WO1999056662A2

WO1999056662A2 - Broken bone screw extractor and method for extracting broken screws

Info

Publication number: WO1999056662A2
Application number: PCT/US1999/010053
Authority: WO
Inventors: Walter Strippgen; Charles F. Heinig
Original assignee: Isola Implants, Inc.
Priority date: 1998-05-06
Filing date: 1999-05-06
Publication date: 1999-11-11
Also published as: AU3790299A; WO1999056662A3

Abstract

A broken bone screw extractor (7) has a handle (10) connected to a body portion (12) which has a longitudinal hollow portion extending therethrough. A longitudinal threaded shaft (14) transverses the longitudinal hollow portion. A chuck device (16) capable of encircling a broken bone screw is provided at the end of the longitudinal threaded shaft, the ends (20) of the chuck that contact the bone being sharpened, and thus capable of cutting in to bone tissue. In operation, the chuck is positioned over a severed bone screw and manipulated to a depth sufficient so that the chuck can be tightened about the bone screw. Once secured, the chuck is rotated to extract the broken bone screw from the bone.

Description

BROKEN BONE SCREW EXTRACTOR AND METHOD FOR EXTRACTING BROKEN SCREWS

FIELD OF THE INVENTION

The present invention is directed to a broken screw extractor and a method for extracting screws, and in particular, the present invention can be used to extract broken bone screws that have been severed, leaving a portion of the bone screw embedded in the bone of a patient.

BACKGROUND OF THE INVENTION The use of screws and pins to connect devices to bone and to bind adjacent bone tissue together is widely recognized around the world as an efficient and stable way to ameliorate various bone related problems. Difficulties, however, arise when such pins and/or bone screws

(hereinafter referred to generically as "bone screws") break and/or are severed through trauma or repeated stress experienced by a patient, thus causing fatigue or stress fractures of the metal. In such events, it is necessary to extract the broken bone screws from the bone. Existing methods and devices for removing such bone screws from bone tissue are not only arduous and difficult for a surgeon to use, but result in extended hospital stays and increased pain and discomfort for the patient. When a bone screw, for example, is broken, the head of the screw is no longer connected to the remainder of the screw, thus leaving an elongated fragment inside a patient's bone. Removal of such a broken screw is necessary to replace it with another bone screw to achieve the binding and/or fixation function the bone screw originally served.

Other orthopedic apparatuses have been used in driving and removing bone screws where the bone screws have an enlarged head attached thereto. For example, Bryant et al. teaches the use of a device having blunt (e.g., non- sharpened) collet fingers 30 and a shaft 16 having a distal end 34 adapted to mate with a recess 24 of an enlarged bone screw head 22. The Bryant et al. device is not suited to remove screws that have broken off in the interior of a bone and thus, that lack an enlarged head to facilitate extraction thereof.

Still other orthopedic apparatuses use threaded interconnections between the apparatus and the bone screw (for example, U.S. Patent Nos. 3,334,624 (Schneider et al.), 4,963,144 (Huene) and 4,995,810 (Sδderberg) . The Bryant et. al device also suffers from deficiencies in that its handle configuration does not make it comfortable for a surgeon's grip, and indeed the extended portion 50 may pierce a surgeon's glove, potentially jeopardizing the sterile operation conditions. As such, there is a need for a relatively simple, efficient device for extracting broken bone screws from bone tissue.

SUMMARY OF THE INVENTION The present invention is directed to a device and method for extraction of broken bone screws using a simple, relatively inexpensive device that is able to secure to one end of a bone screw that has been severed and to hold such end tightly enough so that the bone screw can be extracted, for example, by appropriate clockwise/counter-clockwise rotation. The present method and device facilitates extraction of broken bone screws without significant damage to the bone tissue surrounding the bone screw and without the need to use a bone chisel to chip away bone to expose a portion of the broken screw and thereafter attempt to grip such screw with a plier- type device in an attempt to extract it from the bone.

