Targeting apparatus for bone fixation device

Apparatus is provided for use with a bone fixation device. The apparatus includes a targeting device, adapted to aid in fixation of the bone fixation device to a bone of a subject. The targeting device includes a coupling element, adapted to couple the targeting device to the bone fixation device. The targeting device additionally includes a coupling assembly, adapted to hold the coupling element and to inhibit the coupling element from exiting the coupling assembly even when the coupling element is not coupled to the bone fixation device.

FIELD OF THE INVENTION

The present invention relates generally to implantable devices for treating bone fractures, and specifically to a targeting device for implanting a bone fixation device.

BACKGROUND OF THE INVENTION

Intramedullary (IM) nails are implantable devices used to stabilize fractures and allow for bone healing. IM nails are inserted into the medullary canal of the long bones of the extremities, e.g., the femur, tibia, or humerus. Currently-used IM nails have a head region that generally includes at least one hole, transverse to the longitudinal axis of the nail, for receiving anchoring means, such as a screw, to secure the nail within the medullary canal of the bone.

Reference is made toFIG. 1, which is a schematic illustration of a targeting device10, as known in the prior art. Targeting device10is used to align one or more IM anchoring screws (not shown) with transverse holes12of an IM nail14, by inserting the IM anchoring screws and/or a drill bit through corresponding aligned transverse holes16in targeting device10. IM nail14is inserted into a medullary canal, and targeting device10is attached to a proximal end18of the IM nail, typically by a screw20. Screw20is inserted into a screw hole22at the time of attachment of targeting device10to IM nail14, such that a proximal end24of the screw is readily accessible from outside the screw hole. A conventional screwdriver26is typically used to tighten screw20into IM nail14.

It is typical to take radiographic images, such as X-ray or fluoroscopic images, during the IM nail implantation procedure, in order to check the alignment of the IM anchoring screws before drilling through the bone. At least a portion of targeting device10typically comprises a radiolucent material, such as carbon, in order to minimize the interference of the targeting device with the radiographic images. Screw20, however, typically comprises a radiopaque metal. Although metal interferes with the radiographic imaging, its use is considered necessary to provide strong coupling between targeting device10and IM nail14.

U.S. Pat. No. 6,183,477 to Pepper, which is incorporated herein by reference, describes an attachment tool for attaching a drill guide to a medical implant such as an intramedullary nail. The attachment tool includes a first end and a housing. The first end includes a first opening that allows a fastener to pass through and thread into the implant, thereby attaching the tool. The housing includes a second opening whose longitudinal axis is preferably offset from the longitudinal axis of the first opening. The housing also includes a guide surface with a groove for directing a driving tool to the second opening. The driving tool is inserted through the second opening to drive the fastener. The driving tool can be inserted and removed during the procedure. The housing also includes a plurality of holes that can be used as drill guide holes or to attach separate drill guides or other orthopedic devices.

U.S. Pat. No. 5,334,192 to Behrens, which is incorporated herein by reference, describes a targeting device for attachment to an implant for treating fractures, such as an intramedullary nail. The targeting device has a targeting arm that extends substantially parallel to the nail, and has a plurality of targeting bores for receiving a drill sleeve, such targeting bores extending at different angles with respect to the axis of the targeting arm.

European Patent EP 0 257 118 B1 to Grosse et al., which is incorporated herein by reference, describes an intramedullary femur nail, and a femur neck screw retained and guided in a transverse throughbore of the femur nail.

U.S. Pat. No. 5,176,681 to Lawes et al., which is incorporated herein by reference, describes an intramedullary intertrochanteric fracture fixation appliance comprising an intramedullary rod having an angulated opening to receive a femoral neck screw. The rod has a co-axial bore extending into the angulated opening, and anti-rotation means located in the bore to selectively prevent rotation of the neck screw in the rod. The open end of the bore is provided with means to positively locate a removable fitting device on the proximal end of the rod, and so that the anti-rotation means can be operated with the fitting device in position.

U.S. Pat. No. 6,656,189 to Wilson et al., which is incorporated herein by reference, describes a radiolucent aiming guide for locating and drilling through the holes in the distal end of an implanted intramedullary nail. The aiming guide comprises an elongate handle constructed substantially of a radiolucent material, which does not cast a strong image on a monitor when exposed to radiation. The radiolucent handle is used in conjunction with a protection sleeve, trocar, drill sleeve, and drill bit, which are used to locate and drill through the hole in the nail. Radiopaque components in the distal end of the protection sleeve, trocar, and drill bit are used to align the drill over the nail hole. A pair of radiopaque pins, located within the handle and lying parallel to its longitudinal axis, aid in ensuring the proper rotational alignment of the aiming guide over the nail hole. The aiming guide may also include a structure to facilitate its alignment over a second hole in the distal end of the intramedullary nail.

