WO2009152244A1

WO2009152244A1 - Depth gauge

Info

Publication number: WO2009152244A1
Application number: PCT/US2009/046905
Authority: WO
Inventors: Dieter Schmidli; Gregor Feigenwinter; Adrian Baumgartner
Original assignee: Synthes Usa, Llc; Synthes Gmbh
Priority date: 2008-06-12
Filing date: 2009-06-10
Publication date: 2009-12-17

Abstract

Apparatus for determining dimensions of a hole in a bone in a living body, comprises a probe sized and shaped for insertion into the hole to be measured in combination with a sensor on the probe, the first sensor transmitting energy to tissue adjacent thereto and receiving energy reflected therefrom and a processing arrangement analyzing data from the sensor to determine whether tissue adjacent to the first sensor is compact bone and to calculate locations of compact bone surrounding the hole.

Description

DEPTH GAUGE

Inventors: Dieter Schmidli, Gregor Feigenwinter and Adrian Baumgartner

Field of the Invention

[0001] The present invention relates to a device and method for measuring the dimensions of a hole or opening formed in a bone or other material.

Background

[0002] Depth gauges may be used to determine the depths of bone holes to, for example, select an appropriately sized bone fixation device to be used in treatment. Presently available depth gauges require users to insert a device into the bone hole and then visually observe markers on the device to determine a depth to which it has been inserted. Such depth gauges are difficult to handle and often result in inaccurate or imprecise measurements. Additionally, these depth gauges are not suitable for measuring the lengths of holes passing entirely through bones.

Summary of the Invention

[0003] The present invention is directed to an apparatus for determining dimensions of one of a hole in a bone in a living body and a hole extending through a wall, tube or another mechanical structure, comprises a probe sized and shaped for insertion into the hole to be measured in combination with a sensor/emitter on the probe, the first sensor/emitter transmitting energy to tissue adjacent thereto and receiving energy reflected therefrom and a processing arrangement analyzing data from the sensor/emitter to determine whether tissue adjacent to the first sensor is compact bone and to calculate locations of compact bone surrounding the hole. Brief Description of the Drawings

[0004] [000] Fig. 1 shows a perspective view of a depth gauge according to a first embodiment of the present invention;

Fig. 2A shows a partial cross-sectional view of the device of Fig. 1 in a first operative configuration;

Fig. 2B shows a signal amplitude graph for Fig. 2A;

Fig. 3 A shows a partial cross-sectional view of the device of Fig. 1 in a second operative configuration;

Fig. 3B shows a signal amplitude graph for Fig. 3A;

Fig. 4A shows a partial cross-sectional view of the device of Fig. 1 in a third operative configuration;

Fig. 4B shows a signal amplitude graph for Fig. 4A;

Fig. 5 A shows a partial cross-sectional view of the device of Fig. 1 in a fourth operative configuration;

Fig. 5B shows a signal amplitude graph for Fig. 5A;

Fig. 6A shows a partial cross-sectional view of the device of Fig. 1 in a fifth operative configuration;

Fig. 6B shows a signal amplitude graph for Fig. 6A;

Fig. 7A shows a perspective view of a depth gauge according to a second embodiment of the present invention;

Fig. 7B shows a partial cross-sectional view of the device of Fig. 7A in an operative configuration;

Fig. 7C shows a signal amplitude graph for Fig. 7B;

Fig. 8A shows a perspective view of a depth gauge according to a third embodiment of the present invention;

Fig. 8B shows a partial cross-sectional view of the device of Fig. 8 A in an operative configuration; Fig. 8C shows a signal amplitude graph for Fig. 8B;

Fig. 9 A shows a partial cross-sectional view of the device of Fig. 1 in a sixth operative configuration; and

Fig. 9B shows a signal amplitude graph for Fig. 9A.

Detailed Description

[0005] The present invention is directed to a system and method for measuring the depth and/or width of a hole in a bone of a living body. The device of the present invention is also directed to determining which materials are present at a target site within or adjacent to the bone. For example, the device of the present invention allows a user to determine if a material adjacent to a specified depth of the hole is fluid (e.g., blood), soft tissue, cancellous bone, a bone implant or another material having a density substantially different from a density of the target portion of bone. Embodiments of the present invention may also be configured to measure and compare values of conductibility, reflection, etc., as those skilled in the art will understand and as described in greater detail hereinafter. It is noted that although the present invention is described with respect to particular uses within bones of the body, the device may also be employed in non-medical applications including but not limited to determining dimensions of holes in electrical devices, tubing, walls, floors, etc. As used in this application, the term proximal refers to a direction approaching a physician or other user of the device and the term distal refers to a direction along the device away from the user. In an operative configuration, the distal end of the device is received within the body while the proximal end remains external to the body accessible to the user.

