Abstract
Background
We sought to determine the diagnostic utility of the flexion-compression (F-C) test for carpal tunnel syndrome (CTS). Using electrodiagnostic testing as the gold standard, we hypothesized that the F-C test would be a better diagnostic test for CTS as compared to the wrist flexion (Phalen's) or palmar compression (Durkan's) tests alone.
Methods
We studied patients who presented with and without CTS symptoms, designated as study and control group patients, respectively. At the first clinic visit, all patients were evaluated using the CTS-6 score, and then the Phalen's, Durkan's, and F-C tests in a random order. Patients in the study group were then sent for electrodiagnostic testing.
Results
162 patients were included after power analysis, 81 each in the study and control groups. Among study group patients with electrodiagnostic evidence of CTS, the positive likelihood ratio (LR+) of the Phalen's test (1.29) was higher than the Durkan's (1.06) and F-C (0.95) tests, though less than the CTS-6 score (1.64). Performing any physical exam test in conjunction with the CTS-6 score was not more useful than the CTS-6 alone. As expected, all three physical exam maneuvers were more likely to be positive among study patients compared to control patients.
Conclusions
None of the physical exam maneuvers were highly predictive of electrophysiologically-positive CTS. The CTS-6 score alone better predicts electrodiagnostic evidence of CTS than physical exam, though it only very slightly increases the post-test probability of disease. Formal electrodiagnostic testing remains important in diagnosing CTS when compared to physical exam maneuvers and CTS-6.
1. Introduction
Carpal tunnel syndrome (CTS) is the most common peripheral nerve compression syndrome, causing pain and morbidity, and affects up to 3.8–4.9 % of adults.1,2 Tinel, Phalen, and Durkan described several classic physical examination maneuvers that have played an important role in the evaluation of carpal tunnel syndrome for years.3, 4, 5, 6, 7, 8 More recently, a combined wrist flexion and carpal tunnel compression physical exam test (flexion-compression or F-C test) has been described, but its diagnostic utility is not as well understood.9 A variety of clinical tools and scores have also been developed, such as the brief, 6-item carpal tunnel syndrome scale (CTS-6), initially described by Graham et al., which has been studied in the setting of “classic” CTS symptoms.10, 11, 12, 13 Based on clinical history and examination, management guidelines suggest an initial trial of non-operative management with wrist bracing, though some practitioners also consider a steroid injection. If symptoms persist, surgeons often obtain electrodiagnostic studies to confirm the diagnosis and grade the severity of nerve compression before proceeding with a carpal tunnel release.14,15
Other physical examination tests for CTS have been described, including assessment of thumb lateral pinch strength and the scratch collapse test.16,17 However, direct percussion over the carpal tunnel (Tinel), sustained wrist flexion (Phalen), and direct compression over the carpal tunnel (Durkan) have remained mainstays of physical examination in patients with suspected CTS.4,6 Sensitivities and specificities for the Phalen's test and Durkan's test have been cited as 70/84 % and 87–89/90 %, respectively, depending on the control reference population and diagnostic gold standard used.6,11 The utility of the combined flexion-compression test was previously evaluated by Cheng et al., but this study had several methodological flaws.17 Not only were the gold standard criteria for diagnosis poorly defined, but the F-C test was considered positive only if it generated paresthesias in the median nerve distribution; exacerbation of numbness and/or pain was not considered a positive finding.
Therefore, the purpose of this study was to better determine the diagnostic utility of the flexion-compression (F-C) test for carpal tunnel syndrome (CTS). Furthermore, we sought to understand whether the F-C test could be used to as an adjunct to the CTS-6 score to increase its diagnostic accuracy by adding a physical examination maneuver to this score. Using electrodiagnostic testing as the gold standard, we hypothesized that the F-C test would be a better diagnostic test for CTS when compared to the wrist flexion (Phalen's) or palmar compression (Durkan's) tests alone.
