SURGICAL DEPTH INSTRUMENT

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 in FIG. 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 in FIG. 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 line 5-5 of FIG. 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 in FIG. 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 in FIGS. 15A and 15B showing a rotated display; and

FIG. 15D is a top view of the embodiment shown in FIGS. 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 a first embodiment 100 shown in FIGS. 1 through 5, the surgical depth gauge comprises a tissue guard 120, sealed housing 130, and body 140 that are robust to contamination. In addition, the first embodiment 100 can be quickly disassembled and reassembled for sterilization. In a second embodiment 200 shown in FIG. 7, the surgical depth gauge comprises a fully integrated body 235, 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 the instrument 100 of FIG. 1. The instrument 100 comprises a probe 160 with an indented hook 165, and a tissue guard 120 secured to a body 140. A sealed housing 130 slidably engages with a side groove 144 of the body 140 of the instrument 100. As shown in FIG. 1, the sealed housing 130 comprises a display window 150, ergonomic top ridges 170, and ergonomic side grooves with ridges 180. The present invention is adapted for use by either a left-handed or a right-handed surgeon. The side grooves with ridges 180 are concave to the side surface of the sealed housing 130, and are symmetrically disposed on either side of the sealed housing 130.

An alternative embodiment of the form factor for the present invention is shown in FIG. 7 as the second embodiment 200. In this alternative embodiment, the invention comprises a substantially cylindrical form factor. As discussed above, the second embodiment 200 comprises an integrated body 235 that is robust to contamination and sterilization without disassembly. Referring to FIG. 7, the second embodiment 200 comprises an integrated body 235 with slide groove 239 and display window 250 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 window 250 (and accompanying display) will be provided on both the right and left sides of the instrument. In other words, with respect to FIG. 7, another display window 250 (and display) will be similarly disposed on the other side of the instrument. The distal end of the integrated body 235 includes a tissue guard 220. In an embodiment, the method of the present invention is practiced by positioning the distal end of the tissue guard 220 against the proximal surface of the bone (as shown in connection with FIGS. 2A and 2B, described below). According to an embodiment, the integrated body 235 of the instrument 200 may be fabricated from two substantially symmetrical pieces that may be disassembled and reassembled to facilitate sterilization. As shown in FIG. 7, the two pieces fit together along a line through the middle of the integrated body 235. 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 in FIG. 7, the second embodiment form factor 200 also comprises finger grooves disposed towards its bottom side.

Turning back to the first embodiment of the form factor shown by instrument 100 in FIG. 1, the instrument 100 includes side grooves 180, which are formed in the bottom piece 139 of the sealed housing 130 (see FIG. 3). In other embodiments, however, the side grooves 180 may be formed in both the top piece 138 and bottom piece 139, such that the side grooves extend from top to bottom symmetrically along the sides of the sealed housing 130. As will be appreciated by those of skill in the art, in still other embodiments, the side grooves 180 may be convex to the side surface of the sealed housing 130, 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, the display window 150 is positioned nearer the distal end of the instrument. As will be appreciated by those of skill in the art, the display window 150 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 the instrument 100 in either a right or a left hand. FIG. 2A shows a longitudinal cross-section of the instrument 100 with the probe 160 in a retracted position, and a bone portion 10 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 the bone portion 10. As shown in the enlarged detail of FIG. 2A′, the tip of the indented hook 165 protrudes slightly beyond the distal end 122 of the tissue guard 120, thereby permitting the surgeon to sense the position of the hole when the tip of the indented hook 165 slips into the hole. In this position, the distal end 122 of the tissue guard 120 abuts against the proximal surface 30 of the bone portion 10. In an embodiment, the instrument 100 is calibrated to read zero depth when the catch (or the proximal end) of the hook 165 is flush with the distal end 122 of the tissue guard 120.

In an embodiment, the method of the present invention also comprises a step wherein the surgeon extends the probe 160 into the hole 20 of the bone portion 10. FIG. 2B shows a cross-section of the instrument 100 in an extended position. FIG. 2B′ shows an enlarged detail of FIG. 2B, in which the indented hook 165 has purchase on the distal surface 40 of the hole 20. In the cross-sections shown in FIGS. 2B and 2B′, the distal end 122 of the tissue guard 120 remains against the proximal surface 30 of the bone portion 10 in which a hole 20 is present. From the position shown in FIG. 2B′, the surgeon reads a measurement of depth from an electronic display behind the display window 150 in the compartment 134 of the sealed housing 130.

