Proximal Carpal Tunnel Research Articles

Is Ultrasonography a Reliable Approach for the Evaluation of Carpal Tunnel Syndrome in Patients With Mucopolysaccharidosis?

BackgroundOne of the most common causes of carpal tunnel syndrome (CTS) in childhood is mucopolysaccharidosis (MPS). While ultrasonography (US) can aid in the diagnosis of CTS in adult patients, there is limited experience of this in the pediatric group. We aimed to investigate the results of wrist ultrasonography, which may be a candidate alternative to electrophysiological examination. MethodsThe participants were evaluated for symptoms, physical examination findings, electrophysiological tests and grayscale US. CTS was diagnosed in accordance with the American Academy of Orthopedic Surgeons Management of Carpal Tunnel Syndrome: Evidence-Based Clinical Practice Guideline. ResultsIncluded in the study were 27 MPS patients aged 4.5–32 years and 30 healthy control subjects aged 4.3–26 years. Of the 54 wrists in the MPS group, 30 were diagnosed with CTS. The median cross-sectional area (CSA) at the proximal carpal tunnel, the CSA at the forearm, and the wrist-forearm ratio (WFR) were higher in the wrists of the MPS with CTS group than in those without CTS and the healthy control subjects. The WFR cutoff of ≥1.35, 56.6% (95% CI: 437.4–74.5) sensitivity, and 89.8% (95% CI: 81.0–95.5) specificity were consistent with a diagnosis of CTS (receiver operating characteristics analysis, area under the curve = 0.775, 95% CI: 0.673–0.877). ConclusionAlthough the US provides results with unsatisfactory specificity and sensitivity, it is a candidate for further investigation for the diagnosis of CTS because it is an innovative, noninvasive, and more accessible method. WFR value may produce more meaningful results than wrist or forearm nerve area measurements.

Assessing the Potential for Error in Investigating Intraneural Vascularity: A Need for a Standardized Imaging Protocol

Objective: This study examined the implementation of a Doppler sonography imaging protocol to assess intraneural blood flow, within the median nerve, in healthy individuals. Materials and Methods: A total of 176 participants were examined, and this involved 717 retrospective observations of the images collected. The implemented imaging protocol was assessed, and the data that were collected were cleaned and checked for fidelity and validity. Results: A large percentage of missing evidence (11%–35%) across proximal, mid, and distal carpal tunnel locations. Only a quarter of cases with evidence of intraneural blood flow had the strongest evidence of a power Doppler video clip, of which only three-quarters were valid. The study identified potential areas for improving the imaging protocol to reduce missing data and improve data quality. Conclusion: This study demonstrates the significance of a standardized imaging protocol to guide the sonographic acquisition of Doppler images and provides important insights into potential issues with data quality. The recommendations have the potential to help future studies assess intraneural blood flow in healthy populations in a more rigorous and reliable way. Incorporating the study’s recommendations into a standardized protocol, there is potential to enhance the diagnostic accuracy of carpal tunnel syndrome and improve diagnosis and treatment.

Median nerve versus flexor tendons: visualization of median nerve level changes in the proximal carpal tunnel during wrist movement with dynamic high-resolution ultrasound.

The purpose of this prospective ultrasound study was to document dorso-palmar (vertical) displacement of the median nerve in relation to the superficial flexor tendons at the level of the carpal tunnel. Furthermore, the gliding patterns of the median nerve were characterized. The presence of vertical gliding was intended to serve as an additional bio-kinematic parameter of median nerve movement, and will be referred to as a 'level change'. In this study, a total of 32 healthy young individuals underwent dynamic high-resolution ultrasound examinations of both wrists. The neutral position, and maximum flexion and extension of the wrist had to be reached in active and passive movement. The gliding patterns were determined in relation to the superficial flexor tendons. When no vertical nerve gliding was observed, it was characterized as 'no level change'. The presence of a level change prevailed in the healthy young cohort and was observed in 84% (27/32) of individuals during wrist flexion. The following gliding pattern was distinctively the most common: gliding of the entire nerve in between the flexor tendons in active but not in passive movement of the right and left wrists (13/27; 48%). The extent of vertical displacement was found to be associated with the gliding pattern (Kruskal-Wallis test). Movement in the carpal tunnel allows the median nerve to adapt to biomechanical stress. Dynamic ultrasound can demonstrate median nerve level changes in response to wrist movements. Furthermore, a typical gliding pattern was characterized. The presence of level change and gliding patterns were proposed as additional movement parameters during wrist flexion in healthy individuals.

