A BONE ROD

Abstract

A device and method for correcting a rotational deformity, for use in lengthening a bone or aiding in stabilising a fractured bone. When used to correct a rotational deformity, the device comprises a first member and a second member moveably connected to each other such that when the two members are moved apart along a first axis, the first and/or second members rotate relative to each other about the first axis.

Claims

1. An orthopaedic device for securing between first and second regions of bone separated by a growth plate, the orthopaedic device comprising: a first member having an end to secure to the first bone region; and a second member having an end to secure to the second bone region; wherein the first and second members are moveably connected to each other such that when the ends are moved apart along a first axis, the first and/or second members rotate relative to each other about the first axis.

2. The orthopaedic device of claim 1, wherein the first and/or second members comprise one or more rotational feature.

3. The orthopaedic device of claim 2, wherein the first member extends from a first end to a second end and the first end is securable to the first bone region.

4. The orthopaedic device of claim 3, wherein the first member includes a first bone fixation region located at or adjacent to the first end of the first member and a mating region extending from said first bone fixation region.

5. The orthopaedic device of claim 4, wherein the second member extends from a first end to a second end, the first end securable to the second bone portion and the second end configured to receive at least part of the first member.

6. The orthopaedic device of claim 5, wherein the second member includes a second bone fixation region located at or adjacent to the first end of the second member.

7. The orthopaedic device of claim 4, wherein the second member includes a complementary mating region relative to the mating region of the first member.

8. The orthopaedic device of claim 4, wherein the one or more rotational feature of the first member is located on the mating region of the first member.

9. The orthopaedic device of claim 8, wherein the one or more rotational member is located on the complementary mating region of the second member.

10. The orthopaedic device of claim 2, wherein at least part of the second member has a lumen defined by an internal wall, said one or more rotational feature located on said internal wall.

11. The orthopaedic device of claim 10, wherein at least part of the first member is received in the lumen of the second member.

12. The orthopaedic device of any one of claim 11, wherein the one or more rotational feature of the first member comprises at least one ridge.

13. The orthopaedic device of claim 12, wherein the at least one ridge and/or at least one channel extend helically along a length of an outer surface of the first member.

14. The orthopaedic device of any one of any one claim 2, wherein said one or more rotational feature of the second member comprises at least one crest and/or at least one groove on the internal wall.

15. The orthopaedic device of claim 14, wherein the at least one crest and/or at least one groove extend helically along a length of the internal wall of the second member.

16. The orthopaedic device of claim 2, wherein the one or more rotational feature of the first member comprises at least one elongate surface.

17. The orthopaedic device of claim 16, wherein the at least one elongate surface extends helically along a length of the outer surface of the first member.

18. The orthopaedic device of claim 17, wherein the one or more rotational feature of the second member comprises at least one complementary guiding surface engageable with the at least one elongate surface.

19. The orthopaedic device of any claim 18, wherein the first member is substantially straight and the second member comprises at least a corresponding relatively straight terminal portion to receive the first portion of the first member therein.

20. The orthopaedic device of claim 19 wherein the second member includes one or more further portions which are angled relative to the terminal portion.

21. The orthopaedic device of claim 20, wherein the first member further includes a shoulder stop engageable with an end of the second member.

22-33. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0143] FIG. 1a is a lateral view of a device of the disclosure in an implantation configuration;

[0144] FIG. 1b is a lateral view of the device of FIG. 1a with parts of the device spaced and rotated relative to each other;

[0145] FIG. 2a is an anterior-posterior view of the device of FIG. 1a;

[0146] FIG. 2b is an anterior posterior view of the device of FIG. 1a with parts of the device spaced and rotated relative to each other;

[0147] FIG. 3a is a perspective view of a second member of the device of FIG. 1a;

[0148] FIG. 3b is a close up view of an end of one embodiment of a second member;

[0149] FIG. 3c is a close up view of an end of the embodiment of the second member shown in FIG. 3a;

