Patent Publication Number: US-2009234273-A1

Title: Surgical trocar with feedback

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/064,625 to Intoccia et al. filed on Mar. 17, 2008. 
    
    
     FIELD OF THE INVENTION 
     This disclosure relates generally to a medical device, such as a trocar and, more particularly, to a surgical trocar having feedback capability, and methods of using the same. 
     BACKGROUND OF THE INVENTION 
     In recent years, minimally invasive surgical techniques (e.g., laparoscopic surgery) have become a standard method for performing several common surgical procedures. These procedures are generally performed by using a puncture on the body surface to deliver desired surgical tools to a worksite inside the body. For instance, for removal of the gall bladder, laparoscopic cholecystectomy may be performed in place of conventional surgical cholecystectomy. In place of an abdominal incision to perform conventional cholecystectomy, laparoscopic cholecystectomy is performed using a laparoscope inserted into the abdomen through a puncture created on the abdomen. As compared to conventional open surgical procedures, patient discomfort and recovery time in laparoscopic procedures are generally lower due to the absence of a large incision. Although patient discomfort and associated trauma may have decreased due to laparoscopic procedures, the potential for serious complications (or injuries) still exists during laparoscopic procedures. 
     Laparoscopic surgery may begin by placing a specialized needle, for example a veress needle, into the abdominal cavity and filling the abdominal cavity with carbon dioxide gas in a process called insufflation. Insufflation elevates and holds the abdominal wall away from internal structures. Insertion of a trocar through the abdominal wall may follow. The trocar is a needle like device with a sharp tip protruding from a tubular casing (canulla). The sharp tip of the trocar is used to puncture the abdominal wall. After creating the puncture, the sharp needle may be retracted leaving the canulla in the puncture to provide an access port into the abdominal cavity. This process is sometimes referred to as a primary trocar creating a primary puncture. The laparoscope, equipped with a camera, may be inserted into the abdominal cavity through the canulla port of the primary trocar. The laparoscope may include a metal tube equipped with a camera and one or more access ports that allow a myriad of surgical instruments to be delivered into the abdominal cavity. The camera provides visualization for the surgeon during the laparoscopic procedure. The surgical instruments delivered through the laparoscope may be used to dissect, tie, clip, cauterize blood vessels, or perform any other desired procedure in the abdominal cavity during the procedure. A second and third trocar (secondary trocars) may also be similarly inserted into the abdominal wall. These insertions may be guided by the camera of the laparoscope inserted through the primary puncture. The secondary cannula ports may be used for retractors and graspers which retract tissue, for irrigation-suction devices, or for other desired tools or devices. 
     The primary trocar is typically inserted into the body using a blind puncture. Studies indicate that some complications that arise in laparoscopic surgery arise during blind insertion of the primary trocar (see “Laparoscopic Trocar Injuries: A report from a U.S. Food and Drug Administration (FDA) Center for Devices and Radiological Health (CDRH) Systematic Technology Assessment of Medical Products (STAMP) Committee,” by Janie Fuller et al., report available at http://www.fda.gov/cdrh/medicaldevicesafety/stamp/trocar.html). The blind insertion of the primary trocar may use a technique referred to as a controlled jab. The force required for the controlled jab can vary from patient to patient and from trocar to trocar depending, among others, upon the sharpness of the trocar blade. Due to the differences in density between different types of body tissue, the required force may also vary as the tip penetrates through different layers (for example, skin-fat-muscle-peritoneal layers) of the abdominal wall. For successful blind insertion, the surgeon must apply sufficient force under adequate control to stop the trocar movement upon penetration. When the trocar passes from one layer of tissue to another, there may be an abrupt change in piercing resistance. A surgeon may be unaware of, or may be unable to respond quickly to this changing piercing resistance, with the result that the sharp trocar tip may be thrust into the abdominal cavity, potentially causing injury to the organs or vessels contained therein. There may be numerous other medical procedures where a blind puncture may be used. For example, a blind puncture by a trocar may be used in treatment of female urinary incontinence, Tension free Vaginal Tape (TVT) procedure, or Transobturator Tape (TOT). 
