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- Rigorous Geometric Self-Calibrating Bundle Adjustment for a Dual Fluoroscopic Imaging System. [JOURNAL ARTICLE]
- IEEE Trans Med Imaging 2014 Oct 14.
High-speed dual fluoroscopy is a non-invasive imaging technology for three-dimensional skeletal kinematics analysis that finds numerous biomechanical applications. Accurate reconstruction of bone translations and rotations from dual-fluoroscopic data requires accurate calibration of the imaging geometry and the many imaging distortions that corrupt the data. Direct linear transformation methods are commonly applied for performing calibration using a two-step process that suffers from a number of potential shortcomings including that each X-ray source and corresponding camera must be calibrated separately. Consequently, the true imaging set-up and the constraints it presents are not incorporated during calibration. A method to overcome such drawbacks is the single-step selfcalibrating bundle adjustment method. This procedure, based on the collinearity principle augmented with imaging distortion models and geometric constraints, has been developed and is reported herein. Its efficacy is shown with a carefully controlled experiment comprising 300 image pairs with 48,507 image points. Application of all geometric constraints and a 31 parameter distortion model resulted in up to 91% improvement in terms of precision (model fit) and up to 71% improvement in terms of three-dimensional point reconstruction accuracy (0.3-0.4 mm). The accuracy of distance reconstruction was improved from 0.3±2.0 mm to 0.2±1.1 mm and angle reconstruction accuracy was improved from -0.03±0.55° to 0.01±0.06°. Such positioning accuracy will allow for the accurate quantification of in-vivo arthrokinematics crucial for skeletal biomechanics investigations.
- The Andersen Aerobic Fitness Test: Reliability and Validity in 10-Year-Old Children. [JOURNAL ARTICLE]
- PLoS One 2014; 9(10):e110492.
High aerobic fitness is consistently associated with a favorable metabolic risk profile in children. Direct measurement of peak oxygen consumption (VO2peak) is often not feasible, thus indirect tests such as the Andersen test are required in many settings. The present study seeks to determine the reliability and validity of the Andersen test in 10-year-old children.A total of 118 10-year-old children (67 boys and 51 girls) were recruited from one school and performed four VO2peak tests over three weeks: three Andersen tests (indirect) and one continuous progressive treadmill test (direct). Of these, 104 children provided valid data on all Andersen tests and 103 children also provided valid data on the direct treadmill test. Reliability and validity were assessed using Bland Altman plots and linear regression analysis.Bias (mean change) and random error (limits of agreement) were 26.7±125.2 m for test 2 vs. test 1 (p<.001 for mean difference) and 3.9±88.8 m for test 3 vs. test 2 (p = .514 for mean difference). The equation to estimate VO2peak suggested by Andersen et al. (2008) showed a poor fit in the present sample; thus, we suggest a new equation: VO2peak = 23.262+0.050*Andersen distance -3.858*gender -0.376*body weight (R2 = 0.61, standard error of the estimate = 5.69, p<.001, boys = 0, girls = 1).The Andersen test provided reliable and valid data on a group level. However, a substantial degree of individual variability was found for estimates of VO2peak. Researchers should be aware of the amount of noise in indirect tests that estimate aerobic fitness.
- Effects of the Mycotoxin Nivalenol on Bovine Articular Chondrocyte Metabolism In Vitro. [JOURNAL ARTICLE]
- PLoS One 2014; 9(10):e109536.
Kashin-Beck Disease (KBD) is an endemic, age-related degenerative osteoarthropathy and its cause is hypothesised to involve Fusarium mycotoxins. This study investigated the Fusarium mycotoxin Nivalenol (NIV) on the metabolism of bovine articular chondrocytes in vitro.The effect 0.0-0.5 µg/ml NIV on transcript levels of types I and II collagen, aggrecan, matrix metalloproteinases (MMPs), a disintegrin and metalloproteinase with thrombospondin motif (ADAMTS) and the tissue inhibitors of MMPs (TIMPs) was investigated using quantitative PCR. Amounts of sulphated glycosaminoglycans, MMPs and TIMPs were assessed using the Dimethylmethylene Blue assay, gelatin zymography and reverse gelatin zymography respectively. Cytoskeletal organisation was analysed using confocal microscopy and cytoskeletal gene and protein levels were measured by quantitative PCR and Western blot analysis, respectively.NIV caused a dose-dependent increase in aggrecan transcription with a concomitant retention of sGAG in the cell lysate. Furthermore, NIV significantly increased MMPs-2, -3 & -9, ADAMTS-4 and -5, and TIMP-2 and -3 transcript levels but inhibited type I collagen, MMP 1 and TIMP 1 mRNA levels. NIV promoted extensive cytoskeletal network remodelling, particularly with vimentin where a dose-dependent peri-nuclear aggregation occurred.NIV exposure to chondrocytes decreased matrix deposition, whilst enhancing selective catabolic enzyme production, suggesting its potential for induction of cellular catabolism. This NIV-induced extracellular matrix remodelling may be due to extensive remodelling/disassembly of the cytoskeletal elements. Collectively, these findings support the hypothesis that trichothecene mycotoxins, and in particular NIV, have the potential to induce matrix catabolism and propagate the pathogenesis of KBD.
