Sensory Dysfunction Associated With Repetitive Strain Injuries of Tendinitis and Focal Hand Dystonia: A Comparative Study Nancy Byl, PhD, MPH, PT' Frank Wilson, M D Michael Merzenich, PhD Marsha Melnick, PhD, PT4 Patrick Scott, MPT Alison Oakes, M P T ~ Alison McKenzie, PhD, MS, PT' M usicians. keyboard operators, data entry clerks, writers, and assembly workers perform repetitive, rapid, alternating movements of the fingers or maintained fine motor movements of the fingers under con- ditions of high demand and high productivity (6,18,42).These workers are at risk to develop musculoskeletal problems, including tendinitis, fasci- tis, and postural strain, or neurologi- cal problems, such as neuritis, nerve entrapments, or occupational hand cramps (6,9,18,22,42).These types of cumulative trauma syndromes are reaching epidemic levels in the work force and are costing millions of dol- lars despite management concern and ergonomic changes (6). Rapid repetitive movements un- der high levels of tension and force can interfere with the circulation and deprive the tissues of oxygen, leading to pain, inflammation, and muscle spasm (18.42). Although the body will naturally attempt to repair the tissues, other factors seem to increase the risk for continued symptoms (9,51,57). Repetitive strain injuries are reaching epidemic levels among workers who perform heavy schedules of rapid alternating movements (eg., computer programmers, data entry workers) or repetitive, sustained, coordinated movements (eg., editors, writers, salespeoplel. The purpose of this study was to determine if patients with repetitive strain injury demonstrated degraded sensory motor performance with their hands. Sixty agematched adults were rec~ited, with 15 each assigned to a healthy adult control group, a healthy musician control group, a tendinitis group, or a focal dystonia group. Four sensory motor subtests from the Sensory Integration and Praxis Test were given to the subjects according to a standardized protocol. Using multiple onefactor analyses of variance in the parametric or nonparametric mode followed by post hoc pairwise testing, no significant differences were found between the healthy controls and the musician controls. O n the test of kinesthesia, using the left hand, subjects with tendinitis performed significantly worse than controls and subjects with focal dystonia. Compared with controls, subjects with focal dystonia did significantly worse on graphesthesia and manual form perception (part 1 and part 2). Subjects with focal dystonia also did significantly worse than subjects with tendinitis when using the left hand on graphesthesia and manual form perception (part 2). When treating patients with repetitive strain injury, dimiminative sensory motor skills must be carefully assessed and may need to be addressed as part of an effeaive treatment program. Key Words: repetitive strain injury, tendinitis, sensory integration, focal dystonia ' Associate Professor, Graduate Program in Physical Therapy, University of California, San Francisco, School of Medicine, P.O. Box 0736, 374 Parnassus Ave., San Francisco, CA 94143-0736 Associate Clinical Professor, Department of Neurology, University of California, San Francisco, San Francisco, CA; Staff Physician, Department of Neurology, Kaiser Permanente, Hayward, CA ' Professor, Keck Center for Integrative Neurosciences and the Departments of Otolaryngology and Physiology, University of California, San Francisco, San Francisco, CA Clinical Professor, Graduate Program in Physical Therapy, University of California, San Francisco, San Francisco, CA; Professor, San Francisco State University, San Francisco, CA Staff Physical Therapist, Department of Physical Therapy, St. Mary's Hospital and Medical Center, San Francisco, CA. At the time of this study, Mr. Scon was a graduate student, Program in Physical Therapy, University of California, San Francisco, San Francisco State University, San Francisco, CA. Staff Physical Therapist, Scottsdale Memorial Hospital, Scoltsdale, AZ. At the time of this study, Ms. Oakes was a graduate student, Program in Physical Therapy, University of California, San Francisco, San Francisco State University, San Francisco, CA. ' Assistant Clinical Professor, Graduate Program in Physical Therapy, University of California, San Francisco, San Francisco, CA; Associate Professor, Division of Physical Therapy, Chapman University, Orange County, CA Volume 23 Number 4 April 1996 JOSPT Journal of Orthopaedic & Sports Physical Therapy® Downloaded from www.jospt.org at on March 31, 2023. For personal use only. No other uses without permission. Copyright © 1996 Journal of Orthopaedic & Sports Physical Therapy®. All rights reserved.
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Sensory Dysfunction Associated With Repetitive Strain Injuries of Tendinitis and Focal Hand Dystonia: A Comparative StudySensory Dysfunction Associated With Repetitive Strain Injuries of Tendinitis and Focal Hand Dystonia: A Comparative Study Nancy Byl, PhD, MPH, PT' Frank Wilson, MD Michael Merzenich, PhD Marsha Melnick, PhD, PT4 Patrick Scott, MPT Alison Oakes, MPT~ Alison McKenzie, PhD, MS, PT'
M usicians. keyboard operators, data entry clerks, writers, and assembly workers perform repetitive,
rapid, alternating movements of the fingers or maintained fine motor movements of the fingers under con- ditions of high demand and high productivity (6,18,42). These workers are at risk to develop musculoskeletal problems, including tendinitis, fasci- tis, and postural strain, or neurologi- cal problems, such as neuritis, nerve entrapments, or occupational hand cramps (6,9,18,22,42). These types of cumulative trauma syndromes are reaching epidemic levels in the work force and are costing millions of dol- lars despite management concern and ergonomic changes (6).
