Systems and methods for forming patient-specific spinal rods

A method of preparing for a spine correction surgery that includes placement of a rod in a patient using a system with a processor and a memory and a rod forming machine, the method comprising:

• identifying a segment of a spine of the patient requiring correction using an image of the spine stored in the memory, the segment including a first point along the spine at a first end of the segment and a second point along the spine at a second end of the segment;
• determining a first radius and a first position of a first circle based on the image using the processor such that a portion of the first circle is generally aligned with a curve of the segment and the first circle passes adjacent to or through the first point and the second point;
• based on a planned post-surgical spinal alignment, modifying the first circle to define a second circle using the processor, the second circle having a second radius different from the first radius and a second position based on the image such that the second circle passes adjacent to or through the first point and the second point, a portion of the second circle from the first point to the second point representing a modified post-surgical alignment of the segment adjusted to compensate for an expected loss of contour when the rod is attached to the spine;
• measuring, by the processor, an angle between a first radial line extending between a center of the second circle and the first point and a second radial line extending between the center of the second circle and the second point;
• using the angle and a radius of the second circle to determine a curvature and arc length of the segment having the modified post-surgical alignment;
• and
• forming a rod using the rod forming machine such that the rod has the determined curvature and arc length, the rod being ready for placement in a spine of a patient upon formation.

A method of forming a spinal rod comprising:

• identifying a segment of a spine of a patient requiring correction using an image of the spine, the segment including a first point along the spine at a first end of the segment and a second point along the spine at a second end of the segment;
• determining a first radius and a first position of a first circle based on the images such that a portion of the first circle generally aligns with a curve of the segment and the first circle passes adjacent to or through the first point and the second point;
• modifying the first circle to define a second circle having a second radius different from the first radius and a second position based on the image such that the modified first circle passes adjacent to or through the first point and the second point, an arc length of the second circle extending along the second circle from the first point to the second point representing a post-surgical alignment of the segment;
• and
• forming the spinal rod to have a length based on the arc length of the second circle and a curvature based on the second radius of the second circle.