Measurements of wrist and forearm positions and movements: effect of, and compensation for, goniometer crosstalk.

Flexible biaxial goniometers are extensively used for measuring wrist positions and movements. However, they display an inherent crosstalk error. The aim was to evaluate the effect, of this error, on summary measures used for characterizing manual work. A goniometer and a torsiometer were combined into one device. An algorithm that effectively compensated for crosstalk was developed. Recordings from 25 women, performing five worktasks, were analyzed, both with and without compensation for crosstalk. The errors in the 10th, 50th and 90th percentiles of the flexion/extension distributions were small, on average <1 degrees. The ulnar/radial deviation distributions were weakly dependent on forearm position. The flexion/extension velocity measures were, for the 50th and 90th percentiles, as well as the mean velocity, consistently underestimated by, on average, 3.9%. For ulnar/radial deviation, the velocity errors were less consistent. Mean power frequency, which is a measure of repetitiveness, was insensitive (error <1%) to crosstalk. The forearm supination/pronation angular distributions were wider, and the velocities higher, than for the wrists. Considering wrist/hand exposure in epidemiologic studies, as well as for establishing and surveillance of exposure limits for prevention of work-related upper extremity musculoskeletal disorders, the crosstalk error can, when considering other errors and sources to variation, be disregarded.     

Co-contraction of the pronator teres and extensor carpi radialis during wrist extension movements in humans.

In order to elucidate the functional significance of excitatory spinal reflex arcs (facilitation) between musculus (M.) pronator teres (PT) and M. extensor carpi radialis (ECR, longus: ECRL, brevis: ECRB) in humans, activities of the muscles were studied with electromyography (EMG) and electrical neuromuscular stimulation (ENS). In EMG study, activities of PT, ECRL, ECRB, and M. flexor carpi radialis during repetitive static (isometric) wrist extension and a series of a dynamic motion of wrist flexion/extension in the prone, semiprone, and supine positions of the forearm were recorded in 12 healthy human subjects. In the prone, semiprone, and supine positions, PT and ECR showed parallel activities during the static extension in all, eight, and eight subjects, respectively, and at the extension phase during the dynamic motion in all, eight and five subjects, respectively. These findings suggest that co-contraction of PT and ECR occurs during wrist extension movements at least with the prone forearm. The facilitation must be active during the co-contraction. In ENS study, ENS to PT was examined in 11 out of the 12 and that to ECRL was in the 12 subjects. Before ENS, the forearm was in the prone, semiprone, and supine positions. In all the subjects, ENS to PT induced a motion of forearm pronation to the maximum pronation. ENS to ECRL induced motions of wrist extension to the maximum extension and abduction (radial flexion) to 5-20 degrees of abduction regardless of the positions of the forearm. Moreover, it induced 30-80 degrees supination of the forearm from the prone position. Consequently, combined ENS to PT and ECRL resulted in motions of the extension and abduction while keeping the maximum pronation. These findings suggest that the co-contraction of PT and ECR during wrist extension movements occurs to prevent supinating the forearm. Forearm supination from the prone position should be added to one of the actions of ECRL.     

Experimental investigation of the scaphoid strain during wrist motion

The scaphoid is the most frequently fractured of the carpal bones [Taleisnik, J., The Wrist, Churchill Livingstone, New York (1985)]. This project was undertaken to qualitatively evaluate the strain in the scaphoid during wrist motion using a newly developed strain gage method. Strain gage resettes were mounted within the scaphoid and the range of motion of the hand was monitored using a custom designed electrogoniometer and data acquisition system. Ten specimens were utilized for this study. Results indicated that supination/pronation (S/P) of the forearm did not affect the strain in the scaphoid. A map of the strain in the waist of the scaphoid, as a function of flexion/extension (F/E) and radial/ulnar deviation (R/U), was generated. The contour plot of scaphoid strain vs range of motion (ROM) shows a valley where strains are low. Minimum scaphoid strain was found near neutral F/E and 15° of ulnar deviation.     

Upper-limb surface electro-myography at maximum supination and pronation torques: the effect of elbow and forearm angle.