Rapid repetitive movements un- der high levels of tension and force can interfere with the circulation and deprive the tissues of oxygen, leading to pain, inflammation, and muscle spasm (18.42). Although the body will naturally attempt to repair the tissues, other factors seem to increase the risk for continued symptoms (9,51,57).
Repetitive strain injuries are reaching epidemic levels among workers who perform heavy schedules of rapid alternating movements (eg., computer programmers, data entry workers) or repetitive, sustained, coordinated movements (eg., editors, writers, salespeoplel. The purpose of this study was to determine if patients with repetitive strain injury demonstrated degraded sensory motor performance with their hands. Sixty agematched adults were rec~ited, with 15 each assigned to a healthy adult control group, a healthy musician control group, a tendinitis group, or a focal dystonia group. Four sensory motor subtests from the Sensory Integration and Praxis Test were given to the subjects according to a standardized protocol. Using multiple onefactor analyses of variance in the parametric or nonparametric mode followed by post hoc pairwise testing, no significant differences were found between the healthy controls and the musician controls. On the test of kinesthesia, using the left hand, subjects with tendinitis performed significantly worse than controls and subjects with focal dystonia. Compared with controls, subjects with focal dystonia did significantly worse on graphesthesia and manual form perception (part 1 and part 2). Subjects with focal dystonia also did significantly worse than subjects with tendinitis when using the left hand on graphesthesia and manual form perception (part 2). When treating patients with repetitive strain injury, dimiminative sensory motor skills must be carefully assessed and may need to be addressed as part of an effeaive treatment program.
Key Words: repetitive strain injury, tendinitis, sensory integration, focal dystonia
' Associate Professor, Graduate Program in Physical Therapy, University of California, San Francisco, School of Medicine, P.O. Box 0736, 374 Parnassus Ave., San Francisco, CA 94143-0736
Associate Clinical Professor, Department of Neurology, University of California, San Francisco, San Francisco, CA; Staff Physician, Department of Neurology, Kaiser Permanente, Hayward, CA ' Professor, Keck Center for Integrative Neurosciences and the Departments of Otolaryngology and Physiology, University of California, San Francisco, San Francisco, CA
Clinical Professor, Graduate Program in Physical Therapy, University of California, San Francisco, San Francisco, CA; Professor, San Francisco State University, San Francisco, CA
Staff Physical Therapist, Department of Physical Therapy, St. Mary's Hospital and Medical Center, San Francisco, CA. At the time of this study, Mr. Scon was a graduate student, Program in Physical Therapy, University of California, San Francisco, San Francisco State University, San Francisco, CA.
Staff Physical Therapist, Scottsdale Memorial Hospital, Scoltsdale, AZ. At the time of this study, Ms. Oakes was a graduate student, Program in Physical Therapy, University of California, San Francisco, San Francisco State University, San Francisco, CA. ' Assistant Clinical Professor, Graduate Program in Physical Therapy, University of California, San Francisco, San Francisco, CA; Associate Professor, Division of Physical Therapy, Chapman University, Orange County, CA
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Range limitations, particularly in finger abduction o r forearm prona- tion/supination, have been corre- lated with repetitive injury problems in musicians (57). Improper key- board techniques such as using the hand at extreme ranges, simulta- neously flexing the wrist and fingers, inadequately stabilizing the wrist dur- ing abduction of the thumb or fifth finger, and near simultaneous rec ip rocal contractions of the long finger flexors/extensors have also been re- ported as risk factors (51). ksymmet- rical postures with poor gravitational alignment maintained over a long work day must also be considered risk factors (57). But the most com- mon risk factor is forceful, rapid, re- petitive movements (6).
Initially, the pain may be relieved by rest, but the symptoms frequently reappear when performance is re- sumed (18,42). Anti-inflammatory medications, phonophoresis, injec- tions, heat, ice, and splinting may control the severity and acuity of the symptoms, but when the physical mo- dalities are terminated, symptoms reappear or new symptoms develop (6,18,42). Stretching and strengthen- ing exercises designed to increase flexibility and balance the muscles around the in-jured area may aggra- vate the condition. Conditioning ex- ercises improve the sense of well be- ing but usually d o not relieve the symptoms. Acute inflammations fre- quently become chronic and, ulti- mately, even selfcare activities are impaired (6,18,42). Compensatory movements adapted to reduce the pain (eg., hyperextension of the in- terphalangeal and/or the metacarpal- phalangeal joints during functional hand use, wrist flexion instead of wrist extension in functional activi- ties, and a flattening of the carpal arch) are usually biomechanically unstable and inefficient and ulti- mately make the problem worse (56.57).
