Influence of energy absorbers on Malgaigne fracture mechanism in lumbar-pelvic system under vertical impact load.

Malgaigne fractures are the most common and widespread pelvic injuries resulting from the shear forces the action mechanism of which has not been explained in the literature yet. Military accidents with improvised explosive devices (IED) perfectly reflect this type of pelvic fracture. The finite element (FE) model of lumbar-pelvic complex (LPC) was developed based on computed tomography (CT) scans with the seat including steel frame, padding and soft tissue. The correlation coefficients of both low (100 N) and high (500 N) loads were greater than that currently obtained in the literature due to the presence of muscle force, pubic symphysis and joint cartilage. The dynamic analysis was performed to determine the influence of varying kinds of foam materials i.e. polyurethane, aluminium honeycomb structured and polyurethane auxetic foam on the stress/strain distribution in LPC under vertical impact load with the velocity of 7 m/s. Performed analysis showed the first fracture occurred in the L5 vertebrae resulting in the sacroiliac ligaments disruption and stress concentration in the pelvic ring causing further fractures of the wing of ilium, pubis and ischium bones. This results clearly explain the inconclusive findings about the second fracture that occurs in the pelvic area under a vertical impact load. The applied seat padding foam significantly reduced the stresses transmitted to the anatomical structures, thereby avoiding the risk of pelvic fracture. The analysis has proven that the auxetic polyurethane foam can be used as a good energy absorber.

Nasal septum morphology in human fetuses in computed tomography images.

OBJECTIVES: Nasal septum deformation (NSD) may cause breathing dysfunction. The reason for a septal deviation is the developmental anomaly in growth of the elastic septum or its skeleton. Such a type of deviation is called physiological. Some deviations can result from the prenatal trauma. The aim of the work was the analysis of the anatomy of the nasal cavity with a special interest focused on the nasal septum and its deviation. MATERIAL AND METHODS: The nasal cavity with its bones and septum was analyzed in CT images of 105 spontaneously aborted fetuses (57 males and 48 females) aged 12 and 40 weeks of gestation. We attempted to assess the morphometric development of the nasal cavity with tomographic scanning methods and to detect anatomical variations. RESULTS: In 15 (14.3%) fetuses, NSD were detected on radiological sections. The angle between the virtual line from the sphenoid sinus ostium through limen nasi and the horizontal plane was 33.6 ±2.3°, on average. CONCLUSIONS: NSD may already be found in fetuses. The observation of the nasal cavity development enables to evaluate the growth and symmetry of the nasal septum and to foretell predispositions for dysfunction in the upper respiratory tract.