Bone Plating System
The present invention relates to a bone plating system and method for fracture fixation of bone. The bone plating system includes a bone plate, at least one locking screw, and at least one non-locking screw. The bone plate has locking holes with threads and non-locking holes. The locking screws have a shaft with a thread for engaging bone and a head with a thread configured and dimensioned to mate with the thread of the locking holes. The non-locking screws have a thread for engaging bone and a non-threaded head. Both the locking and non-locking screws remain seated in their respective holes for substantially as long as the bone plate is implanted. The non-locking screws compress the bone plate against the bone and hold fracture reduction while the locking screws are secured to the plate at a fixed angular relationship. The mixed fixation achieved by this bone plating system and method is particularly useful for treatment of per-articular fractures.
The present application is a Continuation of Application of U.S. patent application Ser. No. 10/665,431 filed on Sep. 22, 2003 entitled “Bone Plating System” which is a Continuation of U.S. patent application Ser. No. 09/660,287 filed Sep. 12, 2000, entitled “Bone Plating System” which claims priority to U.S. Provisional Patent Application Ser. No. 60/153,239 filed Sep. 13, 1999. The disclosures of these applications is incorporated herein by reference.
FIELD OF THE INVENTIONThe present invention is directed to a bone plating system for fracture fixation, and in particular to a system including a bone plate having plate holes for both locking and non-locking screws.
BACKGROUND OF THE INVENTIONThe clinical success of plate and screw systems for internal fixation of fractures is well-documented. However, treatment of certain fractures, such as peri-articular fractures, which require a fixed angular relationship between the bone plate and screws, remains problematic. Fixed angle devices for treatment of these fractures are available and include the Dynamic Condylar Screw System commercially available from Synthes (USA) of Paoli, Pa. and a wide variety of blade plates. All of these devices require a high level of surgical skill, suitable bone quantity and quality, and a fracture pattern compatible with the device.
In cases in which these requirements are not satisfied, e.g. severely comminuted bone or missing bone segments, conventional bone plate and screw systems must be used. Although these conventional systems are particularly well-suited to promoting healing of the fracture by compressing the fracture ends together and drawing the bone into close apposition with other fragments and the bone plate, the angular relationships between the plate and screws are not fixed and can change postoperatively. This can lead to mal-alignment and poor clinical results.
The primary mechanism for the change in angular relationship is related to energy storage. As previously noted, threading a bone screw into bone compresses the bone against the plate. The compression results in high strain in the bone, and, consequently, energy storage. With the dynamic loading resulting from physiological conditions, loosening of the plate and screw and loss of the stored energy can result.
Securing the screws to the plate provides a fixed angle relationship between the plate and screw and reduces the incidence of loosening. One method of securing the screw to the plate involves the use of so-called “locking screws.” A locking screw has threading on an outer surface of its head that mates with corresponding threading on the surface of a plate hole to lock the screw to the plate. Bone plates having threaded holes for accommodating locking screws are known. For example, German Patent Application No. 43 43 117 discloses a bone plate with threaded holes for locking screws. As the relationship between the locking screws and the plate is fixed, locking screws provide a high resistance to shear or torsional forces. However, locking screws have a limited capability to compress bone fragments.
In summary, conventional bone screws, i.e. screws that are not secured to a plate so that a fixed angular relationship between the plate and screw is maintained (hereinafter “non-locking screws”) effectively compress bone fragments, but possess a low resistance to shear force that can lead to loosening of the screw. Locking screws have a high resistance to shear force that ensure stability at the bone screw/plate hole interface, but possess a limited ability to compress bone fragments. Thus, a bone plating system that combines non-locking screws with locking screws would be ideal for certain clinical situations.
