US20110009912A1 - Fixed angle dual prong pin fixation system - Google Patents

Abstract

A bone fixation system and method are provided. The system includes a dual prong pin and a bone screw. The pin is especially configured and contoured to fixate fractures of the proximal phalanx, especially hyperextension fractures. Fracture of other long bones of the hand, foot or elsewhere may be managed with this bone fixation system.

Description

CROSS REFERENCES TO RELATED APPLICATIONS
• This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/086,822, filed on Aug. 7, 2008, the complete disclosure of which is incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
• A bone fixation system and method suitable, for example, for fracture fixation of the proximal phalanx of the hand or foot, especially of the hyperextension type, are provided. The system is also suitable for fixating fractures of other long bones of the hand, such as the middle phalanx or the metacarpals, and of the metatarsals in the foot. The system is also suitable for fixating fractures in other bones outside of the hand or foot.
INTRODUCTION
• Hyperextension fractures of the proximal phalanx are typically problematic, especially in the elderly, because such fractures are very difficult to stabilize. Current techniques and devices can often lead to very significant functional impairment and disability. These hyperextension fractures of the proximal phalanx usually result in less optimal outcomes than fractures of larger bones such as the distal radius.
• One of the most common methods for fracture fixation is pinning. In general, a pin has a sharp cutting tip. The pin is driven into bone with the aide of a drill or an equivalent mechanical device. Despite their versatility, pins have limitations especially with fractures that have a significant amount of fragmentation (comminution) of the bone at the fracture site or when the fractured bone is too soft resulting in premature loosening of the pins.
• Another common method for fracture fixation of the small bones of the hand utilizes plate fixation. However, use of plates usually results in scaring which frequently limits the proper gliding motion of the surrounding tendons, especially the extensor tendon. A second surgery is usually necessary to remove the plate and release the extensor tendon. This approach often results in a large scar in the most visible part of the hand (not readily received by most female patients). In the presence of significant comminution and osteoporosis, as is often the case scenario in the elderly female population with these fractures, plate fixation of hyperextension fractures of the proximal phalanx is usually not able to hold the alignment of the fracture because the plate has limited mechanical ability to buttress these fractures and loss of reduction is often frequent after plate fixation.
• In addition, conventional plating of the long bones of the hand frequently results in malalignment of the involved bone after the plate is applied; the operated finger will tend to abnormally scissor or overlap onto an adjacent finger. Thus, plating requires absolute precision because even a small amount of angular malalignment is not well tolerated.
• Yet another fixation method utilizes a flexible nail/pin mated to a locking sleeve. This method offers some advantages over plating and pinning of the long bones of the hand. However, the nail and sleeve configuration is not much different from pins and has limited ability to control hyperextension fractures of the proximal phalanx which frequently results in loss of fracture reduction. In addition, a significant portion of the hardware is prominent outside of the bone, irritating the tendons. Some relief is provided by use of a protective plastic cap. In most cases, a second surgery is needed to remove the nail and the prominent locking sleeve.
BRIEF DESCRIPTION
• In accordance with the principles embodying the invention, a system and method for bone fixation are provided in the form of a two prong buttress pin system. In its basic form, the system has two components—a two prong or dual prong pin and one or more bone screws, e.g., locking screws. The threads of the screw are designed to mate with the dimensions of a locking domain of the two prong pin.
• The two prong pin is suitably contoured to work as a buttress. Such contouring is especially suitable in fixating hyperextension fractures of the proximal phalanx, but may also be used for fixating other bones of the hand, foot or elsewhere. The dual prong pin is also advantageous in addressing the most common flexion deformity of metacarpal fractures. Because of the contoured nature of the pin in accordance with principles embodying the invention, four points of fixation are achieved, two in the proximal fracture fragment and two in the distal fracture fragment.
• The two prong pin can be used by itself or with its one or more bone screws. The bone screw, e.g., locking screw, is constructed and configured to mate to the locking domain of the pin. To facilitate insertion, a drill guide can be mated to the locking domain of the two prong device to drill the precise direction for the locking screw. A drill guide may be desirable but is not necessary because the system is very accommodating.
• In an illustrated embodiment, the two prong device has a single locking domain to which a single bone screw may be mated. In another embodiment, the dual prong pin may have two locking domains to which two bones screw may be mated. More complex configurations can be devised for accommodating more than one screw or to provide an additional buttress in between the locking domains to provide additional fixation and buttress support.
• In another embodiment, the two prong pin has a retaining feature configuration located on the distal portion of the prongs. This retaining configuration can take the form of raised rings or protrusions or barbs on the shank of the prongs. These configuration variations help increase the gripping power of the prongs, thus preventing separation of the fracture.
