On / Off mechanism of the extension loss magnet

Abstract

Disclosed herein are a locking mechanism configured to lock and unlock rotation of a driver and a driven gear system in an implantable extension and compression system, and an implantable medical device and an implantable extension and compression system including such a locking mechanism. The locking mechanism includes a keeper configured to move from a locked position to an unlocked position in response to rotation of the driver, wherein in the locked position, the keeper is configured to resist rotation of the driven feature and the driver under a load against the driven feature, and in the unlocked position, enables rotation of the drive gear and the driver.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This international patent application claims priority to U.S. Patent Application No. 17 / 806,552, filed on June 13, 2022.

[0002] (Technical Field) The present invention generally relates to implantable medical devices, and more specifically to implantable extension and compression devices, and a rotational locking mechanism for use therein, to prevent extension or compression loss under load.

Background Art

[0003] Distraction osteogenesis is a technique that has been used to grow new bone in patients with various defects. For example, limb lengthening is a technique that can increase the length of a bone, such as the femur or tibia. By performing a corticotomy or osteotomy (a cut through the bone) in the bone, the resulting two sections of bone can be separated at a specific rate, for example, 1 (1.0) mm per day, and as they separate, it becomes possible to regenerate new bone between the two sections. This limb lengthening technique can be used when one limb is longer than the other, such as in patients with a previous fracture that did not heal properly, or in patients who suffered or were injured before the growth plates matured. In some patients, it may be desirable to increase height, which is achieved by lengthening both femurs and / or both tibias to increase the patient's height.

[0004] In other clinical applications, the treatment of orthopedic conditions can involve compressing, retracting, or pulling together a portion of the bone. For example, in certain compression applications, it may be desirable to hold or pull together two fractured sections.

[0005] Regardless of whether compression or extension is performed, an implantable compression and extension device can be subject to a significant load on its driving characteristics. These loads can undesirably cause reverse drive and losses of previously achieved extension or compression. Therefore, it is desirable to provide an improved implant, system, and device that can perform extension and retraction / compression procedures while avoiding losses caused by reverse drive of the device under load. Desirably, the improved implant, system, and device operate in both forward and reverse directions, i.e., perform both extension and compression, and resist such losses while enabling the device to do so without compromising the efficiency of the device in generating extension and compression forces. SUMMARY OF THE INVENTION

[0006] A first aspect of the present disclosure provides an implantable medical device comprising a driver, a driven gear system, and a keeper including a body, a keyed opening in the body, an opening in the body configured to receive a central pin of a drive gear of the driven gear system, and locking teeth disposed at a first end of the body. According to this aspect, the keyed opening can be configured to receive a complementary keyed portion of a drive gear of the driven gear system, and the keeper and the drive gear are rotatably fixed to each other. The opening in the body can be configured to receive a central pin of a drive gear of the driven gear system and to allow the body to translate axially with respect to the central pin. The locking teeth can be configured to releasably engage teeth on a ring gear of the driven gear system. The keeper can be configured to move from a locked position to an unlocked position in response to rotation of the driver. In the locked position, the keeper is configured to prevent rotation of the drive gear and the driver under a load on the driven gear system, and in the unlocked position, the keeper is configured to allow rotation of the drive gear and the driver.

[0007] In certain embodiments, the keeper is configured to axially translate relative to the central pin in a direction opposite the first end in response to rotation of the keeper so as to rotate and move from a locked position to an unlocked position, and in response to the translation, disengage the locking teeth from the ring gear of the driven gear system, thereby further configured to move the keeper to the unlocked position.

[0008] In certain embodiments, the keeper further includes a first face configured to engage a driver and a second face configured to engage a driven gear system. The opening extends through the body from the first face to the second face, and the keyed opening extends through a thickness of a portion of the keeper from the second face. In certain embodiments, the opening and the keyed opening are fluidly coupled, the keyed opening is bounded by a drive face configured to drive rotation of the keyed portion of the drive gear, and the opening is bounded by a shaft relief face configured to allow translational movement of the central pin. The keeper may further include a step face between the drive face and the shaft relief face.

[0009] In certain embodiments, the keeper further includes a first detent disposed on the first face. The first detent is disposed between the opening and the first end of the body and includes a first inclined surface. The keeper further includes a second detent disposed on the first face at its second end opposite the first end. The second detent includes a second inclined surface. Each of the first detent and the second detent may be configured to receive a drive pin disposed at an end of the driver.

[0010] In certain embodiments, the keeper further comprises a hole disposed at a second end of the body and opening into the keyed opening, the hole being configured to receive a biasing portion. In the locked position, the locking teeth are configured to engage the ring gear and to maintain such engagement under the biasing force from the biasing portion in the expanded state. In the unlocked position, the locking teeth are configured to disengage from the ring gear in response to compression of the biasing portion upon rotation of the driver and the keeper.

[0011] In certain embodiments, the first inclined portion and the second inclined portion are each substantially V-shaped, and the apex of the first inclined portion, the apex of the second inclined portion, and the locking teeth are laterally aligned such that when the keeper is in the locked position, drive pins disposed in each of the first detent and the second detent are disposed at the apexes of the first inclined portion and the second inclined portion. The drive pins disposed in each of the first detent and the second detent can then move their respective first inclined portion and second inclined portion upward when the keeper moves to the unlocked position.

[0012] In certain embodiments, the first detent and the second detent are further configured to allow rotation of the driver relative to the keeper to an extent limited by the lengths of the first inclined portion and the second inclined portion.

[0013] In certain embodiments, the first detent and the second detent each extend through the thickness of a portion of the keeper.

[0014] A second aspect of the present disclosure provides a locking mechanism configured to lock and unlock the rotation of a driver and a driven gear system in an implantable extension and compression system. The locking mechanism includes a driver of rotational motion having a first drive pin and a second drive pin each extending axially from a first end of the driver, a driven gear configured to be driven by the driver and including a keyed portion, and a keeper disposed on the driven gear and configured to move between a locked position and an unlocked position. The keeper includes a keyed opening configured to rotatably engage a keyed portion of a keyed drive shaft, a locking tooth disposed at a first end of the keeper and configured to releasably engage a ring gear of the driven gear system, a first detent and a second detent configured to engage the first drive pin and the second drive pin, and a biasing portion configured to bias the keeper across a longitudinal axis of the driver and the driven gear. In the locked position, the keeper resists rotation of the driven gear and the driver under a load on the driven gear system. In the unlocked position, the keeper allows rotation of the driven gear and the driver.

[0015] In certain embodiments, in the locked position, the biasing portion is configured to bias the keeper and the locking tooth into meshing engagement with the ring gear, and in the unlocked position, the biasing portion is compressed by the keeper during rotation of the driver, thereby releasing the engagement between the locking tooth and the ring gear and allowing the driver and the drive shaft to rotate.

[0016] In certain embodiments, the driver further includes a central recess opening to a first end of the driver and disposed between the first drive pin and the second drive pin. The driven gear further includes a central pin and a gear, each coupled to the keyed portion of the driven gear at both ends. The central pin may be disposed at least partially within the central recess of the driver.

[0017] In certain embodiments, the locking mechanism further comprises a hole extending from the keyed opening, through the second end of the keeper, and into the keyed portion, the second end being opposite the first end, and the biasing portion being disposed within the hole.

[0018] In certain embodiments, the locking mechanism further comprises a radial bearing configured to maintain a coaxial relationship between two or more of the driver, the keeper, and the keyed drive gear.

[0019] In certain embodiments, each of the first and second detents comprises an inclined surface, and each drive pin is configured to travel along the inclined surface.

[0020] In certain embodiments, the driver comprises a cylindrical permanent magnet configured to rotate upon application of a magnetic field, and a magnet housing disposed around the cylindrical permanent magnet.

[0021] In certain embodiments, the gear is a sun gear, the driven gear system is a planetary gear system, and the sun gear is configured to engage a ring gear via a plurality of planetary gears.

[0022] In certain embodiments, the keyed portion has a square cross-sectional shape, and the keyed opening has a corresponding complementary square cross-sectional shape.

