Posterior Articulation Research Articles

Morphological Diversity and Evolution of Jaw Morphologies in Zeiform Fishes (Teleostei, Paracanthopterygii).

Zeiformes (dories, tinselfishes, and oreos) are primarily benthopelagic acanthomorph fishes, distributed between 50 and 1000 m depth on continental slopes and on flanks of oceanic islands and seamounts. Among the interesting morphological adaptations of zeiform fishes are their unique and highly protrusible jaws involving premaxillae with long ascending processes and a four-bar linkage, including mobile palatines that pivot on their posterior articulation. This adaptation for increased jaw protrusion has enabled zeiform fishes to capture elusive prey more efficiently and is arguably a major factor in their morphological diversity and evolutionary success. This study examines the evolution of zeiform jaw morphologies using 3D landmark-based multivariate morphometrics as well as phylomorphospace analysis. Results show that the descendants of the zeiform ancestor branched rapidly early in their history, retaining conservative jaw morphologies during this early branching, but subsequently strongly diverged in many of the resulting lineages. Results from this study are compared with earlier research based on overall body form, demonstrating that morphological variation within Zeiformes arose along at least two distinct trajectories: body form and jaw morphology. Variation among genera in body form is not associated with variation among the same genera in jaw morphology, and vice versa. Hypotheses to explain the apparent decoupling of body shape and jaw morphology are addressed along with avenues for further study to better understand the morphological evolution of these iconic fishes.

T1rho MRI of the subtalar articular cartilage is increased in those with chronic ankle instability

Purpose: Clear links have been made between both lateral ankle sprains and chronic ankle instability (CAI) and the development of ankle post-traumatic osteoarthritis (PTOA). Current visualization techniques such as arthroscopy and standard MRI are ineffective at quantifying early degenerative changes to the subtalar articular cartilage. The most promising approaches for slowing ankle PTOA progression include early conservative interventions to restore appropriate joint biomechanics. Thus, identifying imaging techniques sensitive to early degenerative changes of the subtalar articular cartilage is needed. Therefore, the purpose of this investigation is to determine if CAI patients have higher T1rho relaxation times and relaxation time variability in their subtalar cartilage compared to uninjured controls. T1rho was chosen because evidence indicates it is a marker of proteoglycan density. Methods: Fifteen CAI (age: 21.2±1.8 years, height: 1.7±.8m, mass: 67.0±7.7kg) and fifteen uninjured controls (age: 21.0±2.5 years, height: 1.7±.8m, weight: 69.6±13.2kg) volunteered to participate. CAI inclusion criteria was in accordance with the International Ankle Consortium guidelines. Relative to the controls, CAI participants had a history of multiple lateral ankle sprains (4.0±2.1 vs. 0.0±0.0 sprains), multiple giving way episodes within the past 6 months (6.6±5.1 vs. 0.0±0.0 episodes), higher Identification of Functional Ankle Instability scores (22.9±2.8 vs. 0.1±0.5), and greater limitations in self-reported function based on the Foot and Ankle Ability Measure (85.9±9.7% vs. 100.0±0.0%) and Foot and Ankle Ability Measure Sport (68.4±20.6% vs. 100.0±0.0%). Proteoglycan density was assessed using T1rho MRI with greater T1rho relaxation times interpreted as reduced proteoglycan density. Higher T1rho variability was interpreted as a more diffuse distribution of degenerative changes in the subtalar cartilage. A Siemens Magnetom TIM 3T Prisma scanner and an 8-channel flex coil in conjunction with three-dimensional Fast Low Angle Shot (FLASH) with a spin lock power at 500Hz, five different spin lock durations (40, 30, 20,10, 0 ms) was used to acquire the T1rho MRI. Participants were non-weight bearing for 30 minutes prior to the scan to unload the cartilage. Voxel by voxel T1rho relaxation times were calculated from a five image sequence created with a MATLAB program. Segmentation of the T1rho subtalar cartilage was performed manually using ITK-SNAP software. Three regions of interest: anterior, medial, posterior were identified during segmentation based on talocalcaneal articulations. Mean T1rho relaxation times in each region of interest were compared between CAI patients and healthy controls using independent sample t-tests and an a priori alpha level of 0.05. Results: The CAI and controls groups were similar in terms of their age, height, and weight (p≥0.433). Measures of injury history and self-reported function differed between the groups (p<0.001) as expected. CAI patients had significantly higher T1rho relaxation times in the posterior subtalar articulation (CAI: 65.05±4.76ms, Control: 59.81±5.96ms, p=0.013) but not the anterior (CAI: 66.98±13.21ms, Control: 65.90±11.45ms, p=0.813) or medial articulation (CAI: 69.60±7.70ms, Control: 64.62±7.84ms, p=0.091). CAI patients had significantly higher T1rho relaxation time variability in the medial subtalar articulation (CAI: 32.46±4.58ms, Control: 28.71±5.10ms, p=0.013) but not the anterior (CAI: 35.62±4.87ms, Control: 31.51±8.27ms, p=0.813) or posterior articulation (CAI: 27.33±5.23ms, Control: 23.93±5.74ms, p=0.091). Conclusions: CAI patients demonstrate higher T1rho relaxation times and variability compared to controls in at least one subtalar joint articulation suggesting reduced proteoglycan density in the subtalar cartilage. This finding supports the hypothesis that early compositional changes, potentially indicative of cartilage degeneration, exist in individuals with CAI in subtalar joint. This finding is also consistent with the research indicating compositional changes at the subtalar joint and in on the talar dome in those with CAI. Further research is needed to determine the underlying mechanisms of these deleterious compositional changes and to identify therapeutic interventions capable of slowing the progression of these compositional changes following lateral ankle sprains and CAI.

