Patent ID: 12193655

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG.1illustrates the per se known double row procedure for suturing a soft tissue to a hard tissue, using the example of reattaching a torn rotator cuff tendon10to humeral bone tissue11(or a corresponding endoprosthesis) in four successive phases (a), (b), (c) and (d). Phase (a) is before the repair operation and shows the location12in which reattachment is necessary. In phase (b) two medial anchors13are anchored in the bone tissue, in locations to eventually be located underneath the tendon10, each one of the medial anchors13attaching at least one suture4to the bone tissue in a slideable manner. In phase (c) the end sections of each suture attached to one of the medial anchors is passed through the torn tendon10and by tensioning the sutures away from the tendon end (not shown), the latter is pulled over the medial anchors13. In phase (d) two lateral anchors14are anchored in the bone tissue just beyond the edge of the tear, the row of lateral anchors14running about parallel to the row of medial anchors13, the end sections of the sutures4being tensioned and locked with the aid of the lateral anchors14in a cross-wise manner, such that the two suture end sections held by one medial anchor13are locked by two different lateral anchors14such forming crossed suture bridges15between the row of medial anchors13and the row of lateral anchors14. Therein each row of anchors may comprise two or more than two anchors and each medial anchor13is used for attaching at least one suture4(two suture end portions) and each lateral anchor14is used for locking at least two suture end portions originating from two different medial anchors13.

As already mentioned further above, the suture anchor and the method according to the invention are in particular advantageously applicable in the lateral row, but correspondingly adapted are also applicable in the medial row.

FIGS.2and3illustrate exemplary embodiments of the suture anchor according to the invention. These suture anchors2comprise a material having thermoplastic properties (liquefiable material) or they are preferably made of such a material and they are anchored in a hard tissue opening by in situ liquefaction of at least part of the material having thermoplastic properties and by making the liquefied material flow into the hard tissue to constitute, when re-solidified, a positive fit connection between the anchor and the hard tissue. The anchoring method on which the anchors, according to the invention, are based is disclosed e.g. in the publication U.S. Pat. No. 7,335,205, the disclosure of which is enclosed herein in its entirety. According to this method a proximal face of the anchor is contacted with a tool which transmits energy into the anchor, in particular a vibration tool which transmits vibrational energy. Simultaneously the anchor is pushed into a hard tissue opening having a cross section which is slightly smaller than the cross section of the anchor portion to be fixated in the opening, such that anchor portions comprising the material having thermoplastic properties get into intimate contact with the hard tissue, which in the case of the use of vibrational energy serves also as counter element necessary for transforming the vibrational energy into friction heat for the in situ liquefaction.

Furthermore, the suture anchors according toFIGS.2and3comprise at least one distal suture conduit (e.g. distal groove, channel, or eyelet) in which the suture is held when the suture anchor is positioned relative to the hard tissue opening and fixated therein, and structures for locking the suture relative to the fixated anchor or the hard tissue respectively either by clamping it between the suture anchor and the wall of the hard tissue opening (FIG.2) or by collapsing the suture conduit and such braking or clamping the suture threaded therethrough (FIG.3).

The suture anchor2as shown inFIG.2comprises a pin portion20and advantageously a head portion21and is shown attached to a tool1, by e.g. a press fit connection between a tool protrusion reaching into a recess in the head portion21(not shown). At least the pin portion20comprises at least at parts of its lateral surfaces the material having thermoplastic properties and advantageously, as illustrated, energy directors e.g. in the form of axial edges extending over part of the pin length and being offset relative to each other in adjoining such part lengths (the pin portion has e.g. as illustrated the form of a stack of misaligned polygon-shaped discs). The head portion21may also comprise the material having thermoplastic properties and may also be anchored in the hard tissue, in which case the hard tissue opening provided for the anchor2will need to have a stepped form including a narrower inner portion for accommodation of the pin portion20and a larger outer portion for accommodation of the head portion21. Alternatively, the distal face of the head portion my be anchored in the hard tissue surface around the mouth of the opening provided for the pin portion.

