Role of Active Range of Motion in Hand and Wrist Joint Photography: A Preliminary Analysis.

INTRODUCTION: Hand photography is effective and advantageous for assessing functional deficits and improvements related to surgery. In this study, it is aimed to investigate whether the correct active range of motion (ROM) is masked by the passive ROM in a wrist joint. METHOD: Eleven patients who were treated for unilateral wrist fractures were included in the study. Photography was performed in all patients by the same surgeon according to the conventional hand surgery photography approach and the active ROM photography approach. Differences between the noninjured side and injured side were assessed. RESULTS: No differences were found between the active ROM and passive ROM during the extension and flexion movements in the noninjured side group. However, in the injured side group, the results from the photographs obtained with the conventional method were significantly better than the results from the photographs obtained when the wrist was actively moved. CONCLUSION: These findings suggest that photographs of wrists during passive motion may affect the results of a treatment or study by showing false positivity. We propose obtaining images of active ROM instead of passive ROM in hand photography.

Accuracy and Validity of Goniometer and Visual Assessments of Angular Joint Positions of the Hand and Wrist.

PURPOSE: To compare goniometric and visual assessments of angular hand joint and wrist joint positions measured by board-certified hand surgeons and certified hand therapists. We hypothesized that visual estimation would be similar to the goniometric measurement accuracy of digital and wrist joint positions. METHODS: The wrist, index finger metacarpophalangeal (MCP) joint, and index finger proximal interphalangeal (PIP) joint were evaluated in different positions by 40 observers: 20 board-certified hand surgeons and 20 certified hand therapists. Each observer estimated the position of the wrist, index MCP joint, and index PIP joint of the same volunteer, who was positioned in low-profile orthoses to reproduce predetermined positions. Following visual estimation, the participants measured the same joint positions using a goniometer. The control measurement was digitally determined by a radiologist who obtained radiographs of the hand and wrist positions in each orthosis. Observers were blinded to the results of control measurements. RESULTS: When considering all joints at all positions, neither visual assessments nor goniometer assessments were consistently within ± 5° of the measurements obtained on control radiographs. When considering individual joints, goniometer measurements were significantly closer to control radiograph measurements than the visual assessments for all 3 PIP joint positions. There was no difference for the measurements at the wrist or for 2 of the 3 MCP joint positions. Significant differences between surgeon and therapist joint angle measurements were not observed when comparing visual and goniometer assessments to radiograph controls. CONCLUSIONS: Compared with radiograph measurements, neither visual nor goniometer assessment displayed high levels of accuracy. On average, visual assessment of the angular positions of the index MCP and wrist joint were as accurate as the goniometer assessment, whereas goniometer assessment of the angular position of the PIP joint was more accurate than visual assessment. There was a relatively high degree of between-observer variability in measurements, and therefore, no one person's measurements could be consistently relied upon to be accurate. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic II.

Joint angles and angular velocities and relevance of eigenvectors during prehension in the monkey.

Hand shaping during prehension involves intricate coordination of a complex system of bones, joints, and muscles. It is widely hypothesized that the motor system uses strategies to reduce the degrees of independent control. Both biomechanical constraints that result in coupling of the fingers and joints and neural synergies act to simplify the control problem. Synergies in hand shaping are typically defined using principal component-like analyses to define orthogonal patterns of movement. Although much less examined, joint angle velocities are also important parameters governing prehension. The primary goal of this study was to evaluate joint angles and joint angle velocities during prehension in monkeys. Fourteen joint angles and angular velocities were measured as monkeys reached to and grasped a set of objects designed to systematically vary hand shapes. Hand shaping patterns in joint angles and velocities were examined using singular value decomposition (SVD). Highly correlated patterns of movements were observed in both joint angles and joint angle velocities, but there was little correlation between the two, suggesting that velocities are controlled separately. Joint angles and velocities can be defined by a small number of eigenvectors by SVD. The unresolved question of the functional relevance of higher-order eigenvectors was also evaluated. Results support that higher-order components are not easily distinguished from noise and are likely not of physiological significance.

