[Correction of a deformity of the proximal end of the tibia with simultaneous restoration of movements in the knee joint].
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A new three-dimensional (3D) method of evaluating the joint space from fast GRE MRI has been developed that allows the reconstruction of the two dimensional (2D) distance map between the femur and the tibia bone plates. This method uses the MRI data, an automated 3D segmentation, and an unsupervised joint space extraction algorithm that identify the medial and lateral compartments of the knee joint. The extracted medial and lateral compartments of the tibia-femur joint space were analyzed by 2D distance maps, where visual as well quantitative information was extracted. This method was applied to study the dynamic behavior of the knee joint space under axial load. Three healthy volunteers' knees were imaged using fast GRE sequences in a clinical scanner under unloaded (normal) conditions and with an axial load that mimics the person's standing load. Furthermore, one volunteer's knee was imaged at four regular time intervals while the load was applied and at four regular intervals without load. The results show that changes of 50 microns in the average distance between bones can be measured and that normal axial loads reduce the joint space width significantly and can be detected by this method.
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Genu varum
Metaphysis
Bowing
Varus deformity
Plain radiography
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Abstract Objectives To investigate the effect of residual rotation deformity on the stress distribution of the knee joint after surgery to treat middle and upper tibial fractures. Methods Fourteen adult cadaver specimens that were preserved with formalin were included, and the tibias were randomly positioned at 0 degree, 5 degrees, 10 degrees, and 15 degrees from the line of force of the lower limb. These positions modeled deformities of 5 degrees, 10 degrees, and 15 degrees from the line of force. Low-pressure pressure-sensitive film technology measured the stress distribution of the knee joint under different degrees of rotation deformity. Results Under a vertical load of 400 N, the difference between the medial and lateral stress of the knee joint was significantly different between the different tibia deformities (P<0.05), and the medial stress of the knee joint was higher than the lateral stress. The current study showed that there were statistically significant differences in the medial stress on the knee joint at all angles (including the neutral position of 0 degrees) (F=89.753, P<0.001) . There was a statistically significant difference in the lateral stresses of the knee joint between different rotation deformities (including the neutral position of 0 degrees) (F=102.998, P<0.001). Conclusions Residual rotation deformity after fracture of middle and upper tibia can lead to poor alignment of lower limb force and change of articular contact characteristics of knee joint, especially external rotation of tibia.Therefore, orthopedic surgeons should correct the malalignment of lower limbs to the greatest extent and reduce the rotation deformity as far as possible.
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847 Elderly adults alter the distribution of joint torques in the lower extremities compared to young adults while walking at the same speed (1). The redistribution includes larger hip extensor and lower knee and ankle extensor torques in elderly subjects. We hypothesized this torque redistribution reduced the forces inside the knee joint. The purpose of the study was to compare knee joint forces in elderly and young adults during walking at 1.5 m/s. 10 elderly (age 69 yr; mass 72 kg) and 27 young (age 21 yr; mass 74 kg) adults walked over a force plate while being video taped. Joint torques were predicted with inverse dynamics. A planar mathematical model predicted gastrocnemius, hamstrings and patellar tendon forces during the stance phase. These forces and the knee joint reaction force were applied to the tibia and femur to determine knee forces. Model results were partially validated by comparing predicted muscle forces from young subjects with those from other models (2,3) and were within 18% of those predictions. Maximum shear, compressive and resultant knee forces were 47, 17 and 17% lower in elderly compared to young adults (all p<.05). The redistribution of joint torques in elderly compared to young adults enabled elderly to walk at the same speed as young adults but with reduced knee joint forces. (Table)Table
Inverse dynamics
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Biomechanics
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Contact force
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Contact region
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BackgroundFlexion-extension gap balancing is recognized as an essential part of total knee arthroplasty (TKA). The gap is often evaluated using spacer blocks, laminar spreader, or tensor device. The evaluation of gap balancing with the patella in the reduced position is more physiological and reproducible than with patellofemoral (PF) joint everted. However, in the knee with a reduced PF joint, it is difficult to comprehend the anteroposterior position of the tibia to the femur. So, we developed a new tensor to lift up the tibia ahead and fix the anteroposterior position of the tibia to the femur with the PF joint reduced [Fig.1].PurposeTo investigate how accurate the extension and flexion gaps would be measured by comparing our new tensor with the conventional tensor which could not fix the position of the tibia to the femur.MethodsThis study includes 60 knees in 48 patients underwent TKA using the Posterior Stabilized (PS) Prosthesis (Striker), for varus osteoarthritis. The mean age of patients was 78.2...
