Anke Klein

A description of spinal fatigue strength

Understanding fatigue failure of the spine is important to establish dynamic loading limits for occupational health and safety. In this study experimental data were combined with published data to develop a description of the predictive parameters for spinal fatigue failure. 41 lumbar functional spinal units (FSUs) from cadaveric spines (age 49.0 ± 11.9 yr) where cyclically loaded. Three different levels of sinusoidal axial compression (0-3 kN, 0-2kN or 1-3kN) were applied for 300,000 cycles. Further, published data consisted of 70 thoracic and lumbar FSUs loaded in axial compression for 5000 cycles. Cyclic forces ranged from lower peaks (Fmin) of 0.7-1kN to upper peaks (Fmax) of 1.2-7.1 kN. Based on Wöhler analysis, a fatigue model was developed accounting for three parameters: I) specimen-specific scaling based on the endplate area, II) specimen-specific strength dependency on age or bone mineral density, III) load-specific correction factors based on Fmax and Fmin. The most predictive model was achieved for a combination of Fmax, endplate area and bone mineral density; this model explained 61% of variation (p<0.001). A model including Fmax, endplate area and age explained only 28% of variation (p<0.001). Inclusion of a load-specific correction factor did not significantly improve model prediction of fatigue failure. This analysis presents the basis for the prediction of specimen-specific fatigue failure of the lumbar spine, provided the endplate area and bone mineral density can be derived.

Blood Trace Evidence on Washed Textiles - a systematic approach

Luminol has been used for a long time for detecting latent blood traces during police investigations because it is easy to use and does not pose any health risks, while providing trace evidence for DNA analysis. It is often the method of choice for examining clothing. Clothes worn during the offense are often destroyed or washed afterwards by the offenders. The purpose of this study is to show the possibilities of blood and DNA detection on washed clothes by documenting the macroscopic results and their chemiluminescence after washing. The tests comprised different fabrics and laundry detergents including different washing and drying methods. Chemiluminescence was detected on almost all blood-marked samples (95.9%), even after all traces visible to the naked eye have been removed by washing. Evidence of a complete DNA profile or individual alleles could be confirmed in almost all of the test cases (93.3%).

On the relationship between stature and anthropometric measurements of lumbar vertebrae

Stature estimation is important for identifying human remains. Analysis of body parts has become an important forensic tool during global operations in the context of cases in which human remains have been dismembered, mutilated or decomposed. However, unless almost the full skeleton or at least a long bone of the lower limb is available, accuracy is still limited to approximate body height. Especially with respect to single vertebral measurements, only a rough prediction is possible. Due to their complex geometry, vertebral measurements are possible at various locations. Nine locations have been considered in this study. Regression equations for stature estimation using lumbar vertebral geometry from computed tomography scans have been evaluated to identify the measurement which gives the most reliable body height estimation. The study group comprised a representative sample of a German metropolitan male population (42 autopsied individuals). Comparing the influence of various vertebral geometry measurements with body height resulted in a coefficient of correlation (R) of 0.19-0.53 and a 95% confidence interval (CI) of ± 11.6 up to ± 13.1cm. The largest correlation with a single vertebral measurement was achieved with the central height of the vertebral body of L2 as predictor; the standard error (SE) of the estimate was 5.9 cm. Using models from CT scans appeared superior to current invasive procedures that use direct measurements of the vertebral body, in terms of reproducibility and time efficiency. For fragmented non-skeletonized human bodies, height prediction based on an all-virtual model of the vertebrae is possible. However, the regression coefficient may be similar to classic caliper measurements that prove easier if skeletonized bones are available.

Fatal air embolism in hospital confirmed by autopsy and postmortem computed tomography

Vascular air embolism is caused by penetration of air into veins or arteries through a surgical wound or other connection between the external and internal aspects of the body. Vascular air embolism has various causes, and iatrogenic air embolisms are the most frequently described. We report a case of fatal air embolism in an 83-year-old woman who was admitted to hospital. At the time of the incident, she was alone in her ward receiving an intravenous infusion of antibiotics via a peripheral line in her right forearm. She was also inhaling air through a mask, which was connected via a tubing system to a compressed air connection in the wall behind her bed. Autopsy and postmortem computed tomography (PMCT) findings are presented. The case illustrates the high diagnostic value of PMCT, which is an effective procedure for detecting the presence of air or gas.

