Adjustable implant with cycloid gear

Abstract

Disclosed herein are stretching and compressing devices configured to be positioned between a first portion of bone and a second portion of bone, and which are scalable to a small implant size. In various embodiments, the device includes a stretching shaft having an internal cavity disposed therein and configured to be fixed to the first portion of bone, and a housing configured to be fixed to the second portion of bone, wherein the stretching shaft is configured to be axially movable relative to the housing and a portion of the housing is disposed therein. A drive element is disposed within the housing and configured to rotatably drive a gear assembly, and a lead screw assembly is disposed at least a portion of the internal cavity of the stretching shaft, and the lead screw assembly is configured to rotatably advance and / or retract a lead screw within the internal cavity and to be rotatably driven by a cycloidal gear assembly.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This international patent application claims priority to U.S. Provisional Patent Application No. 63 / 286,699, filed December 7, 2021, the entirety of which is incorporated by reference as if fully set forth herein. [Background technology]

[0002] The present disclosure relates generally to expansion devices, and more particularly to expansion devices expandable to small implant sizes.

[0003] Leg length discrepancy (LLD) refers to a condition in which a subject's legs are not equal in length, caused by unequal lengths of one or more bones of the leg, such as the femur, tibia, or both. LLD may be present at birth or may develop during an individual's life, for example as a result of a fracture or traumatic injury. LLD may also be caused by infection, tumor, and may be the result of chronic fractures, congenital anomalies, or nonunions. Depending on the severity of the LLD, non-surgical or surgical treatments may be appropriate. Non-surgical treatments may include, for example, simple monitoring or the use of shoe lifts. Surgical treatments suitable for more severe cases may include procedures including epiphysiodesis, leg shortening, external leg lengthening, or internal leg lengthening.

[0004] Intramedullary and extramedullary leg lengthening implants have been described, for example, in WO 2011 / 029021 A1 and WO 2017 / 132646 A1. However, intramedullary and extramedullary implants that can be scaled down to accommodate the needs of smaller patients and conditions involving less bone lengthening are desirable. Summary of the Invention

[0005] A first aspect of the present disclosure provides a device configured to be positioned between a first portion of a bone and a second portion of a bone. The device includes an extension shaft having an internal cavity disposed therein, the extension shaft configured to be secured to the first portion of the bone, and a housing configured to be secured to the second bone portion. The extension shaft is configured to be axially movable relative to the housing and is disposed partially within the housing. The device further includes a drive element disposed within the housing, a cycloidal gear assembly configured to be rotatably driven by the drive element, and a lead screw assembly disposed at least partially within the internal cavity of the extension shaft. The lead screw assembly is configured to rotatably advance and / or retract a lead screw within the internal cavity and to be rotatably driven by the cycloidal gear assembly.

[0006] A second aspect of the present disclosure provides a device configured to be positioned between a first portion of a bone and a second portion of a bone. The device includes an elongated shaft having an internal cavity disposed therein and a first tab projection extending from a shoulder adjacent an open end of the internal cavity. The elongated shaft is configured to be secured to the first portion of the bone. The device further includes a housing configured to be secured to the second bone portion, the elongated shaft configured to be axially movable relative to the housing and disposed partially within the housing. A drive element is disposed within the housing, and the gear assembly is configured to be rotatably driven by the drive element. The lead screw assembly is further configured to rotatably engage the internal cavity and to be rotatably driven by the gear assembly. In such an embodiment, the lead screw assembly includes a lead screw disposed at least partially within the internal cavity of the extension shaft and an anti-jamming feature disposed on the lead screw between the open end of the extension shaft and the gear assembly, the anti-jamming feature including a helical spring having a second tab protrusion configured to matingly engage with a first tab protrusion on the extension shaft.

[0007] A third aspect of the present disclosure provides a device configured to be positioned between a first portion of a bone and a second portion of a bone, the device comprising: an elongated shaft having an internal cavity disposed therein, the elongated shaft having an oval cross-sectional shape and configured to be fixed to the first portion of the bone; and a housing configured to be fixed to the second bone portion. The elongated shaft is configured to be axially movable relative to the housing and is disposed partially within the housing. A drive element is disposed within the housing, and the gear assembly is configured to be rotatably driven by the drive element. A lead screw assembly is disposed at least partially within the internal cavity of the elongated shaft, the lead screw assembly is configured to rotatably advance or retract a lead screw within the internal cavity and is rotatably driven by the gear assembly.

[0008] These and other aspects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the accompanying drawings, in which like parts are designated by like reference characters throughout, disclose embodiments of the present invention. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of an intramedullary extension device in place within a bone. [Diagram 2] FIG. 2 is a top view of a device including an oval stretch rod and a housing, according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a side view of a device including an oval stretch rod and a housing, according to an embodiment of the present invention. [Figure 4] FIG. 4 is a side view of the oval stretch rod shown in FIG. 3 with a housing, in accordance with an embodiment of the present invention. [Diagram 5] FIG. 2 is a side cross-sectional view of a device including an oval stretch rod and a housing, according to an embodiment of the present invention. [Figure 6]FIG. 2 is a top cross-sectional view of a device including an oval stretch rod and a housing, according to an embodiment of the present invention. [Figure 7] FIG. 13 is an exploded side view of a side of a gear and magnet assembly of a device in accordance with an embodiment of the present invention. [Figure 8] FIG. 2 is an exploded side perspective view of a gear and magnet assembly of a device in accordance with an embodiment of the present invention. [Figure 9] FIG. 2 is an exploded side perspective view of a gear and magnet assembly of a device in accordance with an embodiment of the present invention. [Figure 10] FIG. 7 is a side view of the lead screw shown in FIGS. 5-6, in accordance with an embodiment of the present invention. [Figure 11] FIG. 2 is an exploded side perspective view of a gear and magnet assembly of a device in accordance with an embodiment of the present invention. [Figure 12] FIG. 2 is a perspective view of an eccentric magnet cup according to an embodiment of the present invention. [Figure 13A] FIG. 2 is a side perspective view of an anti-jam mechanism according to an embodiment of the present invention. [Figure 13B] FIG. 2 is a side perspective view of an anti-jam mechanism according to an embodiment of the present invention. [Figure 13C] FIG. 2 is a side perspective view of an anti-jam mechanism according to an embodiment of the present invention. [Figure 14A] FIG. 2 is a perspective view of an oblong nut according to an embodiment of the present invention. [Figure 14B] FIG. 2 is a cross-sectional view of an oblong nut according to an embodiment of the present invention. [Figure 15] FIG. 2 is a side perspective view of an oval stretch rod according to an embodiment of the present invention. [Figure 16] 16 is a cross-sectional view of the oval stretch rod of FIG. 15 in accordance with an embodiment of the present invention. [Figure 17] FIG. 1 is a side view of a device attached to vertebrae of the spine of an individual suffering from scoliosis, in accordance with an embodiment of the present invention.

