US20100198227A1 - Surgical depth instrument - Google Patents

Abstract

An instrument that measures the depth of an open or closed hole in a bone or other tissue electronically, provides a rotatable display of information relating to the depth. The surgical depth gauge comprises a probe insertable into the hole that measures a depth that is communicated to the rotatable display. The display may be rotatable in one, two, or three dimensions, and may be implemented as a wired or wireless display. A locking mechanism may be provided to lock the display in a particular orientation best suited for a particular situation.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
• This application is a continuation of co-pending U.S. patent application Ser. No. 12/391,814, filed Feb. 24, 2009, which is a continuation-in-part of U.S. patent application Ser. No. 11/376,399, filed Mar. 15, 2006, now issued as U.S. Pat. No. 7,493,703, which is a continuation-in-part of U.S. patent application Ser. No. 11/081,147, filed on Mar. 16, 2005, now issued as U.S. Pat. No. 7,165,336, the entire content of these being herein incorporated by reference.
BACKGROUND
• The invention relates to an instrument for determining the depth of an open or closed hole and, in particular, a depth gauge for providing a digital measurement of the depth of the open or closed hole in a bone.
• Many surgical procedures require surgeons to secure a device to the bone of a patient. In some procedures, the surgeon spans and secures one or more bones, or pieces of bone, using a bone plate and screws or other fasteners. In other procedures, the surgeon uses a screw or other fastener without another device, for example, to secure a transplanted tendon. In many procedures, the surgeon drills a hole in the bone prior to securing the fastener to the bone. With a hole in place, the surgeon can more easily select a fastener of the appropriate length. Selecting a fastener of appropriate length can be very important. If the fastener is too long, the fastener may protrude from the bone. Typically, the bone abuts against soft tissues that may be harmed if the fastener is too long. Although over-drilling through a metacarpal may result only in minor damage to the fat layer within the finger, if the fastener used after drilling is too long, the patient may experience more serious complications. For example, a fastener that protrudes may be tactilely felt by the patient, prevent soft tissues (such as tendons, ligaments, or muscles) from moving over the bone surface, or even pierce the skin. As a different example, complications such as paralysis may result from a fastener mounted in the pedicle portion of the human spine that protrudes to a point where the fastener contacts the spinal cord.
• During drilling, the surgeon is typically capable of feeling when the drill has penetrated through the bone from a drop in resistance of the drill against the bone. Because the simple act of drilling does not provide an exact measurement of the depth of the bone, surgeons sometimes use an analog depth gauge to measure the depth of the hole.
• Analog depth gauges typically comprise a central probe member having a barb at the distal end, and a reciprocating sleeve that encircles the proximal end of the central probe member. To measure the depth of a hole in a bone, the surgeon abuts the sleeve against the proximal side of the hole, and extends the probe member into the hole. After extending the probe member beyond the distal side of the hole, the surgeon retracts the probe member, attempting to find purchase against the distal side of the hole with the barb. Typically, a marker is secured to the central probe member and the reciprocating sleeve has a graduated scale (in inches or millimeters) along a portion of its length. The surgeon reads the measurement of depth by examining the position along the graduated scale indicated by the marker secured to the central probe member.
• A number of problems are associated with the analog depth gauge. Components of the analog depth gauge are typically manufactured from surgical-grade stainless steel, with the graduated scale embossed along a portion of the length of the reciprocating member, producing a highly reflective surface. Under bright operating room lights, surgeons find it difficult to see the graduated scale of millimeter-wide length increments. An accurate measurement of depth using an analog depth gauge requires the surgeon to make a close examination of the graduated scale while holding the analog depth gauge steady. If the barb loses its purchase on the distal side of the hole, either the accuracy of the measurement is decreased or the time required for surgery must be extended to permit repositioning of the barb. In surgical procedures that require many depth measurements, these difficulties are multiplied.
• There are other problems associated with the analog depth gauge. An accurate reading of the graduated scale requires the eyes of the surgeon to be properly aligned with the graduated scale. Viewed from an angle, the position of the marker relative to the graduated scale may be distorted. The eyes of the surgeon may not be properly aligned with the graduated scale while the surgeon is standing erect. The surgeon may have to bend over while using the analog depth gauge to make an accurate reading because if the depth gauge is tilted in order to make the reading, the sleeve will shift relative to the probe, making the measurement less accurate and possibly causing the barb to lose its purchase on the distal side of the hole, resulting in the same disadvantages mentioned above.
• Accordingly, there has been a need for an improved depth gauge for surgical procedures.
SUMMARY
• The present invention provides a system for faster and more accurate measurements of depth during surgery and permits an adjustment of the orientation screen to permit easy viewing of a display that provides depth measurement information.
• Accordingly, in an embodiment of the invention, a generally elongated instrument is provided for measuring the depth of a hole with a first edge and a second edge, the instrument having a longitudinal axis, the instrument comprising: a first generally elongated member substantially oriented along the longitudinal axis and which is insertable in the hole, the first member comprising a portion positionable against a first surface in which the first edge of the hole is formed; a second generally elongated member substantially oriented along the longitudinal axis and which is slidably connected to the first member, the second member comprising a portion positionable against a second surface in which the second edge of the hole is formed and a sensor that generates an electronic signal that varies in relation to the distance between the first member and the second member; and a rotatable electronic display for displaying information representative of the distance measured by the sensor.
• In another embodiment, a depth measurement gage is provided for measuring a hole depth, comprising: a measurement tool that converts an extension length of a measuring element into a representative electronic signal; a display assembly connected to the depth measurement gage, the display assembly comprising: a rotatable display that comprises: a display screen for displaying a numeric representation corresponding to the extension length based on the electronic signal received from the measuring tool; display electronics that receive the electronic signal, converts it into a displayable value, and drives the display to display the value; and a locking mechanism that holds the display at a particular orientation; wherein the rotatable display is rotatable about an axis normal to a surface of the display screen; the display assembly further comprising: a housing that connects with and supports the rotatable display; the depth measurement gage further comprising: a rotation element that allows the rotatable display to rotate about an axis parallel to a surface of the display screen.
