Volar fixation system

VOLAR FIXATION SYSTEM

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, and particularly to a fixation system adapted to fixate a Colles’ (or distal radial) fracture.

2. State of the Art

Referring to Fig. 1, a Colles’ fracture is a fracture resulting from compressive forces being placed on the distal radius 10, and which causes backward displacement of the distal fragment 12 and radial deviation of the hand at the wrist 14. Often, a Colles’ fracture will result in multiple bone fragments 16,18,20 which are movable and out of alignment relative to each other. If not properly treated, such fractures result in permanent wrist deformity. It is therefore impoitant 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 the 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.

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SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide an improved fixation and alignment system for a Colles’ fracture.

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

It is also an object of the invention to provide a volar fixation system which is highly adjustable to provide a customizable framework for bone fragment stabilization.

In accord with these objects, which will be discussed in detail below, a volar fixation system is provided which generally includes a T-shaped plate intended to be positioned against the volar side of the radial bone, a plurality of bone screws for securing the plate along a non-fractured portion of the radial bone, and a plurality of bone pegs which extend from the plate tmd into bone fragments of a Colles’ fracture.

The plate is generally a T-shaped plate defining an elongate body, a head portion angled relative to the body, a first side which is intended to contact the bone, and a second side opposite the first side. The body 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 non-linearly arranged. According to a second embodiment, the peg holes are preferably linearly arranged. In either embodiment, the peg holes are positioned increasingly distal in a medial to lateral direction along the second side. According to a third embodiment, which preferably uses a volar plate with peg holes arranged according to either of the first and second embodiments, the pegs are adjustable relative to the peg holes and can be independently fixed in selectable orientations.

In use, the volar 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 volar plate to the radius. The bone fragments are then aligned and the guide plate is positioned on the second side of the volar plate. A drill drills holes into the bone fragments.

The pegs are then inserted through the peg holes and into the holes in the bone. In some embodiments, the heads of the pegs are threadably engaged in the volar plate. In other

V/0 01/56452 embodiments, the pegs are inserted into the peg holes and into the drilled holes at an angle chosen by the surgeon, and a set screw is inserted over each peg to lock the peg in the volar plate at the chosen orientation. The volar fixation system thereby stabilizes and secures the bone fragments in their proper orientation.

Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is an illustration of an extremity subject to a Colles’ fracture;

Fig. 2 is a top volar view of a right hand volar fixation system according to a first embodiment of the invention;

Fig. 3 is a side view of a bone peg according to the first embodiment of the volar fixation system of the invention;

Fig. 4 is a side view of a bone screw of the volar fixation system of the invention;

Fig. 5 is a side view of the right hand volar plate of the volar fixation system according to the first embodiment of the invention;

Fig. 6 is a front end view of the right hand volar plate of the volar fixation system according to the first embodiment of the invention;

Fig. 7 is an exploded side view of the right hand volar plate and guide plate according to the first embodiment of the fixation system of the invention;

Fig. 8 is a side view of the guide plate positioned on the right hand volar plate to provide drill guide paths in accord with the invention;

Fig. 9 is an illustration of the first embodiment of the volar fixation system provided in situ aligning and stabilizing a Colles’ fracture;

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Fig. 10 is a top volar view of a left hand volar fixation system according to the second embodiment of the invention;

Fig. 11 is a lateral side view of the left hand volar fixation system according to the second embodiment of the invention;

Fig. 12 is a bottom view of the left hand volar fixation system according to the second embodiment of the invention;

Fig. 13 is an enlarged side elevation of a bone peg according to the second embodiment of the volar fixation system of the invention;

Fig. 14 is a proximal end view of the bone peg of Fig. 13;

Fig. 15 is first partial top view of the head portion of the left hand volar plate according to the second embodiment of the volar fixation system of the invention;

Figs. 16-19 are section views across line 16-16,17-17,18-18, and 19-19, respectively in Fig. 15;

Fig. 20 is second partial top view of the head portion of the left hand volar plate according to the second embodiment of the volar fixation system of the invention;

Figs. 21-24 are section views across line 21-21,2222,23-23־, and 24-24, respectively in Fig. 20;

Fig. 25 is a broken partial longitudinal section view across a distal end of a third embodiment of the volar fixation system of the invention;

Fig. 26 is a proximal perspective view of a bone peg according to the third embodiment of the invention; and

Figs. 27 and 28 are proximal and distal perspective views, respectively, of a set screw according to the third embodiment of the invention.

