Evidence Report/Technology Assessment: Number 62
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Under its Evidence-based Practice Program, the Agency for Healthcare Research and Quality (AHRQ) is developing scientific information for other agencies and organizations on which to base clinical guidelines, performance measures, and other quality improvement tools. Contractor institutions review all relevant scientific literature on assigned clinical care topics and produce evidence reports and technology assessments, conduct research on methodologies and the effectiveness of their implementation, and participate in technical assistance activities.
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Overview / Reporting the Evidence / Methodology / Findings / Future Research / Availability of Full Report
This report is a systematic evaluation of the evidence pertaining to a broad range of issues related to the diagnosis and treatment of worker-related upper extremity disorders (WRUEDs). For the purposes of this report, “worker-related” is defined as a disorder that affects workers, not as a disorder necessarily caused by work. Four disorders are the focus of this report; carpal tunnel syndrome, cubital tunnel syndrome, epicondylitis, and de Quervain's disease.
The first two disorders are the result of nerve entrapment. Carpal tunnel syndrome is the result of increased pressure on the median nerve in the carpal tunnel of the wrist, resulting in sensory and motor disturbances in the parts of the hand innervated by this nerve. Cubital tunnel syndrome results from increased pressure on the ulnar nerve in the cubital tunnel of the elbow, resulting in sensory and motor disturbances in the parts of the forearm and hand innervated by this nerve. The second two disorders are the result of stress to the tendons of the elbow and wrist, respectively. All four disorders can lead to pain, loss of function, and long-term disability.
The overall prevalence of carpal tunnel syndrome in the United States may be as high as 1.9 million people, and each year there are 300,000-500,000 operations for the condition. Epicondylitis has been reported to affect 4.23 individuals per 1,000 adults per year in the U.S. The prevalence of cubital tunnel syndrome and de Quervain's disease has not been established.
In this evidence report, the Evidence-based Practice Center (EPC) assessed the published literature describing the effects of these disorders, before and after treatment, on patients, particularly workers. They did this by examining the literature pertaining to 13 key questions.
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Reporting the Evidence
This report addresses 13 questions regarding worker-related disorders of the upper extremity. Eleven of these are condition-specific. Therefore, the EPC individually addressed them for each of the four above-mentioned disorders. Two questions are not condition-specific. Therefore, the EPC addressed them only once.
The 11 condition-specific Key Questions addressed in this evidence report are:
Question 1: What are the most effective methods and approaches for the early identification and diagnosis of worker-related musculoskeletal disorders of the upper extremity?
Question 2: What are the specific indications for surgery for worker-related musculoskeletal disorders of the upper extremity?
Question 3: What are the relative benefits and harms of various surgical and nonsurgical interventions for persons with worker-related musculoskeletal disorders of the upper extremity?
Question 4: Is there a relationship between specific clinical findings and specific treatment outcomes among patients with worker-related musculoskeletal disorders of the upper extremity?
Question 5: Is there a relationship between duration of symptoms and specific treatment outcomes among patients with worker-related musculoskeletal disorders of the upper extremity?
Question 6: Is there a relationship between factors such as patients' age, gender, socioeconomic status and/or racial or ethnic grouping and specific treatment outcomes among patients with worker-related musculoskeletal disorders of the upper extremity?
Question 7: What are the surgical and nonsurgical costs or charges for treatment of worker-related musculoskeletal disorders of the upper extremity?
Question 8: For persons who have had surgery for worker-related musculoskeletal disorders of the upper extremity, what are the most effective methods for preventing the recurrence of symptoms, and how does this vary depending on subject characteristics or other underlying health problems?
Question 9: What instruments, if any, can accurately assess functional limitations in an individual with a worker-related disorder of the upper extremity?
Question 10: What are the functional limitations for an individual with a worker-related musculoskeletal disorder of the upper extremity before treatment?
Question 11: What are the functional limitations of an individual with a worker-related musculoskeletal disorder of the upper extremity after treatment?
The two Key Questions that are not condition-specific are:
Question 12: What are the cumulative effects on functional abilities among individuals with more than one worker-related musculoskeletal disorder of the upper extremity in the same limb?
