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Enhancement in median nerve mobility during radioulnar wrist compression in carpal tunnel syndrome patients
Accepted Manuscript Enhancement in median nerve mobility during radioulnar wrist compression in carpal tunnel syndrome patients
Yifei Yao, Emily Grandy, Peter J. Evans, William H. Seitz, ZongMing Li PII: DOI: Reference:
S0268-0033(18)30628-4 doi:10.1016/j.clinbiomech.2018.10.017 JCLB 4631
To appear in:
Clinical Biomechanics
Received date: Accepted date:
30 July 2018 11 October 2018
Please cite this article as: Yifei Yao, Emily Grandy, Peter J. Evans, William H. Seitz, ZongMing Li , Enhancement in median nerve mobility during radioulnar wrist compression in carpal tunnel syndrome patients. Jclb (2018), doi:10.1016/j.clinbiomech.2018.10.017
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ACCEPTED MANUSCRIPT Enhancement in Median Nerve Mobility during Radioulnar Wrist Compression in Carpal tunnel Syndrome Patients Yifei Yaoa, Emily Grandya, Peter J. Evansb, William H. Seitz, Jr.b, Zong-Ming Lia,b,c Hand Research Laboratory, Departments of aBiomedical Engineering, bOrthopaedic Surgery, and Physical Medicine and Rehabilitation, Cleveland Clinic, Cleveland, OH, USA
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Corresponding author: Zong-Ming Li;
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Email: [email protected] Web: http://handlab.org/ Phone number: +216-444-1211
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address: Cleveland Clinic, 9500 Euclid Avenue, ND20, Cleveland, OH, 44195, USA
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Word count for main text: 3478
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Word count for Abstract: 181
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Declarations of interest: none
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Abstract Background: Carpal tunnel syndrome is a compression neuropathy at the wrist associated with compromised median nerve mobility. The purpose of this study was to investigate the effects of radioulnar wrist compression on median nerve longitudinal mobility within the carpal tunnel in carpal tunnel syndrome patients as well as healthy subjects.
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Methods: Dynamic ultrasound images captured longitudinal median nerve motion in the carpal
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tunnel during radioulnar wrist compression force application in 11 healthy subjects and 11 carpal
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tunnel syndrome patients.
Findings: We found that median nerve mobility was not significantly affected by radioulnar wrist compression in healthy subjects (P = 0.34), but improved by 10 N radioulnar wrist compression
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in carpal tunnel syndrome patients (P < 0.05). Analysis of segmental median nerve mobility in carpal tunnel syndrome patients showed significantly improved mobility in the proximal tunnel
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section under 10 N radioulnar wrist compression force condition compared to the no compression condition (P < 0.05).
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Interpretation: Moderate radioulnar wrist compression force application helps restore impaired
with carpal tunnel syndrome.
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median nerve mobility and may be effective in improve nerve function and symptoms associated
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Dynamic ultrasound
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Keywords: Carpal tunnel syndrome; Radioulnar wrist compression; Median nerve mobility;
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1. Introduction The carpal tunnel in the wrist is a fibro-osseous structure formed by interconnected carpal bones dorsally and the transverse carpal ligament volarly containing the median nerve and nine flexor tendons. In healthy hands, the median nerve in the carpal tunnel experiences excursion in response to hand motions to dissipate mechanical stress (Topp and Boyd, 2006; Phillips et al., 2004).
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However, median nerve excursion can be hindered by the surrounding environment and is prone
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to excessive mechanical stresses and strains in response to daily hand tasks (Wang et al., 2014).
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Chronic stress of the median nerve in the carpal tunnel eventually leads to compression neuropathy, i.e. carpal tunnel syndrome (CTS). In CTS, median nerve compression due to factors such as small tunnel volume and large tunnel contents can compromise the kinematic behavior of the median
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nerve (McLellan et al., 1976, Valls-Sole et al., 1995, Wright et al., 1996, Bay et al., 1997, Szabo et al., 1994, Kuo et al., 2016). Compression of the median nerve over time can cause endoneurial
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edema and perineurium fibrosis (Mackinnon et al., 1985), which may further alter mobility of the nerve. Previous studies have shown that the median nerve in CTS patients exhibits reduced
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transverse motion (Kuo et al., 2016; Nakamichi and Tachibana, 1995; van Doesburg et al., 2012;
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Wang et al., 2014; Yoshii et al, 2013) as well as reduced longitudinal mobility (Liong et al., 2014; Filius et al., 2015; Hough et al., 2007). In hand rehabilitation, nerve gliding exercises have been attempted for CTS treatment to improve median nerve mobility (Rozmaryn et al., 1998; Akalin et
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al., 2002; Coppieters and Alshami, 2007), to prevent adhesion between the median nerve and flexor tendons (Skirven and Trope, 1994), and to facilitate venous return and edema dispersal
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(Burke et al., 2003).
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Alternatively, decompression of the median nerve in CTS patients can be achieved by increasing carpal tunnel space, mitigating the compromised nerve mobility. We have demonstrated that carpal tunnel space can be augmented by narrowing the carpal arch width between the trapezium and hook of hamate (Li et al., 2009, 2011, 2013). For example, geometric modeling (Li, et al., 2009) and in vitro studies (Li et al., 2009, 2013) showed that arch width narrowing was associated with palmar bowing of the transverse carpal ligament with increased arch height and area. Furthermore, in vivo radioulnar wrist compression (RWC) helped reduce median nerve flattening which is indicative of nerve decompression in CTS patients (Marquardt et al., 2016). However, it is
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ACCEPTED MANUSCRIPT unknown how RWC could affect the kinematic behavior of the median nerve to overcome the impaired nerve mobility.
Therefore, the purpose of this study was to investigate the effects of RWC on median nerve longitudinal mobility within the carpal tunnel in CTS patients as well as in healthy subjects for comparison. We hypothesized that RWC would enhance median nerve mobility in CTS patients,
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patients would be location-dependent along the carpal tunnel.
