Abstract:
An interspinous implant includes a spacer having an upwardly facing concave saddle and a downwardly facing concave saddle. The lateral sides of the implant are pulled inward to force the saddles vertically away from each other, thereby increasing the effective height of the implant. In one version, a strap extends circumferentially around the anterior and posterior surfaces of the spacer, such that tightening the strap causes the saddles to move away from each other. In another version, the spacer includes a first outwardly facing convex segment disposed on a first lateral side of the saddles and a second outwardly facing convex segment disposed on a second lateral side of the saddles. A rod extends between the first and second convex segments and is fixed to the first convex segment and movable relative to the second convex segment.

Description:
BACKGROUND 
     The present invention relates to an expandable device for insertion between anatomical structures and a procedure utilizing same. 
     It is often desirable to insert a device between anatomical structures for several reasons. For example, it can be inserted between two structures in a manner so that it engages the structures and serves as an implant for stabilizing the structures and absorbing shock. Alternately, a device can be temporarily inserted between the structures and function to distract the structures to permit another device, such as a prosthesis, to be implanted between the structures. According to another example, a device can be inserted between the structures and distract the structures to permit another surgical procedure to be performed in the space formed by the distraction, after which the device is released and removed. 
     Although devices have been designed for one or more of the above uses they are not without problems. For example, it is often difficult to insert the device without requiring excessive invasion of the anatomy, damage to the adjacent anatomical structures, or over-distraction. Embodiments of the present invention improve upon these techniques, and various embodiments of the invention may possess one or more of the above features and advantages, or provide one or more solutions to the above problems existing in the prior art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevational view of an adult human vertebral column. 
         FIG. 2  is a posterior elevational view of the column of  FIG. 1 . 
         FIG. 3  is an elevational view of one of the vertebrae of the column of  FIGS. 1 and 2 . 
         FIG. 4A  is a plan view of a device for insertion in the column of  FIGS. 1-3 . 
         FIG. 4B  is a view similar to that of  FIG. 4A  but depicting the device of  FIG. 4A  in an expanded condition. 
         FIG. 5A  is an enlarged, partial, isometric view of a portion of the column of  FIGS. 1 and 2 , including the lower three vertebrae of the column, with the device of  FIG. 4A  inserted between two adjacent vertebrae. 
         FIG. 5B  is a view similar to that of  FIG. 4A , but depicting the inserted device of  FIG. 5A  in its expanded condition of  FIG. 4B . 
         FIGS. 6A and 6B  are views similar to those of  FIGS. 4A and 4B  respectively, but depicting an alternate embodiment. 
         FIGS. 7A and 7B  are views similar to those of  FIGS. 4A and 4B  respectively, but depicting an alternate embodiment. 
         FIGS. 8A and 8B  are views similar to those of  FIGS. 4A and 4B  respectively, but depicting an alternate embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIGS. 1 and 2 , the reference numeral  10  refers, in general, to a human vertebral column  10 . The lower portion of the vertebral column  10  is shown and includes the lumbar region  12 , the sacrum  14 , and the coccyx  16 . The flexible, soft portion of the vertebral column  10 , which includes the thoracic region and the cervical region, is not shown. 
     The lumbar region  12  of the vertebral column  10  includes five vertebrae V 1 , V 2 , V 3 , V 4  and V 5  separated by intervertebral discs D 1 , D 2 , D 3 , and D 4 , with the disc D 1  extending between the vertebrae V 1  and V 2 , the disc D 2  extending between the vertebrae V 2  and V 3 , the disc D 3  extending between the vertebrae V 3  and V 4 , and the disc D 4  extending between the vertebrae V 4  and V 5 . 
     The sacrum  14  includes five fused vertebrae, one of which is a superior vertebrae V 6  separated from the vertebrae V 5  by a disc D 5 . The other four fused vertebrae of the sacrum  14  are referred to collectively as V 7 . A disc D 6  separates the sacrum  14  from the coccyx  16 , which includes four fused vertebrae (not referenced). 
