Researchers Submit Patent Application, "Method of Fastening a Soft Tissue Graft in an Opening Provided in a Human Or Animal Bone and Fastener Suitable for the Method", for Approval
The patent's assignee is
News editors obtained the following quote from the background information supplied by the inventors: "The invention generally relates to the field of orthopedic surgery and concerns a method of fastening a soft tissue graft in an opening provided in a human or animal bone, wherein the soft tissue graft comprises an end portion to which a suture is attached or which is suitable for such attachment.
"The term 'soft tissue graft' or just 'graft' as used in the present text is in particular an autograft, allograft or xenograft, but it may also be an original soft tissue to be re-attached to a bone from which it has been detached by injury or surgery. The soft tissue graft is in particular a tendon or ligament graft or an original tendon or ligament. However, the term 'soft tissue graft' or 'graft' is meant to encompass also prosthetic elements replacing or complementing soft tissue, i.e. in particular artificial tendon or ligament tissue or tendon or ligament substitutes or partial substitutes that are to replace or strengthen a ruptured or otherwise defective tendon or ligament and, for such purpose, are to be fastened in a bone opening. It could also encompass the extension of a meniscus graft or textile ribbons which are known as alternatives to cerclage wires, wires, or plate/screw systems, for example for fixing bone fragments, or for stabilizing fractures or osteotomies.
"The term 'bone' as used in the present text is a piece of a viable bone tissue, which may be complemented with artificial bone replacement material.
"The term 'suture' as used in the present text is a suture as used in surgery but may also be another suitably flexible lengthy fixation element such as, for example, a ribbon, cable or wire.
"At least one end portion of the soft tissue graft has at least one suture attached thereto or is suitable for such attachment. This means that the suture is attached to the soft tissue graft either by a manufacturer or by the operating team, wherein in the latter case such attachment is carried out either ex situ (in the operating room) or in situ (in the operation site). In addition to its function according to the invention, which will be detailed below, the suture will usually have further per se known functions such as, for example, re-enforcing the soft tissue graft, combining a plurality of graft strands, adapting a cross section of an end portion of the graft to a cross section of the bone opening or a fastener, in situ positioning and/or tensioning the graft and so on. The attachment of the suture to the soft tissue graft may, for example, be achieved by stitching (in particular per se known stitched graft ends) or by threading the suture through a folded end of the graft or through an eyelet-like feature provided on the end of the graft. If the soft tissue graft itself is suture-like, i.e., is a suitably flexible fine ribbon or cable, the graft itself may serve as the named suture being attached to the graft in the widest sense of the term 'attached'.
"The opening provided in the bone for the fastening according to the invention is in a per se known manner a tunnel leading through the bone or a blind opening extending into the bone from a bone surface and comprising a closed end within the bone. This opening is preferably provided by drilling but can also be provided by, for example, punching (ultrasonic punching), i.e. this opening will often have a circular or non-circular cross section remaining the same over most of the depth of the opening, but this is not a condition for the invention. The opening may also have a plurality of sections with differing cross sections, may have a conical form, or may be undercut (for example made by milling that allows production of three dimensional geometries within the opening).
"One exemplary application of the method and fastener according to the invention (the same as for known such methods and fasteners) is the replacement of a ruptured anterior cruciate ligament (ACL) in a human knee with a graft that is fastened, on the one hand, in an opening extending from the articular surface of the distal femur end and, on the other hand, in an opening extending from the tibia plateau, for example in a femoral blind opening and a tibial tunnel, wherein the tibial tunnel has a second mouth in the outer surface of the tibia below the tibia plateau. Therein the ruptured anterior cruciate ligament is usually replaced by a graft, such as, for example, a patellar tendon graft comprising two terminal bone blocks, a hamstring tendon graft (semitendinosus tendon, possibly combined with gracilis tendon), usually being folded and stitched in the end region, i.e. not comprising terminal bone blocks, or a quadriceps tendon graft, which is usually harvested with one terminal bone block. The named grafts are usually autografts but may also be donor grafts (allografts). Donor grafts may also be made of achilles tendons. It is further proposed to use synthetic ribbons and suitably treated tendon material of slaughtered animals (xenografts), such as pigs. The named autografts and allografts may furthermore be reinforced with synthetic material.