[0023] A third aspect of the present disclosure is an implantable extension and compression system, comprising a housing configured to be attached to a first bone portion, the housing having a driver, a driven gear system, and a lead screw positioned internally, the lead screw being coupled to the driver via the driven gear system such that rotation of the driver causes rotation of the lead screw; a rod configured to be attached to a second bone portion and configured to interact with the lead screw such that the rod extends or contracts relative to the housing upon rotation of the lead screw; and a locking mechanism configured to lock and unlock rotation of the driver and the driven gear system. The locking mechanism includes a drive gear driven by the driver and configured to input torque to the driven gear system and including a keyed portion, and a keeper engaged with the driver and the keyed portion and configured to move between a locked position and an unlocked position in response to rotation of the driver. In the locked position, the keeper resists rotation of the drive gear and the driver under a load on the lead screw, and in the unlocked position, the keeper allows rotation of the drive gear and the driver.

[0024] These and other aspects, advantages, and salient features of the 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, discloses embodiments of the invention.

Brief Description of the Drawings

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[0026] Note that the disclosed drawings are not necessarily to scale. The drawings are intended to show only typical aspects of the disclosure and should not therefore be regarded as limiting the scope of the disclosure. In the drawings, like numbers represent like elements among the drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0027] As shown above, aspects of the present invention provide various embodiments of an extension and compression implant, including an intraspinal, extramedullary, spinal extension implant, as well as methods and devices for preventing extension or compression loss in such devices. Such implants, methods, and devices can provide improvements over conventional implants, methods, and devices. For example, the implants, methods, and devices of the present disclosure can be related to performing extension and retraction / compression procedures while avoiding losses due to backdriving of the device under load and while avoiding, limiting, or preventing a reduction in the efficiency of generating an extension force.

[0028] Referring to FIGS. 1 and 2, the present disclosure describes various embodiments of an extension and compression device 100. As described above, the device 100 can be, for example, an extramedullary limb extension device, an intraspinal limb extension device, or a spinal extension device. FIGS. 1 and 2 show, respectively, a top view and a cross-sectional view of an exemplary extension and compression device 100 according to an embodiment of the present disclosure. As shown, the device 100 includes a housing 102 having at least one fixed aperture 104 and an extension and compression rod 106 having at least one fixed aperture 108. Specifically, the rod 106 can terminate at a plate 107 having a fixed aperture 108 therein. In certain embodiments, the plate 107 can be curved or angled in any of a number of different configurations depending on the bone to which the device 100 is attached and the location on the particular bone such that the plate 107 forms a contour and can conform to the shape of the bone. Further, the fixed aperture 104 can be positioned around a plate or bulge portion of the housing 102. The at least one fixed apertures 104, 108 can be, in particular, lock screw holes having internal threads 112 for engaging threads disposed on the head of a fixing screw in a manner readily understood by one of ordinary skill in the art. In some embodiments, all of the fixed apertures 104, 108 include internal threads 112.

[0029] The housing 102 is configured to be fixed to bone at a first position, and the rod 106 is configured to be fixed to bone at a second position. In the context of limb lengthening, for example, to grow or lengthen bone, the bone can either be pre-separated or (e.g., via osteotomy) intentionally cut or broken to create this separation, dividing the bone into a first section and a second section. The cutting can be done before implanting and fixing the device 100, or can be done after the device 100 is implanted, for example by using a flexible saw. The rod 106 is configured to contract (e.g., for compression) and / or extend (e.g., for limb lengthening) relative to the housing 102. The device 100 is configured to enable precise controlled translation of the rod 106 relative to the housing 102 by non-invasive remote control, and thus enable precise controlled translational movement of the bone segment fixed to the rod 106 relative to the bone segment fixed to the housing 102.

[0030] For example, over the course of a limb lengthening treatment period, the bone is periodically lengthened to create a new separation in which bone formation can occur. The term "periodically lengthened" means that lengthening occurs regularly or cyclically, for example on a daily or multi-day basis. An exemplary lengthening rate can be 1 millimeter per day, although other lengthening rates can be used. That is, a typical lengthening regimen can include lengthening the device 100 by about 1 millimeter per day. This can be done, for example, by four lengthening sessions per day with 0.25 mm of lengthening each. The device 100 disclosed herein includes a drive system, which can be, for example, magnetically driven. The drive system allows the rod 106 to extend telescopically from the housing 102 and thus enables the first and second sections of bone to be separated from each other.

[0031] As shown in FIG. 2, housing 102 has an opening 118 at one end for receiving rod 106. The end 102 of the housing including opening 118 can be regarded as the end of the distal housing. One or more O-rings 119 can be positioned around rod 106 between rod 106 and housing 102. In some embodiments, a portion of the outer surface of rod 106 and / or a portion of the inner surface of housing 102 can be concave to accommodate O-ring 119. O-ring 119 can facilitate a proper seal between housing 102 and rod 106 so that body fluid does not enter housing 102 when device 100 is implanted. Housing 102 can be sealingly closed at the end opposite opening 118, which can be referred to as the proximal end, by attachment of an end cap. The end cap can be attached to housing 102 by welding, adhesive bonding, or other joining techniques. Further, another O-ring can be provided between the end cap and housing 102 to provide a seal therebetween.

[0032] Referring to FIGS. 2-4, in use, rod 106 is driven from housing 102 by lead screw 122 that rotates inside nut 126 fixed to the inner surface of cavity 128 within rod 106 in which lead screw 122 is disposed. Nut 126 is positioned between lead screw 122 and rod 106. Lead screw 122 is mechanically coupled to a driver in an indirect or direct manner. The driver can be, for example, a cylindrical permanent magnet 202 contained within housing 102, although in other embodiments, the driver can be, for example, a motor or other actuator readily understood by one of ordinary skill in the art. The driver can be mechanically coupled to lead screw 122 by a driven gear system as further described herein. In any case, rotation of the driver achieves rotation of lead screw 122, which is converted into axial movement of rod 106 relative to housing 102. In embodiments where the driver is a cylindrical permanent magnet 202, rotation can be magnetically driven by an external adjustment device 400 (FIGS. 23-25).

[0033] As shown in FIG. 3, the male screw 122 includes a shaft 132 having a first end 134 and a second end 136. The first end 134 of the shaft 132 is configured to be coupled to the magnetic assembly 200 (see FIGS. 2 and 4). The first end 134 may include a first end portion 138 having an externally keyed surface 140, which may be hexagonal for example, and a second portion 142 having an externally keyed surface 144, which may be hexagonal for example. As described herein, the first end portion 138 is configured to engage within an opening 252 (see FIG. 10) of a drive stage 250 (see FIGS. 4 and 10) of the gear assembly 216 (FIGS. 2, 4, and 10). The second portion 142 having the externally keyed surface 144 is configured to engage at least one thrust bearing 146 (see FIGS. 2 and 4, two are shown in FIG. 4), which is positioned adjacent to at least one retainer clip 150 (see FIGS. 2, 4, and 5 for example, two are shown in FIG. 4). Each of the thrust bearings 146 consists of two separate races having ball bearings disposed therebetween. The thrust bearings 146 are configured to transmit high compressive forces during rotation of the male screw 122 and during axial movement of the rod 106 relative to the male screw. Further, as best seen in FIG. 4, the housing 102 may include a retainer 147 for serving as an abutment surface for the thrust bearings 146.

[0034] Returning to FIG. 3, between the two keyed surfaces 138, 142, the male screw 122 is recessed to provide a reduced diameter portion 148. The reduced diameter portion 148 is sized and shaped to receive and / or engage the retainer clip 150 such that the retainer clip 150 is disposed within a recess defined by the reduced diameter portion 148 between the first keyed portion 138 and the second keyed portion 142 (see FIGS. 4 and 5).

[0035] FIG. 5 shows an enlarged view of the retainer clip 150. As shown, the retainer clip 150 includes two separate arcuate members 152A, 152B. Alternatively, the retainer clip 150 may include a single integral substantially cylindrical member structure. The arcuate or cylindrical members 152A, 152B may include recesses 154 for seating an O-ring 156 disposed on their radially outer surfaces within the recesses 154. The male thread 122 is recessed from the small diameter portion 148 to the opposite side of the second portion 142 so as to provide another small diameter portion 162. Like the portion 148, this portion 162 is also sized and shaped to receive and / or engage the retainer clip 150 such that the retainer clip 150 is disposed within a recess defined by the small diameter portion 162. Further, the retainer clip 150 together with the retainer 147 of the housing 102 provides support for the thrust bearing 146 due to the retainer clip 150 being positioned around the male thread 122 on both sides of the thrust bearing 146.