Sonographic reference values for median nerve cross-sectional area: A meta-analysis of data from healthy individuals.

Establish median nerve CSA reference values and identify patient-level factors impacting diagnostic thresholds. Studies were identified through a robust search of multiple databases, and quality assessment was conducted using a modified version of the National Institute of Health Study Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. A meta-analysis was performed to identify normative values stratified by anatomic location. A meta-regression was conducted to examine heterogeneity effects of age, sex, and laterality. The meta-analysis included 73 studies; 41 (56.2%) were high quality. The median nerve CSA [95% CI] was 6.46mm2 [6.09-6.84], 8.68mm2 [8.22-9.13], and 8.60mm2 [8.23-8.97] at the proximal forearm, the carpal tunnel inlet, and the proximal carpal tunnel, respectively. Age was positively associated with CSA at the level of proximal carpal tunnel (β=0.03mm2, p=0.047). Men (9.42mm2, [8.06-10.78]) had statistically larger proximal tunnel CSA (p = 0.03) as compared to women (7.71mm2, [7.01-8.42]). No difference was noted in laterality. A reference value for median nerve CSA in the carpal tunnel is 8.60mm2. Adjustments may be required in pediatrics or older adults. The diagnostic threshold of 10.0mm2 for male patients should be cautiously applied as the upper limit of normative averages surpasses this threshold.

Visualization of the morphological changes in the median nerve after carpal tunnel release using three-dimensional magnetic resonance imaging.

This study aimed to compare the pre- and postoperative morphology of the median nerve using three-dimensional (3-D) MRI in patients with carpal tunnel syndrome (CTS). We assessed 31 patients with CTS who underwent open carpal tunnel release and T2*-weighted MRI of the wrist preoperatively and at 6 months postoperatively. The median nerve morphology was evaluated on the basis of the cross-sectional areas (CSAs) and cross-sectional volumes (CSVs). The association between these MRI findings and nerve conduction studies was also evaluated. The mean preoperative CSA and CSV values at the proximal carpal tunnel level significantly decreased from 22.2 mm2 and 24.4 mm3 to 16.5 mm2 and 18.1 mm3, respectively, postoperatively. Median nerve swelling at the proximal carpal tunnel level was observed in 29 (94%) and 23 (74%) patients before and after surgery, respectively. The mean preoperative CSA and CSV values at the hamate level significantly increased from 9.9 to 12.3 mm2 and from 10.9 to 13.5 mm3 after surgery, respectively. Nerve narrowing at the hamate bone level was preoperatively observed in 28 (90%) patients and postoperatively in 21 (68%) patients. Preoperative CSA and CSV values at the proximal carpal tunnel were significantly associated with preoperative distal motor and sensory latency. Visual confirmation of the median nerve morphology using 3-D MRI is useful when considering postoperative recovery and explaining the nerve condition to the patients. • The 3-D morphology of the median nerve after carpal tunnel release can be delineated using 3-D MRI. • Preoperative swelling of the median nerve in the 2-D and 3-D planes reflects the severity of carpal tunnel syndrome. • Visual confirmation of the median nerve morphology is useful when considering median nerve recovery after carpal tunnel release and for explaining the condition of the nerve to patients.

Comparison of ultrasound-guided pulsed radiofrequency versus steroid injection in the treatment of carpal tunnel syndrome.

Carpal tunnel syndrome (CTS) is the most widespread form of nerve entrapment neuropathy results from increase compression pressure of the median nerve at the wrist under the transverse carpal ligament. To compare ultrasound (US)-guided median nerve steroid injection and pulsed radiofrequency (PRF) on pain intensity, functional status, and patient satisfaction in the treatment of CTS. A total of 90 hands of 59 patients who underwent steroid injection at the level of proximal carpal tunnel or PRF for CTS were retrospectively analyzed. Demographic and clinical characteristics of the patients were recorded. The pain severity was assessed using the Numerical Rating Scale (NRS), and the functional status and clinical outcomes were assessed using the Boston Carpal Tunnel Questionnaire (BCTQ) before the procedure and at Week 1, Month 1, and Month 3 after the procedure. Time to pain relief was evaluated at week 1. Patient satisfaction was evaluated at Month 3. There was no significant difference in the NRS and BCTQ scores between the two treatment methods (p > 0.05 for both). In addition, a significant decrease in the NRS and BCTQ scores were detected at all follow-ups compared to baseline in treatment groups (p < 0.001). The mean time to pain relief was significantly shorter in the PRF group (p < 0.001). Patient satisfaction was similar at Month 3 between the treatment methods (p > 0.05). Our study results suggest that both US-guided steroid injection to the median nerve and PRF are effective and safe methods in the short-term in the treatment of CTS.