Question 13: What level of function can patients achieve in what period of time when they are required to change hand dominance as a result of injury to their dominant hand?
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A panel of nine Technical Experts was employed to assist in defining the scope of this evidence report, developing its questions, and developing the criteria for retrieving and including articles.
To identify information for this evidence report, the EPC searched 31 electronic databases, the World Wide Web, and four U.S. Government databases. In addition to these searches, researchers also reviewed the bibliographies and reference lists of all studies included in this evidence report, searched Current Contents®/Clinical Medicine on a weekly basis, and routinely reviewed over 1,600 journals and supplements maintained in ECRI's collections.
To be included in this evidence report, an article had to meet a set of a priori retrieval criteria and a set of a priori question-specific inclusion criteria. The EPC designed broad retrieval criteria to ensure comprehensive retrieval. They retrieved an article whenever there was uncertainty about whether it met the retrieval criteria. They also retrieved articles when an abstract was not present in the search results, but when the title of the article suggested that it was relevant. The criteria for article retrieval are briefly summarized below:
- The patients had to have been diagnosed with a worker-related disorder of the upper extremity.
- All controlled trials, regardless of whether they were described as randomized or prospective, were retrieved, regardless of year of publication.
- Case series and other reports were evaluated only if published in 1980 or later and included 10 or more patients.
- Only English-language articles were retrieved.
Once an article was retrieved, it was examined to determine whether it met the question-specific criteria. The major criteria are briefly summarized below; additional question-specific inclusion criteria, which are not listed here, were also applied:
- The study could not have a serious design flaw that precluded interpretation of the results.
- The study must have addressed one of the key questions and have included patients with one of the WRUEDs of interest.
- For studies addressing Key Question 3, the study must have been a controlled trial.
- The study must have reported on at least one of the seven key outcomes addressed in this assessment. The outcomes are: pain, function, quality of life, ability to return to work, ability to return to activities of daily living, harms, and global outcome.
A global outcome is any score that attempts to encompass the overall success or failure of the treatment. It may be a numerical rating of overall symptom relief or patient satisfaction, a categorical rating such as excellent, good, fair or poor, or a dichotomous rating such as the answer to the question “Would you undergo this procedure again?”
Data from all articles that met our inclusion criteria were abstracted using electronic data abstraction forms. Separate data abstraction forms were designed for entering data about basic trial design information; patient signs, symptoms, comorbidities, characteristics, and treatments; reporting of treatment outcomes; surgical complications; and nerve conduction measurements.
The EPC employed a variety of statistical methods in this evidence report. Meta-analyses of studies of treatments were conducted using Hedges' d as a measure of each study's effect size, and then computing the precision-weighted summary d from the combined results of all studies. Hedges' d is the difference between the means of any study's two groups expressed in standard deviation units. Researchers employed two tests for heterogeneity, the Q statistic and each study's standardized residual. The EPC researchers regarded the data as heterogeneous if the results of either test were statistically significant.
Diagnostic test meta-analyses were performed according to the method of Littenberg and Moses. The researchers took the mean threshold as the best estimate of a single threshold, and the values of sensitivity and specificity at the mean threshold as the single best global estimate of test effectiveness. Before using the results of a meta-analysis of diagnostics, they verified that there was no statistically significant heterogeneity among the results of the included articles using the Q statistic. If heterogeneity was detected, they removed any subgroups that caused the heterogeneity from the analysis. If there were no subgroups in the analysis, or those subgroups did not cause the heterogeneity, they looked for data points that were outliers, and reported the meta-analytic results with and without exclusion of these outliers.
The EPC performed numerous other statistical computations in addition to those involved in performing meta-analyses. Briefly, these were:
- Corrections for patient attrition.
- Statistical power analyses.
- Multiple regression for certain questions when such results were of interest.
- Computations of effect sizes for all studies, when possible, even when no meta-analysis was performed.
- Determinations of whether there were statistically significant differences between the characteristics of patients in any given study.
- Computation of pretreatment effect sizes.
- Verification of diagnostic test characteristics.
