Abstract:
In order to facilitate insertion and reduce movement of the tendon replacement part in the channel in an implant for fastening of a tendon replacement part to a channel receiving the tendon replacement part in the region of the tibia and/or femur close to the knee, with an abutment element abutting against the channel and with a connecting element, wherein the tendon replacement part and the abutment element may be coupled by means of the connecting element, it is proposed that the abutment element and the connecting element defining a longitudinal direction are configured and reconciled with one another such that the tendon replacement part is fixable in the channel by relative movement between the abutment element and the connecting element in longitudinal direction.

Description:
[0001]    The present disclosure relates to the subject matter disclosed in international application PCT/EP 02/01094 of Feb. 2, 2002, which is incorporated herein by reference in its entity and for all purposes. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The invention relates to an implant for fastening of a tendon replacement part to a channel receiving the tendon replacement part in the region of the tibia and/or femur close to the knee, with an abutment element abutting against the channel and with a connecting element, wherein the tendon replacement part and the abutment element may be coupled by means of the connecting element.  
           [0003]    Such implants are used in the reconstruction of cruciate ligaments, for example. In this case, hamstring tendons (semitendinosus, gracilis or plantaris tendon) or BTB transplants (patellar tendon) are used as tendon replacement part. A polyester tape or polyester thread is usually used for connecting elements, with which the tendon replacement part is anchored in the channel on an extra-ossary titanium anchoring plate remote from the joint.  
           [0004]    On use of the previously usual connecting elements, the so-called “bungee effect” occurs, which results from the elasticity of the connecting elements used. An undesirable consequence of the bungee effect is a lower primary stability after the implant is inserted and also a slight, but nevertheless possible, longitudinal movement (micro-movement) of the transplant in the channel. The latter interferes with ingrowth of the transplant in the channel and therefore renders very careful aftercare necessary. In addition, as a result of this longitudinal movement in the joint a trumpet-shaped broadening of the channels close to the joint can occur, which is referred to as a “bone tunnel enlargement”.  
           [0005]    Moreover, it is very difficult for an operating surgeon to fix the tendon replacement part in the channel without play, since generally the polyester thread must be knotted on the titanium anchoring plate.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention improves an implant of the above-described type in that the abutment element and the connecting element defining a longitudinal direction are configured and reconciled with one another such that the tendon replacement part may is tensingly fixable in the channel by relative movement between the abutment element and the connecting element in longitudinal direction.  
           [0007]    Such a configuration of the implant enables the tendon replacement part to be fixed in the channel only through relative movement between the abutment element and the connecting element. Complicated knotting, e.g. of polyester threads serving as connecting elements on a titanium anchoring plate serving as abutment element, is unnecessary. The tendon replacement part is clamped by only moving the connecting element relative to the abutment element, in which case the position respectively assumed between the connecting element and the abutment element as a result of the relative movement is unchangeable. Thus, the present invention leads to an improvement of the implant such that it can be inserted more simply and the “bungee effect” and the “bone tunnel enlargement” are prevented or at least diminished.  
           [0008]    To improve the healing process and avoid reactions of rejection, it is advantageous if the connecting element and/or the abutment element are made from a material body compatible material.  
           [0009]    It is favourable if the body compatible material is a resorbable plastic. This facilitates in particular a renewed surgical procedure, since the resorbable material can be drilled without any problem. In particular, it cannot wrap around the drill during drilling, as is possible with a polyester tape in the above-described anchoring methods. In addition, it can grow in completely and be absorbed without any problem at all as a result of low accumulations of material.  
           [0010]    In principle, it can be provided that the abutment element has at least one passage recess for the connecting element, so that the abutment element and the connecting element are movable relative to one another transversely to the longitudinal direction. Such a configuration enables the abutment element and the connecting element to be fixed relative to one another by an additional movement transversely to the longitudinal direction of the connecting element. Fixing can be reinforced with a movement transversely to the longitudinal direction in addition to a movement in the longitudinal direction.  
           [0011]    In a further preferred embodiment of the invention it can be provided that the abutment element has at least one passage recess for the connecting element, so that the connecting element and the abutment element are displaceable relative to one another, and that the abutment element has at least one fixture recess, wherein the at least one passage recess and the at least one fixture recess are connected to one another. Thus, as a result of displacement of the connecting element relative to the abutment element, the connecting element is able to extend at least partially into the fixture recess of the abutment element and both elements can be fixed relative to one another.  
           [0012]    It is advantageous in this case if the connecting element comprises a plurality of fixture recesses, which are arranged in the longitudinal direction of the connecting element. The stability of the connection of both elements is additionally increased as a result of this. Moreover, a plurality of fixing positions may thus be provided between the abutment element and the connecting element.  
           [0013]    It is particularly favourable if adjacent fixture recesses are spaced equidistant from one another. This allows fixing positions to be established at defined intervals between the connecting element and the abutment element.  
           [0014]    It can be advantageous if adjacent fixture recesses are separated from one another. This enables each fixture recess to be selectively brought into engagement with the abutment element.  
           [0015]    In a further preferred embodiment of the invention it can be provided that the connecting element is provided with an engagement strip formed by fixture recesses. This engagement strip enables any desired positions to be provided between the abutment element and connecting element, which reduces the preparation effort overall, since no polyester tape needs to be knotted to a defined length. This reduces the potential for error during the surgical procedure. Moreover, it also saves time, since the knot of a polyester tape does not have to be tightened, as there is no knot present.  