[0036] The parent screw 122 also includes a step 170 from the small-diameter portion 162 to the large-diameter portion 172 (see FIG. 3). This large-diameter portion 172 is threaded along at least a portion of its axial range. In use, the threaded portion of the large-diameter portion 172 is at least partially surrounded by a nut 126 (FIGS. 2 and 4) disposed within a cavity 128 in the rod 106 to facilitate the axial movement of the rod 106 relative to the housing 102. The second end 136 of the parent screw 122 includes an inclined portion 174 that transitions from the large-diameter portion 172 to the intermediate-diameter portion 176. The intermediate-diameter portion 176 does not include any threads thereon, so that when the rod 106 engages this region of the parent screw 122, no additional movement of the rod 106 occurs. In certain embodiments, a stopper (not shown) may be disposed at the end of the intermediate portion 176 opposite the inclined portion 174, and the stopper is configured to resist or prevent the rod 106 from completely disengaging from the parent screw 122. The intermediate-diameter portion 176 may have a diameter smaller than the large-diameter portion 172 and larger than the small-diameter portions 148, 162. However, it is contemplated that the intermediate-diameter portion 176 may have the same dimensions as the small-diameter portions 148, 162 or the large-diameter portion 172.

[0037] The apparatus 100 may also include an anti-jamming feature configured to prevent the rod 106 from jamming or stalling when fully retracted. Specifically, the anti-jamming feature provides a spring force to overcome the frictional force of the rod 106 in a scenario where the rod 106 jams or stalls.

[0038] In one embodiment shown in FIGS. 4 and 6 and 7, the anti-jamming feature may include a substantially circular anti-jamming retainer 164 and an anti-jamming ring 166 coupled thereto. The anti-jamming ring 166 can be, for example, semi-circular or partial circular. The anti-jamming retainer 164 includes an opening 180 having a keyed shape, such as a hexagonal shape, to complement the keyed shape 144 of the parent screw 122 at the portion 142. This enables the anti-jamming retainer 164 to be rotatably fixed relative to the parent screw 122, so that when the parent screw 122 rotates, the anti-jamming retainer 164 rotates with the parent screw 122. The anti-jamming retainer 164 also substantially surrounds the retainer clip 150 and includes a collar 182 for maintaining the position of the retainer clip 150 relative to the parent screw 122. As shown, the inner surface of the collar 182 is substantially circular and does not have a keyed shape such as the opening 180. The collar 182 includes a groove 184 formed on its outer surface. The collar 182 also includes tabs and / or protrusions 186 that extend radially and axially therefrom. The anti-jamming ring 166 may include a flange 188 configured to be received within the groove 184 of the anti-jamming retainer 164. The flange 188 has a width that is narrower than the width of the groove 184 to allow for a slight axial movement of the flange 188 within the groove 184 and thus a slight axial movement of the anti-jamming ring 166 relative to the anti-jamming retainer 164. The configuration of the flange 188 and the groove 184 maintains the coupling of the anti-jamming ring 166 to the anti-jamming retainer 164 while allowing the anti-jamming ring 166 and the anti-jamming retainer 164 to rotate and move axially relative to each other. In addition, the anti-jamming ring 166 includes tabs and / or protrusions 190 that extend axially and radially therefrom.

[0039] In another embodiment shown in FIGS. 8A - 8D and 9, the anti - jamming feature described herein may be in the form of an anti - jamming spring 192, which may be an integral helical spring illustrated in FIGS. 8A - 8D and 9 having a substantially circular or oval outer cross - sectional shape. In embodiments including the anti - jamming spring 192, the extension rod 106 may include a first tab projection 194 extending from a shoulder 196 adjacent to the open end of the internal cavity 128 of the extension shaft 106. The tab projection 194 is configured to cooperate with the anti - jamming spring 192 as described herein.

[0040] The anti - jamming spring 192 may include a second tab projection 198 configured to fit - engage with the first tab projection 194 on the extension shaft 106. The anti - jamming spring 192 may further include a keyed opening 199 (see FIG. 8D), which may be, for example, hexagonal in shape. The shape of the keyed opening 199 is configured to complement the cross - sectional shape of the parent screw 122 at the small - diameter portion 162 (FIG. 9). In this way, the anti - jamming spring 192 is configured to be rotatably fixed to the parent screw 122. This configuration allows the anti - jamming spring 192 to remain centered with respect to the parent screw assembly without tilting or floating and to remain constrained at the shoulder position of the parent screw. In use, when the anti - jamming spring 192 is rotated by the parent screw 122, the tab 198 encounters and engages the extension rod tab 194. The resistance provided by the extension rod tab 194 opens the anti - jamming spring 192 into the inner diameter of the housing 102 and provides a spring force to overcome the surface friction described above. The anti - jamming spring 192 is further configured to maintain engagement and surface contact with the shoulder 196 of the extension rod 106 during full retraction of the extension rod 106.

[0041] Regardless of the particular embodiment, the anti-jamming feature is configured to prevent the rod 106 from jamming or stalling when fully retracted. Specifically, in a jam condition, the external adjustment device 400 rotates the lead screw 122 (via the magnet 202 shown in FIG. 4), but the rod 106 may not move axially due to the jam. For example, the rod 106 can jam in the fully retracted position due to frictional forces in the retracted state. Thus, to jump start or overcome the frictional forces in a jam condition, a torque greater than that provided by the external adjustment device 400 (see FIGS. 23 - 25) may be required. As a result, the anti-jamming feature provides a built-in mechanism within the device 100 to provide an additional force that exceeds the force provided by the external adjustment device 400, thereby providing such a jump start force.

[0042] Referring again to FIG. 4, the rotatable magnetic assembly 200 is positioned within the housing 102. The magnetic assembly 200 includes a cylindrical radially polarized permanent magnet 202 housed within a magnet housing 204 having an end cap 206. The permanent magnet 202 can include a rare earth magnet material such as neodymium-iron-boron. The permanent magnet 202 can further have a protective phenolic coating thereon and can be statically held within the magnet housing 204 and end cap 206 by an epoxy or other adhesive. The magnet housing 204, end cap 206, and epoxy form a seal to further protect the permanent magnet 202. The magnet housing 204 can also be welded to the end cap 206 to create an airtight seal. To assist in manufacturing and assembly, the magnet housing 204 can include separate magnet cups 207, 208 (see FIG. 7) for housing the permanent magnet 202 therein. The end cap 206 includes a cylindrical extension or axle 210 that fits within the inner diameter of a radial bearing 212 that allows for low friction rotation.

[0043] As shown at least in FIGS. 2, 4, 9, and 10, the magnetic assembly 200 can be coupled to the gear assembly 216, such that the parent screw 122 is configured to couple to the magnet assembly 200. Referring to FIG. 10, the magnetic assembly 200 can be terminated by a first sun gear 218. The first sun gear 218 rotates in a 1:1 fashion in response to rotation of the magnetic assembly 200 in response to the application of a moving magnetic field applied to the patient from an external location. The first sun gear 218 is configured to be inserted into an opening of a first gear stage 224 having three planet gears 226 rotatably held within the frame 228 by an axle 232. A second sun gear 234, which is the output of the first gear stage 224, rotates with the frame 228. The same components are present in a second gear stage 236 that outputs to a third sun gear 238, and a third gear stage 242 that terminates at a drive stage 250. The drive stage 250 is positioned around the gear assembly 216 that is furthest from the magnetic assembly 200. Along the length that the gear stages 224, 236, 242 extend, the inner wall 244 of the ring gear 246 (seen in FIGS. 12 and 13) has internal teeth 248, and the teeth that extend outside of the planet gears 226 engage along the internal teeth 248 when rotating. Each of the illustrated gear stages has a 4:1 gear ratio, such that the drive stage 250 rotates once for every 64 rotations of the magnetic assembly 200.

