A dynamic model for simulating movements of the elbow, forearm, an wrist

We developed a dynamic model of the upper extremity to simulate forearm and wrist movements. The model is based on the skeletal structure of the arm and is capable of elbow flexion/extension, forearm pronosupination, and wrist flexion/extension and radial/ulnar deviation movements. Movements are produced by activation of a Hill-type model of muscle, and limits on joint motion are imposed by passive moments modeled after experimental results. We investigated the muscle output force sensitivity, as well as wrist flexion/extension motion sensitivity to parameter variations. The tendon slack length and muscle fiber length were found to have the greatest influence on muscle output and flexion/extension wrist motion. The model captured the direction of the moment vectors at the wrist well, but predicted much higher moments than were measured by stimulating the paralyzed muscles of one tetraplegic subject.     

Lipid and lipoprotein distributions in children by ethnic group, gender, and geographic location--preliminary findings of the Child and Adolescent Trial for Cardiovascular Health (CATCH)

Male and female isometric strength curves for elbow fixation, shoulder flexion, and wrist supination-pronation are obtained during systematic variation in arm configuration. The shape of a given moment-angle curve is found to be a function of the orientations of joints kinematically coupled to the primary joint. It is also found that female elbow strength curves are shifted toward flexion with respect to male elbow-strength curves, suggesting that the in situ rest length of upper-limb muscles relative to joint angle may be longer for males than for females. Experimental results were contrasted with simulation results obtained using a three-dimensional musculoskeletal model which estimates the relationships between initial joint orientations, muscle tension-length behavior, and joint moments. In most of the cases, simulation results complimented experimental data and provided insights into likely in situ muscle rest lengths and moments arms, especially for the multiarticular biceps brachii muscle. Where inconsistencies exist between simulated and experimental data, subtle biomechanical complexities within the forearm and the shoulder girdle complex are identified that require future investigation.     

The mechanism of transcriptional synergy of an in vitro assembled interferon-beta enhanceosome

The objectives of this study were (a) to determine errors in wrist angle measurements from a commercially available biaxial electrogoniometer and (b) to develop a calibration routine in order to correct for these errors. Goniometric measurements were collected simultaneously with true angular data using a fixture that allowed wrist movement in one plane while restricting motion in the orthogonal plane. These data were collected in two sets of trials: flexion/extension with radial/ulnar deviation restricted, and radial/ulnar deviation with flexion/extension restricted. During these trials, we studied discrete 30 degrees increments of forearm rotation. The results showed the expected cross talk and zero drift errors during forearm rotation. The application of mathematical equations that describe the effect of goniometer twist resulted in significant error reduction for most forearm rotations. The calibration technique employs both a slope and a displacement transformation to improve the accuracy of angular data. The calibration technique may be used on data collected in the field if forearm rotation is measured simultaneously with the goniometer data.     

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.     

Volkmann's ischemic contracture of the upper extremity

Upper extremity deformity of ischemic contracture usually includes elbow flexion, forearm pronation, wrist flexion, thumb flexion and adduction, digital metacarpophalangeal joint extension, and interphalangeal joint flexion. Treatment of mild contractures consists of either nonoperative management with a comprehensive rehabilitation program (to increase range of motion and strenght) or operative management consisting of infarct excision or tendon lengthening. Treatment of moderate-to-severe contractures consists of release of secondary nerve compression, treatment of contractures (with tendon lengthening or recession), tendon or free-tissue transfers to restore lost function, and/or salvage procedures for the severely contracted or neglected extremity.     

Obstetrical brachial plexus palsy: results following neurolysis of conducting neuromas-in-continuity

Sixteen infants with conducting neuromas-in-continuity at primary brachial plexus exploration underwent microsurgical neurolysis of their lesions. For each patient, the immediate preoperative scores for individual joint movements were compared with scores at the last examination. In the Erb's palsy group (n = 9), significant improvement was seen in shoulder movements, elbow flexion, supination, and wrist extension (paired t test, p < 0.05). Clinically useful improvements in function was seen at the shoulder and elbow (Fisher's exact test, p < 0.05). In the total palsy group (n = 7), significant improvement in shoulder abduction, shoulder adduction, elbow flexion, and extension of the wrist, fingers, and thumb was seen (paired t test, p < 0.05), but there was no significant improvement in the proportion of patients with useful functional outcomes. Neurolysis in Erb's palsy improves both muscle grade and the functional ability of patients. Neurolysis does not provide useful functional recovery in patients with total plexus palsy.     

