Tomoo Ishii

Median nerve deformation and displacement in the carpal tunnel during finger motion

The objective of this study was to evaluate the correlations between deformation and displacement of median nerve and flexor tendons during finger motion in the carpal tunnel for both carpal tunnel syndrome (CTS) patients and healthy controls. Sixty‐two wrists of 31 asymptomatic volunteers and fifty‐one wrists of 28 idiopathic CTS patients were evaluated by ultrasound. The displacement of the median nerve and the middle finger flexor digitorum superficialis (FDS) tendon, as well as area, perimeter, aspect ratio of a minimum enclosing rectangle, and circularity of the median nerve were measured in finger extension and flexion positions. Deformation indices were defined as the ratios of indices in finger extension and flexion positions. The correlations between displacement and deformation indices were evaluated. There were significant correlations between nerve palmar–dorsal displacement and deformation indices (p < 0.05). The aspect ratio deformation index showed the strongest correlation to palmar–dorsal displacement of the nerve (−0.572, p < 0.01). This study showed that there is a relationship between median nerve deformation indices and nerve palmar–dorsal displacement in the carpal tunnel. Since the highest correlations were between palmar–dorsal nerve displacement direction and aspect ratio deformation index, these parameters may be helpful to understand the pathophysiology of CTS.

Reliability of automatic vibratory equipment for ultrasonic strain measurement of the median nerve.

The objective of this study was to test the reliability of ultrasonic median nerve strain measurements using automatic vibratory equipment. Strain ratios of the median nerve in the carpal tunnel model and the reference coupler were measured at three different settings of the transducer: 0, +2 and +4 mm (+ = compressing the model down 2-4 mm initially). After measurement of the carpal tunnel model, a +4-mm setting was chosen for in vivo measurement. The median nerve strains of 30 wrists were measured by two examiners using the equipment. Intra- and inter-examiner correlation coefficients (CCs) for the strain ratios were calculated. The closest ratio was found in the +4-mm placement (strain ratio: 0.73, Youngs modulus ratio: 0.79). The intra-examiner CC was 0.91 (p < 0.01), and the inter-examiner CCs were 0.72-0.78 (p < 0.01). The automatic vibratory equipment was useful in quantifying median nerve strain at the wrist.

Detecting median nerve strain changes with cyclic compression apparatus: a comparison of carpal tunnel syndrome patients and healthy controls.

The objective of this study was to detect differences in median nerve strain between patients with carpal tunnel syndrome and healthy controls using cyclic compression apparatus. Twenty-eight patients with idiopathic carpal tunnel syndrome and 30 normal patients were examined by ultrasound elastography. Median nerve strain, strain ratio of reference coupler and median nerve area and perimeter were measured. The areas under receiver operating characteristic curves were compared among the parameters. Median nerve strains of the patients were significantly smaller than those of the controls (p < 0.001). Strain ratios, areas and perimeters were significantly larger in the patients than in the controls (p < 0.001). The areas under curves were 0.963, 0.917, 0.759 and 0.706 for strain, strain ratio, area and perimeter, respectively. The median nerve strain had the highest area under the curve. The ultrasonic strain measurements of the median nerve provided by the cyclic compression apparatus were superior to morphologic assessment in diagnosing carpal tunnel syndrome.

Ultrasound assessment of the effectiveness of carpal tunnel release on median nerve deformation.

To assess the biomechanical effect of carpal tunnel release (CTR), we evaluated the deformation and displacement patterns of the median nerve before and after CTR in carpal tunnel syndrome (CTS) patients. Sixteen wrists of 14 idiopathic CTS patients who had open CTR and 26 wrists of 13 asymptomatic volunteers were evaluated by ultrasound. Cross‐sectional images of the carpal tunnel during motion from full finger extension to flexion were recorded. The area, perimeter, aspect ratio of a minimum enclosing rectangle, and circularity of the median nerve were measured in finger extension and flexion positions. Deformation indices, determined by the flexion–extension ratio for each parameter, were compared before and after CTR. After CTR, the deformation indices of perimeter and circularity became significantly larger and the aspect ratio became significantly smaller than those before CTR (p < 0.05). Those differences were more obvious when comparing the values between the patients before CTR and the controls. Since the deformation indices after CTR are similar to the patterns of normal subjects, the surrounding structures and environment of the median nerve may be normalized upon CTR. This may be a way to tell how the median nerves recover after CTR.

Strain and Morphological Changes of Median Nerve After Carpal Tunnel Release

Characterization of the changes of ultrasound parameters after carpal tunnel release may be useful for clarifying the effectiveness or the recovery process of the carpal tunnel syndrome treatment. We evaluated strain and morphological changes of the median nerve before and after carpal tunnel release in carpal tunnel syndrome patients.

Correlations of Median Nerve Area, Strain, and Nerve Conduction in Carpal Tunnel Syndrome Patients

Background: The objective of this study was to see if ultrasound-interpreted median nerve strain and cross-sectional area correlate with abnormal nerve conduction studies and thumb opposition strength in patients with carpal tunnel syndrome (CTS). Methods: Sixty wrists of 30 idiopathic CTS patients were assessed by ultrasound and nerve conduction study. Distal motor latency, cross-sectional area, and strain ratio of the median nerve were measured. In addition, thumb opposition strength was classified using the manual muscle testing grade from 0 to 5, clinically. The strain ratio was defined as the strain of the reference coupler divided by the strain of the median nerve. The correlations between clinical examinations of distal motor latency, cross-sectional area, strain ratio, and thumb opposition strength were estimated with the Spearman rank correlation coefficients. Results: The correlation coefficients between distal motor latency and strain ratio, distal motor latency and cross-sectional area, and strain ratio and cross-sectional area were .597, .352, and .324, respectively. The correlation coefficients between thumb opposition strength and distal motor latency, thumb opposition and cross-sectional area, and thumb opposition and strain ratio were −.523, −.307, and −.358, respectively. All of the correlations showed statistical significance. The correlation coefficients between distal motor latency and strain ratio, and thumb opposition and distal motor latency, were relatively high. Conclusions: The results of this study suggest that the nerve conduction delay is related to changes in the material properties of the median nerve. In addition, nerve conduction study was the principal indicator of the thumb opposition strength.