Comprehensive surgical technique guide for trimalleolar ankle fracture ORIF with syndesmotic assessment and structured viva scenarios for FRCS exam preparation
Reviewed by OrthoVellum Editorial Team
Orthopaedic clinicians and medical editors • Published by OrthoVellum Medical Education Team
Foot & Ankle Trauma | Core Procedure
Location: Emerges from lateral compartment in distal third of leg, 10-12cm above lateral malleolus. Protection: Identify before lateral incision, anterior retraction.
Location: Anteromedial leg and ankle, subcutaneous anterior to medial malleolus. Protection: Incision anterior to malleolar apex, identify and retract.
Location: Posterior to lateral malleolus, subcutaneous, runs with small saphenous vein. Protection: Avoid posterior lateral dissection, identify in posterolateral approach.
Location: Posteromedial ankle, under flexor retinaculum between FDL and FHL in tarsal tunnel. Protection: Stay lateral in posterolateral approach, never medial to FHL.
Location: Posterior to lateral malleolus in retrofibular groove. Protection: Identify and retract anteriorly, plate posterolateral not directly lateral.
Location: Runs in groove on posterior tibia under posterior malleolus fragment. Protection: Identify and protect medially in posterolateral approach.
| Category | Items |
|---|---|
| Reduction | Pointed reduction clamps, Weber clamp, dental pick, K-wires |
| Fibula | One-third tubular plate (7-8 hole), precontoured fibular locking plate |
| Screws | 3.5mm cortical screws, 2.7mm cortical screws for lag |
| Medial | 4.0mm partially threaded cancellous screws, medial malleolar plate |
| Posterior | 3.5mm cortical screws, mini-fragment plate if needed |
| Syndesmosis | 3.5mm cortical screw (long), suture button device (TightRope) |
| General | Periosteal elevator, bone clamps, drill guide, depth gauge |
Review AP, lateral, and mortise X-rays. CT scan is essential for posterior malleolus assessment - determines size (% articular surface), number of fragments, impaction, and syndesmotic injury. Apply Weber classification for surgical planning. Assess syndesmosis on CT (widening, fibular diastasis). Measure tibiofibular clear space (>6mm = injury). Plan incisions and fixation strategy.
Exam Pearl
Exam Key: CT is ESSENTIAL for posterior malleolus - X-rays underestimate fragment size. Measure on sagittal CT as percentage of tibial plafond. Posterior malleolus is attachment site of PITFL (posterior inferior tibiofibular ligament) - fixation restores syndesmotic stability.
Position supine with bump under ipsilateral hip for 15-20° internal rotation (aids lateral approach). Apply thigh tourniquet at 350mmHg - exsanguinate by elevation (avoid Esmarch compression over fracture site). Free drape to allow full manipulation. Position C-arm for mortise view - leg 15-20° internal rotation OR C-arm externally rotated.
Mortise view is the KEY intraoperative assessment. The leg must be internally rotated 15-20° to see the mortise en face. If positioning is wrong, you cannot assess reduction quality.
Make lateral longitudinal incision (8-10cm) centred over fracture, typically distal third of fibula for Weber B. Incise fascia, identify and protect superficial peroneal nerve if visible anteriorly. Identify peroneal tendons posteriorly and retract. Expose fracture with periosteal elevator - minimal stripping to preserve blood supply. Clear fracture site of haematoma and debris.
Critical: Restore fibular length (measure from tip to plafond - normally 12-15mm). Restore rotation (posterior surface flat, anterior ridge sharp). Provisional reduction with pointed reduction clamp or K-wires.
Exam Pearl
Exam Quote: "The fibula is the key to the ankle." Fibular length and rotation determine mortise congruity. Too short = lateral talar shift, mortise widening. Malrotated = abnormal biomechanics. Use contralateral ankle X-ray as template if available.
Select one-third tubular plate or precontoured locking fibular plate (3.5mm system). Position plate posterolaterally (not directly lateral) - reduces hardware prominence, protects peroneal tendons.
For oblique fractures: Lag screw first perpendicular to fracture line (interfragmentary compression), then neutralisation plate.
For transverse fractures: Compression through plate using eccentric screw placement or separate lag screw if obliquity allows.
Minimum 6 cortices (3 screws) proximal and distal to fracture. Check length and rotation before final tightening. Avoid screws penetrating syndesmosis proximally.
Exam Pearl
Technique Point: Lag screw must be perpendicular to fracture line for optimal compression. Plate then acts as neutralisation device protecting the lag screw. Modern trend toward locking plates in osteoporotic bone for angular stability.