Effect of radiographic positioning on interpretation of cubital joint congruity in dogs

OBJECTIVE: To ascertain effects of x-ray beam centering and limb position on apparent congruity of a normal cubital joint (elbow). ANIMALS: 6 skeletally mature male Treeing Walker Coonhounds without physical, radiographic, or gross evidence of elbow abnormalities. PROCEDURE: Relative movement among humerus, radius, and ulna and measured joint space width on mediolateral and craniocaudal radiographic views was compared, using various x-ray beam centering and limb positions. RESULTS: Highest agreement and greatest certainty on subjective determination of congruity was for the flexed 90 degrees mediolateral radiographic view with the x-ray beam centered on the elbow. Distortion artifact of the proximal ulnar measurements was significant when the x-ray beam was centered on the midpoint of the radius. On the mediolateral view, the humeroradial joint space became significantly wide when the elbow was flexed. On the craniocaudal view, maximal humeroradial joint space width was obtained when the x-ray beam bisected the angle of the joint or was angled +30 degrees toward the humerus. CONCLUSIONS: Artifact distortion of joint width affected objective and subjective assessment of elbow congruity when the limb was placed in extreme flexion or extension or when the x-ray beam was not centered over the area of interest. Optimal visualization of the humeroradial joint space on the craniocaudal view was achieved when the x-ray beam bisected the angle of the elbow or was slightly angled toward the humerus. CLINICAL RELEVANCE: Elbow congruity was best assessed on the flexed 90 degrees lateral radiographic view with the x-ray beam centered on the joint.     

Wrist action affects precision grip force

When moving objects with a precision grip, fingertip forces normal to the object surface (grip force) change in parallel with forces tangential to the object (load force). We investigated whether voluntary wrist actions can affect grip force independent of load force, because the extrinsic finger muscles cross the wrist. Grip force increased with wrist angular speed during wrist motion in the horizontal plane, and was much larger than the increased tangential load at the fingertips or the reaction forces from linear acceleration of the test object. During wrist flexion the index finger muscles in the hand and forearm increased myoelectric activity; during wrist extension this myoelectric activity increased little, or decreased for some subjects. The grip force maxima coincided with wrist acceleration maxima, and grip force remained elevated when subjects held the wrist in extreme flexion or extension. Likewise, during isometric wrist actions the grip force increased even though the fingertip loads remained constant. A grip force "pulse" developed that increased with wrist force rate, followed by a static grip force while the wrist force was sustained. Subjects could not suppress the grip force pulse when provided visual feedback of their grip force. We conclude that the extrinsic hand muscles can be recruited to assist the intended wrist action, yielding higher grip-load ratios than those employed with the wrist at rest. This added drive to hand muscles overcame any loss in muscle force while the extrinsic finger flexors shortened during wrist flexion motion. During wrist extension motion grip force increases apparently occurred from eccentric contraction of the extrinsic finger flexors. The coactivation of hand closing muscles with other wrist muscles also may result in part from a general motor facilitation, because grip force increased during isometric knee extension. However, these increases were related weakly to the knee force. The observed muscle coactivation, from all sources, may contribute to grasp stability. For example, when transporting grasped objects, upper limb accelerations simultaneously produce inertial torques at the wrist that must be resisted, and inertial loads at the fingertips from the object that must be offset by increased grip force. The muscle coactivation described here would cause similarly timed pulses in the wrist force and grip force. However, grip-load coupling from this mechanism would not contribute much to grasp stability when small wrist forces are required, such as for slow movements or when the object's total resistive load is small.     