As shown in FIGS. 2A′ and 2B′, the bone portion 10 is bicortical, i.e., the bone portion 10 has a first, proximal cortical layer 12 (see FIG. 2A′), a cancellous layer 14, and a second, distal cortical layer 16 (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, the hole 20 may be a hole formed in the bone portion 10. In using the instrument 100 to measure the distance from a proximal surface 30 formed on the proximal cortical layer 12 to a distal surface 40 formed on the distal cortical layer 16, the instrument 100 operates so that the distance between the distal end 122 of the tissue guard 120 (which abuts the proximal surface 12) and the proximal end of the indented hook 165 (which has purchase on the distal surface 16) is determined by an electronic sensor, generating a precise measurement of the distance between the proximal surface 30 and distal surface 40. 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 the compartment 146 of the body 140 (see FIG. 5). More specifically, the probe 160 of the instrument 100 is inserted into the proximal edge 22 of the hole 20, through the hole 20, and out from a distal edge 26 of the hole 20, such that the indented hook 165 of the probe 160 extends beyond the distal surface 40 of the bone portion 10. Extension of the indented hook 165 away from the body 140 is accomplished in accordance with the instrument 100 by pressing a thumb or forefinger against the top ridges 170 on the sealed housing 130. As should be clear to those of ordinary skill in the art, if the hole 20 is a hole formed by a drill bit of cylindrical symmetry, the proximal and distal edges 22 and 26 will be approximately circular.

The distal end of the probe 160 is equipped with an indented hook 165 in the instrument 100 shown in FIGS. 1, 2, 4 and 7. In other embodiments, however, the indented hook 165 may be replaced with another means for detecting the distal surface 40. In particular, FIGS. 6A and 6B show in profile alternative mechanical embodiments of the distal end of the probe 160. FIG. 6A shows a barb 167 at the distal end of the probe 160. FIG. 6B shows a hook 169 at the distal end of the probe 160.

With the indented hook 165 at its distal end, the probe 160 can take purchase on the distal surface 40 of the bone portion 10. The instrument 100 is shown in this position in FIGS. 2B and 2B′. Once the indented hook 165 has completely passed through the distal edge 26, the shaft of the probe 160 is shifted slightly, laterally so that the indentation in the indented hook 165 abuts against the distal edge 26. A slight retraction of the probe 160 then permits the indented hook 165 to engage (or take purchase on) the distal surface 40 of the distal cortical layer 16. Retraction of the indented hook 165 is accomplished in accordance with the instrument 100 by squeezing the side grooves 180 with thumb and forefinger, and pulling lightly. In this manner, the proximal surface of the indented hook 165 and the distal end of the tissue guard 120, respectively, are positioned against the distal surface 40 and proximal surface 30 of the bone portion 10 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 the hole 20 in the bone portion 10.

Although in the embodiment depicted in FIG. 1, the probe 160 includes a mechanical securement (in the form of an indented hook 165), other mechanical and nonmechanical means for positioning the distal end of the probe 160 against the distal surface 40 of the bone portion 10 may be used in other embodiments of the present invention. In particular, electronic sensors may be used in other embodiments to detect where the distal surface 40 terminates. For example, an ultrasonic transducer, optical or other sensor may be used to detect where the distal surface 40 terminates by measuring differential acoustic or optical reflectivity or transmissivity or other characteristics as the probe 160 traverses the hole 20. In such embodiments, an electronic sensor may be mounted to the distal end of the probe 160 in a configuration perpendicular to the length of the probe 160. Alternatively, the distal end of the probe 160 may include only a perforation disposed perpendicular to the length of the probe 160, and a conduit that provides an acoustical, optical, or electrical connection to a sensor included in the sealed housing 130. 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 the probe 160.

