Ultrastructure of the Jurassic serpulid tubes-phylogenetic and paleoecological implications.

The ultrastructural diversity of the Middle and Late Jurassic serpulid tubes from the Polish Basin has been investigated. The inspection of 12 taxa representing the two major serpulid clades allowed for the identification of three ultrastructure types-irregularly oriented prismatic structure (IOP), spherulitic prismatic structure (SPHP), and simple prismatic structure (SP). Six of the studied species are single-layered and six species possess two distinct layers. Ultrastructural diversity corresponds to certain serpulid clades. The members of Filograninae have single-layered tube walls composed of possibly plesiomorphic, irregularly oriented prismatic structure (IOP). Two-layered tubes occur solely within the clade Serpulinae, where the external, denser layer is built of either the ordered spherulitic (SPHP) or simple prismatic microstructure (SP), and the internal layer is composed of irregularly oriented prismatic structure (IOP). Apart from phylogenetic signals provided by the tube ultrastructure, it can be used in analyzing paleoecological aspects of tube-dwelling polychaetes. Compared to the more primitive, irregularly oriented microstructures of Filograninae, the regularly oriented microstructures of Serpulinae need a higher level of biological control over biomineralization. The advent of the dense outer protective layer (DOL) in serpulids, as well as the general increase in ultrastructure diversity, was likely a result of the evolutionary importance of the tubes for serpulids. Such diversity of the tube ultrastructural fabrics allowed for maximizing functionality by utilizing a variety of morphogenetic programs. The biomineralization system of serpulids remains more complex compared to other tube-dwelling polychaetes. Physiologically more expensive tube formation allows for mechanical strengthening of the tube by building robust, strongly ornamented tubes and firm attachment to the substrate. Contrary to sabellids, which perform a fugitive strategy, an increased tube durability allows serpulids a competitive advantage over other encrusters.

Assessment of serpulid-hydroid association through the Jurassic: A case study from the Polish Basin.

The coexistence of sessile, tube-dwelling polychaetes (serpulids) and hydroids, has been investigated. Serpulid tubes bearing traces after hydroids are derived from different stratigraphic intervals spanning the Middle and Upper Jurassic, the rocks of which represent the diverse paleoenvironments of the Polish Basin. Although fossil colonial hydroids classified under the species Protulophila gestroi are a commonly occurring symbiont of these polychaetes during the Late Cretaceous and Cenozoic, they seem to be significantly less frequent during the Jurassic and limited to specific paleoenvironments. The hydroids described here are represented by traces after a thin stolonal network with elongated polyp chambers that open to the outer polychaete tube's surface with small, more or less subcircular apertures. Small chimney-like bulges around openings are an effect of the incorporation of the organism by in vivo embedment (bioclaustration) within the outer layers of the calcareous tube of the serpulid host. Considering the rich collection of well-preserved serpulid tubes (>3000 specimens), the frequency of bioclaustrated hydroids is very low, with an infestation percentage of only 0.6% (20 cases). It has been noticed that only specimens of the genus Propomatoceros from the Upper Bajocian, Lower Bathonian, Middle Bathonian, and Callovian have been found infested. However, the majority of bioclaustrated hydroids (17 cases) have been recorded in the Middle Bathonian serpulid species Propomatoceros lumbricalis coming from a single sampled site. Representatives of other genera are not affected, which is congruent with previous reports indicating that Protulophila gestroi was strongly selective in the choice of its host. A presumably commensal relationship is compared with the recent symbiosis between the hydroids of the genus Proboscidactyla and certain genera of sabellid polychaetes.

Analysis of the Impact of Configuration of the Stabilisation System for Femoral Diaphyseal Fractures on the State of Stresses and Displacements.

INTRODUCTION: The treatment of femoral diaphyseal fractures by intramedullary nailing has become a common procedure in orthopaedic surgery. The purpose of this numerical simulation was to present how the changes in configuration of the stabilisation system can affect the stress and displacement state in the bone tissue and implanted device. MATERIAL AND METHODS: The numerical comparison of the stabilisation variants for the type 32-A2 femoral diaphyseal fracture (according to the AO classification) performed by using the Charfix2 (ChM®) anatomical nail locked in a number of chosen ways. The displacement and the stress distributions both in the bone and implant were obtained and analysed by computational simulation. RESULTS: In all models, there was the same characteristic distribution, which shows there were minimal rotational movements of the bone around the anatomical axis. In all cases, stress concentrations were generated in the nail material in the area of the fracture gap. CONCLUSIONS: The obtained results indicate that there is a visible advantage to one-plane distal stabilisation in the reduction of stresses regardless of the type of proximal stabilisation. The results of calculations indicate that the use of proximal stabilisation with a neck screw reduces the possibility of damage to the implant.

