Intramedullary fixation device for metaphyseal long bone fractures

A fracture fixation system includes a device with a plate portion intended to be positioned against an exterior surface of bone and an intramedullary portion. The plate portion includes a plurality of fixed angle holes defining a respective number of axes which are divergent. Fasteners coupled within the fixed angle holes extend to follow the contour of subchondral bone and provide a framework for support for fracture healing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates broadly to surgical devices. More particularly, this invention relates to a bone fixation system including a plate element and an arrangement of pegs fixed relative to the plate element.

2. State of the Art

Referring toFIG. 1, a Colles' fracture is a fracture resulting from compressive forces being placed on the distal radius10, and which causes backward displacement of the distal fragment12and radial deviation of the hand at the wrist14. Often, a Colles' fracture will result in multiple bone fragments16,18,20which are movable and out of alignment relative to each other. If not properly treated, such fractures result in permanent wrist deformity. It is therefore important to align the fracture and fixate the bones relative to each other so that proper healing may occur.

Alignment and fixation are typically performed by one of several methods: casting, external fixation, interosseous wiring, and plating. Casting is non-invasive, but may not be able to maintain alignment of the fracture where many bone fragments exist. Therefore, as an alternative, external fixators may be used. External fixators utilize a method known as ligamentotaxis, which provides distraction forces across the joint and permits the fracture to be aligned based upon the tension placed on the surrounding ligaments. However, while external fixators can maintain the position of the wrist bones, it may nevertheless be difficult in certain fractures to first provide the bones in proper alignment. In addition, external fixators are often not suitable for fractures resulting in multiple bone fragments. Interosseous wiring is an invasive procedure whereby screws are positioned into the various fragments and the screws are then wired together as bracing. This is a difficult and time consuming procedure. Moreover, unless the bracing is quite complex, the fracture may not be properly stabilized. Plating utilizes a stabilizing metal plate typically against the dorsal side of the bones, and a set of parallel pins extending from the plate into holes drilled in the bone fragments to provide stabilized fixation of the fragments. However, the currently available plate systems fail to provide desirable alignment and stabilization. Likewise, other fractures at the ends of other long bones suffer from similar problems.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide an improved fixation and alignment system for fractures at the end of long bones and which can specifically be used to treat fractures at the end of long bones.

It is another object of the invention to provide a fixation system which desirably aligns and stabilizes multiple bone fragments in a fracture to permit proper healing.

In accord with these objects, which will be discussed in detail below, a fixation system is provided which generally includes a plate intended to be positioned against the bone, a plurality of bone screws for securing the plate along a non-fractured portion of the bone, and a plurality of pegs (fasteners having threaded heads and threaded or non-threaded shafts) which extend from the plate and into bone fragments of the fracture.

According to one embodiment, the plate is generally a T-shaped plate defining an elongate shaft portion, a head portion angled relative to the shaft portion, a first side which is intended to contact the bone, and a second side opposite the first side. The shaft portion includes a plurality of countersunk screw holes for the extension of the bone screws therethrough. The head portion includes a plurality of threaded peg holes for receiving the pegs therethrough. According to a first embodiment, the peg holes are preferably arranged along a curve. According to a second embodiment, the peg holes are preferably linearly arranged. In either embodiment, the peg holes are preferably positioned increasingly distal in a medial to lateral direction along the second side. According to a preferred aspect of the invention, axes through the peg holes are oblique relative to each other, and are preferably angled relative to each other in two dimensions.

In use for stabilization of Colles' fracture, the plate is positioned with its first side against the volar side of the radius and bone screws are inserted through the bone screw holes into the radius to secure the plate to the radius. The bone fragments are aligned and a drill is used to drill holes into the bone fragments in alignment with the axes of the peg holes. The pegs are then inserted through the peg holes and into the holes in the bone, and the heads of the pegs are threadably engaged in the head portion of the plate. The pegs define a support framework which is preferably divergent both medial and laterally such that the pegs are arranged to follow the contour of subchondral bone of the bone being stabilized. The fixation system thereby secures the bone fragments in their proper orientation.

