a closed and angulated position. As discussed above with respect to  FIGS.  17 - 20   , the plates  12  and  14  may angulate about 25 degrees with respect to the rails  118  and  120  to better conform to patient anatomy. The plates  12  and  14  may be locked in position using the set screw  24 . 
     Referring to  FIG.  47   , the barrel  116  is assembled in a manner similar to the barrel  16 , as discussed above with respect to  FIGS.  28 - 30   . The barrel  116  includes a first endplate  140  and a second endplate  142 , two independent actuators with ramps and a central screw  152 . The endplates  140  and  142  are loosely assembled into the actuator ramps and the central screw  152  is inserted into the actuator ramps, which anchor the assembly together. 
     Referring to  FIG.  48   , an example flowchart illustrates an example process  200  for using the medical devices  10  and  100 . For example, process  200  includes inserting a barrel  16  or  116  of the medical device  10  or  100 , respectively, into an interspinous space ( 210 ). As discussed above, the medical device includes the barrel  16  or  116  having a first portion (e.g., rail  18  or  118 ) and a second portion (e.g., rail  20  or  120 ), a first plate  12  having multiple projections  34  extending from one side of the first plate  12  and a second plate  14  having multiple projections  34  extending from one side of the second plate ( 210 ). 
     The process  200  includes expanding the barrel  16  or  116  from a collapsed form having a first height to an expanded form having a second height, where the second height is greater than the first height ( 220 ). As discussed above, the central screw  52  or  152  may be rotated to expand the barrel  16  or  116  from a collapsed form to an expanded form in the interspinous space. 
     The process includes moving the first plate  12  on the first portion (e.g., rail  18  or  118 ) to engage a spinous process ( 230 ) and moving the second plate  14  on the second portion (e.g., rail  20  or  120 ) to engage the spinous process ( 240 ). For example, the projections  34  on each of the plates  12  and  14  may engage the spinous process of adjacent vertebrae as the plates  12  and  14  are slid along the respective rails. 
     Optionally, the process  200  may include positioning the first plate  12  to a desired angle with respect to the first portion and positioning the second plate  14  to a desired angle with respect to the second portion. Once the plates  12  and  14  have been positioned to their desired angles, the plates  12  and  14  may be locked into position using the set screws  24 . 
       FIG.  49    illustrates a medical device  300  according to one example implementation.  FIG.  49    is a perspective view of the medical device  300 . The medical device  300  may be implanted into a patient and referred to as a spinous process fusion device. In the illustrated embodiment, the medical device  300  includes a first plate  302 , a second plate  304  (e.g., locking plate  304 ), and an expandable central barrel (also referred to as a barrel)  306 . 
     With additional reference to  FIGS.  50 - 54   , the medical device  300  of  FIG.  49    will be described in more detail.  FIGS.  50 - 54    illustrate an exploded view, side view, front view, rear view, and top view, respectively, of the medical device  300 , which illustrate the barrel  306  in the collapsed or contracted position with the locking plate  304  removed. The barrel  306  may be inserted into the interspinous space without the locking plate  304  and then expanded. The locking plate  304  may then be attached to the barrel  306  after insertion to the lock the medical device  300  in place in engagement with the spinous process. 
     Win the illustrated embodiment, the barrel  306  includes a first portion  308  (e.g., upper portion  308 ) and a second portion  310  (e.g., lower portion  310 ). The first portion  308  may include a pair of ramped upper sidewalls  312 . The ramped upper sidewalls  312  may include ramped portions  316  on either end of the ramped sidewalls  314 . The second portion  312  may also include a pair of ramped lower sidewalls  314 . The ramped lower sidewalls  314  may include ramped portions  318  on either end. As best seen in  FIG.  51   , the ramped lower sidewalls  314  and the ramped upper sidewalls  312  may overlap when the medical device  10  is collapsed. The ramped upper sidewalls  312  and the ramped lower sidewalls  314  may define a central chamber in the barrel  306 . The central chamber  315  may be used for the packing of bone graft material following the insertion and placement of the medical device  10  in a patient. In one implementation, after the barrel  306  has been expanded, the barrel  306  may be packed with bone graft using the central chamber  315 . In this manner, the central chamber  315  may provide for a larger grafting area and may be packed after expansion of the barrel  306 . 
