Syndesmotic Level | Stability Determines Treatment | Ring Injury Concept
- Weber classification is based on fibular fracture level relative to syndesmosis
- Ankle is a ring structure - isolated fractures rare, look for second injury
- Weber B stability determined by deltoid ligament and syndesmosis integrity
- Medial clear space over 4mm on the mortise view, or greater than the superior clear space, indicates deltoid rupture = unstable
- Syndesmotic screws placed 2-4cm above joint, parallel to joint line
- “Weber C = syndesmosis disrupted by definition = unstable
- “Mortise view: 15-20 degree internal rotation shows true joint space
- “Maisonneuve = proximal fibula fracture + syndesmosis rupture - examine whole leg
- “Lauge-Hansen describes mechanism; Weber describes fibula level
Overview and Epidemiology
Ankle fractures are the most common lower limb fracture requiring surgical intervention. Correct assessment of stability is paramount: an unstable fracture treated non-operatively has a poor outcome, with post-traumatic arthritis in up to 50% at 20 years.
Who. The distribution is bimodal: young males from sport and high-energy injury, elderly females from low-energy falls onto osteoporotic bone, and the female predominance increases with age. Incidence peaks in winter with ice-related falls. Soccer, basketball and skiing are the usual sports.
Mechanism. A twisting injury, inversion or eversion, or a direct blow. Lauge-Hansen names the foot position and the deforming force, and supination-external rotation is the most common pattern; the frequencies of all four are in the classification section.
Anatomy and Biomechanics
The ankle mortise functions as an osseoligamentous ring. Like a pretzel, a ring cannot break in one place, so a fracture on one side means a second disruption somewhere else. Isolated malleolar fractures are rare: the second lesion is a deltoid rupture, a syndesmosis injury or a proximal fibula fracture, and the examination and the films are read looking for it.
The syndesmosis. Four ligaments maintain the tibiofibular relationship. A Weber C fracture disrupts them by definition, and the squeeze test is positive when they are injured.
- AITFL - anterior inferior tibiofibular ligament, the first to tear
- PITFL - posterior inferior tibiofibular ligament, the strongest
- IOL - interosseous ligament
- ITL - inferior transverse ligament, the deep part of the PITFL
The deltoid. The primary medial stabiliser, in two layers. The superficial layer is tibionavicular, tibiocalcaneal and tibiotalar; the deep layer, anterior and posterior tibiotalar, is the critical one, because it resists lateral talar shift. Rupture of the deep deltoid is what widens the medial clear space.
The lateral ligaments. The ATFL, CFL and PTFL provide lateral ankle stability. They are commonly injured in Weber A fractures and usually heal well.
The posterior malleolus. Carries the PITFL attachment and part of the articular surface, which is why reducing it restores the PITFL. Whether to fix it is decided on CT morphology rather than the old 25% size rule, and the criteria are set out under surgical technique.
The superficial peroneal nerve crosses the surgical field anterolaterally, 7-10cm proximal to the tip of the fibula, where it becomes subcutaneous, and it is at risk during the lateral approach. Identify and protect it.
Classification Systems
Two systems are used together and answer different questions. Weber describes the level of the fibular fracture relative to the syndesmosis and guides treatment; Lauge-Hansen describes the mechanism, the foot position and the deforming force. AO/OTA uses the same three levels (44-A, B and C) with subgroups.
Weber Classification (Danis-Weber)
- Fibula Level
- Below syndesmosis
- Syndesmosis
- Intact
- Stability
- Stable
- Treatment
- Non-operative usually
- Fibula Level
- At syndesmosis
- Syndesmosis
- Partial/Intact
- Stability
- Variable
- Treatment
- Stress testing required
- Fibula Level
- Above syndesmosis
- Syndesmosis
- Disrupted
- Stability
- Unstable
- Treatment
- Surgical fixation
Why the level matters. Weber correlates with syndesmotic injury: the higher the fibular fracture, the greater the syndesmotic disruption and the less stable the ankle. A Weber A fracture lies entirely below the joint line with the ligaments intact; a Weber B is trans-syndesmotic and needs stress views; a Weber C lies above a syndesmosis that is disrupted, and is unstable by definition.