2. Materials and methods
Institutional Review Board approval was obtained prior to beginning this clinical study. We performed a prospective, cross-sectional study of adult patients who presented to our hand surgery clinics with symptoms of CTS. The study group included those patients who specifically presented for evaluation of unilateral or bilateral CTS, or those who had another primary reason for evaluation but with suspected diagnosis of CTS based on history. All other patients seen in clinic without obvious signs and symptoms of compression neuropathy, defined as numbness, tingling, or weakness in one or more specific peripheral nerve distributions, were considered for enrollment in the control group. These control patients presented with symptoms of other common hand conditions, such as tendonitis, arthritis, cysts, and sprains. For both groups, exclusion criteria included age less than 18, pregnancy, history of wrist or palm surgery (including carpal tunnel release) on the affected hand, history of cervical stenosis, disc herniation, or prior cervical spinal instrumentation, history of distal radius fracture or carpal fracture on the affected hand within the last 3 months, history of neuropathic diagnosis other than carpal tunnel syndrome (e.g. diabetic peripheral neuropathy, mononeuritis multiplex, multiple sclerosis, Charcot-Marie tooth, ALS, etc.), active worker's compensation claim, history of clinically significant trauma to the affected hand within the last 12 months with potential for neurologic symptoms (e.g. gunshot to the finger, finger amputation, etc.), and inability to flex affected wrist beyond 70°.
Once enrolled in the study, all patients were evaluated using the CTS-6 score during the initial clinic visit. The six components of the CTS-6 evaluation tool were numbness and tingling in the median nerve distribution (3.5 points), nocturnal numbness (4 points), thenar weakness and/or atrophy (5 points), a positive Tinel's sign (4 points), a positive Phalen's test (5 points), and impaired 2-point discrimination in the median nerve distribution (4.5 points). A CTS-6 score of 12 or greater was deemed positive. Recognizing that one physical exam test may affect the results of another test, we performed block randomization to determine the order in which study patients were administered the flexion-compression, Phalen's, and Durkan's tests (all three tests performed with a minimum 1 min break between examination maneuvers until symptoms disappeared or returned to patient baseline). Study group patients were then sent for electrodiagnostic testing and then returned for another office visit with a repeat of all three examination maneuvers while the examiner was blinded to the results of the electrodiagnostic testing. Patients in the control group were also administered all three tests in an order determined by block randomization. These patients were not referred for electrodiagnostic testing.
All examination maneuvers were performed by fellowship-trained attending hand surgeons at a single institution. Clinicians were trained to apply 5 pounds per square inch of pressure with key pinch using a standard dynamometer, and subsequently tested by performing 10 consecutive blinded trials to ensure a reproducible and consistent amount of pressure was being applied to all patients. The Durkan's test was performed by holding the wrist in neutral and applying approximately 5 pounds of force with the examiner's thumb over the base of the palm overlying the carpal tunnel for 30 s. For the Phalen's test, the patient's wrist was held in maximal passive flexion (approximately 90°) for 30 s. Finally, for the flexion-compression test, the patient's wrist was placed into maximal passive flexion and approximately 5 pounds per square inch of force was applied with the examiner's thumb over the carpal tunnel at the base of the palm for 30 s. A positive result for any exam maneuver was symptom onset or worsening (numbness, tingling, discomfort, and/or pain) within the volar aspect of the ring finger, long finger, index finger, and/or thumb within 30 s.
Per the standard of care of our group's practice, electrodiagnostic testing was considered to be positive for CTS if median nerve sensory latency was greater than 3.5 ms (ms) at the wrist, motor latency was greater than 4.2 ms, or if electromyography (EMG) changes were present for muscles of the hand innervated by the median nerve.
The primary outcome was the development or worsening of symptoms during the Phalen's, Durkan's, and flexion-compression tests compared to the results of the gold-standard electrodiagnostic test, reported as likelihood ratio. Secondary outcomes included time to symptom development (in seconds) during the above-mentioned physical exam maneuvers.
An a priori sample size analysis demonstrated that 80 patients were needed in the study group to detect 90 % sensitivity and 95 % specificity for the flexion-compression test (compared to previously published values of the Phalen's and Durkan's tests). Standard descriptive statistics reported include measures of central tendency, variance as well as frequencies and proportions. For bivariate analyses, Fishers Exact tests were used to determine statistically significant differences for categorical data and Wilcoxon rank sum test for continuous variables. Continuous variables among multiple groups were compared using one-way Analysis of Variance (ANOVA) and subsequent Tukey's Honestly Significant Difference (HSD) Test for multiple comparisons. Diagnostic criteria including sensitivity, specificity, positive predictive value, negative predictive value, and likelihood ratio were also calculated for each physical exam test.
