Patent Description:
Distraction osteogenesis procedures cause two bone segments to distract apart, allowing new bone tissue to form between the two bone segments. Distraction osteogenesis procedures may be useful, for example, to increase the length of a bone (e.g., femur, tibia, etc.) at a pre-determined rate, such as one millimeter per day, thereby allowing new bone tissue to form in a gap between the segments. One limitation of devices, systems, and methods known in the art of distraction osteogenesis procedures is the size and/or shape of known devices which limit the implantation site and/or distraction osteogenesis procedures that can be performed.

<CIT> describes implants known in the art.

Embodiments of the present disclosure aim to address these challenges, as well as other challenges generally with distraction osteogenesis devices, systems, and associated methods.

According to the invention it is provided an implant having the features of claim <NUM>. Further advantageous aspects of the invention are set forth in the dependent claims.

An aspect of the disclosure provides an adjustable implant including: a first portion configured to couple to a first bone segment; a drive assembly disposed within the first portion and configured to drive rotational motion about a first axis; a second portion configured to couple to a second bone segment and axially translate relative to the first portion along a second axis; and a lead screw disposed at least partially within the first and second portions along the second axis. The lead screw is rotatably coupled to the drive assembly such that rotational motion about the first axis drives rotational motion of the lead screw about the second axis, thereby causing the second portion to axially translate along the second axis relative to the first portion.

Another aspect of the disclosure provides an adjustable implant including: a first portion configured to couple to a first bone segment; a gear assembly disposed in the first portion; a drive assembly configured to rotatably engage the gear assembly and to rotate about a first axis, wherein the drive assembly is configured to drive rotational motion of the gear assembly about a second axis; a lead screw disposed at least partially within the first portion, and extending along a third axis; and a second portion configured to couple to a second bone segment. The lead screw is at least partially disposed within the second portion and rotatably coupled to the drive assembly, such that rotational motion of the drive assembly about the first axis drives rotational motion of the gear assembly about the second axis, which drives rotational motion of the lead screw about the third axis, thereby causing the second portion to axially translate along the third axis relative to the first portion.

Another aspect of the disclosure provides an adjustable implant including: a first portion configured to couple to a first bone segment; and a drive assembly disposed within the first portion and configured to rotate about a first axis. The drive assembly includes a driver configured to rotate about the first axis, and a drive shaft rotatably coupled to the driver. The adjustable implant further includes a second portion configured to couple to a second bone segment and axially translate relative to the first portion along a second axis; and a ratchet assembly disposed at least partially within the first and second portions. The ratchet assembly is configured to actuate axial translation relative to the first portion along the second axis in response to rotation of the drive assembly about the first axis, and to inhibit retraction of the second portion relative to the first portion along the second axis.

Two or more aspects described in this disclosure, including those described in this summary section, may be combined to form implementations not specifically described herein.

The present disclosure describes various embodiments of adjustable implants, distraction and compression systems, and related methods. methods (not claimed). Such embodiments include, for example, an adjustable implant having a first portion configured to couple to a first bone segment and a second portion configured to couple to a second bone segment of a patient. The second portion may be at least partially disposed within the first portion and configured to axially translate along an axis relative to the first portion. The first and second portions of the adjustable implant may include one or more apertures configured to receive, for example, a fixation anchor therein to couple the first and second portions of the adjustable implant to the first and second bone segments, respectively. The adjustable implant may include a drive assembly configured to drive rotational movement of a lead screw to move the second portion relative to the first portion, thereby adjusting the distance between the first and second bone segments for performing distraction osteogenesis. The adjustable implant may be configured to be externally controlled by an external adjustment device and may therefore be non-invasively adjustable in such embodiments.

As shown in <FIG>, adjustable implant <NUM> includes a first portion <NUM> and a second portion <NUM> at least partially disposed within the first portion <NUM>. For example, the first portion <NUM> may be a housing, and the second portion <NUM> may be a movable rod disposed at least partially within the housing. The illustrated first and second portions <NUM>, <NUM> each include a flat plate shaped and dimensioned to engage a bone segment of a patient. The first portion <NUM> is configured to be fixed to the bone at a first location (e.g., a first bone segment) and the second portion <NUM> is configured to be fixed to the bone at a second location (e.g., a second bone segment). The first and second portions <NUM>, <NUM> may each include one or more fixation apertures <NUM> configured to receive one or more fixation screws therein. The fixation screw(s) may be configured to couple the first and second portions <NUM>, <NUM> to the bone at the first and second locations, respectively. In some embodiments, the one or more fixation apertures <NUM> include a locking screw hole having internal threads for threadingly engaging a thread on a head of a fixation screw, as will be described herein. One or both of the first and second portions <NUM>, <NUM> can be configured for extramedullary attachment to bone.