           [0016]    It is favourable in this case if the connecting element has at least two engagement strips. The stability of the connection is additionally increased as a result of this.  
           [0017]    It can be advantageously provided that a side face of the connecting element is provided with an engagement strip. The engagement strip can be attached particularly simply on one side face of the connecting element.  
           [0018]    It can be additionally advantageous if an engagement strip is arranged on the connecting element between side faces of the connecting element. This allows the connecting element to slide along the side faces practically free from friction.  
           [0019]    It is particularly favourable if the engagement strip is configured in a sawtooth shape. This enables unidirectional displacement of the connecting element relative to the abutment element. Movement in the opposite direction is then no longer possible, the abutment element is fixed in this direction relative to the connecting element. In this way, the tendon replacement part can be clamped simply in the channel. In particular, such a connecting element has a lower elasticity than a polyester tape, so that practically no bungee effect occurs, while all the advantages of a fixture of the implant remote from the joint are retained.  
           [0020]    In a further preferred embodiment it can be provided that an engagement strip comprises rectangular recesses as fixture recesses. Such recesses can be produced particularly simply and with corresponding elements immersing into them allow a fixture that is practically free from play.  
           [0021]    It can also be advantageous if the abutment element has a holding member, which is immersible into a fixture recess and by means of which the abutment element may be connected to the connecting element. The connection is enabled in a simple manner by the holding member immersing into the fixture recess. This can occur as a result of the relative movement of connection element and abutment element in the longitudinal direction of the connecting element, for example, by holding members immersing into fixture recesses of an engagement strip configured in a sawtooth shape.  
           [0022]    To increase the stability of the connection it can be provided that a holding member comprises a plurality of holding teeth for simultaneous engagement into a plurality of fixture recesses.  
           [0023]    It can be advantageously provided that a holding member is arranged at an angle to an abutment face of the abutment element. In this way, movement can be made easier in the longitudinal direction of the connecting element, but made difficult in the opposite direction, as a result of which the connection between the connecting element and abutment element is additionally strengthened.  
           [0024]    In principle it can be provided that the abutment element is connectable to the connecting element as a result of a relative movement of the entire abutment element thereto. This configuration allows abutting the abutment element on the channel of the bone and moving the connecting element relative to the abutment element, e.g. drawing along this or passing it through it, in which case it is preferably only possible to draw the connecting element out of the channel and in this way clamp the tendon replacement part, whereas a movement between the abutment element and connecting element in the opposite direction is prevented because of the respective configuration.  
           [0025]    It is particularly favourable if the connecting element is a body that is inflexible in the longitudinal direction. A bungee effect is effectively prevented because of this lower elasticity in comparison to anchorage of the tendon replacement part by using polyester tapes. This increases the primary stability directly after the surgical procedure and additionally allows a more vigorous aftercare.  
           [0026]    In a further preferred embodiment of the invention, it can be provided that the connecting element is dimensioned such that it has a larger width in a transverse direction to its longitudinal direction than in a transverse direction perpendicular thereto. Such connecting elements can be produced particularly simply and as the case may be provided along guide recesses of side faces.  
           [0027]    It is particularly advantageous if the connecting element has an essentially rectangular cross-section at least in the region extending in the drilling channel. A rectangular cross-section is particularly simple to produce. Moreover, one or more side faces can be easily provided with guide recesses.  
           [0028]    However, in a further preferred embodiment of the invention it can be provided that the connecting element is configured to be essentially rotationally symmetric in its longitudinal direction. This has the advantage, particularly in the case of a channel formed by drilling, that the connecting element can fill the drilling channel to an optimum degree. Moreover, it is particularly simple to produce.  
           [0029]    In this case it can be favourable if in the case of an essentially rotationally symmetric configuration of the connecting element, a fixture recess extends around the periphery of the connecting element. This allows a secure connection with the abutment element to be achieved, irrespective of the orientation of the connecting element inside the channel.  
           [0030]    It can be advantageous if adjacent fixture recesses are separated by a spherical element. This increases in particular the stability of the connecting element and reduces its elasticity.  
           [0031]    In an alternative, likewise advantageous embodiment, it can be provided that the holding part of the abutment element engages in the longitudinal direction into a fixture recess. This facilitates fixture solely on the basis of a relative movement between the connecting element and the abutment element in the longitudinal direction of the connecting element.  
           [0032]    In a further preferred embodiment of the invention, it can be additionally provided that the abutment element may be connected to the connecting element by rotation relative thereto. This enables, for example, an unhindered movement in the longitudinal direction of the connecting element, while a rotation ultimately leads to a connection of both elements.  
           [0033]    It can be advantageous in this case if the abutment element has a holding member, which is engagable into a fixture recess of the connecting element by rotation of the abutment element relative to the connecting element. In this way, it is possible to move both elements practically free from friction in the longitudinal direction of the connecting element, whereas the rotation leads to a connection of the two elements. A further advantage of this connection is that it can be easily released by again twisting to allow, for example, the tendon replacement part to be re-tensioned or relieved of tension.  
           [0034]    In principle, it can be advantageous if the connecting element is flexible transversely to its longitudinal direction. This allows a simple connection between the connecting element and the abutment element and simplifies insertion of the implant.  
           [0035]    In principle, the abutment element can be capable of being fixed positively to the connecting element. However, it is particularly advantageous if the abutment element is fixable non-positively to the connecting element. This additionally increases the stability of the connection of both elements.  
