The present disclosure generally relates to an implant system for use in orthopedic surgery. Specifically, the disclosure relates to an intramedullary nail for internal fixation of bone, such as a femur.
Femur fractures commonly occur in the femoral neck and the trochanteric regions. Typically, trochanteric and sub-trochanteric femur fractures are treated with an intramedullary nail having a transverse bore to receive a bone fastener, such as a femoral neck screw usually provided in the form of a lag screw.
U.S. Pat. No. 5,176,681, which is incorporated by reference herein in its entirety, discloses an intramedullary nail that is adapted to be inserted into an intramedullary canal of a femur and a lag screw that is adapted to be passed through a transverse bore of the intramedullary nail, through the neck of the femur, and into the femoral head. The lag screw is designed to transfer the load of the femoral head into the nail shaft by bridging the fracture line to allow fast and secure fracture healing. Further, the lag screw is allowed to slide in the intramedullary nail so as to accommodate settling of the fracture. A set screw that is inserted into a longitudinal bore of the intramedullary nail engages the lag screw to prevent rotation and uncontrolled medial deviation of the lag screw while allowing for the sliding movement thereof. The intramedullary nail includes a central cannulation along its longitudinal axis for receiving a surgical wire (guidewire), such as a Kirschner-wire. The surgical wire is inserted into the marrow cavity of the femur prior to the insertion of the intramedullary nail.
However, conventional intramedullary nails have several drawbacks, one of which being that conventional set screws occlude the central cannulation of the intramedullary nail. Thus, conventional set screws cannot be preassembled with the intramedullary nail and thus have to be inserted into the intramedullary nail intraoperatively after removal of a guidewire. In this case, the insertion of the relatively small set screw into the shaft of the intramedullary nail is cumbersome. Soft tissue overlapping the opening at the proximal end of the nail may hinder the insertion of the set screw and the mutual engagement of the threads. Thus, the set screw may get stuck within the intramedullary nail and the operation time may be increased due to additional operation steps. There is also the additional concern that misthreading of the set screw with the intramedullary nail can damage the set screw or the intramedullary nail. Moreover, another drawback is that conventional set screws are susceptible to backing out which can negatively affect the performance of the lag screw. Therefore, further improvements are desirable.
In one aspect of the present disclosure, an implant system for fixation of bone, includes a bone fastener that has a groove formed on an outer surface thereof. An intramedullary nail includes a proximal portion and a distal portion. The proximal portion defines a central bore extending along a central axis of the proximal portion. The intramedullary nail defines a transverse bore that extends transverse to the central axis of the proximal portion and intersects the central bore. The transverse bore is configured to receive the bone fastener therein. A coupling insert is configured to be received within the central bore and has first and second portions spaced along a longitudinal axis of the coupling insert. The coupling insert defines a through-opening extending along the longitudinal axis through the first and second portions. The second portion includes a plurality of moveable members extending from the first portion and terminating at respective terminal ends. The moveable members are moveable relative to each other such that the terminal ends of the moveable members are separated from one another in a first configuration and relatively closer together in a second configuration, such that in the second configuration, the terminal ends of the moveable members at least partially occlude the through-opening and are at least partially receivable within the groove of the bone fastener when the bone fastener is disposed within the transverse bore.
In another aspect of the present disclosure, an implant system for fixation of bone includes an intramedullary nail that has a proximal portion and a distal portion. The proximal portion includes a central bore extending along a central axis of the proximal portion. The central bore defines a first camming surface. The intramedullary nail defines a transverse bore that extends transverse to the central axis of the proximal portion and intersects the central bore. A bone fastener is disposed within the transverse bore and has a groove formed on an outer surface thereof. A coupling insert is disposed within the central bore and is moveable along the central axis. The coupling insert has a first portion engaged to the central bore and a second portion has a first moveable member that extends from the first portion. Upon moving the coupling insert along the central axis, the first camming surface engages the first movable member to deflect the first moveable member into alignment with the groove of the bone fastener.
In a further aspect of the present disclosure, a method of securing a bone fracture includes: inserting an intramedullary nail and a coupling insert disposed within a proximal portion of the intramedullary nail distally into a femur along a guidewire; removing the guidewire proximally from the intramedullary nail and the coupling insert, such that the guidewire passes through a central cannulation of the nail and through a through-opening of the coupling insert; driving a bone fastener through a transverse bore in the intramedullary nail; and moving the coupling insert distally toward the bone fastener causing a plurality of leg members of the coupling insert to be displaced from a radially expanded position to a radially contracted position and positioning terminal ends of the leg members at least partially within a groove in the bone fastener so as to prohibit rotation of the bone fastener.
In an additional aspect of the present disclosure, a coupling insert for use with an implant system for fixation of bone includes a first portion and a second portion spaced from the first portion along a longitudinal axis. The second portion includes a plurality of moveable members extending from the first portion and terminating at respective terminal ends. The moveable members being moveable relative to each other such that the terminal ends of the moveable members are separated from one another in a first configuration and relatively closer together in a second configuration. A through-opening extends along the longitudinal axis through the first and second portions. In the second configuration, the terminal ends of the moveable members at least partially occlude the through-opening.