"Further application fields of the method and fastener according to the invention are, for example, surgical procedures regarding the human foot or ankle, such as lateral ankle reconstruction, FDL tendon transfer (flexor digitorum longus), FHL tendon transfer (flexor hallucius longus), or flexor to tendon transfer (second toe); surgical procedures regarding the human hand such as ligament reconstruction tendon interposition, scapholunate ligament reconstruction, collateral ligament reconstruction, or UCL repair (ulnar collateral ligament) of the thumb (also known as 'gamekeeper's thumb'); surgical procedures regarding the human elbow such as UCL repair (ulnar collateral ligament), or distal biceps tendon repair; or surgical procedures regarding the human shoulder such as proximal biceps tendon repair. A further example is the repair of torn or damaged cranial cruciate ligaments (CCL) in stifle joints in particular of dogs but also of other animals, such as cats. The CCL is the most commonly damaged stifle ligament in dogs and the named repair is carried out using nylon bands that are passed around the fabella bone in the back of the femur and are fixed in a bore provided in the front part of the tibia."
As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "It is an object of the invention to create a further method and fastener for fastening a soft tissue graft in an opening provided in a bone of a human or animal patient, wherein the method and fastener improve upon known methods and fasteners serving the same purpose, regarding graft slipping. The method and fastener according to the invention are particularly suitable for soft tissue grafts that need to be fastened in a bone opening while being tensioned, but are also applicable when this is not the case.
"The present invention is a further development of the method and fastener disclosed in the above referenced publication WO 2011/091545, the entire disclosure of which is enclosed herein by reference. This means that, the same as disclosed in the referenced publication, also according to the invention, the soft tissue graft is fastened in the bone opening with the aid of a press-fit fastener, wherein the fastener, when press-fitted in the bone opening and clamping the graft against a first portion of the wall of the opening is anchored in a second portion of the wall of the opening with the aid of a material having thermoplastic properties, which is liquefied in situ and made to penetrate into the wall of the opening where, on re-solidification, forms a positive-fit connection between the fastener and the wall of the opening. The fastener includes a press-fit element and an anchoring element, wherein the anchoring element comprises the material having thermoplastic properties and is either separate from the press-fit element or integrated therein. After these per se known method steps, according to the invention, the soft tissue graft is tied to the anchored press-fit fastener with the aid of the at least one suture attached to the end portion of graft (or possibly, for a suture-like graft of a sufficient length, with the aid of an end piece of the graft itself) thereby indirectly connecting the graft to the anchorage of the fastener and therewith providing an insurance against graft slippage.
"Preferred materials having thermoplastic properties used for the anchoring step have an initial modulus of elasticity of at least 0.5 GPa and a melting temperature of up to about 350.degree. C. They are bio-degradable, such as, for example, polylactides (e.g. LR706PLDLLA 70/30, R208 PLDLA 50/50, L210S or PLLA100% all by Bohringer) or non-degradable such as, for example, Polycarbonateurethane (e.g Bionate by
"The method according to the invention comprises basically the following three steps: press-fitting an end portion of the soft tissue graft in the bone opening with the aid of a fastener, anchoring the fastener in the wall of the bone opening with the aid of in-situ liquefaction of a material having thermoplastic properties, tying the end portion of the graft to the fastener with the aid of at least one suture extending from this end portion.
"Therein the step of anchoring is necessarily carried out after the step of press-fitting, and the step of tying is preferably carried out after the step of anchoring, but may also be carried out simultaneously with the step of anchoring, between the steps of press-fitting and anchoring, or even before the step of press-fitting.
"Depending on the required graft tension and on the strength of the graft retention provided by press-fitting, it is advantageous to keep the graft tensioned by external means not only during the press-fitting step and the anchoring step but also during the tying step. Depending on the manner in which the suture is tied to the fastener it may be advantageous to provide sutures (or other means) for external graft tensioning which are separate from the sutures provided for the tying. If graft tension is maintained during all the method steps by external means or if graft tension is not a major requirement to be achieved by the surgery, the strength of the press-fitting achieved in the press-fitting step may be only little, which means that the major part of the graft and fastener retention in the bone opening is provided by the anchorage of the fastener in the bone wall on the one hand and by the tying of the graft to the fastener on the other hand. This also means that the fastening according to the invention needs to rely on the press-fitting much less than known methods using press-fit fasteners and is therefore possible and successful also in bone tissue in which strong press-fitting is not possible or in which press-fitting relaxes fast such that it cannot retain the graft satisfactorily until graft integration by new tissue growth is able to fully take over such retention. Furthermore, the fastening method according to the invention makes it possible to adapt the press-fit strength to specific operation sites, surgical techniques etc., without regard to graft slipping.