[0044] The frame 228 of the third gear stage 242 includes a drive stage 250. The drive stage 250 includes an opening 252 having a keyed inner surface 254. The keyed inner surface 254 is configured to matingly engage with the keyed outer surface 140 (see FIG. 3) of the end 134 of the lead screw 122. The engagement of the keyed surfaces 254, 140 prevents rotation of the lead screw 122 and the drive stage 250 relative to each other. The keyed surfaces 254, 140 can each be, for example, a male hexagonal shape. However, other shapes that prevent rotation of the lead screw 122 relative to the drive stage 250 are contemplated by the present disclosure. To further maintain the lead screw 122 within the drive stage 250, a first retainer clip 150 is provided within the opening 252 of the drive stage 250 and can at least partially surround the proximal lead screw 122 of the keyed outer surface 140. Specifically, the retainer clip 150 can be positioned around the small diameter portion 148 (see FIG. 3) within the opening 252.

[0045] The torque applied to the magnetic assembly 200 by the action of the rotating magnetic field on the cylindrical permanent magnet 202 is thus increased by approximately 64 times with respect to the rotational torque of the lead screw 122. This makes it possible to move the rod 106 with high precision. Due to the 64:1 gear ratio, the device 100 can axially displace a bone segment coupled to the rod 106 against a strong force, for example, created by soft tissue.

[0046] As shown in FIGS. 2, 4, and 9, one or more thrust bearings 146 serve to protect the magnet assembly 200 and the gear assembly 216 from any significant compressive or tensile stresses. When a compressive force on the device exists, for example, when extending bone and thus resisting the tensile strength of soft tissue, the thrust bearing 146 abuts against the retainer clip 150 and / or the retainer 147. In other embodiments, the device 100 is used to pull bones together. For example, in certain compression applications, it is the goal to hold together two fractured bone sections. In these compression applications, the device 100 may be under tension and the thrust bearing 146 will abut against the retainer clip 150 or the retainer 147. In both situations, it is the thrust bearing 146 and the retainer 147, rather than the magnet assembly 200 or the gear assembly 216 of the drive system, that absorb the large stresses.

[0047] Referring further to FIGS. 12 and 13, as shown, the ring gear 246 includes internal teeth 248 and an inner wall 244 having at least one raised portion 245 and at least one tab and / or protrusion 247. In particular, the ring gear 246 may include two tabs or protrusions 247. The raised portion 245 is positioned on the outer surface of the ring gear 246 such that the raised portion 245 extends radially from the outer surface of the ring gear 246. In some embodiments, the ring gear 246 can include two raised portions 245 positioned on both sides of the ring gear 245. The raised portion 245 engages and / or meshes with complementary notches or recesses 249 (FIG. 14) formed in the housing 102 within its inner surface at a position where the housing 102 surrounds the ring gear 246. If two opposing raised portions 245 are included in the ring gear 246, the housing 102 may include two opposing complementary notches or recesses 249. Without departing from the aspects of the present disclosure, any number of raised portions 245 and complementary notches 249 can be included. Further, it is contemplated that alternative configurations are equally applicable such that the housing 102 can include one or more raised portions that engage and / or mesh with complementary notches or recesses on the ring gear 246.

[0048] The tabs 247 of the ring gear 246 can be positioned around the end of the ring gear 246 and extend radially therefrom. The tabs 247 can engage and / or mesh with complementary grooves 251 formed within the housing 102 on their inner surfaces, and the housing 102 surrounds the ring gear 246 (see FIG. 14). It should be understood that any number of tabs and / or protrusions 247 and complementary grooves 251 can be included without departing from the aspects of the present disclosure. For example, the ring gear 246 can include two tabs 247 on both sides of the ring gear 246. As shown, in some embodiments, each tab 247 can be positioned between the raised portions 245 such that the tabs and raised portions 245 alternate around the ring gear 246. Further, alternative configurations are envisioned to be equally applicable such that the housing 102 can include tabs and / or protrusions that engage and / or mesh with complementary grooves on the ring gear 246. These complementary features on the ring gear 246 and housing 102 prevent the ring gear 246 from moving axially relative to the housing 102.

[0049] Referring again to FIGS. 10 and 11 and further to FIGS. 15 - 22, the apparatus 100 can include a locking mechanism 300, which can be configured to lock and unlock the rotation of the driver and driven gear system. The locking mechanism 300 can be configured to allow the driver to be driven in either the forward or reverse direction in response to rotation of the driver, i.e., to rotate in either direction depending on the desired extension or compression application. Thus, in the unlocked position, the locking mechanism 300 allows the driver and driven gear system to rotate in the clockwise or counterclockwise direction when actuated by the driver. However, in the locked position, the lock resists and in some embodiments completely prevents any rotation in the absence of rotation of the driver. As a result, the locking mechanism 300 resists, reduces, minimizes, or prevents backdriving and extension losses caused by the load on the lead screw 122 when in the locked position.

[0050] In various embodiments, the driver may be any actuator of a rotational motion. In the embodiment shown in FIG. 10, the driver is the magnetic assembly 200 described herein, which includes a cylindrical permanent magnet 202 configured to rotate upon application of a magnetic field, and a magnet housing 204 disposed around the cylindrical permanent magnet 202. However, in other embodiments, the driver may be, for example, a motor. Further, in various embodiments, the driven gear system may be the gear assembly 216 described herein, and in particular, may be a planetary gear system including a sun gear 218 configured to engage a ring gear 246 via a plurality of planetary gears 226 (see FIG. 10). However, in other embodiments, the driven gear assembly may be, for example, a cycloid gear assembly. In still other embodiments, the magnet assembly may engage in the direction of the lead screw 122 without the driven gear assembly intervening between the magnet assembly and the lead screw.

[0051] As described above, FIGS. 10 and 11 illustrate one embodiment in which the driver is in the form of a cylindrical permanent magnet 202 disposed within a magnet housing 204. The magnet housing 204 includes a first drive pin 302 and a second drive pin 304. As best shown in FIG. 11, each of the first drive pin 302 and the second drive pin 304 extends from a first end of the magnet housing 204 in a direction parallel to the longitudinal axis of the cylindrical magnet 202. The first drive pin 302 and the second drive pin 304 may be disposed on the end face of the magnet housing 204 such that they are disposed substantially opposite each other and spaced apart from each other by approximately 180 degrees on the end face of the magnet housing 204. The magnet housing 204 may further include a central recess 307 that opens at a first end of the magnet housing 204 and is disposed between the first drive pin 302 and the second drive pin 304. The central recess 307 may be centered about or concentric with the longitudinal axis of the cylindrical magnet 202 and the magnet housing 204, i.e., the axis of rotation.

[0052] Referring back to FIG. 10, the keyed drive gear 320 is configured to be driven by a driver, such as by the magnet housing 204, via a keeper 330 further discussed herein. The keyed drive gear 320, shown in detail in FIGS. 18 and 19, includes a central pin 322 coupled to a keyed portion 324 and a gear 218 coupled to the keyed portion 324 at an end opposite the end where the keyed portion 324 is coupled to the central pin 322. Thus, the keyed portion 324 is disposed between the central pin 322 and the gear 218, and each of these is coupled to the keyed portion 324 of the drive gear 320 at both ends. The central pin 322, the keyed portion 324, and the gear 218 may be substantially coaxial with each other. As described above, the gear 218 may be the sun gear of the planetary gear system. When assembled as shown in FIG. 20, the central pin 322 is configured to be at least partially disposed within the central recess 307 of the magnet housing 204. The keyed portion 324 may have any non-circular keyed cross-sectional shape configured to transmit torque, such as square, hexagonal, rectangular, star-shaped, etc. In a particular embodiment, the keyed portion 324 may have a square cross-sectional shape.

[0053] The keeper 330 is disposed over at least a portion of the drive gear 320 and is interposed between the drive gear 320 and the driver. The keeper 330 is configured to move from a locked position to an unlocked position, for example by rotating, in response to rotation of the driver, such as the magnet housing 204. In the locked position, the keeper 330 is configured to resist, reduce, minimize, or in certain embodiments prevent rotation of the drive gear 320 and the magnet housing 204 under a load on the driven gear system 216. In the unlocked position, the keeper 330 is configured to allow rotation of the drive gear 320 and the driver, such as the magnet housing 204.

[0054] As best shown in FIGS. 15-17, keeper 330 includes a body having a first face 334 and a second face 336, the first face 334 being configured to engage a driver, such as magnet housing 204, and the second face 336 being configured to engage a driven gear system via keyed drive gear 320.