• In another embodiment, a depth measurement gage is provided for measuring a hole depth, comprising: a measurement tool that converts an extension length of a measuring element into a representative electronic signal; an elongated housing extending along a longitudinal axis of the measurement tool; a rotatable rectangular display that, when in an initial position, has a side that is parallel to the longitudinal axis, the display comprising: a display screen for displaying a numeric representation corresponding to the extension length based on the electronic signal received from the measuring tool; display electronics that receive the electronic signal, converts it into a displayable value, and drives the display to display the value; and a locking mechanism that holds the display at a particular orientation; wherein the rotatable display is rotatable about an axis normal to a surface of the display screen.
• In another embodiment, a depth measurement gage is provided for measuring a depth of a hole, comprising: a measurement tool that converts an extension length of a measuring element into a representative electronic signal that is wirelessly transmitted; a display assembly connected to the depth measurement gage, the display assembly comprising: a wireless rotatable display that comprises: a display screen for displaying a numeric representation corresponding to the extension length based on the electronic signal received from the measuring tool; a wireless antenna and signal receiver that receives the wirelessly transmitted electronic signal; and display electronics that receive the electronic signal, converts it into a displayable value, and drives the display to display the value; the display assembly further comprising: a housing that connects with and supports the rotatable display.
BRIEF DESCRIPTION OF THE DRAWINGS
• The foregoing and other objects, advantages, and features of the present invention will be apparent from the following detailed description and the accompanying drawings illustrating various embodiments of the invention, in which:
• FIG. 1 is a perspective view from above of a surgical depth instrument in accordance with an embodiment of the present invention;
• FIG. 2A is a cross-section of a surgical depth instrument in a retracted position in accordance with an embodiment of the present invention;
• FIG.2A′ is an enlarged pictorial detail view of a circled portion of the cross-section shown inFIG. 2A;
• FIG. 2B is a cross-section of a surgical depth instrument in an extended position and engaged with the distal surface of a bone portion in accordance with an embodiment of the present invention;
• FIG.2B′ is an enlarged pictorial detail view of a circled portion of the cross-section shown inFIG. 2B;
• FIG. 3 is an exploded perspective view of a sealed housing in accordance with an embodiment of the surgical depth instrument of the present invention;
• FIG. 4 is a perspective view from below of a surgical depth instrument in accordance with an embodiment of the present invention;
• FIG. 5 is a cross-section view of the sealed housing and body of a surgical depth instrument in accordance with an embodiment of the present invention, taken at section line5-5 ofFIG. 4;
• FIG. 6A is a pictorial view of a probe with a barb in accordance with an embodiment of the present invention;
• FIG. 6B is a pictorial view of a probe with a hook in accordance with an embodiment of the present invention;
• FIG. 7 shows a surgical depth instrument in accordance with a second embodiment of the present invention;
• FIG. 8 is an exploded perspective view of an exemplary display assembly according to an embodiment of the invention;
• FIG. 9 is an assembled perspective view of the display assembly illustrated inFIG. 8;
• FIG. 10 is a perspective bottom view of a lower display housing;
• FIG. 11 is a perspective view of an exemplary transparent cover of the display assembly;
• FIG. 12 is a perspective view of a locking slider of the display assembly;
• FIG. 13 is a perspective view of the display assembly pivotally mounted to a pivot arm;
• FIG. 14 is a perspective view of a display assembly according to another embodiment of the invention;
• FIGS. 15A,15B are top views of further embodiments of the invention;
• FIG. 15C is a top view of the embodiment shown inFIGS. 15A and 15B showing a rotated display; and
• FIG. 15D is a top view of the embodiment shown inFIGS. 15A-15C illustrating a rotation about the longitudinal axis of a section comprising the display.
DETAILED DESCRIPTION OF THE EMBODIMENTS
• After drilling a hole in a bone during surgery, a surgeon will often use an instrument to measure the depth of the hole before selecting a fastener. The system and method of the present invention are performed using a surgical depth gauge with an electronic sensor and digital display, which provide an easier, faster, and more accurate means for measuring depth during surgery. While a variety of embodiments of the invention are shown in the attached figures, those skilled in the art will recognize that there are other mechanical and electrical arrangements for accomplishing surgical depth measurements digitally in accordance with the present invention. Various alternative embodiments, features and variations are therefore also described herein.
• Instruments used for surgical procedures must be robust both to the solid and liquid contaminants encountered during surgery (such as tissue and blood) and the temperatures, pressures, and fluids encountered during sterilization (such as hydrogen peroxide gas). The two embodiments of the present invention shown in the attached drawings illustrate two alternative form factors for the sterilization-proof and contamination-proof surgical depth gauge in accordance with the present invention. In afirst embodiment100 shown inFIGS. 1 through 5, the surgical depth gauge comprises atissue guard120, sealedhousing130, andbody140 that are robust to contamination. In addition, thefirst embodiment100 can be quickly disassembled and reassembled for sterilization. In asecond embodiment200 shown inFIG. 7, the surgical depth gauge comprises a fullyintegrated body235, in which is sealed an electronic sensor and displays. The second embodiment is robust to repeated contamination and sterilization without disassembly.
• With a hole already drilled, a surgeon might reach for a surgical depth instrument of the present invention as shown by theinstrument100 ofFIG. 1. Theinstrument100 comprises aprobe160 with anindented hook165, and atissue guard120 secured to abody140. A sealedhousing130 slidably engages with aside groove144 of thebody140 of theinstrument100. As shown inFIG. 1, the sealedhousing130 comprises adisplay window150, ergonomictop ridges170, and ergonomic side grooves withridges180. The present invention is adapted for use by either a left-handed or a right-handed surgeon. The side grooves withridges180 are concave to the side surface of the sealedhousing130, and are symmetrically disposed on either side of the sealedhousing130.
