CARPAL TUNNEL SYNDROME (CTS) is a common

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1 ARTICLES Randomized Controlled Trial of Nocturnal Splinting for Active Workers With Symptoms of Carpal Tunnel Syndrome Robert A. Werner, MD, Alfred Franzblau, MD, Nancy Gell, MPH, PT 1 ABSTRACT. Werner RA, Franzblau A, Gell N. Randomized controlled trial of nocturnal splinting for active workers with symptoms of carpal tunnel syndrome. Arch Phys Med Rehabil 2005;86:1-7. Objectives: To determine whether nocturnal splinting of workers identified through active surveillance with symptoms consistent with carpal tunnel syndrome (CTS) would improve symptoms and median nerve function as well as impact medical care. Design: Randomized controlled trial. Setting: A Midwestern auto assembly plant. Participants: Active workers with symptoms suggestive of CTS based on a hand diagram. Intervention: The treatment group received customized wrist splints, which were worn at night for 6 weeks; the control group received ergonomic education alone. Main Outcome Measures: Change in wrist, hand, and/or finger discomfort, carpal tunnel symptom severity index, median sensory nerve function, and the percentage of subjects who had carpal tunnel release surgery. Results: The splinted group, unlike the controls, had a significant reduction in wrist, hand, and/or finger discomfort and a similar trend in the Levine carpal tunnel symptom severity index, which was maintained at 12 months. A secondary analysis showed that more median nerve impairment at baseline was associated with less clinical improvement among controls but not among the splinted group. Conclusions: Workers identified with CTS symptoms in an active symptom surveillance tended to benefit from a 6-week nocturnal splinting trial, and the benefits were still evident at the 1-year follow-up. The splinted group improved in terms of hand discomfort regardless of the degree of median nerve impairment, whereas the controls showed improvement only among subjects with normal median nerve function. Results suggest that a short course of nocturnal splinting may reduce wrist, hand, and/or finger discomfort among active workers with symptoms consistent with CTS. Key Words: Carpal tunnel syndrome; Randomized controlled trials; Rehabilitation. From the Departments of Physical Medicine and Rehabilitation (Werner, Gell) and Emergency Medicine (Franzblau), University of Michigan Health System; Veteran Affairs Medical Center (Werner); Department of Environmental Health Sciences, School of Public Health, University of Michigan (Werner, Franzblau, Gell); and Center for Ergonomics, Industrial and Operations Engineering, University of Michigan (Werner, Franzblau), Ann Arbor, MI. Supported in whole by joint funds from the United Auto Workers (UAW) and General Motors (GM) National Joint Committee on Health and Safety. The results presented herein represent the conclusions and opinions of the authors. Publication does not necessarily imply endorsement by the International Union, UAW, or GM. No commercial party having a direct interest in the results of the research supporting this article has or will confer a benefit on the author(s) or on any organization with which the author(s) is/are associated. Reprint requests to Robert Werner, MD, PM&R, Ann Arbor VAMC, 2215 Fuller Rd (117), Ann Arbor, MI 48105, rawerner@umich.edu /05/ $30.00/0 doi: /j.apmr by American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation CARPAL TUNNEL SYNDROME (CTS) is a common work-related disorder and is a major cause of impairment and disability in the workplace. 1,2 CTS is considered a clinical entity, and diagnosis is based on a symptom complex that includes numbness, tingling, and/or burning in the distribution of the median nerve. CTS is caused by localized compression of the median nerve at the wrist. CTS is the most common nerve entrapment included in reports of repetitive strain injuries. One estimate 3 suggests that repetitive strain injuries make up 48% of all recordable industrial illnesses. The associated costs are estimated at $13 billion per year in the United States (medical costs, lost productivity time). The natural history of workers with CTS is not well established. What is well established is the amount of lost work time associated with management of CTS. Of the most common work-related injuries and illnesses, CTS has the longest average time away from work (27d) of any of the major categories. 4 Treatment protocols vary widely across the United States and Western Europe. Conservative treatment may include wrist splints, modification of hand activity, nonsteroidal anti-inflammatory medications, diuretics, cold laser, vitamin B 6, and steroid injections. A recent review 5 of these treatment options determined that there were few high-quality randomized controlled trials (RCTs) to determine the efficacy of these interventions. Only steroid injections were found to have strong support in the literature. 5 There was a small RCT 6 of full-time splint use versus nighttime-only splint use, which showed improvement in both groups. Despite the lack of scientific study, several organizations that published practice parameters for the management of CTS, and all suggest wrist splinting as a first line intervention. 7,8 Symptom surveys have been instituted in many industrial worksites to identify workers at risk and ergonomic risks associated with work stations whose workers report symptoms associated with repetitive strain disorders. The premise is that early identification of workers with musculoskeletal symptoms will allow for early intervention from a medical and ergonomic perspective. Workers identified with CTS have frequently been treated with nighttime splinting as a first-line conservative intervention. Several studies have suggested that splinting can be an effective intervention in subjects with CTS, although no RCTs have been done with splinting as a sole intervention. 5 No studies have evaluated the effectiveness of early intervention of workers who have symptoms consistent with CTS but who have not sought medical treatment. The objective of our study was to determine whether nocturnal splinting of workers identified through active surveillance with symptoms consistent with CTS would improve symptoms and median nerve function as well as impact medical care. We hypothesized that workers identified with symptoms consistent with CTS would benefit