Some patients d o recover from the inflammatory phase and return to work. However, some begin to note problems of excessive fatigue or incoordination when performing the target task. With increased practice to improve performance, control fur- ther deteriorates (31,34,56). This tar- get-specific degradation of fine hand movement. is called focal dystonia of the hand or writer's cramp and is one of the most disabling overuse syndromes (22,24,34,38,49.56,57). Electromyographically, the condition
The subjects report that their fingers pull uncontrollably into flexion or fly into
extension when the hand contacts the target instrument.
.. .
is characterized as a cocontraction of the agonists and antagonist. (10,21, 47,49). The subjects report that their fingers pull uncontrollably into flex- ion or fly into extension when the hand contacts the target instrument. Then they begin to have difficulty initiating, sequencing, timing, and controlling the force of the move- ments of the hand until they can no longer d o the task. They may also begin to have difficulty with similar tasks (eg., brushing the teeth, shav- ing) (49,56). However, sometimes the onset of focal dystonia is more sud- den, with loss of target-specific motor control reported after a motor vehi- cle accident, a fall on an outstretched hand, o r a nerve entrapment at the cervical level (4,9,11,17,22,38).
Focal dystonia is difficult to treat (4,16,17,25). Temporary relief of symptoms has been achieved with
injection of Botulinum toxin (5,15, 16,19). However, the drug causes some weakness and the dystonia re- turns when the effect of the drug wears off (1 6). Surgical treatment (4,12,14), traditional physical therapy (17), and spinal cord stimulation (20, 32,40.55) have been tried but these also only provide temporary relief.
The demanding work conditions common to patients with repetitive strain injury closely parallel the envi- ronmental conditions used to study neuroplasticity in primates (26,27,35, 36,44-46,54). Primates are trained, under conditions requiring high mo- tivation, to perform repetitive behav- iors with the hand. After weeks of daily training within a variety of con- ditions, including a syndactyl of the digits (2), a peripheral nerve lesion (54), an amputated finger (35), or the delivery of specific tactile stimuli (27,44-46), electrophysiological m a p ping of the primate somatosensory cortex (area 3b) revealed measurable changes in the representation of the hand. When sensory stimuli were re- peatedly applied within several hun- dredths of a millisecond or were a p plied across multiple digit- or across multiple segment. of the same digit, a loss of differentiation of the skin and/or muscle afferents occurred (7,46). Normally, small, precisely or- ganized receptive fields of the digits begin to extend across multiple digits or across multiple segments of the same digit (26.27). Cortical represen- tations of the stimulated digits may either get larger o r shrink depending on the type of sensory stimulation (27,45). Significant degradation of the hand representation in the so- matosensory cortex has also been a s sociated in some conditions with changes in area 3a as well as some disruption in motor control (45).
We asked the question whether repetitive hand use, under highly at- tended conditions, could be associ- ated with degradation in integrative
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M F x (years) SD Range Specific Problems Right Left
Controls 6 9 36.2 11.2 24-62 Healthy Musician controls 9 6 32.3 11.3 22-66 Healthy Tendinitis 10 5 39.1 12.1 24-62 Epicondylitis 8 6
DeQuervains 4 2 Flexor carpi
ulnaris tendinitis 3 2 Focal hand dystonia 10 5 43.9 10.4 27-69 Focal dystonia 15 0
TABLE 1. Description of subjects.
sensory-motor processing similar to the degradations seen in nonhuman primates after behavioral training. The purpose of this study was to de- termine if patients with repetitive strain injury had somatosensory pro- cessing problems compared with age- matched healthy subjects and those without a history of repetitive strain injury who were employed in a job that required a high level of repeti- tion. Sensory tests that measured the ability to discriminate tactile stimuli with the hands (haptic tasks) were used as a clinical estimate of cortical somatosensory processing.
METHODS
Subjects
A convenience sample of 60 male and female subjects between the ages of 19 and 67 years (35 males and 25 females) were recruited from the stu- dents and faculty at the University of California, San Francisco (UCSF) , the patients of the UCSF Health Program for Performing Artists, and the stu- dents from the San Francisco Conser- vatory of Music. All subjects had to have a normal neurological examina- tion as determined by a neurologist or a physical therapist (eg., normal responses to light touch and pain and normal deep tendon reflexes). The diagnosis of repetitive strain in- jury (focal dystonia or tendinitis) was determined by the patient's coordi- nating physician.
The subjects were age matched, with 15 each assigned to: I) a healthy
control group; 2) a healthy musician control group; 3) a tendinitis group; or 4) a focal dystonia group. The healthy control group and the healthy musician control group in- cluded adults with no history of chronic or systemic disease, move- ment disorders, or inflammatory con- ditions which affected the upper ex- tremity. They had to be free of physical complaints surrounding the hand, wrist, or elbow for at least 3 months prior to testing. If these sub- jects had complaints of postural stress, they could not be receiving medical treatment for these com- plaints. The healthy musician control group had to practice at least 1.5 hours/day.