The effect of wrist and arm postures on peak pinch strength

This paper examines the effect of various arm postures on peak pinch strength. Twenty (20) able-bodied, male subjects volunteered to participate in a set of two experiments. The first experiment examined the effect of shoulder and elbow posture on peak pinch strength. The second experiment examined the effect of forearm posture, wrist posture, and pinch type on peak pinch strength. Results from the first experiment indicated that elbow posture had a significant effect on pinch strength. It was documented that extreme elbow flexion decreased pinch strength by up to 9%. Results from the second experiment indicated that deviated wrist postures, forearm postures, and pinch type significantly decreased pinch strength as much as 33%. Ergonomic guidelines which utilize the above factors as significant modifiers of pinch strength capacity may assist ergonomists to reduce the risk of injury and development of cumulative trauma disorders in the workplace.     

Genotoxicity of trophosphamide in mouse germ cells: assessment of micronuclei in spermatids and chromosome aberrations in one-cell zygotes

We have used the muscle history dependence of the sensitivity of muscle spindles to stretch, to provide evidence for their contribution to kinaesthesia, the sense of position and movement. Stretch sensitivity is altered depending on whether or not slack has been introduced in intrafusal fibres [13]. At the human elbow joint detection threshold was measured to passive movements applied at different speeds to the forearm after a conditioning co-contraction of muscles of the upper arm, with the arm held either flexed ('hold short') or extended ('hold long'). Test measurements were made with the elbow joint at 90 degrees. For the three speeds of movement, 2 degrees s-1, 0.2 degree s-1 and 0.02 degree s-1, after 'hold short' conditioning thresholds were lower for movements into extension, after 'hold long' conditioning they were lower for movements into flexion. It is concluded that when muscle conditioning introduces slack in the intrafusal fibres of muscle spindles, this must be taken up by the test movements before they can be detected by the subject. It means that whenever detection thresholds to passive movements are measured at a joint, the contraction history of the muscles acting at that joint must be taken into account.     

Scapholunate interosseous ligament sectioning adversely affects excursions of radial wrist extensor and flexor tendons

Excursions of tendons around the scaphoid were measured in 6 fresh cadaver forearms to evaluate the role of the scapholunate interosseous ligament (SLIL) in wrist joint motion. Excursions of the extensor carpi radialis longus (ECRL) and brevis (ECRB) tendons and the flexor carpi radialis (FCR) tendon were continuously recorded during wrist flexion, extension, and radial and ulnar deviation. Tendon excursions were measured in the intact wrists and after complete sectioning of the SLIL. Tendon excursions were altered significantly in the major ranges of wrist motion after SLIL sectioning. After ligament sectioning, excursions of the ECRL and ECRB tendons increased significantly in wrist flexion and extension. Excursions of the FCR tendon increased significantly during wrist extension and ulnar deviation. These findings support the concepts that integrity of the SLIL plays an important role in wrist function and that injury of the ligament may cause clinical problems.     

Evaluation of behavioural effects of neural melanocortin receptor antagonists injected ICV and in VTA in rats

The purpose of this study was to examine intratester, intertester, and interdevice reliability of range of motion measurements of the elbow and forearm. Elbow flexion and extension and forearm pronation and supination were measured on 38 subjects with elbow, forearm, or wrist disease by 5 testers. Standardized test methods and a randomized order of testing were used to test groups of patients with universal standard goniometers, a computerized goniometer, and a mechanical rotation measuring device. Intratester reliability was high for all 3 measuring devices. Meaningful changes in intratester range of motion measurements taken with a universal goniometer occur with 95% confidence if they are greater than 6 degrees for flexion, 7 degrees for extension, 8 degrees for pronation, and 8 degrees for supination. Intertester reliability was high for flexion and extension measurements with the computerized goniometer and moderate for flexion and extension measurements with the universal goniometer. Meaningful change in interobserver range of motion measurements was expected if the change was greater than 4 degrees for flexion and 6 degrees for extension with the computerized goniometer compared with 10 degrees and 10 degrees, respectively, if the universal goniometer was used. Intertester reliability was high for pronation and supination with all 3 devices. Meaningful change in forearm rotation is characterized by a minimum of 10 degrees for pronation and 11 degrees for supination with the universal goniometer. Reliable measurements of elbow and forearm arm movement are obtainable regardless of the level of experience when standardized methods are used. Measurement error was least for repeated measurements taken by the same tester with the same instrument and most when different instruments were used.     