In order to grow or lengthen bone, the bone can have a pre-existing separation or is purposely cut or broken (e.g., via an osteotomy) to create this separation, dividing the bone into a first bone segment and a second bone segment. The cut may be done prior to implanting and securing the adjustable implant <NUM> or may be done after the adjustable implant <NUM> is fully or partially implanted, for example by use of a flexible Gigli saw. As will be described herein, the implant <NUM> is configured such that the second portion <NUM> can one or both of contract (e.g., for compression) and distract (e.g., for limb lengthening) relative to the first portion <NUM> along a longitudinal axis (A<NUM>) distally or proximally. The adjustable implant <NUM> is configured to allow controlled, precise translation of the second portion <NUM> relative to the first portion <NUM> by non-invasive remote control, and thus controlled, precise translation of the second bone segment coupled to the second portion <NUM> relative to the first bone segment coupled to the first portion <NUM>.

Over the treatment period for limb lengthening, the bone is regularly distracted, creating a new separation, into which osteogenesis can occur. Regularly distracted is meant to indicate that distraction occurs on a regular or periodic basis which may be on the order of every day or every few days. An exemplary distraction rate is one millimeter per day, although other distraction rates may be employed. That is to say, a typical distraction regimen may include a daily increase in the length of the adjustable implant <NUM> by about one millimeter. This may be accomplished, for example, by four lengthening periods per day, each providing <NUM> of lengthening. The adjustable implant <NUM> includes a drive assembly <NUM> configured to drive rotational motion about an axis (A<NUM>), which allows the second portion <NUM> to be telescopically extended from the first portion <NUM>, thus forcing the first and second segments of the bone apart from one another. The rotational axis A<NUM> may be orthogonal to the axis A<NUM>, as shown in <FIG>. In alternative embodiments of the disclosure, the rotational axis A<NUM> and the axis A<NUM> form an oblique angle, as disclosed in more detail below.

Turning to <FIG>, the adjustable implant <NUM> includes a drive assembly <NUM> at least partially disposed within or coupled to the first portion <NUM>. The drive assembly <NUM> includes a driver <NUM> configured to drive rotational motion about the rotational axis A<NUM> of the driver <NUM>. The driver can take any of a variety of forms such as a motor or an externally driven rotatable permanent magnet. The illustrated drive assembly <NUM> further includes a drive shaft <NUM> extending proximally from, and rotatably coupled to, the driver <NUM>. The driver <NUM> and drive shaft <NUM> may be axially fixed within the first portion <NUM> by one or more mechanical hardware components such as one or more bearings <NUM>. In the illustrated embodiment, the driver <NUM> includes a rotatable permanent magnet configured to be rotated by an externally applied magnetic field. An external adjustment device <NUM> including an external magnet <NUM>, <NUM> (see <FIG>) may be configured to actuate rotation of the driver <NUM> in either of a first direction or a second direction about the rotational axis A<NUM> of the driver <NUM>.

Rotation in the first direction may correspond to distraction of the adjustable implant <NUM> and rotation in the second direction may correspond to retraction of the adjustable implant <NUM>. For instance, the driver <NUM> may be configured to rotate about the rotational axis A<NUM> in a first direction corresponding to distal translation of the second portion <NUM> (e.g., distraction), and to rotate in a second direction opposite the first direction corresponding to proximal translation of the second portion <NUM> along the axis A<NUM> (e.g., retraction, as in a compression procedure). Alternatively, the adjustable implant may include a motor configured to rotate in response to an electrical signal (e.g., as provided by an external device). The motor may be electrically coupled to a power source such as an implanted battery or charging capacitor to drive rotation of a drive shaft <NUM>. The power source may be configured for transcutaneous charging using an external power source.

