Abstract
A fixation device for treating an epiphyseal fracture, comprises a shaft extending longitudinally along a central axis from a first end to a second end configured to slidably engage a bone implant opening and a having a maximum radius r and a spherical head element attached to the first end of the shaft and having a radius R>r, the spherical head element configured to be inserted into a fragmented portion of bone such that the fragmented portion rotates about the spherical head element relative to the central axis of the shaft.
Claims
1. A fixation device for treating an epiphyseal fracture of a long bone, comprising: a shaft extending longitudinally along a central axis from a first end to a second end configured to slidably engage an opening of a bone implant, the central axis of the shaft being coaxial with a central axis of the device; a bone anchoring element pivotally coupled to the first end of the shaft, the bone anchoring clement including a spherical cavity, wherein the central axis of the shaft extends through a center of the spherical cavity, the spherical cavity mechanically retaining a ball at the first end of the shaft therein to form a ball and socket joint so that, the bone anchoring element is pivotable relative to the central axis of the shaft, the bone anchoring element further including a threading extending about an outer surface thereof for engaging a fragment portion of bone when inserted therein, wherein the shaft is sized such that, during use, the shaft extends through a neck of the bone and the ball extends at least partially into a head of the long bone.
2. The device according to claim 1, wherein the bone anchoring element is longitudinally movable relative to the central axis of the shaft.
3. The device according to claim 1, wherein the bone anchoring element is not coaxial with the central axis of the shaft.
4. The device according to claim 1, wherein the spherical cavity includes a tapered proximal end.
5. The device according to claim 1, wherein a diameter of the bone anchoring element is larger than a diameter of the shaft.
6. A system for treating an epiphyseal fracture of a long bone, comprising: an elongated bone implant extending along a longitudinal axis and including an opening extending therethrough; and a bone fixation device, including: a shaft extending along a central axis from a distal end to a proximal end configured to slidably engage the opening of the bone implant, the central axis of the shaft being coaxial with a central axis of the bone fixation device; and a bone anchoring element pivotally coupled to the distal end of the shaft by a ball and socket joint and having a diameter that is larger than a diameter of the shaft, wherein the central axis of the shaft extends through a center of the ball and socket joint, the bone anchoring element including a threading extending around an outer surface thereof for engaging bone which it is inserted wherein the shaft is sized such that, during use, the shaft extends through a neck of the long bone and the ball extends at least partially into a head of the long bone.
7. A method for treating an epiphyseal fracture of the long bone comprising the following steps: positioning a guide wire in a long bone in a direction transverse to a longitudinal axis of the long bone and penetrating through a shaft fragment of the long bone and into an epiphyseal fragment; drilling a bore hole into the long bone from a lateral surface thereof; and threading a fixation device into the bore hole so that a bone anchoring element pivotally coupled to a distal end of a shaft via a ball and socket joint is positioned within a desired portion of a fragmented bone portion such that the fragmented bone portion is pivotable relative to a central axis of the shaft when the fixation device is in an inserted position, wherein in the inserted position, the shaft extends through a neck of the long bone and the ball and socket joint extends at least partially into a head of the long bone, the central axis of the shaft being coaxial with a central axis of the fixation device, and wherein the central axis of the shaft extends through a center of the ball and socket joint.
8. The method according to claim 7, further comprising positioning a bone implant along a length of the long bone such that a proximal portion of the longitudinal shaft slidably engages an opening thereof.
9. The method according to claim 8, wherein positioning the bone implant includes inserting an intramedullary nail into the medullary cavity of the long bone.
