Fat infiltration in the gluteus minimus muscle in older adults
Received 17 November 2017
Accepted for publication 11 April 2018
Published 23 May 2018 Volume 2018:13 Pages 1011—1017
Checked for plagiarism Yes
Review by Single-blind
Peer reviewer comments 2
Editor who approved publication: Dr Richard Walker
Yuta Takano,1 Hiroto Kobayashi,2 Takuma Yuri,1 Saori Yoshida,2 Akira Naito,2 Yoshiro Kiyoshige1
1Graduate School of Health Science, Yamagata Prefectural University of Health Science, Yamagata, Japan; 2Department of Anatomy, Yamagata University Faculty of Medicine, Yamagata, Japan
Purpose: Fat infiltration (FI) in the gluteus minimus muscle (GMin) has been reported as being restricted to the anterior part. The aim of this study was to verify whether FI is localized only to the anterior part of the GMin through the dissection of large number of elderly cadavers and to clarify the underlying mechanism of FI localized to a specific region.
Materials and methods: Thirty-eight hips from 20 embalmed elder cadavers were dissected for verification of FI localization. The samples of three regions – the fat infiltrated region of the anterior part (FI), the region without FI (non-FI), and the posterior region – were harvested from nine hips for the histological fiber type assessment.
Results: The FI area was distributed at 2.6°–38° from the anterior border within the anterior part, of which function is responsible for hip extension and internal rotation and is likely reduced by disuse following aging. The number of type I fibers was lowest in FI, followed by non-FI, while the number of type I fibers was highest in the posterior. Meanwhile, the number of type II fibers was equivalent across the three regions. Atrophic type II fibers were observed in overall samples of the three regions, and grouped atrophy, which is evidence of denervation, was observed in FI and non-FI samples. Type grouping, which suggests to be reinnervated, was found in the non-FI and posterior samples but very little in the FI samples.
Conclusion: FI in the GMin in older adults restricted to deep within the anterior part is secondary to disuse and is strongly related to impaired denervation–reinnervation process.
Keywords: gluteus minimus, fat infiltration, disuse, denervation, fiber type
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