US20060015101A1 - Intramedullary fixation assembly and devices and methods for installing the same - Google Patents

Abstract

An intramedullary fixation assembly usable with different long bone types and a guide assembly for guiding deployment of the intramedullary fixation assembly. The intramedullary fixation assembly includes a fixation member that has ends and a curved body extending between the ends. The curved body of the fixation member has a radius of curvature configured to extend through the medullary canal regardless of the long bone anatomy. Fasteners fix the fixation member to the bone fragments and are guided by a guide assembly. The guide assembly includes a guide body defining openings configured to guide the fasteners through openings defined in the fixation member and into the bone fragments. A fixation end of the guide body includes a pair of opposing, converging surfaces that are configured to engage in a positive fit with an exposed end of the fixation member accessible through the side aperture in the first fragment.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention is related to the use of orthopedic fixation devices and devices for installing the same, and in particular, to intramedullary fixation devices and guides for facilitating installation and fixation of the same.
• 2. Description of Related Art
• Long bone fractures are fairly common in the elderly population, often due to the onset of osteoporosis. Long bone fractures may be reduced by the use of assorted conventional bone plates. For example, a bone plate may be attached to the outside surface of two adjacent fragments of a long bone and then secured by inserting bone screws through openings in the bone plate. Problems may arise with such bone plates, however, in that the soft tissues covering the bone plates may become irritated by passage or movement over the bone plates.
• An alternative to bone plates are intramedullary nails or rods that extend through a medullary canal defined within the fractured long bone. The nails or rods are typically fastened to the fractured portions of the long bones with bone screws. The nails or rods are placed into the medullary canal by insertion through a hole which is drilled into one end of the long bone. For instance, to reduce a fractured femur with an intramedullary rod or nail, a hole is drilled through the articular cartilage between the condyles to provide access for the rod. Because the intramedullary nails or rods are contained within the medullary canal, they avoid the problems with soft tissue associated with plates. However, insertion of these rods through holes in the ends of the longs bones requires damaging the articular cartilage on the ends of the long bones.
• U.S. Pat. No. 6,527,775 to Warburton (“the '775 patent”), which is hereby incorporated herein in its entirety by reference, describes an intramedullary fixation device used to reduce a distal fracture of the radius. As shown inFIG. 3A of the '775 patent, theintramedullary fixation device25 includes an elongated axially extendingrod26 with adistal portion27 and aproximal portion28. The fixation device also includes adistal fixation member30 andproximal fixation members35. The distal fixation member extends through the distal portion of the rod and into adistal fracture fragment18. The proximal fixation members extend through the proximal portion of the rod and the portion of the radius proximal the fracture line. The '775 patent describes avoiding end insertion of the rod through the cartilage of the distal radius by using a laterally positionedbone window16 defined in the distal fracture fragment.
• Although the '775 patent discloses an intramedullary fixation device for reducing a distal radius fracture without insertion through cartilage on the end of the distal radius, other long bones, such as the humerus, femur and tibia are also often fractured and require repair.
• Therefore, it would be advantageous to have a fixation device for all long bones that is insertable into the medullary shaft of the long bones. It would also be advantageous if the fixation device were capable of insertion without damaging the articular cartilage of the long bones.
BRIEF SUMMARY OF THE INVENTION
• The present invention addresses the above needs and achieves other advantages by providing an intramedullary fixation assembly usable with different long bone types and a guide assembly for guiding deployment of the intramedullary fixation assembly. The intramedullary fixation assembly includes a fixation member that has ends and a curved body extending between the ends. The curved body of the fixation member has a radius of curvature extending from a first end configured to extend between a side aperture defined in a first fragment through the medulary canal and into a second fragment, regardless of the type of the long bone. Fasteners are used to fix the fixation member to the bone fragments and are guided by a guide assembly. The guide assembly includes a guide body defining openings configured to guide the fasteners through openings defined in the fixation member and into the bone fragments. A fixation end of the guide body includes a pair of opposing, converging surfaces that are configured to engage in a positive fit with an exposed end of the fixation member accessible through the side aperture in the first fragment. Advantageously, the positive fit facilitates accurate positioning of the guide body and, as a result, of the fixation member fasteners.
• In one embodiment, the present invention includes an intramedullary fixation assembly for repairing any of a plurality of long bone types. Each of the long bones defines a medullary canal fractured into at least a first and second adjacent bone fragments. The first bone fragment has a free end with an articular cartilage surface and defines a side aperture. The side aperture is positioned subjacent the articular cartilage surface of the first bone fragment and extends into the medullary canal. Included in the intramedullary fixation device are a plurality of fasteners (e.g., a first fastener and a second fastener) each having an elongate body with a head end and an opposite, bone-securing end. A fixation member of the intramedullary fixation device includes a first end, a second end and a curved body extending between the first and second ends. The curved body defines at least one fastener opening positioned proximate the first end and configured to allow passage of the first fastener therethrough and into the first bone fragment. Also defined by the curved body is a second fastener opening positioned proximate the second end and configured to allow passage of the second fastener therethrough and into the second bone fragment. The curved body has a radius of curvature extending from the first end that is configured to allow passage of the fixation member through the side aperture of the first bone fragment and into the medullary canal until the first end of the fixation member is positioned adjacent the side aperture, and within a portion of the medullary canal defined within the first bone fragment, and the second end of the fixation member is positioned within a portion of the medullary canal defined within the second bone fragment. In this manner, the fixation assembly can be used to reduce and secure a fracture of any of the various types of human long bone types.
• In one aspect, the curved body has a smooth, continuous curvature that extends from its first end to its second end. The radius of curvature is preferably defined by a centerline extending from the first end to the second end. Also, the curved body preferably includes smoothly curving concave and convex sides configured to facilitate passage of the fixation member through the side aperture and into the medullary canal. Also, the first and second ends may be tapered to facilitate insertion through the side aperture and into the medullary canal.
