A biomechanical investigation of dual growing rods used for fusionless scoliosis correction.

BACKGROUND: The use of dual growing rods is a fusionless surgical approach to the treatment of early onset scoliosis which aims to harness potential growth and correct spinal deformity. The purpose of this study was to compare the in-vitro biomechanical response of two different dual rod designs under axial rotation loading. METHODS: Six porcine spines were dissected into seven level thoracolumbar multi-segment units. Each specimen was mounted and tested in a biaxial Instron machine, undergoing nondestructive left and right axial rotation to peak moments of 4 Nm at a constant rotation rate of 8 deg. s(-1). A motion tracking system (Optotrak) measured 3D displacements of individual vertebrae. Each spine was tested in an un-instrumented state first and then with appropriately sized semi-constrained and 'rigid' growing rods in alternating sequence. The range of motion, neutral zone size and stiffness were calculated from the moment-rotation curves and intervertebral range of motion was calculated from Optotrak data. FINDINGS: Irrespective of test sequence, rigid rods showed a significant reduction of total rotation across all instrumented levels (with increased stiffness) whilst semi-constrained rods exhibited similar rotational behavior to the un-instrumented spines (P<0.05). An 11.1% and 8.0% increase in stiffness for left and right axial rotation respectively and 14.9% reduction in total range of motion were recorded with dual rigid rods compared with semi-constrained rods. INTERPRETATION: Based on these findings, the Semi-constrained growing rods were shown to not increase axial rotation stiffness compared with un-instrumented spines. This is thought to provide a more physiological environment for the growing spine compared to dual rigid rod constructs.

Static and dynamic nanomechanical properties of human skin tissue using atomic force microscopy: effect of scarring in the upper dermis.

Following traumatic injury, skin has the capacity to repair itself through a complex cascade of biochemical change. The dermis, which contains a load-bearing collagenous network structure, is remodelled over a long period of time, affecting its mechanical behaviour. This study examines the nanomechanical and viscoelastic properties of the upper dermis from human skin that includes both healthy intact and scarred tissue. Extensive nanoindentation analysis shows that the dermal scar tissue exhibits stiffer behaviour than the healthy intact skin. The scar skin also shows weaker viscoelastic creep and capability to dissipate energy at physiologically relevant frequencies than the adjacent intact skin. These results are discussed in conjunction with a visual change in the orientation of collagenous fibrils in the scarred dermis compared with normal dermis, as shown by atomic force microscopy imaging.

Percutaneous tracheostomy: a 6 yr prospective evaluation of the single tapered dilator technique.

BACKGROUND: The single tapered dilator (STD) percutaneous dilatational tracheostomy (PDT) technique now appears to be the single most common method of performing a tracheostomy in the critical care unit (CCU). METHODS: A single-centre, prospective evaluation of all PDTs performed in an adult mixed surgical and medical CCU between November 2003 and October 2009 was done. All procedures were undertaken by critical care physicians. A proforma recorded intraoperative complications and technical difficulties encountered during the procedure; all patients were followed up for a minimum of 3 months for delayed complications. RESULTS: A tracheostomy was performed on 589 patients during the study period. PDT was attempted in 576 patients and successfully completed in 572. PDT was abandoned in four patients due to bleeding, with three of these subsequently undergoing surgical tracheostomy (ST). ST was performed in 17 patients. Intraoperative technical difficulties were encountered in 149 (26%) cases. Sixteen (3%) procedures were deemed as having early complications. A further four (0.7%) cases had significant late complications including two tracheo-innominate fistulae (TIF). Both TIF patients died as a result of their complications giving a mortality directly attributable to PDT of 0.35%. There were no differences with respect to the occurrence of complications according to grade of operator. CONCLUSIONS: PDT performed by the STD technique is a relatively safe procedure with more than 96% of procedures performed without any early or late complications. Using this technique, more than 97% of tracheostomies undertaken during the study period were performed percutaneously. Further audit at a national level is warranted to fully evaluate long-term complications after PDT.

The effect of endotracheal suction on regional tidal ventilation and end-expiratory lung volume.