T2 mapping of the median nerve in patients with carpal tunnel syndrome and healthy volunteers.

We investigated the changes in MRI T2 mapping values in subjects with carpal tunnel syndrome (CTS) compared to healthy controls. We enrolled 71 patients with CTS and 26 healthy controls. Median nerve T2 values were measured at the distal carpal tunnel, hamate bone, proximal carpal tunnel, and forearm levels. These were compared between patients and controls and correlated with median nerve cross-sectional area (CSA) and nerve conduction measurements. The mean T2 values at the proximal carpal tunnel levels were higher in the CTS group (56.7 ms) than in the control group (51.2 ms, P = .02) and also were higher than at the distal carpal tunnel (51.0 ms, P < .001) and forearm levels (47.6 ms, P < .001). T2 values were not significantly associated with CSA or nerve conduction measurements. T2 mapping of the carpal tunnel provides qualitative information on median nerve pathology but does not reflect CTS severity.

SENSITIVITY AND SPECIFICITY OF MEDIAN NERVE ULTRASONOGRAPHY IN DIAGNOSIS OF CARPAL TUNNEL SYNDROME

Background: Although controversial, recent studies have demonstrated advantages of sonographic techniques in the diagnosis of carpal tunnel syndrome (CTS). The purpose of this study was to assess the utility of median nerve ultrasonography in the diagnosis of CTS in Indian patients. Methods: Ninety patents with clinically suspected CTS were studied. Based on gold standard electromyography/nerve conduction ve-locity studies, wrists with CTS were divided into three groups on the basis of severity of CTS, ie, mild, moderate, and severe. In addition, both sides of the wrist were examined using sonography. Transverse images of the median nerve were obtained and median nerve cross-section areas were measured at three levels, ie, immediately proximal to the carpal tunnel inlet, at the carpal tunnel inlet, and at the carpal tunnel outlet. Furthermore, flexor retinaculum thickness was evaluated. Results: The mean age of the studied patients was 48.52  12.17 years. Median values of the median nerve cross-section at the carpal tunnel in-let, carpal tunnel outlet, and proximal carpal tunnel significantly differed between the wrists with and without CTS (P &lt; 0.05). Comparisons be-tween the CTS groups (mild, moderate, and severe) and non-CTS wrists demonstrated that the median cross-sections of median nerve at the carpal tunnel inlet, carpal tunnel outlet, and inlet proximal carpal tunnel were significantly greater in the severe CTS group than in the other three groups (P &lt; 0.05). The results showed that the median nerve cross-section at the three levels of carpal tunnel could only fairly differentiate se-vere CTS from other cases. Conclusion: The present study demonstrated that median nerve ultrasonography cannot replace the gold standard test (nerve conduction velocity) for the diagnosis of CTS because of low overall sensitivity and specificity, although it might provide useful information in some patients.

A study of median nerve cross sectional area in patients with mild to moderate idiopathic carpal tunnel syndrome

Introduction: Carpal tunnel syndrome is the most common entrapment neuropathy and is caused by median nerve compression at the wrist as it passes through carpal tunnel. Aim: To detect cross sectional area (CSA) of median nerve at the level of distal palmar crease and ratio of cross sectional area at level of proximal carpal tunnel to area 5 cm proximal to carpal tunnel using ultrasound. Materials and Methods: Consecutive patients of age between 18 and 70 years, who presented with paraesthesia of hands (aggravated by holding or keeping hand elevated or with history of nocturnal worsening) and electrophysiological confirmed as mild to moderate idiopathic cases of carpal tunnel syndrome were included in the study. Baseline nerve conduction study was done as per standard protocol for carpal tunnel syndrome. Nerve ultrasound was done with high frequency linear-array transducer (7-14 Hz). Results: 50 wrists in 30 Patients with CTS were studied. Females were more involved with a male: female ratio of 1:5. Mean age was 56.8 years (range 25–82 years). Majority of the cases were bilateral (67%). Dominant hand was involved more (80%) than non-dominant one. Most common symptoms were numbness (100%) and paraesthesia on holding (90.91%). On nerve ultrasound, all patients had CSA of median nerve at proximal carpal tunnel more than 10 square millimetre .The wrist fore-arm CSA ratio was more than 1 in all cases. Majority of the hands were having a cross sectional area 10-11.9 square millimetre and more than 16 square millimetre. We found correlation between CSA at distal palmar crease and median sensory conduction studies. Conclusion: Our study affirms previous studies in demonstrating the usefulness of ultrasonography in diagnosing CTS. Median nerve Cross-sectional area can be used for clinical screening of Carpal tunnel syndrome patients. Keyword: Carpal tunnel syndrome, Cross sectional area, Wrist-ultrasound.