[0055] Keyed opening 341 is disposed within the body and opens to the second face 336. Keyed opening 341 is configured to receive and rotatably engage keyed portion 324 of drive gear 320. Keyed opening 341 may extend through a portion of the thickness of keeper 330 from the second face 336 of the body of keeper 330. Keyed opening 341 is shaped and dimensioned to provide a complementary fit with keyed portion 324 of drive gear 320 such that, for example, keyed portion 324 fits into keyed opening 341 of keeper 330 in a male / female engagement. For example, if keyed portion 324 has a square, hexagonal, rectangular, star, or other shape, keyed opening 341 may have a corresponding square, hexagonal, rectangular, star, or other shape dimensioned to receive the complementary keyed shape in an interference fit. As a result, keeper 330 and drive gear 320 are rotatably fixed to each other via keyed opening 341. For example, in an embodiment where keyed portion 324 is square, keyed opening 341 may also be square.

[0056] The keeper 330 may also include an opening 332 within the body configured to receive the central pin 322 of the drive gear 320. The opening may extend from a first face 334 of the keeper 330 through at least a portion of the thickness of the body. The opening 332 and the keyed opening 341 may be fluidly coupled to each other such that the opening 332 and the keyed opening 341 may partially overlap each other. Thus, the opening 332 may effectively extend from the first face 334 through the entire thickness of the body of the keeper 330 to a second face 336 of a particular region. The keyed opening 341 may be bounded by a drive face 340 configured to drive the rotation of the keyed portion 324 of the drive gear 320, while the opening 332 may be bounded by a shaft relief face 342 configured to allow the translation of the central pin 322. In particular, the opening 332 may include an oval or slot-shaped portion defined by the shaft relief face 342 as shown in FIGS. 17, 21, and 22. This oval shape may allow the body of the keeper 330 to translate relative to the central pin 322 during operation, as illustrated by the change in the relative positions of the central pin 322 and the opening 332 from the lock position of FIG. 21 to the unlock position of FIG. 22. The keeper 330 may further include a step face 338 disposed between the drive face 340 and the shaft relief face 342 as shown in FIG. 15.

[0057] The keeper 330 further includes at least one locking tooth 354 disposed at a first end of the keeper 330 and extending axially therefrom. The locking tooth 354 is configured to releasably mesh or engage with the internal teeth 248 on the inner wall 244 of the ring gear 248 of the driven gear system during use (see FIGS. 21 and 22).

[0058] The keeper 330 may further include a first detent 346 disposed on the first face 334 of the keeper 330, and the first detent 346 is configured to engage the first drive pin 302. The first detent 346 may be disposed, in particular, between the opening 332 and the first end of the body (including the locking teeth 354). The keeper 330 may further include a second detent 350 also disposed on the first face 334 of the keeper 330, and the second detent 350 is configured to engage the second drive pin 304. The second detent 350 is disposed, in particular, at the second end opposite the first end of the keeper 330 and may be in fluid connection with the opening 332. It should be noted that, alternatively, to obtain the same result, the first detent 346 may receive the second drive pin 304 and the second detent 350 may receive the first drive pin 302.

[0059] Each of the first detent 346 and the second detent 350 may include respective inclined surfaces 348, 352, and the respective drive pins 302, 304 are configured to travel along the inclined surfaces 348, 352. The first inclined portion 348 and the second inclined portion 352 may each be configured to curve or incline so as to have a generally or substantially U-shaped or V-shaped inclined surface. Each inclined portion 348, 352 may include a zenith that is laterally aligned with each other and also laterally aligned with the locking teeth 354 on the keeper 330. Accordingly, the drive pins 302, 304 disposed on each of the first detent 346 and the second detent 350 are disposed at the zeniths of the first inclined portion 348 and the second inclined portion 352 when the keeper 330 is in the locked position. The drive pins 302, 304 disposed on each of the respective first detent 346 and the second detent 350 are configured to move the respective first inclined portion 348 and the second inclined portion 352 upward when the keeper 330 moves to the unlocked position. In this way, the first detent 346 and the second detent 350 are configured to allow rotation of a driver, such as the magnet housing 204, relative to the keeper 330 to an extent limited by the lengths of the first inclined portion 348 and the second inclined portion 352. In a particular embodiment, the first detent 346 and the second detent 350 each extend through the thickness of a portion of the keeper 330.

[0060] As illustrated in FIG. 15, keeper 330 further includes a hole 344 that extends from the keyed opening 341 through the second end of keeper 330. The second end of keeper 330 is the end opposite the first end where lock teeth 354 are disposed. The keyed portion 324 of drive gear 320 also includes a hole 328 (see FIGS. 18 and 19), which is aligned with hole 344 when assembled as shown in FIG. 20. Thus, hole 344 and 328 of keeper 330 and the keyed portion 324 of drive gear 320 form a substantially continuous hole or channel. Lock mechanism 300 further includes a biasing portion 306 disposed within the aligned holes 344 and 328. The biasing portion 306 can be, for example, a spring. The biasing portion 306 can be configured to bias keeper 330 across the longitudinal axis of magnet housing 204 and drive gear 320, or in a direction substantially perpendicular thereto. Referring to FIG. 10, lock mechanism 300 can further include a radial bearing 308, which can be disposed around at least a portion of magnet housing 204, keeper 330, and keyed drive gear 320, and can be configured to maintain a coaxial relationship between two or more of the ends of magnet housing 204, keeper 330, and keyed drive gear 320.

[0061] During operation, the locking mechanism 300, including the keeper 330, defaults to the locked position when the driver, e.g., the magnet housing 204, is stationary (see FIG. 21). In the locked position, the biasing portion 306 is configured to bias the keeper 330 relative to the ring gear 246 and the drive gear 320 such that the locking teeth 354 on the keeper 330 are biased to engage the teeth 248 on the inner surface 244 of the ring gear 246. In particular, the locking teeth 354 can maintain engagement between two teeth 248 of the ring gear 246 under the biasing force of the biasing portion 306 in the extended state. This biasing force can be applied across or perpendicular to the longitudinal axis of the magnet housing 204 and the keyed drive gear 320. Due to the return stop shape, the first drive pin 302 and the second drive pin 304 are disposed at the zenith positions of their respective inclined portions 348, 352 in the locked position. In this position, the keeper 330 resists rotation of the drive gear 320 and the magnet housing 204. This resistance to rotation is independent of any load on the driven gear system.

[0062] When the driver, for example, the magnet housing 204 rotates, in response thereto, the keeper 330 moves from the locked position to the unlocked position. When the magnet housing 204 rotates in either the clockwise or counterclockwise direction, the drive pins 302, 304 move from the zenith position following the curvature or inclination of the inclined portions 348, 352. In the embodiment shown in FIG. 22, the magnet housing 204 was rotating in the counterclockwise direction, but the keeper 330 would function in the same manner when the rotation is clockwise. Due to this rotation, the keeper 330 is urged by the interaction between the inclined portions 348, 352 and the drive pins 302, 304 and translates axially with respect to the center pin 322 in the direction of the second end opposite to the first end. The lock teeth 354 are disposed at the rear end of the keeper 330 with respect to the translation of the keeper 330 toward the unlocked position. This translation of the keeper 330 compresses the biasing portion and disengages the lock teeth 354 from the ring gear 246. When the lock teeth 354 are disengaged from the teeth 248 of the ring gear 246, the keeper 330 moves to its unlocked position, where the keyed drive gear 320, and thus the magnet housing 204 and the driven gear assembly 216, can rotate freely with respect to the ring gear 246.

[0063] When the rotation of the magnet housing 204 stops and in response thereto, the opposite process occurs. In the absence of rotation of the magnet housing 204, under the biasing force of the biasing portion 306, the drive pins 302, 304 move downward along the inclined portions 348, 352 and return to the zenith position shown in FIG. 21, and the keeper 330 translates axially with respect to the central pin 322. The locking teeth 354 are at the tip of the keeper 330 with respect to this translational movement towards the locked position. The locking teeth 354 engage the teeth 348 of the ring gear 246, thereby preventing the rotation of the keeper 330 and thus preventing the rotation of the keyed drive gear 320 rotatably fixed to the keeper 330. When the keyed drive gear 320 is rotatably locked, the sun gear 218, the balance of the gear assembly 216, and the lead screw 122 are also rotatably locked. In this way, extension or compression losses can be resisted and in some embodiments prevented, regardless of or independent of the load applied to the lead screw 122 and the gear assembly 216.

