Abstract:
An external fixation assembly for bone fusion or separation is disclosed. The assembly includes a fracture fusion tube, with a bracket slidably engaged thereon. The assembly further includes a collet clamp connected to the bracket, with a ball collet rotatably seated within the clamp, the ball collet having an aperture for receiving a bone bin therethrough and perforations for a compression engagement with a bone pin. The assembly uses a single screw for threadably engaging the ball collet, the clamp and the bracket such that the position of the bone pin, ball collet and bracket are all fixed.

Description:
FIELD OF INVENTION 
     The present invention relates to an external fixation assembly for bone fusion or separation. More specifically, the assembly includes a fracture fusion tube, with a bracket slidably engaged thereon. The assembly further includes a collet clamp connected to the bracket, with a perforated ball rotatably seated within the clamp, the ball having an aperture for receiving a bone bin therethrough. The assembly uses a single screw for threadably engaging the pin collet, the clamp and the bracket such that the position of the ball, bracket, and collet clamp is fixed. Thus, the present invention teaches an assembly for external fixation with multiple axes of rotation for pin placement and setting wherein the desired placement may be fixed through the use of a single screw or similar connector. 
     BACKGROUND OF THE INVENTION 
     External fixation devices have been commonly used for various treatments of bone conditions. Such bone conditions include leg lengthening, osteotomies, arthrodesis, open fracture fixations, compound fracture fixations, and other bone conditions amenable to treatment by use of an external fixation assembly. For example, external fixation devices are typically used in treatment of bones wherein frequent wound care is necessary to treat an open wound or a surgical site within an extremity. 
     Although current external fixation devices are adequate, many external fixation devices are relatively large and include numerous components, are complicated to use, difficult to adjust, and involve challenging postoperative care and use. Thus, improvements may be made. For example, current external fixation devices involve relatively large and numerous components, creating operative difficulties to both the practitioner and postoperative difficulties to the patient. Many devices, for instance, involve a ring or “halo” member disposed about an affected area to provide support to pins for fixating bone matter. Such components, however effective, are relatively bulky and create difficulty for the physician to insert the pin and for the patient to move independently. 
     These ring or halo fixation devices have been used by orthopedic surgeons and podiatrists in the treatment of some foot injuries and maladies. Some injuries or conditions involving the foot or ankle require that these devices be applied to the bones of the foot (e.g., calcaneus, tarsals, metatarsals, and phalanges) and the lower leg bones (e.g., tibia and fibula). In such circumstances, pins may be inserted into both the foot and lower leg bones in order to secure the fixation device. However, assemblies currently available in the art have limited rotational ability for a given pin, which is exacerbated by the complex and varied placement of a set of pins being used in a given assembly. 
     There is a need to provide an external fixation device that involves less components and may be used to articulate a bone pin around multiple axes of rotation while still being relatively easy to use and secure. 
     Thus, the present state of the art reflects a need for an improved external fracture pin assembly which has a simpler fastening arrangement and greater rotational and angular bone pin adjustability features. 
     DESCRIPTION OF THE PRIOR ART 
     One example of a prior art approach is found in U.S. Pat. No. 7,465,303 (Riccione et al.). Among other embodiments, Riccione teaches the use of a plurality of compression nuts, the threads of which are mateable with the threads of a threaded rod. Riccione et al. further comprises one or more collets comprising collet sleeves and collet nuts. The one or more collets are configured to hold a bone pin and to form a compression lock in the apertures when the collet nuts are tightened against the pin holding elements during use. This patent, however, fails to teach multiple orientational components, such as a slideable bracket, a collet and/or other components which may be fixed in location through the use of a single fastener. 
     Another discussion of a prior art approach may be found in U.S. Pat. No. 8,235,994 (Hollawell), which teaches a fixator for use in the reconstruction of acute, chronic and traumatic injuries to the upper and lower extremities. Specifically, Hollawell teaches a unique clamping system that allows for the snapping in of pins and rails, and for multi-planar fixation of bones. However, Hollawell fails to teach the ability to independently rotate and setting a pin within a collet clamp having a fixed location, nor does it teach the ability to have multiple independently rotatable axes for fixing a pin location wherein the system may be fixed in location using a single fastener. 
     What is needed is an external bone pin assembly with increased range of motion and decreased complexity of assembly and use. 
     DEFINITION OF TERMS 
     The following terms are used in the claims of the patent as filed and are intended to have their broadest plain and ordinary meaning consistent with the requirements of the law. 
     A “rod”, “pin”, and “nail” are used interchangeably. All three terms refer to a rigid elongated component that is inserted into one or more bones for the purpose of anchoring, stabilizing, repairing, or supporting the bone(s). The term “rod” usually implies a relatively large device, while the term “pin” implies a somewhat smaller device; however, there is no clear boundary between these terms. In addition, the term “rod” (and the terms “rail,” and “tube,” too) is not limited to a cross-sectional shape, and may in fact be circular, oval, square, rectangular, polygonal or any combination thereof, while still falling within the term “rod” as used herein. 