Clinical Assessment
History. Ask about the mechanism (twisting, inversion or eversion, a direct blow), whether the patient could weight-bear (the Ottawa question), previous ankle injuries that may have left instability or arthritis, and the comorbidities that change the plan: diabetes, peripheral vascular disease and smoking.
Examination. Look for swelling, deformity, the condition of the skin and blisters. Feel for bony tenderness over the medial, lateral and posterior malleoli; a medial malleolar fracture or medial tenderness means the ring is disrupted. Range of motion is limited by pain; test stability. Record the neurovascular status: dorsalis pedis, posterior tibial and sensation.
A Maisonneuve fracture is a proximal fibula fracture with syndesmotic rupture, and the ankle may look relatively benign. Palpate the full length of the fibula in every ankle injury, and assess the interosseous membrane with the squeeze test and the proximal fibula examination; if suspicious, get full-length tibia and fibula views.
Special tests. The table gives the technique for each test and what a positive result means.
- Technique
- Compress fibula to tibia at mid-calf
- Positive Finding
- Pain at ankle syndesmosis
- Interpretation
- Syndesmosis injury
- Technique
- ER force to foot with knee at 90 degrees
- Positive Finding
- Pain at syndesmosis, widening on fluoro
- Interpretation
- Syndesmosis instability
- Technique
- Lateral translation of talus
- Positive Finding
- greater than 3mm translation
- Interpretation
- Deltoid insufficiency
- Technique
- Direct AP stress to fibula
- Positive Finding
- greater than 3mm translation
- Interpretation
- Syndesmosis disruption
Radiographs are indicated for bone tenderness at the posterior edge or tip of either malleolus, or inability to weight-bear four steps both immediately and in the emergency department. Sensitivity is over 98% for fractures.
Investigations
Radiographs. Three views are essential: AP, lateral and mortise. The mortise view is taken with the leg in 15-20 degrees of internal rotation, which brings the intermalleolar axis parallel to the beam and gives a true AP of the mortise; it is the view on which joint congruency and the clear spaces are measured.
CT and MRI. CT is indicated for posterior malleolus assessment, pilon fracture exclusion, preoperative planning of complex patterns and syndesmosis evaluation. MRI is rarely needed: it may help assess deltoid integrity if that is unclear, and it is useful for occult fractures or persistent symptoms.
The isolated Weber B. A Weber B with a normal-looking mortise needs a further film to decide stability, and the choice of film has shifted.
The genuinely hard call is the isolated Weber B with a normal-looking medial clear space on static films: is the deltoid competent (stable, boot) or incompetent (unstable, fix it)?
The traditional answer is a stress radiograph. The gravity stress view (lateral decubitus, injured ankle unsupported so that gravity externally rotates the talus) or a manual external-rotation stress view unmasks deltoid incompetence: a medial clear space over about 4mm, or greater than the superior clear space, means an unstable mortise.
The modern shift is the weight-bearing mortise view. Stress views over-call instability. A substantial proportion of stress-positive isolated Weber B fractures stay congruent under physiological weight-bearing load and do well non-operatively, so a weight-bearing radiograph is increasingly preferred to avoid unnecessary surgery.
The decision. A congruent mortise on a weight-bearing film supports a boot; persistent medial clear space widening or talar shift confirms an unstable injury for ORIF. The gravity stress view remains the more practical screen in the patient too painful to load acutely.
- Normal Value
- less than 4mm AND not exceeding the superior clear space
- Abnormal
- greater than 4mm, or greater than the superior clear space
- Significance
- Deltoid rupture, talar shift
- Normal Value
- less than 4mm
- Abnormal
- greater than 4mm
- Significance
- Talar subluxation
- Normal Value
- less than 6mm
- Abnormal
- greater than 6mm
- Significance
- Syndesmosis widening
- Normal Value
- greater than 6mm (AP), greater than 1mm (mortise)
- Abnormal
- Reduced
- Significance
- Syndesmosis injury
- Normal Value
- 0 degrees
- Abnormal
- greater than 2 degrees
- Significance
- Ligamentous instability
The landmarks. A threshold is useless without the view and the landmarks, and this is where marks are lost. All three syndesmotic measurements are taken 1cm above the tibial plafond, not at the joint line; quote the level as part of the answer.
