US20150112341A1 - Devices for bone fixation using an intramedullary fixation implant - Google Patents

Abstract

The invention comprises an intramedullary fixation implant and a method for joining bones and translating compression between the bones for treating various digital deformities. The intramedullary fixation implant comprises a first fixation portion and a second fixation portion connected to the first fixation portion, wherein the second fixation portion comprises a first projection and a second projection separated by a slot, and wherein the first projection and the second projection comprise a plurality of barbs shaped and arranged along the first and second projections such that they cooperatively form a thread along the second fixation portion.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application claims the benefit of U.S. Provisional Application Ser. No. 61/894,564, filed on Oct. 23, 2013, the entire contents of which are herein incorporated by reference. This application is also related to U.S. application Ser. No. ______, filed ______, entitled “Methods For Bone Fixation Using An Intramedullary Fixation Implant,” (Attorney Docket No. 277-111B), the entire contents of which are herein incorporated by reference.
FIELD OF THE INVENTION
• This invention relates to the field of implant devices for bone fixation, and more particularly, to an intramedullary fixation implant used for the fixation of bones and the correction of deformities in the foot or the hand, such as a hammertoe deformity.
BACKGROUND OF THE INVENTION
• Digital deformities are among the most common forefoot pathologies encountered by podiatrists and orthopedic surgeons. Digital deformities may occur in the form of hammertoes, claw toes, mallet toes, bone spurs, overlapping and underlapping toes, mallet fingers, jersey fingers, and coach's fingers, among others. The deformities typically affect the interphalangeal joints of the hand or the foot, metatarsophalangeal joints of the foot, or metacarpophalangeal joint of the hand. Digital deformities in the fingers or toes result from imbalance of the tendons, causing them to stretch or tighten abnormally. These deformities may be either congenial or acquired. For example, the deformities may be cause by neuromuscular and arthritic disorders, systemic diseases, flat or high-arched feet, or traumatic injuries to the joints. Toe deformities can also be aggravated by poorly fitting footwear.
• Hammertoe, for example, results in a bend in the middle joint of the toe into a claw-like deformity. While at first the patient may be able to move and straighten the toe, overtime the hammertoe may become fixed. In this contracted position, the inside of the shoe rubs against the contracted joints, causing corns to form on the top of the toe and calluses to form on the sole of the foot. In certain patients these corns and calluses may open or ulcerate and form wounds. This causes pain and discomfort in walking or wearing shoes.FIG. 1A depicts ahuman foot100 afflicted with hammertoe deformity.Distal phalanx101,middle phalanx103,proximal phalanx105, and metatarsal107 bones are depicted infoot100. The distalinterphalangeal joint104 is formed between the distal101 andmiddle103 phalanges, proximalinterphalangeal joint106 is formed between themiddle103 and proximal105 phalanges, and themetatarsophalangeal joint108 is formed between theproximal phalanx105 and the metatarsal107. The hammertoe deformity in the foot is apparent in the proximalinterphalangeal joint106.
• A similar digital deformity condition in the hand is depicted inFIG. 1B.FIG. 1B depicts ahuman hand110 afflicted with mallet finger deformity.Distal phalanx111,middle phalanx113,proximal phalanx115, and metacarpal117 bones are depicted inhand110. The distalinterphalangeal joint114 is formed between the distal111 andmiddle113 phalanges, the proximalinterphalangeal joint116 is formed between themiddle113 and proximal115 phalanges, and themetacarpophalangeal joint118 is formed between theproximal phalanx115 and themetacarpal117. The mallet finger deformity in the hand is apparent in the distalinterphalangeal joint114.
• Early treatments for digital deformities include the use of strapping, taping, orthotics, or immobilization of the hand or the foot. However, once the deformity becomes fixed, surgical treatment will be necessary. Surgical treatments include bone fixation devices that fixate the bones in order to fuse them into a stable mass. These orthopedic implant devices realign bone segments and hold them together in compression until healing occurs, resulting in a stable mass. Typical implant devices include intramedullary nails, plates, rods and screws.
• Infection and complications are a major concern in these procedures. Wound closure is technically demanding for the surgeon, and devices that add surface prominence, such as plates or exposed screws, add to the difficulty by requiring greater tissue tension during incision reapproximation. This increases the risk of post-operative wound infections and dehiscence that may ultimately result in limb amputation. While there exist less intrusive devices, many devices lack the application of compression forces to the bone, causing the treated bones to eventually become misaligned from the desired position.
• There is therefore a need for improvements in intramedullary fixation implants and methods of use that overcome some or all of the previously described drawbacks of prior fixation assemblies and processes.
SUMMARY OF THE INVENTION
• The present invention is improved devices and methods for bone fixation.
• The improved devices include an intramedullary fixation implant for joining bones and translating compression between the bones for treating various digital deformities. In a preferred embodiment, the intramedullary fixation implant comprises a first fixation portion and a second fixation portion connected to the first fixation portion, wherein the second fixation portion comprises a first projection and a second projection separated by a slot, wherein the first projection and the second projection comprise a plurality of barbs shaped and arranged along the first and second projections such that they cooperatively form a thread along the second fixation portion.
