Flexor hallucis longus impingement syndrome: A case report

Introduction and importance: Long-term friction of the FHL tendon's sheath (caused by sporting activities) can result in tendinitis, which causes pain in the foot and ankle and consequently interferes with everyday life and foot function. The FHL tendon is crucial for maintaining foot stability and can be damaged by overuse. FHL tendinitis can be also caused by inflammatory tendon sheath filled. Arthroscopy can play a role in the diagnosis and treatment of this condition. Case presentation: A 28-year-old female with left ankle pain was brought to our clinic after slipping on a train platform nine months ago. X-rays and MR imaging revealed a complete tear of the ATFL, minimal joint effusion, and a bony protrusion causing impingement. Arthroscopic surgery was performed, and the patient's pain sensation improved to 0–1 in the visual analogue scale (VAS) within three weeks. The Foot and Ankle Ability Measure (FAAM) score increased from 8 % to 100 %, and the patient was able to walk and perform daily activities normally. Clinical discussion: The FHL tendon sheath begins at the posterior tubercles of the talus and forms a fibroosseous tunnel along the medial calcaneus, potentially leading to impingement during ankle or hallux dorsiflexion. FHL tendon impingement and tendinitis share clinical manifestations, and if conservative treatments (NSAIDs, physical therapy) fail after 6 months, arthroscopic surgery is recommended for its minimally invasive benefits. Both arthroscopic and open surgical techniques yield positive outcomes for FHL pathologies; however, they carry risks such as neurovascular complications, highlighting the necessity for surgical precision and expertise. Conclusion: We concluded that in this case, FHL impingement was caused by the bony protrusion from Stieda process fragment. It was demonstrated that the arthroscopic surgery with loose body removal was successful and practical.