Carpal tunnel syndrome: the association with occupation at a population level

External wrist ratio is not a proxy for internal carpal tunnel shape: Implications for evaluating carpal tunnel syndrome risk

Carpal tunnel syndrome (CTS) is highly prevalent, resulting in decreased function and increased need for costly healthcare services. External wrist ratio (depth/width >0.70) is a strong predictor of the development of CTS and has been suggested to be a proxy for internal carpal tunnel (CT) shape. Conversely, sonography can more directly evaluate CT shape. The purpose of our study was to explore the relationship between wrist ratio and sonographic CT measurements to (1) evaluate the reliability of sonographic CT measurements and (2) explore how external wrist measures relate to anthropometric features of the CT. We used sonographic imaging on a sample of healthy participants (n = 226) to measure CT cross-sectional area, depth, width, and depth/width ratio. We conducted exploratory correlation and regression analyses to identify relationships of these measures with external wrist ratio. Reliability for dominant and nondominant sonographic CT measures ranged from good to excellent (0.79-0.95). Despite a moderate correlation between CT width and depth and their external wrist counterparts (0.33-0.41, p < 0.001), wrist ratio and CT ratio demonstrated weak to no correlation (dominant: r = 0.12, p = 0.053; nondominant: r = 0.20, p = 0.002) and the mean CT ratio was far lower than the mean wrist ratio (0.45 vs. 0.71 bilaterally). Supporting this, we observed several key differences in the relationship between external wrist measures compared to corresponding CT measures. Additionally, regression analyses combining participant factors and CT measurements produced models accounting for less than 15% of the variability in external wrist ratio (linear models) or correctly predicting less than 68% of wrist ratio-based risk categorization (logistic models). Overall, among healthy young adults, wrist shape is not an adequate proxy for CT shape.

Carpal tunnel syndrome

Median neuropathy at the wrist, commonly referred to as carpal tunnel syndrome (CTS), is the most common entrapment neuropathy. It is caused by chronic compression of the median nerve at the wrist within the space-limited carpal tunnel. Risk factors that contribute to the etiology of compression include female gender, obesity, work-related factors, and underlying medical conditions, such as hypothyroidism, pregnancy, and amyloidosis. The diagnosis is made on clinical grounds, although these can be confounded by anatomical variations. Electrodiagnostic studies, which are specific and sensitive in diagnosing CTS, support the diagnosis; however, a subgroup may present with normal results. The advent of imaging techniques, including ultrasound and MRI, further assists the diagnostic process. The management of CTS is divided into the nonsurgical approaches that include hand therapy, splinting and corticosteroid injection, and surgical decompression of the carpal tunnel. Although several surgical techniques have been developed, no one method is more effective than the other. Each of these management approaches are effective at providing symptom relief and are utilized at different severities of the condition. There is, however, a lack of consensus on standardized diagnostic criteria, as well as when and to whom to refer patients for surgery.

Association between carpal tunnel syndrome and the five-year incidence of anxiety disorder and depression in adults followed in general practices in Germany

OBJECTIVE

Little is known about the longitudinal relationship between carpal tunnel syndrome (CTS) and mental health. Therefore, this retrospective cohort study investigated the association between CTS and the five-year incidence of anxiety disorder and depression in adults from Germany.

METHODS

Data from the Disease Analyzer database (IQVIA) were used for the present study. Patients aged ≥18 years diagnosed for the first time with CTS in one of 1284 general practices in Germany in 2005-2020 were included (index date). Individuals without CTS were matched to those with CTS using a propensity score based on age, sex, the mean number of consultations per year during the follow-up, and the index year. In people without CTS, the index date was a randomly selected consultation in 2005-2020.

