CT and radiographic analysis of sagittal profile changes after thoracoscopic anterior scoliosis surgery

Background. Previous studies report an increase in thoracic kyphosis after anterior approaches and a flattening of sagittal contours following posterior approaches. Difficulties with measuring sagittal parameters on radiographs are avoided with reformatted sagittal CT reconstructions due to the superior endplate clarity afforded by this imaging modality. Methods. A prospective study of 30 Lenke 1 adolescent idiopathic scoliosis (AIS) patients receiving selective thoracoscopic anterior spinal fusion (TASF) was performed. Participants had ethically approved low dose CT scans at minimum 24 months after surgery in addition to their standard care following surgery. The change in sagittal contours on supine CT was compared to standing radiographic measurements of the same patients and with previous studies. Inter-observer variability was assessed as well as whether hypokyphotic and normokyphotic patient groups responded differently to the thoracoscopic anterior approach. Results. Mean T5-12 kyphosis Cobb angle increased by 11.8 degrees and lumbar lordosis increased by 5.9 degrees on standing radiographs two years after surgery. By comparison, CT measurements of kyphosis and lordosis increased by 12.3 degrees and 7.0 degrees respectively. 95% confidence intervals for inter-observer variability of sagittal contour measurements on supine CT ranged between 5-8 degrees. TASF had a slightly greater corrective effect on patients who were hypokyphotic before surgery compared with those who were normokyphotic. Conclusions. Restoration of sagittal profile is an important goal of scoliosis surgery, but reliable measurement with radiographs suffers from poor endplate clarity. TASF significantly improves thoracic kyphosis and lumbar lordosis while preserving proximal and distal junctional alignment in thoracic AIS patients. Supine CT allows greater endplate clarity for sagittal Cobb measurements and linear relationships were found between supine CT and standing radiographic measurements. In this study, improvements in sagittal kyphosis and lordosis following surgery were in agreement with prior anterior surgery studies, and add to the current evidence suggesting that anterior correction is more capable than posterior approaches of addressing the sagittal component of both the instrumented and adjacent non instrumented segments following surgical correction of progressive Lenke 1 idiopathic scoliosis.

The incidence and predictors of lower limb split skin graft failure and primary closure dehiscence in day case surgical patients

This project was an observational study of outpatients following lower limb surgical procedures for removal of skin cancers. Findings highlight a previously unreported high surgical site failure rate. Results also identified four potential risk factors (increasing age, presence of leg pain, split skin graft and haematoma) which negatively impact on surgical site healing in this population.

Hip and knee kinematics display complex and time-varying sagittal kinematics during repetitive stepping: Implications for design of a functional fatigue model of the knee extensors and flexors

The validity of fatigue protocols involving multi-joint movements, such as stepping, has yet to be clearly defined. Although surface electromyography can monitor the fatigue state of individual muscles, the effects of joint angle and velocity variation on signal parameters are well established. Therefore, the aims of this study were to i) describe sagittal hip and knee kinematics during repetitive stepping ii) identify periods of high inter-trial variability and iii) determine within-test reliability of hip and knee kinematic profiles. A group of healthy men (N = 15) ascended and descended from a knee-high platform wearing a weighted vest (10%BW) for 50 consecutive trials. The hip and knee underwent rapid flexion and extension during step ascent and descent. Variability of hip and knee velocity peaked between 20-40% of the ascent phase and 80-100% of the descent. Significant (p<0.05) reductions in joint range of motion and peak velocity during step ascent were observed, while peak flexion velocity increased during descent. Healthy individuals use complex hip and knee motion to negotiate a knee-high step with kinematic patterns varying across multiple repetitions. These findings have important implications for future studies intending to use repetitive stepping as a fatigue model for the knee extensors and flexors.

