Abstract:
A vertebral implant for interposition between first and second vertebral bodies comprises a first component for engaging a vertebral endplate of the first vertebral body and a second component for engaging a vertebral endplate of the second vertebral body. The second component is adapted to articulate with respect to the first component. The implant further includes a first sensor for detecting a first physical parameter and a transmitter coupled to the first sensor. The transmitter is adapted for interposition between the first and second vertebral bodies.

Description:
BACKGROUND  
       [0001]     During the past thirty years, technical advances in the design of large joint reconstructive devices has revolutionized the treatment of degenerative joint disease, moving the standard of care from arthrodesis to arthroplasiy. Progress in the treatment of vertebral disc disease, however, has come at a slower pace. Currently, the standard treatment for disc disease remains discectomy followed by vertebral fusion. While this approach may alleviate a patient&#39;s present symptoms, accelerated degeneration of the adjacent discs is a frequent consequence of the forces induced by fusion. Thus, reconstructing the degenerated intervertebral disc with a functional disc prosthesis to provide motion and to reduce deterioration of the adjacent discs may be a more desirable treatment option for many patients. An better understanding of the physical parameters experienced by the functional disc prosthesis within the intervertebral disc space may help to improve the design of future prostheses.  
       SUMMARY  
       [0002]     In one embodiment of the present disclosure, a vertebral implant for interposition between first and second vertebral bodies comprises a first component for engaging a vertebral endplate of the first vertebral body and a second component for engaging a vertebral endplate of the second vertebral body. The second component is adapted to articulate with respect to the first component. The implant further includes a first sensor for detecting a first physical parameter and a transmitter coupled to the first sensor. The transmitter is adapted for interposition between the first and second vertebral bodies.  
         [0003]     In another embodiment of the present disclosure, a system for gathering diagnostic data about a patient comprises an implant for interposition between a pair of vertebral bodies. The implant comprises at least two surfaces adapted for sliding engagement with each other. The system further includes at least one sensor component coupled to the implant and at least one transmitter component coupled to the at least one sensor device and adapted for implantation between the pair of vertebral bodies. The system further comprises a power supply component associated with the at least one transmitter and a receiver component adapted to receive a communication from the at least one transmitter component.  
         [0004]     In another embodiment, a vertebral implant for interposition between first and second vertebral bodies comprises a vertebral body replacement component for replacing a third vertebral body removed from between the first and second vertebral bodies. The implant further includes at least one sensor for detecting at least one physical parameter and a transmitter coupled to the sensor.  
         [0005]     In another embodiment, a diagnostic system for assessing vertebral joint performance comprises a first sensor engaged with a posterior vertebral bone element for detecting a first physical parameter and a transmitter coupled to the first sensor for transmitting data about the first physical parameter. The system further comprises a receiver in communication with the first sensor for receiving the transmitted data about the first physical parameter.  
         [0006]     In another embodiment, a method for gathering data on the operation of a vertebral implant comprises implanting an articulated disc between a pair of vertebral bodies. The articulated disc comprises a pair of slidably engaged surfaces and is fitted with a) at least one sensor for detecting at least one physical parameter and b) a transmitter coupled to the at least one sensor for communicating data about the at least one physical parameter. The method further comprises supplying power to the at least one sensor and transmitting the data from the transmitter to a receiver. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a side view of a vertebral column.  
         [0008]      FIG. 2  is a diagram of a diagnostic system according to one embodiment of the present disclosure.  
         [0009]      FIG. 3  is an instrumented implant according to one embodiment of the present disclosure.  
         [0010]      FIG. 4  is a flowchart of one embodiment of a method of implementing an instrumented implant for diagnostics.  
         [0011]      FIG. 5  is an instrumented implant according to another embodiment of the present disclosure.  
         [0012]      FIG. 6  is an instrumented implant according to another embodiment of the present disclosure.  
         [0013]      FIG. 7  is an instrumented implant according to another embodiment of the present disclosure.  
         [0014]      FIG. 8  is an instrumented implant according to another embodiment of the present disclosure. 
     
    
     DETAILED DESCRIPTION  
       [0015]     The present invention relates generally to vertebral reconstructive devices, and more particularly, to instrumented vertebral implants. For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments, or examples, illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.  
