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Ultrasound evaluation of the ulnar nerve in cubital tunnel syndrome: anatomy, normal and abnormal findings, and postoperative aspects Cover

Ultrasound evaluation of the ulnar nerve in cubital tunnel syndrome: anatomy, normal and abnormal findings, and postoperative aspects

Journal of Ultrasonography
Volume 26 (2026): Issue 104 (April 2026)
By: Aurelio Cosentino,  Yacine Carlier,  Winston J. Rennie and  Lionel Pesquer  
Open Access
|Mar 2026
Figures & tables

Figures & Tables

Fig. 1.

Ulnar nerve neuropathy due to instability. A–E. Proximal to distal axial images in a 55-year-old male patient with ulnar nerve neuropathy due to instability. Ultrasound axial images (first column); MRI axial T1 TSE images (second column); MRI axial PD FS TSE images (third column). A. Arcade of Struthers level: Normal ulnar nerve (arrow), medial head of triceps (MT), basilic vein (V). B–C. Retrocondylar groove level: Neuropathic ulnar nerve − hypoechoic on ultrasound and hyperintense on PD FS MRI. Medial epicondyle (E). D. Cubital tunnel level: Neuropathic ulnar nerve (arrow). Medial epicondyle (E), olecranon (O). E. Flexor carpi ulnaris (FCU) level: Normal ulnar nerve (arrow), olecranon (O), medial margin of humeral trochlea (T), ulnar head of FCU (*), humeral head of FCU (**), flexor digitorum superficialis (***). F. Ultrasound at the same level as (C) during dynamic assessment: F1. Elbow in extension, ulnar nerve in normal position; F2. Ulnar nerve luxation during elbow flexion; F3. Ulnar nerve displaced anteriorly at 90° elbow flexion

Fig. 2.

Ulnar nerve neuropathy due to compression by Osborne’s ligament. A. Transverse ultrasound view and B. Longitudinal ultrasound view at epicondyle level (E). The ulnar nerve appears hypoechoic, enlarged, and swollen (thin arrow). Osborne’s ligament is thickened (multiple thick arrows). Distally to the impingement, the ulnar nerve fascicular pattern is preserved (curved arrow)

Fig. 3.

Ulnar nerve impingement at the FCU level. Ultrasound with longitudinal (A) and axial (B, C) views with corresponding levels (dashed lines). The ulnar nerve (straight arrows) appears hypoechoic, enlarged, and swollen (B) proximal to the FCU arcade (curved arrow). At the FCU level, the nerve appears flattened (C) with intraneural hyperechoic spot due to possible fibrosis. Distal to the compression site, the fascicular pattern is preserved in (A). (NU and dotted circle) ulnar nerve; (E) epicondyle; (O) olecranon; (*) FCU muscle

Fig. 4.

Ulnar nerve transposition at the elbow – surgical view. A. Drawing of anatomical landmarks- 1 – medial epicondyle; 2 – olecranon; 3 – Osborne’s ligament band; 4 – ulnar nerve; 5 – flexor carpi ulnaris (FCU) origins; 6 – arcade of Struthers. B. Identification of FCU: 1 – FCU aponeurosis. C. Release of FCU aponeurosis: 1– superficial aponeurosis ; 2 – deep aponeurosis. D. Anterior transposition of the ulnar nerve in front of the medial epicondyle: 1 – aponeurotic flap; 2 – ulnar nerve. E, F. Coverage of ulnar nerve with aponeurotic flap. 1 – epicondyle

Fig. 5.

Release of Struthers’ ligament – surgical view in two patients. This structure is rigid and creates a “razor blade” effect, compressing the ulnar nerve. The effect is exacerbated during elbow flexion and ulnar nerve instability. A. Identification of Struthers’ ligament, located anterior to the ulnar nerve at the upper border of the medial epicondyle. B. Release of Struthers’ ligament prior to anterior transposition of the ulnar nerve (not shown). C–D. Release of Struthers’ ligament in another patient, note the changes in ulnar nerve angulation between C and D. A–D. 1 – Struthers’ ligament; 2 – ulnar nerve; 3 – flexor carpi ulnaris (FCU)

Fig. 6.

Ulnar nerve impingement at the level of postoperative scar following ulnar transposition: A–D1. Ultrasound; A–D2. PD SPACE reformat. In A2, the square corresponds to the US view in A1 and dotted lines correspond to the axial images in B–D. Arrows: ulnar nerve. A. Longitudinal view showing focal hypoechoic ulnar nerve with caliber change. This alteration is clearer on US than MRI. B. Ulnar nerve proximal to the scar (*); the fascicular pattern is preserved. C–D. At the scar level (* in C), and slightly distally (D), the ulnar nerve appears distorted and hypoechoic, with loss of normal fascicular architecture

Quantitative measurements of the ulnar nerve and CuTS reported in the literature_ CSA: cross-sectional area

ParameterCriteriaNotes
Average CSA of ulnar nerve at ulnar tunnel8 mm2 ± 3 mm2Based on GEL (Ultrasound French study group) reference study(11)
Enlarged CSA at medial epicondyle>10 mm2Indicates possible ulnar nerve enlargement(11,12,13)
Enlarged CSA within the ulnar tunnel>15 mm2
CSA ratio (compressed site vs non-compressed proximal site)>1.4–1.5When associated with pathological changes(13,14)
CSA difference (pathologic vs. contralateral side)>2 mm2Suggests abnormality if asymmetry is present(15)
DOI: https://doi.org/10.15557/jou.2026.0002 | Journal eISSN: 2451-070X | Journal ISSN: 2084-8404
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Language: English
Submitted on: Oct 17, 2025
Accepted on: Dec 17, 2025
Published on: Mar 13, 2026
Published by: MEDICAL COMMUNICATIONS Sp. z o.o.
In partnership with: Paradigm Publishing Services
Publication frequency: 4 issues per year
Keywords:
ulnar nerve,
ultrasound,
cubital tunnel syndrome,
postoperative
Related subjects:
Medicine,
Basic medical science,
Basic medical science, other

© 2026 Aurelio Cosentino, Yacine Carlier, Winston J. Rennie, Lionel Pesquer, published by MEDICAL COMMUNICATIONS Sp. z o.o.
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Volume 26 (2026): Issue 104 (April 2026)
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