Recent Advances in Ultrasound Diagnosis of Carpal Tunnel Syndrome.

With the widespread use of high-resolution ultrasonography, ultrasonic examination has been shown to be useful as a diagnostic method for carpal tunnel syndrome. The main advantages of ultrasonography are that it is simple, quick, non-invasive, and economical. Another advantage is that tissue dynamics can be observed with real-time imaging. In recent reports, it has been shown that ultrasonic examination can provide similar diagnostic accuracy as nerve conduction study in the diagnosis of carpal tunnel syndrome. It has been expected that ultrasound demand in daily medical care will continue to increase. Ultrasonography in carpal tunnel syndrome shows an enlarged median nerve in proximal carpal tunnel, thickening of the flexor retinaculum, and edema around flexor tendons in cross-sectional images. In addition, with the introduction of new technologies such as ultrasonic elastography and speckle tracking, it has become possible to quantify dynamics and material property changes of nerves, tendons, and their surrounding structures. In this review, we describe recent advancements of carpal tunnel syndrome diagnosis based on ultrasound dynamic images, and discuss its pathology.

Location-dependent change of median nerve mobility in the carpal tunnel of patients with carpal tunnel syndrome.

The purpose of this study was to investigate in vivo median nerve longitudinal mobility in different segments of the carpal tunnel associated with active finger motion in carpal tunnel syndrome (CTS) patients in a comparison with healthy controls. Eleven healthy volunteers and 11 CTS patients participated in this study. Dynamic ultrasound images captured location-dependent longitudinal median nerve mobility within the carpal tunnel during finger flexion at the metacarpophalangeal joints using a speckle cross-correlation algorithm. Median nerve longitudinal mobility in the carpal tunnel was significantly smaller in CTS patients (0.0037 ± 0.0011 mm/degree) compared with controls (0.0082 ± 0.0026 mm/degree) (P < .05), especially in the proximal (0.0064 vs 0.0132 mm/degree on average) and middle (0.0033 vs 0.0074 mm/degree on average) carpal tunnel sections. Median nerve mobility can potentially serve as a biomechanical marker when diagnosing CTS, or when assessing the effectiveness of surgical and conservative treatments.

Blood flow velocity but not tendon mechanics relates to nerve function in carpal tunnel syndrome patients

Carpal tunnel syndrome (CTS) develops from chronic compression of the median nerve. Chronic compression results in a number of vascular, structural and functional changes to the carpal tunnel tissues which ultimately manifest in the characteristic symptoms of CTS. The purpose of this study was to investigate the interplay of median nerve function, median nerve hemodynamics, and finger flexor tendon and subsynovial connective tissue (SSCT) mechanics in CTS patients. Thirty-five patients were recruited following nerve conduction study for this double-blinded imaging study. Ultrasound B-mode, pulse-wave Doppler, and colour Doppler images and videos were collected at the proximal carpal tunnel to quantify: (1) median nerve cross-sectional area, (2) intraneural blood flow velocity in 3 wrist postures (neutral (0°), flexion (15°), extension (30°)), and (3) flexor digitorum superficialis and SSCT displacement. Results demonstrate that intraneural blood flow velocity is dependent on median nerve function and wrist posture such that patients with mild CTS are more susceptible to the effects of non-neutral wrist postures. Tendon-SSCT mechanics do not appear to differ based on severity. This study stresses the importance of limiting exposure to non-neutral wrist postures in patients with early signs of the condition.

Characteristics of forearm mixed nerve conduction study in carpal tunnel syndrome: Comparison with ultrasound assessments

This study aimed to characterize forearm mixed nerve conduction study (NCS) findings in carpal tunnel syndrome (CTS). Eighty-two patients with CTS and 48 healthy controls were enrolled. We directly compared the forearm mixed NCS and ultrasonography results from CTS patients with those from the controls. Correlation analyses were performed to identify the relationship between forearm mixed NCS parameters and ultrasound measurements in CTS. We observed reduced forearm mixed nerve amplitude and increased cross-sectional area (CSA) of the median nerve at the proximal carpal tunnel (CT) inlet in CTS. The forearm mixed nerve amplitude negatively correlated with the CSA at the proximal CT inlet. We found a negative correlation between Bland's neurophysiological grade and the forearm mixed nerve amplitude as well as a positive correlation between the CSA of the median nerve at the proximal CT inlet and Bland's neurophysiological grade. We confirmed that the reduced median mixed nerve amplitude is the distinguishing feature of forearm mixed NCS in CTS. Our findings suggest that the forearm mixed NCS is potentially useful in evaluating its severity.

