The role of wrist anthropometric measurement in idiopathic carpal tunnel syndrome

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.

A literature review of carpal tunnel syndrome and its association with body mass index, wrist ratio, wrist to palm ratio, and shape index

STUDY DESIGN

Systematic literature review of case-controlled studies.

INTRODUCTION

Carpal tunnel syndrome (CTS) is one of the most common tubular neuropathies where certain anatomical variations may be accounted for as risk factors for CTS, including body mass index (BMI), wrist ratio (WR), wrist to palm ratio (WPR), shape index (SI), and digit length.

PURPOSE OF THE STUDY

To assess case-control studies examining the association between specific anatomical variations of the wrist as risk factors for developing CTS and whether this effect is the same for both genders.

METHODS

The literature search was conducted between February-June 2020 through PubMed, Cochrane Library, CINAHL Plus and PEDro. The literature search yielded 149 potential publications, fifteen of which were filtered in accordance with eligibility criteria. The methodological quality was assessed by using the Newcastle-Ottawa Quality Assessment Form for Case-Control Studies (NOS).

RESULTS

The total number of subjects included in this review was n=4299. The largest sample was n=1117 participants and the smallest n=54. All studies included patients who had a clinical diagnosis of CTS confirmed with nerve conduction studies and or ultrasonography. CTS was significantly higher in patients with higher BMI, WR, WPR compared to control groups. BMI and WR were the only indicators that can be considered as strong risk factors.

CONCLUSIONS

Discussion: Despite the general patterns on the association of BMI, WPR, WR and SI as risk factors for the development of CTS, there were exceptions to the accepted results and conclusions.

CONCLUSION

Clinicians are recommended to conduct more research to confirm anthropometric measurements as risk factors for the development of CTS, mainly SI and WPR. When determining the cut-off values for BMI and WR, it is recommended to take into account additional risk factors such as occupation.

Independent risk factors of carpal tunnel syndrome: Assessment of body mass index, hand, wrist and finger anthropometric measurements

BACKGROUND: The most prevalent neuropathy in the upper extremity is carpal tunnel syndrome (CTS). A variety of related risk factors such as biomechanical exposures, body mass index (BMI), sex and hand shape are reported to be related to CTS. OBJECTIVE: We aimed to identify the role of BMI, hand, wrist and finger anthropometric dimensions in the development of CTS, and to compare these measured variables between control and CTS participants. METHODS: A cross-sectional, case control study (n = 240, CTS = 120, controls = 120) with participants recruited from a convenience sample diagnosed with CTS and referred for anthropometric measurements. The control participants were matched by age and sex. The body height, weight, hand width, hand length, wrist depth, wrist width, wrist circumference, and finger length were measured. Hand, wrist and finger indices, hand to height ratio, and BMI were calculated. Mean values of all dimensions were compared between cases and controls, and the role of independent risk factors were determined by logistic regression analysis. RESULTS: The mean BMI, age, weight, sex and height were not significant between the two groups. Among the measured dimensions and calculated indices the significantly different variables between two groups were the wrist width, wrist depth, wrist circumference, hand index, hand to height index, and wrist index. Regression analysis showed that the wrist index (β=-1.7, p = 0.0001), wrist depth (β=0.25, p = 0.0001) and wrist width (β=0.21, p = 0.0001) were the strongest factors in CTS development in the sample. CONCLUSION: Wrist parameters have a strong role in predicting the development of CTS, while BMI was not confirmed as an independent risk factor.

Palmar Musculature: Does It Affect the Development of Carpal Tunnel Syndrome? A Pilot Study

