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Objective To determine the angles of trochlear line(TL), antero-posterior line (APL) and posterior condylar line (PCL) with clinical epicondylar axis (CEA), analyze the variability difference in 3 axes relative to CEA. Methods The right knees in 36 patients with knee osteoarthritis (gradeⅣ) and who had underwent total knee arthroplasty were enrolled in this study, 11 male patients aged 60-81 (69.1 ± 6.3) years and 25 female patients aged 33- 85(67.7 ± 12.2) years. All of right knees were scanned using computed tomography. The angles between the CEA and each of the 3 axes (TL, PCL, APL) were measured using software. Results The angles of TL-CEA, APL-CEA and PCL-CEA was (6.10 ± 3.22)°, (85.80 ± 2.86)°and (2.70 ± 1.80)°. The F tests showed that the angel invariability between the TL and CEA the APL axis (α=0.58) or the PCL (α=0.28) for referencing the CEA had no significant differences. Conclusions The TL can be a relatively reliable reference axis to determine rotational alignment of the femoral component similar to PCL and APL.
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Objective To compare the discrepancy and consistency in mechanical axis and component position measured by electromagnetic navigation and radiograph in total knee arthroplasty (TKA)to assess whether the navigation system can be used as a substitute for radiograph.Methods A perspective study was performed on 40 cases (61 knees) undergone primary TKA under electromagnetic navigation from July 2006 to December 2006.There were 4 males and 36 females,at a mean age of (66.9 ±8.1) years (range,58-79 years).Mechanical axis angle,distal femoral and proximal tibial cut slope in coronal view (angles cα,β) were recorded both pre-and post-operatively with an intraoperative navigation system and compared against the mechanical axis angle,coronal femoral and tibial slope (angles α,β)measured via full-length radiograph of the lower limb preoperatively and at postoperative 3 months.Consistency in measurement of the same parameters with the two methods was assessed using intraclass coefficiency correlation (ICC).Results Mechanical axis determined by navigation and radiograph showed a mean valgus angle of 9.60° and 9.99° preoperatively and of 1.23° and 1.64° postoperatively,but the two pair parameters revealed no significant differences in the non-parametric test.Mean angle α determined by navigation and radiograph was 89.98° and 88.96° respectively (P ＜ 0.05),and mean angleβ was 90.21 ° and 89.59°respectively (P ＜ 0.05).With deviation value ≤3°,ICC for pre-and post-operative mechanical axis angles,angle α and angleβ was 0.887,0.754,0.632,0.640 respectively.Conclusions Within the acceptable range of deviation,intraoperative navigation data can reflect the pre-and post-operative mechanical axis and prosthesis position evaluated by radiograph.However,the advantages over the consistency of the two measurement methods rest with the evaluation of pre-and post-operative mechanical
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Objective To compare the lower limb alignment and prosthesis position after total knee arthroplasty (TKA) with or without using electromagnetic navigation.Methods Sixty-four patients (100 knees) underwent TKA under electromagnetic navigation,while 62 patients (100 knees) underwent conventional TKA.Three months after operation,the mechanical axial line angle and prosthesis position (angels α,β,γ) were measured via the full-length radiograph of both lower limbs and anteriorposterior and lateral Xrays of the knee.Results The average mechanical axial line angle and angle α were 1.20°±1.92°and 89.33°±1.64° in navigation group,respectively,and 2.31°±2.25° and 88.68°±2.57° in conventional group.And the differences were significant with regard to the above two indexes between two groups.The average angle β and angle γ were 89.64°±1.47° and 90.86°±2.37° in navigation group,respectively,and 89.26°±2.05° and 90.59°±3.44° in conventional group.However,the differences were not significant with regard to the above two indexes between two groups.After operation,mechanical axial line angle error was within ±3°in 86％ of patients in navigation group,while in 79％ of patients in conventional group; there was no significant difference between them.The angle α error was within 90°±3° in 92％ of patients in navigation group,while in 77％ of patients in conventional group; there was significant difference between them.However,there were no significant differences in percentage of patients whose errors of angle β and angle γ were within 90°±3° between two groups.Conclusion With using electromagnetic navigation in TKA,more precise prosthesis position and the mechanical axis can be achieved compared with the conventional technique.And its advantages mainly contribute to the coronal plane of the femoral side rather than the tibial side.
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PURPOSE: We wanted to evaluate the mechanical strength of proximal tibia as resection distance increased from the joint surface. MATERIALS AND METHODS: We obtained the CT images of twenty knee osteoarthritis patients undergoing total knee arthroplasty. The finite element models were created based on the computed tomography images. The 8-node hexahedron element was made from BIONIX(TM) (CANTIBio. Co, Suwon, Korea), which is automatic mesh generation software program. The finite element model of the proximal tibia was resected at 6 mm, 8 mm, 10 mm, 12 mm, 15 mm and 18 mm from the lateral joint surface. A 1% strain rate was applied to a model by using HyperMesh(TM) software (Altair Engineering. Inc, Seattle, USA). The ultimate stress was calculated from the finite element analysis with using ANSYS 9.0 (ANSYS. Inc, Orlando, USA). RESULTS: The mean ultimate stress was 906.84 MPa, 877.22 MPa, 895.93 Mpa, 852.70 MPa, 742.90 Mpa and 585.51 Mpa at the 6 mm, 8 mm, 10 mm, 12 mm, 15 mm and 18 mm resection levels. As compare to the 6 mm resection level, the bone strengths at 15 mm and 18 mm were decreased with statistical significance (15 mm: p=0.005, 18 mm: p=0.000). CONCLUSION: The ultimate stress was decreased as the resection distance increased from the joint surface. But within a 12 mm resection distance from the lateral condyle articular surface of the tibia, the ultimate stress was not significantly decreased (p>0.05).