Regarding TKA, patient specific cutting guides (PSCG), which have the same fitting surface with patient's bones or cartilages and uniquely specify the resection plane by fitting guides with bones, have been developed to assist easy, low cost and accurate surgery. They have already been used clinically in Europe and the USA. However little has been reported on clinical positioning accuracy of PSCG. Generally, the methods of making PSCG can be divided into 3 methods; construct 3D bone models with Magnetic Resonance (MR) images, construct 3D bone models with Computed Tomography (CT) images, and the last is to construct 3D bone models with both MR and CT images. In the present study, PSCG were made based on 3D bone models with CT images, examined the positioning accuracy with fresh-frozen cadavers. Two fresh-frozen cadavers with four knees were scanned by CT. Image processing software for 3D design (Mimics Ver. 14, Marialise Inc.) was used to construct 3D bone model by image thresholding. We designed femoral cutting guides and tibial cutting guides by CAD software (NX 5.0, Siemens PLM Software Co.). CT free navigation system (VectorVision Knee, BrainLab, Inc.) was used to measure positioning error. Average absolute value of positioning error for each PSCG was derived.Introduction
Materials and Methods
ROBODOC is a well known tool for a computer assisted arthroplasty. However, the incision tends to enlarge with the system because of the restriction of range of motion. We have developed the robot system for minimally invasive arthroplasty. This report shows the accuracy of our system composed of original planning software, navigation and bone cutting robot. We took the DICOM data of cadaver knees from computed tomography. The data were transferred to the workstation for planning. Matching points for registration and cutting planes were determined on the planning software. Cutting tool was the 6th robot which was able to recognize the locations of its apex and the cadaver knee with navigation system. We made five planes for TKA and two planes for UKA on femur. Then we made one plane on tibia. We evaluated the accuracy by measurement the location of cutting plane under navigation system and by CT data. The registration errors of femur and tibia were less than 1.0mm about cadaver knees. The errors of cutting planes were 1.3 mm about the distal end of femur and 0.5 mm about the proximal end of tibia. The accuracies of the angles of cutting planes were 1.9 degrees and 0.8 degrees compared to the mechanical axis. The errors of anterior and posterior plane of femur were increased compared to the distal plane. It was because the accuracy of registration were correct in axial direction but was not satisfied in rotational direction. The error was considered by the location of points which decided the rotation alignment. We will make effort to minimize the errors of registration and put it into practical use as soon as possible.
The aim of this study was to report a 3 year follow up of vitamin E add polyethylene in total knee arthroplasty. UHMWPE powder (GUR1050) was mixed with 0.3% of vitamin E before consolidation by direct compression molding. The vitamin E added UHMWPE was applied to the articular surface and patella in 65 patients (mean age, 69.6 years). Joint fluid concentrations of tocopherol and matrix metalloproteinase 9 were measured in vitamin E added UHMWPE cases one year after surgery, and were compared to those of conventional UHMWPE cases and osteoarthritis patients. Concentrations of α-tocopherol and γ-tocopherol were measured by using HPLC with ultraviolet-visible wavelength detection. Concentrations of matrix metalloproteinase 9 were detected by using enzyme immunoassay. The Average Knee Society score were 91.7(clinical) and 76.7(functional). There were three failures (1 supracondylar fracture, and 2 skin necrosis). The average concentrations of α-tocopherol were 281.8μg/dL (10 cases) in the vitamin E group, 371.8μg/dL (15 cases) in the conventional group, and 317.8μg/dL (46 cases) in the osteoarthritis group. There were no significant differences among three groups. The average concentrations of γ-tocopherol were 43.4μg/dL in the vitamin E group, 52.3μg/dL in the conventional group, and 49.8μg/dL in the osteoarthritis group. There were no significant differences among three groups. The average concentrations of matrix metalloproteinase 9 were 83.2 ng/mL in the vitamin E group, 78.4 ng/mL in the conventional group, and 17.4 ng/mL in the osteoarthritis group. There was no significant difference between the vitamin E group and the conventional group. However, The matrix metalloproteinase 9 concentrations of the osteoarthritis group were significantly lower than others. No cases exhibited measurable polyethylene wear or osteolysis and also no abnormal values relating to vitamin E on joint fluid examinations. At three year follow-up, vitamin E added polyethylene demonstrated the safe use for the human body.