Forearm pronation and supination, and increased muscular activity in the wrist extensors have been both linked separately to work-related injuries of the upper limb, especially humeral epicondylitis. However, there is a lack of information on forearm torque strength at ranges of elbow and forearm angles typical of industrial tasks. There is a need for strength data on forearm torques at different upper limb angles to be investigated. Such a study should also include the measurement of muscular activity for the prime torque muscles and also other muscles at possible risk of injury due to high exertion levels during tasks requiring forearm torques.Twenty-four male subjects participated in the study that involved maximum forearm torque exertions for the right arm, in the pronation and supination directions, and at four elbow and three forearm rotation angles. Surface EMG (SEMG) was used to evaluate the muscular activity of the pronator teres (PT), pronator quadratus (PQ), biceps brachi (BB), brachioradialis (BR), mid deltoid (DT) and the extensor carpi radialis brevis (ECRB) during maximum torque exertions. Repeated measures ANOVA indicated that both direction and forearm angle had a significant effect on the maximum torques (p<0.05) while elbow angle and the interactions were highly significant (p<0.001). The results revealed that supination torques were stronger overall with a mean maximum value of 16.2 Nm recorded for the forearm 75% prone. Mean maximum pronation torque was recorded as 13.1 Nm for a neutral forearm with the elbow flexed at 45 degrees. The data also indicated that forearm angle had a greater effect on supination torque than pronation torque. Supination torques were stronger for the mid-range of elbow flexion, but pronation torques increased with increasing elbow extension. The strength profiles for the maximum torque exertions were reflected in the EMG changes in the prime supinators and pronators. In addition, the EMG data expressed as the percentage of Maximum Voluntary Electrical activity (MVE), revealed high muscular activity in the ECRB for both supination (26-43% MVE) and pronation torques (17-55% MVE). The results suggest that the ECRB acts as a stabiliser to the forearm flexors for gripping during pronation torques depending on forearm angle, but acts as a prime mover in wrist extension for supination torques with little effect of elbow and forearm angle. This indicates a direct link between forearm rotations against resistance and high muscular activity in the wrist extensors, thereby increasing stress on the forearm musculo-skeletal system, especially the lateral epicondyle.     

A musculoskeletal model to estimate the relative changes in wrist strength due to interacting wrist and forearm postures

Wrist rotations about one wrist axis (e.g. flexion/extension) can affect the strength about another wrist axis (e.g. radial/ulnar deviation). This study used a musculoskeletal model of the distal upper extremity, and an optimization approach, to quantify the interaction effects of wrist flexion/extension (FE), radial/ulnar deviation (RUD) and forearm pronation/supination (PS) on wrist strength. Regression equations were developed to predict the relative changes in strength from the neutral posture, so that the changes in strength, due to complex and interacting wrist and forearm rotation postures, can be incorporated within future ergonomics assessments of wrist strength.     

Improving goniometer accuracy by compensating for individual transducer characteristics

Flexible goniometers are useful for direct movement measurements. Crosstalk due to rotation between the endblocks is well known. However, even without any rotation, some crosstalk can occur. The objective of this study was to elucidate the effect of, and compensate for, the inherent crosstalk in biaxial goniometers, with specific relevance for applications with one dominating movement direction. Six biaxial goniometers (M110, Biometrics Ltd., Gwent, UK) were evaluated. A precision jig, for simulating pure flexion/extension angles, was constructed. Each sensor produced a consistent and specific crosstalk pattern, when tested over a ±100° range of motion. A procedure for correction for the inherent crosstalk of individual goniometer, based on polynomial adjust, is presented. The method for compensation, which reduced the root mean square error from, on average for the six goniometers, 3.7° (range 1.8–10.1°) to 0.35° (0.12–0.55°), might be required for obtaining valid goniometer measurements, e.g. of valgus/varus of the knee during gait flexion/extension movements.     

