Hinge Plate Research Articles

A new species and genus of Lower Jurassic rhynchonellide (Brachiopoda) from Livari (Rumija Mountain, Montenegro): taxonomic implications of the shell microstructure

ABSTRACT A new rhynchonellide brachiopod genus and species, Skadarirhynchia semicostata gen. et sp. nov., is described from the late Pliensbachian of Livari, Rumija Mountain, southeastern Montenegro. It occurs in shallow-water brachiopod-crinoid packstone beds (bioclastic limestones) of the periplatform facies of the Dinaric Carbonate Platform. Stratigraphy is constrained by means of 87Sr/86Sr dating indicating a late Pliensbachian age, and by the fact that the brachiopod beds lie immediately below the Toarcian marly limestones, which is consistent with the regional stratigraphical position. The new species has a circular to roundly pentagonal outline and semicostate shells with 10‒12 strong angular ribs. Internally, it shows reduced dental plates, narrow and thin hinge plates inclined dorsally with small crural bases, crescent-like and laterally convex, and hamiform crura. The shell microstructure of the new taxon is characterised by a homogeneous secondary layer (a single layer with no sublayers) built of rhombic fibres that are typically of coarse-fibrous type (eurinoid pattern) 35‒50 μm wide and 20‒30 μm thick. Other co-occurring rhynchonellide species such as Prionorhynchia fraasi and Cuneirhynchia dalmasi are also described. Shell microstructures for the genus Cuneirhynchia are presented.

Reinforcement of Insufficient Transverse Connectivity in Prestressed Concrete Box Girder Bridges Using Concrete-Filled Steel Tube Trusses and Diaphragms: A Comparative Study

To address the issue of insufficient transverse connectivity in prestressed concrete box girder (PCB) bridges, this study investigates two transverse strengthening methods—installing diaphragms and utilizing concrete-filled steel tube trusses (CFSTTs). A finite element model was developed for a typical 30 m PCB bridge and was validated by on-site load test results for reliability. Based on the deflection and load distribution of PCB bridges before and after reinforcement, as well as the maximum stress and strain of the diaphragms and the CFSTTs, comparative analyses were conducted on diaphragms of different thicknesses and materials, as well as on CFSTTs of various strength grades. The results show that the addition of a transverse partition and CFSTTs can effectively improve the load distribution of the PCB bridge and reduce the maximum deflection of the girder, especially when using the CFSTT reinforcement method. The unique structural design improves the reinforcement effect of the material in the post-elastic stage. When using CFSTTs, increasing the steel tube wall strength significantly reduces the maximum deflection of the main girder. For example, using steel tubes with yield strengths of 235 MPa and 420 MPa filled with concrete of 50 MPa compressive strength reduced the maximum deflections by 15.32% and 24.55%, respectively, and improved the load distribution coefficients by up to 7.31% and 11.57%. Additionally, steel diaphragms demonstrated better reinforcement effects compared with concrete diaphragms. The load transverse distribution coefficients for the CFSTT-reinforced PCB bridge were calculated using the hinge plate (beam) and the rigid plate (beam) methods, showing minimal differences between the two approaches. The findings of this study provide valuable insights into the design of diaphragm and CFSTT reinforcement in PCB bridges, aiding in the selection of optimal reinforcement strategies.

Hinge screw or no hinge stabilization provides decreased stability compared to hinge plate in a biomechanical evaluation of distal femoral derotational osteotomies.

Derotational distal femoral osteotomy (DFO) is the causal treatment for patients with femoral torsional deformity. The fixation is achieved by a unilateral angle-stable plate. Delayed- or non-unions are one of the main risks of the procedure. An additional contralateral fixation may benefit the outcome. Therefore, we hypothesize that primary stability in DFO can be improved by an additional fixation with a hinge screw or an internal plate. Derotational DFO was performed in 15 knees and fixed either with an angle-stable plate only (group 'None'), with an additional lateral screw (group 'Screw') or with an additional lateral plate (group 'Plate'). Biomechanical evaluation was carried out under axial loading of 150 N (partial weight bearing) and 800 N (full weight bearing), followed by internal and external rotation. After linear axial loading in step 1, a cyclic torsional load of 5 Nm was applied under constant axial load in step 2. In step 3, the specimens were unloaded. Micromovements between the distal and proximal parts of the osteotomy were recorded at each step for all specimens. In step 1, the extent of micromovements was highest in group 'None' and lowest in group 'Plate' without being significantly different. In step 2, group 'Plate' showed significantly higher stability, reflected by less rotation and lower micromovements. Increasing the axial load from 150to 800 N at step 2 resulted in increased stability in all groups but only reached significance in group 'None'. An additional contralateral plate significantly increased stability in derotational DFO compared to the unilateral angle-stable plate only. Contrary, a contralateral hinge screw did not provide improved stability. Experimental study. IV.

