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Objective To compare transverse and longitudinal safe zones using ultrasonography between healthy individuals and patients with carpal tunnel syndrome (CTS). Methods This was a prospective observational case-control study. Forty wrists from 20 healthy individuals and 40 wrists from 24 patients with CTS were examined. Patients with CTS were classified into three groups (mild, moderate, and severe CTS) based on electrodiagnostic findings. Using ultrasonography, we measured the distance between the median nerve and ulnar vessels to identify the transverse safe zone, and between the distal flexor retinaculum and superficial palmar artery arch to identify the longitudinal safe zone. Results The transverse and longitudinal safe zones were significantly different between participants with CTS and those without CTS. The transverse safe zone significantly differed between the mild and severe CTS groups, while the longitudinal safe zone was not significantly different between the groups. The cross-sectional area of the median nerve negatively correlated with the transverse and longitudinal safe zones. Conclusion Transverse and longitudinal safe zones were narrower in patients with CTS than in the healthy group. A significant difference was observed between patients with mild CTS and those with severe CTS. Furthermore, the cross-sectional area of the median nerve was directly proportional to the degree of narrowing of the transverse and longitudinal safe zones.

Objective To assess the relevance of electrodiagnosis (EDX) in the cross-sectional area (CSA) of the nerve root of patients with cervical radiculopathy (CR) by using high-resolution ultrasonography (HRUS). Methods The CSAs of the cervical nerve roots at C5, C6, and C7 were measured bilaterally using HRUS in 29 patients with unilateral CR whose clinical symptoms, magnetic resonance imaging (MRI) findings, and EDX results corresponded with each other (CR-A group), and in 26 patients with unilateral CR whose clinical symptoms and MRI findings matched with each other but did not correspond with the EDX findings (CR-B group). Results The CSA of the affected side in each nerve root was significantly larger than that of the unaffected side in both the CR-A and CR-B groups. The side-to-side difference in the bilateral CSAs of the nerve root and the ratio of the CSAs between the unaffected and affected sides were statistically larger in the CR-A group than in the CR-B group. Conclusion The increased CSAs in the CR-A group reflect the physiological changes of the cervical nerve root, which is supported by the EDX findings.