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Carpal Tunnel Syndrome
Question 1: What are the most effective methods and approaches for the early identification and diagnosis of carpal tunnel syndrome?
- The evidence base on most individual diagnostic tests for carpal tunnel syndrome is small, even though the total number of articles on CTS diagnosis is large. This is because many different tests have been described. Nerve conduction tests are most frequently reported in the literature, but there is great diversity in their methods.
- The results of our analyses may overestimate the specificity of nerve conduction measurements in typical practice. This is because the trials we examined used healthy, asymptomatic persons as controls. In clinical practice, the test would be used on workers believed to be at risk for CTS or persons suspected of having CTS. Under these conditions, the false positive rate would be higher, and the specificity correspondingly lower.
- The most frequently reported nerve conduction tests were distal motor latency and palmar sensory latency. For both tests, clinicians chose thresholds that yielded high specificity (a low incidence of false-positive results). The EPC's meta-analyses of distal motor latency studies found the sensitivity of the test to be 57-66 percent and the specificity to be 98 percent. Meta-analysis of palmar sensory latency studies found a sensitivity of 76 percent and a specificity of 98 percent.
- Clinical signs and symptoms are also used in the diagnosis of CTS. They attempted to use their meta-analysis techniques to obtain summary values for the sensitivity and specificity of two such signs: Tinel's sign and Phalen's maneuver. In both cases, there was heterogeneity in the published results that could not be explained by differences in patient selection or by single outlier studies. Therefore, they did not calculate summary measurements for sensitivity or specificity. The sensitivity of Phalen's maneuver was lower than its specificity, and two trials reported sensitivity of 80-90 percent. All of the studies of Tinel's sign found that its sensitivity was lower than its specificity, and none found a sensitivity of 75 percent or greater. There was too much heterogeneity in the results for them to conclude that one test was superior to the other, or to compare these tests to nerve conduction testing.
- Regarding sensory tests, composite nerve conduction tests, and imaging tests, there was insufficient evidence for the EPC to perform meta-analyses of clinical trial results.
- Their well-designed study suggests that nerve conduction measurement may be able to identify some workers at risk of developing CTS in the future. By itself, this evidence is not sufficient for the EPC to conclude that nerve conduction screening for CTS is effective.
Question 2: What are the specific indications for surgery for carpal tunnel syndrome?
- Patients who have undergone surgery for carpal tunnel syndrome are predominantly middle aged and female.
- Because of underreporting, no firm evidence-based conclusions can be drawn regarding the signs, symptoms, neuroelectrical characteristics, and comorbidities of these patients.
Question 3: What are the relative benefits and harms of various surgical and nonsurgical interventions for persons with carpal tunnel syndrome?
- Meta-analysis of studies comparing open and endoscopic carpal tunnel release show a small but statistically significant advantage to endoscopic release in global treatment outcome. In addition, the data show a trend toward faster return to work and to activities of daily living among patients receiving endoscopic release. However, these findings must be viewed only as trends in currently available data. This is because they are based on a meta-analysis that contained a number of non-randomized, non-blinded studies. Data from these studies also suggests that endoscopic release has a higher complication rate and a higher rate of reoperation compared to open release. The higher reoperation rates likely arise because of incomplete transection of the transverse carpal ligament. Exact complication rates cannot be determined from presently available data. Presently available data also do not allow one to reach firm evidence-based conclusions about the relative effects of open and endoscopic surgery on the ability of patients to perform daily functions.
- Meta-analysis of global outcomes demonstrates a potential benefit from not performing neurolysis. Available return to work data also shows a trend toward an advantage to not performing neurolysis. There is insufficient data to determine the effect of neurolysis on pain and function. The available evidence suggests there is little or no benefit from performing neurolysis along with surgical release of the carpal tunnel. The possibility remains that neurolysis may be helpful in special cases, such as in the presence of marked scarring or neural adhesion, but no available evidence specifically documents the benefits and harms of neurolysis among such patients.