[0150] FIG. 4 is a perspective view of a first member of the device of FIG. 1a;

[0151] FIG. 5a is a perspective view of the device of FIG. 1a when implanted in a left femur of a subject;

[0152] FIG. 5b is a perspective view of the device of FIG. 1a after the left femur has grown relative to the femur shown in FIG. 5a;

[0153] FIG. 6a is a perspective view of the device of a further embodiment when implanted in a left femur of a subject;

[0154] FIG. 6b is a perspective view of the device of FIG. 6a after the left femur has grown relative to the femur shown in FIG. 5a;

[0155] FIGS. 7a and 7b are perspective views of a second member of the device of FIG. 6a;

[0156] FIG. 8a, is a lateral view of a first member of the device of FIG. 6a;

[0157] FIG. 8b is an anterior-posterior view of the first member of the device of FIG. 6a;

[0158] FIG. 8c is a perspective view of the first member of the device of FIG. 6a;

[0159] FIGS. 9a, 9b and 9c are perspective views of another embodiment of the second member of the disclosure;

[0160] FIGS. 10a, 10b and 10c are perspective views of another embodiment of the first member of the disclosure;

[0161] FIG. 10d is a perspective view of the first member of another example of the device of the disclosure;

[0162] FIG. 11a is a side view of one embodiment of a locking mechanism;

[0163] FIG. 11b is a perspective view of the locking mechanism of FIG. 9a;

[0164] FIG. 12a is a side view of a further embodiment of a locking mechanism;

[0165] FIG. 12b is a perspective view of the locking mechanism of FIG. 10a;

[0166] FIG. 13 shows further examples of the device of the present disclosure when used to correct abnormally rotated spine;

[0167] FIG. 14 shows longitudinal radiographic images of the two experimental animals of Example 1 shown at the time of implantation (Surgery) and at the final harvest (3 months);

[0168] FIG. 15 shows X-ray of the implanted devices of Experiment 1 ex-vivo at the three month harvest; and

[0169] FIG. 16 shows the rotation of the devices of Experiment 1 in the femora, post-harvest as measured by the angle of pins inserted into part of the device.

DESCRIPTION OF EXAMPLES

[0170] In one example, an orthopaedic device 1 includes a first member 10 and a second member 50. Second member 50 is configured to receive first member 10. The assembly of first member 10 and second member 50 forming device 1 may be implanted into a bone of a patient. Particularly, the device 1 is implanted through the medullary canal of a bone.

[0171] The device 1 is positioned over a growth plate of a bone and the engagement between the first member 10 and the second member 50 is such that they are axially and rotatably moveable relative to each other as the bone grows. FIGS. 1b and 2b depict an arrangement of first member 10 and second member 50 relative to each other after the bone, in which device 1 is implanted, has grown. First member 10 moves axially and distally from second member 50 in a direction shown by arrow 2. As the first member 10 moves axially in the direction shown by arrow 2, it also rotates relative to second member 50 as shown by arrow 3.

[0172] First member 10 extends from a first end 11 to a second end 12. A first fixation region 13 is located adjacent to first end 11. In use, the first member 10 is fixed to the bone at the first fixation region 13. The first fixation region 13 comprises a substantially solid cylindrical length of the first member 10 adjacent first end 11. A hole 14 is formed in the first fixation region 13 to receive a locking member 191 to secure at least the fixation region 13 to the surrounding bone. While only one hole 14 is depicted, in other examples, the first fixation region 13 may comprise multiple holes.

[0173] First member 10 further includes a mating region 15 which extends from the first fixation region 13 to the second end 12. The mating region 15 is configured to mate with a complementary structure of the second member 50. In one example, mating region 15 comprises ridges 20a, 20b and 20 c. Channels 21a, 21b and 21c are formed between these ridges. Ridges 20a, 20b and 20c extend from a junction with the first fixation region 13 in a helical configuration around an outer wall of the mating region 15.

