Patent Application
20080086137
The accompanying drawings, incorporated in and constituting a part of this specification, illustrate one or more implementations consistent with the principles of the invention and, together with the description of the invention, explain such implementations. The drawings are not necessarily to scale, the emphasis instead being placed upon illustrating the principles of the invention. In the drawings:
The following description refers to the accompanying drawings. Among the various drawings the same reference numbers may be used to identify the same or similar elements. While the following description provides a thorough understanding of the various aspects of the claimed invention by setting forth specific details such as particular structures, architectures, interfaces, and techniques, such details are provided for purposes of explanation and should not be viewed as limiting. Moreover, those of skill in the art will, in light of the present disclosure, appreciate that various aspects of the invention claimed may be practiced in other examples or implementations that depart from these specific details. At certain junctures in the following disclosure, descriptions of well known devices and methods have been omitted to avoid clouding the description of the present invention with unnecessary detail. Furthermore, in the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”. Also, the term “couple” or “couples” is intended to mean either an indirect or direct mechanical, electrical, or other communicative connection. Thus, if a first component couples to a second component, that connection may be through a direct connection, or through an indirect connection via other devices and connections.
A first barrel 250 may couple to the base plate 210. The first barrel 250 may include a circular cross-section, but other cross-sections (e.g., ovular) are also possible. In one embodiment of the invention, the barrel 250 may have a first open end 236 and a first closed end 235. The first barrel 250 may couple to the first hole 213 in the base plate 210 and to a first screw 220. For example, the first screw 220 may slide within hole 218 that is in barrel 250. The ability of the screw 220 to postoperatively slide within the hole 218 may result in better fixation when, for example, the bone 205 collapses or morphs postoperatively. The ability of the screw 220 to slide may also promote proper loading during, for example, walking or when the patient moves from a sitting to a standing position. A second barrel 251 may include a circular cross-section, or other cross-section, an open end, and a closed end. The second barrel 251 may couple to a hole 214 in the base 210 and to a second screw 221. Screw 221 may slide within hole 216 within barrel 251. A third barrel 252 may include a circular cross-section, or other cross-section, an open end, and a closed end. The third barrel 252 may couple to a hole 215 and to a third screw 222. Screw 222 may slide within hole 217 in barrel 252. In other embodiments of the invention, such as those described below, the barrel may include only open ends without any closed ends.
Again regarding
In one embodiment of the invention, angles 225, 226, and 227 may be substantially the same. For example only, each angle may be between 25 degrees and 55 degrees (e.g., 30 degrees) above a horizontal plane 228 or 115 to 145 degrees from the vertical axis of the plate 210. However, broader angle ranges are included within the scope of the invention. When each angle 225, 226, 227 is substantially the same, the screws 220, 221, 222 may more easily slide within holes 218, 216, 217. However, in one embodiment of the invention each or some of the angles 225, 226, and 227 may be different. For example, in one embodiment of the invention angle 225 may be more displaced from a horizontal plane 228 (e.g., 45 degrees) than angle 227 (e.g., 25 degrees). These differing angles may help accommodate patients of differing sizes. For example, as angle 225 increasingly deflects from the horizontal plane 228 the spread between screws 220 and 222 increases, which may benefit a larger patient.
In one embodiment of the invention, various inserts (not illustrated) may be used to adjust angles 225, 226, and 227. For example, an insert (e.g., plug) may have external threads that screw into internal threads in base plate hole 213. The insert may be keyed so that its insertion position and final position in hole 213 is predetermined. The insert, in its final position, may reside inside the base plate 210 within hole 213. The insert may have a receiving hole for receiving barrel 250. The receiving hole may be offset from the horizontal plane at a predetermined angle that differs from the angle offset directly associated with hole 213. Thus, differing inserts may provide flexibility to a base plate that has holes (e.g., 213) set at predetermined angles. For example, hole 213 may be offset from the horizontal plane by 30 degrees. However, an insert with an additional 5 degrees of deflection may couple to hole 213 to create a 35 degree deflection. Multiple inserts with the same degree of offset may be used to keep all barrels/screws at the same angle. However, inserts with varying degrees of offset may be used in an embodiment where multiples screws should be placed at varying angles. In addition, in an embodiment of the invention, an insert may merely couple to hole 213 and reside outside of the base plate 210 (instead of inside hole 213 as described above). For example, the insert may have a neck with external threads that couple to internal threads in hole 213. In one embodiment of the invention, anther plate 210 is one of a set of plates that includes individual plates with holes oriented at angles different from that of plate 210. The surgeon may select from the various base plates according to the dimensions of the patient's hip.
In one embodiment of the invention, barrel 252 may slidably couple to screw 222. The surgeon may place screw 222 adjacent or near the femoral neck 207 inferior cortex 209. The screw 222 may indirectly couple to the inferior cortex 209 via cancellous bone. In other words, some marrow or less dense bone (e.g., cancellous bone) may be located between screw 222 and the inferior cortex 209. However, the screw 222 may directly contact the inferior cortex 209 (i.e., no cancellous bone between the screw and cortex) in some embodiments of the invention. In other words, when the screw is located “adjacent” to the cortex, the screw may be located functionally or efficaciously proximate (i.e., near) or directly on the hard cortex. Consequently, the cortex may provide stability to the adjacent screw as, for example, bone collapses post operatively or during certain loading events (e.g., a patient standing up). In contrast, if the screw 222 is not placed adjacent (i.e., not functionally near/on the cortex, as is the case when a “center-center” position, known to those of ordinary skill in the art, is used) to the cortex, the surrounding cancellous bone may be unable to provide adequate stability.
