Arthroscopic Release of Flexor Hallucis Longus Tendon Sheath in Female Ballet Dancers: Dynamic Pathology, Surgical Technique, and Return to Dancing Performance  Hiroki Funasaki, M.D., Hiroteru Hayashi, M.D., Kanako Sakamoto, M.D., Rei Tsuruga, M.D., Keishi Marumo, M.D.  Arthroscopy Techniques  Volume 4, Issue 6, Pages e769-e774 (December 2015) DOI: 10.1016/j.eats.2015.07.025 Copyright © 2016 Arthroscopy Association of North America Terms and Conditions

Fig 1 Right ankle joint in a 17-year-old ballet dancer preoperatively. (A) An os trigonum is not evident on the lateral radiograph. (B) The lateral computed tomography image shows an unremarkable os trigonum connected to the posterior aspect of the talus (arrow). Arthroscopy Techniques 2015 4, e769-e774DOI: (10.1016/j.eats.2015.07.025) Copyright © 2016 Arthroscopy Association of North America Terms and Conditions

Fig 2 (A) Sagittal and (B) axial short tau inversion recovery magnetic resonance images show tenosynovitis and fluid collection around the flexor hallucis longus tendon (arrows). Arthroscopy Techniques 2015 4, e769-e774DOI: (10.1016/j.eats.2015.07.025) Copyright © 2016 Arthroscopy Association of North America Terms and Conditions

Fig 3 Arthroscopic views of posterior aspect of ankle and subtalar joint (prone position, right ankle, viewed from posterolateral portal). (A) After shaving of the soft tissues between the Achilles tendon and the talus, the posterior aspect of the os trigonum (OT) and the superior aspect of the calcaneus (C) are visualized. (B) Magnified view of the square in A. The flexor hallucis longus tendon surrounded by edematous retinaculum and synovium is identified on passive motion of the great toe. (Lat, lateral; Med, medial; S, synovium of flexor hallucis longus tendon.) Arthroscopy Techniques 2015 4, e769-e774DOI: (10.1016/j.eats.2015.07.025) Copyright © 2016 Arthroscopy Association of North America Terms and Conditions

Fig 4 Arthroscopic examination of os trigonum (OT) and flexor hallucis longus (FHL) tendon (prone position, right ankle, with arthroscopic view from posterolateral portal). (A) The OT and adhesion between the bone and the sheath are resected with a small punch. (B) A partial tear of the FHL tendon (arrow) is observed at the superior border of the tendon sheath (TS). (C, calcaneus.) Arthroscopy Techniques 2015 4, e769-e774DOI: (10.1016/j.eats.2015.07.025) Copyright © 2016 Arthroscopy Association of North America Terms and Conditions

Fig 5 Arthroscopic technique for release of flexor hallucis longus (FHL) tendon sheath and smoothing of tendon surface (prone position, right ankle, with arthroscopic view from posterolateral portal). (A) The tendon sheath is cut with a retrograde knife from the superior border of the sheath. (B) When fibrillation or a partial tear of the tendon is found (arrow), the tendon surface is smoothed with a radiofrequency device. (OT, os trigonum.) Arthroscopy Techniques 2015 4, e769-e774DOI: (10.1016/j.eats.2015.07.025) Copyright © 2016 Arthroscopy Association of North America Terms and Conditions

Fig 6 Arthroscopic view of flexor hallucis longus (FHL) tendon during release of tendon sheath (prone position, right ankle, with arthroscopic view from posterolateral portal). (A) A narrowed FHL tendon under the tendon sheath (arrow) is observed. (B) Release of the FHL tendon sheath is performed completely down to the entrance of the fibro-osseous tunnel (arrow). Arthroscopy Techniques 2015 4, e769-e774DOI: (10.1016/j.eats.2015.07.025) Copyright © 2016 Arthroscopy Association of North America Terms and Conditions

Fig 7 Arthroscopic examination after release of flexor hallucis longus (F) tendon sheath and resection of os trigonum in a 19-year-old female ballet dancer (prone position, right ankle, with arthroscopic view from posterolateral portal). (A) A narrowed flexor hallucis longus tendon under the sheath (arrow) is remarkable. (B) The entrance of the fibro-osseous tunnel (arrow) is clearly visualized. (C, calcaneus; T, talus.) Arthroscopy Techniques 2015 4, e769-e774DOI: (10.1016/j.eats.2015.07.025) Copyright © 2016 Arthroscopy Association of North America Terms and Conditions