Upper limb joint kinetics of three sitting pivot wheelchair transfer techniques in individuals with spinal cord injury.

STUDY DESIGN: Repeated measures design. OBJECTIVE: This study compared the upper extremity (UE) joint kinetics between three transfer techniques. SETTING: Research laboratory. METHODS: Twenty individuals with spinal cord injury performed three transfer techniques from their wheelchair to a level tub bench. Two of the techniques involved a head-hips method with leading hand position close (HH-I) and far (HH-A) from the body, and the third technique with the trunk upright (TU) and hand far from body. Motion analysis equipment recorded upper body movements and force sensors recorded their hand and feet reaction forces during the transfers. RESULTS: Several significant differences were found between HH-A and HH-I and TU and HH-I transfers indicating that hand placement was a key factor influencing the UE joint kinetics. Peak resultant hand, elbow, and shoulder joint forces were significantly higher for the HH-A and TU techniques at the trailing arm (P < 0.036) and lower at the leading arm (P < 0.021), compared to the HH-I technique. CONCLUSION: Always trailing with the same arm if using HH-A or TU could predispose that arm to overuse related pain and injuries. Technique training should focus on initial hand placement close to the body followed by the amount of trunk flexion needed to facilitate movement.

Change of a motor synergy for dampening hand vibration depending on a task difficulty.

The present study investigated the relationship between the number of usable degrees of freedom (DOFs) and joint coordination during a human-dampening hand vibration task. Participants stood on a platform generating an anterior-posterior directional oscillation and held a water-filled cup. Their usable DOFs were changed under the following conditions of limb constraint: (1) no constraint; (2) ankle constrained; and (3) ankle-knee constrained. Kinematic whole-body data were recorded using a three-dimensional position measurement system. The jerk of each body part was evaluated as an index of oscillation intensity. To quantify joint coordination, an uncontrolled manifold (UCM) analysis was applied and the variance of joints related to hand jerk divided into two components: a UCM component that did not affect hand jerk and an orthogonal (ORT) component that directly affected hand jerk. The results showed that hand jerk when the task used a cup filled with water was significantly smaller than when a cup containing stones was used, regardless of limb constraint condition. Thus, participants dampened their hand vibration utilizing usable joint DOFs. According to UCM analysis, increasing the oscillation velocity and the decrease in usable DOFs by the limb constraints led to an increase of total variance of the joints and the UCM component, indicating that a synergy-dampening hand vibration was enhanced. These results show that the variance of usable joint DOFs is more fitted to the UCM subspace when the joints are varied by increasing the velocity and limb constraints and suggest that humans adopt enhanced synergies to achieve more difficult tasks.

A biomechanical and evolutionary perspective on the function of the lumbrical muscle.

The lumbrical muscles of the hand originate from the flexor digitorum profundus tendons and insert onto the lateral band of the extensor tendons. Owing to these movable attachments, the function of this muscle is difficult to visualize. To better determine the function of this muscle, we considered its relative anatomy, biomechanical characteristics, and evolution. With the smallest physiological cross-sectional area in the upper extremity, the lumbrical muscles have weak motor function, which is only 1/10 of the interosseous muscle. Because they are spindle rich, the lumbrical muscles play an important role in the sensory feedback of the distal interphalangeal, proximal interphalangeal, and metacarpophalangeal joints of the fingers. The first 2 lumbrical muscles have lower variation in anatomy and higher density of muscle spindles compared to the ulnar 2 lumbricals. In addition, the index and middle finger lumbrical muscles are innervated by the median nerve, which also innervates the thenar muscles of the thumb. Therefore, it is possible that the first 2 lumbricals are functionally more important than the 2 ulnar lumbricals, specifically for precision pinch movements.

A multi-level approach to investigate the control of an input device: application to a realistic pointing task.

