Summary

Flexor Hallucis Longus (FHL) Tendonitis, often called "Dancer's Tendonitis", is a stenosing tenosynovitis of the FHL tendon as it passes through the fibro-osseous tunnel on the posterior aspect of the Talus. It is characteristically seen in ballet dancers (en pointe) and footballers who engage in repetitive, extreme plantarflexion. The tendon becomes inflamed and nodular, getting stuck in the tunnel, leading to painful "triggering" or locking of the big toe. Management begins with rest but often requires surgical release of the sheath to restore gliding. [1,2,3]

Key Facts

• The Anatomy: The FHL is the only muscle that arises from the Fibula but acts on the Big Toe. It crosses the ankle posteromedially, passing between the medial and lateral tubercles of the Talus (the tunnel).
• The Impingement: In full plantarflexion (pointe), the FHL muscle belly can get jammed into the back of the ankle tunnel, or an Os Trigonum (extra bone) can crush the tendon.
• Trigger Hallux: If a nodule forms on the tendon, the big toe may lock in flexion and snap straight, exactly like a trigger finger.

Clinical Pearls

"Check the Excursion": To diagnose FHL tightness, stabilize the ankle in neutral and extend the big toe. Then plantarflex the ankle and extend the toe. If extension is significantly reduced in dorsiflexion, the FHL is tight/short.

"Pseudo-Hallux Rigidus": FHL tendonitis can mimic Hallux Rigidus (stiff toe). The difference is that in FHL tendonitis, the stiffness is dynamic and posterior ankle pain is present.

"The Harry": In the Tarsal Tunnel mnemonic (Tom, Dick, and Harry), Harry (Hallucis) is the most posterior structure. It is the last to be released in a Tarsal Tunnel decompression but the first to be injured in a dancer.

                 POSTERIOR ANKLE PAIN
                        ↓
                 SUSPECT FHL PROBLEM
            ┌───────────┴───────────┐
         STEROID INJECTION       FAILED?
            ↓                       ↓
         RESOLVED?               SURGERY
        ┌────┴────┐         (Sheath Release)
       YES       NO                 ↓
                 ↓           OS TRIGONUM?
              REPEAT?       ┌───────┴───────┐
                           NO              YES
                           ↓                ↓
                        RELEASE          EXCISE

Indications

• Acute synovitis.
• No mechanical localized nodule.

Protocol

• Rest: Stop pointe work for 4-6 weeks.
• NSAIDs: Reduce inflammation.
• Injection: Ultrasound-guided Corticosteroid injection into the sheath. (Very effective for pure synovitis).

Indications

• Mechanical triggering (Nodule).
• Failed conservative care (>3 months).
• Associated Os Trigonum impingement.

Techniques

1. Open Release:
   • Medial incision.
   • The Flexor Retinaculum (roof of the tunnel) is slit open.
   • The tendon is inspected. Nodules are debulked. Splits are sutured.
2. Endoscopic Release:
   • Minimally invasive (2 portals).
   • Excellent visualization of the tunnel.
   • Faster return to sport.
   • Can sustain Sural Nerve injury if not careful.

Os Trigonum Excision

• If present, the Os Trigonum is removed to decompress the tunnel.

Endoscopic vs Open

• Hamilton et al: Reported excellent results with open release in dancers.
• Modern Era: Endoscopic release has shown equal success rates with lower wound complication rates and better cosmetics (important for dancers).

The Injury

The tendon that bends your big toe runs through a tight bony tunnel at the back of your ankle. Because of your dancing, the tendon has swollen up and is getting stuck in the tunnel, like a thread with a knot in it trying to pass through a needle.

The Fix

We need to cut the roof of the tunnel to let the tendon glide freely.

The Recovery

You can walk immediately. Return to dancing takes about 6-8 weeks.

Q1: What is the "Knot of Henry"? A: The anatomical crossover point in the midfoot where the Flexor Digitorum Longus (FDL) crosses superficial to the Flexor Hallucis Longus (FHL). Connections here can restrict independent toe movement.

Q2: Why is FHL tendonitis called "Dancer's Tendonitis"? A: Because the extreme plantarflexion required for pointe and demi-pointe work jams the FHL tendon into the posterior talar tunnel, causing mechanical impingement and synovitis.

Q3: How does an Os Trigonum contribute to pathology? A: An Os Trigonum (unfused lateral tubercle of posterior talus) occupies space within the fibro-osseous tunnel, effectively narrowing it and compressing the FHL tendon during plantarflexion (Nutcracker effect).

Q4: Differentiate FHL Tendonitis from Tarsal Tunnel Syndrome. A:

• FHL: Pain is posteromedial, aggravated by toe motion (resisted flexion), mechanical triggering may be present. No neurological deficit.
• Tarsal Tunnel: Pain is burning/neuropathic, aggravated by Tinel's percussion. Sensory loss in the sole.

(End of Topic)