Ancestral morphology of crown-group molluscs revealed by a new Ordovician stem aculiferan.

Exceptionally preserved fossils provide crucial insights into extinct body plans and organismal evolution. Molluscs, one of the most disparate animal phyla, radiated rapidly during the early Cambrian period (approximately 535-520 million years ago (Ma)). The problematic fossil taxa Halkieria and Orthrozanclus (grouped in Sachitida) have been assigned variously to stem-group annelids, brachiopods, stem-group molluscs or stem-group aculiferans (Polyplacophora and Aplacophora), but their affinities have remained controversial owing to a lack of preserved diagnostic characters. Here we describe a new early sachitid, Calvapilosa kroegeri gen. et sp. nov. from the Fezouata biota of Morocco (Early Ordovician epoch, around 478 Ma). The new taxon is characterized by the presence of a single large anterior shell plate and polystichous radula bearing a median tooth and several lateral and uncinal teeth in more than 125 rows. Its flattened body is covered by hollow spinose sclerites, and a smooth, ventral girdle flanks an extensive mantle cavity. Phylogenetic analyses resolve C. kroegeri as a stem-group aculiferan together with other single-plated forms such as Maikhanella (Siphogonuchites) and Orthrozanclus; Halkieria is recovered closer to the aculiferan crown. These genera document the stepwise evolution of the aculiferan body plan from forms with a single, almost conchiferan-like shell through two-plated taxa such as Halkieria, to the eight-plated crown-group aculiferans. C. kroegeri therefore provides key evidence concerning the long debate about the crown molluscan affinities of sachitids. This new discovery strongly suggests that the possession of only a single calcareous shell plate and the presence of unmineralised sclerites are plesiomorphic (an ancestral trait) for the molluscan crown.

Morphological Asymmetry of the Superior Cervical Facets from C3 through C7 due to Degeneration.

INTRODUCTION: Knowledge about facet morphology has already been discussed extensively in literature but is limited regarding asymmetry and its relation to facet degeneration. METHOD: Facet dimensions, surface area, curvature, and degeneration of the superior facets were measured in 85 dried human vertebrae from the anatomical collection of the Vrije Universiteit Brussel. The vertebrae were analysed using the Microscribe G2X digitizer (Immersion Co., San Jose, CA) and a grading system for the evaluation of cervical facet degeneration. Coordinates were processed mathematically to evaluate articular tropism. The statistical analysis includes the paired t-test and the Pearson correlation. RESULTS: On average, no systematic differences between the left and right facets were found concerning morphology and degeneration. However, there were significant differences regardless of the side-occurrence. There was a significant correlation between the dimensions of the total facet surface and the degree of degeneration but not for the recognizable joint surface. CONCLUSIONS: Facet tropism of the upper joint facets occurred often in the cervical spine but without side preference. A bigger difference in degeneration asymmetry was associated with a bigger difference in facet joint dimension asymmetry.

A validation study of a new instrument for low cost bite force measurement.

Quantitative assessment of force in masticatory muscles is not a routine clinical test, probably due to the lack of an "easy-to-use" device. Aim of this study is (1) to present a low cost bite force instrument located in a custom-made housing, designed to guarantee a comfortable and effective bite action, (2) to evaluate its mechanical characteristics, in order to implement it in clinical settings and in experimental setups. Linearity, repeatability and adaptation over time were assessed on a set of four different sensors in bare and housed condition. Application of the housing to the transducer may appreciably alter the transducer's response. Calibration of the housed transducer is thus necessary in order to correctly record real bite force. This solution may represent a low cost and reliable option for biting force measurement and objective assessment of individual force control in the scientific and clinical setting.

Atlanto-axial facet displacement during rotational high-velocity low-amplitude thrust: An in vitro 3D kinematic analysis.