Functional differences between anatomical regions of the anconeus muscle in humans

This study sought to resolve a longstanding debate of the function of anconeus. Intramuscular and surface electromyography electrodes recorded muscle activity from two regions of anconeus and from typical elbow flexion and extension muscles. Eleven participants performed pronation–supination around the medial and lateral axes of the forearm, elbow flexion–extension in pronation, supination and neutral positions of the forearm, and gripping. Maximal voluntary contractions (MVC) and submaximal (10% MVC) force-matching tasks were completed. Activity varied between longitudinal (AL) and transverse (AT) segments of anconeus. Although both muscle regions were active across multiple directions (including opposing directions), AL was more active during pronation than supination, whereas AT showed no such difference. During pronation, activity of AL and AT was greatest about the lateral forearm axis. AT was more active during elbow extension with the forearm in pronation, whereas AL did not differ between pronated and neutral forearm alignment. These findings are consistent with the proposal that AL makes a contribution to control of abduction of the ulna during forearm pronation. Different effects of forearm position on AL and AT activity during elbow extension may be explained by the anatomical differences between the regions. These data suggest anconeus performs multiple functions at the elbow and forearm and this varies between anatomically distinct regions of the muscle.     

Assessment of post-stroke elbow flexor spasticity in different forearm positions

Abstract

Purpose/Aim: There have been conflicting results regarding which muscle contribute most to the elbow spastic flexion deformity. This study aimed to investigate whether flexor spasticity of the elbow changed according to the position of the forearm, and to determine the muscle or muscles that contributed most to the elbow spastic flexion deformity by clinical examination.

Methods: This study is a single group, observational and cross-sectional study. Sixty patients were assessed for elbow flexor spasticity in different forearm positions (pronation, neutral and supination) with Modified Tardieu Scale. The primary outcome measure was a domain of the Modified Tardieu Scale, the dynamic component of spasticity (spasticity angle).

Results: In general, there was a significant difference between forearm positions regarding spasticity angle (p?<?.001). In pairwise comparisons, median spasticity angles in pronation (70 degrees) and neutral position (60 degrees) were significantly higher than those in supination (57.5 degrees) (adjusted p?<?.001 and adjusted p?=?.003, respectively). However, median spasticity angle in pronation did not differ significantly from those in neutral position in favour of pronation (adjusted p?=?.274).

Conclusions: The severity of spasticity changes according to the elbow position which suggests that the magnitude of contribution of each elbow flexor muscle to spastic elbow deformity is different. Reduction of spasticity from pronation to supination leads us to consider brachialis as the most spastic muscle. Since biceps was suggested to be the least spastic muscle in this study, and also to avoid spastic pronation deformity of the forearm, it should be rethought before performing chemodenervation into biceps muscle.     

Quantitative assessment of the accuracy for three interpolation techniques in kinematic analysis of human movement

Marker obstruction during human movement analyses requires interpolation to reconstruct missing kinematic data. This investigation quantifies errors associated with three interpolation techniques and varying interpolated durations. Right ulnar styloid kinematics from 13 participants performing manual wheelchair ramp ascent were reconstructed using linear, cubic spline and local coordinate system (LCS) interpolation from 11-90% of one propulsive cycle. Elbow angles (flexion/extension and pronation/supination) were calculated using real and reconstructed kinematics. Reconstructed kinematics produced maximum elbow flexion/extension errors of 37.1 (linear), 23.4 (spline) and 9.3 (LCS) degrees. Reconstruction errors are unavoidable [minimum errors of 6.7?mm (LCS); 0.29?mm (spline); 0.42?mm (linear)], emphasising careful motion capture system setup must be performed to minimise data interpolation. For the observed movement, LCS-based interpolation (average error of 14.3?mm; correlation of 0.976 for elbow flexion/extension) was most suitable for reconstructing durations longer than 200?ms. Spline interpolation was superior for shorter durations.     

Quantitative assessment of the accuracy for three interpolation techniques in kinematic analysis of human movement

Marker obstruction during human movement analyses requires interpolation to reconstruct missing kinematic data. This investigation quantifies errors associated with three interpolation techniques and varying interpolated durations. Right ulnar styloid kinematics from 13 participants performing manual wheelchair ramp ascent were reconstructed using linear, cubic spline and local coordinate system (LCS) interpolation from 11–90% of one propulsive cycle. Elbow angles (flexion/extension and pronation/supination) were calculated using real and reconstructed kinematics. Reconstructed kinematics produced maximum elbow flexion/extension errors of 37.1 (linear), 23.4 (spline) and 9.3 (LCS) degrees. Reconstruction errors are unavoidable [minimum errors of 6.7 mm (LCS); 0.29 mm (spline); 0.42 mm (linear)], emphasising careful motion capture system setup must be performed to minimise data interpolation. For the observed movement, LCS-based interpolation (average error of 14.3 mm; correlation of 0.976 for elbow flexion/extension) was most suitable for reconstructing durations longer than 200 ms. Spline interpolation was superior for shorter durations.     