This study investigates the subjects' performance during realistic conditions of control of a joystick. An adapted reciprocal aiming task consisting in driving a virtual vehicle along a slalom course as fast as possible was performed while accuracy constraints were manipulated. Realistic dynamical Interface Screen Relationship between the joystick displacements and the displacements of the vehicle was simulated. Vehicle displacements and motor activity (muscle activity and joint kinematics) were recorded. The results highlighted the applicability of the Fitts' law to more realistic conditions where the use of an input device is performed in an intensive control situation. Besides, biomechanical results suggested that neuromuscular responses were different regarding the direction of movement, whereas the performance at a behavioural level were not affected. Thus, this study demonstrates the interest in considering two different aspects of the user's performance (behavioural and biomechanical ones) to make a better agreement between the device design and users' needs. PRACTITIONER SUMMARY: This study considered two different aspects of the subject's performance in a realistic situation of speed­accuracy trade-off: the behavioural and motor activity. The necessity for the design of the future ergonomics pointing devices to meet the expectations of the neuromuscular system in order to facilitate their uses is highlighted.

Range of motion measurements in hand surgery: should they be used for assessing outcomes?

PURPOSE: The purpose of the study was to assess how context influences range of motion measurements in hand surgery. METHODS: One hundred seventy-five consecutive patients presenting to a hand surgery clinic were evaluated over 7 sessions. Passive and active motion were measured with a goniometer and by visual estimation. The affected joint was measured by 3 different examiners-one hand surgeon and 2 research assistants (RAs). Measurements by the RAs were performed under the pretense of imaginary project titles and purposes. RESULTS: Range of motion measurements were easily influenced. As the invented project's purpose became more specific and dependent on physician intervention, the bias became more pronounced. Measurements performed under construed project titles that promoted surgical intervention garnered outcomes that supported surgery (P < 0.01). Conversely, when the manufactured study's intent was to find support in conservative treatment, this outcome could also be generated (P < 0.01). DISCUSSION: Range of motion measurements can easily be influenced by the context of the study, even in seemingly blinded examiners. Reliable range of motion measurements can only be made when the examiner has no knowledge of the study's intent.

The natural angle between the hand and handle and the effect of handle orientation on wrist radial/ulnar deviation during maximal push exertions.

The purpose of this experiment was to quantify the natural angle between the hand and a handle, and to investigate three design factors: handle rotation, handle tilt and between-handle width on the natural angle as well as resultant wrist radial/ulnar deviation ('RUD') for pushing tasks. Photographs taken of the right upper limb of 31 participants (14 women and 17 men) performing maximal seated push exertions on different handles were analysed. Natural hand/handle angle and RUD were assessed. It was found that all of the three design factors significantly affected natural handle angle and wrist RUD, but participant gender did not. The natural angle between the hand and the cylindrical handle was 65 ± 7°. Wrist deviation was reduced for handles that were rotated 0° (horizontal) and at the narrow width (31 cm). Handles that were tilted forward 15° reduced radial deviation consistently (12-13°) across handle conditions. PRACTITIONER SUMMARY: Manual materials handling (MMH) tasks involving pushing have been related to increased risk of musculoskeletal injury. This study shows that handle orientation influences hand and wrist posture during pushing, and suggests that the design of push handles on carts and other MMH aids can be improved by adjusting their orientation to fit the natural interface between the hand and handle.

Associations between MRI-defined synovitis, bone marrow lesions and structural features and measures of pain and physical function in hand osteoarthritis.