Ultrasound (US) Changes in the Median Nerve Cross-Sectional Area After Microinvasive US-Guided Carpal Tunnel Release.

To document changes in the median nerve cross-sectional area (CSA) in the proximal carpal tunnel region after ultrasound (US)-guided carpal tunnel release (CTR). Prospective data were collected on 23 consecutive patients (37 wrists) treated with US-guided CTR by the primary author using the same office-based microinvasive technique. Ultrasound was used to measure the largest CSA of the median nerve in the proximal carpal tunnel region both preoperatively and postoperatively. The primary outcome measure was the change in the preoperative versus 6- to 10-week postoperative median nerve CSA. The mean CSA of the median nerve decreased from 16.08 to 12.75 mm2 at 6 to 10 weeks after US-guided CTR (P < .001). During the same period, the mean Boston Carpal Tunnel Questionnaire (BCTQ) symptom score decreased from 3.23 to 1.67 (P < .001), and mean BCTQ functional score decreased from 2.49 to 1.47 (P < .001), both exceeding minimal clinically important differences. Although the primary end point was the median nerve CSA at 6 to 10 weeks, statistically significant reductions in the median nerve CSA, as well as BCTQ scores, were also observed as early as 2 to 4 weeks after US-guided CTR (median nerve CSA, 12.40 mm2 ; BCTQ symptom score, 2.00; BCTQ functional score, 1.75; all P ≤ .03). To our knowledge, this investigation was the largest to date examining changes in the proximal median nerve CSA after US-guided CTR. Statistically significant reductions in the proximal median nerve CSA were observed within 6 to 10 weeks after ultrasound-guided CTR. These reductions were similar to those previously reported for open and endoscopic CTR and validate the ability of US-guided CTR to relieve median nerve compression.

Estimating the most accurate sonographic measurement in the diagnosis of carpal tunnel syndrome: Which is the best?

This study aims to identify the most accurate method or ultrasonographic measurement for the diagnosis of carpal tunnel syndrome (CTS). Between October 2010 and April 2011, a total of 160 hands of 87 patients (4 males, 83 females; mean age 54.5 years; range, 26 to 84 years) with clinically and electrodiagnostically proven CTS and 80 hands of 40 controls (3 males, 37 females; mean age 53.7 years; range, 32 to 77 years) were evaluated by sonographic examination. The diameters and cross-sectional areas (CSA) of the median nerve and longitudinal diameters of the median nerve were measured at the inlet, proximal carpal tunnel, and outlet of the carpal tunnel. Volar bulging and thickness of the retinaculum were also measured. The most optimal combination for the diagnosis of CTS was proximal CSA, volar bulging, and the proximal transverse diameter. The combination of proximal CSA with volar bulging increased the sensitivity and specificity of sonographic measurements. Based on our study results, ultrasonography can be used as a practical modality to distinguish CTS patients from asymptomatic controls.

Sonographic median nerve change after steroid injection for carpal tunnel syndrome.

The sonographic changes of the median nerve after steroid injection for carpal tunnel syndrome (CTS) still require investigation. Sixty-two patients with CTS were included. The Boston Carpal Tunnel Questionnaire was administered, and ultrasonographic examinations were performed before and at 2, 6, and 12 weeks after steroid injection. At 12 weeks, general improvement was scored on a 6-point Likert scale. After treatment, the cross-sectional area (CSA) of the median nerve was significantly reduced at 2-, 6-, and 12-week follow-ups (for each, P < 0.001, analysis of variance). The "significant improvement" group (n = 39) had a significantly greater reduction in the CSA at the carpal tunnel inlet (P = 0.014) and CSA in the proximal carpal tunnel (P = 0.003) compared with the "little/no improvement" group (n = 23). Sonographic measurement of CSA may be considered complementary to the standard clinical evaluation in monitoring of treatment response in patients with CTS. Muscle Nerve 58: 402-406, 2018.