     There are a number of improvements that have been recommended to reduce the likelihood of injury due to blind insertion of a trocar. While some of these techniques have focused on a modified surgical technique to insert the trocar into the abdominal cavity, most improvements focus on modified trocar designs. Some of these changes include modifications on the shape and sharpness of the sharp tip to reduce the amount of force needed to pierce the body cavity wall, and providing a sheath for the sharp tip to cover the tip after piercing the wall. Although these modified tip designs may reduce the likelihood of injury due to blind trocar insertion, the potential for these injuries still exists (see id.). 
     The present disclosure provides surgical trocars having feedback capability, and methods of using the same to avoid some or all of the aforementioned shortcomings of existing devices. 
     SUMMARY OF THE INVENTION 
     In an exemplary embodiment of the present disclosure, a medical device is disclosed. The medical device includes a handle configured to be grasped by a human hand, and an elongate obturator coupled to the handle. The obturator includes a proximal end proximate the handle and a distal end extending away from the handle. The distal end of the obturator includes a tip configured to pierce a body. The medical device also includes a vibration generating device coupled to the obturator. The vibration generating device is configured to induce a vibration having a frequency and an amplitude on the obturator. 
     Various embodiments of the medical device may include one or more of the following aspects: the vibration generating device is embedded in the medical device; the obturator is configured to change the amplitude of vibration of the obturator as the obturator pierces the body; the medical device is further configured to transmit the vibration to the handle; the obturator is configured to vary the amplitude of vibration as a function of a density of a layer of tissue that the obturator pierces through; the proximal end of the obturator extends into the handle; the vibration generating device is physically coupled to the obturator; the vibration generating device includes at least one of an electric motor and a solenoid; the medical device includes a sensor coupled to the obturator, wherein the sensor is configured to detect a vibration of the obturator; the sensor includes one of a pressure sensor and an accelerometer; the sensor transmits signals indicative of the detected vibrations to a signal processing device; the signal processing device is embedded in the medical device; the signal processing device is embedded in the handle; the signal processing device is a standalone device separate from the medical device; the sensor wirelessly transmits the signals to the signal processing device; the signal processing device is configured to indicate information related to the position of the obturator within the body based on the signal; the information includes the type of tissue that the obturator pierces through; the information is indicated using a visual or an audio signal; the signal processing device is configured to indicate the proximity of the obturator to a bone in the body as the obturator pierces the body; the signal processing device is configured to indicate a contact of the obturator with a bone in the body; and the medical device further includes a vibration isolation bushing between the obturator and the handle. 
     In another exemplary embodiment of the present disclosure, a method of using a medical device to create a puncture in a body is disclosed. The method includes grasping a handle of the medical device with a hand, the handle being coupled to an elongate obturator. The method also includes activating a vibration generating device coupled to the obturator. The vibration generating device induces a vibration having a frequency and an amplitude on the obturator. The method further includes piercing the body with the obturator, detecting a vibration of the obturator during the piercing, and controlling the piercing of the body based on the detected vibration of the obturator. 
     Various embodiments of the method of using the medical device may include one or more of the following aspects: controlling the piercing includes detecting a variation of the amplitude of the vibration as the obturator pierces into the body; controlling the piercing includes detecting a frequency of vibration induced in the obturator; controlling the piercing includes identifying the type of tissue the obturator is piercing through based on the vibration of the obturator; controlling the piercing includes detecting contact of the obturator with a bone in the body based on the vibration of the obturator; detecting the vibration of the obturator includes detecting the vibration on the hand; detecting the vibration of the obturator includes detecting the vibration using a sensor coupled to the medical device; the sensor being coupled to the obturator; detecting the vibration using a sensor includes transmitting a signal representative of the vibration to a signal processing device; the signal processing device is configured to distinguish between a type of tissue that the obturator is piercing through based on the signal; the signal processing device is configured to identify proximity of the obturator with a bone in the body based on the signal; the signal processing device is configured to identify a contact of the obturator with a bone in the body based on the signal; contact of the obturator with a bone is detected based on detecting a frequency of a vibration induced in the obturator due to the contact; the sensor transmits the signal to the signal processing device wirelessly; the signal processing device is configured to indicate information relating to a position of the obturator within the body based on the signal; the information is indicated using an audio or a visual signal; the vibration generating device is embedded in the medical device; and the vibration generating device is embedded in the handle of the medical device. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustrating an exemplary laparoscopic surgical process. 
         FIG. 2  illustrates an exemplary trocar used in the laparoscopic process of  FIG. 1 . 
         FIGS. 3A-3C  illustrate exemplary tip designs of the trocar of  FIG. 2 . 