As further shown by <FIG>, the adjustable implant <NUM> further includes a gear assembly <NUM> (<FIG>) rotatably coupled to the drive shaft <NUM> of drive assembly <NUM>. The gear assembly <NUM> may include a plurality of gears (e.g., one or more output gear, ring gears, sun gears, compound planetary gears, etc.) configured to engage each other to transfer rotational motion from the drive assembly <NUM> about the axis A<NUM> to rotational motion of a lead screw <NUM> about the axis A<NUM>, thereby causing the second portion <NUM> to translate along the axis A<NUM>, as disclosed in more detail below. The gear assembly <NUM> may include, for example, a plurality of compound planetary gears <NUM> disposed about the axis A<NUM> and rotatably coupled to the drive shaft <NUM>, such that rotational motion of the driver <NUM> causes the plurality of compound planetary gears <NUM> to rotate about the axis A<NUM>. In the embodiment shown in <FIG>, the gear assembly <NUM> includes one stage of planetary gears, but it should be understood that any number of stages may be implemented in various embodiments within the scope of the present disclosure. Each stage of the one or more stages of gears in gear assembly <NUM> may provide a gear reduction ratio such as, e.g., a <NUM>:<NUM> gear reduction ratio. Each compound planetary gear <NUM> includes a first gear 126A rotatably coupled to a second gear 126B extending proximally from the first gear 126A, such that rotational motion of the drive shaft <NUM> coupled to sun gear <NUM> causes the first gears 126A to rotate as a group about the axis A<NUM>, thereby causing the second gears 126B as a group to rotate about the axis A<NUM>. The first gear 126A of each compound planetary gear is disposed within a first ring gear <NUM>, and the second gear 126B of each compound planetary gear <NUM> is disposed within a second ring gear <NUM>.

As further shown in <FIG> and <FIG>, the first ring gear <NUM> of the gear assembly <NUM> is rotationally fixed to the first portion <NUM>. The first ring gear <NUM> includes a first cavity 122A configured to receive the driver <NUM> therein, a second cavity 122B opposite the first cavity 122A along the axis A<NUM>, and an aperture <NUM> configured to receive the drive shaft <NUM> therein to enable communication between the first cavity 122A and the second cavity 122B. The first ring gear <NUM> is configured to engage a cover <NUM> to retain the driver <NUM> within the first cavity 122A. The second cavity 122B includes an inner surface having a plurality of gear teeth <NUM> configured to rotatably engage the first gear 126A of each compound planetary gear <NUM> disposed therein. The first gear 126A of each compound planetary gear <NUM> may be configured to rotatably engage the plurality of gear teeth <NUM> in the second cavity 122B, and to rotatably engage a first sun gear <NUM> coupled to the drive shaft <NUM>, such that rotation of the drive shaft <NUM> rotates the first sun gear <NUM>, thereby causing the first gear 126A of each compound planetary gear <NUM> to orbit about the first sun gear <NUM> within the second cavity 122B. Rotational movement of the first gears 126A of the plurality of compound planetary gears <NUM> thereby causes rotational movement about the axis A<NUM> of the second gears 126B extending proximally therefrom. The second gear 126B of each compound planetary gear <NUM> may be configured to be received within, and rotatably engage, a second ring gear <NUM>. The second ring gear <NUM> includes a cavity 130A configured to receive the second gears 126B therein. The cavity 130A includes an inner surface having a plurality of gear teeth <NUM> configured to rotatably engage the second gear 126B of each compound planetary gear <NUM> disposed therein. The second gears 126B orbit about, and rotatably engage, a second sun gear <NUM> rotatably coupled to a distal end of the drive shaft <NUM>. The second sun gear <NUM> is configured to support the second gears 126B, but does not provide torque to any gear or component of gear assembly <NUM> (e.g., second sun gear <NUM> is an "idling gear"). Rotational movement of the second gears 126B thereby causes the second ring gear <NUM> to rotate about the axis A<NUM>. The second ring gear <NUM> is rotatably coupled to a beveled output gear <NUM> (<FIG>), such that rotation of the second ring gear <NUM> thereby causes the beveled output gear <NUM> to rotate about the axis A<NUM>. Rotation of the driver <NUM> therefore rotates the drive shaft <NUM>, which in turn rotates the first sun gear <NUM>, which in turn rotates the plurality of compound planetary gears <NUM>, which in turn rotates the second ring gear <NUM>, and which in turn rotates the beveled output gear <NUM>.