U.S. Pat. No. 5,601,553 discloses a locking plate and bone screw. The plate has a plurality of threaded plate holes for receiving locking screws. The plate also has non-threaded plate holes for receiving temporary screws that keep the plate in place while the locking screws are inserted. After the locking screws are inserted, the temporary screws are removed. Thus, the long term benefits of combining non-locking screws with locking screws are not obtained. U.S. Pat. No. 5,709,686 discloses a bone plate with partially threaded plate holes. The partially threaded holes allow either non-locking or locking screws to be used. Because the plate holes are only partially threaded, the locking screws used may not be able to maintain the fixed angular relationship between the screws and plate under physiological loads. Specifically, the locking screws within the plate are only partially captivated and thus only partially surrounded by threads. Under high stress and loading conditions, the locking plate hole may distort and allow the fixed angular relationship between the locking screw and plate to change. This can result in loss of fixation or loss of established intraoperative plate orientation. Additionally, because of the plate hole geometry, translation of the plate with the non-locking screws is limited to one direction only. This may be a disadvantage in reduction and manipulation of fragments.
Thus, there exists a need for an improved bone plating system that overcomes the deficiencies of the prior art.
SUMMARY OF THE INVENTIONThe bone plating system for fixation of bone according to the present invention includes a bone plate having an upper surface, a bone-contacting surface, at least one first hole passing through the upper and bone-contacting surfaces and having a thread, and at least one second hole passing through the upper and bone-contacting surfaces. The bone plating system also includes a first screw having a shaft with a thread for engaging bone and a head with a thread configured and dimensioned to mate with the thread of the first hole, and a second screw having a shaft with a thread for engaging bone and a head. The first and second screws remain seated in their respective holes for substantially as long as the bone plate is implanted. Preferably, the bone plate includes a plurality of first and second holes, and a corresponding plurality of first and second screws are provided.
In order to facilitate insertion, the first and second screws can be a self-tapping screws. These screws can also be self-drilling screws. Additionally, the first and second screws can be cannulated for insertion of a guide wire to guide screw placement. The first plate hole can have a substantially conical shape with a double-lead thread.
In one embodiment, the bone plate has a trapezoidal shaped cross section in regions between the first and second plate holes for minimizing contact between bone and the bone-contacting surface. Additionally, at least one of the second plate holes is longitudinally elongated and has an edge inclined at an angle to the upper surface toward the bone-contacting surface for displacing the bone plate when engaged by the head of a second bone screw.
In an exemplary embodiment, the bone plate includes a head portion configured and dimensioned to conform to a metaphysis of a bone and a shaft portion configured and dimensioned to conform to a diaphysis of a bone. The head portion has only first plate holes and the shaft portion has both first and second plate holes. In one embodiment, the head portion has a curved surface, includes an anterior fork substantially parallel to an anterior side of the shaft portion, and includes a posterior fork extending out from a posterior side of the shaft portion. In another embodiment, the head portion flares outward from the shaft portion and is curved, tapered, and twisted. The head portion can also be provided with suture holes from suture anchoring of the bone plate.
The method for fracture fixation of bone according to the present invention comprises the steps of reducing the fracture to bring bone fragments in close apposition; compressing a bone plate against the bone with at least one first fastener to hold the fracture reduction; and securing at least one second fastener at a fixed angular relationship to the bone plate. The first fasteners are inserted before the second fasteners and both the first and second fasteners remain in bone for substantially as long as the bone plate is implanted.
The bone plating system according to the present invention includes a bone plate, non-locking screws, and locking screws.
First plate holes 36 are preferably conical in shape. As shown in
As seen best in
Bone-contacting surface 34 on bone plate 30 can be shaped to minimize contact with bone. Limiting contact between the bone plate and bone has a number of biological and mechanical advantages including reduced damage to blood supply and easier plate removal. Providing bone plate 30 with a trapezoidal cross section (
By combining locking screws and non-locking screws on the same bone plate, the present invention provides a novel mixed fixation. With the non-locking screws, fracture reduction is held by friction between the bone plate and bone. This friction is generated by tightening the non-locking screws in bone. However, micromotion between the non-locking screws and bone leads to bone resorption, and loss of reduction. Additionally, insertion of the non-locking screws requires bone to withstand the stresses of tightening of the screws. This results in high stress in bone surrounding the non-locking screws. Ordinarily, the high stress can cause the non-locking screw threads to strip (threads in bone fail in shear) and/or creep in bone (since bone is a viscoelastic material). Either one of these phenomenon also results in loss of reduction.
