Patients with knee osteoarthritis can be divided into subgroups based on tibiofemoral joint kinematics of gait - an exploratory and dynamic radiostereometric study.

OBJECTIVE: Patients with advanced knee osteoarthritis (KOA) frequently alter their gait patterns in an attempt to alleviate symptoms. Understanding the underlying pathomechanics and identifying KOA phenotypes are essential to improve treatments. We investigated kinematics in patients with KOA to identify subgroups of homogeneous knee joint kinematics. METHOD: A total of 66 patients with symptomatic KOA scheduled for total knee arthroplasty and 15 age-matched healthy volunteers with asymptomatic, non-arthritic knees were included. We used k-means clustering to divide patients into subgroups based on dynamic radiostereometry-assessed tibiofemoral joint kinematics. Clinical characteristics such as knee ligament lesions and KOA scores were graded by magnetic resonance imaging and radiographs, respectively. RESULTS: We identified four clusters that were supported by clinical characteristics. The flexion group (n = 20) consisted primarily of patients with medial KOA. The abduction group (n = 17) consisted primarily of patients with lateral KOA. The anterior draw group (n = 10) was composed of patients with medial KOA, some degree of anterior cruciate ligament lesion and the highest KOA score. The external rotation group (n = 19) primarily included patients with medial collateral and posterior cruciate ligament lesions. CONCLUSION: Based on tibiofemoral gait patterns, patients with advanced KOA can be divided into four subgroups with specific clinical characteristics and different KOA-affected compartments. The findings add to our understanding of how knee kinematics may affect the patient's development of different types of KOA. This may inspire improved and more patient-specific treatment strategies in the future.

Bone conduction pathways confer directional cues to salamanders.

Sound and vibration are generated by mechanical disturbances within the environment, and the ability to detect and localize these acoustic cues is generally important for survival, as suggested by the early emergence of inherently directional otolithic ears in vertebrate evolutionary history. However, fossil evidence indicates that the water-adapted ear of early terrestrial tetrapods lacked specialized peripheral structures to transduce sound pressure (e.g. tympana). Therefore, early terrestrial hearing should have required nontympanic (or extratympanic) mechanisms for sound detection and localization. Here, we used atympanate salamanders to investigate the efficacy of extratympanic pathways to support directional hearing in air. We assessed peripheral encoding of directional acoustic information using directionally masked auditory brainstem response recordings. We used laser Doppler vibrometry to measure the velocity of sound pressure-induced head vibrations as a key extratympanic mechanism for aerial sound reception in atympanate species. We found that sound generates head vibrations that vary with the angle of the incident sound. This extratympanic pathway for hearing supports a figure-eight pattern of directional auditory sensitivity to airborne sound in the absence of a pressure-transducing tympanic ear.

Seismic sensitivity and bone conduction mechanisms enable extratympanic hearing in salamanders.

The tympanic middle ear is an adaptive sensory novelty that evolved multiple times in all the major terrestrial tetrapod groups to overcome the impedance mismatch generated when aerial sound encounters the air-skin boundary. Many extant tetrapod species have lost their tympanic middle ears, yet they retain the ability to detect airborne sound. In the absence of a functional tympanic ear, extratympanic hearing may occur via the resonant qualities of air-filled body cavities, sensitivity to seismic vibration, and/or bone conduction pathways to transmit sound from the environment to the ear. We used auditory brainstem response recording and laser vibrometry to assess the contributions of these extratympanic pathways for airborne sound in atympanic salamanders. We measured auditory sensitivity thresholds in eight species and observed sensitivity to low-frequency sound and vibration from 0.05-1.2 kHz and 0.02-1.2 kHz, respectively. We determined that sensitivity to airborne sound is not facilitated by the vibrational responsiveness of the lungs or mouth cavity. We further observed that, although seismic sensitivity probably contributes to sound detection under naturalistic scenarios, airborne sound stimuli presented under experimental conditions did not produce vibrations detectable to the salamander ear. Instead, threshold-level sound pressure is sufficient to generate translational movements in the salamander head, and these sound-induced head vibrations are detectable by the acoustic sensors of the inner ear. This extratympanic hearing mechanism mediates low-frequency sensitivity in vertebrate ears that are unspecialized for the detection of aerial sound pressure, and may represent a common mechanism for terrestrial hearing across atympanic tetrapods.

The excitation of solar-like oscillations in a δSct star by efficient envelope convection.