3. Results
A total of 162 patients were enrolled in the study, 81 each in the control and study groups. Demographics are shown in Table 1. Statistical analysis of baseline demographic variables revealed that, on average, study group patients were older, with a greater percentage of females compared to the control group (p < 0.001 for both). There were also proportionally more patients diagnosed with diabetes and depression in the study group (p < 0.02 for both). Finally, study group patients had symptoms involving the right hand more than the control group (p = 0.03). No statistically significant differences were noted between control and study groups with regard to presence of thyroid disease, tobacco use, alcohol use, diagnosis of anxiety, or use of aromatase inhibitors.
Table 1.
Baseline demographics.
| Control Group (n = 81) | Study Group (n = 81) | P-Value | Overall (n = 162) | |
|---|---|---|---|---|
| Age - Median (IQR) | 47 (32, 60) | 56 (47, 68) | <0.001∗ | 54 (43, 64) |
| Gender n (%) | ||||
| Female | 33 (40.7 %) | 57 (70.4 %) | 0.001∗ | 90 (55.6 %) |
| Male | 48 (59.3 %) | 24 (29.6 %) | 72 (44.4 %) | |
| Randomization n (%) | ||||
| Phalen-Durkan | 42 (51.9 %) | 42 (51.9 %) | 84 (51.9 %) | |
| Durkan-Phalen | 39 (48.1 %) | 39 (48.1 %) | 78 (48.1 %) | |
| Side n (%) | ||||
| Right | 36 (44.4 %) | 50 (61.7 %) | 0.0275∗ | 86 (53.1 %) |
| Left | 45 (55.6 %) | 31 (38.3 %) | 76 (46.9 %) | |
| Diabetes n (%) | ||||
| No | 77 (95.1 %) | 67 (82.7 %) | 0.0124 | 144 (88.9 %) |
| Yes | 4 (4.9 %) | 14 (17.3 %) | 18 (11.1 %) | |
| Hyperthyroidism n (%) | ||||
| No | 79 (98.7 %) | 81 (100 %) | 0.4969 | 160 (99.4 %) |
| Yes | 1 (1.3 % | 0 (0 %) | 1 (0.06 %) | |
| Tobacco n (%) | ||||
| No | 41 (50.6 %) | 49 (60.5 %) | 0.4452 | 90 (55.6 %) |
| Yes | 7 (8.6 %) | 6 (7.4 %) | 13 (8.0 %) | |
| Quit | 33 (40.7 %) | 26 (32.1 %) | 59 (36.4 %) | |
| Alcohol n (%) | ||||
| No | 81 (100.0 %) | 77 (95.1 %) | 0.1204 | 158 (97.5 %) |
| Yes | 0 (0 %) | 4 (4.9 %) | 4 (2.5 %) | |
| Depression n (%) | ||||
| No | 77 (95.1 %) | 65 (80.2 %) | 0.0042∗ | 142 (87.7 %) |
| Yes | 4 (4.9 %) | 16 (19.8 %) | 20 (12.3 %) | |
| Anxiety n (%) | ||||
| No | 81 (100.0 %) | 79 (97.5 %) | 0.4969 | 160 (98.8 %) |
| Yes | 0 (0 %) | 2 (2.5 %) | 2 (1.2 %) | |
| Aromatase Inhibitor n (%) | ||||
| No | 80 (98.8 %) | 78 (96.3 %) | 0.6203 | 158 (97.5 %) |
| Yes | 1 (1.2 %) | 3 (3.7 %) | 4 (2.5 %) | |
IQR: Interquartile range.
Among study group patients with any motor or sensory conduction abnormalities indicative of CTS, the positive likelihood ratio (LR+) of the Phalen's test (1.29) was higher than the Durkan's (1.06) and F-C (0.95) tests (Table 2). The negative likelihood ratio (LR-) followed a similar trend, with Phalen's (0.62) less than Durkan's test (0.80) and F-C (1.33). Within this group, the sensitivity and specificity for Phalen's test were 72.7 % and 43.8 %, respectively. The sensitivity and specificity for Durkan's test were 81.1 % and 23.5 %, respectively. The sensitivity and specificity for F-C test were 83.3 % and 12.5 %, respectively. In comparison, the CTS-6 score had a positive likelihood ratio of 1.64, negative likelihood ratio of 0.20, sensitivity of 91.2 %, and specificity of 44.4 %. Combining each of the physical exam tests with the CTS-6 score did not increase the positive likelihood ratio or decrease the likelihood ratio when compared to using the CTS-6 alone (LR + CTS-6+Phalen's 1.35, CTS-6+Durkan's 1.19, CTS-6+F-C 1.03) (LR- CTS-6+Phalen's 0.60, CTS-6+Durkan's 0.61, CTS-6+F-C 0.88) (Table 3).
