Patent Grant
6955677
The present invention relates generally to the design of fasteners and components to which fasteners are affixed. A specific application of the present invention relates to the design and use of bone screw/plate systems in the course of orthopaedic surgical procedures.
A variety of techniques exist in the field of orthopaedic surgery for treating bone fractures. Many known techniques utilize bone screws and bone fixation plates. Typically, the plate is used to stabilize the site of a bone fracture, and one or more bone screws are inserted through apertures of the plate and threaded into the bone material so as to secure the plate to the bone material. It is also known that bone screw/plate systems can be improved by machining a thread onto the head of the bone screw, in addition to the thread normally machined onto the main shaft of the screw. In connection with the use of threaded-head screws, the apertures of the plate are threaded to matingly receive the threads of the screw head. Thus, as the screw is inserted into an aperture of the plate and threaded into the bone material, the head of the screw likewise is threaded into the aperture. As a result, the screw becomes rigidly affixed to the plate, in effect locking to the plate rather than simply bearing against the plate. Examples of threaded-head bone screws and threaded-aperture bone plates are disclosed in U.S. Pat. No. 5,709,686 to Talus et al.; U.S. Pat. No. 6,206,881 to Frigg et al.; and U.S. Pat. No. 6,306,140 to Siddiqui.
The use of threaded-head screws and threaded-aperture plates provides certain advantages. It is known that some types of small bone fragments tend to change position relative to the plate over time. This deleterious condition can result from the “toggling” of the screws affixed to the plate. However, when multiple screws are rigidly fixed to the plate by mating the respective threads of the screw heads with the threads of the corresponding plate apertures, the screws do not toggle in the plate. The locking action provided by the threaded-head screw in combination with the threaded-aperture plate prevents motion between the bone fragment and the plate as well as premature loosening of the screws.
Although the use of threaded-head screws has provided improvements in orthopaedic surgical techniques, there remains the disadvantage that currently available screw/plate systems are unidirectional. That is, the thread formed on the inside surface of the aperture of the plate is structurally fixed at a constant helical angle with respect to the central axis passing through the center point of the aperture. Hence, the head of a conventional threaded-head screw can only be rigidly affixed to the plate by mating its thread with that of the aperture, such that the bone screw is always inserted and threaded in one direction, e.g., perpendicularly or coaxially with respect to the plate.
It would therefore be advantageous to provide a screw/plate system that allows the surgeon to choose the angle at which the screw is inserted through, and rigidly affixed in, an aperture of the plate. Such an improvement would enable the surgeon to direct the bone screw toward bone fragments that are not situated directly beneath the aperture of the plate, and would also provide flexibility in the placement of the plate in relation to the bone fracture. The ability to choose the angle at which the screw is threaded into the bone material would allow the surgeon to better tailor the application of the screw/plate system to the specific nature of the bone fracture suffered by the individual orthopaedic patient, and additionally allow the surgeon to adjust his or her application strategy as necessary after the surgical site has been accessed but prior to insertion of the screw into the bone material. Additionally, in situations where a screw is intended for coaxial insertion into an aperture, the improvement would allow a secure fit between the screw and aperture even if the screw is unintentionally inserted in non-coaxial relation to the aperture.
The present invention in broad terms provides a plate or other component suitable for affixation by a fastener. The plate has one or more apertures through which one or more corresponding fasteners can be inserted. Notably absent from these apertures are any forms of permanent internal thread structures as found in the prior art and which, as indicated above, are a limitation in applications such as the treatment of bone trauma. Each aperture is bounded by a region structured to enable the fastener, and particularly a threaded head portion of the fastener, to be tapped into the material constituting the region. By providing this tappable region, the fastener can be inserted at any desired angle in relation to the aperture, thereby providing significant flexibility in practice. While it is contemplated that the invention can be applied in a wide range of fastening and fixation techniques, particular advantage is found in the field of orthopaedic surgery. Embodiments of the invention can be practiced in any surgical procedure that conventionally involves the use of bone screw/plate systems. Examples include the treatment of general bone trauma, stabilization of metaphyseal fractures, treatment of osteoporotic bones, bone fusion, joint prosthesis, spinal alignment or correction, and the like.
According to one embodiment of the present invention, a surgical plate adapted for fixation with a bone screw is provided. The plate comprises first and second opposing major surfaces, and an inside surface extending between the first and second major surfaces. The inside surface defines an aperture that is generally coaxially disposed about an aperture axis. A non-threaded tappable contact region is disposed on the inside surface. The tappable contact region has a minimum inside diameter that is large enough to permit a bone screw to pass therethrough at an insertion angle defined between a longitudinal axis of the fastener and the aperture axis. The tappable contact region is adapted for being tapped by an external thread of the bone screw to affix the bone screw to the tappable contact region at the insertion angle.