OBJECTIVES: To explore associations between MRI features and measures of pain and physical function in hand osteoarthritis (OA). METHODS: Eighty-five patients (77 women) with mean (SD) age of 68.8 (5.6) years underwent contrast-enhanced MRI of the interphalangeal joints (dominant hand) and clinical joint assessment. One investigator read the MRIs for presence/severity of osteophytes, joint space narrowing, erosions, bone attrition, cysts, malalignment, synovitis, flexor tenosynovitis, bone marrow lesions (BMLs) and ligament discontinuity according to the proposed Oslo hand OA MRI score. Pain and physical function were assessed by joint palpation (tenderness yes/no), self-reported questionnaires (Australian/Canadian (AUSCAN) hand index, Functional Index of hand osteoarthritis (FIHOA), Arthritis Impact Measurement Scale-2 (AIMS-2) hand/finger) and grip strength. Logistic regression with generalised estimating equations was used to explore associations between the presence of MRI features and joint tenderness, and linear regression for associations between the burden of MRI abnormalities and patient-reported outcomes and grip strength (adjusted for age and sex). MRI features with p<0.25 were introduced into a multivariate model. The final model included features with p≤0.10 (backward selection). RESULTS: MRI-defined moderate/severe synovitis (OR=2.4; p<0.001), BMLs (OR=1.5; p=0.06), erosions (OR=1.4; p=0.05), attrition (OR=2.5; p<0.001) and osteophytes (OR=1.4; p=0.10) were associated with joint tenderness independently of each other (final model adjusted for age and sex). The sum score of MRI-defined attrition was associated with FIHOA (B=0.58; p=0.005), while the sum score of osteophytes was associated with grip strength (B=-0.39; p<0.001). No significant associations were found with AUSCAN pain/physical function or AIMS-2 hand/finger subscales. CONCLUSION: MRI-defined synovitis, BMLs, erosions and attrition were associated with joint tenderness. Synovitis and BMLs may be targets for therapeutic interventions in hand OA.

Evaluation of the effect of balneotherapy in patients with osteoarthritis of the hands: a randomized controlled single-blind follow-up study.

OBJECTIVE: To evaluate the effectiveness of thermal mineral water compared with magnetotherapy without balneotherapy as control, in the treatment of hand osteoarthritis. DESIGN: Randomized controlled single-blind follow-up study. SETTING: Rheumatology specialist clinic of Gunaras Health Spa. SUBJECTS: Patients between 50 and 70 years of age with hand osteoarthritis, randomly assigned into three groups. INTERVENTIONS: The subjects in the first two groups bathed in thermal mineral water of two different temperatures (36°C and 38°C) for three weeks five times a week for 20 minutes a day and received magnetotherapy to their hands three times weekly. The third group received only magnetotherapy. OUTCOME MEASURES: Visual analogue scale scores, handgrip strength, pinchgrip strength, the number of swollen and tender joints of the hand, the duration of morning joint stiffness, Health Assessment Questionnaire, and Short Form-36 questionnaire. The study parameters were administered at baseline, immediately after treatment and after 13 weeks. RESULTS: The study included 63 patients. Statistically significant improvement was observed in several studied parameters after the treatment and during the follow-up study in the thermal water groups versus the control group. The 38°C thermal water treatment significantly improved the pinch strength of the right hand (0.6 (95% confidence interval (CI) 0.2 to 1.1) vs. 0.03 (95% CI -0.3 to 0.4), P < 0.05) and the Health Assessment Questionnaire parameters (-0.4 (95% CI -0.6 to -0.2) vs. -0.1 (95% CI -0.2 to 0.1), P < 0.01) even in the long term. CONCLUSIONS: Balneotherapy combined with magnetotherapy improved the pain and function as well as the quality of life in patients with hand osteoarthritis.

Force synchrony enhances the stability of rhythmic multi-joint arm coordination.