[0010] It should be noted that the drawings of the disclosure are not necessarily to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbers represent like elements between the drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] At least one embodiment of the present invention is described below with reference to its application in connection with an extramedullary distraction device. Although an embodiment of the present invention is illustrated with respect to an extramedullary distraction device, it is understood that the present teachings are equally applicable to other implants, including, but not limited to, intramedullary distraction devices, intramedullary and extramedullary devices for performing bone compression, and adjustable spinal rods configured to be coupled to vertebrae of the spine, for example, via pedicle screws.

[0012] FIG. 1 illustrates a side view of device 110, an intramedullary extension device, deployed from a hole or bore 108 contained within bone 100. The hole or bore 108 may be created by drilling, reaming, etc., and may extend through both cortical (at the ends) and cancellous (spongy) bone. As illustrated in FIG. 1, device 110 includes a housing 112 and an extension shaft 114. Bone 100 may either have a pre-existing separation 106 or may be intentionally cut or broken to create this separation 106, dividing the bone into a first portion 102 and a second portion 104. The cut may be made prior to inserting and securing device 110, or may be made after device 110 is inserted, for example, by use of a flexible Gigli saw. The extension shaft 114 of device 110 is attached to first portion 102 using one or more fasteners 118, which may include, for example, screws known to those skilled in the art. The housing 112 of the device 110 is secured to the second portion 104 of the bone 100 using one or more fasteners 116. The fasteners 116 may again include screws or other types of fasteners known in the art.

[0013] To grow or lengthen the bone 100, the bone 100 is continuously distracted over the treatment period. This enlarges or widens the separation 106 where bone formation can occur. "Continuously distracted" is meant to indicate that the distraction occurs at regular intervals, which may be on the order of half a day, daily, or every few days. An exemplary distraction rate may be, for example, 1 millimeter per day, although other distraction rates may be used. That is, a typical distraction regimen may include an extension of the length of the device 110 by about 1 millimeter every day. This may be done, for example, by 4 distraction periods per day, with each session having an extension of 0.25 mm. The device 110 may include a drive system configured to telescopically extend the distraction shaft 114 from the housing 112, thus forcing the first portion 102 and the second portion 104 of the bone 100 apart from each other. When distraction occurs, a portion of the housing 112 may be configured to slide within a hole or aperture 108 in the first portion 102 of the bone 100 within the displacement portion 120 .

[0014] In various embodiments, the orientation of the device 110 within the bone 100 may be opposite to the orientation shown in Figure 1. For example, the extension shaft 114 may be coupled to the second portion 104 of the bone 100 and the housing 112 may be coupled to the first portion 102 of the bone 100. Thus, the device 110 may be placed in the opposite orientation from a hole or aperture beginning at the distal end of the bone 100.

[0015] In other embodiments, the device may take other forms. In certain embodiments, such as those illustrated in Figures 2-6, the device 210 may be in the form of an extramedullary device 210 configured for use for either distraction or compression of bone, as described in International Patent Application No. PCT / US2021 / 041701, which is incorporated herein by reference as if fully set forth. The device 210 is configured to be placed between a first portion of a bone and a second portion of a bone, similar to the first portion 102 and second portion 104 of the bone 100 shown in Figure 1. The device 210 includes a housing 212 and a distraction shaft 214. The housing 212 may include a sleeve portion, which may have a substantially circular or oval cross-sectional shape. The sleeve portion may be attached to an end portion 230, which includes one or more fixation gaps or holes 222 configured to receive a fastener, such as the fastener 116 (Figure 1). The end portion 230 may include, for example, a plate that may be curved, angled, or contoured according to the particular size and shape of the bone to which it is secured. The end portion 230 may also include an end cap. The extension shaft 214, illustrated separately from the housing 212 in FIG. 4, may include holes 224 configured to receive fasteners, such as fasteners 118 known in the art, to secure the extension shaft 214 to a portion of the bone (FIG. 1). In various embodiments, the holes 222 and 224 may be internally threaded and configured to receive fasteners having a thread pattern complementary to the thread pattern of the holes 222, 224.

[0016] As described above with respect to device 110, device 210 is configured to telescopically extend and retract extension shaft 214 from housing 212, thereby forcing a first portion and a second portion of a bone apart from one another during extension, or drawing the first portion and the second portion together during retraction. Extension shaft 214 is configured to be inserted at least partially within housing 212, as shown in FIGS. 2-3, with the end of extension shaft 214 opposite threaded hole 222 being inserted within housing 212. In the shortest, most retracted configuration of device 210, extension shaft 214 is disposed substantially within a sleeve portion of housing 212. Extension shaft 214 is telescopically movable relative to housing 212. In particular, extension shaft 214 may translate axially to slide in and out of housing 212.