According to another embodiment, a fixation system includes a device having a proximal shaft portion defining an intramedullary nail and relatively flat plate head portion, preferably horizontally and vertically offset relative to the shaft portion by a neck portion. The shaft portion includes screw holes, and the plate portion has a low, narrow profile and includes longitudinally displaced peg holes, each of which is adapted to orient a peg in a different orientation from the others.

In use, a relatively small incision is made in the skin, and the shaft portion is introduced through the incision and through the fracture location into the medullary canal of the bone, and the plate portion of the device is maneuvered against a surface of the bone at the metaphysis. The shaft portion is fixed relative to the bone with one or more screws, while pegs are inserted through holes drilled in alignment with the peg holes and define a framework for stabilization and support of subchondral bone fragments. Moreover, as the pegs preferably enter the subchondral fragments from a plurality of directions, additional fixation of the device into the bone is provided.

The fixation system can be adapted to treatment of fractures at multiple sites. For example, the distal radius, the proximal humerus, the distal femur, the proximal tibia, the distal tibia, and the hip are all suitable for application of the system of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now toFIGS. 2 through 4, a first embodiment of a fixation system100for aligning and stabilizing multiple bone fragments in a Colles' fracture generally includes a substantially rigid T-shaped plate102intended to be positioned against the volar side of the radial bone, a plurality of preferably self-tapping bone screws104for securing the plate102along a non-fractured portion of the radial bone, and a plurality of bone pegs108,108awhich extend from the plate102and into bone fragments of a Colles' fracture.

Referring toFIGS. 2,5and6, more particularly, the T-shaped plate102defines a relatively flat head portion116angled upwards relative to an elongate relatively flat shaft portion118, a first side120which is intended to contact the bone, and a second side122opposite the first side. As the head portion and shaft portion are angled relative to each other, the first side preferably generally defines two planar portions. The angle φ between the head portion116and the shaft portion118is preferably approximately 18° and bent at a radius of approximately 1.00 inch (FIG. 5). The distal edge121of the head portion116is preferably angled proximally toward the medial side at an angle a, e.g., 5°, relative to a line P, which is perpendicular to the shaft portion. In one embodiment, the head portion116preferably has a width of 0.913 inch and a greatest proximal-distal dimension (i.e., from the corner of angle α to the shaft portion) of approximately 0.69 inch, and the shaft portion preferably has a width of 0.375 inch and a length of 1.40 inches, though alternative dimensions may be provided for plates adapted for various individuals, or for plates adapted for use on bones other than the radius. The plate102preferably has a thickness of at least approximately 0.098 inch. The plate102is preferably made from a titanium alloy, such as Ti-6A-4V.

The shaft portion118includes three preferably countersunk screw holes124,126,128for the extension of the bone screws104therethrough. One of the screw holes,128, is preferably generally elliptical (or oval).

The head portion116includes four threaded peg holes130,132,134,136for individually receiving the pegs108,108atherethrough. According to a first preferred aspect of the first embodiment of the invention, the peg holes130,132,134,136, each preferably 0.100 inch in diameter, are preferably substantially linearly arranged along the head portion116, and are provided such that the adjacent peg holes are provided further distally in a medial to lateral direction along the second side. Alternatively, the peg holes may be arranged along a smooth curve such as a shallow parabolic curve.