Background  The etiology of carpal tunnel syndrome (CTS) is multifactorial. Static mechanical characteristics of CTS have been described, but dynamic (muscular) parameters remain obscure. We believe that musculature overlying the transverse carpal ligament may have an effect on carpal tunnel pressure and may explain the prevalence of CTS in manual workers. Questions/Purposes  To utilize magnetic resonance imaging (MRI) imaging to estimate the amount of muscle crossing the area of the carpal tunnel and to compare these MRI measurements in patients with and without documented CTS. Methods  A case-control study of wrist MRI scans between January 1, 2018, and December 1, 2019, was performed. Patients with a diagnosis of CTS were matched by age and gender with controls without a diagnosis of CTS. Axial MRI cuts at the level of the hook of the hamate were used to measure the thenar and hypothenar muscle depth overlying the carpal tunnel. Muscle depth was quantified in millimeters at three points: midcapitate, capitate-hamate border, capitate-trapezoid border. Average depth was calculated by dividing the cross-sectional area (CSA) by the transverse carpal ligament width. Statistical analysis included Student's t -test, chi-square test, and Pearson's correlation coefficient calculation. Results  A total of 21 cases and 21 controls met the inclusion criteria for the study. There were no significant differences in demographics between case and control groups. The location and depth of the musculature crossing the carpal tunnel were highly variable in all areas evaluated. A significantly positive correlation was found between proximal median nerve CSA and muscle depth in the capitate-hamate area (correlation coefficient = 0.375; p  = 0.014). CSA was not significantly associated with chart documented CTS. Conclusions  We found large variability in our measurements. This likely reflects true anatomical variation. The significance of our findings depends on the location of the muscles and the line of pull and their effect on the mechanics of the transverse carpal ligament. Future research will focus on refining measurement methodology and understanding the mechanical effect of the muscular structure and insertions on carpal tunnel pressure. Level of Evidence  This is a Level 3, case-control study.

Cross-sectional Area Just Proximal to the Carpal Tunnel According to the Ulnar Variances: Positive Ulnar Variance and Carpal Tunnel Syndrome

PURPOSE

We evaluated the relationship between the area around the distal radioulnar joint according to the ulnar variances and the cross-sectional area using magnetic resonance imaging (MRI) scans in this prospective study of patients with carpal tunnel syndrome (CTS).

METHODS

From among a total of 243 patients who had been diagnosed with CTS between March 2012 and February 2017 at our hospital, 41 patients with positive ulnar variance were enrolled in group 1. As control groups, 39 healthy volunteers who underwent MRI evaluations were included in group 2 (neutral ulnar variance) and group 3 (negative variance). Basic demographic data, including age, sex, and body mass index, were recorded for all 3 groups. An area encompassing the contents of carpal tunnel (nerves/tendons) was designated as area "A," and the area just beneath the subcutaneous fat was designated as area "B" at the levels of the lunate (L) and pisiform (P) on axial MRI. Ratios of these areas ("A/B at L" and "A/B at P") were evaluated in terms of their correlations with ulnar variance.

RESULTS

Mean age, sex, and body mass index were not statistically different among the groups, respectively. Within each group, there was no difference between "A/B at L" and "A/B at P," respectively. When comparing the 3 groups, "A/B at L" and "A/B at P" were all significantly decreased in group 1 than in other groups. Regardless of the group, ulnar length negatively correlated with both "A/B at L" and "A/B at P" ratios.

CONCLUSIONS

We found a positive relationship between decreased cross-sectional area around the distal radioulnar joint and positive ulnar variance on radiologic investigation. These findings show the importance of variance in the positive ulna variance to the development of CTS.

The Effect of Hamatum Curvature Angle on Carpal Tunnel Volumetry: A Mathematical Simulation Model

In carpal tunnel volume measurements, the angle of the hamatum curvature is not considered a variable, and its effect on carpal tunnel volume has not been investigated. We hypothesize that a change in the anatomical angle of the hamatum curvature changes the carpal tunnel volume. To prove our hypothesis, we used a mathematical simulation model considering the carpal tunnel as a truncated cone. We reviewed the wrist CT scans of 91 adults (>18 years of age), including 51 men and 40 women. We measured the angle of the hamatum curvature in the CT scans. We measured cross-sectional areas at the outlet of the carpal tunnel at the level of the trapezium and hook of hamate (r1) and at the inlet at the level of the scaphoid and pisiform (r2) and the length (h) of the carpal tunnel. We attempted to calculate the effect of 2 degree by 2-degree changes in the angle of the hamatum curvature between the angles of 98° and 140° on the carpal tunnel volume. The mean angle of the hook of hamatum of the subjects was 122.55° ± 8.20° (range, 97.20° − 139.31°). No suitable cutoff point was found for the angle values. There was no difference between the gender groups according to the angle value. The data clearly show that there is a high correlation between carpal tunnel volume and the angle of hamatum curvature. The results of our study emphasize the importance of taking into account the anatomical features of the hamatum bone, especially the angle of curvature, which may play a predisposing role in idiopathic carpal tunnel syndrome.

Reliability of an instrument for screening hand profiles: The Practical Hand Evaluation

STUDY DESIGN

Psychometric study with 2-week interval.

INTRODUCTION

Musculoskeletal hand complaints are common among manual workers. Mismatch between anthropometric hand features and tasks can affect the ability to perform hand activities, with an increased risk of complaints. Although screening of these features may improve diagnosis and treatment, no validated screening tool is available. The Practical Hand Evaluation (PHE) screening tool might fill this gap, but its psychometric properties are unknown.