The overall design of the present device includes a handle, preferably having an oval or egg-shaped configuration with grooves therein to facilitate gripping by a physician's palm or hand, such handle preferably made of delrin, surgical metal or another material that can be sterilized (e.g., using dry heat, gas, chemicals, hot water, or steam) . The handle is operatively associated with an elongated body portion having a relatively hollow interior and which is preferably knurled on its outside to facilitate manipulation by a physician. The egg-shaped handle portion described above is connected to a longitudinal shaft which is carried within the hollow portion of the body portion. In one embodiment, the longitudinal shaft is threaded so that rotation of the handle causes the shaft to turn within the body portion, thus manipulating a means for gripping a bone screw, such as a chuck, as hereinafter described. Connected to the longitudinal shaft, at an end opposite that to which the egg-shaped handle is connected, a means for gripping a bone screw (e.g., a chuck-like device) is provided. Such chuck device is similar to devices found on drills and, in a similar manner, can be rotatably adjusted so as to open or close about a central point. A suitable chuck for the present invention can have a plurality of fingers or jaws, but typically has at least three jaws comprising the chuck. The outermost portion of such jaws (e.g., the portion which is intended to contact bone) is relatively sharp and/or serrated so as to facilitate cutting into bone tissue. The sharpened tips of the jaws permit a physician to cut into bone around an embedded broken bone screw to a sufficient depth so that the jaws can be closed around the bone screw. The chuck is preferably made from hardened and/or hardenable steel

(e.g., 440 stainless steel). Moreover, the inside portions of each finger and/or jaw is grooved and/or threaded so that such interior region of the jaws can interact and engage with threads of a bone screw. Indeed, in one embodiment the chuck is tightened to an extent that the threads of the bone screw are substantially collapsed against the central axis of the screw, thus securely positioning the chuck to the screw.

As one will appreciate, one of the significant advantages of the present invention is the ability to remove a broken bone screw without the danger of the bone screw being accidently dropped into the wound area. The present method and device facilitates the secure grasping of a broken bone screw in a manner that allows extraction of the broken bone screw from the patient's body without a risk that the bone screw would detach from the present device until entirely removed from the wound area. Due to the minimal damage done to the bone screw, it is also possible to evaluate the structural characteristics of the broken bone screw so as to determine the cause of severing thereof, thus facilitating better design of screws for future use.

At the end of the body portion adjacent the egg-shaped handle, as described above, a gripping adjustment means is provided that can be manipulated to adjust the movement of the chuck jaws, for example, about a broken screw portion. For instance, in one embodiment, an additional substantially perpendicular handle is provided which is operatively connected to the body portion and the chuck so as to adjust the tightness of the jaws of the chuck. In other words, an extended handle portion is provided (e.g., connected in a substantially perpendicular plane to the body portion itself) so that a physician can manipulate the extended handle to adjust the tightness of the chuck jaws around, for example, a broken bone screw embedded in bone so that the jaws encircle the end portion of the broken bone screw. By securely tightening the jaws around the broken end of the bone screw a physician can then extract the bone screw by rotating the egg-shaped handle to rotate the embedded broken bone screw and thereby unscrew the broken bone screw from the embedded portion of bone.

In the preferred embodiment, the present invention is capable of being thoroughly cleaned in a manner required in a sterile operative environment. For example, the present invention is capable of being disassembled (without the need for any other tool) in order to thoroughly sterilize each individual part thereof to ensure that all undesired contamination, bacterial, viral, hepatitis, etc., for example, is eliminated. In one embodiment, the handle portion dissociates from a longitudinal shaft, the longitudinal shaft unscrews from the elongated body portion, and thus facilitates the separate cleaning of all three separate parts of the present invention. Thus, in a preferred embodiment, the egg-shape handle portion is simply pulled off of the central shaft, the remaining central threaded shaft is then turned with finger pressure in a clock-wise direction as far as is necessary from the proximal (threaded end) or distal (jaw-bearing end) until the central shaft can be removed from its outer sleeve. The three separate pieces can then be cleaned mechanically with brushes or ultrasonically and then sterilized, disassembled or reassembled depending upon the type or method of sterilization that has been chosen. In operation, the present invention includes a method for extracting a severed bone screw from bone comprising providing a device having a body portion with a longitudinal hollow portion extending therethrough, a longitudinal threaded shaft having first and second ends, with a hand grip on one end and a means for gripping on the other. A means for reversibly tightening the means for gripping is provided so that the means for gripping can be fitted over the severed end of a bone screw and the bone screw can be gripped securely by the device. Once secured, the threaded shaft running through the body portion of the device is rotated (through the use of the handle) so that the bone screw is rotated in an appropriate direction to extract the bone screw from the bone.

