Patent RU-2736119-C2 (RU)
Title: Method of making individual articulatory 3d endoprosthesis replacement spacer of knee-joint
Inventor: ALIEV MAMED DZHAVADOVICH
IPC: A61B17/56
Filed: 2020-05-14
Granted: 2020-11-11
Abstract: FIELD: medicine. 
     SUBSTANCE: invention relates to medicine. Method of making personalized articulatory 3-D knee joint prosthesis-spacer consists in the fact that a CT image of the DICOM format is used to extract an image fragment corresponding to the extremity with a previously installed endoprosthesis, spatial-frequency filtration and segmentation of the image with separation of bone tissue surfaces, internal boundaries of intramedullary canals, surfaces of metal implants and areas of bone cement, obtained surfaces are stored in the form of points which are approximated into a plurality of triangles and a three-dimensional file of STL format is obtained and by reverse design on reference points full closed 3D models of the tibial and femoral parts, their assembly and connection units are constructed. That is followed by "virtual fitting" of the spacer endoprosthesis in three-dimensional graphic editors; evaluating the biorelevance of the structure, joint mobility, ease of manufacture and implantation, developing a reinforcing metal-forming part of the prosthetic-spacer, simulating a peak load with construction of stress and strain diagrams by finite element method using modern CAD. After obtaining the final model of the endoprosthesis spacer in scale 1:1, it is divided into parts and printed on 3D printer. Obtained master model of the future implantable spacer is glued, post-processing of the surface is performed and poured with high-temperature bioinert silicon. In the model there are process recesses for centralization of metal frames from medical stainless steel, which after installation of a metal frame are accumulated with bone cement and before operation. Obtained molds and metal bases undergo sterilization; volume of 3D model is used to calculate the required amount of bone cement. During the revision surgery, the knee joint arthrotomy is performed, the endoprosthesis components are removed, the periprosthetic cavity is subjected to mechanical and medicamentous treatment, required amount of pre-calculated volume of bone cement impregnated with antibiotic is kneaded, method includes installation of a spacer metal frame into a silicone mold, during polymerization, silicone forms of spacer components are filled, after solidification of bone cement, the spacer elements are removed from the molds and the spacer surface is finally treated. Elements of the spacer are fixed in the canal of the femoral and shin bone using bone cement according to the coaxiality principle of the topographic reference points of the bone, according to the individual anatomy. Elements of the spacer are connected to each other by means of congruent surfaces, restoring the right axis of the lower extremity, spacer surfaces are additionally coated with gentamycin impregnated with biosponges, a vacuum, a drainage system is installed, the wound is closed tightly. 
     EFFECT: invention provides manufacturing of endoprosthesis spacer in exact accordance with individual dimensions of removed endoprosthesis and anatomical shape with preservation of quality condition of bones in points of fixation of spacer elements, preserving the functional area of the remote joint, maintaining partial limb support ability, making spacer components during operation, facilitating the endoprosthesis installation at the second stage of re-endoprosthesis replacement, prolonging the use of the endoprosthesis spacer, reduced intensity of osteopenia of bone structures of limb after removal of endoprosthesis, maintaining the functional potential of the joint after the first stage of re-endoprosthesis replacement, developing a program of restorative treatment after the second stage of re-endoprosthesis replacement. 
     1 cl, 1 ex, 14 dwg