Functional psychomotor deficits associated with carpal tunnel syndrome

Health-related quality of life in patients with conditions affecting the hand: meta-analysis

BACKGROUND

Health state utility values provide the quality component of quality-adjusted life years and are essential for health economic analyses, such as the National Institute for Health and Care Excellence Technology Appraisal. The aims of this systematic review were to: catalogue utility values for health states experienced by patients with hand conditions; provide pooled utility estimates for common hand conditions; and determine how utilities have been estimated.

METHODS

A PRISMA-compliant systematic review and meta-analysis was conducted (registered in PROSPERO, the international prospective register of systematic reviews (CRD42021226098)). Five databases were searched from inception until April 2023 (Embase, MEDLINE, PsycINFO, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), and the Cochrane Central Register of Controlled Trials (CENTRAL)). All studies that reported primary utility values for hand health states in adult patients were eligible for inclusion. Pooled utility estimates were determined across conditions and intervention status using random-effects meta-analysis.

RESULTS

A total of 10 254 articles were identified; 57 studies met the full inclusion criteria and reported 363 distinct health state utility values. Health state utility values were estimated using a range of methods; the most common measure was the EQ-5D. Pooled utility estimates for carpal tunnel syndrome and hand osteoarthritis before surgical intervention were 0.69 (95% c.i. 0.66 to 0.73) and 0.63 (95% c.i. 0.60 to 0.67) respectively.

CONCLUSION

Pooled utility estimates for patients with untreated carpal tunnel syndrome and hand osteoarthritis are 11% and 18% lower than age-matched population norms respectively. Hand conditions have a significant detrimental impact on health-related quality of life and this study provides catalogued utility values for use in future economic analyses to support the delivery of value-based hand surgery.

Sensorimotor interventions and assessments for the hand and wrist: a scoping review

STUDY DESIGN

Scoping review.

INTRODUCTION

Sensorimotor deficits can impair function and may be present in individuals with common upper extremity conditions.

PURPOSE OF THE STUDY

To provide clinicians with an understanding of the usefulness of the assessments to evaluate sensorimotor function and the interventions reported in the literature to effect positive change in our patients with sensorimotor deficits affecting the hand and wrist.

METHODS

A systematic search produced seventeen studies involving sensorimotor retraining and assessment of sensorimotor performance for the upper extremity.

RESULTS

Sensorimotor interventions and assessments found in the literature vary in regards to their effectiveness in restoring sensorimotor function in subjects with a number of conditions that affect hand and wrist function.

CONCLUSIONS

There is a potential value of sensorimotor interventions for individuals with specific upper extremity conditions. There is a need for further studies to improve treatment of sensorimotor deficits and understanding of sensorimotor interventions.

Assessment from Functional Perspectives: Using Sensorimotor Control in the Hand as an Outcome Indicator in the Surgical Treatment of Carpal Tunnel Syndrome

To investigate whether sensorimotor control of the hand could be an outcome indicator after carpal tunnel release (CTR), this work examined changes in the results of patients’ manual tactile test (MTT), pinch-holding-up activity (PHUA), two-point discrimination (2PD) and Semmes-Weinstein monofilament (SWM) tests. Participants included 30 predominantly sensory neuropathy CTS patients, as confirmed by a nerve conduction study. The MTT, precision pinch performance in PHUA and traditional sensibility (2PD and SWM) tests were used to examine different aspects of sensory status at the time-points of two weeks before operation and one month post-operation, with a single-blind design. The results showed significant improvements in the sensory function as detected by the 2PD and SWM tests (p<0.001) and sensorimotor function as detected by the MTT (p<0.001) and PHUA test (p<0.05) for patients receiving CTR. The responsiveness of the SWM, MTT and PHUA tests (effect size>0.5, p<0.01) are better than that of two-point discrimination test (effect size<0.5, p<0.001). However, pinch strength saw a decline compared to baseline with a moderate effect sizes (effect size = 0.7, p<0.001). This cohort study found that the MTT and PHUA test can both meet all the statistical criteria with regard to assessing treatment outcomes for patients with CTS. In addition, the results of this work provide clinicians with the information that the sensorimotor functions of the hands, as assessed by MTT and PHUA, are responsive to clinical changes due to CTR.