In contrast to prior art devices that have relied upon the use of high speed air or electrical drills, often using carbide or diamond tip drill points, the present invention does not entail a procedure whereby metal debris can be distributed about a wound. In prior art procedures, it is often necessary to drill into the broken portion of a metal screw in order to extract such screw. Using drill tools

(such as a Midas Rex, and Anspach, etc. equipment) which costs in excess of several tens of thousands of dollars, an operator must wear safety glasses and other safeguards must be taken in the operating room given the potential harm to the operator as well as to the patient resulting from the use of such high speed tools. Such tools also generate heat due to the high speed cutting action. All of these detriments are alleviated using the present invention which provides a tool that is considerably less expensive, does not involve the generation of metal debris from the screw itself and, in preferred embodiments, is not a motorized tool that would require safety glasses and other safety precautions in the operating room. Nor does the present tool generate the heat of prior art implements during the screw extraction procedure. Importantly, since pedicle screws may be located within a few millimeters of sensitive body parts, such as spinal cords, nerves, major arteries, etc., the present invention, unlike prior art devices, provides the precision and exactness required by a surgeon in a screw extraction procedure to avoid damage to such sensitive tissues. Moreover, prior art devices, due to their fast moving parts, often pose the danger of engaging undesired articles such as plastic, metal tips, sponges, articles of clothing, etc. which can further complicate the screw extraction procedure. A significant advantage of the present invention is that the present device and method involves the gripping of the exterior of a broken screw so that the screw can then be clamped and unscrewed or otherwise removed from the bone tissue. In prior art devices, for example, a mill tool having a series of hollow tubes with saw teeth, a clockwise for right handed drilling motion is typically involved. Such prior art devices pose the problem of catching the edges of a right handed threaded screw, thereby forcing the screw deeper into the bone or out of the operative field entirely. Indeed, examples exist where loose broken screws have been forced through anterior vertebra walls into a patient's aorta, thus requiring anterior abdominal surgery to retrieve the broken screw. Such devastating consequences of using prior art devices are eliminated by use of the present device and method.

The present device is light in weight as compared to prior art devices and has a variable throat diameter which can be adjusted to a plurality of dimensions to fit various sized screws (preferably screws of from about 5 to about 7 mm) , thus capable of handling the majority of present screws on the market (e.g., 5.5 mm, 6.25 mm and 7 mm) . The present device can be fitted down the existing screw hole and the throat diameter can be adjusted to fit over the broken screw. The saw-like teeth at the edge of the present device can be turned counter-clockwise, thus helping to turn a right handed screw out of its bony bed. As soon as the broken end of the screw can be engaged by the present device, the jaws can be tightened about the broken screw end and the broken screw can be removed by counter-clockwise turning of the entire device itself. The clamping pressure upon a typical bone screw will collapse and/or indent the broken screw threads to the central axis of the screw, securely capturing the screw for removal . BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of the broken bone screw extractor device of the present invention;

Fig. 2 illustrates the detachable handle portion of the present device;

Fig. 3 shows the elongated body portion of the device with means for tightening the chuck and a chuck-contacting collar;

Fig. 4a shows the longitudinal shaft which fits into the elongated body portion, such longitudinal shaft having a chuck at one end and a threaded portion at the other;

Fig. 4b is an edge-on perspective of the sharpened serrated edge of the chuck jaws.

DETAILED DESCRIPTION OF THE

PREFERRED EMBODIMENT

With reference to Fig. 1, a bone 6 having a broken bone screw 8 embedded therein is shown. The broken bone screw extractor device 7 of the present invention comprises a handle 10 reversibly connected to an elongated shaft 14 that fits within the hollow of a hollow elongated body portion 12. The longitudinal shaft 14 has a means for gripping (e.g. a chuck-like device 16) at the end opposite the handle 10. The means for gripping is formed from separate fingers or jaws 18, such jaws having sharpened cutting edges 20 that facilitate cutting into bone tissue. The jaws 18 are formed at the end of the longitudinal shaft 14 by providing elongated slots with circular stop points. The interior of the jaws 18 are preferably of a roughened texture and/or grooved so as to provide a roughened texture to contact a broken screw 8. The elongated body portion 12 has at one end a means for tightening the chuck 24. The other end of the elongated body portion has a chuck- contacting collar 26. At least a portion of the interior of the elongated body portion 12 is threaded to correspond with the thread 13 of the elongated shaft 14. Thus, rotation of the elongated body portion 12 around the threaded longitudinal shaft 14 causes the elongated body portion 12 to move upward toward the handle 10 or downward toward the chuck 16 to reversibly contract and/or compress the jaws 18 of the chuck 16.

Thus, the figures show an oval/egg-shaped handle 10 preferably made of lightweight plastic, such as Delrim, that can be sterilized. The handle 10 bears longitudinal grooves which allow the gloved hand to more easily grasp and rotate the handle 10. A large portion of the handle 10 is designed to fit comfortably in the palm of the hand. The opposite end contains a drilled hole for receiving a portion of the threaded central shaft 14. There is a spring-like device 28 at this end of the handle 10 that engages the central shaft 14 by locking the handle 10 in a circular groove 30 in the threaded central shaft 14. A small pin 11 in the handle 10 acts as a key to prevent the central shaft 14 from rotating. The pin 11 fits into the longitudinally directed keyway, thus permitting the handle 10 to be joined to the proximal threaded end of the central shaft 14.