• Specifically, a bone pin in accordance with the principles embodying the invention includes a substantially U-shaped member having a central region, a first prong extending from the central region and a second prong extending from the central region, spaced apart and opposite and parallel from the first prong. The central region is configured to receive and mate with one or more bone screws.
• A bone fixation system in accordance with embodiments of the invention includes a bone pin and one or more bone screws. The pin is substantially U-shaped and has a central region, a first prong extending from the central region and a second prong extending from the central region, opposite and parallel to the first prong. The central region is configured to receive and mate with the bone screws. The central region lies in a transverse plane. The one or more screws each have an elongate shaft, and when mated within the central region, the shaft is substantially perpendicular to the plane of the central region.
• A method and kit for fixating bone fractures are also provided.
BRIEF DESCRIPTION OF THE DRAWINGS
• The invention may be better understood and appreciated by reference to the detailed description of specific embodiments presented herein in conjunction with the accompanying drawings of which:
• FIG. 1 illustrates a perspective view of a bone pin in accordance with the invention having a dual prong configuration and a single locking domain;
• FIG. 2 illustrates a side plan view of a bone pin having a single locking domain dual prong configuration;
• FIG. 3 illustrates a top plan view of a bone pin having a single locking domain dual prong configuration;
• FIG. 4 illustrates a perspective view of a bone pin ofFIG. 1 with a locking cortical screw engagingly mating the locking domain;
• FIG. 5 illustrates a perspective view of an embodiment of a bone pin having dual lateral locking domains and a dual prong configuration;
• FIG. 6 illustrates a perspective view of an embodiment of a bone pin ofFIG. 5 with dual locking cortical screws engagingly mating the locking domains;
• FIG. 7 illustrates a perspective view of an embodiment of a bone pin having a dual prong configuration with dual linear locking domains;
• FIG. 8 illustrates a perspective view of a bone pin ofFIG. 7 with dual locking cortical screws engagingly mating the locking domains with the mating feature of the screw;
• FIGS. 9A and 9B illustrates front and rear perspective views of a locking cortical screw, showing the self-cutting tip, the loop mating groove, and the drive socket;
• FIG. 10 illustrates a perspective view of a bone pin having a single locking domain and dual prong configuration with varying prong length;
• FIG. 11 illustrates a perspective view of a bone pin having dual prong configuration and single locking domain with a series of barbs along the shank portion of the prongs;
• FIG. 12 illustrates a perspective view of a bone pin having a dual prong configuration and a single locking domain a series of ringed protrusions along the shank portion of the prongs; and
• FIGS. 13A,13B,13C and13D illustrate the placement of a bone pin system in accordance with the invention at a fracture site.
DETAILED DESCRIPTION
• A bone fixation system embodying the principles of the invention is provided. The system includes a fixed angle dual prong bone pin and one or more bone screws, e.g., locking screws. The system acts as a buttress to resist against the main deforming forces acting on fractures, especially, for example, of the proximal phalanx, such as those acting on hyperextension fractures. The system is also well-suited for fixating fractures of other long bones in the hand, such as the metacarpals and phalanges, and long bones in the foot, such as metatarsals. Fractures of other bones of the body may also be fixated with device and method described herein.
• Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of the structure and function set forth in the following description or illustrated in the appended drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. “Comprising” also encompasses the terms “consisting of” and “consisting essentially of.” The use of “consisting essentially of” means, e.g., that a method may include additional steps, but only if the additional steps do not materially alter the basic and novel characteristics of the claimed method. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.
• No admission is made that any reference, including any patent or patent document, citied in this specification constitutes prior art. In particular, it will be understood that unless otherwise stated, reference to any document herein does not constitute an admission that any of these documents forms part of the common general knowledge in the art in the United States or in any other country. Any discussion of the references states what the author asserts and the applicant reserves the right to challenge the accuracy and pertinence of any of the documents cited herein.
• As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
• Unless otherwise noted, technical terms are used according to conventional usage. However, as used herein, the following definitions may be useful in aiding the skilled practitioner in understanding the invention. Such definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.
• As used herein, the term “substantially” in reference to a shape or direction, for example, “substantially U-shaped,” is meant to refer to a general or overall shape or direction. For “substantially U-shaped,” it is understood, for example, that the legs of the U may vary, e.g., the legs of a U may be equal in length or unequal. The legs may also be curved or angled.