Reassess posterior malleolus on fluoroscopy after fibula fixation. Indications for posterior malleolus fixation:
Approach options:
If posterolateral approach chosen: Incision between lateral malleolus and Achilles tendon (6-8cm). Dissect between peroneal tendons (retract laterally - superficial peroneal nerve) and FHL (retract medially - tibial nerve). Identify posterior malleolus fragment attached to PITFL.
Protect FHL - runs in groove directly under fragment. Reduce fragment anatomically under direct vision. Elevate if impacted (use tamp, may need bone graft). Provisional K-wire fixation.
The posterolateral approach is an internervous plane: peroneals (superficial peroneal nerve) lateral, FHL (tibial nerve) medial. Stay in this interval. The sural nerve is subcutaneous posterolaterally - identify and protect.
Fixation options:
Anterior-to-posterior lag screws (GOLD STANDARD):
Posterior-to-anterior screws (percutaneous):
Buttress plate (if large fragment or comminution):
Exam Pearl
Exam Key: AP lag screws are preferred - better bone purchase, can achieve true lag effect. The starting point is anterior tibial metaphysis (good cancellous bone), directing posteriorly to engage dense posterior cortical fragment.
Make anteromedial curved incision (5-7cm) just anterior to medial malleolar apex - this protects saphenous nerve/vein which are more anterior. Identify and protect great saphenous vein and saphenous nerve (variable anatomy - may be in field). Incise periosteum and expose fracture. Clear debris from fracture site. Reduce anatomically - articular surface and medial plafond must be perfect.
Exam Pearl
Anatomy Point: Saphenous nerve provides sensation to medial foot and ankle. Injury causes painful dysaesthesia. Position incision anterior to malleolar apex (not directly over prominence) to minimise risk.
Fixation determined by fracture pattern:
| Pattern | Fixation | Rationale |
|---|---|---|
| Oblique/Transverse | 2 × 4.0mm partially threaded cancellous screws parallel, perpendicular to fracture | Lag compression across fracture |
| Vertical (SAD) | Buttress plate (one-third tubular or medial malleolar) | Tension forces pull screws out - plate essential |
| Comminuted | Bridge plate with screws in intact bone only | Span comminution, maintain length |
| Small fragment | Tension band wiring (2 K-wires + figure-8 wire) | Alternative if screws won't hold |
Ensure anatomic articular reduction before final fixation. Countersink screw heads to reduce hardware prominence.
Vertical medial malleolar fractures (SAD pattern) MUST have plate fixation. Screws alone will fail - the tension forces from deltoid ligament pull the screws superiorly out of the fragment.
After all fractures fixed, assess syndesmotic stability:
Cotton test: Grasp fibula with bone clamp, apply lateral stress. Should be <2mm translation compared to opposite side.
External rotation stress: Under fluoroscopy, externally rotate foot - assess tibiofibular clear space widening.
Direct palpation: If posterolateral approach used, palpate anterior and posterior tibiofibular ligaments.
Imaging criteria (mortise view):
Exam Pearl
Key Point: Posterior malleolus fixation often stabilises syndesmosis because the fragment is attachment site of PITFL. After posterior malleolus fixation, 50% of previously unstable syndesmoses become stable. Always retest after all fracture fixation.
If Cotton test positive or imaging criteria not met, syndesmosis requires fixation:
Technique for syndesmotic screw:
Alternative: Suture button device (TightRope) - allows physiologic micromotion, lower hardware removal rate.
Fibula must be correctly positioned in incisura before screw insertion. Malreduction is the most common syndesmotic fixation error. Use direct visualisation or CT if uncertain. Fibula too anterior = restricted dorsiflexion. Fibula too posterior = restricted plantarflexion.
Obtain comprehensive fluoroscopic images and critically assess:
Mortise view (15-20° IR):
AP view:
Lateral view:
Exam Pearl
Exam Mantra: "If ANY parameter is wrong - FIX IT NOW." Accepting residual displacement leads to post-traumatic arthritis. Perfect reduction determines outcome. 1mm of lateral talar shift decreases tibiotalar contact area by 42%.
Irrigate all wounds thoroughly. Layered closure: periosteum/fascia with absorbable sutures, subcutaneous layer, skin with interrupted nylon or subcuticular. Consider small drain if significant posterolateral dissection.
