Introduction / Definition

Ankle fractures represent disruption of the bony and ligamentous ring of the ankle mortise formed by the distal tibia (medial malleolus, posterior plafond), distal fibula (lateral malleolus), and the talar dome. As a high-congruence ring structure, instability in one region typically necessitates an injury in another, whether osseous or ligamentous.

Epidemiology

• Incidence: Approximately 120–180 per 100,000 person-years, accounting for 9% of all adult fractures and over 35% of lower extremity injuries.
• Demographics: Bimodal distribution. Higher incidence in young active males sustained via sports or higher-energy trauma, and older females sustained via low-energy fragility falls.
• Risk Factors: Osteopenia/osteoporosis, obesity, diabetes mellitus, peripheral neuropathy, and tobacco use.

Relevant Anatomy

• Articular Congruence: Ramsey and Hamilton (1976) demonstrated that 1 mm of lateral talar shift reduces the tibiotalar contact area by up to 42%, precipitating focal peak joint stresses and post-traumatic arthrosis.
• Medial Complex: Medial malleolus (anterior and posterior colliculi) and the deltoid ligament (superficial component resisting talar eversion; deep posterior tibiotalar component resisting talar external rotation and lateral translation).
• Lateral Complex: Distal fibula acting as the lateral strut maintaining length, rotation, and mortise alignment.
• Syndesmotic Complex: Consists of four ligaments stabilizing the distal tibiofibular joint: anterior inferior tibiofibular ligament (AITFL), posterior inferior tibiofibular ligament (PITFL), transverse tibiofibular ligament, and the interosseous ligament (IOL) terminating at the interosseous membrane (IOM).

Classification

Danis-Weber (AO/OTA 44) Classification

Based on the level of the fibular fracture relative to the syndesmosis:

• Weber A (AO 44A): Infrasyndesmotic fracture. Syndesmosis intact; deltoid ligament usually intact, but vertical medial malleolar fracture may co-exist.
• Weber B (AO 44B): Transsyndesmotic fracture commencing at the level of the plafond and running obliquely proximal-posterior. Syndesmosis torn or compromised in up to 50%.
• Weber C (AO 44C): Suprasyndesmotic fracture. Syndesmosis torn from the joint level up to the fracture level. Includes Maisonneuve fractures (proximal third fibula) and high fibular diaphyseal disruptions.

Lauge-Hansen Classification

Mechanistic classification combining foot position (first word) and deforming force direction (second word):

• Supination-External Rotation (SER) (40–75%):
  • Stage I: AITFL rupture or avulsion (Chaput/Wagstaffe).
  • Stage II: Spiral/oblique lateral malleolus fracture (anteroinferior to posterosuperior).
  • Stage III: PITFL rupture or posterior malleolus fracture (Volkmann fragment).
  • Stage IV: Medial malleolus transverse fracture or deep deltoid ligament rupture.
• Supination-Adduction (SAD):
  • Stage I: Distal fibular avulsion below joint or talofibular ligament rupture.
  • Stage II: Vertical shear fracture of the medial malleolus with marginal impaction of the medial tibial plafond.
• Pronation-External Rotation (PER):
  • Stage I: Medial malleolar transverse fracture or deltoid ligament rupture.
  • Stage II: AITFL rupture.
  • Stage III: High spiral fibular fracture (suprasyndesmotic, posterosuperior to anteroinferior).
  • Stage IV: PITFL rupture or posterior malleolar avulsion.
• Pronation-Abduction (PAB):
  • Stage I: Deltoid rupture or transverse medial malleolus fracture.
  • Stage II: AITFL rupture or avulsion.
  • Stage III: Bending/comminuted fracture of the fibula at or above syndesmosis with lateral butterfly/wedge.

Clinical Presentation & Examination

• Presentation: Inability to bear weight, gross deformity, acute swelling, and ecchymosis.
• Soft-Tissue Assessment: Palpation for tense swelling, fracture blisters (clear fluid vs haemorrhagic), open wounds, or tenting of the skin over bone fragments. Closed reduction must be performed immediately for deformed ankles to relieve neurovascular and soft-tissue compromise.
• Examination:
  • Full-length palpation of the fibula and proximal calf to exclude a Maisonneuve fracture.
  • Assessment of distal neurovascular status (dorsalis pedis, posterior tibial pulses; tibial, superficial/deep peroneal, and sural nerves).
  • Palpation of the base of the 5th metatarsal and midfoot to exclude associated injuries.

