DE3933459A1 - Biomedical implant production equipment - uses computer tomographic image to generate implant profile for component mfr. - Google Patents

Abstract

A computer controlled reconstruction process for biomedical objects, e.g. computer tomography, is used to determine and produce implants. The implant is determined on the basis of a number of linked elements (1). The complete process is based upon five different steps. The primary data are provided by a computer tomographic image and a computer is used to post process the data into a form usable by a machine tool. Typically, a laser cutter or milling machine is used for mfr. USE/ADVANTAGE - Extensively fragmented fractures. Tumour resection. Allows 3-d implantation by robot.

Description

Computer-aided reconstruction of biomedical objects on the basis of imaging Medical procedure (especially computer tomography, CT) is currently still Subject of the research and is only partially commercially available. The aim of the reconstruction is to make individual, already made before the operation of a patient adapted implants as replacements as well as individually made models for Operation planning. This means better fits and shorter operating times possible, obvious advantages over conventional methods in which individual Implants are not available, but only roughly prefabricated or which ones with Standard dimensions. The use of the biocompatible meant in the context of this invention Materials are said to cause the original bone to become biocompatible over time Implant can grow into it. With this goal, completely new aspects arise, so that the combination of the known methods with these innovations to the one written here Invention leads.

In the computer-aided production, the objects are made from stacked disks, whose contours correspond to the object contours in the computer tomogram. From the Grayscale matrices of the CT images are obtained computer-aided by edge detection Coordinates of contour lines that indicate the transition from bone material to soft tissue represent. If necessary, the coordinates are supplemented with a graphic editor or changed where, for example, osseous defects due to comminuted fracture replaced the original Have changed bone shape. These coordinates become computer-aided control used by tool (NC) machines. Preferably one is used for this Laser cutting machine (disk modeling). In another procedure, the serve Object contours as support data for surfaces, which are then traverse paths for milling machines can be derived (surface modeling).

Recent experience shows that there is no biocompatible material available yet that can be easily produced using the surface modeling method or the Manufacturing can be processed: Large blocks of sintered hydroxyapatite are, for example almost always cracked inside so that the blank breaks apart during processing.  

Smaller blocks, on the other hand, can be produced in sufficient quality. You are enough homogeneous and firm.

This is where the invention comes in: it rejects the approach of producing an object from a block wool. Instead, building blocks are used that are like masonry to one Overall object can be built. A first goal is to make a blank as before - but now out small building blocks and therefore inherently solid and not cracked - to get the same as before Post-processing is supplied, for example, the machining removal, so that from the Blank an implant that is true to the original is created. The second and with this invention The main aim is to manufacture the individual building blocks in such a way that the subsequent post-processing is not necessary. It therefore becomes the principle of slice modeling used, and the disks are still divided into building blocks, which then become one Overall object can be built. The main advantage of building a biocompatible Implant from building blocks is that in this way large objects without internal cracks can be produced. It is then essential - and characteristic of the invention - that first, the association is true to the original (i.e. without shifting the coordinates of the Disks to each other) and secondly is built to remain stable.

In the basic idea of the invention, both requirements can be achieved with the aid of the Lego principle. Techniques such as tongue-and-groove or dimpled counter-knobs are also auxiliary techniques so that the disks do not move against one another: on one side of a disk, parallel springs are to be provided and the corresponding grooves on the other side. If the disk is in a Cartesian x, y coordinate system, then two disks whose grooves and tongues interlock in one direction (for example x direction) can no longer be shifted against one another. So that the displacement is also prevented in the y-direction, grooves and corresponding springs should also be provided perpendicular to the spring assembly already mentioned. The springs then degenerate into square nubs ( 1 ) ( Fig. 1).

The technology used in this way prevents the panes from moving in the x and y directions their assembly. When assembled, the invention is as follows characteristic procedure:

The edge of a CT image with, for example, a 512 × 512 gray value matrix forms the limits of the local, u, v coordinate system. So that the local u _i , v _{i of} the image series do not shift in the global coordinate system x, y, z, the edges need only be made to coincide. This then also applies to the slices produced in accordance with the CT images. After cutting the contour ( 14 ), there is a model disc ( 2 ) and a frame disc ( 3 ) per CT slice ( Fig. 2).

The model panes can be easily assembled without moving, because they are one Reference system recognizable to the human eye is missing. It is different with the Frame panes: Your edges just need to be aligned, as mentioned, what is trivial in terms of manageability.

The overall structure is then as shown in Figure 3 as follows: First, a frame disc r ₁ ( 4 ) consisting of building blocks ( 13 ) is pressed with its grooves onto the springs of a base plate ( 5 ) and the corresponding model disc m _{1 is} fitted. Then the frame disc r ₂ ( 6 ) is stacked with its edge flush on the frame disc r ₁ and the corresponding model disc m _{2 is} fitted therein again. The same procedure is followed for the other disks r _i , m _i to r _n ( 7 ), m _n ( 8 ). Then it is ensured that the model disks consisting of building blocks ( 13 ) are not displaced in either the x or the y direction. Figure 3 is now to illustrate the principle. In practice, a finer division of the disks into building blocks and their knobs is the rule.