Patellofemoral joint
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The statistical shape model (SSM) method that uses 2D images of the knee joint to predict the three-dimensional (3D) joint surface model has been reported in the literature. In this study, we constructed a SSM database using 152 human computed tomography (CT) knee joint models, including the femur, tibia and patella and analysed the characteristics of each principal component of the SSM. The surface models of two in vivo knees were predicted using the SSM and their 2D bi-plane fluoroscopic images. The predicted models were compared to their CT joint models. The differences between the predicted 3D knee joint surfaces and the CT image-based surfaces were 0.30 ± 0.81 mm, 0.34 ± 0.79 mm and 0.36 ± 0.59 mm for the femur, tibia and patella, respectively (average ± standard deviation). The computational time for each bone of the knee joint was within 30 s using a personal computer. The analysis of this study indicated that the SSM method could be a useful tool to construct 3D surface models of the knee with sub-millimeter accuracy in real time. Thus, it may have a broad application in computer-assisted knee surgeries that require 3D surface models of the knee.
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Biomechanics
DICOM
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In the description of fracture deformity as shown on the roentgenogram, it is desirable to denote the type of fracture, its location with relation to adjacent joint surfaces, the character and amount of displacement, and the alignment of the fragments. Of all these, the deformity of alignment is probably the most important, especially in cases in which the fracture is near a joint, and is, perhaps, the one most difficult to describe accurately. I wish to propose a method of measurement and description of the deformity which has proven both practical and useful. In arriving at normals, 50 cases each of wrists, knees, and ankles were selected at random, and the angle made by the plane of the joint surface with the longitudinal diameter of the shaft of the bone was measured. In Table I the maximum, the minimum, and the average measurements are given. 1. The Wrist Joint.—In the anteroposterior roentgenogram a line drawn from the tip of the styloid process of the radius to the medial margin of the joint surface makes a maximum angle of 120 degrees, a minimum angle of 105 degrees, and an average angle of 110 degrees, with a line drawn through the long diameter of the shaft of the radius. This angle is measured on the lateral radial surface and I have called it the “lateral radial angle.” In fracture, this angle is usually diminished (Fig. 1-A). In the lateral position a line drawn through the plane of the joint surface of the radius makes a maximum angle of 110 degrees, a minimum angle of 95 degrees, and an average angle of 103 degrees, with the long diameter of the bone. This angle is measured on the dorsal surface and I have called it the “dorsal radial angle.” In fracture, this angle is usually diminished (Fig. 1-B). 2. The Knee Joint.—In the antero-posterior position, a line drawn through the surfaces of the condyles makes a maximum angle of 115 degrees, a minimum angle of 95 degrees, and an average angle of 100 degrees, with the long diameter of the femur. This angle is measured on the medial surface of the femur and I have called it the “medial femoral angle.” This angle is usually increased in fracture of the femur near the knee joint, but may be diminished (Fig. 2). 3. The Ankle Joint.—In the antero-posterior position a line drawn through the plane of the articular surface of the tibia makes a maximum angle of 95 degrees, a minimum angle of 90 degrees, and an average angle of 92 degrees, with the long diameter of the shaft of the tibia. This angle is measured on the medial surface of the tibia and I have called it the “medial tibial angle.” This angle is usually increased in fracture but may be diminished near the ankle joint (Fig. 3).
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