[0017] The distraction shaft 214 may be configured to be secured to a first portion 102 of the bone 100 (FIG. 1), as previously described, while the housing 212 may be configured to be secured to a second portion 104 of the bone 100 (FIG. 1). However, as described with respect to FIG. 1, an opposite orientation of the device 210 is also considered within the scope of the present disclosure. As also described with respect to FIG. 1, in order to grow or lengthen the bone into which the device 210 is implanted, the bone is continually distracted over the treatment period, thereby widening or widening the separation between the first and second portions of the bone where bone formation occurs.

[0018] The device 210 includes a drive element disposed within a housing 212. In one embodiment, shown in Figures 4-6, the drive element may include a permanent magnet 234. The permanent magnet 234 may be cylindrical or substantially cylindrical in shape and may be rotatable relative to the housing 212 about a longitudinal axis of a cylinder within the housing 212. Such rotation may be magnetically driven by an external adjustment device as described in WO 2011 / 029021, which is incorporated herein by reference as if fully set forth.

[0019] Although some embodiments are described herein in which the drive element is a permanent magnet 234, in other embodiments the drive element may take other forms, such as, for example, a motor or micromotor, and these embodiments are equally considered to be part of this disclosure.

[0020] The permanent magnet 234 or another drive element disclosed herein may be rotatably coupled to a lead screw assembly 240, including a lead screw 242. As shown in FIGS. 5-6, the lead screw assembly 240 is disposed at least partially within an internal cavity 237 within the extension shaft 214 (FIGS. 5, 6, 15, 16), where the lead screw assembly 240 is configured to rotatably advance and / or retract the lead screw 242 within the internal cavity 237. In use, rotation of the permanent magnet 234 causes rotation of the lead screw 242, which rotates within a nut 239 secured to an inner surface of the cavity 237 within the extension shaft 214. Such rotation of the lead screw 242 within the nut 239 causes either an advancement or retraction of the lead screw 242 depending on the direction of rotation, i.e., clockwise or counterclockwise. Rotation of the lead screw 242 advances it further into the cavity 237 of the extension shaft 214 and away from the end 230, thereby driving the extension shaft 214 telescopically out of the housing 212. This in turn extends the length of the device 210, distracting the bone in which the device 210 is implanted. When rotation of the lead screw 242 retracts it more shallowly within the cavity 237 of the extension shaft 214 and toward the end 230 of the housing 212, this retracts the extension shaft 214 into the housing 212, thereby compressing the bone in which the device 210 is implanted.

[0021] As shown in Figures 5-6, the permanent magnet 234 may be disposed within the housing 212 and maintained in place on one end by a cap or cup 228 having a central spindle 231 extending therefrom. A keeper 232 and bearings 233 cooperate with each other and with the spindle 231 to support the permanent magnet 234 within the housing 212 and achieve and maintain the proper axial stack height during rotation of the permanent magnet 234. The central spindle 231 may extend past the bearings 233 and keeper 232 near an end of the housing 212, allowing the permanent magnet 234 to rotate about said housing when actuated, for example, by an external adjustment device.

[0022] At the opposite end of the permanent magnet 234, a coupling member, for example in the form of a cup or cap 235, may be disposed on the end of the permanent magnet 234. The cap 235 may include an eccentric shaft 238 extending therefrom in a direction opposite to the spindle 231 and towards the lead screw 242 and extension shaft 214. A bearing 360 may be provided to support the eccentric shaft 238 in use. The cap 235 with the eccentric shaft 238 may couple a drive element, for example the permanent magnet 234, to a gear assembly. In certain embodiments disclosed herein, the gear assembly may in particular be a cycloidal gear assembly 250. The cap 235 is further configured to rotate with the permanent magnet 234 and to rotatably drive the cycloidal gear assembly 250 using the eccentric shaft 238. Further details of the engagement of the permanent magnet 234, the cap 235 and the eccentric shaft 238, and the cycloidal gear assembly 250 are further described below.

[0023] 5-6, in various embodiments described herein, the permanent magnet 234 or other drive element may be coupled to the lead screw assembly 240 by a cycloidal gear assembly 250. The cycloidal gear assembly 250 may be configured to be rotatably driven by the permanent magnet 234, which in turn rotates the lead screw 242. In particular, a magnet cup 235 having an eccentric shaft 238 may be engaged with the cycloidal gear assembly 250. The permanent magnet 234, the cycloidal gear assembly 250, and the lead screw 242 are all configured to rotate relative to the housing 212 and the extension shaft 214, thereby causing axial movement of the lead screw 242 within the internal cavity 237 as described above, thereby, for example, extending or shortening the device 210 without causing rotation of the extension shaft 214 within the housing 212.

[0024] 5-7, the cycloidal gear assembly 250 can include one or more gear stages, e.g., one, two, three, four, or more than four gear stages. In the illustrated example, the cycloidal gear assembly 250 includes three stages, including a first stage 350, a second stage 450, and a third stage 550. In certain embodiments, each stage 350, 450, 550, etc. of the one or more stages in the cycloidal gear assembly 250 can be configured to provide a particular gear reduction ratio. For example, each gear stage 350, 450, 550, etc. can provide a gear reduction ratio of 4:1. Thus, a cycloidal gear assembly having two stages can provide a gear reduction ratio of 16:1, and a cycloidal gear assembly having three stages can provide a gear reduction ratio of 64:1.

