This present invention relates to a surgical methods and apparatus for attaching soft tissue to bone.
Numerous devices are currently available to attach objects to bone. More particularly, screws, staples, cement and sutures have all been used to attach soft tissue (e.g., ligaments, tendons, muscles, etc.) to bone, bone to bone, and inanimate objects (e.g., prostheses) to bone.
Among other things, it can be desirable to anchor a length of conventional suture in bone, so that the free end(s) of the suture can be used to attach a desired object (e.g., a ligament, a tendon, a prostheses, etc.) to the bone. This is typically done by providing a bone anchor having a length of suture attached thereto, and securing the bone anchor in the bone so that the free end(s) of the suture extend from the bone. The free end(s) of the suture can then be used to fasten the desired object to the bone. In practice, such bone anchors have found widespread application in procedures for attaching or re-attaching soft tissue to bone, e.g., to repair a torn rotator cuff in the shoulder.
A wide variety of bone anchors, operating on a number of different principles, have been produced. The commercially-successful bone anchors generally fall into one of four broad categories: (i) “screw-type” bone anchors, (ii) “barb-type” bone anchors, (iii) “expandable casing-type” bone anchors, and (iv) “toggle-type” bone anchors. More particularly, screw-type bone anchors (see, for example, U.S. Pat. No. 4,632,100 issued to Goble et al.) generally comprise a screw body which is deployed in the bone by screwing the bone anchor into the bone.
Barb-type bone anchors (see, for example, U.S. Pat. No. 4,898,156 to Gatturna et al.) generally comprise a cylindrical body having flexible barbs extending outboard thereof, with the body being deployed in a pre-formed hole in the bone and the barbs engaging the side wall of the bone hole.
Expandable casing-type bone anchors (see, for example, U.S. Pat. No. 5,268,001 to Nicholson et al.) generally comprise an expandable body which is deployed in a pre-formed hole in the bone and then the body is expanded so as to engage the side wall of the bone hole.
Toggle-type bone anchors (see, for example, U.S. Pat. No. 5,626,612 to Bartlett) generally comprise an elongated body which is inserted in a pre-formed hole in the bone and then the elongated body is turned so as to engage the side wall of the bone hole, whereby to prevent withdrawal from the bone.
It will be appreciated that barb-type bone anchors and expandable casing-type bone anchors share a common feature, i.e., both types of bone anchors enter the bone hole having a first cross-sectional configuration, and thereafter assume a second, larger cross-sectional configuration, whereby to engage the side wall of the bone hole and thereby prevent withdrawal from the bone.
Some bone anchors use barbs formed out of an elastic material which permits them to be elastically deformed inwardly during insertion so as to permit the bone anchor to enter the bone hole. In most cases, a superelastic material is used to form the barbs so as to provide the degree of elasticity required for the application. More particularly, a shape memory alloy (SMA) appropriately engineered to provide monothermal stress-induced martensite (SIM) (e.g., Nitinol) is used. These applications of Nitinol technology for bone anchors are limited to isothermal applications of the stress-induced martensitic (SIM) properties of these shape memory alloys.
In some situations the barbs are sheathed in a tube prior to insertion into the bone hole so as to assume a streamlined geometry. More particularly, in this arrangement, the bone anchor is inserted into the bone hole with its barbs sheathed and, once the bone anchor is properly positioned in the bone hole, the barbs are released so that they spring outwardly and engage the side wall of the bone hole, whereby to anchor the bone anchor in the bone. Unfortunately, the elastically deformed barbs commonly exert high forces on the inside of the sheath, with the result that significant friction is created as the sheath is withdrawn, thus requiring substantial effort to release the barbs from within the sheath.
Alternatively, the barbed anchor may be simply pressed into the pre-drilled hole in the bone, without the barbs being pre-sheathed within a tube. In this situation, the barbs are folded inwardly by virtue of their engagement with the rim of bone at the mouth of the bone hole. Unfortunately, this approach requires high insertion forces and introduces the additional possibility of causing significant displacement or damage to the bone due to engagement of the barbs with the bone as the anchor is inserted. Larger bone holes may be used to reduce the insertion forces required to install the bone anchor, but this is at the expense of reducing the holding power of the anchor within the bone due to the larger bone hole size. Furthermore, larger bone holes increase bone trauma, due to the need to remove more bone material.
