Tumors of the elbow and forearm

The trend in the treatment of bone and soft tissue sarcomas of the extremities has been away from radical surgery and toward conservative, limb-sparing surgery, a trend that is present throughout other subdisciplines of surgical oncology. Organ-sparing and limb-sparing surgery has been combined with the use of adjuvants to give equivalent local control and in some cases improved survival. This article summarizes the current staging and treatment of bone and soft tissue tumors of the extremities and discusses some of the features that are unique to the elbow and forearm.     

Neurovascular problems in the forearm, wrist, and hand

This article attempted to summarize the most common neurovascular injuries of the upper extremity, particularly the forearm, wrist, and hand. Although these injuries are rarely encountered in athletes, their pathology and treatment must be understood by the treating physician. Failure to recognize these injuries in a timely manner can lead to delay in diagnosis and weeks or months of lost participation by the athlete. The sports medicine physician must be aware of the potential risk for injury to the neurovascular structures, particularly in the athlete exposed to repetitive use or impact of the upper extremity. Timely recognition, diagnosis, and treatment will avoid the potential risk for permanent injury.     

Elbow, forearm and wrist injuries in the athlete

Competitive and recreational athletes sustain a wide variety of soft tissue, bone, ligament, tendon and nerve damage to their upper extremities. Most such injuries are related to direct trauma or repetitive stress, and account for a significant amount of 'down time' for athletes participating in a wide range of sports, particularly those in which the arm is utilised for throwing, catching or swinging. Overuse injuries to the elbow include musculotendinous injuries, ulnar nerve injuries and ligamentous injuries. Osteochondrol lesions of the capitellum and posterior impingement injuries in the joint are frequently seen in athletes as well. Acute traumatic injuries to the elbow include tendon ruptures, elbow dislocations and intra-articular fractures. Forearm overuse injuries in athletes include fracture of the carpal scaphold, fracture of the hook of the hamate, Kienbock's syndrome and pisoquetral syndromes. ligamentous injuries include scapholunate, lunotriquetral and midcarpal instability injuries. Injuries to the distal radio-ulnar joint and triangular fibrocartilage are also quite common in athletes, and require careful evaluation and treatment.     

Activity of spinal interneurons and their effects on forearm muscles during voluntary wrist movements in the monkey

We studied the activity of 577 neurons in the C6-T1 spinal cord of three awake macaque monkeys while they generated visually guided, isometric flexion/extension torques about the wrist. Spike-triggered averaging of electromyographic activity (EMG) identified the units' correlational linkages with 相似文献   

Limit cycle properties of rhythmic forearm movements.

The kinematics of 1- and 2-armed rhythmic forearm movements were examined using the methodology and limit cycle modeling strategy of B. A. Kay, J. A. S. Kelso, E. L. Saltzman, and G. Schoner (see record 1987-23926-001). As frequency was paced from 1 to 6 Hz (in steps of 1 Hz), amplitude decreased in all 7 participants, whereas peak velocity showed different trends for different participants. The data of 2 of the 7 participants could be described with Kay et al.'s model. To account for the data of the remaining 5 participants, a new model was proposed with a dissipative structure involving a frequency-dependent Rayleigh term and a standard Van der Pol term. For 2 of these 5 participants, the coefficient of the Van der Pol term was not significantly different from zero. Contrary to Kay et al.'s model, the new model suggests that the energy bookkeeping of rhythmic forearm oscillations is affected by the frequency of movement. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

A model for dynamic embrittlement

A model is presented to calculate the rate of crack advance in the stepwise decohesion process which can result from the stress-induced penetration of a surface-adsorbed element into a solid, usually along grain boundaries. We call this process dynamic embrittlement. The model employs a diffusion equation containing both the usual random-mixing term and a term reflecting the work done by a tensile stress when surface atoms diffuse inward. Given the diffusion constant of the surface species and the stress profile at the crack tip, the concentration build-up ahead of the crack as a function of time can be calculated. This can be combined with an empirical relationship between the interfacial concentration of the surface species and the stress to cause decohesion to give the crack-growth rate. This model is applied to the case of sulfur-induced cracking of an alloy steel in the process known as stress-relief cracking.     

Step-tracking movements of the wrist. IV. Muscle activity associated with movements in different directions