- Tibiofibular clear space - the horizontal distance from the lateral border of the posterior tibial malleolus (the floor of the incisura) to the medial border of the fibula. Normal is under 6mm on both the AP and the mortise view.
- Tibiofibular overlap - the horizontal overlap between the lateral border of the anterior tibial tubercle and the medial border of the fibula: over 6mm on AP, over 1mm on mortise.
- Medial clear space - measured on the mortise view, between the lateral border of the medial malleolus and the medial border of the talus, at the level of the talar dome.
Which one to trust. Overlap and medial clear space both change with limb rotation, so a malpositioned film can manufacture or conceal an abnormality. The tibiofibular clear space is the least rotation-dependent and therefore the most reliable single measurement, which is why it is the one to quote if an examiner makes you choose. The most robust rule of all is a comparison rather than an absolute: the medial clear space should not exceed the superior clear space, and the uninjured side is the best control available.
Clear-space measurements detect talar shift, but the commonest correctable error is a shortened or malrotated fibula, the classic cause of a malreduced, arthritis-prone ankle. These are the checks that confirm an anatomic fibular reduction:
- Talocrural angle - the angle between a line perpendicular to the tibial plafond and a line through the two malleolar tips. Normal is about 83 degrees, within a few degrees of the uninjured side; a reduced angle means the fibula is short.
- The dime sign or ball sign (Shenton line of the ankle) - on the mortise view there is a smooth, unbroken curve between the recess in the lateral talar process and the tip of the lateral malleolus, like a coin fitting into the contour. A break or step in this arc means the fibula is short, the single best quick check for fibular length.
- Tibiofibular line and equal clear spaces - the medial, superior and lateral clear spaces should be equal and symmetric, and the subchondral bone of the plafond and medial malleolus should form a continuous line into the fibula.
- Rotation - compare the fibular contour and the talocrural angle with the contralateral (template) ankle intra-operatively; loss of the normal fibular twist or an abnormal incisura position signals malrotation.
Exam point: confirm fibular reduction by an intact dime sign, a talocrural angle of about 83 degrees matching the other side, and symmetric clear spaces. A broken dime arc means the fibula is short and must be re-reduced before fixation.
Differential Diagnosis
The painful injured ankle is not always a malleolar fracture, and each alternative has a pitfall of its own.
- Distinguishing Features
- Bony tenderness over malleoli, inability to weight-bear, visible fracture
- Key Investigation
- Mortise + AP + lateral radiographs
- Pitfall to Avoid
- Assuming an isolated fibula fracture is stable without stressing the medial side
- Distinguishing Features
- Tenderness over ATFL/CFL, no bony tenderness, Ottawa rules negative
- Key Investigation
- Clinical; radiograph only if Ottawa positive
- Pitfall to Avoid
- Over-imaging; missing an associated avulsion or Weber A fracture
- Distinguishing Features
- Medial/syndesmotic ankle pain plus proximal fibula tenderness
- Key Investigation
- Full-length tibia/fibula views; check medial clear space
- Pitfall to Avoid
- Examining only the ankle and missing the high fibula fracture
- Distinguishing Features
- High-energy axial load, articular comminution, marked swelling
- Key Investigation
- CT for articular mapping
- Pitfall to Avoid
- Treating it like a rotational ankle fracture and operating through swollen soft tissues
- Distinguishing Features
- Positive squeeze and external-rotation tests, pain above joint line, no fracture
- Key Investigation
- Stress/weight-bearing views; MRI if uncertain
- Pitfall to Avoid
- Labelling a frankly unstable syndesmosis as a simple sprain
- Distinguishing Features
- Persistent deep ankle pain, mechanical catching after a 'sprain'
- Key Investigation
- MRI (radiographs often normal)
- Pitfall to Avoid
- Attributing ongoing pain to soft tissue and missing the lesion
Management Algorithm
Stability decides: a stable injury is treated non-operatively and an unstable one is fixed, and the second tab sets out the operative indications and their urgency.