PURPOSE: To examine the impact of different endotracheal tube (ETT) suction techniques on regional end-expiratory lung volume (EELV) and tidal volume (V(T)) in an animal model of surfactant-deficient lung injury. METHODS: Six 2-week old piglets were intubated (4.0 mm ETT), muscle-relaxed and ventilated, and lung injury was induced with repeated saline lavage. In each animal, open suction (OS) and two methods of closed suction (CS) were performed in random order using both 5 and 8 French gauge (FG) catheters. The pre-suction volume state of the lung was standardised on the inflation limb of the pressure-volume relationship. Regional EELV and V(T) expressed as a proportion of the impedance change at vital capacity (%Z (VCroi)) within the anterior and posterior halves of the chest were measured during and for 60 s after suction using electrical impedance tomography. RESULTS: During suction, 5 FG CS resulted in preservation of EELV in the anterior (non-dependent) and posterior (dependent) lung compared to the other permutations, but these only reached significance in the anterior regions (p < 0.001 repeated-measures ANOVA). V(T) within the anterior, but not posterior lung was significantly greater during 5FG CS compared to 8 FG CS; the mean difference was 15.1 [95% CI 5.1, 25.1]%Z (VCroi). Neither catheter size nor suction technique influenced post-suction regional EELV or V(T) compared to pre-suction values (repeated-measures ANOVA). CONCLUSIONS: ETT suction causes transient loss of EELV and V(T) throughout the lung. Catheter size exerts a greater influence than suction method, with CS only protecting against derecruitment when a small catheter is used, especially in the non-dependent lung.

Risk indicator for agricultural inputs of trace elements to Canadian soils.

Trace elements (TEs) are universally present in environmental media, including soil, but agriculture uses some materials that have increased TE concentrations. Some TEs (e.g., Cu, Se, and Zn) are added to animal feeds to ensure animal health. Similarly, TEs are present in micronutrient fertilizers. In the case of phosphate fertilizers, some TEs (e.g., Cd) may be inadvertently elevated because of the source rock used in the manufacturing. The key question for agriculture is "After decades of use, could these TE additions result in the deterioration of soil quality?" An early warning would allow the development of best management practices to slow or reverse this trend. This paper discusses a model that estimates future TE concentrations for the 2780 land area polygons composing essentially all of the agricultural land in Canada. The development of the model is discussed, as are various metrics to express the risk related to TE accumulation. The elements As, Cd, Cu, Pb, Se, and Zn are considered, with inputs from the atmosphere, fertilizers, manures, and municipal biosolids. In many cases, steady-state concentrations could be toxic, but steady state is far in the future. In 100 yr, the soil concentrations (Century soil concentrations) are estimated to be up to threefold higher than present background, an impact even if not a problematic impact. The geographic distribution reflects agricultural intensity. Contributions from micronutrient fertilizers are perhaps the most uncertain due to the limited data available on their use.

Outcome of late-onset hospital-acquired pneumonia related to causative organism.

Pneumonia caused by Pseudomonas spp. has been associated with an increase in mortality in critical care patients. Previous assessments, however, have failed to compare outcome solely with other pathogens associated with hospital-acquired pneumonia (HAP). We have performed a retrospective review of all critical care patients with late-onset HAP (hospital inpatient stay >72 h at time of diagnosis) due to pure respiratory cultures of Pseudomonas spp., meticillin-resistant Staphylococcus aureus (MRSA) or non-pseudomonal Gram-negative (NPGN) organisms from 1998 to 2007. Casenote review involved assessments of illness severity, clinical pulmonary infection scoring (CPIS), critical care and hospital survival, and critical care length of stay. Out of 252 casenotes, 204 were reviewed. There were 186 treated cases of pneumonia. Ten patients had both pseudomonal and NPGN pneumonias during the same admission and two patients presented with community-acquired infections due to these organisms. These 12 patients were excluded from further analysis. Of the remaining 174 patients, 80 were infected with pseudomonas, 40 with MRSA and 54 had NPGN organisms. The three groups of patients were well-matched, with similar age, sex, CPIS scores, incidence of bacteraemia and Acute Physiology and Chronic Health Evaluation II scores at diagnosis. There were no outcome differences between the groups with respect to hospital and critical care survival and critical care length of stay. In this series, there appears to be no survival disadvantage associated with pseudomonal pneumonia when compared with other hospital-acquired organisms associated with HAP, where disease severity between the groups is similar.

