Back to Operative Surgery
Foot & Ankle

Ankle Fracture ORIF - Trimalleolar

Comprehensive surgical technique guide for trimalleolar ankle fracture ORIF with syndesmotic assessment and structured viva scenarios for FRCS exam preparation

Core Procedure
intermediate
By OrthoVellum Medical Education Team

Reviewed by OrthoVellum Editorial Team

Editorial maintenance, source checking, and correction workflow • Published by OrthoVellum Medical Education Team

Editorial boardMethodologyReview policyReport a correction
High Yield Overview

ANKLE FRACTURE ORIF - TRIMALLEOLAR

Foot & Ankle Trauma | Core Procedure

Mnemonic

F-P-M-SANKLE - Order of Fixation

Mnemonic

MORTISEMORTISE - Reduction Checklist

Critical Danger Structures

Superficial Peroneal Nerve

Location: Emerges from lateral compartment in distal third of leg, 10-12cm above lateral malleolus. Protection: Identify before lateral incision, anterior retraction.

Saphenous Vein & Nerve

Location: Anteromedial leg and ankle, subcutaneous anterior to medial malleolus. Protection: Incision anterior to malleolar apex, identify and retract.

Sural Nerve

Location: Posterior to lateral malleolus, subcutaneous, runs with small saphenous vein. Protection: Avoid posterior lateral dissection, identify in posterolateral approach.

Posterior Tibial NV Bundle

Location: Posteromedial ankle, under flexor retinaculum between FDL and FHL in tarsal tunnel. Protection: Stay lateral in posterolateral approach, never medial to FHL.

Peroneal Tendons

Location: Posterior to lateral malleolus in retrofibular groove. Protection: Identify and retract anteriorly, plate posterolateral not directly lateral.

FHL Tendon

Location: Runs in groove on posterior tibia under posterior malleolus fragment. Protection: Identify and protect medially in posterolateral approach.

Indications for Trimalleolar ORIF

Absolute Indications

  • Displaced trimalleolar fracture with talar shift or mortise incongruity
  • Weber B or C fibula fracture with medial clear space widening >4mm
  • Posterior malleolus >25% articular surface on CT (some argue >2mm displacement any size)
  • Open fracture (emergency debridement, fracture stabilisation)
  • Irreducible fracture-dislocation (interposed soft tissue)

Relative Indications

  • Posterior malleolus 20-25% with step-off >2mm
  • Syndesmotic instability after fibula fixation
  • Young, active patient with any displacement
  • Bilateral fractures (need early mobilisation)

Contraindications to Immediate ORIF

  • Severe soft tissue swelling (wait for wrinkle sign - typically 7-14 days)
  • Fracture blisters over surgical approach (wait for re-epithelialisation)
  • Active infection, significant medical instability
  • Peripheral vascular disease with non-healing potential
  • Non-ambulatory patient with minimal symptoms (relative)

Equipment and Setup

Operating Theatre Setup

Patient Positioning

  • Supine with bump under ipsilateral hip (15-20° internal rotation aids fibula exposure)
  • Alternatively, radiolucent triangle under knee
  • Lateral decubitus if direct posterior approach to posterior malleolus planned
  • Thigh tourniquet at 350mmHg (elevate to exsanguinate, avoid Esmarch over fracture)
  • Free drape entire leg to allow manipulation

Image Intensifier

  • Position perpendicular to table for true mortise view
  • Mortise view requires 15-20° internal rotation of leg OR external rotation of C-arm
  • Ensure can obtain AP, lateral, and mortise views before prepping

Instruments Required

CategoryItems
ReductionPointed reduction clamps, Weber clamp, dental pick, K-wires
FibulaOne-third tubular plate (7-8 hole), precontoured fibular locking plate
Screws3.5mm cortical screws, 2.7mm cortical screws for lag
Medial4.0mm partially threaded cancellous screws, medial malleolar plate
Posterior3.5mm cortical screws, mini-fragment plate if needed
Syndesmosis3.5mm cortical screw (long), suture button device (TightRope)
GeneralPeriosteal elevator, bone clamps, drill guide, depth gauge

Three-Incision Approach

  1. Lateral longitudinal over fibula (8-10cm)
  2. Anteromedial curved anterior to medial malleolus (5-7cm)
  3. Posterolateral between fibula and Achilles (6-8cm) - if needed for posterior malleolus

Operative Technique

Step 1: Preoperative Planning and Imaging Assessment

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.

