Manipulating symmetry in the coordination dynamics of human movement.

J. A. S. Kelso and J. J. Jeka (see record 1992-41720-001) demonstrated that symmetry is a useful conceptual tool to distinguish the coordination between components with similar vs different anatomical properties. The present experiments studied human arm–leg patterns to test whether their coordinative asymmetry was changed by manipulating the inertial properties of a single limb. The results showed that (1) consistent with model predictions, adding weight to the arm or the leg minimized or enhanced coordinative asymmetry, respectively and (2) the response to a perturbation slowed as movement frequency increased but in a fashion that reflected the underlying coordinative asymmetry. The observed coordinative effects suggest the influence of neural phase relationships and emphasize that symmetry plays an important role in understanding coordination in systems in which control cannot be traced unequivocally to a single end-effector or a neurophysiological substrate. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of skin movement on the analysis of skeletal knee joint motion during running

Olfactory thresholds for acetone and vanillin and the unpleasantness rating of concentrated acetone were measured in 20 migraine sufferers and 21 controls. The olfactory threshold for vanillin was lower in migraine sufferers than in controls. In addition, patients who reported that odours frequently seemed stronger during attacks of migraine were able to detect acetone at a lower concentration than most other patients. No differences were found between migraine sufferers and controls for ratings of the unpleasantness of concentrated acetone. These findings suggest that hyperacuity to odours persists between episodes of migraine. Sensitivity to odours could contribute to the migraine predisposition.     

Anterior cruciate ligament reconstruction and joint dynamics during stair climbing

Athletes with anterior cruciate ligament (ACL) deficiencies exert decreased knee extension moments during level walking (quadriceps avoidance gait), and yet within a few months of ACL reconstruction they are often expected to return to competitive sport. To investigate this issue further, 10 normal subjects and seven ACL deficient patients were evaluated both pre- and post-operatively (mean follow-up of 6 months), and each performed multiple trials ascending a staircase which consisted of three steps. Bilateral joint angles, moments, powers, and work were measured and the data were ensemble averaged and statistically analyzed (repeated measures ANOVA with significance level set at 0.05). Anterior-posterior knee laxity decreased significantly (from 7.9 mm to 5.8 mm) while subjective knee function also improved following ACL reconstruction (knee score increased from 70.4 to 88.5). Pre-operatively, there were no statistically significant differences in biomechanical parameters between the patients' ACL-deficient and intact sides and the normal subjects. Post-operatively, however, statistically significant reductions were seen for the peak moment (91.9 vs 22.5 Nm), power (181 vs 84 W), and work performed (28.0 vs -5.6 J) at the injured knee, which was also the knee from which the patellar tendon graft had been harvested. These reductions were accommodated by significant increases in excursion, moment, and power at the contralateral ankle joint. The results indicate that while the ACL reconstruction were successful in restoring anterior-posterior knee stability, the decrease in knee power and work performed post-operatively by the injured (i.e., donor) knee suggests that donor site morbidity may need to be critically evaluated over a long-term period.     

Identification of human joint mechanical properties from single trial data

A method is presented for estimating the time-varying compliance parameters of the elbow-joint from a single movement. The method separates by frequency the perturbed from the voluntary response, then determines the parameters by exponentially weighted least squares. The tracking performance of the method is established by simulation and by a calibrated mechanical joint. Experimental results are presented on time-varying posture and slow movement.     

The population dynamics of Salmonella typhi and Tetrahymena pyriformis during joint cultivation

Scientific researches carried out in the area of environmental sanitation are closely related to the principal lines of activity in industry and farming of Ukraine. The main task of research work is establishing principles, criteria and methods of comprehensive assessment of injury to health secondary to environmental contamination. With the purpose of identification of the real physical and chemical environmental factors load that human body experiences, an inventory has been made at the Ukrainian Scientific Research Centre for Hygiene of carcinogen sources, with the concept having been worked out of creation of the integrated system for control of safe NPS operation, and a concept proposed of genetic monitoring, and of state genetic load surveillance service in different regions of Ukraine, taking account of the degree of environmental pollution.     

