Ankle Fractures and Ligament Injuries

Introduction

The ankle fracture is one of the most common adult fractures, accounting for approximately 9 percent of all fractures and having an annual incidence of approximately 100 to 200 per 100,000 person-years. The injury spans the spectrum from the simple isolated lateral malleolar fracture managed in a walking boot through the trimalleolar fracture-dislocation requiring complex operative reconstruction. The principal management decisions revolve around ankle mortise stability, which depends on the integrity of the bony anatomy (medial malleolus, lateral malleolus, posterior malleolus, syndesmosis, talus) and the ligamentous restraints. The two principal classification systems — the Weber classification by level of fibular fracture and the Lauge-Hansen classification by mechanism — together provide the conceptual framework that guides treatment. The ankle ligament injuries — lateral ankle sprain, syndesmotic injury, deltoid injury — collectively account for many more emergency department visits than ankle fractures, and their management has evolved substantially with the recognition of the persistent symptoms that follow inadequate treatment of “simple” sprains. This chapter draws on Rockwood and Green’s Fractures in Adults, AO Principles of Fracture Management, Apley & Solomon’s, and Miller’s Review of Orthopaedics.

Ankle Anatomy

The ankle (talocrural) joint is a true hinge joint between the tibial plafond (the inferior weight-bearing articular surface of the tibia), the medial malleolus (the medial wall), the lateral malleolus / distal fibula (the lateral wall), and the talar dome (the convex articular surface of the talus). The joint is constrained tightly in the sagittal plane, with dorsiflexion and plantarflexion as the principal motions; coronal and rotational motions occur primarily at the subtalar joint below. The ankle mortise — the U-shaped recess formed by the tibia and fibula — must maintain congruity with the talus for normal ankle function. The classical experimental work of Ramsey and Hamilton (1976) demonstrated that as little as 1 mm of lateral talar shift increases tibiotalar contact pressure by 42 percent and produces accelerated post- traumatic arthritis. The implication is that anatomical reduction of the ankle mortise is essential to good outcomes, and the orthopedic surgeon’s primary task in operative ankle fracture management is the restoration of fibular length, rotation, and lateral position to maintain the mortise. The distal tibiofibular syndesmosis is stabilized by: The anterior inferior tibiofibular ligament (AITFL), the most commonly injured component in syndesmotic injury. The posterior inferior tibiofibular ligament (PITFL), the strongest component. The interosseous ligament and the interosseous membrane.

The transverse tibiofibular ligament. The medial collateral ligament (deltoid ligament) complex includes a superficial component (broad fan-shaped ligament originating from the medial malleolus and inserting onto the navicular, sustentaculum tali, and talar tubercle) and a deep component (the deep deltoid, the principal restraint to lateral talar shift). The integrity of the deep deltoid is critical to mortise stability. The lateral ankle ligaments include the anterior talofibular ligament (ATFL) — the most commonly injured ankle ligament in lateral sprain — the calcaneofibular ligament (CFL), and the posterior talofibular ligament (PTFL). The ATFL is the primary restraint to anterior translation of the talus in plantar flexion and to inversion.

Ankle Fracture Classification

Weber (AO) Classification The Weber classification (1972) is based on the level of the fibular fracture relative to the tibial plafond / syndesmosis: Weber A: Fibular fracture below the syndesmosis (infrasyndesmotic). Typically a transverse avulsion fracture of the distal fibula at or below the joint line, produced by inversion (supination) mechanism. The syndesmosis is typically intact (the AITFL inserts above the fracture line). Generally stable. Weber B: Fibular fracture at the level of the syndesmosis (transsyndesmotic). Typically a spiral or oblique fracture starting at the level of the joint and extending proximally, produced by external rotation mechanism. The syndesmosis may or may not be disrupted (AITFL torn in approximately 40 to 70 percent of Weber B fractures; PITFL less commonly). Stability depends on the integrity of the medial structures and the syndesmosis. Weber C: Fibular fracture above the syndesmosis (suprasyndesmotic). The syndesmosis is disrupted by definition (the fracture is proximal to the syndesmosis, so the syndesmotic ligaments must be torn for the fracture pattern to occur). Typically requires syndesmotic stabilization in addition to fibular fixation. The proximal extent of the fibular fracture can be very high — including the Maisonneuve fracture with proximal fibular involvement. Lauge-Hansen Classification The Lauge-Hansen classification (1950) organizes ankle fractures by mechanism of injury, with each pattern named by the position of the foot at the time of injury (supination or pronation) and the deforming force (adduction, abduction, external rotation). The four principal patterns are: Supination-adduction (SA): Two stages. Stage 1: avulsion fracture of the lateral malleolus or rupture of the lateral ligaments (Weber A pattern). Stage 2: vertical fracture of the medial malleolus from talar adduction force.