         [0016]     Referring first to  FIG. 1 , the numeral  10  refers to a vertebral joint which includes an intervertebral disc  12  extending between vertebrae  14 ,  16 . The vertebra  14  includes a vertebral body  14   a,  a spinous process  14   b,  and a caudal articular process  14   c.  The vertebra  16  includes a vertebral body  16   a,  a spinous process  16   b,  and a rostral articular process  16   c.  Another intervertebral disc  18  extends between vertebrae  16  and  20 . The disc  12  may be partially or entirely removed and an intervertebral implant  22  may be inserted between the vertebrae  14 ,  16  to preserve motion within the joint  10 . Although the illustration of  FIG. 1  generally depicts the vertebral joint  10  as a lumbar vertebral joint, it is understood that the devices, systems, and methods of this disclosure may also be applied to all regions of the vertebral column, including the cervical and thoracic regions. Additionally, although the illustration of  FIG. 1  generally depicts an anterior approach for insertion of the implant  22 , other approaches including posterior, posterolateral, lateral, and anterolateral are also contemplated. Furthermore, the devices, systems, and methods of this disclosure may be used in non-spinal orthopedic applications.  
         [0017]     To better understand the specific physical conditions experienced by a vertebral implant, the implant may be instrumented, or fitted with various diagnostic sensors capable of detecting physical parameters. The parameters may, for example, include pressure, linear displacement, angular displacement, torque, velocity, acceleration, temperature, or pH. The data collected from the various sensors can be used to refine the design of a replacement implant or improve the designs of implants for other patients. For example, understanding forces exerted on the implant and the resulting pressure concentrations within the implant may permit design changes that can reduce the weight of the implant and/or localize material strength though material selection or material thickness.  
         [0018]     Referring now to  FIG. 2 , in one embodiment, a system  30  for analyzing physical parameters within a vertebral column may include an implant  32  which may be used as the prosthesis  22  of  FIG. 1 . The implant  32  may include sensors  34 - 36  coupled to a biotelemetry transmitter  40 . Multiple sensors  34 - 36  may be used to measure multiple physical parameters simultaneously. For example, sensor  34  may measure shear loading, sensor  36  may measure compressive loading, and sensor  38  may measure motion across the disc space. Although the sensors are depicted as incorporated into the implant, it is understood that sensors may also be located at other positions either internal or external to the patient. Using a sensor both in the implant and in a remote location in the patient may allow the system to capture differential motion, for example.  
         [0019]     Referring now to  FIG. 3 , in one embodiment the implant  32  may be an articulated disc implant  42  similar to the implant disclosed in U.S. patent application Ser. No. 09/924,298, entitled “Implantable Joint Prosthesis” and incorporated herein by reference. Although described in more detail in the referenced application, the implant  42  generally includes opposing endplate components  44 ,  46  between which a central body  48  may articulate. The endplate component  44  includes an exterior surface  50  and an interior articulating surface  52 . In this embodiment, the interior surface  52  may be relatively smooth and may have a mirror surface finish. The endplate component  46  may have an exterior surface  55  and an interior articulating surface  56 . The interior surface  56  may also be relatively smooth and may have a mirror surface finish. The surfaces  52 ,  56  may be treated with any of various techniques to improve wear resistance such as ion-implantation, diamond or diamond-like coating, or other methods that make the surface harder than the original surface.  
         [0020]     The implant  42  may also include sensors  53 , corresponding to sensors  34 - 38  of the system  30  for detecting physical parameters. The implant  42  may further include a transmitter  54  which may be electrically coupled to the sensors  53 . The transmitter  54  may correspond to the transmitter  40  of system  30 . It is understood that additional components such as power components, memory components, or a central processing unit (CPU) may be incorporated the implant as needed. The location of the sensors  53  in  FIG. 3  is merely exemplary, and it is understood that the sensors may be located at any position in or on the implant  42  to monitor a desired physical parameter. Physical parameters that may be monitored include, for example, pressure, linear displacement, angular displacement, torque, velocity, acceleration, temperature, or pH.  
         [0021]     A pressure sensor may, for example, use Wheatstone bridge based strain gauge technology. Alternative pressure sensors may include inductive or capacitive measurement systems. A linear displacement sensor may, for example, use linear variable differential transformer (LVDT) technology to measure linear displacements. Likewise, an angular displacement may, for example, use rotational variable differential transformer (RVDT) technology to measure angular displacement. An acceleration sensor may, for example, include an accelerometer. It is understood that multiple sensors of various types may be used in a single implant to measure different physical parameters.  