[0006] Fig. 1 shows a first exemplary device 100 according to the present invention. The device 100 comprises a handle 102 and an elongated probe 104 extending distally therefrom and attached to the handle 102 in any known manner. The handle 102 is formed with an ergonomic groove 106 to aid in handling thereof. However, other shapes may be employed without deviating from the scope of the invention. A proximal end of the handle 102 further comprises an on/off switch 108 configured to control the on/off functionality of the device 100. A power source (not shown) such as a battery is located within the handle 102 and may be encased therein by a removable cover (not shown) to permit replacement or charging thereof as needed. In an alternate embodiment, the handle 102 may comprise a port (not shown) facilitating connection of the device or the battery to an external power source, as those skilled in the art will understand. The handle 102 further comprises a display screen 110 adjacent to a proximal end 109. The display screen 110 displays depth measurements to the user. The device 100 may also comprise any of various electrical components known in the art including but not limited to: a storage medium, a port for connecting to an external electronic device (e.g., a computer, a phone, a flash drive, a power source, etc.), an audible feedback, etc.

[0007] A distal end of the handle 102 comprises an opening 112 within which the probe 104 is received so that a proximal portion (not shown) of the probe 104 may be connected to the above- recited electronic components within the handle 102. The probe 104 which extends distally from the handle 102 to a distal end 114 includes a plurality of sensors 116 disposed over a length thereof. In a preferred embodiment, the sensors 116 are evenly distributed over a length and about a circumference of the probe 104 which, in this embodiment is substantially cylindrical. The sensors 116 may include one or more of ultrasound sensors, optical sensors, electromagnetic sensors, piezoelectric sensors, conductive sensors, capacitive sensors, and resistive sensors as those skilled in the art will understand. It is further noted that any number of sensors 116 may be arranged over the probe 104 in any pattern without deviating from the scope of the present invention.

[0008] Figs. 2A - 2B depict a first exemplary method according to the present invention, wherein the device 100 is used to determine the dimensions of a bone hole 152 extending through a bone 150. The bone hole 152 is a bicortical bone hole and extends completely through the bone 150 in accordance with an exemplary bicortical bone fixation procedure, as those skilled in the art will understand. Specifically, the bone hole 152 extends through first and second compact bone portions 154, 156 as well as through a medullary cavity or spongy bone layer 158 located therebetween and opens to both sides of the bone 150.

[0009] [000] In accordance with the exemplary method of the present invention, the probe 104 is inserted through an incision (e.g., the incision through which the drill was inserted to form the incision) in the skin adjacent into the target bone hole 152 to a target location therein. As would be understood by those skilled in the art, a user of the device 100 may use any suitable imaging technique known in the art to guide the probe 104 to the target position which, in this example, requires that the probe extend completely though the bone hole 152 as shown in Fig. 2A. The device 100 is then turned on via the on/off switch 108 and the sensors 116 begun to emit, for example, ultrasound signals. It is noted that although embodiments of the present invention are described with respect to ultrasound sensors 116, any of the sensors disclosed earlier may be employed without deviating from the spirit and scope of the present invention. In accordance with an exemplary embodiment of the present invention, the sensors 116 are configured to transmit ultrasound signals and receive the signals after they have been reflected by adjacent tissue. Each of the sensors 116 transmits data corresponding to the reflected signals received thereby to a computing apparatus (not shown) in the handle 102. The computing apparatus (not shown) then prepares a signal amplitude graph 160 as shown in Fig. 2B. The signal amplitude graph 160 may be displayed on the display 100, saved in a storage medium in the device 100 or may be transmitted to an external electronic apparatus. In an exemplary embodiment, the computing apparatus (not shown) is configured to compute the length 1 between peaks 162, 164 of the signal amplitude graph 134. Specifically, the ultrasound signals received by the sensors 116 adjacent to the compact bone portions 154, 156 along an outer periphery of the bone 150 are stronger than the signals received by sensors 116 within the medullary cavity/spongy bone layer 158. As those skilled in the art will understand, the difference in signal strength from sensor 116 to sensor 116 correlates directly to the composition of the tissue adjacent to the corresponding sensor 116. Specifically, variations in signal strength correlate directly to a density or other physical property of the material from which the signals are reflected and may be compared with a computed index to determined a density of this material, as those skilled in the art will understand. In another embodiment, a light source may be employed in place of the ultrasound sensors 116 and the system may be configured to measure light absorption and reflection. In yet another embodiment, a current source may be employed in placed of the ultrasound sensors 116, wherein a conductibility of adjacent portions of bone or other material may be determined. The computed index may store values corresponding to signal strengths relating to various materials including blood, water, soft tissue, cancellous bone, etc. to facilitate the identification of the materials adjacent to the various sensors 116, as those skilled in the art will understand. In this manner, the device 100 may also be used to determine the properties (e.g., density) of the various layers of bone and/or other materials adjacent to the bone 150. The device 100 uses the difference in length between the peaks 162, 164 of the signal amplitude graph 160 to determine the length of the bone hole 152. Specifically, as outlying compact bone portions 154, 156 at opposite ends of the bone hole 152 have substantially the same density, the signal strengths corresponding to these portions should be substantially similar and the length 1 between these peaks will correspond to the distance between the sensors 116 from which these similar values are received. This data is quantified and displayed on the display 110 in a predetermined unit of measure. A physician or other use may then use the displayed measurement to select an appropriately sized bone screw for a target procedure.

