Summary

A "High Ankle Sprain" refers to an injury of the Syndesmosis—the complex of ligaments (AITFL, PITFL, Interosseous) that holds the Tibia and Fibula together. Unlike the common lateral sprain (inversion), this injury is caused by forceful External Rotation of the foot (e.g., getting tackled while the foot is planted). These injuries are notorious for two reasons: they take twice as long to heal as standard sprains, and if missed (leading to chronic widening of the ankle mortise), they cause rapid, devastating arthritis. Stable injuries are treated with immobilization, while unstable injuries (diastasis) require surgical stabilization (Screws or Suture Buttons). [1,2,3]

Key Facts

• The Mortise: The ankle joint is a mortise and tenon joint. The Tibia and Fibula form the mortise. The Syndesmosis is the "strong duct tape" holding the two bones together to keep the mortise tight.
• The Widening: If the syndesmosis tears, the fibula springs away from the tibia. The Talus then wobbles around inside the widened mortise (instability), destroying the cartilage. A 1mm shift reduces contact area by 42%.
• Recovery Time: Patients must be warned: "This is not a normal sprain." Return to sport averages 6-8 weeks for Grade I, and 3-4 months for Grade II.

Clinical Pearls

"The Squeeze Test": Squeezing the calf at the mid-shaft compresses the tibia and fibula together proximally, which forces them apart distally (lever effect). Pain at the ankle is a positive test for syndesmosis injury.

"Too painful to push off": Patients with a high ankle sprain have disproportionate pain during the "push off" phase of gait, as this drives the wedge-shaped talus up into the mortise, spreading the bones apart.

"Look out for Maisonneuve": Always palpate the proximal fibula (near the knee). The energy travels up the interosseous membrane and can exit as a fracture at the neck of the fibula.

                 HIGH ANKLE PAIN
                        ↓
             X-RAY: FRANK WIDENING?
            ┌───────────┴───────────┐
           YES                     NO
      (Diastasis)           (Appears Normal)
           ↓                        ↓
        SURGERY            STABLE ON STRESS?
      (Fixation)           ┌────────┴────────┐
                         YES                NO
                          ↓                  ↓
                     CAM BOOT             SURGERY
                    (6 Weeks)           (Fixation)

Indications

• Grade I injuries (Stable).
• Grade II (latent) if MRI confirms intact PITFL and no widening on stress views.

Protocol

• Immobilization: CAM Boot for 2-4 weeks. (Longer than lateral sprain).
• Weight Bearing: Protected weight bearing until pain-free.
• Rehab: Avoid external rotation. Focus on strength. Return to sport 6-8 weeks.

Indications

• Frank Diastasis (X-ray widening).
• Unstable on Stress Test (Medial Clear Space opens up).

Techniques

1. Syndesmotic Screw(s):
   • The classic method.
   • 1 or 2 screws (3.5mm or 4.5mm) through Fibula into Tibia.
   • Position: Parallel to joint, angled 30 degrees anteriorly.
   • Removal: Routine removal at 3-4 months is debated. (If left in, they often break).
2. Suture Button (TightRope):
   • The modern standard.
   • A heavy suture with buttons on either side. Allows physiologic motion ("toggle").
   • Benefit: No need for removal. Earlier weight bearing. No screw breakage.
   • Risk: Soft tissue irritation (knot stack).

Post-Op

• NWB 2-6 weeks depending on fixation type.

Screw vs TightRope

• Coetzee et al (Level 1 RCT): Showed that Suture Button fixation resulted in better functional outcomes (AOFAS scores) and faster return to work compared to screw fixation. It permits physiologic micromotion of the fibula.

Screw Removal?

• Hamid et al: To remove or not to remove? Literature is mixed. Leaving screws in creates a stress riser, and 30% break. Routine removal at 12 weeks is common practice.

The Injury

You have torn the heavy ligaments that hold your two shin bones together. It's like the clamp holding a vice has broken.

The Problem

If we don't fix the clamp, the bones will spring apart every time you step, and your ankle joint will be destroyed in a few years.

The Fix

We need to install an internal "seatbelt" (TightRope) or a screw to hold the bones tight while the ligaments heal.

The Timeline

This is a "bad sprain". It takes twice as long as a normal rolled ankle. Expect 3 months before football.

Q1: What defines a "stable" vs "unstable" syndesmosis injury? A: Stability is defined by the competence of the Deltoid ligament. If the Deltoid is intact, the talus cannot shift laterally, even if the AITFL is torn. If the Deltoid is torn (or the medial malleolus fractured) AND the syndesmosis is torn, the ankle is unstable.

Q2: What is the normal Tibiofibular Clear Space? A: <6mm on both AP and Mortise views. It should not change with stress.

Q3: Describe the Maisonneuve Fracture. A: A spiral fracture of the proximal third of the fibula associated with a distal syndesmotic rupture and deep deltoid ligament rupture (or medial malleolar fracture).

Q4: Why is the TightRope favored in athletes? A: It eliminates the need for a second surgery (screw removal) and allows earlier return to physiologic loading, avoiding the stiffness associated with rigid screw fixation.

(End of Topic)