BACKGROUND: Very little is known about the kinematics of the upper cervical spine in particular during Manual Therapy techniques. In fact no data about displacement of the atlanto-axial joint during High-Velocity Low-Amplitude (HVLA) thrust are available. Knowing the precise kinematics of these vertebrae might allow a better comprehension of such important technique and possible vital structures involvement. METHODS: A Zebris CMS20 ultrasound-based motion tracking system was adopted. Twenty fresh human cervical specimens were used in this study. Facet joint displacements of C1 relative to C2 were analysed during three consecutive HVLA thrusts into rotation. Displacement during the thrust and the maximum displacement reached with the manoeuvre were analysed. RESULTS: Descriptive statistics showed a mean Norm displacement during the thrust of 0.5 mm (SD ± 0.5). The maximum displacement, representing the overall facet movement from neutral to end-range position, indicated a Norm value of 6.0 mm (SD ± 3.4). Heterogeneous displacement directions were found during the thrust. Intra and inter-rater reliability reached an insufficient reproducibility level. Considering the amount of displacement induced, no statistical significant differences between the registrations were shown. CONCLUSION: Displacement during the execution of HVLA thrust is unintentional, unpredictable and not reproducible. On the other hand and in accordance with other studies, the displacement induced with the present technique seems not to be able to endanger vital structure on the Spinal Cord and the Vertebral Artery. This study also adds to a better comprehension of the kinematic of the atlanto-axial segment during the performance of HVLA manipulation.

Anomalocaridid trunk limb homology revealed by a giant filter-feeder with paired flaps.

Exceptionally preserved fossils from the Palaeozoic era provide crucial insights into arthropod evolution, with recent discoveries bringing phylogeny and character homology into sharp focus. Integral to such studies are anomalocaridids, a clade of stem arthropods whose remarkable morphology illuminates early arthropod relationships and Cambrian ecology. Although recent work has focused on the anomalocaridid head, the nature of their trunk has been debated widely. Here we describe new anomalocaridid specimens from the Early Ordovician Fezouata Biota of Morocco, which not only show well-preserved head appendages providing key ecological data, but also elucidate the nature of anomalocaridid trunk flaps, resolving their homology with arthropod trunk limbs. The new material shows that each trunk segment bears a separate dorsal and ventral pair of flaps, with a series of setal blades attached at the base of the dorsal flaps. Comparisons with other stem lineage arthropods indicate that anomalocaridid ventral flaps are homologous with lobopodous walking limbs and the endopod of the euarthropod biramous limb, whereas the dorsal flaps and associated setal blades are homologous with the flaps of gilled lobopodians (for example, Kerygmachela kierkegaardi, Pambdelurion whittingtoni) and exites of the 'Cambrian biramous limb'. This evidence shows that anomalocaridids represent a stage before the fusion of exite and endopod into the 'Cambrian biramous limb', confirming their basal placement in the euarthropod stem, rather than in the arthropod crown or with cycloneuralian worms. Unlike other anomalocaridids, the Fezouata taxon combines head appendages convergently adapted for filter-feeding with an unprecedented body length exceeding 2 m, indicating a new direction in the feeding ecology of the clade. The evolution of giant filter-feeding anomalocaridids may reflect the establishment of highly developed planktic ecosystems during the Great Ordovician Biodiversification Event.

Intended and non-intended kinematic effects of atlanto-axial rotational high-velocity, low-amplitude techniques.

INTRODUCTION: The study of neck kinematics during high-velocity, low-amplitude manipulations of the atlanto-axial segment is essential to understanding cervical motion mechanisms and their impact and possible risk for soft-tissue injuries during treatment of spine disorders. METHODS: Twenty fresh-frozen specimens were tested during manual application of an axial rotation technique. FINDINGS: The kinematics indicate the thrust induced motion components of approximately 1° at the treated segment around all three axes of the local embedded reference frame. Moreover, an equal amount of axial rotation motion took place at the adjacent atlanto-occipital joint. INTERPRETATION: Overall atlanto-axial motion remained below the level of slow regional mobilization of the cervical spine. These findings can be correlated to literature data concerning the limited increase in vertebral artery strain during high-velocity, low-amplitude manipulation.

Reproducibility of the kinematics in rotational high-velocity, low-amplitude thrust of the upper cervical spine: a cadaveric study.

