The flexor hallucis longus: tenographic technique and correlation of imaging findings with surgery in 39 ankles

To examine the use of tenography for evaluation of the flexor hallucis longus (FHL) sheath.

Institutional review board approval was waived, patient consent was obtained, and the study was HIPAA compliant. Retrospective review of 192 FHL tenograms and associated surgical records identified 39 ankles in 37 patients (17 male, 20 female; mean age +/- standard deviation, 38 years +/- 13.8; range, 14-68 years) in which both tenography and surgery had been performed. Two radiologists reviewed tenographic findings, including contrast agent extravasation, synovial irregularity, stenosis, fibrous bands, sheath outpouching, extent of opacification, and communications with adjacent structures. Alterations in pain after anesthesia of the tendon sheath were also recorded. Surgical reports were reviewed.

Thirty-four of 39 tenograms were diagnostic. Some extravasation occurred in nine (45%) of 20 injections with an initial injection method and in two (11%) of 19 with a new injection technique. Synovial irregularity was present in all 34 studies (15 mild, 16 moderate, three severe). Stenoses were identified in 23 (68%) of 34 ankles, fibrous bands were seen in 16 (47%) of 34 ankles, and outpouching of the sheath above a stenosis was present in 13 (38%) of 34 ankles. Communication of the FHL sheath with the ankle, flexor digitorum longus, or subtalar joint occurred in half the cases. Most patients with pain reported relief; relief was complete (100% reduction from preprocedural pain) in eight of 27, moderate (50%-90% reduction) in nine of 27, and mild (<50% reduction) in eight of 27 patients.

Tenography of the FHL sheath produced diagnostic images in almost all patients and effectively demonstrated abnormalities of the tendon sheath. Pain relief with anesthetic injection helped confirm the FHL sheath as the pain generator.