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Coalition by MSKMRI JEE EUN LEE.pdf
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Mechanism of Entrapment
- Bony encroachment: Non-osseous TCC (fibrous/cartilaginous) often produces hook-like excrescences or a deformed sustentaculum tali protruding into the tarsal tunnel.
- Ganglion cysts: Can arise from the fibrocartilaginous coalition or irritated tendon sheath, decompressing into the tunnel as space-occupying lesions.
- Tendon pathology: FHL, FDL, and PT tendons may show entrapment, attenuation, or tenosynovitis, worsening tunnel crowding.
Clinical Presentation
- Pain, paresthesia, burning along tibial nerve distribution.
- MPN involvement most common → sensory loss in medial plantar distribution.
- Tinel’s sign may be positive at the tarsal tunnel.
MRI Findings
- Direct encroachment: Bony overgrowth or ganglion displacing neurovascular bundle.
- Nerve pathology: MPN shows increased T2 signal (≥ adjacent vessels) and focal enlargement; denervation edema may appear in abductor hallucis.
- Prevalence: MPN neuritis seen in ~9% of TCC cases on MRI.
- Tendon disease: FHL most frequently affected (entrapment 21%, attenuation, split tears, tenosynovitis).
- Ganglia: Well-defined fluid lesions arising from coalition or tendon sheath, compressing nerves.
Clinical & Surgical Significance
- Pain may arise from both coalition and secondary soft-tissue disease.
- Resection of coalition alone is often insufficient if MPN entrapment, tendon tears, or ganglion cysts coexist.
- Preoperative MRI should systematically evaluate all tarsal tunnel contents, guiding surgeons toward a comprehensive approach (coalition resection + nerve/tendon decompression or ganglion excision).
#Radiology #MSKMRI #FootMRI #TalocalcanealCoalition #TarsalTunnelSyndrome #MedialPlantarNerve #MRIteaching #OrthopedicImaging #RadiologistLife #MedicalEducation
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