         [0022]     The central body  48  extends between the interior articulating surfaces  52 ,  56 . The central body  48  may have an inner portion  58  and outer surfaces  60 ,  62 . Although not shown, sensors similar to sensors  53  may be incorporated into the central body  48 . The inner portion  58  may be flexible and formed from one or more resilient materials which may have a lower modulus than the outer surfaces. Suitable materials may include polymeric elastomers such as polyolefin rubbers; polyurethanes (including polyetherurethane, polycarbonate urethane, and polyurethane with or without surface modified endgroups); copolymers of silicone and polyurethane with or without surface modified endgroups; silicones; and hydrogels. Polyisobutylene rubber, polyisoprene rubber, neoprene rubber, nitrile rubber, and/or vulcanized rubber of 5-methyl-1,4-hexadiene may also be suitable. In an alternative embodiment, the inner portion  58  may be rigid and formed of any of the materials described below for the outer surfaces or the endplate components.  
         [0023]     The outer surfaces  60 ,  62  of the central body  48  may also be formed of the resilient and flexible materials described above, but in the alternative, they may be modified, treated, coated or lined to enhance the wear resistant and articulating properties of the core component  48 . These wear resistant and articulation properties may be provided by cobalt-chromium alloys, titanium alloys, nickel titanium alloys, and/or stainless steel alloys. Ceramic materials such as aluminum oxide or alumnia, zirconium oxide or zirconia, compact of particulate diamond, and/or pyrolytic carbon may be suitable. Polymer materials may also be used including any member of the PAEK family such as PEEK, carbon-reinforced PAEK, or PEKK; polysulfone; polyetherimide; polyimide; UHMWPE; and/or cross-linked UHMWPE. Polyolefin rubbers, polyurethanes, copolymers of silicone and polyurethane, and hydrogels may also provide wear resistance and articulation properties. Wear resistant characteristics may also or alternatively be provided to the outer surfaces  60 ,  62  by modifications such as cross-linking and metal ion implantation.  
         [0024]     The endplate components  44 ,  46  may be formed of any suitable biocompatible material including metals such as cobalt-chromium alloys, titanium alloys, nickel titanium alloys, and/or stainless steel alloys. Ceramic materials such as aluminum oxide or alumnia, zirconium oxide or zirconia, compact of particulate diamond, and/or pyrolytic carbon may be suitable. Polymer materials may also be used, including any member of the polyaryletherketone (PAEK) family such as polyetheretherketone (PEEK), carbon-reinforced PEEK, or polyetherketoneketone (PEKK); polysulfone; polyetherimide; polyimide; ultra-high molecular weight polyethylene (UHMWPE); and/or cross-linked UHMWPE.  
         [0025]     The exterior surfaces  50 ,  55  may include features or coatings (not shown) which enhance the fixation of the implanted prosthesis. For example, the surfaces may be roughened such as by chemical etching, bead-blasting, sanding, grinding, serrating, and/or diamond-cutting. All or portions of the exterior surfaces  50 ,  55  may receive a coating of a metallic substance which may be applied by sintering or by a spray coating such as a plasma spray. All or a portion of the exterior surfaces  50 ,  55  may also be coated with a biocompatible and osteoconductive material such as hydroxyapatite (HA), tricalcium phosphate (TCP), and/or calcium carbonate to promote bone in growth and fixation. Alternatively, osteoinductive coatings, such as proteins from transforming growth factor (TGF) beta superfamily, or bone-morphogenic proteins, such as BMP2 or BMP7, may be used. Other suitable features may include spikes for initial fixation; ridges or keels to prevent migration in the lateral and anterior direction, for example; serrations or diamond cut surfaces; fins; posts; and/or other surface textures.  
         [0026]     Referring again to  FIG. 2 , the system  30  may further include a power supply unit  70  associated with the transmitter. Although the power supply  70  is depicted as external to the implant  32 , it is understood that in some embodiments all or portions of the power supply may be incorporated into the implant. In one embodiment, the power supply may include a battery pack and a separate radio frequency (RF) signal generator. The battery pack may be coupled to the implant  32  and implanted in the patient. The RF generator may be located externally of the patient and can be used to selectively activate the sensors and transmitter. The battery pack may, for example, power a switch for the sensors and transmitter, and the RF signal generator may activate the switch. An alternative to a battery based power supply unit may be an inductive power system. The sensors and the transmitter may be powered inductively by, for example, an inductive coil fitted externally of the patient on a cervical collar, in the case of a cervical implant. The inductive coil may be located in a torso belt in the case of a lumbar implant.  