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but not in healthy controls. We further hypothesized median nerve mobility enhancement in CTS
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2. Methods 2.1 Human subjects
Eleven patients diagnosed with CTS (age 51.5 (SD 16.3) years; 4 men and 7 women; 8 right hands;
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3 left hands; height of 1.67 (SD 0.11) m; weight of 75.62 (SD 9.66) kg) and eleven healthy volunteers (age 44.7 ± 14.8 years; 4 men and 7 women; 11 right hands; height of 1.70 (SD 0.10)
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m; weight of 79.31 (SD 17.51) kg) participated in this study. The CTS patients were recruited based on a history of paresthesia, pain and/or numbness in the median-innervated hand territory,
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which had persisted for at least 3 months, and at least one positive physical examination of Tinel’s sign, Phalen’s test or carpal compression test, and a mean severity scale greater than 1.5 using the
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Boston CTS questionnaire (Levine et al., 1993). Exclusion criteria for CTS and healthy subjects were systemic disease (i.e. rheumatoid arthritis, diabetes, fibromyalgia), history of major injury or
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surgery to the wrist or hand, treatment, musculoskeletal/neuromuscular disorders, BMI over 30, and pregnancy. The study was approved by the Institutional Review Board and written informed
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consent was obtained from each subject before participation.
2.2 RWC procedures
A custom made compression system was used to non-invasively apply compression across the wrist at the distal level of the carpal tunnel (Marquardt et al., 2015). The system applied force using two pneumatic actuators (Bimba Manufacturing, Monee, IL, USA) which were linked with two end effectors made of thermoplastic materials covered by a thin foam to comfortably fit the curvature of radial and ulnar aspects of the wrist. The actuators were attached to six degrees-of-
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ACCEPTED MANUSCRIPT freedom alignment mounts for positional alignment. Bifurcated plastic tubes were used to connect an air pressure regulator (VBM Medical, Noblesville, IN), a digital pressure gage, and the pneumatic actuators. The pressure regulator drove the actuators to generate and control the desired force magnitude according to a predetermined calibration of the relationship between the regulator pressure and the amount of force applied by the actuators. A height adjustable platform was used
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for position control of hand, wrist and forearm.
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For each subject, the hand with the more severe CTS symptoms (for the CTS group) or dominant
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side (for healthy group) was tested. The subject lay supine on a testing bed with the arm abducted 30° in the thermoplastic splint shaped according to the arm geometry of the subject with the hand
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supinated and palm upturned. The wrist was then positioned comfortably in the height adjustable RWC system. Velcro® straps were used to stabilize the forearm and fix the thumb in 45° extension.
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The proximal/distal interphalangeal joints of the four fingers were secured in an anatomically neutral position along a flat splint using another Velcro® strap, while the metacarpophalangeal
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joints remained free to move simultaneously (Fig 1).
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The centerlines of the RWC system end effectors were aligned so that the applied force coincided with the tunnel level containing the hook of hamate and ridge of trapezium. The end effectors were
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further adjusted in the volar-dorsal direction so that the center of each end effector was positioned at the midpoint between the volar and dorsal surfaces of the wrist. The RWC system applied a
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transverse compressive force (10 or 20 N) across the distal carpal tunnel. The air pressure regulator was set to apply pressure through the bifurcated tubes to simultaneously actuate the two end
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effectors to generate the specific force magnitudes on both the radial and ulnar sides of the wrist.
2.3 Setup of ultrasound imaging An ultrasound system (Acuson S2000, Siemens Medical Solutions USA, Mountain View, CA, USA) with an 18L6HD linear array transducer was used to define the proximal and distal boundaries of the carpal tunnel by visualizing the cross-sectional images that clearly show the proximal level of scaphoid and pisiform and distal level of hook of hamate and trapezium, respectively. The centerlines of the ultrasound probe footprints at proximal and distal boundaries of the carpal tunnel were ink-marked on the skin. A line of radiopaque markers (0.33 mm diameter, 5
ACCEPTED MANUSCRIPT Beekley Corporation, Bristol, CT, USA) were attached to the palmar skin for the purpose of identifying the proximal and distal boundaries of the carpal tunnel on ultrasound images. The radiopaque markers were positioned 10 mm proximal and distal to the proximal and distal inked lines, respectively, minimizing the image artifacts in the tunnel region of interest generated by the markers.
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The median nerve, shown as a hypoechogenic structure on an ultrasound image, was first identified
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at proximal level cross-section of the carpal tunnel. The ultrasound transducer was then rotated to
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follow the nerve in the longitudinal direction to be in line with the median nerve, and then stabilized using the custom adjustable holder. The holder was further adjusted in the radial-ulnar
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direction to locate the image plane in which the median nerve was the thickest, and then the holder
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was locked to maintain the constant imaging location throughout the experiment.
2.4 Setup of an electrogoniometer
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An electrogoniometer (XM65, Biometrics Ltd, Cwmfelinfach, Gwent, UK) was used to record metacarpophalangeal joint motion of four fingers in unison. The end blocks of the goniometer
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were attached to the dorsum of the hand and fingers, respectively. Prior to data collection, the
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electrogoniometer was zeroed with the fingers in the anatomical neutral position.
2.5 Data collection of dynamic ultrasound images during RWC and finger motion
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A RWC trial lasts 3 minutes. At the end of the 3-minute compression, each subject performed cyclic finger flexion/extension while the compression maintained. The finger motion was
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performed by flexing and extending the metacarpophalangeal joints of four fingers between 0 and 90 degrees at a pace of 0.3 Hz. A 3-minute rest was provided between consecutive trials. Each force level (0, 10, or 20 N) was repeated 3 times for a total of 9 trials in a randomized order. For each RWC trial, 18 motion cycles were captured. During finger motion, the median nerve longitudinal motion was captured by ultrasound videos at a rate of 30 frames per second. The ultrasound image has a 640×480 pixels size with a resolution of 0.062 mm. Angular finger motion at the metacarpophalangeal joints were recorded by the electrogoniometer which was synchronized to the ultrasound video.
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2.6 Longitudinal median nerve mobility One trial for each of the 0, 10 and 20 N force conditions was used for median nerve mobility analyses for each subjects; the remaining trials were used as backup. In each selected trial, 3 finger flexions from 0 to 90 degrees were examined. Longitudinal median nerve displacement at each flexion angular position was analyzed using speckle cross-correlation algorithm (Dilley et al.,
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2001). The program determined relative nerve displacement using fine speckle features in the
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selected region of interest (ROI) between adjacent image frames in the ultrasound video. ROIs
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(6.2×1.8 mm) were defined in a 0.62 mm increment along the midline of the median nerve from proximal to distal boundaries of the tunnel. Median nerve displacement in the carpal tunnel was
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calculated as the mean value of individual displacements of all ROIs. Additionally, the median nerve was segmented into three sections of equal length along the longitudinal direction
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corresponding to the proximal, middle and distal segments of the carpal tunnel (Fig 2). Segmental median nerve displacement was calculated as the mean value of individual displacement of ROIs
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in the segment. Least-squares linear regression was performed for median nerve displacement as a function of finger flexion angle. The slope of the linear equation was used to quantify the mobility
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of the nerve.