           [0036]    In a further advantageous embodiment of the invention, it can be provided that the relative movement between the abutment element and the connecting element for fixing the abutment element to the connecting element is performed from a non-fixed position into a fixing position. As a result, it is possible to move the connecting element relative to the abutment element firstly without application of a high force, whereas fixture occurs in a fixing position that is only assumed as a result of the relative movement.  
           [0037]    Advantageously, it can be provided that the end of the connecting element facing the tendon replacement part has a tendon replacement part receptacle for passage or suspension of the tendon replacement part. This enables the tendon replacement part to be connected to the connecting element particularly easily. In principle, other types of connection, e.g. by suturing or gluing, would also be conceivable.  
           [0038]    In this case, it can be favourable if the tendon replacement part receptacle is configured in a loop shape. This has a particularly high stability overall. Moreover, the tendon replacement part can be easily passed through such a loop-shaped tendon replacement part receptacle.  
           [0039]    In principle, the shape of the loop-shaped tendon replacement part receptacle can be as desired. However, it is advantageous if it has an essentially round loop shape. Any sharp edges or pointed corners, which could cause damage to the tendon replacement part, can be avoided as a result of this.  
           [0040]    However, it is also favourable if the loop-shaped tendon replacement part receptacle is essentially triangular. This permits a leg of the tendon replacement part receptacle extending essentially transversely to the longitudinal direction of the connecting element, against which the tendon replacement part can be laid. This causes an optimum transfer of force between the tendon replacement part and the connecting element.  
           [0041]    Moreover, it can be advantageous if the tendon replacement part receptacle is configured in a hook shape. In particular in the case of BTA transplants, in which a free end is provided with a rectangular plate having two drilled holes, these can be connected to the connecting elements in a particularly simple manner, since the hook-shaped tendon replacement part receptacle can be directed through both holes.  
           [0042]    In this case, it can be particularly favourable if a locking element is provided on the free end of the hook-shaped tendon replacement part receptacle and at least one locking element receptacle is provided on the connecting element to move the hook-shaped tendon replacement part receptacle into a loop-shaped tendon replacement part receptacle and lock it in position. This has the advantage that the tendon replacement part located in the tendon replacement part receptacle can be secured against sliding out unintentionally. In addition, the end of the connecting element forming the tendon replacement part receptacle can be sufficiently elastic to facilitate locking. Preparation of the implant is simplified in this way.  
           [0043]    In principle, any desired cross-sections of the tendon replacement part receptacle would be conceivable. However, it is of advantage if these are round, oval or rectangular, at least in sections. Round and/or oval cross-sections have the advantage that damage to the tendon implant can be prevented. Rectangular cross-sections can be produced particularly simply and have an increased stability.  
           [0044]    It is particularly advantageous if the abutment element can be screwed to the connecting element. This allows the position of the connecting element in relation to the abutment element to be infinitely controlled. As a result, the tendon replacement part can be tensioned in an optimum manner as desired.  
           [0045]    It can be favourable in this case if the passage recess of the abutment element is provided with an internal thread, and if the connecting element is provided with a corresponding external thread. Both threads may be produced particularly simply on the two elements.  
           [0046]    Advantageously it can be additionally provided that the abutment element has a section extending into the channel. In contrast to the previously used anchoring plate, which only abuts on the outside, a cavity in the bone can be avoided as a result of this, thus enabling better healing in particular.  
           [0047]    It is favourable in this case if the extending section is configured to be rotationally symmetric. In this way, it can be optimally adapted to a drilled channel, as a result of which the play between the abutment element and the bone is minimised.  
           [0048]    It would be conceivable that the extending section has a constant cross-section in the longitudinal direction. However, it is particularly advantageous if the extending section has a cross-section which decreases in the longitudinal direction of the passage recess towards the tendon replacement part. Such a, for example, conical configuration allows the abutment element to be simply clamped in the channel at its extending section.  
           [0049]    It can also be advantageous if the abutment element has an abutment region abutting externally against the channel and at least partially covering the channel. Such an abutment region prevents the abutment element from immersing into the channel. With the abutment region a stop for the abutment element on the bone is practically formed in order to prevent the abutment element from penetrating into the channel.  
           [0050]    In this case, it can be provided that the abutment region has an external face directed away from the drilling channel, which runs essentially in a plane transversely to the longitudinal direction of the passage recess. Such an abutment element can be produced in a particularly simple manner.  
           [0051]    However, it can be advantageous if the abutment region has an external face directed away from the drilling channel, which with a plane transversely to the longitudinal direction of the passage recess encloses an angle, which corresponds to an angle formed between the channel and a passage face formed by the channel in the tibia or the femur. Particularly with a drilled hole obliquely entering the bone from the bone surface, such a configuration of the abutment region enables the abutment element to abut against the bone in an optimum manner. In particular, the abutment element only projects minimally from the bone in this way.  
           [0052]    It is favourable if the abutment region has a larger cross-section than the immersing section. In this way, it is possible to cover the channel completely and to form a stop on the bone.  
           [0053]    In addition, it can be advantageously provided that the abutment region is pivotally disposed on the immersing section. This has the advantage that the abutment region is always oriented parallel to the surface of the bone and thus only projects minimally from the bone. Moreover, in this way the force acting on the bone by tensioning the tendon replacement part via the abutment element can be transferred in an optimum manner onto the entire edge of the channel on the bone surface.  
           [0054]    In a preferred embodiment of the invention it can be provided that the holding member is displaceably disposed on the abutment element in a direction transverse to the passage recess. In this way, the holding member can be moved purposefully from a release position into a locking position and vice versa.  