"The step of tying the graft to the fastener and the corresponding equipment of the fastener depend in particular on the chosen step sequence, on the type of fastener, on the number of sutures attached or attachable to the graft and on the direction of potential graft slipping. Preferred embodiments of the method according to the invention are applicable using per se known stitched graft end portions, which comprise a plurality of suture ends extending from the very end of the graft. In further embodiments the sutures used for the tying to the fastener extend not from the very graft end but at a small distance therefrom. For enabling the tying, the fastener (press-fit element or anchoring element) and/or a suitable suture retainer used in addition to the fastener preferably comprises at least one suture passage through which at least one suture used for the tying is threaded and relative to which the suture is locked. If only one suture is available for the tying or if an available plurality of sutures is threaded together through one only suture passage, preferably a suture retainer is used for locking the suture(s) in the passage, or the passage is collapsed or the suture(s) extending from the suture passage is stitched to graft near the exit of the suture passage. If a plurality of sutures are available for the tying, these may be threaded in opposite directions through one suture passage or through different suture passages and/or along surface portions of the fastener and are then fastened together by being knotted together and/or with the aid of a suitable suture retainer.
"Threading of the suture(s) through the suture passage(s) may constitute a preliminary step for the tying step, wherein this preliminary step may be carried out ex-situ (before the press-fitting step) or in situ (before or after the anchoring step) and wherein the fastener (press-fit element or anchoring element) and/or the suture retainer is slid along the suture(s) threaded therethrough before the tying is finalized.
"The steps of press-fitting and of anchoring and fasteners equipped for these steps are per se known from the further above referenced publication WO 2011/091545, wherein as above mentioned the fastener comprises a press-fit element and an anchoring element, the latter being a separate element or being integrated in the press-fit element. According to the disclosure of the referenced publication, the press-fit connection is achieved using a fastener dimensioned for being forced into the opening (corresponding dimensioning of fastener and opening) or using a fastener that is positioned in the opening and is then expanded, wherein forcing or positioning the fastener in the opening is carried out either when the soft tissue graft is already positioned in the opening or together therewith and wherein forcing or positioning without rotation of the fastener is preferred but not a necessity. The soft tissue graft to be fastened is arranged in the opening such that it does not cover the whole wall of the opening and the fastener is oriented such that a fastener portion equipped for achieving the anchoring is facing a wall portion not covered by the soft tissue graft. The anchoring element is positioned relative to the press-fit element before the step of press-fitting (anchoring element integrated in press-fit element) or after the step of press-fitting (separate anchoring element) and, in the anchoring step, the anchoring element is advanced relative to the press-fit element using an anchoring tool that simultaneously transmits the energy needed for the in situ liquefaction to the anchoring element.
"As, for example, disclosed in the publications WO2010/045751 and WO2009/141252 (Nexilis), it is possible also to firstly treat the bone wall of the opening with a first portion of liquefiable material such that the trabecular structure of this wall is penetrated and therewith re-enforced by the liquefiable material and only then press-fitting fastener and graft in the opening and carrying out the above described anchoring step, wherein a second portion of liquefiable material is welded to the pretreated wall of the opening. This two step anchoring procedure results in a same positive-fit connection as the above described single step procedure if the first and second portions of liquefiable material comprise the same liquefiable material. However, the first and second portions may comprise different liquefiable materials under the condition that the two materials are weldable to each other under the conditions of the anchoring step.
"For achieving a good anchorage it may be advantageous or even necessary to provide, in addition to or in place of pores or cavities of the trabecular network of the bone tissue, further cavities in the bone wall of the opening to be filled with the liquefied material (e.g. undercut form of opening in the bone tissue).