• Broadly, the methods of the invention for joining and compressing a first bone to a second bone of a joint comprise: creating a first hole in the first bone, creating a second hole in the second bone, advancing the first fixation portion of the intramedullary fixation implant into the second hole in the second bone, counter-rotating the second bone, pressing the second fixation portion of the intramedullary fixation implant linearly into the first hole in the first bone, and rotating the second bone into a final fixation position.
• Instruments are also disclosed for use in practicing the invention. These include an implant driving tool for driving the first fixation portion into the second hole in the second bone.
• Numerous variations may be practiced in the preferred embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
• A further understanding of the invention can be obtained by reference to a preferred embodiment set forth in the illustrations of the accompanying drawings. Although the illustrated embodiment is merely exemplary of systems, methods, and apparati for carrying out the invention, both the organization and method of operation of the invention, in general, together with further objectives and advantages thereof, may be more easily understood by reference to the drawings and the following description. The drawings are not intended to limit the scope of this invention, which is set forth with particularity in the claims as appended hereto or as subsequently amended, but merely to clarify and exemplify the invention.
• FIG. 1A depicts a human foot afflicted with hammertoe deformity;
• FIG. 1B depicts a human hand afflicted with mallet finger deformity.
• FIG. 2 is a perspective view of an intramedullary fixation implant of the present invention inserted into the bones of patient's foot according to the preferred embodiment of the invention;
• FIG. 3A is a perspective view of the intramedullary fixation implant of the present invention according to the preferred embodiment of the invention;
• FIG. 3B is a front view of the intramedullary fixation implant shown inFIG. 3A according to the preferred embodiment of the invention;
• FIG. 3C is a side view of the intramedullary fixation implant shown inFIG. 3A according to the preferred embodiment of the invention;
• FIG. 3D is a top view of the intramedullary fixation implant shown inFIG. 3A according to the preferred embodiment of the invention;
• FIG. 3E is a bottom view of the intramedullary fixation implant shown inFIG. 3A according to the preferred embodiment of the invention;
• FIG. 3F is a side view of the intramedullary fixation implant shown inFIG. 3A in a collapsed position according to the preferred embodiment of the invention;
• FIG. 4 is a cross-sectional view of the intramedullary fixation implant shown inFIGS. 3A-3E according to the preferred embodiment of the invention;
• FIG. 5A is a perspective view of an implant driving tool according to the preferred embodiment of the invention;
• FIG. 5B is a side view of the implant driving tool shown inFIG. 5A according to the preferred embodiment of the invention;
• FIG. 5C is a front view of the implant driving tool shown inFIG. 5A according to the preferred embodiment of the invention;
• FIG. 6A is a cross-sectional view of the implant driving tool shown inFIGS. 5A-5C according to the preferred embodiment of the invention;
• FIG. 6B is an enlarged cross-sectional view of the implant driving tool shown inFIGS. 5A-5C used with the intramedullary fixation implant shown inFIGS. 3A-3E according to the preferred embodiment of the invention;
• FIG. 7 is a flow chart depicting illustrative steps of an embodiment of the invention; and
• FIGS. 8A-8P depict details of certain steps ofFIG. 7.
DETAILED DESCRIPTION OF THE INVENTION
• The invention may be understood more readily by reference to the following detailed description of a preferred embodiment of the invention. However, techniques, systems, and operating structures in accordance with the invention may be embodied in a wide variety of forms and modes, some of which may be quite different from those in the disclosed embodiment. Consequently, the specific structural and functional details disclosed herein are merely representative, yet in that regard, they are deemed to afford the best embodiment for purposes of disclosure and to provide a basis for the claims herein, which define the scope of the invention. It must be noted that, as used in the specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly indicates otherwise.
• The intramedullary fixation implant of present invention is described with reference to the treatment of a hammertoe deformity illustrated inFIG. 1A. However, it should be appreciated that the present invention may be used to treat any other digital deformities, including, but not limited to claw toes, mallet toes, bone spurs, overlapping and underlapping toes, mallet fingers, jersey fingers, coach's fingers, and the like. As such, the present invention may be utilized for the fixation of the following bones in the foot shown inFIG. 1A:distal phalanx101 to themiddle phalanx103 in the distal interphalangeal joint104,middle phalanx103 to theproximal phalanx105 in the proximal interphalangeal joint106, or theproximal phalanx105 to themetatarsal107 in the metatarsophalangeal joint108. Similarly, the present invention may be utilized for the fixation of the following bones in the hand shown inFIG. 1B:distal phalanx111 to themiddle phalanx113 in the distal interphalangeal joint114,middle phalanx113 to theproximal phalanx115 in the proximal interphalangeal joint116, orproximal phalanx115 to the metacarpal117 in the metacarpophalangeal joint118.
• Referring now toFIG. 2, there is shown anintramedullary fixation implant200 that may be used in the practice of the present invention. As shown inFIG. 2,intramedullary fixation implant200 may be used to join themiddle phalanx103 to theproximal phalanx105 in the proximal interphalangeal joint106 offoot100.Intramedullary fixation implant200 is used to translate compression between themiddle phalanx103 and theproximal phalanx105 as will be further apparent below.Intramedullary fixation implant200 may be made of PEEK (polyetheretherketone) material. Theintramedullary fixation implant200 is preferably made of radiolucent material, allowing for clear visualization of the fusion site. In other embodiments,intramedullary fixation implant200 may be made of other materials known in the art, including other PAEK (polyaryletherketone) plastics, SST, titanium, NiTi, Cobalt chrome, polylactic acid, or other similar types of materials. Also,intramedullary fixation implant200 may be coated with an osteoconductive material, such as, for example, plasma spray or other similar types of porous materials, that are capable of supporting or encouraging bone ingrowth into the material.