[0064] 23-25 ​​illustrate an external adjustment device 400 configured to allow non-invasive adjustment of the device 100 by applying a moving magnetic field to rotate a permanent magnet 202 within the device 100, as described. FIG. 23 illustrates the internal components of the external adjustment device 400, showing the permanent magnet 202 of the device 100 without the remainder of the assembly for clear reference. The internal operating components of the external adjustment device 400 may, in certain embodiments, be similar to those described in U.S. Patent Application Publication No. 2012 / 0004494, which is incorporated herein by reference. A motor 402 with a gear box 404 outputs to a motor gear 406. The motor gear 406 engages and rotates a central (idle) gear 408, which has a suitable number of teeth to rotate a first magnet gear 410 and a second magnet gear 412 at the same rotational speed. The first magnet 414 and the second magnet 416 rotate in conjunction with the first magnet gear 410 and the second magnet gear 412, respectively. Each magnet 414, 416 is held within a respective magnet cup 418 (partially shown). An exemplary rotational speed may be 60 RPM or less. This speed range may be configured to limit the amount of current density induced in body tissues and fluids and meet international guidelines or standards. As seen in FIG. 23, the south pole 422 of the first magnet 414 faces in the same direction as the north pole 424 of the second magnet 416, and similarly, the first magnet 414 has a north pole 426 that faces in the same direction as the south pole 428 of the second magnet 416. As these two magnets 414, 416 rotate together in synchronism, they apply complementary and additive moving magnetic fields to the radially polarized permanent magnet 202 having a north pole 432 and a south pole 434. Magnets having multiple north poles (e.g., two) and multiple south poles (e.g., two) are also contemplated in each of the devices. When the two magnets 414, 416 rotate in a first rotational direction 442 (e.g., counterclockwise), magnetic coupling causes the permanent magnet 202 to rotate in an opposite second rotational direction 444 (e.g., clockwise). The direction of rotation of the motor 402 and the corresponding direction of rotation of the magnets 414, 416 are controlled by buttons 446, 448.One or more circuit boards 452 include control circuitry for both sensing rotation of magnets 414, 416 and controlling rotation of magnets 414, 416.

[0065] 24 and 25 show an external adjustment device 400 for use with the device 100 placed in the femur (FIG. 24) or tibia (FIG. 25). The external adjustment device 400 has a first handle 454 for carrying or stabilizing the external adjustment device 400, for example, for stabilizing it against the upper leg 456 (as in FIG. 24) or the lower leg 457 (as in FIG. 25). An adjustable handle 458 is rotatably attached to the external adjustment device 400 at pivot points 460, 462. The pivot points 460, 462 have an easily lockable / unlockable mechanism, such as a spring-loaded brake, ratchet, or tightening screw, so that the adjustable handle 458 can be adjusted to a desired angle and locked in orientation relative to the housing 464. The adjustable handle 458 is shown in two different positions in FIGS. 24 and 25. In FIG. 24, the adjustable handle 458 is set so that the apex 466 of the loop 468 rests against the housing 464. In this position, the patient 470 can grasp one or both of the grips 472, 474 while the adjustment procedure is being performed (e.g., moving the bone between 0.10 mm and 1.50 mm). It is contemplated that the procedure may be a distraction procedure for a bone distraction device or a distraction procedure for a distraction plate that is attached externally to the bone. Looking to FIG. 25, when the bone transport device 100 is implanted in the tibia, the adjustable handle 458 can be changed to a position that allows the patient 470 to grasp the apex 466 such that the magnet region 476 of the external adjustment device 400 is held above the portion of the device 100 that includes the permanent magnet 202. In either case, the patient 470 can clearly see the control panel 478, which includes the display 482. 24, the control panel 478 includes a start button 484, a stop button 486, and a mode button 488. Using the control circuitry contained on the circuit board 452, the surgeon can store important information related to the particular aspects of each particular patient. For example, in some patients, the implant may be placed antegrade in the tibia. In other patients, the implant may be placed either antegrade or retrograde around the femur.In each of these three cases, it may be desirable to move the bone either distally to proximally or proximally to distally. By having the ability to store this type of patient-specific information within the external adjustment device 400, the external adjustment device 400 can be configured to instruct the magnets 414, 416 to rotate automatically in the correct direction, while the patient only needs to place the external adjustment device 400 in the desired position and press the start button 484. Information on the maximum allowable bone transport length per day and the maximum allowable bone transport length per session can also be input and stored by the surgeon for safety purposes. These can also be added via an SD card or USB device, or by wireless input. An additional feature is a camera on the part of the external adjustment device 400 that is placed on the skin. For example, the camera can be located between the first magnet 414 and the second magnet 416. The skin directly covering the implanted permanent magnet 202 can be marked with indelible ink. A live image from the camera is then displayed on the display 482 of the control panel 478, enabling the user to place the first magnet 414 and the second magnet 416 directly above the marked area on the skin. Crosshairs can be overlaid on the live image on the display 482, allowing the user to align the mark on the skin between the crosshairs and thus optimally position the external adjustment device 400.

[0066] Other external adjustment devices can be used to cause the operation of the extension device described herein. Such external adjustment devices include, for example, U.S. Patent No. 8,382,756 filed on November 20, 2009, U.S. Patent No. 9,248,043 filed on June 29, 2011, U.S. Patent No. 9,078,711 filed on June 6, 2012, U.S. Patent No. 9,044,281 filed on October 18, 2012, U.S. Patent Application No. 14 / 698,665 filed on April 28, 2015, U.S. Patent Application No. 14 / 932,904 filed on November 4, 2015, U.S. Patent Application No. 16 / 004,099 filed on December 12, 2016, and International Publication No. PCT / US2020 / 017338 filed on February 7, 2020, all of which are hereby incorporated by reference as if fully set forth herein.

[0067] Referring to FIGS. 26-33, the apparatus 100 may include a locking mechanism 500 that provides an alternative embodiment to the apparatus 100 including the locking mechanism 300 described above. Like the first embodiment of the locking mechanism 300, the second embodiment of the locking mechanism 500 is configured to lock and unlock the rotation of the driver and the lead screw 122. The locking mechanism 500 may be configured to allow the driver to be driven in either the forward or reverse direction in response to rotation of the driver, i.e., to rotate in either the clockwise or counterclockwise direction depending on the desired extension or compression application. Thus, in the unlocked position, the locking mechanism 500, when actuated by the driver, allows the driver and the lead screw to rotate in either the clockwise or counterclockwise direction. However, in the locked position, the locking mechanism 500 resists and, in some embodiments, completely prevents any rotation in the absence of rotation of the driver. As a result, the locking mechanism 500 resists, reduces, minimizes, or prevents the extension loss caused by the load on the lead screw 122 when in the locked position.

[0068] In various embodiments, the driver may be any actuator of rotational motion. For example, in the embodiments shown in FIGS. 26 - 28 and FIG. 34, the driver is the magnetic assembly 200 described herein, which includes a cylindrical permanent magnet 202 configured to rotate upon application of a magnetic field, and a magnet housing 204 that may be disposed around the cylindrical permanent magnet 202. The magnet housing 204 may be composed of separate magnet cups 207, 208 as described above. In other embodiments, the driver may be, for example, a motor.

[0069] As described above, FIGS. 27 and 28 illustrate an embodiment in which the driver is in the form of a cylindrical permanent magnet 202 disposed within a magnet housing 204. The magnet housing 204 includes a first drive pin 502 and a second drive pin 504. As best shown in FIG. 28, each of the first drive pin 502 and the second drive pin 504 extends axially from a first end of the magnet housing 204 in a direction parallel to the axis of rotation of the cylindrical permanent magnet 202. The first drive pin 502 and the second drive pin 504 may be disposed substantially opposite one another and spaced apart from one another by approximately 180 degrees on the end face of the magnet housing 204.

