Flexor Tendon Entrapment Caused by Intratendinous Tumor-Like Chronic Proliferative Tenosynovitis.

The flexor tendon can be enlarged in chronic tenosynovitis, and it may sometimes trigger flexor tendon entrapment, but there have been no reports of its evaluation on preoperative imaging or postoperative pathologic examination. The case of a 54-year-old man who suffered flexor tendon entrapment due to intratendinous tumor-like tissue between the first and second annular pulleys, which was identified on magnetic resonance imaging preoperatively, is described. Ulnar superficialis slip resection and reduction flexor tenoplasty of flexor digitorum profundus were effective procedures for the release of flexor tendon entrapment under wide-awake surgery with local anesthesia. On postoperative pathologic examination, chondroid metaplasia was identified, in association with infiltration of chondrocytes and inflammatory cells into the flexor tendon fibers and tenosynovium. Preoperative imaging was useful in a case of chronic or severe tenosynovitis to assess the condition of flexor tendons, and wide-awake surgery was the appropriate procedure for the treatment of this case.