Congenital hypoplasia of the extensor tendons of the hand

An 18-year-old woman with congenital flexion contractures of the ulnar three digits bilaterally is presented. She had a three-generation family history of this disorder with autosomal dominant inheritance. Magnetic resonance imaging scan of the wrist and forearm was used to demonstrate a hypoplasia of the digital extensor muscles and tendons.     

Organizing principles for voluntary movement: extending single-joint rules

1. Four subjects performed fast flexions of the elbow or shoulder over three different distances. Elbow flexions were performed both in a horizontal, single-degree-of-freedom manipulandum and in a sagittal plane with the limb unconstrained. Shoulder flexions were only performed in the sagittal plane by the unconstrained limb. We simultaneously recorded kinematic and electromyographic (EMG) patterns at the "focal" joint, that which the subject intentionally flexed, and at the other, "nonfocal" joint that the subject had been instructed to not flex. 2. Comparisons of the elbow EMG patterns across tasks show that agonist and antagonist muscles were similar in pattern but not size, reflecting the net muscle torque patterns. Comparisons at the shoulder also revealed similar EMG patterns across tasks that reflected net muscle torques. 3. Comparisons of EMG patterns across joints show that elbow and shoulder flexors behaved similarly. This was not true of the extensors. The triceps EMG burst was delayed for longer distances but the posterior deltoid had an early, distance-invariant onset. 4. Similarities in EMG reflect torque demands required at the focal joint to produce flexion and at the nonfocal joint to reduce extension induced by dynamic interactions with the focal, flexing joint. These similarities appear despite very different kinematic intentions and outcomes. This argues against a strong role for length-sensitive reflexes in their generation. 5. These results support the hypothesis that movements are controlled by muscle activation patterns that are planned for the expected torque requirements of the task. This general rule is true whether we are performing single-joint or multiple-joint movements, with or without external constraints. The similarities between single-joint and multijoint movement control may be a consequence of ontogenetic development of multijoint movement strategies that prove useful and are therefore also expressed under the constrained conditions of specialized tasks such as those performed in single-joint manipulanda.     

Chronic Monteggia injury in a child

The case of a Monteggia fracture neglected from two years of age and seen at the age of fourteen, is described. A shortening of the affected ulna by three cm and a relative elongation of the radius was found. The function of the arm and elbow joint was remarkably unaffected with nearly full extension and flexion, supination and pronation. The carrying angle was ten degrees on both sides. Based on the literature, it is stressed that diagnosis and treatment of Monteggia lesions should be immediate. Complications in non-treated cases and at late treatment are many, and the results of such treatment dubious. It is thus of great importance that, when dealing with ulnar fracture a radiograph is also taken of the elbow joint to secure immediate diagnosis.     

Evaluating the effects of interface factors on the torque exertion capabilities of operating handwheels

This study intends to assess factors affecting human torque exertion capabilities of operating valve handwheels (maximum volitional torque exertion of wrist radial/ulnar deviation, R/U MVTE). Forty student subjects (20 males and 20 females) participated in this study. In addition to gender and subject factors, gloves (one layer of cotton, two layers of cotton and rubber gloves), operating height (elbow, shoulder and overhead), handwheel size and shape were selected. Barehanded condition was also involved. The results indicate that all the main effects and the first order interactions were significant. The gloved R/U MVTEs were found to be greater than the barehanded R/U MVTE. For operating height, shoulder height gave the greatest R/U MVTE, followed by elbow and overhead heights. The handwheel diameters ranging from 75 to 95 mm for males and 65 to 80 mm for females were found to have the greater R/U shear force. The average R/U MVTE of operating valve handwheel for females was about 63% (3.8/6.05) of that of males.     

The hand in the child with juvenile rheumatoid arthritis

Clinical examination of 100 children showed frequent loss of wrist extension and ulnar deviation. Loss of flexion and radial deviation in the metacarpophalangeal joint is more frequent than in the adult. Statistical review of charts and roentgenograms of 200 patients showed all had ulnar shortening up to 9 mm but there was no correlation with ulnar deviation or netacarpophalangeal radial deviation. Conservative treatment is reviewed; surgery is rarely indicated.     