         FIG. 4  illustrates another embodiment of a trocar used in the laparoscopic process of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments of the present disclosure are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 1  depicts an exemplary laparoscopic surgical process  10  performed using surgical tools inserted into the abdominal cavity  70  through one or more punctures created on the abdominal wall  50 . Non-limiting examples of the exemplary laparoscopic surgery may include cholecystectomies, gastrojejunostomies, stomach resections, polypectomies, vasectomies, tubal ligations, etc. It should be emphasized that the illustrated laparoscopic surgical process  10  of  FIG. 1  is exemplary only, and the inventions of the current disclosure may be applied to any suitable surgical application known in the art. 
     To perform the laparoscopic surgical process  10  of  FIG. 1 , a laparoscope  20  is inserted into an abdominal cavity  70  through a primary puncture  60 A on an abdominal wall  70 . The primary puncture  60 A may created by a controlled jab (as described earlier) of a trocar on the abdominal wall. The laparoscope  20  may be fitted with a camera, light and other capabilities that may enable a laparoscopist (surgeon  80 ) to view the procedure from outside the body. The laparoscope  20  may also include one or more lumens passing longitudinally therethrough. These lumens may enable surgical tools to be delivered to the abdominal cavity  70  to aid in the surgical procedure. In some surgical procedures, additional surgical tools (such as, for example, a grasper  30 ) may be delivered to the abdominal cavity  70  through a secondary puncture  60 B created on the abdominal wall. Although one secondary puncture  60 B is illustrated in  FIG. 1 , it is understood that different laparoscopic procedures may use a different number of secondary punctures. For instance, in some procedures, all the necessary surgical tools may be delivered to the abdominal cavity  70  through the laparoscope  20  and no secondary punctures may be needed, while in other procedures, more than one secondary puncture  60 B may be needed. The secondary puncture  60 B may also be created on the abdominal wall  50  using a trocar. The camera in laparoscope  20  may guide the surgeon  80  in the insertion of the trocar to create the secondary puncture  60 B. 
       FIG. 2  illustrates an exemplary trocar  40  that may be used to create the punctures (primary puncture  60 A and secondary puncture  60 B). Trocar  40  may include a handle  42  with an elongate obturator  44  extending therefrom. Handle  42  may include a side surface  42   c , positioned about a longitudinal axis  98 , connecting a front wall  42   a  and a back wall  42   b . Side surface  42   c , front wall  42   a , and back wall  42   b  may define a hollow cavity  54  within handle  42 . In the embodiment of trocar  40  depicted in  FIG. 2 , side surface  42   c  is shown to curve both about the longitudinal axis  98  and along the longitudinal axis  98 . This shape of side surface  42   c  may allow handle  42  to rest comfortably within a palm of a human hand. In general, it is contemplated that side surface  42   c  may have any general shape. For instance, in some embodiments, side surface  42   c  may have a substantially cylindrical shape. 
     Front wall  42   a  and back wall  42   b  may be opposing end faces of handle  42 . In the embodiment of trocar  40  depicted in  FIG. 2 , front wall  42   a  and back wall  42   b  are both shown to have a substantially square shape. However, it is contemplated that, in general, front wall  42   a  and back wall  42   b  may have any general shape. For instance, in some embodiments, one or both of these surfaces may have a circular shape. Back wall  42   b  may include one or more openings that provide access to cavity  54 , for instance a second opening  56   b  and a third opening  56   c . Second opening  56   b  and third opening  56   c  may have any general cross-sectional shape and may be dimensioned to provide access to electrical cables wires into cavity  54 . Front wall  42   a  may also include a first opening  56   a  that opens into cavity  54 . Obturator  44  may extend into cavity  54  of handle  42  through first opening  56   a . First opening  56   a  may have the same general shape as a cross-sectional shape of obturator  44 . In some embodiments, an outer surface of obturator  44  may contact a mating surface of first opening  56   a , while in other embodiments, sealing materials such as a bushing (such as a vibration damping bushing), may separate the mating surfaces of obturator  44  and first opening  56   a.    