OBJECTIVE: This study aimed to investigate the reproducibility of the kinematics in rotational high-velocity, low-amplitude (HVLA) thrust of the upper cervical spine. METHODS: Twenty fresh human cervical specimens were studied in a test-retest situation with 2 manual therapists. Kinematics of C1-C2 and C0-C1 were examined during segmental rotational HVLA manipulation through an ultrasound-based tracking system. The thrust moment was analyzed by 3-dimensional aspects: the range of motion of axial rotation, flexion-extension, lateral banding, and the cross-correlation between the axial rotation and the coupled lateral banding components. RESULTS: During rotational HVLA thrust on C1-C2, the main axial rotation demonstrates an intraexaminer relationship varying from almost perfect to fair (intraclass correlation coefficient =0.71; intraclass correlation coefficient = 0.35) and a substantial interexaminer correlation of 0.73. CONCLUSIONS: This study showed substantial levels of reliability for the main axial rotation component of segmental manual rotational HVLA thrust on C1-C2. Intra- and interrater reliability for flexion-extension, lateral bending, and cross-correlation was low.

A holomorph approach to xiphosuran evolution--a case study on the ontogeny of Euproops.

Specimens of Euproops sp. (Xiphosura, Chelicerata) from the Carboniferous Piesberg quarry near Osnabrück, Germany, represent a relatively complete growth series of 10 stages. Based on this growth sequence, morphological changes throughout the ontogeny can be identified. The major change affects the shape of the epimera of the opisthosoma. In earlier stages, they appear very spine-like, whereas in later stages the bases of these spine-like structures become broader; the broadened bases are then successively drawn out distally. In the most mature stage known, the epimera are of trapezoidal shape and approach each other closely to form a complete flange around the thoracetron (=fused tergites of the opisthosoma). These ontogenetic changes question the taxonomic status of different species of Euproops, as the latter appear to correspond to different stages of the ontogenetic series reconstructed from the Piesberg specimens. This means that supposed separate species could, in fact, represent different growth stages of a single species. It could alternatively indicate that heterochrony (=evolutionary change of developmental timing) plays an important role in the evolution of Xiphosura. We propose a holomorph approach, i.e., reconstructing ontogenetic sequences for fossil and extant species as a sound basis for a taxonomic, phylogenetic, and evolutionary discussion of Xiphosura.

The added value of an actuated ankle-foot orthosis to restore normal gait function in patients with spinal cord injury: a systematic review.

OBJECTIVE: To provide an overview of robot-assisted rehabilitation devices developed for actuation of the ankle-foot complex and their ability to influence the attributes of normal gait in patients with spinal cord injury. METHODS: A search was conducted in MEDLINE, Web of Knowledge, National Academic Research and Collaborations Information System, and Physiotherapy Evidence Data-base (1985-2011), using, "ankle", "foot", "robotics", "orthotics" and "spinal cord injury" as most relevant keywords. Article inclusion was performed in 3 stages; at the level of: (i) title, (ii) abstract and (iii) full text. RESULTS: The actuated ankle-foot orthoses currently available are characterized by several combinations of an actuator and a control mechanism. Both the actuator and the control strategy substantially influence human-machine interaction and therefore the potential of the device to assist in modifying locomotor function and potentially modify the underlying motor control mechanisms. CONCLUSION: Due to small sample sizes, limited studies in patients with spinal cord injury, and limitations in study design, it is difficult to draw firm conclusions on the effect of different types of actuated ankle-foot orthoses. Based on the limited data available, pneumatic artificial muscles in combination with proportional myoelectric control are suggested to have the potential to meet most of the preconditions to restore the attributes of normal gait and therefore facilitate neuroplasticity.

A giant Ordovician anomalocaridid.