We examined the patterns of muscle activity associated with multiple directions of step-tracking movements of the wrist in humans and monkeys. Human subjects made wrist movements to 12 different targets that required varying amounts of flexion-extension and radial-ulnar deviation. Wrist muscles displayed two patterns of electromyographic (EMG) modulation as movement direction changed: amplitude graded and temporally shifted. The amplitude-graded pattern was characterized by modulation of the quantity of muscle activity that occurred during two distinct time periods, an agonist burst interval that began before movement onset and an antagonist burst interval that began just after movement onset. The timing of muscle activity over the two intervals showed little variation with changes in movement direction. For some directions of movement, EMG activity was present over both time intervals, resulting in "double bursts." Modulation of activity during the agonist burst interval was particularly systematic and was well fit by a cosine function. In contrast, the temporally shifted pattern was characterized by a gradual change in the timing of a single burst of muscle activity. The burst occurred at a time intermediate between the agonist and antagonist burst intervals. The temporally shifted pattern was seen less frequently than the amplitude-graded pattern and was present only in selected wrist muscles for specific directions of movement. Monkeys made wrist movements to 8-16 different targets that required varying amounts of flexion-extension and radial-ulnar deviation. These movements were performed more slowly than those of human subjects. The wrist muscles of the monkeys we examined displayed the amplitude-graded pattern of activity but not the temporally shifted pattern. Stimulation of individual wrist muscles in monkeys resulted in wrist movements that were markedly curved, particularly for the wrist extensors. These results indicate that step-tracking movements of the wrist are generated mainly by using the amplitude-graded pattern to modulate muscle activity. We propose that this pattern reflects a central process that decomposes an intended movement into an agonist, "propulsive" component and an antagonist, "braking" component. Separate bursts of muscle activity then are generated to control each component. On the other hand, we argue that the temporally shifted pattern may function to reduce the amount of movement curvature associated with the activation of wrist muscles.     

A CA-LBM model for simulating dendrite growth with forced convection

A two-dimensional coupled model of the cellular automaton(CA)and the lattice Boltzmann method(LBM)was developed to simulate the solute dendrite growth of Fe-C-M...     

A model for conceptualizing the moral dynamic in health care

Ethics involves an organized, reasoned approach to gathering and processing data in order to arrive at decisions about what to do, what to value, and/or what virtues to cultivate. A model is proposed for conceptualizing this complex dynamic, which incorporates elements of both rule-and-principle ethics and the ethic of care. The model suggested here has two levels. The first level identifies the components that comprise philosophical reasoning; the second contextualizes and operationalizes the model in relation to the processor's philosophical stance on the nature of knowing. Three philosophical stances are identified and described: science-dominant, person-dominant, and science-person equilibrium. Physicians tend to process patients from first perspectives, nurses from second. Hence, health team collaboration in moral problem solving is critically important.     

A dynamic model for the cognitive development of Kenyan schoolchildren.

The author presents an integrated analysis of the scores obtained on cognitive tests and school examinations by approximately 110 Kenyan children (aged 6–9 years) in the Embu region of Kenya. A dynamic multivariate model, controlling for the unobserved between-children differences, is formulated for the scores and is estimated using three repeated observations. Children's body mass index, head circumference, hemoglobin concentration (i.e., measures of biological development), and grade level are important predictors of the scores on higher order cognitive tests. The family household's socioeconomic status is positively associated with cognitive scores, and children's morbidity is negatively associated. Only grade level and school attendance, however, are significant predictors of scores on school examinations. The implications of the results are briefly discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A dynamic model for the interaction between a solid particle and an advancing solid/liquid interface

Most models that describe the interaction of an insoluble particle with an advancing solid-liquid interface are based on the assumption of steady state. However, as demonstrated by experimental work, the process does not reach steady state until the particle is pushed for a while by the interface. In this work, a dynamic mathematical model was developed. The dynamic model demonstrates that this interaction is essentially non-steady state and that steady state eventually occurs only when solidification is conducted at subcritical velocities. The model was tested for three systems: aluminum-zirconia particles, succinonitrile-polystyrene particles, and biphenyl-glass particles. The calculated values for critical velocity of the pushing/engulfment transition were in the same range with the experimental ones.     

Corticospinal excitability modulation during mental simulation of wrist movements in human subjects

Motor evoked potentials (MEPs) to magnetic transcranial stimulation (TCS) were simultaneously and bilaterally recorded from flexor carpi radialis (FCR) and extensor communis digitorum (ECD) muscles in seven healthy and trained subjects. Latencies and amplitudes characteristics of MEPs were investigated under the following randomised conditions: muscular and mental relaxation; mental simulation, during absolute muscular relaxation, selective flexion or extension of the right or left wrist muscles; arithmetical calculation with muscular relaxation. Unspecific, diffuse facilitatory effects on MEPs amplitude were induced by mental non motor activity (arithmetical calculation). A further specific and lateralised amplitude potentiation on the agonist muscle acting as 'prime mover' for the mentally simulated movement was consistently found in all the subjects, without significant latency changes. Inhibitory effects on antagonists were evident only in two subjects.     

A ''tachometer'' feedback model of smooth pursuit eye movements

This paper reviews the literature on the effects of luminance and chromatic contrast on reading and object recognition in low vision. The general consensus is that whereas luminance contrast can enhance reading and object recognition for some low vision subjects, chromatic contrast does not aid low vision reading but may be useful in low vision object recognition. Although providing useful theoretical results, the experimental designs have so far been remote from the conditions that low vision patients may experience in the home and work environment. Suggestions are made for an 'ideal' experimental design and details of current research, using conditions more likely to be experienced by low vision subjects in everyday life, are given. This research makes use of a recently developed instrument, the Intuitive Colorimeter.     