As shown in <FIG>, the beveled output gear <NUM> of the gear assembly <NUM> is further configured to rotatably engage a lead screw <NUM>, thereby causing the lead screw <NUM> to rotate about the axis A<NUM>, which in turn drives translation of the second portion <NUM> along the axis A<NUM>. As shown, the lead screw <NUM> includes a shaft extending between a first end having a beveled gear <NUM> configured to rotatably engage the gear assembly <NUM>, and a second end configured to be received within the second portion <NUM>. The lead screw <NUM> further includes an externally threaded portion <NUM> disposed on a radially outward facing surface of the shaft which is configured to threadably engage an internal thread <NUM> of a cavity <NUM> within the second portion <NUM>. Rotating the lead screw <NUM> causes the second portion <NUM> to translate along the externally threaded portion <NUM> of the lead screw <NUM> relative to the first portion <NUM>. Rotation of the lead screw <NUM> about the axis A<NUM> in the first direction may correspond to distraction of the adjustable implant <NUM>, while rotation in the second direction may correspond to retraction of the adjustable implant <NUM>. The rotational axis A<NUM> of the gear assembly <NUM> forms an angle which may be, e.g., orthogonal or oblique with the rotational axis A<NUM> of the lead screw <NUM>. In an example, the smallest angle between A<NUM> and A<NUM> is greater than n degrees where n is any integer between <NUM> degrees and <NUM> degrees, inclusive. In some embodiments, the lead screw <NUM> is configured to drive the second portion <NUM> from the first portion <NUM> by rotating inside a nut that is secured to an inner surface adjacent to a cavity <NUM> of the second portion <NUM> in which the lead screw <NUM> is disposed. The lead screw <NUM> therefore is indirectly mechanically coupled to the drive assembly <NUM>, such that rotation of the driver <NUM> effectuates rotation of the lead screw <NUM>. Rotation of the driver <NUM> therefore rotates the drive shaft <NUM>, which in turn rotates the beveled output gear <NUM> of the drive assembly <NUM> about A<NUM>, which in turn rotates the lead screw <NUM> about axis A<NUM>, and which in turn drives axial translation of the second portion <NUM> relative to the first portion <NUM>.

In another embodiment, such as shown in <FIG> and <FIG>, the adjustable implant <NUM> includes two or more lead screws rotatably coupled to the gear assembly. In such embodiments, each of the two or more lead screws includes a beveled gear configured to rotatably engage the beveled output gear of the gear assembly. The quantity of lead screws that rotatably engage the gear assembly may be determined by the size and shape of the implant, the number of gear teeth on the beveled output gear, and/or the size and shape of each lead screw. The present disclosure is not limited to the number of lead screws shown in the drawings, and encompasses any number of lead screws disposed within an adjustable implant that axially translate in response to rotation of a gear assembly oriented at an angle with respect to the lead screws. In certain embodiments, two or more lead screws may be partially disposed within two or more portions of the adjustable implant (e.g., distraction and compression rods) that are configured to axially translate relative to another portion (e.g., a housing similar to first portion <NUM> shown in <FIG>). Rotation of the drive assembly therefore drives rotational motion of each of two or more lead screws, thereby causing two or more portions of the adjustable implant to axially translate along the respective rotational axis of the two or more lead screws relative to the housing. In some embodiments, each lead screw of the two or more lead screws are substantially identical. In other embodiments, one or more lead screws have a different size and/or shape than another one of the lead screws.

In one embodiment, as shown in <FIG> for example, the adjustable implant <NUM> includes two lead screws 138A, 138B configured to matingly engage the beveled output gear <NUM> and rotate about the same axis A<NUM>, thereby causing two portions (not shown) to axially translate along axis A<NUM> in opposite directions. Rotation of the beveled output gear <NUM> therefore drives rotation of the beveled output gears 140A, 140B of lead screws 138A, 138B, which in turn causes respective portions of the adjustable implant <NUM> to axially translate via external threads 142A, 142B in opposite directions along the axis A<NUM>.

In another embodiment, as shown in <FIG> for example, the adjustable implant includes first lead screw 138A, second lead screw 138B, and third lead screw 138C that are configured to matingly engage beveled output gear <NUM> and rotate about axis A<NUM>, axis A<NUM>, and axis A<NUM>, respectively. Each lead screw 138A, 138B, 138C having a respective beveled gear 140A, 140B, 140C configured to matingly engage the beveled output gear <NUM>. Rotation of the beveled output gear <NUM> therefore drives rotation of the beveled output gears 140A, 140B, 140C of lead screws 138A, 138B, 138C, which in turn causes respective portions of the adjustable implant <NUM> to axially translate via external threads 142A, 142B, 142C in different directions along the respective axis A<NUM>, A<NUM>, A<NUM>. Each axis A<NUM>, A<NUM>, A<NUM> is orthogonal to the rotational axis A<NUM> of beveled output gear <NUM>, and forms an angle (e.g., oblique, orthogonal, etc.) with respect to the other lead screw axis (i.e., θ<NUM> and θ<NUM>).

In the examples of <FIG> and <FIG>, the first portion <NUM> (e.g., the portion of the adjustable implant by which the driver <NUM> and gear assembly <NUM> is retained) can be configured to be directly fixed to bone (e.g., by having one or more fixation apertures <NUM>) or can lack a direct bone connection (e.g., by lacking fixation apertures <NUM>). In an example implementation, the two or more lead screws <NUM> cause respective components fixed to bone (e.g., by having fixation apertures) to translate relative to the first portion.

