Methods and systems for constraint of multiple spine segments
View Patent ↗Methods, apparatus and systems for constraining spinous processes to elastically limit flexion of two or more adjacent spinal segments rely on placing a tether structure over at least three adjacent vertebral bodies or two adjacent vertebral bodies and the sacrum. The tether structures may be continuous, for example in the form of a continuous loop, or may be discontinuous, for example in the form of a loop or elongate element having at least two anchor structures for securing in bone.
1. A method for constraining spinous processes to elastically limit flexion of two or more adjacent spinal segments, said method comprising:
placing a first tether structure over a superior spinous process and an inferior spinous process of a first spinal segment, wherein the first tether structure elastically couples the superior spinous process and the inferior spinous process so as to limit flexion therebetween without substantially limiting extension thereof,
wherein a first portion of the first tether structure extends between the superior spinous process and the inferior spinous process of the first spinal segment, and a second portion of the first tether structure extends between the superior spinous process and the inferior spinous process of the first spinal segment, the first and the second portions disposed symmetrically on opposite sides of the spinous processes, and substantially parallel to one another; and
placing a second tether structure over a superior spinous process and an inferior spinous process or a sacrum of a second spinal segment, the first spinal segment being adjacent and superior to the second spinal segment, wherein the second tether structure elastically couples the superior spinous process and the inferior spinous process or the sacrum of the second spinal segment so as to limit flexion therebetween without substantially limiting extension thereof,
wherein a first portion of the second tether structure extends between the superior spinous process and the inferior spinous process or the sacrum of the second spinal segment, and a second portion of the second tether structure extends between the superior spinous process and the inferior spinous process or the sacrum of the second spinal segment, the first and the second portions disposed symmetrically on opposite sides of the spinous processes, and substantially parallel to one another, and
wherein one of the first or the second tether structures is positioned anteriorly relative to the other tether structure.
2. A method as in claim 1 , wherein the first tether structure or the second tether structure comprises a contiguous tether structure.
3. A method as in claim 1 , wherein the inferior spinous process of the first spinal segment comprises an intermediate spinous process, and the first tether structure is disposed around a first surface of the intermediate spinous process, and wherein the superior spinous process of the second spinal segment comprises the intermediate spinous process, the method further comprises positioning the second tether structure around a second surface of the intermediate spinous process, wherein the second surface is opposite the first surface, and wherein the second tether positioned on the intermediate spinous process such that one tether is anteriorly disposed relative to the other tether structure.
4. A method as in claim 1 , wherein one of the spinous processes in the first or the second spinal segment is disposed on an L4 or L5 vertebrae, or disposed on the sacrum.
5. A method as in claim 1 , wherein spaces between adjacent spinous processes are free from structure which would inhibit extension therebetween.
6. A method as in claim 1 , wherein the first or the second tether structure comprises one or more band elements in series with one or more compliance members, wherein the one or more compliance members provide the elasticity to limit the flexion.
7. A method as in claim 1 , wherein the first or the second tether structure comprises at least two compliance members, the method further comprising positioning the compliance members symmetrically to lie on opposite sides of the spinous processes, and wherein the at least two compliance members provide the elasticity to limit the flexion.
8. A method as in claim 1 , wherein the first or the second tether structure provides an elastic stiffness in compression below 3 N/mm.
9. A method as in claim 8 , wherein the elastic stiffness in compression is below 0.5 N/mm.