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2.7 Statistical analysis
Median nerve mobility was analyzed using a two-way mixed repeated measures analysis of
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variance (ANOVA) with group (healthy subjects and CTS patients) as between subjects factor, and force magnitude (0, 10, and 20 N) as the repeated within subjects factor. Furthermore, a two-
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way repeated measures ANOVA was performed for the CTS patients to examine the dependence of median nerve mobility on nerve location (proximal, middle, and distal) and force magnitude (0, 10 and 20 N). Post-hoc Tukey’s tests were used for pairwise comparisons and p-value less than 0.05 was considered statistically significant. All statistical analyses were performed using SigmaStat 3.4 (Systat Software Inc., San Jose, CA, USA).
3. Results 3.1 Median nerve mobility under RWC in the healthy subjects and CTS patients
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ACCEPTED MANUSCRIPT R2 values of linear regression on the median nerve displacements in the carpal tunnel as a function of flexion angle under 0, 10 and 20 N RWC force conditions for both healthy subjects and CTS are shown in Table 1. The median nerve mobility was significantly dependent on subject group (P < 0.05), but not on force magnitude (P = 0.962). On average, median nerve mobility in CTS patients was 41.5% of that in healthy subjects under the no compression condition (P < 0.001). There was no significant difference between median nerve mobility in CTS patients and in healthy
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subjects under the 10 N condition (P = 0.50). Under the 20 N RWC condition, median nerve
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mobility in CTS patients was 62.5% of that in healthy subjects (P < 0.05).
For healthy subjects, the median nerve mobilities were 0.0082 (SD 0.0026), 0.0064 (SD 0.0042),
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and 0.0072 (SD 0.0033) mm/degree under 0, 10 and 20 N conditions, respectively. Force levels had no significant effect on median nerve mobility (P = 0.34, Fig 3). For CTS patients, median
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nerve mobility was significantly dependent on RWC force levels (P < 0.05, Fig 3). Pairwise comparisons showed that the median nerve mobility under the 10 N force condition (0.0053 (SD
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0.0022) mm/degree) was significantly larger than under the no compression condition (0.0034 (SD 0.0015) mm/degree, P < 0.05), an average increase of 55.9%. However, nerve mobility under 20
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N RWC (0.0045 (SD 0.0030) mm/degree) was not significantly different from that of the no
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compression condition (P = 0.86) or the 10 N force condition (P = 0.26).
3.2 Segmental median nerve mobility in the CTS patients
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The mobility of the median nerve in patients with CTS in the proximal carpal tunnel was 0.0055 (SD 0.0033), 0.0081 (SD 0.0045), 0.0071 (SD 0.0044) mm/degree under 0, 10 and 20 N RWC
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force conditions, respectively (Fig. 4); the mobility of median nerve in the middle carpal tunnel was 0.0042 (SD 0.0023), 0.0036 (SD 0.0028), 0.0047 (SD 0.0036) mm/degree under 0, 10 and 20 N RWC force conditions, respectively; in the distal carpal tunnel, the mobility of median nerve was 0.0024 (SD 0.0022), 0.0036 (SD 0.0024), 0.0026 (SD 0.0019) mm/degree under 0, 10 and 20 N RWC force conditions, respectively. ANOVA results showed that the nerve mobility was significantly dependent on nerve location (P < 0.001), but not on RWC condition (P = 0.351). In the proximal tunnel, median nerve mobility increased significantly by 47.2% under 10 N RWC condition compared to the no compression condition (P < 0.05). However, there was no significant difference between the 20 N RWC condition and the no compression condition (P = 0.24). In the 8
ACCEPTED MANUSCRIPT middle carpal tunnel, there were no significant differences found in median nerve mobility among the three force levels (0 vs. 10 N, P =0.85; 0 vs. 20 N, P =0.89; 10 vs 20 N, P = 0.58). Similarly, nerve mobility at the distal tunnel level did not differ among the three force levels (0 vs. 10 N, P =0.47; 0 vs. 20 N, P =0.97 10 vs 20 N, P = 0.60).
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4. Discussion
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In this study, we investigated the effects of RWC on longitudinal mobility of the median nerve in
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both healthy subjects and CTS patients. Median nerve motion in the carpal tunnel corresponding to finger flexion/extension was captured in vivo using dynamic ultrasonography. We found that median nerve mobility in CTS patients was compromised, and the comprised mobility was
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improved by RWC. Furthermore, the effect of RWC on median nerve mobility in CTS patients
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was dependent on RWC force magnitude and nerve location.
In this study, we observed reduced median nerve mobility in CTS patients under no compression
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condition compared to healthy subjects. Previous studies investigating longitudinal median nerve
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mobility also showed decreased nerve gliding in CTS patients (Liong et al., 2014; Filius et al., 2015; Hough et al., 2007), and our study supported these results. In our study, median nerve mobility in CTS patients was about 40% of that in healthy subjects, demonstrating compromised
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nerve gliding in this patient population. Our results further corroborated existing literature that segmental median nerve mobility in the proximal tunnel is inhibited in patients with CTS (Hough
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et al. 2007; Filius et al. 2015; Liong et al. 2014).
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Previous studies in our laboratory have shown the effects of RWC on the carpal arch morphology. With carpal arch width narrowing, arch area and height increase, an effect which has been demonstrated in modeling (Li et al., 2009), in vitro (Li et al., 2013) and in vivo studies (Marquardt et al., 2015; Marquardt et al., 2016). In healthy subjects, 10 N of radioulnar compression decreased arch width by nearly 1.0 mm, and increased arch height and area by approximately 0.5 and 5.5 mm2, respectively (Marquardt et al., 2015). Under 20 N of radioulnar compression force, arch area increased by an additional 2 mm2. However, the current study showed that neither force condition increased median nerve mobility in healthy subjects. For CTS patients, Marquardt et al. (2016)
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ACCEPTED MANUSCRIPT showed that compressive forces of 10 N and 20 N applied across the wrist of CTS patients increased arch area by 13% and 11%, respectively, and reduced median nerve flattening (a measure which reflects the degree of nerve compression). The current study was designed to enhance median nerve mobility in CTS patients by decreasing arch width via radioulnar wrist compression. Increasing tunnel arch area provided additional space for the carpal tunnel contents, thereby
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decompressing the median nerve and allowing it to move more freely within the tunnel.