• Intramedullary fixation implant200 is shown in greater detail inFIGS. 3A-3E, whereFIG. 3A is a perspective view of theintramedullary fixation implant200,FIG. 3B is a front view thereof,FIG. 3C is a side view thereof,FIG. 3D is a top view thereof, andFIG. 3E is a bottom view thereof. As shown,intramedullary fixation implant200 preferably comprises unitaryelongated body201 extending from afirst end211 to asecond end212 alonglongitudinal axis210.Intramedullary fixation implant200 further comprises afirst fixation portion202 at thefirst end211 and asecond fixation portion204 at thesecond end212 connected viamiddle portion206.
• Thefirst fixation portion202 ofintramedullary fixation implant200 is substantially cylindrical in shape. Alternatively,first fixation portion202 may comprise a taper, with width that decreases from themiddle portion206 to the first end211 (not shown).First fixation portion202 preferably comprises on itsexterior surface216threads215.Threads215 are preferably helical dual-lead threads.First fixation portion202 may also be provided with a self-tappingleading edge213 to provideportion202 with the ability to remove bone material during insertion of thefirst fixation portion202 into the bone.
• Themiddle portion206 is substantially cylindrical in shape or cross-section. However, the middle portion may comprise other shapes or cross-sections—it may have rectangular, square, or hexagonal shape or cross-section.
• Thesecond fixation portion204 preferably comprises afirst projection231 and asecond projection232 extending from themiddle portion206 to thesecond end212. Although two projections are illustrated,second fixation portion204 may comprise three or four projections.FIG. 4 is the cross-sectional view ofintramedullary fixation implant200 taken along line4-4 inFIG. 3D. As shown inFIG. 3B, and in further detail inFIG. 4, the first andsecond projections231 and232 further comprise oppositely-disposed outer-facingconvex surfaces237 and238. In a preferred embodiment, outer facingconvex surfaces237 and238 are substantially parallel to one another. Further, the first andsecond projections231 and232 preferably comprise oppositely-disposed inner-facingflat surfaces235 and236, longitudinally separated by a V-shapedslot243. The oppositely-disposed inner-facingflat surfaces235 and236 are offset from thelongitudinal axis210 by angle A. Angle A is preferably in the range of about 0 degrees to about 45 degrees, more preferably from about 5 degrees to about 30 degrees, and more preferably it is about 10 degrees.Projections231 and232 are flexible such that they can be collapsed from a normal or open position shown inFIG. 4 to a collapsed position shown inFIG. 3F, whereprojections231 and232 are brought toward each other. In a collapsed position, inner-facingflat surfaces235 and236 are preferably substantially parallel to each other and to thelongitudinal axis210. As show inFIG. 4,second fixation portion204 further comprises acircular compression notch234 formed at the meeting-place of the first andsecond projections231 and232 at the inner-facingflat surfaces235 and236.Circular compression notch234 assists in allowingprojections231 and232 to compress towards each other.
• The first andsecond projections231 and232 further comprise a plurality ofbarbs241 and242, respectively. In a preferred embodiment, first andsecond projections231 and232 each comprise fivebarbs241 and242, respectively.Barbs241 and242 extend outwardly from the outer-facingconvex surfaces237 and238 of first andsecond projections231 and232, respectively, away from thelongitudinal axis210.Barbs241 of thefirst projection231 andbarbs242 of thesecond projection232 are shaped and arranged along the outer-facingsurfaces237 and238, respectively, such that they coextensively or cooperatively form ahelical thread250 along thesecond fixation portion204. As a result,barbs241 of thefirst projection231 and thebarbs242 of thesecond projection232 are asymmetrically disposed. In the preferred embodiment, thehelical thread250 comprises a reverse-buttress thread that causes thesecond fixation portion204 to be better secured to a bone against the force of deflection. Thehelical thread250 formed bybarbs241 and242 is used to translate compression between two bones, such as themiddle phalanx103 andproximal phalanx105, by applying torque to theintramedullary fixation implant200 as will be later described.
• As shown inFIG. 4, theelongated body201 comprises length L. In a preferred embodiment, length L is in the range of approximately 13.5 millimeters (mm) to approximately 15 mm.First fixation portion202 comprises length L1 and major diameter 1d, whilesecond fixation portion204 comprises length L2 and major diameter 2d. In a preferred embodiment, length L1 is in the range of approximately 6.5 mm to approximately 7.0 mm, length L2 is in the range of approximately 5.5 mm to approximately 6.8 mm, major diameter 1d is in the range of approximately 2.8 mm to approximately 4.0 mm, and major diameter 2d is in the range of approximately 4.0 mm to approximately 5.5 mm. The size and length of theintramedullary fixation implant200 that may be used in the practice of the invention can vary considerably depending on the size of the bones that are being joined and the surgeon's preferences.Intramedullary fixation implant200 is cannulated along length L having abore221 aligned alonglongitudinal axis210 and extending fromfirst end211 tosecond end212.Bore221 comprises diameter D provided to interact with a guide wire or a Kirschner wire (K-wire) by receiving the K-wire within thebore221 as will be later described. Preferably, diameter D is constant throughout length L ofintramedullary fixation implant200 whenprojections231 and231 are in a normal or open position. Different diameters and K-wire sizes may be used depending on the diameter of the bones that are being joined and the surgeon's preferences. Illustratively, the diameter of the K-wire is in the range of approximately 0.7 mm to approximately 4.0 mm, and more preferably approximately 0.9 mm to approximately 1.6 mm. In a preferred embodiment,intramedullary fixation implant200 comprises various sizes to accommodate variations in bone sizes. For example, theintramedullary fixation implant200 may be available in the following three sizes and dimensions:

