Abstract:
A medical instrument for autologous chondrocyte transplantation comprises a stamp for introducing an implantable nonwoven into a cartilage. This stamp has, on a distal end face, at least one opening to which an underpressure can be applied.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims priority of German patent application No. 10 2005 010 988.8 filed on Mar. 3, 2005.  
       BACKGROUND OF THE INVENTION  
       [0002]     The invention relates to an instrument for autologous chondrocyte transplantation.  
         [0003]     Autologous chondrocyte transplantation (ACT) is a method for the repair of cartilage damage in the human body.  
         [0004]     The articular cartilage in the area of the human knee differs in thickness according to the topography. In the area of the patella, it can reach a layer thickness of 7 to 8 mm. Since the articular cartilage does not have any direct vessel or nerve attachments, it is nourished mainly through diffusion from the synovial fluid of the intraarticular space. The cross-linking of various matrix components to form the cartilage ground substance permits mechanical damping and almost frictionless sliding of the articular surfaces. At the cellular level, there is a complex structure of cartilage cells (chondrocytes), collagen fibers and proteoglycans. The healthy cartilage in the area of the knee of a human adult is able to tolerate loads that can amount to a multiple of the body&#39;s weight.  
         [0005]     Damage to the articular cartilage represents a major problem in routine traumatology and orthopedics. The limited healing capacity of cartilage has long been known and is due essentially to the latter&#39;s particular structure and anatomy.  
         [0006]     Damage to the articular surface, above all in the area of the load-bearing zones of the sliding surface of the joint, therefore entails increased risk of substantial joint damage in the sense of premature arthrosis. Known methods for biological reconstruction of full-layer cartilage damage are in most cases suitable only for small to medium-sized defects. In full-layer cartilage damage, above all in the area of the knee joint, with a defect area covering more than ca. 4 cm 2 , there has therefore been increasing clinical use of autologous chondrocyte transplantation.  
         [0007]     In this method, cartilage tissue is removed, under arthroscopy, from joint parts that are not load-bearing. Cartilage cells are isolated from this tissue and cultured in a cell culture.  
         [0008]     This culturing of the cartilage cells is increasingly being done within a nonwoven-like implant, for example a collagen matrix. Such a nonwoven provides the cartilage cells with a three-dimensional structure on which they are able to grow and spread.  
         [0009]     A nonwoven obtained in this way and occupied by chondrocytes is then transplanted into the cartilage defect zone during a second intervention.  
         [0010]     During this second intervention, the margins of the cartilage defect are dissected, i.e. the margins of the defect area are cut out and the bone in the area of the defect is exposed. In this connection, particular care has to be taken to ensure that the margins of the defect area are cleanly dissected in order to permit smooth attachment of the implant.  
         [0011]     A template of the defect is now usually prepared from a sterile material, and the implantable nonwoven is cut to size with the aid of this template. This implantable nonwoven cut to size in this way is then fitted into the cartilage defect.  
         [0012]     This procedure is generally performed by arthrotomy, that is to say by means of a semi-open procedure. Such a semi-open procedure always entails the possibility of infection at the exposed operating site. In addition, it would place less strain on the patient if such an operation were performed using minimally invasive techniques, that is to say by arthroscopy.  
         [0013]     It is an object of the present invention is to make available an instrument for autologous chondrocyte transplantation with which an implantable nonwoven can be implanted in particular by arthroscopy.  
       SUMMARY OF THE INVENTION  
       [0014]     According to the invention, the object is achieved by an instrument for autologous chondrocyte transplantation, with a stamp which is used for introducing an implantable nonwoven into a cartilage and which has, on a distal end face, at least one opening to which an underpressure can be applied so that an implantable nonwoven can be held on the end face.  