• An alternative embodiment of the form factor for the present invention is shown inFIG. 7 as thesecond embodiment200. In this alternative embodiment, the invention comprises a substantially cylindrical form factor. As discussed above, thesecond embodiment200 comprises anintegrated body235 that is robust to contamination and sterilization without disassembly. Referring toFIG. 7, thesecond embodiment200 comprises anintegrated body235 withslide groove239 anddisplay window250 formed therein. In accordance with an embodiment, so that the same instrument may be used by both right-handed and left-handed surgeons, a display window250 (and accompanying display) will be provided on both the right and left sides of the instrument. In other words, with respect toFIG. 7, another display window250 (and display) will be similarly disposed on the other side of the instrument. The distal end of theintegrated body235 includes atissue guard220. In an embodiment, the method of the present invention is practiced by positioning the distal end of thetissue guard220 against the proximal surface of the bone (as shown in connection withFIGS. 2A and 2B, described below). According to an embodiment, theintegrated body235 of theinstrument200 may be fabricated from two substantially symmetrical pieces that may be disassembled and reassembled to facilitate sterilization. As shown inFIG. 7, the two pieces fit together along a line through the middle of theintegrated body235. In various embodiments, the two pieces may be threaded together, or sealed together by an adhesive resistant to contamination and sterilization. In addition, as shown inFIG. 7, the secondembodiment form factor200 also comprises finger grooves disposed towards its bottom side.
• Turning back to the first embodiment of the form factor shown byinstrument100 inFIG. 1, theinstrument100 includesside grooves180, which are formed in thebottom piece139 of the sealed housing130 (seeFIG. 3). In other embodiments, however, theside grooves180 may be formed in both thetop piece138 andbottom piece139, such that the side grooves extend from top to bottom symmetrically along the sides of the sealedhousing130. As will be appreciated by those of skill in the art, in still other embodiments, theside grooves180 may be convex to the side surface of the sealedhousing130, and may be formed with a surface of bumps rather than ridges, or with other surfaces that provide friction and a tactile surface, even after exposure to solid or liquid contamination. In addition, in all of the embodiments shown in the attached drawings, thedisplay window150 is positioned nearer the distal end of the instrument. As will be appreciated by those of skill in the art, thedisplay window150 may be positioned elsewhere on the instrument, for example, nearer the proximal end. In addition, multiple display windows may be disposed at various locations on the instrument. All such features and variations are contemplated within the scope of the present invention.
• An embodiment of the method for taking depth measurements in accordance with the present invention begins with the surgeon holding theinstrument100 in either a right or a left hand.FIG. 2A shows a longitudinal cross-section of theinstrument100 with theprobe160 in a retracted position, and abone portion10 shown also in cross-section. In accordance with an embodiment of the method of the present invention, the surgeon begins a depth measurement by locating the position of the hole in thebone portion10. As shown in the enlarged detail of FIG.2A′, the tip of theindented hook165 protrudes slightly beyond thedistal end122 of thetissue guard120, thereby permitting the surgeon to sense the position of the hole when the tip of theindented hook165 slips into the hole. In this position, thedistal end122 of thetissue guard120 abuts against theproximal surface30 of thebone portion10. In an embodiment, theinstrument100 is calibrated to read zero depth when the catch (or the proximal end) of thehook165 is flush with thedistal end122 of thetissue guard120.
• In an embodiment, the method of the present invention also comprises a step wherein the surgeon extends theprobe160 into thehole20 of thebone portion10.FIG. 2B shows a cross-section of theinstrument100 in an extended position. FIG.2B′ shows an enlarged detail ofFIG. 2B, in which theindented hook165 has purchase on thedistal surface40 of thehole20. In the cross-sections shown in FIGS.2B and2B′, thedistal end122 of thetissue guard120 remains against theproximal surface30 of thebone portion10 in which ahole20 is present. From the position shown in FIG.2B′, the surgeon reads a measurement of depth from an electronic display behind thedisplay window150 in thecompartment134 of the sealedhousing130.
• As shown in FIGS.2A′ and2B′, thebone portion10 is bicortical, i.e., thebone portion10 has a first, proximal cortical layer12 (see FIG.2A′), acancellous layer14, and a second, distal cortical layer16 (see FIG.2B′). It should be noted, however, that the present invention is suitable for use with bones having other structures, including solid cortical, unicortical, or cancellous bones. The present invention may even be used for surgical depth measurement of holes or cavities in other types of tissue.
• As described above, thehole20 may be a hole formed in thebone portion10. In using theinstrument100 to measure the distance from aproximal surface30 formed on the proximalcortical layer12 to adistal surface40 formed on the distalcortical layer16, theinstrument100 operates so that the distance between thedistal end122 of the tissue guard120 (which abuts the proximal surface12) and the proximal end of the indented hook165 (which has purchase on the distal surface16) is determined by an electronic sensor, generating a precise measurement of the distance between theproximal surface30 anddistal surface40. The electronic sensor may comprise inductive or capacitive elements in a read assembly on a printed circuit board and inductive or capacitive elements in an increment assembly on a printed circuit board within thecompartment146 of the body140 (seeFIG. 5). More specifically, theprobe160 of theinstrument100 is inserted into the proximal edge22 of thehole20, through thehole20, and out from adistal edge26 of thehole20, such that theindented hook165 of theprobe160 extends beyond thedistal surface40 of thebone portion10. Extension of theindented hook165 away from thebody140 is accomplished in accordance with theinstrument100 by pressing a thumb or forefinger against thetop ridges170 on the sealedhousing130. As should be clear to those of ordinary skill in the art, if thehole20 is a hole formed by a drill bit of cylindrical symmetry, the proximal anddistal edges22 and26 will be approximately circular.
• The distal end of theprobe160 is equipped with anindented hook165 in theinstrument100 shown inFIGS. 1,2,4 and7. In other embodiments, however, theindented hook165 may be replaced with another means for detecting thedistal surface40. In particular,FIGS. 6A and 6B show in profile alternative mechanical embodiments of the distal end of theprobe160.FIG. 6A shows a barb167 at the distal end of theprobe160.FIG. 6B shows a hook169 at the distal end of theprobe160.
• With theindented hook165 at its distal end, theprobe160 can take purchase on thedistal surface40 of thebone portion10. Theinstrument100 is shown in this position in FIGS.2B and2B′. Once theindented hook165 has completely passed through thedistal edge26, the shaft of theprobe160 is shifted slightly, laterally so that the indentation in theindented hook165 abuts against thedistal edge26. A slight retraction of theprobe160 then permits theindented hook165 to engage (or take purchase on) thedistal surface40 of the distalcortical layer16. Retraction of theindented hook165 is accomplished in accordance with theinstrument100 by squeezing theside grooves180 with thumb and forefinger, and pulling lightly. In this manner, the proximal surface of theindented hook165 and the distal end of thetissue guard120, respectively, are positioned against thedistal surface40 andproximal surface30 of thebone portion10 and, through the use of slight tension, are retained thereon. In reading the electronic display when the invention is maintained in this physical configuration, the surgeon is provided with an accurate measurement of the depth of thehole20 in thebone portion10.