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In this study, we found that a moderate of 10 N RWC force improved nerve mobility in CTS
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patients, but not in healthy subjects. Predictably, the median nerve in healthy subjects is already in an optimal mobility status and RWC does not further improve or hinder nerve mobility. In CTS
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patients, a 10 N RWC force resulted in a greater than 50% increase in median nerve mobility compared to no force application. This enhanced mobility, although not completely reaching to
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normality, is equivalent of 64.6% of that the intact nerve in healthy subject under no compression. The nerve mobility improvement in CTS patients is most likely attributable to the RWC induced
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increase in carpal arch area for the median nerve to be more freely moveable. Surprisingly, we found that a greater RWC force of 20 N did not further increase median nerve mobility, suggesting
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that median nerve has a complex biomechanical relationship with the carpal arch area, carpal tunnel shape and carpal tunnel contents. In this study, only 10 and 20 N RWC force were applied,
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and future study should further identical the optimal force levels that maximally promote median
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nerve mobility.
We found that changes in median nerve mobility in response to RWC was location dependent in
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CTS patients. Segmental median nerve mobility in the proximal carpal tunnel region was enhanced by nearly 50% under 10 N RWC. However, nerve mobility in middle and distal sections was not affected by RWC at either 10 or 20 N. Although we choose to center the RWC Although the RWC was centered at the distal hamate-trapezium level of the carpal tunnel, the compression force should have distributed along the tunnel through the sizable end-effector such that the more proximal tunnel was also manipulated for carpal arch augmentation (i.e., shortened arch width and increased arch area). It seems that median nerve mobility in the proximal tunnel is more sensitive to RWC force application compared to distal and middle nerve segments, likely due to greater tunnel flexibility and compliance at the proximal level (Li et al., 2014; Xiu et al., 2010). The 10
ACCEPTED MANUSCRIPT differential nerve mobility would create a strain in the tissue, but the median nerve is a relatively elastic material capable of accommodating the longitudinal strain induced in physiological conditions. Notably, there is an association between median nerve cross-sectional area and carpal tunnel level in patients with CTS, and median nerve CSA is larger in proximal tunnel section than in the distal tunnel section (Mhoon et al., 2012; Moran et al., 2009). These results highlight the pathophysiological relevance of proximal tunnel to median nerve compression. To date, studies
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examining the effects of RWC application on various carpal tunnel morphological parameters and
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median nerve morphology have mainly focused on the distal tunnel (Marquardt et al., 2015;
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Marquardt et al., 2016). A comprehensive investigation of median nerve mobility in the entire
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carpal tunnel in three dimensions in warranted in future studies.
There are several limitations to consider in this study. Firstly, tracking of the median nerve in this
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study was performed only in the longitudinal direction, and did not take into account any motion transverse to the carpal tunnel. Experimental and image processing methods can be developed to
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examine nerve motion with dynamic imaging in 3-dimension. Secondly, a limited number of force magnitudes were investigated in this study. Although this study determined that 10 N RWC
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improved median nerve mobility better than 20 N, further investigation is required to determine the force magnitude that maximally restore nerve mobility. Thirdly, the temporal effects of force
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application on the median nerve mobility were not examined in the current study, and future studies can further investigate the effect of RWC duration on nerve mobility. Finally, median nerve
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mobility impairment and restoration may be dependent on CTS severity, and the current study can be expanded to include a larger sample size with more stratified CTS groups having different
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degrees of symptom and function scales.
In conclusion, this study demonstrates that in vivo compressive force applied to the wrist transversely in the radioulnar direction improves median nerve mobility in patients with carpal tunnel syndrome, but not in healthy subjects. The improvement of median nerve mobility in CTS patients is dependent on force magnitude and nerve location in the tunnel. The kinematic behavior of the median nerve restored in CTS patients by RWC may promotes recovery of nerve pathophysiology, relieve CTS symptoms and improve hand function.
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Acknowledgement The authors thank Dr. Zhili Shao and Ms. Lenicia Jerkins for their assistance in patient coordination. The study described in this publication was supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health under Award Number R01AR068278. The content is solely the responsibility of the authors and does not
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necessarily represent the official views of the National Institutes of Health.
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Nerve and tendon gliding exercises and the conservative management of carpal tunnel syndrome. J Hand Ther. 11(3), 171-179.
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27. Skirven, T., Trope, J., 1994. Complications of immobilization. Hand Clin. 10(1), 53-61.
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28. Szabo R.M., Bay B.K., Sharkey N.A., Gaut C., 1994. Median nerve displacement through the carpal canal. J Hand Surg. 19(6), 901-906.
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29. Topp K.S., Boyd B.S., 2006. Structure and biomechanics of peripheral nerves: nerve
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responses to physical stresses and implications for physical therapist practice. Phys Ther. 86(1), 92-109.
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30. Uchiyama, S., Itsubo, T., Yasutomi, T., Nakagawa, H., Kamimura, M., Kato, H., 2005.
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Quantitative MRI of the wrist and nerve conduction studies in patients with idiopathic carpal tunnel syndrome. J Neurol Neurosurg Psychiatry. 76(8), 1103-1108.
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31. Valls‐Solé J., Alvarez R., He M.N., 1995. Limited longitudinal sliding of the median nerve in patients with carpal tunnel syndrome. Muscle Nerve. 18(7), 761- 767. 32. van Doesburg M.H., Henderson J., van der Molen A.B.M., An K.N., Amadio P.C., 2012. Transverse plane tendon and median nerve motion in the carpal tunnel: ultrasound comparison of carpal tunnel syndrome patients and healthy volunteers. PLoS One, 7(5), e37081.
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ACCEPTED MANUSCRIPT 33. Wang Y., Filius A., Zhao C., Passe S.M., Thoreson A.R., An K.N., Amadio, P.C., 2014. Altered median nerve deformation and transverse displacement during wrist movement in patients with carpal tunnel syndrome. Acad Radiol. 21(4), 472-480. 34. Wright T.W., Glowczewskie F., Wheeler D., Miller G., Cowin D., 1996. Excursion and
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strain of the median nerve. J Bone Joint Surg Am. 78(12), 1897-903.
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carpal bone loading. Clin Biomech. 25(8), 776-780.