Delta Scuti (δSct) stars are opacity-driven pulsators with masses of 1.5-2.5 M⊙, their pulsations resulting from the varying ionization of helium. In less massive stars such as the Sun, convection transports mass and energy through the outer 30 per cent of the star and excites a rich spectrum of resonant acoustic modes. Based on the solar example, with no firm theoretical basis, models predict that the convective envelope in δSct stars extends only about 1 per cent of the radius, but with sufficient energy to excite solar-like oscillations. This was not observed before the Kepler mission, so the presence of a convective envelope in the models has been questioned. Here we report the detection of solar-like oscillations in the δSct star HD187547, implying that surface convection operates efficiently in stars about twice as massive as the Sun, as the ad hoc models predicted.

How Internally Coupled Ears Generate Temporal and Amplitude Cues for Sound Localization.

In internally coupled ears, displacement of one eardrum creates pressure waves that propagate through air-filled passages in the skull and cause displacement of the opposing eardrum, and conversely. By modeling the membrane, passages, and propagating pressure waves, we show that internally coupled ears generate unique amplitude and temporal cues for sound localization. The magnitudes of both these cues are directionally dependent. The tympanic fundamental frequency segregates a low-frequency regime with constant time-difference magnification from a high-frequency domain with considerable amplitude magnification.

Is human underwater hearing mediated by bone conduction?

In-air and underwater audiograms and directional hearing abilities were measured in humans. The lowest underwater thresholds were 2.8 µW/m2 or 3.6 mPa at a frequency of 500 Hz. The underwater hearing thresholds were 4-26 dB and 40-62 dB higher than in-air hearing thresholds when measured in intensity and pressure units, respectively. This difference is considerably smaller than what has been reported earlier. At frequencies below 1 kHz, when measured in units of particle velocity, the underwater threshold was much lower than published bone conduction thresholds, suggesting that underwater hearing is not always mediated by bone conduction pathways to the inner ear, as previously thought. We suggest it is the resonance of air in the air-filled middle ear that produces the low underwater thresholds, at least at frequencies below 1 kHz. The ability to determine the direction of a 700 Hz underwater sound source while being blindfolded was extremely poor, with submerged test subjects showing only coarse directional hearing abilities at azimuths of less than 50˚. The physical cues to sound direction are different in air and water, and the poor directional hearing abilities indicate that, in spite of low hearing thresholds, humans have no special adaptations to process directional acoustic cues under water.

Seismology of the sun.

Oscillations of the sun make it possible to probe the inside of a star. The frequencies of the oscillations have already provided measures of the sound speed and the rate of rotation throughout much of the solar interior. These quantities are important for understanding the dynamics of the magnetic cycle and have a bearing on testing general relativity by planetary precession. The oscillation frequencies yield a helium abundance that is consistent with cosmology, but they reinforce the severity of the neutrino problem. They should soon provide an important standard by which to calibrate the theory of stellar evolution.

Asteroseismic detection of latitudinal differential rotation in 13 Sun-like stars.

The differentially rotating outer layers of stars are thought to play a role in driving their magnetic activity, but the underlying mechanisms that generate and sustain differential rotation are poorly understood. We report the measurement using asteroseismology of latitudinal differential rotation in the convection zones of 40 Sun-like stars. For the most significant detections, the stars' equators rotate approximately twice as fast as their midlatitudes. The latitudinal shear inferred from asteroseismology is much larger than predictions from numerical simulations.

Hot super-Earths stripped by their host stars.

Simulations predict that hot super-Earth sized exoplanets can have their envelopes stripped by photoevaporation, which would present itself as a lack of these exoplanets. However, this absence in the exoplanet population has escaped a firm detection. Here we demonstrate, using asteroseismology on a sample of exoplanets and exoplanet candidates observed during the Kepler mission that, while there is an abundance of super-Earth sized exoplanets with low incident fluxes, none are found with high incident fluxes. We do not find any exoplanets with radii between 2.2 and 3.8 Earth radii with incident flux above 650 times the incident flux on Earth. This gap in the population of exoplanets is explained by evaporation of volatile elements and thus supports the predictions. The confirmation of a hot-super-Earth desert caused by evaporation will add an important constraint on simulations of planetary systems, since they must be able to reproduce the dearth of close-in super-Earths.

Basic response characteristics of auditory nerve fibers in the grassfrog (Rana temporaria).