- The effect of multi-level laminoplasty and laminectomy on the biomechanics of the cervical spine: a finite element study. [Journal Article]
- Iowa Orthop J 2014.:150-7.
Laminectomy has been regarded as a standard treatment for multi-level cervical stenosis. Concern for complications such as kyphosis has limited the indication of multi-level laminectomy; hence it is often augmented with an instrumented fusion. Laminoplasty has emerged as a motion preserving alternative. The purpose of this study was to compare the multidirectional flexibility of the cervical spine in response to a plate-only open door laminoplasty, double door laminoplasty, and laminectomy using a computational model. A validated three-dimensional finite element model of a specimen-specific intact cervical spine (C2-T1) was modified to simulate each surgical procedure at levels C3-C6. An additional goal of this work was to compare the instrumented computational model to our multi-specimen experimental findings to ensure similar trends in response to the surgical procedures. Model predictions indicate that mobility was retained following open and double door laminoplasty with a 5.4% and 20% increase in flexion, respectively, compared to the intact state. Laminectomy resulted in 57% increase in flexion as compared to the intact state, creating a concern for eventual kyphosis - a known risk/complication of multi-level laminectomy in the absence of fusion. Increased disc stresses were observed at the altered and adjacent segments post-laminectomy in flexion.
- Sheep cervical spine biomechanics: a finite element study. [Journal Article]
- Iowa Orthop J 2014.:137-43.
Animal models are often used to make the transition from scientific concepts to clinical applications. The sheep model has emerged as an important model in spine biomechanics. Although there are several experimental biomechanical studies of the sheep cervical spine, only a limited number of computational models have been developed. Therefore, the objective of this study was to develop and validate a C2-C7 sheep cervical spine finite element (FE) model to study the biomechanics of the normal sheep cervical spine.The model was based on anatomy defined using medical images and included nonlinear material properties to capture the high flexibility and large neutral zone of the sheep cervical spine. The model was validated using comprehensive experimental flexibility testing. Ten adult sheep cervical spines, from C2-C7, were used to experimentally ascertain overall and segmental flexibility to ±2 Nm in flexion-extension, lateral bending, and axial rotation.The ranges of motion predicted by the computational model were within one standard deviation of the respective experimental motions throughout the load cycle, with the exception of extension and lateral bending. The model over- and under predicted the peak motions in extension and lateral bending, respectively. Nevertheless, the model closely represents the range of motion and flexibility of the sheep cervical spine.This is the first multilevel model of the sheep cervical spine. The validated model affords additional biomechanical insight into the intact sheep cervical spine that cannot be easily determined experimentally. The model can be used to study various surgical techniques, instrumentation, and device placement, providing researchers and clinicians insight that is difficult, if not impossible, to gain experimentally.
- Clinical, biomechanical and histological study on oophorectomy induced menopause. [Journal Article]
- Acta Ortop Bras 2014; 22(5):260-3.
To investigate the clinical implications as well as biomechanical and histological changes and in bone tissue induced by ovariectomy in 64 rats.THE RATS WERE DIVIDED INTO TWO GROUPS: bilateral oophorectomy or placebo, and subdivided into four subgroups, according to time postoperatively: three, six, nine and 12 months. The weight of the animals at the time of sacrifice was taken into consideration. The biomechanical study was performed on the right tibia, to the maximum load and stiffness coefficient. For the histological study we calculated the trabecular bone of the left tibia. Statistical analysis of body weight and mechanical properties was performed by variance analysis, complemented with Tukey's multiple comparison tests; and trabecular area, the non-parametric variance analysis.Ovariectomy-induced menopause caused an increase in body weight, reduction of diaphyseal bone resistance at six months of hormone deprivation, but this effect is equalized over time by aging; bone stiffness was smaller in the ovariectomized group and reduction of bone mass occurred.The removal of the ovaries produced systemic alterations, characterized by metabolic changes that caused weight gain and changes in bone tissue, associated with alteration of the mechanical profile and reduced bone mass. Level of Evidence I, Clinical Study.
