Summary

Subtalar dislocation, also known as "Basketball Foot", is the simultaneous dislocation of the Talocalcaneal and Talonavicular joints, while the Tibiotalar (Ankle) and Calcaneocuboid joints remain intact. The foot swivels underneath the talus. It is a dramatic injury with severe deformity. Most (80%) are Medial Dislocations (Foot goes medial, Head of Talus goes lateral). The prognosis is generally good if reduced promptly, but complications include skin necrosis (from tenting) and subtalar arthritis. [1,2,3]

Key Facts

• The "Acquired Clubfoot": A medial dislocation looks exactly like a clubfoot deformity but in an adult. The foot is inverted and plantarflexed.
• Buttonholing: The prominent Head of the Talus can "buttonhole" through the Extensor Retinaculum or get trapped by the Extensor Digitorum Brevis, making closed reduction impossible.
• Osteochondral Fractures: Up to 40% of cases have invisible chips of cartilage sheared off the joint surface. CT scan post-reduction is mandatory to find them.

Clinical Pearls

"Reduce on the Floor": These are hard to reduce on a trolley. Place the patient on the floor (mattress), bend the knee 90° (relax the gastrocnemius), and use your body weight to pull longitudinal traction.

"The Dimple Sign": If you see a skin dimple over the talar head after an attempted reduction, it means the skin is invaginated into the joint. Do not keep pushing! You need to open it.

"Pivot Point": The calcaneocuboid joint acts as the pivot point. The foot swings around it like a door hinge.

                 SUBTALAR DISLOCATION
                        ↓
            NEUROVASCULAR / SKIN STATUS?
           ┌────────────┴─────────────┐
        COMPROMISED                 STABLE
           ↓                          ↓
    EMERGENCY REDUCTION         X-RAY CONFIRMATION
   (Sedation in ER)             (Then Reduction)
           ↓
      SUCCESSFUL?
      ┌────┴────┐
     YES       NO (Buttonholed)
      ↓         ↓
    CAST       OPEN REDUCTION
   (4 wks)      (Theatre)
      ↓         ↓
    CT SCAN    CT SCAN

Technique (Medial Dislocation)

1. Sedation: Essential for muscle relaxation.
2. Position: Knee flexed 90°.
3. Traction: Assistant holds thigh. Surgeon pulls heel longitudinally.
4. The Maneuver:
   • Exaggerate the deformity (Invert more) to unlock the calcaneus.
   • Pull traction.
   • Evert and Abduct the foot while pushing the Talar Head medially.
5. Clunk: Usually palpable.

Technique (Lateral Dislocation)

• Much harder. Often requires Open Reduction due to tibialis posterior tendon interposition.

Post-Reduction Care

• Below Knee Cast (Non-Weight Bearing).
• Duration: 4 weeks (Ligament healing).
• Then: Physio for stiffness.

Indications

• Irreducible by closed means (10-20%).
• Open Dislocation.
• Associated Fractures requiring fixation.

Barriers to Reduction

• Medial Dislocation: Extensor Digitorum Brevis (EDB) muscle, Extensor Retinaculum, Peroneal tendons.
• Lateral Dislocation: Tibialis Posterior tendon (wraps around neck), Flexor Hallucis Longus.

The "Basketball Foot"

• Studies in NBA players show a relatively quick return to sport (4-6 months) compared to ankle fractures, provided there is no cartilage damage. Proprioception retraining is key.

CT Scanning

• Bibbo et al: Found that 100% of subtalar dislocations had associated intra-articular fractures on CT, but only 60% were visible on X-ray. This changed the standard of care to mandatory post-reduction CT.

The Injury

You have dislocated the "universal joint" of your foot. The ankle moves up and down; the subtalar joint (where you are hurt) moves side-to-side. Your foot has spun off its axis.

The Fix

We popped it back into place. It is now stable.

The Recovery

You need a cast for 4 weeks to let the ligaments tighten up. After that, it will be stiff. You will struggle to run on uneven grass or cobblestones for about a year.

The Risk

There is a chance of "arthritis" (wear and tear) in the future because the cartilage got scraped when it dislocated.

Q1: Which joints are dislocated in a "Subtalar Dislocation"? A: The Talocalcaneal and Talonavicular joints. (The Calcaneocuboid joint is intact, but the foot swivels around it).

Q2: Why is AVN rare in subtalar dislocation compared to talar neck fractures? A: Because the blood supply to the talus enters via the Tarsal Canal and Sinus Tarsi, which are located at the neck. In a pure dislocation, the neck is not broken, so the vascular channels remain patent (though stretched).

Q3: Name two structures that block reduction in a medial dislocation. A:

1. Extensor Digitorum Brevis (EDB) buttonholing.
2. Deep Peroneal Nerve / Extensor Retinaculum.

Q4: What is the "jockey's injury"? A: A variant where the foot is caught in a stirrup and twisted. Often results in a lateral subtalar dislocation.

(End of Topic)