Turning to <FIG>, a perspective view is illustrated of another embodiment of an adjustable implant <NUM> including a drive assembly <NUM> having a worm gear <NUM> configured to rotatably engage a gear assembly <NUM>. As shown, the adjustable implant <NUM> includes a first portion <NUM> configured to be fixed to a patient's bone at a first location, and a second portion <NUM> at least partially disposed within the first portion <NUM> configured to be fixed to the bone at a second location (e.g., a second bone segment). The adjustable implant <NUM> is configured to allow controlled, precise translation of the second portion <NUM> relative to the first portion <NUM> by non-invasive remote control, and thus controlled, precise translation of the second bone segment coupled to the second portion <NUM> relative to the first bone segment coupled to the first portion <NUM>. In contrast to the embodiment shown in <FIG>, the drive assembly <NUM> of the adjustable implant <NUM> includes a driver <NUM> (e.g., a rotatable permanent magnet) configured to drive rotational motion of a drive shaft <NUM> about an axis A<NUM>, thereby causing the gear assembly <NUM> to rotate about an axis A<NUM>. The drive shaft <NUM> includes a worm gear <NUM> configured to matingly engage an input gear <NUM> of the gear assembly <NUM>, which in turn causes a plurality of planetary gears <NUM> of the gear assembly <NUM> to rotate about the axis A<NUM>, thereby causing an output gear <NUM> of the gear assembly <NUM> to rotate about the axis A<NUM>. The gear assembly <NUM> is configured to transfer rotational motion from the drive assembly <NUM> to a lead screw (not shown) disposed within the first portion <NUM> in a manner similar to the gear assembly <NUM> described with respect to <FIG>, details of which have been omitted herein for brevity. It should be noted that other gear assembly designs configured to transfer rotational motion from the drive assembly <NUM> to the lead screw are also contemplated within the scope of this invention. Rotation of the driver <NUM> therefore causes the drive shaft <NUM> to rotate about the axis A<NUM>, which in turn rotates the worm gear <NUM> about the axis A<NUM>, which in turn rotates the input gear <NUM> about the axis A<NUM>, which in turn rotates the plurality of planetary gears <NUM> about the axis A<NUM>, which in turn rotates the output gear <NUM> about the axis A<NUM>, which in turn causes the lead screw to rotate about an axis A<NUM>, and which in turn causes the second portion <NUM> to axially translate along the axis A<NUM> relative to the first portion <NUM>. In some embodiments, the axis A<NUM> of the drive assembly <NUM> is orthogonal to the axis A<NUM> of the gear assembly <NUM>. In other embodiments, the axis A<NUM> of the drive assembly <NUM> forms an oblique angle with the axis A<NUM> of the gear assembly <NUM>.

As shown in <FIG>, an adjustable implant <NUM> according to another embodiment includes a first portion <NUM> (e.g., a housing) configured to receive a second portion <NUM> and a third portion <NUM> therein. Two or more of portions <NUM>, <NUM>, <NUM> can include a flat plate shaped and dimensioned to engage a bone of a patient at respective locations. For example, the first portion <NUM> can (but need not) be configured to be fixed to bone at a first location (e.g., a first bone segment). The second portion <NUM> can be configured to be fixed to bone at a first or second location (e.g., a first or second bone segment). The third portion <NUM> can be configured to be fixed to the bone at a second or third location (e.g., a second or third bone segment). Each portion <NUM>, <NUM>, <NUM> can further include one or more fixation apertures <NUM> configured to receive one or more fixation screws therein that are configured to couple each portion <NUM>, <NUM>, <NUM> to the respective location of the bone. As will be described herein, the second portion <NUM> is configured to distract relative to the first portion <NUM> along a longitudinal axis (A<NUM>) in a first direction, and the third portion <NUM> is configured to distract relative to the first portion <NUM> along the longitudinal axis A<NUM> in a second, opposite direction. The adjustable implant <NUM> is configured to allow controlled, precise translation of the second and third portions <NUM>, <NUM> relative to the first portion <NUM> by non-invasive remote control, and thus controlled, precise translation of the second and third bone segments along the longitudinal axis A<NUM> relative to the first bone segment.