     As used herein, the term “threaded” indicates that a rod or pin has screw-type threads on its external surface; however, a non-threaded rod or pin can have one or more threaded holes passing through it, for fixation screws, so long as the threads are not exposed on the external surface. A rod externally threaded along at least a part thereof is generally referred to as a screw. The screws maybe threaded at one or both ends of the screws based on the preferred use of the screw. However, it should be noted that in some cases non-threaded rods or pins can be used and would still fall within the scope of a “threaded engagement” as used herein, especially where the non-threaded pin is attached to another element (e.g., bone, plate, rod, pin) sufficiently to hold the rod to the element. 
     It should also be noted that, while the terms “rod”, “pin”, or “nail” normally tend to imply that an implant does not have an externally threaded surface, some implanted rods, pins, or nails have external threads. Accordingly, such rods can be provided with one or more externally threaded regions if desired, and would still fall within the term “pin” as used herein. 
     Where alternative meanings are possible, the broadest meaning is intended. All words used in the claims set forth below are intended to be used in the normal, customary usage of grammar and the English language. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     The apparatus and method of the present invention generally includes an external bone pin assembly that includes a fracture fusion tube for slidably engaging one or more bracket (which may be a clamp or similar structure). At least one bracket is connected to a collet clamp or similar structure which is rotatable around the circumference of the fracture fusion tube. The collet clamp has seated therein a perforated ball for receiving a bone pin therethrough, the ball being rotatable within the collet clamp for adjusting the angle of engagement for the bone pin and the bone. The perforated ball is composed of aluminum or a similar crushable material. The collet clamp and the bracket have aligned apertures, at least one of which is threaded, and a single screw can be aligned with both apertures, such that tightening a single screw will secure the bracket and collet clamp into a fixed position, and the compressive force of the collet clamp from the tightening screw on the perforated ball crimps the ball into a fixed position. Thus, a single screw can fix all of the components from a given pin subassembly extending from the fusion fracture tube. 
     The immediate application of the present invention will be seen in providing an external bone pin assembly for a simpler assembly, which provides greater pin insertion into metatarsals and other bones in the foot, though the present invention could be applied to other bodily regions, including the tibia and other bones, using a larger scale but similar principle of operation. 
     Thus, one object of the present invention is to provide an external bone pin assembly wherein multiple axes of orientation can be fixed by a single fastener. 
     A further object of the present invention is to provide an assembly with a collet clamp containing a crushable ball collet support for a bone pin. 
     Still another object of the present invention is to provide modular bracket and collet clamp system components to provide more flexible methods of manufacture and assembly. 
     Yet another object of the present invention is to provide a cut or perforated ball collet for a compression engagement with a bone pin. 
     It should be noted that not every embodiment of the claimed invention will accomplish each of the objects of the invention set forth above. In addition, further objects of the invention will become apparent based the summary of the invention, the detailed description of preferred embodiments, and as illustrated in the accompanying drawings. Such objects, features, and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, and as illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective view of a first preferred embodiment of the present invention in application to a metatarsal application. 
         FIGS. 2 a  and 2 b    shows aperture and side views, respectively, of the ball shaped pin collet of one preferred embodiment of the present invention. 
         FIG. 3  shows a perspective view of a ball shaped pin collet inserted into a peek plastic sleeve in accord with one embodiment of the present invention. 
         FIG. 4  shows a front view of a bracket and collet clamp assembly engaged with the single fastener in accord with one preferred embodiment of the present invention. 
         FIG. 5  shows a side view of a collet clamp body with a rotation support feature in accord with one preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Set forth below is a description of what is currently believed to be the preferred embodiment or best examples of the invention claimed. Future and present alternatives and modifications to this preferred embodiment are contemplated. Any alternatives or modifications which make insubstantial changes in function, in purpose, in structure or in result are intended to be covered by the claims in this patent. 
     As can be seen in  FIG. 1 , in one embodiment of the present invention the assembly  10  comprises a bone fusion tube or rail  12 , at least one bracket  14 , at least one collet clamp  16  which has seated therein a ball collet  18 , the collet clamp  16  being attached to the bracket  14 , and a pin  20  inserted through the ball collet  18 . Generally, the clamp system  10  is configured to connect the rail  12  to the pin  20 , which is connected to a bone for fixation and stabilization. 
     The rails  12  may be any size or shape, and persons of skill in the art will recognize that different application require rails  12  of many differing sizes or shapes, all of which are contemplated herein. The rails  12  may, for example, have a circular, oblong, square, rectangular, or other-shaped cross section. Typically, however, the rails  12  have a round or circular cross-section and are sized in a manner suitable for fixation of small bones, such as those of the foot or hand. Most preferably, foot systems practicing the present invention can use a short rail of 2.25 to 2.75 inches in length, or a standard length rail of 3.75 to 4.75 inches in length. The rails  12  may be composed of many materials including, for example, carbon fiber or high density plastic, which allows the rod to be radiolucent. Optionally, the rails  12  may have one or more recesses  22  or detents  24  which limit the axial sliding capability of brackets  14  mounted thereon. 