[0025] As described herein with respect to the accompanying drawings, the components of the first stage 350, second stage 450, and third stage 550 of the cycloidal gear assembly 250 use reference numbers in the 300, 400, and 500 series, respectively. The use of the same second and third digits indicates like parts and similar functions, for example, within the first stage 350 and second stage 450, respectively. For example, plate member 352 and plate member 452 refer to structurally and functionally similar components to the first stage 350 and second stage 450, respectively. The components of the cycloidal gear assembly 250 may be made from any of a number of biocompatible materials known in the art, although in certain embodiments, anodized titanium may be used.

[0026] 7-9, each stage of the cycloidal gear assembly 250 may include multiple components. For example, the first stage 350 may include a plate member 352 rotatably fixed relative to the housing 212 (shown in FIGS. 5-6). The plate member 352 may have an annular opening 353 therethrough and may include a number of pins 351 spaced about an outer periphery of the annular opening 353 (FIGS. 8-9). The pins 351 may be configured to rotate freely relative to the plate member 352, thereby reducing friction generated by the system. In one particular embodiment, the number of pins 351 may be five. However, other embodiments in which other numbers of pins 351 are possible are also contemplated as part of the present disclosure, for example, the plate member 352 may include one pin, two pins, three pins, four pins, five pins, six pins, etc. Additionally, the plate member 352 may be configured to incorporate a pin surface 361, as shown in FIG. 11. In the embodiment of Figure 11, the pin surfaces 361 prevent rotation but make assembly easier. These pins 351 (Figures 8-9) or pin surfaces 361 (Figure 11) on the plate member 352 may be evenly spaced around the outer edge of the annular opening 353 through the plate member 352. Additionally, as shown in Figure 6, a bearing 360 may be disposed within the plate member 352 adjacent the pins 351.

[0027] The first stage 350 may further include a cycloidal eccentric drive disk 354 having a lobe portion extending longitudinally and including a plurality of lobes 355 having an axially extending annular opening therethrough (best viewed in FIG. 9). The lobe portion may be configured to be axially inserted into annular opening 353 of plate member 352. In certain embodiments, such as the embodiment illustrated in FIGS. 7-9, the number of lobes 355 may be four. In some embodiments, the number of lobes 355 may be at least two. However, in other embodiments, there may be other numbers of lobes 355, e.g., one lobe, two lobes, three lobes, four lobes, five lobes, etc. Regardless of the number of pins 351 or lobes 355 present, the number of lobes 355 is equal to (n-1), where n is the number of pins 351 present, such that a smooth epitrochoidal curve results. The eccentric shaft 238 on the magnet cup 235 is configured to be inserted through the annular opening 353 in the plate member 352 from a direction opposite the longitudinally extending lobes 355 of the eccentric driving disk 354 such that the eccentric shaft 238 extends through the annular opening 353 in the plate member 352 and through the annular opening through the cycloidal eccentric driving disk 354. In this manner, the eccentric shaft 238 of the eccentric magnet cup 235 is configured to drive the rotation of the eccentric driven disk 254 within the plate member 352. In one particular embodiment, the cycloidal eccentric driving disk 354 may follow an epitrochoidal curve in use, providing a smooth rotational load surface. Bearings 360 may be provided to support the eccentric shaft 238 within the plate member 352 (FIGS. 5-8).

[0028] The cycloidal eccentric drive disk 354 may further include a plurality of recess features 356 on a face opposite the longitudinally extending lobes 355. In embodiments having only a single gear stage 350 in the cycloidal gear assembly 250, the recess feature 356 is configured to couple to the lead screw assembly 240, as described further below.

[0029] In other embodiments including two or more stages 350, 450, etc. in the cycloidal gear assembly 250, the recess feature 356 is configured to engage the output shaft member 357. The output shaft member 357 can include a number of pins 358 extending in a first direction and an output shaft 359 extending in a second direction opposite the first direction. The pins 358 can be configured to engage the recess features 356 of the cycloidal eccentric drive disk 354 in a one-to-one manner. The number of pins 358 can be equal to the number of recess features 356 present on the cycloidal eccentric drive disk 354. In one particular embodiment, the number of pins 358 and recess features 356 can be four, although other configurations, e.g., one pin, two pins, three pins, four pins, etc., are within the scope of the present invention. The output shaft 359 of the output shaft member 357 can be an eccentric shaft.

[0030] The output shaft 359 may engage with the second gear stage 450 in the same manner as the eccentric shaft 238 of the magnet cup 235 engages with the plate member 352 and cycloidal eccentric drive disk 354 of the first stage 350. In particular, the eccentric output shaft 359 may extend towards the second gear stage 450. The second gear stage 450 may include a plate member 452 rotatably fixed relative to the housing 212 (shown in FIGS. 5-6). The plate member 452 may have an annular opening 453 therethrough and may include a plurality of pins 451 or pin surfaces 461 (FIG. 11) spaced about an outer periphery of the annular opening 453. In one particular embodiment, the number of pins 451 or pin surfaces 461 may be five. However, other numbers of pins 451 or pin surfaces 461 are possible, for example, plate member 452 including one pin, two pins, three pins, four pins, five pins, six pins, etc., and other embodiments are also contemplated as part of this disclosure. These pins 451 or pin surfaces 461 may be evenly spaced around the outer edge of annular opening 453 through plate member 452. Additionally, as shown in FIG. 6, bearings 460 may be disposed within plate member 452 adjacent pins 451 or pin surfaces 461.