     The central barrel  306  is an expandable barrel that may be in a collapsed position for insertion into a patient in the interspinous space without resistance and then expanded up to the barrel&#39;s maximum height. In one example implementation, the maximum expanded height of the barrel may be about 4 mm greater than the collapsed height or, alternatively, about 6 mm greater than the collapsed height. The central barrel  306  may provide interspinous distraction and may offload the forces of the spikes  328 ,  362  on the plates  302  and  304  to reduce the chances of breaking a spinous process. The barrel  306  may be inserted, laterally or posteriorly, in a smaller height and then expanded to provide distraction, eliminating forces on the spinous process and potential frustration for a surgeon performing the implantation. 
     The first plate  302  may include an upper portion  320  and a lower portion  322 . The upper portion  320  of the first plate  302  may extend generally vertically from the first portion  308  of the barrel  306 . The upper portion  320  may be integrally formed with the first portion  308 . The lower portion  322  of the first plate  302  may extend from the second portion  310  of the barrel  306  in a direction generally opposite to the upper portion  320 . The lower portion  322  may be integrally formed with the second portion  310 . The first plate  302  may be shaped in a lordotic profile to match the lumbar anatomy. 
     The first plate  302  may include a spike assembly  324  on both the upper portion  320  and the lower portion  322 . The spike assemblies  324  may each be received within an opening  326  in both the upper portion  320  and the lower portion  322 . Each spike assembly  324  may include multiple projections (e.g., spikes  328 ) that extend from a spike sphere  330 . The spike spheres  330  may each be a complete sphere, hemisphere, or a spheric section. Each spike assembly  324  may further comprise a wedge  332  and a post  334 . The wedge  332  may be secured onto the post  334  with the spike sphere  330  fit onto the wedge  332  over the post  334 . A pin (not shown) may be used in the opening  326  to prevent rotation of the spike sphere  330  in the opening  326  while allowing articulation of the spike sphere  330  with respect to the first plate  302 . Slots  336  may be disposed in the spike sphere  330 , as best seen on  FIG.  49   . 
     While the term “spikes” may be used for the projections other types of projections may be used that may have a more tapered point or rounded point or other type of ending to the projection. The spikes  328  may be used to attach firmly and bite into the spinous processes above and below an interspinous space. While spike assemblies  324  are shown, other embodiments may include spikes  328  that are integrally formed with the first plate  302 . The spikes  328  may be pyramid shaped with a base portion secured or integrally formed on the spike sphere  330 . The sides of the spikes  328  may extend from the base to form a point in the shape of a pyramid. In other example implementations, the spikes  328  may be formed into other shapes that rise to a point to enable the spike to engage the spinous process. As discussed above, the end of the spikes  328  may include tips other than a point such as, for example, rounded tip, a square tip or other-shaped tip. The example illustration of the medical device  10  includes three (3) spikes  328  on each spike assembly  324  of the first plate  302 . In other example implementations, fewer or more spikes  328  may be included. The first plate  302  and the spikes  328  may be made of titanium. In other implementations, the first plate  302  and the spikes  328  may be made of other biocompatible materials. 
     The medical device  10  may further include an actuator assembly  338  (best seen on  FIG.  50   ) for raising and lowering the first and second portions  308  and  310  of the barrel  306  and, thus, the upper and lower portions  320 ,  322  of the first plate  302 . The actuator assembly  338  may be disposed between the first and second portions  308  and  310  of the barrel  306 . As illustrated, the actuator assembly  338  may comprise a central screw  340 , a front ramped actuator  342  and a rear ramped actuator  344 . The front ramped actuator  342  may be bullet shaped on its front end to facilitate insertion into a patient. The front ramped actuator  342  may have a ramped expansion portion  346  and an extension portion  348 . The ramped expansion portion  346  may be located at a front end of the barrel  306  with the extension portion  348  extending from the ramped expansion portion  346  towards a rear end of the barrel  306 . The central screw  340  may extend through the barrel  306  and engage the extension portion  348 . The first and second portions  308  and  310  of the barrel  306  may slidingly engage the ramped expansion portion  346 . For example, the ramped expansion portion  346  may engage ramped surface  316  of the first and second portions  308  and  310  at a front end of the barrel  306 . The ramped expansion portion  346  may have dovetail connections with the first and second portions  308  and  310 , respectively. The rear ramped actuator  344  may be disposed at a rear end of the barrel  306 . The first and second portions  308  and  310  of the barrel  306  may slidingly engage the rear ramped actuator  344 . For example, the rear ramped actuator  344  may also engage ramped surfaces  316  of the first and second portions  308  and  310  of the barrel. The rear ramped actuator  344  may have dovetail connections with the first and second portions  308  and  310 , respectively. The central screw  340  may extend through the rear ramped actuator  344  to engage the extension portion  348 . 