• Although in the embodiment depicted inFIG. 1, theprobe160 includes a mechanical securement (in the form of an indented hook165), other mechanical and nonmechanical means for positioning the distal end of theprobe160 against thedistal surface40 of thebone portion10 may be used in other embodiments of the present invention. In particular, electronic sensors may be used in other embodiments to detect where thedistal surface40 terminates. For example, an ultrasonic transducer, optical or other sensor may be used to detect where thedistal surface40 terminates by measuring differential acoustic or optical reflectivity or transmissivity or other characteristics as theprobe160 traverses thehole20. In such embodiments, an electronic sensor may be mounted to the distal end of theprobe160 in a configuration perpendicular to the length of theprobe160. Alternatively, the distal end of theprobe160 may include only a perforation disposed perpendicular to the length of theprobe160, and a conduit that provides an acoustical, optical, or electrical connection to a sensor included in the sealedhousing130. As will be recognized by skilled artisans, such a conduit might be provided by a hollow probe, fiber optic, or insulated wire, respectively. Moreover, in some embodiments, a current-sensing device may be placed in electrical connection (for example, with an insulated wire) with the distal end of the sensor to detect a change in the resistivity or conductivity of the environment local to the distal end of theprobe160.
• Theinstrument100 further includes a reference portion that abuts theproximal surface30. In the embodiment of the invention shown in the attached drawings, the reference portion is provided by atissue guard120. Thetissue guard120, as shown by way of example inFIGS. 1,2,4 and7, has a tapered conical shape. The tissue guard includes a cylindrical hollow at its core, through which theprobe160 may extend and retract. In other embodiments, the tissue guard may take a narrower, longer, or more elongated shape to permit easier passage through tissues disposed between the surgeon and theproximal surface30 of thebone portion10. For example, in another embodiment, thetissue guard120 may be replaced with a simple cylindrical sleeve fitted into a conical piece at the distal end of the body of the instrument. The tapered conical shape of thetissue guard120 shown inFIGS. 1,2,4 and7, however, may be desirable for minimizing mechanical stress at the joints between thetissue guard120 andbody140.
• In an embodiment, the end of thebody140 nearest thetissue guard120 has a threaded nipple (not shown inFIG. 1) of diameter larger than the diameter of theprobe160. In theinstrument100, the threaded nipple is integrally formed with the end of thebody140. In another embodiment, the threaded nipple may be secured to the distal end of thebody140 by a mechanical device or an adhesive. In all such embodiments, thetissue guard120 is provided with a complementary threaded surface such that thetissue guard120 andbody140 are secured by threading thetissue guard120 onto the threaded nipple of thebody140. In such embodiments, thetissue guard120 may be formed from injection molded plastic or from machined metal. In other embodiments, thetissue guard120 may be formed as a single, seamless piece with thebody140.
• Thetissue guard120 and probe160 are concentrically arranged such that the distal end of thetissue guard122 abuts theproximal surface30 of thebone portion10 in a manner similar to that of a bone plate or fastener head. Accordingly, thetissue guard120 andindented hook165 cooperate such that their relative position (and, therefore, distance) provides an accurate measurement of the depth of thehole20 such that a screw or fastener may be selected whose length is accommodated by thehole20.
• In the embodiment of the invention provided by theinstrument100, movement of the sealedhousing130 is effective to shift the position of theprobe160 because theprobe160 and sealedhousing130 are attached as shown inFIG. 3. A portion of the bottom side of the sealedhousing130 is formed into amating surface132. Theprobe160 is encircled by and secured within the portion of the bottom side of the sealed housing that forms themating surface132. In an embodiment, theprobe160 is interference press-fit into thebottom piece139 of the sealedhousing130. Also shown inFIG. 3 are the mechanical parts of the sealedhousing130, including thetop piece138,bottom piece139, andseal136. In an embodiment, theseal136 is an o-ring seal, which is robust to repeated contamination and sterilization. In addition,FIG. 3 shows thedisplay window150, which in an embodiment of the invention, is provided by a polycarbonate lens. Thecompartment134 within the sealedhousing130 provides the mechanical support for the electronic sensor and display (not shown inFIG. 3). As described below, the electronics secured to thecompartment134 within the sealedhousing130 comprise the read-head assembly of an inductive or capacitive or other sensor, a display, and a power source (such as a battery).
• In the embodiment of the sealedhousing130 shown inFIG. 3, electronic components (including an electronic sensor, display, and power source) are sealed inside thecompartment134 with an o-ring seal136. In addition, the sealedhousing130 may be sealed with epoxy, glue, or other adhesives. In other embodiments, the sealedhousing130 may be mechanically sealed with hardware, such as screws or snaps within thecompartment134. Although the embodiment of the sealedhousing130 shown inFIG. 3 is designed to remain sealed both during surgery and sterilization, it will be appreciated by those skilled in the art that in an alternative embodiment, the sealedhousing130 may be designed to partially or completely disassemble for sterilization. All these features and variations are contemplated within the scope of the present invention.
• When sealed, the embodiment of the sealedhousing130 shown inFIG. 3 is water resistant to several atmospheres of pressure. Moreover, the materials used to manufacture the sealedhousing130 are selected to be chemically inert to chemical contaminants or sterilization fluids, both at room temperature and at the temperatures required for sterilization in an autoclave. For example, the sealedhousing130 may be molded from acrylic, polyester, PVC, or other chemically inert plastic material. In other embodiments, the sealed housing may be made from metals, such as aluminum, brass, or stainless steel. The sealedhousing130 is also designed to provide only soft, rounded edges that are safe for use in a surgical environment. For example, the embodiment of the sealedhousing130 shown inFIGS. 1 through 5 is in substantial compliance with the Underwriters Laboratories sharpness test UL 1349.
• Although theinstrument100 shown in the attached drawings includes a display, it will be understood by those of skill in the electronic arts that the present invention may be practiced using an external display in communication with a wireless device. In theinstrument100, a wireless transmitter may be connected to the read-head assembly within the sealedhousing130. In such wireless embodiments, a wireless receiver would be positioned a short distance away from the surgical depth gauge (for example, on a platform near the operating table), and an electronic display would be connected to the wireless receiver. In addition, as a supplement to a visual display, the instrument may be provided with an audio readout capability that may, for example, beep or provide another audible signal when the instrument senses that movement of the probe has stopped, and there has been an appropriate interval in which to take a measurement. In addition, the instrument may include the capability for the distance displayed to also be audibly conveyed through a simulated voice from a speaker maintained within the instrument. In this manner, the surgeon's determination of the distance may also be verified from the audible articulation of the distance, providing further confidence in the accuracy of the reading.