PURPOSE OF THE STUDY

To test the reliability of the PHE and to explore the feasibility of item reduction of the PHE.

METHODS

Right-hand profiles of 117 healthy volunteers (66 women, 51 men; mean age, 22.8 years) were independently assessed 4 times by 6 couples of researchers using the PHE, twice on day 1 and twice 2-3 weeks later. Intrarater and inter-rater reliability (intraclass correlations), standard error of measurement (SEM), potential confounding factors (gender, joint hyperlaxity, and measurement order) affecting the instrument's reliability (limits of agreement), and collinearity between the PHE items were determined (variation inflation factor analysis and hierarchical clustering of correlation coefficients).

RESULTS

The intrarater and inter-rater reliabilities of the PHE were good for 12 of 14 items (86%; r = 0.67-0.90). Absolute SEM varied between 2.01 and 9.23 mm. The percentage of shifts of at least 2 classes in a repeated measurement was <15%. Cluster analysis identified 6 clusters of hand items.

DISCUSSION

The reliability for nearly all PHE items is good. Measurement errors were substantial relative to variances in the reference population, but not to gender, joint laxity and order of administration. Clustering into 6 seperated clusters of items was possible.

CONCLUSIONS

The PHE fulfills many of the criteria for screening of anthropometrics of the hand. Its reliability is high. The SEM might be improved with future adaptations toward a digital photographic PHE. Reduction to 6 items seems also possible.

High wrist ratio is a risk factor for carpal tunnel syndrome

Carpal tunnel syndrome (CTS) is the most common upper extremity entrapment neuropathy and various risk factors have been implicated in the etiology. In this study, we aimed to determine whether anthropometric measurements are independent risk factors for CTS. Patients with symptoms of CTS (n = 27) and asymptomatic controls (n = 27) were enrolled following electrophysiological confirmation. Body mass index (BMI) was recorded and anthropometric measurements of the hand were made by a digital caliper. BMI, wrist width, wrist depth, palm length, hand width, wrist ratio, wrist/palm ratio, and wrist/hand ratio were significantly higher in the CTS group. BMI, wrist ratio, wrist/palm ratio, and wrist/hand ratio were independent variables in the logistic regression analysis; wrist ratio was the only significant predictor of CTS. Patients with a wrist ratio higher than 0.69 were 8.2 times more likely to have CTS. This study suggests that wrist ratio may be considered as an independent risk factor for CTS. Clin. Anat. 31:698-701, 2018. © 2018 Wiley Periodicals, Inc.

Association between wrist ratio and carpal tunnel syndrome: Effect modification by body mass index

INTRODUCTION

Previous studies have reported higher wrist ratios (WR) related to carpal tunnel syndrome (CTS) but have not assessed effect modification by obesity and may have inadequately controlled for confounders.

METHODS

Baseline data of a multicenter prospective cohort study were analyzed. CTS was defined by nerve conduction study (NCS) criteria and symptoms.

RESULTS

Among the 1,206 participants, a square-shaped wrist was associated with CTS after controlling for confounders (prevalence ratio = 2.27; 95% confidence interval [95% CI], 1.33-3.86). Body mass index (BMI) was a strong effect modifier on the relationship between WR and both CTS and abnormal NCS results, with normal weight strata of rectangular versus square wrists = 8.18 (95% CI, 1.63-49.96) and 7.12 (95% CI, 2.19-23.16), respectively.

DISCUSSION

A square wrist is significantly associated with CTS after controlling for confounders. Effect modification by high BMI masked the eightfold magnitude adjusted relationship seen between WR and CTS among normal weight participants. Muscle Nerve 56: 1047-1053, 2017.

Severity of Carpal Tunnel Syndrome and Diagnostic Accuracy of Hand and Body Anthropometric Measures

Objective

To study the diagnostic properties of hand/wrist and body measures according to validated clinical and electrophysiological carpal tunnel syndrome (CTS) severity scales.

Methods

We performed a prospective case-control study. For each case, two controls were enrolled. Two five-stage clinical and electrophysiological scales were used to evaluate CTS severity. Anthropometric measurements were collected and obesity indicators and hand/wrist ratios were calculated. Area under the receiver operating characteristic curves (AUC), sensitivity, specificity, and likelihood ratios were calculated separately by gender.