U.S. Pat. No. 5,728,128 to Crickenberger et al., which is incorporated herein by reference, describes a femoral neck anteversion guide for use with a femur having a prepared intramedullary canal. The guide includes a radiolucent stem having a distal end for inserting into the prepared intramedullary canal, and a radiopaque angle locator wire embedded within the stem at a known angle for allowing the femoral neck angle and femoral neck anteversion to be determined. The femoral neck anteversion guide preferably includes a handle, which is attached to the radiolucent stem by a radiolucent screw.

U.S. Pat. No. 5,403,321 to DiMarco, which is incorporated herein by reference, describes a radiolucent drill guide for connection to the proximal end portion of an intramedullary nail for aligning a drill with bores of an intramedullary nail when the nail is surgically positioned within an intramedullary canal of a patient. The drill guide includes a handle member of radiolucent material and a guide barrel embedded within the handle. The handle includes an inner generally cylindrical bore and an outer surface that is bonded to closely surround the radiolucent material of the handle member so that the barrel does not rotate freely relative to the handle. The guide barrel includes flanges for preventing relative movement of the barrel in the direction of the central longitudinal axis of the bore of the barrel. A plurality of openings in the handle are at positions spaced away from the barrel for guiding drills when the barrel is affixed to the intramedullary nail so that the drills align with selected openings of the intramedullary nail.

U.S. Pat. No. 5,178,621 to Cook et al., which is incorporated herein by reference, describes a targeting device that includes a radio-transparent handle and a metal snap fit barrel. The radio-transparent handle reduces obstructions in the radiographic image to provide a clearer image to the surgeon for proper placement of the locking screws. The metal snap fit barrel is retained in the handle by an interference fit between the handle and biased keys carried by the barrel.

U.S. Pat. No. 4,827,917 to Brumfield, which is incorporated herein by reference, describes an IM system including a screw and an intramedullary rod. The screw has a threaded portion and a smooth portion, and the rod has a head, stem and a longitudinal bore. There is at least one pair of coaxial holes through the stem, transverse to the longitudinal axis of the rod, for receiving first anchoring means, such as a nail, screw or bolt, to secure the rod within the marrow canal of the femur. There are at least a proximal pair of coaxial holes and a distal pair of coaxial holes in the head of the rod in an angled direction toward the femoral head relative to the longitudinal axis of the rod. The distal pair of head holes are adapted to slidingly receive the screw so as to permit the threaded portion of the screw, in use, to engage the femoral head and to allow sliding compression of a femoral neck or intertrochanteric fracture.

U.S. Pat. No. 5,032,125 to Durham et al., which is incorporated herein by reference, describes an IM hip screw that includes an IM rod, a lag screw and a sleeve for slidably receiving the lag screw. The sleeve is received in a passage in the IM rod having an axis positioned at an angle relative to the longitudinal axis of the IM rod such that the axis of the sleeve is directed toward the head of the femur. The IM hip screw is described as permitting sliding compression of selected fractures, particularly intertrochanteric fractures and fractures of the femoral neck.

U.S. Pat. No. 6,443,954 to Bramlet et al., which is incorporated herein by reference, describes an IM system that includes a lag screw assembly extending through a radial bore in an IM nail.

U.S. Pat. No. 6,235,031 to Hodgeman et al., which is incorporated herein by reference, describes an IM system that includes an IM rod, a lag screw, and a lag screw collar.

U.S. Patent Application Publication 2002/0151898 to Sohngen et al., which is incorporated herein by reference, describes an IM nail having a modular configuration, including a nail member having a chamber formed on the proximal end thereof.

U.S. Patent Application Publication 2002/0156473 to Bramlet et al., which is incorporated herein by reference, describes an IM system that includes an IM nail for insertion in the femur. The nail has an axial bore and an intersecting transverse bore. A lag screw is inserted through the transverse bore and turned into the head of the femur. A slotted sleeve is inserted over the lag screw and through the transverse bore with the slots aligned with the axial bore. A sleeve lock is inserted into the axial bore, and has a locking tab which engages the slots in the sleeve preventing rotational and longitudinal movement between the sleeve and the nail. A compression screw is turned into the trailing end of the lag screw and engages the encircling sleeve to provide longitudinal translation between the lag screw and sleeve to apply compressive force across a fracture.