         [0015]     By means of the underpressure, the implantable nonwoven adheres to the distal end face of the stamp. The implantable nonwoven can then be suitably inserted by means of the stamp into the prepared cartilage defect. After insertion of the implantable nonwoven, the underpressure is interrupted, the stamp is lifted from the implantable nonwoven, and the latter remains in the prepared cartilage defect.  
         [0016]     It is thus possible, with this kind of stamp-like instrument, to accurately insert an implantable nonwoven for autologous chondrocyte transplantation into a cartilage defect by minimally invasive arthroscopy.  
         [0017]     In one embodiment of the invention, a plurality of openings are provided on the distal end face of the stamp.  
         [0018]     By means of this measure, the implantable nonwoven is held at more than one location of the distal end face. In this way, the implantable nonwoven is held much more firmly and adheres more uniformly on the distal end face. This avoids a peeling-off of the implantable nonwoven or the formation of folds.  
         [0019]     In one embodiment, a multiplicity of the openings are arranged in the area of the circumference of the distal end face of the stamp.  
         [0020]     This measure ensures that the margins of the implantable nonwoven are held securely on the distal end face of the stamp and the implantable nonwoven can be inserted particularly reliably and with an exact fit into the prepared cartilage defect.  
         [0021]     In a further embodiment of the invention, the at least one opening can be subjected to an overpressure.  
         [0022]     After the implantable nonwoven has been fitted into the cartilage defect and the underpressure has been interrupted, it could happen that the implantable nonwoven would remain sticking to the distal end face of the stamp on account of adhesion. This can happen, for example, if the implantable nonwoven, which is a biological material, has to be kept moist.  
         [0023]     If an overpressure is applied via the openings to the implantable nonwoven in the direction of the cartilage defect, the detachment of the implantable nonwoven from the stamp is assisted. This means that detachment can be ensured without changing the position of the already fitted implantable nonwoven.  
         [0024]     The overpressure is applied by providing a flow of fluid through the openings, which fluid can, for example, be sterile water, sterile saline solution or sterile compressed air.  
         [0025]     In a further embodiment of the invention, the instrument further comprises a cartilage puncher for punching out cartilage tissue.  
         [0026]     A cartilage puncher is a particularly simple instrument for dissecting an area of cartilage damage.  
         [0027]     In a further embodiment of the abovementioned measure, the cartilage puncher has a tubular configuration.  
         [0028]     By means of this measure, a cartilage puncher can be used not only via arthroscopy, for punching out the cartilage defect, but also forms a channel through which further instruments can be guided to the cartilage defect.  
         [0029]     These other instruments can include, for example, surgical spoons or curettes, which are used for removing the punched-out tissue from the bone.  
         [0030]     Moreover, a tubular cartilage puncher can also be used for guiding the stamp through it to the cartilage defect. It can therefore also act as a targeting device for the stamp.  
         [0031]     In a further embodiment of the abovementioned measure, the inner cross section of the cartilage puncher corresponds approximately to the cross-sectional contour of the stamp.  
         [0032]     The stamp can therefore be used to insert an implantable nonwoven which corresponds exactly to the punch area.  
         [0033]     An oval cross section has proven to be a suitable cross-sectional contour.  
         [0034]     In a further embodiment of the invention, the instrument further comprises at least one nonwoven puncher for punching out the implantable nonwoven.  
         [0035]     An implantable nonwoven can be prepared particularly easily by means of a nonwoven puncher. The punch blade of the nonwoven puncher has approximately the same contour as that of the cartilage puncher, so that a nonwoven section matching the previously prepared defect is punched out.  
         [0036]     In one embodiment of the aforementioned measure, the nonwoven puncher has a tubular configuration.  
         [0037]     By means of this measure, after the punching procedure, the stamp can be guided through the nonwoven puncher toward the punched-out implantable nonwoven. This makes it much easier to take up the implantable nonwoven by means of the stamp.  
         [0038]     In a further embodiment of the abovementioned measure, the inner cross section of the nonwoven puncher corresponds approximately to the cross-sectional contour of the stamp.  