With reference to Figs. 2 and 4, the handle portion is reversibly disassociable with one end of the longitudinal shaft 14. The handle portion 10 has an elongated handle 9 and an orientation pin 11 that operatively engages an elongated guide slot 15 in the elongated shaft 14. The orientation pin 11 engages the guide slot 15 so that when the handle 10 is engaged with the end of the elongated shaft 14, the handle can rotate the elongated shaft about its axis. A handle retention means, such as a spring lock 28 is provided at one end of the handle, such spring lock 28 being capable of reversible locking engagement with a spring lock engaging collar 30 on the elongated shaft 14. Fig. 2 illustrates the outer sleeve 12, the center two-thirds of which is knurled to facilitate gripping. The proximal end of the elongated body portion 12 is enlarged to accommodate internal threads which act as a nut to advance or retract the central shaft 14 which has matching threads. Projecting from the collar of the elongated body portion 12 is a short rod-like piece of steel 24 which allows for more force to be applied to the jaws of the chuck 16 for crushing or indenting the threads of the broken screw 8. At the distal end of the elongated portion 12 is an enlargement of hardenable steel 26 whose internal tooling is such as to allow for opening for closing of the chuck jaws of the central shaft 14 which fits inside the longitudinal body, much like a collet. At least a portion of the longitudinal shaft 14 is threaded 13 to facilitate threaded rotational movement of the elongated body portion 12, thus causing the longitudinal body portion 12 to move toward the handle 10 or toward the chuck 16 depending upon whether gripping or release of a broken bone screw is desired. In operation, a physician would position the broken bone extractor device 7 at a position where a broken bone screw resides in bone. By gripping the handle 10, the physician is able to rotate the entire device 7 on top of the bone tissue 6, thus causing the sharpened jaw edges 20 to cut into the bone around the broken bone screw 8. Once a sufficient depth of bone 6 has been cut through, preferably at least about 1/16 of an inch, more preferably about 1/8 of an inch, the physician then rotates the elongated body portion 12 to move the elongated body portion along the threads 13 of the longitudinal shafts 14, thus causing the chuck-contacting collar 26 to move toward the chuck 16, thereby collapsing the expandable jaws 18 around the broken bone screw end 8. To ensure that the bone screw 8 is firmly engaged by the chuck 16, the physician can use the means for tightening the chuck 24 (e.g. a substantially perpendicular handle that permits additional leverage during the rotation operation) and thus cause the chuck-contacting collar 26 to firmly press the jaws 18 together about the broken end of the bone screw 8. The physician can then simply rotate the handle portion 10 of the device 7 in an appropriate direction to unscrew the broken bone screw 8 from the bone 6. In this manner, minimal damage is done to the bone 6, and the broken bone screw 8 is extracted in a simple procedure that does not require drilling, pounding, or other techniques typically used in conventional broken bone screw extraction procedures.

With reference to Fig. 3, the central shaft 14 is somewhat longer than the outer longitudinal body 12. On the proximal end of the central shaft 14 are threads into which a circular groove 30 has been machined to receive the spring locking mechanism 28 of the handle 10. Adjoining this and directed more proximately to the tapered end of the threaded central shaft 14 is a keyway 15 machined in a longitudinal direction into which a key in the handle 10 fits to block rotation of the handle on the shaft 14. At the opposite end of the handle 10 is a series of jaws 16 that have compound tapers to allow for opening and closing when drawn into or released from the distal end of the elongated body 12. At the proximal end of each jaw 16 is a small drill hole to relieve stress. The central portion of the threaded shaft 14 is machined to accommodate the desired aperture to facilitate different opening ranges of the jaws 16. A particular advantage of the present invention is that the device 7 can be oriented over the top of a broken bone screw within bone 6 in a manner that essentially self- aligns the device with the orientation of the bone screw, thus facilitating removal of the bone screw without the need to know precisely the particular orientation of the bone screw 8. In contrast, prior art procedures for removing broken bone screws from bone 6 often entailed drilling into the broken bone screw shaft, thus requiring a physician to know with some precision the orientation of the bone screw within the bone so that the drilled hole would align with the center axis of the bone screw. Using the present device, a physician need only locate the surface of the broken bone screw 8 and by rotation of the device 7 about the top of the bone screw 8, the bone 6 is cut away by the sharpened edges 20 of the chuck 16 to expose the top portion of the broken bone screw 8, thus facilitating gripping of the bone screw 8 by the chuck 16 upon tightening of the device 7, leading to the threaded extraction of the bone screw by simple rotation of the device.