The instrument 100 further includes a reference portion that abuts the proximal surface 30. In the embodiment of the invention shown in the attached drawings, the reference portion is provided by a tissue guard 120. The tissue guard 120, as shown by way of example in FIGS. 1, 2, 4 and 7, has a tapered conical shape. The tissue guard includes a cylindrical hollow at its core, through which the probe 160 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 the proximal surface 30 of the bone portion 10. For example, in another embodiment, the tissue guard 120 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 the tissue guard 120 shown in FIGS. 1, 2, 4 and 7, however, may be desirable for minimizing mechanical stress at the joints between the tissue guard 120 and body 140.

In an embodiment, the end of the body 140 nearest the tissue guard 120 has a threaded nipple (not shown in FIG. 1) of diameter larger than the diameter of the probe 160. In the instrument 100, the threaded nipple is integrally formed with the end of the body 140. In another embodiment, the threaded nipple may be secured to the distal end of the body 140 by a mechanical device or an adhesive. In all such embodiments, the tissue guard 120 is provided with a complementary threaded surface such that the tissue guard 120 and body 140 are secured by threading the tissue guard 120 onto the threaded nipple of the body 140. In such embodiments, the tissue guard 120 may be formed from injection molded plastic or from machined metal. In other embodiments, the tissue guard 120 may be formed as a single, seamless piece with the body 140.

The tissue guard 120 and probe 160 are concentrically arranged such that the distal end of the tissue guard 122 abuts the proximal surface 30 of the bone portion 10 in a manner similar to that of a bone plate or fastener head. Accordingly, the tissue guard 120 and indented hook 165 cooperate such that their relative position (and, therefore, distance) provides an accurate measurement of the depth of the hole 20 such that a screw or fastener may be selected whose length is accommodated by the hole 20.

In the embodiment of the invention provided by the instrument 100, movement of the sealed housing 130 is effective to shift the position of the probe 160 because the probe 160 and sealed housing 130 are attached as shown in FIG. 3. A portion of the bottom side of the sealed housing 130 is formed into a mating surface 132. The probe 160 is encircled by and secured within the portion of the bottom side of the sealed housing that forms the mating surface 132. In an embodiment, the probe 160 is interference press-fit into the bottom piece 139 of the sealed housing 130. Also shown in FIG. 3 are the mechanical parts of the sealed housing 130, including the top piece 138, bottom piece 139, and seal 136. In an embodiment, the seal 136 is an o-ring seal, which is robust to repeated contamination and sterilization. In addition, FIG. 3 shows the display window 150, which in an embodiment of the invention, is provided by a polycarbonate lens. The compartment 134 within the sealed housing 130 provides the mechanical support for the electronic sensor and display (not shown in FIG. 3). As described below, the electronics secured to the compartment 134 within the sealed housing 130 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 sealed housing 130 shown in FIG. 3, electronic components (including an electronic sensor, display, and power source) are sealed inside the compartment 134 with an o-ring seal 136. In addition, the sealed housing 130 may be sealed with epoxy, glue, or other adhesives. In other embodiments, the sealed housing 130 may be mechanically sealed with hardware, such as screws or snaps within the compartment 134. Although the embodiment of the sealed housing 130 shown in FIG. 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 sealed housing 130 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 sealed housing 130 shown in FIG. 3 is water resistant to several atmospheres of pressure. Moreover, the materials used to manufacture the sealed housing 130 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 sealed housing 130 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 sealed housing 130 is also designed to provide only soft, rounded edges that are safe for use in a surgical environment. For example, the embodiment of the sealed housing 130 shown in FIGS. 1 through 5 is in substantial compliance with the Underwriters Laboratories sharpness test UL 1349.

Although the instrument 100 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 the instrument 100, a wireless transmitter may be connected to the read-head assembly within the sealed housing 130. 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 the instrument 100 from the bottom is shown in FIG. 4. As shown in FIG. 4, the present invention includes several ergonomic features in addition to the top ridges 170 (shown in FIGS. 1 and 3). In particular, the instrument 100 includes symmetrically shaped side grooves with ridges 180 and finger grooves 190. As shown in the cross-sectional end view of FIG. 5, the finger grooves 190 are formed in the convex bottom side 192 of the body 140. In accordance with an embodiment of the method of the present invention, a surgeon would place a forefinger on a first side groove 180, a thumb on the opposing side groove 180, and the rest of the fingers on the finger grooves 190 integrated with the body 140. 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 the bottom side 192 entirely unobstructed so that the surgeon is always free to grab the body 140.