Rhabdomoplea, a new superorder for the thaumatopsylloid copepods: the consequence of an alternative hypothesis of copepod phylogeny

Abstract The superorder Rhabdomoplea is established for copepods belonging to the order Thaumatopsylloida. Apomorphies for Rhabdomoplea are an adult prosome, including thoracic somites 1-4, complete at copepodid I, development of the posterior articulation of thoracic somite 7 of males delayed to copepodid IV and of abdominal somite 1 delayed to copepodid V, and absence of a posterior articulation of abdominal somites 2-3 forming with the anal somite a rod-like somite complex as part of the urosome. Rhabdomoplea appears to be the earliest branch of copepods because only thoracic somites 1-4 are broad throughout copepodid development, and thoracic somites 5 and 6 remain narrow. On podopleans and gymnopleans thoracic somite 5 is transformed from the anterior narrow somite to the posterior broad somite during the moult to copepodid II. On gymnopleans thoracic somite 6 also is transformed from the anterior narrow somite to the posterior broad somite but during the moult to copepodid III. Thus rhabdomopleans differ from podopleans in their body architecture as much as podopleans differ from gymnopleans. An alternative and traditional phylogeny that posits gymnopleans as the earliest branch of copepods requires reversal of these two transformations during copepod evolution; this hypothesis is not favoured here because the parsimonious hypothesis of direct, progressive transformations seems reasonable and plausible.

New remains from the Spanish Cenomanian shed light on the Gondwanan origin of European Early Cretaceous titanosaurs

Algora is a recently discovered vertebrate fossil site located in the Cenomanian strata of the Arenas de Utrillas Formation (Guadalajara, Central Spain). This fossil site is rich in turtle remains, but other clades of reptiles are also identified, including plesiosaurs, crocodyliforms and dinosaurs. The only remains of dinosaurs from Algora so far studied corresponded to theropod teeth. However, several sauropod remains are here presented and analyzed, revealing the presence of several shared features with members of Titanosauriformes, some common found in derived members belonging to Lithostrotia clade. This sauropod fossil assemblage corresponds to the richest sauropod fossil accumulation found in the Cenomanian of Europe. In addition, one of the first studies of the pneumatic features in dorsal ribs using CT scan is also provided here. The performed cladistic analysis places the Algora sauropod within Lithostrotia, in a more derived position than Malawisaurus (supported, for example, by the presence of convex posterior articulation up to the posterior section of the tail), in a clade which also includes Rapetosaurus (Maastrichtian, Madagascar) and the Italian indeterminate titanosaur MSNM V7157 (late Aptian–early Albian). The Algora titanosaur and MSNM V7157 are recognized as closely related. This analysis shows the presence of two different lineages (Algora titanosaur + MSNM V7157 and Normanniasaurus, from the Albian of France) in the Early and middle Cretaceous of Europe, and at least one with a Gondwanan origin. The close relationship of the Algora titanosaur and MSNM V7157 suggests a pre-late Aptian faunal contact between the Adriatic Plate and Laurasia, in accordance with several previous studies, which proposed faunal exchanges between Laurasia and Gondwana through the Adriatic plate during the Early Cretaceous.