2 2 RCT OF SPLINTING FOR CTS, Werner Fig 1. Flow chart for patients recruited into the RCT of early splinting. from an early wrist splinting program and have reduced symptom severity and fewer lost work days. METHODS Potential subjects were identified during a biannual symptom survey done in a midwestern auto assembly plant. A body diagram was used to identify body regions affected and the severity of discomfort. If the worker had symptoms of numbness, tingling, burning, or pain in the wrist or the hand for more than a week or more than 3 times in the last 6 months, the worker filled out a hand diagram. 9 If the hand diagram was suggestive of CTS that is, there were symptoms of numbness, tingling, burning, or pain in the median nerve distribution the worker was eligible for the study. The initial symptom questionnaire was completed on a rolling basis throughout the plant, and thus recruitment occurred on a rolling basis during the course of 1 year. All subjects provided signed consent that had been approved by the University of Michigan Institutional Review Board. Inclusion Criteria Workers who had symptoms consistent with CTS that is, numbness, tingling, burning, or pain in the distribution of the median nerve in the hand based on a hand diagram score were included in the study. The hand diagrams were scored according to the methods described by Franzblau et al 9 for symptoms suggestive of CTS. The ratings range from 0 to 3 unlikely, possible, probable, and definite. A score of 1, 2, or 3 was used as an entrance criterion. Exclusion Criteria The following subjects were excluded from the study population: (1) workers who had upper-extremity musculoskeletal disorders secondary to acute trauma on or off the job, (2) workers with a history of bilateral carpal tunnel release (CTR) surgery, and (3) pregnant women. Of the 2636 workers who completed the symptom survey, 540 were eligible, and 364 were contacted to participate in the study. A total of 161 agreed to participate, but only 112 completed the study (fig 1). Subjects were randomized to either a treatment or a control group, depending on whether the last digit of their Social Security number was odd or even. Subjects were not informed of the sequence for random allocation nor were they told to which group they were assigned until after consenting to participate. Both groups were given instructions in how to reduce ergonomic stressors in the work and home environments by viewing a 20-minute video on CTS and ergonomic risk factors. The focus of the video was industrial ergonomics and the prevention of repetitive strain disorders. The treatment group was fitted with a custom wrist-hand orthosis that maintained the wrist in a neutral posture (fig 2). If the subject had CTS symptoms in both hands, the most symptomatic side (ie, highest discomfort rating score) was chosen for the study. The treatment group was instructed to wear the splint at night 6 weeks. The outcome measures were assessed in both groups at 3, 6, and 12 months. The treatment group also filled out a questionnaire on splint usage and satisfaction with the treatment at 6 weeks, after they completed their 6-week splinting trial. All subjects completed the symptom questionnaires on their own time and received a half hour of overtime pay for completing each questionnaire. In addition, data in Occupational Health and Safety Administration logs, plant medical records, disability records, days of work missed due to upperextremity problems, and workers compensation status or work restrictions were collected from computerized records. Subjects received their routine medical care as prescribed by the occupational health nurse or physician or their private health care provider. Subjects were not blinded to their treatment, and the primary outcome measure was a self-reported symptom severity score. Outcome Measures The primary outcome measure was a CTS symptom severity scale developed by Levine et al 10 and a 30-day worst-discomfort rating on a 10-point visual analog scale (VAS). 11 The Levine symptom severity scale has 11 questions and uses a 5-point scale of severity for each symptom. The average score for the 11 items is reported. This scale has been validated among subjects treated for CTS and has been shown to be a valid scale with high reliability and sensitive to change after treatment. Surgical rates for CTS were also collected as a secondary outcome measure. All patients recruited into the study completed an expanded symptom questionnaire, 11 hand diagram, 9 VAS pain score by region, the Levine symptom severity scale, 10 surgical history, and medications history. Demographics such as age, height, weight, hand dominance, brief medical history including degree of avocational hand intensive activity, and prior trauma were included in the initial screening. Fig 2. Customized wrist splint used on treatment group.