Carpal tunnel syndrome impairs thumb opposition and circumduction motion

BACKGROUND

Carpal tunnel syndrome is associated with sensory and motor impairments resulting from the compressed and malfunctioning median nerve. The thumb is critical to hand function, yet the pathokinematics of the thumb associated with carpal tunnel syndrome are not well understood.

QUESTIONS/PURPOSES

The purpose of this study was to evaluate thumb motion abnormalities associated with carpal tunnel syndrome. We hypothesized that the ranges of translational and angular motion of the thumb would be reduced as a result of carpal tunnel syndrome.

METHODS

Eleven patients with carpal tunnel syndrome and 11 healthy control subjects voluntarily participated in this study. Translational and angular kinematics of the thumb were obtained using marker-based video motion analysis during thumb opposition and circumduction movements.

RESULTS

Motion deficits were observed for patients with carpal tunnel syndrome even though maximum pinch strength was similar. The path length, normalized by palm width of the thumb tip for the patients with carpal tunnel syndrome was less than for control participants (opposition: 2.2 palm width [95% CI, 1.8-2.6 palm width] versus 3.1 palm width [95% CI, 2.8-3.4 palm width], p < 0.001; circumduction: 2.2 palm width [95% CI, 1.9-2.5 palm width] versus 2.9 palm width [95% CI, 2.7-3.2 palm width], p < 0.001). Specifically, patients with carpal tunnel syndrome had a deficit of 0.3 palm width (95% CI, 0.04-0.52 palm width; p = 0.022) in the maximum position of their thumb tip ulnarly across the palm during opposition relative to control participants. The angular ROM also was reduced for the patients with carpal tunnel syndrome compared with the control participants in extension/flexion for the metacarpophalangeal (opposition: 34° versus 58°, p = .004; circumduction: 33° versus 58°, p < 0.001) and interphalangeal (opposition: 37° versus 62°, p = .028; circumduction: 41° versus 63°, p = .025) joints.

CONCLUSIONS

Carpal tunnel syndrome disrupts kinematics of the thumb during opposition and circumduction despite normal pinch strength.

CLINICAL RELEVANCE

Improving understanding of thumb pathokinematics associated with carpal tunnel syndrome may help clarify hand function impairment associated with the syndrome given the critical role of the thumb in dexterous manipulation.

Functional deficits in carpal tunnel syndrome reflect reorganization of primary somatosensory cortex

Carpal tunnel syndrome, a median nerve entrapment neuropathy, is characterized by sensorimotor deficits. Recent reports have shown that this syndrome is also characterized by functional and structural neuroplasticity in the primary somatosensory cortex of the brain. However, the linkage between this neuroplasticity and the functional deficits in carpal tunnel syndrome is unknown. Sixty-three subjects with carpal tunnel syndrome aged 20-60 years and 28 age- and sex-matched healthy control subjects were evaluated with event-related functional magnetic resonance imaging at 3 T while vibrotactile stimulation was delivered to median nerve innervated (second and third) and ulnar nerve innervated (fifth) digits. For each subject, the interdigit cortical separation distance for each digit's contralateral primary somatosensory cortex representation was assessed. We also evaluated fine motor skill performance using a previously validated psychomotor performance test (maximum voluntary contraction and visuomotor pinch/release testing) and tactile discrimination capacity using a four-finger forced choice response test. These biobehavioural and clinical metrics were evaluated and correlated with the second/third interdigit cortical separation distance. Compared with healthy control subjects, subjects with carpal tunnel syndrome demonstrated reduced second/third interdigit cortical separation distance (P < 0.05) in contralateral primary somatosensory cortex, corroborating our previous preliminary multi-modal neuroimaging findings. For psychomotor performance testing, subjects with carpal tunnel syndrome demonstrated reduced maximum voluntary contraction pinch strength (P < 0.01) and a reduced number of pinch/release cycles per second (P < 0.05). Additionally, for four-finger forced-choice testing, subjects with carpal tunnel syndrome demonstrated greater response time (P < 0.05), and reduced sensory discrimination accuracy (P < 0.001) for median nerve, but not ulnar nerve, innervated digits. Moreover, the second/third interdigit cortical separation distance was negatively correlated with paraesthesia severity (r = -0.31, P < 0.05), and number of pinch/release cycles (r = -0.31, P < 0.05), and positively correlated with the second and third digit sensory discrimination accuracy (r = 0.50, P < 0.05). Therefore, reduced second/third interdigit cortical separation distance in contralateral primary somatosensory cortex was associated with worse symptomatology (particularly paraesthesia), reduced fine motor skill performance, and worse sensory discrimination accuracy for median nerve innervated digits. In conclusion, primary somatosensory cortex neuroplasticity for median nerve innervated digits in carpal tunnel syndrome is indeed maladaptive and underlies the functional deficits seen in these patients.