Role of routine chest radiography after percutaneous dilatational tracheostomy.

BACKGROUND: The role of routine chest radiography (CXR) after percutaneous dilatational tracheostomy (PDT) has been questioned. METHODS: We performed a prospective observational study, on a mixed medical/surgical critical care unit in a university teaching hospital. We studied all patients undergoing PDT as part of their critical care management from November 1, 2003 until July 31, 2007. All PDTs were performed under bronchoscopic guidance. After PDT, we reviewed the immediate post-procedural films to assess the utility of routine postoperative CXR. For the purposes of CXR review, we considered a procedure to be either uncomplicated or technically difficult. Clinically relevant CXR findings were new barotrauma (pneumothorax, pneumomediastinum) or a significant change in consolidation from the pre-procedure film. RESULTS: A total of 384 patients underwent PDT during the study period. Of these, 345 had immediate post-procedural CXRs available for review. There were 252 PDTs (73%) documented as uncomplicated. There were 93 (27%) technically difficult procedures, with 107 adverse events recorded. In 82 (24%) procedures, these difficulties were described as minor procedural complications [multiple attempts at needle insertion (> or = 3), minor bleeding or tracheal ring fracture]. Significant complications (mal-placement in the anterior mediastinum and major bleeding) were documented in 12 (3.5%) patients. New abnormalities were noted on 8 (2.3%) immediate post-procedural CXRs. In only one patient was there a new CXR change in an uncomplicated PDT. CONCLUSIONS: Immediate CXR after uncomplicated PDT performed under bronchoscopic guidance rarely reveals unexpected radiological abnormalities. The role of CXR after PDT appears to be restricted to those patients undergoing technically difficult and complicated procedures. A change in practice to this effect will lead to reductions in both medical costs and exposure of staff and patients to ionizing radiation.

Selection and breeding of plant cultivars to minimize cadmium accumulation.

Natural variation occurs in the uptake and distribution of essential and nonessential trace elements among crop species and among cultivars within species. Such variation can be responsible for trace element deficiencies and toxicities, which in turn can affect the quality of food. Plant breeding can be an important tool to both increase the concentration of desirable trace elements and reduce that of potentially harmful trace elements such as cadmium (Cd). Selection programs for a low-Cd content of various crops, including durum wheat, sunflower, rice and soybean have been established and low-Cd durum wheat cultivars and sunflower hybrids have been developed. In durum wheat (Triticum turgidum L. var durum), low-Cd concentration is controlled by a single dominant gene. The trait is highly heritable, and incorporation of the low-Cd allele can help to reduce the average grain Cd to levels below proposed international limits. The allele for low-Cd concentration does not appear to affect major economic traits and should not cause problems when incorporated into durum cultivars. The cost of Cd selection in a breeding program is initially large both in terms of Cd determination and reduced progress towards development of other economic traits, but declines as more breeding lines in the program carry the low-Cd trait and are utilized in new crosses. Production of low-Cd crop cultivars can be used as a tool to reduce the risk of movement of Cd into the human diet.

Tracheo-innominate artery fistula after percutaneous tracheostomy: three case reports and a clinical review.

Tracheo-innominate artery fistula (TIF) is an uncommon yet life threatening complication after a tracheostomy. Rates of 0.1-1% after surgical tracheostomy have been reported, with a peak incidence at 7-14 days post procedure. It is usually fatal unless treatment is instituted immediately. Initial case reports of TIF resulted from surgically performed tracheostomies. We present three fatalities attributable to TIF, confirmed by histopathology, after percutaneous dilatational tracheostomy (PDT). The use of PDT has resulted in tracheostomies being performed by specialists from different backgrounds and the incidence of this complication may be increasing. Pressure necrosis from high cuff pressure, mucosal trauma from malpositioned cannula tip, low tracheal incision, radiotherapy and prolonged intubation are all implicated in TIF formation. Massive haemorrhage occurring 3 days to 6 weeks after tracheostomy is a result of TIF until proven otherwise. We present a simple algorithm for management of this situation. The manoeuvres outlined will control bleeding in more than 80% of patients by a direct tamponade effect. Surgical stasis is obtained by debriding the innominate artery proximally, then transecting and closing the lumen. Neurological sequelae are few. Post-mortem diagnosis of TIF may be difficult, but specific pathology request should be made to assess innominate artery abnormalities.