• In another aspect, the same radius of curvature extending from the first end can be used for a plurality of lengths for the curved body, allowing the design to be extended to various long bone types. Preferably, the radius of curvature extending from the first end ranges from between 1.5 to 5 inches, and more preferably, about a radius of curvature of approximately 2 to 4 inches, or 2.6 to 3.4 inches.
• In another embodiment, the present invention includes a guide assembly for facilitating placement of a plurality of bone fasteners of an intramedullary fixation assembly through predefined locations on a fixation member of the intramedullary fixation assembly. The fixation member extends through a medullary canal defined within a long bone and has an exposed end accessible through a side aperture defined by the long bone. Included in the guide assembly is at least one guide fastener configured to extend into the exposed end of the fixation member so as to be secured to the fixation member. A guide body includes a fixation end and defines a plurality of fastener guide openings. These guide openings are configured to orient the bone fasteners extending through the guide openings with the predefined locations on the fixation member. The fixation end defines an opening configured to allow passage of the guide fastener through the guide body and into the exposed end of the fixation member. The fixation end includes at least one pair of surfaces positioned opposite each other and generally extending in a converging direction. These surfaces are, as a result, configured to engage in a positive fit with the exposed end of the fixation member when the guide body is secured thereto with the guide fastener. This positive fit reduces the motion between the guide body and the fixation member, thereby improving the ability of the guide openings to accurately guide the bone fasteners through the predetermined locations on the fixation member.
• As an example of the surfaces used for a positive fit, the pair of surfaces may be portions of a convex surface or prong configured to extend within a concave surface defined within the exposed end of the fixation member. Preferably, the convex surface is configured to reach a positive fit prior to full contact between the remaining (non-convex and non-concave) surfaces of the fixation end and the exposed end. In yet another aspect, there may be additional pairs of surfaces or prongs configured for a positive fit, including second, third and fourth pairs of surfaces spaced from each other in a cruciform configuration.
• The present invention has many advantages. For example, the invention has many attributes that facilitate its use for different types of human long bone. Maintaining a constant radius of curvature of a first end of the curved body allows for different sized long bones and different types of long bone to be accommodated merely by extending the arc further to produce a greater “hook” on increasing sizes of fixation members. This overcomes the increase in not only the length of the long bone, but also the increase in distance between widened end and width of the medullary canal, facilitating its use on different and larger types of long bones. It has also been determined that use of a radius of curvature in the ranges of 1.5 to 5 inches facilitates use with different types of long bone, especially when the curved body curves continuously along its length and the ends are tapered for easy insertion. The use of a cruciform shape and positive fit or wedge effect used for the concave indentations and the prongs provides rotational and translational stability of the fixation member when attached to the guide assembly. In addition, the positive fit or wedge effect operates to center and reduce micro-motion between the targeting guide and the rest of the guide assembly.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
• Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
• FIG. 1 is a perspective view of a long bone fracture repaired using an intramedullary fixation assembly of one embodiment of the present invention;
• FIG. 2 is an elevation view of the long bone fracture and intramedullary fixation assembly ofFIG. 1;
• FIG. 3 is a side elevation view of a fixation member of the intramedullary fixation assembly ofFIG. 1;
• FIG. 4 is another side elevation view of a fixation member of the intramedullary fixation assembly ofFIG. 1;
• FIG. 5 is another side elevation view of a fixation member of the intramedullary fixation assembly ofFIG. 1;
• FIG. 6 is another side elevation view of a fixation member of the intramedullary fixation assembly ofFIG. 1;
• FIG. 7 is a sectional view of the fixation member ofFIG. 6;
• FIG. 8 is a sectional view of the fixation member ofFIG. 6;
• FIG. 9 is a sectional view of the fixation member ofFIG. 6;
• FIG. 10 is a sectional view of the fixation member ofFIG. 6;
• FIG. 11 is a sectional view of a portion of the fixation member and a pair of bone fasteners of the intramedullary fixation assembly ofFIG. 1;
• FIG. 12 is a sectional view of one of the bone fasteners shown inFIG. 11;
• FIG. 13 is a side elevation view of a fixation member of another embodiment of the present invention, including a stem extending from one of its ends;
• FIG. 14 is another side elevation view of the fixation member ofFIG. 13;
• FIG. 15 is a plan view of a head end of one of the bone fasteners shown inFIG. 11;
• FIG. 16 is a side elevation view of the bone fastener shown inFIG. 15;
• FIG. 17 is a sectional view of the bone fastener shown inFIG. 15;
• FIG. 18 is a plan view of a head of a k-wire for use as a bone fastener in another embodiment of an intramedullary fixation assembly of the present invention;
• FIG. 19 is a sectional view of the k-wire shown inFIG. 18;
• FIG. 20 is a side elevation view of an outrigger frame of a guide assembly of another embodiment of the present invention shown inFIG. 53;
• FIG. 21 is a plan view of the outrigger frame ofFIG. 20;
• FIG. 22 is another side elevation view of the outrigger frame ofFIG. 20;
• FIG. 23 is plan view of a targeting guide of the guide assembly of the present invention shown inFIG. 53;
• FIG. 24 is a side elevation view of the targeting guide ofFIG. 23;
• FIG. 25 is another plan view of the targeting guide ofFIG. 23;
• FIG. 26 is a sectional view of the targeting guide ofFIG. 25;
• FIGS. 27-30 are various views of the targeting guide of another embodiment of the present invention;
• FIG. 31 is a side elevation view of a screw-in drill guide which is part of the outrigger frame ofFIG. 20;
• FIG. 32 is a sectional view of the screw-in drill guide ofFIG. 31;
• FIG. 33 is a side elevation view of a drill guide of another embodiment of the present invention;
• FIG. 34 is a sectional view of the drill guide ofFIG. 33;
• FIG. 35 is a side elevation view of a screw guide of a guide assembly as shown inFIG. 59;
• FIG. 36 is a sectional view of the screw guide ofFIG. 35;
• FIG. 37 is a side elevation view of guide member of the outrigger frame shown inFIG. 20;
• FIG. 38 is a sectional view of the guide member ofFIG. 37;
• FIGS. 39 and 40 show a perspective view of attachment of a set of four prongs on the guide member ofFIG. 37 within a set of four recesses defined in an end of the fixation member shown inFIG. 6;
• FIG. 41 is an enlarged view of the prongs and recesses ofFIG. 39 forming an interference fit;
• FIGS. 42 and 43 show a side elevation view of a fastener driving drill bit of another embodiment of the present invention;
• FIG. 44 is a side elevation of a drill bit of another embodiment of the present invention;
• FIG. 45 is a plan view of a hand driver of another embodiment of the present invention;
• FIG. 46 is a side elevation view of the hand driver ofFIG. 45;
• FIG. 47 is a sectional view of a cannulated drill bit of another embodiment of the present invention;
