Personalized orthopedic implant CAD model generation
View Patent ↗A computer assisted method creates accurate CAD/CAM models of custom orthopedic implants is provided. Information about bone geometry is acquired through medical imaging such as CT image scans. The desired bone surface region is extracted as a polygonal mesh after processing the 3D images. A smooth and accurate B-Spline surface is fitted to the polygonal mesh that is thickened to a solid CAD model. A patient-specific customized implant is manufactured from the obtained CAD model. The patient-specific customized implant is implanted in a patient by a surgeon in an operating room. A processor based system to generate a CAD/CAM file of the patient-specific customized implant and a manufacturing system enabled to manufacture the implant from the CAD/CAM file are also disclosed.
1. A method of making an implant from an image of a bone, comprising:
a processor receiving image data of the image of the bone;
the processor segmenting a desired bone from the image data to create a segmentation of the desired bone;
the processor creating a polygonal mesh from the segmentation of the desired bone;
the processor extracting a part of the polygonal mesh corresponding to an implant region;
the processor parameterizing the part of the polygonal mesh so that every vertex therein is associated with two parameter values;
the processor resampling the polygonal mesh to generate a grid of 3D points spaced in a predetermined distance in parametric domain;
the processor fitting a B-spline surface to the grid using a least squares process, wherein involves minimizing
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the processor sending a computer-aided manufacturing (CAM) file based on the B-Spline surface fitted to a manufacturing machine; and
the manufacturing machine forming the implant based on instructions derived from the CAM file.
2. The method of claim 1 , comprising creating a solid computer-aided design (CAD) model from the B-spline surface.
3. The method of claim 2 , comprising adding assembly features to the CAD model.
4. The method of claim 3 , wherein the assembly features comprise one or more assembly pins.
5. The method of claim 3 , comprising manufacturing the implant using a CAM system.
6. The method of claim 1 , wherein the polygonal mesh is created using a Marching Cubes process.
7. The method of claim 1 , wherein the polygonal mesh is created using an Afront process.
8. The method of claim 1 , wherein the least squares process is weighted.
9. The method of claim 1 , comprising smoothing the surface.
10. A system for making an implant from an image of a bone, comprising a processor and a memory, wherein the processor segments desired bone from the image stored in the memory to create a segmentation of desired bone; creates a polygonal mesh from the segmentation of desired bone; extracts a part of the polygonal mesh corresponding to an implant region, parameterizes the part of the polygonal mesh so that every vertex is associated with two parameter values; resamples the polygonal mesh to generate a grid of 3D points spaced in a predetermined distance in parametric domain; and fits a B-spline surface to the grid using a least squares process, wherein the processor minimizes
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where w k is a weighting coefficient, S(u k , v k ) is a surface, P k are sample points, λ is a smoothing parameter, and S uu , S uv and S vu are the second derivatives of the surface S(u k , v k ), sends a computer-aided manufacturing (CAM) file based on the B-Spline surface fitted to a manufacturing machine; and the manufacturing machine form the implant based on instructions derived from the CAM file.
11. The system of claim 10 , comprising a computer-aided design (CAD) machine that creates a solid CAD model from the B-spline surface.
12. The system of claim 11 , comprising adding assembly features to the CAD model.
13. The system of claim 12 , wherein the assembly features comprise one or more assembly pins.
14. The system of claim 12 , comprising manufacturing the implant using a CAM system based on the CAD model.
15. The system of claim 10 , wherein the polygonal mesh is created using a Marching Cubes process.
16. A method for making a patient specific implant, comprising:
taking an image of at least a portion of a patient's bone;
a processor receiving the image data of the image of the patient's bone;
the processor segmenting a desired bone from the image data to create a segmentation of the desired bone;
the processor creating a polygonal mesh from the segmentation of the desired bone;
the processor extracting a part of the polygonal mesh corresponding to an implant region;
the processor parameterizing the part of the polygonal mesh so that every vertex therein is associated with two parameter values;
the processor resampling the polygonal mesh to generate a grid of 3D points spaced in a predetermined distance in parametric domain;
the processor fitting a B-spline surface to the grid using a least squares process, wherein involves minimizing
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smooth
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k
=
0
r
w
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k
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vv
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u
k
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v
k
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where w k is a weighting coefficient, S(u k , v k ) is a surface, P k are sample points, λ is a smoothing parameter, and S uu , S uv and S vu are the second derivatives of the surface S(u k , v k );
the processor sending a computer-aided manufacturing (CAM) file based on the B-Spline surface fitted to a manufacturing machine; and
the manufacturing machine forming the implant based on instructions derived from the CAM file.
17. The method of claim 16 , comprising implanting the patient specific implant in the patient.
18. The method of claim 16 , wherein the CAM system manufactures the customized medical implant from a preformed implant.