No detectable genetic correlation between male and female mating frequency in the stalk-eyed fly Cyrtodiopsis dalmanni.

There is much interest in explaining why female insects mate multiply. Females of the stalk-eyed fly Cyrtodiopsis dalmanni can mate several times each day in a lifetime which may span several months. There are many adaptive explanations, but one hypothesis that has received little rigorous empirical attention is that female multiple mating has evolved for non-adaptive reasons as a correlated response to selection for high male mating frequency rather than because of direct or indirect benefits accruing to females. We tested this hypothesis in stalk-eyed flies by measuring the mating frequency of females from lines that exhibited a direct response in males to artificial selection for increased ('high') and decreased ('low') male mating frequency. We found that the mating frequency of high-line females did not differ from that of low-line females. Hence, there was no support for a genetic correlation between male and female mating frequency in this species. Our study suggests that the genes which influence remating may not be the same in the sexes, and that females remate frequently in this species to gain as yet unidentified benefits.

Xylene-free method for histological preparation: a multicentre evaluation.

The backbone of daily pathological diagnostic work is the paraffin section. Paraffin sections are still prepared by methods largely unchanged for over 150 years. A xylene-free method has been developed that excludes xylene, not only as the intermediate step before the paraffin baths, but also for deparaffinizing of the cut sections, which also eliminates the need for rehydration and dehydration for the staining and mounting steps. Elimination of xylene from tissue processing cuts costs, saves time, and improves the laboratory environment. Experience with xylene-free sections since 1995 at the Vrinnevi Hospital is favorable. Our opinion is that the xylene-free sections are equivalent to conventionally processed sections. To test this hypothesis, nine pathologists from three hospitals participated in an evaluation trial. Paired tissue blocks from 10 consecutively submitted samples each of breast, intestine, and skin were processed by either the xylene-free or the conventional method. Sections from each block were deparaffinized and stained with hematoxylin-eosin (H&E), with periodic acid-Schiff (PAS), and with van Gieson's method. A randomized mix of 180 sections (10 samples x 3 tissues x 3 stains x 2) gave 90 matched pairs. Each section was blindly examined and scored by nine pathologists to give 810 paired observations for statistical evaluation. The xylene-free sections were ranked as good as or better than their conventional counterparts in 74% of the comparisons, and poorer in 26%. The major discriminating factor was the staining method. H&E and PAS sections were equivalent. The xylene-free van Gieson sections, cut from the same blocks and randomly assigned to this stain, tended to be downgraded. This could be traced to a faulty stain solution used for this batch. The overall results have demonstrated professional acceptance for the xylene-free method of processing histological sections.

Treatable forms of retinitis pigmentosa associated with systemic neurological disorders.

In this chapter; we have described the role of nutritional supplements or selective dietary restriction (or both) on the maintenance and function of the retina and nervous system in some diseases. Oral vitamin A therapy has proven to be effective in the treatment of the common forms of retinitis pigmentosa. Bassen-Kornzweig disease can be treated with vitamin A and vitamin E and, in some cases, with vitamin K. Vitamin E therapy for Friedreich-like ataxia associated with retinitis pigmentosa has been shown to be effective in the short term. Classic Refsum's disease responds to a low phytol-low phytanic acid diet. Undoubtedly, future research will bring more insight into the biochemical pathways responsible for other diseases and, it is hoped, aid in developing treatments for additional retinal degenerations associated with systemic neurological disease.

Ultrasound biomicroscopy in the diagnosis and management of limbal dermoid.