Muscle moment arm and normalized moment contributions as reference data for musculoskeletal elbow and wrist joint models

A geometric musculoskeletal model of the elbow and wrist joints was developed to calculate muscle moment arms throughout elbow flexion/extension, forearm pronation/supination, wrist flexion/extension and radial/ulnar deviation. Model moment arms were verified with data from cadaver specimen studies and geometric models available in the literature. Coefficients of polynomial equations were calculated for all moment arms as functions of joint angle, with special consideration to coupled muscles as a function of two joint angles. Additionally, a “normalized potential moment (NPM)” contribution index for each muscle across the elbow and wrist joints in four degrees-of-freedom was determined using each muscle's normalized physiological cross-sectional area (PCSA) and peak moment arm (MA). We hypothesize that (a) a geometric model of the elbow and wrist joints can represent the major attributes of MA versus joint angle from many literature sources of cadaver and model data and (b) an index can represent each muscle's normalized moment contribution to each degree-of-freedom at the elbow and wrist. We believe these data serve as a simple, yet comprehensive, reference for how the primary 16 muscles across the elbow and wrist contribute to joint moment and overall joint performance.     

An Investigation of the Locomotor Function of Therian Forearm Pronation Provides Renewed Support for an Arboreal,Chameleon-like Evolutionary Stage

Although investigations of forelimb characteristics are central to therian evolutionary studies, the functional origins of forearm pronation are neglected. However, recent research based on bipedal manipulations strongly suggests that proximal radioulnar joint mobility is highly conserved in tetrapods. This new information calls for a replication of previously published physical simulations of forearm bone movements, to investigate whether active therian pronation/supination evolved from the plesiomorphic mechanism via which locomotor-induced torsion is passively alleviated during forelimb retraction. Preliminary results using representative extant and extinct tetrapod forelimb elements are supportive, and also offer insight into why another overlooked forearm trait, osteological full pronation (mechanically aligned elbow and wrist/finger joints), evolved only in therians and chameleons. During forelimb retraction in tetrapods with unfused radii/ulnae, the radius unexpectedly remains fixed in place as a functional complex with the firmly planted manus/carpus, which the ulnar complex (ulna/humerus) displaces relative to. Therefore, the highly conserved functional morphology of the tetrapod forearm indicates that enhanced therian manual dexterity, which emphasizes isolated radial movements bipedally, was preceded by the locomotor evolution of ulnar supination relative to the radius quadrupedally. This counterintuitive information indicates that the traditional hypothesis, that therian pronation/supination evolved arboreally to amplify radial mobility, requires modification. The authors propose that proximal long-axis rotations of the therian ulnar complex co-evolved with osteological full pronation during a period of arboreal, chameleon-like locomotion, to continue allowing torsion at a reinforced proximal radioulnar joint. These adaptations were later or simultaneously co-opted for object manipulation using active radioulnar pronation/supination.     

A method for in-vivo kinematic analysis of the forearm

PURPOSE: To develop a method for in-vivo kinematic study of normal forearm rotation using computed tomographic (CT) images and a custom apparatus which allows for control of amount of forearm rotation. METHODS: The forearm of one asymptomatic volunteer was CT-scanned in five positions: neutral, 60 degrees pronation, maximal pronation, 60 degrees supination, and maximal supination. Surface registration of the pronated/supinated image datasets with the neutral position was performed. The resulting transformation matrices were decomposed into finite helical axis (FHA) parameters. Kinematics were expressed as motion of the radius relative to the ulna. RESULTS: The axes of the forearm passed through the volar region of the radial head at the proximal radioulnar joint (PRUJ), extending towards the dorsal region of the ulnar head at the distal radioulnar joint (DRUJ). Distinct FHAs were calculated for each forearm position analyzed relative to neutral rotation. Forearm pronation FHAs were different from forearm supination FHAs. CONCLUSIONS: Our experimental methodology is capable of describing the in-vivo kinematics of the forearm with good accuracy and reliability. Future in-vivo studies would need to be performed using a larger sample size to further validate our preliminary results. An ideal clinical application of this methodology would be in the comparative study of patients with forearm dysfunction.     