Another advantage of the present invention relates to the ability to disassemble the device 7 into, for example, three distinct portions: the handle 10, the elongated shaft 14, and the elongated body portion 12. This is particularly important given that it is necessary in surgical procedures to sterilize devices, particularly devices having small cavities/crevices in which undesired biological material may become lodged, such as threads 13. Thus, the present device 7 is capable of disassembly by simply pulling the handle 10 away from the longitudinal shaft 14. The orientation pin 11 of the handle 10 engages a guide slot 15 located at the end of the longitudinal shaft. In addition, a spring lock 28 is provided at the end of the handle 10 which coincides with a spring lock engaging indent and/or collar 30 formed in the elongated shaft 14. Once the handle 10 is removed from the end of the longitudinal shaft 14, the elongated body portion 12 can be rotated about the threads 13 of the longitudinal shaft 14, thereby disassociating the body portion 12 from the elongated shaft 14. This permits the cleaning of the threaded engagement inside the body portion 12 as well as the threads 13 on the elongated shaft 14, and finally, the interior and exterior of the handle 10 can be thoroughly cleaned and sterilized. Another particular advantage of the present invention is that the physician is provided with a non-obstructive view of the end of a bone screw and by use of the present device, eliminates the danger of harming blood vessels, nerves, and other tissues through the use of previously required motorized drills, etc. While alternative embodiments of the present invention can be motorized, it is believed that the simple, efficient construction of the present device facilitates broken bone extraction without complicated motorized mechanisms. Included within the scope of the present invention are alternative means for causing the chuck to encircle a broken bone screw, such as by a lever mechanism wherein an elongated body portion or sleeve would be pushed against the angled jaws to reversibly tighten and release the jaws from a broken bone screw. While this embodiment is not shown in the figures, one of ordinary skill in the art will appreciate that a lever device could be used to move the elongated body portion along the length of the elongated shaft rather than rely upon the threaded engagement as described above. The present device also facilitates the removal of various sized bone screws, and thus eliminates the need of prior art devices to know exactly the dimensions of the bone screw prior to removal. For example, the present device can be used on the typically-encountered 5, 7, and 8 mm screws. It should also be appreciated that disassembly of the present device can be achieved in ways different from that particularly described above. For example, different handle connecting designs can be utilized and the association of an elongated shaft and a surrounding body portion may be configured. It is important, however, for sterilization of the broken bone extractor device that disassembly of the device be made possible, such alternative embodiments within the knowledge of one of skill in the art guided by the teachings of the present invention.

While various embodiments of the present invention have been described in detail, it is apparent that further modifications and adaptations of the invention will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present invention.

While the above described invention and method has been directed specifically to removal of broken bone screws, one of skill in the art will appreciate that the device and method can be used to remove broken screws in a non-medical context, for example, in the building industry or in any other field in which a broken screw must be extracted from other material. It is intended that all such different applications of the present device and method be included within the scope of the appended claims.

Claims

What is claimed is:

1. A broken bone screw extraction device, comprising: a body portion having a longitudinal hollow portion extending therethrough; a longitudinal threaded shaft having first and second ends, wherein a hand grip handle is operatively connected at said first end and a chuck is operatively associated at said second end; and a means for manipulating said chuck, said means for manipulating operatively connected to said body portion.

2. The device as set forth in Claim 1, wherein said chuck has at least three individual jaws.

3. The device as set forth in Claim 2, wherein said jaws have first and second ends, said first end being furthest from said hand grip handle and being sharpened or serrated.

4. A method for extracting a severed bone screw from bone, comprising: providing a device comprising: a body portion having a longitudinal hollow portion extending therethrough; a longitudinal threaded shaft having first and second ends, wherein a hand grip handle is operatively connected at said first end and a chuck is operatively associated at said second end; a means for tightening said chuck, said means for manipulating operatively connected to said body portion; positioning said chuck so that the severed bone screw is capable of being encircled by said chuck; manipulating said means for tightening to secure said chuck around said severed bone screw; and rotating said handle to rotate said bone screw, thereby extracting said bone screw from the bone.

5. A broken bone screw extraction device, comprising a longitudinal shaft having a threaded portion at a first end a means for gripping a broken bone screw at a second end; an elongated body portion having a hollow interior through which said elongated shaft can reside, said body portion having means to engage said threads of said longitudinal shaft; a handle reversibly engagable with said first end of said elongated shaft, said handle being capable of rotating said elongated shaft.

6. The device as set forth in Claim 5, wherein said chuck has sharpened edges that facilitate cutting into bone.