     With reference to  FIG. 3 , the vertebrae V 5  includes two laminae  20   a  and  20   b  extending to either side (as viewed in  FIG. 2 ) of a spinous process  22  that extends posteriorly from the juncture of the two laminae. Two transverse processes  24   a  and  24   b  extend laterally from the laminae  20   a  and  20   b , respectively. Two articular processes  26   a  and  26   b  extend superiorly from the laminae  20   a  and  20   b  respectively, and two articular processes  28   a  and  28   b  extend inferiorly from the laminae  20   a  and  20   b , respectively. The inferior articular processes  28   a  and  28   b  rest in the superior articular process of the vertebra V 2  to form a facet joint. Since the vertebrae V 1 -V 4  are similar to the vertebrae V 5 , and since the vertebrae V 6  and V 7  are not involved in the present invention, they will not be described in detail. 
     It will be assumed that, for one or more of the reasons set forth above, the vertebrae V 4  and V 5  are not being adequately supported by the disc D 4 , and that it is therefore necessary to provide supplemental support and stabilization of these vertebrae. To this end, and referring to  FIGS. 4A and 4B , a device according to an embodiment of the invention is shown, in general, by the reference numeral  40  and, for the purposes of example, is shown inserted between the spinous processes  22  of the vertebrae V 4  and V 5 . 
     The device  40  consists of an enclosed frame  42  formed by four rod-like members  42   a - 42   d . The members  42   a  and  42   b  are generally V-shaped and extend opposite one another and the members  42   c  and  42   d  are generally V-shaped and extend opposite one another. The member  42   a  extends between the corresponding ends of the members  42   c  and  42   d , and the member  42   b  extends between the other ends of the members  42   c  and  42   d . Preferably, the corresponding ends of the members  42   a - 42   d  are formed integrally and a notch is formed between their respective ends to permit slight pivotal movement between the members. 
     Each member  42   a - 42   d  is generally V-shaped, with a notch being formed at the apex of the V to permit pivotal movement. As a result of their V-shaped configuration, each member  42   a  and  42   b  defines a saddle for receiving a process  22 . 
     A retaining member, in the form of a cable tie, or an adjustable strap,  44  extends around the frame  42  and is oriented in the above-mentioned horizontal plane, i.e., in a direction transverse to the axis of the vertebral column  10  ( FIGS. 1 and 2 ). In  FIG. 8A , the tie  74  is relatively loose around the members  42   c  and  42   d , and, when tightened, linear forces are applied to the members in the directions shown by the arrows in  FIG. 4A  as will be described in detail. It is understood that the linear forces exerted by the tie  74  can be adjusted in small increments in the same manner as a conventional cable tie, or by any other appropriate retaining device (not shown). 
     The device  40  is initially inserted between the processes  22  with the tie  74  loosely fitting around the frame  42  as shown in  FIGS. 4A and 5A . In this position the device  40  easily fits between the processes  22 , and the processes generally extend in the above-mentioned saddles in a relatively loose arrangement, i.e., they are not pressed against the device with any appreciable force. The surgeon then tightens the tie  44  around the members  42   c  and  42   d  as needed to apply an inwardly-directed linear, compressive force to the frame  42  in a plane transverse to the axis of the frame  42 , i.e., in the directions shown by the arrows in  FIG. 4A . 
     This causes an articulation, or pivotal movement, of the members  42   a - 42   d  about the notches discussed above, and the frame  42  is deformed to the position of  FIG. 4B . This selective deformation causes the dimension of the frame  42  in a plane transverse to the axis of the vertebral column  10 , i.e., a horizontal plane as viewed in the drawings, to be decreased, while its dimension in the plane of the latter column, i.e., a vertical plane, is increased. Thus, the surfaces of the members  42   a  and  42   b  defining the saddles press against the process  22  with sufficient force to lock, or retain, the device  40  in the inserted position which is similar to the inserted position of the device  40  shown in  FIG. 5B . 
     The presence of the device  40  prevents the collapse of the intervertebral space between the adjacent vertebrae and thus stabilizes the vertebral column  10 . The flexible nature of the device  40  does not cause any damage to the processes  22  and absorbs shock that contributes to the dynamic stabilization of the vertebral column  10 . 
     It can be appreciated that the tie  44  is strong enough to apply the force in the manner described above and to overcome the resistance of the frame  42  to cause the above movement. Therefore, after the device  40  has been implanted in accordance with the above, it will stretch in response to movement of the anatomical structures, such as the processes in the above example, towards each other in response to certain movements of the patient, such as when he or she bends over. In this case, the device  40  can move back from its position shown in  FIGS. 4B and 5B  towards the position of  FIGS. 4A and 5A . Then, after the above movement on part of the patient, the tie  44 , and therefore the frame  42 , would move back to their normal position of  FIGS. 4B and 5B . Alternately, the tie  44  can be relatively rigid (as opposed to stretchable) and the frame members  42   a - 42   d  can be stretchable so as to move in response to the above movement of the anatomical structures. 