Contribution of the biceps brachii and pronator teres muscles to the efforts of pronation or supination. I. Statistical work (author's transl)

The electrical activity of the biceps brachii and pronator teres muscles is studied through the prono-supination of the forearm in some isometrical conditions (static work) with different loads and joint positions. If the pronator teres is always being active in pronation, this activity is a function of the load and of the wrist and elbow positions. The same phenomena can be observed for the biceps brachii but when in supination. From the curvilinear relationships between the integrated electrical activity and the load--observed on both muscles--some torque-angle relationships can be established for the biceps brachii which show that a bifunctional muscle seems to be characterized by a very and unique force-length relationship.     

Design and implementation of an instrumented ulnar head prosthesis to measure loads in vitro

The development of a novel instrumented implant for ulnar head replacement is presented in this study. This implant was instrumented with strain gauges to quantify bending moments about the anatomic axes of the distal ulna, and subsequently the distal radioulnar joint (DRUJ) reaction force magnitude. The implant was surgically inserted in seven cadaveric upper extremities, which were subsequently mounted in a custom joint simulator. Simulated active unresisted pronation and supination motion trials were conducted using computer-controlled pneumatic actuators to simulate forearm musculature. Passive (unloaded) trials were also conducted. The reaction force across the DRUJ ranged from 2 to 10 N in magnitude during this unresisted motion. Increased bending moment magnitudes were measured when the forearm was positioned in supination compared to pronation. The magnitude of joint bending moments showed a consistent pattern with forearm position, regardless of simulated active or passive rotation, or supination and pronation motion trials. This result illustrates that the primary influence on joint load is likely the position and contact with the radial articulation. This study of DRUJ loading should be useful for biomechanical modeling, implant design considerations and improved knowledge of articular mechanics.     

Feasibility of using combined EMG and kinematic signals for prosthesis control: A simulation study using a virtual reality environment

Transhumeral amputation has a significant effect on a person’s independence and quality of life. Myoelectric prostheses have the potential to restore upper limb function, however their use is currently limited due to lack of intuitive and natural control of multiple degrees of freedom. The goal of this study was to evaluate a novel transhumeral prosthesis controller that uses a combination of kinematic and electromyographic (EMG) signals recorded from the person’s proximal humerus. Specifically, we trained a time-delayed artificial neural network to predict elbow flexion/extension and forearm pronation/supination from six proximal EMG signals, and humeral angular velocity and linear acceleration. We evaluated this scheme with ten able-bodied subjects offline, as well as in a target-reaching task presented in an immersive virtual reality environment. The offline training had a target of 4° for flexion/extension and 8° for pronation/supination, which it easily exceeded (2.7° and 5.5° respectively). During online testing, all subjects completed the target-reaching task with path efficiency of 78% and minimal overshoot (1.5%). Thus, combining kinematic and muscle activity signals from the proximal humerus can provide adequate prosthesis control, and testing in a virtual reality environment can provide meaningful data on controller performance.     

Sarcomere length varies with wrist ulnar deviation but not forearm pronation in the extensor carpi radialis brevis muscle

Extensor carpi radialis brevis (ECRB) sarcomere length was measured in seven patients using intraoperative laser diffraction. Sarcomere length was measured with the forearm in one of four positions: wrist in neutral with regard to radial-ulnar deviation and forearm in neutral rotation, wrist in ulnar deviation and forearm in neutral rotation, wrist in neutral and forearm in pronation, and wrist in ulnar deviation and forearm in pronation. Two-way ANOVA comparing sarcomere length between the four positions revealed a significant effect of ulnar deviation (p < 0.05), no significant effect of pronation (p > 0.7) and no significant interaction (p > 0.9). These results demonstrate that the axes of forearm rotation and wrist radial-ulnar deviation act independently, at least with regard to the ECRB and have implications regarding the etiology of tennis elbow.     

