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1.  MRI-identified abnormalities and wrist range of motion in asymptomatic versus symptomatic computer users 
Background
Previous work has shown an association between restricted wrist range of motion (ROM) and upper extremity musculoskeletal disorders in computer users. We compared the prevalence of MRI-identified wrist abnormalities and wrist ROM between asymptomatic and symptomatic computer users.
Methods
MR images at 1.5 T of both wrists were obtained from 10 asymptomatic controls (8 F, 2 M) and 14 computer users (10 F, 4 M) with chronic wrist pain (10 bilateral; 4 right-side). Maximum wrist range of motion in flexion and radioulnar deviation was measured with an electrogoniometer.
Results
Extraosseous ganglia were identified in 66.6% of asymptomatic wrists and in 75% of symptomatic wrists. Intraosseous ganglia were identified in 45.8% of asymptomatic wrists and in 75% of symptomatic wrists, and were significantly (p < .05) larger in the symptomatic wrists. Distal ECU tendon instability was identified in 58.4% of both asymptomatic and symptomatic wrists. Dominant wrist flexion was significantly greater in the asymptomatic group (68.8 ± 6.7 deg.) compared to the symptomatic group (60.7 ± 7.3 deg.), p < .01. There was no significant correlation between wrist flexion and intraosseous ganglion burden (p = .09)
Conclusions
This appears to be the first MRI study of wrist abnormalities in computer users.
This study demonstrates that a variety of wrist abnormalities are common in computer users and that only intraosseous ganglia prevalence and size differed between asymptomatic and symptomatic wrists. Flexion was restricted in the dominant wrist of the symptomatic group, but the correlation between wrist flexion and intraosseous ganglion burden did not reach significance. Flexion restriction may be an indicator of increased joint loading, and identifying the cause may help to guide preventive and therapeutic interventions.
doi:10.1186/1471-2474-11-273
PMCID: PMC2998464  PMID: 21108817
2.  Risk factors for upper-extremity musculoskeletal disorders in the working population 
Arthritis and Rheumatism  2009;61(10):1425-1434.
SUMMARY
Objective
The study aimed to assess the relative importance of personal and occupational risk factors for upper-extremity musculoskeletal disorders (UEMSDs) in the working population.
Methods
A total of 3,710 workers (58% of men) participating in a surveillance program of MSDs in a French region in 2002–2005 were included. UEMSDs were diagnosed by 83 trained occupational physicians performing a standardized physical examination. Personal factors and work exposure were assessed by a self-administered questionnaire. Statistical associations between MSDs, personal and occupational factors were analyzed using logistic regression modeling.
Results
A total of 472 workers suffered from at least one UEMSD. The risk of UEMSDs increased with age for both genders (P<0.001) (O.R. up to 4.9 in men and 5.0 and in women) and in cases of prior history of UEMSDs (OR 3.1 and 5.0, P<0.001). In men, UEMSDs were associated with obesity (OR 2.2, P=0.014), high level of physical demand (OR 2.0, P<0.001), high repetitiveness of the task (OR 1.5, P=0.027), postures with the arms at or above shoulder level (OR 1.7, P=0.009) or with full elbow flexion (OR 1.6, P=0.006), and high psychological demand (O.R. 1.5, P=0.005). In women, UEMSDs were associated with diabetes mellitus (O.R. 4.9, P=0.001), postures with extreme wrist bending (OR 2.0, P<0.001), use of vibrating hand tools (O.R. 2.2, P=0.025) and low level of decision authority (OR 1.4, P=0.042).
Conclusion
The study showed that personal and work-related physical and psychosocial factors were strongly associated with clinically-diagnosed UEMSDs.
doi:10.1002/art.24740
PMCID: PMC3189514  PMID: 19790112
Musculoskeletal disorders; upper extremity; risk factors; personal factors; physical exposure; psychosocial factors; work; Adult; Employment; Female; Humans; Male; Middle Aged; Musculoskeletal Diseases; diagnosis; epidemiology; etiology; Occupational Diseases; diagnosis; epidemiology; etiology; Risk Factors; Safety Management; Upper Extremity; pathology; physiopathology
3.  Specific and non-specific upper extremity musculoskeletal disorder syndromes in automobile manufacturing workers 
Objective
A longitudinal cohort of automobile manufacturing workers (n = 1214) was examined for: 1) prevalence and persistence of specific upper extremity musculoskeletal disorders (UEMSDs) such as lateral epicondylitis and de Quervain's disease, and non-specific disorders (NSDs) defined in symptomatic individuals without any specific disorder, and 2) disorder prognoses based on symptom characteristics and other factors.
Methods
Eight specific disorders were identified through case definitions based on upper extremity physical examinations and symptom surveys administered on three occasions over six years.
Results
At baseline, 41% of the cohort reported upper extremity symptoms; 18% (n = 214) of these had NSDs. In each survey, tendon-related conditions accounted for over half of the specific morbidity. Twenty-five percent had UEMSDs in multiple anatomical sites, and most with hand/wrist disorders had two or more hand/wrist UEMSDs. Persistence for all specific disorders decreased with length of follow-up. Specific UEMSDs were characterized by greater pain severity and functional impairment, and more lost work days than NSDs.
Conclusions
Upper extremity symptoms and diagnoses vary over time. NSDs may be the early stages of conditions that will eventually become more specific. NSDs and overlapping specific UEMSDs should be taken into account in UEMSD classification.
doi:10.1002/ajim.20653
PMCID: PMC2997818  PMID: 19016265
4.  Longitudinal, Lateral and Transverse Axes of Forearm Muscles Influence the Crosstalk in the Mechanomyographic Signals during Isometric Wrist Postures 
PLoS ONE  2014;9(8):e104280.
Problem Statement
In mechanomyography (MMG), crosstalk refers to the contamination of the signal from the muscle of interest by the signal from another muscle or muscle group that is in close proximity.
