Rod reduction device

Abstract

An orthopedic bone rod reduction device and method is disclosed. The device includes an actuator having a drive surface and a bone rod engagement element for engaging with a bone rod. The assembly further includes a spring positioned between the drive surface of the actuator and the rod engagement element. The rod reduction assembly controls movement of a bone rod relative to a bone anchor positioned in a bone.

Claims

1. An orthopedic rod reduction device comprising: an actuator having a drive surface; a rod engagement element for engaging a rod and moving the rod upon movement of the actuator, and a spring positioned between the drive surface of the actuator and the rod engagement element.

2. The orthopedic rod reduction device of claim 1, wherein the actuator comprises a drive head having upper and lower opposed surfaces and further, a drive shaft which extends from a proximal end connected to the lower surface of the head member to a distal end which is connected to the rod engagement element.

3. The orthopedic rod reduction device of claim 2, wherein the drive shaft includes an internal lumen.

4. The orthopedic rod reduction device of claim 3, wherein the spring is at least partially housed within the internal lumen of the elongate shaft.

5. The orthopedic rod reduction device of any one of claims 2 to 4, wherein a length of the drive shaft includes a threaded outer surface.

6. The orthopedic rod reduction device of any one of claims 2 to 5, further comprising a support having a proximal head and a bone anchor engaging portion which extends distally from the proximal head.

7. The orthopedic rod reduction device of claim 6, wherein the proximal head includes a passage defined by at least a partially threaded portion of an internal wall of the proximal head, said passage configured to receive at least a length of the drive shaft.

8. The orthopedic rod reduction device of claim 7, wherein the thread of the partially threaded portion of the internal wall of the proximal head is complementary to the thread of the drive shaft.

9. The orthopedic rod reduction device of claim 8, wherein the drive head is rotatably moveable relative to the proximal head of the support and rotation of the drive head relative to the proximal head of the support effects a linear translational movement of the drive head and drive shaft relative to the proximal head.

10. The orthopedic rod reduction device of any one of claims 6 to 9, wherein the bone anchor engaging portion of the support includes a plurality of elongate legs each extending distally from the proximal head from a first end to a second end, the second end of the elongate legs including one or more bone anchor engaging elements to secure the support to the bone anchor.

11. The orthopedic rod reduction device of any one of claims 6 to 9, wherein the bone anchor engaging portion of the support includes a substantially tubular body which extends distally from the proximal head, the distal end of the tubular body comprising one or more bone anchor engaging elements to secure the support to the bone anchor.

12. The orthopedic rod reduction device of any one of claims 2 to 11, wherein the spring extends from a proximal end to a distal end within the internal lumen of the drive shaft and wherein, the proximal end of the spring engages the lower surface of the drive head.

13. The orthopedic rod reduction device of any one of claims 2 to 12, wherein the distal end of the drive shaft engages the rod engagement element.

14. The orthopedic rod reduction device of claim 13, wherein the rod engagement element includes a base member having a proximal facing surface, a distal facing surface and a spring engagement element which extends from the proximal facing surface and extends into the internal lumen of the drive shaft to engage the distal end of the spring.

15. The orthopedic rod reduction device of claim 14, wherein the spring comprises a helically wound spring member which engages at its proximal end to the drive head and at its distal end to the rod engagement element and which is moveable between a first natural state and a second energy absorbing state, wherein rotation of the drive head and the subsequent linear movement of the drive head causes compression of the spring between the drive head and the rod engagement element to cause the spring to move to its second energy absorbing state.

16. The orthopedic rod reduction device of claim 15, wherein the second energy absorbing state of the spring is achieved by a pre-determined number of rotations of the drive head, said pre-determined number of rotations effecting a pre-determined translational movement of the drive head.

17. The orthopedic rod reduction device of claim 16, wherein further rotations of the drive head beyond the pre-determined number of rotations effects a distal linear movement of the rod engagement element.

18. The orthopedic rod reduction device of any one of claims 14 to 17, wherein the distal facing surface of the rod engagement member comprises a recessed portion shaped to conform to a curved outer surface of the rod.

19. An orthopedic bone rod reduction assembly comprising: a support comprising a proximal head having a threaded passage therethrough and a bone anchor engaging portion extending from the proximal head; an actuator comprising a drive head and an elongate drive shaft extending therefrom; a bone rod engagement element for engaging with and moving the bone rod, the bone rod engagement element comprising a base member and a spring engagement element, a spring extending from a first end which engages the drive head to a second end which engages the spring engagement element of the rod engagement element, wherein the spring is moveable from a natural state to a compressed state by rotation of the drive head relative to the support; wherein the spring is moved to its compressed state by a pre-determined number of rotations of the drive head after which, further rotation of the drive head causes a linear movement of the bone rod engagement element.

