Amin Komeili

Symmetry analysis of talus bone: A Geometric morphometric approach

Objective The main object of this study was to use a geometric morphometric approach to quantify the left-right symmetry of talus bones. Methods Analysis was carried out using CT scan images of 11 pairs of intact tali. Two important geometric parameters, volume and surface area, were quantified for left and right talus bones. The geometric shape variations between the right and left talus bones were also measured using deviation analysis. Furthermore, location of asymmetry in the geometric shapes were identified. Results Numerical results showed that talus bones are bilaterally symmetrical in nature, and the difference between the surface area of the left and right talus bones was less than 7.5%. Similarly, the difference in the volume of both bones was less than 7.5%. Results of the three-dimensional (3D) deviation analyses demonstrated the mean deviation between left and right talus bones were in the range of -0.74 mm to 0.62 mm. It was observed that in eight of 11 subjects, the deviation in symmetry occurred in regions that are clinically less important during talus surgery. Conclusions We conclude that left and right talus bones of intact human ankle joints show a strong degree of symmetry. The results of this study may have significance with respect to talus surgery, and in investigating traumatic talus injury where the geometric shape of the contralateral talus can be used as control. Cite this article: Bone Joint Res 2014;3:139–45.

Monitoring for idiopathic scoliosis curve progression using surface topography asymmetry analysis of the torso in adolescents

BACKGROUND CONTEXT At first visit and each clinical follow-up session, patients with adolescent idiopathic scoliosis (AIS) undergo radiographic examination, from which the Cobb angle is measured. The cumulative exposure to X-ray radiation justifies efforts in developing noninvasive methods for scoliosis monitoring. PURPOSE To determine the capability of the three-dimensional markerless surface topography (ST) asymmetry analysis to detect ≥5° progression in the spinal curvature in patients with AIS over 1-year follow-up interval. STUDY DESIGN/SETTING Cross-sectional study in a specialized scoliosis clinic. PATIENT SAMPLE In this study, baseline and 1-year follow-up full torso ST scans of 100 patients with AIS were analyzed using three-dimensional markerless asymmetry analysis. OUTCOME MEASURES Patients with ΔCobb≥5° and ΔCobb<5° were categorized into progression and nonprogression groups, respectively. METHODS The ST scan of each full torso was analyzed to calculate the best plane of symmetry by minimizing the distances between the torso and its reflection about the plane of symmetry. Distance between the torso and its reflection was measured and displayed as deviation color maps. The difference of ST measurements between two successive acquisitions was used to determine if the scoliosis has progressed at least 5° or not. The classification tree technique was implemented using the local deformity of the torso in the thoracic-thoracolumbar (T-TL) and lumbar (L) regions to categorize curves into progression and nonprogression groups. The change in maximum deviation and root mean square of the deviations in the torso were the parameters effective in capturing the curve progression. Funding for this research is provided by the Scoliosis Research Society, and Women and Childrens Health Research Institute. RESULTS The classification model detected 85.7% of the progression and 71.6% of the nonprogression cases. The resulting false-negative rate of 4% for T-TL curves, representing the proportion of undetected progressions, confirmed that the technique shows promise to monitor the progression of T-TL scoliosis curves. Although 100% L curves with progression were detected using the deviation color maps of the torsos, because of the small number of analyzed L curves, further research is needed before the efficiency of the method in capturing the L curves with progression is confirmed. CONCLUSIONS Using the developed classification tree for the patients analyzed in this study, 43% of nonprogression cases between two visits would not have to undergo an X-ray examination.

Assessing asymmetry using reflection and rotoinversion in biomedical engineering applications

Symmetry is a trait that has been extensively reviewed, especially clinically, as an indication of ideal geometry and health. Many geometric symmetry assessment techniques rely on two-dimensional measurements that do not account for the three-dimensional nature of the object. In this article, two methods, reflection and a process termed rotoinversion, a combination of reflection and rotation, are presented as potential methods to assess an object’s deviation from symmetry. With reflection, the geometric models are reflected about a calculated best plane of symmetry. With rotoinversion, the models are reflected about an arbitrary plane and then rigidly translated and rotated to best align the translated and original models. The methods give the same results for bilaterally symmetric objects, but different results for bilaterally and rotationally symmetric objects. The two methods are applied to assess asymmetry in adolescent idiopathic scoliosis torso geometric models, producing similar results. There was an angle of 0.408° between the normal to the plane of reflection from the reflection process and the normal from the rotoinversion process and average rotation of 0.067° from rotoinversion. The most appropriate method depends on the purpose of the symmetry assessment and must be determined on a case-by-case basis.

Numerical Analysis of High Pressure Cold Bend Pipe to Investigate the Behaviour of Tension Side Fracture

The cold bend pipelines may be affected by the geotechnical movements due to unstable slopes, soil type and seismic activities. An extensive experimental study was conducted by Sen et al. in 2006 to understand the buckling behaviour of cold bend pipes. In their experiments, it was noted that one high pressure X65 pipe specimen failed under axial and bending loads due to pipe body tensile side fracture which occurred after the development of a wrinkle. The behaviour of this cold bend pipe specimen under bending load has been investigated numerically to understand the conditions leading to pipe body tension side fracture following the compression side buckling. Bending load has been applied on a finite element model of the cold bend by increasing the curvature of it according to the experimental studies conducted by Sen [1]. The bending loads have been applied on the model with and without internal pressure. The distribution of the plastic strains and von Mises stresses as well as the load–displacement response of the pipe have been compared for both load cases. In this way the experimental results obtained by Sen [1] have been verified. The visualization of the finite element analysis results showed that pipe body failure at the tension side of the cold bend takes place under equal bending loads only in case of combined loading with internal pressure.Copyright

Assessment of torso deformities using 3D markerless asymmetry analysis and its clinical applications

Methods The full torso ST of 90 AIS patients with different curve types were retrieved from our previous study [2]. The mean Cobb angle was 32.5° (range: 8°-69°). The best plane of symmetry that divides the torso into left and right parts was calculated. Deviations between the left and right parts were measured and displayed as deviation colour maps (DCMs). To propose a surface clarification, the DCMs of 46 patients were appraised by three scoliosis professionals. The DCMs were then classified into three main groups and six subgroups by four novice observers. The intra and inter-observer reliability of the classification was assessed using Kappa coefficients. The vertical position of the maximum deviation point above the PSISs was multiplied by a correction factor to estimate the vertical location of the curve apex. Results The mean kappa coefficient for intra-observer reliability was 0.85 (0.68-0.92) indicating good to excellent classification reliability [3]. The inter-observer kappa coefficient was 0.62 and the percentage of agreement was 80%, indicating moderate reliability [3]. For 88 torsos with thoracic curves (subgroups 2, 4 or 5), the location of the point of maximum deviation predicted the location of the curve apex with a ±2.2cm accuracy (range 0.02-5.5cm, R=0.72). For 39 lumbar curves with Cobb angle >20, prediction accuracy was ±1.6cm (0.02-4.2cm; R=0.42).

Examination of the breast asymmetry associated with adolescent idiopathic scoliosis using surface topography methods.

Background Breast asymmetry in females is significantly more common in adolescent idiopathic scoliosis (AIS) than in nonscoliotic females [1]. Researchers and clinicians currently use the “Cobb angle” from radiographs as the standard assessment method for scoliosis. Since exposure to radiation has been shown to increase the risk of cancer [2], radiography is not the safest method of assessment. Unlike surface topography (ST), radiographic assessments do not measure cosmetic deformities associated with AIS, which is very important to patients and has a psychological impact on the quality of life [3].