According to one aspect of this embodiment, the tappable contact region is formed in the inside surface of the fastener receiving member. According to another aspect, the tappable contact region comprises an insert that is fitted to the inside surface.
According to a further aspect of this embodiment, the tappable contact region comprises a plurality of protrusions extending generally radially inwardly from the inside surface, and a plurality of interstices between the protrusions. According to a yet further aspect, the tappable contact region comprises a porous fiber metal matrix.
According to another embodiment of the present invention, a fastening apparatus adapted for multi-angular insertion is provided. The fastening apparatus comprises a fastener and a fastener receiving member. The fastener comprises an elongate section and an adjoining head section disposed along a fastener axis. The elongate section comprises a first thread and the head section comprises a second thread. The fastener receiving member comprises first and second opposing major surfaces, and an inside surface extending between the first and second major surfaces. The inside surface defines an aperture generally coaxially disposed about an aperture axis. A tappable contact region is disposed on the inside surface. The tappable contact region has a minimum inside diameter that is large enough to permit the elongate section to pass therethrough at an insertion angle defined between the fastener axis and the aperture axis. The tappable contact region is adapted for being tapped by the second thread of the head section to affix the head section to the tappable contact region at the insertion angle.
The present invention also provides a method for affixing a fastener to a fastener receiving member at a desired orientation. A fastener is provided that comprises an elongate section and an adjoining head section disposed along a fastener axis. The elongate section comprises a first thread and the head section comprises a second thread. A fastener receiving member is provided that comprises first and second opposing major surfaces and an inside surface extending between the first and second major surfaces. The inside surface defines an aperture generally coaxially disposed about an aperture axis. A tappable contact region is disposed on the inside surface. An insertion angle, defined between the fastener axis and the aperture axis, is selected as the angle at which the fastener is to be inserted in relation to the fastener receiving member. The elongate section of the fastener is inserted through the aperture until the second thread of the head section contacts the tappable contact region. The fastener is tapped into the receiving member such that the fastener is oriented at the selected insertion angle. This is accomplished by threading the second thread of the head section into the tappable contact region while the fastener is oriented at the selected insertion angle.
According to one aspect of this method, one of the major surfaces of the receiving member is placed against bone material. The first thread of the elongate section of the fastener is threaded into the bone material so as to anchor the fastener to the bone material. This procedure is useful in a number of applications, such as the stabilization and healing of bone fractures. As the first thread of the elongate section is threaded into the bone material, the second thread of the head section eventually contacts the tappable contact region of the fastener receiving member. Further threading of the first thread into the bone material causes the second thread of the head section to be threaded into the tappable contact region of the receiving member.
It is therefore an object of the present invention to provide a plate or other fastener receiving member that enables a threaded fastener to be affixed thereto at a desired angle selected from a range of available angles.
It is another object of the present invention to provide such fastener receiving member with an aperture that does not require a pre-tapped, fixed-position thread structure with which a threaded fastener is to be interfaced.
It is yet another object of the present invention to provide a surgical bone screw/plate system comprising a fastener having a threaded head portion and a fastener receiving member having an aperture lined with a region into which the threaded head portion can be tapped, such that the threaded head portion can be rigidly affixed to the fastener receiving member at an arbitrary angle selected by the user.
Some of the objects of the invention having been stated hereinabove, and which are addressed in whole or in part by the present invention, other objects will become evident as the description proceeds when taken in connection with the accompanying drawings as best described hereinbelow.
Referring now to
In a preferred implementation of the invention in which fastener 10 is utilized as a bone screw for anchoring to bone material B such as a bone fragment, the illustrated “V” profile of first thread 31 is advantageous in that renders fastener 10 self-tapping. The invention, however, is not limited to any particular design for first thread 31. For instance, the profile of first thread 31 could be rectilinear or square, with its crest 31B being a generally flat surface. Alternatively, the profile of first thread 31 could be trapezoidal (i.e., an “Acme” thread). The degree of sharpness or flatness of crest 31B is not limited, and crest 31B could be rounded. Moreover, the invention is not limited to any particular diameter of first outer surface 25, diameter of crest 31B, thread angle TA between the side walls of adjacent thread passes, or thread pitch P (i.e., the axial distance between the crest portions of adjacent thread passes, or the reciprocal of the number of thread passes per inch). Additionally, first thread 31 could be a multiple-threaded or multi-start design, in which two or more individual threads are cut beside each other. First thread 31 could also constitute one or more single threads formed on different axial sections of shaft. Also, pitch P of first thread 31 could be such that adjacent thread passes are separated from each other by an axial distance D over which only first outer surface 25 of shaft exists. Finally, the “hand” or “sense” associated with the turning of first thread 31 about fastener axis FA may or may not follow the standard right-hand rule.