"For the separate fastener functions of pressing the soft-tissue graft against the bone wall of the bone opening and of anchoring (positive-fit connection with bone tissue of the wall of the opening), the fastener according to the invention comprises separate surface portions equipped either for the pressing function or for the anchoring function. The surface portions equipped for the pressing function may, in a per se known manner, have a flat or concave form (shallow groove) and be rough or otherwise structured for retention of the soft tissue graft to be fastened, but may also lack any specific form or structure. The surface portions equipped for the anchoring function are formed to be positioned in close proximity to the wall of the bone opening and include means for guiding the liquefiable material from the fastener inside or from the proximal fastener face to these surface portions or include the liquefiable material. Furthermore, the latter surface portions may include reaming or cutting edges, threads, barbs or other per se known structures for additional support of the fastener in the bone wall of the opening.
"In a preferred fastener embodiment the surface portions equipped for either pressing or anchoring constitute sectors of a circumferential surface, wherein a fastener suitable for fastening a one-strand graft or a multi-strand graft with an end portion in which the strands are not separated (extra-graft fastening), one pressing sector and one anchoring sector, and wherein a fastener suitable for fastening a two-strand or multi-strand graft with an end portion in which the strands or groups thereof are separated (intra-graft fixation) comprises a plurality of such sector pairs. Alternatively, the fastener surface portions equipped for either pressing or anchoring may be arranged beside each other along a fastener axis, or such alternatively arranged surface portions may be provided on the fastener in addition to the above named surface sectors.
"The fastener has, for example, the general form of a cylinder, frustum or cone (continually tapering or stepped), preferably but not necessarily with substantially circular cross sections, i.e. is suitable for being fitted into an opening of a substantially circular cross section (cylindrical or tapering continually or in steps), but it may also have another form such as a parallelepiped or wedge.
"Instead of using vibrational energy for creating the local thermal energy needed for the liquefaction of the material having thermoplastic properties, it is possible also to exploit other energy types, in particular, as disclosed in WO2010/127462 rotational energy turned into friction heat in substantially the same manner as the vibrational energy, or electromagnetic radiation (in particular laser light in the visible or infrared frequency range), which radiation is preferably guided through the material having thermoplastic properties and locally absorbed by an absorber being contained in the material having thermoplastic properties or being arranged adjacent to this material. Electric energy (resistive heating) can also be used.
BRIEF DESCRIPTION OF THE DRAWINGS
"Exemplary embodiments of the method and the fastener according to the invention are described in detail in connection with the appended drawings, wherein:
"FIG. 1 shows five consecutive phases (a) to (e) of an exemplary embodiment of the method according to the invention for fastening a soft tissue graft in a bone tunnel with the aid of a first exemplary embodiment of the fastener according to the invention, wherein graft slippage to be counteracted by the graft being tied to the fastener has a direction which is substantially the same as the direction in which the fastener is introduced into the bone tunnel;
"FIGS. 2 to 6 illustrate a plurality of further exemplary embodiments of the fastener applicable in the method according to the invention and in particular in the method as illustrated in FIG. 1;
"FIGS. 7, 8A/B, 9 illustrate further exemplary embodiments of method and fastener according to the invention, wherein the end portion of the graft comprises two separate strands and wherein at least one suture extends from each one of the graft strands (intra-graft fixation) and wherein graft slippage to be counteracted has a direction as discussed in connection with FIG. 1;
"FIG. 10 shows a soft tissue graft fixation according to the invention in a tibial tunnel;
"FIGS. 11 to 14 illustrate further exemplary embodiments of method and fastener according to the invention, wherein a soft tissue graft is fastened in a bone tunnel or a blind opening, and wherein graft slippage to be counteracted by the graft being tied to the fastener has a direction which is substantially opposite to the direction in which the fastener is introduced into the bone tunnel or blind opening;
"FIGS. 15 to 18 illustrate exemplary tools applicable for removing a fastener being implanted in a bone opening e.g. for fastening a soft tissue graft in this opening.
"Items having the same function and similar items are denominated in all Figs. with the same reference numerals."
For additional information on this patent application, see: Muller, Andrea; Wenger, Andreas; Mayer, Jorg. Method of Fastening a Soft Tissue Graft in an Opening Provided in a Human Or Animal Bone and Fastener Suitable for the Method. Filed
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