[00010] Figs. 3 A - 3B show the device 100 being used to determine the depth of a bone hole

252 extending partially through a bone 250. An exemplary method according to the present embodiment is substantially similar to the method discussed with respect to Figs. 2A - 2B. Specifically, the probe 104 is inserted through a minimally invasive incision adjacent to a target portion of the bone 250 and into the bone hole 252 until the distal end 114 engages a distal end

253 of the bone hole 252. In this case, as the bone hole 252 extends only partially through the compact bone of the bone 250, all of the tissue adjacent to the sensors 116 that are within the bone 250 has a substantially uniform density. In one embodiment, such a bone hole 252 may be formed in accordance with, for example, a monocortical bone fixation procedure, as those skilled in the art will understand. Accordingly, as shown in the signal amplitude graph 260, a signal strength of the bone hole 252 has a substantially constant peak across the length 1 while the sensors proximal of the bone 250 will be adjacent to soft tissue and/or a bone plate and will therefore exhibit different densities. In the absence of peaks formed at extremities of the signal amplitude graph 260 (i.e., corresponding to portions of compact bone separated by softer tissue within the medullary canal, etc.), the device 100 is configured to measure the length along which the signal 262 has a substantially constant non-zero signal strength. This length 1 will correspond to the distance between a proximal-most sensor 116 exhibiting this constant non-zero signal amplitude and the distal end 114 of the probe 104. Thus, an end point of the signal 262 can be determined to be the point at which the signal strength deviates significantly from the value at the start point.

[00011] Figs. 4A - 4B depict an exemplary method of use of the device 100 to determine the depth of a bone hole 352 extending partially through a bone 350. Specifically, the bone hole 342 extends through a near side of the compact bone, through the medullary canal to the radially inner surface of the opposite portion of the compact bone. An exemplary method according to the present embodiment is substantially similar to the method discussed with respect to Figs. 2A - 2B, wherein the bone 350 is also formed with compact bone areas 354, 356 and a less dense central area 358. The bone hole 352 terminates at a distal end 353 at the junction of the compact bone area 356 and the central area 358. In an operative configuration, the probe 104 is inserted through the bone hole 352 until the distal end 114 engages the distal end 353 of the bone hole 352. The device 100 is then turned on and the sensors 116 emit ultrasound signals as discussed above. The sensors 116 receive the reflected signals and compile a signal amplitude graph 360. Since a signal strength of the central area 358 is substantially low, the device 100 computes a length 1 of the bone hole 352 as the distance along a longitudinal axis of the probe 104 between the sensor(s) 116 corresponding to a peak 362 associated with the compact bone area 354 and the distal end 114 of the probe 104, as discussed above with respect to Figs. 3A - 3B. Specifically, the device 100 identifies a signal strength corresponding to the compact bone 354 and lower signal strengths corresponding to the soft tissue outside the bone 350 and the softer tissue within the central area 358. The depth of the hole 352 is calculated as a distance between a proximal- most sensor 116 indicating a signal strength substantially equal to the value associated with the compact bone area 354 and the distal end 114 of the probe 104.