Although rhythmic coordination has been extensively studied in the literature, questions remain about the correspondence of constraints that have been identified in the related contexts of inter-limb and intra-limb coordination. Here we used a 2-DOF robot arm which allows flexible manipulation of forces to investigate the effect on coordination stability of intra-limb coordination of: (i) the synchrony of force requirements and (ii) the involvement of bi-functional muscles. Ten subjects produced simultaneous rhythmic flexion-extension (FE) and supination-pronation (SP) elbow movements in two coordination patterns: (1) flexion synchronized with supination/extension with pronation (in-phase pattern) and (2) flexion synchronized with pronation/extension with supination (anti-phase pattern). The movements were produced with five different settings of the robot arm: a neutral setting that imposed balanced force requirements, and four other settings that increased the force requirements for one direction in both DOF. When combined with specific coordination patterns, these settings created conditions in which either synchronous or alternate patterns of forcing were necessary to perform the task. Results showed that synchronous tasks were more stable than asynchronous tasks (P < 0.05). Within the synchronous tasks, some robot settings were designed to either increase or decrease the use of bi-functional muscles. Although there was no difference for the bi-functional muscle biceps brachii, the coordination was more stable for the condition in which the greatest force requirements corresponded to the mechanical action of the bi-functional pronator teres (P < 0.05). In conclusion, force synchrony increases the stability of rhythmic intra-limb coordination, but further research is needed to clarify the role of bi-functional muscles in this effect.

Gaze facilitates responsivity during hand coordinated joint attention.

The coordination of attention between individuals is a fundamental part of everyday human social interaction. Previous work has focused on the role of gaze information for guiding responses during joint attention episodes. However, in many contexts, hand gestures such as pointing provide another valuable source of information about the locus of attention. The current study developed a novel virtual reality paradigm to investigate the extent to which initiator gaze information is used by responders to guide joint attention responses in the presence of more visually salient and spatially precise pointing gestures. Dyads were instructed to use pointing gestures to complete a cooperative joint attention task in a virtual environment. Eye and hand tracking enabled real-time interaction and provided objective measures of gaze and pointing behaviours. Initiators displayed gaze behaviours that were spatially congruent with the subsequent pointing gestures. Responders overtly attended to the initiator's gaze during the joint attention episode. However, both these initiator and responder behaviours were highly variable across individuals. Critically, when responders did overtly attend to their partner's face, their saccadic reaction times were faster when the initiator's gaze was also congruent with the pointing gesture, and thus predictive of the joint attention location. These results indicate that humans attend to and process gaze information to facilitate joint attention responsivity, even in contexts where gaze information is implicit to the task and joint attention is explicitly cued by more spatially precise and visually salient pointing gestures.

Integrated linkage-driven dexterous anthropomorphic robotic hand.

Robotic hands perform several amazing functions similar to the human hands, thereby offering high flexibility in terms of the tasks performed. However, developing integrated hands without additional actuation parts while maintaining important functions such as human-level dexterity and grasping force is challenging. The actuation parts make it difficult to integrate these hands into existing robotic arms, thus limiting their applicability. Based on a linkage-driven mechanism, an integrated linkage-driven dexterous anthropomorphic robotic hand called ILDA hand, which integrates all the components required for actuation and sensing and possesses high dexterity, is developed. It has the following features: 15-degree-of-freedom (20 joints), a fingertip force of 34N, compact size (maximum length: 218 mm) without additional parts, low weight of 1.1 kg, and tactile sensing capabilities. Actual manipulation tasks involving tools used in everyday life are performed with the hand mounted on a commercial robot arm.

Comparative 3D quantitative analyses of trapeziometacarpal joint surface curvatures among living catarrhines and fossil hominins.