     Obturator  44  may include an elongate shaft extending from a proximal end  110  to a distal end  120  along longitudinal axis  98 . At the proximal end  110 , obturator  44  may extend into cavity  54  through first opening  56   a . At the distal end  120 , obturator  44  may terminate at a tip  46 . Obturator  44  may have a generally circular cross-section, and may have different diameters for different applications. In general, obturator  44  may have any diameter found in obturators known in the art. The length of obturator  44  may also be similar to obturators known in the art. In some embodiments, obturator  44  may extend parallel to longitudinal axis  98 , while in other embodiments, obturator  44  may include a curvature along its length. In the embodiment of trocar  40  shown in  FIG. 2 , obturator  44  is shown to extend substantially parallel to longitudinal axis  98 , with a length of the obturator  44  at distal end  120  making an angle  0  with the longitudinal axis  98 . Angle θ may vary from 0 degrees to about 90 degrees. In general, angle θ may depend upon the medical procedure (TVT, TNT, etc.) for which trocar  40  is used. For example, in an application where trocar  40  is used to deliver ends of a supporting tape (sling) to their respective locking positions, angle θ may vary with the shape of obturator  44  and the anchoring location. In embodiments where angle θ is 0 degrees, obturator  44  may extend from proximal end  110  to distal end  120 , parallel to longitudinal axis  98 . 
     Tip  46  of the obturator may have any shape that is configured to puncture abdominal wall  50  (see  FIG. 1 ). In general, tip  46  may be designed for sharp or blunt penetration. A few exemplary embodiments of tip  46  designed for sharp and blunt penetration are illustrated in  FIGS. 3A-3C . Tip  46 A of  FIG. 3A  has a pyramidal shape with multiple sides that terminate at a sharp point. Tip  46 B of  FIG. 3B  has a conical shape terminating at a sharp point.  FIG. 3C  illustrates a conical tip  46 C configured for blunt penetration. It should be emphasized that tips  46 A- 46 C of  FIGS. 3A-3C  are exemplary only, and trocars of the current disclosure may include an obturator  44  having any type and shape of tip known in the art. Although not illustrated in  FIG. 2  and  FIGS. 3A-3C , in some embodiments, trocar  40  may also include a retractable shield that covers tip  46  before and after insertion. This shield may offer some protection to abdominal and pelvic organs from inadvertent puncture. 
     The proximal end  110  of obturator  44  in cavity  54  may be coupled to a vibrator  48 . Vibrator  48  may include one or more devices that may be configured to impart mechanical vibration to obturator  44 . These mechanical vibrations may include vibrations in the transverse and/or the longitudinal direction. In some embodiments, vibrator  48  may include an electric motor, a solenoid, and/or other electrical devices. Power and signals to and from the vibrator  48  may be provided by cables  52  that extend from handle  42  through second and third opening  56   b ,  56   c  in the back wall  42   b . The vibrator  48 , when activated by an electric current, would produce an alternative electric field. This alternative electric field may directly, or through some transmission parts (such as an offset wheel), impact longitudinal or transverse vibrations on the obturator  44 . In general, the frequency of these vibrations may vary from a few Hertz to tens of kilohertz. The amplitude and frequency of the vibrations may be fixed or variable. In some embodiments of trocar  40 , the frequency and/or amplitude of the vibration may be selected by the user depending upon the application. These vibratory characteristics may be selected, for example, by controlling the excitation current input to the vibrator  48 . In some embodiments, handle  42  may include a knob or other selection device that enables the user to select the amplitude and/or frequency of vibration. In some embodiments, the amplitude and frequency of vibration may have a fixed value. This fixed value may depend upon the characteristics of vibrator  48 . 
     The mechanical vibrations imparted to obturator  44  at the proximal end  110  may travel back and forth along the length of the obturator  44 , and into handle  42 . The vibration transmitted to handle  42  may be felt in the palm of surgeon  80  operating trocar  40 . If the surgeon  80  holds trocar  40  in air, the vibration felt by the surgeon  80  may be a function of the amplitude and frequency of vibration of vibrator  48 . Design parameters of trocar  40  (such as, size, material, damping in the system, etc.) may affect the mode of vibration. For example, if vibrator  48  is excited with an alternating field of 250 Hz at 10 W, the vibration felt by the surgeon  80  would depend upon the size and type of trocar  40 . The vibration felt by the surgeon  80  will also depend upon the materials and construction of trocar  40 . For instance, in a trocar with a 3 mm diameter and 200 mm long steel obturator  44 , the vibration felt by surgeon  80  would be different if handle  42  were constructed out of a soft or a hard material. Likewise, presence of a soft bushing between obturator  44  and first opening  56   a  may also change the vibration felt by surgeon  80 . Although the magnitude and/or frequency of the vibration felt by the surgeon may be amplified or dampened depending upon the construction of trocar  40 , the vibration felt by surgeon  80  would not change over time, when trocar  40  is held in air. 