Numerical modeling of the traction process in the treatment for Pierre-Robin Sequence.

INTRODUCTION: The goal of this numerical study was to identify the results of modulated growth simulation of the mandibular bone during traction in Pierre-Robin Sequence (PRS) treatment. METHODS: Numerical simulation was conducted in the Ansys 16.2 environment. Two FEM (finite elements method) models of a newborn's mandible (a spatial and a flat model) were developed. The procedure simulated a 20-week traction period. The adopted growth measure was mandibular length increase, defined as the distance between the Co-Pog anatomic points used in cephalometric analysis. RESULTS: The simulation calculations conducted on the developed models showed that modulation had a significant influence on the pace of bone growth. In each of the analyzed cases, growth modulation resulted in an increase in pace. The largest value of increase was 6.91 mm. The modulated growth with the most beneficial load variant increased the basic value of the growth by as much as 24.6%, and growth with the least beneficial variant increased by 7.4%. CONCLUSIONS: Traction is a simple, minimally invasive and inexpensive procedure. The proposed algorithm may enable the development of a helpful forecasting tool, which could be of real use to doctors working on Pierre-Robin Sequence and other mandibular deformations in children.

Complication of a Femoral Fracture Treated by Intramedullary Nailing - Numerical Analysis of a Clinical Case.

The aim of this paper is to conduct a numerical analysis of a case of femoral fracture treated by intramedullary nailing and confirm the conditions which led to the formation of a pseudarthrosis at the fracture site. A low-energy femoral fracture was treated by placing a ChFN System intramedullary nail with a derotation pin. Using the finite element method, a bone-implant system was generated which made it possible to observe the displacement area and strains in the region of the fracture gap. The calculations were conducted for 3 variants of the model, using a titanium nail (10 mm and 12 mm) and a steel one (10 mm). Analysis of strain distribution indicated that the highest strain values occur in the fracture gap and that they are higher when a titanium alloy is used (0-17% vs 0-11%). Interfragmentary movements caused by an imposed load were also higher when a titanium alloy implant was used. Strain analysis showed that the percentage of elements in the gap area which are potentially able to grow bone tissue is higher when a steel implant is used. It is possible to indicate sites where unfavourable fracture gap healing will take place, which may lead to the development of a pseudarthrosis. The use of a steel implant increases the probability of obtaining stable bone union.

Biomechanics of distal femoral fracture fixed with an angular stable LISS plate.

Fractures of the distal end of the femur are infrequent and constitute less than 1% of all fractures. Only 3% to 6% of femoral fractures occur at the distal end. The two groups most at risk of the said fractures are young men and older women. The aim of treatment of fractures of the distal femur is to restore normal function of the knee joint. The authors asked themselves whether, following fixation of a 33-C2 fracture (according to the AO classification) with a LISS plate, a rehabilitation program can be undertaken immediately after surgery with the implementation of active movements in the knee joint of the operated limb. In order to answer this question, we created a digital model of a fractured femur fixed with the LISS method. The model was subjected to loads corresponding to the loads generated during active lifting of a limb extended in the knee joint and during flexing of a limb in the knee joint to the 90° angle. Interfragmentary movement (IFM) is one of the key parameters taken into account in the treatment of bone fractures. It allows classification of the treatment in terms of its quality both from the mechanical and histological points of view. We analyzed interfragmentary movement in all fracture gaps. The largest recorded displacement reached in our model was 243 µm, which, in the light of the literature data, should not interfere with bone consolidation, and thus implementation of active movement in the operated knee joint (keeping in mind the simplifications of the experimental method used) is possible in the early postoperative period.

Procedure of generating the individually matched bone scaffolds.

The pace of modern life forced continuous high readiness and proper condition of motion systems on human beings. The techniques used in medicine and orthopaedics enable treatment of even highly complicated injuries and pathological states. One of them involves the use of bone scaffolding - the technique being intensively developed, which seems to have a promising future. Based on a numerical modelling, it is possible to match that type of implant to the needs of individual patient, with consideration for both biomechanical factors (patient weight, bone size and its defects) and the applicable implantation techniques. Vast possibilities are offered by the application of the finite element method as a technique enabling verification of an implant with the individually matched geometry and material. The paper presents the procedure aimed at generating the bone scaffold structure that enables the stresses created in the contact places of implant with the surrounding bone tissue to be reduced. High stresses may lead to local damages to the tissue and, in extreme cases, to the destruction of a scaffold. The present procedure is based on the theory of genetic algorithms and, due to several models widely known in biomechanics, allows stresses in places of bone contact with implant to be significantly reduced.