Fix if fragment >25–30% of tibial plafond, >2 mm displacement, syndesmotic instability, or posterolateral fragment involving PITFL. CT-based morphology guides approach: posterolateral approach common; direct reduction restores incisura and syndesmotic stability. Sequence: posterior malleolus first to stabilize syndesmosis, then fibula/medial malleolus. Fixation: screws posterior‑to‑anterior or buttress plate via posterolateral approach. Restoring posterior fragment reduces need for trans-syndesmotic screws.
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Overview & Anatomy
The posterior malleolus is the posteroinferior lip of the tibia, forming the posterior wall of the tibial plafond (the distal articular surface of the tibia). It is fractured in approximately 40–70% of all ankle fractures — most commonly as a component of trimalleolar ankle fractures. Historically, small posterior malleolus fragments were managed non-operatively, but contemporary evidence demonstrates that the posterior malleolus plays a critical role in ankle stability, fibular notch integrity, articular surface congruency, and syndesmotic competence — leading to a fundamental reassessment of fixation indications.
Anatomy of the posterior malleolus: the posterior malleolus is not a simple flat fragment — it has a complex 3D architecture; it forms the posterior tibial plafond and the posterior wall of the fibular notch (the posterior incisura); the posterior inferior tibiofibular ligament (PITFL) inserts onto the posterior malleolus; the deep portion of the PITFL (posterior intermalleolar ligament) also attaches here; a posterolateral fragment (the most common morphology) involves the fibular notch and the PITFL attachment; a posteromedial fragment involves the medial tibial plafond; the fragment morphology determines stability, articular involvement, and management
Function: as part of the tibial plafond, the posterior malleolus supports articular cartilage and resists posterior subluxation of the talus; as the posterior wall of the fibular notch, it contributes to syndesmotic stability — a displaced posterior malleolus fragment disrupts the fibular notch and compromises syndesmotic integrity even if the ligaments themselves are intact; the PITFL — the strongest tibiofibular ligament — is attached to the posterior malleolus and its avulsion from the tibia represents a ligamentous equivalent injury to the syndesmosis
Classification — Bartoníček, Haraguchi, and Mason-Molloy
Classification
Type
Description
Clinical Significance
Bartoníček classification (CT-based)
Type 1 — Extraincisural
Fragment does NOT involve the fibular notch; purely medial or small posterior; PITFL attachment is intact on the tibia; fibular notch architecture preserved
Syndesmosis is stable (fibular notch intact); fixation based on articular involvement only; generally small, non-surgical if <25% articular
Type 2 — Posterolateral (partial incisural)
Fragment involves the lateral part of the fibular notch (posterolateral corner); the PITFL typically attached to the fragment; MOST COMMON type (>60%)
Fibular notch disrupted — fibula may sublux posteriorly relative to the notch; syndesmosis compromised; fixation of the fragment restores fibular notch anatomy + reduces the syndesmosis without a separate syndesmotic screw; strong evidence supports fixation
Type 3 — Large posterolateral (complete incisural)
Large fragment involving the entire fibular notch; the fibula rides into the notch when the fragment is displaced; involves a large portion of the articular surface (>25–33%)
Major structural fragment; near-universal agreement on fixation; restores notch + articular surface; avoids syndesmotic screw; prevents articular incongruency; most important to fix
Type 4 — Medial extension
Fragment extends medially, involving a large part of the posterior articular surface; extends posteromedially; may involve the posteromedial corner of the plafond
Large posterior articular fragment; complex; fixation mandatory; may require direct posterior approach to address the medial extension adequately
Haraguchi Type
Description
Type I — Posterolateral oblique
The most common type (~67%); the fracture line runs obliquely from posterolateral to anteromedial; the fragment is triangular and involves the posterolateral plafond and fibular notch; PITFL attached to the fragment; typically equivalent to Bartoníček Type 2
Type II — Transverse with medial extension
~19%; fracture line more transverse with medial extension; the fragment includes posteromedial plafond; equivalent to Bartoníček Type 4