• A perspective view of theinstrument100 from the bottom is shown inFIG. 4. As shown inFIG. 4, the present invention includes several ergonomic features in addition to the top ridges170 (shown inFIGS. 1 and 3). In particular, theinstrument100 includes symmetrically shaped side grooves withridges180 andfinger grooves190. As shown in the cross-sectional end view ofFIG. 5, thefinger grooves190 are formed in the convexbottom side192 of thebody140. In accordance with an embodiment of the method of the present invention, a surgeon would place a forefinger on afirst side groove180, a thumb on the opposingside groove180, and the rest of the fingers on thefinger grooves190 integrated with thebody140. The ergonomic design of the present invention permits a surgeon to use the system and perform the method of the present invention with a single hand, either right or left. Moreover, the present invention leaves thebottom side192 entirely unobstructed so that the surgeon is always free to grab thebody140.
• Some structural features of the invention shown inFIG. 5 have the advantage of permitting theinstrument100 to be disassembled and reassembled for sterilization. In particular, the sealedhousing130 andbody140 are slidably connected along amating surface132 of the sealedhousing130 and a reciprocal mating surface142 formed within theside groove144 of thebody140. Theprobe160, which is engaged in the sealedhousing130, slides through theside grooves144 of thebody140 and into a funneled cylindrical channel formed in thetissue guard120. In another embodiment, thetissue guard120 may provide a keyhole-shaped (rather than a cylindrical) channel to permit probe tips without cylindrical symmetry (i.e., tips such as the barb167 or hook169 shown inFIGS. 6A and 6B) to pass through during disassembly and reassembly of theinstrument100. Moreover, in such other embodiments, thetissue guard120 may be rotated after assembly to prevent the distal end of theprobe160 from retracting within thetissue guard120. Such a rotation is permitted when thetissue guard120 threads onto thebody140, as described above. Without a keyhole-shaped channel, probe tips of non-cylindrical symmetry must have a maximum width less than the total diameter of the cylindrical channel in thetissue guard120.
• When slidably connected as shown in theinstrument100, the present invention does not require oil lubricants, such that the materials are entirely compatible with a surgical environment. Referring toFIG. 3, theinstrument100 is shown in cross-section (along the plane4-4 through the sealedhousing130 shown inFIG. 3) viewed facing the distal end. The sealedhousing130 is shown inFIG. 3, with the compartment134 (again, shown without internal electronic components), andtop ridges170. Theseal136 is also shown disposed between thetop piece138 andbottom piece139 of the sealedhousing130. In addition, themating surface132 of thebottom piece139 is shown engaged with the reciprocal mating surface142 formed by and within theside groove144 of thebody140. Also, theprobe160 is shown concentric to the end of themating surface132 of thebottom piece139. By permitting a slidable connection between the sealedhousing130 andbody140, themating surface132 of thehousing130 and complementary mating surface of the body facilitate disassembly and reassembly of theinstrument100 for sterilization. Moreover, because the surfaces are not symmetric from left to right along the line5-5 inFIG. 5, the system can be reassembled only with the display facing the distal end. The non-symmetrical design of the complementary mating surfaces thus prevents the present invention from being reassembled incorrectly.
• The electronic sensors used in the system and method of the present invention comprise capacitive and inductive sensors and sensor assemblies. Sensors and sensor assemblies are readily available commercially from manufacturers such as Sylvac and Mitutoyo. For example, capacitive and inductive read-head and write-head assemblies are used in digital calipers, such as that made by Mitutoyo America Corporation, 965 Corporate Blvd., Aurora, Ill., and by Guilin Measuring and Cutting Works, 106 Chongxin Road, Guangxi, Guilin 541002, Peoples Republic of China. In general, the electronic sensor secured within thecompartment134 of the sealedhousing130 takes the form of a conventional electronic sensor, display, and power source assembly for use in a length measuring device relying on inductive or capacitive or other elements. For some embodiments, inductive elements may provide advantages to the extent that inductors provide more uniform and consistent measurements through a wider variety of environmental conditions. For example, theinstrument100 may be built with a pattern of inductive loops laid down along thesensor pattern compartment146 of thebody140, and a facing read-head assembly secured within thecompartment134 of the sealedhousing130.
• In various embodiments of the present invention, the electronic sensor may be connected with a microprocessor or other digital electronic device in order to produce an output for an electronic display, such as a liquid crystal display or light-emitting diode display. In other embodiments, the microprocessor or other digital electronic device may be connected to a wireless transmitter, as described above. In some embodiments, a signal conditioning circuit may interpose the inductive or capacitive elements of the electronic sensor and the microprocessor or other digital electronic device used to drive the display, thus ensuring that correct input current and voltage levels are provided to the various components. As will be recognized by skilled artisans, a power source, such as a primary or secondary battery, may be connected to the signal conditioning circuit or to the microprocessor directly.
• The microprocessor or other digital electronic device used to drive the display may be configured to provide depth measurements in inches, millimeters, or fractions thereof. In various embodiments, the sealedhousing130 may include buttons that permit the surgeon to select how the preferred unit of measurement is displayed. In an embodiment, the microprocessor or other digital electronic device is configured to provide a positive reading for depth as theprobe160 is extended from theproximal surface30 toward thedistal surface40 of thebone portion10, and a zero reading when theprobe160 is retracted so that the catch of the hook is flush with the distal end of the tissue guard. In another embodiment, the present invention may be configured to permit a re-zeroing of the device by providing a calibration button. In still other embodiments, the present invention may provide on and off buttons (or an on/off toggling button), or a button for storing and holding the measurement presently shown on the display for reading after theprobe160 has been moved. In such embodiments, the buttons may be formed in the sealedhousing130.
• The electronic display of the present invention is selected for quick and easy visual inspection during surgery. The electronic display, however, may provide information in addition to depth measurements. For instance, the present invention may be provided as part of a kit (not shown) including a bone plate that mates with a head and shank formed on a screw. The electronic sensor may be calibrated to compensate for or provide an offset corresponding to a portion of the screw head and shank received within the bone plate. Accordingly, the present invention could be configured to suggest a particular screw selected from the kit for use with the bone plate, rather than a measurement of length. The electronic display may also provide an indication that the reading is not stable, for example, because thetissue guard120 and probe160 are not generally stationary relative to one another. This event is more typical when compressible soft tissue is caught on theindented hook165, or between thetissue guard120 and theproximal surface30, or in general when the distal end of theprobe160 is not securely positioned. In this respect, it should be noted that theprobe160 may be provided without any mechanical securement at its distal end. As an example, the distal end of theprobe160 may be inserted to a depth such that its distal end is coincident with, but generally does not extend beyond, thedistal edge26 of thehole20. In using such an embodiment, the surgeon may place a stop or finger on thedistal surface40 of thebone portion10 to stop theprobe160 when it has reached thedistal edge26.