• FIG. 48 is a side elevation view of a trialing broach assembly of another embodiment of the present invention;
• FIG. 49 is a side elevation of a handle of the trialing broach assembly shown inFIG. 48;
• FIG. 50 is a side elevation view of a depth indicator of another embodiment of the present invention;
• FIG. 51 is a sectional view of the depth indicator ofFIG. 50;
• FIG. 52 is a perspective view of the trialing broach assembly ofFIG. 48 show inserted into a long bone;
• FIG. 53 is a perspective view of the fixation member ofFIG. 3 connected to the guide assembly of the present invention;
• FIG. 54 is a perspective view of the fixation member and guide assembly ofFIG. 53, wherein the fixation member has been positioned in the medullary canal of the fractured long bone;
• FIG. 55 is a perspective view of the guide assembly and fixation member shown inFIG. 54, wherein the guide assembly is guiding drilling through an opening in the fixation member and into the long bone;
• FIG. 56 is a perspective view of the guide assembly and fixation member shown inFIG. 54, wherein drilling is being guided through another opening in the fixation member;
• FIG. 57 is a perspective view of the guide assembly and fixation member ofFIG. 54 guiding placement of a bone fastener, such as the bone fasteners shown inFIGS. 11 and 12, through the bone and the opening in the fixation member;
• FIG. 58 is a perspective view of placement of another bone fastener using the assemblies ofFIG. 57;
• FIG. 59 is a perspective view of placement of yet another bone fastener using the assemblies ofFIG. 57;
• FIG. 60 is a sectional view of a long bone and a fixation member of another embodiment of the present invention, wherein the fixation member includes a split tail;
• FIG. 61 is a sectional view of a bone fastener of another embodiment of the present invention positioned within the split tail of the fixation member ofFIG. 60;
• FIG. 62 is a sectional view of a long bone and a fixation member of another embodiment of the present invention, wherein the fixation member includes a split tail;
• FIG. 63 is a sectional view of the long bone and fixation member ofFIG. 62 wherein one arm of the split tail is threaded to allow splaying of the split tailFIG. 64 is a side elevation view of an impactor having a U-shaped end and fixation member defining U-shaped slots for receiving the end of the impactor in another embodiment of the present invention;
• FIG. 65 is a sectional view of the U-shaped impactor and slot ofFIG. 64;
• FIGS. 66-72 show assorted views of an S-shaped, positive fit connection between a guide assembly and fixation member of another embodiment of the present invention;
• FIG. 73 is a side elevation view of a fixation member of another embodiment of the present invention having a bow tilt;
• FIG. 74 is a side elevation view of a fixation member of another embodiment of the present invention having a linear offset; and
• FIG. 75 is a side elevation view of a fixation member of another embodiment of the present invention having an angular bend.
DETAILED DESCRIPTION OF THE INVENTION
• The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
• Anintramedullary fixation assembly10 of one embodiment of the present invention is shown installed in along bone11 of a patient inFIGS. 1 and 2. The long bone could be any of a number of long bones, such as a femur, tibia, radius or humerus. Thefixation assembly10 is most suited to repairing fractures of thelong bone11 wherein the fracture is at one end near anarticular cartilage surface12 and wherein it is desired to leave the articular surface undisrupted during the repair. Also, the long bone includes awidened end13 that supports the articular cartilage surface which tapers to a morenarrow shaft14. Extending within theshaft14 and a portion of thewidened end13 is amedullary canal15. Generally, every type of long bone will have the afore-described characteristics, such as theshaft14 being relatively narrower than theend13. However, the proportional geometry of the different long bones will vary due to their biology and function.
• When referred to herein, the terms “different long bones,” “various long bones,” and other, related terms, do not refer to the same type of long bone in different people, but different types of long bones, such as a femur versus a tibia, or radius, or humerus. In addition, the intramedullary fixation assembly could be used to repair somewhat more complex fractures, but is shown being used to repair afirst bone fragment16 separated from asecond bone fragment17 by asingle fracture line18. Aside aperture19 is defined in a lateral surface of thewidened end13, subjacent thearticular cartilage surface12, to allow insertion of theintramedullary fixation assembly10.
• Generally, theintramedullary fixation assembly10 includes anelongate fixation member20 and a plurality offasteners21 that extend through the elongate fixation member to attach it to thelong bone11 above and below thefracture line18 and thereby reduce the fracture, for example as shown inFIGS. 1 and 2. Theelongate fixation member20 preferably, when positioned within themedullary canal15 of the long bone11 (regardless of its type), has afirst end22 positioned adjacent theside aperture19. Extending from the first end, through the rest of the aperture and into themedullary canal15 of thefirst bone fragment16, is a curved body24 (shown in broken lines inFIGS. 1 and 2) of thefixation member20. Thecurved body24 extends to asecond end23 which is positioned within themedullary canal15 of thesecond bone fragment17. Advantageously, a radius of curvature of thecurved body24 is selected to promote smooth insertion of the curved body through theside aperture19 and into themedullary canal15 despite differences in the width of thewidened end13 and theshaft14 andmedullary canal15 between the various types oflong bone11.
• For example, one embodiment of thefixation member20 of the present invention is shown inFIGS. 3-14. Thefirst end22 of thefixation member20 has two intersecting flat surfaces, including an exposedfirst end surface27 that is accessible through theside aperture19 and an adjacentfirst end surface28 that is at a right angle to the exposed surface, as shown inFIG. 4. Thesecond end23 of thefixation member20 has a rounded profile with a radius of about 0.08 inches, as shown inFIG. 4, and edges rounded to about a 0.06 inch radius, as shown inFIG. 5.
• Thecurved body24 of thefixation member20 includes aconvex side29 and aconcave side30 that are on opposite sides of the curved body. The sides have radii of curvature with a similar center, but the center of the convex side changes so that the sides converge in a slight taper as they extend to thesecond end23, as shown inFIG. 4. For instance, the radius of curvature of theconcave side30 is about 3.12 inches and the radius of curvature of theconvex side29 is about 3.36 inches near thefirst end22 when measured from afirst center31 positioned about 2.14 inches from the plane of the adjacentfirst end surface28 and about 2.47 inches from the plane of the exposedfirst end surface27. But, the radius of curvature of theconvex side29 shifts to about 2.68 inches at asecond center32 that is positioned about 1.89 inches from the plane of the adjacentfirst end surface28 and about 1.5 inches from the plane of the exposedfirst end surface27.
