Abstract:
An apparatus for monitoring the characteristics of tissue adjacent a surgical site and communicating that information to a health care provider includes a retractor, a sensor, and a processing system. The sensor is disposed on the retractor and is configured to measure a parameter indicative of at least one characteristic of the tissue adjacent the first or the second blade. The processing system is in communication with the sensor and configured and arranged to receive information from the sensor indicative of the measured parameter. It includes a threshold stored therein indicative of excessive trauma to the tissue and it is configured in a manner such that it compares the received information to the stored threshold and communicates information to the health care provider regarding the comparison.

Description:
FIELD OF THE INVENTION 
       [0001]    The present disclosure is directed to a surgical retractor system. More particularly, the present disclosure is directed to a retractor system that monitors parameters indicative of the state of a patient&#39;s tissue adjacent a retractor of the retractor system. 
       BACKGROUND 
       [0002]    Side effects of anterior cervical decompression and fusion procedures may include post-operative dysphagia. This condition, making swallowing difficult or impossible, can be relatively long lasting, with up to twelve percent of patients with dysphagia symptoms still having those symptoms a year after surgery. Surgeons and scientists are researching whether the incidence and recovery from dysphagia corresponds with the size of the surgical dissection, the trauma induced by retractors, and the length of the time the retractors are used to maintain an open surgical site. 
         [0003]    Conventional retractors are placed at a surgical site and used to retract tissue based solely upon a surgeons preference and experience. A surgeon conventionally attempts to “feel” when the retractor applies excessive loading to the tissue. If the loading links to the incidence of dysphagia, it would be helpful to have a system for monitoring loading or other parameters indicative of the state of the tissue. 
         [0004]    The systems and methods disclosed herein address one or more of the shortcomings of the prior art. 
       SUMMARY 
       [0005]    These and other aspects, forms, objects, features, and benefits of the present invention will become apparent from the following detailed drawings and description. 
         [0006]    The present disclosure is directed to a surgical retractor system for monitoring the characteristics of tissue adjacent a surgical site and communicating that information to a health care provider. The surgical retractor system may include a retractor, a sensor, and a processing system. The retractor may include a first blade for interfacing with tissue on a first side of a surgical site, a second blade for interfacing with tissue on a second side of the surgical site opposite the first side of the surgical site, and a body portion supporting the first blade relative to the second blade. The body portion may be adjustable in situ in a manner that changes tissue parameters by displacing the first blade relative to the second blade to displace tissue and provide access to a surgical site. The sensor is disposed on the retractor and is configured to measure a parameter indicative of at least one characteristic of the tissue adjacent the first or the second blade. The processing system is in communication with the sensor and configured and arranged to receive information from the sensor indicative of the measured parameter. The processing system includes a threshold stored therein indicative of excessive trauma to the tissue. The processing system is configured in a manner such that it compares the received information to the stored threshold and communicates information to the health care provider regarding the comparison. 
         [0007]    In another aspect, the present disclosure is directed to a sensor system for use on surgical retractor system. The sensory system includes a detector for receiving a signal or stimulus that creates a signal based on the received signal or stimulus and an anchor portion shaped to removably attach to a portion of the surgical retractor system. In some aspects, the sensor system is one of a sleeve configured to receive a portion of the retractor therein, a C-shaped clip configured to clip onto the retractor, and a flexible patch having an adhesive layer therein. 
         [0008]    In another aspect, the present disclosure is directed to a surgical retractor system for monitoring the characteristics of tissue adjacent a surgical site and communicating that information to a health care provider. The surgical retractor system may include a retractor and a tissue parameter detecting system. The retractor includes a first blade for interfacing with tissue on a first side of a surgical site, a second blade for interfacing with tissue on a second side of the surgical site opposite the first side of the surgical site, and a body portion comprising a first arm and a second arm and an adjustment element adjustably connecting the first and second arms. The first and second arms respectively support the first blade and the second blade. The adjustment element is adjustable in situ in a manner that changes tissue parameters by displacing the first blade relative to the second blade to displace tissue and provide access to a surgical site. The tissue parameter detecting system is structurally configured and arranged to measure a parameter indicative of at least one characteristic of the tissue adjacent the first or the second blade. The tissue parameter detecting system has a threshold stored therein indicative of excessive trauma to the tissue. The tissue parameter detecting system is structurally configured and arranged in a manner such that it compares the measured information to the stored threshold and communicates information to the health care provider regarding the comparison. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The accompanying drawings serve to exemplify some of the embodiments of this invention. 