Corticomotoneuronal postspike effects in shoulder, elbow, wrist, digit, and intrinsic hand muscles during a reach and prehension task

We used spike-triggered averaging of rectified electromyographic activity to determine whether corticomotoneuronal (CM) cells produce postspike effects in muscles of both proximal and distal forelimb joints in monkeys performing a reach and prehension task. Two monkeys were trained to perform a self-paced task in which they reached forward from a starting position to retrieve a food reward from a small cylindrical well. We compiled spike-triggered averages from 22 to 24 separate forelimb muscles at both proximal (shoulder, elbow) and distal (wrist, digits, intrinsic hand) joints. Of 174 cells examined, 112 produced postspike effects in at least one of the target muscles. Of those cells, 45.5% produced postspike effects in both proximal and distal forelimb muscles. A nearly equal number (44.7%) produced postspike effects in distal muscles only, whereas a clear minority (9.8%) produced postspike effects in only proximal muscles. The majority of CM cells (71.4%) produced effects in two or more muscles, with an average muscle field of 3.1 +/- 2.1 (mean +/- SD) for facilitation plus suppression. Of 345 postspike effects identified, 70.7% were facilitation effects and 29.3% were suppression effects. The large majority of effects (72.2%) were in distal muscles. When averaged by joint, the latency and peak magnitude of postspike facilitation showed a stepwise increase from proximal to distal joints. The results of this study show that the majority of CM cells engaged in coordinated forelimb reaching movements facilitate and/or suppress muscles at multiple joints, including muscles at both proximal and distal joints. The results also show that CM cells make more frequent and more potent terminations in motoneuron pools of distal compared with proximal muscles.     

MR imaging of the major nerves about the elbow: cadaveric study examining the effect of flexion and extension of the elbow and pronation and supination of the forearm

Magnetic resonance (MR) imaging provides useful information in the evaluation of peripheral nerves. Recent advances in MR imaging allow for detailed depiction of the soft tissue structures of the elbow joint. Three major nerves are present about the elbow. Six cadaveric elbows were imaged to depict the normal anatomy of these nerves and to determine the best plane and position of the elbow for optimal visualization of each nerve. Axial images of the elbow in full extension with the forearm in supination allow identification of all major nerves. Axial images with the elbow in full flexion allow accurate assessment of the cubital tunnel and the ulnar nerve. Axial images of the elbow in full extension with the forearm in pronation are helpful for assessment of the median and radial nerves in the forearm.     

A dynamic shoulder model for biomechanical measurements of shoulder specimen

The article discusses a dynamic shoulder model capable of simulating the forces generated by the rotator cuff and the deltoid muscle, and elevation movements of the glenohumeral joint using, a computer-aided servohydraulic unit. In 10 cadaver shoulder specimen, the effects of the loss of function of the supraspinatus muscle on maximum elevation was determined with an ultrasound system. Changes in the so-called impingement pressure below the coracoacromial arch were determined with the aid of capacitive pressure sensors. With the supraspinatus muscle inactive/ absent, the maximum elevation of the humerus showed a decrease of 6% (p < 0.05), which, however, was overcome by an increase in deltoid power of only one-third of the supraspinatus muscle power loss. For a simulated isolated supraspinatus defect, the subacromial pressure below the coracoacromial arch decreased by 8% (p > 0.05). These results confirm clinical investigations showing that isolated lesions affecting the supraspinatus tendon often fail to produce symptoms and thus require no surgical reconstruction.     

Effects of motor programming on the power spectral density function of finger and wrist movements.

Power spectral density analysis was applied to the frequency content of the acceleration signal of pen movements in line drawing using 10 right-handed college students. The relative power in frequency bands between 1 and 32 Hz was measured as a function of motoric and anatomic task demands. Results showed a decrease of power at the lower frequencies (1–4 Hz) of the spectrum and an increase in the middle (9–22 Hz) with increasing motor demands. These findings evidence the inhibition of visual control and the disinhibition of physiological tremor under conditions of increased programming demands. Adductive movements displayed less power than abductive movements in the lower end of the spectrum, with a simultaneous increase at the higher frequencies. The relevance of the method for the measurement of neuromotor noise as a possible origin of delays in motor behavior is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Traumatic bowing of the forearm in an adult

A 24-year-old woman sustained a low-velocity, continuous pressure injury to the right forearm from a conveyer belt machine. The accident caused bowing of the radius and ulna, an injury not previously reported in adults. A closed manipulation with the patient under general anesthesia required considerable force to obtain partial reduction of the radial bowing and almost complete correction of the ulnar bowing. Follow-up examination at two years demonstrated no loss of position but persistent radial bowing. The injury is a good illustration of plastic deformation in bone which is a rare condition in adults due to the elastic properties of bone and typical fracture mechanics.