• 	TABLE 1
  	Size

  	Small	Medium	Large

  	Overall length L (mm)	13.5	15	15
  	First fixation portion	6.5	7.0	7.0
  	length L1
  	Second fixation portion	5.5	6.8	6.8
  	length L2
  	Major diameter 1d (mm)	2.8	3.4	4.0
  	Major diameter 2d (mm)	4.0	4.5	5.5
  	Guide wire (mm)	1.1	1.4	1.6
  	compatibility

• Thefirst fixation portion202 andsecond fixation portion204, shown inFIG. 3C, are disposed alonglongitudinal axis210. In alternative embodiment,second fixation portion204 may be offset from thelongitudinal axis210 and from thefirst fixation portion202 at an angle (not shown). Such an angle will determine the angle of the bone fixation. Preferably, thesecond fixation portion204 may be offset from thelongitudinal axis210 at an angle between about 0 degrees and about 30 degrees, and more preferably between about 5 degrees and about 10 degrees. During operation, a surgeon may select anintramedullary fixation implant200 having a desired angle to adopt theintramedullary fixation implant200 to the implantation site.
• As shown inFIGS. 3B and 3D, eachbarb241 and242 further comprises opposingflat side walls244 and245, respectively. As a result, thesecond fixation portion204 comprises a cross section having oppositely disposedconvex edges301 and oppositely disposedflat edges302. Opposingflat side walls244 and245, and thereby oppositely disposedflat edges302, are provided to engage with an implant driving tool as described below.
• FIGS. 5A-5C illustrate a preferred embodiment of animplant driving tool500 used to drive theintramedullary fixation implant200 into the bone of fixation.FIG. 5A illustrates the prospective view of the implant driving tool,FIG. 5B illustrates a side view thereof, andFIG. 5C illustrates the front view thereof.FIG. 6A illustrate the cross section of the implant driving tool taken along line6-6 inFIG. 5C.Implant driving tool500 comprises anelongated body505 extending from afirst end511 to asecond end512 along alongitudinal axis510. Theimplant driving tool500 further comprises ahandle portion501 disposed between animplant receiving portion502 at thefirst end511 and anend portion503 at the second end.Handle portion501 may be ribbed (not shown) or may comprise friction resistant material to assist the surgeon to manually apply torque to theimplant driving tool500. Alternatively, or in addition,end portion503 may be sized to receive a torque transmitting tool (not show). As shown inFIG. 6A,implant driving tool500 is cannulated having abore508 extending alonglongitudinal axis510 ofelongated body505.
• Implant receiving portion502 preferably comprises anaperture504 at thefirst end511 of theimplant driving tool500.Aperture504 extends from anopen end513 at thefirst end511 of theimplant driving tool500 to aninner base wall506. In a preferred embodiment,aperture504 is sized for receiving thesecond fixation portion204 ofintramedullary fixation implant200 in a normal or open position as shown inFIG. 6B.Aperture504 comprises a cross section that complements the cross section of thesecond fixation portion204. As shown inFIGS. 5A and 5C,aperture504 comprises oppositely disposed innerflat side walls507 and oppositely disposed innerconcave side walls509. When thesecond fixation portion204 of theintramedullary fixation implant200 is inserted intoaperture504, as shown inFIG. 6B,second fixation portion204 is aligned withaperture504 such that oppositely disposedconvex edges301 are disposed against theconcave side walls509 ofaperture504, and the oppositely disposedflat edges302 are disposed against the oppositely disposed flat side walls507 (not shown).Aperture504 further comprises depth P sufficient to receive thesecond fixation portion204. Theinner base wall506 prevents theintramedullary fixation implant200 from overinsertion intoaperture504 ofimplant driving tool500. When thesecond fixation portion204 is inserted intoaperture504, thesecond end212 of theintramedullary fixation implant200 abuts theinner base wall506 ofaperture504. In a preferred embodiment,aperture504 comprises depth P equal to the length of thesecond fixation portion204 plus the length of themiddle portion206 of theintramedullary fixation implant200 such that thefirst fixation portion202 is not inhibited byaperture504 when thesecond fixation portion204 is fully inserted intoaperture504 of theimplant driving tool500.Implant receiving portion502 of theimplant driving tool500 may further comprise a pair ofindicators514, such as arrows, on opposite sides of its outer surface, parallel to the oppositely disposed innerflat side walls507.Indicators514 are used to align theintramedullary fixation implant200 with the bones as will be later described.
• Theintramedullary fixation implant200 of the present invention is utilized to join two bones together, such as a first bone and a second bone, and to translate compression between the bones. FIGS.7 and8A-8S depict illustrative operative technique of an embodiment of the invention used to treat hammertoe deformity between the proximal phalanx105 (i.e., a first bone) and the middle phalanx103 (i.e., a second bone) in the proximal interphalangeal joint106. It will be understood that the operative technique is only illustrative, that the order of execution of some steps may vary, and that some steps may not need to be used in the treatment of a particular patient in accordance with the invention.