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35. Xiu, K.H., Kim, J.H., Li, Z.M., 2010. Biomechanics of the transverse carpal arch under
36. Yoshii Y., Ishii T., Tung W.L., Sakai S., Amadio P.C., 2013. Median nerve deformation
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and displacement in the carpal tunnel during finger motion. J Orthop Res. 31(12), 1876-
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Fig 1. Experimental setup of in vivo ultrasound imaging of longitudinal median nerve during finger motion under radioulnar wrist compression
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Fig 2. Median nerve segmentation in the carpal tunnel
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Fig 3. Median nerve mobility in healthy subjects and CTS patients under radioulnar wrist
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compression (* p<0.05)
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Fig 4. Segmental median nerve mobility in CTS patients under radioulnar wrist compression (*
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p<0.05)
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Healthy subjects, Mean (SD)
CTS patients, Mean (SD)
0N
0.89 (0.06)
0.88 (0.11)
10 N
0.89 (0.08)
0.92 (0.07)
20 N
0.92 (0.07)
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RWC condition
0.90 (0.09)
Table 1. R2 value of linear regression on the median nerve displacements in the carpal tunnel as a
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function of flexion angle. SD= standard deviation
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Highlights
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Radioulnar wrist compression was applied to increase carpal arch space. Wrist compression increased nerve mobility in carpal tunnel syndrome patients. Radioulnar wrist compression did not affect nerve mobility in healthy subjects. Increased nerve mobility in patients occurred in the proximal region of the tunnel. Wrist compression may improve nerve function associated compression neuropathy.
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Figure 1
Figure 2
Figure 3
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Yifei Yao, Emily Grandy, Peter J. Evans, William H. Seitz, ZongMing Li PII: DOI: Reference:
S0268-0033(18)30628-4 doi:10.1016/j.clinbiomech.2018.10.017 JCLB 4631
To appear in:
Clinical Biomechanics
Received date: Accepted date:
30 July 2018 11 October 2018
Please cite this article as: Yifei Yao, Emily Grandy, Peter J. Evans, William H. Seitz, ZongMing Li , Enhancement in median nerve mobility during radioulnar wrist compression in carpal tunnel syndrome patients. Jclb (2018), doi:10.1016/j.clinbiomech.2018.10.017
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Enhancement in Median Nerve Mobility during Radioulnar Wrist Compression in Carpal tunnel Syndrome Patients Yifei Yaoa, Emily Grandya, Peter J. Evansb, William H. Seitz, Jr.b, Zong-Ming Lia,b,c Hand Research Laboratory, Departments of aBiomedical Engineering, bOrthopaedic Surgery, and Physical Medicine and Rehabilitation, Cleveland Clinic, Cleveland, OH, USA
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c
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Corresponding author: Zong-Ming Li;
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Email: [email protected] Web: http://handlab.org/ Phone number: +216-444-1211
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address: Cleveland Clinic, 9500 Euclid Avenue, ND20, Cleveland, OH, 44195, USA
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Word count for main text: 3478
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Word count for Abstract: 181
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Declarations of interest: none
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Abstract Background: Carpal tunnel syndrome is a compression neuropathy at the wrist associated with compromised median nerve mobility. The purpose of this study was to investigate the effects of radioulnar wrist compression on median nerve longitudinal mobility within the carpal tunnel in carpal tunnel syndrome patients as well as healthy subjects.
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Methods: Dynamic ultrasound images captured longitudinal median nerve motion in the carpal
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tunnel during radioulnar wrist compression force application in 11 healthy subjects and 11 carpal
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tunnel syndrome patients.
Findings: We found that median nerve mobility was not significantly affected by radioulnar wrist compression in healthy subjects (P = 0.34), but improved by 10 N radioulnar wrist compression
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in carpal tunnel syndrome patients (P < 0.05). Analysis of segmental median nerve mobility in carpal tunnel syndrome patients showed significantly improved mobility in the proximal tunnel
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section under 10 N radioulnar wrist compression force condition compared to the no compression condition (P < 0.05).
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Interpretation: Moderate radioulnar wrist compression force application helps restore impaired
with carpal tunnel syndrome.
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median nerve mobility and may be effective in improve nerve function and symptoms associated
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Dynamic ultrasound
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Keywords: Carpal tunnel syndrome; Radioulnar wrist compression; Median nerve mobility;
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1. Introduction The carpal tunnel in the wrist is a fibro-osseous structure formed by interconnected carpal bones dorsally and the transverse carpal ligament volarly containing the median nerve and nine flexor tendons. In healthy hands, the median nerve in the carpal tunnel experiences excursion in response to hand motions to dissipate mechanical stress (Topp and Boyd, 2006; Phillips et al., 2004).
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However, median nerve excursion can be hindered by the surrounding environment and is prone
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to excessive mechanical stresses and strains in response to daily hand tasks (Wang et al., 2014).
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Chronic stress of the median nerve in the carpal tunnel eventually leads to compression neuropathy, i.e. carpal tunnel syndrome (CTS). In CTS, median nerve compression due to factors such as small tunnel volume and large tunnel contents can compromise the kinematic behavior of the median
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nerve (McLellan et al., 1976, Valls-Sole et al., 1995, Wright et al., 1996, Bay et al., 1997, Szabo et al., 1994, Kuo et al., 2016). Compression of the median nerve over time can cause endoneurial
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edema and perineurium fibrosis (Mackinnon et al., 1985), which may further alter mobility of the nerve. Previous studies have shown that the median nerve in CTS patients exhibits reduced
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transverse motion (Kuo et al., 2016; Nakamichi and Tachibana, 1995; van Doesburg et al., 2012;
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Wang et al., 2014; Yoshii et al, 2013) as well as reduced longitudinal mobility (Liong et al., 2014; Filius et al., 2015; Hough et al., 2007). In hand rehabilitation, nerve gliding exercises have been attempted for CTS treatment to improve median nerve mobility (Rozmaryn et al., 1998; Akalin et
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al., 2002; Coppieters and Alshami, 2007), to prevent adhesion between the median nerve and flexor tendons (Skirven and Trope, 1994), and to facilitate venous return and edema dispersal
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(Burke et al., 2003).
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Alternatively, decompression of the median nerve in CTS patients can be achieved by increasing carpal tunnel space, mitigating the compromised nerve mobility. We have demonstrated that carpal tunnel space can be augmented by narrowing the carpal arch width between the trapezium and hook of hamate (Li et al., 2009, 2011, 2013). For example, geometric modeling (Li, et al., 2009) and in vitro studies (Li et al., 2009, 2013) showed that arch width narrowing was associated with palmar bowing of the transverse carpal ligament with increased arch height and area. Furthermore, in vivo radioulnar wrist compression (RWC) helped reduce median nerve flattening which is indicative of nerve decompression in CTS patients (Marquardt et al., 2016). However, it is
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ACCEPTED MANUSCRIPT unknown how RWC could affect the kinematic behavior of the median nerve to overcome the impaired nerve mobility.