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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to Figs. 2 through 4, a first embodiment of a volar fixation system 100 for aligning and stabilizing multiple bone fragments in a Colles’ fracture generally includes a substantially rigid T-shaped plate 102 intended to be positioned against the volar side of the radial bone, a plurality of preferably self-tapping bone screws 104 for securing the plate 102 along a non-ffactured portion of the radial bone, and a plurality of bone pegs 108 which extend from the plate 102 and into bone fragments of a Colles’ fracture.

Referring to Figs. 2,5 and 6, more particularly, the T-shaped plate 102 defines a head portion 116, an elongate body portion 118 angled relative to the head portion, a first side 120 which is intended to contact the bone, and a second side 122 opposite the first side. The first side 120 at the head portion is preferably planar, as is the first side at the body portion. As the head portion and body portion are angled relative to each other, the first side preferably defines two planar portions. The angle 0 between the head portion 116 and the body portion 118 is preferably approximately 18’ and bent at a radius of approximately 1.00 inch (Fig. 5). The distal edge 121 of the head portion 116 is preferably angled proximally toward the medial side at an angle a, e.g., 5°, relative to a line P, which is perpendicular to the body portion. The head portion 116 preferably has a width of 0.913 inch and a greatest proximal-distal dimension (i.e., from the comer of angle a to the body portion) of approximately 0.69 inch, and the body portion preferably has a width of 0.375 inch and a length of 1.40 inches. The plate 102 preferably has a thickness of approximately 0.098 inch. The plate 102 is preferably made from a titanium alloy, such as Ti-6A-4V.

The body portion 118 includes three preferably countersunk screw holes 124,126,128 for the extension of the bone screws 104 therethrough. The first screw hole 124 has a center preferably 0.235 inch from the end of the body portion, the second screw hole 126 has a center preferably 0.630 inch from the end of the body portion, and the third screw hole 128 is preferably generally elliptical (or oval) and defines foci-like locations at 1.020 inches and 1.050 inches from the end of the body portion. The head portion 116 includes four threaded peg holes 130,132,134,136 for individually receiving the pegs 108 therethrough. According to a first preferred aspect of the first embodiment of the invention, the peg holes 130,132,134,136, preferably 0.100 inch in diameter, are preferably non-linearly arranged along the head portion 116, and are provided such that the adjacent peg holes are provided further distally in a medial to latenil direction along the second side. More particularly, according to a preferred aspect of the first embodiment of the invention, the peg holes are preferably arranged along a parabolic curve,

WO 01/56452 with the center of peg hole 130 located approximately 0.321 inch proximal line P and approximately 0.719 inch medial of the lateral edge 137 of the head portion, the center of peg hole 132 located approximately .296 inch proximal line P and approximately 0.544 inch medial of the lateral edge 137, the center of peg hole 134 located approximately 0.250 inch proximal line P and approximately 0.369 inch medial of the lateral edge 137, and the center of peg hole 136 located approximately 0.191 inch proximal line P and approximately 0.194 inch medial of the lateral edge 137.

In addition, according to a second preferred aspect of the first embodiment of the invention, the peg holes define axes A_b A₂, A₃, A₄ which 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 A] of the first peg hole 130 (that is, the most proximal and medial peg hole) is preferably directed normal to the first side 120 of the head portion 116. The axis A₂ of the adjacent peg hole 132, i.e., the second axis, is preferably angled approximately 1-7’ distal and lateral relative to the first axis A!, and more preferably approximately 2.5° distal and lateral relative to the first axis Α_? The axis A₃ of the peg hole 134 laterally adjacent the second peg hole 132, i.e., the third axis, is preferably angled approximately 7-13’ distal and lateral relative to the first axis A_b and more preferably approximately 10° distal and lateral relative to the first axis Ap The axis A₄ of the peg hole 134 laterally adjacent the third peg hole 132, i.e., the fourth axis, is preferably angled approximately 10-30’ distal and lateral relative to the first axis A_b and more preferably approximately 20° distal and lateral relative to the first axis A_P The second side of the head portion 116, distal of the peg holes 130,132,134,136 is preferably beveled.

Referring back to Fig. 3, the pegs 108, preferably approximately 0.872 inch in length, each have a threaded head 138 adapted to threadably engage the threads about the peg holes 130, 132,134,136, and have a relatively smooth non-threaded cylindrical shaft 140. The shafts 140 are preferably approximately 0.0675 inch 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 pegs 108 are 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.

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Turning now to Figs. 7 and 8, the system 100 preferably also includes a guide plate 146 which temporarily sits on the second side 122 of the volar plate 102 and includes guide holes 148,150,152,154 (illustrated in overlapping section in Fig. 8) oriented according to the axes A_bA₂, A₃, A₄ of 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 plate 102 and guide plate 146 are also preferably provided with mating elements, such as a plurality of holes 156,158 on the second side of the volar plate (Fig. 2), and a plundity of protuberances 160 on the mating side of the guide plate (Fig. 7), to temporarily stabilize the guide plate on the volar plate during the hole drilling process.