Supination-external rotation (SER): The most common pattern (approximately 60 to 75 percent of ankle fractures). Four stages. Stage 1: AITFL rupture or anterior tibiofibular avulsion. Stage 2: spiral fibular fracture (Weber B pattern). Stage 3: PITFL rupture or posterior malleolus fracture. Stage 4: medial malleolus transverse fracture or deltoid ligament rupture. Pronation-abduction (PA): Three stages. Stage 1: medial malleolus transverse fracture or deltoid rupture. Stage 2: AITFL rupture (and often PITFL). Stage 3: short oblique fibular fracture at the level of the syndesmosis (Weber B pattern). Pronation-external rotation (PER): Four stages. Stage 1: medial malleolus or deltoid disruption. Stage 2: AITFL rupture. Stage 3: high fibular fracture (Weber C pattern) — including the Maisonneuve variant with very proximal fibular involvement. Stage 4: PITFL rupture or posterior malleolus fracture. The clinical utility of the Lauge-Hansen system is the prediction of expected injury patterns based on the position-mechanism combination — a Weber C fibular fracture, for instance, implies that the medial side and syndesmosis are disrupted by the pronation-external rotation mechanism, even if these injuries are not radiographically obvious. Comparison and Use In clinical practice, the Weber classification is more commonly used because of its simplicity and direct correlation with treatment (Weber A typically non-operative, Weber B variable, Weber C operative with syndesmotic attention). The Lauge-Hansen classification provides conceptual understanding of the injury complex and predicts the associated injuries that should be specifically sought.

Clinical Assessment

The clinical presentation includes ankle pain, swelling, deformity (in displaced fractures), and inability to bear weight. The examination assesses: Bony tenderness at the lateral malleolus, medial malleolus, syndesmosis, posterior malleolus, and proximal fibula (to identify Maisonneuve variants). Ligamentous tenderness at the deltoid, ATFL, and CFL. Neurovascular status of the foot. Skin integrity with attention to open fractures and impending skin compromise from displaced fractures. The Ottawa Ankle Rules (Stiell et al., 1992) identify patients with ankle injury who require radiographs versus those who can be safely cleared clinically. Indications for ankle radiographs include any pain in the malleolar zone PLUS one of: bony tenderness at the posterior edge or tip of the lateral malleolus, bony tenderness at the posterior edge or tip of the medial malleolus, or inability to bear weight (4 steps) both immediately and in the

emergency department. The rules have sensitivity approaching 100 percent for clinically significant ankle fractures, with specificity of 30 to 50 percent. Imaging consists of AP, lateral, and mortise views (15-degree internal rotation oblique) of the ankle. The mortise view best demonstrates the relationship between the talus and the malleoli (the “talocrural angle” — approximately 8 to 15 degrees on the mortise view, lost in shortened or rotated fibula) and the medial clear space (the distance between the medial talar dome and the medial malleolus, normally less than 4 mm; widening indicates lateral talar shift). Full-length tibia-fibula radiographs are added when proximal fibular tenderness suggests a Maisonneuve fracture. CT is reserved for complex patterns, particularly those with posterior malleolar involvement, and for operative planning.