The pin portion20comprises a suture groove22running across the distal pin face and, in an axial direction, along two opposite pin sides, wherein the suture groove22comprises at least one portion which is undercut, the undercut groove portion23being situated e.g. as illustrated, on the distal pin face (suture conduit). Preferably, the overall cross section of the suture groove22is adapted to the suture or sutures to be locked with the aid of the anchor such that the suture(s) running along the groove does not protrude from the groove, i.e. does not get into contact with the hard tissue when the pin portion20is pushed into the hard tissue opening provided therefore while being vibrated. This measure serves for preventing damage of a friction and/or heat sensitive suture on fixation of the anchor, in particular when using vibrational energy for such fixation. When using a suture of no such sensitivity the suture may as well protrude from the suture groove and therewith rub on the wall of the hard tissue opening, wherein such friction may help to at least primary stabilization of the suture relative to the suture anchor.

The undercut portion23of the suture groove22is dimensioned such that the suture to be locked with the aid of the anchor can be entered into the undercut groove by resiliently deforming the groove entrance and that the suture is safely kept in the undercut groove portion23when no force acting perpendicular to the groove length pulls the suture out of the undercut groove portion23.

The suture groove22continues on both sides of the head portion21, but at the transition between pin and head portion comprises an interruption24, i.e. it has a depth on a proximal end of the pin portion20which decreases with decreasing distance form the head portion21, a zero-depth portion (or portion with relevantly reduced depth) at the transition between the pin and the head portion, and a depth on a distal side of the head portion21which increases with increasing distance from the pin portion20. This measure serves for clamping the suture between the hard tissue and the implanted anchor for locking it.

The head portion21has a larger cross section than the distal end of the tool1such that, when the anchor2is attached to this distal tool end, the proximal face of the head protrudes beyond the distal face of the tool at least on those two sides on which the suture groove reaches this proximal head face. As illustrated, the distal tool end may have a circular cross section and the head portion an oval cross section having a smaller diameter which is the same as the tool diameter and a larger diameter spanning between the mouths of the suture grooves. This measure serves for preventing a friction and/or heat sensitive suture from contact with the tool1, in particular with the edge of the distal tool face, which is particularly advantageous when the tool is a vibration tool and the suture is of a friction and/or heat sensitive type.

For fixating a suture relative to hard tissue using the anchor2as illustrated inFIG.2, a hard tissue opening is provided, a cross section of at least an inner portion of the hard tissue opening being adapted to the pin portion20of the anchor2such that a distal end of the pin portion20having the smallest cross section fits easily into the opening but the rest of the pin portion20can be introduced into the opening using a pressing force only. The pin portion20of the anchor which is attached to the tool being coupled to an energy source (preferably vibration source) is positioned into the mouth of the opening, the suture to be fixated by the anchor running along the suture groove22and extending out of the hard tissue opening on both sides of the anchor. The pressing force is then applied to the suture anchor via the tool, the desired suture tension is established and the energy source is activated (tool and anchor vibrated). Where in intimate contact with the hard tissue wall of the opening, the material having thermoplastic properties is liquefied and penetrates into the hard tissue. At the same time the anchor is pushed further into the opening and is finally anchored when the head portion21abuts the hard tissue surface or a step in the hard tissue opening. Only at the very end of the described anchoring process, the suture is clamped between the hard tissue in the region of the mouth of the hard tissue opening or the step in the opening and the suture anchor at the transition from the pin portion20to the head portion21, which transition location only then reaches the hard tissue. This means that the suture, if correspondingly adapted to the suture groove, remains slideable (possibly against some friction between suture and tissue inside the hard tissue opening) relative to the anchor during an initial part of the fixation step and therefore the suture tension can still be adapted or maintained up to when the anchor is very close to its final fixated position.

Further embodiments of the suture anchor as illustrated inFIG.2may e.g. not comprise a head portion, comprise energy directors of a different type or no energy directors at all and/or may comprise a core not being made of the material having thermoplastic properties but comprising a sleeve of or being coated with the latter at least on the pin portion and possibly excepting the suture groove22and the distal pin end.

When used for locking sutures which are neither friction nor heat sensitive, and without the possibility of the late tension adjustment, the suture groove may be present at the distal face of the pin section20only (zero depth suture groove portion extending along the entire anchor length), where it may be undercut or may have a cross section dimensioned for holding the suture by friction. The same effect can be achieved with a suture anchor as shown inFIG.2and a suture having a cross section greater than the cross section of the suture groove22(possibly not having a zero depth portion at all), wherein the suture protrudes from the groove. For achieving a slideable attachment of the suture to the hard tissue using the suture anchor according toFIG.2or a similar suture anchor, a suture of a diameter smaller than the reduced depth of the zero-depth groove portion is used, or the anchor is introduced into the hard tissue opening only such that the zero-depth groove portion protrudes from the opening or the opening is provided with a mouth of a larger cross section to accommodate the zero-depth groove portion without clamping the suture.