• Notably, this shift produces the taper near thesecond end23 of thefixation member20. Also notable is that maintaining a constant radius of curvature near thefirst end22 of thecurved body24 allows for different sized and different types of long bones to be accommodated merely by extending the arc further to produce a greater “hook.” This overcomes the increase in not only the length of thelong bone11, but also the increase in distance betweenwidened end13 and width of themedullary canal15, facilitating its use on different and larger types of long bones. If measured from the centerline of thecurved body24, the radius of curvature can actually be constant between thesides29,30 and theends22,23 regardless of the amount of taper. This radius of curvature can also be maintained while the arc length of thecurved body24 is extended to account for increased length of thelong bone11 and increased offset between theside aperture19 and the position of themedullary canal15. As a result, an entire kit of fixation members could have the same radius of curvature but be usable in different types and lengths of long bones.
• A second pair of opposite, side surfaces33 extend between theconvex side29 andconcave side30, as shown inFIGS. 3 and 5. Similar to theconvex side29 andconcave side30, the side surfaces33 taper slightly toward each other as they extend from thefirst end22 to thesecond end23 of thecurved body24. However, the side surfaces33 in the illustrated embodiment are relatively planar, as opposed to the curved shape of thesides29,30. Advantageously, the taper of thesides29,30,33, the continuous curve of thecurved body24 between theends22,23 and the rounded profile of thesecond end23 help to facilitate insertion through theside aperture19 and into themedullary canal15. Note that the term “continuous” differs from “constant” in reference to curvature herein in that a continuous curvature is not necessarily a constant curvature. In addition, the use of radii of curvature within about the ranges cited above, with variations of about 1.5 to 5 inches, allow thefixation member20 to be employed in different (preferably human) long bones with only variations in the overall length of the fixation member.
• There may be some adaptations of thefixation member20 beyond extension of the arc length, such as through the application of a tilt. The tilt would generally not be in the curvature defined by the convex andconcave sides29,30 to accommodate curvature in different long bones. For example, a volar tilt may be used to accommodate the volar tilt in the saggital plane of the human radius. In this instance, volar tilt facilitates better filling of the medullary canal of the distal radius and can improve stabilization of thefixation member20. Generally, the tilt can be accomplished, for example, through the use of a radial bow, as shown inFIG. 73, a linear offset, as shown inFIG. 74, or an angular bend, as shown inFIG. 75. The radial bow ranges from about 4 to 8 inches (100 to 200 mm) of curvature. The linear offset is about 2 to 5 mm and the angular bend is about a 10° to 20° angle.
• To allow passage of thefasteners21 through the fixation member, a plurality of fastener openings are defined in the fixation member. These fastener openings include a side apertureaccessible fastener opening34, a pair offastener openings35 extending between the curvedconvex side29 andconcave side30, andfastener openings36 extending between the side surfaces33. Thefastener opening34 extends from the exposed first end surface27 (which is accessible through theside aperture19 when thefixation member20 is installed) through a portion of thecurved body24 and to theconvex side29, as shown inFIGS. 4 and 5. Thefastener opening34 includes aguide portion38 and afastener head portion39 that is generally more narrow than the guide portion. Both of the portions are threaded, as shown inFIGS. 7 and 8, to facilitate a secure fit by thefasteners21 and various installation devices, as will be described in more detail below. Defined around the periphery of theguide portion38 of thefastener opening34 are four concave channels, recesses orindentations40. These indentations are arranged in a cross, or cruciform, shape each radiating out from thefastener opening34 and spaced 90° from each other. As will be described in more detail below, theconcave indentations40 serve to provide for a secure, positive fit with aguide assembly50.
• The pair offastener openings35 which extend between thesides29,30 extend through thecurved body24 nearer thefirst end22 so as to be within thefirst bone fragment16, as shown inFIG. 5. Each of the fastener openings also has a threadedfastener portion39 similar to thefastener opening34, but anon-threaded guide portion38, as shown inFIGS. 9 and 10. Thesefastener openings35 extend at different, divergent angles than each other and the orientation of thefastener opening34 which is relatively orthogonal with respect to the exposedfirst end surface27 and theconvex side29, as shown inFIGS. 3. As a result, the fastener openings of the present invention (such as the fastener openings35) need not all be aligned with the axis of the fixation member.
• These different angles improve fixation by allowing angled insertion of the fasteners into different portions of thefirst bone fragment16, as shown inFIGS. 1 and 2. In addition, the angles of thefastener openings34,35 may be configured so that the fasteners extend subjacent to the articular cartilage for improved fixation. Generally, this will require thefastener openings34,35 to extend at some acute angle, such as an angle between about 50° and 85° (depending on the origin of the fastener opening), and preferably about 60° to 70°, with respect to the fixation member body. Basically, these angles are to match the inclination angle of the articular surface so as to provide a buttress effect for the articular cartilage. For instance, the ulnar inclination angle of the articular cartilage on the radius is about 23° (resulting in a 67° fastener opening angle). The buttress effect is also improved by the sub-chondral placement of thefirst end surface28 that is adjacent and at a right angle with respect to the exposedfirst end surface27 so as to underlie the articular cartilage.
• In the illustrated embodiment shown inFIGS. 4 and 6, threefastener openings36 are defined in thecurved body24 at a position nearer thesecond end23 of thefixation member20. The two outer ones of thefastener openings36 are configured to receive threadedfasteners21, similar to thefastener openings34,35, but the center one of thefastener openings36 is configured to receive a relatively smaller diameter k-wire fastener41, as shown inFIG. 6. Preferably, the larger of thefastener openings36 are not threaded to allow a slip fit of the threadedfasteners21 without damaging the threads, as will be described below.
• The threadedfasteners21 are shown in greater detail byFIGS. 15-17 and the k-wire fastener41 byFIGS. 18 and 19. Each of thefasteners21,41 is shown as being driven by a Phillips-type, or cruciform-type, head (FIGS. 15, 17 and18), but may be configured for mating with a driver in any number of ways, such as with an Allan-type head or flat head. Each of the illustrated threadedfasteners21 includes ahead42, a threadedshaft43, anon-threaded shaft portion45 and a bone-securingend44, as shown inFIG. 16. Thehead42 of each of the threadedfasteners21 has a larger diameter than itsshaft43, so as to prevent the threaded fastener from passing through tapped openings in the first layer of cortical bone. However, the diameter of thehead42 is still small enough to pass through ascrew guide51, or other guide, positioned by theguide assembly50 within theguide portion38, as will be described in more detail below.
• When the threadedfasteners21 are inserted through theopenings34,35 and into thefirst bone fragment16, the head is configured to reside in theguide portion38, the threadedshaft43 in the threadedfastener portion39 and the bone-securing layer is configured to attach to the distant layer of cortical bone opposite theside aperture19 and subjacent thearticular cartilage surface12, as shown inFIGS. 1 and 2. When inserted through theopenings36 and into thesecond bone fragment17, the threadedshaft43 is configured to attach to the first layer of cortical bone, thenon-threaded shaft portion45 is configured to reside in theopenings36 in a slip fit and the bone-securingend44 is configured to attach to the distant layer of cortical bone opposite the first layer of cortical bone, as shown inFIG. 11. Thefastener head42 is configured to abut the first layer of cortical bone, and may have a rounded shape to minimize irritation of the overlying tissues, as shown inFIG. 12. Notably, when used in theopenings36, the threadedfasteners21 become bi-cortical screws, firmly attaching to two layers of cortical bone. As another option, thenon-threaded shaft45 may include achamfer63 to help locate the screw in theopenings36 as it is advanced through thefixation member20.