RESULTS

There were 75,135 patients with and 75,135 patients without CTS included in the study (mean [SD] age 57.2 [16.5] years; 59.7% women). Within five years of the index date, the incidence of anxiety disorder was 3.9% and 3.6% in the group with and the group without CTS, respectively (log-rank p-value<0.001), while figures for depression were 14.8% and 11.5% (log-rank p-value<0.001). These findings were corroborated in the Cox regression analyses adjusted for multiple physical conditions, as CTS was associated with anxiety disorder (HR = 1.14, 95% CI = 1.08-1.21) and depression (HR = 1.29, 95% CI = 1.25-1.33) in the overall sample.

CONCLUSION

CTS was associated with an increased incidence of anxiety disorder and depression in Germany. Further research should identify the mediators involved in these relationships.

Impact of Occupations and Hobbies on the Severity of Carpal Tunnel Syndrome: An Electrodiagnostic Perspective

OBJECTIVE

This study describes the clinical and electrodiagnostic (EDX) findings as well as occupations and hobbies in 613 patients diagnosed with carpal tunnel syndrome (CTS).

METHODS

Patients with moderate, moderately severe, or severe CTS based on EDX criteria were included.

RESULTS

The most common occupations included workers in offices, construction/maintenance, and assembly lines. The occupation severity scores were greatest in garment workers, musicians, and landscapers. Regardless of occupation, patient age and occupation duration were significantly correlated ( P < 0.001). Gardeners had the highest average severity score of the hobbies, followed by painters, those who sew, and individuals who perform house chores.

CONCLUSIONS

Physicians should be aware of particular occupations and hobbies associated with a greater risk of severe CTS and offer modifications to their patients' work duties and hobbies to minimize the likelihood of developing severe CTS.

Prospective Comparative Analysis Study of Minimally Invasive Surgical Decompressions versus Traditional Surgical Decompression of Carpal Tunnel Syndrome

Objective: Carpal tunnel syndrome (CTS) occurs when there is compression on the median nerve within the carpal tunnel in the wrist joint. It commonly affects those who make frequent, repetitive hand movements, with women being more affected than men. The present study was aimed at comparing minimally invasive and classical surgical decompression techniques for carpal tunnel syndrome. Materials and Methods: One hundred and four patients with CTS who were scheduled for carpal tunnel decompression were chosen at random. The patients were divided into two groups. Group A had standard classical long incision decompression, whereas Group B had minimally invasive decompression. The patients were evaluated with the Boston Functional Score Scale. Between the two groups, a comparison of visit reports was made at 3, 6, and 12 months after surgery. Results: There was no significant difference in patient age (Group A was 38 years old and Group B was 36 years old) and availability of bilateral CTS status (A was 34 and B was 31). The female-male ratios in groups A and B were 3.6 to 0.2 and 3.1 to 0.3, respectively, with a p-value of p<0.05 indicating significant difference. Comparing both groups, the minimally invasive decompression technique showed a high rate of functional hand grip and a low rate of complications including early wound healing, rapid resumption of palmar strength grip, and rapid return to daily activities. Conclusion: The findings indicate that patients who underwent the minimally invasive surgical decompression one-stitch technique showed significant improvement over the traditional method.

Manufacturing Workers Have a Higher Incidence of Carpal Tunnel Syndrome

OBJECTIVE

It is unclear whether clerical or labor-type work is more associated with risk for developing work-related carpal tunnel syndrome (WrCTS).

METHODS

National employment, demographic, and injury data were examined from the Bureau of Labor Statistics databases for the years 2003 to 2018. Injuries for clerical and labor industries were compared using linear regression, two-group t test, and one-way analysis of variance (ANOVA) analysis.

RESULTS

WrCTS injuries are decreasing over time (B = -1002.62, P < 0.001). The labor industry demonstrated a significantly higher incidence of WrCTS when compared with the clerical industries (P < 0.001). Within labor industries, the manufacturing industry had the highest incidence of WrCTS over time (P < 0.001).

CONCLUSIONS

Our study showed WrCTS injuries have declined over time. Additionally, our findings may suggest that the labor industry has a stronger association with WrCTS than the clerical industry.