By adding at least one locking screw, loss of reduction is minimized or eliminated by the present invention. Specifically, by securing the locking screws to the bone plate and not the bone, the effect of the viscoelastic behavior of bone is reduced, the threads do not strip, and micromotion is prevented. The attachment between the locking screws and bone plate is a high strength connection in which the locking screw must cut sideways through bone to fail.
As management of certain peri-articular fractures typically involves insertion of screws at various angles with respect to the bone plate and it is highly desirable to maintain the initial angular relationships between the individual screws and the bone plate, the bone plating system according to the present invention is particularly well-suited for these clinical applications.
Bone plate 50 has an upper surface 52 and a bone-contacting surface 54. Bone plate 50 has a plurality of threaded plate holes 56a, 56b, 56c (collectively referred to as threaded plate holes 56) for receiving locking screws 20 and a plurality of non-threaded plate holes 58 for receiving non-locking screws 10. Each of threaded and non-threaded plate holes 56, 58 passes through upper 52 and bone-contacting surfaces 54. As was the case for bone plate 30, the thread on threaded plate holes 56 mates with threaded head 22 of locking screw 20 to secure locking screw 20 to bone plate 50 at a temporally fixed angular orientation and insertion of non-locking screws 10 in non-threaded plate holes 58 draws the bone toward bone-contacting surface 54 to compress the bone.
Bone plate 50 includes a head portion 60 configured and dimensioned to conform to the metaphysis of the distal femur and a shaft portion 62 configured and dimensioned to conform to a diaphysis of a bone. As best seen in
The non-threaded plate holes 58 are preferably dynamic compression unit (DCU) screw holes substantially similar to second plate holes 38. Shaft portion 62 has both threaded plate holes 56a and non-threaded plate holes 58 so that both locking and non-locking screws can be used in shaft portion 62. The ability to use locking screws in shaft portion 62 is particularly useful when the far cortex of part of the diaphysis is missing or severely damaged since fixation with non-locking screws is problematic because of the condition of the far cortex. As best seen in
In contrast to shaft portion 62, head portion 60 contains only threaded holes 56. Specifically, threaded plate holes 56b that surround a centrally located threaded plate hole 56c. Threaded plate hole 56c has a larger diameter than threaded plate holes 56b to accommodate a locking screw with a larger diameter, e.g. threaded plate hole 56b have a diameter of 5.0 mm and threaded plate hole 56c has a diameter of 7.3 mm.
Bone plate 80 includes a head portion 90 configured and dimensioned to conform to the metaphysis of the lateral proximal tibia and a shaft portion 92 configured and dimensioned to conform to a diaphysis of the lateral proximal tibia. As seen in
The non-threaded plate holes 88 are preferably dynamic compression unit (DCU) screw holes substantially similar to second plate holes 38. Shaft portion 92 has both threaded plate holes 86a and non-threaded plate holes 88 so that both locking and non-locking screws can be used in shaft portion 92. The ability to use locking screws in shaft portion 92 is particularly useful when the far cortex of part of the diaphysis is missing or severely damaged since fixation with non-locking screws is problematic because of the condition of the far cortex. As best seen in
In similar fashion to shaft portion 92, head portion 90 contains threaded holes 86 and non-threaded holes 88. Head portion 90 features threaded plate holes 86b and 86c. Holes 86b and 86c have a diameter of 5.0 mm and are oriented as shown in
While it is apparent that the illustrative embodiments of the invention herein disclosed fulfill the objectives stated above, it will be appreciated that numerous modifications and other embodiments may be devised by those skilled in the art. For example, for some fractures only one first plate hole and one second plate hole are needed, although at least two of each is advantageous. Furthermore, additional plate holes without screws can be present in the plate, if desired to allow the surgeon further flexibility in use. Therefore, it will be understood that the appended claims are intended to cover all such modifications and embodiments which come within the spirit and scope of the present invention.