SCOPING REVIEW OF ROTATIONAL GUIDED GROWTH IN THE GROWING BONE

The aim of this scoping review is to understand the extent and type of evidence in relation to the use of guided growth for correcting rotational deformities of long bones. Guided growth is routinely used to correct angular deformities in long bones in children. It has also been proven to be a viable method to correct rotational deformities, but the concept is not yet fully examined. Databases searched include Medline, Embase, Cochrane Library, Web of Science and Google Scholar.All identified citations were uploaded into Rayyan.ai and screened by at least two reviewers. The search resulted in 3569 hits. 14 studies were included: 1 review, 3 clinical trials and 10 pre-clinical trials. Clinical trials: a total of 21 children (32 femurs and 5 tibiae) were included. Surgical methods were 2 canulated screws connected by cable, PediPlates obliquely oriented, and separated Hinge Plates connected by FiberTape. Rotation was achieved in all but 1 child. Adverse effects reported include limb length discrepancy (LLD), knee stiffness and rebound of rotation after removal of tethers. 2 pre-clinical studies were ex-vivo studies, 1 using 8-plates on Sawbones and 1 using a novel z-shaped plates on human cadaver femurs. There were 5 lapine studies (2 using femoral plates, 2 using tibial plates and 1 using an external device on tibia), 1 ovine (external device on tibia), 1 bovine (screws and cable on metacarp) and a case-report on a dog that had an external device spanning from femur to tibia. Rotation was achieved in all studies. Adverse effects reported include implant extrusions, LLD, articular deformities, joint stiffness and rebound. All included studies conclude that guided growth is a viable treatment for rotational deformities of long bones, but there is great variation in models and surgical methods used, and in reported adverse effects.

Technical Advances in Pectus Bar Stabilization in Chest Wall Deformity Surgery: 10-Year Trends and an Appraisal with 1,500 Patients.

We aimed to demonstrate the advances we have achieved in pectus excavatum surgery over the last 10 years, with a particular focus on the refinement of pectus bar stabilization techniques and devices. In total, 1,526 patients who underwent minimally invasive repair of pectus excavatum surgery from 2013 to 2022 were enrolled and analyzed. We have pursued a new paradigm of crane-powered remodeling of the entire chest wall. The method of bar stabilization has changed from claw fixators to hinge plates and, finally, to bridge plate connections. We also evaluated the effectiveness of the hinge plate (group H) and the bridge plate (group B). The bar displacement rates were 0.1% (n=2) for the claw fixator, 0% for the hinge plate (n=0), and 0% for the bridge plate (n=0). We stopped using the claw fixator in 2022 and the hinge plate in 2019. Since 2022, when we shifted to a multiple-bar technique for all patients, the bridge plate has replaced both the claw fixator and the hinge plate. No bar displacement occurred in either group. Group H had more pleural effusion, wound problems (p<0.05), and longer stays (5.5 vs. 6.2 days, p=0.034) than group B. We have made significant progress in pectus repair surgery over the last decade, particularly in stabilizing the pectus bar and reducing perioperative complications. Our current strategy is the multiple-bar approach with bridge stabilization. Since the bridge-only technique resulted in no bar displacement, we could eliminate the invasive claw fixator or hinge plate.

Rotational Guided Growth: A Preliminary Study of Its Use in Children.