• In an embodiment, the electronic sensor and accompanying electronics can be shielded from electromagnetic interference, for example, by coating the inside of the sealedhousing130 with a conductive paint containing metal microspheres. Such shielding may be effective in reducing interference from low frequency magnetic fields, or other stray electromagnetic fields. Shielding is desirable at least because the method of the present invention may be practiced in conjunction with the use of a magnetic pad for holding surgical instruments (not shown inFIGS. 1-3).
• Although the displays shown inFIGS. 1-7 can generally be seen by a user of the device, clearly a display that can be oriented in different directions advantageously assist the viewability of the display, particularly under the conditions in which the device would be used.
• Therefore, referring toFIGS. 8 and 9, arotatable display assembly300 is provided that permits better viewability depending on the orientation of the measuring device. Thisrotatable display assembly300 shown inFIG. 9 may be mounted directly to an end of theprobe100,200, or may be mounted via apivot arm391, as is illustrated inFIG. 13.
• Referring toFIG. 8, the display assembly, according to an embodiment of the invention, is made up of three primary components that can be broken down in more detail: anupper housing310, arotatable display340, and alower housing370. The upper310 and lower370 housing provide a structure in which therotatable display340 may be mounted and locked at a particular orientation.
• Thedisplay340 is preferably a generally circular shape and comprises adisplay screen350 along withdisplay electronics352 that are used to operate thedisplay screen350. Thedisplay screen350 is preferably a liquid crystal display (LCD), since this is a relatively low-power type of display well suited for a measuring instrument. This LCD display could provide some form of back-lighting that is known in the art. Thedisplay screen350 could also be implemented as a light-emitting diode (LED) display. This display, while consuming greater power than the LCD display, could serve to improve readability. Also, other display technologies, such as organic light-emitting diodes (OLED) and the like could be utilized. The display could be arranged in a number of ways, ranging from a simple seven-segment numeric display to a screen display comprising a color pixel grid. Thedisplay screen350 anddisplay electronics352 are affixed within a circular housing comprising an upper342 and a lower360 housing component.
• In order to permit a locking and holding of thedisplay340 at a particular orientation, one or both of the following may be provided: a plurality of lockingholes346 on a side edge of theupper display housing342, and a plurality of lockinggrooves348 also located on a side edge of the upper342 and lower360 housing components. It should be noted that the location of the locking holes346 and/or lockinggrooves348 could be provided on thelower housing360, or even on an upper or lower surface of thehousing components342,360. The operative action of the locking holes346 and lockinggrooves348 will be described in more detail below along with the other elements with which they interact.
• Theupper housing component342 may provide awindow344 through which thedisplay screen350 can be read. It is also possible that theupper housing component342 would have a clear surface through which thedisplay screen350 could also be read.
• Referring toFIGS. 8 and 10, thelower display housing360 comprises apin364 about which thedisplay340 rotates. Additionally, when thedisplay340 is a wired display, the lower display housing may comprisewire slots362 via which wires can be provided to thedisplay screen350 andelectronics352. The wires could be provided via connectors or could be soldered directly to circuitry of the display. Other channels can be provided for getting the wires to thewire slots362. Stops, such as interfering protrusions provided on thedisplay340 and an adjacent part of thedisplay assembly300 could be provided that prevent rotation beyond a certain limit.
• When thedisplay340 is a wireless display, then nosuch access slots362 need to be provided. Such adisplay340 may be easily placed into thedisplay assembly300 and become operative with little effort. For thewireless display340, thedisplay electronics352 comprises an antenna and receiver that can read signals provided by the measuring device itself. Any form of short range wireless communication hardware and protocol may be utilized here.
• In the embodiment shown inFIGS. 8 and 9, thedisplay340 is provided between theupper housing310 and thelower housing370. The display rests on acenter support382 of thelower housing370. Thepin364 fits in apin slot384. Although theslot384 could potentially be a mere hole, it is preferred that this be elongated to permit some lateral movement of the display, which enhances the orientation lockability, to be described below.
• Thedisplay340 rests between a proximal (to the measuring device)support386 and adistal support374. Theproximal support386 has a curved raised edge designed to match a curvature of thedisplay340.Protrusions390 are provided on a raised edge of theproximal support386 that serve to engage the lockinggroove348 of thedisplay340 when at least some minimal force provided by aspring336 and locking slider332 (see alsoFIG. 12) force the display laterally against the raised edge. This helps to maintain the orientation of thedisplay340 once it has been set.
• Thedistal support374 comprises aspring slot378 into which thespring336 rests. It also comprises aslider recess376 into which the lockingslider332 rests, as well as acorresponding pin slot380 in which theslider pin334 rests. The lockingslider332 preferably has aspring hole338 into which a portion of the spring extends. Thespring hole338 helps to maintain the spring in position, although this is not essential, and other mechanisms, such as an additional pin, may be used. Theslider pin334 itself is designed to engage one of the locking holes346 of the display. Thespring336 resting in the slot is in a generally compressed state, such that it provides a force that biases the lockingslider332 and itsslider pin334 into thedisplay340.
• Thus, a user wishing to orient the display, moves the lockingslider332 towards the distal (away from the measuring device) end of thedisplay assembly300 and against thespring336 bias. This causes theslider pin334 to disengage from the lockinghole346 so that thedisplay340 can be rotated about is axis about thepin364. Absent a biasing force, thedisplay340 is also slightly moved in a distal lateral direction such that the protrusion(s)390 disengage the locking groove(s)348. Thelower housing370 also comprises ahandle portion372 that, when combined with ahandle portion312 of theupper hosing310, provides an easy-to-grasp element for the user.
• Theupper housing310 may be designed as a three-piece unit or as a one-piece unit. The three-piece configuration comprises a separateproximal support member320,distal support member314, andtransparent cover324. In the one-piece unit, these theproximal support member320,distal support member314, andtransparent cover324 may be provided as a single unit, either via assembly or construction as a monolithic unit.