Therefore, the purpose of this study was to investigate the effects of RWC on median nerve longitudinal mobility within the carpal tunnel in CTS patients as well as in healthy subjects for comparison. We hypothesized that RWC would enhance median nerve mobility in CTS patients,
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patients would be location-dependent along the carpal tunnel.
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but not in healthy controls. We further hypothesized median nerve mobility enhancement in CTS
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2. Methods 2.1 Human subjects
Eleven patients diagnosed with CTS (age 51.5 (SD 16.3) years; 4 men and 7 women; 8 right hands;
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3 left hands; height of 1.67 (SD 0.11) m; weight of 75.62 (SD 9.66) kg) and eleven healthy volunteers (age 44.7 ± 14.8 years; 4 men and 7 women; 11 right hands; height of 1.70 (SD 0.10)
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m; weight of 79.31 (SD 17.51) kg) participated in this study. The CTS patients were recruited based on a history of paresthesia, pain and/or numbness in the median-innervated hand territory,
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which had persisted for at least 3 months, and at least one positive physical examination of Tinel’s sign, Phalen’s test or carpal compression test, and a mean severity scale greater than 1.5 using the
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Boston CTS questionnaire (Levine et al., 1993). Exclusion criteria for CTS and healthy subjects were systemic disease (i.e. rheumatoid arthritis, diabetes, fibromyalgia), history of major injury or
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surgery to the wrist or hand, treatment, musculoskeletal/neuromuscular disorders, BMI over 30, and pregnancy. The study was approved by the Institutional Review Board and written informed
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consent was obtained from each subject before participation.
2.2 RWC procedures
A custom made compression system was used to non-invasively apply compression across the wrist at the distal level of the carpal tunnel (Marquardt et al., 2015). The system applied force using two pneumatic actuators (Bimba Manufacturing, Monee, IL, USA) which were linked with two end effectors made of thermoplastic materials covered by a thin foam to comfortably fit the curvature of radial and ulnar aspects of the wrist. The actuators were attached to six degrees-of-
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ACCEPTED MANUSCRIPT freedom alignment mounts for positional alignment. Bifurcated plastic tubes were used to connect an air pressure regulator (VBM Medical, Noblesville, IN), a digital pressure gage, and the pneumatic actuators. The pressure regulator drove the actuators to generate and control the desired force magnitude according to a predetermined calibration of the relationship between the regulator pressure and the amount of force applied by the actuators. A height adjustable platform was used
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for position control of hand, wrist and forearm.
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For each subject, the hand with the more severe CTS symptoms (for the CTS group) or dominant
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side (for healthy group) was tested. The subject lay supine on a testing bed with the arm abducted 30° in the thermoplastic splint shaped according to the arm geometry of the subject with the hand
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supinated and palm upturned. The wrist was then positioned comfortably in the height adjustable RWC system. Velcro® straps were used to stabilize the forearm and fix the thumb in 45° extension.
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The proximal/distal interphalangeal joints of the four fingers were secured in an anatomically neutral position along a flat splint using another Velcro® strap, while the metacarpophalangeal
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joints remained free to move simultaneously (Fig 1).
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The centerlines of the RWC system end effectors were aligned so that the applied force coincided with the tunnel level containing the hook of hamate and ridge of trapezium. The end effectors were
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further adjusted in the volar-dorsal direction so that the center of each end effector was positioned at the midpoint between the volar and dorsal surfaces of the wrist. The RWC system applied a
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transverse compressive force (10 or 20 N) across the distal carpal tunnel. The air pressure regulator was set to apply pressure through the bifurcated tubes to simultaneously actuate the two end
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effectors to generate the specific force magnitudes on both the radial and ulnar sides of the wrist.
2.3 Setup of ultrasound imaging An ultrasound system (Acuson S2000, Siemens Medical Solutions USA, Mountain View, CA, USA) with an 18L6HD linear array transducer was used to define the proximal and distal boundaries of the carpal tunnel by visualizing the cross-sectional images that clearly show the proximal level of scaphoid and pisiform and distal level of hook of hamate and trapezium, respectively. The centerlines of the ultrasound probe footprints at proximal and distal boundaries of the carpal tunnel were ink-marked on the skin. A line of radiopaque markers (0.33 mm diameter, 5
ACCEPTED MANUSCRIPT Beekley Corporation, Bristol, CT, USA) were attached to the palmar skin for the purpose of identifying the proximal and distal boundaries of the carpal tunnel on ultrasound images. The radiopaque markers were positioned 10 mm proximal and distal to the proximal and distal inked lines, respectively, minimizing the image artifacts in the tunnel region of interest generated by the markers.
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The median nerve, shown as a hypoechogenic structure on an ultrasound image, was first identified
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at proximal level cross-section of the carpal tunnel. The ultrasound transducer was then rotated to
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follow the nerve in the longitudinal direction to be in line with the median nerve, and then stabilized using the custom adjustable holder. The holder was further adjusted in the radial-ulnar
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direction to locate the image plane in which the median nerve was the thickest, and then the holder
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was locked to maintain the constant imaging location throughout the experiment.
2.4 Setup of an electrogoniometer
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An electrogoniometer (XM65, Biometrics Ltd, Cwmfelinfach, Gwent, UK) was used to record metacarpophalangeal joint motion of four fingers in unison. The end blocks of the goniometer
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were attached to the dorsum of the hand and fingers, respectively. Prior to data collection, the
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electrogoniometer was zeroed with the fingers in the anatomical neutral position.
2.5 Data collection of dynamic ultrasound images during RWC and finger motion
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A RWC trial lasts 3 minutes. At the end of the 3-minute compression, each subject performed cyclic finger flexion/extension while the compression maintained. The finger motion was
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performed by flexing and extending the metacarpophalangeal joints of four fingers between 0 and 90 degrees at a pace of 0.3 Hz. A 3-minute rest was provided between consecutive trials. Each force level (0, 10, or 20 N) was repeated 3 times for a total of 9 trials in a randomized order. For each RWC trial, 18 motion cycles were captured. During finger motion, the median nerve longitudinal motion was captured by ultrasound videos at a rate of 30 frames per second. The ultrasound image has a 640×480 pixels size with a resolution of 0.062 mm. Angular finger motion at the metacarpophalangeal joints were recorded by the electrogoniometer which was synchronized to the ultrasound video.