• The bone-securingend44 preferably has threads and an outer diameter that is smaller than the minimum, trough diameter of the threads on the threadedshaft43 and the diameter of the un-threaded shaft portion to prevent the bone-securing end from locking up or fretting the threads when passing through thefastener portion39. Aneck46 on each of the threadedfasteners21 also prevents lockup by providing space between the threadedfastener shaft43 andfastener head42, as shown inFIGS. 16 and 17. As shown inFIG. 19, the k-wire fastener41 also includes afastener head42, aneck46, a threadedshaft43 and anon-threaded shaft portion45, but itsbone securing end44 is not threaded for easier insertion as the first fastener.
• During installation, the threadedshaft43 of one of the threaded or k-wire fasteners21,41 mates with the threadedfastener portion39 of its respective one of thefastener openings34,35 and36 and the bone-securingend44 extends into thelong bone11 for a secure fit, as shown inFIGS. 1 and 2. It should be noted that although two types of fasteners are described herein that are preferred, other types of fasteners may also be employed, including other types of wires, screws, etc., and still be within the purview of the present invention as long as some portion of the fastener secures itself to thefixation member20 and another portion to thelong bone11.
• FIGS. 20-30 illustrate theguide assembly50 of the present invention that is used to position thescrew guide51, a screw-indrill guide52 and a plurality of other drill guides53, shown inFIGS. 31-36. Theguide assembly50 includes anoutrigger frame54 having a curved, hook-shapedbody55 including afirst end56 forpositioning fasteners21 within thefirst end22 of thefixation member20 and thefirst bone fragment16, and asecond end57 for positioning fasteners within thesecond end23 of the fixation member and thesecond bone fragment17, as shown inFIGS. 20-22.
• Theoutrigger frame54 also includes aguide member58 that has a truncated pyramid shape and extends from a flat surface of thefirst end56 of the hook-shapedbody55, as shown inFIGS. 20 and 22. Theguide member58 tapers as it extends outward from the hook-shaped body and ends in fourprongs59, as shown inFIGS. 37-40. Each of theprongs59 has a rounded shape with opposing edge surfaces60 angled toward each other (i.e., they are generally converging) as they extend outwards from the end of the truncated pyramid shape. These converging surfaces are spaced so as to fit into similarly shaped, but somewhat smaller,concave indentations40 in a positive, or interference, type fit, as shown inFIGS. 39-41. Theguide member58 and its subjacent portion of the hook-shapedbody55 define a stepped opening61, as shown inFIG. 38, that is sized to receive the screw-in drill guide52 (shown inFIGS. 31 and 32). The stepped opening61 includesshoulders62 that prevent the passage of the screw-indrill guide52.
• The screw-indrill guide52 includes aburled knob65, anelongate shaft66, atapered shoulder67 and a threadedtip68. The burled knob provides65 a gripping surface for tightening the screw-indrill guide52 and its relatively large diameter acts as a stop against passage of the screw-in drill guide through the stepped opening61 when inserted therein and tightened. Theelongate shaft66 extends from the burled knob and tapers at the taperedshoulder67 down to the diameter of the threadedtip68. This shape allows passage of the threaded tip through and out of the stepped opening61 so that the threadedtip68 can be advanced into the threads of theguide portion38 of thefastener opening34. Defined within the screw-indrill guide52 is a guide opening that extends from theburled knob52 through to the threadedtip68 and includes alarge diameter portion70 that tapers to asmall diameter portion71 near the threaded tip, as shown inFIG. 32. This change in diameter helps to concentrically center thefasteners21 as they are advanced through the screw-indrill guide52 and into thefastener opening34 defined in thefixation member20, as will be described below.
• When the threaded tip is advanced into the threads of theguide portion38, theguide member58 and itsprongs59, which are also spaced in a cruciform or cross pattern similar to theindentations40, are advanced into the indentations, as shown inFIG. 40. The cruciform pattern, combined with the positive fit, firmly locks theoutrigger frame54 to thefixation member20 before and during guidance of insertion of thevarious fasteners21,41. This firm attachment guards against relative motion of theguide assembly50 with respect to thefixation member20, so that misalignment of theguides51,52,53 is reduced even with just a single point of attachment of the guide assembly to the fixation member.
• The cruciform shape and positive fit are particularly effective at restricting rotation between the guide assembly and fixation member, which can be a problem due to the relative length and cantilevered configuration of the guide assembly and fixation member, especially on the larger long bones such as the tibia and femur. It should be noted, however, that the positive fit of theprongs59 in theconcave indentations40 could be accomplished in other ways, such as by having the indentations on theguide member58 instead of the exposedfirst end surface27 of thefixation member20.
• In addition, different numbers and configurations of the prong and indentation arrangement are also possible to achieve a firm positive fit, even though the cruciform arrangement is preferred for reducing rotational motion. For instance, the positive or press fit may be implemented or facilitated, as shown for example inFIG. 41, by slightly over-sizing a male fitting portion (e.g., the prongs59) with respect to a female portion (e.g., the concave indentations40) so that the angled opposing surfaces (e.g., converging edge surfaces60) are in contact and the tip of the male portion, and other remaining flat surfaces have minimal contact to allow the angled surfaces to wedge into each other.
• Returning to a discussion of thefirst end56 of the hook-shapedbody55 of theoutrigger frame54, thefirst end56 further supports two screw guides51 that are integrally connected to, and extend from, the first end of the hook-shaped body, as shown inFIGS. 20-22. These screw guides51 are cylindrical tubes that define openings extending therethrough and are oriented so as to have an axis collinear and aligned with the axes of the of the pair ofopenings35 defined in thecurved body24 of thefixation member20. Preferably, the screw guides51 are oriented so that thefasteners21 extend at an angle into thefirst bone fragment16 right below thearticular cartilage surface12, as shown inFIGS. 1 and 2. In addition to the screw guides51, thefirst end56 also includes ahandle mount37 defining a threaded opening.