Non-Operative Management
Who. The indications:
- Stable, isolated Weber A fractures
- Stable Weber B fractures (negative stress views, normal medial clear space)
- Non-ambulatory or severely comorbid patients
- Significant soft tissue compromise
How. An isolated Weber A goes into a boot and weight-bears as tolerated. A stable Weber B is treated in a cast or boot with close follow-up, because the risk is late displacement.
Non-Operative Protocol
Below-knee backslab, elevation, ice. Non-weight-bearing or TTWB as tolerated.
Convert to CAM boot or below-knee cast. Check alignment with repeat X-rays.
Progressive weight-bearing as pain allows. Physiotherapy for ROM and strength.
Return to normal activities. May take 3-6 months for full recovery.
A non-operative Weber B needs weekly radiographs for the first 2 weeks to detect late displacement. Any widening converts the patient to operative management.
Surgical Technique
The fibula is the key to ankle stability, and the operation is organised around an anatomic reduction of its length, rotation and alignment.
ORIF Lateral Malleolus
Supine with bump under ipsilateral hip. Tourniquet to thigh. May use lateral decubitus for posterior work.
Direct lateral incision over fibula. Protect superficial peroneal nerve (anterolateral). Full-thickness skin flaps.
Anatomic reduction with pointed reduction clamp. Assess length, rotation, alignment.
1/3 tubular plate or anatomic plate. Interfragmentary lag screw if oblique fracture. 3+ screws proximal, 2+ distal.
Intraoperative stress test under fluoro: hook test, external rotation. If positive, a syndesmosis screw is required, but read the test-performance warning below before trusting a negative.
Two findings change how you should speak about this in a viva.
Most ankles do not need a syndesmotic screw once the malleolus is anatomically fixed. A prospective study of 140 patients with unstable supination-external-rotation fractures applied a standardised 7.5-Nm external-rotation stress test after internal fixation and found only 24 (17%) were still unstable. Anatomic fibular fixation restores most of the stability by itself, which is the argument against fixing the syndesmosis routinely.
But the tests used to make that call miss most instability. In the same study the hook test had a sensitivity of only 0.25 (95% CI 0.12-0.45) with specificity 0.98, and the external-rotation stress test a sensitivity of 0.58 (0.39-0.76) with specificity 0.96. Interobserver agreement was excellent (99% and 98%), so the problem is the tests, not the observers.
Read the direction. A positive hook test is highly trustworthy and mandates stabilisation; a negative one does not exclude an unstable syndesmosis. Say both halves out loud. Note the population: these were supination-external-rotation injuries, so do not quote the 17% as if it described Weber C fractures.
Fibular height alone is not a safe substitute. A level-III study of 62 pronation-external-rotation fractures found height criteria gave a positive predictive value of 0.93 but a negative predictive value of only 0.53 against hook testing: a high fracture predicts instability well, a lower one does not reliably exclude it.
The medial malleolus. Two 4.0mm partially threaded screws placed perpendicular to the fracture line is the most common fixation. A tension band wire or a plate is the alternative, and a small fragment takes K-wires with a tension band.
The posterior malleolus. Decide on CT morphology, not on the percentage: get a CT and classify the fragment (Bartonicek or Haraguchi). Fix it if:
- the fragment enters the fibular incisura, since reducing it restores the PITFL and the notch
- there is an articular step over 2mm
- there is impaction or a posteromedial extension
A small extra-incisural fragment does not need fixation whatever the percentage; a small fragment carrying the PITFL into the notch often does. Fix it through a posterolateral approach or with anterior-to-posterior screws. Restoring the PITFL may allow a syndesmosis screw to be avoided.