     Referring to  FIGS.  56 - 58   , an example implementation of the medical device of  FIGS.  49 - 55    is illustrated with the barrel  306  shown in an expanded state. The barrel  306  expands by forcing the first and second portions  308  and  310  vertically outward in a direction away from one another. In this manner, the upper and lower portions  320  and  322  of the first plate  302  are also expanded vertically outward. The barrel  306  contracts by forcing the first and second portions  308  and  310  to contract in a direction toward one another, thus also moving the upper and lower portions  320  and  322  of the first plate  302  together. In some embodiments, the actuator assembly  338  may be used to raise and lower the first and second portions  308  and  310 . By way of example, the central screw  340  may be turned to contract the actuator assembly  338 . The rear ramped actuator  342  may be held in place while the central screw  340  is turned causing the front ramped actuator  340  to be drawn toward the rear ramped actuator  342 . The rear ramped actuator  342  and the front ramped actuator  340  may engage the ramped upper sidewalls  312  and the ramped lower sidewalls  314  in the first and second portions  308  and  310  forcing the first and second portions  308  and  310  to expand from a collapsed position. A counter rotation of the central screw  340  may cause the front ramped actuator  340  and the rear ramped actuator  342  to separate causing the first and second portions  308  and  310  to collapse from the expanded state. 
     Referring to  FIGS.  59 - 62   , assembly of the barrel  306  of the medical device  300  shown on  FIGS.  49 - 58    will now be described according to an example implementation. As illustrated by  FIG.  59   , the barrel  306  may comprise a first portion  308  and a second portion  310 . The first plate  302  may be defined by upper portion  320  and lower portion  322 . Upper portion  320  may extend from first portion  308  of the barrel  306 , and lower portion  322  may extend in an opposite direction from second portion  310  of the barrel  306 . As further illustrated by  FIG.  59   , the actuator assembly  338  may comprise a central screw  340 , a front ramped actuator  342 , and a rear ramped actuator  344 . In  FIG.  60   , the rear ramped actuator  344  may be slid onto the first portion  308  of the barrel  306 . As illustrated, the rear ramped actuator  344  may be engage (e.g., through a dovetail connection) a rear end of the upper ramped sidewalls  312  of the first portion  308 . In  FIG.  61   , the front ramped actuator  342  may then the slide onto the second portion  310  of the barrel  306 . As illustrated, the ramped expansion portion  346  may engage (e.g., through a dovetail connection) a front end of the lower ramped sidewalls  314  of the second portion  310 . In  FIG.  62   , the first portion  308  and second portion  310  of the barrel  306  have been placed together in a contracted position with a front end of the upper ramped sidewalls  312  engaging the ramped expansion portion  346  and a rear end of the lower ramped sidewalls  314  engaging the rear ramped actuator  344 . 
     Referring to  FIGS.  63 - 65   , assembly of the spike assemblies  324  of the medical device  300  shown on  FIGS.  49 - 58    will now be described according to an example implementation. As illustrated by  FIG.  63   , the spike assemblies  324  each comprise a spike sphere  330 , a wedge  332 , and a post  334 . In  FIG.  64   , the post  334  may be inserted into the wedge  332  coupling the post  334  and the wedge  332 . The wedge  332  may be secured onto one end of the post  334 . Each assembly of the post  334  and wedge  332  may then be placed into the opening  326  in the upper and lower portions  320  and  322  of the first plate  302 . The spike sphere  330  may then be placed onto the other end of the post  334 , which may be then pressed back into the open  326 , as seen in  FIG.  65   . In one embodiment, a snap connection may secure the spike sphere  330  the post  334 . A pin (not shown) may be used in the opening  326  to prevent rotation of the spike sphere  330  assembly  324  in the opening  326  while allowing articulation of the spike sphere  330  with respect to the first plate  302 . In some embodiments, slots  336  in the spike sphere  330  allow the spike sphere  330  to expand and collapse. To lock the spike sphere  330  in a particular orientation, the wedge  332  may be compressed further into the opening  326  causing the spike sphere  330  to expand outward and lock. 