• The terms “transverse plane” and “sagittal plane” are meant to refer to the conventional planes used in describing a human body, i.e., the sagittal plane travels along the Y-axis and the transverse plane is in the horizontal plane perpendicular to the sagittal plane.
• The term “arcuate” is meant to describe a structure or a portion of a structure as being curved or rounded. It is understood that more than one arcuate portion may be present in a structure.
• In view of the foregoing disadvantages inherent in conventional bone fixation systems, the invention provides a novel system and method for fixating bone fractures, for example, proximal phalanx fractures. Given that many fractures have not only transverse fracture components but also oblique or even rather frequently long fracture lines along the bone, it has been found advantageous for pin placement with a dual shaft/prong pin in accordance with principles of the invention.
• In one aspect, the invention provides a bone pin with a fixed angle dual prong or dual shaft configuration, and having screw locking domains. Specifically, the pin is substantially U-shaped, as seen inFIG. 3, having a central region, a first prong extending from the central region and a second prong extending from the central region, opposite and parallel to the first prong. The prongs of the pin are pre-contoured, the exact shape of which depends on the particular application. The central region lies in a transverse plane which is perpendicular to the sagittal planes of the contoured prongs.
• The central region may have one or more screw locking domains to receive and mate with a bone screw, e.g., a locking screw. The locking domains of the pin are suitably one or more arcuate portions, e.g., a loop or looped portion. In use, for example, a locking bone screw is suitably mated in the locking domain. The one or more screws each have an elongate shaft, and when positioned and mated in the central region, i.e., the locking domain, e.g., the loop, the shaft is generally perpendicular to the (transverse) plane of the central region, i.e., the shaft lies in the sagittal plane.
• The direction of the screw placement in the looped portion depends on the optimal configuration for individual fracture fixation and is not limited as in the existing prior art devices. In some embodiments, the bone pin according to principles of the invention may have more than one screw locking domain. The domains may be suitably positioned side by side, laterally or linearly. The locking screw has bone threads that are designed to match and mate with the features in the locking domain of the two pronged pre-contoured pin.
• The full mechanical advantage of the fixed angle dual prong pin configuration in accordance with embodiments of the invention is realized when the bone screw is mated to the arcuate locking domain. For example, in embodiments in which the locking domain is a loop, the head of the screw to be mated to the loop suitably has a head to allow the diameter of the loop to mate with the minor diameter of the threaded portion of the screw proximal end. Having two fixed angle dual prongs oriented in identical directions into the substance of the bone enhances the separation strength of the pin from the bone far beyond that of a single shaft pin oriented in a similar direction.
• The bone pin in accordance with principles of the invention is desirable in multiple fracture scenarios, and especially in fractures of the bones of the hand or foot, for example, the metacarpals and the phalanges. The bone fixation system is simple to insert, has a very low profile, and minimizes tendon irritation.
• The dual prong configuration offers multiple mechanical advantages over a single flexible nail. For example, the bone pin according to principles of the invention has better rotational control, lower profile, improved buttressing effect, and there is no need for a secondary surgery. The system also has many advantages over plating systems. For example, embodiments of the bone pin improve buttressing of hyperextension fractures of the proximal phalanx, a lower profile, and, unlike the plate, there is no need for a secondary surgery to remove the device or to free the scarred tendon resulting in no large scar. In addition, any malrotation is easily corrected with the present two prong device.
• Reference is now made toFIGS. 1-4 in which a bone fixation system, generally designated byreference numeral10, in accordance with embodiments of the invention is shown.System10 includes adual prong pin20 and a screw system21 (e.g., as seen inFIG. 4) for stabilizing bone segments. In an illustrated embodiment,dual prong pin20 is generally overall U-shaped (as shown inFIG. 3), defined by acentral region23, afirst prong22 extending fromcentral region23, and asecond prong24, extending fromcentral region23, that is spaced apart and generally parallel tofirst prong22.Central region23 includes one or morescrew locking domains26 to receive and hold bone screws.Domains26 are suitably one or more arcuate portions, e.g., suitably, aloop28, as shown, e.g., inFIG. 1.Loop28 has a predefined shape and size.Dual prong pin20 may be provided with any size ofloop28 as may be suitable for a specific surgical application.
• Dual prong pin20 in accordance with the principles embodying the invention may have many shapes. As shown in the embodiment ofFIG. 1, prongs22,24 are pre-contoured and suitably have a generallyarched shape25 with, e.g., an arched section aiding to grip the bone inner surface. In the embodiments illustrated inFIGS. 1-4, generally archedshape25 ofprongs22 and24 includes, in the sagittal plane, a first bend orarcuate portion30 connected to a firstlinear portion32 connected to a second bend orarcuate portion34.Bend34 is connected to a secondlinear portion36 which is at an acute angle α tolinear portion32.Linear portion36 is connected to a third bend orarcuate portion38 connected to a thirdlinear portion40.Linear portion40 is at an oblique angle β tolinear portion36.Linear portion40 is connected to a fourth bend orarcuate portion42 and ending in a fourthlinear portion44 angled with respect tolinear portion40 at an angle γ and has aterminus 46. As seen inFIG. 3, the overall configuration ofpin20 is U-shaped. As described, the arched shape coupled with the fixed angle combination enables a buttress pin configuration.