3 RCT OF SPLINTING FOR CTS, Werner 3 Smoking history and exercise levels were self-reported. The symptom questionnaire also included a section of self-reported job satisfaction, perceived stress, and job insecurity, as proposed by Karasek et al. 12 The follow-up questionnaire included a repeat of the symptom survey and questions related to types and intensity of treatment. Subjects gave permission for their plant medical records to be reviewed. Treatment dates and medical evaluations were abstracted from these medical records. Each worker also had nerve conduction studies (NCSs) of the median and ulnar sensory nerves in each hand. Each nerve was tested using antidromic stimulation at 14cm, with the peak and take-off latencies recorded. The ring electrodes were maintained at a 3-cm distance, and the hand was warmed if the palm temperature was below 32 C. 13 A median mononeuropathy was defined if the median-ulnar sensory peak latency was 0.8ms or greater. 14 A clinical diagnosis of CTS was established if the hand diagram was abnormal and there was evidence of a median mononeuropathy. The nerve conduction data were collected at baseline and at the 12-month follow-up. Subjects reported to the medical department to have the testing done during regular work hours, and the person doing the testing was blinded to the treatment assignment. Each subject received a written personal statement of the results of their electrodiagnostic testing, with an interpretation of whether they met the criteria for CTS, based on symptoms and nerve conduction test criteria, along with a recommendation for follow-up with their personal physician. They received this approximately 2 months after the initial testing and after the repeat examination at the end of the study. Statistical Analysis A comparison of demographic factors and all identified confounders was performed between the treatment and control groups. The demographic factors and initial symptoms of the study dropouts were compared with those subjects who completed the study. We used t tests for continuous variables and chi-square tests for ordinal or dichotomous data. The variables included age, sex, baseline electrophysiologic measures, symptom severity (by region), smoking history, exercise level, body mass index (BMI), other medical conditions (eg, diabetes, arthritis), and psychosocial variables. The change in discomfort rating from time 1 to time 4 (12mo) was done within each group, to determine whether there was a significant change from baseline using a paired t test and an equal to.05. Change during each interval of testing and tests of linear trends were also performed. The change in the treatment versus the control group, from baseline to 12-month follow-up, was also tested using an unpaired t test (.05). Multivariate linear regression was used to determine whether the treatment effect was significant when controlling for possible confounders (.05). RESULTS The demographic data from the treatment and control groups are presented in table 1. A total of 63 subjects were recruited for the treatment group and 49 for the control group. The groups did not differ in terms of age, sex, BMI, smoking or exercise history, or most of the psychosocial measures. Subjects who declined or dropped out of the study did not differ from the active participants in terms of age, sex, symptom complaints, demographic variables, or electrophysiologic variables (where available) in terms of their baseline characteristics. The splinted group did differ from the control group in terms of their rating of job dissatisfaction: the splinted group members had a higher rating of job dissatisfaction than controls. The electrophysiologic measures of the median and ulnar sensory-evoked responses were similar in the 2 groups, except for the median nerve peak latency and the difference between the median and ulnar sensory peak latencies (see table 1). The control group had a greater prevalence of prolongation of the median sensory peak latency than of the ulnar peak latency. The discomfort scores at baseline and at 12-month follow-up are presented in table 2. The baseline discomfort ratings for the neck and shoulder, elbow and forearm, and hand and wrist were similar in both groups. There was statistical improvement in the discomfort scores among controls at the hand and wrist but not at any other sites. The treatment group showed improvement in discomfort scores at the elbow and forearm and at the hand and wrist but not at the shoulder and neck. The Levine symptom severity score improved for both the control and treatment groups. The degree of improvement in discomfort at the hand and wrist and elbow and forearm was significantly higher in the treatment group than in the control group. The treatment group had greater improvement in the Levine symptom severity score. The treatment effect reached statistical significance in the multivariate model but not in the univariate analysis (see table 2). For the analysis of change in discomfort score in the