[00012] Figs. 5 A - 5B illustrate a method of use of the device 100 to determine the thickness of a bone 450 at a bone hole 452, wherein the bone 450 may be a thin bone such as a cranium, a pelvic bone, a maxilla, a zygoma, etc. The bone 450 has a cross-section which is substantially entirely made up of compact bone of substantially uniform density. In an operative configuration, the probe 104 is inserted through the bone hole 452 until it reaches a desired position with the distal end 1 14 protruding from the distal side of the bone 450. As would be understood by those skilled in the art, this position may be determined using any suitable imaging technique known in the art or by preoperative planning methods to ensure that the distal end 114 of the probe 104 is positioned distally of a distal end of the bone hole 452, as described in greater detail earlier. The device 100 is then turned on and the sensors 1 16 emit ultrasound signals and receive the reflections of these signals from the surrounding tissue as discussed above. The data is then employed to compile a signal amplitude graph 460 in the same manner described above. The device 100 then computes a length 1 of the bone hole 452 as the distance between the proximal -most and distal-most of the sensors 116 which are outputting a signal strength 462 the amplitude of which indicates proximity to compact bone as opposed to the significantly lower amplitude portions of the signal outputted by sensors 116 adjacent to soft tissue, etc., as those skilled in the art will understand. Those skilled in the art will understand that known noise filtering and signal correcting techniques may be employed to enhance the ability of the device 100 to identify the portions of the signal corresponding to various substances (e.g., compact bone, soft tissue, metal plates, etc.) The length 1 may then be displayed on the display 110 in the predetermined unit of measure.

[00013] Figs. 6A - 6B illustrate a similar use of the device 100 to determine the thickness of a first portion of compact bone 554 through which a bone hole 552 extends to a spongy bone layer 558. In an operative configuration, the probe 104 is inserted into the bone 550 through the bone hole 552 until the distal end 114 is located within the spongy bone layer 558. The device 100 is then turned on and the sensors 116 emit ultrasound signals as discussed above. The sensors 116 receive the reflected signals and compile a signal amplitude graph 560. The device 100 then computes a length 1 of the bone hole 552 as the portion of the signal amplitude graph 560 having a peak 562 substantially greater than outlying portions, as described in greater detail in earlier embodiments. A physician may use this measurement to determine an appropriate length of a bone screw to be used for an exemplary bone fixation procedure. Specifically, those skilled in the art will understand that when the compact outer bone layer often has a greater strength than the spongy bone layer 558. It is noted that this example is exemplary only and the measurement may alternatively be used for any other procedure without deviating from the spirit and scope of the present invention.

[00014] Figs. 7 A - 7C depict a device 100' according to a second embodiment of the invention, wherein the device 100' is configured to measure the length of a bone hole when a bone plate is attached thereto. The device 100' is formed substantially similarly as the device 100 of Fig. 1 with the exception of a slide 118 operably connected to the probe 104 by a slidable attachment 120. The slide 118 projects outward from a radially outermost portion of the slidable attachment 120. A diameter of the substantially cylindrical slidable attachment 120 is selected to be greater than that of a plate or bone hole being measured to prevent the slide 118 and the attachment mechanism 120 from being inserted thereinto. The slide 118 is formed of a material with predetermined properties that permits detection thereof in the same manner as the sensors 116. For example, if ultrasound sensors 116 are used on the probe 104, the slide 118 is formed with ultrasound markers disposed thereupon or alternatively, is formed entirely of a material visible under ultrasound detection, as those skilled in the art will understand. In an exemplary embodiment, the slidable attachment mechanism 120 is formed of the same material as the slider 118 and may be formed of one of stainless steel, titanium, polyaryletheretherketone ("PEEK") or another suitable material. A distal face of the attachment mechanism 120 is configured to lie substantially flush against an outer periphery of the hole or opening being measured. It is further noted that although the slide 118 and slidable attachment 120 are depicted in combination with a bone plate 672, the slide 118 and slidable attachment 120 may also optionally be configured to rest directly on a top surface of a bone without an intervening bone plate without deviating from the spirit and scope of the present invention.