• As shown inFIG. 8A, before beginning the operative procedure, anintra-operative template800 may be used to determine the optimal implant size. Thistemplate800 is radiopaque and can be used with fluoroscopy.Template800 may comprise a plurality ofrectangular extensions803 each corresponding to a differently sizedintramedullary fixation implant200. In this example, threerectangular extensions803 are used corresponding to a small, medium, and large sizedintramedullary fixation implant200. The length and width of eachrectangular extension803 correspond to the length and major diameter of the threaded end of the implant for themiddle phalanx103. Eachrectangular extension803 is aligned with themiddle phalanx103 by the surgeon to determine the optimal implant size.
• After a proper implant size is chosen, instep710 an incision is made in the foot over the dorsal aspect of the proximal interphalangeal joint106, while soft tissue is released as necessary, so as to provide a complete visualization of the articular surfaces of the middle and proximal phalanges. The incision may be a dorsal longitudinal incision or a two semi-elliptical incision. As shown inFIG. 8B, the distal aspect or face125 of theproximal phalanx105 and the proximal aspect or face123 of themiddle phalanx103 are excised instep712 usingblade802 of cuttingtool801. In a preferred embodiment, the distal aspect of theproximal phalanx105 is resected just posterior to the head of the phalange as either a straight cut (FIG. 8C), or at an angle804 (FIG. 8D). Such anangle804 will determine the angle of the bone fixation. Preferably,angle804 is in a range of between about 0 degrees and about 30 degrees, and more preferably between about 5 degrees and about 10 degrees. In a preferred embodiment,angle804 is approximately 10 degrees. The articular cartilage of themiddle phalanx103 may be denuded. In an alternative embodiment, themiddle phalanx103 can be also resected.
• Instep714, a retrograde K-wire805 is advanced into theproximal phalanx105 along its central axis as shown inFIG. 8E, approximately 10 mm in depth. The K-wire805 is advanced by the surgeon in a direction of the desired alignment of theintramedullary fixation implant200 with respect to theproximal phalanx105. As shown inFIG. 8F, If theproximal phalanx105 was resected at anangle804, theguide wire805 is placed perpendicular to the resection of theproximal phalanx105. Then instep716, as shown inFIG. 8G, theproximal phalanx105 is drilled usingdrill bit808 over the K-wire805 to create ahole807 in theproximal phalanx105. The K-wire805 is used to guidedrill bit808 into the desired alignment. Accordingly, thedrill bit808 used in the present invention is preferably cannulated such that it may fit over the K-wire805. Thedrill bit808 may be driven manually or via a torque transmitting tool (not shown). Thedrill bit808 may comprise a pre-marked depth line marking809 to indicate how deep to advance thedrill bit808 into theproximal phalanx105. The K-wire805 is then removed from theproximal phalanx105.
• Instep718, as shown inFIG. 8H the K-wire805 is advanced into themiddle phalanx103, through thedistal phalanx101, until the K-wire805 exits the toe. In a preferred embodiment, the K-wire805 is advanced into themiddle phalanx103 until a minimum of approximately 10 mm of K-wire805 extends out of themiddle phalanx103. The same K-wire805 may be used that was previously used inFIGS. 8E-8G. Alternatively, the surgeon can use a different K-wire. The K-wire805 is advanced by the surgeon in a direction of the desired alignment of theintramedullary fixation implant200 with respect to themiddle phalanx103. Instep720, as shown inFIG. 8I, themiddle phalanx103 is tapped over the K-wire805 to create a threadedhole815 in themiddle phalanx103 usingtap810 driven either manually or by a torque transmitting tool (not shown). The K-wire805 is used to guidetap810 into the desired alignment. Accordingly, tap810 used in the present invention is preferably cannulated such that is may fit over the K-wire805. Threadedhole815 comprises threads that correspond tothreads215 of thefirst fixation portion202.Guide tap810 may comprise a depth line marking811 to indicate how deep to advance theguide tap810 into themiddle phalanx103.
• Next, instep722, thesecond fixation portion204 ofintramedullary fixation member200 is inserted intoaperture504 of theimplant driving tool500 as shown inFIG. 6B. As shown inFIG. 8J, instep724, thefirst fixation portion202 is rotatably advanced into the threadedhole815 in themiddle phalanx103 over the K-wire805 using theimplant driving tool500. As such, the K-wire805 is advanced intobore221 of theintramedullary fixation implant200. The diameter of K-wire805 that may be used in the practice of the present invention preferably is adapted to fit within diameter D ofbore221 ofintramedullary fixation implant200. Thefirst fixation portion202 may be advanced manually into the threadedhole815 by rotating thehandle501 of theimplant driving tool500 or by attaching a torque transmitting tool to endportion503 of the implant driving tool500 (not shown).Threads215 engage the threads tapped into the threadedhole815. In an alternative embodiment, themiddle phalanx103 is not pre-tapped. It may be only pre-drilled or theintramedullary fixation implant200 may be advanced into themiddle phalanx103 using the self-tappingleading edge213. Thefirst fixation portion202 is rotatably advanced into the threadedhole815 in themiddle phalanx103 until thefirst end511 of theimplant driving tool500 meets themiddle phalanx103. This will ensure that thefirst fixation portion202 is within themiddle phalanx103, leaving the unthreaded middle portion206 (FIG. 6B) of the implant at the bone-to-bone interface. After thefirst fixation portion202 is fully inserted into themiddle phalanx103 as desired, as shown inFIG. 