Torsional malalignment of the legs is common in children, and those that do not remodel may benefit from surgical correction. Traditionally, this is corrected with an open osteotomy. Guided growth is the gold standard for minimally invasive angular correction and has been investigated for use in torsional deformities. This study presents our preliminary results of rotationally guided growth in the femur and tibia using a novel technique of peripheral flexible tethers. A total of 8 bones in 5 patients were treated with flexible tethers consisting of separated halves of a hinge plate (Orthopediatrics Pega Medical, Montreal, QC, Canada), which were fixed to the epiphysis and metaphysis at 45° angles to the physis and connected with Fibertape (Arthrex, Naples, FL, USA). The implants are placed medially and laterally in the opposite 45° inclination, determined by the desired direction of rotation. Additionally, the average treatment time was 12 months. All patients corrected the rotational malalignment by clinical evaluation. The average rotational change was 30° in the femurs and 9.5° in the tibias. Further, the average follow-up was 18 months, with no recurrence of the rotational deformity. There was no change in longitudinal growth in the patients who underwent bilateral treatment. Rotational guided growth with flexible tether devices is a novel technique that successfully corrects torsional malalignment without invasive osteotomy surgery.

Element variation in a clam shell and its implications for cold seep irregular eruptions: Calyptogena sp. in the Haima cold seep

Cold seep is characterized by methane-rich fluids released from subsurface reservoirs, and it sustains the chemosynthetic ecosystems on the seafloor. Previous studies suggest that the activity of cold seep could affect the seawater chemistry and ambient temperature. However, the short-term seep activity was hardly reconstructed due to the focus of studies on carbonate or sediment. Vent macrofauna provide such an opportunity by recording in shells the immediate environment in which they grow. The carbonate skeleton of organisms could theoretically preserve environmental variation. Therefore, high-resolution archives are urgently required to understand the influence of cold seep activity on biogeochemistry. In this study, SEM, EDS mapping, EBSD mapping, and LA-ICP-MS analyses were conducted on a clam (Calyptogena sp.) shell collected alive in 2018 from the Haima cold seep in South China Sea. The CaCO3, Na, Mg, Sr, and Ba contents and the Sr/Ca, Ba/Ca, and Na/Ca ratios in the hinge plate were measured on LA-ICP-MS by spot analysis and line scanning. The element contents in the hinge are as follows: Mg (38.5–109 μg/g), Na (3117–5246 μg/g), Sr (970–5371 μg/g), and Ba (2.9–11.5 μg/g). The results show that Sr, Re, and Ba content vary synchronously along the direction of growth, but Na has an opposite trend. The element analyses indicate that the eruption of the Haima cold seep was irregular, causing temperature, redox state, and pH changes in the cold seep ecosystem. These findings show that the irregular cold seep activities exert vital influences on the biogeochemistry of the cold seep ecosystem, which shed a light on cold seep biomonitoring.

Callovian (Middle Jurassic) Sphriganaria (Brachiopoda) from the Jordan Valley (Middle East)

ABSTRACT Middle Jurassic terebratulide brachiopods from the Jordan Valley are herein described and a new taxon is added to the previous faunal list. The Callovian rocks (Mughanniyya Formation) of the Tel el Dhahab section have yielded the following terebratulide taxa: Sphriganaria capax, S. costata, S. costellata, S. curtirostra, S. expansa, S. irregularis, S. subcircularis, S. nasuta, S. sp. 1, and S.? sp. 2. A new species Sphriganaria anyamiae sp. nov. is formally described herein. Internal characters of Sphriganaria costata, S. expansa, and S. nosuta have been studied. On the basis of shell microstructure, crural bases, outer and inner hinge plates were differentiated and defined for the first time in the genus Sphriganaria. The secondary layer is homogeneous built of very fine fibres, predominantly anisometric-like in cross-section, 25‒40 μm wide and 8‒15 μm thick. The Callovian Mughanniyya Formation of northwest Jordan is dominated by highly fossiliferous limestones intercalated with marlstone beds with very diverse brachiopod fauna, deposited in shallow, low-energy waters very near the equator. A paleobiogeographic interpretation of the brachiopod faunas in the Ethiopian Province suggests that brachiopods migrated from the north in the Early Jurassic and later became isolated for the remainder of the period.