[0031] The second stage 450 may further include a cycloidal eccentric drive disk 454 having a longitudinally extending portion with a plurality of lobes 455 having an axially extending annular opening therethrough (as best seen in FIG. 9). The plurality of lobes may be configured to be axially inserted into the annular openings 453 of the plate member 452. In certain embodiments, such as the embodiment illustrated in FIGS. 7-9, the number of lobes 455 may be four. However, in other embodiments, there may be other numbers of lobes 455, e.g., one lobe, two lobes, three lobes, four lobes, five lobes, etc. The output shaft 359 of the output shaft member 357 is configured to be inserted through the annular opening 453 in the plate member 452 from a direction opposite the longitudinally extending lobes 455 of the eccentric drive disk 454 such that the output shaft 359 extends through the annular opening 453 in the plate member 452 and through an annular opening through the cycloidal eccentric drive disk 454. In this manner, the output shaft 359 is configured to drive the rotation of the eccentric drive disk 454 within the plate member 452. In one particular embodiment, the cycloidal eccentric drive disk 454 may follow an epitrochoidal curve in use, providing a smooth rotational load surface. A bearing 460 may be provided to support the eccentric shaft 357 within the plate member 452 (FIG. 6).

[0032] The cycloidal eccentric drive disk 454 may further include a plurality of recess features 456 on opposite sides of the longitudinally extending lobes 455. In embodiments including two gear stages 350, 450 within the cycloidal gear assembly 250, the recess features 456 are configured to couple to the lead screw assembly 240, as described further below.

[0033] In other embodiments including three or more stages 350, 450, 550, etc. in the cycloidal gear assembly 250, the recess feature 456 is configured to engage the output shaft member 457. The output shaft member 457 can include a number of pins 458 extending in a first direction and an output shaft 459 extending in a second direction opposite the first direction. The pins 458 can be configured to engage the recess features 456 of the cycloidal eccentric drive disk 454 in a one-to-one manner. The number of pins 458 can be equal to the number of recess features 456 present on the cycloidal eccentric drive disk 454. In one particular embodiment, the number of pins 458 and recess features 456 can be four, although other configurations, e.g., one pin, two pins, three pins, four pins, etc., are within the scope of the present invention. The output shaft 459 of the output shaft member 457 can be an eccentric shaft.

[0034] The output shaft 459 may engage with the third gear stage 550 in a manner similar to how the output shaft 359 engages with the plate member 452 and cycloidal eccentric drive disk 454 of the second stage 450. In particular, the eccentric output shaft 459 may extend towards the third gear stage 550. The third gear stage 550 may include a plate member 552 rotatably fixed relative to the housing 212 (shown in FIGS. 5-6). The plate member 552 may have an annular opening 553 therethrough and may include a number of pins 551 or pin surfaces 561 (FIG. 11) spaced about an outer periphery of the annular opening 553. In one particular embodiment, the number of pins 551 or pin surfaces 561 may be five. However, other numbers of pins 551 or pin surfaces 561 are possible, for example, the plate member 552 may include one pin, two pins, three pins, four pins, five pins, six pins, etc., and other embodiments are also contemplated as part of this disclosure. The pins 551 or pin surfaces 561 may be evenly spaced around the outer edge of an annular opening 553 through the plate member 552. Additionally, as shown in FIG. 6, bearings 560 may be disposed within the plate member 552 adjacent the pins 551 or pin surfaces 561.

[0035] The third stage 550 may further include a cycloidal eccentric drive disk 554 having a longitudinally extending portion with a plurality of lobes 555 having an axially extending annular opening therethrough (as best seen in FIG. 9). The plurality of lobes may be configured to be axially inserted into annular openings 553 in the plate member 552. In certain embodiments, such as the embodiment illustrated in FIGS. 7-9, the number of lobes 555 may be four. However, in other embodiments, there may be other numbers of lobes 555, e.g., one lobe, two lobes, three lobes, four lobes, five lobes, etc. The output shaft 459 of the output shaft member 457 is configured to be inserted through the annular opening 553 in the plate member 552 from a direction opposite the longitudinally extending lobes 555 of the eccentric drive disk 554 such that the output shaft 459 extends through the annular opening 553 in the plate member 552 and through an annular opening through the cycloidal eccentric drive disk 554. In this manner, the output shaft 459 is configured to drive the rotation of the eccentric drive disk 554 within the plate member 552. In one particular embodiment, the cycloidal eccentric drive disk 554 may follow an epitrochoidal curve in use, providing a smooth rotational load surface. A bearing 560 may be provided to support the eccentric shaft 457 within the plate member 452 (FIG. 6).

[0036] The cycloidal eccentric drive disk 554 may further include a plurality of recess features 556 opposite the longitudinally extending lobes 555. For example, in the embodiment with three gear stages 350, 450, 550 in the cycloidal gear assembly 250 shown in Figures 5-8, the recess features 556 are configured to engage the lead screw assembly 240, as described further below.

[0037] In other embodiments including four or more stages in the cycloidal gear assembly 250, the recess features 556 are configured to engage the output shaft member in a manner similar to the output shaft member 457, in a pattern that may continue through further stage repetitions. Such an output shaft member may include a number of pins extending in a first direction and an output shaft extending in a second direction opposite the first direction. The pins may be configured to engage the recess features 556 of the cycloidal eccentric drive disk 554 in a one-to-one manner. The number of pins may be equal to the number of recess features 556 present on the cycloidal eccentric drive disk 554. In one particular embodiment, the number of pins and recess features 556 may be four, although other configurations, such as one pin, two pins, three pins, four pins, etc., are within the scope of the present invention. The output shaft of the output shaft member may be an eccentric shaft.

[0038] Regardless of the number of gear stages in the cycloidal gear assembly 250, the cycloidal eccentric driving disk 354, 454, 554 of the final stage of gears may be configured to engage the lead screw assembly 240 as described above. The final stage of gears in the embodiments illustrated in Figures 5-8 is the third stage 550. Thus, in these embodiments, the cycloidal eccentric driving disk 554 is configured to engage the lead screw assembly 240. In embodiments having one or two gear stages, the cycloidal eccentric driving disk 354 or 454, respectively, may be configured to engage the lead screw assembly 240.