[0174] A shoulder 16 is formed at the junction of the first fixation region 13 and the mating region 15 in the depicted example. Shoulder 16 abuts with end 52 of second member 50 when device 1 is in its implantation configuration. Shoulder 16 may act as a stop and prevent the first fixation region 13 sliding into the second member 50. This allows hole 14 to remain exposed to permit fixing of the first member 10 to the surrounding bone.

[0175] In the example shown in FIG. 3a, second member 50 comprises an elongate body which extends from a first end 51 to a second end 52. At least a region of the second member 50 adjacent to the second end 52 is tubular to receive the first member 10 as shown in more detail in FIGS. 3b and 3c. An internal wall 60 defines a lumen 61 to receive part of the first member 10. In the example shown in FIG. 3b, the internal wall 60 comprises crests 62a, 62b and 62c. Between crests 62a, 62b and 62c are grooves 63a, 63b and 63c. The crest and grooves extend from the second end 52 of second member 50 in a helical configuration as can best be seen by crest 62a in FIG. 3b.

[0176] In the example shown in FIG. 3c, the internal wall 60 does not define the same protruding ridges 62a, 62b or 62c and instead includes relatively deeper grooves 63a, 63b and 63c to receive the ridges of the first member 10.

[0177] The helical configuration and the dimensions of crests 62a, 62b and 62c and/or grooves 63a, 63b and 63c of second member 50 complement the helical arrangement of first member 10 such that the ridges 20a, 20b and 20c of the first member are moveable along respective grooves 63a, 63b and 63c and similarly, crests 62a, 62b and 62c are moveable along respective channels 21a, 21b and 21c.

[0178] To achieve an implantation configuration as depicted in FIG. 1a, first member 11 is inserted into the lumen 61 of second end 52 of second member 50. Particularly, mating region 15 is inserted into second member 50 until shoulder 16 abuts with end 52 such that only the first fixation region 13 extends from the second end 52 of second member 50. In the implantation configuration, hole 14 in the first fixation region 13 is exposed to receive a locking member and thus allow fixing of at least the first fixation region 13 to the surrounding bone. To insert the first member 10 into second member 50 requires a rotation of the two members relative to each other to guide ridges 20a, 20b and 20c along respective grooves 63a, 63b and 63c and similarly, crests 62a, 62b and 62c along respective channels 21a, 21b and 21c.

[0179] The second member 50 comprises a terminal portion 53, an intermediate portion 54 and a primary portion 55. FIG. 2A, depicts an anterior posterior view of device 1 showing terminal portion 53 extending along a first axis 56. The intermediate portion 54 extends along a second, different axis 57. The primary portion 55 extends along an axis 58 which is different to both the first axis 56 and second axis 57.

[0180] As can be seen in the lateral views of FIGS. 1a and 1b, intermediate portion 54 may not be straight and may bow along its length, either anteriorly or posteriorly. The bowing may be seen relative to line 59 drawn from one end of the intermediate portion 54 to the other. Such bowing of the second member in this manner may be of particular relevance if the device is implanted in an antegrade fashion into a femur of a subject, the femur having a natural anterior bow along at least part of its length.

[0181] The angles between the different portions 53, 54 and 55 may depend upon the bone in which device 1 is implanted. In the examples shown in FIGS. 1a, 1b, 2a, 2b and 3a, the second member 50 is insertable into the medullary canal of a femur 80 in an antegrade manner, that is via the greater trochanter 81, to a final position as shown in FIGS. 5a and 5b. Typically the angle 64 formed between axis 56 and axis 57 is around 5 to 6.