Step 2: Patient Positioning and Tourniquet

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.

Critical Point

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.

Step 3: Fibula Exposure and Reduction

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.

Step 4: Fibula Plate Application

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.

Step 5: Posterior Malleolus - Assessment and Decision

Reassess posterior malleolus on fluoroscopy after fibula fixation. Indications for posterior malleolus fixation:

  1. >25% articular surface (traditional threshold)
  2. >2mm step-off or displacement (increasingly favoured)
  3. Persistent syndesmotic instability after fibula fixation
  4. Large fragment preventing talus reduction

Approach options:

  • Posterolateral (most common): Between peroneals (lateral) and FHL (medial) - internervous plane
  • Direct posterior: Prone or lateral position - best visualisation
  • Through lateral incision: Percutaneous AP screws

Step 6: Posterolateral Approach to Posterior Malleolus

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.

Key Anatomy

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.

Step 7: Posterior Malleolus Fixation

Fixation options:

  1. Anterior-to-posterior lag screws (GOLD STANDARD):

    • Start 1-2cm above joint line on anterior tibial metaphysis
    • Direct posteriorly toward fragment
    • 3.5mm or 4.0mm cortical screws
    • Two parallel screws provide rotational stability
    • Best bone purchase (metaphyseal to cortical)

  2. Posterior-to-anterior screws (percutaneous):

    • Easier insertion but weaker purchase (cortical only)
    • Useful for smaller fragments

  3. Buttress plate (if large fragment or comminution):

    • Mini-fragment plate from posterolateral approach
    • Provides additional stability

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.

Step 8: Medial Malleolus Exposure

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.

Step 9: Medial Malleolus Fixation

Fixation determined by fracture pattern:

PatternFixationRationale
Oblique/Transverse2 × 4.0mm partially threaded cancellous screws parallel, perpendicular to fractureLag compression across fracture
Vertical (SAD)Buttress plate (one-third tubular or medial malleolar)Tension forces pull screws out - plate essential
ComminutedBridge plate with screws in intact bone onlySpan comminution, maintain length
Small fragmentTension 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.

Critical Point

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.

Step 10: Syndesmosis Assessment

After all fractures fixed, assess syndesmotic stability:

  1. Cotton test: Grasp fibula with bone clamp, apply lateral stress. Should be <2mm translation compared to opposite side.

  2. External rotation stress: Under fluoroscopy, externally rotate foot - assess tibiofibular clear space widening.

  3. Direct palpation: If posterolateral approach used, palpate anterior and posterior tibiofibular ligaments.

  4. Imaging criteria (mortise view):

    • Tibiofibular clear space <6mm (measured 1cm above plafond)
    • Tibiofibular overlap >6mm on AP, >1mm on mortise

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.

Step 11: Syndesmosis Fixation (if unstable)

If Cotton test positive or imaging criteria not met, syndesmosis requires fixation:

Technique for syndesmotic screw:

  1. Position screw 2-4cm above joint line (above syndesmosis, not through it)
  2. Angle 25-30° anterior to posterior (parallel to joint line)
  3. Compress fibula into incisura with clamp before drilling
  4. Ensure fibula is correctly positioned - not too anterior (restricts dorsiflexion) or posterior (restricts plantarflexion)
  5. Foot in neutral dorsiflexion (not forced dorsiflexion - overtightens syndesmosis)
  6. 3.5mm cortical screw, 3 cortices (tricortical) or 4 cortices (quadricortical)
  7. One screw usually sufficient; two if severely unstable

Alternative: Suture button device (TightRope) - allows physiologic micromotion, lower hardware removal rate.

Technical Pitfall

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.

Step 12: Final Reduction Assessment

Obtain comprehensive fluoroscopic images and critically assess:

Mortise view (15-20° IR):

  • Medial clear space = Superior clear space (both ~4mm)
  • Symmetric talar dome within mortise
  • Tibiofibular clear space <6mm
  • Tibiofibular overlap >6mm

AP view:

  • No talar shift
  • Fibular length restored (12-15mm to plafond)
  • No step at posterior malleolus

Lateral view:

  • No anterior/posterior talar subluxation
  • Posterior malleolus reduced (<2mm step)
  • Tibiotalar joint congruent

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%.

Step 13: Closure and Post-operative Care

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).

