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KEY FACTS
Terminology
Imaging
Top Differential Diagnoses
Pathology
Clinical Issues
TERMINOLOGY
Abbreviations
- Flexor hallucis longus (FHL)
Definitions
- Os trigonum: secondary ossification center at posterolateral talar process with intervening synchondrosis
- Stieda process: fused os trigonum at posterolateral talar process
- Os trigonum syndrome = compression of bone and soft tissue between posterior malleolus and calcaneus caused by forceful repetitive plantar flexion; may impinge upon FHL
- FHL impingement syndrome: os trigonum, large posterior process, or fracture of posterior process of talus limits gliding of FHL through fibroosseous tunnel at posterior process of talus
- FHL impingement may also occur at knot of Henry or at intersesamoidal ligament
- Check-rein deformity: tethering of FHL by flexor retinaculum
- Due to scar from previous injury
- Master knot of Henry
- Site at plantar aspect of foot where FHL crosses flexor digitorum longus (FDL)
- Tendon sheaths communicate here
- Tendon disease at this point may entrap medial plantar nerve
IMAGING
Radiographic Findings
MR Findings
Ultrasonographic Findings
Other Modality Findings
Imaging Recommendations
DIFFERENTIAL DIAGNOSIS
PATHOLOGY
General Features
Relevant Anatomy
CLINICAL ISSUES
Presentation
Demographics
Treatment
DIAGNOSTIC CHECKLIST
Image Interpretation Pearls
Selected References
- Sharpe BD et al: Posterior ankle impingement and flexor hallucis longus pathology. Clin Sports Med. 39(4):911-30, 2020
- Rajakulasingam R et al: Master knot of Henry revisited: a radiologist's perspective on MRI. Clin Radiol. 74(12):972.e1-8, 2019
- Rungprai C et al: Disorders of the flexor hallucis longus and os trigonum. Clin Sports Med. 34(4):741-59, 2015
- Donovan A et al: Plantar tendons of the foot: MR imaging and US. Radiographics. 33(7):2065-85, 2013
- O'Loughlin P et al: Fracture of the medial tubercle of the posterior process of the talus: magnetic resonance imaging appearance with clinical follow-up. HSS J. 5(2):161-4, 2009
- Lui TH: Arthroscopy and endoscopy of the foot and ankle: indications for new techniques. Arthroscopy. 23(8):889-902, 2007
- Michelson J et al: Tenosynovitis of the flexor hallucis longus: a clinical study of the spectrum of presentation and treatment. Foot Ankle Int. 26(4):291-303, 2005
- Na JB et al: The flexor hallucis longus: tenographic technique and correlation of imaging findings with surgery in 39 ankles. Radiology. 236(3):974-82, 2005
- Renard M et al: Intermittent dislocation of the flexor hallucis longus tendon. Skeletal Radiol. 2003 Feb;32(2):78-81. Epub 2003 Jan 23. Erratum in: Skeletal Radiol. 32(10):608-9, 2003
- Lo LD et al: MR imaging findings of entrapment of the flexor hallucis longus tendon. AJR Am J Roentgenol. 176(5):1145-8, 2001
- Inokuchi S et al: Closed complete rupture of the flexor hallucis longus tendon at the groove of the talus. Foot Ankle Int. 18(1):47-9, 1997
- Wredmark T et al: Os trigonum syndrome: a clinical entity in ballet dancers. Foot Ankle. 11(6):404-6, 1991
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References
Tables
Tables
KEY FACTS
Terminology
Imaging
Top Differential Diagnoses
Pathology
Clinical Issues
TERMINOLOGY
Abbreviations
- Flexor hallucis longus (FHL)
Definitions
- Os trigonum: secondary ossification center at posterolateral talar process with intervening synchondrosis
- Stieda process: fused os trigonum at posterolateral talar process
- Os trigonum syndrome = compression of bone and soft tissue between posterior malleolus and calcaneus caused by forceful repetitive plantar flexion; may impinge upon FHL
- FHL impingement syndrome: os trigonum, large posterior process, or fracture of posterior process of talus limits gliding of FHL through fibroosseous tunnel at posterior process of talus
- FHL impingement may also occur at knot of Henry or at intersesamoidal ligament
- Check-rein deformity: tethering of FHL by flexor retinaculum
- Due to scar from previous injury
- Master knot of Henry
- Site at plantar aspect of foot where FHL crosses flexor digitorum longus (FDL)
- Tendon sheaths communicate here
- Tendon disease at this point may entrap medial plantar nerve
IMAGING
Radiographic Findings
MR Findings
Ultrasonographic Findings
Other Modality Findings
Imaging Recommendations
DIFFERENTIAL DIAGNOSIS
PATHOLOGY
General Features
Relevant Anatomy
CLINICAL ISSUES
Presentation
Demographics
Treatment
DIAGNOSTIC CHECKLIST
Image Interpretation Pearls
Selected References
- Sharpe BD et al: Posterior ankle impingement and flexor hallucis longus pathology. Clin Sports Med. 39(4):911-30, 2020
- Rajakulasingam R et al: Master knot of Henry revisited: a radiologist's perspective on MRI. Clin Radiol. 74(12):972.e1-8, 2019
- Rungprai C et al: Disorders of the flexor hallucis longus and os trigonum. Clin Sports Med. 34(4):741-59, 2015
- Donovan A et al: Plantar tendons of the foot: MR imaging and US. Radiographics. 33(7):2065-85, 2013
- O'Loughlin P et al: Fracture of the medial tubercle of the posterior process of the talus: magnetic resonance imaging appearance with clinical follow-up. HSS J. 5(2):161-4, 2009
- Lui TH: Arthroscopy and endoscopy of the foot and ankle: indications for new techniques. Arthroscopy. 23(8):889-902, 2007
- Michelson J et al: Tenosynovitis of the flexor hallucis longus: a clinical study of the spectrum of presentation and treatment. Foot Ankle Int. 26(4):291-303, 2005
- Na JB et al: The flexor hallucis longus: tenographic technique and correlation of imaging findings with surgery in 39 ankles. Radiology. 236(3):974-82, 2005
- Renard M et al: Intermittent dislocation of the flexor hallucis longus tendon. Skeletal Radiol. 2003 Feb;32(2):78-81. Epub 2003 Jan 23. Erratum in: Skeletal Radiol. 32(10):608-9, 2003
- Lo LD et al: MR imaging findings of entrapment of the flexor hallucis longus tendon. AJR Am J Roentgenol. 176(5):1145-8, 2001
- Inokuchi S et al: Closed complete rupture of the flexor hallucis longus tendon at the groove of the talus. Foot Ankle Int. 18(1):47-9, 1997
- Wredmark T et al: Os trigonum syndrome: a clinical entity in ballet dancers. Foot Ankle. 11(6):404-6, 1991