[0182] Primary portion 55 sits within the greater trochanter 81 of the femur 80 when implanted as shown in FIGS. 5a and 5b. Intermediate portion 54 extends through the diaphysis 82 and terminal portion 53 extends from the diaphysis 82 towards distal growth plate 83. Second end 52 of second member 50 is shown just proximal to the growth plate 83, and in practice, it is desirable to avoid the second member 50 extending across the growth plate. Because the second member 50 may have a larger diameter than the first member 10 it may cause relatively more damage than if only first member 10 extends over the growth plate.

[0183] Second member 50 may also comprise a hole 68 adjacent first end 51 to receive a locking member 192 to secure at least the primary portion 55 of second member 50 to surrounding bone. A further hole 69 is shown in the intermediate portion 54 which may receive another locking member and therefore further secure the second member 50 to surrounding bone. The intermediate portion may comprise further holes to further secure the first member 50 in the bone.

[0184] For a rotational correction of the left femur, the device 1 is assembled into the implantation configuration shown in FIG. 1a and inserted, first member 10 first, through an entry point in the greater trochanter 81. The assembly of first member 10 and second member 50 is moved through the medullary canal until it is positioned as shown in FIG. 5a. First member 10 is secured to bone distal the growth plate 83 in the distal epiphysis 85 by inserting a locking member 191 through hole 14. Although not depicted in FIGS. 5a and 5b, a similar locking member is inserted through one or both of holes 68 and/or 69 to secure the second member 50 to surrounding bone in the greater trochanter and/or the diaphysis 82. Additional locking holes may also be incorporated anywhere along intermediate portion 54 to provide additional fixation.

[0185] In this example, the deformity to be corrected is an internal rotation of the femur 80 with correction requiring an external rotation of the femur 80 in the direction shown by arrow 91.

[0186] The first member 10 is positioned substantially orthogonal with the growth plate 83 to drive the correct rotation of the femur 80.

[0187] With the device in situ and first member 10 secured across the growth plate 83, axial growth of the femur 80 as depicted by arrow 90 exerts an axial force on first member 10 relative to second member 50 to axially pull first member 10 from second member 50 and in the direction of the growth of the femur 80. Due to the helical engagement between ridges 20a, 20b and 20c and grooves 63a, 63b and 63c and similarly, crests 62a, 62b and 62c with respective channels 21a, 21b and 21c, first member 10 is forced into a relative rotational movement in the direction of arrow 90 as the femur 80 grows. In turn, because the first member 10 is fixed to bone in the distal epiphysis 85, a rotational force is exerted by the first member 10 to at least the distal epiphysis to externally rotate a distal region of the femur 80 in the direction of arrow 91.

[0188] Therefore, the motor to drive the rotational force to the device 1 and the femur 80 is growth of the femur 80 itself. In other examples, correction may also be aided by an artificial motor.

[0189] Once the femur 80 has been optimally rotationally corrected as shown in FIG. 5b, the device 1 may be surgically removed. Alternatively, the device 1 may be designed such that the first member 10 becomes disengaged from the second member 50 after a pre-determined axial and rotational movement. In another example, the grooves 63a, 63b and 63c and crests 62a, 62b and 62c do not extend to end 52 such that there is a non-helically threaded region or a gap adjacent the distal end 52 of second member 50. Upon certain lengthening of the femur 80 and thus rotational movement of both the first member 10 relative to second member 50, second end 12 of first member 10 passes into the non-helically threaded region adjacent end 52 and thus the ridges 20a, 20b and 20c and channels 21a, 21b and 21c of first member terminate their rotational engagement with respective crests 62a, 62b and 62c and grooves 63a, 63b and 63c. While further growth of femur 80 will cause an axial movement of first member 10 relative to second member 50 in the direction of arrow 90, the relative rotational movement is terminated.

[0190] Alternatively one or more locking members such as locking member 191 may be removed to terminate the rotational force on the bone.

[0191] An example of a retrograde device 100 for retrograde insertion into a bone is depicted in FIGS. 7a and 7b, 8a to 8c and shown by way of example in a femur in FIGS. 6a and 6b. The retrograde device 100 is implantable in the femur 80 and across growth plate 83 via an entry point in the distal epiphysis 85 of femur 80 rather than entering via the greater trochanter 81 as depicted in FIGS. 5a and 5b.