Results

We consecutively enrolled 370 cases and 747 controls. The wrist-palm ratio, waist-hip-height ratio and waist-stature ratio showed the highest proportion of cases with abnormal values in the severe stages of CTS for clinical and electrophysiological severity scales in both genders. Accuracy tended to increase with CTS severity for females and males. In severe stage, most of the indexes presented moderate accuracy in both genders. Among subjects with severe CTS, the wrist-palm ratio presented the highest AUC for hand measures in the clinical and electrophysiological severity scales both in females (AUC 0.83 and 0.76, respectively) and males (AUC 0.91 and 0.82, respectively). Among subjects with severe CTS, the waist-stature ratio showed the highest AUC for body measures in the clinical and electrophysiological severity scales both in females (AUC 0.78 and 0.77, respectively) and males (AUC 0.84 and 0.76, respectively). The results of waist-hip-height ratio AUC were similar.

Conclusions

Wrist-palm ratio, waist-hip-height ratio and waist-stature ratio could contribute to support the diagnostic hypothesis of severe CTS that however has to be confirmed by nerve conduction study.

Determination of the longitudinal median nerve mobility in different neurodynamic techniques

Background

Neurodynamic techniques which include tensioning and gliding techniques are being employed in the treatment of carpal tunnel syndrome. There are few in vivo studies that have assessed the longitudinal mobility of the nerve using these techniques. The objective of this study was to determine the longitudinal excursion of the median nerve at the level of the wrist and distal arm by having the cervical spine lateral flexion or the wrist extension as terminal movement.

Method

Twenty healthy participants were included in the study. Techniques 1 and 2 had wrist extension as its terminal movement while techniques 3 and 4 had ipsilateral and contralateral neck lateral flexion as its terminal motion. Median nerve longitudinal excursion was determined using dynamic ultrasound and was measured by a motion tracking analysis program employing a fast template tracking method.

Results

Regardless of neurodynamic techniques, longitudinal mobility is highest at the wrist and arm level if the terminal movement is wrist extension. Median nerve excursion at the wrist and arm levels is 15.53 ± 7.04 mm and 6.82 ± 2.97 mm for technique 1 and 13.43 ± 5.64 and 5.33 ± 2.37 mm for technique 2, respectively. There was a significant decrease in median nerve excursion at the wrist level when the terminal movement was at the cervical spine.

Conclusion

The largest median nerve excursion in the arm and wrist occurred when wrist extension is the terminal movement. Contralateral cervical lateral flexion with a prepositioned extended wrist produced the least motion of the median nerve at both sites.

Pre-operative electrodiagnostic testing predicts time to resolution of symptoms after carpal tunnel release

The purpose of this study was to determine if nerve conduction studies predict time to resolution of symptoms after carpal tunnel release. A total of 56 patients undergoing open carpal tunnel release were prospectively enrolled. Pre-operative presence of nocturnal symptoms and daytime numbness/tingling were documented. Pre-operative nerve conduction studies were reviewed and classified as mild, moderate, or severe. After open carpal tunnel release, patients were contacted by phone within 48 hours, at 1 week, and then at 2-week intervals for up to 9 months or until both nocturnal and daytime symptoms had resolved. This study found that patients with mild or moderate carpal tunnel syndrome experience a faster time to resolution of daytime numbness and tingling when compared with patients with severe carpal tunnel syndrome. Nocturnal symptoms resolved quickly in both groups. The results of this study are in contrast to previous studies that found little to no value of nerve conduction studies in predicting post-operative functional and subjective outcomes.

LEVEL OF EVIDENCE

IV.

In the Clinic. Carpal Tunnel Syndrome

This issue provides a clinical overview of carpal tunnel syndrome, focusing on screening and prevention, diagnosis, and treatment. The content of In the Clinic is drawn from the clinical information and education resources of the American College of Physicians (ACP), including MKSAP (Medical Knowledge and Self-Assessment Program). Annals of Internal Medicine editors develop In the Clinic in collaboration with the ACP's Medical Education and Publishing divisions and with the assistance of additional science writers and physician writers.

Anthropometric measurements as a screening test for carpal tunnel syndrome: receiver operating characteristic curves and accuracy

OBJECTIVE

To identify optimal cutoff values for body, hand, and wrist measurements in order to correctly identify individuals with carpal tunnel syndrome (CTS), using receiver operating characteristic (ROC) curves.