     Is also understood the device  40  does not necessarily have to function as an implant as described in the example above, but rather can be used in other different procedures. For example, it can be inserted between the structures, and vertically expanded to an extent that it engages and distracts, or moves, the structures in a direction away from each other, to permit another device, such as a prosthesis, to be implanted between the structures or in an area near the structures. According to another example, the device  40  can be inserted between the structures and vertically expanded to an extent that it engages and distracts the structures to permit another surgical procedure to be performed in the space formed by the distraction. In each of these examples the device  40  would be released and removed after the procedure is completed. 
     With the exception noted below, the embodiment of  FIGS. 6A and 6B  is identical to that of  FIGS. 4A and 4B  and includes components of the latter embodiment, which components are given the same reference numerals. 
     According to the embodiment of  FIGS. 6A and 6B , a device  50  is provided that is identical to the device  40  of the embodiment of  FIGS. 4A and 4B , with the exception that the tie  74  of the latter embodiment is replaced by a cable  54  that extends over and around the members  42   c  and  42   d  of the frame  42 . The end portions of the cable  54  extend through a retaining device  56  to enable the cable to be tightened as necessary to apply linear compressive forces to the frame as shown by the arrows in  FIG. 6A , and held in this tightened position. 
     The device  50  is initially inserted between the processes  22  with the cable  54  loosely fitting around the member  42  as shown in  FIG. 6A . In this position, the device  50  easily fits between the processes  22 , and the processes generally extend in the saddles defined by the members  42   a  and  42   b  in a relatively loose arrangement, i.e., they are not pressed against the device with any appreciable force. The surgeon then tightens the cable  54  to cause an articulation, or pivotal movement, of the members  42   a - 42   d  about the notches discussed above in the directions shown by the arrows in  FIG. 7A , and the frame  42  is deformed to the position of  FIG. 7B . 
     This selective deformation causes the dimension of the frame  42  in a plane transverse to the axis of the vertebral column  10  to be decreased, while its dimension in the plane of the latter column is increased. Thus, the surfaces of the members  42   a  and  42   b  defining the saddles press against the processes  22  with sufficient force to lock or retain the device  50  in the inserted position which is similar to the inserted position of the device  40  shown in  FIG. 5B . 
     The presence of the device  50  prevents the collapse of the intervertebral space between the adjacent vertebrae and thus stabilizes the vertebral column  10 . The flexible nature of the device  50  does not cause any damage to the processes  22  and absorbs shock that contributes to the dynamic stabilization of the vertebral column  10 . 
     It can be appreciated that the cable  54  is strong enough to apply the force in the manner described above and to overcome the resistance of the frame  42  to cause the above movement. However, the cable  54  can also have some stretchability, not unlike that of a strong rubber band. Therefore, after the device  50  has been implanted in accordance with the above, it will stretch in response to movement of the anatomical structures, such as the processes in the above example, towards each other in response to certain movements of the patient, such as when he or she bends over. In this case, the device  50  can move back from its position shown in  FIG. 6B  towards the position of  FIG. 6A . Then, after the above movement on part of the patient, the cable  54 , and therefore the frame  42 , would move back to their normal position of  FIG. 6B . Alternately, the cable  54  can be relatively rigid (as opposed to stretchable) and the frame members  42   a - 42   d  can be stretchable so as to move in response to the above movement of the anatomical structures. 
     It is also understood the device  50  does not necessarily have to function as an implant as described in the example above, but rather can be used in other different procedures. For example, it can be inserted between the structures, and vertically expanded to an extent that it engages and distracts, or moves the structures in a direction away from each other, to permit another device, such as a prosthesis, to be implanted between the structures or in an area near the structures. According to another example, the device  50  can be inserted between the structures and vertically expanded to an extent that it engages and distracts the structures to permit another surgical procedure to be performed in the space formed by the distraction. In each of these examples the device  40  would be released and removed after the procedure is completed. 