Some structural features of the invention shown in FIG. 5 have the advantage of permitting the instrument 100 to be disassembled and reassembled for sterilization. In particular, the sealed housing 130 and body 140 are slidably connected along a mating surface 132 of the sealed housing 130 and a reciprocal mating surface 142 formed within the side groove 144 of the body 140. The probe 160, which is engaged in the sealed housing 130, slides through the side grooves 144 of the body 140 and into a funneled cylindrical channel formed in the tissue guard 120. In another embodiment, the tissue guard 120 may provide a keyhole-shaped (rather than a cylindrical) channel to permit probe tips without cylindrical symmetry (i.e., tips such as the barb 167 or hook 169 shown in FIGS. 6A and 6B) to pass through during disassembly and reassembly of the instrument 100. Moreover, in such other embodiments, the tissue guard 120 may be rotated after assembly to prevent the distal end of the probe 160 from retracting within the tissue guard 120. Such a rotation is permitted when the tissue guard 120 threads onto the body 140, 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 the tissue guard 120.

When slidably connected as shown in the instrument 100, the present invention does not require oil lubricants, such that the materials are entirely compatible with a surgical environment. Referring to FIG. 3, the instrument 100 is shown in cross-section (along the plane 4-4 through the sealed housing 130 shown in FIG. 3) viewed facing the distal end. The sealed housing 130 is shown in FIG. 3, with the compartment 134 (again, shown without internal electronic components), and top ridges 170. The seal 136 is also shown disposed between the top piece 138 and bottom piece 139 of the sealed housing 130. In addition, the mating surface 132 of the bottom piece 139 is shown engaged with the reciprocal mating surface 142 formed by and within the side groove 144 of the body 140. Also, the probe 160 is shown concentric to the end of the mating surface 132 of the bottom piece 139. By permitting a slidable connection between the sealed housing 130 and body 140, the mating surface 132 of the housing 130 and complementary mating surface of the body facilitate disassembly and reassembly of the instrument 100 for sterilization. Moreover, because the surfaces are not symmetric from left to right along the line 5-5 in FIG. 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 the compartment 134 of the sealed housing 130 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, the instrument 100 may be built with a pattern of inductive loops laid down along the sensor pattern compartment 146 of the body 140, and a facing read-head assembly secured within the compartment 134 of the sealed housing 130.

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 sealed housing 130 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 the probe 160 is extended from the proximal surface 30 toward the distal surface 40 of the bone portion 10, and a zero reading when the probe 160 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 the probe 160 has been moved. In such embodiments, the buttons may be formed in the sealed housing 130.

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 the tissue guard 120 and probe 160 are not generally stationary relative to one another. This event is more typical when compressible soft tissue is caught on the indented hook 165, or between the tissue guard 120 and the proximal surface 30, or in general when the distal end of the probe 160 is not securely positioned. In this respect, it should be noted that the probe 160 may be provided without any mechanical securement at its distal end. As an example, the distal end of the probe 160 may be inserted to a depth such that its distal end is coincident with, but generally does not extend beyond, the distal edge 26 of the hole 20. In using such an embodiment, the surgeon may place a stop or finger on the distal surface 40 of the bone portion 10 to stop the probe 160 when it has reached the distal edge 26.

In an embodiment, the electronic sensor and accompanying electronics can be shielded from electromagnetic interference, for example, by coating the inside of the sealed housing 130 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 in FIGS. 1-3).

Although the displays shown in FIGS. 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 to FIGS. 8 and 9, a rotatable display assembly 300 is provided that permits better viewability depending on the orientation of the measuring device. This rotatable display assembly 300 shown in FIG. 9 may be mounted directly to an end of the probe 100, 200, or may be mounted via a pivot arm 391, as is illustrated in FIG. 13.

Referring to FIG. 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: an upper housing 310, a rotatable display 340, and a lower housing 370. The upper 310 and lower 370 housing provide a structure in which the rotatable display 340 may be mounted and locked at a particular orientation.