Platymerella—a cool-water virgianid brachiopod fauna in southern Laurentia during the earliest Silurian

AbstractPlatymerella from the lower Red Mountain Formation in Georgia and Tennessee, the Bowling Green Dolomite of west-central Illinois, and the Elwood Dolomite of northeastern Illinois represents a paleosubtropical, cool-water occurrence of virgianid brachiopods in Laurentia during the early Silurian (middle–late Rhuddanian). These occurrences were located in the southern Appalachian foreland basin and the distal end of the Sebree Trough, likely subjected to frequent cool-water current and upwelling from Gondwana. Compared with broadly coeval species of Virgiana from lower paleotropical to equatorial latitudes, Platymerella has significantly smaller, dorsoventrally flattened shells, with subequal ventral and dorsal umbones and beaks that extend only slightly above the hinge line. Relative to its shell size, however, Platymerella has more prominent thickening of the shell wall, median septum, spondylium, and hinge plates than Virgiana, resembling more closely the extravagant shell thickening of Tcherskidium and Proconchidium from the Late Ordovician (late Katian) equatorial regions. The thickening of hinge plates resulted in the formation of a pseudocruralium, which separates Platymerella from Virgiana. In latest Ordovician–earliest Silurian virgianids, there was a general morphological gradient toward a smaller shell, reduction in the ventral-valve convexity, and reduction in the size and height of the ventral umbo from paleoequatorial to southern subtropical regions, with Platymerella representing the most southerly forms.

LOQTEQ® VA Periprosthetic Plate-A New Concept for Bicortical Screw Fixation in Periprosthetic Fractures: A Technical Note.

Internal fixation using angle stable plates is the treatment standard in periprosthetic fractures around stable implants. To provide instant postoperative full weight-bearing, bicortical screw fixation is advisable but often surgically demanding. This work presents the first clinical results of the LOQTEQ® VA Periprosthetic Plate (aap Implantate AG, Berlin, Germany), a new plate system to simplify screw placement around implants. This plate system uses insertable hinges that allow for variable angle screw anchorage. Data of 26 patients with a mean age of 80 years and a mean follow-up of 13.9 months were retrospectively collected. Patients were clinically and radiologically examined. Bony union was achieved in 14 out of 15 patients with no signs of non-union or implant loosening. One patient, however, presented with implant failure. Clinical scores demonstrated acceptable results. Since the hinge plates are easy to apply, the first results are promising.

Hinge-type FBG acceleration sensor based on double elastic plate

It is critical for the health monitoring of large-scale structures such as bridge, railway and tunnel to acquire the medium-frequency and high-frequency vibration signals. To solve the problems of low sensitivity and poor transverse anti-interference of the medium-frequency and high-frequency fiber acceleration sensor, a hinge-type Fiber Bragg Grating(FBG) acceleration sensor based on double elastic plate has been proposed, and the hinge and elastic plate are used as elastomer to realize the miniaturization and transverse interference suppression of the sensor. The MATLAB and the ANSYS are used for theoretical analysis and optimization of sensor sensitivity and resonance frequency, structural static stress analysis and modal simulation analysis, while the test system is built to test the sensor performance. The results show that the resonance frequency of the sensor is 1300 Hz; the sensor has a flat sensitivity response in the middle-high frequency band of 200–800 Hz; the sensitivity is about 20 pm/g, and the fiber central wavelength drift and acceleration have good linearity and stability, while the transverse anti-interference is about 3.16%, which provides a new idea for monitoring of medium-frequency and high-frequency vibration signals in large-scale structures.

Hinge plate technique for osteosynthesis of comminuted proximal humeral fractures