wrist, hand, and fingers, the study had a statistical power (1 ) of.86 using an equal to.05 when comparing the treated subjects with the control subjects; for the change in the Levine symptom severity score, the power was.49. Data collection was incomplete at the 3- and 6-month follow-up periods. Subjects were contacted by a study site coordinator and were reminded to fill out the questionnaire, but about half of the subjects did not complete the 3- or 6-month questionnaires. The trend in outcome measures at 3 and 6 months was similar to the results at 12 months. The 12-month follow-up data are presented because they represent a more complete data set. After the 6-week trial of splinting, 49% of the splinted group reported significant improvement in their symptoms, although only 1 person reported complete relief. The 12-month follow-up was actually a range of follow-up times, with an average of 12 months and a range of 7 to 15 months. In the multivariate analysis, the length of time for the 12-month follow-up was not a significant factor (see discussion of the multivariate analysis below). The groups did not differ in terms of prior treatments for an upper-extremity disorder. Prior treatments included splints, rest, ice or heat, nonsteroidal anti-inflammatory drugs (NSAIDs), physical therapy (PT), and steroid injections. Almost half the subjects had used NSAIDs or rest; fewer than 25% had been to PT at some time in the past. The record of self-reported treatment interventions, as well as those treatments provided by the plant medical department, was also tracked. The splinted group did report a higher level of continued splinting during the study (19% vs 10%, P.02), but the other treatments did not differ significantly. The splinted group did have a significantly higher number of visits to the plant medical department ( visits vs visits, P.02). The splinted group had more lost work days, but this was skewed by 1 worker and did not reach statistical significance ( d vs d, P.3). Given that the baseline nerve conduction data were not equivalent in the 2 groups after the randomization, a post hoc analysis of the effect of median nerve impairment on change in discomfort rating was performed. The most stable measure of median nerve impairment is the difference of the median nerve sensory peak latency minus the ulnar sensory peak latency. The control group had a mean difference of.6ms compared with a.4-ms difference among the treatment group. We analyzed how

4 4 RCT OF SPLINTING FOR CTS, Werner Table 1: Comparison of Splinted and Control Groups at Baseline Characteristic Controls (n 49) Splinted Group (n 63) P Age (range) (y) ( ) ( ).57 BMI (kg/m 2 ) Sex (% female) Hand dominance (% right-hand dominant) Diabetes (%) Rheumatoid arthritis (%) Current neck and shoulder symptoms (%) Current elbow and forearm symptoms (%) Current wrist, hand, and finger symptoms (%) Current smoking (%) Current exercise (%) CTS at baseline (% based on questionnaire) CTS at baseline (% based on hand diagram 1 and median-ulnar difference 0.5ms) CTS at baseline (% based on hand diagram 1 and median-ulnar difference 0.8ms) Median sensory peak latency (ms) Median sensory amplitude ( v) Median-ulnar peak latency difference (ms) Wrist, hand, and finger & elbow and forearm tendonitis (% based on self-report previous diagnosis) Shoulder tendonitis (% based on self-report previous diagnosis) Neck and shoulder discomfort rating now Neck and shoulder discomfort rating in last 30d Elbow and forearm discomfort rating now Elbow and forearm discomfort rating in last 30d Wrist, hand, and finger discomfort rating now Wrist, hand, and finger discomfort rating in last 30d Levine symptom severity score Skill discretion Creativity Decision authority Supervisor support Job dissatisfaction Coworker support Job insecurity NOTE. Values are mean standard deviation (SD) or as otherwise indicated. subjects with more median nerve impairment compared with subjects with normal median nerve function. We selected a cutoff of a.5-ms difference to dichotomize the groups into subjects with median nerve impairment and subjects with healthy median nerves. A.5-ms cutoff is used in many laboratories as the criterion for abnormality, and this allowed for relatively equal numbers of subjects in each group. We examined the change in discomfort rating over time in the control and treatment groups. The data are presented in table 2. To account for the additional post hoc analyses (an additional 4 comparisons), a Bonferroni adjustment was made and the set at.025 for this analysis (new.05/[no. of comparisons].5 ). Subjects with a healthy median nerve, within the control group, had significant improvement of their hand and wrist discomfort scores, whereas those with median nerve impairment did not improve with time. The treatment group had improvement with time regardless of the baseline health of the median nerve. The same relationship was found for the Levine symptom severity scores and the elbow and forearm discomfort