Generating evenly distributed nondominated solutions in dual response surface optimization

The dual response surface optimization (DRSO) approach attempts to simultaneously optimize the mean and standard deviation of a response variable. In DRSO, the mean and standard deviation of a response are often in conflict and thus, it is extremely critical to compromise the two conflicting functions. Recently, a posterior preference articulation approach for DRSO (P-DRSO) was proposed. P-DRSO generates a set of nondominated solutions and allows a decision-maker (DM) to select the most preferred solution. P-DRSO has an advantage in that the DM can better understand the trade-offs between the mean and standard deviation. Thus, the most satisfactory compromised solution can be easily obtained. One important issue of P-DRSO is to generate uniformly distributed nondominated solutions for the DM to obtain better understanding of the trade-offs between the mean and standard deviation. P-DRSO employs a conventional ε-constraint method. However, it often generates nondominated solutions that are not uniformly distributed. To address this issue, we propose a new approach to generate the nondominated solutions. We demonstrated that the uniformity of the generated nondominated solutions is better than that of P-DRSO in two well-known DRSO case problems.

Lithobius (Ezembius) multispinipes n. sp., a new species of centipede from NorthWest China (Lithobiomorpha: Lithobiidae)

The centipede subgenus Lithobius (Ezembius) Chamberlin, 1919 comprises a group of about 60 species known from the Near East across Siberia and Central Asia to China, and Japan, and Southwards into the Northern Indian subcontinent and the Northern part of the Oriental region (Eason 1992, Zapparoli 1999). It is also known from Alaska in Western North America (Zapparoli & Edgecombe 2011). Although the subgenus was formally proposed as new and described in 1923 (Chamberlin 1923), according to Jeekel (2005) its name had been already validated in 1919 (Chamberlin 1919). Ezembius is characterized by the presence of 2+2 or 3+3 coxosternal teeth, antennal articles fixed at 20 or thereabouts, tergites generally without posterior triangular projections and tarsal articulation of legs 1-13 distinct (Chamberlin 1923, Zapparoli & Edgecombe 2011).

A solution selection approach to multiresponse surface optimization based on a clustering method

ABSTRACTIn Multi-Response Surface Optimization (MRSO), responses are often in conflict. To obtain a satisfactory compromise, the preference information of a Decision Maker (DM) on the tradeoffs among the responses should be considered. One of the promising alternatives is a posterior preference articulation approach. It first generates nondominated solutions and then makes the DM select the best one from the nondominated solutions. In this article, a solution selection approach is presented. It takes the posterior approach and employs a clustering method to aid the selection process of the DM. The DM can obtain the satisfactory compromise solution easily by the proposed method.

On maniraptoran material (Dinosauria: Theropoda) from Vale do Rio do Peixe Formation, Bauru Group, Brazil

Non avian theropod remains are scarce in Brazil and few specimens were referred to Maniraptora. Remains of a non-avian theropod dinosaur (DGM 930-R) from Vale do Rio do Peixe Formation, Bauru Group, found near the Santo Anastacio municipality, Sao Paulo State are described. DGM 930-R is represented by two partial caudal vertebra centra, a partial diaphysis of the right femur with marked lines of arrested development (indicatives of a habitat with marked seasonality), a partial dorsal rib and other rib fragments, a partial bone that possibly represents the proximal portion of the ischium, and some unidentifi able elements. DGM 930-R is referred as a Maniraptoran incertae sedis, possibly related to Deinonychosauria because of the box-like anterior vertebral centrum with quadrangular-shaped posterior articulation. The circumference of the femur of DGM 930-R suggests it was a medium-sized dinosaur (about 3 m long) that shared the same geographic space with other theropods (megaraptorans, abelisauroids, and carcharodontosaurids) and mesoeucrocodylians.