     An example of unique ball collet features used in certain embodiments of the present invention is shown in  FIGS. 2 a  and 2 b   . The ball collet  18  is made of aluminum or a similar crushable material, and includes an aperture  26  for receiving the bone pin  20  therethrough. Those of skill in the art will appreciate that the aperture  26  may be of a preselected size (e.g., 3 mm, 4 mm, 5 mm or 6 mm) to mate with a corresponding diameter pin  20 . The ball collet  18  further preferably includes a first pair of perforations  28  or cuts, and a second pair of perforations  30  or cuts. Looking at the collet from the orientation of the aperture  26  as in  FIG. 2 a   , the first pair of perforations  28  are directly above and below the aperture, while the second pair of perforations are to the left and right of the aperture. As can be seen from the side view of the collet in  FIG. 2 b   , each set of perforations extends approximately 90 percent along the length of the collet, with each pair of perforations  28 ,  30  extending from opposite sides of the collet  18 . In other words, at one of the aperture  26 , only the first pair of perforations  28  will extend from the aperture through to the periphery of the ball collet  18 , while at the other end of the aperture, only the second set of perforations will so extend. Thus, since neither pair of perforations  28 ,  30  extends along the entire length of the ball collet, the ball collet  18  can maintain its structural integrity. However, the presence of the perforations provides a “crush zone” such that the application of a compressive force (as provided and explained below) provides a friction fit between the ball collet  18  and the pin  20 . 
     As shown in  FIG. 3 , the ball collet may be supported by a plastic sleeve  32 , although those of skill in the art will understand that the function of the plastic sleeve  32  may be provided by a recess or groove integrally molded within the collet clamp  16  itself in alternative preferred embodiments. An advantage of the plastic sleeve  32 , however, is that the structure of the collet clamp  16  and bracket  14  are essentially identical, thus allowing a modular, more simple manufacture and assembly. In those embodiments using the plastic sleeve  32 , that feature most preferably comprises a peek plastic sleeve which includes a slit  34  and ridges  36 , with the slit  34  allowing for easier placement of the ball collet  18  during assembly, and the ridges  36  retaining the ball collet  18  once inserted. The ball collet  18 , though, still has the ability to rotate within the plastic sleeve  32  after placement and before being secured by a fastener (explained in greater detail below) such that the surgeon is afforded a high degree of rotation of the pin  20  and ball collet  18  within the sleeve  32 . 
     As shown in  FIG. 4 , once the ball collet  18  is inserted in the plastic sleeve  32 , those components can be seated within the throughbore  39  of collet clamp  16  and mated with the bracket  14 . The collet clamp  16  has a collet clamp support aperture  40  (FIG. 5 ) extending through the flat bottom of that component. Likewise, the bracket  14  (which in a first preferred embodiment has the same structure as the collet clamp  16 ) has a bracket throughbore  41  (which slidably engages the rail  12 ) and bracket support aperture  42 . Thus, when the collet clamp support aperture  40  and the bracket support aperture  42  are aligned with one another as shown in  FIG. 4 , a single screw  44  can connect the bracket  14  to the collet clamp  16 , allowing the collet clamp  16  to rotate with the bracket  14  around the circumference of the rail  12 . In a variant of this preferred embodiment (as shown in  FIG. 5 ) the bracket  14  and collet clamp  16  can further include support markings  46  or machined faces on the sides of the bracket  14  and collet clamp  16 , thus permitting the collet clamp  16  to be rotated relative to the bracket  14  around an axis defined by the collet clamp support aperture  40  and the bracket support aperture. 
     In one preferred embodiment, only the bracket support aperture  42  is threaded to make threading the screw through the collet clamp  16  and the bracket  14  easier, although both the bracket  14  and the collet clamp  16  may be threaded in alternative embodiments to provide truly identical structures for modular manufacture and assembly. Given the U shaped structures of the bracket  14  and the collet clamp  16 , tightening the screw  44  squeezes and provides a friction fit for the bracket  14  around the rail  12 , and prevents further movement of the bracket  14  along the length of the rail  12 . Likewise, that same tightening action squeezes the bracket  14  and collet clamp  16  together, thus preventing further rotation of the two components relative to one another. Further, the squeezing action also squeezes the U shaped the bracket clamp, which in turn squeezes the sleeve  32  and the ball collet  18  and prevents the further rotation of the ball collet. Ultimately, the tightening action crimps or collapses the perforations  28 ,  30 , which in turn fixes the pin  20  in the collet ball  18 . Thus the tightening of a single screw  44  secures each of the different axes of rotation in the assembly  10 . 
     The above description is not intended to limit the meaning of the words used in the following claims that define the invention. Rather, it is contemplated that future modifications in structure, function or result will exist that are not substantial changes and that all such insubstantial changes in what is claimed are intended to be covered by the claims. For instance, certain embodiments of the present invention may not include structures for all of the axes of rotation provided in the most preferred embodiments. One alternative embodiment of the present invention could conceivably use a single fastener  44  without employing the collet ball  18  of the most preferred embodiments, or vice versa. Likewise, it will be appreciated by those skilled in the art that various changes, additions, omissions, and modifications can be made to the illustrated embodiments without departing from the spirit of the present invention. All such modifications and changes are intended to be covered by the following claims.