Treatment Principles — Stable Versus Unstable

The central question in ankle fracture management is stability of the mortise. The mortise is stable when: • The fibula is non-displaced or only minimally displaced, AND • The medial side is intact (intact medial malleolus or competent deltoid), AND • The syndesmosis is intact. Stable injuries are treated non-operatively; unstable injuries require operative reduction and fixation. The stress radiograph (gravity stress view or manual external rotation stress view) is used to assess deltoid integrity in patients with isolated Weber B fibular fractures and no obvious medial malleolar fracture; widening of the medial clear space on stress view indicates deltoid disruption and an unstable injury. Stable Ankle Fractures Weber A fractures: Generally stable, treated in a walking boot or short-leg cast with weight bearing as tolerated for 4 to 6 weeks. Outcomes are excellent. Weber B fractures without medial injury (true isolated lateral malleolus fracture with stress-negative mortise): Stable, treated similarly to Weber A. Isolated medial malleolus fracture that is non-displaced: Treated in a cast for 6 to 8 weeks, with operative management reserved for displacement or for nonunion. Unstable Ankle Fractures Unstable patterns include: Bimalleolar fractures (lateral plus medial malleolar fracture, or lateral malleolar fracture plus deltoid disruption). Trimalleolar fractures (lateral, medial, and posterior malleolar fractures). Fracture-dislocations with frank dislocation of the mortise. Weber C fractures with syndesmotic disruption.

Weber B fractures with stress-positive medial clear space (functional bimalleolar equivalent). These patterns require operative management with anatomical reduction and rigid fixation.

Operative Management

Fibular Fracture Fixation The lateral malleolus / fibula is the key to ankle fracture reduction because of its role in maintaining mortise stability through length, rotation, and lateral position. The standard fixation technique is: Lateral approach to the fibula, with attention to the superficial peroneal nerve which becomes subcutaneous at the junction of the middle and distal thirds of the leg. Reduction of the fibula to anatomical length, rotation, and position. The anatomical reduction is assessed by alignment of the lateral cortex of the fibula with the cortical surface above and below, by restoration of the talocrural angle, and by the medial clear space on intraoperative imaging. Lag screw fixation across the spiral fracture line (interfragmentary compression) to provide axial compression and rotational stability. Neutralization plate applied along the lateral cortex of the fibula, providing protection of the lag screw construct from the rotational and bending forces of weight bearing. Alternative techniques include intramedullary fixation of the fibula (with various rod or nail devices — particularly useful in osteoporotic bone and in patients with compromised soft tissues), tension-band wiring for selected transverse fractures (uncommon application), and distal fibular locking plates for comminuted fractures in osteoporotic bone. Medial Malleolar Fracture Fixation The medial malleolus is typically fixed with two partially threaded cancellous screws or a single screw with anti-rotation K-wire, providing perpendicular compression across the typically transverse fracture line. Tension-band wiring is an alternative for small fragments or osteoporotic bone. The medial malleolar fracture pattern is typically transverse in supination-adduction (from talar avulsion) and shear (more vertical) in supination-external rotation (from talar compression against the medial malleolus). Posterior Malleolar Fracture Fixation The posterior malleolus is the posterior lip of the tibial plafond, fractured in supination- external rotation stage 3 and in pronation-external rotation stage 4 patterns. The classical teaching has been that posterior malleolar fragments involving more than 25 percent of the articular surface on the lateral radiograph required fixation, with smaller fragments accepting non-operative management.