Responses to free-field sound of 401 fibers from the VIIIth nerve of the grassfrog, Rana temporaria, are described. The spontaneous activities of the fibers ranged from 0 to 75 spikes/s, showing only weak correlation with frequency or sensitivity of the fibers. The highest spontaneous activities were approximately twice as high as reported previously for frogs. Best frequencies ranged from 100 to 1600 Hz and thresholds ranged from 21 to 80 dB SPL. The median dynamic range was 20 dB and the slopes of the rate-level curves ranged from 5 to 20 spikes/(s-dB). Most of the units showed post-excitatory suppression (PS) of their spontaneous activity. The duration of PS increased with sound level, also in fibers showing a decrease in firing rate at high intensities. Most fibers showing one-tone suppression did not show PS at their best suppression frequencies. Strong suppression was observed also in very phasic cells giving one spike per stimulation. Therefore, the mechanism underlying PS is probably different from that underlying adaptation. The sharpening of the neural encoding of temporal parameters and the strong encoding of sound offset as well as onset caused by PS very likely is biologically important.

In vitro and in vivo responses of saccular and caudal nucleus neurons in the grassfrog (Rana temporaria).

We present results from in vitro and in vivo studies of response properties of neurons in the saccular and caudal nuclei in the frog. In the in vitro studies the saccular nerve of the isolated brain was stimulated with electrical pulses. In the in vivo experiments, the neurons were stimulated by dorso-ventral vibrations of the intact animal. We identified six response types: (1) primary-like cells with short latencies and follow repetition rates up to 100 Hz; (2) phasic cells responding only to the first pulse in a train; (3) bursting cells firing several spikes in response to any stimulation; (4) late responders with very long latencies; (5) integrator cells showing facilitated responses, and (6) inhibitory cells inhibited by saccular nerve stimulation. The cells have comparable sensitivity and frequency characteristics to the primary fibres (BF 10-80 Hz, thresholds from 0.01 cm/s2) and enable a sophisticated analysis of vibrational stimuli.

[Analgesic effect of low-dose intra-articular morphine after ambulatory knee arthroscopy]. / Analgesi af lavdosis intraartikulaer morfin efter ambulant knaeartroskopi.

The purpose of this study was to demonstrate the effect of intra-articular morphine following knee arthroscopy performed in infiltration analgesia. Fifty-two healthy patients were randomized to receive either morphine 1 mg or placebo. The pain was assessed two, five, eight and 24 hours after the procedure by 1) a VAS scale and 2) the amount of acetaminophen consumed. Demographic data in the two groups were similar. The pain scores at eight and 24 hours and the acetaminophen consumption after eight hours were lower in the morphine group (p < 0.05). Our results confirm the hypothesis of peripherally distributed opioid receptors. Stratifying data in therapeutic vs. diagnostic arthroscopy suggests an additional effect of morphine in patients undergoing therapy (0.05 < p < 0.10), an aspect which supports the hypothesis of peripherally administered morphine acting as a potential suppressor of the substance P mediated cytokine cascade. Intraarticular morphine 1 mg after knee arthroscopy offers efficient analgesia lasting more than 24 hours. The method is devoid of side effects and deserves wider recognition.

[Analgesic effect of 2 different doses of intra-articular morphine after ambulatory knee arthroscopy. A randomized, prospective, double-blind study]. / Analgetisk effekt af to doser intraartikulaer morfin efter ambulant knaeartroskopi. Et randomiseret, prospektivt, dobbeltblindt studie.

The effect of intra-articular morphine following knee arthroscopy has been verified in several studies, but the optimal dose has not been established. An earlier study by the authors showed significant effect of one mg morphine versus placebo. In this study, fifty patients were randomized to receive either two or four mg of intra-articular morphine following day-case knee arthroscopy in infiltration analgesia. The injected volume in both groups was five ml. The pain was assessed preoperatively, two, four, eight, 24, 36 and 48 hours after the procedure by 1) a VAS scale and 2) amount of acetaminophen consumed. Forty-seven patients completed the study. Demographic data in the two groups were similar. The results showed no significant difference in VAS score between the two dose regimes at any time. Onset of pain after cessation of the local analgesia was not influenced by the morphine dose. On this basis it is recommended to limit the dose of intraarticular morphine, as local adverse reactions to morphine cannot be ruled out.

[Unicompartmental knee alloplasty by the St. Georg method. A follow-up of 42 knees after 5-10 years]. / Unikompartmental knaealloplastik a.m. St. Georg. En 5-10 års efterundersøgelse af 42 knae.

The results are presented of 42 arthroplasties by the St. Georg method in 37 patients who could be followed-up clinically and radiologically after median periods of observation of 66 months. The HSS-scoring method (Hospital for Special Surgery Score) was employed to assess the results. Good or excellent results (HSS score greater than 69 points) were obtained in 79% of the arthroplasties and 86% were relieved of pain on weightbearing. In selected patients, the St. Georg hemiarthroplasty is found to be a usable alternative to total condylar arthroplasty in the treatment of unicompartmental osteoarthritis of the knee.

[Displaced proximal humeral fracture--conservative treatment]. / Disloceret proksimal humerusfraktur--konservativt behandlet.