Anomalocaridids, giant lightly sclerotized invertebrate predators, occur in a number of exceptionally preserved early and middle Cambrian (542-501 million years ago) biotas and have come to symbolize the unfamiliar morphologies displayed by stem organisms in faunas of the Burgess Shale type. They are characterized by a pair of anterior, segmented appendages, a circlet of plates around the mouth, and an elongate segmented trunk lacking true tergites with a pair of flexible lateral lobes per segment. Disarticulated body parts, such as the anterior appendages and oral circlet, had been assigned to a range of taxonomic groups--but the discovery of complete specimens from the middle Cambrian Burgess Shale showed that these disparate elements all belong to a single kind of animal. Phylogenetic analyses support a position of anomalocaridids in the arthropod stem, as a sister group to the euarthropods. The anomalocaridids were the largest animals in Cambrian communities. The youngest unequivocal examples occur in the middle Cambrian Marjum Formation of Utah but an arthropod retaining some anomalocaridid characteristics is present in the Devonian of Germany. Here we report the post-Cambrian occurrence of anomalocaridids, from the Early Ordovician (488-472 million years ago) Fezouata Biota in southeastern Morocco, including specimens larger than any in Cambrian biotas. These giant animals were an important element of some marine communities for about 30 million years longer than previously realized. The Moroccan specimens confirm the presence of a dorsal array of flexible blades attached to a transverse rachis on the trunk segments; these blades probably functioned as gills.

Ultrasound findings in injuries of dorsal extensor hood: correlation with MR and follow-up findings.

OBJECTIVE: The aim of this study was to use ultrasound to examine the dorsal hood in nine patients with a clinical suspicion of dorsal hood injuries. MATERIAL AND METHODS: Clinical and imaging files from interesting case logbooks of nine patients were reviewed. Ultrasound was performed by one of the three radiologists experienced in musculoskeletal ultrasound. The examinations were also performed in flexion and in flexion with resistance. MR correlation was obtained in six patients. One patient underwent surgery. To obtain anatomical correlation of the normal dorsal hood 2 embalmed hand specimens were dissected. RESULTS: The sagittal bands were easily depicted in the transverse plane on ultrasound images and presented as hypoechoic bands on both sides of the extensor communis tendons. Injuries of the sagittal bands were seen on ultrasound as hypoechoic thickening of the sagittal bands at the side of the extensor tendons. The normal shape of the sagittal bands was also no longer recognizable. Subluxations or dislocations of the extensor tendons were also seen. When the injuries were located in the fibrous slips between the extensor indicis and the extensor communis of the second finger, subluxations with an increased distance between these 2 tendons were seen, especially in flexion, or in flexion with resistance. CONCLUSION: Ultrasound is a valuable tool for the assessment of the injuries of the dorsal hood and is an easily available method for the diagnosis of the fine soft tissue components of the dorsal hood region.

Ordovician faunas of Burgess Shale type.

The renowned soft-bodied faunas of the Cambrian period, which include the Burgess Shale, disappear from the fossil record in the late Middle Cambrian, after which the Palaeozoic fauna dominates. The disappearance of faunas of Burgess Shale type curtails the stratigraphic record of a number of iconic Cambrian taxa. One possible explanation for this loss is a major extinction, but more probably it reflects the absence of preservation of similar soft-bodied faunas in later periods. Here we report the discovery of numerous diverse soft-bodied assemblages in the Lower and Upper Fezouata Formations (Lower Ordovician) of Morocco, which include a range of remarkable stem-group morphologies normally considered characteristic of the Cambrian. It is clear that biotas of Burgess Shale type persisted after the Cambrian and are preserved where suitable facies occur. The Fezouata biota provides a link between the Burgess Shale communities and the early stages of the Great Ordovician Biodiversification Event.

Critical appraisal and hazards of surface electromyography data acquisition in sport and exercise.

The aim of this critical appraisal and hazards of surface electromyography (SEMG) is to enhance the data acquisition quality in voluntary but complex movements, sport and exercise in particular. The methodological and technical registration strategies deal with telemetry and online data acquisition, the placement of the detection electrodes and the choice of the most adequate normalization mode.Findings compared with the literature suggest detection quality differences between registration methods and between water and air data acquisition allowing for output differences up to 30% between registration methods and up to 25% decrease in water, considering identical measures in air and in water. Various hazards deal with erroneous choices of muscles or electrode placement and the continuous confusion created by static normalization for dynamic motion. Peak dynamic intensities ranged from 111% (in archery) to 283% (in giant slalom) of a static 100% reference. In addition, the linear relationship between integrated EMG (IEMG) as a reference for muscle intensity and muscle force is not likely to exist in dynamic conditions since it is muscle - joint angle - and fatigue dependent. Contrary to expectations, the literature shows 30% of non linear relations in isometric conditions also.SEMG in sport and exercise is highly variable and different from clinical (e.g. neurological) EMG. Choices of electrodes, registration methods, muscles, joint angles and normalization techniques may lead to confusing and erroneous or incomparable results.