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2.6 Longitudinal median nerve mobility One trial for each of the 0, 10 and 20 N force conditions was used for median nerve mobility analyses for each subjects; the remaining trials were used as backup. In each selected trial, 3 finger flexions from 0 to 90 degrees were examined. Longitudinal median nerve displacement at each flexion angular position was analyzed using speckle cross-correlation algorithm (Dilley et al.,
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2001). The program determined relative nerve displacement using fine speckle features in the
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selected region of interest (ROI) between adjacent image frames in the ultrasound video. ROIs
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(6.2×1.8 mm) were defined in a 0.62 mm increment along the midline of the median nerve from proximal to distal boundaries of the tunnel. Median nerve displacement in the carpal tunnel was
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calculated as the mean value of individual displacements of all ROIs. Additionally, the median nerve was segmented into three sections of equal length along the longitudinal direction
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corresponding to the proximal, middle and distal segments of the carpal tunnel (Fig 2). Segmental median nerve displacement was calculated as the mean value of individual displacement of ROIs
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in the segment. Least-squares linear regression was performed for median nerve displacement as a function of finger flexion angle. The slope of the linear equation was used to quantify the mobility
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of the nerve.
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2.7 Statistical analysis
Median nerve mobility was analyzed using a two-way mixed repeated measures analysis of
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variance (ANOVA) with group (healthy subjects and CTS patients) as between subjects factor, and force magnitude (0, 10, and 20 N) as the repeated within subjects factor. Furthermore, a two-
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way repeated measures ANOVA was performed for the CTS patients to examine the dependence of median nerve mobility on nerve location (proximal, middle, and distal) and force magnitude (0, 10 and 20 N). Post-hoc Tukey’s tests were used for pairwise comparisons and p-value less than 0.05 was considered statistically significant. All statistical analyses were performed using SigmaStat 3.4 (Systat Software Inc., San Jose, CA, USA).
3. Results 3.1 Median nerve mobility under RWC in the healthy subjects and CTS patients
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ACCEPTED MANUSCRIPT R2 values of linear regression on the median nerve displacements in the carpal tunnel as a function of flexion angle under 0, 10 and 20 N RWC force conditions for both healthy subjects and CTS are shown in Table 1. The median nerve mobility was significantly dependent on subject group (P < 0.05), but not on force magnitude (P = 0.962). On average, median nerve mobility in CTS patients was 41.5% of that in healthy subjects under the no compression condition (P < 0.001). There was no significant difference between median nerve mobility in CTS patients and in healthy
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subjects under the 10 N condition (P = 0.50). Under the 20 N RWC condition, median nerve
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mobility in CTS patients was 62.5% of that in healthy subjects (P < 0.05).
For healthy subjects, the median nerve mobilities were 0.0082 (SD 0.0026), 0.0064 (SD 0.0042),
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and 0.0072 (SD 0.0033) mm/degree under 0, 10 and 20 N conditions, respectively. Force levels had no significant effect on median nerve mobility (P = 0.34, Fig 3). For CTS patients, median
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nerve mobility was significantly dependent on RWC force levels (P < 0.05, Fig 3). Pairwise comparisons showed that the median nerve mobility under the 10 N force condition (0.0053 (SD
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0.0022) mm/degree) was significantly larger than under the no compression condition (0.0034 (SD 0.0015) mm/degree, P < 0.05), an average increase of 55.9%. However, nerve mobility under 20
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N RWC (0.0045 (SD 0.0030) mm/degree) was not significantly different from that of the no
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compression condition (P = 0.86) or the 10 N force condition (P = 0.26).
3.2 Segmental median nerve mobility in the CTS patients
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The mobility of the median nerve in patients with CTS in the proximal carpal tunnel was 0.0055 (SD 0.0033), 0.0081 (SD 0.0045), 0.0071 (SD 0.0044) mm/degree under 0, 10 and 20 N RWC
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force conditions, respectively (Fig. 4); the mobility of median nerve in the middle carpal tunnel was 0.0042 (SD 0.0023), 0.0036 (SD 0.0028), 0.0047 (SD 0.0036) mm/degree under 0, 10 and 20 N RWC force conditions, respectively; in the distal carpal tunnel, the mobility of median nerve was 0.0024 (SD 0.0022), 0.0036 (SD 0.0024), 0.0026 (SD 0.0019) mm/degree under 0, 10 and 20 N RWC force conditions, respectively. ANOVA results showed that the nerve mobility was significantly dependent on nerve location (P < 0.001), but not on RWC condition (P = 0.351). In the proximal tunnel, median nerve mobility increased significantly by 47.2% under 10 N RWC condition compared to the no compression condition (P < 0.05). However, there was no significant difference between the 20 N RWC condition and the no compression condition (P = 0.24). In the 8
ACCEPTED MANUSCRIPT middle carpal tunnel, there were no significant differences found in median nerve mobility among the three force levels (0 vs. 10 N, P =0.85; 0 vs. 20 N, P =0.89; 10 vs 20 N, P = 0.58). Similarly, nerve mobility at the distal tunnel level did not differ among the three force levels (0 vs. 10 N, P =0.47; 0 vs. 20 N, P =0.97 10 vs 20 N, P = 0.60).
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4. Discussion
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In this study, we investigated the effects of RWC on longitudinal mobility of the median nerve in
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both healthy subjects and CTS patients. Median nerve motion in the carpal tunnel corresponding to finger flexion/extension was captured in vivo using dynamic ultrasonography. We found that median nerve mobility in CTS patients was compromised, and the comprised mobility was
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improved by RWC. Furthermore, the effect of RWC on median nerve mobility in CTS patients
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was dependent on RWC force magnitude and nerve location.
In this study, we observed reduced median nerve mobility in CTS patients under no compression
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condition compared to healthy subjects. Previous studies investigating longitudinal median nerve
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mobility also showed decreased nerve gliding in CTS patients (Liong et al., 2014; Filius et al., 2015; Hough et al., 2007), and our study supported these results. In our study, median nerve mobility in CTS patients was about 40% of that in healthy subjects, demonstrating compromised
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nerve gliding in this patient population. Our results further corroborated existing literature that segmental median nerve mobility in the proximal tunnel is inhibited in patients with CTS (Hough
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et al. 2007; Filius et al. 2015; Liong et al. 2014).