Complications
- Incidence
- 10-20%
- Risk Factors
- Diabetes, smoking, swelling
- Management
- Staged surgery, optimise soft tissues
- Incidence
- 5-15%
- Risk Factors
- Technical error, inadequate imaging
- Management
- Revision if symptomatic, prevent with good technique
- Incidence
- 39% overall (Sagi, bilateral CT)
- Risk Factors
- Closed rather than open reduction (see below)
- Management
- Direct visualisation, post-operative CT compared with the uninjured side, revise if malreduced
- Incidence
- 10-30%
- Risk Factors
- Initial cartilage damage, malreduction
- Management
- Depends on initial injury severity
- Incidence
- 10-30%
- Risk Factors
- Subcutaneous implants
- Management
- Removal after union if symptomatic
- Incidence
- under 5%
- Risk Factors
- Smoking, diabetes, osteoporosis
- Management
- Bone graft, revision fixation
- Incidence
- 1-5%
- Risk Factors
- Immobilisation, tourniquet
- Management
- Chemoprophylaxis, early mobilisation
Syndesmosis malreduction is common. Sagi's prospective bilateral-CT study found 39% malreduced against the uninjured side (44% after closed reduction, 15% after open, though P = 0.11 for that comparison), and Bartonicek's review quotes malposition after closed reduction in up to 50%. Even 2mm of malreduction is associated with worse outcomes. Ensure the fibula is out to length and correctly rotated first, since a short or externally rotated fibula is the classic cause of a malreduced ankle, and consider intraoperative or post-operative CT compared with the contralateral ankle.
Postoperative Care and Rehabilitation
Rehabilitation Timeline
Backslab, strict elevation. Wound check at 10-14 days. Non-weight-bearing.
CAM boot. Begin ROM exercises out of boot. Touch weight-bearing progressing to partial.
Progress to full weight-bearing and active mobilisation. A syndesmosis screw, if used, is left in place.
Wean from boot. Full weight-bearing. Proprioception and strength training.
Sport-specific rehabilitation. Full return when strength 90% of contralateral.
Outcomes and Prognosis
The 1mm rule. Anatomic reduction is the single most important factor for outcome: 1mm of lateral talar shift reduces tibiotalar contact area by 42%, which dramatically increases contact pressures and accelerates post-traumatic arthritis.
- Impact
- Most important
- Notes
- The 1mm rule
- Impact
- Critical
- Notes
- Malreduction = worse outcomes
- Impact
- Significant
- Notes
- Cannot be modified surgically
- Impact
- Moderate
- Notes
- Younger better functional outcomes
- Impact
- Negative
- Notes
- Higher complication rates
- Impact
- Negative
- Notes
- Impaired healing, higher infection
Guidelines, Registries & Global Practice
- Ankle fractures are among the most common lower-limb fractures, roughly 100-190 per 100,000 per year and around 9% of all fractures in older adults (AIM trial population)
- Bimodal pattern: young men (high-energy/sport) and older women (low-energy/osteoporotic)
- Incidence is rising in the elderly worldwide as populations age
- Winter and ice-related falls drive seasonal peaks in temperate regions
- Weber and Lauge-Hansen are the universal classification languages for communication
- Stability assessment (clinical + stress imaging) drives the operative decision everywhere
- Anatomic reduction of fibular length/rotation and the mortise is the shared goal
- Stress testing of isolated Weber B is treated as standard of care internationally
- Region
- International
- Key Position on Ankle Fractures
- Reduction-first principles; fibula is key to length/rotation; intra-operative stress (hook/external rotation) mandatory before deciding on syndesmotic fixation
- Region
- UK
- Key Position on Ankle Fractures
- Time-critical care for open fractures, soft-tissue-led timing, senior decision-making; supports non-operative pathways (e.g. close contact casting) in selected older adults
- Region
- US
- Key Position on Ankle Fractures
- Emphasis on anatomic mortise restoration and syndesmotic reduction quality; growing acceptance of suture-button devices and early weight-bearing after stable fixation
- Region
- Europe
- Key Position on Ankle Fractures
- Supports intra-operative syndesmotic reduction assessment and consideration of post-operative CT for high-risk syndesmotic injuries
- Region
- UK RCT
- Key Position on Ankle Fractures
- In patients over 60, close contact casting is functionally equivalent to ORIF at 6 months with fewer wound problems but more malunion - informs shared decision-making
Where intra-operative fluoroscopy, CT and suture-button implants are readily available, practice trends toward open syndesmotic reduction, post-operative CT verification and early weight-bearing. In limited-resource settings, robust syndesmosis screw fixation (cheap, reliable, no special instrumentation) and clinically guided cast management remain entirely appropriate; close contact casting is a valuable low-cost option for frail elderly patients regardless of setting.