Feasibility of a novel functional sensibility test as an assisted examination for determining precision pinch performance in patients with carpal tunnel syndrome

To understand the feasibility of a novel functional sensibility test for determining precision pinch performance in patients with carpal tunnel syndrome, this study investigates the validity, sensitivity and specificity of functional sensibility derived from a pinch-holding-up activity (PHUA) test. Participants include 70 clinically defined carpal tunnel syndrome (CTS) patients with 119 involved hands and 70 age- and gender-matched controls. To examine the discriminating ability of the functional sensibility test, the differences in the ability of pinch force adjustments to the inertial load of handling object between CTS and control subjects are analyzed. The results of functional sensibility are correlated with the severity of CTS to establish concurrent validity. The receiver operating characteristic (ROC) curve is constructed to demonstrate the accuracy of the proposed test. The functional sensibility score significantly discriminates the patients and control groups (respectively, 12.94±1.72 vs. 11.51±1.15N in peak pinch force (FP_Peak), p<0.001; 2.92±0.41 vs. 2.52±0.24 in force ratio, p<0.001) and is moderately correlated (r = 0.42–0.54, p<0.001) with the results of traditional sensibility tests (touch-pressure threshold and two-point discrimination test). In addition, there is a statistical difference in the results of functional sensibility (p<0.001) among the subgroups of CTS severity based on electrophysiological study. The sensitivity and specificity are 0.79 and 0.76, respectively, for the functional sensibility test. The areas under the ROC curve are 0.85 and 0.80 for the force ratio and FP_Peak, respectively. In conclusion, the functional sensibility test could be feasibly used as a clinical tool for determining both the sensibility and precision pinch performance of hands for the patients with CTS.

Poorer elbow proprioception in patients with lateral epicondylitis than in healthy controls: a cross-sectional study

Two groups of women, 15 patients with lateral epicondylitis and 21 healthy controls, were studied to compare proprioception in the elbows and knees between the groups. Outcome measures were absolute error and variable error for joint position sense and for threshold to detection of a passive movement. Both absolute error and variable error of threshold to detection of a passive movement were greater in the lateral epicondylitis-diagnosed elbows than in the controls' elbows (lateral epicondylitis, 1.8 degrees vs controls 1.1 degrees, P = .026; lateral epicondylitis, 0.8 degrees vs controls 0.3 degrees, P = .015), and there was a tendency toward a greater absolute error of joint position sense compared with the control elbows (lateral epicondylitis, 8.2 degrees vs controls, 5.6 degrees; P = .078). Absolute error of joint position sense was greater in the elbows than in the knees of the lateral epicondylitis patients, but no group differences were found for knees. Proprioception seems, therefore, to be poorer in elbows with lateral epicondylitis elbows than in the controls' elbows. This needs to be taken into consideration in the management of lateral epicondylitis.