To be eligible for admission to the tendinitis group, the subjects had to be involved in a job that required repetitive use of the hands and dem- onstrate: 1) unilateral or bilateral complaints; 2) swelling, inflamma- tion, pain, or tenderness in the in- volved tendon (s) as determined by palpation or increased pain with ac- tive contraction; and 3) tendinitis of the flexor or extensor tendon(s) serv- ing the wrist or fingers (eg., DeQuer- vains tendinitis, epicondylitis, flexor carpi ulnaris tendinitis). The subjects could have secondary complaints of a nerve entrapment syndrome without objective neurological deficits as long as electromyographic and nerve con- duction studies were normal or the signs of neurological impairment did not warrant further diagnostic testing.
To be eligible for the focal dyste nia group, the subjects needed to be
involved in a job that required repeti- tive use of the hands and demon- strate the following: 1) specific motor skill impairment in terms of errors in timing, force, or trajectory with ab- sence of stereotypical tonic postures and/or cramping sensations absent at rest; 2) abnormal, involuntary move- ments initiated when performing a specific motor task in a given context (eg., writing, playing a musical instru- ment, entering data, typing); 3) de- graded movements that impaired function; 4) loss of motor skills which could not be explained by a decrease in practice or task performance; and 5) persistence of the abnormal move- ment despite resolution of any previ- ous inflammatory, neuropathic, trau- matic, or myopathic abnormalities.
A description of the subjects a p pears in Table 1. Of subjects with tendinitis, 10 of the 15 had bilateral complaints of tendinitis. Seven of the 15 subjects with tendinitis also had signs of nerve entrapment (cubittal tunnel, carpal tunnel, or thoracic outlet syndrome). The subjects who had unilateral tendinitis had mild nerve entrapment signs bilaterally. Thirteen of the 15 subjects with ten- dinitis were right handed. All of the subjects with focal dystonia reported the right hand as the affected hand. Thirteen of these 15 subjects were right handed.
This study was approved by the Committee on Human Research at the University of California, San Francisco, San Francisco, CA. All sub- jects reviewed the study protocol and
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gave informed consent prior to par- ticipating in the study.
Test Procedures
All subjects were given four of 17 subtests from the standardized Sen- sory Integration and Praxis Test (SIPT, Western Psychological Associa- tion, Los Angeles, CA) (3). Localiza- tion of tactile stimuli, kinesthesia, graphesthesia, and manual form per- ception were selected for this study. These specific sensory tests were se- lected because previous research studies showed a specifically corre- lated increase in blood flow (as mea-
A l/ subjects were given four of 17 subtests
from the standardized Sensory ln tegra tion
and Praxis Test.
sured with positive emission tomogra- phy) in the pareital cortex, the supple- mentary motor cortex, and the premotor cortex when subjects per- formed sensory tasks involving loca- tion, position, and tactile exploration of objects (49). These tests were typi- cal of the discriminative sensory tests included in a complete neurological examination (1 3,29,30,32,37), and they involved superficial and deep cutaneous stimuli which have com- monly been used in behavioral train- ing and neuroplasticity experiments (27,46).
All of the subjects except the muscian controls were also given the motor accuracy test to evaluate differ- ences in fine motor control in the two repetitive strain injury groups. Test administration time averaged 45 minutes for four tests and 1 hour for all five tests.
The following scoring procedures were used:
Tactile Motor Tests
Localization of tactile stimuli With the subject blindfolded, the evaluator marked the skin with a point stimulus at multiple points on the dorsal and palmar surfaces of the hand and fore- arm. After each stimulus, the subject took the index finger of the opposite hand to the point they felt had been touched and the distance between the actual point marked and the point touched was measured (cm).
Kinesthesia While the subject was blindfolded and sitting at a table, the examiner took the subject's index finger from the starting position to a designated point on a scoring sheet and then returned the finger to the starting position. The subject tried to return the finger to the target site and the difference between the ac- tual target position and the at- tempted returned position was mea- sured (cm).
Tactile Perceptual Tests
Graphesthesia While sitting blindfolded, the examiner drew a series of predefined figures on the dorsum of the hand. The subject had to redraw each figure using the oppo- site hand. The score was an ordinal score based on the correctness of the direction of lines and shape of the figure.
Manual fm perception While blindfolded, the subject palpated a form in one hand. In test 1, the s u b ject had to visually match the object. In test 2, the subject had to palpate another series of objects and match the target object. The score was based on the percent of the trials that were correct. The time to do the match was also recorded.
Fine Motor Test
Motor accuracy With eyes open, the subject carefully traced a line with a pen. An adjusted score was calculated based on the length of the line where the tracing was exactly on
the line adjusted by the length of the line it was off target. This length was then adjusted by time.