Split leverage : attacking the confidentiality of linked databases by partitioning

This article considers the risk of disclosure in linked databases when statistical analysis of micro-data is permitted. The risk of disclosure needs to be balanced against the utility of the linked data. The current work specifically considers the disclosure risks in permitting regression analysis to be performed on linked data. A new attack based on partitioning of the database is presented.

Long-term follow-up of flexor digitorum longus transfer and calcaneal osteotomy for stage II posterior tibial tendon dysfunction

Flexor digitorum longus transfer and medial displacement alcaneal osteotomy is a wellrecognised form of treatment or stage II posterior tibial tendon dysfunction. Although excellent short- and medium-term results have been reported, the long-term outcome is unknown. We reviewed the clinical outcome of 31 patients with a symptomatic flexible flatfoot deformity who underwent this procedure between 1994 and 1996. There were 21 women and ten men with a mean age of 54.3 years (42 to 70). The mean follow-up was 15.2 years (11.4 to 16.5). All scores improved significantly (p < 0.001). The mean American Orthopedic Foot and Ankle Society (AOFAS) score improved from 48.4 pre-operatively to 90.3 (54 to 100) at the final follow-up. The mean pain component improved from 12.3 to 35.2 (20 to 40). The mean function score improved from 35.2 to 45.6 (30 to 50). The mean visual analogue score for pain improved from 7.3 to 1.3 (0 to 6). The mean Short Form-36 physical component score was 40.6 (SD 8.9), and this showed a significant correlation with the mean AOFAS score (r = 0.68, p = 0.005). A total of 27 patients (87%) were pain free and functioning well at the final follow-up. We believe that flexor digitorum longus transfer and calcaneal osteotomy provides long-term pain relief and satisfactory function in the treatment of stage II posterior tibial tendon dysfunction.

Incidence and predictors of lower limb split-skin graft failure and primary closure dehiscence in day-case surgical patients

BACKGROUND After general surgery, the lower limb experiences some of the highest complication rates. However, little is known about contributing factors to surgical site failure in the lower limb dermatological surgery population. OBJECTIVE To determine the incidence of lower limb surgical site failure and to explore the predictors that contribute to surgical site failure. METHODS A prospective observational study design was used to collect data from 73 participants, from July 2010, to March 2012. Incidence was determined as a percentage of surgical site failure from the total population. Predictors were determined by the use of a binary logistic regression model. RESULTS The surgical site failure rate was 53.4%. Split-skin grafting had a higher failure rate than primary closures, 66% versus 26.1%. Predictors of lower limb surgical site failure were identified as increasing age (p = .04) and the presence of postoperative hematoma (p = .01), with all patients who developed surgical site infection experiencing surgical site failure (p = .01). CONCLUSION Findings from this study confirmed that the lower limb is at high risk of surgical site failure. Two predictors of surgical site failure from this cohort were determined. However, to understand this phenomenon and make recommendations to assist and reduce surgical site complications, further research in this field is required.

Adjustable stiffness, external fixator for the rat femur osteotomy and segmental bone defect models

The mechanical environment around the healing of broken bone is very important as it determines the way the fracture will heal. Over the past decade there has been great clinical interest in improving bone healing by altering the mechanical environment through the fixation stability around the lesion. One constraint of preclinical animal research in this area is the lack of experimental control over the local mechanical environment within a large segmental defect as well as osteotomies as they heal. In this paper we report on the design and use of an external fixator to study the healing of large segmental bone defects or osteotomies. This device not only allows for controlled axial stiffness on the bone lesion as it heals, but it also enables the change of stiffness during the healing process in vivo. The conducted experiments have shown that the fixators were able to maintain a 5 mm femoral defect gap in rats in vivo during unrestricted cage activity for at least 8 weeks. Likewise, we observed no distortion or infections, including pin infections during the entire healing period. These results demonstrate that our newly developed external fixator was able to achieve reproducible and standardized stabilization, and the alteration of the mechanical environment of in vivo rat large bone defects and various size osteotomies. This confirms that the external fixation device is well suited for preclinical research investigations using a rat model in the field of bone regeneration and repair.