The peg holes define axes A1, A2, A3, A4which are oblique (not parallel) relative to each other, and more preferably are angled in two dimensions (medial/lateral and proximal/distal) relative to each other; i.e., the pegs once inserted into the peg holes are also angled in two dimensions relative to each other. More particularly, the first axis A1of the first peg hole130(that is, the most proximal and medial peg hole) is preferably directed normal to the first side120of the head portion116. The axis A2of the adjacent peg hole132, i.e., the second axis, is preferably angled approximately 1-7° distal and lateral relative to the first axis A1, and more preferably approximately 2.5° distal and lateral relative to the first axis A1. The axis A3of the peg hole134laterally adjacent the second peg hole132, i.e., the third axis, is preferably angled approximately 7-13° distal and lateral relative to the first axis A1, and more preferably approximately 10° distal and lateral relative to the first axis A1. The axis A4of the peg hole134laterally adjacent the third peg hole132, i.e., the fourth axis, is preferably angled approximately 10-30° distal and lateral relative to the first axis A1, and more preferably approximately 20° distal and lateral relative to the first axis A1. The second side of the head portion116, distal of the peg holes130,132,134,136is preferably beveled.

Referring back toFIGS. 3 and 3a, the pegs108,108a, preferably approximately 0.872 inch in length, each have a threaded head138adapted to threadably engage the threads about the threaded peg holes130,132,134,136. Such dimensions permit the pegs to adequately support the bone fragments such that the bone is able to heal correctly. The pegs may have a relatively smooth shaft140(FIG. 3) or a threaded shaft (FIG. 3a). If threaded, the shafts140aare preferably threaded at a pitch different from the threads on the head138of the pegs108a. The pegs108are also preferably made from titanium alloy, and may be coated in a ceramic, e.g., titanium nitride, to provide a bone interface which will not adversely affect bone healing.

Turning now toFIGS. 7 and 8, the system100may also include a guide plate146which temporarily sits on the second side122of the volar plate102and includes guide holes148,150,152,154(illustrated in overlapping section inFIG. 8) oriented according to the axes A1, A2, A3, A4of the peg holes for guiding a drill into the bone fragments at the required orientation. That is, the guide holes together with the peg holes define a drill guide path along the axes with sufficient depth to accurately guide a drill (not shown) to drill holes at the desired pin orientations. The volar plate102and guide plate146are also preferably provided with mating elements, such as a plurality of holes156,158on the second side of the volar plate (FIG. 2), and a plurality of protuberances160on the mating side of the guide plate (FIG. 7), to temporarily stabilize the guide plate on the volar plate during the hole drilling process. Alternatively, a threaded drill guide or other guide means may be used to guide a drill to drill holes in appropriate orientations relative to the peg hole axes, as is known in the art.

Referring toFIGS. 2 through 9, in use, the volar plate102is positioned with its first side120against the volar side of the radius. Bone screws104(either self-tapping or inserted with the aid of pre-drilled pilot holes) are inserted through the bone screw holes124,126,128into the radius bone10to secure the volar plate102to the radius. The bone fragments16,18,20are then aligned with the radius10. Next, the guide plate146is positioned on the second side of the volar plate. A drill, guided by a guide path formed by the peg holes and the guide holes, drills holes into and between the bone fragments16,18,20(and possibly also a portion of the integral radius, depending upon the particular location and extent of the fracture), and the guide plate is then removed. The pegs108,108a(any combination thereof including solely non-threaded shaft pegs108and solely threaded shaft pegs108a) are then inserted through the peg holes130,132,134,136and into the holes drilled into the fragments, and the heads of the pegs are threadably engaged in the volar plate. The pegs108,108a, extending through the oblique-axis peg holes130,132,134,136, are positioned immediately below the subchondral bone of the radius and support the bone fragments for proper healing. The volar fixation system thereby secures the bone fragments in their proper orientation.

Referring toFIGS. 10-12, a second embodiment of a volar plate210, substantially similar to the first embodiment (with like parts having numbers incremented by100) and used in substantially the same manner as the first embodiment is shown. The plate210preferably has a length of approximately 2.35 inches, which is approximately 0.35 inch greater than in the first embodiment. This additional length accommodates an extra bone screw hole229in the shaft portion of the volar plate such that the volar plate preferably includes four bone screw holes224,226,228,229. The additional bone screw in screw hole229increases plate stability over the three holes of the first embodiment. The plate210preferably tapers in thickness from the shaft portion218to the head portion216. A preferred taper provides a proximal shaft portion218thickness of approximately 0.098 inch and head portion216thickness of approximately 0.078 inch. The taper decreases the thickness of the head portion216relative to the shaft portion such that the weight of the volar plate is reduced and an improved tendon clearance is provided. The distal edge of the head portion216has an increased taper (preferably approximately 60° relative to a line normal to the head) to a distal edge221. The edge221is broken (i.e., made blunt) to prevent irritation or disturbance to the surrounding anatomy.