METHODS

We enrolled patients with CTS and control subjects at a 1:2 ratio, regardless of age and sex. The diagnosis of CTS was based on clinical findings and delayed distal conduction velocity of the median nerve. The anthropometric measurements included weight, height, waist circumference, hip circumferences, wrist depth/width, third digit length, and palm length/width. Obesity indicators and hand/wrist ratios were calculated. Area under the ROC curve (AUC), sensitivity, specificity, and likelihood ratios were calculated separately according to sex. To assess the role of multiple anthropometric measurements, we fit multivariable logistic regression models including age, wrist ratio, shape index, body mass index, and waist-to-hip ratio.

RESULTS

The study group comprised 1,117 subjects (250 female patients and 474 female controls; 120 male patients and 273 male controls). In women, the accuracy of all anthropometric measures was low (AUC ≤0.64). In men, the accuracy of the hand ratio, shape index, and wrist-to-palm ratio was moderate (AUC = 0.75). The estimates from the multivariable models confirmed the well-known associations between the selected variables and the risk of CTS, but the use of multiple predictors did not dramatically improve the diagnostic performance observed for single anthropometric indexes.

CONCLUSION

In clinical practice, the cutoff values for many anthropometric measurements have limited value as tools for the diagnosis of CTS.

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.

Waist circumference and waist-to-hip ratio in carpal tunnel syndrome: a case-control study

BACKGROUND

The association between carpal tunnel syndrome (CTS) and high body mass index (BMI) and some hand measures is well known. No study has been specifically focused on waist circumference (WC) and waist-to-hip-ratio (WHR). The aim of this prospective case-control study is to evaluate the association between CTS and WC, WHR and other body and hand anthropometric measures.

METHODS

We consecutively enrolled one "idiopathic" CTS case for two controls in 3 outpatient electromyography labs. The main anthropometric measures were BMI, WC, WHR, wrist ratio (WR) and hand ratio (HR). We performed univariate and multivariate analyses.

RESULTS

Female cases and controls were 250 and 474 and male cases and controls were 120 and 273, respectively. At univariate analysis there were differences in many anthropometric measures between cases and controls. At multivariate logistic regression analyses high BMI, WC and WHR and abnormal HR and WR were independent risk factors for CTS. Crossing two categories between BMI, WC and WHR, the overweight subjects, especially females, were at risk only if they had very high WC or high WHR. The risk increased if they were obese.

CONCLUSIONS

High WC/WHR doubles the risk of CTS, the risk further increased if overweight/obese subjects have also very high WC or high WHR. The obese subjects were always at risk regardless of WC and WHR values. Metabolic causes of this association with CTS were hypothesised. BMI is not the only and most powerful body predictor of "idiopathic" CTS, but also WHR and WC should be considered. These measures may not be interchangeable and it may be desirable to consider the utility of their joint use.

Longitudinal design for sonographic measurement of median nerve swelling with controlled exposure to physical work using an animal model

In the study described here, we examined the feasibility of a longitudinal design to measure sonographically swelling of the median nerve caused by controlled exposure to a work task and to evaluate the relationship of changes in morphology to diagnostic standards. Fifteen macaques, Macaca fascicularis, pinched a lever in various wrist positions at a self-regulated pace (8 h/d, 5 d/wk, 18-20 wk). Nerve conduction velocity (NCV) and cross-sectional area (CSA) were measured every 2 wk from baseline through working and a 6-wk recovery. Trending across all subjects revealed that NCV slowed and CSA at the carpal tunnel increased in the working arm, whereas no changes were observed in CSA either at the forearm or for any measure in the non-working arm. There was a small negative correlation between NCV and CSA in the working arm. This study provides validation that swelling can be observed using a longitudinal design. Longitudinal human studies are needed to describe the trajectory of nerve swelling for early identification of median nerve pathology.

Importance of tissue morphology relative to patient reports of symptoms and functional limitations resulting from median nerve pathology

Significant data exist for the personal, environmental, and occupational risk factors for carpal tunnel syndrome. Few data, however, explain the interrelationship of tissue morphology to these factors among patients with clinical presentation of median nerve pathology. Therefore, our primary objective was to examine the relationship of various risk factors that may be predictive of subjective reports of symptoms or functional deficits accounting for median nerve morphology. Using diagnostic ultrasonography, we observed real-time median nerve morphology among 88 participants with varying reports of symptoms or functional limitations resulting from median nerve pathology. Body mass index, educational level, and nerve morphology were the primary predictive factors. Monitoring median nerve morphology with ultrasonography may provide valuable information for clinicians treating patients with symptoms of median nerve pathology. Sonographic measurements may be a useful clinical tool for improving treatment planning and provision, documenting patient status, or measuring clinical outcomes of prevention and rehabilitation interventions.