• However, pin20 can be configured in many different shapes and sizes to accommodate any situation. For example,FIG. 1 illustrates a single loop dual prong configuration withprongs22 and24 of equal length and shape.FIG. 4 illustrates the embodiment ofFIG. 1 showing a lockingcortical screw21 engagingly mating the locking domain.FIGS. 5 and 6 show perspective view of a lateraldual loop configuration64 withFIG. 6 illustrating screws21 engagingly mating with thelateral loop64.FIGS. 7 and 8 show perspective view of a lineardual loop configuration66, withFIG. 8 illustrating screws21 engagingmating lateral loop66.FIG. 10 further illustrates the prong configuration variation with two varying prong lengths-one short and straight30 and the other prong with an arch31.
• In some embodiments, the prongs have a cylindrical shape, i.e., a round cross-section. The pin profile is not limited to a round cross-section and may also be constructed using any profile e.g. square, hexagon, and triangle. In addition, the contour of the prongs may also take any form pertaining to its particular application. The inner surface of the cylindrical shape in the dual linear loop area would be positioned against the bone surface.
• Loop28 is configured to receive abovescrew21 therethrough.Screw21 is used to anchordual prong pin20 to the particular bone segments that require fixation. As shown inFIG. 9, screw21 has ahead region50 respectively at aproximal end52.Screw21, which includes a threadedportion54, extends from thehead region50 to adistal end56 of the screw. The locking cortical screw engages the loop with the mating feature of the screw.
• To facilitate insertion, the threaded screws can be self-tapping screws. The screw can also be self-drilling screw or pre-drilled with the aide of a drill guide. Additionally, the screws can be cannulated for insertion of a guide wire to guide screw placement. The length of the individual screw shaft can be selected for the particular application.FIG. 13 illustrates the placement ofpin20 in accordance with the invention at a fracture site.
• That two prongs can be mated to the screw provides additional fixation to bone because a screw, oriented into the bone, will offer much more resistance to pull out than any existing configuration. Torsional resistance is also theoretically greatly increased.
• Prongs22,24 may have ashank portion60. In an embodiment, prongs22,24 havebarbs62 disposed alongshank60, as shown inFIG. 11. In another embodiment, as shown inFIG. 12, twoprong pin20 in accordance with embodiments of the invention has a retaining feature configuration located on the distal portion of the prongs. This retaining configuration can take the form of raised ring orprotrusions64 on the underside of the prongs. These configuration variations help increase the gripping power of the prongs thus preventing separation of the fracture.
• As described herein, the dual prong pin may be sized and configured for particular application, thus allowing the pin to be applied to the tibia, femur, humerus, forearm bone, and other bones with which the invention may be used.
• One of ordinary skill in the art will know and appreciate thatdual prong pin20 may be provided with other types and configurations of prongs in addition to the dual prongs as illustrated. For example,dual prong pin20 may be provided with substantially varied configurations to its prongs and mounting, with prongs consisting of varied shapes, configurations, and mountings on a single device as shown in the drawings, or any other type of configuration known to one of ordinary skill in the art, e.g., one of the two prongs could be smooth with the other having a barbed feature.
• In practice, the two prong device is designed to “snap” in place at the fracture site. In various embodiments, the second bend of the prongs after the locking loop in the sagittal plane is intended to secure the dorsal cortex of the bone at the fracture site, thus providing a first point of fixation. The third bend of the device in the sagittal plane works to provide the second point of support for the device in the proximal fracture end. The third and gentler bend in the sagittal plane works to provide the first point of fixation to the distal fracture fragment across the fracture site. A second point of support to the fragment across the fracture site is provided by the two long prongs of the device. Basically four points of fixation are achieved, two in the proximal fracture fragment and two in the distal fracture fragment.
• The invention also provides a method of fixating bone fractures. The method includes positioning a dual prong pin having, e.g., a loop, at the site of a fracture, and inserting bone screw through the loop of the dual prong pin, thus locking the pin and fragments to fixate the fracture.FIG. 13 illustrates the placement of the bone fixation system at the site of the fracture.
• The foregoing description is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes may readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents are considered to fall within the scope of the invention. Various features and advantages of the invention are set forth in the following claims.
• All publications, patents and patent applications referenced in this specification are indicative of the level of ordinary skill in the art to which this invention pertains. All publications, patents and patent applications are herein expressly incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated by reference. In case of conflict between the present disclosure and the incorporated patents, publications and references, the present disclosure should control.