Furthermore, the head portion21may comprise a protrusion suitable for attachment of the anchor2to the tool1which has a corresponding recess in its distal face. Furthermore, the suture anchor according toFIG.2, in particular the embodiment comprising a core of e.g. a metal may comprise a tapering or sharpened distal end for being able to be forced at least into cancellous bone without the necessity of providing an opening therein beforehand or of providing such opening only through the cortical bone. The forcing of the suture anchor2into the bone tissue is preferably effected using the same tool as used for the anchoring step but without transmitting energy for the liquefaction to the suture anchor.

The anchor as illustrated inFIG.3differs form the anchor as illustrated inFIG.2mainly regarding the means provided for the suture locking, which in this case are located at the distal anchor end being equipped for holding the suture. This distal end has a smaller cross section than the rest of the anchor and comprises two eyelets25(suture conduit) and it consists of a material which is plastically deformable or becomes plastically deformable under the influence of energy transmitted into the anchor for its fixation in the hard tissue such that a compressive load, caused through the suture tension and/or by abutment against a bottom wall of a blind hard tissue opening is able to collapse it (collapsible suture conduit). The suture4to be fixated and locked with the aid of the anchor2is threaded through the two eyelets75and runs along the anchor length e.g. in a suture groove as described further above in connection withFIG.2, but not shown inFIG.3.

The anchor2as illustrated inFIG.3is fixated in a hard tissue opening5much as discussed above in connection withFIG.2, wherein the distal pin end comprising the two eyelets25is made to collapse by the suture being tensioned against the anchor and/or by pushing it against the hard tissue on the bottom of the opening5provided for the anchor2, wherein by such collapse the suture4is locked due to its bending radius between the two eyelets25being reduced and therewith suture braking increased in such a manner that the suture cannot slide therethrough any more and/or due to the decreasing cross section of the eyelets25which causes the suture4to be clamped. In such a case the zero-depth portion of the suture groove as described above is not needed for securely locking the suture, which means that in this latter case, there may be no contact at all between the suture4and the hard tissue within the opening5.

FIG.3shows, in a very schematic manner, the anchor2in three successive phases (a), (b) and (c) during the fixation and locking process. In phase (a) the anchor2being attached to the distal end of the tool1is positioned in the mouth of the hard tissue opening5, the suture4running through the two eyelets25and out of the opening5at one side of the anchor2to be held by any suitable means. In phase (b) the tool1is activated by the not shown energy source and the anchor2is pushed further into the opening5, while the suture4is kept tensioned or the suture tension is increased, possibly against friction between the suture and the tissue in the hard tissue opening. In phase (c), fixation of the anchor2and locking of the suture4are complete, the distal end of the anchor2abutting the bottom of the hard tissue opening5and comprising the two eyelets25being collapsed to brake and/or clamp the suture. The moment during the anchoring process in which the suture conduit is collapsed is determined by the suture tension which for this purpose needs to be sufficiently high and/or by the depth of the hard tissue opening5. Up to the moment of the collapse of the eyelets25, the suture4may remain slideable relative to the anchor, the same as discussed above in connection withFIG.2.

For providing a slideable suture attachment using the suture anchor according toFIG.3, the suture tension is to be kept sufficiently low and/or the hard tissue opening needs to be sufficiently deep.

The features listed above for further embodiments of the suture anchor according toFIG.2are, correspondingly adapted, also applicable for the suture anchor according toFIG.3. Furthermore, features of the suture anchors according toFIGS.2and3can also be combined which results in further embodiments such as e.g. the suture anchor ofFIG.2comprising a distal channel or eyelet for holding the suture, or comprising any distal suture conduit being collapsible, or the suture anchor ofFIG.3comprising a collapsible distal groove which may be undercut, or comprising axial suture grooves with or without a proximal zero-depth portion.

FIGS.4to6illustrate further exemplary embodiments of the suture anchor and method according to the invention, wherein some of these embodiments are mentioned already above as possible variations of the suture anchors according toFIGS.2and3.

FIG.4shows a suture anchor2which is quite similar to the anchor as shown inFIG.2but other than the latter comprises a pin portion20only (no head portion) and instead of one suture groove for accommodation of one suture comprises two (or possibly more than two) suture grooves22and22′ for accommodation of two (or possibly more than two) sutures, wherein the two suture grooves extend cross-wise across the distal anchor face (suture conduits), where they are possibly undercut, and continue in an axial direction along the circumferential pin portion surface, preferably as illustrated regularly spaced from each other and ending at a distance from the proximal anchor face (zero-depth groove portions24).