Table 2.
Diagnostic utility of physical exam maneuvers and CTS-6 score Likelihood Ratios.
| Electrodiagnostic Findings | Phalen's | Durkan's | Flexion-Compression | CTS-6 |
|---|---|---|---|---|
| Motor or Sensory Abnormality | LR+ 1.29 | LR +1.06 | LR+ 0.95 | LR+ 1.64 |
| LR- 0.62 | LR- 0.80 | LR- 1.33 | LR- 0.20 | |
| EMG Changes | LR+ 0.62 | LR+ 0.80 | LR+ 0.62 | LR+ 1.03 |
| LR- 2.02 | LR- 2.03 | LR- 3.96 | LR- 0.84 |
CTS-6: 6-item carpal tunnel syndrome symptoms scale; EMG: electromyography; LR+: positive likelihood ratio; LR-: negative likelihood ratio.
Table 3.
Diagnostic utility of physical exam maneuvers combined with CTS-6 score.
| Electrodiagnostic Findings | Phalen's + CTS-6 |
Durkan's + CTS-6 |
Flexion-Compression + CTS-6 | CTS-6 |
|---|---|---|---|---|
| Motor or Sensory Abnormality | LR+ 1.35 | LR +1.19 | LR+ 1.03 | LR+ 1.64 |
| LR- 0.60 | LR- 0.61 | LR- 0.88 | LR- 0.20 | |
| EMG Changes | LR+ 0.63 | LR+ 0.83 | LR+ 0.57 | LR+ 1.03 |
| LR- 1.96 | LR- 1.73 | LR- 3.79 | LR- 0.84 |
CTS-6: 6-item carpal tunnel syndrome symptoms scale; EMG: electromyography; LR+: positive likelihood ratio; LR-: negative likelihood ratio.
When patients had electromyography (EMG) changes consistent with severe CTS, none of the physical exam tests had a positive likelihood ratio greater than 1 (Phalen's 0.62, Durkan's 0.80, F-C 0.62), compared to 1.03 for the CTS-6. Similarly, none of the physical exam tests had a negative likelihood ratio less than 1 (Phalen's 2.02, Durkan's 2.03, F-C 3.96), compared to 0.20 for the CTS-6 (Table 2). Within this group, the sensitivity and specificity for Phalen's test were 45.5 % and 27.0 %, respectively. The sensitivity and specificity for Durkan's test were 66.7 % and 16.4 %, respectively. The sensitivity and specificity for F-C test were 54.6 % and 11.5 %, respectively, when EMG abnormalities were detected. Again, combining each of the physical exam tests with the CTS-6 score did not increase the positive likelihood ratio or decrease the negative likelihood ratio of diagnosing CTS when compared to using the CTS-6 alone among patients with EMG changes (LR+: CTS-6+Phalen's 0.63, CTS-6+Durkan's 0.83, CTS-6+F-C 0.57) (LR-: CTS-6+Phalen's 1.96, CTS-6+Durkan's 1.73, CTS-6+F-C 3.79) (Table 3).
Among the study group, the F-C test resulted in more rapid onset of symptoms (8s) than the Phalen's (13s) or Durkan's (12s) tests (p = 0.001) (Table 4).
Table 4.
Time to symptom onset among study group patients with physical exam maneuvers. Time to Symptom Onset (seconds).
| Phalen's | Durkan's | Flexion-Compression | |
|---|---|---|---|
| Median (IQR) | 13 (9, 19.5) | 12 (7, 19) | 8 (5, 12)a |
IQR: Interquartile range.
Indicates statistically significant difference after ANOVA and Tukey's HSD Test.
As expected, all three physical exam maneuvers were more likely to be positive among study patients compared to control patients (p < 0.001 for all), with the F-C and Durkan's test producing symptoms more rapidly among the study patients (p < 0.001 and p = 0.003, respectively).