10. The method according to claim 8, wherein positioning the bone implant includes arranging a bone plate along a portion of a length of the bone.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Several embodiments of the invention will be described in the following by way of example and with reference to the accompanying drawings in which:
(2) FIG. 1 illustrates a lateral view of an embodiment of the bone implant according to the invention;
(3) FIG. 2 illustrates a lateral view of the embodiment of the bone implant of FIG. 1 with the femoral head fragment rotated about the spherical head element;
(4) FIG. 3 illustrates a lateral view of another embodiment of the bone implant according to the invention;
(5) FIG. 4 illustrates a lateral view of the embodiment of the bone implant of FIG. 3 with the femoral head pivoted and the fracture gap closed;
(6) FIG. 5 illustrates a top view of the embodiment of the bone implant of FIG. 3;
(7) FIG. 6 illustrates a top view of the embodiment of the bone implant of FIG. 3 with the femoral head pivoted and the fracture gap closed;
(8) FIG. 7 illustrates a lateral view of again another embodiment of the bone implant according to the invention;
(9) FIG. 8 illustrates an exploded view of the fixation element of the embodiment of FIG. 3 and an insertion tool;
(10) FIG. 9 illustrates a longitudinal section through the fixation element of the embodiment of FIG. 3 together with an insertion tool;
(11) FIG. 10 illustrates a longitudinal section through a fixation element of a further embodiment of the bone implant according to the invention;
(12) FIG. 11 illustrates a lateral view of an anchoring element of another embodiment of the bone implant according to the invention;
(13) FIG. 12 illustrates a front view of the anchoring element of FIG. 11 viewed in the direction A indicated in FIG. 11;
(14) FIG. 13 illustrates a lateral view of an anchoring element of a further embodiment of the bone implant according to the invention;
(15) FIG. 14 illustrates a front view of the anchoring element of FIG. 13 viewed in the direction B indicated in FIG. 13;
(16) FIG. 15 illustrates a lateral view of an anchoring element of again a further embodiment of the bone implant according to the invention;
(17) FIG. 16 illustrates a front view of the anchoring element of FIG. 15 viewed in the direction C indicated in FIG. 15;
(18) FIG. 17 illustrates a longitudinal section through the fixation element of the embodiment of the bone implant according to FIG. 3;
(19) FIG. 18 illustrates a longitudinal section through a fixation element of another embodiment of the bone implant according to the invention;
(20) FIG. 19 illustrates a lateral view of a fixation element of again another embodiment of the bone implant according to the invention;
(21) FIG. 20 illustrates a lateral view of a fixation element of yet another embodiment of the bone implant according to the invention;
(22) FIG. 21 illustrates a lateral view of a fixation element of still another embodiment of the bone implant according to the invention;
(23) FIG. 22 illustrates a lateral view of a fixation element of a further embodiment of the bone implant according to the invention;
(24) FIG. 23 illustrates a longitudinal section through a further embodiment of the bone implant in case of a treatment of a subcapital humeral head fracture;
(25) FIG. 24 illustrates a longitudinal section through the embodiment of the bone implant of FIG. 23 with the fracture gap after dynamization;
(26) FIGS. 25a and 25b illustrate the maximal axial dynamization in a longitudinal section through a front portion of a fixation element of the embodiment of the bone implant according to FIG. 23;
(27) FIG. 26 illustrates the maximal angulation without axial dynamization in a longitudinal section through a front portion of a fixation element according to FIG. 23;
(28) FIG. 27 illustrates a lateral view of another embodiment of the bone implant according to the invention;
(29) FIG. 28 illustrates a front view of the embodiment of the bone implant according to FIG. 27 viewed in the direction indicated by arrow A in FIG. 27;
(30) FIG. 29 illustrates a lateral view of the embodiment of the bone implant of FIG. 27 with the femoral head fragment rotated about the spherical head element;
(31) FIG. 30 illustrates a lateral view of the embodiment of the bone implant of FIG. 27 with the rotated femoral head fragment displaced in a proximal direction;
(32) FIG. 31 illustrates a sectional view of yet another embodiment of the bone implant according to the invention in a first non-expanded configuration;
(33) FIG. 32 illustrates a section view of the embodiment shown in FIG. 31 in a second expanded configuration;
(34) FIG. 33 illustrates a sectional view of a part of the bone implant shown in FIG. 31 in the first non-expanded configuration; and
(35) FIG. 34 illustrates a sectional view of a part of the bone implant shown in FIG. 31 in the second expanded configuration.
DETAILED DESCRIPTION
(36) The present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The present invention relates to a device for treating fractures and, in particular, relates to a device for treating a fracture in an epiphyseal portion of a long bone such as a femur. Exemplary embodiments of the present invention describe a fixation element that may be used with an implant such as a bone plate or an intramedullary nail to be inserted via a lateral surface of the bone through the fracture and into a head portion thereof. The fixation element comprises a longitudinal shaft including a spherical portion at an end thereof, which is positioned within the head portion of the bone such that the head portion is pivotable about the spherical portion to facilitate proper reduction of the fracture. It should be note that the terms proximal and distal, as used herein, are intended to refer to a direction toward (proximal) and away from (distal) a user of the device.