Test Reliability
The SIPT test has standardized administration procedures to mini- mize variations in testing (%%). Each test component includes multi- ple test trials usually delivered to a defined regional site (eg.. the hand). The control subjects served as the reference for expected performance for this study. The SIPT tests have been normed primarily on children (2) with only limited normative data available on adults (23). The studies with adults suggested that there was a ceiling effect on some of the subtests which limited the ability to detect differences in subjects with mild defi- cits (23). Abnormal performance by an adult would thus represent a con- servative indication of somatosensory dysfunction.
Interrater reliability for the SIFT is reported to be greater than 0.95 for all of the subtests. Test-retest reli- ability ranged from 0.53 to 0.93 (33). The test-retest reliability for the subtests selected for this study were reported as: localization = 0.53; kin- esthesia = 0.50; graphesthesia = 0.74; manual form perception = 0.70; and motor accuracy = 0.84. Given the low level of reliability for localization, kinesthesia, and graphes- thesia, the primary investigator car- ried out a test-retest reliability study including eight subjects with repeti- tive strain in.juries, six of whom were not included in this study.
Research Design and Data Analysis
This was a descriptive study using two control and two repetitive injury groups. Descriptive statistics were cal- culated for all of the dependent vari- ables (subtests). Each test and each side were considered independent families and tested for significance, with group as the factor of interest. Six one-factor analysis of variance
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hand on the test of kinesthesia when
compared with either controls or subjects with focal dystonia.
tests (p 5 0.05) followed by post hoc testing using the Student t test were carried out for localization and kines- thesia (ratio data) and the Dunn method to control for the experi- ment-wise error (p 5 0.0167). Twelve one-factor, nonparametric Kruskall Wallis test. (p < 0.05) followed by post hoc testing with the two-sample Wilcoxon (p 5 0.0167) were carried out for graphesthesia, manual form perception, and motor accuracy (nominal and ordinal data). In the nonparametric mode, only one-factor analysis of variance test. are available, preventing the opportunity to use a 2 X 2 analysis of variance with group and side as factors (43). If no signifi- cant differences were found between the healthy controls and the healthy musicians, the two groups would be combined into a single control group. Statistical comparisons were not made between sides within groups. Except for the motor accu- racy test, all of the sensory test. re- quired the subject to use both hands when performing the task.
The test-retest correlation coeffi- cients (Pearson correlation coeffi- cient) were r = 0.92, 0.90, and 0.91, respectively, for the tests of localiza- tion, kinesthesia, and graphesthesia. There were no significant differences
- - .…
M usicians. keyboard operators, data entry clerks, writers, and assembly workers perform repetitive,
rapid, alternating movements of the fingers or maintained fine motor movements of the fingers under con- ditions of high demand and high productivity (6,18,42). These workers are at risk to develop musculoskeletal problems, including tendinitis, fasci- tis, and postural strain, or neurologi- cal problems, such as neuritis, nerve entrapments, or occupational hand cramps (6,9,18,22,42). These types of cumulative trauma syndromes are reaching epidemic levels in the work force and are costing millions of dol- lars despite management concern and ergonomic changes (6).
Rapid repetitive movements un- der high levels of tension and force can interfere with the circulation and deprive the tissues of oxygen, leading to pain, inflammation, and muscle spasm (18.42). Although the body will naturally attempt to repair the tissues, other factors seem to increase the risk for continued symptoms (9,51,57).
Repetitive strain injuries are reaching epidemic levels among workers who perform heavy schedules of rapid alternating movements (eg., computer programmers, data entry workers) or repetitive, sustained, coordinated movements (eg., editors, writers, salespeoplel. The purpose of this study was to determine if patients with repetitive strain injury demonstrated degraded sensory motor performance with their hands. Sixty agematched adults were rec~ited, with 15 each assigned to a healthy adult control group, a healthy musician control group, a tendinitis group, or a focal dystonia group. Four sensory motor subtests from the Sensory Integration and Praxis Test were given to the subjects according to a standardized protocol. Using multiple onefactor analyses of variance in the parametric or nonparametric mode followed by post hoc pairwise testing, no significant differences were found between the healthy controls and the musician controls. On the test of kinesthesia, using the left hand, subjects with tendinitis performed significantly worse than controls and subjects with focal dystonia. Compared with controls, subjects with focal dystonia did significantly worse on graphesthesia and manual form perception (part 1 and part 2). Subjects with focal dystonia also did significantly worse than subjects with tendinitis when using the left hand on graphesthesia and manual form perception (part 2). When treating patients with repetitive strain injury, dimiminative sensory motor skills must be carefully assessed and may need to be addressed as part of an effeaive treatment program.
Key Words: repetitive strain injury, tendinitis, sensory integration, focal dystonia
' Associate Professor, Graduate Program in Physical Therapy, University of California, San Francisco, School of Medicine, P.O. Box 0736, 374 Parnassus Ave., San Francisco, CA 94143-0736
Associate Clinical Professor, Department of Neurology, University of California, San Francisco, San Francisco, CA; Staff Physician, Department of Neurology, Kaiser Permanente, Hayward, CA ' Professor, Keck Center for Integrative Neurosciences and the Departments of Otolaryngology and Physiology, University of California, San Francisco, San Francisco, CA
Clinical Professor, Graduate Program in Physical Therapy, University of California, San Francisco, San Francisco, CA; Professor, San Francisco State University, San Francisco, CA
Staff Physical Therapist, Department of Physical Therapy, St. Mary's Hospital and Medical Center, San Francisco, CA. At the time of this study, Mr. Scon was a graduate student, Program in Physical Therapy, University of California, San Francisco, San Francisco State University, San Francisco, CA.