Referring to Figs. 2 through 9, in use, the volar plate 102 is positioned with its first side 120 against the volar side of the radius. Bone screws 104 (either self-tapping or inserted with the aid of pre-drilled pilot holes) are inserted through the bone screw holes 124,126,128 into the radius bone 10 to secure the volar plate 102 to the radius. The bone fragments 16,18,20 are then aligned with the radius 10. Next, the guide plate 146 is 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 fragments 16,18,20 (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 pegs 108 are then inserted through the peg holes 130,132,134,136 and into the holes drilled into the fragments, and the heads of the pegs are threadably engaged in the volar plate. The pegs 108, extending through the oblique-axis peg holes 130,132,134,136, are positioned immediately below the siibcondylar bone of the radius and support the bone fragments for proper healing. The volar fixation system thereby secures the bone fragments in their !)roper orientation.

Referring to Figs. 10-12, a second embodiment of a volar plate 210, substantially similar to the first embodiment (with like parts having numbers incremented by 100) and used in substantially the same manner as the first embodiment is shown. The plate 210 preferably 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 hole 229 in the body of the volar plate such that the volar plate preferably includes four bone screw holes 224,226,228, 229. The additional bone screw in screw hole 229 increases plate stability over the three holes of the first embodiment. The plate 210 preferably tapers in thickness from the body portion 218 to the head portion 216. A preferred taper provides a proximal body portion 218 thickness of approximately .098 inch and head portion 216 thickness of approximately .078 inch. The taper

WO 01/56452 decreases the thickness of the head portion 216 relative to the body such that the weight of the volar plate is reduced and an improved tendon clearance is provided. The distal edge of the head portion 216 has an increased taper (preferably approximately 60° relative to a line normal to the head) to a distal edge 221. The edge 221 is broken (i.e., made blunt) to prevent irritation or dismrbance to the surrounding anatomy.

The head portion 216 includes four threaded peg holes 230,232,234,236 for individually receiving pegs 208 therethrough (Figs. 13 and 14), and a guide hole 256 for alignment of a guide plate. According to a preferred aspect of the second embodiment of the invention, the peg holes 230,232,234,236, preferably 0.100 inch in diameter, are preferably linearly arranged along lhe head portion 216, 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 to Fig. 15, more particularly, according to a preferred dimensions of the second embodiment of the invention, the center of peg hole 230 is located approximately 0.321 inch proximal line P and approximately 0.750 inch medial of the lateral edge 237 of the head portion, the center of peg hole 232 is located approximately 0.306 inch proximal line P and 0.557 inch medial of the lateral edge 237, the center of peg hole 234 is located approximately 0.289 inch proximal line P and appro:cimately 0.364 inch medial of the lateral edge 237, and the center of peg hole 236 is located approximately 0.272 inch proximal line P and approximately 0.171 inch medial of the lateral edge 237. As such, the distance from each of the peg holes to the distal edge 221 of the volar plate is relatively greater than in the first embodiment, and provides a preferred alignment with respect to the tapered distal edge 221.

Referring to Figs. 15-24, in addition, as in the first embodiment, the peg holes define axes A_b A₂, A₃, A₄ which 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 pegs 208 once 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 A! of the first peg hole 230 is preferably directed normal (Figs. 16 and 21) to the first side 220 of the head portion 216. The axis A₂ of peg hole 232 is preferably angled approximately 1-7’ distal (Fig. 17) and approximately 1-7’ lateral (Fig. 22) relative to the axis A;, and more preferably approximately 2.5’ both distal and lateral relative to axis A_? The axis A₃ of peg hole 234 is preferably angled approximately 7-13’ distal (Fig. 18) and approximately 7-13’ lateral (Fig. 23) relative to axis A_b and more preferably approximately 10’ both distal and lateral relative to axis A]. Axis A₄ of the peg hole 234 is preferably angled approximately 10-30’ distal (Fig. 19) and approximately 10-30’ lateral (Fig.

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24) relative to axis A!, and more preferably approximately 20° both distal and lateral relative to axis Ap

Referring to Figs. 13 and 16-19, each of the peg holes has a countersunk portion 270, 272,274,276, respectively, for receiving the head 238 of peg 208. Countersunk portions 270, 272 are each preferably approximately .030 inch deep and threaded according to the head of the pegs, tis described below. Countersunk portion 274 is preferably approximately .042 inch deep and likewise threaded. Countersunk portion 276 is preferably approximately 0.056 inch deep and also threaded. The respective depths of the countersunk portions are adapted to better accommodate the heads 238 of the pegs 208 relative to the respective axes of the peg holes.