Similar problems occur with barb-type bone anchors that use mechanical activation to deploy the barbs, and/or with expandable casing-type bone anchors that use mechanical activation to expand the diameter of the bone anchor.
The present invention is directed to a bone anchor that uses the temperature transition of a shape memory material to expand the anchor within a bone. The illustrated embodiments are generally directed toward barb-type bone anchors, although applications to expandable casing-type bone anchors will be apparent to those skilled in the art in view of the present disclosure. In one embodiment, the bone anchor uses thermal transformation of the metallic crystal state (and hence the stress/strain properties) of shape memory alloy (e.g., Nitinol, NiTi) elements (e.g., engagement elements), whereby to change the configuration of the bone anchor from a retracted configuration to an expanded configuration.
The present bone anchors are typically provided with engagement elements that protrude from the anchor body in the expanded configuration. In one embodiment, the engagement elements are retained inboard during insertion of the bone anchor into the pre-drilled hole, and then are permitted to spring outwardly so as to engage the side walls of the pre-drilled hole. In another embodiment, the present bone anchor is inserted into the bone without the use of a pre-drilled hole.
The illustrated embodiments significantly reduce (or eliminate) the load complications discussed above with respect to prior art elastic engagement elements, including prior art elastic engagement elements formed out of shape memory alloys. In embodiments where the engagement elements are to be held within a sheath, the use of shape memory alloy elements adapted for appropriate temperature transition reduces or substantially eliminates the internal forces exerted by the engagement elements on an overlying sheath, thus resulting in easier loading of the barbed anchor into the sheath and easier (i.e., lower friction) release of the anchor from the sheath.
Correspondingly, where the bone anchor is to be set into the bone without using an overlying sheath, the use of shape memory elements with appropriate temperature transition substantially reduces the insertion forces needed to insert unsheathed engagement elements, thereby facilitating anchor deployment and permitting the use of smaller pre-drilled holes which in turn provides better anchor gripping and reduced bone trauma. Furthermore, the present bone anchors are particularly well suited for self-embedding insertion into bone without the use of pre-drilled holes.
The present invention is also applicable to expandable casing-type bone anchors. Significantly, the ease of insertion of bone anchors formed in accordance with the present invention, and the resulting higher pull-out forces produced by such bone anchors, equal or exceed those of comparable devices not incorporating the present invention.
The present invention is directed to a bone anchor that includes temperature-activated engagement elements formed from a shape memory metal, such as for example a NiTi material sold by NDC Corporation of Fremont, Calif. and designated SE 508 (50.8% Ni content). As used herein, “engagement elements” refers to a temperature activated, shape memory alloy structure adapted to retain a bone anchor in bone. The engagement elements can have a variety of configurations, such as for example, barbs, hooks, serrated or threaded members, and the like.
One preferred embodiment of the present bone anchor 20 is shown in
The distal end 24 of the bone anchor 20 is preferably a self-embedding tip 24A that does not require a pre-drilled hole. Alternatively, the tip 24A my include threads, teeth, chiseled cutting edges, tip blades, or other structures that permit the bone anchor 20 to be inserted through cortical bone without a pre-drilled hole.
The shape memory alloy engagement elements 32 are preferably configured so that when in the retracted configuration they normally lie within about the maximum cross-section of the body 22 during anchor insertion. In the illustrated embodiment, the pointed distal end 24 has a cross section greater than, or equal to, the cross section of the engagement elements 32 in the retracted configuration. The engagement elements 32 extend well beyond the cross section of the distal end 24 when in the expanded configuration, as illustrated in
The engagement elements 32 are temperature-activated once the bone anchor 20 is in place so as to cause them to move to an expanded configuration. In the expanded configuration the engagement elements 32 extend radially outward from the body 22 and press against the bone to fix the bone anchor 20. Thus, the shape memory alloy engagement elements 32 are activated from the retracted configuration to the expanded configuration through temperature transition upon insertion. This is in marked contrast to prior art elastic barb constructions, which are designed to harness the isothermal SIM elastic characteristics of the shape memory alloy.