Functional tests to quantify recovery following carpal tunnel release

BACKGROUND

An objective test is needed to evaluate outcome following carpal tunnel release. A method to evaluate sensory and motor function related to carpal tunnel syndrome was investigated.

METHODS

Thirty-six candidates for carpal tunnel surgical procedures underwent a physical examination and nerve-conduction studies and completed a survey regarding symptoms. A battery of psychomotor and sensory tests was administered bilaterally immediately before surgery and again six weeks after surgery. The outcome variables included dynamic sensory gap-detection thresholds and rapid pinch-and-release rates.

RESULTS

The average gap-detection threshold for the index finger in the surgical-treatment group demonstrated a 43% improvement, decreasing from 0.14 mm preoperatively to 0.08 mm at six weeks postoperatively (p < 0.01). The average gap-detection threshold for the index finger in the non-surgical-treatment group demonstrated no significant improvement, decreasing from 0.10 mm preoperatively to 0.08 mm postoperatively (p = 0.10). With the upper force level set at 10% of the maximum voluntary contraction, the average pinch rate in the surgical-treatment group demonstrated a 20% improvement, increasing from 6.65 pinches per second preoperatively to 7.96 pinches per second postoperatively (p < 0.001). The average pinch rate in the non-surgical-treatment group demonstrated a 7% improvement, increasing from 6.89 pinches per second preoperatively to 7.37 pinches per second at six weeks postoperatively (p < 0.05).

CONCLUSIONS

Measurable and significantly greater improvement was observed when the surgical-treatment group was compared with the non-surgical-treatment group in terms of these two sensory and psychomotor functional testing outcomes at six weeks.

LEVEL OF EVIDENCE

Therapeutic study, Level II-1 (prospective cohort study). See Instructions to Authors for a complete description of levels of evidence.

Work-related musculoskeletal disorders of the hand and wrist: epidemiology, pathophysiology, and sensorimotor changes

The purpose of this commentary is to present recent epidemiological findings regarding work-related musculoskeletal disorders (WMSDs) of the hand and wrist, and to summarize experimental evidence of underlying tissue pathophysiology and sensorimotor changes in WMSDs. Sixty-five percent of the 333 800 newly reported cases of occupational illness in 2001 were attributed to repeated trauma. WMSDs of the hand and wrist are associated with the longest absences from work and are, therefore, associated with greater lost productivity and wages than those of other anatomical regions. Selected epidemiological studies of hand/wrist WMSDs published since 1998 are reviewed and summarized. Results from selected animal studies concerning underlying tissue pathophysiology in response to repetitive movement or tissue loading are reviewed and summarized. To the extent possible, corroborating evidence in human studies for various tissue pathomechanisms suggested in animal models is presented. Repetitive, hand-intensive movements, alone or in combination with other physical, nonphysical, and nonoccupational risk factors, contribute to the development of hand/wrist WMSDs. Possible pathophysiological mechanisms of tissue injury include inflammation followed by repair and/or fibrotic scarring, peripheral nerve injury, and central nervous system reorganization. Clinicians should consider all of these pathomechanisms when examining and treating patients with hand/wrist WMSDs.

Performance of a high-repetition, high-force task induces carpal tunnel syndrome in rats

STUDY DESIGN

A randomized controlled prospective experimental study with some repeated measures.

OBJECTIVES

To characterize behavioral, sensory, motor, and nerve conduction decrements, and histological changes in the median nerve in rats trained to perform a high-force repetitive task.

BACKGROUND

Understanding of work-related carpal tunnel syndrome is hampered by the lack of experimental studies of the causes and mechanisms of nerve compression induced by repetitive motion. Most animal models of nerve compression have not employed voluntary repetitive motion as the stimulus for pathophysiological changes.