Staff Physical Therapist, Scottsdale Memorial Hospital, Scoltsdale, AZ. At the time of this study, Ms. Oakes was a graduate student, Program in Physical Therapy, University of California, San Francisco, San Francisco State University, San Francisco, CA. ' Assistant Clinical Professor, Graduate Program in Physical Therapy, University of California, San Francisco, San Francisco, CA; Associate Professor, Division of Physical Therapy, Chapman University, Orange County, CA
Volume 23 Number 4 April 1996 JOSPT
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d.
Range limitations, particularly in finger abduction o r forearm prona- tion/supination, have been corre- lated with repetitive injury problems in musicians (57). Improper key- board techniques such as using the hand at extreme ranges, simulta- neously flexing the wrist and fingers, inadequately stabilizing the wrist dur- ing abduction of the thumb or fifth finger, and near simultaneous rec ip rocal contractions of the long finger flexors/extensors have also been re- ported as risk factors (51). ksymmet- rical postures with poor gravitational alignment maintained over a long work day must also be considered risk factors (57). But the most com- mon risk factor is forceful, rapid, re- petitive movements (6).
Initially, the pain may be relieved by rest, but the symptoms frequently reappear when performance is re- sumed (18,42). Anti-inflammatory medications, phonophoresis, injec- tions, heat, ice, and splinting may control the severity and acuity of the symptoms, but when the physical mo- dalities are terminated, symptoms reappear or new symptoms develop (6,18,42). Stretching and strengthen- ing exercises designed to increase flexibility and balance the muscles around the in-jured area may aggra- vate the condition. Conditioning ex- ercises improve the sense of well be- ing but usually d o not relieve the symptoms. Acute inflammations fre- quently become chronic and, ulti- mately, even selfcare activities are impaired (6,18,42). Compensatory movements adapted to reduce the pain (eg., hyperextension of the in- terphalangeal and/or the metacarpal- phalangeal joints during functional hand use, wrist flexion instead of wrist extension in functional activi- ties, and a flattening of the carpal arch) are usually biomechanically unstable and inefficient and ulti- mately make the problem worse (56.57).
Some patients d o recover from the inflammatory phase and return to work. However, some begin to note problems of excessive fatigue or incoordination when performing the target task. With increased practice to improve performance, control fur- ther deteriorates (31,34,56). This tar- get-specific degradation of fine hand movement. is called focal dystonia of the hand or writer's cramp and is one of the most disabling overuse syndromes (22,24,34,38,49.56,57). Electromyographically, the condition
The subjects report that their fingers pull uncontrollably into flexion or fly into
extension when the hand contacts the target instrument.
.. .
is characterized as a cocontraction of the agonists and antagonist. (10,21, 47,49). The subjects report that their fingers pull uncontrollably into flex- ion or fly into extension when the hand contacts the target instrument. Then they begin to have difficulty initiating, sequencing, timing, and controlling the force of the move- ments of the hand until they can no longer d o the task. They may also begin to have difficulty with similar tasks (eg., brushing the teeth, shav- ing) (49,56). However, sometimes the onset of focal dystonia is more sud- den, with loss of target-specific motor control reported after a motor vehi- cle accident, a fall on an outstretched hand, o r a nerve entrapment at the cervical level (4,9,11,17,22,38).
Focal dystonia is difficult to treat (4,16,17,25). Temporary relief of symptoms has been achieved with
injection of Botulinum toxin (5,15, 16,19). However, the drug causes some weakness and the dystonia re- turns when the effect of the drug wears off (1 6). Surgical treatment (4,12,14), traditional physical therapy (17), and spinal cord stimulation (20, 32,40.55) have been tried but these also only provide temporary relief.
The demanding work conditions common to patients with repetitive strain injury closely parallel the envi- ronmental conditions used to study neuroplasticity in primates (26,27,35, 36,44-46,54). Primates are trained, under conditions requiring high mo- tivation, to perform repetitive behav- iors with the hand. After weeks of daily training within a variety of con- ditions, including a syndactyl of the digits (2), a peripheral nerve lesion (54), an amputated finger (35), or the delivery of specific tactile stimuli (27,44-46), electrophysiological m a p ping of the primate somatosensory cortex (area 3b) revealed measurable changes in the representation of the hand. When sensory stimuli were re- peatedly applied within several hun- dredths of a millisecond or were a p plied across multiple digit- or across multiple segment. of the same digit, a loss of differentiation of the skin and/or muscle afferents occurred (7,46). Normally, small, precisely or- ganized receptive fields of the digits begin to extend across multiple digits or across multiple segments of the same digit (26.27). Cortical represen- tations of the stimulated digits may either get larger o r shrink depending on the type of sensory stimulation (27,45). Significant degradation of the hand representation in the so- matosensory cortex has also been a s sociated in some conditions with changes in area 3a as well as some disruption in motor control (45).