[00015] Fig. 7B shows a partial cross-sectional view of the device 100' in an operative configuration. Specifically, the device 100' is configured to measure the combined depth of a bone plate hole 672 extending through a bone plate 670 and a bone hole 652 formed through a target bone 650. Those skilled in the art will understand the viability of such a measurement in determining, for example, a size of a bone screw (not shown) to be used to lock the bone plate 670 to the bone 650. In accordance with an exemplary method of the present invention, the bone plate 670 is positioned against a target portion of the bone and temporarily held in place using a technique known in the art. The probe 104 is then inserted through the plate hole 672 and through the bone hole 652. Specifically, an incision may be formed adjacent the target portion of the bone 650 to permit insertion of the device 100' therethrough. The incision (not shown) is preferably sized to receive both the probe 104 and the slide 118 therethrough. The probe 104 is then advanced through the plate hole 672 and the attachment mechanism 120 is positioned against a proximal surface thereof. As described above, a user of the device 100 may employ any suitable known imaging technique known in the art to confirm that the probe 104 has been inserted completely though the bone hole 652, as those skilled in the art will understand. The device 100 is then turned on via the on/off switch 108 so that the sensors 116 begin to emit and receive ultrasound signals. The device 100 then measures the reflected ultrasound signals and computes a signal amplitude graph 660 as shown in Fig. 7C. A length 1 of the combined plate and bone hole 672, 652 is then computed as the distance between starting point 662 and end point 664 corresponding to the distance from an outer surface of the bone 650 on which the plate 670 rests and an outer surface of the bone 650 at the far end of the bone hole 652. Specifically, the starting point 662 corresponds to an outer surface of the compact bone layer 656 and has a significantly greater signal strength than the soft tissue adjacent to the bone 650, as described in greater detail above. The end point 664 is defined by a location of a slider signal 666. Specifically, a signal strength 666 of the slider 118 is determined by preoperative planning. The device 100' is then configured to mark the location of the slider signal 666 as the end point 664. The length 1 may be displayed on the display 110 and a physician or other user may use the displayed measurement, for example, to select an appropriately sized bone screw for a target procedure.

[00016] As shown in Figs. 8A - 8C, a device 700 according to a third embodiment of the invention is substantially similar to the device 100 with the exception of a sensing mechanism thereof. Specifically, whereas the device 100 included a plurality of sensors 116 distributed along and around the probe 104, the device 700 comprises a sensor 716 that is movable along the length of a probe 704 (e.g., a motor-operated sensor). The device 700 comprises a handle 702 with an opening 712 formed at a distal end thereof to receive the probe 704. The probe 704 extends from the handle 702 to a distal end 714. In an exemplary embodiment, the probe 704 comprises a longitudinal channel 706 extending therethrough and closed at the distal end 714. The channel 706 is configured to permit slidable movement of the sensor 716 along a wire 708. The wire 708 is fixed along a longitudinal axis of the channel 706 and is attached, at a proximal end to a motor 720. The motor 720 is connected to a power source (not shown) to drive the sensor 716 along the wire 708 at a predetermined speed, which may be selected by a user of the device 700. Specifically, when the device 700 is turned on by an on/off switch (not shown), the sensor 716 moves back and forth over the entire length of the probe 704 at the predetermined speed. The motor 720 may be configured to only drive the sensor 716 for a predetermined period of time or, in an alternate embodiment, may be manually controlled by an operator of the device 700.

[00017] The sensor 716 transmits data to the device 200 to compute a signal amplitude graph 760 as shown in Fig. 8C in the same manner as was done by the array of sensors 116 in the device 100. Start and end points 764, 766 corresponding to peaks of the signal amplitude graph 760 indicate the location of compact bone portions 754, 756, as described in greater detail earlier. A length 1 between the start and end points 764, 766 indicates a length of a bone hole 752 extending through a bone 750 is computed based on the position of the sensor 716 along the wire 708 corresponding to the various points on the signal amplitude graph. The length 1 may be displayed on a display window 710 and employed by a user in the same manner described above.

[00018] Figs. 9A - 9B depict the device 100 of the present invention being used to determine a width of a bone hole 852 extending through a bone 850. The method discussed hereinafter may be used to determine a width of a hole extending through any long bone or other bone in a living body or, alternatively, a width of a hole through a tube, wall, etc. The exemplary method according to the present embodiment is substantially similar to the method discussed with respect to Figs. 2A - 2B and may be employed in supplement thereto. Specifically, the sensors 116 may be configured to measure a time or phase shift of a reflected signal when the device 100 is turned on. The time or phase shift is indicative of the time the signal needs to travel to and back from a wall of the bone hole 852, wherein a greater travel distance will be indicative of a greater width of the bone hole 852. Accordingly, as shown in signal amplitude graph 860 of Fig. 9B, a signal strength of the bone hole 862 may comprise a signal 862 that varies in signal strength across the length of the bone. The device 100 is configured to determine the highest and lowest signal strengths 864, 866, respectively and display these values on the display 110, wherein the signal strengths 864, 866 correspond to the widest and narrowest portions of the bone hole 852. A physician or other user of the device 100 may then use the diameter values on the display 110 to determine an appropriately sized bone fixation device to be employed in a target procedure. Specifically, the lower signal strength 866 corresponding to a narrowest diameter of the bone hole 852 defines a largest possible diameter of the bone fixation device, as those skilled in the art will understand.