A neural network representation of electromyography and joint dynamics in human gait

This study sought to evaluate postvention provided to two schools following student suicides. A risk index for suicidal behavior among exposed adolescents was devised. The index clearly differentiated high (n = 272) and low (n = 534) scorers on a range of outcome variables. While two-thirds of students attending postvention counselling had two or more putative risk factors for suicidal behavior, a further 231 uncounselled students had similar risk scores. Counselled students (n = 63) did not differ from matched controls (n = 63) at 8-month follow-up on a range of outcome variables. Measures to improve future postvention are discussed.     

Changes in dorsal neck muscle activity related to imposed eye movement in the decerebrate pigeon

Movements of the head and eyes are known to be intimately related. Eye position has also been shown to be closely related to the electromyographic activity of dorsal neck muscles; however, extraocular muscle proprioception has not generally been considered to play a part in the control of such movements. We have previously shown that, in the pigeon, imposed movements of one eye modify the vestibular responses of several dorsal neck muscles in ways that are dependent on stimulus parameters such as the amplitude and velocity of imposed eye movement. The present study examines more closely the interactions between imposed eye movements and different muscle pairs. The three neck muscle pairs studied each responded to afferent signals from the extraocular muscles in discrete and specific ways which appeared to be correlated with their different actions. Complementary effects of imposed eye movements in the horizontal plane were seen for both the complexus and splenius muscle pairs, with imposed eye movements in one direction producing the largest inhibition of the ipsilateral muscle's vestibular response and imposed eye movements in the opposite direction the largest inhibition of the contralateral muscle's vestibular response. During roll tilt oscillation (ear-up/ear-down) in the frontal plane, similar complementary effects of imposed eye movement were seen in the complexus muscle pair, but the splenius muscle pair showed little tuning, with similar inhibition for imposed eye movement directed either upwards or downwards. In contrast to these complementary effects, the biventer cervicis muscle pair showed no vestibular modulation during vestibular stimulation in the horizontal plane and their spontaneous activity was not altered by imposed eye movement. During roll-tilt oscillation (ear-up/ear-down) in the frontal plane imposed eye movement directed vertically upwards increased both muscles' vestibular responses and imposed eye movement directed vertically downwards inhibited both muscles' vestibular responses. Section of the ophthalmic branch of the trigeminal nerve (deafferenting the eye muscles) abolished the effects of imposed eye movement on the neck muscle pairs. In conjunction with further control experiments these results provide compelling evidence that proprioceptive signals from the extraocular muscles reach the neck muscles and provide them with a functionally significant signal. We have previously shown that signals from the extraocular muscles appear to be involved in the control of the vestibulo-ocular reflex. It follows from the experiments reported here that proprioceptive signals from the extraocular muscles are also likely to be involved in the control of gaze.     

Therapy of ankle joint fractures (author's transl)

Even severely dislocated ankle joint fractures can be fixed in the right position and healed by immediate reposition. Irreponible fractures, ruptures of the syndesmosis, shortening of the fibula and abruptions of tibial edges require timely operative treatment with osteosynthesis, the individual forms of which are demonstrated. The screws fixing the syndesmosis must be removed in time in order to prevent their loosening or breaking. Fixations in hypercorrective position have proved to be unphysiological. Walking plaster, however, are better than training with crutches without the possibility of loading. The combination of osteosynthesis and walking plaster will contribute to the development of an early self-sufficiency on the part of the operated patient.     

Contribution of the anterolateral joint capsule to the mechanical stability of the ankle

Published reports describe the clinical efficacy of modified Brostrom anatomic repairs, surgical procedures that involve repair and fortification of the lateral capsuloligamentous complex of the ankle for patients suffering from chronic lateral instability of this joint. A cadaveric serial sectioning study of the anterior talofibular ligament, the calcaneofibular ligament, and the remainder of the anterolateral joint capsule was completed to quantitate the contribution of the superior portion of the anterolateral joint capsule, independent of the other two structures, to the overall mechanical stability of the lateral ankle. Using 20 fresh frozen specimens, talar tilt and anterior drawer stress radiographs were taken before and after sectioning these anatomic structures in an order established by one of two protocols. Sectioning of the superior anterolateral joint capsule caused 17% to 18% of the total displacement in a Grade II sprain simulation and 29% to 33% of the total displacement in a Grade III sprain simulation. This work suggests that disruption of the segment of ankle joint capsule superior to the anterior talofibular ligament creates approximately 30% of the overall laxity encountered in a Grade III inversion sprain, substantiating the principle of restoring the integrity of the entire anterolateral joint capsule when operating on a chronically unstable ankle.     