Purpose
The aim of the present study was two-fold: i) to quantify the level of crosstalk in the mechanomyographic (MMG) signals from the longitudinal (Lo), lateral (La) and transverse (Tr) axes of the extensor digitorum (ED), extensor carpi ulnaris (ECU) and flexor carpi ulnaris (FCU) muscles during isometric wrist flexion (WF) and extension (WE), radial (RD) and ulnar (UD) deviations; and ii) to analyze whether the three-directional MMG signals influence the level of crosstalk between the muscle groups during these wrist postures.
Methods
Twenty, healthy right-handed men (mean ± SD: age = 26.7±3.83 y; height = 174.47±6.3 cm; mass = 72.79±14.36 kg) participated in this study. During each wrist posture, the MMG signals propagated through the axes of the muscles were detected using three separate tri-axial accelerometers. The x-axis, y-axis, and z-axis of the sensor were placed in the Lo, La, and Tr directions with respect to muscle fibers. The peak cross-correlations were used to quantify the proportion of crosstalk between the different muscle groups.
Results
The average level of crosstalk in the MMG signals generated by the muscle groups ranged from: 34.28–69.69% for the Lo axis, 27.32–52.55% for the La axis and 11.38–25.55% for the Tr axis for all participants and their wrist postures. The Tr axes between the muscle groups showed significantly smaller crosstalk values for all wrist postures [F (2, 38) = 14–63, p<0.05, η2 = 0.416–0.769].
Significance
The results may be applied in the field of human movement research, especially for the examination of muscle mechanics during various types of the wrist postures.
doi:10.1371/journal.pone.0104280
PMCID: PMC4121292  PMID: 25090008
5.  Dissection of a Single Rat Muscle-Tendon Complex Changes Joint Moments Exerted by Neighboring Muscles: Implications for Invasive Surgical Interventions 
PLoS ONE  2013;8(8):e73510.
The aim of this paper is to investigate mechanical functioning of a single skeletal muscle, active within a group of (previously) synergistic muscles. For this purpose, we assessed wrist angle-active moment characteristics exerted by a group of wrist flexion muscles in the rat for three conditions: (i) after resection of the upper arm skin; (ii) after subsequent distal tenotomy of flexor carpi ulnaris muscle (FCU); and (iii) after subsequent freeing of FCU distal tendon and muscle belly from surrounding tissues (MT dissection). Measurements were performed for a control group and for an experimental group after recovery (5 weeks) from tendon transfer of FCU to extensor carpi radialis (ECR) insertion. To assess if FCU tenotomy and MT dissection affects FCU contributions to wrist moments exclusively or also those of neighboring wrist flexion muscles, these data were compared to wrist angle-moment characteristics of selectively activated FCU. FCU tenotomy and MT dissection decreased wrist moments of the control group at all wrist angles tested, including also angles for which no or minimal wrist moments were measured when activating FCU exclusively. For the tendon transfer group, wrist flexion moment increased after FCU tenotomy, but to a greater extent than can be expected based on wrist extension moments exerted by selectively excited transferred FCU. We conclude that dissection of a single muscle in any surgical treatment does not only affect mechanical characteristics of the target muscle, but also those of other muscles within the same compartment. Our results demonstrate also that even after agonistic-to-antagonistic tendon transfer, mechanical interactions with previously synergistic muscles do remain present.
doi:10.1371/journal.pone.0073510
PMCID: PMC3742526  PMID: 23967344
6.  Association between Upper Extremity Musculoskeletal Disorders and Psychosocial Factors at Work: A Review on the Job DCS Model's Perspective 
Safety and Health at Work  2010;1(1):37-42.
Over years it has been increasingly concerned with how upper extremity musculoskeletal disorders (UEMSDs) are attributed to psychosocial job stressors. A review study was conducted to examine associations between UEMSDs and psychosocial work factors, and to recommend what to consider for the associations. For studies in which the job demand-control-support (DCS) model or its variables were specifically employed, published papers were selected and reviewed. A number of studies have reported relationships between UEMSDs symptoms and psychosocial exposure variables. For example, the findings are: higher numbness in the upper extremity was significantly attributed to by less decision latitude at work; work demands were significantly associated with neck and shoulder symptoms while control over time was associated with neck symptoms; and the combination of high psychosocial demands and low decision latitude was a significant predictor for shoulder and neck pain in a female working population. Sources of bias, such as interaction or study design, were discussed. UEMSDs were shown to be associated with psychosocial work factors in various studies where the job DCS model was addressed. Nonetheless, this review suggests that further studies should be conducted to much more clarify the association between UEMSDs and psychosocial factors.
doi:10.5491/SHAW.2010.1.1.37
PMCID: PMC3430936  PMID: 22953161
Upper extremity musculoskeletal disorders; Psychosocial work factors; Job DCS model
7.  Do workers with self-reported symptoms have an elevated risk of developing upper extremity musculoskeletal disorders three years later? 
Objectives
Few prospective studies have evaluated outcomes of workers with self-reported symptoms of upper extremity musculoskeletal disorders (UEMSD). Our objective was to study the three-year outcomes of workers with self-reported symptoms, with or without a positive physical examination.
Methods
In 1993–1994, 598 subjects highly exposed to repetitive work filled out a Nordic-style questionnaire. They underwent a standardised physical examination at that time and again in 1996–1997 by the same occupational physician. The three-year outcomes (based on physical examination) of workers with a self-administered questionnaire positive at baseline for UEMSD, with or without a positive physical examination, were studied.