         [0027]     The system  30  may further include a receiver  72  in communication with the transmitter  40 . The transmitter  40  and the receiver  72  may communicate data about the physical parameters detected by the sensors  34 - 38  through the use of RF signals, however alternative wired or wireless techniques may be used. The receiver  72  may monitor and record the RF signals while attached externally to the patient on, for example, a cervical collar in the case of a cervical implant. A torso belt may be used to position the receiver in the case of a lumbar implant.  
         [0028]     The receiver  72  may be connected to a computer  74  for processing the received data about the physical parameters detected by the sensors  34 - 38 . The computer  74  may, for example include a receiver interface component  76 , a CPU  78 , a memory component  80 , and an input/output device  82 . Although a computer  74  may be directly connected to the receiver  72 , the receiver may also or alternatively be connected via a public or private computer network  84 , such a private intranet or the public internet, to a remote computer  86 . Computer  86  may be configured similarly to the computer  74 .  
         [0029]     Referring now to  FIG. 4 , a process  90  for implementing the system  30  of  FIG. 2  may begin with the step  92  of implanting the implant  32  into the vertebral column. Using an anterior, posterior, posterolateral, lateral, or anterolateral approach, the desired location of the implant may be accessed and the implant installed. For example, using an anterior approach, the articulated disc implant  42  may be implanted into the vertebral joint  10  in the void created by the removed disc  12  such that the exterior surface  50  engages an endplate of the vertebral body  14  and the exterior surface  55  engages an endplate of the vertebral body  16 .  
         [0030]     Proceeding now to step  94 , after the implant  32  is installed, the sensors and transmitters may be powered and calibration and reference measurements may be recorded. At step  96 , the patient may perform an activity such as standing up, bending, walking, or running. At step  98 , the sensors  34 - 38  may detect the physical parameters associated with the performance of the patient&#39;s physical activity. Data associated with the physical parameter may be conveyed to the transmitter. At step  100 , the transmitter  40  may transmit the physical parameter data to the receiver  72 . At step  102 , the physical parameter data may be collected by the computer  74  or  86 . At step  104 , the physical parameter day may be analyzed to evaluate the design and performance of the implant  32 . This procedure  90  may be repeated at various stages of the patient&#39;s recovery to evaluate the function of the implant  32  and/or to monitor the progression of any degenerations such as adherence problems, bone wear, subsidence, or implant misalignment. Analysis of the physical parameters may suggest revisions that may be made to the implant in situ. Alternatively, the collected data may suggest redesign strategies that may be used to prepare a replacement disc or discs for other patients.  
         [0031]     Referring now to  FIG. 5 , the implant  32  for implantation in the vertebral column may be any of a variety of implants. In this embodiment, an articulating implant  110  includes a first articular component  112  and a second articular component  114 . The articular components  112 ,  114  cooperate to form the articulating joint  110 . The articulating joint  110  provides relative pivotal and rotational movement between the adjacent vertebral bodies to maintain or restore motion substantially similar to the normal bio-mechanical motion provided by a natural intervertebral disc. More specifically, the articular components  112 ,  114  are permitted to pivot relative to one another about a number of axes, including lateral pivotal movement and anterior-posterior pivotal movement. The implant may be formed of any of the materials described above for the components  44 ,  46  of implant  42 . This implant  110  may be similar to the implant described in U.S. Pat. No. 6,740,118, entitled “Intervertebral Prosthetic Joint” which is incorporated herein by reference.  
         [0032]     The implant  110  may include fins  116 ,  118  for penetrating the endplates of the adjacent vertebral bodies to enhance fixation. The implant  110  may also include sensors  120  which may correspond to sensors  34 - 38  of the system  30  for detecting physical parameters. The implant  110  may further include a transmitter  122  which may be wired or wirelessly coupled to the sensors  120 . The transmitter  122  may correspond to the transmitter  40  of system  30 . It is understood that additional components such as power components, memory components, a CPU, or additional transmitters may be incorporated the implant as needed. The location of the sensors  120  in  FIG. 3  is merely exemplary, and it is understood that the sensors may be located at any position in or on the implant  110  to monitor a desired physical parameter. Physical parameters that may be monitored include, for example, pressure, linear displacement, angular displacement, torque, velocity, acceleration, temperature, or pH. The implant  110  may be implanted and operated using the method  90  of  FIG. 4 .  