External rotational injury of tha ankle joint with displacement of the talus

The mechanism of second-degree external rotational injury of the ankle, with fracture of the lower end of the fibula, is discussed with reference to experiments on an anatomical model. It is concluded that with this type of injury there is lateral displacement of the talus because the deltoid ligament is ruptured, but there is no diastasis of the inferior tibiofibular syndesmosis. The results of conservative treatment of 10 patients with second-degree external rotational injury of tha ankle are reviewed.     

Right to left differences in the ankle joint complex range of motion

In most eukaryotic cells, synthesis of the iron storage protein, ferritin is regulated by iron levels and redox conditions. Proper iron storage is important to protect against damaging iron-catalysed free radical reactions. Although iron-catalysed reactions are believed to contribute to oxidative damage and cataractogenesis, little is known about iron storage in the lens. In this study, ferritin concentration was measured in cultured canine lens epithelial cells. Baseline ferritin concentration ranged from 76-163 ng (mg protein)-1; cells cultured in low-iron media had significantly lower ferritin levels than cells cultured in iron-supplemented media. Addition of a large excess of iron as hemin resulted in an eight-fold increase in ferritin concentration. The iron chelator, Desferal, significantly decreased ferritin concentration. The reducing agent dithiothreitol decreased the hemin-induced increase in ferritin levels, but not baseline levels. In contrast, ascorbic acid induced a large increase in ferritin content. Other studies have shown that induction of ferritin synthesis can protect against oxidative damage. Regulation of ferritin levels may represent a mechanism by which the lens epithelium is protected from oxidative damage. In vivo, epithelial cells are normally exposed to much lower iron concentrations than the cultured lens epithelial cells in this study. However, in pathological circumstances, the iron content and redox state of the aqueous humor is dramatically altered and may affect the steady state levels of ferritin within the lens. This remains to be determined.     

Identification of photoacoustic transients during pulsed laser ablation of the human temporal bone: an experimental model

Laser ablation of hard tissues during neurotologic operations has been accomplished with continuous-wave (CW) lasers in the visible and midinfrared spectrum. The mechanism of ablation at these wavelengths is secondary to photothermal-induced tissue destruction. As a result, significant thermal damage to surrounding tissue may occur. Pulsed ultraviolet (UV) lasers have been suggested as an alternative to the argon, KTP-532, and CO2 lasers currently used in clinical practice. The pulse length of Excimer lasers are considerably shorter than the thermal diffusion time of bone tissue, and as a consequence thermal injury is minimal. This makes pulsed lasers an attractive tool for tissue ablation in the ear: in essence a "cold knife." However, the short pulse width of Excimer lasers (typically 10-150 ns) can create large thermoelastic stresses in the ablation specimen. This study identifies the presence of these photoacoustic waves during the Excimer laser treatment of the cadaveric human temporal bone. A XeCl (lambda = 308 nm, tau p = 12 ns) excimer laser was used to ablate hard tissue surrounding the oval window and facial ridge with energies of 75, 45, 25, and 12 mJ/pulse. Spot size was estimated to be 0.5 mm2. Custom high-frequency polyvinyldifluoride (PVDF) piezoelectric film transducers were fabricated and attached to the promontory, round window niche, and facial ridges. The signals were amplified using a low-noise preamplifier and recorded on a digitizing oscilloscope. Photoacoustic waves were clearly identified. Notably, large acoustic waves were measured on the promontory and on both sides of the facial ridge. The implications and clinical relevance of these findings is discussed and compared to findings obtained from a model system.     