In some embodiments of the invention, an additional screw such as, for example, screw 221 may couple, directly or indirectly, to the posterior cortex 214. Screw 220 may also couple, directly or indirectly, with cortex (e.g., anterior cortex). For example, screws 220 and 221 may be positioned by the surgeon adjacent or near cortex tissue. Again, locating one or more screws 220, 221, 222 at or near the cortex provides stability due to the proximity of the screws to the dense cortex, as compared to softer inner bone. The additional stability may result in greater angular stability for the fracture 230. While none of the screws must be on the cortex to ensure angular stability, placing one or more of the screws adjacent, near, or on (i.e., directly coupled) the cortex may better ensure angular stability.
To facilitate placement of one or more of the screws adjacent or on the cortex, the barrels 250, 251, 252 (as described above), and consequently the holes 213, 214, 215 may be spaced predetermined distances from one another. For example, as seen in
In one embodiment of the invention, barrels 250, 251, 252 each include an inner diameter of less than about 8 mm (e.g., 6.5 mm). The upper proximal end 211 of the base 210 may include a horizontal diameter or breadth greater than 20 mm (e.g., 28 mm) and a horizontal thickness of approximately 7 mm. The base lower distal end 212 may include a horizontal diameter less than 12 mm (e.g., 10 mm) and a horizontal thickness of approximately 5 mm. The screws 220, 221, 222 may include a maximum outer diameter necessary to properly couple to the inside of the barrel, e.g., approximately 6.5 mm, so the screws 220, 221, 222 may slide within the barrels 250, 251, 252. In some embodiments of the invention, some or all of the screws, and corresponding barrels, may have different diameters. For example, screw 222 (and barrel 252) may have a larger diameter to support a heightened load experienced in the inferior cortex region 209 of the bone 205. Furthermore, using smaller screws in the superior femoral head may help prevent avascular necrosis. Specifically, using smaller screws in the superior femoral head or more superior regions may avoid, for example, damaging the medial femoral circumflex artery and/or the retinacular vessel while distributing heavy loads to a larger diameter screw/screws located, for example, in the inferior femoral head. Placing a large diameter screw near the superior femoral head may lead to avascular necrosis.
In one embodiment of the invention, barrels 250, 251, 252 each include an open end to receive screws 220, 221, 222 and a closed end to prevent the screws from “backing out” of the bone post operatively. As bone settles post operatively, screws may begin to exit the bone and, for example, exit holes 213, 214, 215 if not prevented from doing so. As the screws exit holes 213, 214, 215 they may begin to irritate surrounding soft tissue. However, use of a barrel with a closed end 235 (or analogous cap, plug, etc.) will preclude such movement beyond a predetermined range of motion. Such a desired range of motion understandably stops short of allowing the screw to irritate soft tissue as described above.
In one embodiment of the invention the barrels are conduits with two open ends. With barrels of substantial lengths, the sliding and settling of the screws should be of a limited nature such that the pins or screws would not back out of the barrels. The conduits or barrels are used to guide and slidably receive screws 220, 221, 222. In an embodiment of the invention, the screws may have, for example, a projection or projections (not shown) to “catch” the barrels or the base itself if the screw moves beyond a desired sliding range. As another example, plugs may be inserted (e.g., screwed) into the base with the plug limiting the sliding range. The barrels may be permanently (e.g., welded or formed) or removably (e.g., screwed) coupled to the base. The barrels may directly or indirectly couple to the base. For example, as stated above, the barrels may couple to the base 210 via inserts of differing angles.
In block 510, the base plate may be temporarily removed and a step drill may be used to drill holes over the guide wires. The step drill may include a drill bit of graduating diameters. For instance, the smallest diameter may form a pilot hole for the threaded portion of the screws 220, 221, 222. The next larger diameter may be approximately equal to any non-threaded portion of the screws 220, 221, 222. The next larger diameter may approximate the outer diameter of the barrels 250, 251, 252. In an embodiment of the invention, the base plate may be configured so that it need not be removed before using the step drill as described above. For example, enlarged holes 213, 214, 215 may be used to accommodate the drill. In an embodiment of the invention, various inserts may couple to the holes 213, 214, 215 to provide different diameters to the holes. For example, an insert with a smaller hole may be used for guide wire placement and an insert (or no insert) may be used for placing the barrels in the bone.
In block 515, the screws may be placed over the guide wires and into the holes drilled in block 510. As each screw is placed in the bone, torque is generated and rotational forces are applied to the bone. However, using a plurality of screws allows the surgeon to use screws of smaller diameters that, collectively, still manage the loads applied to the femoral neck. Placing screws with smaller diameters generates less torque per screw insertion. Furthermore, the initial placement of the multiple guide wires into the bone may stabilize the fracture and offset the rotational forces generated during screw placement.