           [0055]    To assure a defined movement of the holding member, it is advantageous if a guide recess running transversely to the passage recess is provided for guiding and supporting the holding member.  
           [0056]    In addition, it is favourable if the holding member is biased towards the passage recess. As a result, the holding member can be held constantly in a locking position and secured as a result of the prestress.  
           [0057]    A particularly simple structure of the implant results if an elastic element is provided to generate a prestress.  
           [0058]    The elastic element is advantageously configured in one piece with the holding member. A restraining element in one piece comprising both the holding member and the elastic element reduces the number of structural elements necessary. Moreover, the assembly of the abutment element is substantially simplified.  
           [0059]    According to a preferred embodiment of the invention it can be provided that the fixture recess comprises a fixture recess face oriented transversely, and one oriented obliquely, to the longitudinal direction of the connecting element. This enables the abutment element to move in only one direction relative to the connecting element. The fixture recess face oriented obliquely to the longitudinal direction in this case serves as a slide face, the fixture recess face oriented transversely to the longitudinal direction of the connecting element serving as a stop for the abutment element or parts thereof.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0060]    The following description serves to provide a more detailed explanation in conjunction with the drawing:  
         [0061]    [0061]FIG. 1 is a schematic view of a knee joint with a tendon replacement part fixed in the femur and in the tibia;  
         [0062]    [0062]FIG. 2 is a cross-sectional view of a first embodiment of an abutment element according to the invention;  
         [0063]    [0063]FIG. 3 is a top view onto the abutment element from FIG. 2;  
         [0064]    [0064]FIG. 4 is a cross-sectional view of a second embodiment of an abutment element;  
         [0065]    [0065]FIG. 5 is a cross-sectional view of a third embodiment of an abutment element;  
         [0066]    [0066]FIG. 6 is a cross-sectional view of a fourth embodiment of an abutment element;  
         [0067]    [0067]FIG. 7 is a schematic side view of a loop-shaped tendon replacement part receptacle;  
         [0068]    [0068]FIG. 8 is a side view in the direction of arrow A in FIG. 7;  
         [0069]    [0069]FIG. 9 is a cross-sectional view along line  9 - 9  in FIG. 7 or FIG. 13;  
         [0070]    [0070]FIG. 10 is a cross-sectional view along line  10 - 10  in FIG. 7 or FIG. 13;  
         [0071]    [0071]FIG. 11 is a cross-sectional view along line  11 - 11  in FIG. 7 or FIG. 13;  
         [0072]    [0072]FIG. 12 is a cross-sectional view along line  12 - 12  in FIG. 7 or FIG. 13;  
         [0073]    [0073]FIG. 13 is a side view of a loop-shaped tendon replacement part receptacle in the shape of a triangle;  
         [0074]    [0074]FIG. 14 is a side view of a lockable hook-shaped tendon replacement part receptacle;  
         [0075]    [0075]FIG. 15 is a side view in the direction of arrow B in FIG. 14;  
         [0076]    [0076]FIG. 16 is a side view of a first embodiment of a connecting element with associated abutment element;  
         [0077]    [0077]FIG. 17 is a cross-sectional view along line  17 - 17  in FIG. 16;  
         [0078]    [0078]FIG. 18 is a side view of a second embodiment of a connecting element with associated abutment element;  
         [0079]    [0079]FIG. 19 is a top view in the direction of arrow C in FIG. 18;  
         [0080]    [0080]FIG. 20 is a side view in the direction of arrow D in FIG. 18;  
         [0081]    [0081]FIG. 21 is a cross-sectional view through a third embodiment of a connecting element with associated abutment element;  
         [0082]    [0082]FIG. 22 is a top view onto the abutment element in FIG. 21 in the direction of arrow E;  
         [0083]    [0083]FIG. 23 is a side view of the connecting element from FIG. 21 in the direction of arrow F;  
         [0084]    [0084]FIG. 24 is a side view of a fourth embodiment of a connecting element with associated abutment element;  
         [0085]    [0085]FIG. 25 is a top view onto the abutment element in FIG. 24 in the direction of arrow G;  
         [0086]    [0086]FIG. 26 is a side view of the connecting element from FIG. 24 in the direction of arrow H;  
         [0087]    [0087]FIG. 27 is a side view of a fifth embodiment of a connecting element with associated abutment element;  
         [0088]    [0088]FIG. 28 is a top view onto the abutment element from FIG. 27 in the direction of arrow I;  
         [0089]    [0089]FIG. 29 is a side view of a sixth embodiment of a connecting element with associated abutment element;  
         [0090]    [0090]FIG. 30 is a top view onto the abutment element from FIG. 29 in the direction of arrow K;  
         [0091]    [0091]FIG. 31 is a side view of the connecting element from FIG. 29 in the direction of arrow L;  
         [0092]    [0092]FIG. 32 is a side view of a seventh embodiment of a connecting element with associated abutment element;  
         [0093]    [0093]FIG. 33 is a top view onto the abutment element from FIG. 32 in the direction of arrow M;  
         [0094]    [0094]FIG. 34 is a side view of an eighth embodiment of a connecting element with associated abutment element;  
         [0095]    [0095]FIG. 35 is a top view onto the abutment element from FIG. 34 in the direction of arrow N;  
         [0096]    [0096]FIG. 36 is a view in partial longitudinal section through a ninth embodiment of a connecting element with associated abutment element;  
         [0097]    [0097]FIG. 37 is a side view of the ninth embodiment shown in partial section in FIG. 36, and  
         [0098]    [0098]FIG. 38 is a top view onto a restraining element forming a component of the ninth embodiment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0099]    In order to replace a destroyed cruciate ligament in a knee joint  100 , longitudinal channels  106  and  108 , which are essentially aligned with one another when the knee joint  100  is straightened and extend from the front to the rear of the knee joint  100  to pass obliquely through this, are respectively drilled into the head  102  of the femur and the head  104  of the tibia.  