     The embodiment of  FIGS. 7A and 7B  is identical to that of  FIGS. 4A and 4B  and includes components of the latter embodiment, which components are given the same reference numerals. 
     According to the embodiment of  FIGS. 7A and 7B , a device  60  is provided that is identical to the device  50  of the embodiment of  FIGS. 6A and 6B , with the exception that the tie  54  of the latter embodiment is replaced by a bolt  64  and a nut  66 . The bolt  64  extends from the member  42   d  and through the member  42   c , and the nut  66  extends outside the frame  42  and is threaded on the threaded end portion of the bolt. Thus, when torque is applied to the nut  66  to tighten it over the bolt  64 , an inwardly-directed linear force is applied to the frame  42  in the directions shown by the arrows in  FIG. 7A , i.e., in a plane transverse to the axis of the frame  42 . 
     The device  60  is initially inserted between the processes  22  in the position shown in  FIG. 8A , with the bolt  64  and the nut  66  exerting little, or no force on the frame  42 . In this position the device  60  easily fits between the processes  22  and the processes generally extend in the saddles formed by the frame members  42   a  and  42   b  in a relatively loose arrangement, i.e., they are not pressed against the member with any appreciable force. 
     The surgeon then tightens the nut  66  on the bolt  64 , creating a linear compressive force in the directions shown by the arrows in  FIG. 7A , sufficient to cause an articulation, or pivotal movement, of the members  42   a - 42   d  about the notches discussed above. This selective movement causes the dimension of the frame  42  in a plane transverse to the axis of the vertebral column  10  to be decreased, while its dimension in the plane of the latter column is increased. Thus, the surfaces of the members  42   a  and  42   b  defining the above-mentioned saddles press against the processes  22  with sufficient force to lock or retain the device  60  in the position of  FIG. 7B  which is similar to the inserted position of the device  50  shown in  FIG. 5B . 
     The presence of the device  60  prevents the collapse of the intervertebral space between the adjacent vertebrae and thus stabilizes the vertebral column  10 . The flexible nature of the device  60  does not cause any damage to the processes  22  and absorbs shock that contributes to the dynamic stabilization of the vertebral column  10 . 
     It is understood that the frame members  42   a - 42   d  can also have some stretchability, as discussed above, so as to permit movement of the anatomical structures, such as the processes in the above example, towards each other in response to certain movements of the patient, such as when he or she bends over. Therefore, after the device  60  has been implanted in accordance with the above, the frame  42  will stretch in response to the load caused by the above movement of the anatomical structures, so that the device can move somewhat from its position shown in  FIG. 7B . After the above movement, the frame  42 , would move back to its normal position of  FIG. 7B . 
     It is also understood the device  60  does not necessarily have to function as an implant as described in the example above, but rather can be used in other different procedures. For example, it can be inserted between the structures, and vertically expanded to an extent that it engages and distracts, or moves the structures in a direction away from each other, to permit another device, such as a prosthesis, to be implanted between the structures or in an area near the structures. According to another example, the device  60  can be inserted between the structures and vertically expanded to an extent that it engages and distracts the structures to permit another surgical procedure to be performed in the space formed by the distraction. In each of these examples the device  40  would be released and removed after the procedure is completed. 
     Referring to  FIGS. 8A and 8B , an intervertebral disc prosthetic device according to an embodiment of the invention is shown, in general, by the reference numeral  70  and is also designed to be inserted between two anatomical structures, such as the spinous processes  22  of the vertebrae V 4  and V 5 . The device  70  consists of a member  72  having a generally rectangular shape with two end walls  72   a  and  72   b , two side walls  72   c  and  72   d , an upper wall  72   e  and a lower wall (not shown). The member is fabricated from a material that is characterized by the following. 
     The side walls  72   c  and  72   d  are relatively stiff so as to resist any deformation when a load is applied to the walls, as will be described. The two end walls  72   a  and  72   b  are relatively flexible so that they can expand in a manner to be described. The upper wall  72   e  and the opposite lower wall (not shown) are adapted to contract in a horizontal plane, as viewed in the drawings in the direction indicated by the arrows in  FIG. 8A , but are adapted to resist any expansion and contraction in a vertical plane extending perpendicular to the latter horizontal plane. This can be achieved in many ways, such as by adding relatively strong fibers in the material of the member  72  and orienting the fibers in a manner to permit the above contraction and resistance, or by forming the upper wall  72   e  and the lower wall with vertically extending bellows. 