[0070] The keyed drive stage 520, shown in detail in FIGS. 32 and 33 and shown in relation to FIGS. 26, 27, and 34 - 36, is configured to be driven by a driver, such as the magnet housing 204. The keyed drive stage 520 includes a first rotational slot 522 and a second rotational slot 524 on the torque input end, each configured to receive one of the first drive pin 502 and the second drive pin 504. Thus, the first rotational slot 522 and the second rotational slot 524 can be arranged such that they are disposed substantially opposite each other and spaced apart from each other by approximately 180 degrees on the input end of the keyed drive stage 520. Each of the first rotational slot 522 and the second rotational slot 524 can have an arcuate shape configured to allow a limited amount of rotation of the driver relative to the rotational slots 522, 524. The input end receives a keeper 530, as described herein, and may further include a recess 527 shaped and dimensioned to allow the keeper 530 to translate across the axis of rotation of the keyed drive stage 520, as further described herein. Still further, the recess 527 can include a vertical guide surface 529 configured to define or guide the keeper 530 along its translation path. The recess 527 is further configured, as further described herein, to allow the keeper 530 to translate beyond or across the outer perimeter of the end of the keyed drive stage 520 and to allow the keeper 530 to engage a ring gear 246 disposed around the keyed drive stage 520.

[0071] At the second torque output end of the keyed drive stage 520, an opening 252 having a keyed inner surface 254 is provided, as described elsewhere in this specification. The opening 252 can be configured to fittingly receive and engage a keyed male function, such as an externally keyed surface 140 on the end 134 of the parent screw 122, and transmit torque. The keyed opening 252 can have any cross-sectional shape configured to transmit torque, such as square, rectangular, hexagonal, or star-shaped. The keyed drive stage 520 can further include, for example, a retainer 150 described herein with respect to FIG. 5.

[0072] The keeper 530, shown in detail in FIGS. 29-31 and shown in the context of FIGS. 26, 27, and 34-36, can be configured to be disposed within the recess 527 of the keyed drive stage 520. The keeper 530 is configured to move from a locked position to an unlocked position in response to rotation of a driver, such as the magnet housing 204. Specifically, the keeper 330 is configured to rotate and translate in response to rotation of the driver, thereby moving from the locked position to the unlocked position. In the locked position, the keeper 530 is configured to resist, reduce, minimize, or in certain embodiments prevent rotation of the keyed drive stage 520 and the magnet housing 204 under a load on the parent screw 122. In the unlocked position, the keeper 530 is configured to allow rotation of the keyed drive stage 520 and the driver, such as the magnet housing 204.

[0073] As best seen in FIGS. 29-31, the keeper 530 includes a body configured to be received within the keyed drive stage 527. The keeper 530 can include a drive surface 540 configured to cooperate with a vertical guide surface 529 on the recess 527 to allow the keeper 530 to translate along the recess 527 and to allow the keeper 530 to drive rotation of the keyed drive stage 520. The drive surfaces 540 can be flat or substantially flat surfaces that are parallel or substantially parallel to each other and perpendicular to the axis of rotation of the keyed drive stage 520.

[0074] The keeper 530 may include at least one locking tooth 554 disposed at a first end of the keeper 530 and extending axially therefrom. The locking tooth 554 is configured to releasably engage or mate with the internal teeth 248 on the inner wall 244 of the ring gear 248 during use (see FIGS. 35 and 36). The locking teeth may be of any mating male / female shape, such as a square or triangular tooth shape. The keeper 530 may further include a first detent 546, which may be disposed at the first end near the locking tooth 554 and may be laterally aligned with the locking tooth 554. The first detent 546 may be configured to engage the first drive pin 502 during use. The keeper 530 may further include a second detent 550 disposed at a second end of the keeper 530 opposite the first end, and the second detent 550 is configured to engage the second drive pin 504. The second detent may also be laterally aligned with the first detent 546 and the locking tooth 554. Alternatively, it should be noted that the first detent 546 may engage the second drive pin 504 and the second detent 550 may, with equal effect, engage the first drive pin.

[0075] Each of the first detent 546 and the second detent 550 may include respective inclined surfaces 548, 552, and respective drive pins 502, 504 are configured to travel along the inclined surfaces 548, 552. The first inclined portion 548 and the second inclined portion 552 may each be configured to curve or incline, similar to the first inclined portion 348 and the second inclined portion 352 (see FIG. 17) which each have a generally or substantially U-shaped or V-shaped inclined surface. Each inclined portion 548, 552 may include a zenith that is laterally aligned with the other and also laterally aligned with the locking teeth 554 on the keeper 530. Accordingly, the drive pins 502, 504 disposed on each of the first detent 546 and the second detent 550 are disposed at the zeniths of the first inclined portion 548 and the second inclined portion 552 and aligned with the locking teeth 554 when the keeper 530 is in the locked position. The drive pins 502, 504 disposed on each of the respective first detent 546 and second detent 550 are configured to move the respective first inclined portion 548 and second inclined portion 552 upward when the keeper 530 moves to the unlocked position. In certain embodiments, the first detent 546 and the second detent 550 each extend through the full thickness of the keeper 530.

[0076] As shown in FIGS. 29 - 30, the keeper 530 further includes a spring guide slot 544. Unlike the detents 546 and 550, the spring guide slot 544 may extend through only a portion of the thickness of the keeper 530. The spring guide slot 344 may curve and may be configured to receive a biasing portion or a portion of the spring 506 (see FIG. 27). Accordingly, the shape and size of the spring guide slot 544 may be complementary to the shape and size of a portion of the spring 506.

[0077] The locking mechanism 500 further includes a biasing member or spring 506 that is partially disposed within the spring guide slot 344 and may be partially disposed within the spring contour 528 within the recess 527. The biasing member 506 may be configured to bias the keeper 530 away from the spring contour 528. The recess 527 may open at the end 526 on the opposite side of the spring contour 528. Thus, the biasing member is configured to bias the keeper 530 across or substantially perpendicular to the axis of rotation of the magnet assembly such that the locking teeth 554 extend beyond the outer periphery of the keyed drive stage 520. In use, this enables the locking mechanism 500 to achieve the locked position shown in FIG. 35.

[0078] Referring to FIGS. 26, 27, and 34, the locking mechanism 500 may further include a radial bearing 508, which may be disposed around at least a portion of the magnet housing 204 and configured to assist in maintaining the spatial relationship between the magnet housing 204, the keeper 530, and the keyed drive stage 520.

[0079] During operation, the locking mechanism 500 including the keeper 530 defaults to the locked position (see FIG. 35) when the driver, e.g., the magnet housing 204, is stationary. In the locked position, the biasing member 506 is configured to bias the keeper 530 toward the open end 526 and against the spring contour 528 of the recess 527. Under the force of the biasing member 506 in the extended state, the keeper 530 translates across the axis of rotation, toward and at least partially through the open end 526 of the recess 527, such that the locking teeth 554 on the keeper 530 extend beyond the outer periphery of the keyed drive stage 520 and are biased into meshing engagement with the teeth 248 on the inner surface 244 of the ring gear 246. Due to the shape of the first detent 546 and the second detent 550, the first drive pin 502 and the second drive pin 504 are disposed at the zenith positions of their respective inclined portions 348, 352. In this position, the keeper 530 resists rotation of the keyed drive stage 520 and loading against the lead screw 122 (see FIG. 34).

[0080] When the driver, for example, the magnet housing 204 rotates and in response thereto, the keeper 530 moves from the locked position to the unlocked position. When the magnet housing 204 rotates in either the clockwise or counterclockwise direction, the drive pins 502, 504 move from the zenith position following the curvature or inclination of the inclined portions 548, 552. In the embodiment shown in FIG. 36, the magnet housing 204 was rotating in the counterclockwise direction, but the keeper 530 would function in the same manner if the rotation were clockwise. Due to this rotation, the keeper 530 translates axially with respect to the recess 527 in a direction away from the open end 526. With respect to this translational movement, the locking teeth 554 are disposed at the rear end of the keeper 530. Due to this translation, the locking teeth 554 are disengaged from the ring gear 246, and the biasing portion 506 is compressed by the keeper 530, particularly by the spring guide slot 544. When the locking teeth 554 are disengaged from the teeth 248 of the ring gear 246, the keeper 530 moves to its unlocked position, where the keyed drive stage 520, and thus the lead screw 122, can rotate freely with respect to the ring gear 246.