         [0100]    A cruciate ligament replacement part  116 , which comprises a band-shaped piece  118  of a tendon replacement part, e.g. a part of the patellar tendon, at the ends of which loop-shaped ends  124  and  126 , drawn through openings  120 ,  122 , of fastening rails  128 ,  130  preferably made from resorbable plastic are arranged, is drawn into channel sections  112  or  114  of the longitudinal channels  106  or  108 . These channel sections are widened in diameter in one step and arranged to face the joint cavity  110  located between the head  104  of the tibia and the head  102  of the femur. The elongated fastening rails  128  or  130 , which respectively pass completely through the longitudinal channels  106  or  108  and project out of the head  102  of the femur or head  104  of the tibia, have a respective coupling section  136  or  138 , which faces their respective second free end  132  or  134  and can be respectively connected to a corresponding region of a fastening block  140  or  142 , which partially extends into the longitudinal channels  106  or  108  and partially abuts against the outside of the head  102  of the femur or the head  104  of the tibia.  
         [0101]    During insertion of the cruciate ligament replacement part  116 , the band-shaped piece  118  is drawn in as far as the stop of the channel sections  112  or  114  formed by the single-step widened portion and prestressed by the fastening rails  128  and  130  being drawn in the opposite direction out of the knee joint  100  and moved relative to the fastening blocks  140  and  142 , that is until the band-shaped piece  118  is positioned inside the channel sections  112  and  114  in the desired manner.  
         [0102]    The fastening blocks  140  and  142  and also the fastening rails  128  and  130  with the loop-shaped ends  124  and  126  arranged thereon can be structured differently. Various configurations of the individual elements are shown in FIGS.  2  to  35  and explained in more detail below. In this case, the base forms of the fastening blocks  140 ,  142  can be combined as desired with loop-shaped ends  124 ,  126  and also with different coupling sections  136 ,  138  with respectively corresponding configurations of fastening blocks  140 ,  142 . Therefore, the individual elements of the cruciate ligament replacement part  116  are each explained separately below.  
         [0103]    Four different basic types of fastening blocks  140 ,  142  are shown in FIGS.  2  to  6 . FIGS. 2 and 3 show a block  150  that is fully rotationally symmetric relative to the axis of symmetry  157  with a hollow cylindrical body section  152 , which may be inserted into the longitudinal channel  106  or  108 , and with a head  154  of larger diameter adjoining it. The side face  156  of the head  154  facing the body section  152  serves as a stop on the head  102  of the femur or head  104  of the tibia for the block  150  in order to prevent penetration into the longitudinal channel  106  or  108 .  
         [0104]    Contrary to the case with block  150 , with block  160  shown in FIG. 4, the head  164  projecting above the hollow cylindrical body section  162  in diameter is inclined relative to the axis of symmetry  167  of the body section  162 . As shown in FIG. 1, this provides the possibility of the body section  162  extending into the longitudinal channels  106  or  108  with its axis of symmetry  167  parallel to the longitudinal axis thereof, whereas the side face  166  of the head  164  abuts fully against the external face of the head  102  of the femur or the head  104  of the tibia in spite of the obliquely drilled longitudinal channels  106  or  108 . In this way, the force acting on the side face  166  can be transferred onto the head  102  of the femur or the head  104  of the tibia in an optimum manner during tensioning of the cruciate ligament replacement part  116 .  
         [0105]    [0105]FIGS. 5 and 6 show blocks  170  and  180  that are conical with respect to their axes of symmetry  177  and  187  and respectively have a central hole  171  or  181 . At their end with the largest diameter, they have a plane, ring-shaped external face  175  or  185 , wherein external face  175  is oriented perpendicular to the axis of symmetry  177 , whereas the external face  185  is inclined relative to the axis of symmetry  187 . Both block  170  and block  180  are inserted into the longitudinal channels  106  or  108  from the outside and are clamped in these as a result of their conical shape. The inclined external face  185  is advantageous, in particular in the case of longitudinal channels  106  or  108  arranged obliquely in the head  102  of the femur or head  104  of the tibia, so that block  180  projects only minimally from the surface of the two bones.  
         [0106]    At their end plunging into the longitudinal channel  106  or  108 , blocks  150 ,  160 ,  170  and  180  have holding elements  159 ,  169 ,  179  and  189  projecting inwards towards the axes of symmetry  157 ,  167 ,  177  and  187  from the inside surface of the drilled holes  151 ,  161 ,  171  and  181 . These are only shown schematically in FIGS.  2  to  6 , possible alternative embodiments are described in more detail in association with FIGS.  16  to  35 .  
         [0107]    The loop-shaped ends  124  and  126  of the fastening rails  128  and  130  can be configured differently, as already indicated. Examples thereof are shown in FIGS.  7  to  15 .  