Referring to Figs. 13 and 14, the pegs 208, preferably approximately 0.872 inch in length, each have a threaded head 238 adapted to threadably engage threads about the peg holes 230, 232,234,236, and have a relatively smooth non-threaded cylindrical shaft 240. The heads 238 preferably include a no. 5 thread 280 at a count of 44 per inch. In addition, the heads 238 are rounded and include a hex socket 282 to facilitate stabilized threading into the peg holes. This design accommodates the reduced thickness of the volar plate at the head portion 216. The shafts 240 are 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 pegs 208 are also preferably made from titanium alloy, and are preferably *tiodized’ to provide a strong finish which does not adversely affect bone healing.

Turning now to Fig. 25, a volar fixation system 300 according 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 plate 302, four pegs 308, and four set screws 310, as well as bone screws, not shown but described above, for mounting the volar plate to the radius.

The volar plate 310 is 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 hole 312 in the volar plate includes a cylindrical upper bore 314 provided with threads 316 and a lower portion 318 having a radius of curvamre. The surface 320 of the lower portion and/or the surface 330 of 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 opening 322 of each peg hole includes a circumferential bevel 324.

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Referring to Figs. 25 and 26, each peg 308 includes a head 330 and a cylindrical shaft 332. The proximal portion 334 of the head 330 includes a cup 336 having an outer radius Rq substantially corresponding to the radius of the lower portion 318 of the peg holes 312, and a relatively smaller inner radius R₁ of curvature. The head 330 defines preferably approximately 160° of a sphere. The shaft 332 includes a slight taper 336 at the intersection with the head 330, and a rounded distal end 338. According to a preferred manufacture of the pegs 308, the cylindrical shaft 332 is first provided with a sphere (not shown) or a hemispher (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 taper 336 is provided at the intersection.

Turning now to Figs. 25,27 and 28, each set screw 310 includes a proximal hex socket 340, circumferential threads 342 adapted to engage the threads 316 of the upper bore 314 of the peg hole, and distal hemispherical portion 344 having substantially the same radius of curvature as the inner radius of curvature of the cup 336, and preferably substantially smaller than a radius of the peg holes 312.

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 then 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 fracture location 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 A_N to 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 peg 308 is inserted therein. The bevel 324 at the lower end 322 of the peg hole 312 and the taper 336 on the shaft cooperate to permit the peg to be oriented with greater angularity relative to the axis A_N, if required, as interference between the peg hole and peg shaft is thereby reduced. Once the peg 308 has been appropriately positioned within the peg hole, one of the set screws 310 is threaded into the upper bore 314 of the peg hole 312. The hemispherical portion 344 contacts the head 330 of the peg, seating in the concavity of the cup 336. As the set screw 310 is 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.

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There have been described and illustrated herein embodiments of a volar fixation system and a method of aligning and stabilizing a Colles’ fracture. While particular 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 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, while a particular number of screw holes in the volar plates and bone screws have been described, it will be understood another number of screw holes and screws may be provided. Further, fewer screws than the number of screw holes may be used to secure to the volar plate to the radius. Also, fewer or more peg holes and bone pegs may be used, preferably such that at least two pegs angled in two dimensions relative to each other are provided. Moreover, while in the first embodiment it is preferred that the peg holes lie along a parabolic curve, it will be appreciated that they can lie along another curve. In addition, while a particular preferred angle between the head portion and body portion has been disclosed, other angles can also be used. Furthermore, while particular distances are disclosed between the peg holes and line P, it will be appreciated that the peg holes may be provided at other distances relative thereto. Moreover, while particular preferred medial/lateral and proximal/distal angles for the peg hole axes has been disclosed, it wm I3e appreciated that yet other angles may be used in accord with the invention. Also, while a right-handed volar plate is described with respect to the first embodiment, and a left-handed volar plate is described with respect to the second embodiment, it will be appreciated that each embodiment may be formed in either a right- or left-handed model, with such alternate models being mirror images of the models described. In addition, while a range of 20° in which the pins may articulate is disclosed, the peg holes and pegs may be modified to permit a greater or smaller range of articulation. Furthermore, while a hex socket is disclosed on the set screws for applying rotational force thereto, it will be appreciated that other rotational engagement means, e.g., a Phillips, slotted, star, rectangular, or other configuration may be used. In addition, aspects from each of the embodiments may be combined. 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.