The contemporary understanding has shifted with CT imaging and the Bartoníček- Rammelt classification (2015) of posterior malleolar fractures, which uses CT to define the fragment morphology and recommends operative fixation based on the fragment pattern rather than the simple 25 percent rule. Fragments are classified by type: type 1 extra-articular avulsion, type 2 posterolateral triangle, type 3 posteromedial extension, type 4 large posterior involvement. Operative fixation is recommended for displaced types 2, 3, and 4. Fixation of the posterior malleolus can be achieved by: Anteroposterior screws placed indirectly with the patient supine, after the lateral and medial sides are addressed. Posterior approach with direct posterior plating, providing better articular reduction and more reliable fixation, particularly for the posteromedial and large posterior fragments. The posterior approach has gained increasing popularity for substantial posterior malleolar fragments, with improved articular reduction and reduced posterior subluxation outcomes. Syndesmotic Stabilization The syndesmosis must be stabilized in any ankle fracture pattern where the syndesmotic ligaments are disrupted. The classical indications include Weber C fractures (syndesmosis disrupted by definition), Maisonneuve variants, and Weber B fractures where intraoperative testing (hook test, external rotation stress test) demonstrates syndesmotic instability. The classical syndesmotic fixation is by tricortical or quadricortical syndesmotic screw (3.5 mm or 4.5 mm) passing from the fibula into the tibia, with the ankle held in dorsiflexion during placement (to avoid over-tightening that produces ankle stiffness). The screw is typically removed at 8 to 12 weeks before weight bearing is fully advanced, though this practice is debated. The suture-button device (TightRope, Zip Tight) has gained substantial popularity as an alternative to screw fixation. The device allows physiological micromotion of the syndesmosis while maintaining reduction, eliminates the need for hardware removal, and has been shown in multiple trials to produce comparable or superior outcomes to screw fixation. The reduction quality of the syndesmosis is the critical determinant of outcome, regardless of fixation method; CT assessment of reduction quality has been advocated as routine because of the recognized difficulty of achieving anatomical syndesmotic reduction.

Special Fracture Patterns

Maisonneuve Fracture The Maisonneuve fracture (Maisonneuve, 1840) is a proximal fibular fracture (often near the fibular neck) with associated syndesmotic disruption and medial-sided ankle injury (either medial malleolar fracture or deltoid disruption). The pattern represents the

pronation-external rotation stage 3-4 injury with continuation of the force up the fibula to fracture at its weakest point. The proximal fibular fracture is often missed if not specifically sought — palpation of the entire fibular length and dedicated proximal fibular radiographs are essential in any pronation-external rotation pattern. Treatment involves fixation of the medial side (medial malleolus or deltoid management), syndesmotic stabilization (the principal mechanical concern), and typically non-fixation of the proximal fibular fracture (which heals well with syndesmotic stabilization restoring the mortise). Bosworth Fracture-Dislocation The Bosworth fracture is a Weber B-pattern with the proximal fibular fragment trapped posteriorly behind the tibia, preventing reduction. The injury requires open reduction to disengage the trapped fibula and is one of the few absolute indications for emergent operative intervention in ankle fractures (because the ongoing displacement compromises the skin and the syndesmotic ligaments). Open Ankle Fractures Open ankle fractures (often Weber B or C with medial wound from displaced fragment) require the principles of open fracture management (Topic Trauma-5): urgent antibiotic administration, surgical debridement, anatomical reduction, and rigid fixation. The proximity of the joint to the skin in this region means that even small wounds may communicate with the joint and require careful management.

Pediatric Ankle Fractures Pediatric ankle fractures involve the distal tibial and fibular physes and are classified by Salter-Harris patterns. The Tillaux fracture (Salter-Harris III of the lateral aspect of the distal tibia) and the Triplane fracture (Salter-Harris IV with multiple planes of fracture line) occur in adolescents during the asymmetric closure of the distal tibial physis (medial closure first, then central, then lateral). Both require careful evaluation by CT and may require operative reduction for displaced patterns to restore articular congruity and prevent growth disturbance.

Lateral Ankle Sprain

The lateral ankle sprain is one of the most common musculoskeletal injuries — incidence in the general population is approximately 7 per 1,000 person-years, with much higher rates in athletes. The mechanism is inversion of the plantarflexed foot, producing injury to the lateral ligament complex in a predictable sequence: ATFL first, then CFL, then PTFL. The grading: Grade I: Stretching of the ligament without macroscopic tear. Mild swelling and tenderness; full weight bearing possible.