[0192] Notably, while implanted in a retrograde manner for the femur 80, the depicted device 100 is suitable for antegrade implantation in a tibia.

[0193] First member 110 extends from a first end 111 to a second end 112. A first fixation region 113 is located adjacent first end 111. In use, the first member 110 is fixed to the bone at the first fixation region 113. The first fixation region 113 is a substantially solid cylindrical length of the first member 110 adjacent first end 111. First fixation member 113 comprises a hole 114 to receive a locking member 191 to secure at least the fixation region 113 to the surrounding bone as shown in FIGS. 6a and 6b. Although not depicted, the first fixation region 113 may comprise multiple holes.

[0194] First member 110 further includes a mating region 115 which extends from the first fixation region 113 to the second end 112. The mating region 115 is configured to mate with a complementary structure of the second member 150.

[0195] Mating region 115 comprises ridges 120a, 120b and 120c. Channels 121a, 121b and 121c are formed between these ridges. Ridges 120a, 120b and 120c extend from a junction with the first fixation region 113 in a helical configuration.

[0196] A shoulder 116 is formed at the junction of the first fixation region 113 and the mating region 115. Shoulder 116 abuts with end 152 of second member 150 when device 1 is in its implantation configuration as shown in FIG. 6a.

[0197] Second member 150 comprises a substantially straight tubular body which extends from a first end 151 to a second end 152. An internal wall 160 defines a lumen 161 to receive part of the first member 110. The internal wall 160 comprises helically arranged grooves 163a, 163b and 163c. Because the second member is implanted in a retrograde fashion it is shorter in length than second member 50 which is designed for antegrade implantation.

[0198] The dimensions and helical configuration of grooves 163a, 163b and 163c are complementary to the helical arrangement of ridges 120a, 120b and 120c of first member 110. Specifically, ridges 120a, 120b and 120c are sized to be moveable along respective grooves 163a, 163b and 163c.

[0199] Second member 150 also comprises a hole 168 adjacent first end 151. Hole 168 is configured to receive a locking member to secure the first member 150 to surrounding bone.

[0200] To achieve an implantation configuration as depicted in FIG. 6a, first member 110 is inserted into the lumen 161 of second end 152 of the second member 150. Mating region 115 is inserted into second member 150 until shoulder 116 abuts with end 152 such that only the first bone fixation region 113 extends from the second end 152 of second member 150. In the implantation configuration, hole 114 in the first fixation portion 113 is exposed to receive a locking member and thus allow fixing of at least the first fixation region 113 to the surrounding bone. To insert the first member 110 into second member 150 requires a rotation of the two members relative to each other to guide ridges 120a, 120b and 210c along respective grooves 163a, 163b and 163c.

[0201] For a rotational correction of the left femur 80 as shown in FIGS. 6a and 6b, device 100 is assembled into the implantation configuration and inserted, second member 150 first, through an entry point in the distal epiphysis 85 and through the medullary canal until the first end 151 of second member 150 is positioned in the diaphysis 82 and the second end 152 of second member is positioned just proximal to the growth plate 83. First member 110 extends distally from end 152 of second member 150 and crosses the growth plate 83. First end 111 of first member 110 is positioned distal to the growth plate 83 and in the distal epiphysis of the femur 80.

[0202] First member 110 is secured to bone in the distal epiphysis 85 by inserting a locking screw 191 through hole 114. Similarly, locking member 192 is inserted through hole 168 of second member 150 to secure the second member 150 in the bone of the diaphysis 82.

[0203] In the example shown in FIGS. 6a and 6b, the device 100 is used to externally rotate the femur 80 to correct a deformity. In this example, the femur 80 of FIG. 6a is abnormally internally rotated and requires external rotation in the direction of arrow 91 for correction.