• Referring now to thesecond end57 of the hook-shapedbody55, there is supported achannel member72 of theoutrigger frame54 that extends away from the second end of the hook-shaped body. Thechannel member72 has an elongate rectangular shape, as shown byFIGS. 21 and 22, and includes a pair ofchannel arms73 extending away and along the length of the rectangular shape, as shown in FIGS.20 and21. Each of the arms defines anangled surface74 extending toward the other one of the arms and the arms are spaced from each other and parallel so as to define a channel. Extending into the channel defined between thearms73 is astop75. In addition, thesecond end57 and thechannel member72 define a locking member opening76 that extends into the channel between thearms73. The lockingmember opening76 is sized and includes threads to receive advancement of a lockingmember77, as shown inFIGS. 20 and 22. The locking member includes its ownburled knob78 to facilitate its advancement and also has a frusto-conical shaped distal locking tip79 that extends out of the lockingmember opening76 and into the channel between thearms73 when the lockingmember77 is fully advanced, as shown inFIGS. 20 and 21.
• Also included in theguide assembly50 is a targeting guide80 (as shown inFIGS. 23-26) that is configured to support and orient the drill guides53 and screw guides51 that are used to guide insertion of thefasteners21,41 through thefixation member20 and into thelong bone11. Different targeting guides80 can also be used for different sized fixation members20 (e.g., as shown inFIGS. 27-30), and can be employed in right and left handed configurations depending on the type of long bone being treated and the orientation of theside aperture19. The targeting guide includes aguide portion81 and aslide attachment portion82. Theguide portion81 defines a plurality ofguide openings83 sized for the passage of screw guides51 or drill guides53 sized for threadedfasteners21 or for the smaller diameter k-wire fasteners41. Theguide openings83 are positioned along an arc (as shown inFIGS. 23 and 25) to correspond to the placement of theopenings36 through the side surfaces33 of thecurved body24 so as to guide thefasteners21,41 into theopenings36. Optionally, one of thesmaller diameter openings83 may be placed to orient insertion of one of the k-wire fasteners41 external to thefixation member20 to avoid additional holes in the fixation member and provide for temporary securing of theguide assembly50.
• Theslide attachment portion82 is generally rectangular and defines a pair ofslots84 that extend to one edge of the side attachment portion. As is shown inFIG. 26, these slots are defined by a pair of angled, opposing surfaces85. In addition, at about a midpoint along one edge of theslide attachment portion82 is defined a circular centering divot86 with sloped sides, as shown inFIGS. 24 and 26. During attachment of the targetingguide80 to thechannel member72, the pair ofslots84 of theslide attachment portion82 are inserted between thechannel arms73 until approximately at the end of travel of the slots. Then, the lockingmember77 is advanced in theopening76 until the locking tip79 enters the centering divot86. The sloped sides of the centering divot86 interact with the sloped edges of the locking tip79 which forces the targetingguide80 to center and forms a relatively tight, positive fit. Once the locking tip79 bottoms within the centering divot86, further advancement of the locking tip pushes the angled, opposingsurfaces85 of the slots against theangled surfaces74 of thechannel arms73. This also has the effect of centering the targetingguide80 between thechannel arms73 and also forms a relatively tight, positive fit. In this manner, a positive fit is used once again to ensure tight assembly of the parts and accurate guidance for the insertion ofvarious fasteners21,41.
• As shown inFIGS. 33-36, each of the screw and drill guides51,53 include agrip flange48 at one end of anelongate shaft49 that definesteeth47 at its other end. Defined within theelongate shaft49 of the drill guide is a guide shaft opening that tapers from a wider to narrower diameter near theteeth47, as shown inFIG. 34. This corresponds with the dualdiameter drill bit90 shown inFIG. 44, wherein the larger diameter of the drill bit prevents travel of the drill bit beyond the shoulder defined within theshaft49 of thedrill guide53 so as to prevent drilling past a selected depth for safety. Theelongate shaft49 of thescrew guide51 also defines a guide shaft, but this guide shaft has a constant diameter because, as described above, thefasteners21,41 are restrained by the structure of thefixation member20 from advancing too far.
• During use the drill guides53 are first inserted into theguide openings83 of theguide portion81 of the targeting guide and are advanced until theteeth47 contact skin or bone (so as to prevent rotation of the guides). A pilot hole is drilled using thedrill bit90 guided by the drill guides53. Then, the drill guides53 are removed and screw guides51 are inserted in theguide openings83 until theteeth47 contact skin or bone. The selected one of the threaded or k-wire fasteners21,41 are advanced at the end of a driver91 (as shown inFIGS. 42 and 43) until penetrating thefixation member20 through one of theopenings36 and into the long bone11 (in this case the second bone fragment17). Thedriver91 ordrill bit90 may be advanced using power or by hand, such as by ahand driver92, as shown inFIGS. 45 and 46.
• During installation of theintramedullary fixation assembly10, a k-wire is inserted into a lateral side of thewidened end13 of thelong bone11 subjacent thearticular cartilage surface12 and used to guide a cannulateddrill bit94, as shown inFIG. 47. The cannulated drill bit clears theside aperture19 and a conventional bone awl (not shown) is used to open themedullary canal15 of cancellous bone.
• A trialingbroach95, as shown inFIGS. 48 and 52, is pushed, twisted, hammered, etc., into thelong bone11 through theside aperture19 to approximate the size of thefixation member20. The trialing broach includes ahandle98 and anawl point99. Thehandle98 includes ahead100 that facilitates gripping and hammering at one end and a threadedconnector101 at the other end, as shown inFIG. 49. This threaded connector is similar to the threadedtip68 of the screw-in drill guide allowing the exchange of theawl point99 with other awl points of different sizes, each having threaded opening at one end similar to the threadedopening34 on thefixation member20. Preferably, theawl point99 has some type of teeth or cutter (as shown symbolically by the cross-hatch pattern96) to aid in bone removal and sizing.
• Advantageously, the trialing broaches95 may eliminate the need for many awls and cutting tools. However, other conventional tools, such as reamers and awls could also be employed to clear bone. Each of thebroaches95 may also include a depth indicator, such as thenotch97 shown inFIG. 48, that indicates the correct depth for that size offixation member20. The depth indicator or notch97 may include the use of fluorescent paint so as to be easily visually detectable.
• Once theside aperture19 has been formed and themedullary canal15 cleared and sized, an appropriatelysized fixation member20 is selected based on the various above-described measurements. Thehandle98 of the trialingbroach95 is removed from theawl point99 and attached to the threaded opening defined in thehandle mount37 via the threadedconnector101 on the handle, as shown inFIG. 53. Then, theoutrigger frame54 of theguide assembly50 is attached to the fixation member. In particular, the screw-indrill guide52 is extended through the stepped opening61 of theguide member58 and its threadedtip68 is advanced into the threadedopening34 of the guide assembly. This assembly mates theprongs59 with theconcave indentations40, thereby locking out micro-motion and rotation between theoutrigger frame54 and thefixation member20, as shown inFIGS. 39 and 40.
• After fixation of theoutrigger frame54, the targetingguide80 is attached to thechannel member72 by sliding thechannel arms73 within the pair ofslots84 on theguide portion81 until the targeting guide is against thestop75. Then, the lockingmember77 is advanced in theopening76 until the locking tip79 enters the centering divot86. The sloped sides of the centering divot86 interact with the sloped edges of the locking tip79 which forces the targetingguide80 to center and forms a relatively tight, positive fit. Once the locking tip79 bottoms within the centering divot86, further advancement of the locking tip pushes the angled, opposingsurfaces85 of the slots against theangled surfaces74 of thechannel arms73.