Comparisons of joint surface curvature at the base of the thumb have long been made to discern differences among living and fossil primates in functional capabilities of the hand. However, the complex shape of this joint makes it difficult to quantify differences among taxa. The purpose of this study is to determine whether significant differences in curvature exist among selected catarrhine genera and to compare these genera with hominin fossils in trapeziometacarpal curvature. Two 3D approaches are used to quantify curvatures of the trapezial and metacarpal joint surfaces: (1) stereophotogrammetry with nonuniform rational B-spline (NURBS) calculation of joint curvature to compare modern humans with captive chimpanzees and (2) laser scanning with a quadric-based calculation of curvature to compare modern humans and wild-caught Pan, Gorilla, Pongo, and Papio. Both approaches show that Homo has significantly lower curvature of the joint surfaces than does Pan. The second approach shows that Gorilla has significantly more curvature than modern humans, while Pongo overlaps with humans and African apes. The surfaces in Papio are more cylindrical and flatter than in Homo. Australopithecus afarensis resembles African apes more than modern humans in curvatures, whereas the Homo habilis trapezial metacarpal surface is flatter than in all genera except Papio. Neandertals fall at one end of the modern human range of variation, with smaller dorsovolar curvature. Modern human topography appears to be derived relative to great apes and Australopithecus and contributes to the distinctive human morphology that facilitates forceful precision and power gripping, fundamental to human manipulative activities.

Reliability of quantitative ultrasound measurement of flexor digitorum superficialis and profundus muscles in stroke.

Aim: This study aims to investigate reliability of quantitative ultrasound measurement of the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) muscles in stroke. Materials & methods: Patients with a history of stroke were recruited. FDP and FDS muscles on both upper extremities were investigated with ultrasound. Two independent assessors acquired images and analyzed them using a program and Heckmatt scale. Results: Forty-eight patients were included. The inter-rater intraclass correlation coefficient for echo intensities was calculated as 0.91 while intrarater intraclass correlation coefficient as 0.80. For Heckmatt scale, the inter-rater reliability for FDS was Kw = 0.74 (p < 0.0005) and for FDP it was Kw = 0.73 (p < 0.0005). Mean echo intensity values showed significant strong correlations with Heckmatt scores (r = 0.663 and r = 0.633 with both p values <0.001). Conclusion: Quantitative ultrasound imaging of FDS and FDP is a reliable method to demonstrate echo intensity changes of muscles in stroke.

Manual digital pressures during knuckle-walking in chimpanzees (Pan troglodytes).

Considerable attention has been given to hand morphology and function associated with knuckle-walking in the African apes because of the implications they have for the evolution of bipedalism in early hominins. Knuckle-walking is associated with a unique suite of musculoskeletal features of the wrist and hand, and numerous studies have hypothesized that these anatomical features are associated with the dynamics of load distribution across the digits during knuckle-walking. We collected dynamic digital pressures on two chimpanzees during terrestrial and simulated arboreal locomotion. Comparisons were made across substrates, limb positions, hand positions, and age categories. Peak digital pressures were similar on the pole and on the ground but were distributed differently across the digits on each substrate. In young animals, pressure was equally high on digits 2-4 on the ground but higher on digits 3 and 4 on the pole. Older animals experience higher pressures on digits 2 and 3 on the ground. Hand posture (palm-in vs. palm-back) influenced the distribution and timing of peak pressures. Age-related increases in body mass also result in higher overall pressures and increased variation across the digital row. In chimpanzees, digit 5 typically bears relatively little load regardless of hand position or substrate. These are the first quantitative data on digital pressures during knuckle-walking in hominoids, and they afford the opportunity to develop hypotheses about variation among hominoids and biomechanical models of wrist and forearm loading.

Extensor tendon reconstruction for zones II and IV using local tendon flap: a cadaver study.