Key documentation requirements:
- Document examination of full length of fibula (Maisonneuve)
- Document neurovascular status pre and post-operatively
- Document stress testing results for Weber B fractures
- Informed consent must include: infection, DVT, malunion, nonunion, post-traumatic arthritis, need for hardware removal
- If non-operative: document patient informed of need for close follow-up and risk of late displacement
Specific risks to discuss: Wound complications (especially if swollen, diabetic, smoker), superficial peroneal nerve injury, need for syndesmosis screw removal, hardware irritation requiring removal, post-traumatic arthritis regardless of treatment, DVT/PE.
Controversies and Areas of Uncertainty
Suture buttons reduce implant failure and removal and allow physiological motion, but high-quality long-term RCT data show functional outcomes are broadly equivalent to screws. Cost and surgeon familiarity still favour screws in many settings - the "best" device remains debated.
Whether to engage 3 or 4 cortices, use 3.5 or 4.5mm screws, and whether to routinely remove screws are all unresolved. Many surgeons now leave intact or even broken screws in asymptomatic patients rather than performing routine removal.
Routine deltoid ligament repair in supination-external rotation injuries with medial clear space widening has not been shown to improve outcomes when the lateral column and syndesmosis are anatomically stabilised; selective repair remains controversial.
The AIM trial shows casting can equal surgery in selected older adults. In diabetics and neuropaths, the optimal construct (extended fixation, transarticular nails, prolonged non-weight-bearing) and the threshold for surgery are still debated given high complication rates.
The classic "fix if over 25% of the articular surface" threshold is increasingly questioned. Modern thinking favours fixing based on syndesmotic stability, fragment morphology (Bartonicek/Haraguchi classification) and articular step, not size alone - because even small fragments carrying the PITFL can restore syndesmotic stability when fixed.
The morphology classifications named above are themselves examinable, because fragment shape (not just size) now drives the decision to fix and the approach:
Haraguchi (CT-based, 3 types):
- Type I - posterolateral-oblique: the commonest; a triangular posterolateral fragment.
- Type II - medial-extension (transverse): the fracture extends across to the medial malleolus (a posteromedial component) - higher chance of an intra-articular die-punch fragment.
- Type III - small-shell: a small avulsion shell off the posterior rim.
Bartonicek/Rammelt (CT-based, 5 types, emphasises the fibular notch/incisura and stability):
- Type 1: extra-incisural fragment (rim only, intact notch) - stable.
- Type 2: posterolateral fragment extending into the incisura.
- Type 3: posteromedial two-part fragment (involving the medial malleolus).
- Type 4: large posterolateral triangular fragment (over a third of the notch).
- Type 5: irregular osteoporotic fragment.
Why it matters: fragments involving the incisura (Bartonicek 2-4) are the ones whose fixation restores syndesmotic stability via the attached PITFL and improves articular congruity - so a CT to characterise the fragment, and posterior (posterolateral or posteromedial) buttress fixation of an incisura-involving fragment, is preferred over a stand-alone syndesmosis screw.
Exam point: classify the posterior malleolus on CT - Haraguchi I/II/III by location and Bartonicek 1-5 by incisura involvement - and fix the incisura-involving fragments to restore both the joint surface and syndesmotic stability.