20. An orthopedic rod reduction device comprising: an actuator having a first drive head and a second drive head, a drive shaft extending between said first and second drive heads; a rod engagement element for engaging a rod and moving the rod upon movement of the actuator, and a spring positioned between the second drive head of the actuator and the rod engagement element.

21. The orthopedic rod reduction device of claim 20, wherein the first drive head has an upper and a lower opposed surface and the drive shaft extends from a proximal end connected to the lower surface of the head member to a distal end which is connected to the second drive head.

22. The orthopedic rod reduction device of claim 21, wherein the second drive head comprises a lower spring engaging surface.

23. The orthopedic rod reduction device of any one of claims 20 to 22, wherein a length of the drive shaft includes a threaded outer surface.

24. The orthopedic rod reduction device of any one of claims 20 to 23, further comprising a support having a proximal head to receive at least part of the actuator and a bone anchor engaging portion, wherein the proximal head includes a passage defined by at least a partially threaded portion of an internal wall of the proximal head, said passage configured to receive at least a length of the drive shaft.

25. The orthopedic rod reduction device of claim 24, wherein the actuator is rotatably moveable to effect an initial linear movement of the actuator relative to the support.

26. The orthopedic rod reduction device of any one of claims 22 to 25, wherein the spring extends from a proximal end which engages the lower spring engaging surface of the second drive head to a distal end which engages the rod engagement element.

27. The orthopedic rod reduction device of claim 26, wherein the spring comprises a helically wound spring member and is moveable between a first natural state and a second energy absorbing state, wherein rotation of the drive head causes linear movement of the second drive head to compress the spring between the second drive head and the rod engagement element and thus cause the spring to move to its second energy absorbing state.

28. The orthopedic rod reduction device of claim 27, wherein the second energy absorbing state of the spring is achieved by a pre-determined number of rotations of the first drive head.

29. The orthopedic rod reduction device of claim 28, wherein further rotations of the drive head beyond the pre-determined number of rotations effects distal linear movement of the rod engagement element.

30. The orthopedic rod reduction device of any one of claims 20 to 29, wherein the rod engagement member comprises a distal rod engaging surface which includes a recessed portion shaped to conform with a curved outer surface of the rod.

31. The orthopedic rod reduction device of any one of claims 24 to 30, wherein the bone anchor engaging portion of the support engages the second drive head and the rod engagement element.

32. The orthopedic rod reduction device of claim 31, wherein the bone anchor engaging portion comprises a plurality of legs which extend from the proximal head and through respective passages in the second drive head and the rod engagement element.

33. An orthopedic bone rod reduction assembly comprising: a support comprising a proximal head having a threaded passage therethrough and a bone anchor engaging portion extending from the proximal head; an actuator comprising a first drive head, a second drive head and an elongate drive shaft extending therebetween; a bone rod engagement element for engaging with and moving the bone rod, the bone rod engagement element comprising a base member and a spring engagement element, a spring extending from a first end which engages the second drive head to a second end which engages the spring engagement element of the rod engagement element, wherein the spring is moveable from a natural state to a compressed state by rotation of the first drive head relative to the support; wherein the spring is moved to its compressed state by a pre-determined number of rotations of the first drive head after which, further rotation of the first drive head causes a linear movement of the bone rod engagement element.

34. A method of supporting the spinal column of a patient including: providing a plurality of rod reduction devices, wherein each rod reduction device comprises: an actuator having a drive surface; a rod engagement element for engaging a rod and moving the rod upon movement of the actuator, and a spring member positioned between the drive surface of the actuator and the rod engagement element; actuating the actuator to cause the rod engagement element to advance the rod towards a bone anchor, and maintaining a controlled force between the rod engagement element and the rod upon movement of the rod relative to the actuator.

35. The method of claim 34, wherein the device further comprises a support having a proximal head and the actuator comprises a drive head and a drive shaft extending therefrom, the drive shaft extendable from a proximal end which engages the drive head to a distal end which engages the rod engagement element through a passage in the proximal head of the support; and wherein the step of actuating the actuator comprises a first actuating step of rotating the drive head relative to the support to effect a linear movement of the drive head and drive shaft relative to the support.

36. The method of claim 35, wherein the spring comprises a helical coil extending from a proximal end which engages the drive head to a distal end which engages part of the rod engagement element, the helical coil moveable from a natural state to a compressed state upon rotation of the drive head and wherein the first actuating step of rotation of the drive head causes compression of the spring between the drive head and the rod engagement element.