         [0108]    [0108]FIGS. 7 and 8 show a first embodiment of a loop  200 , which defines an essentially drop-shaped passage  202 , wherein a free end  134  of one of the fastening rails  128  or  130  is directed back on itself and is, for example, welded, glued, knotted or clamped thereto. A band-shaped piece  118  of a cruciate ligament replacement part  116  can then be passed through the passage  202 , as is shown in FIG. 8.  
         [0109]    FIGS.  9  to  12  show different possible cross-sections of the loop  200 . FIG. 9 shows a circular cross-sectional area  210 , FIG. 10 an elongated oval cross-sectional area  212 , FIG. 11 shows an in transverse direction elongated oval cross-sectional area  214  and finally FIG. 12 shows a rectangular cross-sectional area  216 . Each of the cross-sectional areas  210 ,  212 ,  214  and  216  shown in FIGS.  9  to  12  may be combined in any desired way with the shape of the loop  200  shown in FIGS. 7 and 8.  
         [0110]    [0110]FIG. 13 shows a loop  220  slightly modified from loop  200 , which defines a triangular passage  222  with the shape of an isosceles triangle, the base of which defines a holding section  224  running perpendicular to the longitudinal direction of the fastening rail  128  or  130 . The two loop sections  228  and  229  of equal length are joined together at a connection point  226 , which can be formed, for example, by a gluing point, a welding point or by clamping.  
         [0111]    The holding section  224  can have different shapes in cross-section, e.g. circular or elongated oval cross-sectional areas  210 ,  212  or  214  shown in FIGS.  9  to  11  are conceivable.  
         [0112]    In order to stabilise the shape of the loop  220 , the cross-section of the two loop sections  228  and  229  of equal length is rectangular, as shown in FIG. 12. Like in the loop  200 , the band-shaped piece  118  in loop  220  is directed through the passage  222  and abuts against the holding section  224 .  
         [0113]    A third embodiment of a loop  240  according to the invention is shown in FIGS. 14 and 15. The shape of the loop  240  essentially corresponds to that of loop  220 . The essential difference is, however, that the loop  240  can be opened. For this, the fastening rail  128  or  130  has an elongated hole  242  extending in the longitudinal direction, at the end of which remote from the loop  240  an insertion opening  244  configured with a larger diameter than the elongated hole is arranged. The free end  246  of the fastening rail  148  or  130  is provided with a locking pin  248  projecting rectilinearly from the free end  246  in extension of the fastening rail  128 ,  130 , said locking pin has a head  250 .  
         [0114]    For fastening the band-shaped piece  118  to the fastening rail  128 ,  130 , the opened loop  240 , which is hook-shaped in this position, is directed through one of the openings  120 ,  122  of the band-shaped piece  118 . The locking pin  248  is passed completely through the insertion opening  244  with its head  250  and can then be displaced from the insertion opening  244  into the elongated hole  242 . As a result, the band-shaped piece  118  is secured in the loop  240  forming a drop-shaped loop like loop  200  in a closed position.  
         [0115]    FIGS.  16  to  35  show different variants of coupling sections  136  or  138  and corresponding holding elements  159 ,  169 ,  179  and  189  schematically shown in association with FIGS.  2  to  6 . In association with FIGS.  16  to  33 , fastening blocks are respectively used, which correspond in external structure to the block  150 , i.e. are configured to be completely rotationally symmetric and have a hollow cylindrical body section. However, fastening blocks with a base body such as the blocks  160 ,  170  or  180  shown in FIGS. 4, 5 and  6  have are also possible.  
         [0116]    [0116]FIG. 16 shows a section from a fastening rail  128  with a coupling section  260 , which is formed completely rotationally symmetric to the longitudinal axis  261 . The coupling section  260  is formed by a plurality of identical annular recesses  262 , so that an elongated structure remains, which consists of the same number of cone bodies  263  having a spherical base area  266  oriented transversely to the longitudinal axis, wherein the point of each cone body  263  penetrates into the base area of the adjacent cone body. The coupling section  260  thus has a Christmas tree-like appearance in side view.  
         [0117]    A block  265  serving as abutment element has a ring-shaped projection  267  corresponding to the annular recesses  262 , which projects towards the longitudinal axis  261  and, like the cone bodies  263 , has a sloping external face  268 .  
         [0118]    When connecting the block  265  to the fastening rail, the block  265  is pushed over the fastening rail until the external faces  268  slide over sloping cone faces  264  of the cone bodies  263 . A connection is created between the block  265  and the fastening rail in the region of the coupling section  260  as soon as the catch face  269  of the projection  267  arranged to run transversely to the longitudinal axis  261  engages behind the cone base area  266 . While it is still possible to slide the block  265  up further onto the fastening rail, it is not possible to pull it back because of the catch connection formed. To tension the band-shaped piece  118 , one of the two fastening rails can be respectively displaced in stages in the longitudinal direction, that is precisely at the spacing between two cone base areas  266 .  
         [0119]    FIGS.  18  to  20  show an alternative configuration of a coupling section  280  with associated block  285 . On a base body  281  of the coupling section  280  with a rectangular cross-section, a plurality of sawteeth  283  are spaced at equal distance on one side face  282 , thus forming a toothed strip. Each sawtooth  283  has a tooth face  284  oriented transversely to the longitudinal axis  286 . Along its longitudinal axis  286  the block  285  has a perforation  288  with a rectangular cross-section, wherein the cross-section of the perforation corresponds to the cross-section of the coupling section  280  in the region of the tooth faces  284 . On their side remote from a head  289  of the block  285 , the block  285  has a locking tooth  290 , which can fill a fixture recess  287  formed between two sawteeth  283 .  