[0039] The lead screw assembly 240 may include a lead screw 242 (FIG. 10), which may be, for example, a hex drive. The lead screw assembly 240 may further include an output shaft and lead screw stop 243 (FIGS. 6-9), which may include a plurality of axially extending pins 241 (FIG. 7) extending in a first direction, which are configured to engage recess feature 556 in use. It will be appreciated that in other embodiments, for example in embodiments having only one gear stage, the output shaft and lead screw stop 243 may directly engage recess feature 356 in use, and in embodiments having two gear stages, the output shaft and lead screw stop 243 may engage recess feature 456 in use. In any event, the pin 241 may be shaped and configured substantially similarly to the pins 358, 458, etc. on the output shaft member 357, 457 previously described herein.

[0040] Opposite the plurality of pins 241 is a lead screw stop mechanism that threadably receives an end of a lead screw 242. For example, as shown in Figures 5-6, the lead screw stop mechanism can include an internally threaded mechanism configured to receive and engage a threaded end 244 (Figure 10) of the lead screw 242. The lead screw stop mechanism, which collectively comprises the output shaft and lead screw stop 243, and the pin 241, can be integrally formed or can include two or more components welded or otherwise bonded together, as understood in the art.

[0041] The lead screw assembly 240 further includes a bidirectional thrust bearing 245 (FIGS. 4-6) disposed about the lead screw 242 and configured to support an axial load thereof. The bidirectional thrust bearing 245 is disposed adjacent the output shaft lead screw stop 243. A retaining ring 246, which may be, for example, a split washer, may be disposed about the lead screw 242 and adjacent the bidirectional thrust bearing 245. As shown in FIGS. 4-6, the lead screw 242 is coupled at one end to the cycloidal gear assembly 250 by the output shaft and the lead screw stop 243. From this connection, the lead screw 242 extends through the bidirectional thrust bearing 245 and the retaining ring 246 into the cavity 237 of the stretch rod 214. A nut 239 is secured to an inner surface of the cavity 237 and engages a threaded portion 266 along the length of the lead screw 242, as shown in FIGS. 5-6.

[0042] The use of cycloidal gear assemblies to achieve the gear reduction ratios described herein provides several advantages. Because cycloidal gears do not contain teeth that provide limitations regarding the ability to scale, the cycloidal gear assemblies are easily scalable to implants designed for smaller sized bones and patients, e.g., jaw or finger bones. In particular, the device 210 may be scaled to provide a plate thickness or nail outer diameter of approximately 6.4 mm thick. Through the use of bearings and / or bushings, the cycloidal gear assembly 250 as described herein can transmit loads with up to 96% efficiency. This efficiency also contributes to scalability, as smaller magnets and / or fewer gear stages can be used to generate the torque required to perform distraction.

[0043] In certain embodiments of the device 210, the anti-jam feature may be disposed about the lead screw 242 at an axial location between the open end or shoulder 249 of the extension shaft 214 and the cycloidal gear assembly 250. In certain embodiments, one or more other components may also be disposed on the lead screw 242 at an axial location between the open end of the extension shaft 214 and the cycloidal gear assembly 250, such that the anti-jam feature may be disposed, for example, directly between the open end or shoulder 249 of the extension shaft 214 and the retaining ring 246.

[0044] In embodiments including the anti-jam features described herein, such as those illustrated in Figures 4-6, the anti-jam feature can function to reduce or completely avoid the possibility of "bottoming out" or jamming between components, such as between the extension rod 214 in a fully retracted state and the lead screw stop 243. The anti-jam feature adds to the torque delivered by the drive element and gear assembly, such as the cycloidal gear assembly 250, to provide additional spring force to overcome surface friction, thereby helping to unjam the components and initiate extension of the rod 214.

[0045] The anti-jam mechanism described herein may be in the form of an anti-jam spring 248, which may be a one-piece helical spring having a substantially circular or oval outer cross-sectional shape, as illustrated in Figures 13A-13C. In embodiments including the anti-jam spring 248, the extension rod 214 may include a first tab projection 247 (Figures 4, 15, 16) extending from a shoulder 249 (Figures 15, 16) adjacent the open end of the internal cavity 237 of the extension shaft 214. The tab projection 247 is configured to cooperate with the anti-jam spring 248 described herein.

[0046] The anti-jam spring 248 may include a second tab projection 261 configured to matingly engage with the first tab projection 247 on the extension shaft 214. The anti-jam spring 248 may further include a keyed opening 264 (FIG. 13C), which may be, for example, hexagonal in shape, around which the spiral of the spring 248 is arranged. The shape of the keyed opening 264 is configured to complement the cross-sectional shape of the lead screw 242 at the corresponding axial location 262 (FIG. 6). Thus, in an embodiment in which the lead screw 242 has a hexagonal cross-sectional shape at the corresponding axial location 262, the anti-jam spring 248 is configured to be hexagonally driven and rotatably fixed to the lead screw 242. This configuration allows the anti-jam spring 248 to remain centered with respect to the lead screw assembly 240 and restrained at the lead screw shoulder without tilting or floating. In use, as the anti-jam spring 248 is rotated by the lead screw 242, the tab 261 encounters and engages the stretch rod tab 247. The resistance provided by the stretch rod tab 247 causes the anti-jam spring 248 to open into the inner diameter of the housing 212, providing a spring force to overcome surface friction as described above. The anti-jam spring 248 is further configured to maintain engagement and surface contact with the shoulder 249 of the stretch rod 214 while the stretch rod 214 is fully retracted.