[0204] The implantation of device 100 orientates the first member 110 substantially orthogonal with the growth plate 83 to drive the correct rotation of the femur 80.

[0205] When the device 100 is implanted, first member 110 is secured across the growth plate 83. Growth of the femur 80 as depicted by arrow 90 exerts an axial force on first member 110 relative to second member 150 to distally pull first member 110 from second member 150 and in the direction of the growth of the femur 80. Due to the helical engagement between ridges 120a, 120b and 120c and grooves 163a, 163b and 163c, first member 110 is forced into a relatively rotational movement in the direction of arrow 91 as the femur 80 grows. In turn, because the first member 110 is fixed to bone in the distal epiphysis 85, a rotational force is exerted by the first member 110 to at least the distal epiphysis 85 to externally rotate a distal region of the femur in the direction of arrow 91.

[0206] Again, in this example, the motor to drive the rotational force of the device 100 and the femur 80 is growth of the femur 80 itself. In other examples, correction may also be aided by an artificial motor.

[0207] Once the femur 80 has been optimally rotationally corrected as shown in FIG. 6b, the device may be surgically removed. Alternatively, the device 100 may be designed such that the first member 110 become disengaged from the second member 150 after a pre-determined axial and rotational movement. In another example, the grooves 163a, 163b do not extend fully along the entire length of second member 150 Particularly, in an example there may be a gap between the second end 152 and the start of the grooves 163a, 163b and 163c such as to terminate rotational engagement of the first member 110 relative to the second member 150 at a certain point of lengthening of the femur 80, thus also terminating a rotational force on the femur 80.

[0208] Alternatively, one or more locking member(s) 191 may be removed to terminate the rotational force on the femur 80.

[0209] A further example of first member 210 is shown in FIGS. 10a, 10b and 10c. First member 210 comprises a substantially solid elongate body which extends from a first end 211 to a second end 212. First member 210 comprises a first fixation region 213 from which a mating region 215 extends towards second end 212. The first fixation region 213 is substantially cylindrical having a circular cross section. The first fixation region 213 comprises a hole 214 therethrough, the hole 214 sized to receive a locking member to fix the first member to surrounding bone.

[0210] The mating region 215 extends from a junction with first fixation region 213. A shoulder 216 is formed at the junction between first fixation region 213 and mating region 215, the shoulder acting as described above to prevent the entire length of the first member 210 moving into the second member 250.

[0211] Mating region 215 is depicted as having a square cross section although it is envisaged that any non-circular cross section would be a suitable adaptation of this example. The mating region comprises an elongate twisted body having four elongate surfaces 220a, 220b, 220c and 220d. Each elongate surface extends helically along the length of the mating region 215. FIG. 10a depicts a lateral view of the first member 210 wherein elongate surfaces 220a and 220b are visible. FIG. 10b depicts the first member 210 rotated approximately 90 to also show surfaces 220c and 220d.

[0212] FIG. 10d depicts a further example of first member 230. First member 230 also comprises a substantially solid elongate body which extends from a first end 231 to a second end 232. First member 230 comprises a first fixation region 233 from which a mating region 235 extends towards second ends 232. The first member 230 includes a head 236 which is positioned at second end 210. In the depicted example, the head 236 comprises a substantially cubed member although other shapes are envisaged. In the depicted example, the head 236 is spaced from the mating region 235 by spacer portion 237. When first member 230 is inserted into second member 250 ready for implantation in a subject, the head 236 prevents the first member 230 from readily disengaging from second member 250 because the configuration of the head 236 is such that it is offset relative to squared lumen 261 of second member 250 such that its corners 238a, 238b, 238c and 238d abut with a respective guiding surfaces 262a, 262b, 262c and 262d.

[0213] The first fixation region 233 is substantially cylindrical having a circular cross section. The first fixation region 213 comprises a hole 214 therethrough, the hole 214 sized to receive a locking member to fix the first member to surrounding bone.