8K, theimplant driving tool500 is oriented so that anindicator514 of theimplant driving tool500 is aligned with the dorsal aspect of the middle phalanx103 (12 o'clock position). This ensures the proper orientation of the implant in the phalanx. Then, theimplant driving tool500 is removed from thesecond fixation portion204.
• As shown inFIG. 8L, the K-wire805 is pulled further intomiddle phalanx103 until it is housed within thefirst fixation portion202 and does not extend past themiddle portion206 ofintramedullary fixation implant200. Instep726, the first andsecond projections231 and232 ofsecond fixation portion204 are collapsed in directions D2 and D3 to a collapsed position shown inFIG. 3F. The first andsecond projections231 and232 may be collapsed by being compressed withforceps812.
• In a preferred embodiment, as shown inFIG. 8N, themiddle phalanx103 is counter-rotated in direction D1 instep728. Preferably, the angle of rotation is in the range of about 0 degrees to about 90 degrees, more preferably about 10 degrees to about 80 degrees, and more preferably it is about 60 degrees. Next, instep730, thesecond fixation portion204 is pressed linearly intohole807 in theproximal phalanx105 in direction D4 lateral to theproximal phalanx105 andhole807. The joint is firmly compressed until the implant is completely buried and the surfaces of the resectioned joint are fully opposed as shown inFIG. 8O. Because no pressure is provided to the first andsecond projections231 and232 ofsecond fixation portion204 by the forceps, first andsecond projections231 and232 will deploy to substantially normal or open position as shown inFIGS. 3A-3B.
• As shown inFIG. 8O, instep732, themiddle phalanx103 is rotated to the final and desired fixation position in direction D5, thereby further advancingsecond fixation portion204 into theproximal phalanx105 via the help of thehelical thread250 formed on thesecond fixation portion204. Preferably the angle of rotation is in the range of about 0 degrees to about 90 degrees, more preferably about 10 degrees to about 80 degrees, and more preferably it is about 60 degrees. The rotation in direction D5 adds further compression in directions D6 and D7 betweenmiddle phalanx103 andproximal phalanx105. Generally, the opposing threads of thesecond fixation portion204 allow for approximately an additional 0.25 mm of compression for every 30 degree of counter-rotation. In a preferred embodiment, an angle of rotation of about 60 degrees adds about 0.5 mm compression in directions D6 and D7.
• In a preferred embodiment, instep734, as shown inFIG. 8P, the K-wire805 is advanced in direction D4 throughbore221 in between first andsecond projections231 and232 to further deploy first andsecond projections231 and232 outwardly into an open position in theproximal phalanx105. After the procedure, theguide wire805 can then be removed. In an alternative embodiment, as shown inFIG. 8P, theguide wire805 can be driven proximally into themetatarsal107 to stabilize the metatarsophalangeal joint108. Theguide wire805 may be left in place for the initial recovery period to allow the soft tissue to heal and prevent metatarsophalangeal joint108 subluxation. After the initial recovery, theguide wire805 can be removed.
• As will be apparent to those skilled in the art, numerous variations may be practiced within the spirit and scope of the present invention. For example, a variety of different tools—screw drivers, wrenches, reduction instruments and drill guides—may be used in the practice of the invention. Implants of different sizes and different shapes may be used. Likewise different thread sizes and configurations may be used. There may also be variation in the procedure used to implant the intramedullary fixation implant in the bones. Certain steps can be omitted or combined with other steps and certain steps can be performed in a different order. For example, in some procedures it may not be necessary to excise the bone faces, use a K-wire, or pre-drill or pre-tap holes in the bones.
• While the invention has been described with reference to the preferred embodiment and alternative embodiments, which embodiments have been set forth in considerable detail for the purposes of making a complete disclosure of the invention, such embodiments are merely exemplary and are not intended to be limiting or represent an exhaustive enumeration of all aspects of the invention. The scope of the invention, therefore, shall be defined solely by the following claims. Further, it will be apparent to those of skill in the art that numerous changes may be made in such details without departing from the spirit and the principles of the invention. It should be appreciated that the invention is capable of being embodied in other forms without departing from its essential characteristics.