(37) As shown in FIGS. 1 and 2, an implant 1 according to an exemplary embodiment of the present invention comprises a fixation element 2 configured as a hip screw for treating a femoral neck fracture and a bone plate 6. The fixation element 2 includes a shaft 5 extending longitudinally along a central axis 17 from a first distal end 47 to a second proximal end 48 and a spherical head element 3 at the first end 47. The spherical head element 3 has a center 15 and a diameter D that is larger than a diameter d of the shaft 5. The spherical head element 3 may be integrally formed with the shaft 5 or coupleable to the first end 47 of the shaft 5. The diameter d of the shaft 5 may be about 75% of the diameter D of the spherical head element 3. Further, the fixation element 2 may also include a cannulation 21 extending through the fixation element 2 coaxially with the central axis 17.
(38) The bone plate 6 includes a longitudinal body portion 53 and a barrel 23 extending transversely from the body portion 53. The body portion 53 according to this embodiment sized and shaped to be attached to a long bone 4 (e.g., the femur) and includes an opening sized and shaped to receive therethrough a bone fixation screw 24 for fixing the bone plate 6 to the bone. The barrel 23 includes a through hole 25 sized and shaped to slidably accommodate the shaft 5 of the fixation element 2 such that the spherical head element 3 extends distally past a distal end of the barrel 23. The slidable arrangement between the shaft 5 and the barrel 23 of the bone plate 6 permits the fixation element 2 to be moved relative to the bone plate 6 along the central axis 17 of the fixation element 2, facilitating dynamization of the fracture in the direction of the central axis 17 of the fixation element 2. The fixation element 2 extending through the barrel 23 also provides angular stability between the fixation element 2 and the bone plate 6.
(39) In use, the barrel 23 is positioned over the shaft 5 after the spherical head element 3 has been located correctly in a bone fragment. The shaft 5 is slidable within the barrel 23 and is able to move, for example, post-operatively. In this way, a reduction of the bone fragment is achieved under the natural influence of the muscles, gravity, etc., trying to return to the bone to its original pre-fracture configuration. The fixation element 2 remains in position post-operatively due to the same natural influences. However, as would be understood by the skilled person additional features can be used to resist unexpected or unwanted movement of the fixation element 2. For example, the internal diameter of the barrel 23 can be sized to provide friction forces that resist movement other than the movement due to the natural influences. In another example, an o-ring type device can be used to resist the unwanted movement. Other ways are of course possible, as the skilled person would understand.
(40) A bore hole 10 is drilled into the proximal femur from a lateral surface of the femur substantially coaxial with or parallel to the axis of the femoral neck. The bore hole 10 has a diameter corresponding to the diameter D of the spherical head element 3 so that the spherical head element 3 fits through the bore hole 10 to be positioned in the femoral head. The fixation element 2 is advanced through the bore hole 10 in the proximal femur until the spherical head element 3 reaches an end of the bore hole 10 and the femoral head fragment is seated on the spherical head element 3. Since the diameter of the bore hole 10 in the proximal femur is larger than the diameter d of the shaft 5, the femoral head fragment is polyaxially rotatable about the center 15 of the spherical head element 3 within a predetermined range of angulation.
(41) In some cases where the femoral neck fracture is improperly and/or inadequately reduced prior to the placement of the fixation element 2, the two bone fragments will have only a limited contact area relative to each other, as shown in FIG. 1. The dynamization alone, i.e. a coaxial movement of the fixation element 2 towards the bone plate 6, cannot compensate for inadequate fracture reduction. It will be understood by those of skill in the art that an insufficient fracture contact area may lead to delayed fracture healing which in turn may lead to cyclic overload of the anchorage of the fixation element 2 in the femoral head. A cyclic overload may result in implant loosening and/or implant cutout. An insufficient fracture reduction often occurs in the sagittal plane as the visualization in this plane is very difficult during surgical intervention.
(42) Rotation of the femoral head fragment about the center 15 of the spherical head element 3 at least partially compensates for inadequate fracture reduction. Thus, as illustrated in FIG. 3, fracture stability is improved via both the axial dynamization and rotation of the femoral head fragment since the physiological load is spread over a larger contact area of the bone fragments.
(43) As shown in FIGS. 3 to 6, a bone implant 100 according to another exemplary embodiment of the present invention is substantially similar to the bone implant 1, as described above. The bone implant 100 comprises a fixation element 102 configured as a hip screw for treating a femoral neck fracture and a bone plate 106. The bone plate 106 is substantially similar to the bone plate 6, comprising a longitudinal body portion 153 and a barrel 123 extending transversely therefrom. The fixation element 102 is also substantially similar to the fixation element 2, but further comprises an anchoring element 108 coupled to a first end 147 of a longitudinal shaft 105 thereof such that the fixation element 102 may be anchored in the femoral head portion of the bone.