scores. The multiple linear regression model used change in the wrist, finger, and hand discomfort score as the dependent variable and looked at splinting treatment as the primary independent variable. The change in the Levine CTS symptom severity score was also used as a dependent outcome variable. We also included a number of possible confounding variables, such as age, sex, medical history, exercise level, and smoking, as well as initial discomfort ratings and duration of symptom episodes as independent variables. Psychosocial variables included scales for job insecurity, job dissatisfaction, and perceived stress, and these were considered independent variables. Other independent variables included new treatment for hand and wrist complaints during the study interval and self-assessment of splint usage during the 6-week trial. The length of time from the first to the last follow-up was also included in the model. The regression models showed that the treatment with splints was a significant variable, even when controlling for other confounders. When modeling the change in hand and wrist discomfort scores (n 83: 45 cases, 38 controls), the variables that were significant in the model included initial discomfort score, presence of median nerve impairment, job insecurity, a history of treatment for a hand and wrist problem, and the length of time that episodes of discomfort symptoms typically lasted. A higher initial discomfort score was related to more relief during the study period. Less impairment of the median nerve was associated with better outcomes. A higher rating of

5 RCT OF SPLINTING FOR CTS, Werner 5 Region Table 2: Change in 30-Day Discomfort and Levine Symptom Severity Scores at Baseline and at 12 Months Splinted Group Baseline Change in 30-Day Discomfort and Levine Symptom Severity Scores by Region Splinted Group Follow-Up P Control Baseline Control Follow-Up P P for Comparison of Change in Score Between Splinted Group and Controls Wrist, hand, and finger discomfort in the last 30d (n 58) (n 58) (n 45) (n 45) Elbow and forearm discomfort in the last 30d (n 61) (n 61) (n 48) (n 48) Levine symptom severity score (n 63) (n 63) (n 47) (n 47) Treatment and Control Groups; Stratified by MUDIFF Change in 30-Day Discomfort Scores for the Wrist, Hand, and Finger, Stratified by Baseline MUDIFF Baseline Discomfort Rating Follow-Up Discomfort Rating P Mean Change in Discomfort Rating Splinted group with MUDIFF 0.5ms Controls with MUDIFF 0.5ms Splinted group with MUDIFF 0.5ms Controls with MUDIFF 0.5ms NOTE. Values are mean SD. Abbreviation: MUDIFF, median-ulnar peak latency difference. job insecurity was associated with less improvement with time. Workers with a history of treatment for a wrist and hand problem were less likely to improve. A history of longer episodes of discomfort was associated with poorer outcomes. The model was significant at P less than.001 and had an R 2 value of.40. All other independent variables fell out of the regression model. The results of the regression analysis are presented in table 3. When the change in the Levine symptom severity score was modeled (n 94: 52 cases, 42 controls), the main effect of treatment was significant at the P equal to.02 level. There had been a trend toward significance in the univariate model, but when controlling for the other variables, the main effect of treatment was significant. The other variables that were significant in the model included the initial Levine symptom severity score, the presence of median nerve impairment, the duration of each discomfort episode, and whether symptoms woke the subjects from sleep. As with the discomfort modeling, a higher initial Levine symptom severity score was associated with more improvement, more impairment of the median nerve was associated with poorer improvement, and a longer duration of each episode was related to less improvement. Waking during sleep was related to less improvement. The model as a whole was significant at P less than.001 and had an R 2 equal to.31. Table 3: Results of Regression Analysis: Modeling Change in Discomfort and Levine Symptom Severity Scores Linear Regression Model With Change in the Wrist, Hand, and Finger 30-Day Discomfort Score as the Dependent Variable* Independent Variables Coeff SE t P t 95% CI Splint treatment Baseline worst discomfort rating in last 30d Job insecurity to 0.03 Baseline MUDIFF ( 0.5ms or 0.5ms) History of treatment for hand and wrist to 0.16 Length of average episode of wrist, hand, and finger discomfort to 0.14 Linear Regression Model With Change in the Levine Symptom Severity Score as the Dependent Variable Independent Variables Coeff SE t P t 95% CI Splint treatment Baseline Levine score Baseline MUDIFF ( 0.5ms or 0.5ms) Length of each episode of wrist, hand, and finger discomfort to 0.02 Nocturnal symptoms to 0.04 Abbreviations: CI, confidence interval; Coeff, coefficient; SE, standard error. *N 83; F 8.43; probability greater than F.001; R N 94; F 8.06; probability greater than F.001; R 2.31.