PURPOSE: To report the use of ultrasound biomicroscopy in the diagnosis and management of limbal dermoid. METHOD: We used ultrasound biomicroscopy to examine an 18-month-old Asian girl with a congenital limbal mass with corneal extension. A biopsy of the mass was obtained. RESULTS: Clinical examination, ultrasound biomicroscopy, and biopsy confirmed the diagnosis of limbal dermoid. CONCLUSION: Ultrasound biomicroscopy may serve as a useful diagnostic adjunct for limbal dermoids. Additionally, it may be helpful in delineating the extent of these lesions.

Evaluation of recombinant adeno-associated virus as a gene transfer vector for the retina.

PURPOSE: To evaluate recombinant adeno-associated virus (AAV) as an in vivo gene transfer vector for the retina. METHODS: A recombinant AAV, vCMVp-lacZ, in which the bacterial beta-galactosidase reporter gene (lacZ) was placed under the control of a cytomegalovirus (CMV) early promoter, was injected into the vitreous body or the subretinal space of mouse eyes. The reporter gene expression was followed by histochemical analyses from 10 to 100 days post-injection. The effect of several variables on the extent of AAV-mediated gene transfer was examined, including routes of delivery, presence of an underlying mutation that caused retinal degeneration, and prior treatment with hydroxyurea. RESULTS: As measured by reporter gene expression, the AAV vector mediated gene transfer to three major cell types in the retina: the retinal pigment epithelium (RPE), ganglion cells and photoreceptor cells. Following a single injection, more than half of the total retinal areas were typically positive for gene transfer. Reporter gene expression was stable for at least 3 months, the farthest time point examined. Gene transfer to photoreceptor cells was observed only following subretinal delivery, and was greatly enhanced in mice undergoing early retinal degeneration. Cells in the inner nuclear layer were rarely transduced. Systemic administration of a genotoxic drug, hydroxyurea, 2 days prior to AAV delivery did not affect the patterns and extent of reporter gene expression. There was minimal histopathology associated with AAV transduction in the retinas of recipient mice, as determined by light microscopy. CONCLUSION: Recombinant AAV mediates efficient gene transfer to RPE and ganglion cells, and to photoreceptor cells under certain conditions. Persistence of transgene expression is of long duration and without apparent histopathology. The greater stability, lower cytopathicity, and the ability to transduce retinal ganglion cells are three distinct features of the AAV vector compared to current adenovirus-based vectors.

Women who kill: the impact of abuse.

Only 12% of all homicides in the United States are committed by women (Browne & Williams, 1989; Jones, 1981), and the majority of these women are killing their abusive and violent partners. The woman who has killed her partner is now a criminal defendant, which adds a very complicated dimension to her plight. The battered woman who kills her assaulter is additionally handicapped by a legal system that lacks consensus concerning the proper legal response to her case. Maguigan (1991) estimates that there are about 750 men killed each year by wives, girlfriends, and lovers, and argues that the female homicide defendant is almost always a battered woman. When a battered woman becomes a defendant in a criminal case it becomes crucial for the introduction of psychological information about the dynamics of her circumstances to be presented in a court of law so that her actions can be understood by those judging her behavior. Nurses, particularly psychiatric nurses, may be in critical positions as expert witnesses, therapists, and crisis counselors to assist the battered woman and her legal representative in developing a comprehensive understanding of her response to her violent partner. Psychiatric nurses are well aware of violence against women, and this article provides another level of understanding of the effects of violence and trauma on a woman who kills in response to violence.

Drawing a connection from victim to victimizer.

1. The biological basis of the altered alarm/dissociative process during and after sexual trauma impedes the development of information processing essential for discerning intention, personal responsibility, sense of control over events, and trust in others. 2. Once this imbalance occurs, the child is restricted in developing cognitive schema to deal with interpersonal intimacy. This in turn results in secondary patterns of aggressiveness or avoidance. 3. The implication of this biological understanding of trauma and information processing for treatment underscores the necessity of reducing arousal, thus lessening the dissociative process. Drawings of the criminal act and the victim experience elicit cues connecting the two events, facilitating an increase in personal control over repeated aggressive acts.