The head portion216includes four threaded peg holes230,232,234,236for individually receiving pegs208therethrough (FIGS. 13 and 14), and a guide hole256for alignment of a guide plate. According to a preferred aspect of the second embodiment of the invention, the peg holes230,232,234,236, preferably 0.100 inch in diameter, are preferably linearly arranged along the head portion216, and are provided such that the adjacent peg holes are provided further distally in a medial to lateral direction along the first and second sides. Referring toFIG. 15, more particularly, according to a preferred dimensions of the second embodiment of the invention, the center of peg hole230is located approximately 0.321 inch proximal line P and approximately 0.750 inch medial of the lateral edge237of the head portion, the center of peg hole232is located approximately 0.306 inch proximal line P and 0.557 inch medial of the lateral edge237, the center of peg hole234is located approximately 0.289 inch proximal line P and approximately 0.364 inch medial of the lateral edge237, and the center of peg hole236is located approximately 0.272 inch proximal line P and approximately 0.171 inch medial of the lateral edge237. As such, the distance from each of the peg holes to the distal edge221of the volar plate is relatively greater than in the first embodiment, and provides a preferred alignment with respect to the tapered distal edge221.

Referring toFIGS. 15-24, in addition, as in the first embodiment, the peg holes define axes A1, A2, A3, A4which are oblique relative to each other, and more preferably are angled in two dimensions (medial/lateral and proximal/distal) relative to each other; i.e., the pegs208once inserted into the peg holes are also angled in two dimensions relative to each other. More particularly, as in the first embodiment, the first axis A1of the first peg hole230is preferably directed normal (FIGS. 16 and 21) to the first side220of the head portion216. The axis A2of peg hole232is preferably angled approximately 1-7° distal (FIG. 17) and approximately 1-7° lateral (FIG. 22) relative to the axis A1, and more preferably approximately 2.5° both distal and lateral relative to axis A1. The axis A3of peg hole234is preferably angled approximately 7-13° distal (FIG. 18) and approximately 7-13° lateral (FIG. 23) relative to axis A1, and more preferably approximately 10° both distal and lateral relative to axis A1. Axis A4of the peg hole234is preferably angled approximately 10-30° distal (FIG. 19) and approximately 10-30° lateral (FIG. 24) relative to axis A1, and more preferably approximately 20° both distal and lateral relative to axis A1.

Referring to FIGS.13and16-19, each of the peg holes has a countersunk portion270,272,274,276, respectively, for receiving the head238of peg208. Countersunk portions270,272are each preferably approximately 0.030 inch deep and threaded according to the head of the pegs, as described below. Countersunk portion274is preferably approximately 0.042 inch deep and likewise threaded. Countersunk portion276is preferably approximately 0.056 inch deep and also threaded. The respective depths of the countersunk portions are adapted to better accommodate the heads238of the pegs208relative to the respective axes of the peg holes.

Referring toFIGS. 13 and 14, the pegs208, preferably approximately 0.872 inch in length, each have a threaded head238adapted to threadably engage threads about the peg holes230,232,234,236and cylindrical shaft240which may be threaded or non-threaded. The heads238preferably include a no. 5 thread280at a count of 44 per inch. In addition, the heads238are rounded and include a hex socket282to facilitate stabilized threading into the peg holes. This design accommodates the reduced thickness of the volar plate at the head portion216. The shafts240are preferably approximately 0.0792 inch (2 mm) in diameter and 0.765 inch in length. Such dimensions permit the pegs to adequately support the bone fragments such that the bone is able to heal correctly. The pegs208are also preferably made from titanium alloy, and are preferably ‘tiodized’ to provide a strong finish which does not adversely affect bone healing.