After removing the frame panes, the original model remains. The Frame panes can be removed, for example, by a melting process when the The materials of the model and frame panes have different melting points. For the purpose of Later separability, the panes have to be made twice: First, from biocompatible material for the model window and secondly made of removable (for example meltable) material for the frame pane.

According to what has been said above, implants are created according to disk modeling, which is known per se / 1 /. What is new is the use of the tongue and groove principle, which is used together with removable frame washers as an auxiliary technique for coordinate consistency. In addition to these auxiliary techniques, the core of the invention is the division of the disks into building blocks. For example, a square disk of 100 × 100 × 3 mm is divided into 100 pieces 10 × 10 × 3 mm in size. A method is only possible on the basis of this idea, since it enables large implants to be built from the currently available biocompatible material. Because small building blocks made of this material are sufficiently strong, but large ones are not.

Surprisingly, there is another advantage: If you partially manufacture blocks hollow, there is the possibility of adapting the specific weight from the biocompatible (replacement) material to the (original) bone material. The aim is to find a replacement that is as true to the original as possible. This applies to the geometry as well as to the material, which is why the adjustment of the specific weight - for example in the case of end implants - is of crucial importance. The biocompatible hydroxyapatite, for example, has a higher specific weight than bone substance. The blocks can be made with cavities ( 9 ), for example, by providing deeper grooves than filling the corresponding springs ( Fig. 4).

The use of the tongue and groove principle has the welcome side effect that the Discs are thus very easily fixed for the cutting process and after the cutting process can be easily removed again, which was previously the case with very thin panes has been unsatisfactorily resolved, which is why the use of thicker washers has been instructed. However, very thin disks are desirable for smoother surfaces are caused by a small slice increment in the CT scan or by subsequent Interlayer interpolation won.

The individual blocks ( 13 ) are pressed with their grooves onto discs ( 10 ) corresponding to CT slices onto the springs of a holding plate ( 11 ), so that they are fixed for the cutting process. The holding plate itself is held in place by the claws ( 12 ) on the travel table of a laser cutting machine ( Fig. 5). It is driven with such energy and focus that the bone contours are cut within the discs, but the holding plate is spared (or only slightly scratched). It must not be cut, otherwise its holding function would be lost. The holding function is necessary, as otherwise the panes fall off the travel table in an uncontrolled manner or small structures are sucked away when using a suction device.

Building blocks that are offset from pane to pane can improve the stability when later building the Increase 3D model or implant. After cutting, they are made of building blocks existing disks stacked as discussed above. The stability can in many cases already sufficient if only models for illustration or operation planning are necessary are. Even greater stability is required for implants, which is supported by an additional one Gluing takes place. The additional gluing then brings about a durability that the even surpass homogeneous materials. (This effect is, for example, from Glued wood boards ago.) The components are fixed by their grooves and tongues pressed against each other so that no other, the rapid construction of the implant retarding device for fixing the components during the setting of the adhesive must be provided. This is another advantage of the structure after the tongue and groove Principle.  

Surprisingly, there is another aspect after the above considerations:

So far, if artificial biocompatible material was assumed, the transferred considerations with advantage also to natural material. Namely whenever there are not enough large blanks available from one piece.

The construction and stabilization of 3D disc models is with that Method and solved with the arrangement described.

However, it was assumed that the setup would be done manually. This is where Bottleneck of the overall process, that with its sub-components, namely CT first, second Contour detection, thirdly 3D disk modeling, fourthly production from building blocks computer-based and fully automatic. In the fifth and final step, the Process chain through the use of a robot to form an integrated overall system closed, in which manual activity is no longer necessary. Because the coordinate system Known internally and consistently in the computer, you need it when building with one computer-controlled robots in principle also no frame panes. You can (and for that In general, they must also serve as a retaining wall during the construction. The Grooves / tongues of the blocks, which were originally only used to fix the blocks with each other are now also used as attack bodies for the robot grippers.

Claims (38)

1. Arrangement for individual implant build-up from biocompatible building blocks, ie manufacture of replacements, in particular of bone parts, characterized in that the arrangement comprises the following components:

• a) an image generator for generating the primary data representing the organ,
• b) a converter for converting the primary data into travel data of machine tools,
• c) a tool (NC) machine that produces sections of the implant,
• d) a mechanism for joining the sections into an implant.