A robust posterior preference decision-making approach to multiple response process design

Setting of process variables to meet required specification of quality characteristics is one of the important problems in quality control processes. In general, most industrial and production systems are dealing with several different responses and the problem is to simultaneously optimise these responses. To obtain the most satisfactory solution, a decision-makers (DM) preference on the trade-offs among the quality characteristics should be incorporated into the optimisation procedure. This study suggests a robust posterior preference articulation approach based on a non-dominated sorting genetic algorithm (NSGA-II) to optimise multiple responses. In order to minimise the variation in deviation of responses from targets, maximum and sum of deviations are taken into consideration. To investigate the performance of the suggested approach, a computational analysis on a real world chemical engineering example is performed. Results show the superiority of the proposed approach compared to the existing techniques.

A Robust Posterior Method to Multiresponse Optimization Using the VIKOR Method

Setting of process variables to meet a required specification of quality characteristic (or response variable) in a process is one of common problems in the process quality control. But generally there are more than one quality characteristics in the process. In these situations, to obtain a satisfactory compromise in such a case, a decision maker (DM)’s preference information about the tradeoffs among the responses should be considered. In some cases, it is difficult for a DM to express an explicit approximation of the preference function. Therefore it can be effective to allow the decision maker to choose from a set of solutions. To this end, an algorithm is used to determine a representation of the nondominated solutions set. Such methods incorporate a posterior articulation of preferences. This paper proposes a posterior method based on taguchi’s signal-to-noise (S/N) ratios to facilitate the preference articulation process and incorporate both systematic and random deviations from target in a single criterion. Finally, the VIKOR method is used to extract of optimal compromise solution that leads to minimum variation in relative deviations of responses.

Ankle Injury - Gymnastics

HISTORY: 17yo male level 10 gymnast presents with intermittent right ankle pain for 6 months, especially worse in the last 4 months with vaulting, jumping, and occasionally running. He states it hurts more when walking on banked surface. He denies any injury prior to ankle problems. He has been resting it since returning from competition in Brazil 1 month ago. Ankle x-rays were negative. Pain is located primarily on lateral aspect. He presents for further workup. PHYSICAL EXAMINATION: R ankle exam: No swelling. Pain is located anterolaterally in the region of the ATFL. No pain over CFL or PTFL. There is increased laxity bilaterally but ankle is stable. No pain with resisted inversion, eversion, plantar, or dorsiflexion. There is decreased proprioception on right side. No pain with weight bearing. DIAGNOSES: 1. ATFL sprain 2. Sinus Tarsi Syndrome 3. Talo-calcaneal joint arthrosis 4. Stress fracture of Talus 5. Syndesmosis sprain 6. Anterolateral impingement TEST AND RESULTS: X-ray of the ankle was negative. Given high impact sport, MRI was obtained to evaluate soft tissue vs. stress fracture. MRI showed sclerosis of the talus and at the posterior articulation with the calcaneus. Also identified was some underlying talar edema. These findings fit a pattern of arthrosis. Sinus tarsi appeared within normal limits FINAL WORKING DIAGNOSIS: Sclerosis of the talus and arthrosis of talo-calcaneal joint in a level 10 gymnast TREATMENT AND OUTCOMES: 1. Conservative management with PT to increase ROM, stretch, and maintain neutral foot position and normal arch support. 2. Athlete returned to elite level competition without incident 3. Athlete then returned to sports clinic 9 months later with an unrelated injury and stated that "by the way" he had re-injured the right ankle, inverting it 1 month prior to this clinic visit. However, he was able to continue competing without significant impact to his performance. Exam revealed pain with anterior drawer test. X-ray showed a vertical stress fracture at the posterolateral talus. He was placed in a lace up brace with non-impact activity. Repeat radiographs after 3 weeks showed a healing fracture. He was allowed to perform closed chain activites. 4. Current status: Repeat radiographs after another 2 weeks showed further healing and he was returned to practice/competition.

A posterior preference articulation approach to dual-response-surface optimization

In dual-response-surface optimization, the mean and standard deviation responses are often in conflict. To obtain a satisfactory compromise, a Decision Maker (DM)'s preference information on the trade-offs between the responses should be incorporated into the problem. In most existing works, the DM expresses a subjective judgment on the responses through a preference parameter before the problem-solving process, after which a single solution is obtained. This study proposes a posterior preference articulation approach to dual-response-surface optimization. The posterior preference articulation approach initially finds a set of non-dominated solutions without the DM's preference information, and then allows the DM to select the best solution among the non-dominated solutions. The proposed method enables a satisfactory compromise solution to be achieved with minimum cognitive effort and gives the DM the opportunity to explore and better understand the trade-offs between the two responses.