In block 520, barrels are placed over the screws. In block 525, if the barrels are not permanently affixed to the base plate, they may be affixed to the base plate at this time. The barrels may have, for example, external threads that mate with internal threads in the base holes (e.g., 213, 214, 215). In another embodiment of the invention, the barrels are first placed over the guide wires and then the screws may be placed over the guide wires and into the holes drilled in block 510.
In one embodiment of the invention, if the barrels are permanently affixed to a plate, the plate with permanently affixed barrels may be affixed to the bone with the barrels being inserted into the bone. This base with permanently affixed barrels may be used in conjunction with, for example, an initial base that serves as a template for placing multiple screws in a predetermined pattern. In one embodiment of the invention, plugs may be used to seal one end of barrels having two opposed open ends. The plugs may have external threading that couples to internal threading in the barrel.
In one embodiment of the invention, the base of the implant is located substantially within a femoral intramedullary canal. The implant may function similarly to one or more of the above embodiments, albeit the base for the implant would be located in the intramedullary canal and not on the exterior of the femoral shaft. In one embodiment of the invention, the surgical technique used to insert the intramedullary implant may include the following steps. First, a 2 cm surgical incision may be placed proximal to the greater trochanter. Next, a channel would be surgically created from the tip of the greater trochanter into the medullary canal of the femur using, for example, an awl or mechanical drill. Next, the intramedullary device would be inserted into the medullary canal of the femur. Afterwards, a guiding device coupled to the intramedullary implant would be used to guide pins, drills, or screws through small incisions below the greater trochanter through the lateral cortex of the femur, through the intramedullary implant, and finally into the bone of the femoral head. As described above, there may be three or more holes in the implant to orient screws and the like so they receive support from adjacent cortex tissue in the femoral neck. The holes in the implant may be sized to receive sliding barrels that couple to sliding screws as described above. In one embodiment of the invention, the lower or distal portion of the intramedullary implant may have a 12 mm diameter while the upper or proximal portion has a 16 mm diameter. The implant shaft may include, for example, a customary four degree bend angling the upper portion of the implant away from the femoral neck, as those of ordinary skill in the art will appreciate. The screw to be located adjacent or near the femoral neck inferior cortex, as described above, may be positioned at an angle of, for example, 125 degrees from the lower or distal implant shaft.
Thus, in one embodiment of the invention, a femoral neck fracture fixation device 200 may include a base 210 having an upper end 211, lower end 212, inside surface, and outside surface; at least one bone fixation element 245 coupled to the lower end of the base component that fixes the inside surface of the base component 210 to the femoral bone 205; a first screw 220 coupled to the upper end 211 of the base component (e.g., via barrel 250) and extending into the femoral bone at an angle of eighty degrees (80°) to one hundred sixty degrees (160°) relative to the longitudinal axis (perpendicular to horizontal plane 228) of the base component; and at least a second screw 222 coupled to the upper end of the base component (e.g., via barrel 251) and extending into the femoral bone at an angle of eighty degrees (80°) to one hundred sixty degrees (160°) relative to the longitudinal axis of the base component. The fixation element can be a screw or multiple screws. Further, the device may include guide wires that penetrate the femoral bone prior to coupling the screws into place.
In various embodiments of the invention, the first screw and at least a second screw can be cannulated screws, compression screws, and the like. As noted above, the base component 210 can include a first receiving barrel 250 and at least a second receiving barrel 252 at the upper end 211 where the first screw 220 compressively couples to the first receiving barrel 250 and the at least a second screw 222 compressively couples to the at least a second receiving barrel 252. The compressively coupling screws may be compression screws. In at least one embodiment of the invention, the device includes three receiving barrels 250, 251, 252 at the upper end 211 of the base component and three screws 220, 221, 222 compressively coupled to the receiving barrels 250, 251, 252.
Alternatively, the device may include two, three, four, or more screws coupled to the upper end of the base component where each screw extends into the femoral bone at an angle of eighty degrees (80°) to one hundred sixty degrees (160°) relative to the longitudinal axis of the base component.
Although exemplary embodiments of the invention have been disclosed, it will be apparent to those skilled in the art that various changes and modifications can be made which will achieve some of the advantages of the invention without departing from the spirit and scope of the invention. For example, it will be obvious to those reasonably skilled in the art that, although the description was primarily directed to particular devices, other devices could be used in the same manner as that described. Other aspects, such as the specific methods utilized to achieve a particular function, as well as other modifications to the inventive concept are intended to be covered by the appended claims. For example, while one embodiment concerns stabilizing a femoral neck fracture of a human, other embodiments of the invention may be utilized for other animals including dogs.
While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.
This application claims priority to U.S. Provisional Patent Application No. 60/828,172 filed on Oct. 4, 2006 in the name of Robert Probe, entitled FIXATION OF FEMORAL NECK FRACTURES.
| Number | Date | Country | |
|---|---|---|---|
| 60828172 | Oct 2006 | US |
