Ankle Syndesmosis Fixation

Indication. Symptomatic syndesmotic disruption that remains unstable after the fibula has been anatomically reduced and fixed — most commonly a Weber C (pronation-external rotation) ankle fracture, a Maisonneuve injury, or an isolated high ankle sprain with Grade III instability. The decision to add syndesmotic fixation is always made intra-operatively, after stress testing. Absolute indications

• Weber C or pronation-external rotation (Lauge-Hansen) ankle fracture with confirmed intra-operative syndesmotic instability after anatomic fibular plate fixation — a positive hook test, external rotation stress test, or Cotton test under fluoroscopy.
• High ankle sprain (isolated syndesmotic disruption) with Grade III instability — complete disruption of the AITFL, PITFL, and interosseous ligament on MRI or stress radiography, with clinical or radiographic talar shift.
• Syndesmotic diastasis greater than 6 mm on the AP radiograph (versus the contralateral side) with clinical instability. Relative indications
• Maisonneuve fracture (proximal fibular fracture with syndesmotic disruption and medial injury) — fixation of the syndesmosis after anatomic fibular reduction.
• Chronic syndesmotic instability with persistent pain and confirmed diastasis on weight-bearing CT or stress radiography — delayed reconstruction with suture-button or screw plus ligamentous repair.
• Ankle fracture with a posterior malleolar fragment greater than 25% of the articular surface and PITFL disruption where posterior fixation alone does not restore syndesmotic stability on intra-operative testing. Contraindications. Absolute: instability that resolves after anatomic fibular plate fixation (do not over-fix a stable syndesmosis); active deep infection or open-fracture contamination at the planned fixation site; a significant tibial plafond or pilon fracture that precludes accurate syndesmotic assessment. Relative: poor skin condition or soft-tissue compromise at the lateral ankle (delay until swelling resolves); severe osteoporosis where screw purchase is unreliable (consider suture-button or bicortical purchase); patient non-compliance with weight-bearing restrictions (suture-button preferred over screw). The three things that must be true before you place any syndesmotic fixation.

Consent specifically for malreduction and its consequences (chronic pain, early arthritis), hardware breakage (screws), the need for a planned screw removal (a second procedure), suture-button knot or button irritation, wound infection, non-union or malunion of associated fractures, complex regional pain syndrome, and the possibility of eventual ankle fusion or replacement for post-traumatic arthritis. Setup. Supine on a radiolucent table with a bump under the ipsilateral hip to internally rotate the leg and bring the lateral malleolus into an accessible position. A true AP and a true mortise view (15-20 degrees of internal rotation, so the talar dome is perfectly symmetric and the medial and lateral clear spaces are equal) must be obtainable before draping, with the contralateral ankle available for comparison images.

The goal: restore anatomic fibular length and rotation first, confirm true syndesmotic instability, reduce the fibula anatomically within the incisura under direct vision, hold that reduction with a screw or a suture-button, and confirm stability before closing. The exposure and the reduction are where the operation is won or lost — they are laid out in full below (and in depth on the anterolateral approach to the ankle and posterolateral approach to the ankle pages).

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Rehabilitation — weight-bearing matched to the implant The protocol is governed by whether the implant is designed to bear load. A syndesmotic screw is positional and must be protected; a suture-button is dynamic and tolerates earlier loading.

If a screw is retained (no planned removal), keep the patient non-weight-bearing for 8-10 weeks then graduate to full weight-bearing over 4-6 weeks; the screw may break (10-30%) but a broken retained screw in an anatomic reduction is usually asymptomatic. Expected outcomes. Most patients reach weight-bearing by 3-4 months. Ankle range of motion typically recovers to 80-90% of the contralateral side by 6 months. Functional scores (AOFAS, OMAS) are good to excellent in patients with an anatomic reduction; malreduced patients do significantly worse. Return to sport is around 70-85% at one year in competitive athletes. Post-traumatic ankle arthritis develops in 15-30% at 5-10 years (higher in malreduced or chondrally injured ankles), with ankle arthrodesis the salvage option for end-stage disease. Complications

Anatomy — the ligamentous complex. The syndesmosis is a fibrous joint connecting the distal tibia and fibula, stabilised by four structures. Understanding each one explains the mechanism, the imaging, and why a posterior malleolar fragment matters.

The incisura fibularis. The groove on the distal lateral tibia where the fibula sits varies between individuals. A deep (concave) incisura cups the fibula and is inherently more stable; a shallow (flat) incisura relies more on the ligaments and predisposes to instability and malreduction from lower-energy injuries. Pre-operative contralateral CT characterises the incisura shape and serves as a reduction reference. Radiographic landmarks — normal values.

Structures at risk.

Mechanism and epidemiology. The syndesmosis is disrupted in virtually all Weber C fractures (a fibular fracture above the syndesmosis) and in high ankle sprains (isolated ligamentous injury), but not every Weber C fracture requires fixation — many are stable after anatomic fibular plating. Pronation-external rotation (Lauge-Hansen PER) is the classic mechanism: with the foot pronated, external rotation sequentially tears the deltoid, the AITFL, the interosseous ligament and then fractures the fibula. The Maisonneuve variant propagates up the interosseous membrane to a proximal fibular fracture, so a seemingly minor ankle injury with medial-sided pain demands a full-length fibular radiograph. Key evidence. The debate between screw and suture-button fixation is among the best-studied questions in ankle trauma. The Andersen RCT and its five-year follow-up (Raeder) found comparable short-term outcomes and superior long-term outcomes for the suture-button, with earlier weight-bearing and no planned removal; bilateral-CT studies (Kortekangas; Naqvi) showed the suture-button achieves more accurate, more durable reduction. The Sagi study established that malreduction — not the implant — is the single strongest predictor of poor outcome, which is why direct incisura visualisation and intra-operative CT matter more than screw versus suture-button.