With continuing reference to
In the illustrated example, second thread 51 has a conical or “V” profile and thus tapers from second outer surface 45 to crest 51B. The “V” profile of second thread 51 is preferred because it facilitates the self-tapping of head section 40 into a plate or other fastener receiving member 60 (see, e.g.,
In an alternative embodiment, elongate section 20 is not threaded, and fastener 10 takes the form of a peg or a pin. This alternative embodiment may be preferred in certain procedures where, for instance, the main object is to prevent tilting of a bone segment, as well as other procedures where there is no concern of fastener 10 pulling out from the bone and hence no need for elongate section 20 to be threaded. In these implementations, head section 40 is threaded, and thus the advantages and benefits of the present invention as described herein apply.
Turning to
Fastener receiving member 60 comprises a first major outer surface 62, an opposing second major outer surface 64, and outer lateral edges 66, 67, 68 and 69 at the perimeter. In orthopaedic applications, second outer surface 64 can in some cases be used for contact with bone material B (see
One or more apertures, generally designated A (e.g., apertures A1 and A2 shown in
As indicated above, the invention departs from the conventional use of a thread formed on inside surface 81 of aperture A for mating with the thread of a screw head. That is, apertures A of fastener receiving member 60 do not contain a permanent helical thread structure of fixed orientation. Instead, a tappable contact region, generally designated 85, is disposed on each inside surface 81 of fastener receiving member 60. The term “tappable” is used herein to denote that contact region 85 is structured such that it can be tapped by second thread 51 of head section 40 of fastener 10 in response to forceful insertion and rotation of head section 40 into the material of contact region 85. As described below in connection with
In the embodiment illustrated in
It will be noted that the density of protrusions 87 over the area of inside surface 81, and the size of individual protrusions 87, are not limited by the invention, so long as the matrix formed on inside surface 81 renders contact region 85 tappable. Accordingly, the matrix of protrusions 87 can appear as a bristle board or a porous surface. The characteristic cross-sectional dimension of each protrusion 87 (e.g., diameter, width, or the like) can range from approximately 1 micron to approximately 25 mm, although the invention is not limited to this range. The density of protrusions 87 over the area of inside surface 81 from which they protrude can range from approximately 5 to approximately 65%, although the invention is not limited to this range. Protrusions 87 can be formed by any suitable means, such as growing protrusions 87 by material deposition, forming protrusions 87 by coating, welding protrusions 87 to inside surface 81, or forming ridges or grooves and subsequently cutting transversely through the ridges to discretize the ridges into protrusions 87.
It will be further noted that in the embodiment illustrated in
As seen from the perspective of
While the profile of lower section 95 in
Referring now to
An example of a method for affixing fastener 10 to fastener receiving member 60 will now be described by referring back to
Turning now to
The manner by which head section 40 of fastener 10 is affixed to aperture A of receiving member 60 depends on whether contact region 85 illustrated in
Depending on the nature of the procedure being executed, the surgeon can affix additional fasteners 10 to additional apertures A of receiving member 60, either at the same insertion angle IA as the illustrated fastener 10 or at different angles. It will be noted that, depending on the number of fasteners 10 utilized and how far each is threaded into its corresponding aperture A, the mechanical strength of the interface between each corresponding second thread 51 and contact region 85 or 105 can be made sufficient to cause compression of receiving member 60 against bone material B if desired by the surgeon.
As an alternative to the embodiments specifically illustrated in
It will be understood that various details of the invention may be changed without departing from the scope of the invention. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation, as the invention is defined by the claims as set forth hereinafter.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3741205 | Markolf et al. | Jun 1973 | A |
| 3906550 | Rostoker et al. | Sep 1975 | A |
| 5198308 | Shetty et al. | Mar 1993 | A |
| 5607426 | Ralph et al. | Mar 1997 | A |
| 5709686 | Talos et al. | Jan 1998 | A |
| 5735853 | Olerud | Apr 1998 | A |
| 5797912 | Runciman et al. | Aug 1998 | A |
| 5954722 | Bono | Sep 1999 | A |
| 6206881 | Frigg et al. | Mar 2001 | B1 |
| 6214049 | Gayer et al. | Apr 2001 | B1 |
| 6306140 | Siddiqui | Oct 2001 | B1 |
| 6379359 | Dahners | Apr 2002 | B1 |
| 6454769 | Wagner et al. | Sep 2002 | B2 |
| Number | Date | Country | |
|---|---|---|---|
| 20040073218 A1 | Apr 2004 | US |