Application and measurement properties of EQ-5D to measure quality of life in patients with upper extremity orthopaedic disorders: a systematic literature review.

The EuroQol-5 Dimension (EQ-5D) is the most widely used generic instrument to measure quality of life (QoL), yet its application in upper extremity orthopaedics as well as its measurement properties remain largely undefined. We implemented a systematic literature review to provide an overview of the application of EQ-5D in patients with upper extremity disorders and analyse its measurement properties. We searched Medline, EMBASE, Cochrane and Scopus databases for clinical studies including orthopaedic patients with surgical interventions of the upper extremity who completed the EQ-5D. For all included studies, the use of EQ-5D and quantitative QoL data were described. Validation studies of EQ-5D were assessed according to COSMIN guidelines and standard measurement properties were examined. Twenty-three studies were included in the review, 19 of which investigated patients with an intervention carried out at the shoulder region. In 15 studies, EQ-5D assessed QoL as the primary outcome. Utility index scores in non-trauma patients generally improved postoperatively, whereas trauma patients did not regain their recalled pre-injury QoL levels. EQ-5D measurement properties were reported in three articles on proximal humerus fractures and carpal tunnel syndrome. Positive ratings were seen for construct validity (Spearman correlation coefficient ≥ 0.70 with the Short Form (SF)-12 or SF-6D health surveys) and reliability (intraclass correlation coefficient ≥ 0.77) with intermediate responsiveness (standardised response means: 0.5-0.9). However, ceiling effects were identified with 16-48% of the patients scoring the maximum QoL. The methodological quality of the three articles varied from fair to good. For surgical interventions of the upper extremity, EQ-5D was mostly applied to assess QoL as a primary outcome in patients with shoulder disorders. Investigations of the measurement properties were rare, but indicate good reliability and validity as well as moderate responsiveness in patients with upper extremity conditions.

Measurement of Median Nerve Strain and Applied Pressure for the Diagnosis of Carpal Tunnel Syndrome

The objective of this study was to evaluate the diagnostic utility of strain and applied-pressure measurements of the median nerve in carpal tunnel syndrome (CTS). Thirty-five wrists of 23 idiopathic CTS patients and 30 wrists of 15 normal patients were examined. Median nerve strain, pressure to the skin and the pressure/strain ratio were measured at the proximal carpal tunnel level. Parameters were compared between CTS patients and controls. The areas under the receiver operating characteristic curves (AUCs) were compared for the parameters. Median nerve strain was significantly lower in the patients than in the controls (p < 0.01). Pressure and pressure/strain ratio were significantly higher in the patients than in the controls (p < 0.05: pressure, p < 0.01: ratio). The AUCs were 0.926, 0.681 and 0.937 for strain, pressure and pressure/strain ratio, respectively. Pressure/strain ratio is useful for evaluating the condition of the median nerve with respect to the hardness of the surrounding structures in CTS.

The influence of wrist posture, grip type, and grip force on median nerve shape and cross-sectional area.

During grasping, the median nerve undergoes mechanical stress in the carpal tunnel which may contribute to carpal tunnel syndrome. This study investigated the effects of wrist posture, grip type, and grip force on the shape and cross-sectional area of the median nerve. Ultrasound examination was used to obtain cross-sectional images of the dominant wrist of 16 healthy subjects (8 male) at the proximal carpal tunnel during grasping. The cross-sectional area, circularity, and axis lengths of the median nerve were assessed in 27 different conditions (3 postures × 3 grip types × 3 force levels). There were no significant changes in median nerve cross-sectional area (P > 0.05). There were significant interactions across posture, grip type, and grip force affecting nerve circularity and axis lengths. When the wrist was flexed, increasing grip force caused the median nerve to shorten in the mediolateral direction and lengthen in the anteroposterior direction (P < 0.04), becoming more circular. These effects were significant during four finger pinch grip and chuck grip (P < 0.05) but not key grip (P > 0.07). With the wrist extended, the nerve became more flattened (less circular) as grip force increased during four finger pinch grip and chuck grip (P < 0.04) but not key grip (P > 0.3). Circularity was lower during the four finger pinch compared to chuck or key grip (P < 0.03). The findings suggest that grip type and wrist posture significantly alter the shape of the median nerve. Clin. Anat. 30:470-478, 2017. © 2017 Wiley Periodicals, Inc.

D6-2 The Effect of Keyboard Typing on the Median Nerve at the Proximal Carpal Tunnel

D6-2 The Effect of Keyboard Typing on the Median Nerve at the Proximal Carpal Tunnel