(44) The fixation element 102 includes a shaft 105 extending longitudinally along a central axis 117 from a first end 147 to a second end 148 and a spherical head element 103 at the first end 147. The spherical head element 103 has a center 115 and a diameter D larger than a diameter d of the shaft 105. The diameter d may be approximately 75% of the diameter D of the spherical head element 103.
(45) The fixation element 102 further comprises the anchoring element 108 coupled to the spherical head element 103. The anchoring element 108 includes a spherical cavity 109 sized and shaped to receive the spherical head element 103 so that a ball-and-socket joint is formed between the anchoring element 108 and the shaft 105. The anchoring element 108 has an external thread 120 with a diameter D.sub.A configured to be screwed into the femoral head fragment. Further, the fixation element 102 includes a cannulation 121 extending through said the shaft 105, the spherical head element 103 and the anchoring element 108 of the fixation element 102 coaxial or parallel to the central axis 117.
(46) Similarly to the embodiment of FIGS. 1 and 2, a bore hole 110 is drilled into the proximal femur from the lateral surface of the femur to extend coaxially with or parallel to the axis of the femoral neck. The bore hole 110 has a diameter corresponding to the core diameter of the external thread 120 of the anchoring element 8 so that the external thread 120 can cut into the bone tissue of the femoral head fragment. Thus, the femoral head fragment is fixed to the anchoring element 108 once the anchoring element 108 has been completely advanced into the bone.
(47) The fixation element 102 is advanced into the bore hole 110 in the proximal femur until the anchoring element 108 is positioned at an end of the bore hole 110 with the femoral head fragment seated on the spherical head element 103 via the anchoring element 108. Because the diameter of the bore hole 110 in the proximal femur is larger than the diameter d of the shaft 5, the femoral head fragment is polyaxially rotatable about the center 15 of the spherical head element 103 within a predetermined range of angulation.
(48) Similarly to the bone implant 1 described above, the shaft 105 of the fixation element 102 is slidably received through a through hole 125 of a barrel portion 123 of the bone plate 106. The slidable arrangement of the longitudinal shaft 105 in the through hole 125 facilitates dynamization of the fracture in the direction of the central axis 117 of the fixation element 102 as well as an angular stability between the fixation element 102 and the bone plate 106. Similarly to FIG. 1, FIGS. 3 and 5 illustrate an improper and/or inadequate reduction of a femoral neck fracture prior to the placement of the fixation element 102 such that the two bone fragments have only a limited contact area relative to with one another. The dynamization alone, i.e. coaxial movement of the fixation element 102 towards the bone plate 106, will not fully compensate for the inadequate fracture reduction. As shown in FIGS. 4 and 6, however, the fixation element 102 permits rotation of the anchoring element 108 and, consequently, of the femoral head fragment in which the anchoring element 108 is implanted, about the center 115 of the spherical head element 103, at least partially compensating for the inadequate fracture reduction. The axial dynamization along with the rotation of the femoral head fragment together are able to compensate for the inadequate reduction by spreading the physiological load over a larger contact area of the bone fragments.
(49) FIG. 7 illustrates a bone implant 200 that is substantially similar to the bone implant 100, as described above, but comprises a fixation element 202 inserted through a portion of an intramedullary nail 207 instead of a bone plate. The fixation element 202 is substantially similar to the fixation element 102 and is configured as a hip screw comprising a longitudinal shaft 205 including a spherical head element 203 at an end thereof and an anchoring element 208 that can be screwed into the femoral head and that has a spherical cavity 209 for receiving the spherical head element 203. As those of skill in the art will understand, the shaft 205 may be slidable within a barrel 223. However, in this embodiment, the shaft 205 is integrally formed with the barrel 223. In this way, the fixation element 202 has the shaft portion 205 and the barrel portion 223, the shaft portion 205 being of a smaller diameter than the barrel portion 223. The fixation element 202 is slidably arranged in a through bore 222 extending through the intramedullary nail 207 transversely relative to a longitudinal axis of the intramedullary nail 207. The slidable arrangement of the fixation element 202 in the through bore 222 in the intramedullary nail 207 permits the fixation element 202 to be moved axially relative to a central axis of the through hole 222 to facilitate dynamization of the fracture in the direction of the central axis 217 of the fixation element 202 while enhancing an angular stability between the fixation element 202 and the intramedullary nail 207. Similarly to the bone fixation element 102, the anchoring element 208 and, consequently, the femoral head fragment in which the anchoring element 208 is implanted, is permitted to rotate about the spherical head element 203 to compensate for inadequate fracture reduction.