Post-operative Protocol

Rehabilitation Timeline

TimeframeActivityGoals
Day 1-14NWB in backslab, elevation, ankle pumpsWound healing, swelling control
2 weeksSuture removal, transition to CAM bootBegin gentle ROM exercises
2-6 weeksNWB in CAM boot, active ROM exercisesRegain dorsiflexion/plantarflexion
6-8 weeksProgressive weight-bearing if healedConfirm radiographic union
8-12 weeksFull weight-bearing, intensive physiotherapyStrengthen, proprioception
3-4 monthsReturn to driving, light activitiesFunctional recovery
6-12 monthsReturn to sport/heavy labourFull recovery

Syndesmotic Screw Management

  • Quadricortical screw: Consider removal at 3-4 months if symptomatic or before high-demand activity
  • Tricortical screw: Often left in situ - may break with weight-bearing (acceptable)
  • Suture button: No removal needed
  • Modern evidence: Routine removal not mandatory if asymptomatic

Follow-up Schedule

  • 2 weeks: Wound check, suture removal, X-ray
  • 6 weeks: Clinical and radiographic assessment, advance weight-bearing
  • 3 months: Assess union, consider syndesmotic screw removal if indicated
  • 6 months: Functional assessment
  • 1 year: Long-term assessment, screen for arthritis

Complications

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

EXAMINER

"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."

EXCEPTIONAL ANSWER
This is a trimalleolar ankle fracture with a significant posterior malleolus requiring operative fixation. My approach would be systematic: **Pre-operative planning**: I would classify this as likely Weber B or C based on fibula fracture level. The 35% posterior malleolus clearly exceeds the 25% threshold for fixation and is the attachment site of the PITFL, so fixation will also help stabilise the syndesmosis. I would assess the CT for posterior fragment impaction, number of fragments, and syndesmotic injury (tibiofibular widening). **Positioning**: Supine with bump under ipsilateral hip for 15-20 degrees internal rotation, thigh tourniquet, and image intensifier positioned for mortise view. **Fixation sequence - FPMS**: 1. **Fibula first**: Lateral longitudinal incision, restore length (12-15mm from tip to plafond) and rotation. One-third tubular plate posterolaterally with lag screw if oblique fracture pattern. 2. **Posterior malleolus second**: Via posterolateral approach between peroneals and FHL if open reduction needed, or anterior-to-posterior lag screws if can reduce percutaneously. Two 3.5mm cortical screws AP direction provides excellent purchase. 3. **Medial malleolus third**: Anteromedial incision anterior to apex to protect saphenous nerve. Two 4.0mm partially threaded cancellous screws perpendicular to fracture for oblique pattern, or buttress plate if vertical. 4. **Syndesmosis assessment**: Cotton test after all fractures fixed - lateral translation should be less than 2mm. Check mortise view criteria. Posterior malleolus fixation often stabilises syndesmosis via PITFL, but I would add a syndesmotic screw if instability persists. **Final check**: Mortise view confirming medial clear space equals superior clear space, tibiofibular clear space less than 6mm, and anatomic reduction of all components.
VIVA SCENARIOStandard

EXAMINER

"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?"

EXCEPTIONAL ANSWER
A positive Cotton test with 4mm of translation indicates significant syndesmotic instability that requires fixation. My approach: **Confirmation**: I would confirm the instability with external rotation stress fluoroscopy showing widening of the tibiofibular clear space beyond 6mm. I would also check the mortise view for loss of tibiofibular overlap (should be greater than 6mm on AP, greater than 1mm on mortise). **Reduction technique**: 1. Use a large pointed reduction clamp or Weber clamp to compress the fibula into the incisura 2. Ensure the fibula is correctly positioned - not too anterior (restricts dorsiflexion) or posterior (restricts plantarflexion) 3. Hold the foot in **neutral dorsiflexion** - not forced dorsiflexion which would over-tighten the syndesmosis 4. Confirm reduction fluoroscopically before drilling **Fixation technique**: 1. Position the screw **2-4cm above the joint line** (above the syndesmosis, not through it) 2. Angle **25-30 degrees from lateral to medial**, parallel to the joint line 3. Use a **3.5mm fully-threaded cortical screw** 4. **Three cortices** (tricortical) is my preference - allows some micromotion and lower removal rate than quadricortical 5. One screw is usually sufficient; I would add a second if severe instability or comminuted fracture pattern **Alternative**: I would consider a suture button device (TightRope) in a young, active patient - allows physiologic syndesmotic motion and doesn't require removal. **Confirmation**: Repeat mortise view confirming tibiofibular clear space less than 6mm and restoration of overlap. Cotton test should now show less than 2mm translation. **Post-operative**: I would counsel the patient that if symptomatic, syndesmotic screw can be removed at 3-4 months, though modern evidence suggests routine removal is not mandatory if asymptomatic.
VIVA SCENARIOStandard

EXAMINER

"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?"