Accuracy of biplane videoradiography for quantifying dynamic wrist kinematics

Accurately assessing the dynamic kinematics of the skeletal wrist could advance our understanding of the normal and pathological wrist. Biplane videoradiography (BVR) has allowed investigators to study dynamic activities in the knee, hip, and shoulder joint; however, currently, BVR has not been utilized for the wrist joint because of the challenges associated with imaging multiple overlapping bones. Therefore, our aim was to develop a BVR procedure and to quantify its accuracy for evaluation of wrist kinematics. BVR was performed on six cadaveric forearms for one neutral static and six dynamic tasks, including flexion-extension, radial-ulnar deviation, circumduction, pronation, supination, and hammering. Optical motion capture (OMC) served as the gold standard for assessing accuracy. We propose a feedforward tracking methodology, which uses a combined model of metacarpals (second and third) for initialization of the third metacarpal (MC3). BVR-calculated kinematic parameters were found to be consistent with the OMC-calculated parameters, and the BVR/OMC agreement had submillimeter and sub-degree biases in tracking individual bones as well as the overall joint’s rotation and translation. All dynamic tasks (except pronation task) showed a limit of agreement within 1.5° for overall rotation, and within 1.3 mm for overall translations. Pronation task had a 2.1° and 1.4 mm limit of agreement for rotation and translation measurement. The poorest precision was achieved in calculating the pronation-supination angle, and radial-ulnar and volar-dorsal translational components, although they were sub-degree and submillimeter. The methodology described herein may assist those interested in examining the complexities of skeletal wrist function during dynamic tasks.     

Crosstalk in surface electromyography of the proximal forearm during gripping tasks.

Electromyographic (EMG) crosstalk was systematically analyzed to evaluate the magnitude of common signal present between electrode pairs around the forearm. Surface EMG was recorded and analyzed from seven electrode pairs placed circumferentially around the proximal forearm in six healthy individuals. The cross-correlation function was used to determine the amount of common signal, which was found to decrease as the distance between electrode pairs increased, but was not significantly altered by forearm posture (pronation, neutral, supination). Overall, approximately 40% common signal was detected between adjacent electrode pairs (3 cm apart), dropping to about 10% at 6 cm spacing and 2.5% at 9 cm. The magnitude of common signal approached 50% between adjacent electrode pairs over the extensor muscles, while over 60% was observed between neighbouring sites on the flexor aspect of the forearm. Although flexor and extensor EMG amplitude was similar, less than 2% common signal was present between flexor and extensor electrode pairs during both pinch and grasp tasks. Maximum grip force production was not affected by forearm rotation for pinch, but reduced 18% from neutral (mid-prone) to pronation during grasp (p=0.01). In spite of differences in grip force, mean muscle activity did not vary between the three forearm postures during maximum pinch or grasp trials. While this study improved our knowledge of crosstalk and electrode spacing issues, further examination of forearm EMG is required to improve understanding of muscle loading, EMG properties and motor control during gripping tasks.     

Ambulatory measurement of 3D knee joint angle

Three-dimensional measurement of joint motion is a promising tool for clinical evaluation and therapeutic treatment comparisons. Although many devices exist for joints kinematics assessment, there is a need for a system that could be used in routine practice. Such a system should be accurate, ambulatory, and easy to use. The combination of gyroscopes and accelerometers (i.e., inertial measurement unit) has proven to be suitable for unrestrained measurement of orientation during a short period of time (i.e., few minutes). However, due to their inability to detect horizontal reference, inertial-based systems generally fail to measure differential orientation, a prerequisite for computing the three-dimentional knee joint angle recommended by the Internal Society of Biomechanics (ISB). A simple method based on a leg movement is proposed here to align two inertial measurement units fixed on the thigh and shank segments. Based on the combination of the former alignment and a fusion algorithm, the three-dimensional knee joint angle is measured and compared with a magnetic motion capture system during walking. The proposed system is suitable to measure the absolute knee flexion/extension and abduction/adduction angles with mean (SD) offset errors of -1 degree (1 degree ) and 0 degrees (0.6 degrees ) and mean (SD) root mean square (RMS) errors of 1.5 degrees (0.4 degrees ) and 1.7 degrees (0.5 degrees ). The system is also suitable for the relative measurement of knee internal/external rotation (mean (SD) offset error of 3.4 degrees (2.7 degrees )) with a mean (SD) RMS error of 1.6 degrees (0.5 degrees ). The method described in this paper can be easily adapted in order to measure other joint angular displacements such as elbow or ankle.