Anatomic Landmarks to Locate the Median Nerve for Safe Wrist Block or Carpal Tunnel Steroid Injection

Ron Brooks, MD; Amanda Kistler, MD; Saeed Chowdhry, MD; Andrew Swiergosz, BS; Katharina Perlin, BS; Morton L. Kasdan, MD; Bradon J. Wilhelmi, MD

Disclosures

ePlasty. 2019;19(e19)

Conclusion

Injection-related MN injury can cause lasting and debilitating sensory motor deficits. As such, precision in needle placement for injection is paramount. Many studies exist with respect to injection location, but a lack of consistent data related to injury prevention exists. On the basis of anatomic measurements, we have concluded that the safest injection location site is located on the ulnar aspect of the FCR tendon or 8 to 10 mm radial to the midpoint of the wrist while maintaining an injection site that is radial to the PL tendon.

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Table 1. Calculated anatomic measurements (mm)*
Average width of the MN
Average width of the PL
Average distance between the uMN to uPL
Average distance between uMN to MP
Average distance between uMN to uFCR

*MN indicates median nerve; PL, palmaris longus; u, measurement or calculation from the ulnar aspect of the anatomic structure; MP, midpoint of the wrist; FCR, flexor carpi radialis.

Table 2. Recommended anatomic locations for prevention of iatrogenic median nerve injury caused by injection*
Author(s)	Year of publication	Anatomic location
Gelberman et al²²	1980	1 cm proximal to the distal wrist crease between the PL and FCR tendons with 45°-60° angle
Green⁶	1984	Ulnar to PL
Linskey and Segal¹⁷	1990	Ulnar to PL tendon at the distal wrist crease, if present. If not present, injection in line with the fourth digit
Frederick et al¹⁶	1992	Midway between PL tendon and FCU tendon just proximal to the wrist crease. If PL not present, inject in line with the FDS tendon of the fourth digit
Kasten and Louis¹⁵	1996	Distal and dorsal direction starting on the radial border of the pisiform toward the mid portion of the carpal tunnel
Dammers et al²¹	1999	Volar side of the forearm between PL tendon and FCR tendon, 4 cm proximal to the wrist crease
Graham et al²³	2004	Just ulnar to FCR
Dubert and Racasan²⁰	2006	Through FCR tendon, 1 cm proximal to the wrist crease with the needle angled at 45° toward the medial edge
MacLennan et al¹⁹	2009	Ulnar to FCR tendon at the wrist crease
Kamanli et al¹⁸	2011	Ulnar to PL tendon distal to the wrist crease
Menge et al⁸	2016	30%-33% of wrist width from the radial styloid

*PL indicates palmaris longus; FCR, flexor carpi radialis; FCU, flexor carpi ulnaris; FDS, flexor digitorum superficialis.

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Anatomic Landmarks to Locate the Median Nerve for Safe Wrist Block or Carpal Tunnel Steroid Injection

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