           [0010]      FIG. 1  is an illustration of a perspective view of a surgical retractor of the present disclosure with a sensor for detecting data indicative of the state of tissue adjacent the retractor. 
           [0011]      FIG. 2  is an illustration of a top view of two surgical retractors in a surgical application, one of the surgical retractors having a sensor thereon and in communication with a retraction monitor and system in accordance with the disclosure of  FIG. 1 . 
           [0012]      FIG. 3  is an illustration of an exemplary retraction monitor connectable to the sensor in  FIGS. 1 and 2 . 
           [0013]      FIG. 4  is an illustration of a sensor system in the form of a sensor sleeve having a built-in sensor in accordance with the present disclosure. 
           [0014]      FIG. 5  is an illustration of a sensor system in the form of a clip having a built-in sensor in accordance with the present disclosure. 
           [0015]      FIG. 6  is an illustration of the sensor system in  FIG. 5 . 
           [0016]      FIG. 7  is an illustration of a sensor system in the form of an adhesive patch having a built-in sensor in accordance with the present disclosure. 
           [0017]      FIG. 8  is an illustration of a perspective view of a surgical retractor of the present disclosure with a sensor for detecting data indicative of the state of tissue adjacent the retractor usable in a wireless environment. 
           [0018]      FIG. 9  is a diagram of an exemplary wireless transmission system using inductive coupling. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    The present disclosure relates generally to the field of orthopedic surgery, and more particularly to devices, systems and methods for monitoring tissue displaced by a retractor system. For the purposes of promoting an understanding of the principles of the invention, reference will now be made to embodiments or examples illustrated in the drawings, and specific language will be used to describe these examples. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alteration 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 disclosure relates. 
         [0020]    This disclosure is directed to instruments and methods for performing percutaneous surgery, including spinal surgeries that include one or more techniques such as laminotomy, laminectomy, foramenotomy, facetectomy, discectomy, interbody fusion, spinal nucleus or disc replacement, and implant insertion including plates, rods, and bone engaging fasteners, for example. A retractor system, including a retractor, permits a surgeon to perform through a working channel or passageway through skin and tissue of the patient. The retractor is adjustable in situ to increase the size of the working channel to facilitate access to the working space at the distal end of the retractor while minimizing trauma to tissue surrounding the retractor. The retractor can be used with any surgical approach to the spine, including anterior, posterior, posterior mid-line, lateral, postero-lateral, and/or antero-lateral approaches, and in other regions besides the spine. 
         [0021]      FIG. 1  shows an exemplary a retractor system  100 , including a retractor  102  and a processing system  103  that, in this embodiment, includes a monitor  104  and a console, such as a computer system  106 . The retractor  102  includes a variable width main body tube  108  formed of a first blade  110  and a second blade  112 . It also includes a first arm  114  and a second arm  116  extending from the main body tube  108 . These are adjustably connected to each other at a proximal end by an adjustment element  118 . The adjustment element  118  adjusts the distance between the first and second arms  114 ,  116 , and likewise, adjusts the distance between the first and second blades  110 ,  112 . 
         [0022]    In this embodiment, the blades  110 ,  112  have an arcuate cross section with a concave inner surface and a convex outer surface. In other embodiments, the blades have other configurations such as flat, curved, or other geometries. The first blade  110  has a distal end  120  and an opposite proximal end  122 . The second blade  112  has a distal end  124  and an opposite proximal end  126 . The distal ends  120 ,  124  may be beveled to facilitate insertion, although non-beveled ends are also contemplated. A working channel  128  is formed between the first and second blades  110 ,  112 . After insertion into a patient, the working channel  128  is enlarged by spreading the first and second blades  110 ,  112  apart using the adjustment element  118 . In this embodiment, the adjustment element  118  is a rack and pinion assembly, although outer adjustment elements are contemplated. In some examples, the adjustment element  118  comprises a motor, such as an electric, hydraulic, or pneumatic motor that spreads apart the first and second blades. 