(50) FIGS. 8 and 9 illustrate a hollow insertion tool 130 for inserting the anchoring element 108 into the femoral head fragment. It will be understood by those of skill in the art, however, that the hollow insertion tool 130 may be used for the insertion of any of the anchoring elements described herein. The hollow insertion tool 130 includes protrusions 132 at a distal end 133 thereof for engaging a diametrically extending groove 131 with a substantially rectangular cross section at a proximal end 134 of the anchoring element 108 so that the hollow tube 130 may be used to apply a driving (e.g., rotational) force to the anchoring element 108. A shown by FIGS. 8 and 9, the groove 131 is located in a wall of the bone anchoring element 108. In use, after the fixation element 102 including the shaft 105 and anchoring element 108 are inserted, the insertion tool 130 is slid over the shaft 105 to rotate the anchoring element 108. That is, the protrusions 132 are engaged with the grooves 131 and the insertion tool 130 is rotated to screw the anchoring element 108 into the bone fragment. Since the fixation element 102 includes a cannulation 121 extending through the bone anchoring element 108 and the longitudinal shaft 105, the bone anchoring element 108 may be slid along a guiding element, e.g. a Kirschner-wire, when the bone anchoring element 108 is advanced into the bone using the hollow insertion tool 130. As would be understood by the skilled person, the insertion tool 130 can be any suitable size to allow rotation thereof, for example, the shaft of the insertion tool 130 that extends along the longitudinal shaft 105 can be sized so that it extends externally of the bone implant and can be directly manipulated by the operator or surgeon.
(51) As shown in FIG. 10, a fixation element 302 according to a further embodiment of the present invention is substantially similar to the anchoring element 102 of the bone implant 100, but differs from the fixation element 102 only in that a head element 303 and a cavity 309 in the bone anchoring element 308 each have flattened surface portions 311, 312, respectively, which correspond to one another so that the head element 303 and the cavity 309 are only partially spherical. The flattened surface portions 311, 312 are limited in a cross section orthogonal to a central axis 317 of the fixation element 302 by circular edges 313, 314, respectively, with each circular edge 313, 314 located between two of the flattened surface portions 311, 312. A center formed via the circular edges 314 of the cavity 309 coincides with a center 315 of the head element 303 formed by the circular edges 313. When the spherical head element 303 is inserted in the spherical cavity 309 in the bone anchoring element 308 the bone anchoring element 308 is rotatable in a variety of planes containing the central axis 317 with each plane being defined by one pair of engaged circular edges 313, 314. Thus, the head element 303 and the 309 each have a hexagonal cross-sectional area orthogonal to the central axis 317 of the fixation element 302.
(52) As shown in FIGS. 11 and 12, an anchoring element 408 according to an alternate embodiment is substantially similar to the anchoring element 108 of the bone implant 100 and includes a cavity 409 for accommodating a head element 403 of the bone fixation element 402. However, rather than an external thread, the anchoring element 408 includes a blade 433 extending distally therefrom to engage a femoral head bone fragment when implanted therein.
(53) As shown in FIGS. 13 and 14, an anchoring element 508 according to a further embodiment is substantially similar to the anchoring element 408. The anchoring element 508, however, comprises a cross blade 534. The cross blade 534 includes first and second blade portions 535, 536, respectively, arranged substantially perpendicularly relative to one another when implanted therein.
(54) As shown in FIGS. 15 and 16, an anchoring element 608 according to a further embodiment is substantially similar to the anchoring element 408. However, the anchoring element 608 includes a helical blade 635 extending distally therefrom to engage the formal head bone fragment when implanted therein.
(55) FIG. 17 illustrates a fixation element 702 according to another exemplary embodiment that is substantially similar to the fixation element 102 of the bone implant 100. The fixation element 702, however, comprises an anchoring element 708 including an opening 718 extending from the proximal end 734 of the anchoring element 708 to the spherical cavity 709. A diameter of the opening 718 decreases towards the spherical cavity 709 so that the opening 718 is largest at the proximal end 734 to allow a greater range of angulation between a shaft 705 of and the anchoring element 708. The spherical cavity 709 tapers toward the proximal end 734 so that the spherical head element 703 may be snapped into and/or retained therein.
(56) FIG. 18 illustrates a fixation element 802 according to another embodiment that is substantially similar to the fixation element 102, but which differs therefrom only in that a spherical cavity 809 in the bone anchoring element 808 is open to and arranged closer to a proximal end 834 of the bone anchoring element 808. The cavity 809 extends over an angle which is only little over 180 so that a spherical head element 803 is retained therein while also permitting the bone anchoring element 808 to rotate within a suitable angular range with respect to the central axis 817 without the proximal end 834 of the anchoring element 808 interfering with the shaft 805.