The display 340 is preferably a generally circular shape and comprises a display screen 350 along with display electronics 352 that are used to operate the display screen 350. The display screen 350 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. The display screen 350 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. The display screen 350 and display electronics 352 are affixed within a circular housing comprising an upper 342 and a lower 360 housing component.

In order to permit a locking and holding of the display 340 at a particular orientation, one or both of the following may be provided: a plurality of locking holes 346 on a side edge of the upper display housing 342, and a plurality of locking grooves 348 also located on a side edge of the upper 342 and lower 360 housing components. It should be noted that the location of the locking holes 346 and/or locking grooves 348 could be provided on the lower housing 360, or even on an upper or lower surface of the housing components 342, 360. The operative action of the locking holes 346 and locking grooves 348 will be described in more detail below along with the other elements with which they interact.

The upper housing component 342 may provide a window 344 through which the display screen 350 can be read. It is also possible that the upper housing component 342 would have a clear surface through which the display screen 350 could also be read.

Referring to FIGS. 8 and 10, the lower display housing 360 comprises a pin 364 about which the display 340 rotates. Additionally, when the display 340 is a wired display, the lower display housing may comprise wire slots 362 via which wires can be provided to the display screen 350 and electronics 352. 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 the wire slots 362. Stops, such as interfering protrusions provided on the display 340 and an adjacent part of the display assembly 300 could be provided that prevent rotation beyond a certain limit.

When the display 340 is a wireless display, then no such access slots 362 need to be provided. Such a display 340 may be easily placed into the display assembly 300 and become operative with little effort. For the wireless display 340, the display electronics 352 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 in FIGS. 8 and 9, the display 340 is provided between the upper housing 310 and the lower housing 370. The display rests on a center support 382 of the lower housing 370. The pin 364 fits in a pin slot 384. Although the slot 384 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.

The display 340 rests between a proximal (to the measuring device) support 386 and a distal support 374. The proximal support 386 has a curved raised edge designed to match a curvature of the display 340. Protrusions 390 are provided on a raised edge of the proximal support 386 that serve to engage the locking groove 348 of the display 340 when at least some minimal force provided by a spring 336 and locking slider 332 (see also FIG. 12) force the display laterally against the raised edge. This helps to maintain the orientation of the display 340 once it has been set.

The distal support 374 comprises a spring slot 378 into which the spring 336 rests. It also comprises a slider recess 376 into which the locking slider 332 rests, as well as a corresponding pin slot 380 in which the slider pin 334 rests. The locking slider 332 preferably has a spring hole 338 into which a portion of the spring extends. The spring hole 338 helps to maintain the spring in position, although this is not essential, and other mechanisms, such as an additional pin, may be used. The slider pin 334 itself is designed to engage one of the locking holes 346 of the display. The spring 336 resting in the slot is in a generally compressed state, such that it provides a force that biases the locking slider 332 and its slider pin 334 into the display 340.

Thus, a user wishing to orient the display, moves the locking slider 332 towards the distal (away from the measuring device) end of the display assembly 300 and against the spring 336 bias. This causes the slider pin 334 to disengage from the locking hole 346 so that the display 340 can be rotated about is axis about the pin 364. Absent a biasing force, the display 340 is also slightly moved in a distal lateral direction such that the protrusion(s) 390 disengage the locking groove(s) 348. The lower housing 370 also comprises a handle portion 372 that, when combined with a handle portion 312 of the upper hosing 310, provides an easy-to-grasp element for the user.

The upper housing 310 may be designed as a three-piece unit or as a one-piece unit. The three-piece configuration comprises a separate proximal support member 320, distal support member 314, and transparent cover 324. In the one-piece unit, these the proximal support member 320, distal support member 314, and transparent cover 324 may be provided as a single unit, either via assembly or construction as a monolithic unit.

The transparent cover 324 (see also FIG. 11), which permits viewing of the display screen 350, may comprise legs 326 that rest upon leg supports 318, 322 of the distal support 314 and proximal support 320 respectively. Preferably, the legs 326 and leg supports 318, 322 are proportioned such that an upper surface of the transparent cover is flush with upper surfaces of both the distal support 314 and the proximal support 320.

