Tenosynovitis of the flexor hallucis longus: a clinical study of the spectrum of presentation and treatment.

BACKGROUND: Symptoms associated with flexor hallucis longus (FHL) pathology can manifest themselves anywhere along its length from the posterior leg to the plantar foot and the hallux. This study describes the spectrum of clinical presentations seen with FHL pathology, illustrates the relevant physical examination findings, and outlines a treatment approach. MATERIALS: Computerized medical data was prospectively collected on 81 patients treated between January, 1997 and March, 2002. The 55 females and 26 males had an average age of 38.3 years, with a mean follow-up of 21.3 months. Forty-five of 81 had previous therapy that failed, usually for "plantar fasciitis." Twenty-seven were active athletically and 24 related the onset of symptoms to a specific traumatic episode. Pain was located at the posteromedial ankle in 40, plantar heel in 23, plantar midfoot in 22, and multiple locations in 16. All patients had tenderness of the FHL. Restriction of FHL excursion was demonstrated in 30 patients by limited hallux metatarsophalangeal joint dorsiflexion when the ankle was dorsiflexed ("FHL stretch test"). Thirty-four patients had magnetic resonance imaging of the FHL, 28 (82%) of which were positive for synovitis of the FHL. Treatment included an FHL stretching program, short-term immobilization, and operative decompression and synovectomy in patients for whom nonoperative treatment failed.
RESULTS: Of the 58 patients treated nonoperatively, 37 (64%) had successful results. Twenty-three patients had surgery, 20 at the posterior ankle fibro-osseous tunnel, and three in the sesamoid region. All patients treated operatively had successful outcomes. A subset of 10 patients had hallux rigidus symptoms without significant osteophyte formation. All 10 obtained successful results with treatment directed at restoring normal FHL excursion (nine nonoperatively, one by FHL release). This suggests that limited FHL excursion may be an etiology for the development of hallux rigidus.
CONCLUSIONS: Clinical syndromes related to the FHL are more frequent than previously reported. The close relationship of the FHL to commonly injured structures (such as the plantar fascia) contributes to significant delays in effective treatment.