6 6 RCT OF SPLINTING FOR CTS, Werner Surgical rates for CTS during the follow-up period were low in both groups. There were 3 CTR surgeries among the splinted group (5%) and 2 among the controls (4%) (P.9). The number of clinic visits for CTS-related symptoms was higher in the splinted group, but this reflected the postoperative visits of 2 of the CTR subjects. The other surgically treated subjects did not report to the medical department for follow-up visits. DISCUSSION This is the first RCT of wrist splinting for presumptive symptoms of CTS. It showed that a 6-week trial of wrist splinting reduced discomfort scores, that there was a trend toward improvement in the Levine symptom severity scores among the treatment group, and that the improvements persisted for a year. Both the treatment and control groups had improvement of symptoms over time, but the rate of improvement tended to be higher among the splinted group. The improvement was significant after controlling for other covariants, such as median nerve impairment and initial presentation of symptom intensity and duration. The results were significant when measuring global hand discomfort ratings and showed a similar trend with the Levine severity rating. Despite the wide use of splinting as a primary treatment of CTS, there has not been an RCT of splinting versus other conservative management of CTS. 5 There has been an RCT of splinting plus steroid injection versus conventional conservative care that showed that the combination of interventions was beneficial among people with mild CTS. 15 Another RCT was recently completed in Europe that compared splinting and CTR surgery for management of CTS. 16 The study showed that surgery was the more effective intervention, with 85% having a favorable outcome with surgical release versus 65% with splinting. Many of the people in the splinted group were crossovers to surgery, and this may have improved the outcomes for the splinted group. All these studies involved patients who presented for medical care and were diagnosed with CTS. In contrast, our study examined the efficacy of splints among subjects with symptoms consistent with CTS but not necessarily having the diagnosis established. The loss of work days is primarily due to the surgical intervention frequently used for management of CTS. If identification of workers with early symptoms and use of wrist splints as a primary intervention can significantly reduce symptoms associated with CTS, then it is reasonable to project that early splinting may reduce the likelihood of developing CTS with its associated surgery and lost work time. In our study, only 5 subjects went on to surgical release of the carpal tunnel, which is too small a sample size to assess this outcome. The treatment group had more lost work days, but this was driven by 1 outlier and did not reach statistical significance. The splinted group did have more plant medical visits, but these were not specific for CTS. Further study with a larger sample size and/or a longer follow-up will be necessary to prove this hypothesis. The splinted group also had relief of symptoms at the elbow and forearm region. This may simply reflect referred pain from the median nerve entrapment, but it is possible that the splinting was also beneficial for other generalized musculoskeletal disorders, including tendonitis, localized muscle fatigue, or arthritis. The finding that controls with more severe median nerve impairment did not have improvement of their elbow and forearm symptoms suggests that these symptoms are more likely related to carpal tunnel symptoms than to other musculoskeletal disorders. The self-reported amount of time the splint was worn did not seem to influence the results that is, workers who wore the splints for longer times did not have more improvement. A subset of the splinted group (n 13) wore a splint that had a monitoring device a that determined the actual usage of the splint. The device monitors temperature and movement to determine the time the splint is being actively used. The selfreported use did not correlate well with the actual use data. Most participants overestimated their use patterns. Given the findings from the small subset, it is clear that self-reported use is not an accurate portrayal of actual usage, and the value of the self-reported use data is questionable. The study by Walker et al 6 did suggest that the amount of time the splint was worn influenced the outcome, with people who wore the splint day and night having better results than nighttime-only users. The