The distal support 314 comprises a slot 316 into which a top portion of the locking slider 332 protrudes. A lever 331 may be affixed to a top surface of the locking slider 332 and serves to form a relatively secure seal of the slider slot 316 such that contaminants cannot readily enter the slider slot 316. Thus, when the user wishes to reorient the display 340, the user moves the lever 331 towards the distal end of the display assembly 300 and against the spring 336 bias to disengage the display 340 from the locking mechanisms (332, 390). Once the display 340 is disengaged, it may be rotated into a locking position (one in which the slider pin 334 aligns with the locking hole 346 and the locking groove 348 aligns with the protrusion 390). The user releases the lever 331 and the spring 336 biases the locking slider 332 to move the slider pin 334 into the locking hole 346 and biases the display 340 against the curved side surface 388 of the proximal support 386, thereby engaging the locking groove(s) 348 with the protrusion(s) 390.

Referring to FIG. 13, a pivot arm 391 is provided that permits an additional axis of rotation for the display assembly 300. The pivot arm 391 comprises, at a distal end (away from the measuring device) a receiving slot 392 for a proximal end of the display assembly 300. The proximal supports 320, 386 can comprise a hole into which a pivot pin 398 can be inserted. The pin 398 is supported by a pivot hole 396 in an arm end 394 of the pivot arm 391 formed by a receiving slot 392 into which the proximal end of the display assembly 300 is provided. The rotational freedom of the display assembly 300 about the pivot pin 398 can be hampered by a frictional fit of the hole of the display assembly against the pivot pin 398. Alternately, or additionally, interacting protrusions and grooves, or bumps and holes may be provided between the wall edges of the receiving slot 392 and side edges of the proximal supports 320, 386.

It should be noted that the embodiment shown provides for a rectangular cross section of the support elements of the display assembly 300 and the pivot arm 391. 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 the pivot arm 391 described above could be provided at the end of the pivot arm 391 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, the display 340 itself can be located at either a proximal or distil end of the display assembly 300 instead of in a central region.

FIG. 14 illustrates another embodiment of the display. At the distal end of the body 140, a rotatable body section 311 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, the display screen 350 is provided directly on the rotatable body section 311. In this embodiment, a series of grooves and protrusions or bumps and holes may be provided on an inner surface of the body 140 and outer surface of the rotatable body section 311 in order to provide discrete orientation positions for this section. Alternately, the rotatable body section 311 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 in FIG. 14, a display 340 similar to that illustrated in FIGS. 8-13 is provided that can be rotated about an axis A perpendicular to the longitudinal axis B. A similar groove 348 and protrusion (not shown) scheme may be utilized to secure the orientation, and the slider pin (not shown) operable by a lever 331 on a distal support 374 can be provided to engage holes 346 of the display 340. In this way, the display screen 350 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 the distal support 374 is illustrated in FIG. 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 in FIGS. 15A and 15B in which a generally cylindrical body comprises the extension actuator 237 and groove 239. In FIG. 15A, the display 340 is generally a flat and rectangular housing on a rotatable body section 311 of the tool body 140 that houses the display screen 350 and mounts to the body via a pin 364 that is located in a generally central position of the display. This permits the display 340 to be rotated for ease of viewing. As illustrated in FIG. 15B, the pin 364 can be offset from the center. This rectangular display 340 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 in FIG. 15C, the characters on the display screen 350 are oriented differently depending on the relative angle of the display screen 350 (and display 340 itself) with respect to the body 311. 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 the display screen 350 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 in FIGS. 15A-15C and illustrates a rotation about the longitudinal axis of a body section 311 comprising the display 340, 350, although an embodiment not having this section 311 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

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 in claim 1, wherein the rotatable electronic display rotates about the longitudinal axis.

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

4. The instrument as claimed in claim 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 in claim 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 in claim 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 in claim 5, wherein the housing comprises upper and lower portions, and the display rests on the lower portion.

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

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

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

19. The gage as claimed in claim 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 in claim 20, further comprising a locking mechanism that holds the display at a particular orientation.

22. The gage as claimed in claim 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.