Results
The three-year incidence rate was 44.1%, with one third of these incident cases who had self-reported symptoms in 1993–1994. Workers with a positive questionnaire had a significantly higher risk of UEMSD at physical examination three year later (80.1% UEMSD cases with positive questionnaires n=354, versus 44.2% cases without positive questionnaires n=69, p<0.0001). Moreover, workers with positive questionnaires but without UEMSD diagnosed in 1993–1994 (n=177) had also a significantly higher risk of UEMSD at physical examination three years later (60.5% cases with positive questionnaires n=26, versus 38.8% cases without positive questionnaires n=52, p=0.01). Results were similar when gender and age were taken into account.
Conclusion
Workers highly exposed to repetitive movements had a high risk of developing UEMSD and should be followed closely in surveillance programmes. Workers with self-reported symptoms without UEMSD diagnosed in physical examination represented only one third of new cases three years later. However, their risk to develop UEMSD was significantly increased, compared with those without symptoms.
doi:10.1136/oem.2007.033357
PMCID: PMC2265784  PMID: 17766426
8.  Quantifying forearm and wrist joint power during unconstrained movements in healthy individuals 
Background
Wrist movement-related injuries account for a large number of repetitive motion injuries. Remarkably little, if any, empirical data exist to quantify the impact of neuromuscular disorders affecting the wrist or to validate the effectiveness of rehabilitation training programs on wrist functions. The aim of this project was to develop a biomechanical model for quantifying wrist and forearm kinetics during unconstrained movements, to assess its reliability and to determine its sensitivity.
Methods
Twenty healthy subjects with no history of upper arm and wrist pain volunteered for the experiment. To evaluate the reliability of the data, we quantified their forearm and wrist kinetics on two different days (minimum and maximum number of days between experimental sessions were 1 and 4 days respectively). To measure forearm and wrist kinetics, an apparatus was built to offer rotational inertia during forearm and wrist movements. An inertial measurement unit was located near the top of the device measuring its angular position along the frontal and sagittal planes. We used a mathematical model to infer forearm and wrist torque. Thereafter, we calculated the product of torque and angular velocity to determine forearm and wrist power.
Results
Results revealed that for 75% of the power and torque measurements the ICC was greater than 0.75 (range: 0.77 – 0.83). Torque and power measurements for adduction movements, however, were less reliable (i.e., ICC of 0.60 and 0.47, respectively) across testing sessions. The biomechanical model was robust to small measurement errors, and the power peaks between the first and second testing session were not different indicating that there was no systematic bias (i.e., motor performance improvement) between testing sessions.
Conclusions
The biomechanical model can be used to assess the effectiveness of rehabilitation programs, document the progression of athletes or conduct research-oriented testing of maximum forearm and wrist kinetic capacities. Nonetheless, caution should be taken when assessing forearm and wrist power adduction movements. Future studies should aim at defining a set of normative values, for various age groups, for forearm and wrist joint torque and power in healthy individuals.
doi:10.1186/1743-0003-11-157
PMCID: PMC4237781  PMID: 25403340
9.  Various Treatment Techniques on Signs and Symptoms of Delayed Onset Muscle Soreness 
Journal of Athletic Training  1996;31(2):145-152.
Eccentric activities are an important component of physical conditioning and everyday activities. Delayed onset muscle soreness (DOMS) can result from strenuous eccentric tasks and can be a limiting factor in motor performance for several days after exercise. An efficacious method of treatment for DOMS would enhance athletic performance and hasten the return to activities of daily living. The purpose of this study was to identify a treatment method which could assist in the recovery of DOMS. In the selection of treatment methods, emphasis was directed toward treatments that could be rendered independently by an individual, therefore making the treatment valuable to an athletic trainer in team setting. DOMS was induced in 70 untrained volunteers via 15 sets of 15 eccentric contractions of the forearm extensor muscles on a Lido isokinetic dynamometer. All subjects performed a pilot exercise bout for a minimum of 9 weeks before data collection to assure that DOMS would be produced. Data were collected on 15 dependent variables: active and passive wrist flexion and extension, forearm girth, limb volume, visual analogue pain scale, muscle soreness index, isometric strength, concentric and eccentric wrist total work, concentric and eccentric angle of peak torque. Data were collected on six occasions: pre- and post-induced DOMS, 20 minutes after treatment, and 24, 48, and 72 hours after treatment. Subjects were randomly assigned to 1 of 7 groups (6 treatment and 1 control). Treatments included a nonsteroidal anti-inflammatory drug, high velocity concentric muscle contractions on an upper extremity ergometer, ice massage, 10-minute static stretching, topical Amica montana ointment, and sublingual A. montana pellets. A 7 × 6 ANOVA with repeated measures on time was performed on the delta values of each of the 15 dependent variables. Significant main effects (p < .05) were found for all of the dependent variables on time only. There were no significant differences between treatments. Therefore, we conclude that none of the treatments were effective in abating the signs and symptoms of DOMS. In fact, the NSAID and A. montana treatments appeared to impede recovery of muscle function.
PMCID: PMC1318445  PMID: 16558388
10.  Steindler flexorplasty to restore elbow flexion in C5-C6-C7 brachial plexus palsy type 
Background
Loss of elbow flexion due to traumatic palsy of the brachial plexus represents a major functional handicap.
Then, the first goal in the treatment of the flail arm is to restore the elbow flexion by primary direct nerve surgery or secondary reconstructive surgery.
There are various methods to restore elbow flexion which are well documented in the medical literature but the most known and used is Steindler flexorplasty.
This review is intended to detail the author's experience with Steindler flexorplasty to restore elbow flexion in patients with brachial plexus palsy C5-C6-C7 where wrist extensors are paralyzed or weakened.
Methods
We conducted a retrospective follow-up study of 12 patients with absent or extremely weak elbow flexion (motor grade 2 or less), wrist/finger extensor and triceps palsy associated; who had undergone surgical reconstruction of the flail upper limb by tendon transfer (Steindler flexorplasty) and wrist arthrodesis to restore elbow flexion. The aetiology of elbow weakness was in all patients brachial plexus palsy (C5-C6-C7 deficit). Data were collected from medical records and from the information obtained during follow-up visits.