Customised osteotomy guides and endoprosthetic reconstruction for periacetabular tumours

Purpose We sought to analyse clinical and oncological outcomes of patients after guided resection of periacetabular tumours and endoprosthetic reconstruction of the remaining defect. Methods From 1988 to 2008, we treated 56 consecutive patients (mean age 52.5 years, 41.1 % women). Patients were followed up either until death or February 2011 (mean follow up 5.5 years, range 0.1–22.5, standard deviation ± 5.3). Kaplan–Meier analysis was used to estimate survival rates. Results Disease-specific survival was 59.9 % at five years and 49.7 % at ten and 20 years, respectively. Wide resection margins were achieved in 38 patients, whereas 11 patients underwent marginal and seven intralesional resection. Survival was significantly better in patients with wide or marginal resection than in patients with intralesional resection (p = 0.022). Survival for patients with secondary tumours was significantly worse than for patients with primary tumours (p = 0.003). In 29 patients (51.8 %), at least one reoperation was necessary, resulting in a revision-free survival of 50.5 % at five years, 41.1 % at ten years and 30.6 % at 20 years. Implant survival was 77.0 % at five years, 68.6 % at ten years and 51.8 % at 20 years. A total of 35 patients (62.5 %) experienced one or more complications after surgery. Ten of 56 patients (17.9 %) experienced local recurrence after a mean of 8.9 months. The mean postoperative Musculoskeletal Tumor Society (MSTS) score was 18.1 (60.1 %). Conclusion The surgical approach assessed in this study simplifies the process of tumour resection and prosthesis implantation and leads to acceptable clinical and oncological outcomes.

Split-Freedom And Mvd-Intersection - A New Characterization Of Multivalued Dependencies Having Conflict-Free Covers

Sets of multivalued dependencies (MVDs) having conflict-free covers are important to the theory and design of relational databases [2,12,15,16]. Their desirable properties motivate the problem of testing a set M of MVDs for the existence of a confiict-free cover. In [8] Goodman and Tay have proposed an approach based on the possible equivalence of M to a single (acyclic) join dependency (JD). We remark that their characterization does not lend an insight into the nature of such sets of MVDs. Here, we use notions that are intrinsic to MVDs to develop a new characterization. Our approach proceeds in two stages. In the first stage, we use the notion of “split-free” sets of MVDs and obtain a characterization of sets M of MVDs having split-free covers. In the second, we use the notion of “intersection” of MVDs to arrive at a necessary and sufficient condition for a split-free set of MVDs to be conflict-free. Based on our characterizations, we also give polynomial-time algorithms for testing whether M has split-free and conflict-free covers. The highlight of our approach is the clear insight it provides into the nature of sets of MVDs having conflict-free covers. Less emphasis is given in this paper to the actual efficiency of the algorthms. Finally, as a bonus, we derive a desirable property of split-free sets of MVDs,thereby showing that they are interesting in their own right.

Complex permittivity measurements of RF plasma polymerized polyterpenol organic thin films employing split post dielectric resonator

In the fields of organic electronics and biotechnology, applications for organic polymer thin films fabricated using low-temperature non-equilibrium plasma techniques are gaining significant attention because of the physical and chemical stability of thin films and the low cost of production. Polymer thin films were fabricated from non-synthetic terpinen-4-ol using radiofrequency polymerization (13.56 MHz) on low loss dielectric substrates and their permittivity properties were ascertained to determine potential applications for these organic films. Real and imaginary parts of permittivity as a function of frequency were measured using the variable angle spectroscopic ellipsometer. The real part of permittivity (k) was found to be between 2.34 and 2.65 in the wavelength region of 400–1100 nm, indicating a potential low-k material. These permittivity values were confirmed at microwave frequencies. Dielectric properties of polyterpenol films were measured by means of split post dielectric resonators (SPDRs) operating at frequencies of 10 GHz and 20 GHz. Permittivity increased for samples deposited at higher RF energy – from 2.65 (25 W) to 2.83 (75 W) measured by a 20-GHz SPDR and from 2.32 (25 W) to 2.53 (100 W) obtained using a 10-GHz SPDR. The error in permittivity measurement was predominantly attributed to the uncertainty in film thickness measurement.