In the same manner as illustrated inFIG.4, the suture anchor according toFIG.3may be equipped for anchoring more than one suture by comprising two or more than two distal suture conduits (eyelets) arranged at an angle to each other and possibly axial suture groves extending in a proximal direction from the mouths of the conduits.

FIG.5shows a suture anchor2similar to the suture anchors according toFIGS.2and4but comprising a suture groove22with an undercut distal groove portion23(suture conduit) constituting two groove levels, wherein the groove23.1of the inner level comprises a smaller cross section and in particular a narrower mouth than the groove23.2of the outer level, such that a thinner suture will enter the inner groove23.1and be safely held therein and a thicker suture possibly not being able to enter the inner groove23.1will be safely held in the outer groove23.2. The suture anchor according toFIG.5is e.g. capable of resiliently holding sutures of a thread size from 0 to 3-0, wherein a thicker suture (e.g. size 0) will be held in the outer groove23.2and a thinner suture (e.g. 3-0) in the inner groove23.1. This means that the anchor according toFIG.5is the same applicable for quite different thread sizes.

FIG.6illustrates a further means for safeguarding the suture to be fixated and possibly locked in hard tissue with the aid of the suture anchor according to the invention against possibly damaging influences caused by vibration or heat produced in the anchoring process. These further means are an equivalent to the head portion having a larger cross section than the tool used for implanting the anchor as shown inFIG.2. Other than according toFIG.2, in the present case, the safeguarding means are arranged on the tool1which is used for fixating the suture anchor in the hard tissue opening and which comprises at least on a distal end portion lateral grooves26which are arranged to be aligned with the proximal ends of the suture groove22of the suture anchor2. The same as the protruding anchor head portions illustrated inFIG.2, these lateral grooves26of the tool1prevent the suture from coming into contact with the edge of the distal face of the tool, which is in particular important for a vibration tool and for a suture which is friction and/or heat sensitive. If a zero-depth groove portion adjoins the proximal anchor face as illustrated inFIGS.4and5and the tool comprises a distal face adapted to the proximal anchor face or being slightly smaller, such measure does not have any advantage.

FIG.7shows a distal face of a tool1comprising the lateral grooves26as discussed above and further comprising a protrusion27having an elongate, e.g. rectangular or oval cross section. In cooperating with a correspondingly shaped depression in the proximal anchor face attachment of the suture anchor to the distal tool end automatically results in proper alignment of the suture grooves22and the lateral grooves26. Instead of a protrusion of an elongate cross section on the distal tool face and a corresponding depression in the proximal anchor face, two protrusions of an e.g. circular cross section and two corresponding bores in the proximal anchor face can be provided. The same is achieved obviously by the protrusion(s) being provided on the proximal anchor face and the depression(s) on the distal tool face.

FIGS.8to11illustrate distal ends of exemplary embodiments of the suture anchor according to the invention which embodiments constitute alternatives to distal anchor ends as shown inFIGS.2to6. The suture anchor embodiments according toFIGS.8to11comprise in the same manner as the suture anchor embodiments according toFIGS.2to6a distal suture conduit (groove, channel or eyelet) extending angled relative to an anchor axis across a distal anchor face or through a distal anchor end portion. The anchor comprising a material having thermoplastic properties at least in the region of its circumferential surface is fixated in a hard tissue opening by having a cross section which is slightly larger than the cross section of the hard tissue opening and by being forced into the hard tissue opening and simultaneously being vibrated preferably by applying to a proximal anchor face a vibration tool being coupled e.g. to an ultrasonic vibration generator. The material having thermoplastic properties is liquefied at the interface between the vibrating suture anchor and the hard tissue of the wall of the opening provided for the suture anchor and penetrates this hard tissue to form on re-solidification a positive fit connection between the suture anchor and the hard tissue.