European Patent Application Publication EP 0 521 600 to Lawes, which is incorporated herein by reference, describes an IM system that includes an IM rod having an angulated opening to receive a femoral neck screw having a threaded portion at its distal end, and locking means acting between the neck screw and the wall of the angulated opening to prevent relative rotation between the screw and the rod.

PCT Publication WO 02/083015 to Ferrante et al., which is incorporated herein by reference, describes an orthopedic screw having a screw head, a screw body with a distal tip, a shank with an enlarged diameter at the trailing end and a thread extending radially outward from the shank, and an internal capture surface. The screw is used with an orthopedic implant system, which includes an orthopedic implant and a driver capable of engaging the internal capture of the screw.

SUMMARY OF THE INVENTION

In some embodiments of the present invention, a targeting device, for aiding in the fixation of a bone fixation device to a bone, comprises a coupling assembly for coupling the targeting device to the bone fixation device. The coupling assembly is typically shaped so as to define a retaining arrangement, such as a chamber, pin, or screw assembly, adapted to hold a coupling element, such as a screw, and to prevent the coupling element from exiting the coupling assembly even when the coupling element is not coupled to the bone fixation device. This arrangement enables the coupling element to be shorter than conventional screws used for similar purposes in conventional targeting devices.

Typically, a large portion of the targeting device comprises a radiolucent material, such as carbon, and the coupling element comprises a strong, radiopaque substance, such as a metal, in order to strongly couple the targeting device to the bone fixation device. Because the coupling element is shorter than conventional screws used for similar purposes in conventional targeting devices, the coupling element creates substantially less interference with radiographic images than do such conventional screws.

There is therefore provided, in accordance with an embodiment of the present invention, apparatus for use with a bone fixation device, the apparatus including a targeting device, adapted to aid in fixation of the bone fixation device to a bone of a subject, the targeting device including:

a coupling element, adapted to couple the targeting device to the bone fixation device; and

a coupling assembly, adapted to hold the coupling element, and to inhibit the coupling element from exiting the coupling assembly even when the coupling element is not coupled to the bone fixation device.

In an embodiment, the targeting device includes at least one radiolucent material.

In an embodiment, the bone fixation device includes an intramedullary (IM) nail, and the targeting device is adapted to aid in fixation of the IM nail to the bone.

In an embodiment, the bone fixation device includes a plate, and the targeting device is adapted to aid in fixation of the plate to the bone.

In an embodiment, the bone fixation device includes at least one anchoring screw, and the targeting device is shaped so as to define at least one transverse hole therethrough, for aiding in aligning the anchoring screw with the bone fixation device.

In an embodiment, the coupling element includes a screw.

In an embodiment, the coupling element includes a snap-like coupling element.

In an embodiment, the coupling element includes metal.

In an embodiment, the coupling assembly includes at least one radiopaque material.

In an embodiment, the targeting device includes a support element shaped so as to define a support region, which region is adapted to engage the coupling element when the coupling element is coupled to the bone fixation device.

In an embodiment:

the targeting device is shaped to define a longitudinal axis thereof in a portion of the targeting device that couples with the bone fixation device,

the bone fixation device is shaped to define a longitudinal axis thereof, and

the longitudinal axis of the portion of the targeting device diverges by an angle greater than 2 degrees from the longitudinal axis of the bone fixation device when the coupling element is coupling the targeting device to the bone fixation device.

In an embodiment, the coupling assembly is shaped so as to define a chamber that is adapted to hold the coupling element.

In an embodiment, the chamber is shaped so as to define one or more holes extending between inside the chamber and outside of the targeting device.

In an embodiment, the coupling assembly is shaped so as to define a blocking element that is adapted to inhibit the coupling element from exiting the coupling assembly.

In an embodiment, the coupling element is shaped so as to define a coupling surface at a distal end thereof, and such that a portion of the coupling element that includes the coupling surface is proximal to the blocking element.

In an embodiment, the blocking element is generally cylindrical in shape, and defines a bore through which access is provided to a proximal end of the coupling element.

In an embodiment, the blocking element is shaped so as to define a protrusion from an inner surface of the coupling assembly.

In an embodiment, the coupling element has a proximal end and a distal end, and a distance between the proximal end and the distal end is less than about 15 mm. In an embodiment, the distance is less than about 11 mm. In an embodiment, the distance is less than about 9 mm.

In an embodiment:

the coupling element has a proximal coupling element end,

the targeting device is shaped so as to define an elongated bore having a distal bore end and, at a proximal bore end thereof, a proximal opening,

the coupling assembly is positioned in a vicinity of the distal bore end, and

a distance from the proximal coupling element end to the proximal bore end is greater than about 25 mm, when the coupling element couples the targeting device to the bone fixation device.