Second to fourth digit ratio (2D:4D) in women with carpal tunnel syndrome

BACKGROUND

Carpal tunnel syndrome (CTS), a median nerve compressive neuropathy at the wrist, is the most common entrapment nerve disorder. Sex is an important risk factor of CTS as this condition is to five times more common in women than in men (sex-hormone dependent). There are no studies concerning 2D:4D (biomarker of prenatal sex steroids exposure) in patients with CTS.

AIM

Here we consider the relationship between 2D:4D and CTS in women.

STUDY DESIGN AND METHODS

The study involved 90 female participants (40 with a severe CTS (the mean age - 52.78 yrs., SD 11.44) and 50 control women (the mean age - 47.2 yrs., SD 8.23)). Anthropometric measurements were performed and the following indices were calculated: BMI, WHR and right and left 2D:4D.

RESULTS

A stepwise logistic regression model showed that higher WHR and lower right 2D:4D increase the risk of CTS in women (AUC = 0.8865).

CONCLUSIONS

These associations may suggest a role for prenatal and post-natal sex-hormones in CTS development, i.e. in the context of oestrogen receptor activation (number and/or sensitivity) and the pattern of fat distribution. Further studies examining the role of hormonal influence in this disorder may help to plan prophylaxis of CTS (e.g. early HRT).

Predicting surgical intervention in patients presenting with carpal tunnel syndrome in primary care

Purpose

Carpal tunnel syndrome (CTS) is a symptomatic compression neuropathy of the median nerve. This study investigated the value of candidate prognostic factors (PFs) in predicting carpal tunnel release surgery.

Patients and methods

This is a retrospective cohort study set in the Clinical Practice Research Datalink. Patients ≥18 years presenting with an incident episode of CTS were identified between 1989 and 2013. Candidate PF’s defined in coded electronic patient records were identified following literature review and consultation with clinicians. Time to first carpal tunnel release surgery was the primary end point. A manual backward stepwise selection procedure was used to obtain an optimal prediction model, which included all the significant PFs.

Results

In total, 91,412 patients were included in the cohort. The following PFs were included in an optimal model (C-statistic: 0.588 [95% CI 0.584–0.592]) for predicting surgical intervention: geographical region; deprivation status; age hazard ratio (HR 1.02 per year, 95% CI 1.01–1.02); obesity (HR 1.23, 95% CI 1.19–1.27); alcohol drinker (HR 1.05, 95% CI 1.00–1.10); smoker (HR 1.06, 95% 1.03–1.10); inflammatory condition (HR 1.13, 95% CI 0.98–1.29); neck condition (HR 1.13, 95% CI 1.03–1.23); and multisite pain (HR 1.10, 95% CI 1.05–1.15). Although not included in the multivariable model, pregnancy (if gender female) within 1 year of the index consultation, reduced the risk of surgery (HR 0.24, 95% CI 0.21–0.28).

Conclusion

This study shows that patients who are older and who have comorbidities including other pain conditions are more likely to have surgery, whereas patients presenting with CTS during or within a year of pregnancy are less likely to have surgery. This information can help to inform clinicians and patients about the likely outcome of treatment and to be aware of which patients may be less responsive to primary care interventions.

Trends in the prevalence, incidence and surgical management of carpal tunnel syndrome between 1993 and 2013: an observational analysis of UK primary care records

OBJECTIVES

To describe the prevalence, incidence and surgical management of carpal tunnel syndrome (CTS), between 1993 and 2013, as recorded in the Clinical Practice Research Datalink (CPRD).

DESIGN

We completed a series of cross-sectional epidemiological analyses to observe trends over time.

SETTING

Primary care data collected between 1993 and 2013, stored in the CPRD.

POPULATION

Individuals aged ≥18 years were selected. Prevalent and incident episodes of CTS and episodes of surgical intervention were identified using a list of preidentified Read codes.

ANALYSIS

We defined incident episodes as those with no preceding diagnostic code for CTS in the past 2 years of data. Episodes of surgery were expressed as a percentage of the prevalent population during the same calendar year. Joinpoint regression was used to determine significant changes in the underlying trend.