Using the suture anchors according toFIGS.8to11, the fixation or anchorage established with the aid of the material having thermoplastic properties and the vibration energy (similar to the fixation or anchorage as discussed in connection with the previous figures), is enhanced by forcing apart distal anchor sections or expanding anchor portions, the forcing apart and the expansion being caused by the suture which during the fixation process is tensioned against the pushing force of the vibration tool and is therewith forced into or against the anchor portion proximal to the suture conduit and/or by the distal suture end being pushed against the bottom of a blind hard tissue opening into which the anchor is forced. Preferably this effect is further enhanced by providing for this anchor portion a material which is softened and thereby weakened on application of the liquefaction energy and/or by designing this anchor portion mechanically weaker than other anchor portions. Such spreading or expansion will enhance the retainment of the suture anchor constituted by the material having thermoplastic properties penetrated into the hard tissue of the wall of the opening, which is particularly advantageous if this hard tissue is e.g. cancellous bone tissue of only little mechanical strength positioned underneath a cortical bone layer. It is possible also that the spread anchor sections or the expanded anchor portion are situated beyond the hard tissue opening (on a non accessible side of a bone plate or cortical bone layer) and by having a larger cross section than the opening help retaining the anchor in the opening. It is obvious that in the latter case spreading and expansion can only be achieved through the suture tension.

FIGS.8to10show exemplary embodiments of distal ends of suture anchors2comprising distal anchor sections2.1and2.2on either side of the distal portion of the suture groove22(undercut or not undercut) which distal anchor sections are forced apart and therewith pressed against the walls of the hard tissue opening such producing an additional press fit or positive fit by compressing the tissue of these walls during or possibly before the anchoring process. The distal anchor sections2.1and2.2are forced apart by the suture running through the distal groove22being pulled in a proximal direction (through exterior suture tension or through friction between the suture and the wall of the opening during advancement of the anchor into the hard tissue opening) and forced into the groove bottom, possibly assisted by a corresponding anchor design and/or a softening effect of the energy transmitted into the anchor for the liquefaction process.

FIGS.8to10are very schematic axial sections through distal end portions of suture anchors2comprising a suture groove22extending at an angle (preferably a right angle) to the anchor axis and separating the distal anchor portion into two distal sections2.1and2.2. On the left hand side of the figures, a suture4is held in the suture groove22, the suture not being tensioned (pulled in a proximal direction) or not tensioned enough for being able to deform the distal anchor portion, and on the right hand side of the figures, the suture4is tensioned and moved in a proximal direction therewith forcing apart or spreading the distal anchor sections2.1and2.2.

FIG.8shows in addition a pair of transversal bores36orientated parallel to the distal suture groove22and situated underneath the groove bottom for weakening the corresponding anchor portion and therewith allowing the suture under tension, and possibly with the anchor material further weakened by the energy transferred into it for the liquefaction process, to be pulled into the suture material of the groove bottom and therewith spreading the lateral suture sections apart as shown on the right hand side ofFIG.8.

FIG.9shows an undercut distal suture groove22and an additional spreader element37located in the suture groove underneath the suture and having e.g. the form of a wedge. The spreader element37which preferably consists of a harder material or of a material with a higher melting or softening temperature than the suture anchor2is able to cut into the anchor material when forced against the bottom of the suture groove22by the tensioned suture.

FIG.10shows the distal suture groove22and the suture4running through the latter. The suture groove22and the suture4extend at an angle (preferably a right angle) to the spreader element37for which a further groove37.1is provided. The two grooves22and37.1separate the distal anchor portion into four sections wherein the two sections on the one side of the spreader groove37.1are forced apart from the two sections on the other side of the spreader groove by the spreader element37being forced into the bottom of the spreader groove37.1by the suture being tensioned, and wherein the two sections on the one side of the suture groove22may in addition be forced apart from the two sections on the other side of the suture groove, if the tensioned suture is also forced into the bottom of the suture groove22.

FIG.11illustrates the additional expansion by collapse of an anchor portion caused by the suture tension and/or by the distal anchor end being pushed against the bottom of the hard tissue opening. The anchor2comprises again a distal suture groove22and at least one (e.g. two) transversal bore36extending through the anchor2in a direction angled relative to the suture groove22. The transversal bores36, which cannot serve as a sort of perforation of the distal anchor portion as discussed in connection withFIGS.18and19, form thin material portions which locally initiate absorption of the vibration such weakening the corresponding anchor portion and enabling collapse of the transversal bores and therewith local expansion of the anchor as shown on the right hand side ofFIG.11.