Pectoral anatomy of Tribodus limae (Elasmobranchii: Hybodontiformes) from the Lower Cretaceous of northeastern Brazil

ABSTRACT New, undescribed material of the hybodont shark Tribodus limae, from the Lower Cretaceous of northeastern Brazil, provides new information on the pectoral endoskeleton in this taxon. This allows for a revision of its pectoral morphology, which may be broadly applicable to other Hybodontoidei. Four new specimens of Tribodus with well-preserved pectoral girdles are described, including the first complete, three-dimensionally preserved hybodont scapulocoracoid and partial pectoral fin. These specimens permit examination of the posterior surface of the scapulocor-acoid, not visible in previously described hybodonts. Overall pectoral morphology of Tribodus is similar to that of other hybodontiforms and neoselachians. However, the new material shows that the pectoral articulation in Tribodus comprises an oblique posterior ridge on the scapulocoracoid, unlike previous reconstructions of pectoral anatomy in Tribodus and other hybodonts based on two-dimensionally preserved specimens. However, other elasmobranchs, including many neoselachians, Orthacanthus, and ctenacanths, also have an oblique posterior articulation, indicating that this feature may be primitive for elasmobranchs. The pectoral articulation of Tribodus differs noticeably from that of Cladoselache and similar Paleozoic chondrichthyans, which have an elongated, laterally positioned articular process, and from the outgroup (osteichthyans, acanthodians and placoderms). Tribodus also differs from the Paleozoic hybodontiform Ony-choselache in which the articular region comprises a laterally positioned glenoid fossa and posterior condyle. Tribodus has an additional diazonal foramen not found in other hybodonts. Other pectoral features of Tribodus are in agreement with previous phylogenetic hypotheses, supporting the position of Tribodus within Hybodontoidei.

Assessment of subtalar joint neutral position: a cadaveric study

Subtalar joint (STJ) neutral position is the position typically used by clinicians to obtain a cast representation of a patient's foot before fabrication of biomechanical functional orthosis. But no method for measuring STJ neutral position has been proven accurate and reproducible by different testers. This study was conducted to investigate the STJ neutral position in normal feet in cadavers. Twelve fresh-frozen specimens of amputated lower legs were used. Pressure-sensitive films were inserted into the anterior and posterior articulation of STJ. The contact areas for various foot positions and under axial loads of 600 N were determined based on the gray level of the digitized film. The STJ neutral positions were determined as the ankle-foot position where the maximum contact area was achieved, because the neutral position of a joint was defined as the position where the concave and convex surfaces were completely congruous. In ankle-foot neutral position, the contact area of STJ was (2.79 +/- 0.24) cm(2). In the range of motion of adduction-abduction (ADD-ABD), the maximum contact area was (3.00 +/- 0.26) cm(2) when the foot was positioned 10 degrees of ABD (F = 221.361, P < 0.05). In the range of motion of dorsiflexion-plantarflexion (DF-PF), the maximum contact area was (3.61 +/- 0.25) cm(2) when the foot was positioned 20 degrees of DF (F = 121.067, P < 0.05). In the range of motion of inversion-eversion (INV-EV), the maximum contact area was (3.14 +/- 0.26) cm(2) when the foot was positioned 10 degrees of EV (F = 256.252, P < 0.05). Joints, such as STJ, therefore, are not necessarily in neutral position when the ankle-foot is placed in the traditional concept of neutral position. The results demonstrate that the most approximate STJ neutral position was in the foot position of 10 degrees of abduction, 20 degrees of dorsiflexion and 10 degrees of eversion.

A multiobjective evolutionary approach for linearly constrained project selection under uncertainty

In the project selection problem a decision maker is required to allocate limited resources among an available set of competing projects. These projects could arise, although not exclusively, in an R&D, information technology or capital budgeting context. We propose an evolutionary method for project selection problems with partially funded projects, multiple (stochastic) objectives, project interdependencies (in the objectives), and a linear structure for resource constraints. The method is based on posterior articulation of preferences and is able to approximate the efficient frontier composed of stochastically nondominated solutions. We compared the method with the stochastic parameter space investigation method (PSI) and illustrate it by means of an R&D portfolio problem under uncertainty based on Monte Carlo simulation.