BackgroundSeveral surgical techniques of osteosynthesis have been described for treatment of proximal humeral fractures. There is evidence that the quality of reduction improves the clinical outcome and decreases the number of complications. Reduction of the medial calcar is tricky when standard manoeuvres are performed. We have therefore augmented our standard surgical technique with a low-profile medial hinge plate which aims at better reconstructing the medial metaphysis without extensile soft tissue dissection in combination with proximal humerus locked plating. ObjectiveEvaluate the radiological and clinical outcome after application of an augmented fixation with a low-profile medial hinge plate. We questioned: (i) The quality of reduction, (ii) The rate of complications, (iii) The clinical function in terms of the Oxford Shoulder Score (OSS). MethodsA retrospective single-centre case series. Between 2016 and 2019, patients who had undergone open reduction and osteosynthesis by an anatomical locking plate associated with a 2.0 mm locking compression plate used as a hinge to support the medial metaphysis. Thirty-four patients, with an average age of 64 years had a clinical and/or radiological average follow-up of 36 months. ResultsThe preoperative imaging identified three fractures in two parts, 19 fractures in three parts and 12 fractures in four parts. Seven cases with fracture-dislocation were identified, one head-split fracture, and 14 cases with a metaphyseal head extension of less than 8 mm. After comparing head-shaft displacement, cranialisation of the greater tuberosity as well as head-shaft alignment in the preoperative and postoperative radiographs, overall anatomical or near-anatomical fracture reduction was achieved in 27 of the patients.Only two cases presented postoperative complications. The two cases were complicated with nonunion without screw perforation requiring surgical intervention by re-osteosynthesis. The clinical outcome assessed by the OSS showed an average of 45/48.The age of the group with anatomical or near anatomical reduction and the group with at least one parameter of malreduction was significantly different, 65 and 74 years respectively (p<0.05). No significant differences were found when comparing the sex, surgical time, time to operation or the number of fracture parts. ConclusionThe technique described provides a surgical treatment option with lower complication rates and a quality of reduction consistent with the current literature as well as a satisfactory clinical outcome.

Intraspecific Variation in the Common Pea Clam, Pisidium casertanum (Poli, 1791) (Bivalvia: Sphaeriidae): A Geometric Morphometric Analysis

The morphological plasticity of bivalve species may impair their correct identification. Pisidium species (Sphaeriidae) are difficult to distinguish, notably the common pea clam, Pisidium casertanum (Poli, 1791), which is a polymorphic species, often misidentified and confused with other Pisidium species. This is especially true since this species is the most euryecious of the genus, being able to colonize very different habitats. In this study, elliptic Fourier Analysis, a geometric morphometric method, was used to assess intraspecific variation in P. casertanum. Sampling of specimens was done in three habitat types – springs, lakes and streams – in the Mediterranean biodiversity hotspot region, using the Sebou basin in Morocco as a study area. In addition to the geometric morphometric method, linear measurements of the shell were used to assess growth patterns. Results revealed differences in the hinge plate, which is broader in shells collected from lakes, whereas it is higher in shells of springs. The geometric morphometric method clearly showed shape differences between individuals of the three habitats. Specimens of lakes were the most distinguishable, presenting more elongated shells than those from springs and streams, which are shorter but higher. Individuals from the three habitat types presented a negative allometric growth pattern whereby the shell of animals grows more slowly in height than in length. The use of linear and geometric morphometric methods led to conclude that the morphology of P. casertanum is, in fact, highly influenced by its environment, in particular, its habitat type.

Temperature-induced microstructural changes in shells of laboratory-grown Arctica islandica (Bivalvia).

Bivalve shells are increasingly used as archives for high-resolution paleoclimate analyses. However, there is still an urgent need for quantitative temperature proxies that work without knowledge of the water chemistry–as is required for δ18O-based paleothermometry–and can better withstand diagenetic overprint. Recently, microstructural properties have been identified as a potential candidate fulfilling these requirements. So far, only few different microstructure categories (nacreous, prismatic and crossed-lamellar) of some short-lived species have been studied in detail, and in all such studies, the size and/or shape of individual biomineral units was found to increase with water temperature. Here, we explore whether the same applies to properties of the crossed-acicular microstructure in the hinge plate of Arctica islandica, the microstructurally most uniform shell portion in this species. In order to focus solely on the effect of temperature on microstructural properties, this study uses bivalves that grew their shells under controlled temperature conditions (1, 3, 6, 9, 12 and 15°C) in the laboratory. With increasing temperature, the size of the largest individual biomineral units and the relative proportion of shell occupied by the crystalline phase increased. The size of the largest pores, a specific microstructural feature of A. islandica, whose potential role in biomineralization is discussed here, increased exponentially with culturing temperature. This study employs scanning electron microscopy in combination with automated image processing software, including an innovative machine learning–based image segmentation method. The new method greatly facilitates the recognition of microstructural entities and enables a faster and more reliable microstructural analysis than previously used techniques. Results of this study establish the new microstructural temperature proxy in the crossed-acicular microstructures of A. islandica and point to an overarching control mechanism of temperature on the micrometer-scale architecture of bivalve shells across species boundaries.