RESULTS

The prevalence of CTS increased over the study period, with a particular incline between 2000 and 2004 (annual percentage change 7.81). The female-to-male prevalence ratio reduced over time from 2.74 in 1993 to 1.93 in 2013. The median age of females and males with CTS were noted to increase from 49 and 53 years, respectively in 1993 to 54 and 59 years, respectively in 2013. Incidence was also noted to increase over time. After an initial increase between 1993 and 2007, the percentage of prevalent patients with a coded surgical episode began to decrease after 2007 to 27.41% in 2013 (annual percentage change -1.7).

CONCLUSION

This study has demonstrated that the prevalence and incidence of CTS increased over the study period between 1993 and 2013. Rates of surgery for CTS also increased over the study period; however after 2007, the per cent of patients receiving surgery showed a statistically significant decline back to the rate seen in 2004.

Motor Examination in the Diagnosis of Carpal Tunnel Syndrome

The relative importance and use of motor evaluation to diagnose carpal tunnel syndrome (CTS) is not clear. Because the ulnar nerve is not affected in CTS, we evaluated comparing the strength of the median-nerve innervated muscles to the ulnar innervated muscles in the same patient, through manual muscle testing (MMT) and a handheld dynamometer. Our purpose was to evaluate whether this method, which takes into account patient-dependent factors that would affect both groups of muscles equally, can provide better assessment of CTS. A retrospective case-control review of MMT and dynamometer-measured strength for CTS was performed. The study was performed retrospectively but prior to surgery or other treatment. There were 28 cases (CTS) and 14 controls (without CTS). Positive nerve conduction tests defined cases. MMT of the thenar musculature was found to be unreliable as a test for CTS. Comparisons to ulnar nerve innervated muscle strength did not improve sensitivity or specificity of the MMT examination. Use of the dynamometer improved sensitivity and specificity of motor testing in CTS over MMT. Motor evaluation is important for the diagnosis of CTS, but further study is warranted, specifically to define the method of motor evaluation and delineate the subgroup of patients (predominantly thenar motor presentation) that would benefit most from motor testing and motor-focused treatment.

Distal Symmetric Polyneuropathy: A Review

IMPORTANCE

Peripheral neuropathy is a highly prevalent and morbid condition affecting 2% to 7% of the population. Patients frequently experience pain and are at risk of falls, ulcerations, and amputations. We aimed to review recent diagnostic and therapeutic advances in distal symmetric polyneuropathy, the most common subtype of peripheral neuropathy.

OBSERVATIONS

Current evidence supports limited routine laboratory testing in patients with distal symmetric polyneuropathy. Patients without a known cause should undergo a complete blood cell count, comprehensive metabolic panel, vitamin B12 measurement, serum protein electrophoresis with immunofixation, fasting glucose measurement, and glucose tolerance test. The presence of atypical features such as asymmetry, non-length dependence, motor predominance, acute or subacute onset, and prominent autonomic involvement should prompt a consultation with a neurologist or neuromuscular specialist. Electrodiagnostic tests and magnetic resonance imaging of the neuroaxis contribute substantial cost to the diagnostic evaluation, but evidence supporting their use is lacking. Strong evidence supports the use of tricyclic antidepressants, serotonin norepinephrine reuptake inhibitors, and voltage-gated calcium channel ligands in the treatment of neuropathic pain. More intensive glucose control substantially reduces the incidence of distal symmetric polyneuropathy in patients with type 1 diabetes but not in those with type 2 diabetes.

CONCLUSIONS AND RELEVANCE

The opportunity exists to improve guideline-concordant testing in patients with distal symmetric polyneuropathy. Moreover, the role of electrodiagnostic tests needs to be further defined, and interventions to reduce magnetic resonance imaging use in this population are needed. Even though several efficacious medications exist for neuropathic pain treatment, pain is still underrecognized and undertreated. New disease-modifying medications are needed to prevent and treat peripheral neuropathy, particularly in type 2 diabetes.

