Armin Nikzad, BSc; Farid Abbaszade, MSc; Zahra Saghaei, MSc; Soheil Mehdipoor, MD; Firooz Madadi, MD; Morad Karimpoor, PhD
Abstract
Background: Total knee arthroplasty is an accepted method for treatment of osteoarthritis of the knee. Measuring the distal femoral rotation is one of the most important problems in such operations. In the conventional 2D method, measuring the angle is based on CT scan images but these methods usually ...
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Background: Total knee arthroplasty is an accepted method for treatment of osteoarthritis of the knee. Measuring the distal femoral rotation is one of the most important problems in such operations. In the conventional 2D method, measuring the angle is based on CT scan images but these methods usually contain errors. In this study, the three-dimensional measurement of the aforementioned angle was investigated.
Methods: In this research, using CT scans and 3D modeling, 3D lower extremity models of 40 patients were extracted. The rotation of distal femur was measured for plane perpendicular to the anatomical and the plane of mechanical axis of femur. Four axes were drawn on these planes using anatomical landmarks: posterior condylar line (PCL), anatomical and surgical transepicondylar line (ATEA+STEA), and the Whiteside line (WL).
Results: The mean difference of these measurements on the plane perpendicular to the mechanical axis of the femur, between PCL and WL, STEA, ATEA was 3.41, -1.31, 5.53; and angles on the plane perpendicular to the anatomical axis of femur were -0.74, -1.26, and 5.67, respectively. In addition, Bland-Altman diagram was plotted between every two measurements and no relationship found, except for STEA and ATEA.
Conclusions: The measurements between PCL, ATE, and STEA are not affected by the plane on which these measurements are carried out on, except for the 4 degrees difference present in WL axis. With a greater sample size and proper grouping, some relationship might be found between the aforementioned axes.
Mina Iravani, MSc; Farzam Farahmand, PhD; Soheil Mehdipour, MD
Abstract
Background: High tibial osteotomy (HTO) is a common surgical procedure for treatment of patients with varus malalignment. The success rate of the procedure is strongly dependent on the quality of correction. The purpose of this study was to simulate the HTO in a patient with varus deformity in order ...
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Background: High tibial osteotomy (HTO) is a common surgical procedure for treatment of patients with varus malalignment. The success rate of the procedure is strongly dependent on the quality of correction. The purpose of this study was to simulate the HTO in a patient with varus deformity in order to explore the interactions between the wedge angle, the mechanical axis, and the knee joint configuration.
Methods: A finite-element model of the knee joint of a patient with varus deformity was developed. The geometry was obtained using the whole limb CT scans and the knee MR images. The bones were assumed as rigid bodies, the articular cartilage and the meniscus as elastic solids, and the ligaments as nonlinear springs. A 600N force was applied at the femoral head in the line of the mechanical axis and the resulting knee configuration was investigated. The HTO was simulated by insertion of wedges with different angles beneath the tibial plateau and application of the resulting alteration of the loading axis in the model.
Results: The results indicated that the actual change of the mechanical axes was always smaller than was predicted by a geometric pre-planning approach that does not consider the effect of soft tissue on the post-operative configuration of the knee joint.
Conclusions: It was suggested that subject-specific models can improve the results of the HTO by simulating the operation before surgery and determining the optimal wedge angle that locates the mechanical axis in the middle of the knee.
Pooneh Dehghan, MD; Zahra Saghaei ,MSc; Farid Abbaszadeh, MSc; Morad Karimpour, PhD; Soheil Mehdipoor, MD
Abstract
Background: Femoral neck anteversion is usually measured on the 2-dimensional (2D) images on CT slices. The 3D method uses 3-dimensional model of the femur reconstructed from CT scan images. The aim of this study was to compare these two methods of measurement of femoral ante-version. Methods: In ...
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Background: Femoral neck anteversion is usually measured on the 2-dimensional (2D) images on CT slices. The 3D method uses 3-dimensional model of the femur reconstructed from CT scan images. The aim of this study was to compare these two methods of measurement of femoral ante-version. Methods: In a retrospective study, CT scans of 40 patients (6 men, 34 women) of a teaching hospital in Tehran-Iran were included. Both methods use the same anatomical landmarks, i.e. center of femoral head, femoral neck axis and posterior apex of the femoral condyles. In the 3D method, anteversion angle was measured on a plane perpendicular to the anatomical axis of femur. Whereas in the 2D method the measurement is performed on CT scan slices.Results: Mean anteversion was found to be 9.8 for the 2D and 16.11 for the 3D method. Bland-Altman plot shows that the difference between the two methods is significant.Conclusions: This difference between 2D ad 3D measurement of femoral anteversion may be depend on the level of the selected CT slices, patients positioning during CT examination, and the impact of the deformity. The 3D method eliminates obvious sources of error, namely identifying landmarks and individual orientation of femur. Due to the lack of any gold standard there is a need to further review and study the measurement of this angle.
Fatemeh Farshidi; Nasser Fatouraee; Soheil Mehdipoor; Mahmood Borhan Shams
Abstract
Background: The knee anterior cruciate ligament (ACL) rupture is one of the common damages among athletes. To compensate for ACL deficiency, ligament reconstruction is done to recreate the function of ACL. The aim of this study was to investigate the effect of single bundle and double bundle ACL reconstruction ...
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Background: The knee anterior cruciate ligament (ACL) rupture is one of the common damages among athletes. To compensate for ACL deficiency, ligament reconstruction is done to recreate the function of ACL. The aim of this study was to investigate the effect of single bundle and double bundle ACL reconstruction on the compression stresses of menisci. Methods: We simulated 4 cases with geometrical modeling: intact knee sectioned ACL, single and double bundle ACL reconstruction. We then built a three dimensional finite element geometrical model of knee from MRI images of normal knee. First, the bone and soft tissue points cloud models and then the geometrical models were built. The bones were modeled as rigid bodies, articular cartilage, menisci as linear elastic and ligaments as nonlinear springs. The loading condition was application of a 50 N anterior load to tibia. Results: The maximum compression stress was similar to intact knee and was lower than two reconstruction cases. Distribution of compression stress wasn’t similar to intact knee but in reconstruction cases, it was similar. The contact areas in intact knee were higher in lateral section, while in reconstructed knees were higher in medial section of the knee. Conclusions: ACL removal changes the distribution of compression stress of menisci in comparison with intact knee, single bundle and double bundle reconstruction. Furthermore evaluating contact areas in these four cases showed that removing the ACL may lead to decrease in the contact area but reconstruction may compensate for this.