         [0120]    The block  285  can be locked in one direction with the fastening rail in the region of the coupling section  280 , i.e. by a sloping side face of the locking tooth  290  sliding on over a sloping side face of one of the sawteeth  283  until the locking tooth  290  extends into the fixture recess  287 . In this configuration of the coupling section  280  a stepwise adjustment of the prestress of the band-shaped piece  118  is possible.  
         [0121]    A further coupling section  300  is shown in FIGS.  21  to  23 . A base body  301  of the coupling section  300  with a rectangular cross-section is provided transversely to its longitudinal direction with essentially rectangular perforations  303 , which are arranged equidistant along the base body  301 . A corresponding block  305  serving as abutment element is provided with a perforation  306  likewise with a rectangular cross-section, wherein at one end this has two opposing locking teeth  307  and  308  respectively pointing from an inside wall of the perforation  306  towards the opposite wall.  
         [0122]    For clamping the band-shaped piece  118  in position, the fastening rail is pushed through the perforation  306  of the block  305 , in fact until the locking teeth  307  and  308  plunge into one of the perforations  303 . Since each of the locking teeth  307  and  308  has a tooth face  309  oriented transversely to the longitudinal direction  302 , movement of the block  305  relative to the fastening rail is only possible in one direction. By advancing the fastening rail further into the block  305 , the band-shaped piece  118  can be tensioned in the desired manner in defined steps respectively corresponding to the distance between two perforations  303 .  
         [0123]    A further possibility of connecting a block  325  to a fastening rail is shown in FIGS.  24  to  26 . A coupling section  320  comprises as base body  321  with a rectangular cross-section, wherein its narrow sides respectively have a row of rectangular teeth  322  spaced at equal distance. The block  325  has a perforation  326  of a loop-shaped base body likewise with a rectangular cross-section, wherein from the narrow side faces thereof a parallelepipedal tab with three locking teeth  327  arranged thereon respectively projects in the longitudinal direction of the coupling section  320 , in fact such that they can extend into depressions formed between the teeth  322 , when the block  325  is pushed over the coupling section  320 .  
         [0124]    A further conceivable coupling section  340  is shown in FIGS. 27 and 28. The principle corresponds to that in association with the coupling section  300  shown in FIGS.  21  to  23 . However, two parallel rows of perforations  342  spaced at equal distance and running transversely to the longitudinal direction of the fastening rail are arranged on a base body  341  with a rectangular cross-section. Accordingly, a block  345  serving as abutment element has a passage  346  with a rectangular cross-section passing completely through this in the longitudinal direction. Two teeth  347  respectively project from the two wide inside walls of the passage  346  towards the opposite wall of the passage  346 .  
         [0125]    To clamp the band-shaped piece  118  in position, the fastening rail is inserted through the passage  346  until the four teeth  347  extend into four corresponding perforations  342  of the coupling section  340 . As a result of a sloping side face of the teeth  347 , displacement of the block  345  relative to the fastening rail is possible in only one direction.  
         [0126]    A completely different locking mechanism is provided in the case of the coupling section  360  shown in FIGS.  29  to  31 . While this fully corresponds to the coupling section  320  described in association with FIGS.  24  to  26 , a block  365  has a different structure. In its base form it corresponds to the block  150  known from FIG. 2. This has a cylindrical hole  366  along its axis of symmetry, wherein one end of the block  365  is provided with a projection  367  projecting radially outwards in a ring shape. In addition, a locking projection  368  in a ring shape projecting radially towards the axis of symmetry is provided, said projection having two diametrically opposed breaks  369  and  370 . The diameter of the hole  366  and the width of the coupling section  360  are coordinated to one another in such a way that the two toothed strips formed from equidistant teeth  362  on the narrow sides of the parallelepipedal base body  361  may be pushed through the hole  366  in such a way that the teeth  362  protrude into breaks  369  and  370 . The fastening rail can thus be drawn through the hole  366  of the block  365  without friction and without locking in any form.  
         [0127]    In order to fix a position of the block  365  relative to the fastening rail, the block  365  and the fastening rail are rotated relative to one another so that the locking projection  368  engages between two adjacent teeth  362 . Thus, the position is doubly locked because of the two toothed rods. Such a locking position can be released again by rotating the block  365  back relative to the fastening rail by the teeth  362  being moved into the region of the breaks  369  and  370 .  
         [0128]    A further type of connection between a block  385  and a coupling section  380  is shown in FIGS. 32 and 33. The coupling section consists of rotationally symmetric spherical bodies  381  spaced from one another in a chain. The block  385  has a hollow cylindrical body section  382 , which is completely sealed with a cover  383  of larger diameter. An elongated hole  384 , one half of which facing away from the axis of symmetry is widened by a hole  386 , is machined into the cover to be rotationally symmetric to its axis of symmetry.  
         [0129]    A connection between the block  385  and the fastening rail is possible by directing the coupling section  380  through the hole  386  of the cover  383  of the block  385 . To lock the block  385  with the fastening rail, the block  385  needs only be displaced relative to the fastening rail towards the axis of symmetry of the coupling section  380 , and in fact in such a manner that the unwidened portion of the elongated hole  384  engages between two spherical bodies  381 . In this position, the block  385  and the fastening rail are fixed relative to one another. This position may also be released by the fastening rail being displaced relative to the block  385  until the spherical bodies  381  can be directed through the hole  386  again.  