Is the Control of Applied Digital Forces During Natural Five-digit Grasping Affected by Carpal Tunnel Syndrome?

BACKGROUND

The impaired sensory function of the hand induced by carpal tunnel syndrome (CTS) is known to disturb dexterous manipulations. However, force control during daily grasping configuration among the five digits has not been a prominent focus of study. Because grasping is so important to normal function and use of a hand, it is important to understand how sensory changes in CTS affect the digit force of natural grasp.

QUESTIONS/PURPOSES

We therefore examined the altered patterns of digit forces applied during natural five-digit grasping in patients with CTS and compared them with those seen in control subjects without CTS. We hypothesized that the patients with CTS will grasp by applying larger forces with lowered pair correlations and more force variability of the involved digits than the control subjects. Specifically, we asked: (1) Is there a difference between patients with CTS and control subjects in applied force by digits during lift-hold-lower task? (2) Is there a difference in force correlation coefficient of the digit pairs? (3) Are there force variability differences during the holding phase?

METHODS

We evaluated 15 female patients with CTS and 15 control subjects matched for age, gender, and hand dominance. The applied radial forces (Fr) of the five digits were recorded by respective force transducers on a cylinder simulator during the lift-hold-lower task with natural grasping. The movement phases of the task were determined by a video-based motion capture system.

RESULTS

The applied forces of the thumb in patients with CTS (7 ± 0.8 N; 95% CI, 7.2-7.4 N) versus control subjects (5 ± 0.8 N; 95% CI, 5.1-5.3 N) and the index finger in patients with CTS (3 ± 0.3 N; 95% CI, 3.2-3.3 N) versus control subjects (2 ± 0.3 N; 95% CI, 2.2-2.3 N) observed throughout most of the task were larger in the CTS group (p ranges 0.035-0.050 for thumb and 0.016-0.050 for index finger). In addition, the applied force of the middle finger in patients with CTS (1 ± 0.1 N; 95% CI, 1.3-1.4 N) versus the control subjects (2 ± 0.2 N; 95% CI, 1.9-2.0 N) during the lowering phase was larger in CTS group (p ranges 0.039-0.050). The force correlations of the thumb-middle finger observed during the lowering phase in the patients with CTS (0.8 ± 0.2; 95% CI, 0.6-0.9) versus the control subjects (0.9 ± 0.1; 95% CI, 0.8-1.0; p = 0.04) were weaker in the CTS group. The thumb-little finger during holding in the patients with CTS (0.5 ± 0.2; 95% CI, 0.3-0.7) versus the control subjects (0.8 ± 0.2; 95% CI, 0.6-0.9; p = 0.02), and the lowering phase in the patients with CTS (0.6 ± 0.2; 95% CI, 0.3-0.8) versus the control subjects (0.9 ± 0.1; 95% CI, 0.8-1.0; p = 0.01) also were weaker. The force variabilities of patients with CTS were greater in the CTS group than in the control subjects: in the thumb ([0.26 ± 0.11 N, 95% CI, 0.20-0.32 N] versus [0.19 ± 0.06 N; 95% CI, 0.16-0.22 N], p = 0.03); index finger ([0.09 ± 0.07 N; 95% CI, 0.05-0.13 N] versus [0.05 ± 0.03 N; 95% CI, 0.04-0.07 N], p = 0.03); middle finger ([0.06 ± 0.04 N; 95% CI, 0.04-0.08 N] versus [0.03 ± 0.01 N; 95% CI, 0.02-0.04 N], p = 0.02), and ring finger ([0.04 ± 0.03 N; 95% CI, 0.20-0.06 N] versus [0.02 ± 0.01 N; 95% CI, 0.02-0.02 N], p = 0.01).

CONCLUSIONS

Patients with CTS grasped with greater digit force associated with weaker correlation and higher variability on specific digits in different task demands. These altered patterns in daily grasping may lead to secondary problems, which will need to be assessed in future studies with this model to see if they are reversible in patients undergoing carpal tunnel release.