• Thehandle98 and guideassembly50 are then used to slide thefixation member20, as facilitated by the tapered ends22,23 through theside aperture19 and into themedullary canal15, as shown inFIG. 54. Thehandle98 is then unscrewed from thehandle mount37. As an option, thefixation member20 may include radio-lucent targeting indicia to aid in positioning of the fixation member and guideassembly50. The length of thehandle98 allows for easy readjustment of the position of thefixation member20.
• Smaller guide openings83 on the targetingguide80 are used to place a temporary k-wire fastener41, such as by using the smaller opening falling outside of thefixation member20. This allows for a temporary fixation into both the first and second bone fragments16,17. The drill guides53 are placed into the appropriatelysized openings83. The dual-diameter drill bit90 is advanced into the drill guides53, the screw guides51 connected to the hook-shaped body55 (if necessary) and theguide member58 to form pilot holes in thelong bone11, as shown inFIGS. 55 and 56.
• The depth of these holes are then tested using adepth gauge102, as shown inFIGS. 50 and 51. Thedepth gauge102 may also employ fluorescent paint to ensure clear readability, such as on measurement numbers and hash marks103. The depth measurements facilitate selection offasteners21,41 of the appropriate length. If necessary, the drilled holes are then tapped (not shown) to prepare them for insertion of threadedfasteners21. After tapping, the drill guides53 are replaced with the screw guides51 (if necessary) and the threadedfasteners21 are advanced through the alignedopenings34,35,36 in thefixation member20 and thelong bone11 so as to connect the bone fragments16,17, as shown inFIGS. 57, 58 and59. Theguide assembly50 and handle98 can then be removed by removal of the temporary k-wire fastener41 and the screw-indrill guide52.
• In another embodiment of the present invention, thefixation member20 of theintramedullary fixation assembly10 may include atail portion105 extending from, or as part of, thesecond end23, as shown inFIGS. 13 and 14. The tail portion has a much smaller diameter or thickness than thecurved body24 and is relatively straight to conform to the straightness of theshaft14 of thelong bone11. The tail portion in some circumstances can improve the tightness of fit of thefixation member20 in thesecond bone fragment17 with its extra length. Another option for improving the fit within the second bone fragment is to employ the use of asplit tail106, as shown inFIG. 60. The split tail defines aslot107 that separates the split tail into two spaced arms that are drawn against the cortical wall and urged apart as atapered screw108 is advanced through the slot, as shown inFIG. 61. Alternatively, theslot107 of thesplit tail106 may also be placed in an opposite plane with a threaded opening in one of the arms so that passage of a standard screw therethrough pushes the arms apart for additional stability, as shown inFIGS. 60 and 61. In another embodiment, thesplit tail portion105 has a spring bias due to construction from a flexible material, such as a metal material, and wherein the split tail is defined by a coronal slot.
• In still another embodiment of the present invention, thefixation member20 may be shaped to accommodate a driving handle110 by having defined in its first end22 a pair ofU-shaped slots112 on either side of the fixation member, as shown inFIGS. 62 and 63. The driving handle110 includes a horseshoe or U-shaped impact end111 that straddles thefixation member20, inserting into theU-shaped slots112 wherein the rounded shapes avoid eccentric loading while the fixation member is being driven into themedullary canal15. Clearance may also be defined in theguide assembly50 for the impact end111 to allow the guide assembly to remain attached during driving. As another alternative, theslots112 may also be defined in theguide assembly50 for driving thefixation member20 via its attachment to the guide assembly.
• In yet another embodiment of the present invention, in lieu of the afore-described connection between theprongs59 and theconcave indentations40, theguide member58 may include a pair of S-curved fittings113, as shown inFIGS. 64, 65,66 and67, that are configured to mate in a positive fit with S-curved slots114 defined on thefirst end22 of thefixation member20, as shown inFIGS. 68, 69 and70.
• The present invention has many advantages. For example, the invention has many attributes that facilitate its use for different types of humanlong bone11 wherein the fixation device extends from the metaphysis to the diaphysis (via the positioning of the side aperture19), but not through the epiphysis, so as to avoid damaging the articular cartilage. Maintaining a constant radius of curvature near thefirst end22 of thecurved body24 allows for different sized long bones to be accommodated merely by extending the arc further to produce a greater “hook.” This overcomes the increase in not only the length of thelong bone11, but also the increase in distance betweenwidened end13 and width of the medullary canal, facilitating its use on different and larger types of long bones. It has also been determined that use of a radius of curvature in the range of 1.5 to 5 inches facilitates use with different types oflong bone11, especially when thecurved body24 curves continuously along its length and theends22,23 are tapered for easy insertion.
• The use of a cruciform shape and positive fit or wedge effect used for theconcave indentations40 and theprongs59 provides rotational and translational stability of thefixation member20 when attached to theguide assembly50. In addition, the positive fit or wedge effect operates to center and reduce micro-motion between the targetingguide80 and the rest of theguide assembly50. Use of the positive fit of thechannel arms73, the locking tip79, theslots84 and the centering divot86 is capable of achieving an accuracy in the range of one hundredths of an inch. Further, the improved positioning from the positive fit allows thesingle guide assembly50 to facilitate placement of all of the fasteners, eliminating the need to use multiple assemblies and select openings via X-rays or other visual or manual method.
• Use of k-wire fasteners41 and k-wiresized guide openings83 andopenings36 in thecurved body24 of thefixation member20 allow thefixation member20 and guideassembly50 to be temporarily fixed to thelong bone11 after reduction of the fracture. This allows the health care personnel to use both hands to insert the remainingfasteners21,41. The cannulated, screw-indrill guide52 with its internal guide shaft allows for insertion offasteners21,41 into both the first and second bone fragments16,17 without removal or reconfiguration of theguide assembly50. The progressively smaller diameters of thefastener head42, threadedshaft43,non-threaded shaft43 and threaded, bone-securingend44, and the smoothness of the non-threaded shaft, limit fretting of the threads on the bone-securing end. Thestop75 prevents mounting of a left oriented targetingguide80 to a left-handedoutrigger frame54 and vice-versa for a right handed outrigger frame. Thedual diameters70,71 of the drill guides53 ensure concentricity of the dual-diameter drill bit90.
• Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. For example, thefixation member20 may have defined on its outer surface grooves or texture (similar to the awl point99) that facilitates a tight fit in themedullary canal15 or can hold biologic or pharmacologic materials to facilitate bone ingrowth. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (18)