Age, sex, preoperative strength (rated on a 0 to 5 scale for the flexors of the elbow, wrist flexors, pronator and triceps), previous surgery, length of follow-up, other associated operative procedures, results and complications were recorded.
Results
The results are the follows: Eleven patients were found to have very good or good function of the transferred muscles. One patient had mild active flexion of the elbow despite the reconstructive procedure.
There were no major intraoperative complications. Two patients experienced transient, intermittent nocturnal ulnar paresthesias postoperatively. In both patients these symptoms subsided without further surgery.
Conclusion
Our study suggests that in patients with C5-C6-C7 palsy where the wrist and finger extensors are paralyzed or weaked, the flexor-pronators muscles of the forearm are strong but the triceps is not available for transfer; Steindler flexorplasty to restore elbow flexion should be complemented with wrist arthrodesis.
doi:10.1186/1749-7221-2-15
PMCID: PMC1939841  PMID: 17625015
11.  An ergonomic study of women workers in a woolen textile factory for identification of health-related problems 
The observational cross-sectional study conducted on a sample of 100 women workers who volunteered, outlines their cardio-respiratory and musculo-skeletal profile before, during and at end of work. In addition, information on their health status in general was collected in advance.
Contrary to expectation, there was no significant change in respiratory function. However, the musculo-skeletal problems were found to be abundantly present with pain in 91% of the subjects. Region-wise mapping of pain revealed that postural pain in low back was present in 47% while in neck was 19%. Scapular muscles on the right side were involved in stabilizing shoulder, which never went overhead. On the contrary, left shoulder was raised as high (>90 degrees) in spinning action, while pulling thread. This muscle work involved trapezius, deltoid and triceps action concentrically in lifting and while coming to starting position slowly, eccentrically. There was no pause since the wheel continued to spin the thread continuously, unless a worker opted to stop the work. Accordingly, left wrist and hand were in holding contraction while the right wrist and hand holding the handle were also in a fixed position with wrist in flexion with supinated forearm. Though the overall job was light as per peak HR, there was pain due to fatigue and grip strength weakened by around 10%, at the end of the day's work. In conclusion, pain and fatigue were found to be the main problems for women in the spinning section of the small-scale industry under this study. Women have to take up dual responsibility of a full-time job as well as the domestic work. It was considered that ergonomic factors such as provision of a backrest and frequent rest periods could remediate the musculo-skeletal symptoms.
doi:10.4103/0019-5278.40810
PMCID: PMC2796762  PMID: 20040992
Ergonomics; health hazards; pain; posture; women workers; woolen industry
12.  Upper limb motion analysis in children with hemiplegic cerebral palsy: proximal kinematic changes after distal botulinum toxin or surgical treatments 
Purpose
The purpose of this study is to describe the kinematic changes in children with cerebral palsy (CP) after treatments performed on the forearm, wrist or thumb, with specific attention to the changes around the trunk, shoulder and elbow kinematics.
Methods
With the use of a specific kinematic protocol, we first described the upper limb kinematics in a group of 27 hemiplegic patients during two simple daily tasks. Eight of these children were treated with botulinum toxin (Botox®, Allergan) injection or surgery and were, thereafter, evaluated with another kinematic analysis in order to compare the pre- and post-therapeutic condition. The target muscles were the pronator teres, flexor carpi radialis, flexor carpi ulnaris, flexor digitorum superficialis, flexor pollicis longus and the adductor pollicis.
Results
Significant kinematic changes were found after treatment. Patients increased forearm supination (P < 0.05) and wrist extension (P < 0.05) during both tasks. Patients also decreased trunk flexion/extension range of motion (ROM) (P < 0.05), improved elbow ROM (P < 0.05) and improved internal shoulder rotation (P < 0.05).
Conclusions
Dynamic shoulder or elbow limitations in children with mild hemiplegia involvement could be related to a compensatory movement strategy and/or co-contractions. As these proximal kinematics anomalies are improved after treatments performed at the forearm, wrist and thumb, they should not be treated first but should be reconsidered after the treatment of more distal problems.
doi:10.1007/s11832-011-0365-z
PMCID: PMC3179533  PMID: 23024728
Cerebral palsy; Upper limb; Kinematic analysis; Hemiplegia
13.  Muscle fatigue in relation to forearm pain and tenderness among professional computer users 
Background
To examine the hypothesis that forearm pain with palpation tenderness in computer users is associated with increased extensor muscle fatigue.
Methods
Eighteen persons with pain and moderate to severe palpation tenderness in the extensor muscle group of the right forearm and twenty gender and age matched referents without such complaints were enrolled from the Danish NUDATA study of neck and upper extremity disorders among technical assistants and machine technicians. Fatigue of the right forearm extensor muscles was assessed by muscle twitch forces in response to low frequency (2 Hz) percutaneous electrical stimulation. Twitch forces were measured before, immediately after and 15 minutes into recovery of an extensor isometric wrist extension for ten minutes at 15 % Maximal Voluntary Contraction (MVC).
Results
The average MVC wrist extension force and baseline stimulated twitch forces were equal in the case and the referent group. After the fatiguing contraction, a decrease in muscle average twitch force was seen in both groups, but the decrease was largest in the referent group: 27% (95% CI 17–37) versus 9% (95% CI -2 to 20). This difference in twitch force response was not explained by differences in the MVC or body mass index.
Conclusion
Computer users with forearm pain and moderate to severe palpation tenderness had diminished forearm extensor muscle fatigue response. Additional studies are necessary to determine whether this result reflects an adaptive response to exposure without any pathophysiological significance, or represents a part of a causal pathway leading to pain.
doi:10.1186/1745-6673-2-17
PMCID: PMC2245952  PMID: 18067676
14.  Functional Fatigue and Upper Extremity Sensorimotor System Acuity in Baseball Athletes 
Journal of Athletic Training  2007;42(1):90-98.