Claims (21)

1. A bone fixation system, comprising:

a bone pin and one or more bone screws,

the pin being substantially U-shaped, the pin having a central region, a first prong extending from the central region and a second prong extending from the central region, opposite and parallel to the first prong,

the central region configured to receive and mate with the bone screws,

the central region lying in a transverse plane,

the one or more screws each having an elongate shaft, and when mated in the central region, the shaft is substantially perpendicular to the plane of the central region.

2. The system ofclaim 1, wherein the central region is a screw locking member capable of mating with one screw.

3. The system ofclaim 1, wherein the central region is a screw locking member capable of mating with two screws.

4. A bone pin, comprising:

a substantially U-shaped member having a central region, a first prong extending from the central region and a second prong extending from the central region, opposite and parallel from the first prong,

the central region configured to receive and mate with one or more bone screws.

5. The pin ofclaim 4, wherein the central region is an arcuate portion defining a single screw locking member.

6. The pin ofclaim 4, wherein the central region is two arcuate portions defining a dual screw locking member.

7. The pin ofclaim 4, wherein the first and second prong are equal in length.

8. The pin ofclaim 4, wherein the first and second prong each are substantially arched, each include a first arcuate portion extending from the central region, a first straight line portion extending from the first arcuate portion, substantially perpendicular to the plane of the central region, a second arcuate portion extending from the first straight line portion, a second straight line portion extending from the second arcuate portion and at an angle from the first straight line portion, a third arcuate portion extending from the second straight line portion, and an end portion which is straight line and at angle from the second straight line portion.

9. The pin ofclaim 4, wherein the first and second prongs are unequal in length.

10. The pin ofclaim 8, wherein the first straight line portions of the first and second prongs are perpendicular to the plane of the central region.

11. The pin ofclaim 5, wherein the single screw locking member is an arcuate loop lying a horizontal plane.

12. The pin ofclaim 6, wherein the dual screw locking member has a first and second arcuate loops.

13. The pin ofclaim 12, wherein the second arcuate loop lies laterally in the horizontal plane of the first arcuate loop.

14. The pin ofclaim 12, wherein the second arcuate loop lies linearly in the horizontal plane of the first arcuate loop.

15. The pin ofclaim 12, wherein the second arcuate loop comprises arcuate portions of the first and second prongs, the portions being opposite each other and oppositely contoured to each other.

16. The pin ofclaim 4, wherein the prongs have a substantially round cross-section.

17. The pin ofclaim 4, wherein the prongs have a substantially square cross-section.

18. The pin ofclaim 4, wherein the prongs have rings or raised protrusions about a portion of the prong.

19. The pin ofclaim 4, wherein the prongs have barbs on a portion of the prong.

20. A method of fixating bone fractures, comprising positioning a dual prong pin having first and second substantially parallel prongs and an arcuate loop portion capable of receiving a bone screw to a fracture site, and inserting a bone screw through the loop portion into a bone or bone fragments to fixate the fracture.

21. A kit, comprising:

a bone pin and one or more screws,

the pin being substantially U-shaped, the pin having a central region, a first prong extending from the central region and a second prong extending from the central region, opposite and parallel to the first prong,

the central region for receiving and mating with the bone screws,

the central region lying in a transverse plane,

the one or more screws each having an elongate shaft, and when mated in the central region, the shaft is substantially perpendicular to the plane of the central region.

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