         [0023]    The first and second blades  110 ,  112  are respectively coupled with the first and second arms  114 ,  116  which are engaged with adjustment element  118 . It should be appreciated that the blades  110 ,  112  may be coupled with the arms  114 ,  116  in any suitable arrangement, including dovetail connections, fasteners, threaded coupling members, clamping members, snap rings, compression bands, straps, ball-detent mechanisms, releasably interlocking cams or tabs, welding, fusing, and/or adhering, just to name a few possibilities. In some embodiments, the blades  110 ,  112  are integrally formed with the arms  114 ,  116 . Still further, the blades  110 ,  112  may be removably coupled with the arms  114 ,  116 , and alternative retractor blades may be chosen from a plurality of retractor blades to replace retractor blades  110 ,  112  to better suit a particular application in which the retractor  102  may be used. In addition, it should be noted that alternative embodiments use more than two plates, and in further alternative embodiments, a single blade may be used. 
         [0024]    In use, after insertion into the patient, the working channel  128  can be enlarged by separating first retractor blade  110  and second retractor blade  112 . Separation of the retractor blades  110 ,  112  increases the size of working channel  128 . However, as with any invasive surgery, this separation applies some level of stress and trauma to the tissue about the surgery site. 
         [0025]      FIG. 2  is a top view showing two retractors  140 ,  142 , respectively, in use at a surgical site to maintain or retract tissue in a position providing surgical access according to an exemplary aspect of the present disclosure. Here, the retractors  140 ,  142  are similar in many respects to the retractor  102  described above, and for efficiency, will not be re-described in great detail. It is sufficient to note that the retractors  140 ,  142  each include first and second blades, arms, and an adjustment element that controls the separation between the arms and blades. 
         [0026]    To quantify the level of stress and trauma to the tissue at the surgical site, each of the retractor  102  in  FIG. 1  and the retractor  140  in  FIG. 2  includes a sensor  150  associated therewith. The sensor  150  provides information indicative of one or more parameters of the loading stress, trauma, status, or other parameter of the tissue at the surgical site. For example, the sensor  150  may provide information including mechanical, thermal, chemical fluidity (such as pressure, time, heat, blood flow, lactid acid build-up, or other parameters) determined to be useful in a surgical setting. In the embodiment in  FIG. 1 , the sensor  150  is disposed upon the blade  110  of the retractor  102 . Accordingly, in addition to sensing the pressure on the blade  110 , the sensor may interface directly with the tissue and may provide information relating to either the state of the retractor or directly measure parameters of the tissue. In some examples, a sensor  150  may be used on each blade. In other examples, the sensor  150  may be used only on a single blade. The blade may be the medial blade, responsible for retracting the midline structures from the anterior aspect of the spine. For example only, the sensor  150  may be a strain sensor, a thermocouple, a flow meter such as a Transonic VLF-21 Laser Doppler Flowmeter, other sensors, or a plurality of sensors arranged in a manner known in the art. 
         [0027]    In the embodiment in  FIG. 2 , the sensor  150  is disposed upon a retractor arm of the retractor  142 . In this embodiment, the sensor  150  is a strain sensor arranged to sense the arm strain indicative of pressure applied to the retractor blade  110  by patient tissue during use. 
         [0028]    In either case, the monitor  104  is structurally configured to receive information from the sensor  150 . In the embodiment shown, the monitor  104  is connected to the sensor  150  via a wired connection  134 . Signals transmitted over the wired connection  134  provide information that may be filtered or processed to identify information gathered by the sensor  150 . 
         [0029]      FIG. 3  shows an exemplary monitor  104 . It includes both a display portion  160  and an input portion  162 . The display portion includes a visual indicator  164  labeled “Normal,” a visual indicator  166  labeled “Alarm,” and a visual indicator  168  labeled “Blade Size.” The display portion  160  provides real time feedback based on information received from the sensor indicative of the level of tissue trauma. For example, the monitor  104  may indicate that the received information indicates that the tissue at the surgical site is subject to trauma above or below a pre-established threshold. In some embodiments, the monitor  104  is configured to be operable with different blade sizes, and the threshold value may be different based on the retractor blade size. 