A NEW VENEROID GENUS (MOLLUSCA: BIVALVIA) OF THE DANIAN OF PATAGONIA (CHUBUT PROVINCE, ARGENTINA)

Abstract. The endemic Patagonian genus Titomaya gen. nov. is erected to include the Danian Meretrix chalcedonica (Lefipan and Salamanca formations) and T. longobucca sp. nov. (Salamanca Formation) from the Chubut Province (Argentina). Although Meretrix and Titomaya share the same characteristic sculpture of their nymphs, Titomaya is differentiated by having medium to small, subtriangular, higher than long shells, a narrower and shorter hinge plate, smaller cardinal and anterior teeth, and by the development of a deeper pallial sinus. This new genus rules out the presence of Meretrix in Patagonia as long believed and increases the list of endemic taxa that characterize the Danian assemblages of Patagonia.

Altered Glenohumeral Biomechanics in Proximal Humeral Fracture Malunion.

There is little biomechanical evidence to support the traditional guideline that 45° represents acceptable proximal humerus deformity. We evaluated glenohumeral contact pressure (GP) and area, subacromial contact pressure, and joint abduction to assess biomechanical changes with different proximal humerus deformities. Fifteen fresh-frozen cadaver shoulders were used. Intact specimens were tested on a custom dynamic shoulder frame. Subsequently, a surgical neck fracture was made in each specimen and fixed using a custom dual hinge plate for fixation of 15°, 30°, and 45° deformities in varus, valgus, antecurvatum, retrocurvatum, and combined varus-antecurvatum and valgus-retrocurvatum. Specimens were then retested. Compared with the intact state, GP was markedly lower with all levels of varus and varus-antecurvatum deformity. Valgus and combined valgus-retrocurvatum deformity of 45° led to notable increases in GP compared with the intact state. Varus deformities of 30° and 45° caused significant increases in subacromial pressures and limited abduction markedly from 60° to 54.2° and 44.6° (P < 0.001). Varus and antecurvatum proximal humerus deformities as small as 15° were associated with notable alterations in glenohumeral joint mechanics. With valgus and retrocurvatum deformity, statistically significant joint alterations occurred only at higher deformity levels.

Early Stage Variation Simulation and Visualization of Compliant Part Based on Parametric Space Envelope

Compliant, nonrigid parts are widely used in many industries today. Existing variation simulation analysis on the manufacturing part focuses on orientation and position deviation with part shape errors being largely omitted. This is a valid approach for the rigid part, but it is unrealistic and can be problematic for the compliant part. In this study, a new methodology has been introduced to compliant assembly early phase design to generate various probable variated manufacturing parts that conform to predefined tolerance specification or meet the certain industrial requirement. The proposed method is based upon the novel idea of a parametric space envelope, a purpose-designed variation tool constructed from parametric curves. Variation of embedded manufacturing part is linked to and controlled by a compact set of envelope’s boundary control points. Part variation instances are generated by simulating the control points’ movement in a systematic and efficient way. Importantly, simulated variations can be visualized in 3-D virtual space to provide user insight into part variation. The proposed methodology can help identify assembly high-risk regions, select proper fixtures, guide assembly engineering changes, and optimize assembly operations. An industrial case study on a deformable vehicle door hinge plate is presented to illustrate the methodology. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —This article is motivated by two acute problems encountered in geometric variation simulation analysis for compliant parts in the early design stage. First, form errors of the nonrigid part are not fully captured in existing methods. Second, variation visualization can significantly enhance understanding of the geometric variation effects, but it is difficult to achieve under existing approaches. Inspired by the idea of a parametric space envelope, this article proposes a new methodology by building a variation tool to aid the task. Under the proposal, the geometric variation of the compliant part is indirectly modeled through the constructed variation tool. This indirect modeling enables capturing intrapart interactions that are the major source of the inaccuracy of existing methods. The simulated geometric variation can be visualized through the variation tool. In addition, the developed method does not rely on historical manufacturing experience. This can be valuable for early stage designer when such production information is not available or expensive to get. Furthermore, the proposed method can be integrated into existing computer-aided design (CAD), computer-aided manufacturing (CAM), and computer-aided engineering (CAE) systems to improve overall design quality and reduce reliance on multiple physical prototyping.