(57) FIG. 19 illustrates a fixation element 902 according to another embodiment that is substantially similar to the fixation element 102, described above. The fixation element 902, however, does not include a spherical head element and a corresponding spherical cavity. Rather, the fixation element 902 comprises an anchoring element 908 coupled to a first end 947 of a longitudinal shaft 905 via a cardan joint 936.
(58) FIGS. 20 to 22 illustrate a fixation element 1002 according to another embodiment substantially similar to the fixation element 902. Rather than a cardan joint, however, the bone anchoring element 1008 is coupled to a first end 1047 of a shaft 1005 via a compliant member 1026. The compliant member 1026 may comprise an elastomer, as illustrated in FIG. 20, or be configured as a bellows 1027, as illustrated in FIG. 21, or as a spring, preferably a helical spring 1028, as illustrated in FIG. 22.
(59) As shown in FIGS. 23 and 24, a bone implant 1100 according to a further embodiment of the present invention may be used for treating of a subcapital humeral head fracture. The bone implant 1100 comprises a fixation element 1102 and a sleeve 1137.
(60) The fixation element 1102 comprises a shaft 1105, a spherical head element 1103 and an anchoring element 1108. The shaft 1105 extending longitudinally along a central axis 1117 from a first distal end 1147 to a second proximal end 1148. The first end 1147 includes a head 1138 having an enlarged diameter. The spherical head element 1103 may be slidably arranged on a distal portion 1144 of the shaft 1105, proximally of the distal head 1138 of the shaft 1105, such that the shaft 1105 extends through a center 1115 of the spherical head element 1103. A diameter d of the shaft 1105 may be approximately 50% of a diameter D of the spherical head element 1103. A proximal portion 1145 of the shaft 1105 includes a hole 1146a extending transversely therethrough, the hole 1146a configured to receive a shaft portion of a bone screw 1124 therethrough.
(61) The anchoring element 1108 includes a cavity 1139 extending distally from the proximal end 1134 thereof. The cavity 1139 includes an opening 1118 tapering toward a distal end of the anchoring element 1108 and open to a partially spherical section 1140 having the diameter D for receiving the spherical head element 1103 in a polyaxially rotative manner. A diameter of the opening 1118 decreases towards the spherical section 1140 so that the opening is largest at the proximal end 1134 to permit a greater range of angulation is permitted between the longitudinal shaft 1105 of the fixation element 1102 and the anchoring element 1108. The spherical section 1140 includes curved surfaces having a diameter at proximal and distal ends thereof that is smaller than a diameter of a midsection thereof so that the spherical head element 1103 is retained in the spherical section 1140 of the anchoring element 1108. The cavity 1139 further comprises a cylindrical section 1141 extending distally from the spherical section 1140 toward a distal end 1142 of the cavity 1139 for accommodating the head 1138 of the shaft 1105. The anchoring element 1108 is slidable between an extended state where the head 1138 of the shaft 1105 abuts against the spherical head element 1103 and a shortened state where the head 1138 of the shaft 1105 abuts against the distal end 1142 of the cavity 1139. The anchoring element 1108 may have an external thread 1120 configured to be screwed into the femoral head fragment. Further, the fixation element 1102 may comprise a cannulation 1121 extending through the shaft 1105 and the anchoring element 1108 substantially coaxially to the central axis 1117.
(62) Alternatively, as similarly described in the embodiments above, the bone anchoring element 1108 can be slidably and articulately coupled to the longitudinal shaft 1105 via a cardan joint or the bone anchoring element 1108 may be slidably and flexibly linked to the longitudinal shaft 1105 via a compliant member such as, for example, a metallic or plastic bellow, a metallic or plastic spring or an elastomeric element.
(63) The sleeve 1137 extends longitudinally along the central axis 1117 from a proximal end 1149 to a distal end 1150 and includes a central bore 1143 sized and shaped to receive a proximal portion 1145 of the shaft 1105 therein. The sleeve 1137 includes a hole 1146b extending transversely through a portion thereof such that when the sleeve 1137 is slide over the proximal portion 1145 of the shaft 1105, the hole 1146b aligns with the hole 1146a in the shaft 1105 to permit the screw 1124 to be inserted through both holes 1146a, 1146b to fix the bone implant 1100 in the bone.