[0047] The anti-jam mechanism 248 described herein may be used in the context of various distraction devices. For example, the anti-jam mechanism 248 may be used in conjunction with the device 210 including the cycloidal gear assembly 250 described and illustrated herein. However, the anti-jam mechanism 248 may also be used in similar contexts in both intramedullary and extramedullary distraction and compression devices, devices having various drive elements, e.g., magnetic and motor-based, and in the context of implant devices including various gear assemblies, e.g., cycloidal gear assembly 250 or planetary gear assemblies, such as those described in International Publication WO 2017 / 132646(A1) and International Patent Application No. PCT / US2021 / 041701, filed July 14, 2021, each of which is incorporated herein by reference as if fully set forth.

[0048] In a stretching device such as device 210, it may be clinically undesirable for the stretch rod 214 to rotate about its longitudinal axis within the housing 212. Thus, in certain embodiments shown in FIGS. 15-16, an anti-rotation feature may be provided in the form of a stretch rod 214 having an oval cross-sectional shape. In certain embodiments, the stretch rod 214 may have an oval outer cross-sectional shape and the internal cavity 237 may have an oval cross-sectional shape. In embodiments having an internal cavity 237 with an oval cross-sectional shape, the nut 239 may also have an outer surface that is oval in cross-section to match the contour of the inner surface of the cavity 237 of the stretch rod 214, as shown in FIGS. 14A-14B. The lead screw 242 can rotate within the nut 239, as described above and as illustrated in FIGS. 5-6, but because of the oval outer shape of the nut 239, the oval inner and outer shapes of the stretch rod 214, and the corresponding oval shape of the housing 212, the housing 212, the stretch rod 214, and the nut 239 cooperate to maintain a fixed rotational position relative to one another.

[0049] The oval nut 239 and oval extension rod 214 described herein may be used in the context of various distraction devices. For example, the oval nut 239 and oval extension rod 214 may be used in conjunction with the device 210 including the cycloidal gear assembly 250, as described and illustrated herein. However, the cooperating oval nut 239 and oval extension rod 214 may also be used in similar contexts in both intramedullary and extramedullary distraction and compression devices, devices having various drive elements, e.g., magnetic and motor-based, and may be used in the context of implant devices including various gear assemblies, e.g., cycloidal gear assembly 250 or planetary gear assemblies, such as those described in International Publication WO 2017 / 132646(A1) and International Patent Application No. PCT / US2021 / 041701, filed July 14, 2021. The cooperating oval nut 239 and oval extension rod 214 may also be used in device embodiments in combination with an anti-jam spring 248. In such embodiments, the anti-jam spring 248 may also have an oval outer cross-sectional shape similar to the nut 239. In other embodiments, the cooperating oval nut 239 and oval extension rod 214 may be used in devices that do not include the anti-jam spring 248.

[0050] Although the present invention has been shown and described in relation to an extramedullary leg lengthening device, it should be understood that the embodiments herein can be used for intramedullary lengthening devices. Furthermore, as described herein, it should be understood that the device is capable of both lengthening and retraction, and thus the present invention can also be used for bone compression (e.g., in correcting nonunion). Furthermore, the embodiments described herein can also be used to correct spinal curvature, and thus can be configured as an adjustable spinal rod 310 (FIG. 17) that can be coupled to the vertebrae of the spine, for example, via pedicle screws. For example, in the embodiment of FIG. 17, instead of holes 222 and 224 in the housing 212 and lengthening rod 214 (FIGS. 2-3), the ends of the device 310 can be secured to first and second portions of the bone by placing each end in the tulips or receivers of the pedicle screws.

[0051] As used herein, terms such as "first," "second," and the like, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another, and the terms "a" and "an" herein do not denote a limitation on quantity, but rather denote the presence of at least one of the referenced items. The modifier "about" used in connection with a quantity is inclusive of the stated value and has the meaning indicated by the context (e.g., including the degree of error associated with the measurement of a particular quantity). The suffix "(s)" as used herein is intended to include both the singular and the plural of the term it modifies, thereby including one or more of that term (e.g., metal(s) includes one or more metals). Ranges disclosed herein are inclusive, independently, and combinable (e.g., the range "up to about 25 mm, or, more specifically, about 5 mm to about 20 mm" includes the endpoints and all intermediate values ​​of the range "about 5 mm to about 25 mm").

[0052] While various embodiments have been described herein, it will be understood from the specification that various combinations of elements, variations, or improvements therein may be made by one skilled in the art and are within the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. 1. A device configured to be placed between a first portion of a bone and a second portion of the bone, an elongated shaft having an internal cavity disposed therein, the elongated shaft being configured to be secured to the first portion of a bone; a housing configured to be secured to a second portion of the bone, the elongated shaft configured to be axially movable relative to the housing and disposed partially within the housing; a drive element disposed within the housing; a cycloidal gear assembly configured to be rotatably driven by the drive element; and a lead screw assembly disposed at least partially within the internal cavity of the elongated shaft, the lead screw assembly configured to rotatably advance and / or retract a lead screw within the internal cavity and to be rotatably driven by the cycloidal gear assembly; A device comprising:

2. The device of claim 1 , wherein the cycloidal gear assembly further comprises one or more cycloidal gear stages.

3. 3. The device of claim 2, wherein each of the one or more cycloidal gear stages has a gear reduction ratio of 4:

1.

4. Each of the one or more cycloidal gear stages comprises: a plate member rotatably fixed to said housing and having an annular opening therethrough, said plate member having five pins evenly spaced about an outer periphery of said annular opening; a cycloidal eccentric drive disk having a longitudinally extending portion with four lobes, the four lobes configured to be inserted into the annular opening, the cycloidal eccentric drive disk further comprising a plurality of recess features configured to matingly engage a corresponding plurality of pins; an output shaft member including a plurality of pins configured to matingly engage with the plurality of recess features, the output shaft member extending in a direction opposite to a direction of the plurality of pins; The device of claim 2 further comprising:

5. The device of claim 4 , wherein the cycloidal eccentric driving disk further comprises an epitrochoidal curve.

6. The device of claim 2 , wherein the one or more cycloidal gear stages further comprise two cycloidal gear stages.

7. 7. The device of claim 6, wherein the output shaft of a first stage is an eccentric shaft and said output shaft of a second stage is connected to said lead screw.

