Optimal Fluoroscopic Angulation to Determine Intercondylar Notch Violation during Pediatric Medial Patellofemoral Ligament Reconstruction.

Previous anatomic data has suggested that during pediatric medial patellofemoral ligament (MPFL) reconstruction, the femoral tunnel must be angled distally and anteriorly to avoid damage to the distal femoral physis and then intercondylar notch. The purpose of this study was to determine the optimal degree of fluoroscopic angulation necessary to radiographically determine the presence of intercondylar notch violation. Fourteen adult cadaveric human femora were disarticulated and under fluoroscopic guidance, Schöttle's point was identified. A 0.62-mm Kirschner wire was then drilled through the condyle to create minimal notch violation. The femur was then placed on a level radiolucent table and coronal plane radiographs angled from -15 to 60 degrees were obtained in 5-degree increments to determine the fluoroscopic angle at which intercondylar notch violation was most evident. Grading of optimal fluoroscopic angle between two authors found that violation of the notch was the best appreciated at a mean angle of 43 ± 15 degrees from neutral. Results from this study emphasize the importance of angling the beam to essentially obtain a notch view to assess for a breech.

Longitudinal analysis of pediatric distal radius alignment parameters in a cohort of serial radiographs.

BACKGROUND: Growth in pediatric patients necessitates changes to bony structures throughout the entire body to suit development. Changes in the distal radius during growth are of interest in the pediatric population due to the high incidence of fractures. The purpose of this study was to assess for trends in three radiographic measurements (height of the radial styloid process, radial inclination, ulnar variance) of the distal radius using serial radiographs in subjects aged between 6 and 14 years of age. MATERIALS AND METHODS: Longitudinal radiographs from 68 healthy children (n = 34 males, 34 females) with a minimal of three annual radiographs between 6 and 14 years of age were analyzed. Measurements of height of the radial styloid process, radial inclination, and ulnar variance were performed in each available radiograph. Repeated measures analysis of variance (ANOVA) was performed to measure the association between alignment values and subject age. RESULTS: A total of 436 images in 68 subjects were analyzed, comprising a mean of 6.5 ± 2.0 radiographs per subject. Repeated measures ANOVA demonstrated that all measurement variables changed significantly with age (p < .001). Ulnar variance demonstrated the most variability with negative ulnar variance in younger children, and trends towards a more neutral ulnar variance by approximately 7 years in females and 11 years in males, while height of the radial styloid process and radial inclination changed relatively minimally with development. CONCLUSIONS: In the adolescent age range, ulnar variance, height of the radial styloid process and inclination are all relatively stable and adult parameter values can be used to judge restoration of distal radius alignment.

Lung cancer incidence in Canadian petroleum workers.

OBJECTIVES: This study's purpose was to conduct a more in-depth analysis of the potential association between lung cancer, occupational exposures and smoking using data on cohort members from a Canadian petroleum company and refined statistical analyses. METHODS: Information on various exposures including asbestos and petroleum coke dust, as well as job type and operating segment were collected via manual and computerised company records. We performed life-table analyses, Poisson regression and restricted cubic splines to model exposure-response patterns while controlling for smoking status and age. Model diagnostics included the assessment of dispersion and offset parameters. RESULTS: These analyses show that lung cancer risk is strongly related to age and smoking, and to a lesser extent to province of last residence. When controlling for these covariates, there is suggestive evidence that maintenance work may also be related to lung cancer risk. Some analyses also indicate that asbestos exposure may be associated with lung cancer risk, although a clear exposure-response trend is not seen. Other exposures, including petroleum coke dust, were not strongly related to lung cancer risk, particularly when expressed as a continuous measure. CONCLUSIONS: These data suggest that maintenance work may be associated with lung cancer incidence, although exposures to the single agents studied did not emerge as strong predictors of lung cancer incidence. Maintenance work may be a surrogate for general exposures to several agents (eg, polycyclic aromatic hydrocarbons, metals, welding fumes, radiation, etc), although these results may be affected by residual confounding due to smoking or other socio-demographic factors.

Exposure assessment methods for a study of mortality and cancer morbidity in relation to specific petroleum industry exposures.

In 1987 a Canadian company implemented an exposure tracking and health information system. The exposure tracking method aligned closely with published concepts for describing workplace exposure, with over 1800 similar exposure groups being used to describe occupational exposures. The database has been actively maintained and is subject to a number of quality checks. Recently, the company initiated a cancer morbidity study, with one objective being to examine whether the exposure tracking data could be used to reconstruct exposure estimates for the cohort. Five agents--hydrogen sulfide, petroleum coke/spent catalyst, hydrocarbon solvents and fuels, hydrocarbon lubricants, and an index for exposure to operations derived from noise exposure--were selected for development of occupational exposure estimates for each cohort member. The cohort consisted of workers first employed between January 1964 and December 1994 and who were employed for at least 1 year. Work history records were associated with a similar exposure group, using human resources data and knowledge of local industrial hygienists. Only employees with >90% duration of their work history assigned were kept in the cohort (25,292 people out of a possible 25,617). For each similar exposure group inventory, the substances were identified that contributed to each of the five agents being studied. Exposure estimates before 1987 were modified using historic occupational exposure limits. Rules were created to sum the exposure from multiple substances found in any one similar exposure group. The validity of exposure estimates was tested via comparison with results documented in industrial hygiene survey reports. Industrial hygienists who were unaware of the derived exposure estimates evaluated several hundred industrial hygiene surveys and prepared benchmark information. The two lists were then evaluated for concordance, which was found to be significantly different from that occurring by chance. We conclude that the process described can create valid exposure estimates for use in epidemiology studies.

Equilibrium statistics of a slave estimator in Langevin processes.

We analyze the statistics of an estimator, denoted by xi(t) and referred to as the slave, for the equilibrium susceptibility of a one dimensional Langevin process x(t) in a potential phi (x). The susceptibility can be measured by evolving the slave equation in conjunction with the original Langevin process. This procedure yields a direct estimate of the susceptibility and avoids the need, when performing numerical simulations, to include applied external fields explicitly. The success of the method, however, depends on the statistical properties of the slave estimator. The joint probability density function for x(t) and xi(t) is analyzed. In the case where the potential of the system has a concave component the probability density function of the slave acquires a power law tail characterized by a temperature dependent exponent. Thus we show that while the average value of the slave, in the equilibrium state, is always finite and given by the fluctuation-dissipation relation, higher moments and indeed the variance may show divergences. The behavior of the power law exponent is analyzed in a general context and it is calculated explicitly in some specific examples. Our results are confirmed by numerical simulations and we discuss possible measurement discrepancies in the fluctuation dissipation relation which could arise due to this behavior.