Grade II: Partial tear of the ligament. Moderate swelling, ecchymosis, and tenderness; weight bearing painful but possible. Grade III: Complete tear of the ligament. Severe swelling, ecchymosis, and tenderness; weight bearing typically not possible. The Ottawa Ankle Rules (described above) are used to clear patients without need for radiographs. Stress radiographs (anterior drawer, talar tilt) may show increased excursion but are not commonly used acutely. Treatment of Lateral Ankle Sprain The treatment is almost universally non-operative, with the POLICE (Protection, Optimal Loading, Ice, Compression, Elevation) protocol replacing the older PRICE protocol because of the recognized benefits of early loading. Functional treatment with a brace (Aircast, ASO) or supportive boot, early range of motion, and progressive return to activity produces good outcomes in the great majority of patients. Operative repair of the lateral ligaments is reserved for the rare patient with chronic functional instability after appropriate conservative treatment (typically 6 to 12 weeks of formal rehabilitation). Chronic Lateral Ankle Instability Chronic lateral ankle instability with recurrent giving-way affects approximately 10 to 20 percent of patients after Grade III sprain. Surgical reconstruction options include the modified Broström-Gould procedure (anatomical repair of the ATFL and CFL with mobilization of the extensor retinaculum, the standard for primary surgical management) and anatomical reconstruction with allograft or autograft for revision or for severely deficient ligaments. Outcomes of the modified Broström-Gould are generally good (80 to 90 percent satisfactory).

Syndesmotic Injuries Without Fracture

The high ankle sprain or isolated syndesmotic injury is the syndesmotic disruption without fibular fracture, typically produced by external rotation of the dorsiflexed foot. The injury is more disabling than the lateral ankle sprain and has a more prolonged recovery course. The grading parallels the lateral ankle sprain: Grade I: Stretching of the AITFL without macroscopic tear. No widening on stress imaging. Grade II: Partial tear of the AITFL with stable mortise. Grade III: Complete syndesmotic disruption with widening of the mortise on stress imaging. Grade I and II are treated non-operatively with progressive return to activity, typically requiring 6 to 12 weeks; Grade III requires syndesmotic stabilization (screw or suture- button) similar to fracture-associated syndesmotic injuries.

Summary and Take-Home Points

The ankle fracture is among the most common adult fractures, with the Weber classification (A infrasyndesmotic, B transsyndesmotic, C suprasyndesmotic) providing the most useful clinical framework and the Lauge-Hansen classification (supination- adduction, supination-external rotation, pronation-abduction, pronation-external rotation) providing the conceptual understanding of injury mechanism and associated structures. The central management decision is mortise stability, with stable patterns (Weber A, isolated Weber B with intact medial structures) treated non-operatively and unstable patterns (bimalleolar, trimalleolar, Weber C, Weber B with deltoid disruption) requiring operative reduction and rigid fixation. The anatomical reduction of the fibula (length, rotation, lateral position) is the key to restoring mortise stability, with lag screw plus neutralization plate being the standard technique. The medial malleolus is typically fixed with two cancellous screws. The posterior malleolus, formerly addressed only for fragments greater than 25 percent of the articular surface, is increasingly addressed by the morphological Bartoníček-Rammelt classification with a lower threshold for fixation. The syndesmosis, disrupted in all Weber C patterns and in many Weber B patterns, is stabilized with syndesmotic screw or suture- button device, with the quality of syndesmotic reduction being the critical outcome determinant. The Maisonneuve fracture must be specifically sought in pronation-external rotation patterns, with palpation of the entire fibula and dedicated proximal fibular imaging. The Bosworth fracture-dislocation with trapped proximal fibular fragment is a true emergency requiring open reduction. The lateral ankle sprain, common and generally benign, is treated by functional protocol; chronic lateral ankle instability after Grade III sprain is treated by the modified Broström- Gould procedure when refractory to conservative management. The isolated syndesmotic injury (high ankle sprain) is more disabling than the lateral sprain and requires syndesmotic stabilization for grade III injuries. The chapter that follows turns to the hindfoot and midfoot — the talus, calcaneus, and midfoot fractures and dislocations that complete the lower extremity trauma sequence.