Ann Rehabil Med.  2022 Dec;46(6):284-291. 10.5535/arm.22123.

Ultrasonographic Assessment of the Safe Zone for Carpal Tunnel Intervention: A Comparison Between Healthy Individuals and Patients With Carpal Tunnel Syndrome

• Kang BH
• Woo SR
• Park HJ
• Chung SY
• Kang S
• Jeong SH
• Yoon JS

• KMID: 2537159
• DOI: http://doi.org/10.5535/arm.22123

Abstract

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.

Keyword

Carpal tunnel syndrome; Ultrasonography; Safety; Procedure; Disease severity

Figure

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  Fig. 1. Ultrasonographic measurement of (A) the transverse safe zone as the distance between the medial margin of the median nerve and lateral margin of the ulnar vessels; (B) the longitudinal safe zone as the distance between the distal end of the flexor retinaculum and proximal end of the superficial palmar arch artery.

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  Fig. 2. Comparison of safe zones based on the severity of electromyographic (EMG) findings: (A) transverse safe zone (TSZ) and (B) longitudinal safe zone (LSZ). *p<0.05 using the Bonferroni test.

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