37. The method of claim 36, wherein the spring is caused to move to its compressed state by a pre-determined number of rotations of the drive head.

38. The method of claim 37, wherein the step of actuating the actuator includes a second actuating step wherein further rotation of the drive head beyond the pre-determined number causes a distal linear movement of the rod engagement element which in turn causes the rod to move towards the bone anchor.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0070] FIGS. 1a, 1b and 1c depict schematically, certain elements used in a device of the present disclosure;

[0071] FIGS. 2a and 2b depict the components of FIGS. 1a, 1b and 1c, in use;

[0072] FIGS. 3a and 3b shows schematically a known system without a spring when in use;

[0073] FIG. 4a is a side view of a device of the present disclosure;

[0074] FIG. 4b is a cross sectional view of the device of FIG. 4a;

[0075] FIG. 5a is a side view of a device of another embodiment of the present disclosure; and

[0076] FIG. 5b is a cross sectional view of the device of FIG. 5a.

DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE DISCLOSURE

[0077] An actuator 11, rod engagement element 12 and a spring 13 are shown in FIGS. 1a to 1c, 2a and 2b. These elements may be included as part of a rod reduction device 100 as shown in FIGS. 4a and 4b, or a rod reduction device 200 as shown in FIGS. 5a and 5b.

[0078] Devices 100, 200 are used to reduce a rod 14 into a bone anchor 15. Spring 13 is configured to impart a force on rod engagement element 12 such that rod engagement element 12 maintains a controlled force on rod 14 even if external forces cause movement of rod 14 relative to actuator 11.

[0079] In FIG. 1, spring 13 is in a natural state connected at a proximal end 16 to actuator 11 and at a distal end 17 to rod engagement element 12. Rod 14 is positioned above anchor 15 ready for reduction into a head 151 of anchor 15. In FIG. 1b, the actuator 11 is shown to have moved linearly towards bone anchor 15. While details of the linear movement of the actuator will be described in more detail below in relation to rod reduction devices 100, 200, movement from the position of actuator 11 in FIG. 1a, to the position of actuator 11 in FIG. 1b causes compression of spring 13. While a helical spring is depicted in these figures for simplicity, it is envisaged that other types of springs previously mentioned may be used. The spring, whatever type, is caused to move from a natural state depicted for example in FIG. 1a to a second, energy storing state, depicted for example in FIG. 1b, by virtue of the rod engagement element moving into contact with, and applying a force to, the rod 14.

[0080] Further linear movement of the actuator 11 towards bone anchor 15 as shown in FIG. 1c substantially linearly translates the rod engagement element and thus the engaged rod 14 towards head 151 of bone anchor 15. While there may be a slight further compression or expansion of spring 13 during this step, the majority of the movement comprises linear movement of the actuator 11 and the rod engagement element 12.

[0081] An important feature of this arrangement is that the rod engagement element 12 is kept in a force applying engagement with rod 14. Therefore, if external forces during a procedure cause the rod to move towards anchor 15, the spring releases its energy and moves back towards its natural state to maintain a force on the rod engagement element 12 and therefore the rod 14. An example of this can be seen in FIG. 2a, wherein the depicted portion of rod 14 has been caused to drop towards the anchor 15 due to manipulation of other parts of the rod. The spring 13 moves towards its natural state configuration to cause the rod engagement element to “chase” rod 14 and maintain some force upon it. A comparative example in relation to this scenario, where a rod reduction device is provided without a spring between the actuator and the rod engagement element is represented in FIG. 3a. In this example, again the rod has been manipulated such that it drops towards anchor 15 but the rod engagement element is static and loses contact with rod 14.

[0082] In a scenario where manipulation of the rod downstream or upstream of the portion of rod 14 depicted in FIG. 2b causes that portion of rod 14 to be urged away from the bone anchor 15, spring 13 compresses, absorbing some of the force exerted by the rod 14 on the rod engagement element 12. A comparative example in relation to this scenario, where a rod reduction device is provided without a spring between the actuator 11 and the rod engagement element 12 is represented in FIG. 3b. In this example, again the rod has been manipulated such that it is urged away from the bone anchor 15, but the rod engagement element is static and bears the full force imparted by rod 14.