     Referring to  FIGS.  49  and  66 - 67   , the second or locking plate  304  will now be described in more detail with respect to one example implementation.  FIG.  49    is a perspective view of the medical device  10  with the locking plate  304 .  FIGS.  66  and  67    are side and front views, respectively, of the locking plate  304 . The locking plate  304  may be inserted onto the central screw  340  after the barrel  306  has been expanded to lock the barrel  306  in position. 
     As illustrated, the locking plate  304  may comprise an upper portion  350  and a lower portion  352 . A central portion  354  may connection the upper portion  350  to the lower portion  352 . The upper portion  350 , lower portion  352 , and central portion  354  may be integrally formed as a single plate component. The central portion  354  includes an opening (e.g., a central opening) to receive trunion assembly  356  (best seen on  FIG.  67   ). The locking plate  304  may rotate about the trunion assembly  356  and can be locked at various angles at any position within its range of motion. In some embodiments, the trunion assembly  356  may be configured so that the locking plate  304  rotates about its center. The locking plate  304  may include a spike assembly  358  on both the upper portion  350  and the lower portion  352 . The spike assemblies  358  may each be received within an opening in both the upper portion  350  and the lower portion  352  of the locking plate  304 . Each spike assembly  358  may comprise a spike sphere  360  having multiple projections, such as spikes  362 . Each spike assembly  358  may further comprise a wedge  364  and a post  366 . The spike assemblies  358  and its various components may be similar in function and assembly to the spike assembly  324  of the first plate  302  discussed above with respect to  FIGS.  49 - 58  and  63 - 65   . 
     With additional reference to  FIGS.  68  and  69   , the trunion assembly  356  will described in more detail with respect to one example implementation. As illustrated, the trunion assembly  356  may comprise a housing  368 . The housing  368  may have laterally extending projections  370  for rotatably coupling the trunion assembly  368  to the central portion  354  of the locking plate  304  while allowing the locking plate  304  to rotate with respect to the trunion assembly  368 . As illustrated, there may be a pair of projections  370  that extend from opposite sides of the housing  368  and are each received in corresponding openings  372  in the central portion  354 . The housing  368  may further have a through bore  374  for receiving the central screw  340 . The housing  368  may further comprise a pair of chambers  376  on either side of the through bore  374 . The housing  368  may further include a ratchet pawl  378  in each chamber  376 . Embodiments of the ratchet pawls  378  may be spring loaded so that the ratchet pawls  378  may maintain contact with the central screw  340  while the locking plate  304  rotates about the trunion assembly  368 . The ratchet pawls  378  may be assembled from the side of the housing  368 . The ratchet pawls  378  may each have spring cuts to allow the ratchet pawls  378  to compress further into the chambers  376 . The spring cuts may be the height of an electric discharge machining wire to create a small gap within each leaf of the ratchet pawls  378  being self-limiting as it collapses upon itself. Insertion of the central screw  340  into the through bore  374  (e.g., from right to left of  FIG.  68   ) should cause the teeth (or threading) of the central screw  340  to engage the ratchet pawls  378  causing the ratchet pawls  378  to recess into the chambers  376 . The angling of the teeth on the ratchet pawls  378  should resist backwards motion of the central screw  340  after insertion into the through bore  374 . In this manner, the ratchet pawls  378  may be operable to secure the trunion assembly  368  and thus the locking plate  304  onto the central screw  340 . 
       FIG.  70    illustrates a tube  380  that can be used to release the ratchet pawls  378  in accordance one example implantation. The tube  380  may be sized to fit over the central screw  340 . The tube  380  may be advanced over the central screw  340  and into the back end of the through bore  374  until the leading end or nose  382  of the tube  380  engages the ratchet pawls  378 . Pressure from the tube  380  combined with large chamfers on the ratchet pawls should cause the ratchet pawls  378  to compress. When fully inserted, the tube  380  includes one or more teeth  384  configured to snap into the ratchet pawls  378  allowing complete release of the central screw  340 . 