Type III — Small shell fragment
~14%; small cortical shell fragment; does NOT involve the fibular notch; extraincisural (Bartoníček Type 1); generally non-surgical
Traditional vs Contemporary Indications for Fixation
Paradigm
Threshold for Fixation
Basis
Evidence / Limitations
Traditional (size-based threshold)
Fragment involving >25% of the articular surface on lateral plain X-ray → fixation recommended; <25% → non-operative or indirect fixation acceptable
Biomechanical studies (Jaskulka 1989) showing that fragments >25% of articular surface cause ankle instability under load; became the standard clinical threshold for decades
Measurement of articular surface on plain X-ray is unreliable — the lateral view of the posterior malleolus significantly UNDERESTIMATES actual fragment size; CT is required for accurate assessment; the 25% threshold does not address fibular notch involvement or syndesmotic stability — these factors are now recognised as equally important
Contemporary (fragment morphology-based)
CT-guided morphological classification (Bartoníček/Haraguchi) determines fixation; fixation recommended for: (1) any fragment involving the fibular notch (Bartoníček Type 2/3/4 — regardless of size); (2) any fragment causing talar subluxation or step-off >2 mm; (3) any fragment >25% articular involvement on CT (not plain X-ray); (4) syndesmotic instability with posterior malleolus fracture (fixation of PM may restore syndesmotic stability without syndesmotic screw)
Multiple studies (Drijfhout van Hooff et al., Gardner et al., Haraguchi et al.) demonstrating that fibular notch involvement and PITFL avulsion — not articular size alone — are the principal drivers of ankle instability and poor outcomes after posterior malleolus fractures; CT pre-operatively has demonstrated that the traditional 25% threshold on plain X-ray was misguided because plain X-ray underestimates fragment size
Surgical Technique & Approaches
Posterolateral approach (most commonly used for Type I/II Haraguchi / Bartoníček Type 2): the patient is positioned prone; a posterolateral incision is made between the peroneal tendons (laterally) and the flexor hallucis longus (medially); this interval provides direct access to the posterolateral fragment and the fibular notch; advantages — direct visualisation of the fragment, fibular notch, and the distal fibula (which may need separate fixation); the fragment can be reduced under direct vision and fixed with lag screws (anteroposterior direction) or a posterior antiglide plate; the sural nerve and short saphenous vein must be protected in the posterolateral incision
Posterior approach (for Bartoníček Type 3/4 with medial extension): a more medially positioned posterior incision or a separate posteromedial incision provides access to the posteromedial fragment component; the flexor hallucis longus is retracted laterally; direct plate fixation of the posteromedial component; often required in addition to the posterolateral approach for complex large fragments
Anteroposterior lag screws vs posterior antiglide plate: two main fixation strategies for the posterior malleolus; (1) Anteroposterior lag screws — the traditional technique; screws are placed from anterior to posterior under fluoroscopic guidance, compressing the fragment; minimally invasive but limited control over fragment; does not address articular surface directly; less optimal for large displaced fragments; (2) Posterior antiglide plate — a low-profile plate applied directly posterior to the distal tibia through a posterolateral approach; the plate resists posterior translation of the fragment (antiglide function) without requiring a lag screw across a small fragment; allows articular reduction under direct vision; biomechanically stronger construct; increasingly preferred for larger fragments and when the posterolateral approach has been used for the fibula; disadvantage — plate prominence posteriorly may be symptomatic requiring removal
Impact on syndesmotic stability: a key contemporary concept is that fixation of the posterior malleolus fragment (when it is a Bartoníček Type 2/3 incisural fragment carrying the PITFL) may restore syndesmotic stability without requiring a supplementary syndesmotic screw; cadaveric and clinical studies have demonstrated that after anatomical fixation of the fibular-notch-involving posterior malleolus fragment, the syndesmosis stress test (Cotton test, external rotation stress test intraoperatively) is negative — eliminating the need for syndesmotic screw; this is clinically important as syndesmotic screws require re-operation for removal and restrict ankle motion during healing; HOWEVER — if the syndesmosis remains unstable after posterior malleolus fixation (uncommon), a syndesmotic screw or tightrope fixation must be added
