Case Report
Copyright ©The Author(s) 2023. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Cases. Oct 6, 2023; 11(28): 6857-6863
Published online Oct 6, 2023. doi: 10.12998/wjcc.v11.i28.6857
Entrapment neuropathy of common peroneal nerve by fabella: A case report
Jing-Chun Lin, Mu-Hung Tsai, Wei-Pin Lin, Ta-Shen Kuan, Wei-Chih Lien
Jing-Chun Lin, Mu-Hung Tsai, Wei-Pin Lin, Ta-Shen Kuan, Wei-Chih Lien, Department of Physical Medicine and Rehabilitation, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan 704, Taiwan
Ta-Shen Kuan, Wei-Chih Lien, Department of Physical Medicine and Rehabilitation, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan
Author contributions: Tsai MH, Lin WP, and Lien WC planned the case report; Lin JC, Tsai MH, Lin WP, and Lien WC contributed to the analysis; Tsai MH, Lin WP, and Lien WC contributed to the interpretation of the results; Lin JC, Tsai MH, Lin WP, and Lien WC drafted the initial manuscript; Tsai MH, Lin WP, Kuan TS, and Lien WC revised the manuscript; and all authors have read and approved the final manuscript.
Supported by the National Cheng Kung University Hospital, Taiwan, No. NCKUH-11210036.
Informed consent statement: Informed written consent was obtained from the patient for publication of this report and any accompanying images. This research has been reviewed and recognized as a case report by National Cheng Kung University Hospital Institutional Review Board (NCKUH IRB number: B-EC-111-028) on October 7, 2022.
Conflict-of-interest statement: All the authors report no relevant conflicts of interest for this article.
CARE Checklist (2016) statement: The authors have read the CARE Checklist (2016), and the manuscript was prepared and revised according to the CARE Checklist (2016).
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Wei-Chih Lien, MD, PhD, Doctor, Department of Physical Medicine and Rehabilitation, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, No. 138 Sheng-Li Road, Tainan 704, Taiwan. lwclwhab@ms8.hinet.net
Received: June 22, 2023
Peer-review started: June 22, 2023
First decision: August 8, 2023
Revised: August 12, 2023
Accepted: September 4, 2023
Article in press: September 4, 2023
Published online: October 6, 2023
Abstract
BACKGROUND

Neuropathy of the common peroneal nerve caused by compression by a fabella is an extremely rare form of compression neuropathy. Involving both the superficial and deep peroneal nerves, it usually manifests as either impaired sensation from the lower lateral leg to the top of the foot or drop foot, or as a combination of both.

CASE SUMMARY

We report the case of a 58-year-old Asian female who presented with inversion of the right foot during the stance phase of gait without sensory complaints related to the lower leg. Electrodiagnostic testing revealed the neuropathy of the common peroneal nerve at the level of the knee, exclusively affecting the muscular branch of the superficial peroneal nerve. A neuromuscular ultrasound disclosed swelling of the right common peroneal nerve just before it crossed over a large fabella as well as atrophy and fatty infiltration of the right peroneus longus and peroneus brevis muscles. Surgical excision of the fabella and neurolysis were performed. Subsequently, the strength of the right foot evertors improved, but the unsteady gait with occasional falls persisted for nine months after the surgery. Therefore, another procedure was performed to transfer the split posterior tibialis tendon to the peroneus brevis in order to correct the gait.

CONCLUSION

This is the first case of neuropathy of the common peroneal nerve caused by compression by a fabella affecting exclusively the muscular branch of the superficial peroneal nerve. Clinicians should be aware of this unusual peripheral neuropathy while evaluating and treating patients with gait disturbance.

Keywords: Common peroneal neuropathy, Fabella, Compression neuropathy, Case report

Core Tip: This is the first case of common peroneal nerve entrapment neuropathy caused by compression by a fabella affecting exclusively the muscular branch of the superficial peroneal nerve. Instead of features typically found in neuropathy of the common peroneal nerve, such as drop foot, steppage gait, and numbness in the anterolateral leg and the dorsum of the foot, the case reported here presented with inversion of the right foot during the stance phase of gait for every step taken without any sensory problems. Therefore, clinicians should be aware of this unusual peripheral neuropathy while evaluating and treating patients with gait disturbance.