EXCEPTIONAL ANSWER
This is a deep surgical site infection with exposed hardware - a serious complication requiring urgent management. **Immediate assessment**: - Clinical: fever, systemic signs, extent of wound breakdown, condition of surrounding tissue - Bloods: FBC, CRP, ESR - baseline inflammatory markers - Wound swab: for MC&S including extended cultures - X-ray: assess fracture position, look for signs of osteomyelitis (though early changes may not be visible) **Initial management**: - Admit for IV antibiotics - empirical broad spectrum (flucloxacillin plus gentamicin, or vancomycin if MRSA risk) pending culture results - Keep wound clean with daily dressings - Elevate limb, optimise nutrition, glycaemic control if diabetic **Surgical decision**: The key question is whether fractures have healed. At 3 weeks, union is unlikely. **If fractures not united** (most likely at 3 weeks): 1. Urgent surgical debridement - thorough washout, removal of all necrotic tissue 2. Retain stable hardware - metalwork is essential for fracture stability 3. Deep tissue samples for culture 4. Consider antibiotic-loaded PMMA beads in wound 5. Negative pressure wound therapy (VAC) for wound management 6. Plan for serial debridements (every 48-72 hours) until wound clean 7. Definitive closure: delayed primary, split skin graft, or local/free flap if large defect 8. Prolonged IV antibiotics (6 weeks minimum) guided by cultures **If fractures have united** (less likely but possible): - More aggressive debridement including hardware removal is an option - Stabilise with external fixator or cast if concern about stability post-removal **Long-term considerations**: - This patient has a high risk of chronic osteomyelitis - May require long-term suppressive antibiotics - Outcome for the ankle is compromised - higher risk of arthritis, stiffness, chronic infection - Multidisciplinary approach: orthopaedics, infectious disease, plastic surgery if flap needed **Prevention reflection**: This complication emphasises importance of waiting for soft tissue swelling to resolve (wrinkle sign), meticulous soft tissue handling, and appropriate antibiotic prophylaxis.

Trimalleolar Ankle Fracture ORIF - Exam Summary

High-Yield Exam Summary

References

  1. Court-Brown CM, McBirnie J, Wilson G. Adult ankle fractures--an increasing problem? Acta Orthop Scand. 1998;69(1):43-47.

  2. Tornetta P, Axelrad TW, Sibai TA, Creevy WR. Treatment of the stress positive ligamentous SE4 ankle fracture: incidence of syndesmotic injury and clinical decision making. J Orthop Trauma. 2012;26(11):659-661.

  3. Gardner MJ, Demetrakopoulos D, Briggs SM, Helfet DL, Lorich DG. The ability of the Lauge-Hansen classification to predict ligament injury and mechanism in ankle fractures: an MRI study. J Orthop Trauma. 2006;20(4):267-272.

  4. Miller AN, Carroll EA, Parker RJ, Borber SP, Mauricio L, Helfet DL. Direct visualization for syndesmotic stabilization of ankle fractures. Foot Ankle Int. 2009;30(5):419-426.

  5. Sagi HC, Shah AR, Sanders RW. The functional consequence of syndesmotic joint malreduction at a minimum 2-year follow-up. J Orthop Trauma. 2012;26(7):439-443.

  6. Ramsey PL, Hamilton W. Changes in tibiotalar area of contact caused by lateral talar shift. J Bone Joint Surg Am. 1976;58(3):356-357.

  7. Gardner MJ, Brodsky A, Briggs SM, Nielson JH, Lorich DG. Fixation of posterior malleolar fractures provides greater syndesmotic stability. Clin Orthop Relat Res. 2006;447:165-171.

  8. Clanton TO, Paul P. Syndesmosis injuries in athletes. Foot Ankle Clin. 2002;7(3):529-549.

  9. Norkus SA, Floyd RT. The anatomy and mechanisms of syndesmotic ankle sprains. J Athl Train. 2001;36(1):68-73.

  10. Andersen MR, Frihagen F, Hellund JC, Madsen JE, Figved W. Randomized trial comparing suture button with single syndesmotic screw for syndesmosis injury. J Bone Joint Surg Am. 2018;100(1):2-12.