From the foregoing embodiments, it is appreciated that the peg holes define a plurality of axes at least two of which are oblique relative to each other and at least one of which is oblique relative to the lower surface of the head of the plate immediately surrounding such hole. In addition, the threaded peg holes define axes which diverge in a direction away from the lower surface of the plate. As such, pegs coupled within such holes define a support framework which is preferably divergent both medial and laterally such that the pegs are arranged to follow the contour of subchondral bone of the bone being stabilized.

Furthermore, the head portion provides substantial support structure both proximal and distal of the threaded holes for supporting the bone fragments. So that substantial surface structure of the plate is provided for the support, preferably the peg holes define less than fifty percent of the area of the head portion, as clearly shown inFIGS. 2 and 15. Furthermore, as also shown in the embodiment ofFIG. 15, a greater area of the head portion is preferably provided distal of the arrangement of the peg holes (on the side of the pegs holes opposite the shaft portion) relative to the area on the head portion proximal of the arrangement of peg holes (on the portion of the head portion adjacent the shaft portion). This large distal area provides a buttress for supporting bone fragments thereunder.

Turning now toFIG. 25, a volar fixation system300according to a third embodiment is shown in which each peg can be articulated through a range of angles within a respective peg hole and fixed at a desired angle within the range. The system includes a volar plate302, four pegs308, and four set screws310, as well as bone screws, not shown but described above, for mounting the volar plate to the radius.

The volar plate310is substantially similar to the first or second embodiments, with the exception of the shape of the peg holes described below, and is used in substantially the same manner as the first embodiment. Each peg hole312in the volar plate includes a cylindrical upper bore314provided with threads316and a lower portion318having a radius of curvature. The surface320of the lower portion and/or the surface330of the head of the peg is preferably roughened, e.g., by electrical, mechanical, or chemical abrasion, or by the application of a coating or material having a high coefficient of friction. The lower opening322of each peg hole includes a circumferential bevel324.

Referring toFIGS. 25 and 26, each peg308includes a head330and a cylindrical shaft332. The proximal portion334of the head330includes a cup336having an outer radius Rosubstantially corresponding to the radius of the lower portion318of the peg holes312, and a relatively smaller inner radius Riof curvature. The head330defines preferably approximately 160° of a sphere. The shaft332includes a slight taper336at the intersection with the head330, and a rounded distal end338. According to a preferred manufacture of the pegs308, the cylindrical shaft332is first provided with a sphere (not shown) or a hemisphere (not shown) at a proximal end. If a sphere is provided, it is cut to a hemisphere. The hemisphere is then hollowed and further reduced to the 160° shape. Finally, the taper336is provided at the intersection.

Turning now toFIGS. 25,27and28, each set screw310includes a proximal hex socket340, circumferential threads342adapted to engage the threads316of the upper bore314of the peg hole, and distal hemispherical portion344having substantially the same radius of curvature as the inner radius of curvature of the cup336, and preferably substantially smaller than a radius of the peg holes312.

In accord with the third embodiment, the volar plate is positioned on the radius, a hole is drilled through the elliptical screw hole on the volar plate and into the radius. A bone screw is inserted through the plate and into the bone. The fractured bones are adjusted under the plate into their desired stabilized positions, and the bone screw is tightened. Then, through the peg holes, the surgeon drills holes into the bone for the stabilization pegs. Unlike the previous embodiments, the holes may be drilled at any angle within a predefined range, and preferably at any angle within a range of 20° relative to an axis normal ANto the lower surface of the head of the volar plate. Each hole may be drilled at the same angle or at relatively different angles. After each hole is drilled, a peg308is inserted therein. The bevel324at the lower end322of the peg hole312and the taper336on the shaft cooperate to permit the peg to be oriented with greater angularity relative to the axis AN, if required, as interference between the peg hole and peg shaft is thereby reduced. Once the peg308has been appropriately positioned within the peg hole, one of the set screws310is threaded into the upper bore314of the peg hole312. The hemispherical portion344contacts the head330of the peg, seating in the concavity of the cup336. As the set screw310is tightened, the head of the peg, which may be roughened, is sandwiched between the set screw and the roughened inner surface of the lower portion of the peg hole, thereby securing the peg in the selected orientation. The other pegs are similarly positioned and angularly fixed.