METHODS AND MEASURES

Thirty Sprague-Dawley rats served as controls for 1 or more studies. Ten rats were trained to pull on a bar with 60% maximum force 4 times per minute, 2 h/d, 3 d/wk for 12 weeks. Motor behavior and limb withdrawal threshold force were characterized weekly. Grip strength and median nerve conduction velocity were measured after 12 weeks. Median nerves were examined immunohistochemically for ED1-positive macrophages, collagen, and connective tissue growth factor.

RESULTS

Reach rate and duration of task performance declined over 12 weeks. Grip strength and nerve conduction velocity were significantly lower after 12 weeks than in controls. Limb withdrawal threshold increased between weeks 6 and 12. Median nerves at the level of the wrist showed increases in macrophages, collagen, and connective-tissue growth-factor-positive cells. These effects were seen in both the reach and nonreach limbs.

CONCLUSIONS

This animal model exhibits all the features of human carpal tunnel syndrome, including impaired sensation, motor weakness, and decreased median nerve conduction velocity. It establishes a causal relationship between performance of a repetitive task and development of carpal tunnel syndrome.

Functional deficits in carpal tunnel syndrome

BACKGROUND

Carpal tunnel syndrome (CTS) is a major occupational illness in the US. The Wisconsin Test is a quantitative computer-controlled test battery designed for measuring sensory and psychomotor function. Subjects were recruited from industrial jobs at high-risk for CTS to determine if subtle sensory and motor deficits were observable in a working population. Outcomes were studied for potential use as an injury surveillance instrument.

METHODS

A total of 208 subjects participated (72 males and 136 females). Participants completed a symptom survey, were given a physical examination, administered nerve conduction tests, and were tested using the Wisconsin Test battery.

RESULTS

The greatest functional deficits were observed when nerve conduction findings were positive and were accompanied by either positive symptom survey outcomes or positive physical exam findings. The presence of symptoms alone were not significantly associated with motor deficits and no significant sensory threshold differences were observed among subjects categorized using any single criterion (i.e., nerve conduction, symptom reports, or examination).

CONCLUSIONS

Measurable and quantifiable sensory and psychomotor deficits were observed in a working industrial population, and were greatest when positive symptoms or physical exam was accompanied by positive nerve conduction test findings. These data show that clinical criteria used in the diagnosis of CTS corresponds with functional psychomotor and sensory impairments measured in these tests.

Median nerve trauma in a rat model of work-related musculoskeletal disorder

Anatomical and physiological changes were evaluated in the median nerves of rats trained to perform repetitive reaching. Motor degradation was evident after 4 weeks. ED1-immunoreactive macrophages were seen in the transcarpal region of the median nerve of both forelimbs by 5-6 weeks. Fibrosis, characterized by increased immunoexpression of collagen type I by 8 weeks and connective tissue growth factor by 12 weeks, was evident. The conduction velocity (NCV) within the carpal tunnel showed a modest but significant decline after 9-12 weeks. The lowest NCV values were found in animals that refused to participate in the task for the full time available. Thus, both anatomical and physiological signs of progressive tissue damage were present in this model. These results, together with other recent findings indicate that work-related carpal tunnel syndrome develops through mechanisms that include injury, inflammation, fibrosis and subsequent nerve compression.

Trunk movements and load support strategy in simulated handling tasks carried out by workers with and without musculoskeletal symptoms

OBJECTIVE

To compare two groups of worker with and without upper limb musculoskeletal symptoms when simulating handling tasks, regarding trunk movements and load support.

DESIGN

Simultaneous lumbar movements and load support were quantified by a flexible electrogoniometer and load cell, respectively.

BACKGROUND

Workers can adopt different motor strategies to perform similar tasks, possibly resulting in different physical demands. No previous studies on different movement patterns as a possible strategy for coping with physical demands by injured workers are available.

METHODS

9 asymptomatic and 10 symptomatic industrial workers, carried a device for measuring contact between load and trunk during simulated tasks. An ANOVA was performed to compare results between symptomatic and asymptomatic workers.

RESULTS

Most of the symptomatic workers supported the load on their trunk, whilst most of the asymptomatic workers did not. Higher values of lumbar flexion occurred for the symptomatic workers (P<0.05).