[0083] The elements described above in relation to FIGS. 1a to 2b are present in a rod reduction device 100 according to an embodiment of the present disclosure, as illustrated in FIGS. 4a and 4b, which is used to position rod 14 in a bone anchor 15 as part of a procedure to correct a deformity of the spinal column. While a single device 100 and only part of rod 14 (segments) are depicted in the Figures, the device 100 would usually be used as part of a larger system comprising a plurality of rod reduction devices 100, respectively positioned over bone anchors in the vertebrae of a patient and an elongate rod to be fixed to the bone anchors along a length of the spine.

[0084] Rod 14 is usually pre-shaped as desired and positioned over the bone anchors 15. Devices 100 force segments of rod 14 into respective anchor heads 15. In this regard, a surgeon typically progressively reduces various rod segments along the rod length until the entire rod is fixed to respective anchors and the vertebrae forced into the shape of the rod 14. However, given the range of forces and shifting of forces along the rod during the rod reduction, many segments of rod 14 undergo excessive changes of load. For example, as a segment of rod is manipulated using one rod reduction device 100, the forces between a different segment of rod and another of the rod reduction devices 100 can change significantly. Depending on the direction of the forces, in some instances they may be sufficient to cause the anchors to be pulled from the bone, or cause the rod to disengage from a rod reduction device.

[0085] The device 100 provides a means to maintain a relatively constant force against the rod segments, including absorbing any excessive forces during a surgical procedure.

[0086] As shown in FIGS. 4a and 4b, rod reduction device 100 comprises actuator 11, rod engagement element 12 and spring 13.

[0087] Rod reduction device 100 further comprises a support having a main body 18 which has an upper surface 19, lower surface 20 and a passage 21 therethrough.

[0088] Passage 21 receives actuator 11 in a threaded engagement as shown in FIG. 4b.

[0089] Actuator 11 comprises a drive head 22 and a drive shaft 23 which depends from drive head 22 and has an outer threaded surface 24.

[0090] Rotation of drive head 22 effects a linear translational movement of the drive head 22 and drive shaft 23 relative to main body 18 as depicted by Arrow A.

[0091] In FIG. 4b, spring 13 is internally housed within part of drive shaft 23. Drive shaft 23 extends from a first end 25 connected to the drive head 22 to second end 26. Spring 13, housed within drive shaft 23, extends from proximal end 16 to distal end 17. Proximal end 16 of spring 13 is in engagement with a lower surface 27 of drive head 22.

[0092] As shown in FIGS. 4a and 4b, drive shaft 23 comprises a tubular structure with an outer threaded surface 23. While fixed at first end 25 to drive head 22, a second end 26 of drive shaft 23 is open and slidably receives a rigid spring engagement shaft 28 which is connected to, or forms part of, rod engagement element 12.

[0093] With drive shaft 23 and main body 18 in threaded engagement, rotation of drive head 22 effects the linear translational movement of the drive head and drive shaft relative to the main body 18. Rotation of drive head and drive shaft against rigid spring engagement shaft 28 forces internally housed spring 13 into a compressed state.

[0094] In device 200, as illustrated in FIGS. 5a and 5b, spring 213 is positioned external to drive shaft 223.

[0095] Second end 226 of drive shaft 223 is connected to a second drive head 229. Second drive head 229 comprises a lower spring engaging surface 231 for engagement with spring 213. In this embodiment, lower spring engaging surface 231 is the drive surface.

[0096] Spring 213 is connected at its proximal end 216 to lower spring engaging surface 231 of the second drive head 229 and at its distal end 217 to rod engagement element 212. Rotation of first drive head 222 again effects the linear translational movement of the drive head and drive shaft relative to the main body. Rotation of first drive head 222 and drive shaft 223 applies a force against second drive head 229 which imparts a force against spring 213. Force applied by the second drive head 229 on spring 213 causes spring 213 to compress.

[0097] Rod engagement element 212 comprises a rod engaging surface 230 which includes a centrally positioned recess 232 which is shaped to conform to a curved outer surface of rod 214.

[0098] Both rod reduction device 100 and device 200 further comprise two legs 33a and 33b and 233a and 233b respectively.

[0099] Second end 35 of each leg 33a and 33b and second end 235 of legs 233a and 233b are configured to engage with a bone anchor 15 as shown in FIGS. 4a and 4b. The rod engaging element 12 includes opposed passages 34a and 34b through which respective legs 33a and 33b extend. In a preferred embodiment, the hub body includes two passages to receive two legs therethrough. The passages 34a, 34b are sized such that the rod engaging element 12 is translatable along a length of each leg between the mounting end and the second end.

[0100] Similarly in device 200, legs 233a and 233b extend through respective passages 234a and 234b of rod engagement element 212. In this embodiment similar passages are provided in the second drive head 229 to allow passage therethrough of the legs.

[0101] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.