[0081] When the rotation of the magnet housing 204 stops and in response thereto, the opposite process occurs. When there is no rotation of the magnet housing 204, under the biasing force of the biasing portion 506, the drive pins 502, 504 move downward along the inclined portions 548, 552 and return to the zenith position shown in FIG. 35, and the keeper 530 translates axially with respect to the recess 527. The locking teeth 554 are at the front end of the keeper 530 with respect to this translational movement. The locking teeth 554 engage with the teeth 248 of the ring gear 246, thereby preventing the rotation of the keyed drive stage 520. If the keyed drive stage 520 is rotatably fixed, the lead screw 122 is also rotatably fixed. In this way, regardless of or independent of the load applied to the lead screw 122, reverse drive and the resulting elongation or compression losses can be resisted and in some embodiments prevented.

[0082] As used herein, terms such as "first", "second", etc. do not indicate any order, quantity or importance, but rather are used to distinguish one element from another, and the terms "a" and "an" in this specification do not indicate a limitation of quantity, but rather indicate that at least one of the items being referred to exists. The modifier "about" when used in connection with a quantity includes the recited 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 plural of the term it modifies, thereby including one or more of that term (e.g., metal(s) includes one or more metals). The ranges disclosed herein are inclusive and, independently, combinable (e.g., the range "up to about 25 mm, or more particularly, about 5 mm to about 20 mm" includes the endpoints and all intermediate values of the range "about 5 mm to about 25 mm", etc.).

[0083] Although various embodiments are described herein, it will be understood from this specification that various combinations of elements, variations or improvements within this specification may be made by those skilled in the art and are within the scope of the invention. Further, numerous modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Accordingly, the invention is not limited to the particular embodiments disclosed as the best mode contemplated for carrying out the invention, but the invention is intended to cover all embodiments falling within the scope of the appended claims.

Claims

1. a driver, a driven gear system, and a keeper, comprising an implantable medical device, wherein the keeper comprises a body, and a keyed opening of the body configured to receive a complementary keyed portion of a drive gear of the driven gear system, wherein the keeper and the drive gear are rotationally fixed to each other; and an opening of the body configured to receive a central pin of the drive gear of the driven gear system and further configured to allow the body to translate axially with respect to the central pin; and locking teeth disposed at a first end of the body and configured to releasably engage teeth on a ring gear of the driven gear system; wherein the keeper is configured to move from a locked position to an unlocked position in response to rotation of the driver; and wherein the keeper is configured to resist rotation of the drive gear and the driver under a load on the driven gear system in the locked position and to allow rotation of the drive gear and the driver in the unlocked position. An implantable medical device.

2. wherein the keeper rotates to move from the locked position to the unlocked position, and in response to the rotation of the keeper, translates axially with respect to the central pin in a direction opposite to the first end, and in response to the translation, disengages the locking teeth from the ring gear of the driven gear system, thereby further configured to move the keeper to the unlocked position. The implantable medical device according to claim 1.

3. The keeper further includes a first surface configured to engage with the driver and a second surface configured to engage with the driven gear system, for the implantable medical device according to claim 1.

4. The opening extends from the first surface through the body to the second surface, and the keyed opening extends from the second surface through a portion of the thickness of the keeper, for the implantable medical device according to claim 3.

5. The opening and the keyed opening are fluidly coupled, The keyed opening is bounded by a drive surface configured to drive the rotation of the keyed portion of the drive gear, and the opening is bounded by a shaft relief surface configured to allow the translation of the central pin, The keeper further includes a stepped surface between the drive surface and the shaft relief surface, for the implantable medical device according to claim 4.

6. The keeper is a first detent disposed on the first surface and disposed between the opening and the first end of the body, and includes a first inclined surface, a first detent; and a second detent disposed on the first surface at a second end opposite to the first end, and includes a second inclined surface, a second detent, and further includes, each of the first detent and the second detent is configured to receive a drive pin disposed at an end of the driver, for the implantable medical device according to claim 3.

7. The keeper is disposed at the second end of the body and further includes a hole that opens into the keyed opening, and the hole is configured to receive a biasing portion, In the locked position, the locking teeth are configured to engage with the ring gear and to maintain such engagement under the biasing force from the biasing portion in the extended state. In the unlocked position, the locking teeth are configured to be disengaged from the ring gear in response to compression of the biasing portion when the driver and the keeper are rotated. The implantable medical device according to claim 6.

8. The first inclined portion and the second inclined portion are each substantially V-shaped, and the apex of the first inclined portion, the apex of the second inclined portion, and the locking teeth When the keeper is in the locked position, the drive pins respectively disposed on each of the first detent and the second detent are disposed at the apexes of the first inclined portion and the second inclined portion, and When the keeper moves to the unlocked position, the drive pins respectively disposed on each of the first detent and the second detent are laterally aligned so as to move the respective first inclined portion and the second inclined portion upward. The implantable medical device according to claim 7.

9. The first detent and the second detent are further configured to allow rotation of the driver relative to the keeper to an extent limited by the lengths of the first inclined portion and the second inclined portion. The implantable medical device according to claim 8.

10. The first detent and the second detent each extend through a thickness of a portion of the keeper. The implantable medical device according to claim 6.

11. A locking mechanism configured to lock and unlock rotation of a driver and a driven gear system in an implantable extension and compression system, A driver of rotational motion comprising a first drive pin and a second drive pin each extending axially from a first end of the driver, A drive gear configured to be driven by the driver and having a keyed portion, the drive gear, A keeper disposed on the drive gear and configured to move between a locked position and an unlocked position, comprising: The keeper is A keyed opening configured to rotatably engage with the keyed portion of the keyed drive shaft, Lock teeth disposed at a first end of the keeper and configured to releasably engage with a ring gear of the driven gear system, the lock teeth, A first detent and a second detent configured to engage with the first drive pin and the second drive pin, A biasing portion configured to bias the keeper across the longitudinal axis of the driver and the drive gear, comprising: In the locked position, the keeper resists rotation of the drive gear and the driver under a load on the driven gear system, and in the unlocked position, the keeper allows rotation of the drive gear and the driver. Locking mechanism.

12. In the locked position, the biasing portion is configured to bias the keeper and the lock teeth so as to mesh and engage with the ring gear, and in the unlocked position, the biasing portion is compressed by the keeper during rotation of the driver, thereby releasing the engagement between the lock teeth and the ring gear and enabling the driver and the drive shaft to rotate. The locking mechanism according to claim 11.

13. The driver has an opening at a first end of the driver and further includes a central recess disposed between the first drive pin and the second drive pin. The drive gear further includes a central pin and a gear, each of which is coupled to the keyed portion of the drive gear at both ends, and the central pin is at least partially disposed within the central recess of the driver. The locking mechanism according to claim 11.

14. Further comprising a hole extending from the keyed opening through the second end of the keeper to the keyed portion, The second end is on the opposite side of the first end, The biasing portion is disposed within the hole. The locking mechanism according to claim 11.

15. The locking mechanism according to claim 11, further comprising a radial bearing configured to maintain a coaxial relationship between two or more of the driver, the keeper, and the keyed drive gear.

16. Each of the first and second detents includes an inclined surface, and each of the drive pins is configured to travel along the inclined surface. The locking mechanism according to claim 11.

17. The driver includes a cylindrical permanent magnet configured to rotate by application of a magnetic field, and a magnet housing disposed around the cylindrical permanent magnet. The locking mechanism according to claim 11.

18. The drive gear is a sun gear, and the driven gear system is a planetary gear system. The sun gear is configured to engage with the ring gear via a plurality of planetary gears. The locking mechanism according to claim 11.

19. The keyed portion has a square cross-sectional shape, and the keyed opening has a corresponding complementary square cross-sectional shape. The locking mechanism according to claim 11.

20. An embeddable extension and compression system, A housing configured to be attached to a first bone portion, having a driver, a driven gear system, and a lead screw positioned internally, the lead screw being coupled to the driver via the driven gear system such that rotation of the driver causes rotation of the lead screw. A rod configured to be attached to a second bone portion and configured to interact with the lead screw such that the rod extends or contracts relative to the housing upon rotation of the lead screw. A locking mechanism configured to lock and unlock rotation of the driver and the driven gear system. The locking mechanism includes A drive gear driven by the driver and configured to input torque to the driven gear system, the drive gear including a keyed portion. A keeper engaged with the driver and the keyed portion and configured to move between a locked position and an unlocked position in response to rotation of the driver. The keeper resists rotation of the drive gear and the driver under a load on the lead screw in the locked position and allows rotation of the drive gear and the driver in the unlocked position. An embeddable extension and compression system.

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