Claims (39)

What is claimed is:

1. An intramedullary fixation implant comprising:

an elongated body extending from a first end to a second end;

a first fixation portion at the first end; and

a second fixation portion at the second end comprising a first projection and a second projection longitudinally separated by a slot, wherein the first projection and the second projection comprise a plurality of barbs extending outwardly from oppositely-disposed outer-facing surfaces of the first and second projections.

2. The intramedullary fixation implant ofclaim 1, wherein said plurality of barbs are shaped and arranged along the outer-facing surfaces of the first and second projections such that they cooperatively form a thread along the second fixation portion.

3. The intramedullary fixation implant ofclaim 1, wherein the elongated body comprises material selected from the group consisting of PEEK, PAEK, SST, titanium, NiTi, Cobalt chrome, polylactic acid, osteoconductive material, and a combination thereof.

4. The intramedullary fixation implant ofclaim 1, wherein the first fixation portion is substantially cylindrical in shape.

5. The intramedullary fixation implant ofclaim 1 further comprising a middle portion disposed between the first fixation portion and the second fixation portion.

6. The intramedullary fixation implant ofclaim 5, wherein the middle portion comprises a cross section selected from the group consisting of a cylinder, a rectangle, a square, and a hexagon.

7. The intramedullary fixation implant ofclaim 5, wherein the first fixation portion is tapered with width that decreases from the middle portion to the first end of the elongated body.

8. The intramedullary fixation implant ofclaim 1, wherein the first fixation portion comprises threads on its exterior surface.