[0214] The mating region 215 extends from a junction with first fixation region 213. A shoulder 216 is formed at the junction between first fixation region 213 and mating region 215, the shoulder acting as described above to prevent the entire length of the first member 210 moving into the second member 250.

[0215] Mating region 215 is depicted as having a square cross section although it is envisaged that any non-circular cross section would be a suitable adaptation of this example. The mating region comprises an elongate twisted body having four elongate surfaces 220a, 220b, 220c and 220d. Each elongate surface extends helically along the length of the mating region 215. FIG. 10a depicts a lateral view of the first member 210 wherein elongate surfaces 220a and 220b are visible. FIG. 10b depicts the first member 210 rotated approximately 90 to also show surfaces 220c and 220d.

[0216] FIGS. 9a and 9b depict second member 250 which comprises a substantially straight tubular body extending from a first end 251 to a second end 252. Second member 250 may be used for both retrograde or antegrade implantation. If used for antegrade implantation, second member 250 may be substantially longer than depicted and generally configured as shown in FIG. 1a.

[0217] An internal wall 260 defines a lumen 261 to receive part of the first member 210. Although the entire length of internal wall 260 may include a complementary surface to engage with elongate surfaces 220a, 220b, 220c and 220d , in the example depicted in FIG. 9b, only a length 263 of internal wall 260 adjacent second end 252 comprises helically arranged complementary guiding surfaces 262a, 262b, 262c and 262d. The remainder length 264 of internal wall 260 is substantially circular in cross section and devoid of a rotational feature.

[0218] The dimensions and helical configuration of guiding surfaces 262a, 262b, 262c and 262d are complementary to the elongate surfaces 220a, 220b, 220c and 220d of first member 210. Specifically, elongate surfaces 220a, 220b, 220c and 220d are sized and configured to be moveable along guiding surfaces.

[0219] Second member 250 also comprises a hole 268 adjacent first end 251. Hole 268 is configured to receive a locking member to secure the first member 250 to surrounding bone.

[0220] To bring the first member 210 and second member 250 together, first member 210 is inserted into the lumen 261 of second end 252 of the second member 250. Mating region 215 is inserted into second member 250 until shoulder 216 abuts with end 252.

[0221] In an implantation configuration, mating region 215 extends into length 264 of the lumen 261 of second member 250 and part of the length of elongate surfaces 220a, 220b, 220c and 220d of first member 210 abut with guiding surfaces 262a, 262b, 262c and 262d of second member 250. The orientation of the elongate surfaces and corresponding guiding surfaces is such that it causes rotation of the first member 210 relative to the second member 250 when the first member 210 moves axially relative to the second member 250.

[0222] FIGS. 11 and 12 depict examples of locking mechanisms to secure either or both the first member 10, 110, 210 or second member 50, 150, 250 in surrounding bone. References in these drawings will be made to the features of device 1 but are equally applicable to the other examples depicted.

[0223] The first member 10 shown in FIGS. 11a and 11b comprises a key-shaped hole 70 which receives pin 75. Pin 75 comprises a tapered body 76 extending from a first end 77 to a second end 78. Fins 79 extend from body 76 and are received in complementary recesses of key-shaped hole 70. The fins 79 are configured to bite into surrounding bone as the tapered body 76 is wedged into the bone.

[0224] The first member 10 of FIGS. 12a and 12b comprises a substantially cylindrical hole 14 to receive a locking member 191. Locking member 191 in this depicted example is a locking screw 193 comprising a head 194 and an elongate threaded body 195 extending therefrom. The locking screw 193 may be screwed through hole 14 in either first member 10 or second member 50 such that the thread bites into surrounding bone to secure the first 10 or second member 50 to the bone.