Claims
1-54. (canceled)
55. A bone plate comprising:
- a head portion having a curved surface configured and dimensioned to conform to a metaphysis of a bone;
- a shaft portion configured and dimensioned to conform to a diaphysis of a bone, the shaft including an anterior fork extending substantially parallel to an anterior of the shaft portion and a posterior fork extending from a posterior of the shaft portion;
- a first screw hole passing through the plate from an outer surface to a bone-facing surface of the head portion, the first screw hole being dimensioned to slidingly receive therein a threaded, bone-engaging shaft of a first screw and including a thread dimensioned to engage a corresponding thread of a head of the first screw to retain the first screw seated in the first screw hole for substantially as long as the bone plate is implanted; and
- a second, non-threaded screw hole passing through the plate from an outer surface to a bone-facing surface of the shaft for receiving therein a second screw having a threaded, bone-engaging shaft and a head.
56. The bone plate of claim 55, wherein the head portion is twisted.
57. The bone plate of claim 55, wherein the head portion is tapered.
58. The bone plate of claim 55, wherein the head portion includes at least one suture hole.
59. The bone plate of claim 55, wherein the head portion includes no non-threaded holes.
60. The bone plating system of claim 55, wherein the shaft portion terminates in a tapered tail.
61. A bone plate defining an outer surface and a bone-facing surface, the bone plate comprising:
- a curved head portion configured and dimensioned to conform to a metaphysis of a bone, the head portion including first and second threaded holes extending therethrough from the outer surface to the bone-facing surface thereof, diameters of the first and second holes being different from one another, the threading of the first and second threaded holes being dimensioned to engage threadings on heads of first and second screws, respectively;
- a shaft portion extending from the head portion and configured and dimensioned to conform to a diaphysis of a bone, the shaft portion including an anterior fork extending substantially parallel to an anterior side of the shaft portion and a posterior fork extending from a posterior side of the shaft portion, wherein at least a first threaded hole and a second threaded hole are located in the head portion, and the first threaded hole and the second threaded hole have different diameters; and
- at least one non-threaded hole passing through the plate from the outer to the bone-facing surface thereof.
62. The bone plate of claim 61, wherein axes of the first and second threaded holes converge.
63. The bone plate of claim 61, wherein axes of the first and second threaded holes converge on a bone-facing side of the plate.
64. A bone plate defining an outer surface and a bone-facing surface opposite the outer surface, the bone plate comprising:
- a head portion configured and dimensioned to conform to a metaphysis of a bone, the head portion including a plurality of first screw holes extending therethrough from the outer surface to the bone-facing surface, each of the first screw holes including an internal threading dimensioned to engage a threading formed on a head of a screw to be inserted thereinto; and
- a shaft portion configured and dimensioned to conform to a diaphysis of a bone, the shaft portion including a plurality of second screw holes extending therethrough from the outer surface to the bone-facing surface, the second screw holes including at least one threaded hole including an internal threading dimensioned to engage a threading formed on a head of a screw to be inserted thereinto and at least one non-threaded hole.
65. The bone plate of claim 64, wherein the at least one threaded second hole has a double lead thread.
66. The bone plate of claim 64, wherein the head portion is twisted.
67. The bone plate of claim 64, wherein the head portion is tapered.
68. The bone plate of claim 64, wherein the head portion is curved.
69. The bone plate of claim 64, wherein the head portion includes at least one suture hole.
70. The bone plate of claim 64, wherein an end of the shaft portion opposite the head portion terminates in a tapered tail.
71. The bone plate of claim 64, wherein the shaft portion has a substantially trapezoidal shaped cross-section in a region between the threaded and non-threaded screw holes to minimize contact between the bone-facing surface and a bone on which the plate is mounted.
72. The bone plate of claim 64, wherein the head portion flares outward from the shaft portion.
Type: Application
Filed: Jan 22, 2008
Publication Date: Jun 5, 2008
Inventors: Paul C. Weaver (Douglassville, PA), Jeff W. Mast (Reno, NV), Keith A. Mayo (Harrison Township, MI), Brett R. Bolhofner (St. Petersburg, FL), David Little (Malvern, PA)
Application Number: 12/017,834
International Classification: A61B 17/56 (20060101); A61B 17/58 (20060101);