Erratum to: Blood Trace Evidence on Washed Textiles - a systematic approach

The original version of this article unfortunately contained an error in fig. 12 and 13. The correct fig. 12 with the DNA results of cotton denim sample A you can find below. The fig. 12 in the article shows the DNA results of micro fleece, blended fabrics and cotton jersey (see original subtitle of fig. 13). Fig. 13 in the article shows the results of sample B as stated in the last paragraph of BDNA analysis^.

Failure of the human lumbar motion-segments resulting from anterior shear fatigue loading.

An in-vitro experiment was designed to investigate the mode of failure following shear fatigue loading of lumbar motion-segments. Human male lumbar motion-segments (age 32–42 years, n=6) were immersed in Ringer solution at 37°C and repeatedly loaded, using a modified materials testing machine. Fatigue loading consisted of a sinusoidal shear load from 0 N to 1,500 N (750 N±750 N) applied to the upper vertebra of the motion-segment, at a frequency of 5 Hz. During fatigue experiments, several failure events were observed in the dynamic creep curves. Post-test x-ray, CT and dissection revealed that all specimens had delamination of the intervertebral disc. Anterior shear fatigue predominantly resulted in fracture of the apophyseal processes of the upper vertebrae (n=4). Exposure to the anterior shear fatigue loading caused motion-segment instability and resulted in vertebral slip corresponding to grade I and ‘mild’ grade II spondylolisthesis, as observed clinically.

Homicide or suicide? Xylophagia: a possible explanation for extraordinary autopsy findings

Determining the cause of death and differentiating self-inflicted injuries from non-self-inflicted injuries is a primary goal in legal medicine. Especially with unidentified decedents, autopsy findings alone are often not sufficient; there is no knowledge of pre-existing conditions and only circumstantial evidence is available from the scene of death. In our case, radiological, histological, and toxicological examinations provided an explanatory model for extraordinary autopsy findings consistent with pica, a rare eating disorder. In cases of pica, variable and potentially lethal complications emerge, depending on the type and amount of material ingested. Our case is of an apparently uncontrolled intake of wooden objects (xylophagia). The resulting mechanical damage to the gastrointestinal tract and subsequent soft tissue damage supports that this behavioral disorder is not only of medical concern, but also identifies it as a mental disease with medico-legal relevance.

Strain changes on the cortical shell of vertebral bodies due to spine ageing: A parametric study using a finite element model evaluated by strain measurements

The probability of fractures of the cortical shell of vertebral bodies increases as ageing progresses. Ageing involves all the spinal component changes. However, the effect of the spinal component ageing on the fracture risk of the cortical shell remains poorly understood. In this study, the influence of the ageing of the spinal components on cortical shell strain was investigated. A lumbar spinal specimen (L3–L5) was mechanically tested under a quasi-static axial compressive load. Clinical computed tomography images of the same specimen were used to create a corresponding finite element model. The material properties were determined by calibrating the finite element model using the L4 cortical shell strains of the anterior centre measurement site. The remaining experiment data (axial displacement, the intra-discal pressures, L4 cortical shell strain on the lateral measurement site) were used to evaluate the model. The individual ageing process of the six spinal components (cortical shell, cancellous bone, bony endplate, posterior elements, nucleus pulposus and annulus matrix) was simulated by changing their Young’s moduli and Poisson’s ratios, and the effect on cortical shell strain was investigated. Results show that the cortical shell strain is more sensitive to the ageing of the cortical shell and the cancellous bone than to the ageing of the nucleus pulposus, the annulus matrix, and the bony endplates and of the posterior elements. The results can help the clinicians focus on the aspects that mainly influence the vertebral cortex fracture risk factor.

SHEAR LOAD SHARING IN THE HUMAN LUMBAR SPINE

There is growing concern that low back pain is related to shear load [Norman, 1998]. However, in contrast to axial compressive properties, little is known about the shear mechanical properties of spine. At shear failure in human spine, the disc supports 77% of the shear load [Cripton. 1995]. Evaluation of shear load sharing using porcine spine showed that in the initial overload phase the neural arch was not involved [Yingling, 1999]. We hypothesised that shear load sharing mechanisms in the human and porcine spine are different and that there is early involvement of the neural arch in the human spine.