     As obturator  44  of trocar  40  penetrates abdominal wall  50  (to create a puncture), the tissue of abdominal wall  50  may absorb some of the energy, thereby reducing the amplitude of vibration. Although the amplitude changes as the obturator  44  penetrates tissue, the frequency of vibration may remain relatively unchanged. The surgeon  80  holding trocar  40  would feel the reduced amplitude of vibration. Depending upon the type of tissue and depth of obturator  44  penetration, the reduction in amplitude may be different. For instance, when obturator  44  penetrates soft tissue, the reduction in amplitude may be lower than when obturator  44  penetrates dense tissue or muscle layers. Additionally, the reduction in amplitude may also increase with increased depth of penetration. The surgeon  80  may get an indication of the location of tip  46  of obturator  44  by detecting variations in the amplitude of vibration felt in his/her hand. 
     When tip  46  of obturator  44  touches a bone, a second vibratory signal (or a shock wave) having a different frequency may be generated. This second vibratory signal may be the result of the impact of obturator  44  on bone. This second vibratory signal may also travel along the length of obturator  44  and be felt by surgeon  80 . The different frequency and amplitude of the second vibratory signal, from the vibration generated by the vibrator  48 , may enable the surgeon  80  to distinguish between the two vibratory signals. Using these vibratory signals as a guide, the surgeon  80  may guide trocar  40  through a desired path to create a puncture. 
     In some embodiments, a sensor  62  may be provided to detect the vibratory response of obturator  44 .  FIG. 4  illustrates an embodiment of trocar  40 A with a sensor  62  coupled to obturator  44 . Although  FIG. 4  illustrates sensor  62  coupled to the proximal end  110  of obturator  44 , sensor  62  may be coupled at any location of trocar  40 A as long as the vibrations in obturator  44  can be detected by the sensor  62 . Sensor  62  may be any type of device (for example, a pressure sensor, strain gage, accelerometer, etc.) that is known in the art. In some embodiments of a trocar  40 A with sensor  62 , vibration of the obturator  44  may be transmitted to the hand of surgeon  80 , and be detected by the sensor  62 . In these embodiments, the sensor  62  may serve as a back-up mechanism to detect vibratory signals that may be too weak to be detected by the surgeon  80 . In other embodiments of trocar  40  with sensor  62 , the handle  42  may be insulated from the obturator  44 , such that the vibrations transmitted to the handle  42  may be minimized. In these embodiments, a layer of vibro-insulation or bushing  58  may be provided between the mating surfaces of obturator  44  and first opening  56   a  (or handle  42 ). 
     Sensor  62  may detect the vibrations of the obturator  44  and transmit them to a signal processing device  64 . The signal processing device  64  may be embedded in trocar  40 A or may be a separate unit. In embodiments where the signal processing device  64  is a separate unit, sensor  62  may convert the detected vibrations and transmit them wirelessly, or through a wired connection, to the signal processing device  64 . In embodiments where the signal processing device  64  is embedded in the trocar  40 A, the signal processing device  64  may be embedded anywhere in trocar  40 A. In some embodiments the signal processing device  64  may also be located in the hollow cavity  54  of handle  42 . 
     The signal processing device  64  may be configured to differentiate between different layers of body tissue (tissue, fat, tendons, muscle, bone etc.) that the obturator  44  is penetrating through, or is adjacent to. As an illustrative example, one method that may be used by the signal processing device  64  to differentiate between different layers of body tissue is described below. The obturator  44  may be excited by a harmonic vibration having an equation y(t)=A o  cos(ωt+φ o ), where y(t) is the displacement at time t, A o  is the amplitude of oscillation, ω is the frequency, t is the elapsed time, and φ o  is the phase of oscillation. The displacement at any point of the obturator  44 , in response to this excitation, may be given by the equation x(t)=A cos(ωt+φ). While the frequency component (ωt) may remain a constant irrespective of the type of tissue that the obturator  44  is penetrating through, the amplitude and the phase delay components (A, φ) may be a function of the density of this layer of tissue. The higher the density of the tissue that obturator  44  is penetrating through, the lower would be the amplitude and higher would be the phase delay at any point on the obturator  44 . 