difference was most profound regarding the change in nerve conduction function over time, with the day-and-night users having improvement in nerve function; the night-only users did not have improvement in nerve function, but both groups had improvement in symptoms. Our results were very similar to those of the Walker study, 6 in which the night-only users had no change in nerve conduction but did have significant reduction in symptom severity. The other factors that influenced the change in discomfort rating over time include the intensity of symptoms at baseline, the duration of symptom episodes, the degree of impairment of the median nerve, perceived job insecurity, and the history of treatments for an upper-extremity problem. The higher the initial discomfort rating, the more likely the person was to report improvement. This may reflect a simple regression to the mean. Because workers were recruited on a rolling basis, it is unlikely related to any seasonal variation in the work intensity. All subjects did get instruction in industrial ergonomic principles, and this may have had an impact on the subjects with the highest level of discomfort. The association between a longer duration of symptoms during each episode and lower rates of improvement has biologic plausibility. Those workers with more chronic complaints may represent a subset of workers who are more resistant to treatment and may have failed other home remedies and thus would not be as likely to improve with time, regardless of the intervention. Similarly, workers with a history of seeking treatment for a wrist, hand, or finger disorder (diagnosed by a physician or by self-assessment) in the past were less likely to improve with time. This also seems to suggest a more chronic and resistant process, and it is understandable that this group of workers might not resolve spontaneously. The workers who reported waking at night were more likely to have less improvement with time on the Levine symptom severity scale. Symptoms at night may reflect a more severe case of CTS, which may not respond to treatment. Several of the questions that make up the Levine symptom severity questionnaire ask specifically about nocturnal symptoms; if these symptoms persist, then the scores are less likely to improve. If the splint is worn for only 6 weeks and the subject responds at 12 months that his/her nocturnal symptoms are persisting, this may reflect the timing of the questionnaire and the lack of splint use later in the study. The workers who reported more perceived job insecurity were less likely to improve. This may reflect a higher stress level; psychosocial variables have been strongly related to outcomes for low back pain, but they are less commonly related to upper-extremity musculoskeletal disorders. Reported job insecurity has been associated with higher reporting of general health complaints, and this may be a factor in the relative lack of improvement in symptoms. 17 The finding that the control group had more median nerve impairment than the splinted group, despite the randomization

7 RCT OF SPLINTING FOR CTS, Werner 7 process, was a concern. The more median nerve impairment identified, the less likely the worker would improve with time. Although this was a significant relationship, there appears to be a differential response to this factor dependent on the treatment group. Among controls, there was a significant difference between the subset of workers with the most impairment of the median nerve and those with a normal median nerve function (.5-ms difference). The controls with a normal median nerve got better with time, whereas those workers with a significant impairment of the median nerve did not improve with time. However, in the treatment group, both subsets of workers made significant improvement. Impairment of the median nerve is a characteristic finding of CTS. Workers with normal median nerve function probably had other sources of hand discomfort that were not associated with CTS, and their symptoms resolved over time without any treatment; however, control subjects with median nerve involvement were more likely to have classic CTS and therefore without treatment would not be expected to improve. In the splinted group with median nerve impairment, the intervention was successful, and most workers had a decrease in their hand symptoms despite the median nerve impairment. The follow-up NCSs did not show an improvement in median nerve function with time, but the electrophysiologic measures are not a particularly sensitive measure of change, and a median sensory response may persist even after surgery and resolution of symptoms. 