         [0033]     Referring now to  FIG. 6 , an implant  130  may be used following a corpectomy procedure to replace the vertebral body  16  and the adjacent pair of discs  12 ,  18 . In this embodiment, the implant  130  includes a body portion  132  threadedly coupled between two articulating disc implants  134 ,  136 . The implants  134 ,  136  may be similar to implant  42  described above. The body component may be similar to components described in U.S. Pat. No. 5,702,453, entitled “Adjustable Vertebral Body Replacement” and incorporated herein by reference.  
         [0034]     The implant  130  may include sensors  138  which may correspond to sensors  34 - 38  of the system  30  for detecting physical parameters. The implant  130  may further include a transmitter  140  which may be wired or wirelessly coupled to the sensors  130 . The transmitter  140  may correspond to the transmitter  40  of system  30 . The implant  130  may also include a power supply  142  which may be a battery electrically connected to the transmitter  140  and or the sensors  138  It is understood that additional components such as power components, memory components, a CPU, or additional transmitters may be incorporated the implant as needed. The power supply  142 , the transmitter  140 , and/or the sensors  138  may be housed within the body portion  132 . The location of the sensors  138  in  FIG. 3  is merely exemplary, and it is understood that the sensors may be located at any position in or on the implant  130  to monitor a desired physical parameter. Physical parameters that may be monitored include, for example, pressure, linear displacement, angular displacement, torque, velocity, acceleration, temperature, or pH. The implant  130  may be implanted and operated using the method  90  of  FIG. 4 .  
         [0035]     Referring now to  FIG. 7 , an interspinous implant  150  may be installed between spinous processes  14   b,    16   b.  Portions of the implant  150  may be similar to any number of interspinous implants including U.S. Pat. No. 6,626,944, entitled “Interspinous Prosthesis.” The implant  150  may act as a dampener and/or a distraction mechanism to restore or maintain intervertebral height. The implant  110  may also include a diagnostic package  152  which includes sensors corresponding to sensors  34 - 38  of the system  30  for detecting physical parameters. The diagnostic package may further include a transmitter which may be wired or wirelessly coupled to the sensors. The transmitter may correspond to the transmitter  40  of system  30 . It is understood that additional components such as power components, memory components, a CPU, or additional transmitters may be incorporated the implant  150  as needed. It is understood that the sensors may be located at any position in or on the implant  150  to monitor a desired physical parameter. Physical parameters that may be monitored include, for example, pressure, linear displacement, angular displacement, torque, velocity, acceleration, temperature, or pH. The implant  150  may be implanted using a minimally invasive posterior or posterolateral approach. The method of operation described in steps  94 - 104  may be used to perform diagnostic testing using the implant  150 .  
         [0036]     Referring now to  FIG. 8 , a facet implant  160  may be installed to augment or replace portions of the articular processes  14   c,    16   c  and/or the facet capsule located between the articular processes. The implant  160  may include a pair of articulating surfaces  162 ,  164  to restore motion to the facet joint. Portions of the implant  160  may be similar to facet replacement or augmentation systems known in the art. The implant  160  may additionally include sensors  166  corresponding to sensors  34 - 38  of the system  30  for detecting physical parameters. The implant  160  may further include a transmitter which may be wired or wirelessly coupled to the sensors. The transmitter may correspond to the transmitter  40  of system  30 . It is understood that additional components such as power components, memory components, a CPU, or additional transmitters may be incorporated the implant  160  as needed. It is understood that the sensors may be located at any position in or on the implant  160  to monitor a desired physical parameter. Physical parameters that may be monitored include, for example, pressure, linear displacement, angular displacement, torque, velocity, acceleration, temperature, or pH. The implant  160  may be implanted using a minimally invasive posterior or posterolateral approach. The method of operation described in steps  94 - 104  may be used to perform diagnostic testing using the implant  160 .  
         [0037]     In alternative embodiments, the diagnostic implant may be located within a vertebral body or attached to the posterior bony elements at non-joint locations.  
         [0038]     Although only a few exemplary embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this disclosure. Accordingly, all such modifications and alternative are intended to be included within the scope of the invention as defined in the following claims. Those skilled in the art should also realize that such modifications and equivalent constructions or methods do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. It is understood that all spatial references, such as “horizontal,” “vertical,” “top,” “upper,” “lower,” “bottom,” “left,” “right,” “rostral,” “caudal,” “upper,” and “lower,” are for illustrative purposes only and can be varied within the scope of the disclosure. In the claims, means-plus-function clauses are intended to cover the elements described herein as performing the recited function and not only structural equivalents, but also equivalent elements.