Comparative analysis of breast cancer contamination in mobilized and nonmobilized hematopoietic grafts

We report a case of an 18-month-old female who presented with three supernumerary upper limbs of varying lengths on the right side. Each limb had a proximal, middle, and distal segment, and an intercalated elbow and wrist joint. A single digit was present in the superior limb, three digits in the middle limb, and two digits in the caudal-most limb. Right plagiocephaly, congenital torticollis, scoliosis involving the upper and mid thoracic region, and a hypoplastic right pectoralis major were the other abnormal features noted. Radiography showed two scapulae, humerus, a single forearm bone in each limb, and rudimentary metacarpals and phalanges. Limb duplication may rarely be encountered in parasitic conjoined twins. The role of mutagens, drugs, cellular contributions, and morphogens in the growth and differentiation of limbs has been studied in animals. It is rather difficult to deduce the time of action of the factors responsible for such a malformation.     

Distribution of muscle weakness of central and peripheral origin

According to the established clinical tradition about the distribution of weakness, the ratios of flexor/extensor strength of patients with upper motor neuron lesions are expected to be relatively high for the elbow and wrist and low for the knee. To assess the diagnostic value of these patterns of weakness, muscle strength of 70 patients with limb weakness of central or peripheral origin was measured with a hand held dynamometer. The ratios of flexor/extensor strength at the knee, elbow, and wrist did not differ significantly between patients with central or peripheral origin of muscle weakness. The examination of tendon jerks proved to be of more value as a localising feature. The traditional notion about the distribution of weakness in upper motor neuron lesions may be explained by an intrinsically greater strength in antigravity muscles, together with the effects of hypertonia.     

Distribution and characteristics of poststimulus effects in proximal and distal forelimb muscles from red nucleus in the monkey

We used stimulus-triggered averaging (StTA) of electromyographic (EMG) activity to investigate two major questions concerning the functional organization of the magnocellular red nucleus (RNm) for reaching movements in the macaque monkey. The first is whether the clear preference toward facilitation of extensor muscles we have reported in previous studies for distal (wrist and digit) forelimb muscles also exists for proximal muscles (shoulder and elbow). The second question is whether distal and proximal muscles may be cofacilitated from RNm suggesting the representation of functional muscle synergies for coordinated reaching movements. Two monkeys were trained to perform a prehension task requiring multijoint coordination of the forelimb. EMG activity was recorded from 24 forelimb muscles including 5 shoulder, 7 elbow, 5 wrist, 5 digit, and 2 intrinsic hand muscles. Microstimulation (20 microA at 20 Hz) was delivered throughout the movement task. From 137 microstimulation sites in the RNm, a total of 977 poststimulus effects was obtained including 733 poststimulus facilitation effects (PStF) and 244 poststimulus suppression effects (PStS). Of the PStF effects, 58% were obtained from distal muscles; 42% from proximal muscles. Digit muscles were more frequently facilitated (35%) than the wrist, elbow, or shoulder muscles (20, 24, and 18%, respectively). The intrinsic hand muscles were infrequently facilitated (3%). At all joints tested, PStF was more common in extensor muscles than flexor muscles. This extensor preference was very strong for shoulder (85%), wrist (85%), and digit muscles (94%) and weaker for elbow muscles (60%). Of the PStS effects, 65% were in distal muscles and 35% in proximal muscles. Interestingly, the flexor muscles were more frequently inhibited from RNm than extensor muscles. At 72% of stimulation sites, at least two muscles were facilitated. The majority of these sites (61%) cofacilitated both proximal and distal muscles. At the remaining sites (39%), PStF was observed in either the proximal (17%) or distal muscles (22%). Facilitation most often involved combinations of shoulder, elbow, and distal muscles (30%) or shoulder and distal muscles (26%). Only rarely were intrinsic hand muscles part of the total muscle synergy. Our results show that the RNm 1) controls both proximal and distal muscles but the strength of influence is biased toward distal muscles, 2) preferentially controls extensor muscles not only at distal forelimb joints but also at proximal joints, and 3) output zones cofacilitate synergies of proximal and distal muscles involved in the control of forelimb reaching movements.