In an embodiment, the distance is greater than about 30 mm. In an embodiment, the distance is greater than about 35 mm. In an embodiment, the distance is greater than about 45 mm.

There is further provided, in accordance with an embodiment of the present invention, apparatus for use with a bone fixation device, the apparatus including a targeting device, adapted to aid in fixation of the bone fixation device to a bone of a subject, the targeting device shaped so as to define an elongated bore having a proximal opening at a proximal bore end thereof, and including:

a coupling element having distal and proximal coupling element ends, the coupling element adapted to be insertable into the bore via the proximal opening, and to couple the targeting device to the bone fixation device,

the coupling element and bore shaped such that a coupling element length between the distal coupling element end and the proximal coupling element end is less than about 30 mm, and a bore distance between the proximal coupling element end and the proximal bore end is greater than about 25 mm when the coupling element couples the targeting device to the bone fixation device.

There is still further provided, in accordance with an embodiment of the present invention, a method for coupling a bone fixation device to a targeting device, the targeting device adapted to aid in fixation of the bone fixation device to a bone of a subject, including:

coupling the targeting device to the bone fixation device by means of a coupling assembly that includes a coupling element, the coupling assembly being adapted to hold the coupling element, and to inhibit the coupling element from exiting the coupling assembly even when the coupling element is not coupled to the bone fixation device.

There is yet further provided, in accordance with an embodiment of the present invention, a method for coupling a bone fixation device to a targeting device, the targeting device adapted to aid in fixation of the bone fixation device to a bone of a subject, and the targeting device shaped so as to define an elongated bore having a proximal opening at a proximal bore end thereof, the method including:

inserting, into the bore via the proximal opening, a coupling element having distal and proximal coupling element ends; and

coupling the targeting device to the bone fixation device, using the coupling element,

the coupling element and bore shaped such that a coupling element length between the distal coupling element end and the proximal coupling element end is less than about 30 mm, and a bore distance between the proximal coupling element end and the proximal bore end is greater than about 25 mm when the coupling element couples the targeting device to the bone fixation device.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 2is a schematic illustration of a targeting device40, in accordance with an embodiment of the present invention. Targeting device40typically comprises a coupling portion42and an elongated alignment portion44. For some applications, coupling portion42and alignment portion44are separate components that are coupled together, either during manufacture or during use, while for other applications, targeting device40is formed as an integrated unit that is shaped so as to define coupling portion42and alignment portion44. Typically, a large portion of targeting device40, e.g., at least about 95%, 90%, or 75% by volume, comprises at least one radiolucent material, such as carbon, carbon fiber composite, or thermoplastic (e.g., Delrin®). For example, substantially all (i.e., at least about 95% by volume) of alignment portion44may comprise at least one radiolucent material, and a large portion (i.e., at least about 95%, 90%, or 75% by volume) of alignment portion44may comprise at least one radiolucent material.

Targeting device40is adapted to aid in the fixation of a bone fixation device48to a bone of a subject. Typically, targeting device40is used to align one or more anchoring screws (not shown) with transverse holes46of bone fixation device48after the device has been applied to a fractured bone. For some applications, bone fixation device48comprises an intramedullary (IM) nail, which is inserted into a medullary canal of a bone, such as a femur. Alternatively, bone fixation device48comprises a plate or other bone fixation device known in the art. Coupling portion42of targeting device40is attached to a proximal end50of bone fixation device48, and the anchoring screws and/or a drill bit are guided through holes52in alignment portion44, which holes are aligned with corresponding transverse holes46of bone fixation device48.

A distal portion60of coupling portion42of targeting device40comprises a coupling assembly62for coupling portion42to proximal end50of bone fixation device48. Coupling assembly62is typically shaped so as to define a chamber64adapted to hold a coupling element66, such as a screw67, as shown inFIG. 2. Chamber64includes sufficient space to hold coupling element66even when the coupling element is not coupled to proximal end50of bone fixation device48. Typically, coupling assembly62is configured to prevent coupling element66from exiting the coupling assembly even when the coupling element is not coupled to proximal end50. For example, a distal end68of a blocking element70may block coupling element66from exiting chamber64. For example, blocking element70may be generally cylindrically shaped, and may surround and define a bore72, as shown inFIG. 2.

A distal end of coupling element66is shaped so as to define a coupling surface74for securing coupling element66to a surface in proximal end50of bone fixation device48. For example, when coupling element66comprises screw67, coupling surface74may be shaped so as to define a screw thread. A proximal end of coupling element66is shaped so as to define an engagement surface76, such as an indentation, for receiving a distal end78of an activator tool80. For example, engagement surface76and distal end78may be hexagonal, square, slotted, or any other shape appropriate for engagement. Activator tool80comprises an elongated shaft82that is shaped and sized so as to be insertable into bore72of coupling portion42of targeting device40.