[0225] FIG. 13 shows an arrangement of orthopaedic devices 300 and 400 to correct a rotational deformed spine 500. As can be seen, the spine 500 is deformed and has a double curve. The central region (CR) of the spine has been fused. On each convexity of spine 500 (convexity C1 and convexity C2) a device 300 or 400 is positioned such that with future growth the spine will de-rotate, at least partially correcting the curvatures.

[0226] Particularly, orthopaedic devices 300 includes a first member 310 and device 400 includes a first member 410. Each device 300, 400 includes and a second member 350, 450 respectively. Second member 350 is configured to receive first member 310 and second member 450 is configured to receive first member 410.

[0227] In the example depicted in FIG. 13, first member 310 is secured to vertebra 501 by pedicle screw 510. Second member 350 is secured to vertebrae 502, 503 and 505 by respective pedicle screws 511, 512 and 513.

[0228] First member 410 is secured to vertebra 506 by pedicle screw 514. Second member 450 is secured to vertebrae 502, 503 and 504 by respective pedicle screws 515, 516 and 517.

[0229] As the subject grows, the first member 310 moves linearly and rotatably relative to second member 350 and first member 410 and second member 450 similarly moves linearly and rotatably relative to each other to correct the abnormal curvature of the spine 500 in regions C1 and C2.

Experiment 1

[0230] Devices in accordance with the examples described above in relation to FIGS. 9a, 9b, 10a, 10b and 10c were manufactured in stainless steel GP1 using SLS methods, partially polished and sterilised by autoclave prior to implantation.

[0231] Surgery was conducted in two Large White/Landrace cross male piglets 10-15 kg (6-8 weeks old) (Pig 1 and Pig 2). Upon arrival, the animals were allowed two weeks to acclimatise prior to surgery.

[0232] The animals were sedated with 4.4 mg/kg Zoletil, 0.05 mg/kg Atropine and 2.2 mg/kg Xylazine. The operative site was shaved and wiped with iodine solution. Following intubation, isoflurane gas was delivered through inhalation during surgery to maintain sedation. The distal femur was accessed by a medial parapatellar approach, a 1.6 mm K-wire was used to find the centre of the femoral canal. The K-wire was then overdrilled with a 9 mm cannulated drill to fit the device. The device was inserted into the femoral canal and locked distally and then proximally using 4.5 mm HA coated half-pins under Image Intensifier guidance.

[0233] Post-surgery, animals were allowed to recover on heating mats and monitored overnight. Pigs were given Enrofloxacin (Baytril) 50 mg/kg IV for recovery and infection prevention for 6 days following surgery and 0.05 mg/kg Buprenorphine analgesic relief 2-3 times daily for 4 days following surgery. After the first post-op week, animals were checked twice a week and X-rayed monthly for three months. Animals were euthanised with Pentobarbitone 150 mg/kg IV after Zoletil 4.4 mg/kg IM sedation.

Results

[0234] Longitudinal X-ray (FIG. 14) reveals that the devices lengthened in the three months between surgical implantation and harvest. X-rays of the implants ex vivo reveal an extension of 12.2 mm for Pig 1 and 13.8 mm for Pig 2 (FIG. 15).

[0235] This lengthening correlated with a rotation of the device by 15 and 14 for Pig 1 and 2 respectively (see FIG. 16 and Table 1). CT scans compared to the non-operated side showed rotation differences of 8.4 and 11.2 for Pig 1 and 2 respectively. The differences between the device and bone rotation was likely due to slack in the device and/or bone remodelling.

TABLE-US-00001 TABLE 1 Measurement of the rotations of the devices of Experiment 1 at the three month harvest time from Pig 1 and Pig 2 Measurement Pig 1 Pig 2 Device rotation 15 14 Measured bone rotation 8.4 11.2 Difference between device 5.6 3.8 and bone rotation

[0236] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described examples, without departing from the broad general scope of the present disclosure. The present examples are, therefore, to be considered in all respects as illustrative and not restrictive.