Analysis-By-Synthesis Based Switched Transform Domain Split Vq Using Gaussian Mixture Model

Using analysis-by-synthesis (AbS) approach, we develop a soft decision based switched vector quantization (VQ) method for high quality and low complexity coding of wideband speech line spectral frequency (LSF) parameters. For each switching region, a low complexity transform domain split VQ (TrSVQ) is designed. The overall rate-distortion (R/D) performance optimality of new switched quantizer is addressed in the Gaussian mixture model (GMM) based parametric framework. In the AbS approach, the reduction of quantization complexity is achieved through the use of nearest neighbor (NN) TrSVQs and splitting the transform domain vector into higher number of subvectors. Compared to the current LSF quantization methods, the new method is shown to provide competitive or better trade-off between R/D performance and complexity.

Comparison of Prediction Based LSF Quantization Methods using Split VQ

Further improvement in performance, to achieve near transparent quality LSF quantization, is shown to be possible by using a higher order two dimensional (2-D) prediction in the coefficient domain. The prediction is performed in a closed-loop manner so that the LSF reconstruction error is the same as the quantization error of the prediction residual. We show that an optimum 2-D predictor, exploiting both inter-frame and intra-frame correlations, performs better than existing predictive methods. Computationally efficient split vector quantization technique is used to implement the proposed 2-D prediction based method. We show further improvement in performance by using weighted Euclidean distance.

Risk assessment for airborne infectious diseases between natural ventilation and split-system air conditioner in a university classroom

Indoor air quality is a critical factor in the classroom due to high people concentration in a unique space. Indoor air pollutant might increase the chance of both long and short-term health problems among students and staff, reduce the productivity of teachers and degrade the student’s learning environment and comfort. Adequate air distribution strategies may reduce risk of infection in classroom. So, the purpose of air distribution systems in a classroom is not only to maximize conditions for thermal comfort, but also to remove indoor contaminants. Natural ventilation has the potential to play a significant role in achieving improvements in IAQ. The present study compares the risk of airborne infection between Natural Ventilation (opening windows and doors) and a Split-System Air Conditioner in a university classroom. The Wells-Riley model was used to predict the risk of indoor airborne transmission of infectious diseases such as influenza, measles and tuberculosis. For each case, the air exchange rate was measured using a CO2 tracer gas technique. It was found that opening windows and doors provided an air exchange rate of 2.3 air changes/hour (ACH), while with the Split System it was 0.6 ACH. The risk of airborne infection ranged between 4.24 to 30.86 % when using the Natural Ventilation and between 8.99 to 43.19% when using the Split System. The difference of airborne infection risk between the Split System and the Natural Ventilation ranged from 47 to 56%. Opening windows and doors maximize Natural Ventilation so that the risk of airborne contagion is much lower than with Split System.

Gaussian mixture model based switched split vector quantization of LSF parameters

We address the issue of rate-distortion (R/D) performance optimality of the recently proposed switched split vector quantization (SSVQ) method. The distribution of the source is modeled using Gaussian mixture density and thus, the non-parametric SSVQ is analyzed in a parametric model based framework for achieving optimum R/D performance. Using high rate quantization theory, we derive the optimum bit allocation formulae for the intra-cluster split vector quantizer (SVQ) and the inter-cluster switching. For the wide-band speech line spectrum frequency (LSF) parameter quantization, it is shown that the Gaussian mixture model (GMM) based parametric SSVQ method provides 1 bit/vector advantage over the non-parametric SSVQ method.