We asked the question whether repetitive hand use, under highly at- tended conditions, could be associ- ated with degradation in integrative
JOSPT Volume 23 Number 4 April 1996
J ou
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o f
O rt
ho pa
ed ic
M F x (years) SD Range Specific Problems Right Left
Controls 6 9 36.2 11.2 24-62 Healthy Musician controls 9 6 32.3 11.3 22-66 Healthy Tendinitis 10 5 39.1 12.1 24-62 Epicondylitis 8 6
DeQuervains 4 2 Flexor carpi
ulnaris tendinitis 3 2 Focal hand dystonia 10 5 43.9 10.4 27-69 Focal dystonia 15 0
TABLE 1. Description of subjects.
sensory-motor processing similar to the degradations seen in nonhuman primates after behavioral training. The purpose of this study was to de- termine if patients with repetitive strain injury had somatosensory pro- cessing problems compared with age- matched healthy subjects and those without a history of repetitive strain injury who were employed in a job that required a high level of repeti- tion. Sensory tests that measured the ability to discriminate tactile stimuli with the hands (haptic tasks) were used as a clinical estimate of cortical somatosensory processing.
METHODS
Subjects
A convenience sample of 60 male and female subjects between the ages of 19 and 67 years (35 males and 25 females) were recruited from the stu- dents and faculty at the University of California, San Francisco (UCSF) , the patients of the UCSF Health Program for Performing Artists, and the stu- dents from the San Francisco Conser- vatory of Music. All subjects had to have a normal neurological examina- tion as determined by a neurologist or a physical therapist (eg., normal responses to light touch and pain and normal deep tendon reflexes). The diagnosis of repetitive strain in- jury (focal dystonia or tendinitis) was determined by the patient's coordi- nating physician.
The subjects were age matched, with 15 each assigned to: I) a healthy
control group; 2) a healthy musician control group; 3) a tendinitis group; or 4) a focal dystonia group. The healthy control group and the healthy musician control group in- cluded adults with no history of chronic or systemic disease, move- ment disorders, or inflammatory con- ditions which affected the upper ex- tremity. They had to be free of physical complaints surrounding the hand, wrist, or elbow for at least 3 months prior to testing. If these sub- jects had complaints of postural stress, they could not be receiving medical treatment for these com- plaints. The healthy musician control group had to practice at least 1.5 hours/day.
To be eligible for admission to the tendinitis group, the subjects had to be involved in a job that required repetitive use of the hands and dem- onstrate: 1) unilateral or bilateral complaints; 2) swelling, inflamma- tion, pain, or tenderness in the in- volved tendon (s) as determined by palpation or increased pain with ac- tive contraction; and 3) tendinitis of the flexor or extensor tendon(s) serv- ing the wrist or fingers (eg., DeQuer- vains tendinitis, epicondylitis, flexor carpi ulnaris tendinitis). The subjects could have secondary complaints of a nerve entrapment syndrome without objective neurological deficits as long as electromyographic and nerve con- duction studies were normal or the signs of neurological impairment did not warrant further diagnostic testing.
To be eligible for the focal dyste nia group, the subjects needed to be
involved in a job that required repeti- tive use of the hands and demon- strate the following: 1) specific motor skill impairment in terms of errors in timing, force, or trajectory with ab- sence of stereotypical tonic postures and/or cramping sensations absent at rest; 2) abnormal, involuntary move- ments initiated when performing a specific motor task in a given context (eg., writing, playing a musical instru- ment, entering data, typing); 3) de- graded movements that impaired function; 4) loss of motor skills which could not be explained by a decrease in practice or task performance; and 5) persistence of the abnormal move- ment despite resolution of any previ- ous inflammatory, neuropathic, trau- matic, or myopathic abnormalities.
A description of the subjects a p pears in Table 1. Of subjects with tendinitis, 10 of the 15 had bilateral complaints of tendinitis. Seven of the 15 subjects with tendinitis also had signs of nerve entrapment (cubittal tunnel, carpal tunnel, or thoracic outlet syndrome). The subjects who had unilateral tendinitis had mild nerve entrapment signs bilaterally. Thirteen of the 15 subjects with ten- dinitis were right handed. All of the subjects with focal dystonia reported the right hand as the affected hand. Thirteen of these 15 subjects were right handed.
This study was approved by the Committee on Human Research at the University of California, San Francisco, San Francisco, CA. All sub- jects reviewed the study protocol and
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gave informed consent prior to par- ticipating in the study.