         [0039]     By means of this measure, the stamp can be inserted with a snug fit into the nonwoven puncher and guided toward the punched-out section of nonwoven. The stamp is positioned with precise targeting over the punched-out implantable nonwoven and is able to take the latter up.  
         [0040]     In a further embodiment of the invention, sets of stamps, cartilage punchers and nonwoven punchers are provided which are differently configured and adapted to one another.  
         [0041]     By means of this measure, an operating surgeon is able to select, from a plurality of instrument sets, the particular set whose shape and size corresponds to the defect that is to be treated. It has been found that, with three different sizes, it is possible to cover about  90 % of the usual defect sizes.  
         [0042]     It will be appreciated that the aforementioned features and those features still to be explained below can be used not only in the respectively cited combination, but also in other combinations or singly, without departing from the scope of the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0043]     The invention is described and explained in more detail below on the basis of a selected illustrative embodiment and with reference to the attached drawings, in which:  
         [0044]      FIG. 1  shows a perspective view of a stamp of an instrument for ACT,  
         [0045]      FIG. 2  shows a perspective view of a cartilage puncher of an instrument for ACT,  
         [0046]      FIG. 3  shows a perspective view of a nonwoven puncher of an instrument for ACT,  
         [0047]      FIG. 4  shows a highly schematic view of a first step of a method for ACT using an instrument according to the invention,  
         [0048]      FIG. 5  shows a highly schematic view of a second step of the method from  FIG. 4 ,  
         [0049]      FIG. 6  shows a highly schematic view of a third step of the method from  FIG. 4 ,  
         [0050]      FIG. 7  shows a highly schematic view of a fourth step of the method from  FIG. 4 ,  
         [0051]      FIG. 8  shows a highly schematic view of a fifth step of the method from  FIG. 4 ,  
         [0052]      FIG. 9  shows a highly schematic view of a sixth step of the method from  FIG. 4 ,  
         [0053]      FIG. 10  shows a highly schematic view of a seventh step of the method from  FIG. 4 ,  
         [0054]      FIG. 11  shows a highly schematic view of an eighth step of the method from  FIG. 4 ,  
         [0055]      FIG. 12  shows a highly schematic view of a ninth step of the method from  FIG. 4 , and  
         [0056]      FIG. 13  shows a highly schematic view of a tenth step of the method from  FIG. 4 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0057]     In  FIG. 1 , a stamp of an instrument for ACT is designated in its entirety by reference number  10 .  
         [0058]     The stamp  10  has a rod-shaped body  12  with a distal portion  14  and a proximal portion  16 .  
         [0059]     The proximal portion  16  widens to form a handle  18 .  
         [0060]     The distal portion  14  terminates in a plane end face  20  which roughly has the shape of a rectangle with rounded corners. This approximately oval shape is particularly suitable for ACT, since most cartilage defects are in the form of tears, so that in most cases an approximately oval implant has to be used.  
         [0061]     Openings  22  are formed in the end face  20 , these openings  22  being uniformly distributed and in particular being arranged in the area of the circumference. By means of these openings  22 , an implantable nonwoven can be sucked onto the stamp  10 . The arrangement of the openings  22  ensures that the margins of the implantable nonwoven are sucked onto the stamp  10  and adhere firmly thereto. The openings  22  are connected via bores in the body  12  to a first attachment piece  24  and to a second attachment piece  26  at the proximal portion  16  of the body  12  of the stamp  10 .  
         [0062]     The first attachment piece  24  can be connected to a source for an underpressure, for example via a hose. In this way, the openings  22  can be subjected to an underpressure, and an implantable nonwoven can be sucked onto the end face  20  of the stamp  10 .  
         [0063]     The second attachment piece  26  can be connected to a source for a sterile fluid, as a result of which a flow can be generated in the direction of the distal portion  14  of the body  12 . By means of this flow, an implantable nonwoven can be detached from the end face  20  of the stamp  10 . A valve (not shown here) permits switching between the different operating modes.  