         [0030]    When the Normal visual indicator  164  is active, the sensor information is indicative of trauma levels below a preset threshold. In some instances the threshold value level is configured to automatically adjust over time. For example, the monitor  104  may be programmed so that the threshold decreases over a surgical period, such that even a lower level of trauma is not maintained too long. 
         [0031]    When the Alarm visual indicator  166  is active, the sensor information is indicative of trauma levels above a preset threshold. This alerts the surgeon to reduce the pressure on the tissue at least for a period of time. In addition to a visual Alarm indicator, the monitor includes an audible indictor. Further, some embodiments include a tactile indicator where the monitor  104  vibrates as an alarm indicator. Also, in some embodiments, the visual indicators have color-based lighting schemes, for example, with green indicating that measured parameters are below a threshold, red indicating that measured parameters are above a threshold, and flashing red or yellow indicating that tissue should be relaxed for a period of time. Other alarm schemes are also contemplated. Accordingly, the surgeon may be alerted to over-trauma levels in any of multiple ways. 
         [0032]    The input portion  162  of the monitor  104  includes a power selector  170 , a blade selector  172 , a record selector  174 , and a mute selector  176 . These are shown as buttons, but may be icons on a touch screen, or may be selectable by a mouse, keyboard, or other input device. The record selector  174  turns on a recorder that records the feedback from the sensor  150 . The recorder may be a microcomputer or chip capable of receiving, recording, or processing information communicated by the sensor  150  on the retractor  102 . 
         [0033]    In some examples, the monitor  104  is configured to monitor retraction force/pressure and force/pressure vs. time. In other examples the monitor is configured to monitor temperature, chemical fluidity (e.g., pressure, time, heat, blood flow, lactid acid build-up) or other parameters. 
         [0034]    In some embodiments, the monitor  104  is also a safety mechanism. For example, when a detected sensor signal exceeds a pre-established threshold, then in addition to the alarm system being activated as described above, a safety mechanism may be activated. This may include automatically controlling the retractor to relieve pressure on the tissue. This may cooperate with retractors having an automatic distraction control as is disclosed in U.S. Patent Publication No. 2009/0306480, filed Jun. 6, 2008, incorporated herein by reference. The automatic control may provide a gradual reduction in pressure by distracting the blades, may provide oscillation, or massaging vibration, or other safety mechanisms that provide relief to the tissue. As the pressure decreases, the alarm function on the monitor  104  may likewise adjust, such as changing from a solid light indicator to a flashing indicator, for example. 
         [0035]    In the embodiment shown, the monitor  104  connects to the computer system  106 . This may be a personal computer or other computer system, and may include its own input devices, such as a keyboard, mouse, and other standard input devices. The computer system  106  may further process the sensor signal and may provide graphs or additional information indicative of the information detected by the sensor. In some embodiments, the computer system  106  is component that records the detected information when the record input is selected on the monitor  104 . In some embodiments the monitor  104  and computer system  106  are combined into a single unit that monitors the tissue. In other embodiments, the computer and the monitor are used independently of each other, without being attached together. 
         [0036]      FIGS. 4-7  disclose sensor systems for removably attaching the sensor  150  to the retractor  102 . Accordingly, in some embodiments, the sensor system may be removed and discarded after use and before the retractor is sterilized. 
         [0037]      FIG. 4  discloses a sensor system  200  including an anchor portion for attachment to the retractor  102  and the sensor  150 . In this embodiment, the anchor portion is a sleeve  202 . The sleeve  202  includes at least one end with an opening  204  for receiving at least part of the retractor  102 . Accordingly, the sleeve  202  may be sock-like, with a single open end, or may be tube-like, with two open ends. In this embodiment, the sleeve  202  is sized and shaped to receive at least a part of the first blade  110 . In some embodiments, it is formed to have a particular shape matching the retractor  202 , while in other embodiments, the sleeve  202  is configured of a conformable material, such as a fabric, that may conform to the shape of the retractor  102 . The disposable sleeve  202  can be made of any suitable material, including flexible or elastic polymers, such as polyurethane, silicone, and rubber, among many others. 
