Elsevier

The Journal of Hand Surgery

Volume 46, Issue 10, October 2021, Pages 930.e1-930.e9
The Journal of Hand Surgery

Scientific Article
Anatomical Study of Stabilizing Structures of the Extensor Carpi Ulnaris Tendon Around the Wrist

https://doi.org/10.1016/j.jhsa.2021.02.008Get rights and content

Purpose

The sixth dorsal extensor compartment is a relatively common site of stenosing tenosynovitis in the upper extremity, but the exact location of stenosis is not fully understood. The objective of this study was to investigate the detailed anatomy of structures surrounding the extensor carpi ulnaris (ECU) tendon around the wrist.

Methods

Fifty fresh human cadaveric wrists were used for gross observation and morphology measurements of the sixth dorsal compartment and the ECU subsheath. An additional 13 wrists were used for histological examination. We evaluated the morphology of supporting structures in 3 regions: the ulnar groove (zone I), the ulnar styloid process (zone II), and the triquetrum (zone III).

Results

The fibro-osseous tunnel comprising the ulnar groove and the overlying subsheath (zone I) stabilized the ECU tendon, and the subsheath had thin membranous collagen fibers attached to the periosteum. We consistently found the distal extension of ECU subsheath (zone II), which connected the ulnar styloid process and the dorsal radioulnar ligament. Variations in the length of the distal extension increased with the forearm in pronation. Collagen fiber thickness around the ECU tendon in zone II was greater than that of zone I. In zone III, the overlying extensor retinaculum and septa, which were composed of thick circumferential collagen structures, supported the ECU tendon by attaching to the triquetrum on both sides of the ECU tendon. We found the presence of an ulnar septum of the sixth compartment attached to the triquetrum in 84% of dissected wrists.

Conclusions

The ECU tendon was supported by the ECU subsheath, which had thin and elastic collagen fibers over the ulnar groove. Distal extension of the subsheath and surrounding radial and ulnar extensor retinaculum septa attached to the triquetrum provided thicker supporting structures.

Clinical relevance

Stenosing ECU tenosynovitis may occur not only in the ulnar groove but also in the more distal ulnar styloid process and triquetrum areas.

Section snippets

Material and Methods

Fifty fresh human cadaveric upper extremities (specimens aged 62–85 years) were used for gross observation and morphologic measurements of the ECU subsheath and the sixth dorsal compartment and its septa, and to examine the incidence and variation of an ECU accessory tendon. An additional 13 wrists (specimens aged 68–86 years) were used for histological examination of the surrounding structures stabilizing the ECU tendon. The ECU stabilizers in 3 regions were observed: the ECU tendon groove of

Gross dissection

The extensor retinaculum originated from the pisiform and passed over the dorsal wrist compartment and attached to the distal radius. The distal and proximal extents of the retinaculum, which originated from the fascia of the hypothenar and FCU muscles, variably supported the first to sixth extensor compartments.16 We found the sixth compartment septum attached to the triquetrum in 84% of specimens (42 of 50 wrists; age range, 62–85 years), located ulnar to the ECU tendon. Figure 1 shows

Discussion

The ECU tendon is stabilized in the ulnar groove by separate overlying layers of the extensor retinaculum and ECU subsheath. Microstructures of the thin membranous tissue supporting the tendon are composed of mixed loose and densely oriented collagen fibers with adipose tissue and blood vessels, similar to a previous report.17 If the ECU subsheath ruptures or elongates, the ECU tendon may move out of the ulnar groove, leading to recurrent dislocation of the ECU tendon.18 Previous authors

Acknowledgments

This study was supported by Chiang Mai University. The authors sincerely thank all donor cadavers included in this study. The authors acknowledge Dr Hisao Moritomo for his help in cadaver dissection and for his suggestion related to dynamic features of the ECU tendon subsheath.

References (29)

No benefits in any form have been received or will be received related directly or indirectly to the subject of this article.

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