• The transparent cover324 (see alsoFIG. 11), which permits viewing of thedisplay screen350, may compriselegs326 that rest upon leg supports318,322 of thedistal support314 andproximal support320 respectively. Preferably, thelegs326 and leg supports318,322 are proportioned such that an upper surface of the transparent cover is flush with upper surfaces of both thedistal support314 and theproximal support320.
• Thedistal support314 comprises aslot316 into which a top portion of the lockingslider332 protrudes. Alever331 may be affixed to a top surface of the lockingslider332 and serves to form a relatively secure seal of theslider slot316 such that contaminants cannot readily enter theslider slot316. Thus, when the user wishes to reorient thedisplay340, the user moves thelever331 towards the distal end of thedisplay assembly300 and against thespring336 bias to disengage thedisplay340 from the locking mechanisms (332,390). Once thedisplay340 is disengaged, it may be rotated into a locking position (one in which theslider pin334 aligns with thelocking hole346 and the lockinggroove348 aligns with the protrusion390). The user releases thelever331 and thespring336 biases the lockingslider332 to move theslider pin334 into thelocking hole346 and biases thedisplay340 against thecurved side surface388 of theproximal support386, thereby engaging the locking groove(s)348 with the protrusion(s)390.
• Referring toFIG. 13, apivot arm391 is provided that permits an additional axis of rotation for thedisplay assembly300. Thepivot arm391 comprises, at a distal end (away from the measuring device) areceiving slot392 for a proximal end of thedisplay assembly300. The proximal supports320,386 can comprise a hole into which apivot pin398 can be inserted. Thepin398 is supported by apivot hole396 in anarm end394 of thepivot arm391 formed by a receivingslot392 into which the proximal end of thedisplay assembly300 is provided. The rotational freedom of thedisplay assembly300 about thepivot pin398 can be hampered by a frictional fit of the hole of the display assembly against thepivot pin398. Alternately, or additionally, interacting protrusions and grooves, or bumps and holes may be provided between the wall edges of the receivingslot392 and side edges of theproximal supports320,386.
• It should be noted that the embodiment shown provides for a rectangular cross section of the support elements of thedisplay assembly300 and thepivot arm391. However any practical cross-sectional shape can be implemented, such as round, oval, polygonal or other closed curved shape. Furthermore, an additional pivot arm similar to thepivot arm391 described above could be provided at the end of thepivot arm391 in order to permit rotation of the display in three full dimensions.
• Furthermore, the rotating mechanisms described above relating to a pin and hole or slot to permit rotation could also be implemented using supporting roller, spherical, or other forms of bearings, or could also be implemented with a ball socket type arrangement. In the latter arrangement, the locking mechanism could simply be a frictional fit that may or may not be adjustable in the frictional forces created. When a pivoting mechanism is used, the pivot may be placed central to the display, or offset. Furthermore, thedisplay340 itself can be located at either a proximal or distil end of thedisplay assembly300 instead of in a central region.
• FIG. 14 illustrates another embodiment of the display. At the distal end of thebody140, arotatable body section311 is provided that can rotate about a longitudinal axis B. This section can either be connected by wires or connected wirelessly to the actual measurement electronics. When connected with wires, stops, e.g., in the way of interfering protrusions, may be provided the prevent rotation beyond an allowable limit.
• In an embodiment, thedisplay screen350 is provided directly on therotatable body section311. In this embodiment, a series of grooves and protrusions or bumps and holes may be provided on an inner surface of thebody140 and outer surface of therotatable body section311 in order to provide discrete orientation positions for this section. Alternately, therotatable body section311 can be designed to operate with a frictional fit so that it can be rotated when a certain force is deliberately applied but is unlikely to rotate during normal measurement use.
• In a further embodiment, as illustrated inFIG. 14, adisplay340 similar to that illustrated inFIGS. 8-13 is provided that can be rotated about an axis A perpendicular to the longitudinal axis B. Asimilar groove348 and protrusion (not shown) scheme may be utilized to secure the orientation, and the slider pin (not shown) operable by alever331 on adistal support374 can be provided to engageholes346 of thedisplay340. In this way, thedisplay screen350 itself can be provided with two rotational degrees of freedom, thereby permitting the display position to be optimized during use. It should be noted that although a rigid attachment of thedistal support374 is illustrated inFIG. 14, the attachment could also be implemented in the form of, e.g., a ball socket, thereby permitting an additional degree of freedom when orienting the display.
• Two final embodiments are illustrated inFIGS. 15A and 15B in which a generally cylindrical body comprises theextension actuator237 andgroove239. InFIG. 15A, thedisplay340 is generally a flat and rectangular housing on arotatable body section311 of thetool body140 that houses thedisplay screen350 and mounts to the body via apin364 that is located in a generally central position of the display. This permits thedisplay340 to be rotated for ease of viewing. As illustrated inFIG. 15B, thepin364 can be offset from the center. Thisrectangular display340 can be implemented in the designs shown in all previous figures.
• In all of these designs, it is possible to include an option in which the image on display itself can rotate as well, although this would be practical when the display comprises an array of pixels.FIG. 15C illustrates such an implementation. As can be seen inFIG. 15C, the characters on thedisplay screen350 are oriented differently depending on the relative angle of the display screen350 (and display340 itself) with respect to thebody311. An angular sensor could be provided to detect the angle of the display relative to the body. If the angle falls within, e.g., various 90° quadrants, the image on the display could be rotated accordingly by display electronics that sense this angle and adjust the pixels on thedisplay screen350 accordingly. More complex designs could be implemented with, e.g., gravity sensors and the like to determine a preferred orientation, although this design would considerably increase costs and would not work as effectively when the plane of rotation is perpendicular to a fixed reference such as a gravity vector.
• FIG. 15D is a top view of the embodiment shown inFIGS. 15A-15C and illustrates a rotation about the longitudinal axis of abody section311 comprising thedisplay340,350, although an embodiment not having thissection311 rotatable about the longitudinal axis (or rather, having this section fixed relative to a front portion) is also possible.
• All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
• The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
• A variety of embodiments of the invention are described and illustrated herein; variations of those embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context. It is not the intent of the inventors to surrender or otherwise dedicate any valid claim to the subject matter described herein to the public, and the following claims are intended to capture the entire scope of the invention herein described.