MCQ Practice Points
Q: Which structure is the primary restraint to lateral talar shift? A: The deep deltoid ligament (specifically the deep tibiotalar fibers). The superficial deltoid resists eversion. Disruption of the deep deltoid allows the talus to shift laterally, increasing medial clear space.
Q: A Weber B fracture is defined by the fibula fracture being at what level? A: At the level of the syndesmosis. This correlates with partial syndesmosis injury potential. Weber A is below (intact syndesmosis), Weber C is above (disrupted syndesmosis).
Q: What is the upper limit of normal for medial clear space on a mortise view? A: 4mm (or equal to superior clear space). Greater than 4-4.5mm suggests deltoid ligament rupture and indicates an unstable injury requiring surgical management.
Q: What is the effect of 1mm lateral talar shift on tibiotalar contact? A: 42% reduction in contact area. This is the basis for emphasis on anatomic reduction - even small amounts of talar shift dramatically increase contact pressures and accelerate post-traumatic arthritis.
Q: At what level should a syndesmosis screw be placed above the joint line? A: 2-4cm above the joint line, parallel to the tibial plafond. Some surgeons prefer 3-4cm to minimize risk of articular damage. Screw directed 25-30 degrees anterior to coronal plane.
Exam Viva Scenarios
Practise clinical reasoning and management decisions out loud
“A 45-year-old woman presents after twisting her ankle stepping off a curb. She is unable to weight-bear. X-rays show a spiral oblique fracture of the lateral malleolus at the level of the syndesmosis with no obvious medial injury. How would you classify and manage this fracture?”
“You decide to proceed with ORIF for an unstable Weber B fracture with positive stress views. The patient is in theatre. Walk me through your surgical technique.”
“You review a patient 6 months post ankle ORIF in clinic. They have persistent lateral ankle pain and stiffness. CT shows malreduced syndesmosis with external rotation of the fibula. How do you manage this?”
Key Anatomy
- Ring structure - isolated injury rare, look for second lesion
- Syndesmosis: AITFL, PITFL, IOL, ITL - PITFL strongest
- Deep deltoid = primary restraint to lateral talar shift
- Superficial peroneal nerve 7-10cm above fibula tip
Weber Classification
- Weber A = below syndesmosis = stable
- Weber B = at syndesmosis = need stress views
- Weber C = above syndesmosis = unstable by definition
- Lauge-Hansen describes mechanism (SER most common 40-75%)
Treatment Algorithm
- Stable Weber A/B: Non-operative, CAM boot, close follow-up
- Unstable Weber B (MCS over 4mm or exceeding the superior clear space): ORIF fibula +/- syndesmosis
- Weber C: ORIF fibula + syndesmosis fixation always
- Bimalleolar/Trimalleolar: ORIF all components
Surgical Pearls
- Operate within 6-8h or wait for wrinkle sign (7-14 days)
- Protect superficial peroneal nerve anterolaterally
- Always stress syndesmosis intraoperatively
- Syndesmosis screw: 2-4cm above joint, 3-4 cortices, parallel to plafond
Complications
- Syndesmosis malreduction 15-50% (CT detects more than plain XR)
- 1mm talar shift = 42% reduction in contact area
- Wound complications 10-20% (higher if swollen/diabetic)
- Post-traumatic arthritis 10-30% at 10 years
Evidence Base
Suture Button vs Syndesmosis Screw - Long-Term RCT
- RCT of 43 patients with PER-type/Weber C unstable syndesmosis injuries randomised to a single tricortical syndesmosis screw or a suture button. At a mean 7.1-year follow-up, both implants maintained reduction equally well (2 malreductions screw vs 1 suture button), with comparable osteoarthritis rates and functional scores (mean OMAS 88 screw vs 78 suture button, not statistically significant).
Suture Button vs Screw - Meta-analysis of RCTs
- Meta-analysis of 5 RCTs (280 patients): suture button gave a slightly higher 1-year AOFAS score (mean difference 5.5 points) and a markedly lower implant failure rate (OR 0.03) than syndesmosis screws, with no difference in most other outcomes.