     A retaining member, in the form of a cable tie, or an adjustable strap,  74  extends around the member  72  and is oriented in the above-mentioned horizontal plane, i.e., in a direction transverse to the axis of the vertebral column  10  ( FIGS. 1 and 2 ). In  FIG. 8A , the tie  74  is relatively loose around the frame  42 , and, when tightened, a radial force is applied to the member in the direction shown by the arrows in  FIG. 4A  to move the member  72  to a vertically expanded position, such as the one shown in  FIG. 8B . It is understood that the radial force exerted by the tie  74  can be adjusted in small increments in the same manner as a conventional cable tie, or by any other appropriate retaining device (not shown). 
     Thus, when the tie  74  is tightened around the member  72 , the relatively stiff walls  74   c  and  74   d , the relatively flexible walls  72   a  and  72   b , the wall  72   e  and the lower wall (not shown) opposite the wall  72   c  causes the member to expand in a vertical plane and contract in a horizontal place, as viewed in the drawings, as it moves from its position of  FIG. 8A  to the position of  FIG. 8B . Thus, the member  72  responds in a manner similar to that of the frame  42  in the previous embodiments as it moves to the position of  FIG. 8B , in which it prevents the collapse of the intervertebral space between the adjacent vertebrae and thus stabilizes the vertebral column  10 . The flexible nature of the device  70  absorbs shock which contributes to the dynamic stabilization of the vertebral column  10 . 
     It can be appreciated that the tie  74  is strong enough to apply the force in the manner described above and to overcome the resistance of the member  42  to cause the above movement. However, the tie  74  can also have some stretchability, not unlike that of a strong rubber band. Therefore, after the device  70  has been implanted in accordance with the above, it will stretch in response to movement of the anatomical structures, such as the processes in the above example, towards each other in response to certain movements of the patient, such as when he or she bends over. In this case, the device  70  can move back from its position shown in  FIG. 8B  towards the position of  FIG. 8A . Then, after the above movement on part of the patient, the tie  74 , and therefore the member  72 , would move back to their normal position of  FIG. 8B . Alternately, the tie  74  can be relatively rigid (as opposed to stretchable) and the members  72  can be stretchable so as to move in response to the above movement of the anatomical structures. 
     Is also understood the device  70  does not necessarily have to function as an implant as described in the example above, but rather can be used in other different procedures. For example, it can be inserted between the structures, and vertically expanded to an extent that it engages and distracts, or moves the structures in a direction away from each other, to permit another device, such as a prosthesis, to be implanted between the structures or in an area near the structures. According to another example, the device  70  can be inserted between the structures and vertically expanded to an extent that it engages and distracts the structures to permit another surgical procedure to be performed in the space formed by the distraction. In each of these examples the device  40  would be released and removed after the procedure is completed. 
     VARIATIONS 
     It is understood that variations may be made in the foregoing without departing from the invention and examples of some variations are as follows:
         (1) The insertions of the devices  40 ,  50 ,  60  and  70  between the spinous processes, as disclosed above, was disclosed above only for the purpose of example, and it is understood that the devices can be used in connection with other anatomical structures.   (2) The frame in one or more of the above embodiments can be rigid and standard hinges can be provided in place of the notches described above to permit the articulating movement.   (3) The devices  40 ,  50 ,  60  and  70  can be inserted between two vertebrae following a corpectomy in which at least one vertebrae is removed.   (4) Other techniques, such as a ratchet arrangement or a rack and pinion arrangement can be used for applying the forces to the frame  42  and the member  72 .   (5) The frame  42  and the member  72  can be oriented perpendicular to the spinous process rather than parallel as shown in the drawings.   (6) Another member of a different shape can replace the frame  42  or the member  72 .   (7) The particular location of the devices  40 ,  50 ,  60  and  70  in the human anatomy can be varied.   (8) Any spatial references made above, such as “under”, “over”, “between”, “upper”, “lower”, “top”, “bottom”, etc. are for the purpose of illustration only and do not limit the specific orientation or location of the structure described above.       

     The preceding specific embodiments are illustrative of the practice of the invention. It is to be understood, therefore, that other expedients known to those skilled in the art or disclosed herein, may be employed without departing from the invention or the scope of the appended claims, as detailed above. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw are equivalent structures.