- Results of four studies suggest that injection of steroid into the carpal tunnel yields superior global outcomes compared to no treatment, placebo, or oral steroids. However, relief from steroid treatments is not complete. Carpal tunnel injection was significantly better than intramuscular injection at a 1 month followup time. Because no further time points were reported, researchers are unable to determine whether this difference persists beyond this time. There are no data available that indicate whether any type of steroid may be superior to any other, or whether any particular dose is optimum. Although the effects of steroid injection may wear off over time, there is no information indicating the expected duration of relief for the average patient, or whether any patients can expect to experience permanent relief.
- Two double-blinded randomized controlled trials suggest that oral steroids may lead to a reduction in symptoms of CTS. However, the effects of oral steroids are short-lived and may not be sufficient for patient satisfaction. The effects of higher steroid doses or longer treatment regimens have not been examined in published controlled trials.
- A single published randomized controlled trial indicates that oral tenoxicam (a NSAID) and trichlormethiazide (a diuretic) do not reduce the symptoms of CTS under the dosing regimens described. Further trials are needed to confirm this observation, and to test the effects of additional drugs and dosing regimens.
- Results of a single study suggest that manual therapy may have some use in the treatment of carpal tunnel syndrome. This study suggests that carpal bone mobilization provides pain relief, improves function, and delays or eliminates the need for surgery among patients with carpal tunnel syndrome. However, this small study was unblinded. Results from neurodynamic mobilization show a similar trend, but because of a lack of statistical power one cannot conclude that this trend is real. For the same reason, differences in effectiveness between these two treatment groups cannot be determined. A large, blinded, randomized controlled trial is necessary to confirm these results.
- A larger, more statistically powerful study found no difference between the effects of a physical therapy program and home exercise instructions on pain or function. However, patients receiving physical therapy returned to work faster than those instructed to exercise at home.
- Although these studies indicate a trend toward some forms of physical therapy having an effect on carpal tunnel syndrome, their small size and design difficulties make it difficult to arrive at a firm evidence-based conclusion.
- Only one study meeting inclusion criteria addresses the use of ultrasound for carpal tunnel syndrome. Because of this, and because of its associated design and analysis difficulties, one cannot reach a firm evidence-based conclusion.
- Splint use was addressed only by a single trial that had design difficulties. Because of this, one cannot reach a firm evidence-based conclusion about splint use. There may be conditions under which splints offer an advantage and conditions under which they do not, but this is not addressed by available evidence.
- The results of one study suggest that suboptimal outcomes are obtained when patients receive ligament reconstruction. However, this trial was neither randomized nor blinded, so one cannot draw firm evidence-based conclusions from it.
- Although the low statistical power of the one relevant study prevents any solid conclusion from being drawn, this study does not support the therapeutic effectiveness of Vitamin B6. This is because it showed a trend toward a greater percentage of improved patients in the placebo group.
Question 4: Is there a relationship between specific clinical findings and specific treatment outcomes among patients with carpal tunnel syndrome?
- The only clinical finding variable shown by more than one study to significantly predict treatment outcomes was electrodiagnostic testing. Patients with mildly impaired or normal results of electrodiagnostic tests had longer sick leaves and were less likely to be satisfied with the results of treatment. This finding was statistically significant in three of the four studies examining this relationship.
- This apparent lack of consistency of results could indicate that, although the relationship between electrodiagnostic tests and treatment outcomes is statistically significant, it may not be substantial. The possibility that this relationship is small is supported by the results of stratified studies that examined the relationship between electrodiagnostic test results and global outcomes. Six of seven studies did not find a statistically significant relationship.
Question 5: Is there a relationship between duration of symptoms and specific treatment outcomes among patients with carpal tunnel syndrome?
- The majority of available evidence is less than optimal because it consists primarily of retrospective studies. The highest quality study (prospective with multiple regression analysis) suggested that there was no statistically significant correlation between duration of symptoms and global outcome after surgery. One prospective and two retrospective stratified studies found similar results. Two retrospective studies (one performing multiple regressions, one stratified) found a statistically significant relationship between shorter duration of symptoms and symptom resolution or patient satisfaction after surgery. The retrospective nature of these trials could have created bias that influenced these findings. An additional high quality prospective study is needed before firm conclusions can be reached.