Outcomes
Evidence for fixation benefit: several studies demonstrate significantly better functional outcomes, lower rates of post-traumatic ankle osteoarthritis, and improved ankle stability with anatomical fixation of posterior malleolus fragments (particularly those involving the fibular notch) compared to non-operative management; Drijfhout van Hooff et al. (2015) demonstrated that Bartoníček Type 2/3 fragments managed non-operatively had significantly worse outcomes and higher OA rates than those fixed; Verhage et al. showed anatomical reduction of the posterior malleolus was the strongest predictor of good functional outcome in trimalleolar fractures; a `small` fragment (<25% on plain X-ray) classified as Bartoníček Type 2 (fibular notch involvement) should be fixed
Post-traumatic osteoarthritis: the most common long-term complication; articular incongruency (>2 mm step-off) after any ankle fracture correlates with early OA; posterior malleolus non-union is rare but causes persistent posterior ankle pain; adequate reduction of articular cartilage congruency is the primary goal of surgery
Exam Pearls
Posterior malleolus = posteroinferior tibial lip + posterior fibular notch wall; PITFL attaches here; fracture in ~40–70% of ankle fractures; most common pattern = posterolateral (Haraguchi Type I, Bartoníček Type 2)
Traditional threshold (>25% articular surface on lateral X-ray) — OUTDATED; plain X-ray significantly UNDERESTIMATES true fragment size; CT mandatory for classification and surgical planning
Contemporary indications for fixation: any fragment involving the fibular notch (Bartoníček Type 2/3/4); talar subluxation; articular step-off >2 mm on CT; syndesmotic instability persisting after fibular fixation; size >25% on CT; the fibular notch involvement is the critical factor regardless of articular percentage
Bartoníček classification: Type 1 (extraincisural — notch intact, generally non-surgical); Type 2 (posterolateral, partial notch — MOST COMMON, PITFL avulsion, fix); Type 3 (large posterolateral, complete notch — always fix); Type 4 (medial extension — complex, always fix)
Posterior malleolus fixation restores syndesmotic stability: incisural fragment (Type 2/3) carries the PITFL; anatomical fixation restores fibular notch + syndesmotic stability; may ELIMINATE the need for a syndesmotic screw (check stability after fixation intraoperatively); significant clinical advantage — avoids screw removal re-operation
Posterolateral approach: prone position; between peroneal tendons and FHL; direct access to fragment, fibular notch, and distal fibula; protect sural nerve
Posterior antiglide plate vs anteroposterior screws: posterior plate = direct visualisation + stronger construct; AP screws = minimally invasive but indirect; posterior plate increasingly preferred for larger incisural fragments
Articular step-off >2 mm: independently predicts post-traumatic OA; primary goal of surgery is anatomical articular reduction; fracture morphology determines which approach achieves this most reliably
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References
Bartoníček J et al. Posterior malleolar fractures — anatomical classification and proposal of fixation method. Int Orthop. 2015.
Haraguchi N et al. Pathoanatomy of posterior malleolar fractures of the ankle. J Bone Joint Surg Am. 2006.
Jaskulka RA, Ittner G, Schedl R. Fractures of the posterior tibial margin — their role in the prognosis of malleolar fractures. J Trauma. 1989.
Drijfhout van Hooff CC et al. Relevance of fragment size in trimalleolar fractures. Foot Ankle Int. 2015.
Gardner MJ et al. The importance of the posterior malleolus in ankle fractures — a biomechanical study. J Bone Joint Surg Am. 2006.
Verhage SM et al. Clinical and radiological results of posterior malleolar fractures. Foot Ankle Int. 2017.
Huber M et al. Posterior malleolus fractures and syndesmotic stability. J Orthop Trauma. 2015.
Mangnus L et al. Posterior malleolus fractures in the new millennium — a systematic review. Injury. 2015.
Campbells Operative Orthopaedics. 14th Edition. Elsevier.
Orthobullets — Posterior Malleolus Fractures; Trimalleolar Ankle Fractures; Syndesmotic Injuries.