     The signal processing device  64  may extract the difference in amplitude and/or phase delay from the sensor  62  signal. The signal processing device  64  may also include calibration data that quantifies the amplitude and phase delay for different types of tissue. Based on the sensor signal and the calibration data, signal processing device  64  may identify the location of the obturator tip  46  in the abdominal wall  50 . If the tip  46  hits a bone, the second vibratory signal generated due to the contact may be captured by sensor  62 . The second vibratory signal may be composed of frequency components that may be distinguishable from the vibration induced by vibrator  48 . These different frequency components may be detected by the signal processing device  64 . In some embodiments, the calibration data may also include data that indicates the proximity of the tip  46  to a bone. In these embodiments, signal processing device  64  may also indicate the proximity of the obturator  44  to a bone. It should be emphasized that the illustrated method of differentiating between different body tissue layers (and identifying the location of the obturator  44 ) by the signal conditioner is exemplary only. Any known method may be used identify the location of the obturator  44  in the body from the vibration signals detected by the signal processing device  64 . 
     The signal processing device  64  may also be configured to indicate to surgeon  80  information relating to the location of the obturator  44  in the body. This information may be conveyed to surgeon  80  by any known means. In some embodiments, this information may be conveyed to surgeon  80  using a visual indicator, an audible signal, or a tactile signal. For instance, sound signals may indicate when the obturator  44  pierces through different layers of the abdominal wall. The pitch or intensity of the sound signal may change when the tip  46  approaches and/or contacts a bone. In some embodiments, a visual indicator (such as, lights, etc.) may indicate the location of the obturator  44 . In some embodiments, the location of the obturator  44  may be displayed on a monitor overlaid on an image of the abdominal wall  50  to indicate the layer of tissue that the obturator  44  is piercing through. It is also contemplated that a combination of auditory, visual, and tactile signals may be used to relate information from the signal processing device  64  to surgeon  80 . 
     Using a trocar  40  with vibratory feedback indicating the tissue layer that the trocar is piercing through, may serve to guide the surgeon  80  during insertion of trocar  40  during laparoscopic surgery. The feedback from the trocar  40  may help reduce the likelihood of injury due to blind insertion of trocar  40  during primary insertion. The sensor  62  combined with the signal processing device  64  may reduce the need for surgeon  80  to be sensitive to the variations in vibrations (felt in his/her hand holding the trocar) to guide the trocar  40 A, while creating a puncture. Additionally, the vibrating obturator  44  may improve the ability of the trocar  40  to pierce through tissue, thereby reducing the force needed to pierce tissue and advance the obturator  44  through the tissue. 
     An exemplary method of using a trocar  40  of the current disclosure to create a puncture on a body surface will now be explained. With the handle  42  of trocar  40  firmly grasped by a hand of surgeon  80 , the tip  46  of trocar  40  may be positioned proximate the body surface. The power to the vibrator  48  may be switched on to start the vibration of the obturator  44 . The surgeon may now be able to feel the vibration on his hand holding the trocar  40 . In embodiments of trocar  40  fitted with sensor  62  to detect the vibratory response, these vibrations may alternatively or additionally be detected by the signal processing device  64  as a reference signal. The trocar  40  may be moved towards the body surface so that the tip  46  of the obturator  40  pierces through the body surface. As the trocar  40  pierces through the body surface, the obturator  44  travels through different layers of body tissue. As the obturator  44  proceeds through different layers of body tissue, the surgeon  80  will feel variations in the amplitude of vibration through the handle  42  of the trocar  40 . In embodiments of trocar  40  with sensor  62 , the signal processing device  64  may indicate the layer of tissue that the obturator  44  is piercing through. Using this feedback from the trocar  40  as a guide, the surgeon  80  may maneuver the trocar  40  into the body while avoiding internals organs and parts of the body that he/she wishes to avoid. If the obturator  44  contacts a bone, the impact of the obturator  44  on the bone may induce a second vibratory signal on the obturator  44 . This second vibratory signal may be a shock wave or a vibration having a different frequency than the reference vibration, and may be detected by the surgeon and/or the signal processing device  64 . When the surgeon  80  detects that the obturator  44  has contacted a bone, he may reposition the trocar  40  within the body to avoid the bone. 
     Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.