- [Evaluation of the usefulness of the EOS 2D/3D system for the measurement of lower limbs anatomical and biomechanical parameters in children]. [English Abstract, Journal Article]
- Orv Hetil 2014 Oct 1; 155(43):1701-12.
Lower limbs anatomical and biomechanical parameters are essential in several paediatric orthopaedic disease, which makes their exact measurement necessary.The aim of the author was to evaluate the reliability of the EOS 2D/3D System, a 3D reconstruction capable imaging device in children.3D reconstructions were performed in 523 cases aged between 2 and 16 years in whom no abnormality influencing lower limbs biomechanics was observed. For statistical analysis intraclass correlation, paired-samples t-test, Spearman-correlation and Welch-test were used.Excellent results were found for all parameters in reliability test used by the operator. The step-forward position used during the examination influenced the sagittal tibiofemoral angle only. All examined parameters showed significant correlation with age and gender. Height correlated with neck-shaft angle, hip-knee shift, femoral and tibial torsion only.The EOS technology proved to be an appropriate method to measure lower limbs anatomical parameters in children. Changes in these parameters during development correlated with age and gender. Orv., Hetil., 2014, 155(43), 1701-1711.
- Reconstruction of multiple myeloma lesions around the pelvis and acetabulum. [JOURNAL ARTICLE]
- Eur J Orthop Surg Traumatol 2014 Oct 19.
Multiple myeloma is a malignancy of monoclonal plasma cells (plasma cells are of B-lymphocyte lineage of the hematopoietic system). It is the second most prevalent blood malignancy after non-Hodgkin's lymphoma. It accounts for approximately 1 % of all malignancies and 2 % of all cancer deaths. Bony involvement is very common; the incidence of pelvic and periacetabular involvement in MM is reported to be around 6 %. Lytic lesions comprise a hallmark of multiple myeloma, which may be complicated with pathologic fractures in a substantial percentage of patients. Pelvic and periacetabular bony involvement of multiple myeloma is associated with some unique characteristics regarding the biomechanics of this specific anatomical region, the morbidity, the overall survival, and prognosis, which all reflect to impairment of quality of life. In this paper, we review the special features of multiple myeloma lesions around the pelvis and acetabulum and present an algorithm of management with the use of current surgical techniques.
- Patient-specific spinal stiffness in AIS: a preoperative and noninvasive method. [JOURNAL ARTICLE]
- Eur Spine J 2014 Oct 19.
The clinical tests currently used to assess spinal biomechanics preoperatively are unable to assess true mechanical spinal stiffness. They rely on spinal displacement without considering the force required to deform a patient's spine. We propose a preoperative method for noninvasively quantifying the three-dimensional patient-specific stiffness of the spines of adolescent idiopathic scoliosis patients.The technique combines a novel clinical test with numerical optimization of a finite element model of the patient's spine.A pilot study conducted on five patients showed that the model was able to provide accurate 3D reconstruction of the spine's midline and predict the spine's stiffness for each patient in flexion, bending, and rotation. Statistically significant variation of spinal stiffness was observed between the patients.This result confirms that spinal biomechanics is patient-specific, which should be taken into consideration to individualize surgical treatment.
- Tibial tubercle osteotomy for patello-femoral joint disorders. [JOURNAL ARTICLE]
- Knee Surg Sports Traumatol Arthrosc 2014 Oct 19.
Tibial tubercle osteotomy has a long history in the management of patella instability and patello-femoral arthritis. This review aims to provide a comprehensive review of the literature describing the biomechanics of the patello-femoral joint and the rationale behind the use of the tibial tubercle osteotomy in modern day practice. Several different tibial tubercle osteotomies are available and we aim to detail the concepts behind their use and the subsequent clinical results. With continued developments of chondrocyte implantation techniques, the potential to fill defects on the chondral surface of either the patella or trochlea in conjunction with a tibial tubercle osteotomy may well become more commonplace in a group that is commonly young and difficult to manage. Level of evidence III.