In a yet further aspect of the present disclosure, a method of securing a bone fracture includes: moving a coupling insert within a proximal portion of an intramedullary nail distally toward a bone fastener disposed within a transverse bore in the intramedullary nail, causing a plurality of leg members of the coupling insert to be displaced from a radially expanded position to a radially contracted position and positioning terminal ends of the leg members at least partially within a groove in the bone fastener so as to prohibit rotation of the bone fastener.
The features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings in which:
When referring to specific directions in the following discussion of certain implantable devices, it should be understood that such directions are described with regard to the implantable device's orientation and position during exemplary application to the human body. Thus, as used herein, the term “proximal” means close to the heart and the term “distal” means more distant from the heart. The term “inferior” means toward the feet and the term “superior” means toward the head. The term “anterior” means toward the front of the body or the face, and the term “posterior” means toward the back of the body. The term “medial” means toward the midline of the body, and the term “lateral” means away from the midline of the body. Also, as used herein, the terms “about,” “generally” and “substantially” are intended to mean that slight deviations from absolute are included within the scope of the term so modified.
Intramedullary nail 40 is a rod-shaped body that includes a proximal portion 42, a distal portion 44, and an intermediate bent portion 47. In other words, the intermediate bent portion 47 connects proximal portion 42 and distal portion 44. Distal portion 44 includes one or more screw openings for bone screw 30. Intramedullary nail 40 also includes a central cannulation or central longitudinal bore 41 that extends along and through the entire length of nail 40, and a transverse bore 49 that extends entirely through nail 42 in a direction transverse to a longitudinal axis of central bore 41. In this regard, transverse bore 49 intersects central bore 41 and is preferably angled relative to the central axis of central bore 41 at an oblique angle.
Proximal portion 42 of nail 40, as best shown in
Head portion 62 is a ring-shaped or annular structure that includes an inner tool engagement surface 63 which is configured to engage a tool, such as a screw driver, hex driver, or the like. In addition, head portion 62 has an outer thread 64 extending about a longitudinal axis of head portion 62 and along its length. Thread 64 is configured to engage second threaded portion 45 of intramedullary nail 40.
Screw engagement portion 66 includes a plurality of moveable members or legs 70. Legs 70 are cantilevered to head portion 62 such that they each extend from a fixed end at head portion 62 to a terminal end 78. Legs 70 are integrated into head portion 62 such that head portion 62 and legs 66 form a monolithic or unitary structure.
Each leg 70 is separated from an adjacent leg 70 via an inter-leg slot 68 and from an opposed leg 70 by through-opening 61. Each slot 68 is defined by a pair of legs 70 such that slot 68 has a constant width portion 71 and a tapered portion 73. In another embodiment, slot 68 may define a keyhole shape such that the constant width portion 71 is instead a circular portion. Constant width portion 71 is located closer to head portion 62 than tapered portion 73. Tapered portion 73 tapers outwardly in a direction away from head portion 62 and terminates at terminal ends 78 of legs 70. In the embodiment depicted, there are six legs 70 which are circumferentially arranged about the longitudinal axis of coupling insert 60 at evenly spaced intervals such that legs 70 and slots 68 between them are circumferentially offset from each other at an angle θ. In the embodiment depicted, angle θ is 60 degrees. However, in other embodiments where there are more or less than six legs 70, angle θ may differ from that shown. For example, in embodiments where coupling insert 60 includes four legs 70, angle θ may be 90 degrees. In another example, where coupling insert 60 includes eight legs 70, angle θ may be 45 degrees.
Each leg 70 includes an outer surface, an inner surface 77, and side surfaces 75 extending therebetween. The outer surfaces of each leg 70 include cylindrically-curved surface 72, a first convex or bulbous surface 74, a second convex or bulbous surface 76, and a concave or indented surface 79. Cylindrically-curved surface 72, as described in more detail below, defines a cylinder with the remaining legs 70 when the legs 70 are brought together. Thus, cylindrically-curved surface 72 is curved in only one plane and about an axis. In contrast, bulbous surfaces 74 and 76 are curved in more than one plane. First bulbous surface 74 is located between cylindrically-curved surface 72 and indented surface 79. In addition, indented surface 79 is positioned between first bulbous surface 74 and second bulbous surface 76. Second bulbous surface 76 partially defines the terminal end 78 of leg 70. First and second bulbous surfaces 74, 76 each have a radius of curvature. For example, the radius of curvature of first bulbous surface 74 may be 1 mm, while the radius of curvature of the second bulbous surface 76 may be 1.5 mm. In this regard, the radius of curvature of first bulbous surface 74 may be smaller than that of second bulbous surface 76. Moreover, first bulbous surface 74 protrudes further radially outwardly than second bulbous surface 76.