         [0064]     In  FIG. 2 , a cartilage puncher is designated in its entirety by reference number  30 .  
         [0065]     The cartilage puncher  30  has a body  32  which is of a tubular configuration. The inner cross section of the body  32  corresponds to the cross-sectional contour of the body  12  of the stamp  10  from  FIG. 1 .  
         [0066]     The body  32  has a distal portion  34  and a proximal portion  36 . The distal portion  34  is ground to form a punch blade  38  that extends about the whole circumference of the body  32 .  
         [0067]     In  FIG. 3 , a nonwoven puncher of an instrument for ACT is designated in its entirety by reference number  40 .  
         [0068]     The nonwoven puncher  40  has a tubular body  42  with a distal portion  44  and a proximal portion  46 .  
         [0069]     The body  42  essentially corresponds in structure and diameter to the body  32  of the cartilage puncher  30  from  FIG. 2 , the distal portion  44  likewise being ground to form a punch blade  48  extending round the whole circumference.  
         [0070]     The punch blade  48  has the same shape and size as the punch blade  38  of the cartilage puncher  30  from  FIG. 2 .  
         [0071]     This dimensioning ensures that the nonwoven puncher  40  punches out an implantable nonwoven which has the same shape and size as the cartilage area punched out by the cartilage puncher  30 .  
         [0072]      FIG. 4  shows a schematic view of a first step of a method for ACT.  
         [0073]     Here, the cartilage puncher  30  is advanced toward a bone  50  which is covered by cartilage  52 .  
         [0074]     The bone  50  is located in the knee joint. The surface of the bone  50  is shown flat for the sake of simplicity only. The bone surfaces in the knee joint are almost exclusively curved bone surfaces.  
         [0075]     The arthroscopic instruments used for insertion of the cartilage puncher  30 , for example an arthroscope for visual monitoring, are likewise not shown, for the sake of simplicity.  
         [0076]     The cartilage  52  has a cartilage defect  54 , here in the form of a loss of cartilage tissue.  
         [0077]     The punch blade  38  is oriented around the cartilage defect  54 .  
         [0078]     The cartilage puncher  30  is now advanced in the direction of an arrow  56  onto the bone  50  and the cartilage  52 . The punch blade  38  is pressed into the cartilage  52  and cuts through it, as a result of which the margins of the cartilage defect  54  are punched out.  
         [0079]      FIG. 5  shows that the punch blade  38  of the cartilage puncher  30  has cut through the cartilage  52  and comes to lie against the surface of the bone  50 .  
         [0080]     The pieces  57  of the cartilage  52  that have been punched out by the punch blade  38  are removed from the cartilage puncher  30  in the direction of an arrow  58  with the aid of a surgical spoon (not shown here).  
         [0081]      FIG. 6  shows a further step of the method for ACT. This step and the following method steps for preparation of an implantable nonwoven can be carried out before, during or after the two method steps described above.  
         [0082]     Here, the nonwoven puncher  40  is moved in the direction of an arrow  59  toward a nonwoven  60  and is pressed into the latter.  
         [0083]     The nonwoven  60  is a pig collagen matrix on which chondrocytes from a patient to be treated have been cultured beforehand in the laboratory. The thickness of the nonwoven  60  corresponds approximately to the thickness of the cartilage  52  that is to be treated. The nonwoven  60  rests on a support  62 , here a metal plate, which is strong enough to offer resistance to the punching operation.  
         [0084]     As will be seen from  FIG. 7 , the punch blade  48  has been pressed into the nonwoven  60  and has cut out an implantable nonwoven  64  from this. As a result of the dimensioning of the nonwoven puncher  40  and of the cartilage puncher  30 , the implantable nonwoven  64  has the same size as the area of the cartilage  52  previously punched out by the cartilage puncher  30 .  