Paleoecology and proliferation of the bivalve Chondrodonta joannae (Choffat) in the upper Cenomanian (Upper Cretaceous) Adriatic Carbonate Platform of Istria (Croatia)

Chondrodonta joannae (Choffat) is a morphologically variable oyster-like bivalve with a predominately calcitic shell. An exceptional exposure of C. joannae-bearing strata of late Cenomanian age crops out along the seaside in northern Istria (Croatia) and permits a taphonomical and functional analysis in order to define the life habit and growth strategies of this bivalve. The C. joannae population from the studied succession is characterized by highly-elongated, large and curved shells, reaching about 50 cm in height and 5 cm in length. This shell shape is typical of the club-like bivalve morphotype, which was adapted to soft-bottom substrates with high sediment accumulation. The shell is slightly inequivalve and characterized by a reduced body cavity, a few centimetres high, and a dorsal region up to 10 times longer. The shell opening mechanism was mostly based on the resilium located between the chondrophores which protrude in the body cavity. The abandoned dorsal cavity is filled by a calcite hinge plate, the ventral edge of which acted as fulcrum for the valve flexibility. In the hinge plate, the function of chondrophores changed. They acted as a hinge to keep tightly interlocked the valves, which considerably emerged above the sediment-water interface. The individuals were arranged in low shrub-type congregations, which produced low-relief mounds. The functional morphology and taphonomic signature suggest that C. joannae individuals collected food at a greater distance from the bottom with respect to the co-occurring rudists. We speculate that the C. joannae proliferation could be related to a late Cenomanian phase of environmental instability predating the OAE2 with fluctuating climatic conditions and ocean fertility.

Periprosthetic fracture fixation in Vancouver B1 femoral shaft fractures: A biomechanical study comparing two plate systems.

IntroductionPeriprosthetic fractures of the femur are an increasing problem in today's trauma and orthopaedic surgery. Owing to the hip stem, implant anchorage is very difficult in the proximal femur. This study compares two plate systems regarding their biomechanical properties and the handling in periprosthetic fracture fixation of the proximal femur.Materials and methodsUsing eight pairs of fresh, frozen human proximal femora the Locking Compression Plate/Locking Attachment Plate construct (LCP/LAP) (group I, DePuy Synthes) was compared to the new LOQTEQ® periprosthetic distal lateral femur plate (group II, AAP Implantate AG). After implantation of press fit femoral hip stems a Vancouver B1 fracture model was used. Biomechanical testing was performed by cyclic axial loading with a constant increment of 0.1 N/cycle starting from 750 N axial loading. Every 250 cycles an a.p. x-ray was done to evaluate failure.ResultsThe Group II showed significant higher axial stiffness (+42%) compared with Group I. In addition, Group II withstood significantly more load-cycles until failure (20%). The mode of catastrophic failure was plate breakage in Group II, whereas, in Group I, all plates showed an early bending followed by plate breakage.Discussion and conclusionBoth plate systems enable screw placement around hip stems. The hinge plate showed superior biomechanical results compared with the locking compression plate/locking attachment plate construct. Furthermore, the hinge plate offers variable hinges and variable angel locking making bicortical screw placement around hip stems more comfortable and safe.The translational potential of this articleThe results of this study can be directly transferred to patient care. With the innovative hinge plate, the surgeon has a biomechanically superior implant, which also offers improved options for screw placement compared to a standard locking plate.

Varus ankle arthritis: a modified operation with a novel osteotomy and lateral hinge plate fixation technique.

Varus ankle arthritis: a modified operation with a novel osteotomy and lateral hinge plate fixation technique.