Test Procedures
All subjects were given four of 17 subtests from the standardized Sen- sory Integration and Praxis Test (SIPT, Western Psychological Associa- tion, Los Angeles, CA) (3). Localiza- tion of tactile stimuli, kinesthesia, graphesthesia, and manual form per- ception were selected for this study. These specific sensory tests were se- lected because previous research studies showed a specifically corre- lated increase in blood flow (as mea-
A l/ subjects were given four of 17 subtests
from the standardized Sensory ln tegra tion
and Praxis Test.
sured with positive emission tomogra- phy) in the pareital cortex, the supple- mentary motor cortex, and the premotor cortex when subjects per- formed sensory tasks involving loca- tion, position, and tactile exploration of objects (49). These tests were typi- cal of the discriminative sensory tests included in a complete neurological examination (1 3,29,30,32,37), and they involved superficial and deep cutaneous stimuli which have com- monly been used in behavioral train- ing and neuroplasticity experiments (27,46).
All of the subjects except the muscian controls were also given the motor accuracy test to evaluate differ- ences in fine motor control in the two repetitive strain injury groups. Test administration time averaged 45 minutes for four tests and 1 hour for all five tests.
The following scoring procedures were used:
Tactile Motor Tests
Localization of tactile stimuli With the subject blindfolded, the evaluator marked the skin with a point stimulus at multiple points on the dorsal and palmar surfaces of the hand and fore- arm. After each stimulus, the subject took the index finger of the opposite hand to the point they felt had been touched and the distance between the actual point marked and the point touched was measured (cm).
Kinesthesia While the subject was blindfolded and sitting at a table, the examiner took the subject's index finger from the starting position to a designated point on a scoring sheet and then returned the finger to the starting position. The subject tried to return the finger to the target site and the difference between the ac- tual target position and the at- tempted returned position was mea- sured (cm).
Tactile Perceptual Tests
Graphesthesia While sitting blindfolded, the examiner drew a series of predefined figures on the dorsum of the hand. The subject had to redraw each figure using the oppo- site hand. The score was an ordinal score based on the correctness of the direction of lines and shape of the figure.
Manual fm perception While blindfolded, the subject palpated a form in one hand. In test 1, the s u b ject had to visually match the object. In test 2, the subject had to palpate another series of objects and match the target object. The score was based on the percent of the trials that were correct. The time to do the match was also recorded.
Fine Motor Test
Motor accuracy With eyes open, the subject carefully traced a line with a pen. An adjusted score was calculated based on the length of the line where the tracing was exactly on
the line adjusted by the length of the line it was off target. This length was then adjusted by time.
Test Reliability
The SIPT test has standardized administration procedures to mini- mize variations in testing (%%). Each test component includes multi- ple test trials usually delivered to a defined regional site (eg.. the hand). The control subjects served as the reference for expected performance for this study. The SIPT tests have been normed primarily on children (2) with only limited normative data available on adults (23). The studies with adults suggested that there was a ceiling effect on some of the subtests which limited the ability to detect differences in subjects with mild defi- cits (23). Abnormal performance by an adult would thus represent a con- servative indication of somatosensory dysfunction.
Interrater reliability for the SIFT is reported to be greater than 0.95 for all of the subtests. Test-retest reli- ability ranged from 0.53 to 0.93 (33). The test-retest reliability for the subtests selected for this study were reported as: localization = 0.53; kin- esthesia = 0.50; graphesthesia = 0.74; manual form perception = 0.70; and motor accuracy = 0.84. Given the low level of reliability for localization, kinesthesia, and graphes- thesia, the primary investigator car- ried out a test-retest reliability study including eight subjects with repeti- tive strain in.juries, six of whom were not included in this study.
Research Design and Data Analysis
This was a descriptive study using two control and two repetitive injury groups. Descriptive statistics were cal- culated for all of the dependent vari- ables (subtests). Each test and each side were considered independent families and tested for significance, with group as the factor of interest. Six one-factor analysis of variance
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hand on the test of kinesthesia when
compared with either controls or subjects with focal dystonia.
tests (p 5 0.05) followed by post hoc testing using the Student t test were carried out for localization and kines- thesia (ratio data) and the Dunn method to control for the experi- ment-wise error (p 5 0.0167). Twelve one-factor, nonparametric Kruskall Wallis test. (p < 0.05) followed by post hoc testing with the two-sample Wilcoxon (p 5 0.0167) were carried out for graphesthesia, manual form perception, and motor accuracy (nominal and ordinal data). In the nonparametric mode, only one-factor analysis of variance test. are available, preventing the opportunity to use a 2 X 2 analysis of variance with group and side as factors (43). If no signifi- cant differences were found between the healthy controls and the healthy musicians, the two groups would be combined into a single control group. Statistical comparisons were not made between sides within groups. Except for the motor accu- racy test, all of the sensory test. re- quired the subject to use both hands when performing the task.
The test-retest correlation coeffi- cients (Pearson correlation coeffi- cient) were r = 0.92, 0.90, and 0.91, respectively, for the tests of localiza- tion, kinesthesia, and graphesthesia. There were no significant differences
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