Functional anatomy of the dorsal hood or the hand: correlation of ultrasound and MR findings with cadaveric dissection.

The main aim of this study was to provide an overview of the anatomy of the dorsal hood (DH) based on the dissection of sixteen cadaver hands, correlated with magnetic resonance (MR) and ultrasound findings. A secondary aim was to assess the function of components of the DH. Sixteen embalmed hands were evaluated by MRI and ultrasound before being dissected. Each hand was photographed during each stage of dissection. Secondly we evaluated the role of the different structures of the DH in the stability of the extensor tendon by transection of the different components alternatively at the ulnar and radial sides. MR, ultrasound, and dissection showed that the extensor tendon (ET) is stabilized by the sagittal band (SB) at the level of the metacarpophalangeal (MCP) joint and more distally by the transverse and the oblique bands, respectively. Transection of the radial SB of the second finger leads systematically to ulnar dislocation of the ET. The transection of the ulnar DH does not lead to instability of the ET. The SB is the most important structure of the DH in the stability of the ET at the MCP level. Rupture of the radial SB of the second finger leads systematically to ulnar dislocation of the ET.

Sonography of the normal ankle: a target approach using skeletal reference points.

OBJECTIVE: Sonographic examination of the ankle depends on exact knowledge of the specific probe positions to acquire the best images. CONCLUSION: In this article, we discuss these positions and illustrate them with drawings, anatomic slices or dissection, and sonograms. Positions studied include those for best imaging of the anterior tibiotalar joint, anterior tibiofibular ligament, anterior talofibular ligament, calcaneofibular ligament, peroneal tendons, Achilles tendon, flexor hallucis longus, posterior deltoid ligament, anterior deltoid ligament, and posterior medial tendons.

In vitro three dimensional morphometry of the lateral atlantoaxial articular surfaces.

STUDY DESIGN: The present study verifies the 3-dimensional anatomic features of the lateral atlantoaxial joints with reference to a local reference frame using a direct in vitro approach. OBJECTIVE: To study the concordance between the axial and atlantal articular surfaces. SUMMARY OF BACKGROUND DATA: Detailed information of joint-configurations is imperative for understanding the complex kinematics of the upper cervical joint. Data on the quantitative morphology of the human spinal facet joints has been published, but did not include the atlanto-occipital and atlantoaxial joints. METHODS: In 20 fresh spine specimens, metal markers were implanted on the cranium, the atlas, and the axis. After registration of the intact specimens, the bony segments were separated and markers and anatomic landmarks were digitized. The size, shape, and orientation relative to the local reference frame of the axis were derived from the relative position data of the joint surface landmarks. RESULTS: The diameters and surface areas of the inferior articular surfaces of the atlas are slightly smaller than the corresponding surfaces on the superior aspects of the axis (17.7 mm and 235 mm vs. 17.0 and 212 mm). In this sample of older-aged specimens, the curvature of the articulating surfaces is nearly flat. The absolute angle between the left and right surface areas is about 130 degrees and corresponds well between axis and atlas. The orientation of the joint surfaces of axis and atlas with respect to the sagittal plane of the axis indicates a good congruency. CONCLUSION: There seems to be a strong relationship between the anatomic features of the lateral articulating surfaces of atlas and axis. Differences in the orientation of joint surfaces to the frontal plane may be related to deviations from the neutral position. This issue raises the problem of the definition of three-dimensional-neutral joint positions.

Machaeridians are Palaeozoic armoured annelids.