Apply bulky padded dressing with plaster backslab in neutral position (90° dorsiflexion, hindfoot neutral). Elevate limb above heart level. Initiate DVT prophylaxis (LMWH 40mg daily or aspirin depending on protocol).
| Timeframe | Activity | Goals |
|---|---|---|
| Day 1-14 | NWB in backslab, elevation, ankle pumps | Wound healing, swelling control |
| 2 weeks | Suture removal, transition to CAM boot | Begin gentle ROM exercises |
| 2-6 weeks | NWB in CAM boot, active ROM exercises | Regain dorsiflexion/plantarflexion |
| 6-8 weeks | Progressive weight-bearing if healed | Confirm radiographic union |
| 8-12 weeks | Full weight-bearing, intensive physiotherapy | Strengthen, proprioception |
| 3-4 months | Return to driving, light activities | Functional recovery |
| 6-12 months | Return to sport/heavy labour | Full recovery |
| Complication | Recognition | Prevention | Management |
|---|---|---|---|
| Post-traumatic arthritis | Progressive ankle pain, stiffness, radiographic joint space narrowing (10-30%) | ANATOMIC reduction of ALL components - medial clear space = superior clear space, <2mm step posterior malleolus, stable fixation for early motion | Conservative: activity modification, AFO, NSAIDs, injections. Surgical: debridement, supramalleolar osteotomy if malaligned, ankle fusion (gold standard), ankle replacement (selected) |
| Syndesmotic malreduction/instability | Chronic lateral ankle pain, instability, widened mortise on stress views (10-20%) | Cotton test after all fixation, proper screw technique (2-4cm above joint, 25-30° angle, fibula correctly positioned in incisura) | Acute: revision reduction and fixation. Chronic: syndesmotic reconstruction with ligament graft, may need associated procedures |
| Malunion (fibular shortening/rotation) | Lateral ankle pain, instability, talar shift on X-ray, valgus hindfoot (5-15%) | Meticulous fibular reduction - restore length (12-15mm to plafond) and rotation. Use contralateral X-ray as template | Corrective osteotomy: fibular lengthening, derotation, supramalleolar osteotomy if tibial involvement. Complex with mixed results |
| Wound complications | Dehiscence, erythema, drainage, exposed hardware (5-10%) | Wait for wrinkle sign before surgery (7-14 days), careful tissue handling, appropriate incision placement, layered closure | Superficial: local wound care, oral antibiotics. Deep: IV antibiotics, surgical debridement, possible hardware removal, flap coverage if needed |
| Hardware irritation/prominence | Painful prominence over screws or plate, especially medial malleolus (20-40%) | Countersink screws, low-profile plates, posterolateral fibular plate position, warn patient preoperatively | Hardware removal after union (12-18 months for fracture fixation, 3-4 months for syndesmotic screws if symptomatic) |
| Nerve injury (SPN, saphenous, sural) | Numbness, dysaesthesia in nerve distribution, Tinel sign at injury site (5-15%) | Know anatomy, careful dissection, identify nerves before retraction, protect saphenous vein/nerve medially | Observation (most are neuropraxia with recovery). Neuroma: desensitisation, nerve blocks. Persistent: neuroma excision. Complete division: repair |
| Nonunion | Persistent pain, motion at fracture, radiographic lucency, no callus at 3-4 months (<5%) | Anatomic reduction, stable fixation, avoid NSAIDs perioperatively, smoking cessation, optimise nutrition/diabetes | Revision ORIF with bone graft, consider bone stimulator, address biology (BMP, autograft). Medial malleolus nonunion may be asymptomatic |
| DVT/PE | Calf pain, swelling, positive Homan's sign. PE: dyspnoea, chest pain, tachycardia (2-10%) | Pharmacological prophylaxis (LMWH or aspirin), early ankle pumps, elevation, hydration, early mobilisation when safe | Venous ultrasound for DVT, anticoagulation (LMWH bridge to warfarin or DOAC). PE: CT-PA, anticoagulation, ICU if massive |
Practice these scenarios to excel in your viva examination
"A 45-year-old man presents with a displaced trimalleolar ankle fracture. The CT shows a posterior malleolus fragment of 35% of the articular surface. Walk me through your surgical planning and fixation sequence."
"You have reduced and plated the fibula in an ankle fracture. On Cotton test, there is 4mm of lateral translation of the fibula compared to the opposite side. How do you manage this syndesmotic instability?"
"A patient returns to clinic 3 weeks post-trimalleolar ORIF with wound dehiscence over the lateral incision and visible plate. There is purulent discharge. How do you manage this?"
High-Yield Exam Summary
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