     As illustrated by  FIGS.  68  and  69   , the housing  368  may have an upper surface  386  and a lower surface  388 . In embodiments, the upper and lower surfaces  386  and  388  may each be curved. As illustrated, the upper and lower surfaces  386  and  388  may be sloped inward from the rear to the front of the housing  368 . In some embodiments, the upper and lower surfaces  386  and  388  may each comprise a projection  390 . The projection  390  may engage the locking plate  304  to limit its rotation about the trunion assembly  356 . 
     Referring to  FIGS.  71 - 75   , assembly of the locking plate  304  shown on  FIGS.  66  and  67    will now be described according to an example implementation. As illustrated by  FIG.  71   , the locking plate  304  may comprise an upper portion  350 , a lower portion  352 , and a central portion  354  coupling the upper portion  350  and the lower portion  352 . The trunion assembly  356  may comprise a housing  368  and a pair of ratchet pawls  378 . The housing  368  may comprise a pair of windows  392  for receiving the ratchet pawls  378  into chambers  376  ( FIG.  68   ). The ratchet pawls  378  may be inserted into the housing  368  from the side via windows  392 , as shown on  FIG.  72   . The trunion assembly  356  comprising the housing  368  having the ratchet pawls  378  disposed therein may then be inserted into the opening in the central portion  354  of the locking plate  302 , as best seen in  FIG.  73   . The trunion assembly may comprise projections  370  that are received in openings  372  in the central portion  354  to secure the trunion assembly  356  in the central portion  354 . The projections  370  may be chamfered or otherwise angled on their leading edges to allow insertion into the openings  372 . The plate assemblies  358  may then inserted into the upper portion  350  and lower portion  352  of the locking plate  304 . In embodiments, the spike assemblies  358  may be assembled and inserted into the locking plate  304  in a manner similar to that discussed above with respect to  FIGS.  63 - 65   . 
     As previously mentioned, the locking plate  304  may be free to rotate about the trunion assembly  356  even where the trunion assembly  356  is in engagement with central screw  340 .  FIG.  74    is a side view of the locking plate  304  illustrating rotation of the locking plate  304  according to one example implementation. Additionally, the spike spheres  360  may also be free to articulate with respect to the locking plate  304 .  FIG.  74    illustrates articulation of the spike spheres  360  in accordance to one example implantation. Rotation of the locking plate  304  and/or articulation of the spike spheres  360  can provide an adaptable medical device  10  that can accommodate variances in spinous process geometry, for example, with the goal of anterior and secure placement. 
     An embodiment for using the medical device  300  will now be described in accordance with one example implementation. For example, a method may comprise inserting the barrel  306  of the medical device  300  into an interspinous space. The method may further comprise expanding the barrel  306  from a collapsed form having a first height to an expanded form having a second height, where the second height is greater than the first height. As discussed above, the central screw  340  may be rotated to expand the barrel  306  from a collapsed form to an expanded form in the interspinous space. The process may further include inserting the locking plate  304  onto the central screw  340  and moving the locking plate  304  towards the first plate such that the locking plate  304  and the first plate  302  engage a spinous process. The locking plate  304  may be free to rotate about its center (e.g., the trunion assembly  356 ) to accommodate spinous process geometry. In addition, the spike spheres  324  and  360  of the first plate  302  and the locking plate  304 , respectively, may also be free to articulate for accommodation of spinous process geometry. The spike spheres  324  and  360  may be locked into place during compression into the spinous process. 
     The various components of the medical device  10 , medical device  100 , and medical device  300  described herein can be formed with any biocompatible material used for such a medical device. For example, each of the various components can be formed with one or more biocompatible plastics and/or one or more biocompatible metals such as, for example, titanium and stainless steel. 
     While certain features of the described implementations have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the scope of the embodiments. It should be understood that they have been presented by way of example only, not limitation, and various changes in form and details may be made. Any portion of the apparatus and/or methods described herein may be combined in any combination, except mutually exclusive combinations. The embodiments described herein can include various combinations and/or sub-combinations of the functions, components and/or features of the different embodiments described.