Context: The sensorimotor system controls the balance between upper extremity stability and mobility during athletic performance. Research indicates that fatigue hampers sensorimotor system function; however, few investigators have studied functional fatigue or multijoint, multiplanar measures.
Objective: To examine the effect of functional fatigue on upper extremity position reproduction in overhead throwing athletes.
Design: Single-session, repeated-measures design.
Setting: University musculoskeletal laboratory.
Patients or Other Participants: Sixteen healthy collegiate baseball players (age = 21.0 ± 1.6 years, height = 175.8 ± 10.2 cm, mass = 82.8 ± 4.3 kg).
Intervention(s): Subjects threw a baseball from a single knee with maximum velocity (every 5 seconds) and rated their level of upper extremity exertion after every 20 throws. Subjects stopped after reporting above level 14 on the Borg scale and began posttests immediately.
Main Outcome Measure(s): We measured active multijoint reproduction of 2 positions: arm cock and ball release. Dependent variables were absolute and variable error for 10 joint motions: scapulothoracic internal-external rotation, upward rotation, and posterior tilt; glenohumeral internal-external rotation, horizontal abduction-adduction, and flexion-extension; elbow pronation-supination and flexion-extension; and wrist ulnar-radial deviation and flexion-extension. We calculated acuity for each joint and the entire upper extremity using 3-dimensional variable error.
Results: Fatigue occurred after an average of 62 ± 28 throws and increased 3-dimensional variable error scores (ie, decreased acuity) of the entire upper extremity and all joints in both positions (P < .05) except for the wrist in arm cock. Fatigue increased errors (ranging from 0.6° to 2.3°) at arm cock for scapulothoracic internal-external rotation, upward rotation, and posterior tilt; glenohumeral internal-external rotation and flexion-extension; elbow flexion-extension; and wrist ulnar-radial deviation and at ball release for scapulothoracic internal-external rotation and upward rotation, glenohumeral horizontal abduction-adduction, elbow pronation-supination, and wrist ulnar-radial deviation and flexion-extension (P < .05).
Conclusions: Functional fatigue affects the acuity of the entire upper extremity, each individual joint, and multiple joint motions in overhead throwers. Clinicians should consider the deleterious effects of upper extremity fatigue when designing injury prevention and rehabilitation programs and should incorporate multijoint and multiplanar endurance exercises. Compromised neuromuscular control of the scapulohumeral relationship may hold pathologic implications for this population as well.
PMCID: PMC1896072  PMID: 17597949
proprioception; multijoint position reproduction; overhead throwing athletes
15.  Secondary Reconstructive Procedures in Obstetrical Brachial Plexus Palsy: Forearm, Wrist, and Hand Deformities 
Seminars in Plastic Surgery  2005;19(1):96-102.
ABSTRACT
Obstetrical brachial plexus paralysis (OBPP) is a complex, multifaceted disorder with potentially disabling sequalae. Although the shoulder is the most frequently affected joint, the forearm, wrist, and hand may also display diabling deformities. In sequalae involving the forearm, the most frequent deformity is supination contractures followed by pronation contractures. Treatment of OBPP has recently focused on early microsurgical repair; nonetheless, palliative surgery still plays a critical role in the overall reconstructive planning in order to diminish the sequalae of OBPP and improve function of the upper extremity. The preferred palliative surgical proceures for the forearm and hand include flexor or extensor tendon transfers, free muscle transfers, opponensplasty, and bone fusion. The most commonly restored functions are elbow flexion and extension, finger flexion and extension, and, in some cases, shoulder abduction and intrinsic substitution.
doi:10.1055/s-2005-867115
PMCID: PMC2884735
Obstetrical paralysis; supination deformity; ulnar deviation; wrist drop
16.  Comparison of Muscle Activation during Dominant Hand Wrist Flexion when Writing 
Journal of Physical Therapy Science  2014;25(12):1529-1531.
[Purpose] This study investigated the difference in muscle activation of the dominant upper extremity in right-handed and left-handed persons during writing. [Subjects] There were 36 subjects (16 left- handers/ 20 right- handers), and the study was conducted from 03/01/2012 to 30/3/2012. [Methods] Six electrodes were attached to the FCU (flexor carpi ulnaris), FCR (flexor carpi radialis), ECU (extensor carpi ulnaris), ECR (extensor carpi radialis), and both UT (upper trapezius) muscles. [Results] FCU muscle activation was 16.77±9.12% in left-handers and 10.29±4.13% (%MVIC) in right-handers. FCR muscle activation was 19.09±9.43% in left-handers and 10.64±5.03% in right-handers. In addition, the UT muscle activation on the writing hand side was 11.91±5.79% in left-handers and 1.66±1.19% in right-handers. [Conclusion] As a result of this study, it was discovered that left-handers used more wrist flexion in performance of the writing task with the dominant upper extremity than right-handers, and that the left-handers activated the wrist and shoulder muscles more than the right-handers. These results indicate a potential danger of musculoskeletal disease in left-hander.
doi:10.1589/jpts.25.1529
PMCID: PMC3885832  PMID: 24409013
Hand function; Left-hander; Muscle activation
17.  Higher Expression of Myosin Heavy Chain IIx in Wrist Flexors in Cerebral Palsy 
Background
Children with cerebral palsy (CP) use their paretic arm less than normal but have a relative overactivity of wrist flexors, causing an impairing flexed position of the wrist. Voluntary use of a muscle downregulates myosin heavy chain (MyHC) IIx, but it is unclear whether the relative overactivity of wrist flexors and extensors in children with CP affects MyHC expression compared to normal subjects.
Questions/purposes
We therefore asked whether MyHC expression composition differs in wrist flexors compared to extensors in children with CP and in controls and whether it is related to clinical findings.