Turning to <FIG>, additional internal features of the adjustable implant <NUM> are shown. The adjustable implant <NUM> includes a drive assembly <NUM> at least partially disposed within the first portion <NUM> (<FIG>). The drive assembly <NUM> includes a driver <NUM> configured to drive rotational motion about the rotational axis A<NUM> of the driver <NUM> such as, e.g., a rotatable permanent magnet or motor. The drive assembly <NUM> further includes a drive shaft <NUM> extending proximally from, and rotatably coupled to, the driver <NUM>. The driver <NUM> and drive shaft <NUM> may be axially fixed within the first portion <NUM> by one or more mechanical hardware components. Drive assembly <NUM> may further include a driver output gear <NUM> disposed along the drive shaft <NUM>. As shown in <FIG>, the driver <NUM> may include a rotatable permanent magnet configured to be rotated by an externally applied magnetic field. An external adjustment device <NUM> including an external magnet <NUM>, <NUM> (see <FIG>) may be configured to actuate rotation of the driver <NUM> in either of a first direction or a second direction about the rotational axis A<NUM> of the driver <NUM>. Rotation in at least one of the first direction or the second direction may correspond to, for example, distraction of the second and third portions <NUM>, <NUM> along the axis A<NUM> relative to the first portion <NUM>. Alternatively, the adjustable implant <NUM> may include a motor configured to rotate in response to an electrical signal (e.g., as provided by an external device). The motor may be electrically coupled to a power source such as, e.g., a battery or charging capacitor, to drive rotation of a drive shaft. The power source may be configured for transcutaneous charging using an external power source.

As further shown by <FIG>, the adjustable implant <NUM> further includes a gear assembly <NUM> rotatably coupled to the drive assembly <NUM> via the driver output gear <NUM>. The gear assembly <NUM> includes a plurality of gears (e.g., input gear, output gear, etc.) configured to engage each other to transfer rotational motion from the driver <NUM> about the axis A<NUM> to a ratchet assembly <NUM> disposed along an axis A<NUM>. This causes the ratchet assembly <NUM> to actuate axial translation of the second and third portions <NUM>, <NUM> relative to the first portion <NUM>, as discussed herein. Gear assembly <NUM> may include, for example, an input gear <NUM> rotatably coupled to the drive shaft <NUM>, an output gear <NUM> configured to rotatably engage the input gear <NUM>, and an eccentric shaft <NUM> configured to rotatably engage the output gear <NUM>. Rotation of the driver <NUM> therefore rotates the drive shaft <NUM>, which in turn rotates the input gear <NUM>, which in turn rotates the output gear <NUM>, and which in turn rotates the eccentric shaft <NUM>. The eccentric shaft <NUM> is coupled with the ratchet assembly <NUM>, such that rotation of the eccentric shaft <NUM> actuates the ratchet assembly <NUM>.

In some embodiments, as shown in <FIG>, the ratchet assembly <NUM> includes a first ratchet arm 332A and a second ratchet arm 332B, each of which is disposed within the first portion <NUM> and rotatably coupled with the eccentric shaft <NUM>. The first and second ratchet arms 332A, 332B are configured to rotate within the first portion <NUM> about the eccentric shaft <NUM> in response to rotation of the drive assembly <NUM>, thereby causing the second and third portions <NUM>, <NUM>, respectively, to axially translate along the axis A<NUM> (<FIG>) relative to the first portion <NUM>. The first ratchet arm 332A includes a first end coupled to a first ratchet 334A and a second end rotatably coupled to the eccentric shaft <NUM>. The second ratchet arm 332B includes a first end coupled to a second ratchet 334B and a second end rotatably coupled to the eccentric shaft <NUM>. As shown in <FIG>, the ratchet assembly <NUM> further includes a first linear rack 336A disposed on the second portion <NUM> and a second linear rack 336B disposed on the third portion <NUM>. Each of the first and second linear racks 336A, 336B may have a plurality of ratchet teeth <NUM> configured to engage the first and second ratchets 334A, 334B, respectively, to incrementally drive axial translation along the axis A<NUM>. The ratchet assembly <NUM> further includes a first pawl 338A configured to engage the first linear rack 336A and a second pawl 338B configured to engage the second linear rack 336B. The first and second pawls 338A, 338B are dimensioned to allow distraction of the second and third portions <NUM>, <NUM>, respectively, in a first direction along the axis A<NUM>, yet inhibit retraction of the second and third portions <NUM>, <NUM>, respectively, in a second direction opposite the first direction. The ratchet assembly <NUM> may further include mechanical hardware such as, e.g., springs <NUM>, that are configured to position the ratchets 334A, 334B and/or pawls 338A, 338B within the ratchet teeth <NUM> of respective linear racks 336A, 336B in the absence of rotational movement from the drive assembly <NUM>. Rotation of the driver <NUM> therefore rotates the drive shaft <NUM>, which in turn rotates the input gear <NUM>, which in turn rotates the output gear <NUM>, which in turn rotates the eccentric shaft <NUM>, and which in turn causes the ratchet assembly <NUM> to actuate axial translation of the second and third portions <NUM>, <NUM> along the axis A<NUM> relative to the first portion <NUM>.