CLINICAL RELEVANCE

The current results helped to identify altered patterns of grasping force during simulated daily function in patients with CTS and to provide the clinician with potential information that might help guide the rehabilitation of grasp in these patients.

Incidence of symptomatic compressive peripheral neuropathy after shoulder replacement

BACKGROUND

The incidence of post-operative compressive peripheral neuropathy (CPN) after shoulder arthroplasty is not known. We hypothesized that the likelihood following shoulder arthroplasty would be higher compared to a non-operative cohort.

METHODS

Retrospective study compared the incidence of symptomatic CPN after shoulder replacement to a 1:1 age- and gender-matched non-operative control group with shoulder arthritis. Six hundred six consecutive shoulder replacements from a regional shoulder arthroplasty registry were analyzed. This included 319 primary total shoulder arthroplasties (TSR), 168 hemiarthroplasties (HA), 31 humeral resurfacings (HHR), 71 reverse arthroplasties (RTSA), and 17 revision arthroplasties. Diagnosis of post-operative CPN was obtained by documented clinical examination by a physician consistent with CPN based on patient complaints, positive nerve study results, and/or nerve decompression. Age, gender, body mass index, diabetes status, thyroid abnormalities, operative side, and anesthesiology (ASA) score were examined.

RESULTS

The surgery group had 15 cases (2.5 %) of post-operative CPN (ten carpal tunnel syndrome, five cubital tunnel syndrome). This included seven TSR, six HA, one revision TSR, and one RTSA. Diagnoses included ten osteoarthritis, four rotator cuff arthropathies, and one chondrolysis. Control group had eight cases (1.3 %) of CPN (seven carpal tunnel syndrome, one cubital tunnel syndrome). In univariate analysis, age, gender, body mass index, ASA score, operative side, thyroid status, and diabetes were not predictors of post-operative CPN. CPN incidence between surgical and control groups was not statistically significant.

CONCLUSION

The 1-year incidence rate of new onset clinical post-operative CPN symptoms was 2.5 %. There was no significant difference of CPN rates between surgical and non-operative groups.

Outcome of carpal tunnel release--correlation with wrist and wrist-palm anthropomorphic measurements

Wrist and wrist-palm measurements have been associated with the diagnosis of carpal tunnel syndrome. We found no reported study about how this correlation affects the outcome after surgery. We investigated the role of the measurements in predicting outcome after open carpal tunnel release. A total of 131 patients (88 female, 43 male) responded to our postal questionnaire using the Boston Carpal Tunnel assessment (65% response rate) at a minimum of 9 months post-operatively. Symptom and functional scores showed a strong correlation. There was no statistical difference in the outcome between wrist ratio (≥0.7 vs <0.7), wrist-palm ratio (≥0.41 vs <0.41) and gender, but a better functional score was very weakly correlated with a higher wrist ratio. A very large study would be needed to show any statistical correlation between both measurement and outcome.

Anatomical landmarks for safer carpal tunnel decompression: an experimental cadaveric study

BACKGROUND

Carpal tunnel syndrome is a common presentation to surgical outpatient clinics. Treatment of carpal tunnel syndrome involves surgical division of the flexor retinaculum. Palmar and recurrent branches of the median nerve as well as the superficial palmar arch are at risk of damage.

METHODOLOGY

Thirteen cadavers of Sri Lankan nationality were selected. Cadavers with deformed or damaged hands were excluded. All selected cadavers were preserved with the conventional arterial method using formalin as the main preservative. Both hands of the cadavers were placed in the anatomical position and dissected carefully. We took pre- determined measurements using a vernier caliper. We hypothesized that the structures at risk during carpal tunnel decompression such as recurrent branch of the median nerve and superficial palmar arch can be protected if simple anatomical landmarks are identified. We also hypothesized that an avascular area exists in the flexor retinaculum, identification of which facilitates safe dissection with minimal intra operative bleeding. Therefore we attempted to characterize the anatomical extent of such an avascular area as well as anatomical landmarks for a safer carpal tunnel decompression.Ethical clearance was obtained for the study.