Turning now toFIGS. 29 through 33, a fixation device410for the treatment of a fracture at an end of a long bone, i.e., a metaphyseal fracture, is provided. The device410is preferably made of metal, e.g., titanium or stainless steel, and includes an intramedullary nail shaft portion412and a plate-like head portion414that is preferably horizontally and vertically offset relative to the shaft portion at a neck portion (or transition zone)16. As such, the shaft portion412and the head portion414are fixed in a parallel, but non-coaxial relationship, with the head portion414longitudinally displaced relative to the shaft portion412.

The shaft portion412is preferably substantially circular in cross section and includes a tapered resilient (flexible) section420, and a relatively rigid section422generally substantially larger in diameter adjacent the shoulder portion416. The rigid section422preferably tapers toward and into the resilient section420. Referring toFIGS. 32 and 33, the rigid section422of the shaft portion412preferably includes two optionally threaded screw holes424,426preferably extending vertically through the diameter of the shaft portion412and longitudinally displaced along the length of the rigid section422. The screw holes424,426, if threaded are adapted to receive machine screws as described in detail in U.S. Pat. No. 6,706,046, and if not threaded are adapted to receive cortical screws, as described in detail in U.S. Pat. No. 6,730,090, both of which are hereby incorporated by reference herein in their entireties.

With respect toFIGS. 29 through 33, the plate-like head portion414is substantially rigid and has a low and narrow profile. The head portion414has a slightly concave bottom surface444(adapting the head portion to the anatomy) and a slightly convex upper surface446(reducing potential irritation of tendons and other tissue). The concave and convex surfaces444and446may be defined by facets approximating curved surfaces. The head portion414also includes preferably three longitudinally displaced, threaded peg holes450,452,454, each of which is preferably adapted to orient a respective peg (e.g., pegs108and108aofFIGS. 3 and 3a) in a different orientation from the others; i.e., the axes of the peg holes are oblique relative to each other so that the pegs inserted therethrough diverge away from the bottom surface444and define a framework under the subchondral surface which supports the fracture. In use, the shaft portion412of the device410is inserted in the intramedullary canal and the plate-like head portion414is provided external of the bone, as described in detail in previously incorporated U.S. Pat. Nos. 6,706,046 and 6,730,090.

There have been described and illustrated herein embodiments of an orthopedic fixation system suitable for numerous applications related to the fixation of various bone fractures. While embodiments of the invention have been described, it is not intended that the invention be limited thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise. Thus, while in one embodiment a volar plate for fixation of a fracture at the distal radius has been shown and described, it is appreciated that a plate with divergent threaded peg holes may be optimized in shape and size for placement on the dorsal radius or for fractures of other bones, such as of the ulna, humerus, femur, tibia, fibula, adjacent the ankle joint, etc. Furthermore, while particular materials for the elements of the system have been disclosed, it will be appreciated that other materials may be used as well. In addition, fewer or more peg holes and pegs than shown may be used, preferably such that at least two pegs angled in two dimensions relative to each other are provided. Also, while a right-handed volar plate for the distal radius is described with respect to an embodiment of the invention, it will be appreciated that both right- and left-handed models are intended, with such alternate models being mirror images of each other. Also, the plate, nail-plate device, and pegs may be provided in different sizes adapted for implant into different size people. It will therefore be appreciated by those skilled in the art that yet other modifications could be made to the provided invention without deviating from its spirit and scope as claimed.