Claims (23)

1. A generally elongated instrument for measuring the depth of a hole with a first edge and a second edge, the instrument having a longitudinal axis, the instrument comprising:

a first generally elongated member substantially oriented along the longitudinal axis and which is insertable in the hole, the first member comprising a portion positionable against a first surface in which the first edge of the hole is formed;

a second generally elongated member substantially oriented along the longitudinal axis and which is slidably connected to the first member, the second member comprising a portion positionable against a second surface in which the second edge of the hole is formed and a sensor that generates an electronic signal that varies in relation to the distance between the first member and the second member; and

a rotatable electronic display for displaying information representative of the distance measured by the sensor.

2. The instrument as claimed inclaim 1, wherein the rotatable electronic display rotates about the longitudinal axis.

3. The instrument as claimed inclaim 1, wherein the rotatable electronic display rotates about a lateral axis that is perpendicular to the longitudinal axis.

4. The instrument as claimed inclaim 1, wherein the rotatable electronic display rotates about both the longitudinal axis and the lateral axis.

5. A depth measurement gage for measuring a hole depth, comprising:

a measurement tool that converts an extension length of a measuring element into a representative electronic signal;

a display assembly connected to the depth measurement gage, the display assembly comprising:

a rotatable display that comprises:

a display screen for displaying a numeric representation corresponding to the extension length based on the electronic signal received from the measuring tool;

display electronics that receive the electronic signal, converts it into a displayable value, and drives the display to display the value; and

a locking mechanism that holds the display at a particular orientation;

wherein the rotatable display is rotatable about an axis normal to a surface of the display screen;

the display assembly further comprising:

a housing that connects with and supports the rotatable display;

the depth measurement gage further comprising:

a rotation element that allows the rotatable display to rotate about an axis parallel to a surface of the display screen.

6. The gage as claimed inclaim 5, wherein the rotation element comprises:

a pivot arm having a proximal end connected to the measurement tool; and

a distal end connected to the display assembly and having a pivot assembly that permits the rotatable display to rotate about the axis parallel to the display screen.

7. The gage as claimed inclaim 5, wherein the rotation element comprises a cylindrical rotatable body section rotatably mounted to a main body of the gage.

8. The gage as claimed inclaim 5, wherein the housing comprises upper and lower portions, and the display rests on the lower portion.

9. The gage as claimed inclaim 5, wherein the locking mechanism comprises at least one of: a) a pin and hole, and b) a groove and ridge/protrusion element.

10. The gage as claimed inclaim 9, wherein the locking mechanism comprises a biasing spring that forces at least one of the pin into the hole and the groove into the ridge/protrusion.

11. The gage as claimed inclaim 9, wherein the locking mechanism further comprises a slider with biasing mechanism for engaging and disengaging the locking mechanism.

12. The gage as claimed inclaim 11, wherein the slider comprises a lever affixed to the slider that seals a hole that houses a portion of the slider.

13. The gage as claimed inclaim 5, wherein the rotation element comprises a pin and a hole into which the pin is inserted, the parallel axis defined by a longitudinal axis of the pin.

14. The gage as claimed inclaim 5, wherein the rotation element comprises a ball and socket that further allows the rotatable display to rotate about a central point defined by a center of the ball.

15. A depth measurement gage for measuring a hole depth, comprising:

a measurement tool that converts an extension length of a measuring element into a representative electronic signal;

an elongated housing extending along a longitudinal axis of the measurement tool;

a rotatable rectangular display that, when in an initial position, has a side that is parallel to the longitudinal axis, the display comprising:

a display screen for displaying a numeric representation corresponding to the extension length based on the electronic signal received from the measuring tool;

display electronics that receive the electronic signal, converts it into a displayable value, and drives the display to display the value; and

a locking mechanism that holds the display at a particular orientation;

wherein the rotatable display is rotatable about an axis normal to a surface of the display screen.

16. The gage as claimed inclaim 15, wherein the rotatable display comprises at least one of a pin and a hole that mates with a respective hole or pin either directly or indirectly attached to the housing.

17. The gage as claimed inclaim 16, wherein the at least one of the pin and hole is located at a center of the display.

18. The gage as claimed inclaim 16, wherein the at least one of the pin and hold is located near an edge of the display.

19. The gage as claimed inclaim 16, further comprising electronics for rotating characters relative to the display based on a detected angle of the display to the body or other fixed reference angle.

20. A depth measurement gage for measuring a depth of a hole, comprising:

a measurement tool that converts an extension length of a measuring element into a representative electronic signal that is wirelessly transmitted;

a display assembly connected to the depth measurement gage, the display assembly comprising:

a wireless rotatable display that comprises:

a display screen for displaying a numeric representation corresponding to the extension length based on the electronic signal received from the measuring tool;

a wireless antenna and signal receiver that receives the wirelessly transmitted electronic signal; and

display electronics that receive the electronic signal, converts it into a displayable value, and drives the display to display the value;

the display assembly further comprising:

a housing that connects with and supports the rotatable display.

21. The gage as claimed inclaim 20, further comprising a locking mechanism that holds the display at a particular orientation.

22. The gage as claimed inclaim 20, further comprising:

an element permitting rotation of the display about an axis normal to a surface of the display screen; and

a further rotation element that allows the rotatable display to rotate about an axis parallel to the surface of the display screen.

23. A generally elongated instrument for measuring the depth of a hole with a first edge and a second edge, the instrument having a longitudinal axis, the instrument comprising:

a first generally elongated member substantially oriented along the longitudinal axis and which is insertable in the hole, the first member comprising a portion positionable against a first surface in which the first edge of the hole is formed;

a second generally elongated member substantially oriented along the longitudinal axis and which is slidably connected to the first member, the second member comprising a portion positionable against a second surface in which the second edge or a base of the hole is formed and a sensor that generates an electronic signal that varies in relation to the distance between the first member and the second member; and

audio electronics that audibly conveys information representative of the distance measured by the sensor to a user of the instrument.

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