Comparative morphology of mandibular structures in lycid larvae and its phylogenetic implications (Polyphaga, Hexapoda)

AbstractThe morphology of the larval mandibular structures of the family Lycidae (Polyphaga) is characterized by facultative dicondyly, posterior articulation with long mandibular rods, lateral location of the anterior condyle and its articulation with a paired non‐cranial structure. It is compared to that of Eucrustacea, Chilopoda, Entognatha, Microcoryphia and Zygentoma and found to be more reminiscent of the Entognatha. The phylogenetic implications of this conclusion are discussed, with the Pterygota and Dicondylia hypothesized to be non‐monophyletic.

Anatomy and kinematics of the human ankle joint

In the ankle (talocrural) joint, the lower end of the tibia and fibula embrace the trochlea tali. Thus, an approximately uniaxial joint is formed which permits dorsiflexion and plantarflexion of the foot against the leg. Due to the geometry of the trochlea tali, conjunct lateral rotation of the fibula against the tibia occurs at the tibiofibular articulations synchronously with active dorsiflexion at the ankle joint. Movements at the talocrural joints are mainly limited by the opposing muscles as well as by strong collateral ligaments. Talus and calcaneus form a functional unit connected by posterior and anterior articulations. The posterior articulation is the subtalar (talocalcaneal) joint; in the anterior articulation, talar facets of the calcaneus together with the posterior surface of the navicular and the superior fibrocartilaginous surface of the plantar calcaneonavicular ligament form a concavity for the talar head. Thus, the talocalcaneonavicular joint is a compound and--like the subtalar joint--a multiaxial articulation. On the weight-bearing foot, the distal tarsus and metatarsus are pronated and supinated against the talus in order to maintain plantigrade contact. When the foot is off the ground, these movements are modified to eversion and inversion, also involving the calcaneocuboid joint. In addition, movements between the calcaneus and cuboid also occur during pronative or supinative changes between the fore- and hindfoot. Limitation of movements is due to leg muscles as well as strong ligaments. Finally, the cuneonavicular, cuboideonavicular, intercuneiform and cuneocuboid joints permit some additional alterations of the loaded foot in contact with the ground.

Le recalibrage dans le traitement du canal lombaire �troit

Lumbar stenosis has been well discussed recently, especially at the 64th French Orthopaedic Society (SOFCOT: July 1989). The results of different surgical treatments were considered as good, but the indications for surgical treatment were not clear cut. Laminectomy is not the only treatment of spinal stenosis. Laminectomy is an approach with its own rate of complications (dural tear, fibrosis, instability... ).Eight years ago, J. Sénégas described what he called the "recalibrage" (enlargement). His feeling was that, in the spinal canal, we can find two different AP diameters. The first one is a fixed constitutional AP diameter (FCAPD) at the cephalic part of the lamina. The second one is a mobile constitutional AP diameter (MCAPD) marked by the disc and the ligamentum flavum. This diameter is maximal in flexion, minimal in extension. The nerve root proceeds through the lateral part of the canal: first above, between the disc and the superior articular process, then below, in the lateral recess bordered by the pedicle, the vertebral body and the posterior articulation. With the degenerative change the disc space becomes shorter, the superior articular process is worn out with osteophytes. These degenerative events are complicated by inter vertebral instability increasing the stenosis. The idea of the "recalibrage" is to remove only the upper part of the lamina with the ligamentum flavum and to cut the hypertrophied anterior part of the articular process from inside. If needed the disc and other osteophytes are removed. The surgery is finished with a ligamentoplasty reducing the flexion and preventing the extension by a posterior wedge.Our experience in spine surgery especially in scoliosis surgery, showed us that it was possible to cure a radicular compression without opening the canal. The compression is then lifted by the 3D reduction and restoration of an anatomy as normal as possible. Lumbar stenosis is the consequence of a degenerative process. Indeed, hip flexion, obesity or quite simply overuse, involve an increase in the lumbar lordosis. The posterior articulations are worn out and the disc gets damaged by shear forces. The disc space becomes shorter with a bulging disc, and the inferior articular process of the superior vertebra goes down. This is responsible of a loss of lordosis. For restoring the sagittal balance the patient needs more extension of the spine. Above and below the considered level the degenerative disease carries on extending to the whole spine. At the level considered, because of local extension, the inferior facet moves forward, the disc bulges, the ligamentum flavum is shortened and the stenosis is increased. This situation is improved by local kyphosis: the inferior facet moves backward, the disc and the ligamentum flavum are stretched with a quite normal posterior disc height and most often there is no more stenosis. Myelograms show this very well with a quite normal appearance lying, clear compression standing, worse in extension and improved, indeed disappeared in flexion. CT scan and MRI don't show that because they are done lying. The expression of the clinical situation is the same, mute lying and maximum standing with restriction of walking. For us lumbar stenosis is operated with lumbar reconstruction without opening the canal. The patient is in moderate kyphosis on the operating table. Pedicle screws rotated to match a bent rod allow reduction of the spine. The posterior disc height is respected and not distracted, and the anterior part of the disc is stretched in lordosis. The inferior facet is cut for the arthrodesis and no longer compresses the dura. The canal is well enlarged and the lumbar segment in lordosis is the best protection of the adjacent levels at follow-up. This behaviour responds to the same analysis as the ≪recalibrage≫ (enlargement). The mobile segment is damaged by the degenerative disease, the stenosis is a consequence of this damage. It's logical to treat the instability and to restore the normal static anatomy; thus bone resection is not necessary. At the present time all the lumbar stenoses with reduction in flexion are instrumented with spinal reduction and arthrodesis without opening the canal. The laminoarthrectomy and the enlargement are done when there is a fixed arthrosis which is rare in our practice and found in an older population. The follow-up shows a loss of reduction in some cases after reduction-instrumentation-arthrodesis and poses the question of an interbody fusion. We don't open the canal only for fusion (PLIF) if this is not necessary for the treatment of the stenosis. We think that, in such a situation, the future is ALIF with endoscopical approach. The problem is to determine which disc demanding this anterior fusion, is able to regenerate or not.