9. The intramedullary fixation implant ofclaim 8, wherein the threads are helical dual-lead threads.

10. The intramedullary fixation implant ofclaim 1, wherein the first fixation portion comprises a self-tapping leading edge for removing bone material during insertion of the first fixation portion into a bone.

11. The intramedullary fixation implant ofclaim 1, wherein the first projection and the second projection are flexible such that they can be collapsed from an open position to a collapsed position.

12. The intramedullary fixation implant ofclaim 1, wherein the outer-facing surfaces of the first and second projections are convex.

13. The intramedullary fixation implant ofclaim 1, wherein outer-facing surfaces are substantially parallel.

14. The intramedullary fixation implant ofclaim 1, wherein the slot is V-shaped.

15. The intramedullary fixation implant ofclaim 1, wherein the first projection and the second projection comprise oppositely-disposed inner-facing flat surfaces separated by the slot.

16. The intramedullary fixation implant ofclaim 15, wherein the first projection and the second projection are collapsible, wherein when the first projection and the second projection are in a collapsed position the inner-facing flat surfaces are substantially parallel.

17. The intramedullary fixation implant ofclaim 15, wherein the second fixation portion extends along a longitudinal axis and wherein the inner-facing flat surfaces are offset from the longitudinal axis by an angle.

18. The intramedullary fixation implant ofclaim 17, wherein the angle is in the range of about 0 degrees to about 45 degrees.

19. The intramedullary fixation implant ofclaim 17, wherein the angle is in the range of about 5 degrees to about 30 degrees.

20. The intramedullary fixation implant ofclaim 17, wherein the angle is about 10 degrees.

21. The intramedullary fixation implant ofclaim 1, wherein the elongated body comprises a circular compression notch formed at the meeting-place of the first projection and the second projection to assist in collapsing the first projection and second projection towards each other.

22. The intramedullary fixation implant ofclaim 2, wherein the thread formed by the plurality of barbs along the second fixation portion comprises a reverse-buttress helical thread.

23. The intramedullary fixation implant ofclaim 2, wherein the thread formed by the plurality of barbs along the second fixation portion translates compression between a first bone and a second bone when the intramedullary fixation implant is implanted between the first and second bones.

24. The intramedullary fixation implant ofclaim 1, wherein the elongated body is cannulated.

25. The intramedullary fixation implant ofclaim 1, wherein the elongated body comprises a bore extending from the first end to the second end.

26. The intramedullary fixation implant ofclaim 25, wherein the bore receives a guide wire.

27. The intramedullary fixation implant ofclaim 26, wherein the guide wire is used to deploy the first and second projections into an open position during implantation of the intramedullary fixation implant.

28. The intramedullary fixation implant ofclaim 1, wherein each barb of the plurality of barbs comprises opposing outer-facing flat side walls.

29. The intramedullary fixation implant ofclaim 28, wherein the opposing outer-facing flat side walls of each barb of the plurality of barbs are formed to cooperate with an implant driving tool.

30. The intramedullary fixation implant ofclaim 29, wherein the implant driving tool comprises an elongated body extending from a first end to a second end along a longitudinal axis, and an aperture at the first end of the elongated body of the implant driving tool, wherein said aperture is sized for receiving the second fixation portion of the intramedullary fixation implant.

31. The intramedullary fixation implant ofclaim 30, wherein the implant driving tool comprises a handle portion used for transmitting torque to the implant driving tool.

32. The intramedullary fixation implant ofclaim 30, wherein the implant driving tool further comprises an end portion at the second end of the elongated body of the implant driving tool, wherein the end portion is sized for receiving a torque transmitting tool.

33. The intramedullary fixation implant ofclaim 29, wherein the implant driving tool is provided for driving the first fixation portion of the intramedullary fixation implant into a bone.

34. The intramedullary fixation implant ofclaim 30, wherein the aperture of the implant driving tool comprises an inner base wall for preventing the second fixation portion from being overinserted into the aperture of the implant driving tool.

35. The intramedullary fixation implant ofclaim 1, wherein the second fixation portion is offset from the first fixation portion at an angle.

36. The intramedullary fixation implant ofclaim 35, wherein the angle is in the range of about 0 degrees to about 30 degrees.

37. The intramedullary fixation implant ofclaim 35, wherein the angle is in the range of about 5 degrees to about 10 degrees.

38. The intramedullary fixation implant ofclaim 35, wherein the angle defines the angle of the bone fixation.

39. An intramedullary fixation implant comprising:

a first fixation portion; and

a second fixation portion connected to the first fixation portion;

wherein the second fixation portion comprises a first projection and a second projection separated by a slot, wherein the first projection and the second projection comprise a plurality of barbs shaped and arranged along the first and second projections such that they cooperatively form a thread along the second fixation portion.

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