(64) A bore hole 1110 may be drilled into the proximal humerus from the lateral surface of the humerus extending obliquely relative to a longitudinal axis of the humerus. The bore hole 1110 has a diameter substantially corresponding to a core diameter of the external thread 1120 of the anchoring element 1108 so that the external thread 1120 cuts into the bone tissue of the humeral head fragment as the anchoring element 1108 is driven therein so that the humeral head fragment is fixed to the anchoring element 1108 once the bone anchoring element 1108 has been completely advanced into the bone.
(65) The anchoring element 1108 is advanced into the bore hole 1110 in the proximal humerus until the anchoring element 1108 is positioned at a distal end of the bore hole 1110 and the humeral head fragment is seated on the spherical head element 1103 via the anchoring element 1108. Because the diameter of the bore hole 1110 in the proximal humerus is larger than the diameter d of the shaft 1105 and the cavity 1139 in the anchoring element 1108 has an opening 1118 that is larger at the proximal end 1134 of the anchoring element 1108, the spherical section 40 permits the humeral head fragment to polyaxially rotate about the center 1115 of the spherical head segment 1103 within a predetermined range of angulation.
(66) Once the fixation element 1102 has been advanced into the bone, the sleeve 1137 is slid distally over said the proximal portion 1145 of the shaft 1105 of the fixation element 1102 and inserted into the portion of the bore 1110 which extends within the shaft fragment of the humerus. The shaft 1105 of the fixation element 1102 is axially guided within the central bore 1143 of the sleeve 1137. The transverse hole 1146a of the longitudinal shaft 1105 and the transverse hole 1146b of the sleeve 1137 are aligned to receive the bone screw 1124 to fix the sleeve 1137 and the fixation element 1102 in the bone. The spherical head segment 1103 and the anchoring element 1108 attached thereto are slidably arranged on the shaft 1105 of the fixation element 1102. The slidable arrangement between the shaft 1105 of the fixation element 2 and the anchoring element 1108 allows the anchoring element 1108 to move axially thus allowing a dynamization of the fracture in the direction of the central axis 1117 of the fixation element 1102 as illustrated in FIG. 24. A maximum axial displacement Z of the anchoring element 1108 relative to the shaft 1105 of the fixation element 1102 is limited by the head 1138 of the fixation element 1102 which abuts against the spherical head element 1103 when the anchoring element 1108 is in its fully advanced position, as shown in FIG. 25a, and which abuts the distal end 1142 of the cavity 1139 when the anchoring element 1108 is in its retracted position, as shown in FIG. 25b. The angulation between the anchoring element 1108 and the shaft 1105 of the fixation element 1102, as shown in FIG. 26, is limited by either the opening 1118 at the proximal end 1134 of the anchoring element 1108 or by the cylindrical section 1141 of the cavity 1139 which accommodates the head 1138 at the first end 1147 of the shaft 1105. Thus, the anchoring element 1108 and the shaft 1105 of the fixation element 1102 has a maximum angle of angulation .sub.max when the anchoring element 1108 is in its fully extended position as illustrated in FIG. 26.
(67) FIGS. 27 to 30 illustrate another exemplary embodiment of a bone implant 1200, which is substantially similar to the bone implant 1, as described above, comprising a fixation element 1202 which may be inserted through an opening of a bone plate 1206 into a femoral head bone fragment. The bone implant 1200, however, differs from the bone plate 1 only therein that the bone plate 1206 comprises a pivotable sleeve 1252 rather than a barrel fixed thereto. The sleeve 1252 extends through a bore 1251 in the bone plate 1206 and may be affixed to the bone plate 1206 via two radially extending connecting elements 1249, which permit the sleeve 1252 to pivot thereabout. The bore 1251 has a larger diameter than an outer diameter of the sleeve 1252 such that the sleeve 1252 may be pivoted within the bore 1251. In a cross-section orthogonal to a central axis 1217 of the shaft 1205, the two connecting elements 1249 are located on diametrically opposed sides of the sleeve 1252 and may be integrally formed with or coupled to the inner wall 1254 of the bore 1251. The connecting elements 1249 of the sleeve 1252 may be received within corresponding recesses in the inner wall 1254 of the bore 1251 such that the sleeve 1252 is pivotably coupled to the bore 1251. Alternatively, the connecting elements 1249 may be integrally formed with or fixed to the sleeve 1252 such that the connecting elements 1249 may be plastically deformed to define a pivot axis 1253 extending orthogonal to the central axis 1217 of the shaft 1205. Thus, the connecting elements 1249 form a joint 1250 including two coaxially arranged and plastically deformable pivot pins between the sleeve 1252 and the bore hole 1251 of the bone plate 6. Alternatively, the joint 1250 may be configured as a cardan joint including two pairs of pivot pins orthogonally arranged with respect to each other.