Contact areas and pressure distributions in the subtalar joint

We investigated how foot position and ankle arthrodesis affect the contact characteristics of the subtalar joint. Nine fresh-frozen specimens of amputated lower legs were used. Pressure-sensitive films were inserted into the anterior and posterior articulation of the subtalar joint. The contact areas and pressure for various foot positions and under axial loads of 600, 1200, and 1800 N were determined based on the gray level of the digitized film. In neutral position and under a 600 N load, the maximum contact pressure in the subtalar joint was 5.13 ± 1.16 MPa. The contact area (1.18 ± 0.35 cm 2) was only 12.7% of the whole subtalar articulation area (9.31 ± 0.66 cm 2), and the total force (348.5 ± 41.7 N) transmitted via this contact area was about 58% of the applied load (600 N). Dorsiflexion of the foot increased the contact area and the force transmitted, but decreased the average contact pressure in the subtalar joint, while the reverse occurred in plantar flexion. Eversion increased the subtalar contact stress, whereas inversion up to 10° decreased it. Ankle joint arthrodesis shifted the contact areas in the subtalar joint posteriorly in all inversion/eversion positions. Moreover, total force transmitted through the subtalar joint as well as the contact pressure increased.

Activity and directional sensitivity of leg campaniform sensilla in a stick insect

1. The mechanoreceptive campaniform sensilla, which are arranged in groups on insect legs, were studied in the stick insect Cuniculina impigra. In middle and rear legs, the most posterior trochanteral campaniform group (group 1) is oriented so as to be stimulated by compressional cuticular forces acting on the posterior articulation of the trochanter with the coxa. 2. Recordings from nerve Tr2, which innervates this campaniform group, confirmed that the sensilla were directionally sensitive to cuticular stress generated by imposed or active movements of the femur. Different individual sensilla had different thresholds of response, but all responded qualitatively in the same way to a given stimulus. 3. Posteriorward horizontal deflection of the femur-trochanter relative to the coxa (at right angles to the normal plane of movement) produced a strong excitation of the group 1 sensilla. Anteriorward horizontal deflection caused a sharp reduction of on-going background activity in the group. Imposed vertical movements of the femur usually had little effect on the activity of the campaniform sensilla. 4. Active depression of the femur-trochanter by the animal reduced on-going background activity in proportion to the strength of the depression movement. Elevation that simulated muscle-generated lifting of the leg strongly increased activity. 5. It is concluded that campaniform group 1 functions to signal passive horizontal and active vertical movements around the trochantero-coxal joint of the leg. This dual pattern of response means that the animal cannot interpret signals from this campaniform group without also having information about muscle activity.