The systematic affinities of several Palaeozoic skeletal taxa were only resolved when their soft-tissue morphology was revealed by the discovery of exceptionally preserved specimens. The conodonts provide a classic example, their tooth-like elements having been assigned to various invertebrate and vertebrate groups for more than 125 years until the discovery of their soft tissues revealed them to be crown-group vertebrates. Machaeridians, which are virtually ubiquitous as shell plates in benthic marine shelly assemblages ranging from Early Ordovician (Late Tremadoc) to Carboniferous, have proved no less enigmatic. The Machaeridia comprise three distinct families of worm-like animals, united by the possession of a dorsal skeleton of calcite plates that is rarely found articulated. Since they were first described 150 years ago machaeridians have been allied with barnacles, echinoderms, molluscs or annelids. Here we describe a new machaeridian with preserved soft parts, including parapodia and chaetae, from the Upper Tremadoc of Morocco, demonstrating the annelid affinity of the group. This discovery shows that a lineage of annelids evolved a dorsal skeleton of calcareous plates early in their history; it also resolves the affinities of a group of problematic Palaeozoic invertebrates previously known only from isolated elements and occasional skeletal assemblages.

Sonography of the finger flexor and extensor system at the hand and wrist level: findings in volunteers and anatomical correlation in cadavers.

We present a review of sonography of the flexor and extensor system of the hand and wrist in volunteers and cadavers. CT tenography also was performed in cadaveric specimens. Anatomical structures of the extensor system that were assessed with sonography included the extensor tendons and insertions, retinaculum, and dorsal hood. On the flexor side, the variable relationship between the flexor superficialis and profundus could be appreciated. Volar plates, tendon insertions, and annular pulleys could also be investigated. Sonography can show details of the finger flexor and extensor system.

Prevalence and MRI-anatomic correlation of bone cysts in osteoarthritic knees.

OBJECTIVE: The objectives of this study were to determine the prevalence of cysts in the weight-bearing areas and interspinous bone cysts in tibial plateau specimens derived from knees with advanced osteoarthritis, to perform MRI-anatomic correlation of these cysts, and to define their histologic characteristics. MATERIALS AND METHODS: Forty-two tibial plateau specimens were recovered from patients undergoing total knee replacement surgery for severe osteoarthritis (14 men and 28 women; mean age, 74 years; age range, 58-87 years). The tibial specimens underwent MRI with T1- and T2-weighted MR sequences. No radiographic data were available before MRI. Tibial specimens were sectioned using a high-speed rotating diamond disk into 3-mm-thick slices. MR images and anatomic specimens were analyzed for the presence of cysts in the interspinous and weight-bearing areas. Histologic staining methods included routine Harris hematoxylin stain, trichrome stain, and Alcian blue-PAS stain. RESULTS: Twenty-three (54%) of 42 specimens contained one or more cystic areas, with a total of 30 cystic areas. The cysts were distributed in the weight-bearing area (14/30) and interspinous area (16/30). All cysts seen on the anatomic slices could also be depicted on both MRI sequences. Histologic findings were identical for all noncommunicating cysts and revealed necrotic bone fragments with dead denuclearized cells. The cavities were surrounded by a layer of fibrous connective tissue containing adipocytes and osteoblasts. No evidence of epithelial components was found in the lining of the cavities. CONCLUSION: Interspinous and weight-bearing tibial cysts are common in severe knee osteoarthritis. The cysts contain necrotic bone fragments and are lined by a nonepithelial fibrous wall. Our findings support the hypothesis that interspinous cysts could result from repetitive bone stresses through the cruciate ligaments. Our findings do not support the use of the term "herniation cyst."

Normal MR imaging anatomy of the rotator cuff tendons, glenoid fossa, labrum, and ligaments of the shoulder.

The shoulder is commonly imaged using MR imaging, with or without intraarticular contrast medium. Some anatomic structures, such as the rotator cuff tendons and bony components, can be assessed without arthrographic technique, whereas the glenohumeral ligaments and labrum require arthrographic technique for more accurate assessment. In either case, an understanding of the normal anatomy of the shoulder with regard to bony and soft tissue structures is essential for MR imaging interpretation. In this article we discuss normal anatomy and variations of the glenohumeral joint(bone and soft tissues), rotator cuff tendons, and coracoacromial arch.