1. An intramedullary fixation assembly for repairing any of a plurality of human long bone types, each of the long bones defining a medullary canal fractured into at least a first and second adjacent bone fragments, the first bone fragment having a free end with an articular surface thereon and defining a side aperture, said side aperture positioned subjacent the articular surface and extending into the medullary canal, said intramedullary fixation assembly comprising:

at least a first and second fasteners, each of said fasteners having an elongate body with a head end and an opposite, bone-securing end; and

a fixation member having a first end, a second end and a body extending between the first and second ends,

said body defining a first fastener opening positioned proximate the first end and configured to allow passage of the first fastener therethrough and into the first bone fragment,

said body defining a second fastener opening positioned proximate the second end and configured to allow passage of the second fastener therethrough and into the second bone fragment, and

said body having a radius of curvature at least near the first end within a range of 1.5 to 5 inches to allow passage of the fixation member through the side aperture of the first bone fragment and into the medullary canal until the first end of the fixation member is positioned adjacent the side aperture and within a portion of the medullary canal defined within the first bone fragment, and the second end of the fixation member is positioned within a portion of the medullary canal defined within the second bone fragment, wherein the bone fragments are from any of the plurality of human long bone types.

2. An intramedullary fixation assembly ofclaim 1, wherein the body continuously curves from its first end to its second end.

3. An intramedullary fixation assembly ofclaim 1, wherein the radius of curvature is defined by a centerline extending from the first end to the second end.

4. An intramedullary fixation assembly ofclaim 3, wherein the body includes a smoothly curving concave and convex sides configured to facilitate passage of the fixation member through the side aperture and into the medullary canal.

5. An intramedullary fixation assembly ofclaim 4, wherein at least one of the first and second ends is tapered.

6. An intramedullary fixation assembly ofclaim 2, wherein the radius of curvature is with a range of about 2.6 to 3.4 inches.

7. An intramedullary fixation assembly ofclaim 1, wherein the fixation member includes a tilt.

8. An intramedullary fixation assembly ofclaim 1, wherein at least one of the fasteners is a bi-cortical fastener having a threaded shaft with a wider diameter than the bone-securing end and separated from the bone-securing end by a non-threaded shaft portion.

9. An intramedullary fixation assembly ofclaim 1, wherein the second end includes a tail portion having a relatively smaller diameter than the body.

10. An intramedullary fixation assembly ofclaim 9, wherein the tail portion includes a pair of spaced arms defining a split configured to receive a fastener, and wherein insertion of the fastener forces the spaced arms apart.

11. An intramedullary fixation assembly ofclaim 1, wherein at least one of the first and second ends has a taper and wherein the body has a continuous curvature extending between the ends.

12. An intramedullary fixation assembly ofclaim 1, wherein the first end of the body includes additional fastener openings extending at divergent angles with respect to the first fastener openings.

13. An intramedullary fixation assembly ofclaim 12, wherein the fastener openings at the first end of the body extend at an inclination angle matched to the articular surface.

14. An intramedullary fixation assembly ofclaim 13, wherein the first end of the fixation member defines a surface configured to extend under and support the articular cartilage.

15. An intramedullary fixation assembly ofclaim 14, wherein the body defines an exposed end surface accessible through the side aperture and having the first fastener opening extending therethrough.

16. An intramedullary fixation assembly ofclaim 15, wherein the surface extending under the articular cartilage is at about a right angle to the exposed end surface.

17. An intramedullary fixation assembly ofclaim 16, wherein the fixation member is configured to extend from a metaphysis of the long bone to the diaphysis of the longbone without extending into the epiphysis of the longbone, thereby avoiding damage to the articular cartilage.

18. A bi-cortical bone fastener for use with a fixation member defining a fixation member opening having a diameter, said bone fastener comprising:

a first bone-securing shaft portion having threads configured for fixation into a first layer of bone, said first bone-securing shaft portion having a maximum diameter smaller than the fixation member opening diameter;

a mid-shaft portion adjacent the bone-securing shaft portion and configured to extend into the fixation member opening, said mid-shaft portion having a maximum diameter greater than the maximum diameter of the bone-securing shaft portion; and

a second bone-securing shaft portion adjacent the mid-shaft portion and opposite the first bone-securing shaft portion, said second bone-securing shaft portion having threads configured for fixation into a second layer of bone, said second bone-securing shaft portion having a maximum diameter greater than the diameter of the mid-shaft portion.

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