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Previous studies in our laboratory have shown the effects of RWC on the carpal arch morphology. With carpal arch width narrowing, arch area and height increase, an effect which has been demonstrated in modeling (Li et al., 2009), in vitro (Li et al., 2013) and in vivo studies (Marquardt et al., 2015; Marquardt et al., 2016). In healthy subjects, 10 N of radioulnar compression decreased arch width by nearly 1.0 mm, and increased arch height and area by approximately 0.5 and 5.5 mm2, respectively (Marquardt et al., 2015). Under 20 N of radioulnar compression force, arch area increased by an additional 2 mm2. However, the current study showed that neither force condition increased median nerve mobility in healthy subjects. For CTS patients, Marquardt et al. (2016)
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ACCEPTED MANUSCRIPT showed that compressive forces of 10 N and 20 N applied across the wrist of CTS patients increased arch area by 13% and 11%, respectively, and reduced median nerve flattening (a measure which reflects the degree of nerve compression). The current study was designed to enhance median nerve mobility in CTS patients by decreasing arch width via radioulnar wrist compression. Increasing tunnel arch area provided additional space for the carpal tunnel contents, thereby
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decompressing the median nerve and allowing it to move more freely within the tunnel.
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In this study, we found that a moderate of 10 N RWC force improved nerve mobility in CTS
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patients, but not in healthy subjects. Predictably, the median nerve in healthy subjects is already in an optimal mobility status and RWC does not further improve or hinder nerve mobility. In CTS
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patients, a 10 N RWC force resulted in a greater than 50% increase in median nerve mobility compared to no force application. This enhanced mobility, although not completely reaching to
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normality, is equivalent of 64.6% of that the intact nerve in healthy subject under no compression. The nerve mobility improvement in CTS patients is most likely attributable to the RWC induced
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increase in carpal arch area for the median nerve to be more freely moveable. Surprisingly, we found that a greater RWC force of 20 N did not further increase median nerve mobility, suggesting
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that median nerve has a complex biomechanical relationship with the carpal arch area, carpal tunnel shape and carpal tunnel contents. In this study, only 10 and 20 N RWC force were applied,
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and future study should further identical the optimal force levels that maximally promote median
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nerve mobility.
We found that changes in median nerve mobility in response to RWC was location dependent in
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CTS patients. Segmental median nerve mobility in the proximal carpal tunnel region was enhanced by nearly 50% under 10 N RWC. However, nerve mobility in middle and distal sections was not affected by RWC at either 10 or 20 N. Although we choose to center the RWC Although the RWC was centered at the distal hamate-trapezium level of the carpal tunnel, the compression force should have distributed along the tunnel through the sizable end-effector such that the more proximal tunnel was also manipulated for carpal arch augmentation (i.e., shortened arch width and increased arch area). It seems that median nerve mobility in the proximal tunnel is more sensitive to RWC force application compared to distal and middle nerve segments, likely due to greater tunnel flexibility and compliance at the proximal level (Li et al., 2014; Xiu et al., 2010). The 10
ACCEPTED MANUSCRIPT differential nerve mobility would create a strain in the tissue, but the median nerve is a relatively elastic material capable of accommodating the longitudinal strain induced in physiological conditions. Notably, there is an association between median nerve cross-sectional area and carpal tunnel level in patients with CTS, and median nerve CSA is larger in proximal tunnel section than in the distal tunnel section (Mhoon et al., 2012; Moran et al., 2009). These results highlight the pathophysiological relevance of proximal tunnel to median nerve compression. To date, studies
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examining the effects of RWC application on various carpal tunnel morphological parameters and
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median nerve morphology have mainly focused on the distal tunnel (Marquardt et al., 2015;
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Marquardt et al., 2016). A comprehensive investigation of median nerve mobility in the entire
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carpal tunnel in three dimensions in warranted in future studies.
There are several limitations to consider in this study. Firstly, tracking of the median nerve in this
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study was performed only in the longitudinal direction, and did not take into account any motion transverse to the carpal tunnel. Experimental and image processing methods can be developed to
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examine nerve motion with dynamic imaging in 3-dimension. Secondly, a limited number of force magnitudes were investigated in this study. Although this study determined that 10 N RWC
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improved median nerve mobility better than 20 N, further investigation is required to determine the force magnitude that maximally restore nerve mobility. Thirdly, the temporal effects of force
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application on the median nerve mobility were not examined in the current study, and future studies can further investigate the effect of RWC duration on nerve mobility. Finally, median nerve
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mobility impairment and restoration may be dependent on CTS severity, and the current study can be expanded to include a larger sample size with more stratified CTS groups having different
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degrees of symptom and function scales.
In conclusion, this study demonstrates that in vivo compressive force applied to the wrist transversely in the radioulnar direction improves median nerve mobility in patients with carpal tunnel syndrome, but not in healthy subjects. The improvement of median nerve mobility in CTS patients is dependent on force magnitude and nerve location in the tunnel. The kinematic behavior of the median nerve restored in CTS patients by RWC may promotes recovery of nerve pathophysiology, relieve CTS symptoms and improve hand function.
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Acknowledgement The authors thank Dr. Zhili Shao and Ms. Lenicia Jerkins for their assistance in patient coordination. The study described in this publication was supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health under Award Number R01AR068278. The content is solely the responsibility of the authors and does not
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necessarily represent the official views of the National Institutes of Health.
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ACCEPTED MANUSCRIPT 33. Wang Y., Filius A., Zhao C., Passe S.M., Thoreson A.R., An K.N., Amadio, P.C., 2014. Altered median nerve deformation and transverse displacement during wrist movement in patients with carpal tunnel syndrome. Acad Radiol. 21(4), 472-480. 34. Wright T.W., Glowczewskie F., Wheeler D., Miller G., Cowin D., 1996. Excursion and
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Fig 1. Experimental setup of in vivo ultrasound imaging of longitudinal median nerve during finger motion under radioulnar wrist compression
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Fig 2. Median nerve segmentation in the carpal tunnel
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Fig 3. Median nerve mobility in healthy subjects and CTS patients under radioulnar wrist
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compression (* p<0.05)
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Fig 4. Segmental median nerve mobility in CTS patients under radioulnar wrist compression (*
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p<0.05)
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Healthy subjects, Mean (SD)
CTS patients, Mean (SD)
0N
0.89 (0.06)
0.88 (0.11)
10 N
0.89 (0.08)
0.92 (0.07)
20 N
0.92 (0.07)
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RWC condition
0.90 (0.09)
Table 1. R2 value of linear regression on the median nerve displacements in the carpal tunnel as a
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function of flexion angle. SD= standard deviation
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Highlights
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Radioulnar wrist compression was applied to increase carpal arch space. Wrist compression increased nerve mobility in carpal tunnel syndrome patients. Radioulnar wrist compression did not affect nerve mobility in healthy subjects. Increased nerve mobility in patients occurred in the proximal region of the tunnel. Wrist compression may improve nerve function associated compression neuropathy.
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Figure 1
Figure 2
Figure 3
Figure 4