Methods
We took muscle biopsies from wrist flexors and extensors during hand surgery in children with CP (n = 9) and during open reduction of forearm fractures in control children (n = 5). The expression of the MyHC I, IIa, and IIx isoforms were determined on silver-stained 6% SDS-PAGE.
Results
CP flexors showed a higher proportion of MyHC IIx (40%) than control flexors (16%) and CP extensors (20%). MyHC IIa isoform proportion was lower in CP flexors (27%) than in control flexors (46%) and in CP extensors (45%). MyHC I expression was lower in CP (36%) than in controls (46%) for wrist extensors only.
Conclusions
Both the brain injury in CP and the different demands on flexors and extensors affect the expression of MyHCs. The higher amount of MyHC IIx in CP could be caused by a decreased voluntary use of the hemiplegic arm.
Clinical Relevance
More information on the structural difference between flexors and extensors in normal and spastic muscle could improve the understanding of strain of wrist extensors and possibly the development of flexion contractures in CP.
doi:10.1007/s11999-011-2035-3
PMCID: PMC3314746  PMID: 21882064
Medicine & Public Health; Conservative Orthopedics; Orthopedics; Sports Medicine; Surgery; Surgical Orthopedics; Medicine/Public Health, general
18.  Real-Time Magnetic Resonance Imaging (MRI) during Active Wrist Motion—Initial Observations 
PLoS ONE  2013;8(12):e84004.
Background
Non-invasive imaging techniques such as magnetic resonance imaging (MRI) provide the ability to evaluate the complex anatomy of bone and soft tissues of the wrist without the use of ionizing radiation. Dynamic instability of wrist – occurring during joint motion – is a complex condition that has assumed increased importance in musculoskeletal medicine. The objective of this study was to develop an MRI protocol for evaluating the wrist during continuous active motion, to show that dynamic imaging of the wrist is realizable, and to demonstrate that the resulting anatomical images enable the measurement of metrics commonly evaluated for dynamic wrist instability.
Methods
A 3-Tesla “active-MRI” protocol was developed using a bSSFP sequence with 475 ms temporal resolution for continuous imaging of the moving wrist. Fifteen wrists of 10 asymptomatic volunteers were scanned during active supination/pronation, radial/ulnar deviation, “clenched-fist”, and volarflexion/dorsiflexion maneuvers. Two physicians evaluated distal radioulnar joint (DRUJ) congruity, extensor carpi ulnaris (ECU) tendon translation, the scapholunate (SL) interval, and the SL, radiolunate (RL) and capitolunate (CL) angles from the resulting images.
Results
The mean DRUJ subluxation ratio was 0.04 in supination, 0.10 in neutral, and 0.14 in pronation. The ECU tendon was subluxated or translated out of its groove in 3 wrists in pronation, 9 wrists in neutral, and 11 wrists in supination. The mean SL interval was 1.43 mm for neutral, ulnar deviation, radial deviation positions, and increased to 1.64 mm during the clenched-fist maneuver. Measurement of SL, RL and CL angles in neutral and dorsiflexion was also accomplished.
Conclusion
This study demonstrates the initial performance of active-MRI, which may be useful in the investigation of dynamic wrist instability in vivo.
doi:10.1371/journal.pone.0084004
PMCID: PMC3877133  PMID: 24391865
19.  Elbow Position Affects Distal Radioulnar Joint Kinematics 
The Journal of hand surgery  2009;34(7):1261-1268.
Previous in vivo and in vitro studies of forearm supination/pronation suggest that distal radioulnar joint kinematics may be affected by elbow flexion. The primary hypotheses tested by this study were that in vivo: 1) ulnar variance changes with elbow flexion and forearm rotation and 2) the arc of forearm rotation changes in relationship to elbow flexion.
Materials and Methods
Changes in radioulnar kinematics during forearm supination/pronation and elbow flexion (0–90°) were studied in five uninjured subjects using computed tomography, dual-orthogonal fluoroscopy, and three-dimensional modeling. Analysis of variance and post-hoc testing was performed.
Results
Proximal translation of the radius was greatest with the elbow flexed to 90° with the arm in mid-pronation. With the arm in mid-pronation, the translation of the radius was significantly greater at 0° versus 45° of elbow flexion (0.82 ± 0.59 mm v. 0.65 ± 0.80 mm, F: 4.49, Post Hoc: 0.055; p = 0.05), and significantly smaller at 45° versus 90° of elbow flexion (0.65 ± 0.80 mm v. 0.97 ± 0.35 mm, F: 4.49, Post Hoc: 0.048; p = 0.05). Proximal translation of the radius in mid-pronation was significantly greater than when the forearm was in a supinated position when the elbow was at 0° or 90° flexion (F: 14.90, post-hoc: < 0.01; p < 0.01, F: 19.11, post-hoc: < 0.01, p < 0.01). The arc of forearm rotation was significantly decreased at 0° compared to 90° of elbow flexion (129.3 ± 22.2° v 152.8 ± 14.4°, F: 3.29, post-hoc: 0.79; p = 0.09). The center of rotation shifted volarly and ulnarly with increasing elbow extension.
Discussion
Elbow position affects the kinematics of the distal radioulnar joint. The kinematics of the distal radioulnar joint are primarily affected by forearm rotation and secondarily affected by elbow flexion. These findings have clinical relevance to our understanding of ulnar impaction, and how elbow position affects the proximal-distal translation of the radius. These findings have implications upon the treatment of ulna impaction, radiographic evaluation of the distal ulna, and future biomechanical studies.
doi:10.1016/j.jhsa.2009.04.025
PMCID: PMC2730984  PMID: 19576700
elbow; distal radioulnar; kinematics; biomechanics; forearm
20.  Decoding subtle forearm flexions using fractal features of surface electromyogram from single and multiple sensors 
Background
Identifying finger and wrist flexion based actions using a single channel surface electromyogram (sEMG) can lead to a number of applications such as sEMG based controllers for near elbow amputees, human computer interface (HCI) devices for elderly and for defence personnel. These are currently infeasible because classification of sEMG is unreliable when the level of muscle contraction is low and there are multiple active muscles. The presence of noise and cross-talk from closely located and simultaneously active muscles is exaggerated when muscles are weakly active such as during sustained wrist and finger flexion. This paper reports the use of fractal properties of sEMG to reliably identify individual wrist and finger flexion, overcoming the earlier shortcomings.