Question 6: Is there a relationship between factors such as patients' age, gender, socioeconomic status and/or racial or ethnic grouping and specific treatment outcomes among patients with carpal tunnel syndrome?
- The available evidence suggests that patients who are not receiving workers' compensation tend to return to work faster than those receiving such compensation. This is suggested by one of two “multiple regression” studies of this relationship and by a combination of 10 prospective and retrospective stratified studies. Evidence of a relationship does not constitute evidence of causality.
- Some evidence also suggests that patients who are not receiving workers' compensation have better global outcomes, but this evidence is derived exclusively from retrospective studies. Therefore, these latter findings require confirmation.
- Available evidence suggests that there is no strong relationship between gender, employment status, or hand dominance and return to work or global outcomes.
- There is insufficient evidence to arrive at a firm evidence-based conclusion on the relationship between type of work, presence of diabetes, or age and patient outcomes.
Question 7: What are the surgical and nonsurgical costs or charges for treatment of carpal tunnel syndrome?
- According to the Medicare Provider Analysis and Review (MEDPAR) database, which covers hospital inpatient services, average total charges per patient for the DRG (diagnosis-related group) of carpal tunnel release are $8,185.24 (calculated by dividing total charges by number of discharges). This DRG includes open and endoscopic release.
- The Median Costs for Hospital Outpatient Services Dataset contains median costs for services that are reimbursed under Medicare for the hospital outpatient prospective payment system. The reported median cost for endoscopic release of the transverse carpal ligament is $849.84 (cost of open release was not reported by this database). The reported median cost for application of a short arm static splint is $72.69.
Question 8: For persons who have had surgery for carpal tunnel syndrome, what are the most effective methods for preventing the recurrence of symptoms, and how does this vary depending on subject characteristics or other underlying health problems?
- No controlled trials have been published that report on the efficacy or effectiveness of any technique for the prevention of recurrence of carpal tunnel syndrome. In the absence of controlled trials, no analysis may be performed and no evidence-based conclusions may be drawn.
Question 9: What instruments, if any, can accurately assess functional limitations in an individual with carpal tunnel syndrome?
- Three prospective cohort trials have indicated that the SF-36 is not a useful instrument for assessing functional limitations in individuals with carpal tunnel syndrome. The SF-36 was reported to be unresponsive to treatment and unable to predict ability to work.
- Four prospective cohort trials have indicated that the Levine CTS-I may be a useful instrument for assessing functional limitations in individuals with carpal tunnel syndrome. This instrument was reported to be responsive to treatment, and to have concurrent validity as measured by grip and pinch strength. However, the studies that addressed the Levine CTS-I did not examine its internal reliability, content validity, or its ability to predict how well patients could perform activities of daily living. In addition, the Levine CTS-I has been reported by one study to be unable to predict ability to work.
- No other instrument has been evaluated by more than one study. It is difficult to reach an evidence-based conclusion as to the usefulness of the other instruments evaluated in this report due to the limited evidence base.
Question 10: What are the functional limitations for an individual with carpal tunnel syndrome before treatment?
- There is some evidence to suggest that most untreated patients with carpal tunnel syndrome have mild to moderate functional difficulties before treatment. However, this evidence is derived from only two studies comprised of a total of 51 patients. This is too few patients and too few studies to allow one to reach a firm evidence-based conclusion.
Question 11: What are the functional limitations of an individual with carpal tunnel syndrome after treatment?
- Although studies of non-surgical therapies suggested that most patients experience only mild difficulty with functional activities after treatment, it is unclear whether the results of these two studies are generalizable to the larger patient population.
- Studies with surgical outcomes suggested that most patients report no-to-moderate difficulty with functional activities (mean 1.4-2.6 on the Levine CTS-I) after surgery.
- Although there were no statistically significant differences between specific patient groups, there was a trend toward more difficulty with functional activities among workers' compensation patients in surgical studies. This trend was based on the results of two studies.
- The available data are insufficient to determine a cutoff point on measuring scales above which patients are unable to work.
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