CONCLUSIONS

Apparently, differences in movement and load support were adopted by injured workers as a possible strategy to share upper limb overload with other body regions.

RELEVANCE

Workers suffering from work-related musculoskeletal disorders may adopt different motor strategies to cope with their job physical demands. An effort should be made to reallocate injured workers if major cost is to be avoided.

Pathophysiological tissue changes associated with repetitive movement: a review of the evidence

Work-related musculoskeletal disorders (WMSDs) represent approximately one third of workers' compensation costs in US private industry, yet estimates of acceptable exposure levels for forceful and repetitive tasks are imprecise, in part, due to lack of measures of tissue injury in humans. In this review, the authors discuss the scope of upper-extremity WMSDs, the relationship between repetition rate and forcefulness of reaching tasks and WMSDs, cellular responses to injury in vivo and in vitro, and animal injury models of repetitive, forceful tasks. The authors describe a model using albino rats and present evidence related to tissue injury and inflammation due to a highly repetitive reaching task. A conceptual schematic for WMSD development and suggestions for further research are presented. Animal models can enhance our ability to predict risk and to manage WMSDs in humans because such models permit the direct observation of exposed tissues as well as motor behavior.

Effect of musculoskeletal disorders on prehension strength

The purpose of this study was to compare the maximum and job simulated hand grip strength in both healthy workers and those suffering from mild and severe stages of musculoskeletal disorders. Three groups of 10 female industrial workers each were recruited after a detailed screening for musculoskeletal disorders: one group of 10 healthy workers (GI) and two other groups (GII and GIII) consisting of workers suffering from mild and severe upper limbs disorders, respectively. A special device was built to reproduce a similar prehension pattern (open palmar) to that used on the job. This was calibrated against a Jamar dynamometer. Job simulated and maximum prehension strength were tested in three consecutive trials. Pearson's correlation coefficient was calculated for the calibration procedure. Descriptive analysis of the musculoskeletal data was computed. ANOVA and Duncan post hoc multiple comparisons were conducted to test the main effects on muscular strength and interactions. Significant differences between types of strength (p<0.00001) and groups of subject (p<0.0001) were identified. The maximum strength decreased progressively from groups I to III. Although job simulated strength also decreased as disorder severity increased, this trend was weaker than the one observed for the maximum strength. These results suggest that a re-allocation of workers suffering from musculoskeletal disorders be considered.

Computer key switch force-displacement characteristics and short-term effects on localized fatigue

This study investigates the effects of key switch design parameters on short-term localized muscle fatigue in the forearm and hand. An experimental apparatus was utilized for simulating and controlling key switch make force and travel using leaf spring mechanisms, and provided direct measurement of applied key strike force using strain gauge load cells. Repetitive key tapping was performed as fast as possible using the dominant index finger for 500 s per condition (8.3 min) and a work-rest schedule consisting of 15 s of key tapping alternating with 10 s of rest. One combination of two make force levels (0.31 and 0.71 N) and two over travel distances (0.5 and 4.5 mm) was presented randomly on four different days. Nine subjects participated. Localized muscle fatigue in the hand and forearm was assessed subjectively using a 10 cm visual analogue scale, and objectively using surface electromyography (EMG). Average peak key strike force exerted was 0.35 N less for the smaller make force and 0.59 N less for the longer over travel distance. Fatigue occurred in all cases but no significant differences were observed between key switch parameters based on RMS EMG. Subjective reports of localized fatigue after 500 s were less when the key switch make force was less; however, a corresponding over travel effect was not observed despite the greatly reduced key strike force for the longer over travel distance. This discrepancy may be explained by the greater finger movement that was observed with increased over travel. Although there was no apparent improvement in short-term discomfort from fatigue when over travel was increased, this study did not consider the potential long-term health benefits from reduced key strike force.