The results of 42 patients with displaced proximal humeral fractures treated by conservative methods were reviewed. Follow-up evaluation included clinical and radiographic examination median two years after the trauma. The results were assessed using Neer's protocol. The patients were asked to assess the results. The patients assessed the results better than the Neer score (p < 0.001). The patients' response to non-operative treatment was satisfactory. It is concluded that the Neer classification of the results underestimates the degree of satisfaction achieved by the patients. It is concluded that displaced proximal humeral fractures can be treated satisfactorily by non-operative methods.

Local anaesthesia versus intravenous regional anaesthesia in endoscopic carpal tunnel release: a randomized controlled trial.

We carried out a prospective randomized trial in 38 patients to compare intravenous regional anaesthesia with local anaesthesia in endoscopic carpal tunnel release using the Agee single-portal technique. There was no significant difference in reported pain during surgery. Immediately after surgery, patients in the local anaesthesia group reported significantly less pain in the hand and at the tourniquet. Two hours after surgery, patients in the local anaesthesia group reported significantly less hand pain. Moreover, significantly fewer patients in the local anaesthetic group required additional analgesics during the first 2 hours after operation. We conclude that local anaesthesia reduces post-operative pain in endoscopic carpal tunnel release compared with intravenous regional anaesthesia.

Effects of organic plant oils and role of oxidation on nutrient utilization in juvenile rainbow trout (Oncorhynchus mykiss).

Producing organic fish diets requires that the use of both fishmeal and fish oil (FO) be minimized and replaced by sustainable, organic sources. The purpose of the present study was to replace FO with organic oils and evaluate the effects on feed intake, feed conversion ratio (FCR), daily specific growth rate (SGR) and nutrient digestibility in diets in which fishmeal protein was partly substituted by organic plant protein concentrates. It is prohibited to add antioxidants to organic oils, and therefore the effects of force-oxidizing the oils (including FO) on feed intake and nutrient digestibility was furthermore examined. Four organic oils with either a relatively high or low content of polyunsaturated fatty acids were considered: linseed oil, rapeseed oil, sunflower oil and grapeseed oil. Substituting FO with organic oils did not affect feed intake (P > 0.05), FCR or SGR (P > 0.05) despite very different dietary fatty acid profiles. All organic plant oils had a positive effect on apparent lipid digestibility compared with the FO diet (P < 0.05), whereas there were no effects on the apparent digestibility of other macronutrients when compared with the FO diet (P > 0.05). Organic vegetable oils did not undergo auto-oxidation as opposed to the FO, and the FO diet consequently had a significantly negative effect on the apparent lipid digestibility. Feed intake was not affected by oxidation of any oils. In conclusion, the study demonstrated that it is possible to fully substitute FO with plant-based organic oils without negatively affecting nutrient digestibility and growth performance. Furthermore, plant-based organic oils are less likely to oxidize than FOs, prolonging the shelf life of such organic diets.

Kepler detected gravity-mode period spacings in a red giant star.

Stellar interiors are inaccessible through direct observations. For this reason, helioseismologists made use of the Sun's acoustic oscillation modes to tune models of its structure. The quest to detect modes that probe the solar core has been ongoing for decades. We report the detection of mixed modes penetrating all the way to the core of an evolved star from 320 days of observations with the Kepler satellite. The period spacings of these mixed modes are directly dependent on the density gradient between the core region and the convective envelope.

HD 181068: a red giant in a triply eclipsing compact hierarchical triple system.

Hierarchical triple systems comprise a close binary and a more distant component. They are important for testing theories of star formation and of stellar evolution in the presence of nearby companions. We obtained 218 days of Kepler photometry of HD 181068 (magnitude of 7.1), supplemented by ground-based spectroscopy and interferometry, which show it to be a hierarchical triple with two types of mutual eclipses. The primary is a red giant that is in a 45-day orbit with a pair of red dwarfs in a close 0.9-day orbit. The red giant shows evidence for tidally induced oscillations that are driven by the orbital motion of the close pair. HD 181068 is an ideal target for studies of dynamical evolution and testing tidal friction theories in hierarchical triple systems.

Ensemble asteroseismology of solar-type stars with the NASA Kepler mission.

In addition to its search for extrasolar planets, the NASA Kepler mission provides exquisite data on stellar oscillations. We report the detections of oscillations in 500 solar-type stars in the Kepler field of view, an ensemble that is large enough to allow statistical studies of intrinsic stellar properties (such as mass, radius, and age) and to test theories of stellar evolution. We find that the distribution of observed masses of these stars shows intriguing differences to predictions from models of synthetic stellar populations in the Galaxy.