Methods
SEMG signal was recorded when the participant maintained pre-specified wrist and finger flexion movements for a period of time. Various established sEMG signal parameters such as root mean square (RMS), Mean absolute value (MAV), Variance (VAR) and Waveform length (WL) and the proposed fractal features: fractal dimension (FD) and maximum fractal length (MFL) were computed. Multi-variant analysis of variance (MANOVA) was conducted to determine the p value, indicative of the significance of the relationships between each of these parameters with the wrist and finger flexions. Classification accuracy was also computed using the trained artificial neural network (ANN) classifier to decode the desired subtle movements.
Results
The results indicate that the p value for the proposed feature set consisting of FD and MFL of single channel sEMG was 0.0001 while that of various combinations of the five established features ranged between 0.009 - 0.0172. From the accuracy of classification by the ANN, the average accuracy in identifying the wrist and finger flexions using the proposed feature set of single channel sEMG was 90%, while the average accuracy when using a combination of other features ranged between 58% and 73%.
Conclusions
The results show that the MFL and FD of a single channel sEMG recorded from the forearm can be used to accurately identify a set of finger and wrist flexions even when the muscle activity is very weak. A comparison with other features demonstrates that this feature set offers a dramatic improvement in the accuracy of identification of the wrist and finger movements. It is proposed that such a system could be used to control a prosthetic hand or for a human computer interface.
doi:10.1186/1743-0003-7-53
PMCID: PMC2984484  PMID: 20964863
21.  Chronic whiplash and central sensitization; an evaluation of the role of a myofascial trigger points in pain modulation 
Objective
it has been established that chronic neck pain following whiplash is associated with the phenomenon of central sensitization, in which injured and uninjured parts of the body exhibit lowered pain thresholds due to an alteration in central pain processing. it has furthermore been hypothesized that peripheral sources of nociception in the muscles may perpetuate central sensitization in chronic whiplash. the hypothesis explored in the present study was whether myofascial trigger points serve as a modulator of central sensitization in subjects with chronic neck pain.
Design
controlled case series.
Setting
outpatient chronic pain clinic.
Subjects
seventeen patients with chronic and intractable neck pain and 10 healthy controls without complaints of neck pain.
Intervention
symptomatic subjects received anesthetic infiltration of myofascial trigger points in the upper trapezius muscles and controls received the anesthetic in the thigh.
Outcome measures: pre and post injection cervical range of motion, pressure pain thresholds (ppt) over the infraspinatus, wrist extensor, and tibialis anterior muscles. sensitivity to light (photophobia) and subjects' perception of pain using a visual analog scale (vas) were also evaluated before and after injections. only the ppt was evaluated in the asymptomatic controls.
Results
immediate (within 1 minute) alterations in cervical range of motion and pressure pain thresholds were observed following an average of 3.8 injections with 1–2 cc of 1% lidocaine into carefully identified trigger points. cervical range of motion increased by an average of 49% (p = 0.000) in flexion and 44% (p = 0.001) in extension, 47% (p = 0.000) and 28% (p < 0.016) in right and left lateral flexion, and a 27% (p = 0.002) and 45% (p = 0.000) in right and left rotation. ppt were found increased by 68% over the infraspinatus (p = 0.000), by 78% over the wrist extensors (p = 0.000), and by 64% over the tibialis anterior (p = 0.002). among 11 subjects with photophobia, only 2 remained sensitive to light after the trigger point injections (p = 0.033). average vas dropped by 57%, from 6.1 to 2.6 (p = 0.000). no significant changes in ppt were observed in the control group following lidocaine infiltration of the thigh.
Conclusion
the present data suggest that myofascial trigger points serve to perpetuate lowered pain thresholds in uninjured tissues. additionally, it appears that lowered pain thresholds associated with central sensitization can be immediately reversed, even when associated with long standing chronic neck pain. although the effects resulting from anesthesia of trigger points in the present study were temporary, it is possible that surgical excision or ablation of the same trigger points may offer more permanent solutions for chronic neck pain patients. further study is needed to evaluate these and other options for such patients.
doi:10.1186/1749-7221-4-2
PMCID: PMC2680858  PMID: 19389231
22.  How Thoughts Give Rise to Action - Conscious Motor Intention Increases the Excitability of Target-Specific Motor Circuits 
PLoS ONE  2013;8(12):e83845.
The present study shows evidence for conscious motor intention in motor preparation prior to movement execution. We demonstrate that conscious motor intention of directed movement, combined with minimally supra-threshold transcranial magnetic stimulation (TMS) of the motor cortex, determines the direction and the force of resulting movements, whilst a lack of intention results in weak and omni-directed muscle activation.
We investigated changes of consciously intended goal directed movements by analyzing amplitudes of motor-evoked potentials of the forearm muscle, flexor carpi radialis (FCR), and extensor carpi radialis (ECR), induced by transcranial magnetic stimulation over the right motor cortex and their motor outcome. Right-handed subjects were asked to develop a strong intention to move their left wrist (flexion or extension), without any overt motor output at the wrist, prior to brain stimulation.
Our analyses of hand acceleration and electromyography showed that during the strong motor intention of wrist flexion movement, it evoked motor potential responses that were significantly larger in the FCR muscle than in the ECR, whilst the opposite was true for an extension movement. The acceleration data on flexion/extension corresponded to this finding. Under no-intention conditions again, which served as a reference for motor evoked potentials, brain stimulation resulted in undirected and minimally simultaneous extension/flexion innervation and virtually no movement.