Limitations of quasi-static estimation of human joint loading during locomotion

The forces and moments at the ankle, knee and hip joints of the human lower limbs are divided into static and inertial components. They are calculated for various activities ranging from slow walking to running. The relative roles of these two components in the 'total' joint loads are studied, and the limitations of using a quasi-static analysis approach for joint load approximation are discussed. The results indicate that the static loads only reflect the gravitational and external reactions between the body and the environment, whereas the inertial loads provide dynamic information on each body segment involved. The effect of the inertial forces and moments becomes more important as the speed of locomotion increases; where the more proximal joints in the human lower extremity are concerned; and where the shear components of the force and moment are of interest. On the other hand, it seems that most of the joint moments in the lower extremity during walking and even running could reasonably be approximated by static components.     

Use of hot wire anemometry to measure velocity of the limb during human movement

Hot film anemometry, x-configuration probes were used in two experiments to evaluate their effectiveness at measurement of limb velocity. Data from tests with a probe attached to the end of a pendulum establish that the hot films measure velocity in the swing phase within 0.098 ms-1. The kinetic energy per unit mass of the pendulum was predicted within +/- 0.005 m2 s-2, from the measured velocity. In gait experiments with one human subject at speeds greater than 0.25 ms-1, the hot film anemometer and a video system predicted speeds within 0.083 ms-1. The hot film data are electronic signals that are easily stored and processed. The results from these experiments demonstrate that hot film anemometry is an effective and efficient method for direct measurement and analysis of the limb velocity.     

Arthroscopy of the upper ankle joint. List of indications from the literature--realistic expectations--complications

PROBLEM: Antiphospholipid antibodies (APLs) consist of very heterogenous autoantibodies. It has not been fully explored what kind of specificities are most relevant to recurrent pregnancy loss. Thus, we investigated the effects of specific APLs on recurrent aborters. METHOD: IgG and IgM antibodies against PE (treated with 1% acetic acid) and five negatively-charged phospholipids were measured by ELISA among 334 recurrent aborters without autoimmune disease. The relationships between APL specificities and subsequent pregnancy outcome were prospectively investigated in 38 recurrent aborters with positive APL who did not receive treatment with prednisolone and aspirin. Antibody levels exceeding the 99th percentile of 280 healthy women were considered positive. RESULTS: Positive IgG and/or IgM APLs were detected in 14%, IgG APLs in 12%, and IgG antibodies against PA, PG, PI, PS, CL and PE, respectively, in 9%, 7%, 7%, 7%, 8%, and 8%. In a prospective study of the 38 untreated patients, fetal loss recurred in 82% of the 33 IgG APL-positive patients, but in 40% of the five patients positive for only IgM APLs. The incidence of fetal loss in the next pregnancy of patients with IgG specific APL-positive against PE, PI, PS, or Cl was even higher at 90% and over, and fetal loss recurred in all of 21 patients with two or more IgG APL-positive against PE, PI, PS, or CL. CONCLUSION: These results suggest the possibility that two or more IgG APL-positive value against treated PE, PI, PS, or CL, may be more accurate as a predictive variable than that of only one IgG APL-positive in patients with recurrent pregnancy loss.     

The use of splints in the treatment of joint stiffness: biologic rationale and an algorithm for making clinical decisions

The purpose of this article are (1) to discuss the rationale for using splints to increase range of motion (ROM) and (2) to describe an algorithm that can guide therapists' clinical decisions when splints are used to treat patients who have limited ROM. The primary rationale for using splints is to apply relatively long periods of tensile stress to shortened connective tissues to induce tissue lengthening through biologic remodeling. The process of remodeling is contrasted with more temporary mechanical phenomena that occur in biologic tissues. The proposed algorithm guides the use of splints based on measurements of pain and ROM. We describe three variables of splint use that may be adjusted: frequency, duration, and intensity. The relative importance of each of these variables is discussed. The algorithm is not joint or injury specific and requires continual modification of splint use based on a patient's response to treatment. Deciding which patients are appropriate for end-range splinting and deciding when to discontinue splint use are also discussed.