Flat plate mechanisms for bone lengthening

An adjustable implant comprising:

• 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, wherein the lead screw is at least partially disposed within the second portion,
• wherein the lead screw is 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, and
• wherein the third axis is parallel to the first axis and orthogonal to the second axis.

An adjustable implant comprising:

• a first portion configured to couple to a first bone segment;
• a drive assembly disposed within the first portion and configured to rotate about a first axis, wherein the drive assembly comprises a driver configured to rotate about the first axis, and a drive shaft rotatably coupled to the driver;
• 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,
• wherein 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, and
• wherein the driver comprises a rotatable permanent magnet configured to be rotated by an externally applied magnetic field.