By constructing the bone anchor 20 so that the shape memory alloy engagement elements 32 have the retracted configuration shown in
At the ambient conditions in the operating room (about 20° C.) the engagement elements 32 of the bone anchor 20 are in a martensitic crystal structure state. In this state, the engagement elements 32 exhibit the stress/strain properties as shown in
A vertical line in
As illustrated in
External heating can optionally be applied to the bone anchor 20 to accelerate temperature transition of the shape memory alloy to Af and above. By way of example but not limitation, this can be done by locally applying a warm (e.g., >37° C.) saline bath to the bone anchor 20 through a syringe or through the inserter attached to the bone anchor.
Other methods may be used to speed up warming of the bone anchor 20 to a temperature at or above Af. For example, as illustrated in
The use of a temperature-activated, shape memory alloy is applicable to a wide variety of bone anchor structures, inserters, and suture attachment mechanisms, such as disclosed in commonly assigned U.S. Patent Publication Nos. 20070260259 entitled Bone Anchor Installer And Method Of Use; 20070255317 entitled Suture Passer Devices And Uses Thereof; 20070156176, 20070156150, 20070156149, and 20070156148 all entitled Ring Cinch Assembly To Attach Bone To Tissue; 20060282083, 20060282082 and 20060282081 all entitled; Apparatus And Method For Securing Tissue To Bone With A Suture; and 20050245932 entitled Apparatus And Methods For Securing Tissue To Bone, all of which are hereby incorporated by reference.
The bone anchor 20 includes a pair of locking rings 64, 66. Pin 68 extends through openings 70, 72 to attach the locking rings 64, 66, respectively. The locking rings 64, 66 are preferably positioned parallel to each other and can move axially relative to each other along axis 74.
As illustrated in
The self-locking assembly 60 of
The presently described embodiments may optionally be provided in combination with an installer system adapted for use in deploying the presently described bone anchors to the operative site.
As best illustrated in
In one embodiment, suture 152 is fed through upper portion 170 of the slot 162 above the ball 164, around the ball 164, and then back out through lower portion 172 of the slot 162 below the ball 164. As best illustrated in
The tension force 184 on the tissue can be reduce by pulling on the first end 174 of the suture 152 to reduce the compression force 186 exerted by the ball 164. The surgeon can advance the suture 152 in the reverse direction 188.
As best illustrated in
in the illustrated embodiment, rod 232 is provided to move the ball 206 out of engagement with the top 230 of the slot 208, thereby permitting the suture 202 to be moved through the bone anchor 204. During insertion of the bone anchor 204 the rod 232 also pushes the ball 206 downward within the slot 208, creating a compression force 234 that compresses the suture 202 between the ball 206 and bottom 236 of the slot 208.
Distal end 254 of suture 256 is attached to the first bone anchor 204A using conventional techniques. The suture 256 engages with the second bone anchor 204B generally as illustrated in
Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the inventions. The upper and lower limits of these smaller ranges which may independently be included in the smaller ranges is also encompassed within the inventions, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either both of those included limits are also included in the inventions.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which these inventions belong. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present inventions, the preferred methods and materials are now described. All patents and publications mentioned herein, including those cited in the Background of the application, are hereby incorporated by reference to disclose and described the methods and/or materials in connection with which the publications are cited.
The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present inventions are not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed.
Other embodiments of the invention are possible. Although the description above contains many specificities, these should not be construed as limiting the scope of the invention, but as merely providing illustrations of some of the presently preferred embodiments of this invention. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the inventions. It should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed inventions. Thus, it is intended that the scope of at least some of the present inventions herein disclosed should not be limited by the particular disclosed embodiments described above.
Thus the scope of this invention should be determined by the appended claims and their legal equivalents. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims.
The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/966,087 entitled Bone Anchor Comprising a Shape Memory Element and Utilizing Temperature Transition to Secure the Bone Anchor in Bone, filed Aug. 24, 2007.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US08/73807 | 8/21/2008 | WO | 00 | 7/20/2011 |
Number | Date | Country | |
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60966087 | Aug 2007 | US |