RESULTS

In a majority of specimens the recurrent branch was a single trunk (n =20, 76.9%). Similarly 84.6% (n = 22) were extra ligamentous in location. Mean distance from the distal border of the TCL to the recurrent branch was 7.75 mm. Mean distance from the distal border of TCL to the superficial palmar arch was 11.48 mm. Mean length of the flexor retinaculum, as measured along the incision, was 27.00 mm. Mean proximal and distal width of the avascular area on TCL was 11.10 mm and 7.09 mm respectively.

CONCLUSION

We recommend incision along the radial border of the extended ring finger for carpal tunnel decompression. Extending the incision more than 8.16 mm proximally and 7.75 mm distally from the corresponding borders of the TCL should be avoided. Incision should be kept to a mean length of 27.0 mm, which corresponds to the length of TCL along the above axis. We also propose an avascular area along the TCL, identification of which minimizes blood loss.

Personal and workplace psychosocial risk factors for carpal tunnel syndrome: a pooled study cohort

BACKGROUND

Between 2001 and 2010, six research groups conducted coordinated multiyear, prospective studies of carpal tunnel syndrome (CTS) incidence in US workers from various industries and collected detailed subject-level exposure information with follow-up symptom, physical examination, electrophysiological measures and job changes.

OBJECTIVE

This analysis of the pooled cohort examined the incidence of dominant-hand CTS in relation to demographic characteristics and estimated associations with occupational psychosocial factors and years worked, adjusting for confounding by personal risk factors.

METHODS

3515 participants, without baseline CTS, were followed-up to 7 years. Case criteria included symptoms and an electrodiagnostic study consistent with CTS. Adjusted HRs were estimated in Cox proportional hazard models. Workplace biomechanical factors were collected but not evaluated in this analysis.

RESULTS

Women were at elevated risk for CTS (HR=1.30; 95% CI 0.98 to 1.72), and the incidence of CTS increased linearly with both age and body mass index (BMI) over most of the observed range. High job strain increased risk (HR=1.86; 95% CI 1.11 to 3.14), and social support was protective (HR=0.54; 95% CI 0.31 to 0.95). There was an inverse relationship with years worked among recent hires with the highest incidence in the first 3.5 years of work (HR=3.08; 95% CI 1.55 to 6.12).

CONCLUSIONS

Personal factors associated with an increased risk of developing CTS were BMI, age and being a woman. Workplace risk factors were high job strain, while social support was protective. The inverse relationship between CTS incidence and years worked among recent hires suggests the presence of a healthy worker survivor effect in the cohort.

Prevalence and incidence of carpal tunnel syndrome in US working populations: pooled analysis of six prospective studies

OBJECTIVES

Most studies of carpal tunnel syndrome (CTS) incidence and prevalence among workers have been limited by small sample sizes or restricted to a small subset of jobs. We established a common CTS case definition and then pooled CTS prevalence and incidence data across six prospective studies of musculoskeletal outcomes to measure CTS frequency and allow better studies of etiology.

METHODS

Six research groups collected prospective data at > 50 workplaces including symptoms characteristic of CTS and electrodiagnostic studies (EDS) of the median and ulnar nerves across the dominant wrist. While study designs and the timing of data collection varied across groups, we were able to create a common CTS case definition incorporating both symptoms and EDS results from data that were collected in all studies.

RESULTS

At the time of enrollment, 7.8% of 4321 subjects met our case definition and were considered prevalent cases of CTS. During 8833 person-years of follow-up, an additional 204 subjects met the CTS case definition for an overall incidence rate of 2.3 CTS cases per 100 person-years.

CONCLUSIONS

Both prevalent and incident CTS were common in data pooled across multiple studies and sites. The large number of incident cases in this prospective study provides adequate power for future exposure-response analyses to identify work- and non-work-related risk factors for CTS. The prospective nature allows determination of the temporal relations necessary for causal inference.