         [0130]    A further possibility of connecting the fastening rail to a rotationally symmetric block  395  serving as abutment element is shown in FIGS. 34 and 35. The fastening rail is provided with a coupling section  390 , which has an external thread  391 . The block  395  comprises a central hole  396 , which is provided with an internal thread  397  corresponding to the external thread  391 . The block  395  has a hemispherical base body  398 , on the arched side of which a cylinder section  399  is disposed. A parallelepipedal section  392 , which can be brought into engagement with a fastening tool, e.g. a fork wrench, adjoins the flat side of the base body  398 . A disc  393  with an opening  394  coordinated to the spherical surface of the base body  398  abuts against the spherical surface of the base body  398 . As a result, the disc  393  can be rotated relative to the base body  398  and pivoted along the surface of the base body  398 .  
         [0131]    For insertion of the cruciate ligament replacement part  116 , the fastening rail with the coupling section  390  is guided to the cylinder section  399  of the block  395  and the internal thread  397  screwed to the external thread  391 . This enables an infinite adjustment of the prestress of the band-shaped piece  118  arranged on the free end of the fastening rail. The disc  393  allows adaptation to the surface of either the head  102  of the femur or the head  104  of the tibia in the case of an obliquely drilled longitudinal channel  106  or  108 . The disc  393  always locates parallel to the surface thereof and because of the spherical configuration of the base body  393  can transfer the effective tensile forces onto the surface of the bones in an optimum manner.  
         [0132]    A ninth embodiment of a connecting element with associated abutment element is shown in FIGS. 36 and 37. The connecting element in the form of a fastening rail, only shown in sections, is provided with a coupling section  402 , which essentially corresponds to the coupling section  260  of the first embodiment shown in FIG. 16. It is formed rotationally symmetric to a longitudinal axis  404  and has a plurality of identical annular recesses  406  so that an elongated structure results with a number of spherical bodies  410  with a cone base area  408  oriented transversely to the longitudinal axis  404  corresponding to the number of annular recesses  406 , wherein the point of each cone body  410  extends into the cone base area  408  of the adjacent cone base body  410 . As a result, the coupling section  402  has a Christmas tree-like appearance in side view.  
         [0133]    As part of an abutment element  412  a sphere  416  having a central hole  414  is provided, wherein the inside diameter of the hole  414  is adapted to the largest outside diameter of the coupling section  402 , so that the sphere is displaceable in the direction of the longitudinal axis  404  on the coupling section  402 .  
         [0134]    In an equatorial plane running transversely to the longitudinal axis  404 , the sphere  416  has an annular groove  418  completely surrounding it, the depth and width thereof being adapted to a spring wire ring  20  disposed therein. A perforation  422  with a parallelepipedal cross-section oriented transversely to the longitudinal axis is provided in the equatorial plane, said perforation intersecting the hole  414 , as a result of which two locking body receptacles  424  and  425  are formed, which respectively extend radially outwards from the hole  414  and into which a locking body  426  or  427  is respectively inserted. The two locking bodies  426  and  427  are held in the locking body receptacles  424  and  425  by the spring wire ring  420 . An end  428  or  429  of the locking body  426  or  427  respectively facing the hole  414  is configured to correspond to the annular recesses  406  and can extend into these.  
         [0135]    A ring-shaped disc  434  is disposed on the sphere surface  432  to enable rotation and pivoting movement so that any desired angle of inclination  436  between a plane defined by the disc  434  and the longitudinal axis  404  can be set.  
         [0136]    For insertion of the cruciate ligament replacement part  116 , the fastening rail with the coupling section  402  is pushed through the hole  414  in the direction of arrow  403  until the locking bodies  426  and  427  prestressed by the spring wire ring  420  towards the longitudinal axis  404  extend into the annular recesses  405  with their ends  428  and  429 . Because of the configuration of the cone bodies  410 , when the sphere  416  is held fast, the fastening rail with the coupling section  402  arranged thereon can only be moved in the direction of arrow  430 , in the opposite direction the ends  428  and  429  located on the cone base area  408  act as a block for any movement. The band-shaped piece  118  arranged on the free end of the fastening rail can be prestressed as a result of corresponding relative movement between the fastening rail and the sphere  416 . The disc  434  enables adaptation to the surface either of the head  102  of the femur or the head  104  of the tibia in the case of an obliquely drilled longitudinal channel  106  or  108 . Because of the special mounting on the sphere  416 , the disc  434  can always locate parallel to the surface of the head  102  of the femur or the head  104  of the tibia, as a result of which it can transfer the effective tensile forces onto the surface of the bones in an optimum manner because of the prestress of the band-shaped piece  118 .  
         [0137]    In place of the two locking bodies  426  and  427  described in association with FIGS. 36 and 37, a restraining element shown in FIG. 38 and given the overall reference  440  can be used. It comprises a holding element  442 , which corresponds to the locking bodies  426  and  427  and is moulded symmetrically onto a C-shaped holding ring  444  made of a spring steel, so that the restraining element  440  has a flat configuration overall. As a result of the symmetrical arrangement of the holding element  442  on the holding ring  444 , two spring arms  446  and  447  with dimensions selected so that they fit into the annular groove  418  are formed on the holding ring. Free ends of the spring arms  446  and  447  are provided with holding lugs  448  and  449 , which point approximately onto a centre point of the holding ring  444 . The length of the spring arms  446  and  447  is selected so that the holding lugs  448  and  449  extend at least partially into the parallelepipedal perforation  422  and hold the holding element  442  under prestress on the coupling section  402 .