4. Discussion
To our knowledge, this is the first study to compare the diagnostic utility of the Phalen's test, Durkan's test, and flexion-compression test among patients suspected to have carpal tunnel syndrome. Using electrodiagnostic testing as the gold standard, we found that none of these physical exam maneuvers were highly predictive of a positive electrodiagnostic test. Furthermore, we found the CTS-6 score alone to be a better predictor of electrodiagnostic test abnormalities. We had hypothesized that adding one or more of the physical examination maneuvers would increase the likelihood of the CTS-6 predicting positive electrodiagnostic testing, but that was not the case.
Prior studies have demonstrated low clinical utility of the Phalen's and Durkan's tests in predicting electrodiagnostic changes. Specifically, published positive likelihood ratios of the Phalen's test have ranged from 0.7 to 2.1, with a pooled result of 1.3. The literature also shows low clinical utility of the Durkan's test, with published positive likelihood ratios of 0.8–1.1 (pooled result 1.0).18 The results from our study group fall within these ranges (Phalen's LR+ 1.29, Durkan's LR+ 1.06), indicating that patients included in the present study seem to appropriately represent the general population. The positive likelihood ratio of the flexion-compression test among our study patients was even lower at 0.95, with a sensitivity and specificity of 83 % and 13 %, respectively. In contrast, a recent study showed a sensitivity and specificity of 92 % and 85 %, respectively.19 However, there were several notable limitations to the previous study, including small sample size, only a single examiner, and a lack of blinding as patients in the study group already presented with abnormal electrodiagnostic studies at the time of examination. Furthermore, we found the CTS-6 to have higher diagnostic utility than the tested physical exam maneuvers, with a positive likelihood ratio of 1.64. Finally, our results show that all physical exam tests have even less utility in severe CTS, as evidenced by electromyographic abnormalities.
Though we believe the present study accurately portrays the diagnostic value of the three physical exam maneuvers, there are limitations worth discussing. First, we used electrodiagnostic testing as the “gold standard” for this study. Many other studies have also used this as a confirmatory test, but other published literature has shown that there can be high false positive and false negative rates with electrodiagnostic testing, with significant variability among those who perform these studies.20,21 We were unable to account for such false or inconsistent test results. Various recent studies have also validated the use of neuromuscular ultrasound for the diagnosis of carpal tunnel syndrome.22 However, based on current practice standards in our group, we believed the electrodiagnostic test to be the most appropriate reference standard when designing this study. Furthermore, mixed palmar nerve comparison has been shown to have the highest sensitivity for CTS with regard to electrodiagnostic testing, which is not routinely performed in our practice and was therefore not included in the present study. This may have underreported patients with CTS based on nerve testing. Next, due to the logistical challenges of running a large clinical trial, we were unable to arrange for more than one physician to examine each patient in the study. As such, each patient's results could have potentially been different if examined by another provider. That given, we believe that physical exam training and standardization exercises for providers at the beginning of the study should have mitigated some intra- and inter-examiner variability. Furthermore, the CTS-6 evaluation tool incorporates the use of the Phalen's test in order to determine the final score. We acknowledge that this may have incorporated bias into the results of the physical exam maneuvers performed. Finally, we recognize that practitioners may employ additional means of confirming or validating the diagnosis of carpal tunnel syndrome, especially if electrodiagnostic testing or ultrasound is not readily available. These may include a trial of wrist bracing or corticosteroid injection. With our study design, we were unable to evaluate the diagnostic utility of these interventions.
In summary, our study shows that none of the physical exam maneuvers tested are more useful than the CTS-6 score in diagnosing carpal tunnel syndrome, though we do still recognize the importance of performing a thorough physical exam for all patients. Overall, we believe electrodiagnostic testing retains a role in the addition to the CTS-6 in the evaluation of patients suspected to have carpal tunnel syndrome.
5. Conclusion
None of the physical exam maneuvers, including flexion-compression, were highly predictive in diagnosing CTS, and even less useful for severe CTS. The CTS-6 score alone better predicts electrodiagnostic evidence of CTS than physical exam testing, though it only very slightly increases the post-test probability of disease.
Statement of Informed Consent
Institutional Review Board approval was obtained to conduct this study, and written informed consent was obtained for all patients enrolled.
Acknowledgments of grant support
None.
Statement of Human and Animal Rights
All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008 (5). Informed consent was obtained from all patients for being included in the study.
Statement of funding
No external funding was required or obtained to conduct this study.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
None.
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