         [0038]    In some embodiments, the sensor  150  is built into or embedded within the sleeve  202  such that the sensor  150  is applied against the retractor  102 , and configured to measure a particular parameter of the retractor  102 . For example, the sensor  150  may be configured to measure, for example only, force, displacement, contact stress, torque deflection, tension, compression, strain, and pressure on the retractor  102 . In other embodiments, the sensor is associated with the sleeve in a manner that enables it to measure parameters of the tissue adjacent the sleeve. For example, the sensor  150  may be configured to measure temperature, pressure, blood flow, lactid acid build-up, or other parameters. When placed on the retractor, the sleeve  202  and the sensor  150  are configured to cooperate with the processing system  103  to record and/or process the pressure or strain information communicated from the sensor  150  during the surgery. 
         [0039]    It is worth noting that the more than one disposable sleeve may be used with the retractor  102  at a single time. For example, the blades  110 ,  112  may each by outfitted with a sleeve-type sensor system  200 . Further, each sleeve  202  may include more than one sensor  150  disposed thereon for measuring more than one parameter. These may be sensors of the same or different types. As explained above, the sensors  150  may include one or more of any those that measure the following data: temperature, force, displacement, contact stress, torque deflection, tension, compression, pressure, and strain, among others. The disposable sensors  150  may track, record, transmit, or store the above data as a function of time. 
         [0040]      FIG. 5  shows another embodiment of a retractor  102  with a first arm  114 , a second arm  116 , and a sensor system  210  for removable attachment to the retractor. In this embodiment, the sensor system  210  includes an anchor portion as a flexible C-shaped clip that snaps onto the retractor. In  FIG. 5 , the sensor system  210  is attached to the first arm  114 , but may be configured to attach to any suitable portion on the retractor  102 .  FIG. 6  shows the sensor system  210  in greater detail. As can be seen, the sensor system  210  comprises the clip body  212 , a sensor  150 , and in this embodiment, a coil  213  for wireless transmission using inductive coupling, explained further below. Here, the clip body  212  includes two legs  214 ,  216  and a side  218  that together form a C-shape. A lip  220  at the ends of the legs  214 ,  216  permits the clip body  212  to snap onto the retractor  102 , securing it in place. The clip body  212  can be made of any suitable material, including flexible or elastic polymers, such as polyurethane, silicone, and rubber, among many others. 
         [0041]    In some embodiments, the sensor  150  is built into or embedded within the body  212  such that the sensor  150  is applied against the retractor  102  and configured to measure a particular parameter of the retractor  102 , as explained above. In other embodiments, the sensor  150  is associated with the clip body  212  and the retractor  102  in a manner that enables it to measure parameters of the tissue adjacent the clip body, as explained above. When placed on the retractor, the sleeve  202  and the sensor  150  are configured to cooperate with the processing system  103  to record and/or process the pressure or strain information communicated from the sensor  150  during the surgery. 
         [0042]      FIG. 7  shows another sensor system  220  as an adhesive patch. This sensor system  220  includes an anchor portion for removable attachment to the retractor  102  in the form of an adhesive layer  222 . The adhesive patch includes the adhesive layer  222 , a backing layer  224 , and the sensor  150 . The adhesive layer  222  may be formed of any adhesive that securely holds the sensor  150  in place and that can be removed from the retractor  102  prior to sterilization. The backing layer  224  may be a flexible woven or non-woven material. The sensor system  220  may be placed either on the blade to be contact with tissue or on the retractor arm, out of contact with the tissue. This sensor system  220  may be removed from a sterile packet and attached to an appropriate location on the retractor. 
         [0043]    In all the embodiments in this disclosure, more than one sensor may be used at the same time in the same region or different regions of the retractor, for measuring the same parameter or for measuring different parameters. Accordingly, the sensor systems as well as directly placed sensors as in  FIG. 1 , may include a plurality of sensors  150 . As explained above, the sensors  150  may include one or more of any sensors that measure the following data: temperature, force, displacement, contact stress, torque deflection, tension, compression, pressure, and strain, among others. The disposable sensors  150  may track, record, transmit, or store the above data as a function of time. 