FIG.12illustrates in the same manner asFIGS.8to11, a further measure for enhancing suture anchor retainment in bone tissue of an only limited mechanical strength, in particular in a blind opening of such a bone tissue. For enhancing softening and liquefaction in the distal anchor face even with very little counteraction by the bottom wall of the opening, the distal anchor end portion comprises thin and therewith mechanically weak portions of the material having thermoplastic properties, which weak portions tend to get softened or liquefied under the influence of the vibration used for the fixation process with hardly any friction on a counter element which in the present case is the bone tissue. This measure results in a collapse and therewith slight radial expansion of the distal anchor end portion and/or in a good penetration of the bone tissue situated around the distal anchor end portion, which may take over a main part of the anchoring function such that for lateral anchorage necessary friction on the lateral wall of the hard tissue opening may be reduced to a minimum.

Good results in corresponding experiments were achieved with distal anchor faces38of a concave shape (e.g. hollow cone or frustum as shown inFIG.12), but can also be achieved with distal anchor faces with other hollow shapes, possibly additionally slotted or with distal anchor sections separated by grooves (e.g. suture groove) as shown in several previous Figures. The distal end of the suture anchor according toFIG.12additionally comprises two (or more than two) transversal bores36serving as weakening structures as discussed in connection withFIGS.8,9, and11and/or as possibly collapsible suture conduits.

All the measures illustrated inFIGS.8to12are applicable e.g. in anchors as previously described. However, they are also applicable in anchors having other characteristics. For this reason, the invention also concerns an anchor (preferably suture anchor) and a method for fixating the anchor in a hard tissue opening comprising only the features as disclosed inFIGS.8to12and serving for enhancing anchor retainment in the hard tissue opening. The corresponding anchor is characterized by a distal end portion comprising end sections separated by a groove, by a concave distal face, or by a weakened anchor portion proximally adjoining a distal suture conduit. The corresponding method is characterized by spreading the end sections, or by collapsing and therewith expanding the weakened anchor portion, the concave distal face or the end sections through tensioning of the suture or through abutting the anchor against the bottom of a blind hard tissue opening.

In the above described embodiments, according toFIGS.8to11, the suture being fixated relative to hard tissue may have a specific function (spreading or expanding a distal anchor portion) in the method according to which the suture anchor is fixated in the hard tissue. If these embodiments of anchors are to be used in other applications than as suture anchors or in combination with sutures which are mechanically too weak for the named functions, it is possible to make use of a suture substitute, to position and use this suture substitute instead of or in addition to the suture as described and to finally remove it or clip end portions of it. Such suture substitutes may be any flexible and elongated item such as e.g. a wire, a ribbon or a suture of suitable characteristics. The term “suture” as used in the above description encompasses such suture substitutes.

The above described invention concerns in particular suture anchors suitable for soft tissue attachment to hard tissue. In all the described embodiments of methods for fixating such suture anchors in hard tissue, the sutures may be further safeguarded against damage by heat dissipating from the material having thermoplastic properties when liquefied, by being soaked with liquid (water or saline solution) preferably before being threaded through the distal suture conduit or before being positioned in the hard tissue opening and necessarily before liquefaction of the material having thermoplastic properties.

In all above described methods for attaching soft tissue to hard tissue with the aid of a suture anchor and a suture, a material having thermoplastic properties is liquefied to preferably penetrate hard tissue or cavities provided in the hard tissue to constitute when re-solidified a positive-fit connection between the anchor or part thereof and the hard tissue of the wall of the opening. Such positive fit connections can in all described cases be achieved also in a two-step procedure, wherein the walls of the hard tissue opening are pre-treated according to a method as described in the publications WO-2010/045751 or WO-2009/141252 (Nexilis), wherein a material having thermoplastic properties is forced in a liquefied state into the hard tissue of the wall of the opening to form together with this tissue a sort of composite substantially without coating this wall with the material having thermoplastic properties. In a second step the anchoring process is then carried out as described in the present description and in the cited publications, wherein the liquefied material is not able to penetrate the composite material of the wall of the opening established in the pre-treatment step, but instead is welded to the composite material of this wall. For such welding it is a condition that the material having thermoplastic properties used in the second or fixation step is weldable to the material having thermoplastic properties used in the first or pre-treatment step. Preferably the two materials having thermoplastic properties comprise the same thermoplastic polymer.

If the named pre-treatment step is carried out in a manner to form the composite material comprising the hard tissue and the material having thermoplastic material right to the mouth of the hard tissue opening, this mouth is strengthened and therewith has an enhanced capacity to resist being cut by the suture fixated in the hard tissue opening by the anchor fixated therein, when this suture is tensioned.