As shown in <FIG>, in some embodiments, the adjustable implant <NUM> includes a ratchet assembly <NUM> configured to actuate axial translation of the second portion <NUM> relative to the first portion <NUM>. In contrast to the embodiment shown in <FIG>, the adjustable implant <NUM> of <FIG> does not include the third portion <NUM> and related components of the ratchet assembly <NUM> that are configured to engage the third portion <NUM>.

<FIG> illustrate an external adjustment device <NUM> configured for applying a moving magnetic field to allow for non-invasive adjustment of the adjustable implant <NUM>, <NUM>, <NUM> by turning a driver <NUM>, <NUM>, <NUM> within the adjustable implant <NUM>, <NUM>, <NUM>, as described. External adjustment device <NUM> may also be referred to as an external remote controller or external remote control device, and may operate analogously with respect to drive assembly <NUM>, <NUM>, <NUM> of the adjustable implant <NUM>, <NUM>, <NUM>. <FIG> illustrates the internal components of the external adjustment device <NUM>, and for clear reference, shows the driver <NUM> of the adjustable implant <NUM> (as representative of drivers <NUM>, <NUM>, <NUM> and implant systems <NUM>, <NUM>, <NUM> disclosed herein) without the rest of the assembly. The internal working components of the external adjustment device <NUM> may, in certain embodiments, be similar to those described in <CIT>. A motor <NUM> with a gear box <NUM> outputs to a motor gear <NUM>. The motor gear <NUM> engages and turns central (idler) gear <NUM>, which has the appropriate number of teeth to turn first and second magnet gears <NUM>, <NUM> at identical rotational speeds. First and second magnets <NUM>, <NUM> turn in unison with the first and second magnet gears <NUM>, <NUM>, respectively. Each magnet <NUM>, <NUM> is held within a respective magnet cup <NUM> (shown partially). An exemplary rotational speed may be <NUM> RPM or less. This speed range may be configured to limit the amount of current density induced in the body tissue and fluids, to meet international guidelines or standards. As seen in <FIG>, the south pole <NUM> of the first magnet <NUM> is oriented the same as the north pole <NUM> of the second magnet <NUM>, and likewise, the first magnet <NUM> has its north pole <NUM> oriented the same as the south pole <NUM> of the second magnet <NUM>. As these two magnets <NUM>, <NUM> turn synchronously together, they apply a complementary and additive moving magnetic field to the radially-poled driver <NUM>, having a north pole <NUM> and a south pole <NUM>. Magnets having multiple north poles (for example, two) and multiple south poles (for example, two) are also contemplated in each of the devices. As the two magnets <NUM>, <NUM> turn in a first rotational direction <NUM> (e.g., counter-clockwise), the magnetic coupling causes the driver <NUM> to turn in a second, opposite rotational direction <NUM> (e.g., clockwise). The rotational direction of the motor <NUM> and corresponding rotational direction of the magnets <NUM>, <NUM> is controlled by buttons <NUM>, <NUM>. One or more circuit boards <NUM> contain control circuitry for both sensing rotation of the magnets <NUM>, <NUM> and controlling the rotation of the magnets <NUM>, <NUM>.

<FIG> and <FIG> show the external adjustment device <NUM> for use with a device placed in the femur (<FIG>) or the tibia (<FIG>). The external adjustment device <NUM> has a first handle <NUM> for carrying or for steadying the external adjustment device <NUM>, for example, steadying it against an upper leg <NUM> (as in <FIG>) or lower leg <NUM> (as in <FIG>). An adjustable handle <NUM> is rotationally attached to the external adjustment device <NUM> at pivot points <NUM>, <NUM>. Pivot points <NUM>, <NUM> have easily lockable/unlockable mechanisms, such as a spring-loaded brake, ratchet, or tightening screw, so that a desired angulation of the adjustable handle <NUM> in relation to housing <NUM> can be adjusted and locked in orientation. In <FIG>, adjustable handle <NUM> is set so that apex <NUM> of loop <NUM> rests against housing <NUM>. In this position, patient <NUM> is able to hold onto one or both of grips <NUM>, <NUM> while the adjustment procedure (for example transporting bone between <NUM> to <NUM>) is taking place. It is contemplated that the procedure could also be a lengthening procedure for a bone lengthening device or a lengthening procedure for a lengthening plate which is attached external to the bone. Turning to <FIG>, when the adjustable implant <NUM> is implanted in a tibia, the adjustable handle <NUM> may be changed to a position in which the patient <NUM> can grip onto the apex <NUM> so that the magnet area <NUM> of the external adjustment device <NUM> is held over the portion of the adjustable implant <NUM> containing the driver <NUM>. In both cases, the patient <NUM> is able to clearly view control panel <NUM> including a display <NUM>. In a different configuration from the two directional buttons <NUM>, <NUM> in <FIG>, the control panel <NUM> includes a start button <NUM>, a stop button <NUM> and a mode button <NUM>. Control circuitry contained on circuit boards <NUM> may be used by the surgeon to store important information related to the specific aspects of each particular patient. For example, in some patients an implant may be placed antegrade into the tibia. In other patients the implant may be placed either antegrade or retrograde about the femur. In each of these three cases, it may be desired to move the bone either from distal to proximal or from proximal to distal. By having the ability to store information of this sort that is specific to each particular patient within the external adjustment device <NUM>, the external adjustment device <NUM> can be configured to direct the magnets <NUM>, <NUM> to turn in the correct direction automatically, while the patient need only place the external adjustment device <NUM> at the desired position, and push the start button <NUM>. The information of the maximum allowable bone transport length per day and maximum allowable bone transport length per session can also be input and stored by the surgeon for safety purposes. These may also be added via an SD card or USB device, or by wireless input. An additional feature is a camera at the portion of the external adjustment device <NUM> that is placed over the skin. For example, the camera may be located between the first magnet <NUM> and second magnet <NUM>. The skin directly over the implanted driver <NUM> may be marked with indelible ink. A live image from the camera is then displayed on the display <NUM> of the control panel <NUM>, allowing the user to place the first and second magnets <NUM>, <NUM> directly over the area marked on the skin. Crosshairs can be overlaid on the display <NUM> over the live image, allowing the user to align the mark on the skin between the crosshairs, and thus optimally place the external adjustment device <NUM>.