PURPOSE: To assess the feasibility of reconstructing extensor tendon segmental defects in zones II (over the middle phalanx) and IV (over the proximal phalanx) using local tendon flaps (LTFs), explore in these 2 zones the anatomical constraints that limit the use of the LTF as regards the maximum defect that could be reconstructed, and compare this flap with distant tendon grafts (DTG) reconstruction for similar size defects. METHODS: We dissected 33 fresh-frozen cadaver extensor tendons from the fingers of 9 fresh-frozen cadaver forearms. A 0.5-cm defect was created in each extensor tendon of 21 fingers: 12 in zone II and 9 in zone IV. In each of 12 additional fingers, we created a 1.0-cm defect in zone IV. In 25 fingers, LTFs measuring 0.5 and 1.0 cm in length were harvested from the extensor tendon proximal to each defect and were turned distally to reconstruct the respective 0.5- and 1.0-cm defects. In 8 fingers, palmaris longus tendon grafts measuring 0.5 and 1.0 cm in length were used to reconstruct the respective 0.5- and 1.0-cm defects. Limited kinematic analysis was performed on the repaired fingers by maximally flexing the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints in sequential fashion. RESULTS: In zone II, repair was technically feasible using LTFs in all 9 of the 0.5-cm extensor tendon defects. Likewise, LTFs were feasible for zone IV to repair 6 of 8 and all 9 of the respective 0.5- and 1.0-cm extensor tendon defects. Two failed repairs occurred early in the study by suture gapping following LTF of 0.5 cm to repair extensor tendon defects in zone IV of a long and small finger during maximal flexion. We determined the anatomical constraints for the use of the LTFs. The maximum length of repairable defect using the LTF was 0.5 cm in zone II of the index, long, ring, and small fingers, and zone IV of the small finger. In zone IV of the index, long, and ring fingers, the largest defect that could be repaired was 1.0 cm. Similarly, DTGs were feasible in zone II to repair all 4 of the 0.5-cm defects and in zone IV to repair all 4 of the 0.5- and 1.0-cm extensor tendon defects. CONCLUSIONS: In a cadaver model, both the LTF and the DTG are anatomically feasible and technically easy to perform. However, the LTF avoids a distant donor site, provides morphologically similar donor tendon that is readily accessible, and avoids morbidity that may be associated with the use of DTG. In this study, however, the LTF was limited in its use to zones II and IV of the extensor tendon.

Jerk Decomposition during Bimanual Independent Arm Cranking.

The relationship between the smoothness of the upper limb endpoint movement and multi joint angular motion is a function of the individual joint angular velocities, accelerations, and jerks as well as the instantaneous arm configuration and its rate of change during movement execution. We compared the contribution of jerk components to the total endpoint jerk in able bodied participants who performed arm cranking movements on an arm cranking device where the two arms could crank independently. The results of this investigation suggest that the most dominant components of the end effector jerk are related to both the angular jerks and to the change of arm configuration pose. This jerk partitioning is much stronger as it was found previously for both reaching arm movements and single hand cranking. This shows the task specificity of the decomposition of endpoint jerk and the effect that bi-manual tasks can have on the smoothness of movements. The proposed decomposition may give useful information in why certain bi-manual rehabilitation processes are more useful than others.

Hand Gesture Recognition and Finger Angle Estimation via Wrist-Worn Modified Barometric Pressure Sensing.

This paper presents a new approach to wearable hand gesture recognition and finger angle estimation based on the modified barometric pressure sensing. Barometric pressure sensors were encased and injected with VytaFlex rubber such that the rubber directly contacted the sensing element allowing pressure change detection when the encasing rubber was pressed. A wearable prototype consisting of an array of ten modified barometric pressure sensors around the wrist was developed and validated with experimental testing for three different hand gesture sets and finger flexion/extension trials for each of the five fingers. The overall hand gesture recognition classification accuracy was 94%. Further analysis revealed that the most important sensor location was the underside of the wrist and that when reducing the sensor number to only five optimally placed sensors, classification accuracy was still 90%. For continuous finger angle estimation, aggregate R2 values between actual and predicted angles were thumb: 0.81 ± 0.10, index finger: 0.85±0.06, middle finger: 0.77±0.08, ring finger: 0.77 ± 0.12, and pinkie finger: 0.75 ± 0.10, and the overall average was 0.79 ± 0.05. These results demonstrate that a modified barometric pressure wristband can be used to classify hand gestures and to estimate individual finger joint angles. This approach could serve to improve the clinical treatment for upper extremity deficiencies, such as for stroke rehabilitation, by providing objective patient motor control metrics to inform and aid physicians and therapists throughout the rehabilitation process.