Reference is now made toFIGS. 3A and 3B, which are schematic illustrations of additional configurations of coupling assembly62, in accordance with embodiments of the present invention. In these embodiments, blocking element70comprises a blocking element170. As shown in bothFIGS. 3A and 3B, blocking element170is shaped as a small protrusion on an inner aspect of coupling assembly62. For some applications, as shown inFIG. 3B, coupling element66is configured such that a portion thereof that includes engagement surface76is proximal to blocking element170.

Reference is now made toFIG. 4, which is a schematic illustration of a detent comprising a snap-like coupling element200, in accordance with an embodiment of the present invention. In this embodiment, coupling element66comprises snap-like coupling element200. Coupling surface74of coupling element200comprises one or more movable engagement elements210, such as spring-loaded ball bearings. An inner surface of proximal end50of bone fixation device48is shaped so as to define one or more indentations212, corresponding to engagement elements210. Indentations212are adapted to receive engagement elements210, in order to couple coupling element200to proximal end50. Activator tool80is used to apply pressure to and rotate snap-like coupling element200in order to engage engagement elements210with indentations212, and to disengage the engagement elements from the indentations.

Reference is again made toFIG. 2. Coupling element66typically comprises a substance having a high strength, such as a metal, in order to strongly couple coupling portion42of targeting device40to proximal end50of bone fixation device48. The substance is typically radiopaque. A length L1from a distal end84to a proximal end86of coupling element66is typically less than about 15 mm, such as less than about 11 mm or less than about 9 mm. Typically, a distance D1from proximal end86of coupling element66to a proximal end88of bore72is greater than about 25 mm, such as greater than about 30 mm, greater than about 35 mm, or greater than about 45 mm, e.g., about 75.3 mm.

Coupling assembly62typically further comprises a generally radially symmetrical support element90, which is shaped so as to define a connection support region92and a generally cylindrically-shaped attachment region94. Support region92engages coupling element66when the coupling element is tightened. Attachment region94attaches support element90to coupling portion42of targeting device40. Coupling assembly62typically comprises a substance having a high strength, such as a metal.

In an embodiment of the present invention, chamber64is shaped so as to define one or more holes96extending between (a) inside the chamber, and (b) outside of coupling portion42of targeting device40. For some applications, attachment region94is also shaped so as to define holes96. Holes96are typically useful for facilitating cleaning of chamber64between uses, such as by flushing chamber64with a cleaning solution via holes96.

In an embodiment, a longitudinal axis of coupling portion42of targeting device40diverges by an angle alpha from a longitudinal axis of bone fixation device48. For some applications, alpha is between about 2 and about 6 degrees (e.g., 4 degrees), or greater than 6 degrees, e.g., 10 degrees.

Reference is now made toFIG. 5, which is a schematic illustration of a targeting device100, in accordance with an embodiment of the present invention. Targeting device100is generally similar to targeting devices known in the art, such as targeting device10, described hereinabove with reference toFIG. 1. However, unlike in the prior art devices, a coupling element102, such as a screw, for attaching targeting device100to a bone fixation device104, such as an IM nail, has a length L2from a distal end106to a proximal end108of screw102that is less than about 30 mm, such as less than about 15 mm, less than about 11 mm, or less than about 9 mm. A screwdriver110having an elongated shaft112is provided for tightening and loosening screw102. For some applications, screw102and a distal tip114of screwdriver110are magnetized, to aid in insertion and removal of screw102through an elongated bore116of targeting device100. Alternatively or additionally, distal tip114comprises gripping elements to aid in insertion of screw102. Typically, a distance D2from proximal end108of screw102to a proximal end118of bore116is greater than about 25 mm, such as greater than about 30 mm, greater than about 35 mm, or greater than about 45 mm, when screw102couples targeting device100to bone fixation device104.

As appropriate, techniques described herein are practiced in conjunction with methods and apparatus described in U.S. patent application Ser. No. 10/616,218, filed Jul. 8, 2003, entitled, “Intramedullary nail system and method for fixation of a fractured bone,” which is incorporated herein by reference.

As appropriate, dimensions of various components described hereinabove are varied in accordance with the dimensions of a bone which is being treated. For example, smaller bones (e.g., phalanges) may be treated with smaller components.

It will be appreciated that although some embodiments of the present invention have been shown and described herein for use in a femur, these embodiments may be adapted for use in other bones of the extremities, such as the tibia and humerus,mutatis mutandis. It will also be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.