These results indicate that conscious intentions govern motor function, which in turn shows that a neuronal activation representing an “intention network” in the human brain pre-exists, and that it functionally represents target specific motor circuits. Until today, it was unclear whether conscious motor intention exists prior to movement, or whether the brain constructs such an intention after movement initiation. Our study gives evidence that motor intentions become aware before any motor execution.
doi:10.1371/journal.pone.0083845
PMCID: PMC3873337  PMID: 24386291
23.  Wrist tendon forces during different dynamic wrist motions 
The Journal of hand surgery  2010;35(4):628-632.
Purpose
A common treatment of arthritis of the first carpometacarpal joint requires all or a portion of the flexor carpi radialis tendon (FCR) to be used as an interpositional graft. The purpose of this study was to examine the in vitro tendon forces in six wrist flexor and extensors to determine if their force contribution changes during different dynamic wrist motions along with a specific application to the FCR.
Methods
Sixty two fresh frozen cadaver wrists were tested in a wrist joint motion simulator. During wrist flexion-extension, radioulnar deviation, dart throwing and circumduction motions, the peak and average tendon forces were determined for the extensor carpi ulnaris, extensor carpi radialis brevis and longus, abductor pollicis longus, flexor carpi radialis and flexor carpi ulnaris.
Results
During a dart throwing motion, the mean and peak FCR forces were statistically less than during the other 3 motions. Conversely, the mean and peak flexor carpi ulnaris forces were statistically greater during the dart throwing motion than during the other 3 motions.
Discussion
Patients who have undergone a surgical procedure in which all or a portion of the FCR has been harvested, may experience a decrease in wrist strength with wrist motion as the FCR tendon normally applies force during wrist motion. The motion least likely to be affected by such surgery is the dart throwing motion when the force on the remaining FCR is minimized.
doi:10.1016/j.jhsa.2010.01.006
PMCID: PMC2872177  PMID: 20353863
Tendon Force; Wrist tendons
24.  Objective Outcomes Following Semi-Constrained Total Distal Radioulnar Joint Arthroplasty 
Journal of Wrist Surgery  2013;2(4):319-323.
A dysfunctional distal radioulnar joint (DRUJ) can significantly compromise an individual's forearm rotation, grip, and weight bearing at the hand and wrist. This retrospective study reports surgeon- and therapist-collected objective wrist function and subjective pain scores of 10 patients who received the Scheker total DRUJ prosthesis. A review of these patients' medical records was performed to collect preoperative measurements of wrist range of motion (ROM), grip strength, and pain scores (0–10 scale). The degree of pronation, supination, flexion, extension, radial deviation, and ulnar deviation were the outcome measures used to evaluate wrist ROM. Postoperative measurements were collected at a follow up of 5 ± 1.1 years in our clinic (minimum follow-up of 2yrs). Mean final wrist flexion and extension were 32.1 ± 22.8° and 44.8 ± 13.9°, respectively. Mean final supination and pronation were 72.5 ± 14.4° and 69.5 ± 14.6°, respectively. Average grip strength was 54.9 ± 23.7 lbs. The mean pain score was 3.6 ± 3.1. Although there were no statistically significant changes in any of these outcome measures, the Scheker prosthesis improved wrist ROM (with the exception of wrist flexion) and decreased pain. Grip strength decreased by less than 1 lb but was still higher than the postoperative grip strength measurements in the literature for this prosthesis. Because of the self-stabilizing nature of this prosthesis and the satisfactory functional outcomes from this study and other studies, the Scheker prosthesis is still a viable option for DRUJ pathology that is refractory to nonimplant arthroplasties. This is a therapeutic level IV study.
doi:10.1055/s-0033-1358544
PMCID: PMC3826245  PMID: 24436836
distal radioulnar joint; arthroplasty; wrist; Scheker prosthesis
25.  Meta-Analysis: Association Between Wrist Posture and Carpal Tunnel Syndrome Among Workers 
Safety and Health at Work  2014;5(1):27-31.
Background
Carpal tunnel syndrome (CTS) is a common work-related peripheral neuropathy. In addition to grip force and repetitive hand exertions, wrist posture (hyperextension and hyperflexion) may be a risk factor for CTS among workers. However, findings of studies evaluating the relationship between wrist posture and CTS are inconsistent. The purpose of this paper was to conduct a meta-analysis of existing studies to evaluate the evidence of the relationship between wrist posture at work and risk of CTS.
Methods
PubMed and Google Scholar were searched to identify relevant studies published between 1980 and 2012. The following search terms were used: “work related”, “carpal tunnel syndrome”, “wrist posture”, and “epidemiology”. The studies defined wrist posture as the deviation of the wrist in extension or flexion from a neutral wrist posture. Relative risk (RR) of individual studies for postural risk was pooled to evaluate the overall risk of wrist posture on CTS.
Results
Nine studies met the inclusion criteria. All were cross-sectional or case–control designs and relied on self-report or observer's estimates for wrist posture assessment. The pooled RR of work-related CTS increased with increasing hours of exposure to wrist deviation or extension/flexion [RR = 2.01; 95% confidence interval (CI): 1.646–2.43; p < 0.01: Shore-adjusted 95% CI: 1.32–2.97].
Conclusion
We found evidence that prolonged exposure to non-neutral wrist postures is associated with a twofold increased risk for CTS compared with low hours of exposure to non-neutral wrist postures. Workplace interventions to prevent CTS should incorporate training and engineering interventions that reduce sustained non-neutral wrist postures.
doi:10.1016/j.shaw.2014.01.003
PMCID: PMC4048004  PMID: 24932417
carpal tunnel syndrome; meta-analysis; systematic review

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