Muscle-driven and torque-driven centrodes during modeled flexion of individual lumbar spines are disparate.

Lumbar spine biomechanics during the forward-bending of the upper body (flexion) are well investigated by both in vivo and in vitro experiments. In both cases, the experimentally observed relative motion of vertebral bodies can be used to calculate the instantaneous center of rotation (ICR). The timely evolution of the ICR, the centrode, is widely utilized for validating computer models and is thought to serve as a criterion for distinguishing healthy and degenerative motion patterns. While in vivo motion can be induced by physiological active structures (muscles), in vitro spinal segments have to be driven by external torque-applying equipment such as spine testers. It is implicitly assumed that muscle-driven and torque-driven centrodes are similar. Here, however, we show that centrodes qualitatively depend on the impetus. Distinction is achieved by introducing confidence regions (ellipses) that comprise centrodes of seven individual multi-body simulation models, performing flexion with and without preload. Muscle-driven centrodes were generally directed superior-anterior and tail-shaped, while torque-driven centrodes were located in a comparably narrow region close to the center of mass of the caudal vertebrae. We thus argue that centrodes resulting from different experimental conditions ought to be compared with caution. Finally, the applicability of our method regarding the analysis of clinical syndromes and the assessment of surgical methods is discussed.

Load Distribution in the Lumbar Spine During Modeled Compression Depends on Lordosis.

Excessive or incorrect loading of lumbar spinal structures is commonly assumed as one of the factors to accelerate degenerative processes, which may lead to lower back pain. Accordingly, the mechanics of the spine under medical conditions, such as scoliosis or spondylolisthesis, is well-investigated. Treatments via both conventional therapy and surgical methods alike aim at restoring a "healthy" (or at least pain-free) load distribution. Yet, surprisingly little is known about the inter-subject variability of load bearings within a "healthy" lumbar spine. Hence, we utilized computer tomography data from 28 trauma-room patients, whose lumbar spines showed no visible sign of degeneration, to construct simplified multi-body simulation models. The subject-specific geometries, measured by the corresponding lumbar lordosis (LL) between the endplates of vertebra L1 and the sacrum, served as ceteris paribus condition in a standardized forward dynamic compression procedure. Further, the influence of stimulating muscles from the M. multifidus group was assessed. For the range of available LL from 28 to 66°, changes in compressive and shear forces, bending moments, as well as facet joint forces between adjacent vertebrae were calculated. While compressive forces tended to decrease with increasing LL, facet forces were tendentiously increasing. Shear forces decreased between more cranial vertebrae and increased between more caudal ones, while bending moments remained constant. Our results suggest that there exist significant, LL-dependent variations in the loading of "healthy" spinal structures, which should be considered when striving for individually appropriate therapeutic measures.

Lumbar spinal ligament characteristics extracted from stepwise reduction experiments allow for preciser modeling than literature data.

Lumbar ligaments play a key role in stabilizing the spine, particularly assisting muscles at wide-range movements. Hence, valid ligament force-strain data are required to generate physiological model predictions. These data have been obtained by experiments on single ligaments or functional units throughout the literature. However, contrary to detailed spine geometries, gained, for instance, from CT data, ligament characteristics are often inattentively transferred to multi-body system (MBS) or finite element models. In this paper, we use an elaborated MBS model of the lumbar spine to demonstrate how individualized ligament characteristics can be obtained by reversely reenacting stepwise reduction experiments, where the range of motion (ROM) was measured. We additionally validated the extracted characteristics with physiological experiments on intradiscal pressure (IDP). Our results on a total of in each case 160 ROM and 49 IDP simulations indicated superiority of our procedure (seven and eight outliers) toward the incorporation of classical literature data (on average 71 and 31 outliers).

SNP-array based whole genome homozygosity mapping: a quick and powerful tool to achieve an accurate diagnosis in LGMD2 patients.

A large number of novel disease genes have been identified by homozygosity mapping and the positional candidate approach. In this study we used single nucleotide polymorphism (SNP) array-based, whole genome homozygosity mapping as the first step to a molecular diagnosis in the highly heterogeneous muscle disease, limb girdle muscular dystrophy (LGMD). In a consanguineous family, both affected siblings showed homozygous blocks on chromosome 15 corresponding to the LGMD2A locus. Direct sequencing of CAPN3, encoding calpain-3, identified a homozygous deletion c.483delG (p.Ile162SerfsX17). In a sporadic LGMD patient complete absence of caveolin-3 on Western blot was observed. However, a mutation in CAV3 could not be detected. Homozygosity mapping revealed a large homozygous block at the LGMD2I locus, and direct sequencing of FKRP encoding fukutin-related-protein detected the common homozygous c.826 C>A (p.Leu276Ile) mutation. Subsequent re-examination of this patient's muscle biopsy showed aberrant α-dystroglycan glycosylation. In summary, we show that whole-genome homozygosity mapping using low cost SNP arrays provides a fast and non-invasive method to identify disease-causing mutations in sporadic patients or sibs from consanguineous families in LGMD2. Furthermore, this is the first study describing that in addition to PTRF, encoding polymerase I and transcript release factor, FKRP mutations may cause secondary caveolin-3 deficiency.

Incidência dos tipos faciais de Ricketts (dolicofacial, mesofacial e braquifacial) nas maloclusões de classe I e classe II divisão 1ª / Incidence of ricketts facial types (dolicofacial, mesofacial and brachyfacial) on individuals with Angle class I or class II, division 1 malocclusions

Este estudo visa a determinar a incidência dos tipos faciais de Ricketts (braquifacial, mesofacial e dolicofacial) em portadores de maloclusão de Classe I e Classe II divisão 1ª, segundo a classificação de Angle, visto que a definição dos tipos faciais é de suma importância para o diagnóstico e planejamento ortodôntico. A amostra foi composta por telerradiografias em norma lateral de pacientes leucodermas, filhos ou netos de brasileiros descendentes de portugueses, espanhóis e/ou italianos, com 12 anos e 4 meses de idade, em média, sendo 40 pacientes portadores de maloclusão de Classe I (20 do gênero masculino e 20 do gênero feminino) e 40 pacientes portadores de maloclusão de Classe II divisão 1ª de Angle (20 do gênero masculino e 20 do gênero feminino). De acordo com a metodologia empregada neste trabalho, verificou-se uma tendência à maior distribuição de mesofaciais, seguido de braquifaciais e em menor número os dolicofaciais, segundo os tipos faciais de Ricketts. Analisando-se os resultados obtidos, observou-se que não ocorreram diferenças estatisticamente significantes na distribuição dos tipos faciais tanto no gênero masculino quanto no gênero feminino e a incidência dos tipos faciais nos grupos de maloclusão de Classe I e Classe II divisão 1ª se comportou de maneira semelhante, ou seja, os grupos tenderam à igualdade e as diferenças existentes nas comparações devem ser atribuídas a flutuações estatísticas. Na verdade, esses resultados tendem a indicar uma independência dos tipos faciais em relação às maloclusões dentais.