         [0044]      FIG. 8  shows another embodiment of the of the retractor in  FIG. 2 . In this embodiment, instead of employing a wired communication system, the device employs a wireless communication between the sensor  130  and the monitor  104 . Accordingly, the information collected by the sensor  130  may be communicated via a wireless transmission the monitor  104 . This wireless communication may be accomplished via any suitable wireless method, including RF, Bluetooth, inductive, coupling, transmissions via ultrasound, microwave, or other ranges and frequencies. 
         [0045]      FIG. 9  discloses one example of a wireless system  300  for communicating between the sensor  150  and the monitor  104 . This embodiment uses inductive coupling to wirelessly power the sensor and retrieve data. Here, the sensor or sensor system comprises the sensor  150 , circuitry  302 , and a transmission coil  304 . The monitor  104  comprises a reader coil  306  as an inductive antenna. The reader coil  306  need not be contained within the monitor housing, but may extend from the housing for placement somewhere adjacent the surgical site. The reader coil  306  and the transmission coil  304  cooperate by transfer data and energy. In use, the reader coil  306  supplies energy to the transmission coil  304 . This in turn powers the circuit  302  and retrieves data from the sensor  150 . This information maybe processed at the sensor or may be wirelessly transmitted from the transmission coil  304 . Once received, the information may be processed as described above. 
         [0046]    Wireless communications other than those described above also may be used. For example, the sensor  150  may be associated with a power source and transmitter disposed on the retractor  102 . Accordingly, the range of the wireless transmitted signals may be greater than when inductive coupling is used. In some instances, the sensor  150  may be a passive sensor, while in other embodiments, the sensor  150  may be an active sensor. In addition, the sensor may be either a one way or two way sensor, and may be internally powered or externally powered. In some aspects, the sensors are connected to an antenna for improved wireless signaling. As described above, the sensor  150  may be either disposable or non-disposable. All the features described above are also relevant when wireless technology is used to transmit and process information. For example, even using wireless technology, the monitor  104  or computer system  106  may, record and interpret data. 
         [0047]    In use, a surgeon makes an incision into a patient. If a sensor is not attached to the retractor, the surgeon may attach the sensor. As described above, this may be accomplished by attaching a removable and flexible sleeve including the sensor about a portion of the retractor, attaching a clip including the sensor, or adhering an adhesive patch including the sensor. Other attachment methods are contemplated. 
         [0048]    With the retractor prepared, the surgeon inserts the retractor blades into the incision. In some examples, the blades are formed to create a working channel between them. In other examples, the adjustment element spreads apart the arms and blades, and the spreading blades spread the tissue, creating a working channel. During this spreading step and/or with the blades in place against the tissue, the sensor detects changes in measurable parameters indicative of the state of the tissue adjacent the blades. As described above, the measurable parameter may be strain on the blades or arm, direct force on the blades, pressure, temperature, or any of the other listed or unlisted parameters. 
         [0049]    The monitor receives signals from the sensor with information indicative of the measured parameter. In some embodiments, the monitor stores a threshold value for the retractor that coincides with a value beyond which there is an increased risk of tissue damage. The monitor may compare the received information with the stored threshold. If the received information exceeds the threshold, the monitor may give a warning as discussed above. For example, the warning may be activated with a pressure greater than 100 mmHg has been sustained for more than 15 minutes or when a pressure greater than 50 mmHg has been sustained for more than 30 minutes. 
         [0050]    The monitor or an associated computer system also may record the information and display graphs or charts indicative of the measured parameters of the status of the tissue. 
         [0051]    While the present invention has been illustrated by the above description of embodiments, and while the embodiments have been described in some detail, it is not the intention of the applicant to restrict or in any way limit the scope of the invention to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant&#39;s general or inventive concept. It is understood that all spatial references, such as “longitudinal axis,” “horizontal,” “vertical,” “top,” “upper,” “lower,” “bottom,” “left,” and “right,” are for illustrative purposes only and can be varied within the scope of the disclosure.