2. Arrangement according to claim 1, characterized in that the imager is a computer Tomography (CT) device is. 3. Arrangement according to claim 1, characterized in that the converter is a computer, on which a program system runs, which corresponds to the claims mentioned below generated specific data. 4. Arrangement according to claim 1, characterized in that the NC machine Laser cutting machine is. 5. Arrangement according to claim 1, characterized in that the NC machine Milling machine is. 6. Arrangement according to claim 1, characterized in that the implant structure made of NC cut sections are made that resemble Lego blocks so that they look like Lego models build up.   7. Arrangement according to claim 1-6, characterized in that the converter data from the CT generates the transition of the bones to the soft tissue, d. H. Contour lines, generated. 8. Arrangement according to claim 1-6, characterized in that the transducer the contour lines arithmetically pulls downwards so that disks are created. 9. Arrangement according to claim 1-6, characterized in that the converter in the disks Divided sections that are sufficiently small that they are still made of biocompatible material can be won. 10. Arrangement according to claim 1-6, characterized in that the converter such Traverse paths generated that the sections grooves and tongues on the top and bottom received so that the sections can later be joined together like burdock. 11. The arrangement according to claims 1-6, characterized in that the regulation on Implant structure provides model and frame discs. The frame panes serve as Stencils so that an exact construction is enforced. The construction can then be done manually and done by poorly trained personnel. 12. The arrangement according to claim 1-6, characterized in that for the implant structure Robot is called in, which is controlled by the data available in the computer in such a way that the sections are built up exactly in x, y, z position. 13. Method for individual implant build-up from biocompatible building blocks, ie production of replacements, in particular of bone parts, characterized in that the method comprises the following components:

• a) an image generator for generating the primary data representing the organ,
• b) a converter for converting the primary data into travel data of machine tools,
• c) a machine tool that produces sections of the implant,
• d) a mechanism for joining the sections into an implant.

14. The method according to claim 13, characterized in that the imaging device Tomography device is. 15. The method according to claim 13, characterized in that the converter is a computer, on which a program system runs, which corresponds to the claims mentioned below generated specific data. 16. The method according to claim 13, characterized in that the NC machine a Laser cutting machine is. 17. The method according to claim 13, characterized in that the implant structure made of NC cut sections are made that resemble Lego blocks so that they look like Lego models build up. 18. The method according to claim 13, characterized in that as an imaging method Anything is possible from which coplanar contour lines can be derived. 19. The method according to claim 13, characterized in that each machine tool can be used that move according to the geometry of the contour and sections can. 20. The method according to claim 13, characterized in that the converter data from the CT generates the transition of the bones to the soft tissue, d. H. Contour lines, generated. 21. The method according to claim 13, characterized in that the transducer the contour lines arithmetically pulls downwards so that disks are created. 22. The method according to claim 13, characterized in that the converter in the disks Divided sections that are sufficiently small that they are still made of biocompatible material can be won. 23. The method according to claim 13, characterized in that the implant biocompatible sections. 24. The method according to claim 23, characterized in that the biocompatible sections in their geometry based on the Lego principle.   25. The method according to claim 15 and 24, characterized in that the converter such Traverse paths generated that the sections with grooves and tongues on the top and bottom be made so that they build up like a burdock to an overall association to let. 26. The method according to claim 23, characterized in that the sections as in one Masonry are offset, so that an increased overlap Stability results. 27. The method according to claim 23, characterized in that the sections with biocompatible glue are put together so that the overall dressing is stable receives, which is not inferior to homogeneous material from a block, but in many cases even surpasses. 28. The method according to claim 23, characterized in that the individual building blocks be made that with the overall structure evenly distributed cavities arise with the goal of achieving the same specific weight as that of the bone to be replaced. 29. The method according to claim 25 and 28, characterized in that the cavities arise from the fact that the grooves of the blocks are deeper than that fill in the appropriate pen. 30. The method according to claim 13, characterized in that when building quadrangular Slices are used that have their outer edge according to the CT matrix (for example 512 × 512 pixels). 31. The method according to claim 13 and 30, characterized in that within the square slices will be cut contours, making the transition of the bones too Represent soft tissues. The model disc is then created inside. It is surrounded by the frame disc, which serves as a template when building the model or implant. 32. The method according to claim 31, characterized in that the frame discs prevent the model panes from being set up so that anyone who is not used to the model Can set up exactly and safely. 33. The method according to claim 13, characterized in that the implant structure Parts are made whose position in space is known to the computer-internal model, so that  the computer can transfer this position to a robot, which then divides the sections into one Comprehensive association. 34. The method according to claim 13, characterized in that the sections with springs (Knobs) are provided, which serve as an attack body for gripping fingers of a robot. 35. The method according to claim 15 and 16, characterized in that the converter the data interpolated in such a way that the outer sections of a disc are so inclined at their edges be that a polyhedral instead of one caused by the disk technique stair-step surface is created. 36. The method according to claim 31, characterized in that the entirety of the Frame panes, which can also be understood as a supporting form, according to this Intended use is thermally removed (melted). 37. The method according to claim 31, characterized in that the entirety of the Frame panes, which can also be understood as a supporting form, according to this Purpose is removed chemically or mechanically. 38. Arrangement and method according to claims 1-37, characterized in that the same In this way, models were also produced for the purpose of preoperative planning and simulation can be. Appropriate materials can then be used for models, such as for example wood, acrylic glass.