8. The device of claim 2 , wherein the one or more cycloidal gear stages further comprise three or more cycloidal gear stages.

9. 9. The device of claim 8, wherein the output shaft of a first stage and the output shaft of a second stage are eccentric shafts, and the output shaft of a third stage is connected to the lead screw.

10. a coupling member having an eccentric shaft extending therethrough; the coupling member is configured to couple the drive element and the cycloidal gear assembly, and is further configured to be rotated by the drive element and to rotatably drive the cycloidal gear assembly using the eccentric shaft. The device of claim 1 .

11. The device of claim 10 , further comprising a bearing configured to support the eccentric shaft of the coupling member.

12. The device of claim 1 , wherein the drive element further comprises a permanent magnet disposed within the housing and configured to be rotatable relative to the housing.

13. 13. The device of claim 12, wherein rotation of the permanent magnet rotates the cycloidal gear assembly and the lead screw relative to the housing and the extension shaft, thereby causing axial movement of the lead screw within the internal cavity, thereby lengthening or shortening the device.

14. The device of claim 1 , wherein the drive element further comprises a motor.

15. The device of claim 1 , wherein the internal cavity further comprises a nut secured to an inner surface thereof, the nut configured to engage the lead screw.

16. a first tab projection extending from a shoulder adjacent an open end of the internal cavity of the elongated shaft; an anti-jam mechanism disposed on the lead screw between the open end of the extension shaft and the cycloidal gear assembly; Further comprising: the anti-jam mechanism comprising a helical spring having a second tab projection configured for mating engagement with the first tab projection on the extension shaft; The device of claim 1 .

17. The device of claim 1 , wherein the elongated shaft has an oval cross-sectional shape.

18. 1. A device configured to be placed between a first portion of a bone and a second portion of the bone, an elongated shaft having an internal cavity disposed therein and a first tab projection extending from a shoulder adjacent an open end of the internal cavity, the elongated shaft being configured to be secured to the first portion of a bone; a housing configured to be secured to a second portion of the bone, the elongated shaft configured to be axially movable relative to the housing and disposed partially within the housing; a drive element disposed within the housing; a gear assembly configured to be rotatably driven by the drive element; and a lead screw assembly configured to rotatably engage the internal cavity and to be rotatably driven by the gear assembly, a lead screw disposed at least partially within the internal cavity of the elongated shaft; an anti-jam mechanism disposed on the lead screw between the open end of the extension shaft and the gear assembly; a lead screw assembly comprising: Equipped with the anti-jam mechanism comprising a helical spring having a second tab projection configured for mating engagement with the first tab projection on the extension shaft; device.

19. the anti-jam feature has an outer cross-sectional shape that is one of substantially circular or oval; and further comprising an opening having a key shape that is complementary to a cross-sectional shape of the lead screw at a corresponding axial location such that the anti-jam feature is rotationally fixed relative to the lead screw when the anti-jam feature is engaged to prevent a jam.

20. The device of claim 18.

20. 20. The device of claim 19, wherein the key shape is hexagonal.

21. The lead screw assembly comprises: a lead screw stop rotatably secured to an output shaft of the gear assembly and to the lead screw; a bidirectional thrust bearing disposed above the lead screw and adjacent a lead screw stop; a retaining ring disposed on the lead screw and between the bidirectional thrust bearing and the anti-jam mechanism; The device of claim 18 further comprising:

22. 22. The device of claim 21, wherein the retaining ring further comprises a split washer.

23. 20. The device of claim 18, wherein the gear assembly is a cycloidal gear assembly.

24. 20. The device of claim 18, wherein the elongated shaft has an oval cross-sectional shape.

25. 1. A device configured to be placed between a first portion of a bone and a second portion of the bone, an elongated shaft having an internal cavity disposed therein, the elongated shaft having an oval cross-sectional shape and configured to be secured to the first portion of a bone; a housing configured to be secured to a second portion of the bone, the elongated shaft configured to be axially movable relative to the housing and disposed partially within the housing; a drive element disposed within the housing; a gear assembly configured to be rotatably driven by the drive element; and a lead screw assembly disposed at least partially within the internal cavity of the elongated shaft, the lead screw assembly configured to rotatably advance or retract a lead screw within the internal cavity and to be rotatably driven by the gear assembly; A device comprising:

26. 26. The device of claim 25, wherein the internal cavity has an oval cross-sectional shape.

27. 27. The device of claim 26, wherein the internal cavity further comprises a nut secured to an inner surface thereof, the nut having an oval cross-sectional shape, the nut configured for rotation with the lead screw.

28. 27. The device of claim 26, wherein the drive element further comprises a permanent magnet disposed within the housing and configured to be rotatable relative to the housing.

29. 30. The device of claim 28, wherein rotation of the permanent magnet rotates the gear assembly and the lead screw relative to the housing and the extension shaft, thereby causing axial movement of the lead screw within the internal cavity, thereby lengthening or shortening the device.

30. 26. The device of claim 25, wherein the drive element is a motor.

31. 26. The device of claim 25, wherein the gear assembly is a cycloidal gear assembly.

32. a first tab projection extending from a shoulder adjacent an open end of the internal cavity of the elongated shaft; an anti-jam mechanism disposed on the lead screw between the open end of the extension shaft and a cycloidal gear assembly; Further comprising: the anti-jam mechanism comprising a helical spring having a second tab projection configured for mating engagement with the first tab projection on the extension shaft; 26. The device of claim 25.

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