Side surfaces 75 of each leg taper toward each other in a direction toward the longitudinal axis of coupling insert 60 and toward inner surface 77. In addition, the outer surface and inner surface 77 of each leg 70 each have a width that extends from one side surface 75 to the other. Such width tapers in a proximal-distal direction, which when combined with the curvatures of second bulbous surface 76, results in legs 70 narrowing to a point at terminal end 78, as best shown in
When insert 60 is at rest, legs 70 are biased toward a first position or expanded configuration is shown in
Once the intramedullary canal is prepared and with guidewire 80 disposed within and extending from the proximal femur, nail 40 is advanced over guidewire 80 and into the intramedullary canal. Nail 40 is preferably provided with coupling insert 60 pre-assembled with nail 40. In this regard, coupling insert 60 is shipped to the operating theater with the coupling insert 60 already inserted into central bore 41. Alternatively, coupling insert 60 is inserted into bore 41 of nail 40 in the operating theater prior to insertion into femur 10. This may be done by using a driver to thread head portion 62 of coupling insert 60 to second threaded section 45 of nail 40. In this regard, first threaded section 43 is generally of a larger cross-sectional dimension than that of second threaded section 45 such that coupling insert 60 is passed through first threaded section 43 without engagement of threads 64 therewith. However, in some embodiments, first and second threaded sections 43, 45 may have the same cross-sectional dimension or they may blend together to form a single, longer threaded section. Regardless of where coupling insert 60 is inserted into bore 41, it is preferably done prior to insertion of nail 40 into the patient's femur 10. This helps ensure threads 64 of coupling insert 60 are properly engaged with second threaded section 45 of nail 40. It also helps simplify the procedure as the operator does not have to insert coupling insert 60 into nail 40 while nail 40 is in the patient's bone 10. Thus, once nail 40 is inserted into femur 10, guidewire 80 passes through central bore 41 of nail 40 and also through through-opening 61 of coupling insert 60, as best shown in
In order to help ensure that coupling insert 60 is not inserted too deeply when pre-loading nail 40, head portion 62 may be configured such that a limited number of turns of coupling insert 60 relative to second threaded section 45 can be achieved to couple insert 60 with nail 40 without moving legs 70 or without moving legs 70 too much that guidewire 80 cannot be advanced therethrough. For example, threads 64 may be configured such that 1 to 3 complete turns of coupling insert 60 would be effective to pre-load insert 60 without concerns that insert would move out of engagement with threaded section 45 during transport and implantation and that through-opening 61 would be obstructed. In another embodiment, a recess (not shown) may be positioned between first and second threaded sections 43, 45, and first and second threaded sections 43, 45 may both be engageable with threads 64 of head portion 62. In this regard, head portion 62 can be threaded through first threaded section 43 and into the recess between first and second threaded sections 43, 45 so as to secure insert 60 while nail 40 is transported and implanted. In such position, legs would be in their expanded configuration. Thereafter, insert 60 can be advanced from the recess and into engagement with second threaded section 45.
Thereafter, guidewire 80 is removed by advancing guidewire 80 through nail 40 and coupling insert 60 and out of femur 10. At this point, lag screw 20 may be passed through transverse bore 49, across the fracture, and into the femoral neck and head. Lag screw 20 is rotated so that one of its grooves 24 is aligned with central bore 41 of nail and faces superiorly toward coupling insert 60, as shown in
With the lag screw 20 properly inserted, a driver 90 is inserted into central bore 41 and into through-opening 61 of coupling insert 60 so that an operative end of driver 90 engages tool surface 63 within head portion 62, as also shown in
Continued advancement of coupling insert 60 eventually results in the legs 70 coming together and contacting each other such that terminal ends 78 of each leg 70 are aligned with groove 24 of nail 20 and such that second bulbous surface 76 of each leg come together to form the rounded nub, which is configured to match the curvature of groove 24, as shown in
At this point, first bulbous surface 74 is advanced beyond conical camming surface 46. It is noted that the narrowest cross-sectional dimension of conical section 2 is such that it allows for legs 70 to be brought together into contact with each other but still allow advancement into cylindrical section 4. In this regard, the cross-sectional dimension of the narrowest part of conical section 2 and also of the cylindrical section 4 is slightly larger than that of coupling insert 60 as measured at the cylindrical-curved surfaces 72 of legs 70 when legs 70 are in their contracted position.
When first bulbous surfaces 74 of legs 70 advance into cylindrical section 4 and legs 70 are brought together, cylindrically-curved surfaces 72 of legs 70 form an approximate cylindrical form that fits within cylindrical section 4. However, due to the bias of legs 70, cylindrically-curved surfaces 72 bear against cylindrical surface 48 creating frictional resistance to back-out of coupling insert 60, as best shown in
End cap 50 may then be inserted into central bore 41 and threaded to first threaded section 43. Also, bone screw 30 may be passed through distal portion 44 of nail 40 for further fixation.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.
This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 62/861,017, filed Jun. 13, 2019, the disclosure of which is hereby incorporated herein by reference.
Number | Date | Country | |
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62861017 | Jun 2019 | US |