5 Our study had several limitations that could have influenced the interpretation of the findings. The sample size was small, and this limits the power of the study to determine statistical significance of some of the secondary outcome measures and stratified analyses. A larger study is necessary to confirm these findings and to show generalizability to other work sites. The lack of full data at 3- and 6-month follow-up limits the interpretation of the outcome measures. Because the intervention was for only 6 weeks, the optimal effects would be expected at the 3-month evaluation. Although the trend toward improvement was present at 3 months, the reduced sample size limited the statistical analysis, and this should be addressed in future studies. Additionally, the missing data in the logistic regression model may have biased the analysis. The Levine symptom severity scale was not significant in the univariate analysis but was significant in the logistic regression. The trend was similar in each analysis, but the loss of study subjects in the logistic model may have confounded the analysis. A larger randomized study would have greater likelihood of controlling for these confounders without use of logistic regression. CONCLUSIONS Active surveillance via a simple symptom survey can identify workers at risk for CTS, and early use of a nighttime splint can reduce symptoms in the hand and elbow region. The rate of surgery for workers treated with a splint was the same as for controls. A larger study with a longer follow-up is needed to clarify whether this intervention results in reduced morbidity and cost savings reflected in fewer lost work days. References 1. Adams ML, Franklin GM, Barnhart S. Outcome of carpal tunnel surgery in Washington State workers compensation. Am J Ind Med 1994;25: Franklin GM, Huang J, Heyer N, Checkoway H, Peck N. Occupational carpal tunnel syndrome in Washington state, Am J Pub Health 1991;81: Occupational disease surveillance: carpal tunnel syndrome. MMWR Morb Mortal Wkly Rep 1989;38: Bureau of Labor Statistics website. Available at: Accessed August 5, Gerittsen AA, de Krom MC, Struijs MA, Scholten RJ, de Vet HC, Bouter LM. Conservative treatment options for carpal tunnel syndrome: a systemic review of randomized controlled trials. J Neurol 2002;249: Walker WC, Metzler M, Cifu DX, Swartz Z. Neutral wrist splinting in carpal tunnel syndrome: a comparison of night-only versus full-time wear instructions. Arch Phys Med Rehabil 2000;81: Practice parameters for electrodiagnostic studies in carpal tunnel syndrome (summary statement). American Academy of Neurology, American Association of Electrodiagnostic Medicine, and American Academy of Physical Medicine and Rehabilitation [published erratum in: Neurology 1994;44:367]. Neurology 1993; 43: Russell GS, Wong DA, Henke JA. Clinical policies American Academy of Orthopaedic Surgeons. Park Ridge: AAOS; p Franzblau A, Werner RA, Albers JW, Olinski D, Johnston E. Workplace surveillance for carpal tunnel syndrome using hand diagrams. J Occup Rehabil 1994;4: Levine DW, Simmons BP, Koris MJ, et al. A self-administered questionnaire for the assessment of severity of symptoms and functional status in carpal tunnel syndrome. J Bone Joint Surg Am 1993;75: Franzblau A, Werner RA, Valle J, Johnston E. Workplace surveillance for carpal tunnel syndrome: a comparison of methods. J Occup Rehabil 1993;3: Karasek R, Brisson C, Kawakami N, Houtman I, Bongers P, Amick B. The Job Content Questionnaire (JCQ): an instrument for internationally comparative assessments of psychosocial job characteristics. J Occup Health Psychol 1998;3: Kimura J. Electrodiagnosis in diseases of nerve and muscle: principles and practices. Philadelphia: FA Davis; p Salerno DF, Franzblau A, Werner RA, Bromberg MB, Armstrong TJ, Albers JW. Median and ulnar conduction studies among workers: normative values. Muscle Nerve 1998;21: Gelberman RH, Aronson D, Weisman MH. Carpal-tunnel syndrome. Results of a prospective trial of steroid injection and splinting. J Bone Joint Surg Am 1980;62: Gerritsen AA, de Vet HC, Scholten RJ, Bertelsmann FW, de Krom MC, Bouter LM. Splinting vs surgery in the treatment of carpal tunnel syndrome: a randomized controlled trial. JAMA 2002;288: Mohren D, Swaen G, van Amelsvoort L, Borm P, Galama J. Job insecurity as a risk factor for common infections and health complaints. J Occup Environ Med 2003;45: Supplier a. Compliance Laboratories, W 80th St, Lenexa, KS