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.

Citations

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• Ultrasound-guided release of carpal tunnel syndrome — Anterograde technique
  Carla Ricardo Nunes, Olivier Marès, Vincent Martinel
  Hand Surgery and Rehabilitation.2025; 44: 102091.     CrossRef
• Ultrasonographic Assessment of Median Nerve and Carpal Tunnel Variations
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  Journal of Ultrasound in Medicine.2025; 44(10): 1819.     CrossRef
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  British Journal of Radiology.2025; 98(1176): 2011.     CrossRef
• Ultrasound-guided anterograde Carpal Tunnel release: Anatomical landmarks of the distal boundary – A cadaveric study
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  Hand Surgery and Rehabilitation.2025; : 102562.     CrossRef
• Body composition analysis as a comprehensive method for assessing the effectiveness of medical rehabilitation for lymphedema associated with radical breast cancer treatment
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  Bulletin of Rehabilitation Medicine.2025; 24(6): 42.     CrossRef
• USG-Guided Percutaneous Thread Carpal Tunnel Release
  Nishith Kumar, Alfa Shamim Saifi, Upinderjeet Singh, Dharmendra Kumar Singh
  Indian Journal of Radiology and Imaging.2024; 34(04): 745.     CrossRef
• Clinical-applied anatomy of the carpal tunnel regarding mini-invasive carpal tunnel release
  Peter Kaiser, Gernot Schmidle, Simone Bode, Ulrike Seeher, Hanne-Rose Honis, Bernhard Moriggl, Elisabeth Pechriggl, Hannes Stofferin, Marko Konschake
  Archives of Orthopaedic and Trauma Surgery.2024; 144(11): 4753.     CrossRef
• Ultrasound-guided interventions in primary carpal tunnel syndrome: perineural injection to thread carpal tunnel release
  Nishith Kumar, Shishir Kumar Chandan, Divesh Jalan, Skand Sinha, Binita Jaiswal, Dharmendra Kumar Singh
  The British Journal of Radiology.2023;[Epub]     CrossRef