(68) Various embodiments of an osteosynthetic implant including an embedded hinge or cardan joint are described in U.S. Pat. No. 6,663,632 to FRIGG. The entire content of the aforementioned document is incorporated herein by reference thereto.
(69) As illustrated in FIG. 27, the fixation element 1202 is inserted through a bore hole 1210 drilled into the bone such that the spherical head element 1203 is seated within the femoral head bone fragment. The sleeve 1252 is mounted on a proximal portion of the shaft 1205 so that the femoral head fragment may pivot about the spherical head element 1203, as illustrated in FIG. 29. The bone implant 1200 then permits the femoral head to be displaced in a direction A, as shown in FIG. 30, by pivoting the sleeve 1252 about a pivot axis 1253 defined by the connecting elements 1249 as indicated by arrow B in FIG. 30. The sleeve 1252 is pivoted about the pivot axis 1253 via, for example, a relatively long lever instrument which exerts a large force onto the plastically deformable connecting elements 1249. The force exerted onto the connecting elements 1249 via the lever is much higher than any force which can occur anatomically on the femoral head so that once the deformation of the connecting elements 1249 has taken place, the connecting elements 1249 remain stable (e.g., deformed) providing sufficient stability to the bone implant 1200. It will be understood by those of skill in the art that the above-described articulated connection between the shaft 1205 of the fixation element 1202 and the bone plate 1206 via the sleeve 1252 may be similarly applied to a bone implant including an intramedullary nail, as shown in FIG. 7, rather than a bone plate. Where bone implant 1200 comprises an intramedullary nail, the sleeve 1252 may be configured as a bushing insertable through a through bore and coupleable thereto via a connection similar to the above described joint 1250. Similarly, the above-described articulated connection may also be applied to the bone implant 1100, as shown in FIGS. 23 and 24.
(70) Another exemplary embodiment of the present invention is shown in FIGS. 31 to 34. This embodiment of a bone implant 1300 is substantially similar to embodiments shown in FIGS. 1, 2, 27, 28 and 29. In this exemplary embodiment the bone implant 1300 comprises a fixation element 1302 including a spherical head element 1303 that is expandable to increase the radius from a first radius to a second radius for anchoring the fixation element in the bone fragment. The spherical head element 1303 has a slit arranged to divide it into expandable parts 1303a, 1303b. The expandable parts 1303a, 1303b are connected at proximal ends 1350a, 1350b to a shaft 1305. The opposed distal ends 1351a, 1351b of the expandable parts 1303a, 1303b are unconnected and are expandable relative to the connection point at the proximal end 1350a, 1350b. As would be understood by the skilled person, the expandable parts 1303a, 1303b can have a uniform separation across the slit, they can taper from the proximal end to the distal end, or they can have any other suitable starting, reduced diameter, configuration. A cannulation 1321 within the shaft 1305 that allows, for example, a K-wire to be received by the fixation element 1302 for guidance purposes can extend into the spherical head element 1303. To expand the expandable parts 1303a, 1303b, a tool 1360 with a tapered engagement end (not shown) is pushed down the cannulation and into engagement with the expandable parts 1303a, 1303b. The spherical head element 1303 shows two expandable parts 1303a, 1303b. However, as would be understood by the skilled person, the spherical head element can be divided into any number of expandable parts to allow the head element 1303 to be expanded.
(71) In the embodiment where the expandable parts have uniform separation across the slit, the diameter of the cannulation 1321 is greater than the separation. The tool 1360, having a greater diameter than the separation, is inserted into the spherical head element 1303 to expand the head element 1303. The expansion from the reduced diameter configuration to the increased diameter configuration is achieved by pushing the tool 1360 in between the expandable parts 1303a, 1303b to force them apart due to the greater diameter of the tool 1360.
(72) In the embodiment where the expandable parts 1303a, 1303b taper towards each other, the cannulation 1321 can have the same diameter or an increased diameter depending on the amount of expansion required. As would be understood by the skilled person, the expansion is achieved due to the tool acting on the wall to straighten or expand the taper.
(73) Although the invention and its advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, composition of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. It will be appreciated by those skilled in the art that various modifications and alterations of the invention can be made without departing from the broad scope of the appended claims. Some of these have been discussed above and others will be apparent to those skilled in the art.
