Methods and systems for increasing the bending stiffness and constraining the spreading of a spinal segment

Abstract

A system for restricting spinal flexion includes superior and inferior tether structures joined by a pair of compliance members. Compliance members comprise tension members which apply a relatively low elastic tension on the tether structures. By placing the tether structures on or over adjacent spinous processes, flexion of a spinal segment can be controlled in order to reduce pain.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of application Ser. No. 12 / 106,103 (Attorney Docket No. 026398-000410US), filed on Apr. 18, 2008, which claims the benefit of provisional application 60 / 936,897, (Attorney Docket No. 026398-000400US), filed on Jun. 22, 2007, the full disclosures of which are incorporated herein by reference.[0002]The present invention is related to but does not claim priority from application Ser. No. 11 / 076,469, filed on Mar. 9, 2005, now U.S. Pat. No. 7,458,981, which claimed the benefit of prior provisional application 60 / 551,235, filed on Mar. 9, 2004; application Ser. No. 11 / 777,366 (Attorney Docket No. 026398-000110US); filed on Jul. 13, 2007; application Ser. No. 11 / 827,980 (Attorney Docket No. 026398-000120US); filed on Jul. 13, 2007; PCT application no. US 2007 / 081815 (Attorney Docket No. 026398-000130PC); filed on Oct. 18, 2007; PCT application no. US 2007 / 081822 (Attorney Docket No. 026398-000140PC); ...

AI Technical Summary

Benefits of technology

[0016]In another aspect of the present invention, the symptoms of lumbar pain associated with flexion may be relieved by constraining flexion of a spinal segment by limiting spreading of the spinous processes of a spinal segment to a maximum distance in the range from 1 mm to 10 mm, preferably from 2 mm to 8 mm. Optionally, the bending stiffness will be increased over the constrained range of flexion which is allowed. For example, the range of movement may be limited and the bending stiffness increased using a device having an elastic component together with stops or other mechanical constraints which provide a “hard stop” to prevent extension of the device beyond the allowed limited spreading distance of the spinous processes.

[0036]For some patients, particularly those having spinal segments which are very lax, having lost most or all of their natural segmental stiffness, the present invention can provide for “pre-tensioning” of the constraining structure. As described above, one way to accomplish this is by shortening the constraining structure such that a small amount of tension is held by the constraining structure when the spine is in the neutral or slightly extended initial position. Alternatively, pre-tensioned compliance elements can be provided to pre-tension the constraining structure without changing its length. The tension or compression elements utilized in the compliance members of the present invention, such as coil springs, elastomeric bodies, and the like, will typically present little or no elastic resistance when they are first deformed. Thus, there will be some degree of elongation of the compliance members prior to the spinal segment receiving a therapeutic resistance. To provide a more immediate relief, the tension or compression members may be pre-tensioned to have an initial static resistive force which must be overcome to initiate deformation. In this way, a constrained spinal segment will not begin to flex at the instant the patient begins to flex her or his spine which is an advantage when treating lax spinal segments. Certain specific embodiments for achieving such pre-tensioning are described in detail below.

Problems solved by technology

For example, the range of movement may be limited and the bending stiffness increased using a device having an elastic component together with stops or other mechanical constraints which provide a “hard stop” to prevent extension of the device beyond the allowed limited spreading distance of the spinous processes.

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