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Case Reports in Orthopedics
Volume 2015, Article ID 705237, 3 pages
Case Report

Carpal Tunnel Syndrome with Wrist Trigger Caused by Hypertrophied Lumbrical Muscle and Tenosynovitis

1Department of Orthopaedics, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa 259-0198, Japan
2Department of Orthopaedic Surgery, Shonan Central Hospital, 1-3-43 Hatori, Fujisawa, Kanagawa 251-0056, Japan

Received 24 March 2015; Accepted 7 June 2015

Academic Editor: Jae Taek Hong

Copyright © 2015 Ayuko Shimizu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We present a case of carpal tunnel syndrome involving wrist trigger caused by a hypertrophied lumbrical muscle with flexor synovitis. The case was a 40-year-old male heavy manual worker complaining of numbness and pain in the median nerve area. On active flexion of the fingers, snapping was observed at the carpal area, and forceful full grip was impossible. Tinel’s sign was positive and an electromyographic study revealed conduction disturbance of the median nerve at the carpal tunnel. Magnetic resonance imaging revealed edematous lumbrical muscle with synovial proliferation around the flexor tendons. Open carpal tunnel release was performed under local anesthesia. Synovial proliferation of the flexor tendons was found and when flexing the index and middle fingers, the lumbrical muscle was drawn into the carpal tunnel with a triggering phenomenon. After releasing the carpal tunnel, the triggering phenomenon and painful numbness improved.