Preliminary evaluation of a sensory and psychomotor functional test battery for carpal tunnel syndrome: Part 1--Confirmed cases and normal subjects

Two new computer-controlled functional tests were developed, known as the Wisconsin test battery, for carpal tunnel syndrome (CTS). The gap detection sensory test quantifies tactile thresholds for areas of the hand innervated by the median nerve. The rapid pinch and release psychomotor test measures the initiation and control of specific muscles innervated by the median nerve motor branch. Ten confirmed CTS patients (based on electrophysiological parameters and examination; 18 CTS hands) and eight confirmed normal subjects (16 hands) with a similar average age were administered both tests. The CTS patients showed significant functional deficits for both tactility and psychomotor tests. Average CTS performance was 24 to 104% poorer than for the normal subjects, depending on the performance measure. The results indicated high correlations (r = 0.5 to 0.8) between median nerve electrophysiological parameters and tactility or psychomotor performance variables. No single functional test variable had sufficient sensitivity for detecting CTS among the subject pool. The combination of the two tests using 95% confidence level cutoff points achieved a sensitivity of 0.78 and a specificity of 0.81. Stepwise discriminant analysis resulted in two performance variables capable of a sensitivity of 0.72 and a specificity of 0.94 for differentiating well-defined CTS subjects from normal subjects. Despite these promising results, limitations of the study include small sample size and subject selection bias. Further studies are needed for verifying the utility of the functional test battery for detecting CTS in a general population.

Preliminary evaluation of a sensory and psychomotor functional test battery for carpal tunnel syndrome: Part 2--Industrial subjects

This study evaluated the Wisconsin functional sensory and psychomotor test battery for carpal tunnel syndrome (CTS). Subjects were 27 employees recruited from a food processing plant. Both hands of all subjects were examined and categorized by presence or absence of symptoms and nerve conduction study (NCS) findings (Symptom-/NCS-, Symptom+/NCS-, Symptom-/NCS+, and Symptom+/NCS+). Symptom-/NCS- category hands had significantly better performance (15-60%) for most of the functional test battery variables than Symptom+/NCS+ category hands. A significant gap detection threshold difference (32%) was observed between NCS+ and NCS- hands regardless of symptoms, with NCS- having impaired performance. No significant effect of CTS symptoms on performance was observed. Stepwise discriminant analysis was used to select the best variables to differentiate between groups. The ratio of the change in pinch rate with respect to required pinch force differentiated NCS+ from NCS- hands, with a sensitivity of 0.71 and a specificity of 0.68. The same variable had a sensitivity of 0.74 and specificity of 0.83 for distinguishing Symptom-/NCS- hands from all other categories. Pinch rate had a sensitivity of 0.82 and a specificity of 0.81 for separating Symptom+/NCS+ hands from all other categories. Use of both gap detection threshold and the ratio of the change in pinch rate with respect to required pinch force could best differentiate Symptom+/NCS+ from Symptom-/NCS- cases for a sensitivity of 0.91 and specificity of 0.87. Outcomes could not be generalized to a specific work population but demonstrate that the non-invasive test battery may be useful for providing objective measures of deficits associated with CTS symptoms and electrophysiological parameters.

Activation force and travel effects on overexertion in repetitive key tapping

Key switch design parameters, including make force, make travel, and over travel, were investigated for minimizing operator-exerted force while maximizing key-tapping speed. A mechanical apparatus was designed, constructed, and used for independently controlling key switch parameters and for directly measuring finger exertions during repetitive key tapping using strain gauge load cells. The task for the 25 participants involved using the index finger of the dominant hand to repeatedly depress a single key as rapidly as possible. Participants received visual and auditory feedback upon a successful keystroke. Peak force exerted decreased 24% and key-tapping rate increased 2% when over travel was distended from 0.0 to 3.0 mm. Although peak force exerted was not significantly affected by make point travel, key-tapping rate increased 2% when make point travel was reduced from 4.0 to 1.0 mm. These results indicate that key switch mechanisms that provide adequate over travel might enable operators to exert less force during repetitive key tapping without inhibiting performance.