         [0085]     As is shown in  FIG. 8 , the stamp  10  is now introduced into the nonwoven puncher  40  from the proximal direction until the end face  20  of the stamp  10  comes to lie on the implantable nonwoven  64 .  
         [0086]     As a result of the dimensioning of the stamp  10  and of the nonwoven puncher  40 , the stamp  10  is introduced with a snug fit into the nonwoven puncher  40 . This ensures that the end face  20  comes to lie exactly above the implantable nonwoven  64 .  
         [0087]     An underpressure is now applied in the direction of the arrows  68  within bores  66  in the body  12  of the stamp  10 .  
         [0088]     The bores  66  are connected to the openings  22  in the end face  20  of the stamp  10 . By means of this underpressure, the implantable nonwoven  64  that has been punched out beforehand is sucked onto the end face  20  of the stamp  10 .  
         [0089]     When the implantable nonwoven  64  is sucked onto the end face  20  of the stamp  10 , the latter can, as is shown in  FIG. 9 , be withdrawn from the nonwoven puncher  40  in the direction of an arrow  70 , that is to say in the proximal direction. In doing so, the implantable nonwoven  64  is removed from the nonwoven puncher  40  and remains securely adhering to the end face  20  of the stamp  10 . This permits the further handling of the combination comprising stamp  10  and implantable nonwoven  64 , the latter adhering firmly in place.  
         [0090]     The stamp  10  and the adhering implantable nonwoven  64  are now introduced from the proximal direction into the cartilage puncher  30  which is still in place (as shown in  FIG. 5 ) in the cartilage  50 , as will be seen from  FIG. 10 .  
         [0091]     The implantable nonwoven  64  is introduced, as shown in  FIG. 11 , into the prepared cartilage defect and bears on the surface of the bone  50 . Its height means it is approximately flush with the cartilage  52 . In a next step, a flow of fluid is now generated in the bores  66  in the direction of the arrows  74 . This is done here by introducing sterile water. By means of this flow of fluid, an overpressure is generated at the openings  22  and helps detach the implantable nonwoven  64  from the end face  20  of the stamp  10 .  
         [0092]     The stamp  10  is then withdrawn from the cartilage puncher  30  in the direction of an arrow  76 .  
         [0093]     As is shown in  FIG. 12 , the implantable nonwoven  64  remains bearing on the surface of the bone  50 , while the stamp  10  has already been largely withdrawn from the cartilage puncher  30 . In a step following on from the withdrawal of the stamp, the cartilage puncher  30  is now also removed from the body of a patient.  
         [0094]      FIG. 13  shows the situation after completion of the ACT method.  
         [0095]     After removal of the stamp  10  and of the cartilage puncher  30 , only the implantable nonwoven  64  remains in the patient&#39;s body. It now lies flush with the surface of the bone  50  and has approximately the same height as the cartilage  52 . At the places where the blade  38  of the cartilage puncher  30  has penetrated into the cartilage  52 , a small gap  78  still remains where the implantable nonwoven  64  can be bonded to the cartilage  52  by means of fibrin adhesive.  
         [0096]     The cartilage cells present in the implantable nonwoven  64  grow in the course of the healing process and attach themselves to the already existing cartilage  52 . The matrix of the implantable nonwoven  64 , that is to say the pig collagen, is at the same time degraded. After a certain time, the implantable nonwoven  64  is then completely replaced by new cartilage tissue, and the cartilage damage is completely rectified.  
         [0097]     To promote the attachment of the implantable nonwoven  64 , an instrument as described in a parallel German patent application, file no. 10 2005 010 989.6, filed on Mar. 3, 2005, with the title “Medical instrument for performing microfractures in a bone”, can be used to perform “microfracturing” on the bone exposed in  FIG. 5  which document is fully incorporated by reference as part of that description. The clot emerging from the microfractures can distribute within the implantable nonwoven and form cartilage tissue.