Investigations

• Plain Radiographs: Anteroposterior (AP), Lateral, and Mortise (15–20° internal rotation) views of the ankle, supplemented by full-length tibia/fibula films if proximal tenderness or isolated medial widening is present.
• Radiographic Parameters (Mortise View):
  • Medial Clear Space (MCS): Normal ≤ 4 mm; must be equal to or less than the superior clear space. > 4 mm (or > 5 mm on stress) indicates deltoid disruption.
  • Tibiofibular Clear Space (TFCS): Normal < 6 mm (measured 1 cm proximal to plafond on AP/Mortise).
  • Tibiofibular Overlap: Normal > 6 mm on AP, > 1 mm on Mortise view.
  • Talar Tilt: Difference of > 2 mm between medial and lateral articular joint space.
• Stress Radiography: External rotation gravity stress views or manual stress under fluoroscopy for isolated Weber B fibular fractures to assess deltoid competence.
• Computed Tomography (CT): Crucial for trimalleolar fractures, posterior malleolar fragments, articular comminution/impaction, and planning posterior approach fixation.

Management

Non-Operative Management

• Indications: Isolated Weber A or stable SER II/Weber B fractures with an intact deltoid ligament (MCS < 4 mm on gravity/manual stress views), or non-ambulatory patients with prohibitive medical comorbidities.
• Technique: Below-knee cast or rigid walking boot for 6 weeks, with weight-bearing permitted as tolerated in demonstrated stable fractures. Serial radiographs at 1, 2, and 6 weeks to confirm maintenance of mortise reduction.

Operative Management

• Indications: Unstable fractures (bimalleolar, trimalleolar, bimalleolar-equivalent with deltoid rupture, failed closed reduction, open fractures, or syndesmotic widening).
• Timing: Urgent closed reduction in the emergency department. Definitive open reduction and internal fixation (ORIF) should be performed within 24–48 hours if swelling allows, or delayed 7–14 days in a temporary bridging external fixator until the "wrinkle sign" appears.

Surgical Approaches and Techniques

• Lateral Malleolus:
  • Approach: Direct lateral or posterolateral approach.
  • Fixation: Interfragmentary 2.7 mm or 3.5 mm lag screw with a lateral neutralisation plate (1/3 tubular or anatomical locking plate), or posterolateral antiglide plating (ideal for supination-external rotation fractures, reducing soft tissue profile and screw prominence).
• Medial Malleolus:
  • Approach: Anteromedial longitudinal approach, taking care to protect the long saphenous vein and nerve.
  • Fixation: Two parallel 3.5 mm or 4.0 mm partially threaded cannulated lag screws (transverse fractures), or an antiglide/buttress plate (vertical shear SAD Stage II fractures).
• Posterior Malleolus:
  • Indications: Articular involvement > 15–25%, articular step-off > 1–2 mm, or syndesmotic instability via PITFL attachment.
  • Approach: Posterolateral approach (between peroneal tendons and flexor hallucis longus). Provides direct visualisation and buttress plating of the fragment.
• Syndesmosis:
  • Assessment: Intraoperative Cotton hook test or external rotation stress test under fluoroscopy after malleolar fixation.
  • Fixation: Diastasis requires stabilisation using 1 or 2 quadricortical or tricortical 3.5 mm/4.5 mm syndesmotic screws, or dynamic flexible suture-button constructs (e.g. TightRope) positioned 2–3 cm above the joint line angled 30° anteromedially.

Complications

• Early: Wound dehiscence, superficial or deep surgical site infection, peroneal or saphenous nerve neurapraxia, compartment syndrome, loss of reduction.
• Late: Malunion (fibular shortening or external rotation, leading to valgus talar tilt), non-union (higher in diabetic populations), post-traumatic osteoarthritis, chronic syndesmotic instability, complex regional pain syndrome (CRPS).

Exam Pearls

• In a non-displaced Weber B fibular fracture, medial tenderness or ecchymosis alone is not an absolute indication for surgery; deltoid competence must be evaluated with a gravity or manual stress radiograph.
• 1 mm of lateral talar shift results in a 42% reduction in tibiotalar contact area (Ramsey & Hamilton 1976).
• A normal medial clear space is ≤ 4 mm and must not exceed the superior tibiotalar clear space.
• Antiglide plating on the posterior fibula has biomechanical superiority and lower hardware prominence compared to lateral neutralisation plating for SER II injuries.
• Diabetics with neuroarthropathy (Charcot) require rigid "super-constructs"—often with double the screws, spanning fixators, or hindfoot nails, and twice the duration of non-weight-bearing.