[00019] It is noted that any of a number of modifications may be made to the depth gauges disclosed herein without deviating from the scope of the present invention. In one example, the probe 104 of the device 100 may be configured to expand after insertion into a bone plate hole. The probe 104 may be formed of a substantially flexible material and may be connected, at a proximal end, to an inflation source to permit expansion thereof. An outer surface of the probe 104 comprises a plurality of pressure sensors (not shown) which transmit signals indicative of a resistance encountered after inflation. The resulting data may be used to compute a signal amplitude graph to indicate dimensions of the bone plate hole, as described in greater detail in earlier embodiments.

[00020] Although the present invention has been described with reference to preferred embodiments, it is submitted that various modifications can be made to the exemplary system and method without departing from the spirit and scope of the invention.

Claims

What is claimed is:

1. Apparatus for determining dimensions of a hole in a bone in a living body, comprising:

a probe sized and shaped for insertion into the hole to be measured;

a sensor on the probe, the first sensor transmitting energy to tissue adjacent thereto and receiving energy reflected therefrom;

a processing arrangement analyzing data from the sensor to determine whether tissue adjacent to the first sensor is compact bone and to calculate locations of compact bone surrounding the hole.

2. The apparatus of claim 1 , wherein the sensor comprises a plurality of sensors distributed along a length of the probe, the processing arrangement analyzing data from the plurality of sensors to calculate, based on locations of the sensors, locations of compact bone surrounding the hole having a predetermined location relative to the first sensor.

3. The apparatus of claim 2, wherein the sensors include one of ultrasound sensors, optical sensors, electromagnetic sensors, piezoelectric sensors, conductive sensors, capacitive sensors, and resistive sensors.

4. The apparatus of claim 2, wherein the first and second sensors are distributed along the length of the probe in a substantially uniform pattern.

5. The apparatus of claim 4, wherein the sensors are distributed about a circumference of the probe substantially uniformly.

6. The apparatus fo claim 2, wherein the first and second sensors are distributed along the length of the probe in a non-uniform pattern.

7. The depth gauge of claim 1 , further comprising a display screen on a handle which, during use, remains outside the body.

8. The depth gauge of claim 1, further comprising a projection slidably attached to the probe for movement distally thereover to an operative position contacting a proximal end of the hole, the projection being formed of a material selected to reflect energy from the sensor in a manner clearly distinguishable by the processing arrangement from compact bone and soft tissue.

9. The depth gauge of claim 1, wherein the sensor is movably mounted to the probe, the processing arrangement monitoring a position of the sensor within the probe and associating data from the sensor with the position of the sensor to determine one of a depth and a width of a portion of compact bone adjacent to the hole.

10. The depth gauge of claim 9, further comprising a motor driving the first sensor through the probe.

11. The depth gauge of claim 1, wherein the processing arrangement determines dimensions of the hole based on a signal property of the reflected signals received by the sensor.

12. A method for measuring dimensions of an opening in a bone, the method comprising:

inserting a probe of a depth gauge into the opening, the probe including a sensor mounted thereon;

transmitting a energy from the sensor to tissue adjacent thereto; receiving energy reflected from the adjacent tissue by the sensor;

measuring a signal strength of the received energy; and

identifying locations at which compact bone is adjacent to the opening based on the measured signal strength.

13. The method of claim 11 , wherein the probe includes an array of sensors, wherein the locations at which compact bone is adjacent to the opening are determined based on a signal strength received from the sensors and locations of the sensors along the probe.

14. The method of claim 11, wherein the sensor is movable along the probe, the locations at which compact bone is adjacent to the opening being determined based on a plurality of signal strength values received from the sensor and locations of the sensor along the probe corresponding to the signal strength values.

15. The method of claim 11, further comprising identifying locations at which one of a bone plate, spongy bone and soft tissue is adjacent to the opening based on the measured signal strength.

16. The method of claim 11 , further comprising sliding a reflective member along the probe to a target position abutting a proximal end of the opening, the reflective member being formed of a material selected to reflect energy from the sensor in a manner clearly distinguishable from compact bone and soft tissue.