Other external adjustment devices can be used to cause actuation of the distraction devices described herein. Such external adjustment devices include, for example, those described in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>.

Examples described herein can benefit from techniques described in other applications. In an example, the maintenance feature described in <CIT>, as<CIT>. In an example, a modified keeper mechanism described in <CIT>).

The present disclosure provides a method of distraction osteogenesis by post-operatively and non-invasively actuating an actuator of a distraction device implanted in a patient, the method is not part of the scope of the invetion. Actuating the actuator of the distraction device may occur transcutaneously through intact skin. The method may further include implanting the distraction device in the patient, and implanting one or more fixation anchors to couple the distraction device to bone segments of the patient. The method may include forming one or more incisions in the patient to implant the distraction device or fixation anchor(s) through the one or more incisions. The method may further include rotating one or more internal magnets of the distraction device by rotating one or more external magnets of an external adjustment device, thereby post-operatively and non-invasively actuating the actuator. For instance, as shown in <FIG>, a method <NUM> of the present disclosure may include the steps of: implanting <NUM> an adjustable implant to a first bone segment and second bone segment; actuating <NUM> a drive assembly about a first axis; distracting <NUM> the second bone segment relative to the first bone segment along a second axis; and permitting <NUM> continued bone growth.

While implementations above are primarily in the context of externally magnetically driven adjustable implant systems, other drive systems can also be used. For example, in addition to or instead of the magnet-based driving, one or more of the drive elements can take the form of an implanted electric motor. The implanted electric motor can be powered by an external power source (e.g., via a radiofrequency link, via an ultrasonic energy transfer technique, via an inductive connection, via another technique, or via combinations thereof) or an implanted power source (e.g., a battery or charging capacitor, which may be charged by the external power source). The implanted power source may be within the implant (e.g., within a housing thereof) or separate from the implant and coupled to the implant via a cable.

Claim 1:
An adjustable implant (<NUM>; <NUM>; <NUM>) comprising:
- a first portion (<NUM>; <NUM>; <NUM>) configured to couple to a first bone segment;
- a drive assembly (<NUM>; <NUM>; <NUM>) disposed within the first portion (<NUM>; <NUM>; <NUM>) and configured to drive rotational motion about a first axis (A<NUM>);
- a second portion (<NUM>; <NUM>; <NUM>) configured to couple to a second bone segment and axially translate relative to the first portion (<NUM>; <NUM>; <NUM>) along a second axis (A<NUM>); and
- a lead screw (<NUM>; 138A, 138B) disposed at least partially within the first (<NUM>; <NUM>; <NUM>) and second (<NUM>; <NUM>; <NUM>) portions along the second axis (A<NUM>), characterized in that
- the lead screw (<NUM>; 138A, 138B) is rotatably coupled to the drive assembly (<NUM>; <NUM>; <NUM>) such that rotational motion about the first axis (A<NUM>) drives rotational motion of the lead screw (<NUM>; 138A, 138B) about the second axis (A<NUM>), thereby causing the second portion (<NUM>; <NUM>; <NUM>) to axially translate along the second axis (A<NUM>) relative to the first portion (<NUM>; <NUM>; <NUM>).